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Mtsitso 3

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Mtsitso 2

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Mzeno

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Mabandla

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Mchuyo

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Mtsitso 1

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Mgeniso

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Mtsitso 5

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Chibhudhu

- Venancio Mbande and his Chopi timbila xylophone group, Tracey, Andrew T N

Standardization of Raven's standard progressive matrices for secondary school African pupils in the Grahamstown region

- Vass, Vasili Arthur

  • Authors: Vass, Vasili Arthur
  • Date: 1992
  • Subjects: Black people -- Education -- South Africa , Intelligence tests -- South Africa , Educational tests and measurements -- South Africa , Cognition and culture , Raven's Progressive Matrices
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3078 , http://hdl.handle.net/10962/d1002587 , Black people -- Education -- South Africa , Intelligence tests -- South Africa , Educational tests and measurements -- South Africa , Cognition and culture , Raven's Progressive Matrices
  • Description: Arising out of a need, expressed by Clinical Psychologists in the Grahamstown region, for the fair assessment of secondary School African pupils, norms for the Raven's Standard Progressive Matrices (SPM) were established. Two methods of presentation were used, the first using the original instructions of John Raven translated into the students' first language of Xhosa, hence-forth referred to as the Alternate sample. The second method of presenting the instructions was adapted, to include the use of visual aids and active participation in the instruction phase of the test, hence-forth referred to as the Normative sample. In addition to the establishment of norms, the two methods of test presentation were investigated to see if the method of presentation had an effect on the results of the Raven's SPM. The population was drawn from the three African Secondary Schools in the Grahamstown municipality. The total population consisted of 3 232 students. Classes were randomly sampled across the three schools, with the average age of the Normative sample being 19.3 years. The sample consisted of 812 pupils, 711 in the Normative sample and 101 in the Alternate Sample. The following results and conclusions arose from the study: 1) Norms generated were considerably lower than previously established norms in similar studies. 2) t-Test results indicated that the method of test presentation on the Raven's SPM is important when assessing students that may be regarded as 'disadvantaged'. 3) Respondents scored significantly higher when the method of presenting the instructions ensured a greater understanding of the task demanded of the respondents. 4) The analyses of covariance indicate that male subjects score significantly higher than female subjects, and that there is a significant difference between the ages and educational standard, on the scores of the Raven's SPM. 5) The differences found contradict previous findings using the test, and question the cultural fairness of the test.
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  • Date Issued: 1992

Participatory research for community development: an annotated bibliography

- Van Vlaenderen, Hilda

  • Authors: Van Vlaenderen, Hilda
  • Date: 1992
  • Subjects: Participant observation -- Bibliography Participant observation Community development -- Bibliography
  • Language: English
  • Type: Book , Text
  • Identifier: http://hdl.handle.net/10962/1920 , vital:20239 , ISBN 0868102377
  • Description: This Working Paper reports on the results conducted into the nature and extent of the embryonic venture capital industry in South Africa. It represents part of an on-going research programme dealing with Black economic development undertaken by the Development Studies Unit (DSU) at Rhodes University. , Digitised by Rhodes University Library on behalf of the Institute of Social and Economic Research (ISER)
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  • Date Issued: 1992

The administration and organisation of independent study topics with special reference to secondary school geography

- Van Harmelen, U

  • Authors: Van Harmelen, U
  • Date: 1992
  • Subjects: Geography -- Study and teaching (Secondary) , Project method in teaching
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1419 , http://hdl.handle.net/10962/d1003300
  • Description: Traditional school subjects are having to compete for a place in a curriculum which is increasingly judged according to its perceived utilitarian value. According to current educational theory, geography's role in the curriculum is to develop concepts, skills, values and attitudes that allow pupils to understand the human and environmental issues which face their communities and communities throughout the world. In order to achieve these aims, teachers need to adopt a learner-centred teaching approach, yet geography teachers are faced with the dilemma of having to develop participatory teaching strategies within an existing structure which is largely product oriented. This thesis attempts to illustrate how changes can be effected in the approach to the teaching of geography, while working within existing syllabus constraints and while continuing to meet the demands made by the current examination system. To this end, Independent Study Topics are analysed as a means to bring about the desired changes in geographical education. The concept, Independent Study Topics as a 'blanket term' (Diepeveen, 1986) for pupil-centred activities is relatively recent in terms of the South African geography syllabus. In order to obtain greater clarity about the concept and its implications for geography teaching, this study examines current geographical theory relating to learner-centred approaches and relates them to teachers' perceptions of the role of IST in the geography curriculum. The second aspect of the study is concerned with the implementation of Independent Study Topics in a classroom research setting. The organisation and administration of Independent Study Topics in a single school setting is analysed and evaluated as a process of change. This analysis provides guidelines for developing a learner-centred approach which is necessary to ensure that geography retains its position in the school curriculum of the 1990's and beyond.
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  • Date Issued: 1992

