A critical analysis of the marketing of mohair in South Africa with special reference to the period 1963 to 1989
- Authors: Norton, Eustace Herbert Fraser
- Date: 1992
- Subjects: Mohair -- South Africa -- Marketing , Mohair industry -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1020 , http://hdl.handle.net/10962/d1002755 , Mohair -- South Africa -- Marketing , Mohair industry -- South Africa
- Description: The objective of the research was to determine the extent to which marketing in general, and the Mohair Scheme in particular, played a part in the re-emergence of South Africa as the world's leading mohair producer. The two major components of the Scheme, the 'voorskot', or initial payment, and reserve prices were analysed separately. In an adaptive expectations, distributed lag model of supply adjustment, only the weighted rainfall and the average real net price of mohair during the previous season, were found to be important determinants of mohair production. The significant negative correlation between the average real net 'voorskot' price and mohair production was contrary to expectations, and probably due to the 'voorskot' always having been set well below the market price. The 'voorskot' may nevertheless have played an important part in making the Scheme as a whole acceptable to producers. As no record is kept of the reserve price, its influence was tested indirectly in two stages. In the first, its influence on price stability was determined by a comparison of ranges, standard deviations and variances, and by several multiple linear demand regressions. Three of the four models showed clearly that price stability was increased by the Mohair Scheme. In the second stage, formulae and diagrammatic analyses were used to assess the welfare gains and losses resulting from the Mohair Scheme. There was a welfare gain to local producers and most of the welfare costs of the Scheme were borne by foreign consumers. With this gain to producers and the more stable price, it was concluded that the reserve price had stimulated mohair production. It was therefore established that the Mohair Scheme had played a major part in the re-emergence of South Africa as the world' s leading mohair producer. Nevertheless, in view of the massive stockpiling in recent seasons, because the reserve price was set too high, the result was a substantial loss to the Scheme; it was therefore recommended that the Mohair Scheme be discontinued or, at least, that the reserve price should be set at a much lower long-run, market clearing level.
- Full Text:
- Date Issued: 1992
The interactive effects of light, temperature and CO₂/O₂ ratios in photosynthesis of Coix lachryma-jobi L
- Authors: Mjwara, Jabulani Michael
- Date: 1992
- Subjects: Coix , Plants -- Effect of light on , Plants -- Effect of oxygen on , Plants -- Effect of carbon dioxide on , Photosynthesis , Plants -- Effect of temperature on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4216 , http://hdl.handle.net/10962/d1003785
- Description: A portable infra red gas analyzer was used to investigate the interactive effects of light, temperature, and CO,jO, ratios under controlled environmental conditions in an attempt to model gas exchange characteristics of Coix Iachryma-jobi L. Plotting light response curves as a function of temperature (20, 25 30 and 35°C) revealed no sign of light saturation even at a photosynthetic photon flux density (PPFD) close to 2000 !Lmol m-' sol. High net assimilation rates (A) of approximately 24 !Lmol CO, m"s'! were realized at 30-35°C. Assimilation (A) versus internal CO, partial pressure (C,) curves showed a steep rise with increase in C, but saturated at approximately 150 (JLII-!) and all the results, either in the absence or presence of 0" showed a similar response under all temperature regimes. C. Iachryma-jobi exhibited low CO, compensation points cr ) between 0 and 10 JLlI-! under similar experimental temperatures and either at 0 or 21%0,. The slopes of double reciprocal plots of llA versus llCi, were nearly identical and crossed the yintercept at almost identical points under all 0, concentrations. These data indicate first; that there was no apparent 0, inhibition and second; indicated that the apparent inhIbitor constant (K,) for 0, at the site of carboxylation did not change with increase in [OJ from 0 to 21% oxygen. These observations were further confirmed by results obtained from the analysis of apparent carboxylation efficiency (CE, as defined as the slope of response of A to increasing CO,), as no inhibition of A with increase of [OJ occurred. These characteristics were consistent with typical features of C,photosynthesis. The absence of 0, inhibition and low r values indicated that an efficient CO, concentrating mechanism which eliminates photorespiration exists in C. Iachryma-jobi. At the light microscope level, leaf anatomy exhibited typical C, structure viz. bundle sheath with large chloroplasts and this sheath is further surrounded by a radiate Kranz mesophyU cells. Furthermore the anatomical features suggested that C. wchryma-jobi was an NADP-ME species. Stomatal conductance (g,) to assimilation (g,/A) indicated an increase in A with decrease in g" an essential feature of improving water use efficiency (WUE), but one which drastically reduces CO, diffusion rate. The physical lintitation (stomatal lintitation, t) to CO, diffusion under various [0,] and temperatures, but constant PPFD, did not exhibit statistically significant change in t values at either 0 or 21% a, within each temperature regime, however there was a marked decrease in t as the plant approached its optimum photosynthetic temperature.
