Aspects of the structure and function of some gastropod columellar muscles (Mollusca)
- Authors: Frescura, Mandy
- Date: 1991
- Subjects: Gastropoda -- Research Mollusks -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5642 , http://hdl.handle.net/10962/d1005324
- Description: The columellar muscle of both limpets and coiled shell gastropods is of the paramyosin smooth type. Collagen forms an integral part of the musculature constituting about 35% of the tissue. In limpets, muscle organisation is typical of a muscular hydrostat. Tightly packed blocks of muscle, dense arrays of cross-linked collagen, large muscle cells (9 µm diameter) and thick filaments (70 nm diameter, 30 µm long) produce a tough, relatively rigid but powerful muscle. In coiled shell gastropods, muscle organisation is intermediate between a muscular and a fluid hydrostat. Finer muscle cells (6 µm diameter), thick filaments (60 nm diameter) and a loose intercellular network of collagen interspersed with fluid vesicles are features of a more pliable and extensible muscle. In addition, ultrastructural differences, such as larger numbers of mitochondria and sarcolemmal invaginations distinguish the tarsal from the columellar muscle in both limpets and coiled shell gastropods. About 25% of muscle cells in most species examined, contain a novel arrangement of thin filaments with periodic electron-dense regions. These are similar in appearance to intrafusal cells and stress-fibres of non-muscle cells. Structural analysis of isolated filaments, optical diffraction and SDS gel electrophoresis confirm the, large dimensions and the paramyosin nature of the thick filaments. Microdensitometry of the gel proteins confirms the high proportion of collagen present. No significant differences in muscle ultrastructure were found between limpets from different tidal heights. Muscle attachment areas are shown to be species-specific and positively correlated to tenacity and wave exposure. The muscle attachment mechanism is similar to that described for other molluscs. It consists of a special epithelial layer and a mucous-like material at the muscle-shell interface that possibly has an adhesive function. Although the ultrastructure of Patella is very similar to that of the anterior byssus retractor of Mytilus, its mechanical behaviour is not. The muscle has a narrow working range where maximum tensions and "catch-like" contractions develop. This narrow length range is co-incident with the in situ length at which clamping occurs. It is suggested that the large component of collagen has an important influence over the mechanical behaviour of the muscle during clamping, by cross-linking in a manner similar to that described for some echinoderm connective tissues.
- Full Text:
- Date Issued: 1991
- Authors: Frescura, Mandy
- Date: 1991
- Subjects: Gastropoda -- Research Mollusks -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5642 , http://hdl.handle.net/10962/d1005324
- Description: The columellar muscle of both limpets and coiled shell gastropods is of the paramyosin smooth type. Collagen forms an integral part of the musculature constituting about 35% of the tissue. In limpets, muscle organisation is typical of a muscular hydrostat. Tightly packed blocks of muscle, dense arrays of cross-linked collagen, large muscle cells (9 µm diameter) and thick filaments (70 nm diameter, 30 µm long) produce a tough, relatively rigid but powerful muscle. In coiled shell gastropods, muscle organisation is intermediate between a muscular and a fluid hydrostat. Finer muscle cells (6 µm diameter), thick filaments (60 nm diameter) and a loose intercellular network of collagen interspersed with fluid vesicles are features of a more pliable and extensible muscle. In addition, ultrastructural differences, such as larger numbers of mitochondria and sarcolemmal invaginations distinguish the tarsal from the columellar muscle in both limpets and coiled shell gastropods. About 25% of muscle cells in most species examined, contain a novel arrangement of thin filaments with periodic electron-dense regions. These are similar in appearance to intrafusal cells and stress-fibres of non-muscle cells. Structural analysis of isolated filaments, optical diffraction and SDS gel electrophoresis confirm the, large dimensions and the paramyosin nature of the thick filaments. Microdensitometry of the gel proteins confirms the high proportion of collagen present. No significant differences in muscle ultrastructure were found between limpets from different tidal heights. Muscle attachment areas are shown to be species-specific and positively correlated to tenacity and wave exposure. The muscle attachment mechanism is similar to that described for other molluscs. It consists of a special epithelial layer and a mucous-like material at the muscle-shell interface that possibly has an adhesive function. Although the ultrastructure of Patella is very similar to that of the anterior byssus retractor of Mytilus, its mechanical behaviour is not. The muscle has a narrow working range where maximum tensions and "catch-like" contractions develop. This narrow length range is co-incident with the in situ length at which clamping occurs. It is suggested that the large component of collagen has an important influence over the mechanical behaviour of the muscle during clamping, by cross-linking in a manner similar to that described for some echinoderm connective tissues.
- Full Text:
- Date Issued: 1991
Beyond all words : a psychoanalytic approach to the phenomenon of mysticism in literature
- Authors: Bunyan, David Christopher
- Date: 1991
- Subjects: Mysticism in literature Mysticism -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2242 , http://hdl.handle.net/10962/d1002285
- Description: The principal claim of this thesis is that the mystical experience is a wide-ranging influence upon literature. It is a recurrent thematic concern of poets, novelists and playwrights; but even when mysticism is not an overt element in a text, analysis of its symbols can reveal references to emotions and experiences of a mystical character - as is frequently the case with fantasy. In a more essential way, certain widely-used techniques of poetry effectively reproduce the character of mystical events for the reader. Some theory does indeed imply that the mystical bearing is quite fundamental, at a certain level, to all creative literature. This thesis explores the link between mysticism and literature through widely differing examples, to show how it continues to be found in otherwise divergent texts and contexts. Indeed, no attempt is made to provide an exhaustive overview; rather, certain special areas of interest are represented by selected cases. Mystical elements in Modernism, for example (especially in T.S. Eliot and Virginia Woolf), are contrasted with Romantic attitudes to mysticism, which Wordsworth and Coleridge are taken to represent. A further goal is to analyse the character of literary mysticism, and to account for the connection between mysticism and literary practice. The view is adopted that the circumstances in which the infant first acquires language is of crucial importance in this regard, and that literary language often draws upon submerged recollections of these early circumstances. Literature, it is argued, can employ signs and patterns of symbolisation in ways that actually attempt to 'undo' many of the everyday functions of words. The ultimate ideal of such literary techniques is to 'reverse' the process by which language was acquired and to 'return' the reader to a state resembling pre-linguistic experience, a goal which has much in common with the ambitions of mystics. Jacques Lacan's theoretical writings touch at many points upon the early development of the child and the significance of its acquisition of language. This thesis consequently has recourse to Lacan's work and, where relevant, to related psychoanalytic writings by Sigmund Freud and Julia Kristeva. After an investigation of the main characteristics of mystical experience as such, the Introduction broadly outlines Lacan's theoretical position. Chapter 1 is concerned more specifically with Lacan's discussions of mysticism. Part Two (Chapters 2-4) deals principally with the links between mystical yearnings and the Romantic ideal of the 'sublime'. In Part Three (Chapters 5-7) the relation between mysticism and Modernist developments affecting both theme and artistic technique is examined in works by three writers: T.S. Eliot, Virginia Woolf, and Fernando Pessoa. Part Four discusses particular literary presentations of 'evil' and of 'good' as embodiments of mystical perceptions. Late nineteenth- and early twentieth-century 'supernatural' fiction is selected to represent the first case, and certain New Testament and early Christian texts the second.
- Full Text:
- Date Issued: 1991
- Authors: Bunyan, David Christopher
- Date: 1991
- Subjects: Mysticism in literature Mysticism -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2242 , http://hdl.handle.net/10962/d1002285
- Description: The principal claim of this thesis is that the mystical experience is a wide-ranging influence upon literature. It is a recurrent thematic concern of poets, novelists and playwrights; but even when mysticism is not an overt element in a text, analysis of its symbols can reveal references to emotions and experiences of a mystical character - as is frequently the case with fantasy. In a more essential way, certain widely-used techniques of poetry effectively reproduce the character of mystical events for the reader. Some theory does indeed imply that the mystical bearing is quite fundamental, at a certain level, to all creative literature. This thesis explores the link between mysticism and literature through widely differing examples, to show how it continues to be found in otherwise divergent texts and contexts. Indeed, no attempt is made to provide an exhaustive overview; rather, certain special areas of interest are represented by selected cases. Mystical elements in Modernism, for example (especially in T.S. Eliot and Virginia Woolf), are contrasted with Romantic attitudes to mysticism, which Wordsworth and Coleridge are taken to represent. A further goal is to analyse the character of literary mysticism, and to account for the connection between mysticism and literary practice. The view is adopted that the circumstances in which the infant first acquires language is of crucial importance in this regard, and that literary language often draws upon submerged recollections of these early circumstances. Literature, it is argued, can employ signs and patterns of symbolisation in ways that actually attempt to 'undo' many of the everyday functions of words. The ultimate ideal of such literary techniques is to 'reverse' the process by which language was acquired and to 'return' the reader to a state resembling pre-linguistic experience, a goal which has much in common with the ambitions of mystics. Jacques Lacan's theoretical writings touch at many points upon the early development of the child and the significance of its acquisition of language. This thesis consequently has recourse to Lacan's work and, where relevant, to related psychoanalytic writings by Sigmund Freud and Julia Kristeva. After an investigation of the main characteristics of mystical experience as such, the Introduction broadly outlines Lacan's theoretical position. Chapter 1 is concerned more specifically with Lacan's discussions of mysticism. Part Two (Chapters 2-4) deals principally with the links between mystical yearnings and the Romantic ideal of the 'sublime'. In Part Three (Chapters 5-7) the relation between mysticism and Modernist developments affecting both theme and artistic technique is examined in works by three writers: T.S. Eliot, Virginia Woolf, and Fernando Pessoa. Part Four discusses particular literary presentations of 'evil' and of 'good' as embodiments of mystical perceptions. Late nineteenth- and early twentieth-century 'supernatural' fiction is selected to represent the first case, and certain New Testament and early Christian texts the second.
- Full Text:
- Date Issued: 1991
Binary and ternary pyrotechnic systems containing manganese, molybdenum, barium peroxide and strontium peroxide
- Authors: Drennan, Robin Lennox
- Date: 1991
- Subjects: Thermochemistry -- Research Thermal analysis -- Research Chemistry, Analytic -- Research Manganese Molybdenum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4411 , http://hdl.handle.net/10962/d1006765
- Description: Barium peroxide was selected as oxidant in a fundamental physico-chemical study of binary pyrotechnic systems on account of its apparently simple decomposition stoichiometry. With this selection, the choice of fuel was governed by the requirements of a self-sustaining reaction at combustion temperatures below the melting point of the platinum/rhodium thermocouples (∼1760°C) used for recording temperature-time profiles during burning, and at burning rates not exceeding the response of the sensors used to monitor combustion. Both manganese and molybdenum metal powders satisfied the above requirements. Strontium peroxide was also available as an oxidant and so the combustion of binary metal/oxidant systems using both fuels and both BaO₂ and SrO₂ oxidants was investigated. The Mn/BaO₂, MoBaO₂ and Mn/SrO₂ systems burnt over a wide range of compositions, but the range of ignitable compositions for the Mo/SrO₂ system was very limited. The linear burning rates, for all these systems, ranged from 2 to 12 mm s⁻¹ and burning rates were increased by the use of smaller particle-sizes of fuel and greater loading pressures. Inert additives generally decreased the burning rate. Temperature-time profiles were recorded for all the compositions which sustained combustion. Kinetic parameters were estimated from the shapes of these profiles using procedures developed by Hill et al and Boddington and Laye. Activation energies derived from the profiles were low (3 to 40 kJ mol⁻¹) and support suggestions that reactions at high temperatures are controlled by diffusion processes. Thermal analysis was used to identify the processes occurring in the four systems. The main exothermic events were observed to correspond approximately with the onset of oxidant decomposition. A pre-ignition reaction was tentatively identified in the Mn/BaO₂ system. Oxidation of the metal fuels was generally incomplete, probably because of the formation of protective layers of product. Activation energies, derived from thermal analysis results, were in the range of from 70 to 720 kJ mol⁻¹. Ternary systems containing either mixed fuels or mixed oxidants were also examined. No interactions hetween the fuels or between the oxidants were observed. Other techniques used included bomb calorimetry, measurement of thermal conductivity, X-ray powder diffraction, infrared spectroscopy and scanning electron microscopy.
- Full Text:
- Date Issued: 1991
- Authors: Drennan, Robin Lennox
- Date: 1991
- Subjects: Thermochemistry -- Research Thermal analysis -- Research Chemistry, Analytic -- Research Manganese Molybdenum
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4411 , http://hdl.handle.net/10962/d1006765
- Description: Barium peroxide was selected as oxidant in a fundamental physico-chemical study of binary pyrotechnic systems on account of its apparently simple decomposition stoichiometry. With this selection, the choice of fuel was governed by the requirements of a self-sustaining reaction at combustion temperatures below the melting point of the platinum/rhodium thermocouples (∼1760°C) used for recording temperature-time profiles during burning, and at burning rates not exceeding the response of the sensors used to monitor combustion. Both manganese and molybdenum metal powders satisfied the above requirements. Strontium peroxide was also available as an oxidant and so the combustion of binary metal/oxidant systems using both fuels and both BaO₂ and SrO₂ oxidants was investigated. The Mn/BaO₂, MoBaO₂ and Mn/SrO₂ systems burnt over a wide range of compositions, but the range of ignitable compositions for the Mo/SrO₂ system was very limited. The linear burning rates, for all these systems, ranged from 2 to 12 mm s⁻¹ and burning rates were increased by the use of smaller particle-sizes of fuel and greater loading pressures. Inert additives generally decreased the burning rate. Temperature-time profiles were recorded for all the compositions which sustained combustion. Kinetic parameters were estimated from the shapes of these profiles using procedures developed by Hill et al and Boddington and Laye. Activation energies derived from the profiles were low (3 to 40 kJ mol⁻¹) and support suggestions that reactions at high temperatures are controlled by diffusion processes. Thermal analysis was used to identify the processes occurring in the four systems. The main exothermic events were observed to correspond approximately with the onset of oxidant decomposition. A pre-ignition reaction was tentatively identified in the Mn/BaO₂ system. Oxidation of the metal fuels was generally incomplete, probably because of the formation of protective layers of product. Activation energies, derived from thermal analysis results, were in the range of from 70 to 720 kJ mol⁻¹. Ternary systems containing either mixed fuels or mixed oxidants were also examined. No interactions hetween the fuels or between the oxidants were observed. Other techniques used included bomb calorimetry, measurement of thermal conductivity, X-ray powder diffraction, infrared spectroscopy and scanning electron microscopy.
