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A study of the alkaloid content of the Senecio speciosus/Macrocephalus complex

  • Authors: Grue, Margaret Ruth
  • Date: 1992
  • Subjects: Alkaloids -- Research , Pyrrolizidines -- Research , Botanical chemistry
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4362 , http://hdl.handle.net/10962/d1005027 , Alkaloids -- Research , Pyrrolizidines -- Research , Botanical chemistry
  • Description: The isolation and identification of pyrrolizidine alkaloids from various plant species from 1988 to May 1991 are reviewed and the alkaloids of two indigenous plant species, Senecio speciosus Willd and Senecio macrocephalus DC, were investigated. A brief review of the methods used for isolation and identification of pyrrolizidines is also given. S. speciosus was found to contain two new alkaloids, 7-senecioyl-9-sarracinylheliotridine and 7-isosarracinyl-9- sarracinyl-heliotridine, which were identified using highfield NMR techniques. A number of other alkaloids were tentatively identified using GC-MS. S. macrocephalus contains very little alkaloid, but a number of pyrrolizidine alkaloids were tentatively identified using GC-MS. Standard alkaloids for GC-MS work were obtained both by extraction from a number of plant species and by synthesis of simple monoester alkaloids. In this process the alkaloid neosarracine, previously described by GC-MS, was isolated and NMR data for this compound are reported for the first time. S. speciosus and S. macrocephalus are morphologically very similar and their counterparts in the Grahamstown district exhibit features characteristic of both species. This could be due to hybridization, genetic mutation or simple variation within the species. The alkaloids of four local plant populations were examined in order to collect taxonomic markers whereby it was hoped that the Grahamstown plants could be satisfactorily classified. Three of the plant populations were found to contain 7-senecioyl-9-sarracinylheliotridine and 7-angelyl-9-sarracinyl-heliotridine. One population was found to contain the known alkaloid retrorsine along with the new alkaloid 2-hydroxy-l, 2-dihydrosenkirkine. The alkaloidal fractions of all four populations were compared using GC-MS and NMR techniques. Tentative taxonomic conclusions were drawn.
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  • Date Issued: 1992

A study of the biopharmaceutics and pharmacokinetics of the macrolide antibiotic, erythromycin