- Full Text:
- 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.
- Full Text: false
- Date Issued: 1992
Interaction of selected fungicides with insoluble bovine skin collagen in the presence of the non ionic surfactant Triton X-100
- Authors: Fowler, William Mackenzie
- Date: 1992
- Subjects: Collagenases -- Research Fungicides -- Research Hides and skins -- Preservation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4318 , http://hdl.handle.net/10962/d1004976
- Description: In the leather industry fungicides are often used for the protection of wet-blue leather. These fungicides are usually only sparingly soluble and are therefore formulated together with surfactants in order to increase their solubility and to ensure an even distribution over the surface of the hide after treatment. Solutions containing both fungicides and surfactant are complex. The nature of these solutions was investigated. By means of UV/Vis spectroscopy and viscometry it was shown that the surfactant and fungicides form micelles and mixed micelles in solution. The nature of these micelles and mixed micelles was dependent on the solution temperature as well as on the concentrations of the surfactant and fungicides. At the higher temperatures and concentrations transition to large, possibly rod-shaped, mixed micelles occurred. The interaction between the selected fungicides 2-(thiocyanomethylthio)benzothiazole and n-octyl-4-isothiazol-3-one with bovine skin collagen in the form of both limed and lightly chromed hide powder in the presence of the non ionic surfactant Triton X -100 was investigated. Fungicide uptake was determined by difference measurements on the float solutions at regular intervals during treatment. Binding was rapid with equilibrium being established within the first six hours even for the solutions with the highest surfactant concentration. Binding failed to follow a normal mass-action binding-type isotherm approaching a saturation limit, but increased continuously indicating a co-operative effect whereby binding site affinity actually increased with the amount of ligand bound. Binding was accompanied by a drop in the free surfactant in the solution at the higher biocide levels indicating the formation of complex mixed micelles which bind to the collagen fibres. The uptake and antifungal activity of commercial fomulations of the fungicides on chrome-tanned wet-blue leather was investigated at various treatment temperatures. At lower fungicide treatment concentrations, binding tended to follow a typical mass-action type binding isotherm, increasing slightly with temperature. At higher float concentrations, an inflexion point was apparent beyond which uptake showed a marked increase with concentration. This inflexion point, signifying a change in binding characteristics, occurred at progressively lower concentrations with increasing temperature. Antifungal activity in terms of storage periods to onset of fungal growth was determined on the wet-blue leather cuttings immediately after treatment and drainage and also on sample discs after exhaustive extraction of free fungicide using dichloromethane. Storage performance testing of the various treated wet-blue leathers was carried out by different methods. Residual protective periods showed a curvilinear increase with dosage offer and surface uptake. In the low dosage range treatment temperature had only a relatively slight effect in promoting uptake and improving storage protection. At higher dosages, the influence of temperature on uptake and storage protection was greater due to the increase in surface binding of the fungicides at the elevated temperatures. Only a portion of the fungicide uptake was recovered by direct solvent extraction of the treated wet-blue leather. Solvent extraction reduced storage margins. The storage response in relation to fungicide content was, however comparable after extraction, indicating that both irreversibly bound and physically associated fungicide offered effective protection. Results of the study provide further insight into the mode of interaction of fungicide emulsion dispersion with bovine skin collagen, and the importance of the emulsion dispersions and its stability in determining the uptake of fungicide.