- Full Text:
- Date Issued: 1991
Design, development and evaluation of encapsulated oral controlled release theophylline mini-tablets
- Authors: Munday, Dale Leslie
- Date: 1991
- Subjects: Drugs -- Administration , Drugs -- Bioavailability , Drugs -- Controlled release , Drugs -- Dosage forms , Tablets (Medicine) , Biopharmaceutics , Drugs -- Testing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3777 , http://hdl.handle.net/10962/d1003255 , Drugs -- Administration , Drugs -- Bioavailability , Drugs -- Controlled release , Drugs -- Dosage forms , Tablets (Medicine) , Biopharmaceutics , Drugs -- Testing
- Description: Conventional solid dosage forms often lead to fluctuations which exceed the maximum safe therapeutic level and/or decline below the minimum effective level. It is recognised that many drugs for chronic administration should be administered on a schedule that maintains plasma drug concentration within the therapeutic window. Research in controlled release dosage forms aims at designing a system with a zero-order input (eg, ideally to deliver 8.33% of the dose per hour over a 12 hour duration), producing steady state plasma drug levels. Oral dministration of drugs prepared as a controlled release formulation is extremely popular, and has attracted the attention of pharmaceutical scientists during the last decade. This has been due to the simultaneous convergence of various factors (eg, discovery of novel polymers and devices, better understanding of formulation and physiological constraints, expiration of existing patents, prohibitive cost of developing new drug entities), involved in the development of these delivery systems. Controlled release oral products can be formulated as single or multiple unit dosage forms and the relative merits of multiple unit forms with their own rate controlling systems are well established. This work describes the development of a relatively inexpensive multiple-unit capsule dosage form of theophylline containing coated mini-tablets for drug delivery throughout the gastrointestinal tract. Preformulation studies on theophylline anhydrous included solubility and dissolution rate determinations. Techniques including X-ray powder diffraction, differential scanning colorimetry and infrared spectroscopy provided no evidence of true polymorphism after recrystallisation from various solvents. However, scanning electron micrographs showed the effects of solvent polarity and cooling rate on the size and shape of recrystallised particles. Theophylline granules were manufactured by using various binders and were film coated by fluidised bed technology with various proportions of ethylcellulose, containing varying amounts of PEG 1540. In vitro release rates were dependent upon coating thickness and the proportion of PEG, which, being water soluble, created pores in the coating during dissolution studies as observed by a scanning electron microscope. However, substantial proportions of the drug remained unreleased from the granules. In order to overcome the problems of drug retention, plain granules were used and theophylline mini-tablets (3 mm diameter, weighing 15 - 20 mg) were manufactured and film coated with various Eudragits ® and other polymeric mixtures (soluble and insoluble). In vitro dissolution profiles from samples enclosed in hard gelatin capsules were determined using the USPXXI paddle apparatus in test media at pH 1.2 (HCI), pH 5.4 and 7.4 (phosphate buffers) at 37'C. Monitoring of in vitro theophylline release over 12 h, under identical hydrodynamic conditions, showed that the dissolution rate at pH 1.2 is substantially greater (95% of total drug content released in < 10 h) than that in phosphate buffers. The maximum release after 12 h was approximately 20 and 30% of total drug content of the tablet at pH 5.4 and 7.4, respectively. However, in vivo bioavailability after oral administration of tablets to rabbits corresponded to over 95% of total drug, compared with the same dose administered intravenously. The retarded drug release during in vitro dissolution in phosphate buffer was attributed to a possible interaction of phosphate ions with theophylline molecules at the tablet core-coat interface. These findings indicate that both rate and extent of theophylline release from the slow release coated mini-tablets are highly sensitive to phosphate buffers. The data also emphasise the usefulness of an animal model for assessment of in vivo drug release and subsequent absorption during the development of modified release dosage forms. Mini-tablets were subjected to isothermal and cyclic stresses to reach conditions for up to 6 months at different temperatures and relative humidity. The film integrity was maintained but ageing of the coating occurred which impeded dissolution. Reduced drug release was temperature related while the effect of relative humidi% was insignific~t. Encapsulated mini-tablets (uncoated and coated with Eudragit RL and RS 2% w/w) equivalent to a 300 mg dose, were evaluated both in vitro and in vivo using beagle dogs. The pharmacokinetic parameters from single and multiple dose studies showed several advantages over Theo-Dur® 300 mg tablets. Precise dosage titration is possible by careful adjustment of the number of encapsulated mini-tablets. This multiple unit mini-tablet delivery system will allow for greater flexibility in dosage adjustment compared to the currently available preparations, allowing individualised fine dose titration in those patients requiring therapeutic drug monitoring. The developmentof the multiple unit mini-tablet formulation appears to provide an optimal dosage form with maximum flexibility in respect of dose, duration range and ease of production.
- Full Text:
- Date Issued: 1991
Design, development and evaluation of encapsulated oral controlled release theophylline mini-tablets
- Authors: Munday, Dale Leslie
- Date: 1991
- Subjects: Drugs -- Administration , Drugs -- Bioavailability , Drugs -- Controlled release , Drugs -- Dosage forms , Tablets (Medicine) , Biopharmaceutics , Drugs -- Testing
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3777 , http://hdl.handle.net/10962/d1003255 , Drugs -- Administration , Drugs -- Bioavailability , Drugs -- Controlled release , Drugs -- Dosage forms , Tablets (Medicine) , Biopharmaceutics , Drugs -- Testing
- Description: Conventional solid dosage forms often lead to fluctuations which exceed the maximum safe therapeutic level and/or decline below the minimum effective level. It is recognised that many drugs for chronic administration should be administered on a schedule that maintains plasma drug concentration within the therapeutic window. Research in controlled release dosage forms aims at designing a system with a zero-order input (eg, ideally to deliver 8.33% of the dose per hour over a 12 hour duration), producing steady state plasma drug levels. Oral dministration of drugs prepared as a controlled release formulation is extremely popular, and has attracted the attention of pharmaceutical scientists during the last decade. This has been due to the simultaneous convergence of various factors (eg, discovery of novel polymers and devices, better understanding of formulation and physiological constraints, expiration of existing patents, prohibitive cost of developing new drug entities), involved in the development of these delivery systems. Controlled release oral products can be formulated as single or multiple unit dosage forms and the relative merits of multiple unit forms with their own rate controlling systems are well established. This work describes the development of a relatively inexpensive multiple-unit capsule dosage form of theophylline containing coated mini-tablets for drug delivery throughout the gastrointestinal tract. Preformulation studies on theophylline anhydrous included solubility and dissolution rate determinations. Techniques including X-ray powder diffraction, differential scanning colorimetry and infrared spectroscopy provided no evidence of true polymorphism after recrystallisation from various solvents. However, scanning electron micrographs showed the effects of solvent polarity and cooling rate on the size and shape of recrystallised particles. Theophylline granules were manufactured by using various binders and were film coated by fluidised bed technology with various proportions of ethylcellulose, containing varying amounts of PEG 1540. In vitro release rates were dependent upon coating thickness and the proportion of PEG, which, being water soluble, created pores in the coating during dissolution studies as observed by a scanning electron microscope. However, substantial proportions of the drug remained unreleased from the granules. In order to overcome the problems of drug retention, plain granules were used and theophylline mini-tablets (3 mm diameter, weighing 15 - 20 mg) were manufactured and film coated with various Eudragits ® and other polymeric mixtures (soluble and insoluble). In vitro dissolution profiles from samples enclosed in hard gelatin capsules were determined using the USPXXI paddle apparatus in test media at pH 1.2 (HCI), pH 5.4 and 7.4 (phosphate buffers) at 37'C. Monitoring of in vitro theophylline release over 12 h, under identical hydrodynamic conditions, showed that the dissolution rate at pH 1.2 is substantially greater (95% of total drug content released in < 10 h) than that in phosphate buffers. The maximum release after 12 h was approximately 20 and 30% of total drug content of the tablet at pH 5.4 and 7.4, respectively. However, in vivo bioavailability after oral administration of tablets to rabbits corresponded to over 95% of total drug, compared with the same dose administered intravenously. The retarded drug release during in vitro dissolution in phosphate buffer was attributed to a possible interaction of phosphate ions with theophylline molecules at the tablet core-coat interface. These findings indicate that both rate and extent of theophylline release from the slow release coated mini-tablets are highly sensitive to phosphate buffers. The data also emphasise the usefulness of an animal model for assessment of in vivo drug release and subsequent absorption during the development of modified release dosage forms. Mini-tablets were subjected to isothermal and cyclic stresses to reach conditions for up to 6 months at different temperatures and relative humidity. The film integrity was maintained but ageing of the coating occurred which impeded dissolution. Reduced drug release was temperature related while the effect of relative humidi% was insignific~t. Encapsulated mini-tablets (uncoated and coated with Eudragit RL and RS 2% w/w) equivalent to a 300 mg dose, were evaluated both in vitro and in vivo using beagle dogs. The pharmacokinetic parameters from single and multiple dose studies showed several advantages over Theo-Dur® 300 mg tablets. Precise dosage titration is possible by careful adjustment of the number of encapsulated mini-tablets. This multiple unit mini-tablet delivery system will allow for greater flexibility in dosage adjustment compared to the currently available preparations, allowing individualised fine dose titration in those patients requiring therapeutic drug monitoring. The developmentof the multiple unit mini-tablet formulation appears to provide an optimal dosage form with maximum flexibility in respect of dose, duration range and ease of production.
- Full Text:
- Date Issued: 1991
Immigrant adaptation in South Africa
- Authors: Couper, Michael Patrick
- Date: 1991
- Subjects: Immigrants -- South Africa South Africa -- Emigration and immigration -- Social aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3330 , http://hdl.handle.net/10962/d1003118
- Description: Although the immigrant flow to South Africa has been relatively small compared to that of other immigrant receiving countries, when considered in terms of the size of South Africa's population and the fact that immigrants are restricted to the White population group, the role of immigrants in this society is considerable. Despite this, few comprehensive studies of the experiences of immigrants in South Africa have been attempted. The aim of this study is to examine the adaptation of immigrants from various countries according to a number of dimensions. Adaptation is conceived of as a dynamic and multidimensional process. A mail survey of seven immigrant groups in South Africa was undertaken during 1985. A total of 3,520 completed questionnaires were obtained from respondents representing British, German, Dutch, Italian, Portuguese, British African and Portuguese African immigrants. The relationships among dimensions of subjective adaptation (satisfaction, identification and acceptance) and objective adaptation (social, cultural, economic, religious and political adaptation) are examined. The role of settlement and citizenship intentions are also investigated, as are various factors (country of origin, length of residence, etc.) that affect immigrant adaptation in South Africa. Multivariate analyses are undertaken to explore the nature of the relationships among these variables. Following these analyses a model of immigrant adaptation in South Africa is proposed. This model is intended to serve as a framework to guide future research on the adaptation of immigrants in South Africa.
- Full Text:
- Date Issued: 1991
- Authors: Couper, Michael Patrick
- Date: 1991
- Subjects: Immigrants -- South Africa South Africa -- Emigration and immigration -- Social aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3330 , http://hdl.handle.net/10962/d1003118
- Description: Although the immigrant flow to South Africa has been relatively small compared to that of other immigrant receiving countries, when considered in terms of the size of South Africa's population and the fact that immigrants are restricted to the White population group, the role of immigrants in this society is considerable. Despite this, few comprehensive studies of the experiences of immigrants in South Africa have been attempted. The aim of this study is to examine the adaptation of immigrants from various countries according to a number of dimensions. Adaptation is conceived of as a dynamic and multidimensional process. A mail survey of seven immigrant groups in South Africa was undertaken during 1985. A total of 3,520 completed questionnaires were obtained from respondents representing British, German, Dutch, Italian, Portuguese, British African and Portuguese African immigrants. The relationships among dimensions of subjective adaptation (satisfaction, identification and acceptance) and objective adaptation (social, cultural, economic, religious and political adaptation) are examined. The role of settlement and citizenship intentions are also investigated, as are various factors (country of origin, length of residence, etc.) that affect immigrant adaptation in South Africa. Multivariate analyses are undertaken to explore the nature of the relationships among these variables. Following these analyses a model of immigrant adaptation in South Africa is proposed. This model is intended to serve as a framework to guide future research on the adaptation of immigrants in South Africa.