Phenology of the important coleopterous pests of pine forests in the Western Cape, South Africa

- Tribe, Geoffrey Darryl

  • Authors: Tribe, Geoffrey Darryl
  • Date: 1992
  • Subjects: Beetles -- South Africa Bark beetles -- South Africa -- Cape of Good Hope Scolytidae Phenology -- South Africa Phenology -- South Africa -- Cape of Good Hope
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5737 , http://hdl.handle.net/10962/d1005423
  • Description: The phenology of the three exotic pine bark beetles present in South Africa was determined in the south-western Cape Province. Results from weekly trapping of adult beetles using trap-logs over a period of five years showed that the different species had activity peaks at different times of the year. Hylastes angustatus was the most consistent with 95% of the beetles captured in September and October. The Orthotomicus erosus activity peak was more variable but always occurred in the summer months (October to February) when 84% of the beetles were captured. Hylurgus ligniperda was the most variable, being found in every month of the year, although an autumn peak representing 37% of the beetles occurred in April/May. Activity peaks of each species coincided with distinct climatic conditions. Buried and partially-buried pine logs placed vertically in the soil to simulate roots and stems of seedlings were used to determine the colonisation sites of the three bark beetle species. Ninety-eight percent of O. erosus beetles were found in the protruding parts of the logs while 86% of H. ligniperda beetles were found mainly below soil level. H. angustatus were intermediate, entering the logs at or just below the soil interface but colonising mainly the buried parts in which 64% of the beetles were found. Both H. angustatus and H. ligniperda were able to detect and colonise logs buried horizontally at depths of 400mm, but O. erosus beetles were unable to do so. For adequate protection of seedlings from bark beetles, insecticide should be applied to both stems and roots. The phenology of the indigenous pine needle feeders Oosomus varius (Curculionidae) and Prasoidea sericea (Chrysomelidae) was determined by counting, at weekly intervals, the number of beetles present on 10 young pine trees. The O. varius activity peak occurred in August where 42% of all beetles were active, with 87% of the beetles present in July, August and September. P. sericea also had their activity peak in August when 60% of all beetles were active, but with August and September alone accounting for 87% of the beetles. The occurrence of the activity peaks was consistent each year over the five-year study period. This information facilitates the correct timing of prophylactic insecticide sprays.
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  • Date Issued: 1992

The surface geology of the Lavino Chrome Mine of the farm Grootboom 336KT, eastern Transvaal

- Tinney, Christopher Bruce

  • Authors: Tinney, Christopher Bruce
  • Date: 1992
  • Subjects: Chromium ores -- Geology -- South Africa -- Mpumalanga
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5067 , http://hdl.handle.net/10962/d1013404
  • Description: A mapping project of the surface geology of the Lavino chrome mine and its surroundings was initiated in order to establish the surface geological relationships in the area. In so doing the chromitite layer presently being mined has been identified and potential exploration targets in the area have been outlined. The Lavino Chrome mine field area is situated within the eastern lobe of the Bushveld Igneous Complex. The area is bounded by in the north by the Steelpoort Lineament, in the west by the Dwars River fault and in the east by the contact with the Transvaal Sequence floor rocks. Layered igneous rocks (pyroxenites, norites and anorthosites) of the Rustenburg Layered Suite dominate the geological landscape at the Lavino mine. The fact that outcropping igneous rocks of the Critical Zone abut directly against the quartzite floor rocks on the mine property makes this area unique in the Bushveld Complex. The hills in the field area are capped by mafic/ultramafic iron-rich sheet - like bodies. Extensive strike-slip faulting is seen in outcrop in the area to the north/northwest of present mining operations. On the basis of field relationships, the main chromitite layer presently being mined at Lavino is identified as the Middle Group chromitite layer MG 1. Three other prominent chromitite layers stratigraphically associated with MG 1 are identified as the Middle Group chromitites MG 2, MG 3 and MG 4. Several other less prominent outcropping chromitite layers are tentatively identified as those belonging to the Lower and Upper group of chromitites. The disconformable nature of the contact between the layered igneous rocks and the Transvaal Sequence floor rocks has resulted in the development of a wedge of undifferentiated pyroxenites in the north of the field area. The economically important LG 6 chromitite layer may be developed in subcrop within this wedge.
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  • Date Issued: 1992