  • Authors: Terespolsky, Susan Ann
  • Date: 1992
  • Subjects: Erythromycin -- Bioavailability , Erythromycin -- Pharmacokinetics
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3795 , http://hdl.handle.net/10962/d1003273 , Erythromycin -- Bioavailability , Erythromycin -- Pharmacokinetics
  • Description: Erythromycin, a macrolide antibiotic isolated from Streptomyces erythreus, was first introduced into clinical medicine in 1952. It is active against most gram-positive bacteria, some gram-negative bacteria and is currently the agent of choice for Legionella pneumophila. Erythromycin is an acid-labile compound rapidly degrading in acidic solutions such as the acid environment of the stomach. As such, erythromycin absorption following oral administration of solid dosage forms is relatively poor. Accordingly there have been various approaches used to protect the drug against gastric inactivation. These precautions include enteric-coating of tablets, capsules or pellets of erythromycin base, the synthesis of acid stable 2' esters of erythromycin (ethylsuccinate and propionate) and salts of these esters (erythromycin estolate), and more recently, the synthesis of a range of new acid-stable, semi-synthetic macrolide antibiotics. The 2' esters are antimicrobially inactive or much less active than the parent compound and must be converted to the free erythromycin base in vivo in order to exhibit antibacterial activity. Intrinsic dissolution rates determined on raw material can provide extremely useful information relating to the gastrointestinal absorption of drugs from solid dosage forms. The large inter- and intrasubject variability associated with erythromycin base has, to date, mainly been attributed to gastric acid inactivation of the drug. However, changes in duodenal pH resulting in altered solubility and intrinsic dissolution rates may account for the observed variability. Thus, the intrinsic dissolution rates of erythromycin base at pH 6.0, 6.5, 7.0, 7.5 and 8.0 were compared in order to investigate the possible effects of pH changes which may occur in the duodenal contents, on the in vivo dissolution and subsequent absorption of this compound. The standard intrinsic dissolution rate test procedure employing a rotating disc of pure erythromycin base powder which only allows for dissolution from a constant surface area, was adapted and the drug quantitatively determined by reversed phase high performance liquid chromatography (HPLC) using ultraviolet detection. Results of intrinsic dissolution studies at both 22°C and 37°C indicate that the solubility, and therefore the rate of dissolution of erythromycin base is pH dependent, being more soluble at pH 6.0 than pH 8.0 (an approximate 800 times and 1000 times reduction in the amount dissolved after 30 minutes, at 22°C and 37°C respectively, when the pH of the medium was increased from 6 to 8). Although the stability of erythromycin and its ester derivatives in aqueous acidic solutions has been well documented, very little has been reported on the compound's stability in organic solvents. Methanol is recommended by official drug compendia (U.S.P. and B.P.) for use in erythromycin identification tests as well as in the sample preparation steps during assay procedures. Thus, the effect of methanol and acetonitrile, organic solvents of similar polarities and densities, on the stability of erythromycin base, erythromycin ethylsuccinate, propionyl erythromycin and erythromycin estolate at room temperature (22°C ± 0.5°C), using HPLC with electrochemical detection, was investigated. Erythromycin base is relatively stable in both methanol and acetonitrile, remaining intact for over 168 hours in acetonitrile and showing less than 5% degradation in methanol over the same period. Erythromycin ethylsuccinate in acetonitrile shows less than 5% degradation over 168 hours whereas in methanol, rapid hydrolysis occurs resulting in almost total conversion to base within 40 hours. Approximately 87% of erythromycin propionyl ester remained intact after 168 hours in acetonitrile whilst methanol caused rapid hydrolysis to erythromycin base (35% remaining after 28 hours). Erythromycin estolate appeared to be unstable in both acetonitrile and methanol. In acetonitrile, only 13% of the estolate remained intact after 168 hours, whereas in methanol, the reaction was much more rapid with 35% of the estolate remaining after 28 hours. The use of methanol as a solvent for erythromycin estolate reference standards is thus contraindicated. A number of conflicting reports on the half- life as well as the body compartment model that best describes erythromycin base serum concentration-time profiles (lBCM generally used to describe orally administered erythromycin, whilst a 2BCM has been used to describe erythromycin administered intravenously), appear in the literature. These differences may be largely attributed to the sampling period (between 6 and 12 hours) used in the repective studies. The objective of this study was to determine the body compartment model that best describes erythromycin base serum concentration-time curves by increasing the sampling time to 24 hours. In addition, the effect of chronic dosing of erythromycin on erythromycin pharmacokinetics, in the same group of subjects, was investigated. The single and multiple oral dose pharmacokinetics of erythromycin enteric coated base pellets within a gelatin capsule (250mg), were studied in 6 healthy, normal volunteers (19.5 ± 0.76 years, 71.5 ± 8.18 kg, 180.33 ± 5.99 cm). Furthermore, steady state concentrations were predicted using the pharmacokinetic parameters obtained from the single dose study, and compared with those obtained in the multiple dose study. Plasma concentrations were determined using a sensitive high-performance liquid chromatographic method with electrochemical detection. For the single dose study, after a tlag of 2.5 ± 0.71 hr, Cmax (1.12 ± 0.47 μ/ml) was reached at a tmax of 4.08 ± 0.93 hr post dose, with serum concentrations ranging from 0.31 - 1.62 μ/ml. The half-life was found to be 5.42 ± 1.31 hr. On multiple dosing (250mg six hourly), serum concentrations for the fifth, ninth and thirteenth dosing intervals ranged from 0.67 - 2.92 μ/ml, 1.69 - 3.65 μ/ml and 0.61 - 3.01 μ/ml, occurring at 3.75 ± 0.69 hr, 3.17 ± 1.03 hr and 3.17 ± 1.03 hr post dose with a Cmax of 1.89 ± 0.68 μ/ml, 2.35 ± 0.70 μ/ml and 1.94 ± 0.74 μ/ml, respectively. The area under the serum concentration- time curve for the single dose study (AUC₀₋∞) was 4.67 ± 0.88 hr.μ/ml, whilst the AUC₀₋τ. for the fifth, ninth and thirteenth dosing intervals of the multiple dose study were 5.77 ± 1.76 hr.μ/ml, 6.46 ± 1.33 hr.μ/ml and 5.97 ± 2.36 hr.μ/ml respectively, indicating an approximately 33% increase in AUC on chronic dosing of erythromycin. The observed increase in AUC may be a result of increased bioavailability or a decrease in clearance on chronic dosing.
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  • Date Issued: 1992

A study of the effect of progesterone on the body weight regulation in intact female rats

  • Authors: Ravelingien, Jo
  • Date: 1992
  • Subjects: Progesterone -- Physiological effect , Body weight -- Regulation , Rats -- Research
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:3787 , http://hdl.handle.net/10962/d1003265 , Progesterone -- Physiological effect , Body weight -- Regulation , Rats -- Research
  • Description: It is the aim of this study to elucidate the influence of progesterone on body weight regulation in intact female rats. A study of the literature includes a description of the body weight regulation and the effects of ovarian hormones on it. The controlled-system approach tries to link behavioral and physiological factors altering energy balance. The experimental study is subdivided into food-intake - and food-selection studies, a locomotor activity study, a study eliciting a possible role of thermogenesis, and finally rat liver studies which consist of a gas chromatography analysis of hepatic fatty acids and an electron microscopy study examining the ultrastructure of hepatocytes. It can be concluded that the effect of progesterone treatment on the body weight of intact female rats depends on the route of administration. There is a significant increase in body weight after subcutaneous progesterone injections without changes in total caloric intake and nutrient selection habits, indicating the importance of energy expenditure. But changes in spontaneous activity make no contribution in the progesterone-induced energy storage. It is also concluded that peripherally located brown adipose tissue thermogenesis is not changed, without ruling out the effect of more centrally located thermogenic organs as the liver. In this organ, small but significant changes in the fatty acid profile occur during the subcutaneous progesterone treatment.
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  • Date Issued: 1992

A study of the role of nature conservation law enforcement officers as facilitators of environmental education