- Full Text:
- Date Issued: 1991
Mineralogy, petrology and geochemistry of the lower and lower critical zones, Northwestern Bushveld Complex
- Authors: Teigler, Bernd
- Date: 1991
- Subjects: Mineralogy -- South Africa -- North-Western Transvaal Petrology -- South Africa -- North-Western Transvaal Geochemistry -- South Africa -- North-Western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4978 , http://hdl.handle.net/10962/d1005590
- Description: This study of the lower part of the Rustenburg Layered Suite in the Western Bushveld Complex is based mainly on drill core samples from three localities, which are approximately 130 km apart. The NG-sequence, situated in the northwestern sector of the complex (Union Section, R.P.M.) extends from the floor of the complex to the base of the upper Critical Zone. The sequence is ca. 1800 m thick and it comprises mainly ultramafic cumulates, namely pyroxenites, olivine pyroxenites, harzburgites and dunites. Norites and anorthos ites are present only in minor proportion. Within the upper half of the NG-sequence ten prominent chromitite layers are correlated with the LGI MG4-interval. Correlation is also established between published sequences and the two other sequences studied, located 8 km and 55 km, respectively, east of Rustenburg. Whole-rock chemical data (major and trace elements), microprobe and Sr isotope data are presented. Petrographic studies provide modal analyses and measurements of grain size. All petrographic, mineralogical and other geochemical data point to an origin of the cumulates of the NG-sequence by crystallization from liquids of the U-type lineage and derivatives thereof. No evidence is found for the involvement of parental liquids with a distinctly different composition or crystallization order (A-liquids). However, subtle compositional variations of the parental liquids are evident in slight changes of the Cr content in orthopyroxene or in variations of Sr isotope ratio. The NG-sequence is characterized by intervals with reversed fractionation trends caused by repeated influxes of pristine magma (during periods of high magmatic activity) resulting in a high degree of rejuvenation. These intervals are overlain by others with a normal fractionation trend, interpreted as cumulates formed in periods with low or no magmatic activity, in which fractional crystallization controlled bulk composition of the evolving liquid. The Lower Zone in the NG-sequence is dominated by a progressive shift towards more primitive compositions, while in the Critical Zone fractionation was the major operating process in the magma chamber. However, during deposition of the pyroxenitic lower Critical Zone several replenishment events occurred, during which fresh Cr-rich magma was emplaced. Massive chromitite layers were deposited after mixing between the newly emplaced magma and the resident residual liquid shifted bulk compositions into the primary field of chrome-spinel. Cumulus plagioclase crystallized after bulk composition of the residual liquid was driven to the orthopyroxene plagioclase cotectic by continued fractional crystallization; this occurred once in the Lower Zone, yielding a single, thin norite layer, and again in the upper Critical Zone of the NG-sequence. A facies model is proposed based on the stratigraphic and compositional variations along strike in the Western Bushveld Complex. This model explains the variations by means of the position of the sequence with regard to a feeder system. The olivine- and orthopyroxene-rich, but plagioclase-poor NG-sequence represents the proximal facies, while the SF-sequence (poor in ferromagnesian phases, but plagioclase-rich) is developed as a distal facies, close to the Brits graben.
- Full Text:
- Date Issued: 1991
- Authors: Teigler, Bernd
- Date: 1991
- Subjects: Mineralogy -- South Africa -- North-Western Transvaal Petrology -- South Africa -- North-Western Transvaal Geochemistry -- South Africa -- North-Western Transvaal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4978 , http://hdl.handle.net/10962/d1005590
- Description: This study of the lower part of the Rustenburg Layered Suite in the Western Bushveld Complex is based mainly on drill core samples from three localities, which are approximately 130 km apart. The NG-sequence, situated in the northwestern sector of the complex (Union Section, R.P.M.) extends from the floor of the complex to the base of the upper Critical Zone. The sequence is ca. 1800 m thick and it comprises mainly ultramafic cumulates, namely pyroxenites, olivine pyroxenites, harzburgites and dunites. Norites and anorthos ites are present only in minor proportion. Within the upper half of the NG-sequence ten prominent chromitite layers are correlated with the LGI MG4-interval. Correlation is also established between published sequences and the two other sequences studied, located 8 km and 55 km, respectively, east of Rustenburg. Whole-rock chemical data (major and trace elements), microprobe and Sr isotope data are presented. Petrographic studies provide modal analyses and measurements of grain size. All petrographic, mineralogical and other geochemical data point to an origin of the cumulates of the NG-sequence by crystallization from liquids of the U-type lineage and derivatives thereof. No evidence is found for the involvement of parental liquids with a distinctly different composition or crystallization order (A-liquids). However, subtle compositional variations of the parental liquids are evident in slight changes of the Cr content in orthopyroxene or in variations of Sr isotope ratio. The NG-sequence is characterized by intervals with reversed fractionation trends caused by repeated influxes of pristine magma (during periods of high magmatic activity) resulting in a high degree of rejuvenation. These intervals are overlain by others with a normal fractionation trend, interpreted as cumulates formed in periods with low or no magmatic activity, in which fractional crystallization controlled bulk composition of the evolving liquid. The Lower Zone in the NG-sequence is dominated by a progressive shift towards more primitive compositions, while in the Critical Zone fractionation was the major operating process in the magma chamber. However, during deposition of the pyroxenitic lower Critical Zone several replenishment events occurred, during which fresh Cr-rich magma was emplaced. Massive chromitite layers were deposited after mixing between the newly emplaced magma and the resident residual liquid shifted bulk compositions into the primary field of chrome-spinel. Cumulus plagioclase crystallized after bulk composition of the residual liquid was driven to the orthopyroxene plagioclase cotectic by continued fractional crystallization; this occurred once in the Lower Zone, yielding a single, thin norite layer, and again in the upper Critical Zone of the NG-sequence. A facies model is proposed based on the stratigraphic and compositional variations along strike in the Western Bushveld Complex. This model explains the variations by means of the position of the sequence with regard to a feeder system. The olivine- and orthopyroxene-rich, but plagioclase-poor NG-sequence represents the proximal facies, while the SF-sequence (poor in ferromagnesian phases, but plagioclase-rich) is developed as a distal facies, close to the Brits graben.
- Full Text:
- Date Issued: 1991
Peter Warlock: a study of the composer through the letters to Colin Taylor between 1911 and 1929
- Authors: Smith, Barry, 1939-
- Date: 1991
- Subjects: Warlock, Peter, 1894-1930 -- Correspondence Taylor, Colin, 1881-1973 -- Correspondence Composers -- Great Britain -- Correspondence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2657 , http://hdl.handle.net/10962/d1002323
- Description: This thesis involves a comprehensive study of the letters written by Philip Heseltine (Peter Warlock) to Colin Taylor from 1911 to 1929. Warlock first came into contact with Taylor at Eton in 1908 when he studied the piano with him as a schoolboy. Through Taylor's imaginative teaching during the next four years Warlock's interest in and understanding of music, particularly modern music, grew and matured. At the same time a strong bond of friendship developed between the two men and continued until Warlock's early death in 1930. This is clearly illustrated in the surviving 87 letters. Warlock was a great letter writer and over a thousand of them have been preserved, mostly in the British Library. His letters to Taylor have a special significance in that they were written during the entire period of his adult life, most of them during the early formative and creative years. They cover a wide range of topics including the influential friendships with the composers Frederick Delius and Bernard van Dieren, contemporary British and foreign music and his own work as a composer, writer, and scholar. They also give us many important insights into his life and personality, written as they are with rare candour and humour. In this thesis each letter has been carefully and systematically studied and the resulting information used to augment and expand the existing knowledge of Warlock's life and personality, his friendship with Taylor, his music and writings. Because of the wide field which the life and works of Peter Warlock cover, this study has been limited to subjects arising out of the correspondence with Taylor. Where necessary, additional information has been interpolated from other sources, mainly to give a sense of continuity and to explain references which might otherwise seem obscure. For a detailed study of Warlock's music readers are referred to Ian Copley's book, The Music of Peter Warlock, (Dennis Dobson, London, 1979). A definitive biography has yet to be written.
- Full Text:
- Date Issued: 1991
- Authors: Smith, Barry, 1939-
- Date: 1991
- Subjects: Warlock, Peter, 1894-1930 -- Correspondence Taylor, Colin, 1881-1973 -- Correspondence Composers -- Great Britain -- Correspondence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2657 , http://hdl.handle.net/10962/d1002323
- Description: This thesis involves a comprehensive study of the letters written by Philip Heseltine (Peter Warlock) to Colin Taylor from 1911 to 1929. Warlock first came into contact with Taylor at Eton in 1908 when he studied the piano with him as a schoolboy. Through Taylor's imaginative teaching during the next four years Warlock's interest in and understanding of music, particularly modern music, grew and matured. At the same time a strong bond of friendship developed between the two men and continued until Warlock's early death in 1930. This is clearly illustrated in the surviving 87 letters. Warlock was a great letter writer and over a thousand of them have been preserved, mostly in the British Library. His letters to Taylor have a special significance in that they were written during the entire period of his adult life, most of them during the early formative and creative years. They cover a wide range of topics including the influential friendships with the composers Frederick Delius and Bernard van Dieren, contemporary British and foreign music and his own work as a composer, writer, and scholar. They also give us many important insights into his life and personality, written as they are with rare candour and humour. In this thesis each letter has been carefully and systematically studied and the resulting information used to augment and expand the existing knowledge of Warlock's life and personality, his friendship with Taylor, his music and writings. Because of the wide field which the life and works of Peter Warlock cover, this study has been limited to subjects arising out of the correspondence with Taylor. Where necessary, additional information has been interpolated from other sources, mainly to give a sense of continuity and to explain references which might otherwise seem obscure. For a detailed study of Warlock's music readers are referred to Ian Copley's book, The Music of Peter Warlock, (Dennis Dobson, London, 1979). A definitive biography has yet to be written.
- Full Text:
- Date Issued: 1991
Sir Godfrey Lagden : colonial administrator
- Authors: Burton, David Raymond
- Date: 1991
- Subjects: Lagden, Godfrey Yeatman, Sir, 1851-1934 South Africa -- History -- 1836-1909
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2519 , http://hdl.handle.net/10962/d1001848
- Description: The thesis attempts to provide a chronological analysis of Lagden's colonial career between 1877 and 1907. The youngest son of a parish priest, Lagden received limited formal education and no military training. By a fortuitous set of circumstances, he was able, as a man on the spot, to attain high ranking posts in colonial administration. As a young man, he acquired considerable experience in the Transvaal, Egypt and the Gold Coast. However, blatant disobedience led to his dismissal from Colonial service. Fortunately for Lagden, Marshal Clarke, newly appointed Resident Commissioner of Basutoland, insisted on Lagden being appointed to his staff. Except for a brief stint in Swaziland, Lagden remained in Basutoland until 1900. With Clarke, Lagden played a prominent role in the implementation of the Imperial policy of securing the support of the Koena chiefs by allowing them to retain and consolidate their power and influence. Lagden became Resident Commissioner in Basutoland when Clarke was transferred to Zululand. He continued established policies and championed the Basotho cause by opposing the opening of Basutoland to prospectors and by stressing the industrious habits of the Basotho. His tactful and energetic handling of the rinderpest crisis reduced dramatic repercussions amongst the Basotho and enabled cooperative Koena chiefs to increase their economic and political leverage. Despite his reservations over Basotho loyalty, Lagden emerged from the South African War with an enhanced reputation as the Basotho remained loyal and energetically participated in the Imperial war effort. Largely because of his Basutoland experience, Lagden was appointed the Transvaal Commissioner of Native Affairs in 1901. He was responsible for regulating African labour supplies for the mines and delineation of African locations. His failure to procure sufficient labour and his defence of African rights earned Lagden much abusive settler condemnation. As chairman of the South African Native Affairs Commission, Lagden produced an uninspiring report conditioned by the labour shortage and his personal distaste for decisive action. Nevertheless, its advocacy of political and territorial segregation influenced successive Union governments.
- Full Text:
- Date Issued: 1991
- Authors: Burton, David Raymond
- Date: 1991
- Subjects: Lagden, Godfrey Yeatman, Sir, 1851-1934 South Africa -- History -- 1836-1909
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2519 , http://hdl.handle.net/10962/d1001848
- Description: The thesis attempts to provide a chronological analysis of Lagden's colonial career between 1877 and 1907. The youngest son of a parish priest, Lagden received limited formal education and no military training. By a fortuitous set of circumstances, he was able, as a man on the spot, to attain high ranking posts in colonial administration. As a young man, he acquired considerable experience in the Transvaal, Egypt and the Gold Coast. However, blatant disobedience led to his dismissal from Colonial service. Fortunately for Lagden, Marshal Clarke, newly appointed Resident Commissioner of Basutoland, insisted on Lagden being appointed to his staff. Except for a brief stint in Swaziland, Lagden remained in Basutoland until 1900. With Clarke, Lagden played a prominent role in the implementation of the Imperial policy of securing the support of the Koena chiefs by allowing them to retain and consolidate their power and influence. Lagden became Resident Commissioner in Basutoland when Clarke was transferred to Zululand. He continued established policies and championed the Basotho cause by opposing the opening of Basutoland to prospectors and by stressing the industrious habits of the Basotho. His tactful and energetic handling of the rinderpest crisis reduced dramatic repercussions amongst the Basotho and enabled cooperative Koena chiefs to increase their economic and political leverage. Despite his reservations over Basotho loyalty, Lagden emerged from the South African War with an enhanced reputation as the Basotho remained loyal and energetically participated in the Imperial war effort. Largely because of his Basutoland experience, Lagden was appointed the Transvaal Commissioner of Native Affairs in 1901. He was responsible for regulating African labour supplies for the mines and delineation of African locations. His failure to procure sufficient labour and his defence of African rights earned Lagden much abusive settler condemnation. As chairman of the South African Native Affairs Commission, Lagden produced an uninspiring report conditioned by the labour shortage and his personal distaste for decisive action. Nevertheless, its advocacy of political and territorial segregation influenced successive Union governments.