"Constructive critic" or "donor agency": does the World Bank have a role to play in sub-Saharan Africa's development beyond that of providing economic aid?

- Thompson, Christine Audra

  • Authors: Thompson, Christine Audra
  • Date: 1992
  • Subjects: Africa, Sub-Saharan -- Economic conditions -- 20th century , World Bank -- Africa, Sub-Saharan , Africa, Sub-Saharan -- Economic conditions
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2835 , http://hdl.handle.net/10962/d1003045 , Africa, Sub-Saharan -- Economic conditions -- 20th century , World Bank -- Africa, Sub-Saharan , Africa, Sub-Saharan -- Economic conditions
  • Description: This thesis attempts to evaluate the role of the World Bank in Sub-Saharan Africa's development. It argues that the World Bank has stepped beyond the boundaries of a typical lending institution by linking its aid to political reform. The study argues that in this capacity the Bank has contributed to the halting democratization process currently underway in Africa. The economic effects of the World Bank's Structural Adjustment Programmes have been less successful. As yet, the programmes have not produced the expected results and there is no evidence of long-term, sustainable economic recovery in Sub-Saharan Africa. These programmes are, however, long-term strategies and it may therefore be too premature to reach a final conclusion. They may also have been affected negatively by unfavourable political environments. This study, noting the negative effects of the international terms of trade and prices for African exports, concludes that although economic recovery in Sub-Saharan Africa will be facilitated by domestic political and economic policy reform, there is also a need for reform of the international economic order. The World Bank has correctly identified the need for domestic improvement, but it has a tendency to disregard the negative consequences of the existing structure of the international economy.
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  • Date Issued: 1992

A cost-benefit analysis of electricity supply in a developing country, with reference to Venda

- Themeli, Tshimangadzo Booi

  • Authors: Themeli, Tshimangadzo Booi
  • Date: 1992
  • Subjects: Electrification -- Economic aspects -- South Africa -- Venda , Electric utilities -- South Africa -- Venda , Cost effectiveness , Electrification -- Cost effectiveness
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:1022 , http://hdl.handle.net/10962/d1002757 , Electrification -- Economic aspects -- South Africa -- Venda , Electric utilities -- South Africa -- Venda , Cost effectiveness , Electrification -- Cost effectiveness
  • Description: This study concentrates specificaUy on assessing those elements of private and external costs and benefits which need to be accounted for in analyzing the role of electricity supply in a developing region. To facilitate this aim, three interrelated questions are addressed. The first question examines the reasons why a critical need for electrification in developing areas exists. In this regard, a selective review of the literature on development economics is offered, illuminating the previous neglect of the rural dimension in development and the associated problems of poverty and inequality, a lack of infrastructure and the general inability to fulfill basic needs. The second question is devoted exclusively to an economic analysis of the supply of electricity in developing areas. A broad theoretical review on whether an unregulated or regulated (private or public) sector should be responsible for the provision of electrification is presented. This evaluation highlights the various welfare implications and efficiency considerations that appear to be relevant in the present context. The final question, which constitutes the central proposition of the thesis, establishes how electrification should be supplied in developing areas. To this end, the conditions specific to a region in Venda are discussed. An attempt is made to identify the private and external costs and benefits relating to electricity supply and the corresponding costs and benefits pertaining to alternative sources of energy. Since the incidence and nature of these costs and benefits could only be ascertained from individual households, it was deemed necessary to undertake a questionnaire study of residents in Makwarela township and its periurban settlement of Lufule-Tshisele. A number of basic trends were evident from the research results. As far as the various benefits are concerned, respondents tended to place a much higher value on both the private and external benefits associated with electricity than its alternatives. At the same time, the survey found that although the private (or monetary) cost of electricity far exceeded the corresponding cost of alternative energy sources, the external costs were significant in the case of alternative energy sources, but virtually non-existent in the case of electricity. On the whole, the Venda survey seems to suggest that an economic case can be made for involving the broader community in subsidising the supply of electricity in Makwarela, Lufule-Tshisele and other areas. While such a subsidy can perhaps be justified on distribution grounds alone, and more specifically in terms of the rapid and pronounced effect it is likely to have on the quality of life in the region, its real worth lies in the fact that it may confer certain external benefits on the community.
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  • Date Issued: 1992