  • Authors: Barrett, Janice Anne
  • Date: 1992
  • Subjects: Environmental education Nature conservation
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1783 , http://hdl.handle.net/10962/d1003668
  • Description: This study explores the potential roles of a sample of 18 nature conservation law enforcement officers, as facilitators of environmental education. More specifically it examines their attitudes towards their dual duties of enforcing laws and providing extension services. Attitudes were examined by means of qualitative data analysis from semi-structured interviews. Officers' environmental attitudes, as well the relative emphasis placed on law enforcement and extension, and their own perspectives of working with communities, are explored. The historical and cultural context of officers' work, as well as worldviews and personality traits are also discussed. Certain recommendations regarding officers' roles as facilitors of environmental education are made.
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  • Date Issued: 1992

A.P.A. Chubb's letter to Rhodes Museum Curator, dated 26 April 1992

Accuracy and reproducibility of the multiple-reading skin blanching assay

  • Authors: Smith, Eric W , Meyer, Eric , Haigh, John M
  • Date: 1992
  • Language: English
  • Type: Book chapter
  • Identifier: vital:6439 , http://hdl.handle.net/10962/d1006625
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  • Date Issued: 1992

Algal biotechnology and the beneficiation of saline effluent wastes

  • Authors: Rose, P D (Peter Dale)
  • Date: 1992
  • Subjects: Algae -- Biotechnology , Algae culture , Tanneries -- Waste disposal
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4135 , http://hdl.handle.net/10962/d1015967
  • Description: Saline deterioration in the South African public water system has been documented and disposal of brine wastes has been identified as part of the problem. The broad aim of this research programme was to undertake an initial technical study to evaluate the feasibility of integrating algal biotechnology into a disposal function for these wastes. A demonstration of utility in the form of products and waste treatment could produce a beneficiation of saline effluents and provide incentives necessary to deal with the disposal issue. The study attempted to demonstrate a synthesis between the two main thrusts in algal biotechnology that have produced large-scale practical applications - stable, predictable algal production in saline media and the cost effective High Rate Oxidation Ponding (HROP) process for incorporating algal production into a waste treatment function. Tannery organic saline effluents and the biotechnology of Dunaliella salina culture producing β- carotene were chosen as paradigms for the study. 1. The alga was shown to grow in certain tannery effluents producing enhanced biomass yields compared to defined inorganic medium cultivation. The potential for amino acid or protein supplementation of defmed culture media was noted. 2. A reduction in organic load simultaneous with the growth of D.salina was recorded in laboratory-scale simulations of the HROP process. Rates similar to the fresh water HROP equivalent were demonstrated. 3. These results suggested the uptake and storage of organic nitrogen by D.salina. The consequent inhibition of β-carotene accumulation by the organism presented a potentially insurmountable obstacle to the feasibility of β-carotene production in this medium. Uptake and release of organic compounds, previously demonstrated in phytoplankton and other micro-algae, was confirmed in this study for D.salina. The evidence acquired indicated the internalization of both glycine and bovine serum albumin. An ultrastructural study demonstrated mechanisms by which this process might occur. 4. The release of substantial quantities of glycerol was shown. A mechanism whereby D. salina may use this to regulate ammonia availability via control of its associated bacterial population was observed. Glycerol release was identified as presenting an application in treating refractory organic wastes, such as secondary sewage sludges, by elevating C:N ratios. This could demonstrate a significant utility for brine waste impoundments. 5. A multistage production process was proposed to deal with the problem of β-carotene inhibition by separation of the growth and metabolite accumulation functions into separate unit operations. It was shown in this study that the stress of nitrogen deficiency combined with high salinity provides for effectiveβ-carotene accumulation under the conditions of low illumination that pertain in dense cultures. Subjected to these conditions effluent-grown cells show delayed but unimpaired {j-carotene accumulation. 6. A role for the plant hormone abscisic acid in mediating the stress response was demonstrated in D.salina. Fluorescence induction studies suggested the presence of a signalling process forming part of a sensitivity control mechanism. Stress induction of β-carotene accumulation could occur through four clearly defined stages. Potential was identified for using this response as a physiological probe for monitoring and regulating the stress induction process. 7. The multistage processing concept requires effective algal cell separation technology. The use of cross-flow ultrafiltration and diafiltration with a polyethersulfone tubular membrane system was demonstrated as an effective process for the recovery and washing of D. salina. Cell concentrates were produced in a viable form. 8. Process designs incorporating the findings of the research programme are presented demonstrating how effluent and organic waste treatment functions may be combined with the production of D.salina and its products. Application of the multi-stage processing concept to β-carotene production in a defined medium process was identified as offering a potential four-fold yield enhancement. This could have a significant impact on a high cost, marginal algal biotechnology process. Aspects of novelty have been claimed in provisional patents applications. A provisional demonstration of the feasibility of D.salina production in tannery effluent indicates that algal biotechnology may provide a utility for, and hence the beneficiation of saline effluent wastes.
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  • Date Issued: 1992

An assessment of a new personality measure of authoritarianism in the South African context