- Full Text:
- Date Issued: 1991
Studies in asymmetric synthesis
- Authors: Learmonth, Robin Alec
- Date: 1991
- Subjects: Organic compounds -- Synthesis Stereochemistry Organosilicon compounds Chirality Chemical tests and reagents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4353 , http://hdl.handle.net/10962/d1005018
- Description: The concept of combining two well established areas of organic chemistry, viz., organosilicon chemistry and the use of chiral auxiliaries, into a viable, alternative method of asymmetric synthesis has only very recently begun to receive attention. At the outset of this investigation, no asymmetric reactions of silyl enol ethers, chiral by virtue of optically active substituents on the silicon, had been reported. A range of novel chiral silyl enol ethers have thus been prepared from a variety of ketones, including pinacolone, cyclohexanone, and α-tetralone, and employing menthol, borneol, and cholesterol as chiral auxiliaries. These preparations have been achieved via several distinct routes, including a novel convergent approach involving the isolation of either the chloro(menthyloxy)dimethylsilane or the (bornyloxy)chlorodimethylsilane. The MS and NMR spectra of these silyl enol ethers were examined in detail and, in the case of the crystalline cholesteryloxy silyl enol ether, the X-ray structure has been determined. The potential of chloroalkoxysilanes to act as general, chiral derivatizing agents has been established by the preparation of diastereomeric silyl acetal mixtures of racemic secondary alcohols (e.g. I-phenylethanol and 2-octanol). The experimental diastereomeric ratios, obtained by GLC and ¹H NMR spectroscopy, approached the expected value of unity, confirming the potential of the alkoxychlorosilanes as chiral probes. The chiral silyl enol ethers have been successfully oxidized to the corresponding α-siloxy ketones employing MCPBA, MMPP, and 2-(phenylsulphonyl)-3-phenyloxaziridine as oxidizing agents and the diastereomeric excesses obtained, which varied from 0 to 16%, indicated some potential for stereochemical control. Alkylation and hydroxyalkylation reactions of the silyl enol ethers have yielded the expected α-iert-butyl and β-hydroxy ketones in good to excellent material yields, with the enantiomeric excesses, as determined by chiral shift reagent studies, reaching 14%. To improve the stereo control in these reactions, attempts have been made to prepare chiral silyl enol ethers with auxiliaries possessing the potential for transition state complex co-ordination in the reactions under consideration. The preparation of such silyl enol ethers, incorporating the proline-derived auxiliaries, N-methyl-2-hydroxymethylpyrrolidine and 2-methoxymethylpyrrolidine met with only limited success. In an alternative approach, three derivatives of 2,3-dihydroxybornane have been prepared. However, two of these auxiliaries, viz., 3-exo-benzyloxy-2-exo-hydroxybornane and 3-exo-(1-methoxyethoxy)-2-exo-hydroxybornane failed to form silyl enol ethers, even under considerably more vigorous conditions than normally employed. The third derivative, 3,3-ethylenedioxy-2-hydroxybornane has been successfully utilized in the preparation of a pinacolone-derived chiral silyl enol ether. Hydroxyalkylation of this compound with benzaldehyde has yielded the β-hydroxyketone with significantly improved enantiomeric excess (26%) and a transition state complex has been proposed to rationalize this improvement.
- Full Text:
- Date Issued: 1991
- Authors: Learmonth, Robin Alec
- Date: 1991
- Subjects: Organic compounds -- Synthesis Stereochemistry Organosilicon compounds Chirality Chemical tests and reagents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4353 , http://hdl.handle.net/10962/d1005018
- Description: The concept of combining two well established areas of organic chemistry, viz., organosilicon chemistry and the use of chiral auxiliaries, into a viable, alternative method of asymmetric synthesis has only very recently begun to receive attention. At the outset of this investigation, no asymmetric reactions of silyl enol ethers, chiral by virtue of optically active substituents on the silicon, had been reported. A range of novel chiral silyl enol ethers have thus been prepared from a variety of ketones, including pinacolone, cyclohexanone, and α-tetralone, and employing menthol, borneol, and cholesterol as chiral auxiliaries. These preparations have been achieved via several distinct routes, including a novel convergent approach involving the isolation of either the chloro(menthyloxy)dimethylsilane or the (bornyloxy)chlorodimethylsilane. The MS and NMR spectra of these silyl enol ethers were examined in detail and, in the case of the crystalline cholesteryloxy silyl enol ether, the X-ray structure has been determined. The potential of chloroalkoxysilanes to act as general, chiral derivatizing agents has been established by the preparation of diastereomeric silyl acetal mixtures of racemic secondary alcohols (e.g. I-phenylethanol and 2-octanol). The experimental diastereomeric ratios, obtained by GLC and ¹H NMR spectroscopy, approached the expected value of unity, confirming the potential of the alkoxychlorosilanes as chiral probes. The chiral silyl enol ethers have been successfully oxidized to the corresponding α-siloxy ketones employing MCPBA, MMPP, and 2-(phenylsulphonyl)-3-phenyloxaziridine as oxidizing agents and the diastereomeric excesses obtained, which varied from 0 to 16%, indicated some potential for stereochemical control. Alkylation and hydroxyalkylation reactions of the silyl enol ethers have yielded the expected α-iert-butyl and β-hydroxy ketones in good to excellent material yields, with the enantiomeric excesses, as determined by chiral shift reagent studies, reaching 14%. To improve the stereo control in these reactions, attempts have been made to prepare chiral silyl enol ethers with auxiliaries possessing the potential for transition state complex co-ordination in the reactions under consideration. The preparation of such silyl enol ethers, incorporating the proline-derived auxiliaries, N-methyl-2-hydroxymethylpyrrolidine and 2-methoxymethylpyrrolidine met with only limited success. In an alternative approach, three derivatives of 2,3-dihydroxybornane have been prepared. However, two of these auxiliaries, viz., 3-exo-benzyloxy-2-exo-hydroxybornane and 3-exo-(1-methoxyethoxy)-2-exo-hydroxybornane failed to form silyl enol ethers, even under considerably more vigorous conditions than normally employed. The third derivative, 3,3-ethylenedioxy-2-hydroxybornane has been successfully utilized in the preparation of a pinacolone-derived chiral silyl enol ether. Hydroxyalkylation of this compound with benzaldehyde has yielded the β-hydroxyketone with significantly improved enantiomeric excess (26%) and a transition state complex has been proposed to rationalize this improvement.
- Full Text:
- Date Issued: 1991
The computer in secondary school mathematics : an analysis and classification of possible modes of application, with suggested implications for the mathematics curriculum in South Africa
- Authors: Marsh, Terence Anthony
- Date: 1991
- Subjects: Mathematics -- Computer-assisted instruction Mathematics -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1459 , http://hdl.handle.net/10962/d1003340
- Description: There is a variety of possible ways in which computers can be used to enhance mathematics education. This thesis attempts to identify, analyse and classify these possibilities, particularly at the secondary school level. It describes and exemplifies applications ranging from drill-and-practice through games and simulations to problem solving by computer programming. Software evaluation procedures are considered in some depth. Illuminative evaluations of various items of software and there classroom use are reported. The underlying methodology is small-scale action research. Insights gained during the process of investigating each class of software lead to the eventual formulation of a scheme for classifying mathematics education software by means of 'multidimensional attributes'. It is contended that this scheme will help mathematics teachers to make well informed and sound professional judgements regarding the evaluation and use of computer programs for teaching/learning purposes. Also, it is hoped that this scheme and the thesis as a whole will contribute towards the establishment of well founded standards and procedures for software development in the field of mathematics education. Several implications of the computer for the mathematics curriculum in South Africa are suggested. A note of caution is sounded regarding possible detrimental effects of the computer and several questions requiring further research are posed. A recommendation arising from the thesis is that in-service training courses concerning computer applications in mathematics education should be run for secondary school teachers.
- Full Text:
- Date Issued: 1991
- Authors: Marsh, Terence Anthony
- Date: 1991
- Subjects: Mathematics -- Computer-assisted instruction Mathematics -- Study and teaching (Secondary) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1459 , http://hdl.handle.net/10962/d1003340
- Description: There is a variety of possible ways in which computers can be used to enhance mathematics education. This thesis attempts to identify, analyse and classify these possibilities, particularly at the secondary school level. It describes and exemplifies applications ranging from drill-and-practice through games and simulations to problem solving by computer programming. Software evaluation procedures are considered in some depth. Illuminative evaluations of various items of software and there classroom use are reported. The underlying methodology is small-scale action research. Insights gained during the process of investigating each class of software lead to the eventual formulation of a scheme for classifying mathematics education software by means of 'multidimensional attributes'. It is contended that this scheme will help mathematics teachers to make well informed and sound professional judgements regarding the evaluation and use of computer programs for teaching/learning purposes. Also, it is hoped that this scheme and the thesis as a whole will contribute towards the establishment of well founded standards and procedures for software development in the field of mathematics education. Several implications of the computer for the mathematics curriculum in South Africa are suggested. A note of caution is sounded regarding possible detrimental effects of the computer and several questions requiring further research are posed. A recommendation arising from the thesis is that in-service training courses concerning computer applications in mathematics education should be run for secondary school teachers.
- Full Text:
- Date Issued: 1991
The development of East London through four decades of municipal control, 1873-1914
- Tankard, Keith Peter Tempest
- Authors: Tankard, Keith Peter Tempest
- Date: 1991
- Subjects: East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2560 , http://hdl.handle.net/10962/d1002413 , East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Description: This thesis is a study in Urban History which explores the development of East London, a port in the Border region of the Eastern Cape, South Africa, through four decades of municipal control from 1873 to 1914. The town had been established in 1847 as a supply route for the British forces during the War of the Axe (7th Frontier War) but the frontier nature of the port led to economic and physical stagnation during its initial 25 years of existence. Indeed, by the time that the municipality was established in 1873, there were still no streets beyond cart tracks, no established water supply, and sanitary conditions were medieval. The Town Council therefore had much to occupy its attention but lack of positive leadership resulted in failure to capitalise on prosperous economic conditions, while a depression in the 1880's led to a further truncation of growth. It was only in the 1890's that a combination of economic growth and vibrant leadership brought about rapid civic advance, with large-scale expenditure on street construction, as well as the establishment of electricity and a tramway system. The outbreak of the Anglo-Boer War in 1899 slowed progress, however, and a post-war depression placed renewed stress on the municipality. The thesis examines the progress of the town on a broad front, dealing with the issues of economic fluctuations, the growth of the harbour as the heart of the trading sector, the physical advance of the municipality, the search for a viable water supply, the evolution of public health and sanitation, and the establishment of the port as a coastal resort. In addition, it studies the conflict of social attitudes among the townspeople, the evolution of racial segregation, and the effects of the Anglo-Boer War on the town, with the influx of some 5 000 Uitlander refugees and the establishment of a Boer concentration camp. A final chapter attempts an analysis of the reasons behind the Town Council's inability to make the best use of its opportunities to foster the development of East London.
- Full Text:
- Date Issued: 1991
- Authors: Tankard, Keith Peter Tempest
- Date: 1991
- Subjects: East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2560 , http://hdl.handle.net/10962/d1002413 , East London (South Africa) -- History , East London (South Africa) -- Economic conditions , East London (South Africa) -- Social conditions
- Description: This thesis is a study in Urban History which explores the development of East London, a port in the Border region of the Eastern Cape, South Africa, through four decades of municipal control from 1873 to 1914. The town had been established in 1847 as a supply route for the British forces during the War of the Axe (7th Frontier War) but the frontier nature of the port led to economic and physical stagnation during its initial 25 years of existence. Indeed, by the time that the municipality was established in 1873, there were still no streets beyond cart tracks, no established water supply, and sanitary conditions were medieval. The Town Council therefore had much to occupy its attention but lack of positive leadership resulted in failure to capitalise on prosperous economic conditions, while a depression in the 1880's led to a further truncation of growth. It was only in the 1890's that a combination of economic growth and vibrant leadership brought about rapid civic advance, with large-scale expenditure on street construction, as well as the establishment of electricity and a tramway system. The outbreak of the Anglo-Boer War in 1899 slowed progress, however, and a post-war depression placed renewed stress on the municipality. The thesis examines the progress of the town on a broad front, dealing with the issues of economic fluctuations, the growth of the harbour as the heart of the trading sector, the physical advance of the municipality, the search for a viable water supply, the evolution of public health and sanitation, and the establishment of the port as a coastal resort. In addition, it studies the conflict of social attitudes among the townspeople, the evolution of racial segregation, and the effects of the Anglo-Boer War on the town, with the influx of some 5 000 Uitlander refugees and the establishment of a Boer concentration camp. A final chapter attempts an analysis of the reasons behind the Town Council's inability to make the best use of its opportunities to foster the development of East London.