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

- Terespolsky, Susan Ann

  • 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

Exploratory studies of novel ligand systems

- Taylor, Steven John

  • Authors: Taylor, Steven John
  • Date: 1992
  • Subjects: Ligands , Coordination compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4315 , http://hdl.handle.net/10962/d1004973 , Ligands , Coordination compounds
  • Description: A range of novel ligand systems have been developed in three distinct phases and preliminary studies have been initiated to evaluate their complexation potential. Phase I incorporated the synthesis of single strand ligand systems, which were mainly based on amino acid residues. Techniques have been developed for the attachment of these ligand systems onto, firstly, a styrene monomer, and then later onto a pseudo-styrene linking group, viz. the p-toluoyl group. The linking reactions were based on the formation of amides or esters by the reaction of an acid chloride system with an amine or alcohol. Phase II involved the synthesis of bis-chain ligand systems and their attachment onto the p-toluoyl linking group. A further linking group was also developed at this stage, viz. the xylyl group. In the preparation of phase II ligand systems, use was made of malonic ester and iminodiacetic acid derivatives. Phase III has involved the synthesis of cyclic ligand systems, with skeletons based upon the structures used in phase I and phase II and two crown ether type systems have been prepared.
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  • Date Issued: 1992

The evaluation of indomethacin and theophylline oral controlled/modified-release dosage forms in vitro-in vivo correlations

- Tandt, Ludo Alfons Germaan Luc

  • 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.
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  • Date Issued: 1992

The chemistry of a new water-recirculation aquaculture system with emphasis on the influence of ozone on water quality

- Stobart, Michael David

  • Authors: Stobart, Michael David
  • Date: 1992
  • Subjects: Water quality -- Environmental aspects -- Testing , Ozone -- Physiological effect , Aquatic ecology , Aquaculture
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5244 , http://hdl.handle.net/10962/d1005087 , Water quality -- Environmental aspects -- Testing , Ozone -- Physiological effect , Aquatic ecology , Aquaculture
  • Description: Water quality changes that occur during establishment and maintenance of nitrification in two identical recirculating aquaculture systems containing rainbow trout are described. The time taken for the nitrification process to become established was 40-45 days. Mortality of fish attributed to elevated nitrite concentrations were recorded during the initial conditioning phase of the systems. Un-ionised ammonia concentrations did not attain lethal levels during this period. Nitrate concentrations accumulated slowly throughout the study, while the pH and alkalinity of the water decreased with progressive nitrification. Levels of carbon dioxide, calcium, dissolved and suspended solids remained relatively stable until the carrying capacity of the systems was increased, upon which they increased rapidly and general water quality deteriorated. Permanently elevated concentrations of ammonia and nitrite served as an indication that the carrying capacity of the systems had been exceeded. The use of ozone as a water enhancement treatment in aquaculture systems during one- and six-hour applications was also considered in this study. Ozonation significantly reduced nitrite levels at · low concentrations (0,1 - 0,15 mg/l), although they returned to pre-treatment levels within a few hours of cessation of the treatment. The formation of an unstable, intermediate product that reforms as nitrite in the absence of ozone, rather than the complete oxidation of nitrite to nitrate, is proposed. Ozonation also resulted in decreased dissolved solids, and improved the clarity and odour of the water. Ozone had no effect on ammonia concentrations (at pH > 7,0), or on nitrate or calcium levels, and did not conclusively increase the redox potential of the water. Residual ozone concentrations up to 0,04 mg/l in a sixhour treatment had no harmful effects on rainbow trout, and there were no signs of gas-bubble disease arising from supersaturation of the water with oxygen. Activated carbon filters were effective at removing residual ozone from the water after treatment. Treatment of the water with oxygen alone had no effect on nitrite concentrations.
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  • Date Issued: 1992
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