  • Authors: Léger, Paul
  • Date: 1992
  • Subjects: Authoritarianism (Personality trait) -- Research , Authoritarianism -- Research -- South Africa , Psychological tests -- Research , Personality tests -- Research
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3007 , http://hdl.handle.net/10962/d1002516 , Authoritarianism (Personality trait) -- Research , Authoritarianism -- Research -- South Africa , Psychological tests -- Research , Personality tests -- Research
  • Description: The aim of the research was to assess the psychometric properties of Altemeyer's (1981) Right-Wing Authoritarianism scale (RWA scale)- developed in response to identified methodological weaknesses in personality measures of authoritarianism to date - within a South African setting. A modified version of the 24-item attitudinal scale, together with a demographic questionnaire was administered to a white and black sample of South African university students. Subsequent psychometric analysis of the data indicated that the scale was a significantly less powerful measure of authoritarianism in a cross-cultural context, than originally hoped for. Not only did the analysis show an absence of psychometric equivalence but revealed substantial problems within the content of the scale itself. An ensuing discussion of these findings situated the debate within a broader theoretical context. It was argued that the RWA scale, and its underpinning conceptualization, although possibly comprising a methodological refinement over existing measures of authoritarianism, did not constitute grounds for a viable approach to research on authoritarianism in the South African context. It was concluded that a model of authoritarianism resting on the assumptions of positivistic psychology, inevitably failed to account for the social and political dynamics of a changing society. As a socially relevant enterprise, it was suggested that the debate on authoritarianism be extended beyond the confines of individualistic psychology and research priority directed instead to the crucial role of societal factors giving rise to the individual manifestation of the phenomenon.
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  • Date Issued: 1992

An evaluation of the use of computers in a South African primary school

  • Authors: Mostert, Orla
  • Date: 1992
  • Subjects: Education, Elementary -- South Africa -- Computer-assisted instruction Computer-assisted instruction -- South Africa Educational technology -- South Africa
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1528 , http://hdl.handle.net/10962/d1003410
  • Description: The introduction of the computer into the educational arena is unique as pressure for its inclusion has come not from educationalists, but from public demand based on the conviction that exposure to computers is an essential ingredient of modern education. This has resulted in computers being added to school curricula before there has been careful research into its educational implications, making huge demands on teachers involved in the innovation. South African primary schools involved in computer education have followed international trends in their adoption of computers, initially perceiving computer education as a separate subject added on to the present curriculum. However, changing trends in computer use internationally are now beginning to reflect educators' changing perceptions of the nature of primary education, and educators are calling for the use of computers to be integrated into the curriculum rather than being seen as an area of study in themselves. This investigation attempts to outline general trends and perceptions of computer use in a South African primary school. Despite a high level of computer usage at the observed school, the computer was seen by teachers, in the main, as an extra subject, and has not yet led to any significant changes in teaching styles and methods. The research suggests that two main issues need to be resolved before computer education in primary schools reflects the present paradigm shift towards learner-centered educational practices. Firstly, there is a need to rethink the delivery of the curriculum towards one which promotes a greater degree of problem solving and decision making on the part of the learner. Secondly, it would appear that teachers need to be made more aware of this trend.
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  • Date Issued: 1992

An examination of the sonnets of E.E. Cummings

  • Authors: Hughes, Jeremy Francis
  • Date: 1992
  • Subjects: Cummings, E. E. (Edward Estlin), 1894-1962 -- Criticism and interpretation Sonnets, English -- Criticism and interpretation
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2244 , http://hdl.handle.net/10962/d1002287
  • Description: This dissertation examines E. E. Cummings's writings in the sonnet genre and in those genres to which the sonnet is related in various ways. Its fundamental point is that, despite the surface impression of poetic iconoclasm for which Cummings has a popular reputation, in choosing to write sonnets he engages in a traditional literary practice. He does this because his purpose is always to be an artist, as defined by the Aesthetic movement which influenced him. In order to argue his embracing of a traditional artistic role, the theory of genres espoused by Alastair Fowler in his book, Kinds of Literature, is used. Chapter 1 of the thesis comprises general introductory material, both to the range of Aesthetic ideas to which Cummings subscribed, and to Fowler's theory of genres. Several key generic kinds are also described. The second chapter makes use of two of these generic models, the sonnet sequence and the silva, as a way of examining Cummings's deployment of the sonnet within the larger context of his poetry collections. It is a survey of the structure of the anthologies he compiled from Tulips & Chimneys (1922) to 95 Poems (1958). The third chapter explores the three sonnet modes which Cummings first identifies and names when compiling the manuscript of Tulips & Chimneys, and continues to use in his collections up to and including is 5 (1926). Chapter 4 shows how certain themes and concerns from these early sonnets are altered and synthesised as Cummings matures from an aesthete to a Romantic poet. Sonnets from his later books are taken to be representative of three central kinds in all of his work after is 5. Chapters 3 and 4 proceed by means of relatively close readings of individual sonnets. This practice fulfils a double role: it penetrates the apparent obscurity of the more difficult poems, and it attempts to preserve the integrity of individual poems which exemplify different generic tendencies in Cummings's work. One of Cummings's reasons for writing sonnets is that the form favours the achievement of what Wordsworth calls "a feeling of intense unity". In undertaking close readings of a few sonnets I have attempted to preserve that feeling.
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  • Date Issued: 1992

An examination of the suitability of some contemporary South African fiction for readers in the post-developmental reading stage

