A hydrogeological investigation of the Grootegeluk mine
- Authors: Johnstone, Andrew Clifford
- Date: 1989
- Subjects: Hydrogeology -- South Africa Coal mines and mining -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4795 , http://hdl.handle.net/10962/d1001895
- Description: The study concerns an assessment of the hydrogeological impact of an open cast coal mine in the North Western Transvaal Province of South Africa. The hydrogeological impact of the mine is assessed in terms of groundwater quality and levels. A monitoring system was installed to enable the present and future impact of mining operations on the hydrogeological regime to be assessed. Grootegeluk Mine is situated in the Waterberg Coal Field of South Africa and began production in 1980. The mine extracts fifteen million tons of mine material annually from a single open pit. Forty percent of the mined material is saleable product and the remaining sixty percent is stacked on discard dumps. The Daarby fault forms the northern boundary of the open pit and serves to bring the younger Letaba and Clarens Formations into contact with the older Beaufort and Ecca Groups. The mine discards are deposited north of the fault on a different hydrogeological environment from which they are mined. Dewatering of the mine open pit has resulted in a steady decline in water levels in the Ecca Group, south of the Daarby fault. In contrast, water levels north of the Daarby fault in the Letaba and Clarens Formations have risen. The short term hydrochemical impact of the mine discard dumps and slimes dams have resulted in a rise in the calcium, sulphate, chloride, fluoride and nitrate concentrations of the ambient groundwater . The longer term hydrochemical impact from the waste dumps, acid mine drainage, is not evident at present in the groundwater below the waste dumps. However, it is expected to manifest itself during the next ten years. A monitoring system was installed at the mine to allow groundwater levels and quality to be monitored. By measuring groundwater quality and levels the impact of the mine on the regional hydrogeology can be monitored and assessed presently, and during the next forty years of production. Monitoring will also enable the timeous implementation of remedial measures at an early stage and eliminate the need for large late stage "clean up" operations. Future monitoring of both water levels and quality will be crucial in evaluating the mine's impact on the regional groundwater regimes over the next forty years of production. The remedial measures recommended for leachate presently emanating from the waste dumps and slimes dams north of the Daarby fault, are a number of collector wells drilled into the basalts and sandstone north of the Daarby fault. The proposed positions of the wells (boreholes) are as close as possible to the dumps and slimes dams with expansion taken into consideration. The boreholes should be designed to lower the water level in the vicinity of the dumps in order to create a nett groundwater gradient towards the dumps and as a result, halt the spread of leachate away from the dumps. Grootegeluk plans to backfill the open pit with plant discards on completion of the mining of zone 2. The backfilled material will consist of the currently produced plant waste and will be covered with overburden and topsoil. It is expected that the backfilling will have a major impact on groundwater quantity if no remedial measures are implemented. The two remedial measures discussed are chemical treatment of the discard material before backfilling or the continual abstraction of water from the pit resulting in a nett groundwater inflow into the pit. No material from the present waste dumps and slimes dams will be transported into the open pit as backfill material
- Full Text:
A possible mechanism for enzymic depilation of skins
- Authors: Brady, Dean
- Date: 1989
- Subjects: Chemistry, Technical , Tanning
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3877 , http://hdl.handle.net/10962/d1001611
- Description: Streptomyces fradiae is a bacterium which has been previously found to produce extracellular enzymes which are capable of wool degradation and skin depilation. Streptomyces fradiae 3739 and other strains of Streptomyces were found in this study to be able to degrade a keratin source (wool) to a considerable degree. However according to the evidence of SEM micrographs presented here the highly keratinised spindle cells of the paracortex are fairly resistant to protease attack, and it is the cementation material which binds these cells together which is initially degraded by the proteases. A large degree of correlation was found with the strains of Streptomyces studied, between the ability of the individual strains to degrade wool and the ability of their extracellular proteases to reduce the depilation load of sheepskins. With further analysis S. fradiae 3739 was found to produce at least one amylase and four or more proteases. The proteases as a group had maximal proteolytic activity in the 8.0-9.0 pH unit range, and were considerably thermostabilised by the inclusion of calcium ions into the reaction solution. The protease group was found to cause depilation of merino sheepskins. For comparative purposes a protease produced by a strain of Proteus vulgaris isolated from a staling hide with hair slip (natural depilation) was studied. The protease activity was maximal in the alkaline region between 8.0-9.0 pH units. Tbe protease appeared to be a single enzyme with a molecular mass of approximately 44 000 daltons. The protease was maximally active at 40°C, although it was only thermostable to 30°C. The enzyme was ineffectual as a depilant except when the skin was pre-treated with a strong