- Full Text:
- Date Issued: 1991
The ecology and management of the fishes of the Okavango Delta, Botswana, with particular reference to the role of the seasonal floods
- Authors: Merron, Glen Steven
- Date: 1991
- Subjects: Fishes -- Ecology -- Botswana Fishes -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5268 , http://hdl.handle.net/10962/d1005112
- Description: The Okavango is a vast inland delta system in northern Botswana which receives an annual flood from the highlands of southern Angola. There are distinct communities of fish in the Okavango which can be separated from each other by the physical characteristics of the different habitat types with which they co-evolved. This thesis provides an account of the biology and ecology of selected fish species in the Okavango Delta. Their response to the annual flood regime, and the environmental factors which limit their distribution and abundance, are examined. The thesis emphasizes the importance of water fluctuations in determining the nature of the fish fauna and the reaction of the fishes in terms of community structure, movements, breeding, predator-prey interactions and feeding. Four major ecotones were studied in the Okavango Delta. In the riverine floodplain and perennial swamp ecotones a higher species diversity was recorded than in the seasonal swamp and drainage rivers ecotones where diversity was lowest and comprised mainly of smaller fish species. A greater variety of habitat types was associated with the riverine floodplain and perennial swamp relative to the seasonal swamp and drainage rivers. The variety of habitat types between ecotones is associated with the degree of flood inundation in the respective ecotones. During the course of this study, annual recruitment of fish into the drainage rivers was from refugia in the seasonal swamp whereas the greatest degree of lateral and longitudinal movement was in the riverine floodplain and perennial swamp. Movement was in response to both biological requirements, such as availability of food and spawning sites, and physical features of the environment, such as the changing water depth. The total catch per unit effort (CPUE) of fish throughout the year was more constant in the riverine floodplain and perennial swamp than in the seasonal swamp and drainage rivers where CPUE fluctutated widely. An increase in CPUE during the duration of this study was apparent and related to the magnitude of the annual flood. In contrast to most other African wetlands, the arrival of the annual flood in the Okavango Delta coincides largely with the dry winter months. This situation presented an opportunity to compare the influence of floods and water temperature on the reproductive biology of the selected fish species. The results show a definite pattern and indicate that both the flood cycle and increased water temperatures greatly influence the breeding cycles of the selected species. The tilapia Oreochromis andersonii exhibited a considerable degree of phenotypic plasticity. Fish from the seasonally inundated areas showed a smaller mean size, egg size and larger number of eggs relative to fish in the perennially flooded areas. The size at sexual maturity was also smaller. These different reproductive characteristics exhibited by O. andersonii are dependent on the degree of water retention in the different habitats. The fishes of the Okavango have adopted other reproductive strategies to survive the changing environmental conditions brought about by an annual flood cycle. These strategies include the construction of foam nests, as described for Hepsetus odoe, for guarding the young and to provide an oxygen-rich environment. Two main non-piscivorous feeding pathways were identified in the Okavango. These are a detritus pathway based on dead plant and animal material, and an epiphyte pathway, based on algae and invertebrates that are attached to plant stems. Seasonal changes in diet in relation to the annual flood were recorded. The most dramrtic change was demonstrated by the catfish Clarias gariepinus which congregates in mass aggregations in the northern regions of the Delta and hunt in packs. Pack-hunting by catfish is a regular response to the annual fluctuations in water level. It is my conclusion that the main flow of biotic and abiotic stimuli within the Okavango Delta originates from the relatively hydrologically stable riverine floodplain and perennial swamp ecotones to the widely fluctuating seasonal swamp and drainage rivers ecotones. The relatively stable ecotones allow a diverse and biotically interdependent fish community to develop, whereas the widely fluctuating seasonal swamp and drainage rivers ecotones are characterized by a less diverse and interdependent fish community. The degree of abiotic and biotic interdependence among fish in an ecotone is very important for the long term management of the Okavango Delta. Potential developers have to determine whether the effect of a given action by man is likely to result in a long term disturbance or merely in an elastic recoil to a more or less similar state. Recommendations are made on the conservation and management of Okavango fishes taking into account the ecological characteristics of the delta.
- Full Text:
- Date Issued: 1991
- Authors: Merron, Glen Steven
- Date: 1991
- Subjects: Fishes -- Ecology -- Botswana Fishes -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5268 , http://hdl.handle.net/10962/d1005112
- Description: The Okavango is a vast inland delta system in northern Botswana which receives an annual flood from the highlands of southern Angola. There are distinct communities of fish in the Okavango which can be separated from each other by the physical characteristics of the different habitat types with which they co-evolved. This thesis provides an account of the biology and ecology of selected fish species in the Okavango Delta. Their response to the annual flood regime, and the environmental factors which limit their distribution and abundance, are examined. The thesis emphasizes the importance of water fluctuations in determining the nature of the fish fauna and the reaction of the fishes in terms of community structure, movements, breeding, predator-prey interactions and feeding. Four major ecotones were studied in the Okavango Delta. In the riverine floodplain and perennial swamp ecotones a higher species diversity was recorded than in the seasonal swamp and drainage rivers ecotones where diversity was lowest and comprised mainly of smaller fish species. A greater variety of habitat types was associated with the riverine floodplain and perennial swamp relative to the seasonal swamp and drainage rivers. The variety of habitat types between ecotones is associated with the degree of flood inundation in the respective ecotones. During the course of this study, annual recruitment of fish into the drainage rivers was from refugia in the seasonal swamp whereas the greatest degree of lateral and longitudinal movement was in the riverine floodplain and perennial swamp. Movement was in response to both biological requirements, such as availability of food and spawning sites, and physical features of the environment, such as the changing water depth. The total catch per unit effort (CPUE) of fish throughout the year was more constant in the riverine floodplain and perennial swamp than in the seasonal swamp and drainage rivers where CPUE fluctutated widely. An increase in CPUE during the duration of this study was apparent and related to the magnitude of the annual flood. In contrast to most other African wetlands, the arrival of the annual flood in the Okavango Delta coincides largely with the dry winter months. This situation presented an opportunity to compare the influence of floods and water temperature on the reproductive biology of the selected fish species. The results show a definite pattern and indicate that both the flood cycle and increased water temperatures greatly influence the breeding cycles of the selected species. The tilapia Oreochromis andersonii exhibited a considerable degree of phenotypic plasticity. Fish from the seasonally inundated areas showed a smaller mean size, egg size and larger number of eggs relative to fish in the perennially flooded areas. The size at sexual maturity was also smaller. These different reproductive characteristics exhibited by O. andersonii are dependent on the degree of water retention in the different habitats. The fishes of the Okavango have adopted other reproductive strategies to survive the changing environmental conditions brought about by an annual flood cycle. These strategies include the construction of foam nests, as described for Hepsetus odoe, for guarding the young and to provide an oxygen-rich environment. Two main non-piscivorous feeding pathways were identified in the Okavango. These are a detritus pathway based on dead plant and animal material, and an epiphyte pathway, based on algae and invertebrates that are attached to plant stems. Seasonal changes in diet in relation to the annual flood were recorded. The most dramrtic change was demonstrated by the catfish Clarias gariepinus which congregates in mass aggregations in the northern regions of the Delta and hunt in packs. Pack-hunting by catfish is a regular response to the annual fluctuations in water level. It is my conclusion that the main flow of biotic and abiotic stimuli within the Okavango Delta originates from the relatively hydrologically stable riverine floodplain and perennial swamp ecotones to the widely fluctuating seasonal swamp and drainage rivers ecotones. The relatively stable ecotones allow a diverse and biotically interdependent fish community to develop, whereas the widely fluctuating seasonal swamp and drainage rivers ecotones are characterized by a less diverse and interdependent fish community. The degree of abiotic and biotic interdependence among fish in an ecotone is very important for the long term management of the Okavango Delta. Potential developers have to determine whether the effect of a given action by man is likely to result in a long term disturbance or merely in an elastic recoil to a more or less similar state. Recommendations are made on the conservation and management of Okavango fishes taking into account the ecological characteristics of the delta.
- Full Text:
- Date Issued: 1991
The healer's art : Cape Nguni diviners in the townships of Grahamstown
- Authors: Hirst, Manton Myatt
- Date: 1991
- Subjects: Healers -- South Africa , Nguni (African people) -- Social life and customs , Divination -- South Africa , Medicine, Magic, mystic, and spagiric -- South Africa , Nguni (African people) -- Religion
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: vital:2084 , http://hdl.handle.net/10962/d1001601
- Description: This is a study of Cape Nguni diviners practising in the townships of Grahamstown where, during the 1970s, there was a large and active concentration of diviners treating clients from the locality, the rural areas and even the large urban centres further afield. The study situates local diviners in the socio-economic, cultural and religious context of contemporary township Iife during the 1970s (see chapter 1 and section 2.1). The personalities and socio-economic circumstances of diviners (and herbalists) are described as well as their case-loads, the various problems they treat, the relations between them and their clients, the economics of healing and the ethics pertaining to the profession (see chapter 2) . Chapter three focuses on the various problems and afflictions - which are largely of an interpersonal nature - suffered by those who are eventually inducted as diviners and the ritual therapy this necessarily entails. Here we see how the diviner, what Lewis (1971) terms a 'wounded healer', becomes an expert in interpersonal and social relations as a result of suffering problems - largely connected to the family but not necessarily limited to it - in interpersonal relations and that require a ritual, and thus social, prophylaxis. The main theoretical argument is that the diviner, qua healer, functions as a hybrid of Levi-Strauss' s bricoleur and Castaneda's 'man of knowledge' artfully combining the ability of the former to invert, mirror or utilise analogies from linguistics to make everything meaningful and the ability of the latter to creatively bend reality . The diviner's cosmology is described in terms of a 'handy', limited but extensive cultural code/repertoire of signs, symbols and metaphors that is utilised in getting the message across to others and in which animals bear the main symbolic load (see chapter 4). This leads logically to a reappraisal of Hammond-Tooke's (1975b) well-known model of Cape Nguni symbolic structure particularly in so far as it pertains to the way in which diviners classify animals, both wild and domestic (see section 4.6). A striking evocation and confirmation of the view argued here, namely of the diviner as bricoleur/'man of knowledge', is contained in chapter five dealing with an analysis of the diviner's 'river' myth and the context, form and content of the divinatory consultation itself. Finally, the conclusions, arising out of this study of contemporary Cape Nguni diviners in town, are evaluated in the ligrht of Lewis's (1966, 1971, 1986) deprivation hypothesis of spirit possession (see chapter 6)
- Full Text:
- Date Issued: 1991
- Authors: Hirst, Manton Myatt
- Date: 1991
- Subjects: Healers -- South Africa , Nguni (African people) -- Social life and customs , Divination -- South Africa , Medicine, Magic, mystic, and spagiric -- South Africa , Nguni (African people) -- Religion
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: vital:2084 , http://hdl.handle.net/10962/d1001601
- Description: This is a study of Cape Nguni diviners practising in the townships of Grahamstown where, during the 1970s, there was a large and active concentration of diviners treating clients from the locality, the rural areas and even the large urban centres further afield. The study situates local diviners in the socio-economic, cultural and religious context of contemporary township Iife during the 1970s (see chapter 1 and section 2.1). The personalities and socio-economic circumstances of diviners (and herbalists) are described as well as their case-loads, the various problems they treat, the relations between them and their clients, the economics of healing and the ethics pertaining to the profession (see chapter 2) . Chapter three focuses on the various problems and afflictions - which are largely of an interpersonal nature - suffered by those who are eventually inducted as diviners and the ritual therapy this necessarily entails. Here we see how the diviner, what Lewis (1971) terms a 'wounded healer', becomes an expert in interpersonal and social relations as a result of suffering problems - largely connected to the family but not necessarily limited to it - in interpersonal relations and that require a ritual, and thus social, prophylaxis. The main theoretical argument is that the diviner, qua healer, functions as a hybrid of Levi-Strauss' s bricoleur and Castaneda's 'man of knowledge' artfully combining the ability of the former to invert, mirror or utilise analogies from linguistics to make everything meaningful and the ability of the latter to creatively bend reality . The diviner's cosmology is described in terms of a 'handy', limited but extensive cultural code/repertoire of signs, symbols and metaphors that is utilised in getting the message across to others and in which animals bear the main symbolic load (see chapter 4). This leads logically to a reappraisal of Hammond-Tooke's (1975b) well-known model of Cape Nguni symbolic structure particularly in so far as it pertains to the way in which diviners classify animals, both wild and domestic (see section 4.6). A striking evocation and confirmation of the view argued here, namely of the diviner as bricoleur/'man of knowledge', is contained in chapter five dealing with an analysis of the diviner's 'river' myth and the context, form and content of the divinatory consultation itself. Finally, the conclusions, arising out of this study of contemporary Cape Nguni diviners in town, are evaluated in the ligrht of Lewis's (1966, 1971, 1986) deprivation hypothesis of spirit possession (see chapter 6)
- Full Text:
- Date Issued: 1991
The sedimentology of the Zerrissene turbidite system, Damara Orogen, Namibia
- Authors: Swart, Roger
- Date: 1991
- Subjects: Sedimentology Sediments (Geology) -- Namibia Sedimentation and deposition Turbidites
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5000 , http://hdl.handle.net/10962/d1005613
- Description: The Zerrissene turbidite system of central-western Namibia is a late Proterozoic sequence which consists of dominantly siliciclastic turbidites interbedded with minor turbiditic and hemipelagic marbles. The basin in which these sediments were deposited is located at the junction of the coastal and intra-cratonic arms of the Pan-African Damara Orogen, and an understanding of the sedimentary evolution of this basin is therefore important to the understanding of the development of the orogen as a whole. One major and two minor phases of folding have deformed the sediments, but the grade of metamorphism is low and sedimentary structures are often well preserved. Further, the area lies entirely within the Namib Desert and the lack of vegetation cover results in good outcrops providing an unusual opportunity for examining a large Precambrian turbidite system. The system consists of five formations: three siliciclastic and two mixed carbonatesiliciclastic units. The floor of the system is not exposed, and the oldest sedimentary rocks which outcrop are siliciclastics of the Zebrapiits Formation. This is overlain successively by the Brandberg West Formation (dominantly calcareous), the Brak River Formation (siliciclastic), the Gemsbok River Formation (calcareous) and the Amis River Formation (siliciclastic). Nine silicilastic turbidite facies have been recognised in the basin. These are facies A₂ (disorganised onglomerates), B₁ (horizontally laminated to massive greyackes), C₂ ("classical" turbidites), Dl (sandstone-shale couplets with base cut-out Bouma sequences), D₂ (sandstone-shale couplets with less sand than shale and base cut-out Bouma sequences), E (coarse, discontinuous sandstone-shale couplets), F (slumped units), G (shale) and H (glacial dropstones). Four facies are associated with the carbonate horizons, and these carbonate facies are given the suffix c to distinguish them from similar siliciclastic facies. These are facies Ac (disorganised and graded marble breccias), facies Cc (graded carbonates), facies Gc (hemi-pelagic marbles) and facies G (pelagic shales). The basal Zebrapiits Formation is made up of relatively thin packages of thin- to thickbedded, laterally continuous facies D₁, D₂ and B₁ beds encased in thick envelopes of shale. This type of sequence is typical of a distal lobe-fringe, and requires an unconfined basin-floor on which it can develop. The overlying Brandberg West Formation consists of a basal portion of interbedded facies Cc and G, followed by a sequence dominanted by facies Gc. This sequence is interpreted as representing outer-apron carbonate turbidites, derived from multiple point sources (facies Cc), with background pelagic settling (facies G) overlain by hemi-pelagic deposits (facies Gc). A reversal back to siliciclastic turbidites followed with deposition of the Brak River Formation. This sequence comprises relatively thick packages of laterally continuous facies B₁, D₁, and D₂ beds sandwiched between facies G shales, a succession characteristic of a lobe to lobe-fringe environment with intermittent abandonment of lobes. An unconfined basin floor adjacent to a passive margin is required for the development of this type of sequence. Glacial dropstones (facies H) are found in the upper portions of this formation, and slumped beds are also present (facies F), but are uncommon. The facies F beds are only found in association with facies H and are therefore considered to be genetically related. Slumping of beds was possibly caused by an oversupply of sediment from ice-rafting which caused instability. The overlying Gemsbok River Formation has a sequence similar to the Brandberg West Formation in that the basal portion consists of interbedded facies Cc and G, which is overlain by a thick sequence of largely facies Gc beds. Minor facies Ac beds occur near the top of the overall sequence. This formation is interpreted as an outer-apron succession with the facies Ac beds representing distal inner-apron deposits, indicating progradation of the system. The youngest unit in the basin, the Amis River Formation, shows strong lateral variation from west to east. In the west the sequence comprises laterally continuous facies B₁, C₂, D₁ and D₂ with rare, discontinuous facies E beds. Facies G is relatively minor in the sequence. In the east the succession is dominated by facies D₁, D₂ and G, and this succession is interpreted as a sequence of distal turbidites which were deposited on a basin-plain. The system developed by aggradation rather than progradation as only minor cycles are developed. Geochemical and petrological features indicate that the entire siliciclastic system was derived from a granite-recycled orogen terrane. Palaeocurrent data are unreliable because of the deformation, but transport was initially from the south-west, moving later to the west and north-west. The provenance of the carbonates is uncertain as reliable palaeocurrent indicators are rare, but they could have been derived either from South America or from the extensive carbonate deposits developed on the north-western margins of the basin. The Zenissene siliciclastic turbidite system represents the distal portion of a major submarine turbidite system, the more proximal parts of which now lie west of the exposed basin, either under the Atlantic Ocean or in eastern South America. The calcareous deposits developed as an apron adjacent to a multiple point source, the position of which is at present unknown.