  • Authors: Cole, Lorna
  • Date: 1992
  • Subjects: Children's literature, South African -- History and criticism Children -- Books and reading -- South Africa
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1530 , http://hdl.handle.net/10962/d1003412
  • Description: Adverse criticism regarding the quantity and quality of children's books in South Africa appear in such respected sources as The Oxford Companion to Children's Literature and The Companion to South African English Literature, the authors of which are of the opinion that South African children are dependent solely upon Eurocentric literature for their reading material. In recent years however, local publishers have attempted to redress this imbalance by offering prizes for unpublished works. These prizes have acted as incentives for aspiring writers, many of whom have had novels published specifically for children in the post-developmental reading stage. This study critically examines some of these prizewinning works of fantasy and contemporary realism, in an effort to gauge their literary worth within the context of accepted criteria for judging children's literature. Accolades from adults are not however a guarantee that the prizewinning books will be received with equal acclaim by the children for whom they are written. For this reason, five children in the post-developmental reading stage were asked to pass their opinions and non-literary judgments on the books. Although the critical evaluation of the indigenous works proves them to be eminently worthy of the prizes which they received on publication, the children did not rate them as highly as certain imported works. The works of fantasy by Marguerite Poland rated poorly in terms of their popularity despite the fact that the children said that in a non-circumscribed context, they choose fantasy in preference to contemporary realism. Within the context of the indigenous literature which they read for this study though, they preferred the works of contemporary realism as they were able to identify with particular aspects of the novels. Indigenous literature for children in the post-developmental reading stage is a comparatively new phenomenon which needs to be nurtured if it is to attain any lasting status. The onus rests upon the teachers of literature and librarians to introduce the literature and make the books more accessible to young readers. Publishers need perhaps to engage the views and opinions of the audience for whom the books are written in an effort to publish books which, without in any way detracting from their literary worth, will deal with subjects favoured by young readers.
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  • Date Issued: 1992

An exploratory field study into schoolgirl pregnancies, with emphasis on the role the school can play in their prevention

  • Authors: Kooverjee, Ishwar
  • Date: 1992
  • Subjects: Teenage pregnancy -- South Africa Sex instruction -- South Africa
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1537 , http://hdl.handle.net/10962/d1003419
  • Description: This piece of research explores the problem of schoolgirl pregnancies and suggests a role which the school might play in their prevention. Concern over the growing number of unplanned pregnancies under the age of eighteen years at the author's school, culminated in the .present study. Experts on the subject often perceive the problem to be self-defeating to the young girls, medically contra-indicated and socially disruptive. The purpose of this investigation was to determine attitudes towards the description of the problem, to identify causative factors predisposing to pregnancy, and to obtain views on how the school can reconcile efforts to address the problem. The relevant research data was obtained through a comprehensive 64 item attitudinal and knowledge-base questionnaire which was administered to a sample of 187 subjects. The sample comprised seven different occupational groups namely, senior schoolgirls, parents of senior schoolgirls, ex-schoolgirl primigravidae, parents of ex-schoolgirl primigravidae, school teachers, members of the clergy and various health care professionals. The appendices contain full statistical tables as well as full responses to the open-ended essay based on the research questionnaire so that the reader is free to check the reasonableness of the conclusions drawn. In the final chapter the author provides a brief summary of findings, offers justification why the teaching of sex education should be a priority in public schools, and makes recommendations, in the main, for the inclusion of school-based sex education as a component of Guidance in terms of rationale and implementation. In addition, suggestions are made with regard to school policy formulation and networking with parents and other community resources. Finally, a choice of four current model programmes for sex education are proposed in an effort to improve and build upon existing programmes in the present South African curriculum. It is the author's belief that this investigation may contribute to course design and perhaps provide hypotheses for more specific studies in the future.
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  • Date Issued: 1992

An investigation into the use of weather type models in the teaching of South African climatology at senior secondary school level

  • Authors: Schürmann, Leon
  • Date: 1992
  • Subjects: Climatology -- Study and teaching (Secondary) , Geography -- Study and teaching (Secondary)
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:2009 , http://hdl.handle.net/10962/d1015948
  • Description: The synoptic chart encodes climatological and meteorological information in a highly abstract manner. The pupil's level of cognitive development, the nature of the syllabus and the teaching strategies employed by the geography teacher influence the pupil's conceptualisation of information. The synoptic chart is a valuable tool for consolidating the content of the S.A climatology syllabus. Recent research has established that climatology-meteorology, and especially synoptic chart reading and interpretation, is difficult for the concrete thinker. These pupils find difficulty in visualising the weather processes and systems. Provided that they are simple and clear, models are useful teaching devices that integrate and generalise information in a manner that is easily retrievable. The intention of the author is to provide weather type models and other supporting strategies and aids as a means to improve the senior secondary pupil's assimilation of southern African climatological-meteorological information. This model-based approach is tested in the classroom using an action research framework to judge its efficacy. Conclusions are drawn and recommendations are made.
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  • Date Issued: 1992

Analyzing communication flow and process placement in Linda programs on transputers