alkali, preferably including sodium sulphite in the protease preparation. One of the most important differences between the extracellular proteases of S. fradiae and P. vulgaris was that the former were greater in variety and caused a greater decrease in the depilation load of sheepskins than the latter. Further research with mixtures of commercial proteases provided evidence that a synergistic depilatory effect occurs when proteases of complementary bond specificities are used in conjunction in enzymic depilatory preparations. Some form of strong alkali treatment of skins was found to be necessary to produce leather of the prerequisite quality when the skin was depilated by proteases, otherwise the skin was found to be depleted and stiff. Calcium hydroxide alone was found to be inadequate for this task, probably owing to the fact that it is less alkaline than the lime-sulphide mixture. The calcium hydroxide (lime) must therefore be used in conjunction with sodium hydroxide (which makes the solution as alkaline as that of the lime-sulphide solution) to produce leather comparable to that produced by the lime sulphide treatment. A combination of the information provided by the present research and that gleaned from the relevent literature allows for the construction of a model to represent the possible mechanism of enzymic depilation of skins, in which depilation is caused by the disruption of the basement membrane at the dermal-epidermal junction by the degradation of its constituent molecular components by general proteases, resulting in the removal of the epidermis and its associated wool or hair
- Full Text:
An adaptive discrete cosine transform coding scheme for digital x-ray images
- Authors: Mclean, Ivan Hugh
- Date: 1989
- Subjects: X-rays -- Digitization Image processing -- Digital techniques Diagnostic imaging Computer storage devices
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4567 , http://hdl.handle.net/10962/d1002032
- Description: The ongoing development of storage devices and technologies for medical image management has led to a growth in the digital archiving of these images. The characteristics of medical x-rays are examined, and a number of digital coding methods are considered. An investigation of several fast cosine transform algorithms is carried out. An adaptive cosine transform coding technique is implemented which produces good quality images using bit rates lower than 0.38 bits per picture element
- Full Text:
An assessment of the South African longline fishery with emphasis on stock integrity of kingklip, Genypterus capensis (Pisces : ophidiidae)
- Authors: Japp, David William
- Date: 1989
- Subjects: Genypterus capensis , Ophidiidae , Fisheries -- South Africa , Longlining (Fisheries) -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5209 , http://hdl.handle.net/10962/d1004660 , Genypterus capensis , Ophidiidae , Fisheries -- South Africa , Longlining (Fisheries) -- South Africa
- Description: The South African demersal longline experiment is assessed with emphasis on the target species, kingklip Genypterus capensis. The hypothesis that kingklip on the South African coast comprise a unit stock is tested. Recommendations for the management of the fishery are made. Longlining was found to be commercially viable. Techniques have been developed to target on either kingklip or the Cape hakes, Herluccius capensis and H. paradoxus. Longline fishermen exploit the kingklip spawner stock from August to No v ember by taking advantage of prespawning aggregations on the South-East Coast . Effort switches to the West Coast in late summer and early winter where kingklip are less abundant and a larger proportion of hake is caught. Catch rates of kingklip on the South Coast have declined sharply and the resource there has been exploited at a rate greater than that required to retain 50% of the unexploited biomass . There is a 17,6% probability that the spawner biomass on the South Coast has already been depleted below its pristine level. On the West Coast the catch rates of kingklip are lower than on the South Coast and have not changed significantly, although within the 95% confidence limits there is a possibility that the resource there has also been depleted below 50% of its pristine level. Genypterus capensis on the South African coast comprise a unit stock. Comparison of kingklip morphology using multivariate and discriminant function analysis and of otolith morphology using univariate statistics shows that there are no significant differences between the fish on the West and South Coasts. They are a slow growing species and were aged up to 25 years. Kingklip on the West Coast are smaller and have a lower L~ than those on the South Coast, but this is not a characteristic of discrete stocks. Kingklip on the South Coast mature earlier than those on the West Coast and aggregate to spawn on the South - East Coast in spring. There is no obvious spawning period on the West Coast. It is hypothesized that kingklip spawning on the South-East Coast is in response to favourable environmental conditions that enhances the survival of their eggs and larvae. It is recommended that demersal longlining be established as a permanent kingklip-directed fishery but that effort should not be allowed to increase. The West and South Coasts should be managed .separately. A TAC of 5 OOOt for kingklip should be introduced for 1989 of which 2 OOOt should be allocated to the West Coast and 3 OOOt to the South Coast . A closed season for kingklip from 1 August to 30 September on the South-East Coast is recommended. Hake-directed longlining should not be allowed as its effect on the hake spawner stocks are unknown and could be a potential threat to the stability of the demersal trawl fishery.