- Full Text:
- Date Issued: 1992
In vitro effects of three organic calcium channel blockers on the rat pineal gland
- Authors: Brown, Clint
- Date: 1992
- Subjects: Calcium -- Antagonists , Pineal gland -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3745 , http://hdl.handle.net/10962/d1003223 , Calcium -- Antagonists , Pineal gland -- Research
- Description: The calcium signal has emerged as an imponant component of intracellular regulation. Pineal function was thought to be slowed by the prominent calcification seen with increasing age, but recently it has been shown that calcium plays a crucial role in the adrenergic regulation of the gland. Beta-adrenoceptor stimulation increases melatonin (aMT) synthesis by increasing the activity of cyclic 3 '-5' adenosine mono phosphate (cAMP). Cyclic-AMP regulates the production of the pineal hormone, melatonin, from serotonin via the rate-limiting enzyme N-acetyltransferase (NAT). Increased intracellular cAMP is essential to the adrenergic induction of NAT. Noradrenaline(NA)also elevates pinealocyte cyclic guanosine monophosphate (cGMP). Adrenergic regulation of these cyclic nucleotides involves both α₁ - and β-adrenoceptors. Beta-adrenoceptor stimulation is an absolute requirement. Alphal-adrenoceptor activation, which is ineffective alone, serves to amplify the β-stimulated cAMP and cGMP responses via a positive effect on a Ca²⁺⁻/ phospholipiddependent protein kinase (Protein kinase-C) and a net influx of Ca²⁺ into the pinealocyte. Previous studies suggest the use of organic calcium channel blockers (CCBs) as probes of calcium-mediated processes. Applying this concept, the study set out to investigate the influence of a representative of each of the structurally diverse groups of calcium channel blockers viz. verapamil, diltiazem and nifedipine, and to examine their effect on β-adrenoceptor stimulation. It used the β-agonist isoprenaline (ISO) and the mixed [α₁/β]agonist noradrenaline (NA), for its combined [α₁/β]adrenoceptor stimulation, on agonist-induced increases in the production of radio-labelled aMT and N-acetylserotonin(aHT) -measured as the sum of N-acetylated product- from [¹⁴C] serotonin. This was done using organ cultures of rat pineal glands. It was speciously assumed that this drug paradigm would allow the determination of Ca²⁺ influx and/or the blocking thereof in the reported potentiation by using ISO as a non Ca²⁺ -entry stimulating agonist, compared with NA and its Ca²⁺ -entry stimulating properties. Surprisingly, all 3 CCB's potentiated the effect of NA. Only diltiazem was found not to potentiate the effect of ISO. In an attempt to uncover the reason for these results, the study moved toward a mechanistic approach,focusing in an antecedent manner on the various steps in the indole metabolic pathway to identify the point at which the change occurred, and hence possibly elucidate the mechanism responsible for the paradoxical increase. Experiments which assayed the levels of NAT, under the same drug conditions, showed the paradoxical increase to be already evident at this stage. Secondary experiments confirmed that NA stimulation of the pineal is dependent on Ca²⁺, both in organ culture and with NAT: the Ca²⁺ chelator EGTA abolished adrenergically-induced stimulation, while Ca²⁺ added after EGTA, restored the enzyme activity. The ionophore A23187 (which is able to transport Ca²⁺ directly into the pinealocyte via a mechanism which differs from the α₁ - mechanism) when used in conjunction with ISO or NA, was able to potentiate the responses of these two agonists relative to control values (agonist-alone), but by itself had no effect. With the enzyme NAT critically dependent upon cAMP for its induction, it was decided to determine the levels of cAMP and then those of its regulator, cAMP-phosphodiesterase (cAMP-PDE). This reasoning was prompted by reports of anti-calmodulin activity shown by the CCBs, in addition to their channel blocking effects. By binding to calmodulin (CaM), the CCBs are reportedly able to inhibit the CaM-dependent activation of cAMP-PDE. Following NA stimulation, verapamil caused a significant decrease in cAMP-PDE levels and an increase in cAMP. The other CCBs showed a similar trend. Glands stimulated with ISO in the presence of verapamil and nifedipine showed no significant differences in cAMP or cAMP-PDE levels. Diltiazem, however, was found to decrease the effect of ISO on cAMP while causing a concomitant increase in cAMP-PDE. This i) supported a possible hypothesis that the observed enhancement is a result of cAMP levels remaining elevated due to an inhibition of cAMP-PDE by the CCEs and ii) pointed to the possible presence of a CaM-sensitive PDE within the rat pineal gland. To test this hypothesis, two drugs which are more specific in their actions on CaM effects were chosen to see if the earlier results could be mimicked and thereby confirmed. Glands stimulated with NA in the presence of the specific CaM inhibitor R 24571 showed increased NAT activity and [¹⁴C]-aMT production. cAMP-PDE levels were clearly down, thus corroborating the possibility of cAMP-PDE inhibition. Glands incubated in the presence of M&B 22948, a CaM-sensitive PDE inhibitor, showed similar increases in NAT activity and [¹⁴C]-aMT. These findings therefore support the initial results and although indirect, confirm the hypothesis that the paradoxical increase following predominantly NA stimulation could be a result of cAMP levels remaining elevated, due to inhibition by the CCEs of the CaM-dependent activation of its regulator cAMP-PDE. In summary, data presented herein concur with proposals that: i) the CCEs are not specific enough to be used as tools to research Ca²⁺ -mediated events, as they appear to have sites of action other than the voltage operated channel (VOC); eg. binding to calmodulin, ii) there are functional differences between the CCEs as shown by diltiazem in this series of experiments, iii) there is a CaM-sensitive-PDE present in the pineal.