- Full Text:
- Date Issued: 1991
- Authors: Swart, Roger
- Date: 1991
- Subjects: Sedimentology Sediments (Geology) -- Namibia Sedimentation and deposition Turbidites
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5000 , http://hdl.handle.net/10962/d1005613
- Description: The Zerrissene turbidite system of central-western Namibia is a late Proterozoic sequence which consists of dominantly siliciclastic turbidites interbedded with minor turbiditic and hemipelagic marbles. The basin in which these sediments were deposited is located at the junction of the coastal and intra-cratonic arms of the Pan-African Damara Orogen, and an understanding of the sedimentary evolution of this basin is therefore important to the understanding of the development of the orogen as a whole. One major and two minor phases of folding have deformed the sediments, but the grade of metamorphism is low and sedimentary structures are often well preserved. Further, the area lies entirely within the Namib Desert and the lack of vegetation cover results in good outcrops providing an unusual opportunity for examining a large Precambrian turbidite system. The system consists of five formations: three siliciclastic and two mixed carbonatesiliciclastic units. The floor of the system is not exposed, and the oldest sedimentary rocks which outcrop are siliciclastics of the Zebrapiits Formation. This is overlain successively by the Brandberg West Formation (dominantly calcareous), the Brak River Formation (siliciclastic), the Gemsbok River Formation (calcareous) and the Amis River Formation (siliciclastic). Nine silicilastic turbidite facies have been recognised in the basin. These are facies A₂ (disorganised onglomerates), B₁ (horizontally laminated to massive greyackes), C₂ ("classical" turbidites), Dl (sandstone-shale couplets with base cut-out Bouma sequences), D₂ (sandstone-shale couplets with less sand than shale and base cut-out Bouma sequences), E (coarse, discontinuous sandstone-shale couplets), F (slumped units), G (shale) and H (glacial dropstones). Four facies are associated with the carbonate horizons, and these carbonate facies are given the suffix c to distinguish them from similar siliciclastic facies. These are facies Ac (disorganised and graded marble breccias), facies Cc (graded carbonates), facies Gc (hemi-pelagic marbles) and facies G (pelagic shales). The basal Zebrapiits Formation is made up of relatively thin packages of thin- to thickbedded, laterally continuous facies D₁, D₂ and B₁ beds encased in thick envelopes of shale. This type of sequence is typical of a distal lobe-fringe, and requires an unconfined basin-floor on which it can develop. The overlying Brandberg West Formation consists of a basal portion of interbedded facies Cc and G, followed by a sequence dominanted by facies Gc. This sequence is interpreted as representing outer-apron carbonate turbidites, derived from multiple point sources (facies Cc), with background pelagic settling (facies G) overlain by hemi-pelagic deposits (facies Gc). A reversal back to siliciclastic turbidites followed with deposition of the Brak River Formation. This sequence comprises relatively thick packages of laterally continuous facies B₁, D₁, and D₂ beds sandwiched between facies G shales, a succession characteristic of a lobe to lobe-fringe environment with intermittent abandonment of lobes. An unconfined basin floor adjacent to a passive margin is required for the development of this type of sequence. Glacial dropstones (facies H) are found in the upper portions of this formation, and slumped beds are also present (facies F), but are uncommon. The facies F beds are only found in association with facies H and are therefore considered to be genetically related. Slumping of beds was possibly caused by an oversupply of sediment from ice-rafting which caused instability. The overlying Gemsbok River Formation has a sequence similar to the Brandberg West Formation in that the basal portion consists of interbedded facies Cc and G, which is overlain by a thick sequence of largely facies Gc beds. Minor facies Ac beds occur near the top of the overall sequence. This formation is interpreted as an outer-apron succession with the facies Ac beds representing distal inner-apron deposits, indicating progradation of the system. The youngest unit in the basin, the Amis River Formation, shows strong lateral variation from west to east. In the west the sequence comprises laterally continuous facies B₁, C₂, D₁ and D₂ with rare, discontinuous facies E beds. Facies G is relatively minor in the sequence. In the east the succession is dominated by facies D₁, D₂ and G, and this succession is interpreted as a sequence of distal turbidites which were deposited on a basin-plain. The system developed by aggradation rather than progradation as only minor cycles are developed. Geochemical and petrological features indicate that the entire siliciclastic system was derived from a granite-recycled orogen terrane. Palaeocurrent data are unreliable because of the deformation, but transport was initially from the south-west, moving later to the west and north-west. The provenance of the carbonates is uncertain as reliable palaeocurrent indicators are rare, but they could have been derived either from South America or from the extensive carbonate deposits developed on the north-western margins of the basin. The Zenissene siliciclastic turbidite system represents the distal portion of a major submarine turbidite system, the more proximal parts of which now lie west of the exposed basin, either under the Atlantic Ocean or in eastern South America. The calcareous deposits developed as an apron adjacent to a multiple point source, the position of which is at present unknown.
- Full Text:
- Date Issued: 1991
The transitional role of the Xhosa oral poet in contemporary South African society
- Authors: Kaschula, Russell H
- Date: 1991
- Subjects: Folk poetry, Xhosa Xhosa (African people) -- Religion Xhosa (African people) -- Social life and customs Xhosa poetry Laudatory poetry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3563 , http://hdl.handle.net/10962/d1002085 , https://orcid.org/0000-0002-5481-6748
- Description: This thesis outlines the changing role of the Xhosa imbongi in contemporary South African society. The changing socio-economic and political scenario in South Africa, and the way in which the imbongi is adapting in order to accommodate new pressures created by these changes, form an integral part of this thesis. The effects of education and increasing literacy on the tradition are outlined. The interaction between oral and written forms is explored in chapter 2. The role of the imbongi within the religious sphere is included in chapter 3. Xhosa preachers within the independent churches often make use of the styles and techniques associated with oral poetry. Iimbongi who are not necessarily preachers also operate within this context. The relationship between the Congress of South African Trade Unions, the African National Congress and iimbongi has also been researched and forms part of chapters 4, 5, and the epilogue. The modern imbongi is drawn towards powerful organisations offering alternative leadership to many of the traditional chiefs. In the epilogue collected poetry is analysed in the context of Mandela's visit to Transkei in April 1990. Interviews have been conducted with chiefs, iimbongi attached to chiefs as well as those attached to different organisations. Poetry has been collected and analysed. In chapter 5, three case studies of modern iimbongi are included. The problems facing these iimbongi in their different contexts, as well as the power bases from which they draw, are outlined. Finally, an alternative definition of the imbongi is offered in the conclusion
- Full Text:
- Date Issued: 1991
- Authors: Kaschula, Russell H
- Date: 1991
- Subjects: Folk poetry, Xhosa Xhosa (African people) -- Religion Xhosa (African people) -- Social life and customs Xhosa poetry Laudatory poetry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3563 , http://hdl.handle.net/10962/d1002085 , https://orcid.org/0000-0002-5481-6748
- Description: This thesis outlines the changing role of the Xhosa imbongi in contemporary South African society. The changing socio-economic and political scenario in South Africa, and the way in which the imbongi is adapting in order to accommodate new pressures created by these changes, form an integral part of this thesis. The effects of education and increasing literacy on the tradition are outlined. The interaction between oral and written forms is explored in chapter 2. The role of the imbongi within the religious sphere is included in chapter 3. Xhosa preachers within the independent churches often make use of the styles and techniques associated with oral poetry. Iimbongi who are not necessarily preachers also operate within this context. The relationship between the Congress of South African Trade Unions, the African National Congress and iimbongi has also been researched and forms part of chapters 4, 5, and the epilogue. The modern imbongi is drawn towards powerful organisations offering alternative leadership to many of the traditional chiefs. In the epilogue collected poetry is analysed in the context of Mandela's visit to Transkei in April 1990. Interviews have been conducted with chiefs, iimbongi attached to chiefs as well as those attached to different organisations. Poetry has been collected and analysed. In chapter 5, three case studies of modern iimbongi are included. The problems facing these iimbongi in their different contexts, as well as the power bases from which they draw, are outlined. Finally, an alternative definition of the imbongi is offered in the conclusion
- Full Text:
- Date Issued: 1991
A pastoral theological examination of inner healing
- Authors: Velthuysen, Daniel Nicholas
- Date: 1990
- Subjects: Pastoral theology , Healing -- Religious aspects -- Christianity , Mental healing -- Religious aspects -- Christianity , Inner child -- Religious aspects -- Christianity , Primal therapy -- Religious aspects -- Christianity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1300 , http://hdl.handle.net/10962/d1016248
- Description: Doing a survey of the ministry of inner healing, one is arrested by three salient features: its pragmatic and correlative development, its lay orientation, and the inconsistent and naïve theoretical explanation of the phenomenon. Inner healing, or as it was first known, the healing of the memories, appears to have its roots with Agnes Sanford during the 1940's (Sandford 1982: 3-4). Over a period of time and through a series of events, Sanford experienced what she termed a healing of memories. After some reflection on her experiences she began to teach her views at the School of Pastoral Care started by her husband in 1958, at Camps Farthest Out (CFO), and at numerous churches and conferences.
- Full Text:
- Date Issued: 1990
- Authors: Velthuysen, Daniel Nicholas
- Date: 1990
- Subjects: Pastoral theology , Healing -- Religious aspects -- Christianity , Mental healing -- Religious aspects -- Christianity , Inner child -- Religious aspects -- Christianity , Primal therapy -- Religious aspects -- Christianity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1300 , http://hdl.handle.net/10962/d1016248
- Description: Doing a survey of the ministry of inner healing, one is arrested by three salient features: its pragmatic and correlative development, its lay orientation, and the inconsistent and naïve theoretical explanation of the phenomenon. Inner healing, or as it was first known, the healing of the memories, appears to have its roots with Agnes Sanford during the 1940's (Sandford 1982: 3-4). Over a period of time and through a series of events, Sanford experienced what she termed a healing of memories. After some reflection on her experiences she began to teach her views at the School of Pastoral Care started by her husband in 1958, at Camps Farthest Out (CFO), and at numerous churches and conferences.