- Full Text:
An investigation into the dietary requirements of Oreochromis Mossambicus fry and the formulation and preparation of a dry food for use in aquaculture
- Authors: Thorpe, Peter Stuart
- Date: 1989
- Subjects: Cichlids , Tilapia -- Nutrition , Aquaculture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5184 , http://hdl.handle.net/10962/d1001960 , Cichlids , Tilapia -- Nutrition , Aquaculture
- Description: The need for developing a dry feed which satisfied the nutrient requirements of Oreochromis mossambicus fry was identified. The spawning and grading techniques which resulted in a higher fecundity and ensured uniformity within and between samples of fry are discussed. Preparation techniques were developed which met the physical requirements of fry feeds. An analysis of the flesh and yolk sac fry for amino acid composition was undertaken. The initial test diet was based on these results, as well as on the natural feeding ecology of the species. Feeding trials were undertaken and growth responses monitored to determine the optimum levels of the various dietary components. A feed was developed which gave superior growth to that obtained with natural food organisms. This feed consisted of Torula yeast (47%), Weider Super Protein (44.39%), Vitamin supplement (0.45% - multivitamin), additional vitamin C supplement (0.16%), Spirulina (5%), and methionine supplement (3%). An optimum particle size range for O. mossambicus fry (between 5 & 25mm) was established at 125-200um. The fry should be fed the following feed ratios depending on age: 30.4% body weight/day up to day 5, 30.6% body weight/day up to day 10 and 25.1% body weight/day up to day 15. An optimum feeding frequency of 8/10hr day was recommended. A feed conversion ratio of 1.24:1 and a protein efficiency ratio of 0.682:1 was obtained. Digestable energy of the feed was determined at 16.1 kj/g feed. The established dry feed is suitable for use in commercial hatcheries, and as a formulation for further research on the intensive rearing of O. mossambicus fry.
- Full Text:
An investigation into the properties of cotton fibres as used in nonwoven fabrics
- Authors: Lutseke, Nothando Sazikazi
- Date: 1989
- Subjects: Cotton -- Analysis , Fibers -- Analysis , Nonwoven fabrics -- Analysis , Textile chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4552 , http://hdl.handle.net/10962/d1018241
- Description: The purpose of this investigation was to determine the properties that characterise cotton fibres in the various stages in the CPNF process as well as to determine which fibre characteristics a r e required to entangle the fibres to produce a successful CPNF . The criteria adopted in this work for a successful CPNF include: 1. the tensile strength of the fabrics 2. a well-defined pattern 3. absorbency and wicking The properties selected for investigation were 1. the cotton fibre surface (using SEM and DSC analyses) 2. the degree of degradation of the cotton fibre as a result of the CPNF process (using cellulose fluidity measurements) 3. the non-cellulosic content of the fibre (using IR, DSC, and Chemical analyses) 4. fibre friction 5. absorbency and wicking 6. tensile properties Analysis of the results indicates clearly what the fundamental properties of the cotton fibre must be for a successful cotton CPNF to be manufactured. The conclusions also indicate the necessary properties a man-made fibre must have to produce a successful CPNF.