- Full Text:
- Date Issued: 1992
A classroom-based investigation into the potential of the computer spreadsheet as a learning tool within the secondary school mathematics curriculum
- Authors: Funnell, Lynette
- Date: 1992
- Subjects: Mathematics -- Computer-assisted instruction Mathematics -- Study and teaching (Secondary) Electronic spreadsheets
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1448 , http://hdl.handle.net/10962/d1003329
- Description: The influence of modern technology on education is becoming more noticeable and has implications for the curriculum and the teaching methods of mathematics. The microcomputer can be used effectively as a powerful teaching and learning aid within the mathematics classroom. This study considers the role of the computer as an aid to teachers and pupils in the teaching and learning of mathematics and shows it as having great potential. At present relatively few schools in South Africa are using the computer as a teaching aid in the mathematics classroom. The researcher proposes that some reasons are a shortage of suitable programs, the fact that few teachers have adequate skills in educative uses of the computer and most teachers are not skilled in programming techniques. Based on this assessment of the problem, spreadsheet programs related to some mathematics lessons, together with teaching notes and pupils' material have been developed. Besides describing the potential of the computer in mathematics, this study outlines the development of three spreadsheet packages and suitable teaching methodologies used for each package, and assesses an action research investigation undertaken by the researcher, teachers and pupils when using these spreadsheet packages in six classes. The findings of the investigation are most encouraging. The overall conclusion is that computer spreadsheet packages can assist the teacher in making the learning of mathematics more effective, more interesting and more enjoyable.
- Full Text:
- Date Issued: 1992
Up Beat Issue Number 7 1992
- Authors: SACHED
- Date: 1992
- Subjects: SACHED
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/116493 , vital:34392
- Description: Life often doesn’t turn out as you had hoped. The world isn’t always a fair place. Some teenagers I know, just accept their lot. Others work hard to make even small dreams come true. This issue is full of stories about young people. They are not pop stars, famous TV heroes or powerful leaders. They are ordinary people like you and me. But they have something in common. They are all determined to make something of their lives. Meet Patrick from Uitenhage, he’s a basketball player who’s off to Japan. Meet Nomnikelo, at 23 she’s a domestic worker. But she’s determined to become a nurse. There’s Lucky. He was forced to leave school in Std 4. He couldn’t find a job, but now he’s making money from scraps. Meet Lerata, she never believed in love. Then one day after a school debate. You’ll find stories about teenagers overseas too. Read about Hodan, Emadul and Van Lac. They are all struggling to start a new life in London. When we read about Lucky, Nomnikelo or Lerata, we can learn something. We admire the way they have got on with it, faced new challenges. But we can also learn from them - about ourselves. We all have it in us, to change our world and make the most of our lives. Enjoy reading!
- Full Text:
- Date Issued: 1992
Selecting educational computer software and evaluating its use, with special reference to biology education
- Authors: Beyers, Ronald Noel
- Date: 1992
- Subjects: Biology -- Study and teaching -- Computer programs Education -- Data processing Biology -- Computer-assisted instruction
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1764 , http://hdl.handle.net/10962/d1003649
- Description: In the field of Biology there is a reasonable amount of software available for educational use but in the researcher's experience there are few teachers who take the computer into the classroom/laboratory, Teachers will make use of video machines and tape recorders quite happily, but a computer is a piece of apparatus which they are not prepared to use in the classroom/laboratory. This thesis is an attempt to devise an educational package, consisting of a Selection Form and an Evaluation Form, which can be used by teachers to select and evaluate educational software in the field of Biology. The forms were designed specifically for teachers to use in preparation of a computer lesson. The evaluation package also provides the teacher with a means of identifying whether the lesson has achieved its objectives or not. The teacher may also be provided with feedback about the lesson. The data is gathered by means of a questionnaire which the pupils complete. It would appear that teachers are uncertain as regards the purchase of software for their subject from the many catalogues that are available. The evaluation package implemented in this research can be regarded as the beginnings of a data base for the accumulation of information to assist teachers with details on which software to select. Evidence is provided in this thesis for the practical application of the Selection and Evaluation Forms, using Biology software.
- Full Text:
- Date Issued: 1992
Facies mapping of the Vaal Reef placer as an aid to remnant pillar extraction and stope width optimisation
- Authors: O'Donovan, Anthony Gareth
- Date: 1992
- Subjects: Facies (Geology) -- South Africa -- Vaal Reef placer
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4947 , http://hdl.handle.net/10962/d1005559 , Facies (Geology) -- South Africa -- Vaal Reef placer
- Description: The Vaal Reef placer is situated on the unconformable junction of the Strathmore and Stilfontein formations of the Johannesburg Subgroup. Within the South Division of the Vaal Reefs Exploration and Mining company lease, the Vaal Reef Placer is shown to be composed of several different units. Each unit exhibits its own specific characteristics and trend direction which can be used to establish distinct "Reef packages". These packages can be mapped in such a way as to provide a preliminary lithofacies map for the Vaal Reef Placer. The delineation of such geologically homogenous zones, and the development of a suitable depositional model, can be utilised in several ways. The characteristics of a particular zone are shown to influence the control of stoping width, evaluation of remnant pillars and the geostatistical methodology of evaluating current and future ore reserve blocks.