- Full Text:
- Date Issued: 1990
A study of the reading interests and reading habits of English (first language) secondary-school pupils in South Africa: with particular reference to the Province of Natal
- Authors: Gardner, John Murray
- Date: 1990
- Subjects: Reading interests English language -- Study and teaching (Secondary) -- South Africa -- KwaZulu-Natal Books and reading -- South Africa -- KwaZulu-Natal Readership surveys -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1781 , http://hdl.handle.net/10962/d1003666
- Description: The study derives from a belief, based on many researchers' writings, that wide and frequent book-reading aids the development of knowledge, emotional maturity and human sympathy, which are all essential attributes in a fragmented culture such as South Africa's. It is not accepted that conventional secondary-school literature-teaching in this country promotes a lifelong reading habit among the majority of pupils and a plea is made for the recognition of Reading as a curricular entity in its own right. The study suggests that, owing to a paucity of local research in this field, South African teachers and educational authorities are severely disadvantaged. If they are unable to offer advice based on a proper study of their pupils as readers, they run the risk of guiding many pupils' reading along paths that cannot promise satisfaction and fulfilment. Such stultifying of reading habits would contradict the aims of the present National Core Syllabuses for English (First Language). The thesis sets little store by the investigation of specific bookchoices, pointing out that the validity of such incidental findings, if gleaned from a latitudinal survey, is questionable. Instead, using the findings of questionnaires administered to nearly 2 800 pupils and their teachers, the thesis investigates the relationships between voluntary leisure-time reading and such factors as age, gender, intelligence, academic achievement and standard of living. It also looks at the influences of parents, teachers, peers, contemporary literature-teaching practices, school and public libraries, and leisure- time pursuits other than reading. Many suggestions are offered for further research into finer aspects of those considerations. Many of the findings serve merely to corroborate research from abroad, particularly in respect of age, gender and intelligence. That is none the less alarming when a striking decline in reading is found to occur in the early years of the secondary school. A number of other interesting findings emerge. Standard of living is shown to be inversely correlated with amount of reading, and television-viewing is not found to displace reading. Nor are other leisure-time pursuits found to affect amount of reading: avid readers are by and large extremely active and committed pupils. Reading emerges from the study as providing its own peculiar satisfaction, as does each of the other leisure activities investigated. The challenge is to ensure that infrequent readers become aware of what reading has to offer, and strategies for attempting to achieve that are posited, particularly with regard to the roles of public and school libraries. The roles of teachers and parents are found to be crucial to the development of an appetite for books, and it is suggested that schools and parents liaise formally and closely in this matter. The study groups pupils by a number of personal variables, and investigates their reactions to common forms and genres as well as to certain specifics of style, thereby discussing the relationship between reading, social maturity and academic achievement It argues strongly for recognition of the fact that educating secondary-school pupils in the development of keen and sensitive lifelong reading habits is a process which cannot be systematically taught as a set of skills.
- Full Text:
- Date Issued: 1990
- Authors: Gardner, John Murray
- Date: 1990
- Subjects: Reading interests English language -- Study and teaching (Secondary) -- South Africa -- KwaZulu-Natal Books and reading -- South Africa -- KwaZulu-Natal Readership surveys -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1781 , http://hdl.handle.net/10962/d1003666
- Description: The study derives from a belief, based on many researchers' writings, that wide and frequent book-reading aids the development of knowledge, emotional maturity and human sympathy, which are all essential attributes in a fragmented culture such as South Africa's. It is not accepted that conventional secondary-school literature-teaching in this country promotes a lifelong reading habit among the majority of pupils and a plea is made for the recognition of Reading as a curricular entity in its own right. The study suggests that, owing to a paucity of local research in this field, South African teachers and educational authorities are severely disadvantaged. If they are unable to offer advice based on a proper study of their pupils as readers, they run the risk of guiding many pupils' reading along paths that cannot promise satisfaction and fulfilment. Such stultifying of reading habits would contradict the aims of the present National Core Syllabuses for English (First Language). The thesis sets little store by the investigation of specific bookchoices, pointing out that the validity of such incidental findings, if gleaned from a latitudinal survey, is questionable. Instead, using the findings of questionnaires administered to nearly 2 800 pupils and their teachers, the thesis investigates the relationships between voluntary leisure-time reading and such factors as age, gender, intelligence, academic achievement and standard of living. It also looks at the influences of parents, teachers, peers, contemporary literature-teaching practices, school and public libraries, and leisure- time pursuits other than reading. Many suggestions are offered for further research into finer aspects of those considerations. Many of the findings serve merely to corroborate research from abroad, particularly in respect of age, gender and intelligence. That is none the less alarming when a striking decline in reading is found to occur in the early years of the secondary school. A number of other interesting findings emerge. Standard of living is shown to be inversely correlated with amount of reading, and television-viewing is not found to displace reading. Nor are other leisure-time pursuits found to affect amount of reading: avid readers are by and large extremely active and committed pupils. Reading emerges from the study as providing its own peculiar satisfaction, as does each of the other leisure activities investigated. The challenge is to ensure that infrequent readers become aware of what reading has to offer, and strategies for attempting to achieve that are posited, particularly with regard to the roles of public and school libraries. The roles of teachers and parents are found to be crucial to the development of an appetite for books, and it is suggested that schools and parents liaise formally and closely in this matter. The study groups pupils by a number of personal variables, and investigates their reactions to common forms and genres as well as to certain specifics of style, thereby discussing the relationship between reading, social maturity and academic achievement It argues strongly for recognition of the fact that educating secondary-school pupils in the development of keen and sensitive lifelong reading habits is a process which cannot be systematically taught as a set of skills.
- Full Text:
- Date Issued: 1990
Alternative mythical structures in the fiction of Patrick White
- Authors: Bosman, Brenda Evadne
- Date: 1990
- Subjects: White, Patrick, 1912-1990 , White, Patrick, 1912-1990 -- Criticism and interpretation , Myth in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2170 , http://hdl.handle.net/10962/d1001821
- Description: The texts in this study interrogate the dominant myths which have affected the constructs of identity and history in the white Australian socio-historical context. These myths are exposed by White as ideologically determined and as operating by processes of exclusion, repression and marginalisation. White challenges the autonomy of both European and Australian cultures, reveals the ideological complicity between them and adopts a critical approach to all Western cultural assumptions. As a post-colonial writer, White shares the need of both post-colonising and post-colonised groups for an identity established not in terms of the colonial power but in terms of themselves. As a dissident white male, he is a privileged member of the post- colonising group but one who rejects the dominant discourses as illegitimate and unlegitimating. He offers a re-writing of the myths underpinning colonial and post-colonising discourses which privileges their suppressed and repressed elements. His re-writings affect aboriginal men and women, white women and the 'privileged' white male whose subjection to social control is masked as unproblematic freedom. White's re-writing of myth enbraces the post-modern as well as the post- colonial. He not only deconstructs and demystifies the phallogocentric/ethnocentric order of things; he also attempts to avoid totalization by privileging indeterminacy, fragmentation, hybridization and those liminary states which defy articulation: the ecstatic, the abject, the unspeakable. He himself is denied authority in that his re-writings are presented as mere acts in the always provisional process of making interpretations. White acknowledges the problematics of both presentation and re-presentation - an unresolved tension between the post-colonial desire for self-definition and the post-modern decentring of all meaning and interpretation permeates his discourse. The close readings of the texts attempt, accordingly, to reflect varying oppositional strategies: those which seek to overturn hierarchies and expose power-relations and those which seek an idiom in which contemporary Australia may find its least distorted reflexion. Within this ideological context, the Lacanian thematics of the subject, and their re-writing by Kristeva, are linked with dialectical criticism in an attempt to reflect a strictly provisional process of (re) construction
- Full Text:
- Date Issued: 1990
- Authors: Bosman, Brenda Evadne
- Date: 1990
- Subjects: White, Patrick, 1912-1990 , White, Patrick, 1912-1990 -- Criticism and interpretation , Myth in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2170 , http://hdl.handle.net/10962/d1001821
- Description: The texts in this study interrogate the dominant myths which have affected the constructs of identity and history in the white Australian socio-historical context. These myths are exposed by White as ideologically determined and as operating by processes of exclusion, repression and marginalisation. White challenges the autonomy of both European and Australian cultures, reveals the ideological complicity between them and adopts a critical approach to all Western cultural assumptions. As a post-colonial writer, White shares the need of both post-colonising and post-colonised groups for an identity established not in terms of the colonial power but in terms of themselves. As a dissident white male, he is a privileged member of the post- colonising group but one who rejects the dominant discourses as illegitimate and unlegitimating. He offers a re-writing of the myths underpinning colonial and post-colonising discourses which privileges their suppressed and repressed elements. His re-writings affect aboriginal men and women, white women and the 'privileged' white male whose subjection to social control is masked as unproblematic freedom. White's re-writing of myth enbraces the post-modern as well as the post- colonial. He not only deconstructs and demystifies the phallogocentric/ethnocentric order of things; he also attempts to avoid totalization by privileging indeterminacy, fragmentation, hybridization and those liminary states which defy articulation: the ecstatic, the abject, the unspeakable. He himself is denied authority in that his re-writings are presented as mere acts in the always provisional process of making interpretations. White acknowledges the problematics of both presentation and re-presentation - an unresolved tension between the post-colonial desire for self-definition and the post-modern decentring of all meaning and interpretation permeates his discourse. The close readings of the texts attempt, accordingly, to reflect varying oppositional strategies: those which seek to overturn hierarchies and expose power-relations and those which seek an idiom in which contemporary Australia may find its least distorted reflexion. Within this ideological context, the Lacanian thematics of the subject, and their re-writing by Kristeva, are linked with dialectical criticism in an attempt to reflect a strictly provisional process of (re) construction
- Full Text:
- Date Issued: 1990
Aspects of the biology of the infaunal bivalve Mollusc Solen cylindraceus (Hanley) in the Kariega estuary
- De Villiers, Casper Johannes
- Authors: De Villiers, Casper Johannes
- Date: 1990
- Subjects: Mollusks -- South Africa -- Eastern Cape Bivalves -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5639 , http://hdl.handle.net/10962/d1005321
- Description: Solen cylindraceus is an infaunal filter-feeding bivalve inhabiting the intertidal mud banks of many southern African estuaries. It is particularly abundant in the Kariega estuary (33°41'S; 26°42'E) where it reaches densities of 400m⁻² (192g shell-free dry wt. m⁻²). The Kariega is a permanently open, marine dominated estuary about 18km in length, and S. cylindraceus is most abundant in its middle and upper reaches. Some physical characteristics of the estuary (temperature, salinity, sediment and water turbidity) are described, and the possible role of these factors in determining the density and distribution of S. cylindraceus within the Kariega estuary, is discussed. The structure of the alimentary system, gills and labial palps of S. cylintfraceus is described, all of which showed no major variation from the "typical" eulamellibranchiate form. Solen cylintfraceus was found to be a euryhaline osmoconformer with a salinity tolerance range of 15-65%. When animals were removed from their burrows, osmotic equilibration of the haemolymph was rapid (1-2 hours). By contrast, in animals left undisturbed in their burrows, osmotic equilibration was retarded (72-204 hours). It is suggested that the observed decrease in the rate of change of haemolymph osmolarity for animals in their burrows is linked to the stability of the interstitial salinity. A temperature tolerance range of 5-44°C was determined for S. cylintfraceus (in situ), in which prolonged exposure to 5°C and 40-45°C (12-36 hours respectively) resulted in a decreased burrowing ability, coma and death. Animal burrowing responses were not affected by temperatures in the range 15-35°C. Field experiments were carried out over several tidal cycles, in which the measurement of crystalline style volume was used as a means of assessing extracellular digestive activity. No major variation in style volume was recorded and it appeared that S. cylindraceus did not exhibit any cyclical pattern of style dissolution and regeneration. It is suggested that S. cylindraceus feeds continuously from the water column during high tide and possibly within its burrow, at or below the water table, during low tide. At a suspensoid concentration of 5Omg l⁻¹, S. cylindraceus was found to filter water almost continuously (90-95% of the time). Time spent filtering dropped to 68% at 100mg l⁻¹ and 32% at 500mg l⁻¹. Filtration rates for summer collected animals (25°C) were 22.86 ± 4.36ml min.⁻¹, some 3ml min.⁻¹ greater than that recorded for winter (16°C) collected animals. Filtration rate may be expressed as a function of shell length by the equations: y=0.247x¹̇⁰⁶⁶ (winter) and y=0.758x⁰̇⁸²⁶ (summer). Solen cylindraceus was capable of acclimating its filtration rate to both high and low temperatures under laboratory conditions. Filtration rate exhibited a thermal optimum in the range 15-35°C, declining at higher and lower temperatures. Q₁₀ values of filtration decreased rapidly from greater than 4 to less than 2, when the thermal optimum was reached. Maximum rates generally occurred at approximately 5°C above the temperature to which the animal had been acclimated. Optimal filtration rates (19-23ml min.⁻¹) were recorded in the salinity range 15-45%. When subjected to abrupt changes in salinity, filtration rates were immediately depressed. The extent and duration of these decreased filtration rates were dependent upon the magnitude and direction of salinity change, and were always less in animals exposed to hyper- than hyposaline conditions. Animals exposed to increased temperature and simultaneous elevated or unchanged salinity, showed a slight increase in filtration rate followed by rapid acclimation. A decrease in both temperature and salinity resulted in an initial decrease in filtration rate and a longer acclimation period. The ability of S. cylindraceus to acclimate fully within a wide temperature and salinity range, and to filter maximally in hypersaline conditions may, in part, explain its unusually high abundance in the Kariega estuary, despite it being close to the southernmost limit of the animal's geographical distribution. No significant difference in flItration rate was recorded at suspensoid concentrations of 5-100mg 1⁻¹. However, at 250 and 500mg l⁻¹ filtration rates decreased significantly, and coincided with increased levels of pseudofaecal production. Solen cylindraceus retained particles down to 2.5-3.0µm with great efficiency (ca. 60-90% efficiency). Below this particle size, retention efficiency decreased rapidly and a net production of particles was recorded below 1.51µm. Particle retention was independent of temperature (15 and 25°C) and salinity (15 and 35%). Use was made of stable carbon isotope analyses (¹³C/¹²C ratios) in an attempt to determine the important food sources of S. cylindraceus within the Kariega estuary. The results obtained demonstrated an enrichment in δ¹³ values for S. cylindraceus from the upper (-27.9%) to the middle (-25%c) and lower (-21.6%o ) reaches of the estuary, with no seasonal variation apparent. The bivalve was substantially more depleted in ¹³C relative to the dominant aquatic macrophytes Zostera capensis (-9.1 to -15.6%o) and Spartina maritima (-12.5%o). The use of δ¹³ alone, however, to unequivocally "pin point" specific food sources of a filter feeder in a predominantly detritus based food web, is limited. It is suggested that in the Kariega estuary, riparian litter and other terrestrially derived vegetation contribute to the carbon pool. A possible contribution of ¹³C depleted food sources via chemoautotrophic and/or anaerobic pathways, to the diet of S. cylindraceus, is suggested.
- Full Text:
- Date Issued: 1990
- Authors: De Villiers, Casper Johannes
- Date: 1990
- Subjects: Mollusks -- South Africa -- Eastern Cape Bivalves -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5639 , http://hdl.handle.net/10962/d1005321
- Description: Solen cylindraceus is an infaunal filter-feeding bivalve inhabiting the intertidal mud banks of many southern African estuaries. It is particularly abundant in the Kariega estuary (33°41'S; 26°42'E) where it reaches densities of 400m⁻² (192g shell-free dry wt. m⁻²). The Kariega is a permanently open, marine dominated estuary about 18km in length, and S. cylindraceus is most abundant in its middle and upper reaches. Some physical characteristics of the estuary (temperature, salinity, sediment and water turbidity) are described, and the possible role of these factors in determining the density and distribution of S. cylindraceus within the Kariega estuary, is discussed. The structure of the alimentary system, gills and labial palps of S. cylintfraceus is described, all of which showed no major variation from the "typical" eulamellibranchiate form. Solen cylintfraceus was found to be a euryhaline osmoconformer with a salinity tolerance range of 15-65%. When animals were removed from their burrows, osmotic equilibration of the haemolymph was rapid (1-2 hours). By contrast, in animals left undisturbed in their burrows, osmotic equilibration was retarded (72-204 hours). It is suggested that the observed decrease in the rate of change of haemolymph osmolarity for animals in their burrows is linked to the stability of the interstitial salinity. A temperature tolerance range of 5-44°C was determined for S. cylintfraceus (in situ), in which prolonged exposure to 5°C and 40-45°C (12-36 hours respectively) resulted in a decreased burrowing ability, coma and death. Animal burrowing responses were not affected by temperatures in the range 15-35°C. Field experiments were carried out over several tidal cycles, in which the measurement of crystalline style volume was used as a means of assessing extracellular digestive activity. No major variation in style volume was recorded and it appeared that S. cylindraceus did not exhibit any cyclical pattern of style dissolution and regeneration. It is suggested that S. cylindraceus feeds continuously from the water column during high tide and possibly within its burrow, at or below the water table, during low tide. At a suspensoid concentration of 5Omg l⁻¹, S. cylindraceus was found to filter water almost continuously (90-95% of the time). Time spent filtering dropped to 68% at 100mg l⁻¹ and 32% at 500mg l⁻¹. Filtration rates for summer collected animals (25°C) were 22.86 ± 4.36ml min.⁻¹, some 3ml min.⁻¹ greater than that recorded for winter (16°C) collected animals. Filtration rate may be expressed as a function of shell length by the equations: y=0.247x¹̇⁰⁶⁶ (winter) and y=0.758x⁰̇⁸²⁶ (summer). Solen cylindraceus was capable of acclimating its filtration rate to both high and low temperatures under laboratory conditions. Filtration rate exhibited a thermal optimum in the range 15-35°C, declining at higher and lower temperatures. Q₁₀ values of filtration decreased rapidly from greater than 4 to less than 2, when the thermal optimum was reached. Maximum rates generally occurred at approximately 5°C above the temperature to which the animal had been acclimated. Optimal filtration rates (19-23ml min.⁻¹) were recorded in the salinity range 15-45%. When subjected to abrupt changes in salinity, filtration rates were immediately depressed. The extent and duration of these decreased filtration rates were dependent upon the magnitude and direction of salinity change, and were always less in animals exposed to hyper- than hyposaline conditions. Animals exposed to increased temperature and simultaneous elevated or unchanged salinity, showed a slight increase in filtration rate followed by rapid acclimation. A decrease in both temperature and salinity resulted in an initial decrease in filtration rate and a longer acclimation period. The ability of S. cylindraceus to acclimate fully within a wide temperature and salinity range, and to filter maximally in hypersaline conditions may, in part, explain its unusually high abundance in the Kariega estuary, despite it being close to the southernmost limit of the animal's geographical distribution. No significant difference in flItration rate was recorded at suspensoid concentrations of 5-100mg 1⁻¹. However, at 250 and 500mg l⁻¹ filtration rates decreased significantly, and coincided with increased levels of pseudofaecal production. Solen cylindraceus retained particles down to 2.5-3.0µm with great efficiency (ca. 60-90% efficiency). Below this particle size, retention efficiency decreased rapidly and a net production of particles was recorded below 1.51µm. Particle retention was independent of temperature (15 and 25°C) and salinity (15 and 35%). Use was made of stable carbon isotope analyses (¹³C/¹²C ratios) in an attempt to determine the important food sources of S. cylindraceus within the Kariega estuary. The results obtained demonstrated an enrichment in δ¹³ values for S. cylindraceus from the upper (-27.9%) to the middle (-25%c) and lower (-21.6%o ) reaches of the estuary, with no seasonal variation apparent. The bivalve was substantially more depleted in ¹³C relative to the dominant aquatic macrophytes Zostera capensis (-9.1 to -15.6%o) and Spartina maritima (-12.5%o). The use of δ¹³ alone, however, to unequivocally "pin point" specific food sources of a filter feeder in a predominantly detritus based food web, is limited. It is suggested that in the Kariega estuary, riparian litter and other terrestrially derived vegetation contribute to the carbon pool. A possible contribution of ¹³C depleted food sources via chemoautotrophic and/or anaerobic pathways, to the diet of S. cylindraceus, is suggested.
- Full Text:
- Date Issued: 1990
Aspects of the nutritional physiology and dietary requirements of juvenile and adult sharptooth catfish, Clarias Gariepinus (Pisces : clariidae)
- Authors: Uys, Wynand
- Date: 1990
- Subjects: Clariidae Catfishes Catfishes -- Nutrition-requirements Clarias
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5225 , http://hdl.handle.net/10962/d1005068
- Description: Past and current research on the biology and culture of the sharptooth catfish (Clarias gariepinus) has stimulated the development of its commercial production. At the inception of this project in 1985, it was decided that the development of an optimal dry feed was the most important step in developing a more complete culture technology for the species. The objectives of the project were, therefore, to investigate aspects of the nutritional physiology and dietary requirements of the species to provide the necessary information for the formulation of optimum economical feeds. A review of the natural feeding biology of the species provided valuable information with regard to its food preferences. From this information, and by estimating the nutritional composition of its preferred natural diet, it could be concluded that the animal requires a relatively high dietary protein content. This conclusion was substantiated by studies of the functional morphology of the digestive system (gross and fine structure). The characteristics of the digestive system and external anatomy were found to be typical of an opportunistic, omnivorous predator. The ontogenetic development of the digestive system is relatively fast, and enables the utilization of a variety of diets efficiently from an early stage. Since the ability of an animal to digest a given substance is predominantly dependent on the presence of appropriate enzymes the quantification and characterization of C. gariepinus digestive enzyme activities were investigated on an experimental basis. This work revealed that the animal has relatively high levels of digestive enzyme activities, and that its proteolytic enzyme activities correspond with those of other carnivorous fishes, while its starch digesting abilities correspond with those of specialized herbivores. Also, the high levels of lysozyme and alkaline phosphatase indicate an adaptation to detritivory, making this fish a truly opportunistic omnivore. Evidence was found to suggest that sharptooth catfish are able to re-absorb secreted digestive enzymes in the posterior section of its intestinal tract. It was shown that digestive enzyme activities were induced by food intake, and that no inherent rhythmicity in digestive activities seemed to occur. The development of digestive enzyme systems in the early life history of this animal was found to be also extremely rapid (complete within 10-16 days after hatching). It was also shown that artificial dry feed stimulates higher levels of digestive enzyme activities in larvae and juveniles than natural food. Although increased cellulase activity was found in larvae and juveniles that were fed on live zooplankton, the relative contribution of exogenous prey enzymes to protein digestion could not be ascertained. Specific nutritional requirements were investigated by means of feeding trials. The results of these trials confirmed the above indications regarding the dietary requirements of sharptooth catfish. It was concluded that for optimal growth and production performance, this animal requires a dietary protein content of 40-42%, a dietary lipid content of 10-12% and that diets should contain 14-16 kJ/g digestible energy. The optimum protein-to-energy ratio was found to be 26-29mg protein per kJ of digestible energy. Dietary requirements are evidently the same for juveniles and adults, except that younger fish require higher relative feeding levels. Finally, practical feed formulations were evaluated in terms of their economic feasibility. The results of these trials are presented along with recommendations on the formulation of commercial feeds for C. gariepinus. A computer program with which to implement least cost feed formulation by means of linear programming is provided.
- Full Text:
- Date Issued: 1990
- Authors: Uys, Wynand
- Date: 1990
- Subjects: Clariidae Catfishes Catfishes -- Nutrition-requirements Clarias
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5225 , http://hdl.handle.net/10962/d1005068
- Description: Past and current research on the biology and culture of the sharptooth catfish (Clarias gariepinus) has stimulated the development of its commercial production. At the inception of this project in 1985, it was decided that the development of an optimal dry feed was the most important step in developing a more complete culture technology for the species. The objectives of the project were, therefore, to investigate aspects of the nutritional physiology and dietary requirements of the species to provide the necessary information for the formulation of optimum economical feeds. A review of the natural feeding biology of the species provided valuable information with regard to its food preferences. From this information, and by estimating the nutritional composition of its preferred natural diet, it could be concluded that the animal requires a relatively high dietary protein content. This conclusion was substantiated by studies of the functional morphology of the digestive system (gross and fine structure). The characteristics of the digestive system and external anatomy were found to be typical of an opportunistic, omnivorous predator. The ontogenetic development of the digestive system is relatively fast, and enables the utilization of a variety of diets efficiently from an early stage. Since the ability of an animal to digest a given substance is predominantly dependent on the presence of appropriate enzymes the quantification and characterization of C. gariepinus digestive enzyme activities were investigated on an experimental basis. This work revealed that the animal has relatively high levels of digestive enzyme activities, and that its proteolytic enzyme activities correspond with those of other carnivorous fishes, while its starch digesting abilities correspond with those of specialized herbivores. Also, the high levels of lysozyme and alkaline phosphatase indicate an adaptation to detritivory, making this fish a truly opportunistic omnivore. Evidence was found to suggest that sharptooth catfish are able to re-absorb secreted digestive enzymes in the posterior section of its intestinal tract. It was shown that digestive enzyme activities were induced by food intake, and that no inherent rhythmicity in digestive activities seemed to occur. The development of digestive enzyme systems in the early life history of this animal was found to be also extremely rapid (complete within 10-16 days after hatching). It was also shown that artificial dry feed stimulates higher levels of digestive enzyme activities in larvae and juveniles than natural food. Although increased cellulase activity was found in larvae and juveniles that were fed on live zooplankton, the relative contribution of exogenous prey enzymes to protein digestion could not be ascertained. Specific nutritional requirements were investigated by means of feeding trials. The results of these trials confirmed the above indications regarding the dietary requirements of sharptooth catfish. It was concluded that for optimal growth and production performance, this animal requires a dietary protein content of 40-42%, a dietary lipid content of 10-12% and that diets should contain 14-16 kJ/g digestible energy. The optimum protein-to-energy ratio was found to be 26-29mg protein per kJ of digestible energy. Dietary requirements are evidently the same for juveniles and adults, except that younger fish require higher relative feeding levels. Finally, practical feed formulations were evaluated in terms of their economic feasibility. The results of these trials are presented along with recommendations on the formulation of commercial feeds for C. gariepinus. A computer program with which to implement least cost feed formulation by means of linear programming is provided.
- Full Text:
- Date Issued: 1990