- Full Text:
Apneic Bradycardia : terrestrial and aquatic responses in man under working conditions
- Authors: Manley, Elizabeth
- Date: 1989
- Subjects: Apnea Respiration -- Measurement Heart rate monitoring Work -- Physiological aspects Underwater -- Physiology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5098 , http://hdl.handle.net/10962/d1001838
- Description: The focus of this research was the reappraisal in physiological and psychophysical terms of current equivocal theories regarding the onset, course and termination of apneic bradycardia. Sixteen healthy male subjects participated in four separate testing sessions . Maximal oxygen consumption (VO₂ max) was measured on land and underwater using an identical direct, continuous progressive cycle ergometer test. On each of two other occasions subjects exercised in either environment at 50, 70 and 90% of the appropriate VO₂ max, during which time heart rate was continuously recorded. An initial apneic bout at each exercise intensity was followed by performance of the same workload without apnea for an equivalent period of time. Ratings of perceived exertion (RPE) were also monitored. While apneic bradycardia occurred at each exercise intensity studied underwater, it was apparent only at 50% VO₂ max on land. With the exception of between 50 and 90% VO₂ max on land, the mean apneic heart rates did not differ with varying exercise intensity (p<0.05); nor did the lowest heart rate recorded, although this was lower underwater than on land. Apart from 70% VO₂ max on land, apneic heart rates were lower than the equivalent values measured during exercise without apnea. Land and underwater heart rates during apneic and non-apneic conditions did not differ until 90% VO₂ max. The effects of increasing exercise intensity upon the onset of bradycardia were evident in that it occurred earlier at 50% VO₂ max underwater than at the heavier workloads, and only at 50% VO₂ max on land. The mean breath-hold duration did not differ between the land and underwater environments, nor was it affected by increasing exercise intensity. The order in which breath-holds was performed did not alter the length of apnea. Land and underwater RPE did not differ and increased with increasing exercise intensity in both environments. During apneic exercise RPE was greater than the equivalent exercise without apnea. Twelve of the original 16 subjects were divided equally into two groups on the basis of vital capacity expressed relative to body surface area. Vital capacity was measured during the first laboratory session. Neither the mean heart rate response to apneic exercise at 50% V0₂ max in both environments, nor the lowest heart rates recorded differed between groups, prompting the conclusion that lung volume did not affect apneic bradycardia. Despite a longer breath-hold duration for Group A (large relative lung volume) than Group B (small relative lung volume), the onset point of bradycardia was the same for either group when expressed relative to total breath-hold duration
- Full Text:
Assessment of factors influencing the quality of surface and ground water in the Hout Bay river catchment
- Authors: Pearce, Meryl Winsome
- Date: 1989
- Subjects: Water -- South Africa -- Hout Bay Hydrology Water -- Pollution -- South Africa -- Hout Bay Water quality -- South Africa -- Hout Bay Aquatic ecology Water quality Hout Bay river (South Africa) Groundwater -- South Africa -- Hout Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4800 , http://hdl.handle.net/10962/d1001900
- Description: An investigation into the quality of surface water and ground water was conducted during 1988 in the 38,8 km² Hout Bay River catchment near Cape Town. The main objective of the study was to determine those areas and activities which constitute a pollution source and to ascertain the relative proportion which each contributes to the pollution problem and health risk of the surf zone of the beach at Hout Ba . The objective was achieved by monitoring the chemical and microbiological attributes of the Hout Bay River, its tributaries and stormdrains in wet and dry conditions on a routine basis and during storm events. Hout Bay is a rapidly developing residential area in which sewage disposal occurs by means of septic tank soakaway systems. Ground water quality was monitored to investigate the contribution to contamination by septic tank effluent. Results showed that stormdrain effluent in dry and wet conditions and surface runoff during rainfall were the main vectors of pollution. Although the pollution concentration was high during dry conditions the greatest pollution discharge to the surf zone of Hout Bay occurred during storm events. In view of the proposed residential development it is imperative that pollution control measures be undertaken so as to secure the future recreational and aesthetic value of Hout Bay
- Full Text:
Comparison of different notions of compactness in the fuzzy topological space
- Authors: Morapeli, E Z
- Date: 1989
- Subjects: Fuzzy mathematics Fuzzy topology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5393 , http://hdl.handle.net/10962/d1001982