  • Authors: De-Heer-Menlah, Frederick Kofi
  • Date: 1992 , 2012-11-28
  • Subjects: LINDA (Computer system) , Transputers , Parallel programming (Computer science)
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4675 , http://hdl.handle.net/10962/d1006698 , LINDA (Computer system) , Transputers , Parallel programming (Computer science)
  • Description: With the evolution of parallel and distributed systems, users from diverse disciplines have looked to these systems as a solution to their ever increasing needs for computer processing resources. Because parallel processing systems currently require a high level of expertise to program, many researchers are investing effort into developing programming approaches which hide some of the difficulties of parallel programming from users. Linda, is one such parallel paradigm, which is intuitive to use, and which provides a high level decoupling between distributable components of parallel programs. In Linda, efficiency becomes a concern of the implementation rather than of the programmer. There is a substantial overhead in implementing Linda, an inherently shared memory model on a distributed system. This thesis describes the compile-time analysis of tuple space interactions which reduce the run-time matching costs, and permits the distributon of the tuple space data. A language independent module which partitions the tuple space data and suggests appropriate storage schemes for the partitions so as to optimise Linda operations is presented. The thesis also discusses hiding the network topology from the user by automatically allocating Linda processes and tuple space partitons to nodes in the network of transputers. This is done by introducing a fast placement algorithm developed for Linda. , KMBT_223
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  • Date Issued: 1992

Applicability of the SERVQUAL instrument under South African conditions : an assessment of four situations

  • Authors: Pitt, Leyland Frederick
  • Date: 1992
  • Subjects: SERVQUAL instrument , Customer service , Measurement , Service quality , South Africa
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:1160 , http://hdl.handle.net/10962/d1001627
  • Description: On-going research in recent years has shown quality of product and service, as perceived by customer, relative to competition, to be the single most important factor contributing to organizational well-being. Quality of product and service also presents one of the most significant opportunities for corporate differentiation. A major requirement for the successful management of quality is therefore effective measurement. In the case of physical goods, progress has been made over a long period. However, in the case of services, real advances have only occurred within the past decade. The importance of service quality is also highlighted by the fact that most businesses today are losing customers due to its inadequacy, rather than poor products. Indeed, from the customer's point of view, services and products probably do not exist in a dichotomy, but, rather, along a spectrum. Therefore, the measurement of service quality is critical, not only in traditional service organizations, but in manufacturing situations as well. The development of the SERVQUAL questionnaire in 1988, offered researchers, perhaps for the first time, an apparently reliable and valid instrument for the measurement of service quality. However, to date the instrument has not been subjected to rigorous testing for reliability and validity in South Africa, across a range of service organizations, within a typology. In this study, the SERVQUAL instrument was used to measure service quality across a range of firms within the Larsson-Bowen contingency framework, under South African conditions. Its main objectives were to assess its reliability and validity in these circumstances. It was found that SERVQUAL performed well across all organizations within the Larsson-Bowen framework, under South African conditions, with regard to reliability, convergent and nomological validity. Its construct validity proved to be less sound, and it was not found to possess discriminant validity. It is suggested that this is less attributable to South African circumstances than to the nature of the organizations. In cases of low diversity of demand, the instrument appears to capture the essence of service quality less effectively. Means of overcoming this in future studies are suggested, as well as other directions for research in the area of service quality measurement
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  • Date Issued: 1992

Aspects of fuzzy spaces with special reference to cardinality, dimension, and order-homomorphisms

  • Authors: Lubczonok, Pawel
  • Date: 1992
  • Subjects: Fuzzy sets Topological spaces
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5399 , http://hdl.handle.net/10962/d1005213
  • Description: Aspects of fuzzy vector spaces and fuzzy groups are investigated, including linear independence, basis, dimension, group order, finitely generated groups and cyclic groups. It was necessary to consider cardinality of fuzzy sets and related issues, which included a question of ways in which to define functions between fuzzy sets. Among the results proved, are the additivity property of dimension for fuzzy vector spaces, Lagrange's Theorem for fuzzy groups ( the existing version of this theorem does not take fuzziness into account at all), a compactness property of finitely generated fuzzy groups and an extension of an earlier result on the order-homomorphisms. An open question is posed with regard to the existence of a basis for an arbitrary fuzzy vector space.
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  • Date Issued: 1992

Aspects of the biology of two inshore sparid fishes (Diplodus sargus capensis and Diplodus cervinus hottentotus) off the south-east coast of South Africa