- Full Text:
- Date Issued: 1992
Educational needs of adults in Mdantsane
- Authors: McAllister, Patrick A , Young, Michael , Manona, Cecil Wele , Hart, Jo
- Date: 1992
- Subjects: Adult education -- South Africa -- Mdantsane (Ciskei) Adult education -- South Africa -- Mdantsane (Ciskei) -- Case studies
- Language: English
- Type: Book , Text
- Identifier: http://hdl.handle.net/10962/2079 , vital:20253 , ISBN 0868102423
- Description: The purpose of the study was to collect some preliminary information in advance of the inauguration of a new educational project at Fort Hare University which, under the guidance of a new Vice-Chancellor, Dr. S.M.E. Bengu, is forging for itself a new course of development as a people's University. The new project arises out of a report prepared by the International Extension College for the University of Fort Hare. The hope is that a number of innovations can be introduced into adult education in the Eastern Cape which will prove of value in meeting the needs of people living in different kinds of localities. The planning will begin in the early winter, as soon as staff have assembled, and as soon as Dr. David Warr, the international consultant to the project, is in post. It seemed sensible to conduct, in advance, one of the surveys which will be needed to underpin plans. To do this at short notice and complete it in a short time (the work did not commence until February, 1992) the best course was to rely on an experienced team from a neighbouring University, Rhodes, which had already conducted surveys in different districts within the Eastern Cape, and to bring in further support from the University of Natal , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
- Full Text:
- Date Issued: 1992
The evaluation of indomethacin and theophylline oral controlled/modified-release dosage forms in vitro-in vivo correlations
- Authors: Tandt, Ludo Alfons Germaan Luc
- Date: 1992
- Subjects: Theophylline , Indomethacin , Drugs -- Controlled release , Drugs -- Dosage forms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3794 , http://hdl.handle.net/10962/d1003272 , Theophylline , Indomethacin , Drugs -- Controlled release , Drugs -- Dosage forms
- Description: Over the past few decades many researchers have investigated the utility of in vitro - in vivo correlations for the assessment of dosage forms. These investigations are, however, dependent on reproducible dissolution data and well conducted biostudies in order to establish meaningful and robust correlations. Despite the fact that the establishment of such correlations is perhaps idealistic, considerable interest has still been shown in this area of research. Various Controlled/Modified Release Dosage Forms (CMRD's) of theophylline, a weakly basic drug, and indomethacin, a weakly acidic drug, were assessed in order to establish in vitro - in vivo correlations. Dissolution rate studies were carried out using either the USP basket or paddle apparatus. The dissolution rate studies were conducted in a range of dissolution media of varying pH. Bioavailability studies were conducted on the dosage forms used by the Biopharmaceutics Research Institute at Rhodes University. The results of these biostudies were kindly made available for use in this research project. Type A correlations were established using a mathematical simulation process whereby expected in vivo responses are simulated and compared to actual profiles obtained for the dosage forms. In order to perform the simulations the dissolution rate profiles were stripped and using linear regression and the methods of residuals the dissolution rate order and the relevant dissolution rates were obtained. The results of the s imulations indicated that the in vivo serum concentration-time curves could be accurately predicted for the theophylline dosage forms but to a lesser extent, for the indomethacin formulations. The dissolution rate studies indicated that the paddle method is a suitable method for dissolution rate studies of theophylline CMRD's, although it appeared that the optimum pH of the dissolution medium was formulation dependent. Dissolution rate studies conducted on indomethacin formulations indicated that the USP specified basket method for extended-release indomethacin formulations was not able to distinguish between two formulations which exhibited different in vivo profiles. The conversion to the paddle method was, however, able to highlight the differences between these formulations. The use of three dimensional topographs to depict dissolution rate profiles was demonstrated for formulations of both theophylline and indomethacin. The topographs enabled the successful differentiation between bioinequivalent formulations. The dissolution rate profiles were also fitted to the Wei bull equation and the parameters obtained from this were compared to the Weibull parameters obtained from the in vivo absorption plots obtained using the Wagner-Nelson method. The results indicated that the Weibull function was suitable to describe both the in vivo and in vitro data. The following recommendations for the preformulation dissolution studies of weakly acidic and weakly basic drugs are proposed. The dissolution rate studies of weakly acid drugs, such as indomethacin, should be carried out over a range of pH utilising the paddle apparatus. Three dimensional topographs based on the dissolution data should be constructed and used as a comparative tool for different formulations. Based on these comparisons the appropriate formulation can then be selected for a pilot scale in vivo bioavailability study. The dissolution rate studies of weakly basic drugs, such as theophylline, should be carried out over a range of pH utilising the paddle apparatus. The dissolution data should then be used to simulate the expected in vivo profile and on this basis the appropriate formulation selected for a pilot scale bioavailability study. The above approach to the preformulation studies of new CMRO's would allow for the more careful selection of new dosage forms and could thus eliminate costly and unnecessary bioavailability studies performed on inferior formulations.