- Description: Various notions of compactness in a fuzzy topological space have been introduced by different authors. The aim of this thesis is to compare them. We find that in a T₂ space (in the sense that no fuzzy net converges to two fuzzy points with different supports) all these notions are equivalent for the whole space. Furthermore, for N-compactness and f-compactness (being the only notions that are defined for an arbitrary fuzzy subset) we have equivalence under a stronger condition, namely, a T₂ space in the sense that every prime prefilter has an adherence that is non-zero in at most one point
- Full Text:
Energetic and kinematic responses to morphology-normalised speeds of walking and running
- Authors: Williams, Martin Andrew
- Date: 1989
- Subjects: Running -- Physiological aspects , Walking -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5166 , http://hdl.handle.net/10962/d1016240
- Description: This study investigated the influence of human morphology upon selected physiological, biomechanical and psychological responses to horizontal locomotion. In so doing, it was possible to evaluate the effectiveness with which morphology-normalised speeds of walking and running reduced the between-subject variability that is inherent in human locomotor responses. Twenty caucasian males were divided into two groups on the basis of stature - ten subjects in each of a "short" category (<170cm) and a "tall" category (>185cm). All subjects were habituated to treadmill locomotion prior to exposure to three walking treatments (0.83, 1.39 and 1.94m.s⁻¹) and three running treatments (2.50, 3.06 and 3.61m.s⁻¹). During each of these five-minute locomotor conditions, energetic (V02), kinematic (cadence and stride length) and psychophysical (central and local RPE) data were captured. From these data, lines of best fit were calculated for each subject, allowing for a prediction of the abovementioned locomotor variables from known absolute rates of progression. Using suitable regression equations, subject responses to morphology-normalised speeds of walking and running were effectively extrapolated. When the rate of progression was expressed in absolute terms (m.s⁻¹), significant differences (P <0.05) were found between the stature-related groups with respect to both energetic and kinematic locomotor responses. Such differences were successfully eliminated when use was made of locomotor speeds relativised on the basis of morphology. This study concludes that the use of appropriately prescribed morphology-normalised rates of progression are effective in reducing the variability in locomotor responses between subjects differing significantly in stature.
- Full Text:
High-performance liquid chromatographic studies of the acid degradation, pharmacokinetics and comparative bioavailability of erythromycin
- Authors: Glew, Fiona
- Date: 1989
- Subjects: High performance liquid chromatography , Erythromycin -- Analysis , Erythromycin -- Pharmacokinetics , Erythromycin -- Bioavailability
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3737 , http://hdl.handle.net/10962/d1001529
- Description: Erythromycin is a macrolide antibiotic with a spectrum similar to penicillin and is used mainly in the treatment of infections caused by gram-positive organisms. Since its discovery in 1952, erythromycin has achieved wide-spread clinical use. Susceptibility of erythromycin base to inactivation by acid results in decreased availability following exposure to acidic gastric fluids. Formulation of acid resistant dosage forms and the preparation of acid stable chemical derivatives have been attempted to improve absorption and subsequent clinical efficacy . Two of the most commonly used erythromycin derivatives are the stearic acid salt (erythromycin stearate) and the lauryl sulphate salt of the propionyl ester (erythromycin estolate). Although it has been known for many years that erythromycin is susceptible to acid degradation, very few reports on the stability of erythromycin in aqueous solutions appear in the literature. In this study, a high-performance liquid chromatographic system using electrochemical detection was employed for a kinetic study of erythromycin degradation. The effect of varying acid pH on the degradation rate of both erythromycin base and erythromycin stearate, and the effect on the hydrolysis rate of erythromycin estolate is presented. In addition, the effect of temperature on erythromycin degradation was also investigated. Until recently, the majority of pharmacokinetic and bioavailability studies have utilized relatively non-specific microbiological assay procedures. However, in this study a solid phase extraction, followed by the use of a high-performance liquid chromatographic system using electrochemical coulometric detection was employed for the determination of erythromycin in biological fluids. Human volunteers each received enteric coated erythromycin base pellets in capsule dosage form and also film coated erythromycin stearate tablets on separate occasions. Results from the clinical trials revealed the enteric coated erythromycin base pellets had a greater bioavailability than the film coated erythromycin stearate tablets. Computer fitting of data revealed no intra-volunteer variability in elimination rate constants, suggesting differences in serum levels following administration of both dosage forms are due to variation in absorption. Results from the clinical trials were also compared with those obtained from a further trial, during which the same volunteers received erythromycin estolate