  • Authors: Mann, Bruce Quintin
  • Date: 1992
  • Subjects: Sparidae , Diplodus
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5222 , http://hdl.handle.net/10962/d1005065 , Sparidae , Diplodus
  • Description: The blacktail, Diplodus sargus capensis and the zebra, Diplodus cervinus hottentotus, sparid fishes endemic to South Africa, are important components of the recreational shore-fishery. To provide a basis for the management of these fish, aspects of the biology of both species were investigated in the Tsitsikamma National Park (TNP). In particular, the role of the TNP was evaluated as a management option for the conservation of both species. Examination of stomach contents showed that juveniles of both species fed predominantly on amphipods, polychaetes and harpacticoid copepods. Adult !h. sargus were omnivorous and fed opportunistically on a wide variety of reef associated invertebrates and algae including echinoids, polychaetes, anthozoans, ascidians and rhodophytes. The diet of adult D. cervinus was more specialized with a preference shown for polychaetes and amphipods. Seasonal differences were apparent in the diets of both species where considerably more amphipods were consumed in winter than in summer. Feeding requirements of both species were reflected in their habitat preferences. Visual underwater assessment revealed that both species were most abundant on turbulent inshore reefs (1-10m). !h. sargus were observed over a wide variety of reef associated habitats. In the literature they have also been recorded in the surf zone of sandy beaches and in the lower reaches of estuaries. !h. cervinus, on the other hand, were more specific in their habitat requirements and were observed in greatest abundance on inshore reefs, often in close association with caves or overhangs. A comparison between the relative abundance and size structure of both species in the TNP with that of an exploited area immediately adjacent to the reserve, showed no significant differences. This was attributed to the low level of exploitation by rock-and-surf anglers occurring in the exploited study area, as well as the possibility of seeding of eggs and larvae, or emigration of adults from the TNP. An investigation of the reproductive biology of both fish showed that !h. sargus had an extended summer spawning season while in !h. cervi nus it was more restricted. Detailed histological examination of gonadal development showed that !h. sarqus were dygynous with partial protandry occuring in the male population. ~ cervinus were shown to be rudimentary hermaphrodites. Size at 50% maturity in ~ sargus and ~ cervinus was determined at 225 and 285mm fork length respectively, corresponding to ages of 4 and 6 years. An age and growth study based on the examination of sectioned otoliths showed that both species were slow growing capable of reaching ages in excess of 20 years. Growth in ~ sargus and ~ cervinus was described by the von Bertalanffy growth equations: L(t) = 309.44(1-e-0 . 247[t+l. 048 l) and L(t) = 396.85(1-e-0.146[t+2.148J) respectively. Life history characteristics of D. sargus and D. cervinus including slow growth, late maturation and occupation of a localised, demersal habitat showed that both species were vulnerable to the effects of over-fishing. Due to the present increase in the number of participants and the decrease in catch per unit effort in the recreational shore-fishery, more stringent management recommendations were proposed to ensure the adequate protection of both species. These included an increased minimum size limit and a decreased bag limit for both species. Based on the residency shown by both species and their high relative abundance in the TNP, marine reserves were considered to be a valuable addition to the suite of management options available for the conservation of these species . In this respect the reserve provided both protection for the spawner stock as well as the potential to seed adjacent areas.
  • Full Text:
  • Date Issued: 1992

Assessment of the profit sharing schemes

  • Authors: NUM
  • Date: 1992
  • Subjects: NUM
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/149616 , vital:38869
  • Description: In 1991 and 1992, the NUM accepted basic wage Increases on the gold mines that were far below the annual Inflation rate because of the crisis in the industry. The priority of the union was to preserve employment. But this left the door wide open for rich mines (like Kloof, Elandsrand and Vaal Reefs) to hide behind the low increases that are set in the Chamber negotiations at levels that Freegold, Buffelsfontein and marginal mines can live with. The NUM decided that workers need a way of adding more money onto their wages If the mines can afford to pay more.
  • Full Text:
  • Date Issued: 1992

Benthic assemblage structure, and the feeding biology of sixteen macroinvertebrate taxa from the Buffalo River, Eastern Cape, South Africa