- Full Text:
- Date Issued: 1992
Developing a problem solving approach to primary mathematics teaching: a case study
- Authors: Naidoo, Anandhavelli
- Date: 1992
- Subjects: Mathematics -- Study and teaching (Elementary) Problem solving -- Study and teaching (Elementary)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1493 , http://hdl.handle.net/10962/d1003374
- Description: According to recent research a focus in teaching mathematics to children is the development of problem solving abilities. Problem solving means the process of applying mathematical knowledge and skills to unfamiliar situations. A case study was done using a problem solving approach to the learning and teaching of mathematics with a sample of teachers registered at the Umlazi College For Further Education. These teachers were familiar with the traditional approach of teaching mathematics through drill and practice methods. The new syllabus that is to be implemented emphasises a problem solving approach to the teaching of mathematics. This study set out to implement a problem solving approach with primary school mathematics teachers so that they would be someway prepared for the innovations of the new syllabus. Workshops were conducted using an action research approach with discourse and practice leading to reconstruction with improvements. Early theorists like Piaget and Bruner offered ways of understanding children's learning, to help the teacher develop his teaching. Dienes introduced an element of play and Dewey spoke of the importance of experience. Dienes and Dewey show the first positive signs of recognising the importance of social interaction in the learning situation. Social interaction lays emphasis on language and discussion in the mathematics classroom. A social constructivist model of teaching and learning was used for the research. This research includes a study of the established ideas on developing a problem solving approach to mathematics teaching. These ideas were incorporated into the workshops that the group of teachers attended. During the workshops teachers were gradually exposed to the essence of problem solving techniques through much group discussion and doing practical exercises, which they could then implement in their classes. The teachers reported back at each subsequent workshop. A non-participant observer evaluated the development at the workshops. The workshops' success was evident from the change in the teachers' attitudes and behaviour as well as their feedback of what transpired in the classroom. They reported on the change in their roles as information suppliers to facilitators where the thinking process was focused on, rather than the importance of a correct answer. In the workshops the teachers themselves moved from passive listeners to active participants. It would appear from this preliminary investigation that through using a problem solving approach in workshops, inservice teachers can benefit constructively from this approach and will attempt to use it in their own teaching.
- Full Text:
- Date Issued: 1992
The artificial recharge of urban stormwater runoff in the Atlantis coastal aquifer
- Authors: Wright, Alan
- Date: 1992
- Subjects: Atlantis water resource management scheme , Urban hydrology -- South Africa , Urban runoff -- South Africa , Storm sewers -- South Africa , Water resources development -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4817 , http://hdl.handle.net/10962/d1005491 , Atlantis water resource management scheme , Urban hydrology -- South Africa , Urban runoff -- South Africa , Storm sewers -- South Africa , Water resources development -- South Africa
- Description: The thesis covers the investigation of the storm water runoff and artificial recharge components of the Atlantis Water Resource Management Scheme in the Southwestern Cape. The objective of the study was to obtain an in-depth knowledge of the process of artificial recharge of urban storm water runoff, in order to identify the most efficient recharge management strategy for the Atlantis aquifer. To achieve the objective it was necessary to first study the existing knowledge on urban storm water hydrology and artificial recharge by spreading, and to create a conceptual model of what might be expected. The study area was then investigated to examine how closely the actual situation was reflected by the conceptual model, enabling recommendations to be made for the sound management of the system. The stormwater runoff component was found to differ from most urban hydrological studies as a result of its large baseflow component. The sandy nature of the catchment, small percentage area of effective impervious surface, and high groundwater table resulted in the baseflow constituting more than 40% of the total storm water runoff and accounting for over 60% of the pollution load. The "first flush" effect established as a major source of pollution in other studies, was found to be of minor significance in this study area. The overall stormwater quality (excluding the noxious industrial baseflow) was found acceptable for artificial recharge within the study area, although the baseflow from the industrial sub-catchments showed the potential for being a major source of pollution in the future. The treated wastewater used for artificial recharge prior to 1987 was found to be unacceptable for recharge purposes. The treated industrial effluent should under no circumstances be recharged up-gradient of the Witzand well field. The treated domestic effluent although of a poorer quality than the resident Witzand well field groundwater could be recharged in order to boost recharge volumes and form a buffer against further intrusion by the poor quality groundwater from the Brakkefontein area. This would however only be acceptable if strict water quality control is maintained and recharge does not take place west of the present basin. The recharge basin was found to be well situated with respect to influencing the Witzand wellfield and maintaining a groundwater buffer against poor quality groundwater flow from the northeast towards the central area of the wellfield. Unfortunately the surrounding low-lying topography and sandy retaining walls have resulted in return flow and raised groundwater-levels. The raised groundwater mound does not comply with the conceptual model and together with the sandy nature of the unsaturated zone resulted in less effective purification during infiltration. The practice of letting large portions of the basin floor dry-out during summer was shown to be beneficial and the periodic cleaning of the deeper portions of the basin essential. The artificially recharged water was found to have influenced the upper portion of the aquifer well beyond the West Coast Road. The study of groundwater quality being a good method for tracing artificially recharged water. The groundwater quality has improved as a result of artificial recharge since the removal of treated wastewater from the recharge basin. The groundwater was (ii) found to be very responsive to the slightest changes in recharge basin water quality or/and quantity. Management of the recharge basin therefore had to be very much of a compromise between qualitative and quantitative approaches. The present approach of recharging all the stormwater runoff throughout the year providing the most efficient compromise under the present conditions. The study revealed that the most efficient recharge management strategy would be the recharge of treated domestic sewage effluent in the present recharge basin and all residential storm water runoff plus industrial "storm flow" stormwater runoff in a new recharge basin located northwest of the present basin. Strict water quality control must be maintained on the water discharged into the basins and an annual wet/dry cycle implemented within the basins to boost infiltration. The entire system should continue being monitored to safe guard the groundwater resource from pollution and over exploitation.
- Full Text:
- Date Issued: 1992
A critical analysis of school computer studies syllabuses in South Africa with reference to university computer science curricula
- Authors: Roets, Rina Annette
- Date: 1992
- Subjects: Electronic data processing -- Study and teaching (Secondary) -- South Africa Electronic data processing -- Study and teaching (Higher) -- South Africa Electronic data processing -- Curricula -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1471 , http://hdl.handle.net/10962/d1003352
- Description: This thesis analyses the existing and proposed Computer Studies syllabuses in South African schools. Thereafter it compares the South African syllabuses with syllabuses in the United Kingdom. An attempt is made to assess the objectives of the design of the new S.A. syllabus. University Computer Science syllabuses are examined in order to gauge the purported overlap between what is taught at schools and universities. Opinions are obtained on the problems which apparently exist in offering or teaching the subject at schools and universities by conducting surveys on syllabus designers and university Computer Science departments. Finally recommendations are made for future Computer Studies syllabuses.
- Full Text:
- 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.
- Full Text:
- Date Issued: 1992
Illness as intersubjectivity: a sociological perspective
- Authors: Pitfield, Doreen Jennie
- Date: 1992
- Subjects: Humanism , Medical care -- Sociological aspects , Intersubjectivity , Medical ethics -- Sociological aspects
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3329 , http://hdl.handle.net/10962/d1003117 , Humanism , Medical care -- Sociological aspects , Intersubjectivity , Medical ethics -- Sociological aspects
- Description: This thesis explores the historical roots of scientific medicine in an effort to highlight the lack of humanist intersubjectivity within the contemporary medical model. The study notes that contemporary medicine is overtly scientific and that its scientific framework is upheld and furthered by a medical model which draws legitimation from the irrefutability of what is referred to variously within this work, as its scientific "regime". It is shown that in terms of the humanist tradition people, not science, constitute the epicentre of meaningful experiential participation in the defining of human social reality. This, it is argued, implies a radically different ontology from other sociological perspectives on medicine. The thesis suggests that the contemporary medical model loses sight of the patient's ability to cognitively participate in the defining of illness, diagnosis and treatment in terms of his/her experience thereof , and argues that contemporary medicine, by advancing the idea that it alone has the correct and only answer to such problems, has led to a situation which promotes an overmedicalisation of society . The study gives an indication of the way in which this overmedicalisation has led to areas of human life becoming conceived of only in relation to medical expertise. In this respect it is noted that medicine has so successfully infiltrated the human consciousness (involving areas as diverse as childbirth, genetic engineering, transplant surgery and death), that decisions on health are invariably taken from a foundation of scientific legitimation which seems to exclude the patient as subject. It is argued that this way of making decisions reinforces the requirement for a scientific medical model which as it negates the human element insidiously amplifies its power over human life; thereby devaluing the very people it seeks to serve. The thesis suggests that in terms of a humanist reading of the Oath of Hippocrates, medical decisions can only be taken within a framework of experiential involvement which includes both medical expertise and lay understanding. It is indicated that when this happens, social reality functions in terms of a symbolic participation which fosters a commitment to equalise the conditions of human existence, and promotes a dialogical negotiatory process which is both intersubjectively and ongoingly produced.
- Full Text:
- Date Issued: 1992
The geology and geochemistry of the north-western portion of the Usushwana Complex, South-Eastern Transvaal
- Authors: Riganti, Angela
- Date: 1992
- Subjects: Geology -- South Africa -- Transvaal , Geochemistry -- South Africa -- Transvaal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4958 , http://hdl.handle.net/10962/d1005570 , Geology -- South Africa -- Transvaal , Geochemistry -- South Africa -- Transvaal
- Description: The 2.9 Ga old Usushwana Complex in the Piet Retief-Amsterdam area (south-eastern Transvaal) represents an exposed segment of a layered intrusion. It has the form of a dyke-like body elongated in a northwesterly direction, and extends to an estimated depth of 3000 -5500 m. Lithologically, the Complex consists of a cumulate succession of mafic rocks capped by granitoids and has intruded along the contact between the basement and the supracrustal sequences of the Kaapvaal Craton. Differentiation of an already contaminated gabbroic magma resulted in an ordered stratigraphic sequence comprising progressively more evolved lithotypes, with at least two imperfect cyclic units developed over a stratigraphic thickness of about 700 metres (Hlelo River Section). Meso- to orthocumulate textured gabbros and quartz gabbros grade upwards into magnetite- and apatite-bearing quartz gabbros, interlayered with discontinuous magnetitite horizons. The gabbros in turn grade into hornblende-rich, granophyric granodiorites. The differentiation process is regarded as having been considerably enhanced by the assimilation of acidic material, derived by partial melting of the felsic country rocks at the roof of the magma chamber. Recrystallisation of these rocks gave rise to the microgranites that locally overlie the granodiorites. Mineralogical, textural and geochemical features indicate a relatively advanced fractionation stage, suggesting that the exposed sequence of the Usushwana Complex in the study area represents the upper portion of the intrusion. No significant mineralised occurrences were identified. However, on the basis of similarities between the Usushwana Complex and other mafic layered intrusions which host significant ore deposits, it is suggested that economic concentrations of base metal(Cu-Ni) sulphides, PGE and chromitites are likely to be developed at lower stratigraphic levels.
- Full Text:
- Date Issued: 1992
Fuzzy uniform spaces
- Authors: Burton, Michael Howard
- Date: 1992
- Subjects: Fuzzy sets -- Research Uniform spaces -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5408 , http://hdl.handle.net/10962/d1005222
- Description: For a fuzzy uniform space, the notion of a Cauchy prefilter, a precompact fuzzy set, a complete fuzzy set and a bounded fuzzy set are defined in such a way that these notions are good extensions of the corresponding notions for a uniform space. A theory of fuzzy uniform spaces is developed which generalises the theory of uniform spaces.
- Full Text:
- Date Issued: 1992
Up Beat Issue Number 3 1992
- Authors: SACHED
- Date: 1992
- Subjects: SACHED
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/116201 , vital:34332
- Description: There are two sides to every story. You’ve surely heard that before. Well, it is true. Sometimes there are even three or four sides to a story. It depends how many people were there to tell the tale. Behind every story there is a writer. Behind a picture there is a photographer. And they are ordinary people, like you and me. They eat, sleep and play like the rest of us. Like us, they have their own ideas and feelings about the world. And these ideas show in their stories, books or photographs. So what you read is not the truth. It is someone’s version of it. Always read with an open mind. Be a detective when you read! Ask questions, think, search for clues and weigh up the facts. Then decide for yourself which story comes closest to the truth. You must have learnt about Christopher Columbus at school. Well there’s another side to that story in our article called ‘Who discovered America?’. Read it and decide what YOU think really happened. Upbeat writes a lot about young peoples’ experiences of growing up. There’s another side to being a teenager - being the mother of one. Nomasondo Hadebe openly shares with us the pain and joy of having teenage children. We don’t only learn from grown-ups or famous people (or both). Upbeat is full of stories about youth, their ideas and feelings about the world. By sharing experiences, problems and ideas we can learn from each other. So don’t miss our letters page, advice column and talkshop. Read what young people have to say. You can agree or disagree with their ideas. And when you close the magazine you may feel a little sadder, happier or angrier. But you will always be wiser
- Full Text:
- Date Issued: 1992