- Full Text:
Interactions between ants, herbivorous insects and bracken (Pteridium aquilinum), a fern with extrafloral nectaries
- Authors: Rashbrook, Vanessa Karin
- Date: 1989
- Subjects: Arthropod pests -- South Africa Ants -- South Africa Ferns -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5592 , http://hdl.handle.net/10962/d1002042
- Description: Bracken (Pteridium aquilinum) is a cosmopolitan species of fern which possesses extrafloral nectaries. A survey of the arthropod fauna associated with the plant throughout its range in South Africa identified the most widespread and damaging bracken herbivores and those species most likely to be influenced by ants visiting the extrafloral nectaries. Seventeen herbivorous arthropods were found to be definitely feeding on bracken and a further thirteen species with a less certain status were recorded. In addition, several species of ants were observed on the fronds and feeding at the extrafloral nectarie. On the basis of their widespread distribution and abundance, four bracken herbivores emerged as being particularly detrimental to the plant in South Africa. They were an eriophyid gall mite, a leafhopper and two moths. The biology of the two lepidopterans, Appana cinisigna and Panotima sp., suggested that they were potentially vulnerable to ants at various stages of their life histories. Laboratory experiments were undertaken to observe ant-lepidopteran interactions under controlled conditions. The ant Crematogaster peringueyi rapidly removed exposed A. cini igna eggs, but did not appear to regard Panotima eggs as food items. Small instar larvae of both species proved vulnerable, but the larger larvae appeared capable of escaping ant predation. Ant exclusion experiments in the field, using natural and artificially augmented ant densities, were carried out at two sites near Grahamstown. The dominant ant species was C. peringueyi. Neither the numbers of lepidopterans nor levels of herbivory were significantly reduced by the presence of ants . Despite the implications of the laboratory tests, the results of these field experiments did not support the hypothesis that ants which visit bracken extrafloral nectaries benefit the plant. Ant-bracken field studies on other continents also reported no significant ant-related effects, though marginal reductions in the abundance of certain herbivores have been noted at one site in the U.K. Since ant protection does not appear to be an inevitable consequence of having extrafloral nectaries, their value to bracken is in some doubt. The most likely situation where effective protection will occur is when high densities of vulnerable herbivores are preyed upon by large numbers of aggressive ants. However, even under these conditions, enhancement of plant fitness is not inevitable. This raises the question of why extrafloral nectaries have been retained in a plant that is as successful and widespread as bracken.
- Full Text:
Investigation of the causative agents of the 1982 Gazankulu poliomyelitis outbreak, using four biochemical techniques
- Authors: Gibson, Katherine Margaret
- Date: 1989
- Subjects: Poliomyelitis -- Analysis , Poliomyelitis -- History -- South Africa , Poliomyelitis vaccine -- Analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3878 , http://hdl.handle.net/10962/d1001612
- Description: Comparison of poliovirus strains was carried out to determine the origin of the virus in two isolates obtained during the 1982 outbreak of poliomyelitis in Gazankulu. Comparisons of the outbreak isolates with vaccine and wild-type strains of the same poliovirus type were carried out using four biochemical techniques. SDS-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional thin-layer chromatography (TLC) and reversed-phase high-performance liquid-chromatography (RP-HPLC) were used for comparing viral capsid proteins. Comparison of poliovirus strains at a genetic level was carried out using two-dimensional oligonucleotide mapping of viral RNA. Results showed the type 1 poliovirus isolate, 5061, to be a novel wild-type poliovirus. The type 2 isolate, 5068, was closely related to the poliovirus type 2 Sabin vaccine strain, P712. It was concluded that the intrinsic variability of poliovirus strains was responsible for the appearance of isolate 5068
- Full Text:
Isolation, purification and effect of ligands on the nicotinic cholinergic receptor
- Authors: Kapp, Eugene Anthony
- Date: 1989
- Subjects: Ligands (Biochemistry) , Nicotinic receptors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4550 , http://hdl.handle.net/10962/d1018235