  • Authors: Palmer, Carolyn Gay
  • Date: 1992
  • Subjects: Aquatic invertebrates -- South Africa -- Eastern Cape Benthos -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5646 , http://hdl.handle.net/10962/d1005328
  • Description: The River continuum concept (RCC) (Vannote et al. 1980) attempted to provide a unifying theory of river function. The Functional Feeding Group (FFG) concept (Cummins 1973, 1974) became a major component of the RCC. The FFG concept provides testable hypotheses about the changes in proportions of FFGs along a downstream gradient in a river, in response to the changing nature of food resources. The following short-comings of the FFG concept have been identified: 1) the variability of macroinvertebrate feeding, 2) problems with gut analysis as a method for assigning taxa to FFGs, and 3) inconsistent criteria defining FFGs. The objective of this study was to investigate the macroinvertebrate fauna of the Buffalo River in order to assess the applicability of aspects of the RCC and the FFG concept. The specific aims of the study were: 1) to describe the distribution of macroinvertebrate assemblages in the Buffalo River; 2) to clarify aspects of the FFG concept listed above; 3) to establish whether selected taxa could be assigned to FFGs; 4) to assess whether the proportions of different FFGs in successive reaches of a southern African river conformed to the predictions of the RCC; and 5) to test whether a functional classification is a useful alternative to a taxonomic classification. Macroinvertebrates were collected seasonally from a variety of biotopes at three sites, one each in the upper, middle and lower reaches. Riffles were sampled in summer at 16 sites. Over 100 taxa were identified and an hierarchical classification was prepared using two-way indicator species analysis. Invertebrate assemblages in the narrow headwater stream were taxonomically distinct from those of the middle/lower reaches and were not positively associated with subjectively identified biotopes. Biotopes were characterised by distinct assemblages in the wider middle/lower reaches. Sixteen abundant taxa whose feeding had not been previously investigated were selected for feeding studies, four from the headwaters and 12 from the middle/lower reaches. Methods used included gut content analysis, behavioural observations, food choice experiments and morphological studies using scanning electron microscopy. Three aspects of the functional feeding group concept were clarified. 1) Dietary variability was assessed using gut contents as an index of diet. The gut contents of both early (small) and late (large) instar larvae of all 16 taxa collected from different sites and biotopes, and in different seasons were compared using a multifactor analysis of variance. For all taxa the most consistently significant differences in gut contents were between large and small larvae. These were due to differences in the amount of material in the gut and in varying amounts of rarer dietary items. Dietary variability did not prevent taxa from being assigned to FFGs. 2) Gut content analysis satisfactorily provided basic information about the feeding biology of taxa but proved to be an inadequate single method for positively assigning taxa to FFGs. 3) Before taxa could be assigned to FFGs the definitions for some FFG categories had to be described clearly. It is suggested that the term shredder be based on the observation of shredding and a predominance of leaf fragments in the foregut. The presence of algae was not diagnostic of scrapers and a morphological basis is suggested. A morphological basis for the brusher FFG is described for the first time. All 16 taxa were assigned to FFGs. Three headwater taxa were shredders ((Goerodes caffrariae (Lepidostomatidae), Dyschimus ensifer (Pisulidae), Afronemoura spp. (Notonemouridae)) and one was a collector:brusher (Adenophlebia auriculata (Leptophlebiidae). These results were consistent with RCC predictions. All 12 of the taxa from the middle/lower reaches were filterers or collectors and this result was also consistent with RCC predictions. The Hydropsychidae, Cheumtopsyche afra and Macrostemum capense, were passive net filterers; Neurocaenis reticulatus (Tricorythidae) was a passive setal filterer; Caenidae sp. Band Pseudocloeon maculosum (Baetidae) were active filterers; caenidae sp. A, and the Baetidae, Baetis harrisoni, Centroptilum excisum and Cloeon africanum, were collector: gatherers; the Leptophlebiidae, Choroterpes elegans and Choroterpes nigrescens, were collector:brushers; and Afronurus harrisoni (Heptageniidae) was a scraper. Gut content analyses alone were insufficient to assign taxa to FFGs, but when augmented by morphological and/or behavioural data, taxa could be assigned to FFGs with confidence. In all cases the FFG designation referred to the most frequent style of feeding. N. reticulatus, A. harrisoni and A. auriculata were particularly flexible in their feeding behaviour. A functional classification of macro invertebrates in the Buffalo River was compared with a taxonomic classification. In both cases similar groups were identified, but their taxonomic and functional descriptions yielded different information. It is suggested that functional and taxonomic classifications should be viewed as complementary rather than alternative options.
  • Full Text:
  • Date Issued: 1992

Biopharmaceutics and pharmacokinetics of the macrolide antibiotic Josamycin

  • Authors: Skinner, Michael Fredrick
  • Date: 1992
  • Subjects: Antibiotics -- Bioavailability , Antibiotics -- Pharmacokinetics
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3791 , http://hdl.handle.net/10962/d1003269
  • Description: The investigations detailed herein have been conducted to address various aspects of the biopharmaceutics and pharmacokinetics of josamycin which to-date, have received little or no attention in the literature. Areas of investigation have included the selective determination of josamycin in serum and urine samples, the stability of josamycin in stored biological samples, intrinsic dissolution rates, solubility, acid and alkali stability and bioavailability and pharmacokinetics after dosing with a solution, powder and tablets. High performance liquid chromatography (HPLC) was used as the main analytical tool throughout these studies and proved to be highly versatile for the determination of josamycin in a number of different media. HPLC analysis afforded simple yet accurate determination of josamycin in samples from dissolution, solubility, tablet content and stability studies. Furthermore, the specificity afforded by HPLC was particularly useful for the separation of josamycin from degradation products formed in acid and alkali media. Since metabolites of josamycin are microbiologically active, microbiological assays do not determine the concentration solely of josamycin. An analytical method capable of the selective determination of josamycin in serum and urine samples is therefore required for the procurement of reliable bioavailability and pharmacokinetic data. HPLC affords this selectivity and a method for the selective determination of josamycin in serum and urine was successfully developed. The assay was simple yet precise, accurate and sensitive. Furthermore, it was well suited to the determination of josamycin in a large number of biological samples. Its success was largely due to the use of a solid phase extraction step using C₁₈ extraction columns, with a highly specific wash sequence followed by a phase separation step after elution from the extraction column. Chromatography was performed on a C₁₈ reversed-phase analytical column with UV detection of josamycin and internal standard at 231 nm and at 204 nm respectively using a programmable multi-wavelength detector. Only slight modification of the assay described should enable the selective determination of the metabolites of josamycin. This assay, therefore, lays the groundwork for future investigations into the pharmacokinetics of these metabolites. The re-usability of extraction columns was assessed in an attempt to reduce the cost of sample analysis. It was found that extraction columns could be used twice for the extraction of serum samples and up to four times for the extraction of urine samples. The difference between the re-usability of extraction columns for serum and urine samples was ascribed to various differences in the composition of the sample matrix. The stability of josamycin in stored serum and urine samples was also assessed.
  • Full Text:
  • Date Issued: 1992
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