- Description: The nicotinic cholinergic receptor protein of the fish electric organ, Torpedo fuscomaculata, has been isolated, purified and shown to represent a true model for the nAChR from other species and higher vertebrates. It is an integral membrane protein composed of four different subunits, tightly associated with other functional, but non-specific proteins. Purification of the nicotinic cholinergic receptor by chromatofocusing demonstrates an improved method over that of affinity and ion-exchange chromatography. Gel chromatography and SDS-polyacrylamide gel electrophoresis show evidence of four subunits; a(40-44 kDa), 6(53 kDa ),'Y(63 kDa) and 6(66 kDa) despite some degradation of receptor molecules by intracellular proteases. Spectrophotometric and fluorimetric studies of receptor-ligand interactions, show the functional and chemical integrity of the receptor to remain intact after solubilisation. The effect of cholinergic ligands on purified receptor preparations indicate quenching of the intrinsic fluorescence of the receptor. Agonists, like acetylcholine, bind and cause local conformational transitions, changing the active region from a hydrophobic to a hydrophilic environment. This phenomenon is illustrated by the 10-fold increase in fluorescence when the receptor is in a desensitised state. Antagonists, such as d-Tubocurarine, block this conformational transition. In vitro rectus abdominis muscle preparations . show the nitrosamines, dimethylnitrosamine and diphenylnitrosamine, to be true agonists of the nAChR. However their low affinity and specificity for the receptor precludes them as photoaffmity labelling agents. Photoactivation of dimethylnitrosamine occurs when associated with an acidic hydrogen at the active site of the receptor, suggesting energy-transfer labelling to be more facile than photoaffmity labelling. The membrane-bound receptor, in the presence of these nitrosamines, undergoes conformational transitions regulating the opening and closing of the ion-channel. Desensitisation and receptor activation are shown to involve one and the same molecular transition.
- Full Text:
Parallel process placement
- Authors: Handler, Caroline
- Date: 1989
- Subjects: Parallel programming (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4568 , http://hdl.handle.net/10962/d1002033
- Description: This thesis investigates methods of automatic allocation of processes to available processors in a given network configuration. The research described covers the investigation of various algorithms for optimal process allocation. Among those researched were an algorithm which used a branch and bound technique, an algorithm based on graph theory, and an heuristic algorithm involving cluster analysis. These have been implemented and tested in conjunction with the gathering of performance statistics during program execution, for use in improving subsequent allocations. The system has been implemented on a network of loosely-coupled microcomputers using multi-port serial communication links to simulate a transputer network. The concurrent programming language occam has been implemented, replacing the explicit process allocation constructs with an automatic placement algorithm. This enables the source code to be completely separated from hardware considerations
- Full Text:
Part four of the Rhodes University Skymap Program
- Authors: Wright, Michael Robert
- Date: 1989
- Subjects: Southern sky (Astronomy) Radio astronomy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5435 , http://hdl.handle.net/10962/d1001988
- Description: The results of the fourth part of the Rhodes University Skymap Program are presented. The observations cover the area of sky between right ascension 14h00m and 02h30m and declination -26⁰ and + 13⁰ at a frequency of 2.3 GHz. Contour maps of this region, with a resolution of 0.38⁰, are presented. Various methods of reducing the effect of the Galactic disc emission are analyzed. The results demonstrate the effectiveness of one of these methods in the production of a flat base level. The filamentary structure of the North Polar Spur is enhanced and results are obtained which support current theories of the origin of this object. The HII region surrounding Ophiuchi is examined in detail. A number of parameters are derived for the HII region. The spur associated with the HII region S54 is also examined. A listing of 1105 point sources appearing in the maps is presented. The limiting flux density of this listing is 0.5 Jy
- Full Text:
Seasonal changes in the physiological and hormonal aspects of reproduction in the male long-fingered bat, Miniopterus schreibersii (Mammalia : Chiroptera)
- Authors: Paton, Joy Carol
- Date: 1989
- Subjects: Bats -- Reproduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5590 , http://hdl.handle.net/10962/d1002040
- Description: The reproductive cycle of Miniopterus schreibersii is modified as a consequence of a period of torpor/hibernation over the winter months. This bat is one of three genera which employ the reproductive strategy of delayed implantation in which the blastocyst remains free in the uterine lumen during the winter months. Spermatogenesis is initiated in February, with spermiogenesis occuring in March. Copulation, ovulation and fertilization takes place between March and May after which the testes regress and remain in an inactive condition until the following summer. Activity in the accessory gland complex is initiated in March and continues until early June. Plasma testosterone concentrations reach a peak in May, decline over the winter months and reach a second, unexplainable peak in October. Leydig cells are secretorily active in February/early March after which they undergo vacuolation and final degeneration. The question of the life cyle of Leydig cells is addressed and an increase in a certain cell after Leydig cell activity suggests that this cell type may be the precursor of Leydig cells.
- Full Text:
The design and implementation of a fourth generation programming language
- Authors: Iverson, Carn Martin
- Date: 1989 , 2013-03-04
- Subjects: Programming languages (Electronic computers) , Fourth generation computers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4584 , http://hdl.handle.net/10962/d1004652 , Programming languages (Electronic computers) , Fourth generation computers
- Description: IV is a very high level language designed for use in a real time production control environment. While most fourth generation languages are intended for use by end users, IV is more suitable for skilled professional programmers. One of the major design objectives of IV is a dramatic improvement in programmer efficiency during application program development. Non-procedural constructs provided by the language and the use of a number of interactive development tools provide an environment for achieving this goal. This report presents a language proposal for IV, and addresses related design and implementation issues.
- Full Text:
The exploration and evaluation of groundwater units in the Van Rynevelds Pass Dam Basin, north of Graaff-Reinet, Cape Province
- Authors: Woodford, A C
- Date: 1989 , 2013-08-30
- Subjects: Aquifers -- South Africa -- Graaff-Reinet , Hydrogeology -- South Africa , Groundwater -- South Africa -- Graaff-Reinet
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4880 , http://hdl.handle.net/10962/d1013275
- Description: This thesis deals with a groundwater investigation conducted in the Van Rynevelds Pass Dam basin, north of Graaff-Reinet, in the Cape Province. The objective of the study was to assess the groundwater potential of the basin in terms of its development and exploitation as a municipal supply. In order to achieve this objective, fieldwork was carried out involving a hydrocensus, geological/geophysical mapping, drilling, aquifer testing and hydrochemical sampling. The fieldwork was conducted during the period January 1983 to February 1984. The investigation revealed that the most significant ground water occurrence in the study area is an alluvial/weathered bedrock aquifer (Graaff-Reinet aquifer ) . The volume of ground water stored in the Graaff-Reinet aquifer is in the order of 27 x 10⁶ m³, while its exploitation potential is conservatively estimated at 9 300 m³/day. However, the quality of this water is poor and should be blended with dam water or better quality groundwater. Two minor fractured aquifer units were also identified.
- Full Text:
The karyology and taxonomy of the southern African yellowfish (Pisces : cyprinidae)
- Authors: Oellermann, Lawrence Keith
- Date: 1989
- Subjects: Barbus -- South Africa Cyprinidae -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5192 , http://hdl.handle.net/10962/d1001968
- Description: The southern African yellowfish (Barbus aeneus, B. capensls, B. kimberleyensis, B. natalensis and B. polylepis) are very similar, which limits the utility of traditional taxonomic methods. For this reason yellowfish similarities were explored using multivariate analysis and karyology. Meristic, morphometric and Truss (body shape) data were examined using multiple discriminant, principal component and cluster analyses. The morphological study disclosed that although the species were very similar two distinct groups occurred; B. aeneus-B. kimberleyensis and B. capensis-B. polylepis-B. natalensis. Karyology showed that the yellowfish were hexaploid, B. aeneus and B. kimberleyensis having 148 chromosomes while the other three species had 150 chromosomes. Because the karyotypes of the species were variable the fundamental number for each species was taken as the median value for ten spreads. Median fundamental numbers were B. aeneus = 196, B. natalensis = 200, B. kimberleyensis = 204, B. polylepis = 206 and B. capensis = 208. The lower chromosome number and higher fundamental number was considered the more apomorphic state for these species. Silver-staining of nucleoli showed that the yellowfish are probably undergoing the process of diploidization. Southern African Barbus and closely related species used for outgroup comparisons showed three levels of ploidy. The diploid species karyotyped were B.anoplus (2N=48), B. argenteus (2N=52), B. trimaculatus (2N=42-48), Labeo capensis (2N=48) and L. umbratus (2N=48); the tetraploid species were B. serra (2N=102), B. trevelyani (2N=±96), Pseudobarbus afer (2N=96) and P. burgi (2N=96); and the hexaploid species were B. marequensis (2N=130-150) and Varicorhinus nelspruitensis (2N=130-148). The taxonomic implications of polyploidy for the African cyprinids were considered, and its effect on species was discussed.
- Full Text: