A process for the detanning of chrome leather wastes utilising tannery effluents
- Authors: Glaum, Deanne Melanie
- Date: 1994
- Subjects: Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4029 , http://hdl.handle.net/10962/d1004089 , Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Description: The considerable volume of chromium-bearing wastes generated during the process of leather tanning, exacerbated by the potential for trivalent chromium in the wastes to be oxidised to the toxic hexavalent state, has created a major waste disposal dilemma for the tanning industry. While methods are available for the safe and effective treatment of residual chrome-tanning liquors, little has been done to address the issue of the chrome-bearing solid wastes. Given the increasingly stringent environmental compliance standards facing tanneries, unless an appropriate treatment process is developed in the immediate future, the continued use of chromium as a tanning agent could be compromised. Recent investigations have demonstrated the potential of heated alkaline conditions for dechroming these solid wastes. This study expanded upon these considerations and examined the feasibility of utilising the highly alkaline tannery waste effluents as cost-effective, substitute alkaline media. The three effluents considered in this study, classed as lime sulphide liquors, were shown to be capable of dechroming wet blue shavings, with resultant separation of the solid wastes into a protein and a concentrated chromium product. The solubilised protein product contained low chromium concentrations which comply with legal discharge limits. The precipitated chromium product offers opportunity for reutilisation in the tannery. A novel industrial-scale treatment process, based on these investigations, indicated the process to be capable of treating the quantity of shavings produced on a daily basis by a medium to large scale tannery. Application of this method for the dechroming of other chrome-tanned solid wastes was also shown to be feasible.
- Full Text:
- Date Issued: 1994
- Authors: Glaum, Deanne Melanie
- Date: 1994
- Subjects: Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4029 , http://hdl.handle.net/10962/d1004089 , Tanneries -- Waste disposal , Recycling (Waste, etc.) , Leather
- Description: The considerable volume of chromium-bearing wastes generated during the process of leather tanning, exacerbated by the potential for trivalent chromium in the wastes to be oxidised to the toxic hexavalent state, has created a major waste disposal dilemma for the tanning industry. While methods are available for the safe and effective treatment of residual chrome-tanning liquors, little has been done to address the issue of the chrome-bearing solid wastes. Given the increasingly stringent environmental compliance standards facing tanneries, unless an appropriate treatment process is developed in the immediate future, the continued use of chromium as a tanning agent could be compromised. Recent investigations have demonstrated the potential of heated alkaline conditions for dechroming these solid wastes. This study expanded upon these considerations and examined the feasibility of utilising the highly alkaline tannery waste effluents as cost-effective, substitute alkaline media. The three effluents considered in this study, classed as lime sulphide liquors, were shown to be capable of dechroming wet blue shavings, with resultant separation of the solid wastes into a protein and a concentrated chromium product. The solubilised protein product contained low chromium concentrations which comply with legal discharge limits. The precipitated chromium product offers opportunity for reutilisation in the tannery. A novel industrial-scale treatment process, based on these investigations, indicated the process to be capable of treating the quantity of shavings produced on a daily basis by a medium to large scale tannery. Application of this method for the dechroming of other chrome-tanned solid wastes was also shown to be feasible.
- Full Text:
- Date Issued: 1994
Aspects of the biology and ecology of some intertidal Holothurians (Echinodermata) along the Eastern Cape coast of South Africa
- Authors: Foster, Gregory George
- Date: 1994
- Subjects: Echinodermata , Echinodermata -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5638 , http://hdl.handle.net/10962/d1005320 , Echinodermata , Echinodermata -- South Africa
- Description: Four species of dendrochirote holothurians, Roweia stephensoni John, Pseudocnella sykion Lampert, Aslia spyridophora Clark, Roweia frauenfeldi frauenfeldi Ludwig, and one aspidochirote holothurian, Neostichopus grammatus Clark, are common inhabitants of the intertidal regions of the eastern Cape rocky shores of South Africa. All five species are sympatric for most of their geographical distribution. The intertidal distributions, densities and biomasses of R. stephensoni, P. sykion and N. grammatus were examined at six sites from Port Elizabeth to East London in the eastern Cape. At all sites the three species showed similar overlapping zonations with R. stephensoni and P. sykion reaching their highest maximum mean densities and biomasses (drained wet weight) in the lower mid-shore region (401m² and 684g/m², 181m² and 269g/m², respectively at Port Elizabeth), whilst N. grammatus in the low-shore region (61m² and 72g/m², at Port Elizabeth). The highest densities and biomasses of all three species were recorded on boulder shores that had minimal sand inundation. Seasonality of reproduction of R. stephensoni, P. sykion and N. grammatus was compared at Port Elizabeth, using gonad index values, gonadal tubule diameters, egg diameters and spermatozoon content in tubules from January 1992 until August 1993. All three species are dioecious and did not deviate from a 1: 1 sex ratio. Sizes at first sexual maturity were 2.5-2.9 cm³ for R. stephensoni and P. sykion, and 3.0-3.9cm³ for N. grammatus. The gonads of R. stephensoni and P. sykion consist of a bunch of unbranched tubules of equal diameter, with males having more tubules of a smaller diameter than females. By contrast, the gonad of N. grammatus consists of two tufts of multiple branched tubules. All three species followed annual reproductive cycles, and in R. stephensoni and P. sykion gametogenesis occurred from March 1992 until August/September 1992, and maturity was maintained until the main spawning event in January 1993. By contrast, in N. grammatus gametogenesis occurred from July 1992 until September 1992, and maturity was maintained until the main spawning event in December 1992/January 1993. Unlike R. stephensoni and P. sykion the reproductive cycle of N. grammatus was more pronounced, in that the gonad regressed after spawning. Aspects of the feeding biology of R. stephensoni, P. sykion, A. spyridophora, R.ffrauenfeldi and N. grammatus were compared, using the gross buccal tentacle morphology, type and size range of ingested food particles, and gut lengths. Scanning electron microscopy revealed that the buccal tentacles of R. stephensoni, P. sykion and A. spyridophora could be classified as dendritic, branching numerous times with the tips terminating in numerous nodes covered with discs of papillate projections. The buccal tentacle structure of R. f frauenfeldi deviated from the typical dendrochirote dendritic form. The tentacles are stout with few branches which terminate in large bulbous nodes lacking discs of papillate projections. Neostichopus grammatus possesses buccal tentacles that could be classified as peltate, terminating in large nodes which also lacked discs of papillate projections. Roweia stephensoni, P. sykion and A. spyridophora are suspension-feeders, ingesting food particles mostly <53μm in size. Roweia f frauenfeldi was classed as a "heavy" suspension-feeder, ingesting food particles mostly between 250μm-1.18μm, while N. grammatus is a deposit-feeder, ingesting benthic sediments mostly between 106-500μm. The gut lengths of the dendrochirote holothurians were found to be significantly longer than that of the aspidochirote, and may be attributed to the nature of the food ingested.
- Full Text:
- Date Issued: 1994
- Authors: Foster, Gregory George
- Date: 1994
- Subjects: Echinodermata , Echinodermata -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5638 , http://hdl.handle.net/10962/d1005320 , Echinodermata , Echinodermata -- South Africa
- Description: Four species of dendrochirote holothurians, Roweia stephensoni John, Pseudocnella sykion Lampert, Aslia spyridophora Clark, Roweia frauenfeldi frauenfeldi Ludwig, and one aspidochirote holothurian, Neostichopus grammatus Clark, are common inhabitants of the intertidal regions of the eastern Cape rocky shores of South Africa. All five species are sympatric for most of their geographical distribution. The intertidal distributions, densities and biomasses of R. stephensoni, P. sykion and N. grammatus were examined at six sites from Port Elizabeth to East London in the eastern Cape. At all sites the three species showed similar overlapping zonations with R. stephensoni and P. sykion reaching their highest maximum mean densities and biomasses (drained wet weight) in the lower mid-shore region (401m² and 684g/m², 181m² and 269g/m², respectively at Port Elizabeth), whilst N. grammatus in the low-shore region (61m² and 72g/m², at Port Elizabeth). The highest densities and biomasses of all three species were recorded on boulder shores that had minimal sand inundation. Seasonality of reproduction of R. stephensoni, P. sykion and N. grammatus was compared at Port Elizabeth, using gonad index values, gonadal tubule diameters, egg diameters and spermatozoon content in tubules from January 1992 until August 1993. All three species are dioecious and did not deviate from a 1: 1 sex ratio. Sizes at first sexual maturity were 2.5-2.9 cm³ for R. stephensoni and P. sykion, and 3.0-3.9cm³ for N. grammatus. The gonads of R. stephensoni and P. sykion consist of a bunch of unbranched tubules of equal diameter, with males having more tubules of a smaller diameter than females. By contrast, the gonad of N. grammatus consists of two tufts of multiple branched tubules. All three species followed annual reproductive cycles, and in R. stephensoni and P. sykion gametogenesis occurred from March 1992 until August/September 1992, and maturity was maintained until the main spawning event in January 1993. By contrast, in N. grammatus gametogenesis occurred from July 1992 until September 1992, and maturity was maintained until the main spawning event in December 1992/January 1993. Unlike R. stephensoni and P. sykion the reproductive cycle of N. grammatus was more pronounced, in that the gonad regressed after spawning. Aspects of the feeding biology of R. stephensoni, P. sykion, A. spyridophora, R.ffrauenfeldi and N. grammatus were compared, using the gross buccal tentacle morphology, type and size range of ingested food particles, and gut lengths. Scanning electron microscopy revealed that the buccal tentacles of R. stephensoni, P. sykion and A. spyridophora could be classified as dendritic, branching numerous times with the tips terminating in numerous nodes covered with discs of papillate projections. The buccal tentacle structure of R. f frauenfeldi deviated from the typical dendrochirote dendritic form. The tentacles are stout with few branches which terminate in large bulbous nodes lacking discs of papillate projections. Neostichopus grammatus possesses buccal tentacles that could be classified as peltate, terminating in large nodes which also lacked discs of papillate projections. Roweia stephensoni, P. sykion and A. spyridophora are suspension-feeders, ingesting food particles mostly <53μm in size. Roweia f frauenfeldi was classed as a "heavy" suspension-feeder, ingesting food particles mostly between 250μm-1.18μm, while N. grammatus is a deposit-feeder, ingesting benthic sediments mostly between 106-500μm. The gut lengths of the dendrochirote holothurians were found to be significantly longer than that of the aspidochirote, and may be attributed to the nature of the food ingested.
- Full Text:
- Date Issued: 1994
Babesia canis : a characterization of five field stocks in Southern Africa
- Authors: Van Heerden, Garth William
- Date: 1994
- Subjects: Babesia canis -- Africa, Southern , Tick-borne diseases -- Africa, Southern , Dogs -- Parasites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5645 , http://hdl.handle.net/10962/d1005327 , Babesia canis -- Africa, Southern , Tick-borne diseases -- Africa, Southern , Dogs -- Parasites
- Description: This study attempted to characterise 5 field stocks of B. canis, collected from various geographic areas of southern Africa in terms of pathogenicity, immune response, cross resistance and antigenic composition. This was done by means of artificial infection of two to four year old Beagle dogs. Serological tests included indirect fluorescent antibody tests, polyacrylamide gel electrophoresis , Western blotting of B. canis antigen and immune serum transfers. The ZIM1, GHT1 , QTN1 and DBN1 stocks were found to be virulent and the JHB1 stock, which might be a cardiac form of babesiosis, was found to be highly virulent. Immune responses of dogs to primary challenges were poor. A second challenge or relapse was important in the development of a resistant immunity. Heterologous challenges showed that dogs which were immune to the ZIM1, QTN1 and DBN1 stocks were partially immune to the JHB1 stock. The dog that was immune to the GHT1 stock was the only one that was totally resistant to the JHB1 stock. Western blots revealed interstock antigenic variation between the JHB1 and the other four stocks. These differences were, however, not great enough to separate the stocks taxonomically.
- Full Text:
- Date Issued: 1994
- Authors: Van Heerden, Garth William
- Date: 1994
- Subjects: Babesia canis -- Africa, Southern , Tick-borne diseases -- Africa, Southern , Dogs -- Parasites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5645 , http://hdl.handle.net/10962/d1005327 , Babesia canis -- Africa, Southern , Tick-borne diseases -- Africa, Southern , Dogs -- Parasites
- Description: This study attempted to characterise 5 field stocks of B. canis, collected from various geographic areas of southern Africa in terms of pathogenicity, immune response, cross resistance and antigenic composition. This was done by means of artificial infection of two to four year old Beagle dogs. Serological tests included indirect fluorescent antibody tests, polyacrylamide gel electrophoresis , Western blotting of B. canis antigen and immune serum transfers. The ZIM1, GHT1 , QTN1 and DBN1 stocks were found to be virulent and the JHB1 stock, which might be a cardiac form of babesiosis, was found to be highly virulent. Immune responses of dogs to primary challenges were poor. A second challenge or relapse was important in the development of a resistant immunity. Heterologous challenges showed that dogs which were immune to the ZIM1, QTN1 and DBN1 stocks were partially immune to the JHB1 stock. The dog that was immune to the GHT1 stock was the only one that was totally resistant to the JHB1 stock. Western blots revealed interstock antigenic variation between the JHB1 and the other four stocks. These differences were, however, not great enough to separate the stocks taxonomically.
- Full Text:
- Date Issued: 1994
Cogitator : a parallel, fuzzy, database-driven expert system
- Authors: Baise, Paul
- Date: 1994 , 2012-10-08
- Subjects: Expert systems (Computer science) , Artificial intelligence -- Computer programs , System design , Cogitator (Computer system)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4667 , http://hdl.handle.net/10962/d1006684 , Expert systems (Computer science) , Artificial intelligence -- Computer programs , System design , Cogitator (Computer system)
- Description: The quest to build anthropomorphic machines has led researchers to focus on knowledge and the manipulation thereof. Recently, the expert system was proposed as a solution, working well in small, well understood domains. However these initial attempts highlighted the tedious process associated with building systems to display intelligence, the most notable being the Knowledge Acquisition Bottleneck. Attempts to circumvent this problem have led researchers to propose the use of machine learning databases as a source of knowledge. Attempts to utilise databases as sources of knowledge has led to the development Database-Driven Expert Systems. Furthermore, it has been ascertained that a requisite for intelligent systems is powerful computation. In response to these problems and proposals, a new type of database-driven expert system, Cogitator is proposed. It is shown to circumvent the Knowledge Acquisition Bottleneck and posess many other advantages over both traditional expert systems and connectionist systems, whilst having non-serious disadvantages. , KMBT_223
- Full Text:
- Date Issued: 1994
- Authors: Baise, Paul
- Date: 1994 , 2012-10-08
- Subjects: Expert systems (Computer science) , Artificial intelligence -- Computer programs , System design , Cogitator (Computer system)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4667 , http://hdl.handle.net/10962/d1006684 , Expert systems (Computer science) , Artificial intelligence -- Computer programs , System design , Cogitator (Computer system)
- Description: The quest to build anthropomorphic machines has led researchers to focus on knowledge and the manipulation thereof. Recently, the expert system was proposed as a solution, working well in small, well understood domains. However these initial attempts highlighted the tedious process associated with building systems to display intelligence, the most notable being the Knowledge Acquisition Bottleneck. Attempts to circumvent this problem have led researchers to propose the use of machine learning databases as a source of knowledge. Attempts to utilise databases as sources of knowledge has led to the development Database-Driven Expert Systems. Furthermore, it has been ascertained that a requisite for intelligent systems is powerful computation. In response to these problems and proposals, a new type of database-driven expert system, Cogitator is proposed. It is shown to circumvent the Knowledge Acquisition Bottleneck and posess many other advantages over both traditional expert systems and connectionist systems, whilst having non-serious disadvantages. , KMBT_223
- Full Text:
- Date Issued: 1994
Constituent processes of leaf senescence in Hordeum vulgare cv. Dyan
- Afitlhile, Meshack Mosimanegape
- Authors: Afitlhile, Meshack Mosimanegape
- Date: 1994
- Subjects: Leaves , Leaves -- Development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4184 , http://hdl.handle.net/10962/d1003752
- Description: Changes in chlorophyll content, carotenoid content and composition, abscisic acid and phaseic acid levels, hydrolytic enzyme activity and polypeptide pattern were monitored during senescence of the primary attached leaves of Hordeum vulgare L. cv. Dyan. Senescence occurred due to the normal course of leaf development or was induced by incubation of leaves in darkness. Loss of chlorophyll and total leaf protein was retarded in light whereas it continued rapidly in leaves from dark-incubated seedlings. Chlorophyll alb ratio increased with the progression of senescence, suggesting that chlorophyll b was referentially degraded during this process. Loss of total protein coincided with enhanced activity of acid and neutral proteases. In contrast, loss of chlorophyll was not accompanied by an increase in· peroxidase activity, suggesting that this enzyme was not responsible for initiating chlorophyll breakdown. Carotenoid and abscisic acid levels were monitored in the same tissue extracts. The results obtained show that the increase in endogenous levels of abscisic acid, induced by senescence, correlated with enhanced epoxidation of the xanthophyll cycle, ie., increased conversion of zeaxanthin to antheraxanthin and all-trans-violaxanthin. In addition, an increase in abscisic acid levels occurred concomitant with a decrease in all-trans-violaxanthin and 9'-cis-neoxanthin, suggesting an apparent 1:1 relationship on a molar basis. It is therefore proposed that enhanced abscisic acid production, due to foliar senescence, arises from fluctuations in carotenoid turnover. Polypeptide patterns in isolated chloroplasts, purified thylakoid and stromal fractions were very similar for leaves incubated in either light or darkness. A decrease in intensity of bands was observed in isolated chloroplasts and stromal fractions. Intensity of bands in thylakoids remained unchanged with the progression of senescence. Protein standards of peroxidase and lipoxygenase co-migrated with proteins of the isolated chloroplast. Although tentative, some proteins of the chloroplast may be representative of precursors of hydrolytic enzymes which are known to increase during senescence.
- Full Text:
- Date Issued: 1994
- Authors: Afitlhile, Meshack Mosimanegape
- Date: 1994
- Subjects: Leaves , Leaves -- Development
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4184 , http://hdl.handle.net/10962/d1003752
- Description: Changes in chlorophyll content, carotenoid content and composition, abscisic acid and phaseic acid levels, hydrolytic enzyme activity and polypeptide pattern were monitored during senescence of the primary attached leaves of Hordeum vulgare L. cv. Dyan. Senescence occurred due to the normal course of leaf development or was induced by incubation of leaves in darkness. Loss of chlorophyll and total leaf protein was retarded in light whereas it continued rapidly in leaves from dark-incubated seedlings. Chlorophyll alb ratio increased with the progression of senescence, suggesting that chlorophyll b was referentially degraded during this process. Loss of total protein coincided with enhanced activity of acid and neutral proteases. In contrast, loss of chlorophyll was not accompanied by an increase in· peroxidase activity, suggesting that this enzyme was not responsible for initiating chlorophyll breakdown. Carotenoid and abscisic acid levels were monitored in the same tissue extracts. The results obtained show that the increase in endogenous levels of abscisic acid, induced by senescence, correlated with enhanced epoxidation of the xanthophyll cycle, ie., increased conversion of zeaxanthin to antheraxanthin and all-trans-violaxanthin. In addition, an increase in abscisic acid levels occurred concomitant with a decrease in all-trans-violaxanthin and 9'-cis-neoxanthin, suggesting an apparent 1:1 relationship on a molar basis. It is therefore proposed that enhanced abscisic acid production, due to foliar senescence, arises from fluctuations in carotenoid turnover. Polypeptide patterns in isolated chloroplasts, purified thylakoid and stromal fractions were very similar for leaves incubated in either light or darkness. A decrease in intensity of bands was observed in isolated chloroplasts and stromal fractions. Intensity of bands in thylakoids remained unchanged with the progression of senescence. Protein standards of peroxidase and lipoxygenase co-migrated with proteins of the isolated chloroplast. Although tentative, some proteins of the chloroplast may be representative of precursors of hydrolytic enzymes which are known to increase during senescence.
- Full Text:
- Date Issued: 1994
Delineation of buried stream channels using geophysical techniques
- Authors: Biedler, Murray W
- Date: 1994
- Subjects: Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4823 , http://hdl.handle.net/10962/d1005498 , Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Description: This study sets out to evaluate the use of geophysical methods for delineating buried stream channels, which can act as zones of preferential flow within a less hydraulically conductive aquifer. This information is important for gaining an understanding of flow dynamics of alluvial systems. The most reliable method of delineating the dimensions of aquifers is by drilling, which is an expensive proposition and is best preceded by a preliminary geophysical study to help define target zones for a drilling program. The study area is located adjacent to the Coerney River in the Sundays River Valley. Geologically it consists of approximately 5 metres of alluvial fines, covering 3 metres of coarse cobbles and boulders, all underlain by alternating siltstone and sandstone beds of indeterminate thickness. Throughout the area the water is very shallow at approximately 2 metres depth and the groundwater tends to be very saline. An air photo study revealed an old oxbow channel that had been covered over by subsequent agricultural land use. The geophysical methods available for the study were portable seismic refraction, electrical resistivity and electromagnetics. Preliminary field tests clearly showed that seismics did not produce valid results. The methods of electrical resistivity and electromagnetics produced good data and were subjected to further assessment. A grid was surveyed over the study area and both geophysical methods were applied at regularly spaced stations. Soil samples were taken over the same survey grid and analyzed for electrical conductivity in a soils laboratory. The results were compared to the geophysical data in an attempt to quantify the relationship between geophysical response and soil salinity. The data from the electromagnetic survey showed areas of low electrical conductivity which was a possible indication of zones of preferential groundwater flow. A transect of boreholes was drilled over selected electrical conductivity lows and successfully intersected the buried stream channel. A comparison of the borehole logs with the layered earth models from the Vertical Electrical Soundings indicated that the electrical resistivity method was not responding to the features of the buried stream channel and the cobblestone layer. This proved the electromagnetic method to be more valuable for this particular study
- Full Text:
- Date Issued: 1994
- Authors: Biedler, Murray W
- Date: 1994
- Subjects: Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4823 , http://hdl.handle.net/10962/d1005498 , Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Description: This study sets out to evaluate the use of geophysical methods for delineating buried stream channels, which can act as zones of preferential flow within a less hydraulically conductive aquifer. This information is important for gaining an understanding of flow dynamics of alluvial systems. The most reliable method of delineating the dimensions of aquifers is by drilling, which is an expensive proposition and is best preceded by a preliminary geophysical study to help define target zones for a drilling program. The study area is located adjacent to the Coerney River in the Sundays River Valley. Geologically it consists of approximately 5 metres of alluvial fines, covering 3 metres of coarse cobbles and boulders, all underlain by alternating siltstone and sandstone beds of indeterminate thickness. Throughout the area the water is very shallow at approximately 2 metres depth and the groundwater tends to be very saline. An air photo study revealed an old oxbow channel that had been covered over by subsequent agricultural land use. The geophysical methods available for the study were portable seismic refraction, electrical resistivity and electromagnetics. Preliminary field tests clearly showed that seismics did not produce valid results. The methods of electrical resistivity and electromagnetics produced good data and were subjected to further assessment. A grid was surveyed over the study area and both geophysical methods were applied at regularly spaced stations. Soil samples were taken over the same survey grid and analyzed for electrical conductivity in a soils laboratory. The results were compared to the geophysical data in an attempt to quantify the relationship between geophysical response and soil salinity. The data from the electromagnetic survey showed areas of low electrical conductivity which was a possible indication of zones of preferential groundwater flow. A transect of boreholes was drilled over selected electrical conductivity lows and successfully intersected the buried stream channel. A comparison of the borehole logs with the layered earth models from the Vertical Electrical Soundings indicated that the electrical resistivity method was not responding to the features of the buried stream channel and the cobblestone layer. This proved the electromagnetic method to be more valuable for this particular study
- Full Text:
- Date Issued: 1994
Development of an artificial weaning diet for the South African abalone, Haliotis midae (Haliotidae: Gastropoda)
- Authors: Knauer, Jens
- Date: 1994
- Subjects: Abalone culture -- Research -- South Africa , Ichthyology , Abalones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5204 , http://hdl.handle.net/10962/d1004099 , Abalone culture -- Research -- South Africa , Ichthyology , Abalones
- Description: An adequate supply of diatoms during the weaning stage (generally 5 - 10 mm shell length (SL)) is one of the primary constraints to the commercial culture of the South African abalone, Haliotis midae. Because of the seriousness of the problem, a project aimed at the development of an artificial weaning diet was initiated. Initially, the chemical composition (proximate composition, amino acid, fatty acid and mineral element profile) of juvenile H. midae was analyzed, as a general lack of such information was identified in a review. Due to the lack of knowledge on the nutritional requirements of H. midae, the formulation of the weaning diet was based on the essential amino acid (EAA) pattern of the shucked tissue, and the known nutrient requirements of haliotids. Subsequently, a water stable gel and pellet form of the diet were developed. The best water stability of a gel was obtained with a 1:3 agar/gelatine mixture which retained 70.7 ± 2.7 % of its dry weight after 24 h. Starch based pellets, however, retained 89.0 ± 0.6 % of their dry weight after 24 h. In a comparative growth trial, pellets produced a significantly better increase in SL and weight than gels after only 15 days. This was probably due to the better water stability of pellets, which resulted in a better nutritional quality than in gels. The feeding behaviour on both forms of the diet did not differ. Activity patterns were exclusively nocturnal and feeding frequency was consistently low. The percentage composition of the pelleted weaning diet, on a dry weight basis, was 5 % casein, 15 % gelatine, 15 % fish meal, 10 % Spirulina spp., 2.5 % fish oil, 2.5 % sunflower oil, 21.0 % dextrin, 23.0 % starch, 4.0 % of a mineral and 2.0 % of a vitamin mixture. The correlation coefficient between the EAA pattern of H. midae and the dietary EAA pattern was r⁷= 0.8989. Pellets were fed to juveniles in a 30 day growth trial to study the effect of photoperiod (12, 16, 20 and 23 hours of darkness) on growth and general nutritional parameters. A comparative experiment feeding diatoms was conducted under a 12hL: 12hD light regime at the same time. The SL and weight of the juveniles did not increase significantly with an increase in hours of darkness. The growth of juveniles fed on pellets did not differ significantly from those fed on diatoms. Percentage feed consumption (PFC), percentage feeding rate (PFR), feed conversion ratio (FCR), protein efficiency ratio (PER) and percentage protein deposited (PPD) were determined for the animals fed on pellets. None of the parameters were significantly affected by photoperiod. However, there were trends in that PFC increased with longer periods of darkness, while PPD decreased. The FCRs (0.44 ± 0.04 to 0.60 ± 0.19) and PERs (5.06 ± 1.74 to 6.64 ± 0.77) indicated that juveniles used the feed, and in particular the protein, very efficiently. Photoperiod did not have an effect on the specific activity of the digestive enzymes amylase, protease and lipase. The specific activity of amylase in the juveniles fed on diatoms was significantly higher than in the pellet fed groups. This was surprising as the main carbohydrate of diatoms is the ß-(l-3) glucan chrysolaminarin, and not starch, a ß-(l-4) glucan. Protease specific activity, on the other hand, was significantly higher in the pellet fed groups, indicating an ability to adapt to the high protein content in the artificial diet (35.48 %), compared to diatoms which had a protein content of 5 %. The specific activity of lipase did not differ significantly between groups, probably because of a similar lipid concentration (5 - 10 %) in diatoms and pellets. Finally, the effect of stocking density, ranging from 1250 to 10,000 juveniles/m2, on the growth of juveniles was evaluated. A model of hatchery productivity was developed based on this investigation. Hatchery productivity was defined as the number of juveniles per unit space reared through to the grow-out stage per unit time. The model predicted that maximum productivity would be achieved at a stocking density of 10,000 juveniles/m2. The results have shown that H. midae can be successfully weaned on an artificial diet, as the growth on the diet was not significantly different to growth obtained on diatoms. Long-term growth trials are needed to confirm these results. The importance of standardized experiments on the nutritional requirements and digestibility of abalone was emphasized. The importance of improved artificial diets, optimal culture conditions, as well as the application of biotechnological techniques to further abalone aquaculture was highlighted.
- Full Text:
- Date Issued: 1994
- Authors: Knauer, Jens
- Date: 1994
- Subjects: Abalone culture -- Research -- South Africa , Ichthyology , Abalones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5204 , http://hdl.handle.net/10962/d1004099 , Abalone culture -- Research -- South Africa , Ichthyology , Abalones
- Description: An adequate supply of diatoms during the weaning stage (generally 5 - 10 mm shell length (SL)) is one of the primary constraints to the commercial culture of the South African abalone, Haliotis midae. Because of the seriousness of the problem, a project aimed at the development of an artificial weaning diet was initiated. Initially, the chemical composition (proximate composition, amino acid, fatty acid and mineral element profile) of juvenile H. midae was analyzed, as a general lack of such information was identified in a review. Due to the lack of knowledge on the nutritional requirements of H. midae, the formulation of the weaning diet was based on the essential amino acid (EAA) pattern of the shucked tissue, and the known nutrient requirements of haliotids. Subsequently, a water stable gel and pellet form of the diet were developed. The best water stability of a gel was obtained with a 1:3 agar/gelatine mixture which retained 70.7 ± 2.7 % of its dry weight after 24 h. Starch based pellets, however, retained 89.0 ± 0.6 % of their dry weight after 24 h. In a comparative growth trial, pellets produced a significantly better increase in SL and weight than gels after only 15 days. This was probably due to the better water stability of pellets, which resulted in a better nutritional quality than in gels. The feeding behaviour on both forms of the diet did not differ. Activity patterns were exclusively nocturnal and feeding frequency was consistently low. The percentage composition of the pelleted weaning diet, on a dry weight basis, was 5 % casein, 15 % gelatine, 15 % fish meal, 10 % Spirulina spp., 2.5 % fish oil, 2.5 % sunflower oil, 21.0 % dextrin, 23.0 % starch, 4.0 % of a mineral and 2.0 % of a vitamin mixture. The correlation coefficient between the EAA pattern of H. midae and the dietary EAA pattern was r⁷= 0.8989. Pellets were fed to juveniles in a 30 day growth trial to study the effect of photoperiod (12, 16, 20 and 23 hours of darkness) on growth and general nutritional parameters. A comparative experiment feeding diatoms was conducted under a 12hL: 12hD light regime at the same time. The SL and weight of the juveniles did not increase significantly with an increase in hours of darkness. The growth of juveniles fed on pellets did not differ significantly from those fed on diatoms. Percentage feed consumption (PFC), percentage feeding rate (PFR), feed conversion ratio (FCR), protein efficiency ratio (PER) and percentage protein deposited (PPD) were determined for the animals fed on pellets. None of the parameters were significantly affected by photoperiod. However, there were trends in that PFC increased with longer periods of darkness, while PPD decreased. The FCRs (0.44 ± 0.04 to 0.60 ± 0.19) and PERs (5.06 ± 1.74 to 6.64 ± 0.77) indicated that juveniles used the feed, and in particular the protein, very efficiently. Photoperiod did not have an effect on the specific activity of the digestive enzymes amylase, protease and lipase. The specific activity of amylase in the juveniles fed on diatoms was significantly higher than in the pellet fed groups. This was surprising as the main carbohydrate of diatoms is the ß-(l-3) glucan chrysolaminarin, and not starch, a ß-(l-4) glucan. Protease specific activity, on the other hand, was significantly higher in the pellet fed groups, indicating an ability to adapt to the high protein content in the artificial diet (35.48 %), compared to diatoms which had a protein content of 5 %. The specific activity of lipase did not differ significantly between groups, probably because of a similar lipid concentration (5 - 10 %) in diatoms and pellets. Finally, the effect of stocking density, ranging from 1250 to 10,000 juveniles/m2, on the growth of juveniles was evaluated. A model of hatchery productivity was developed based on this investigation. Hatchery productivity was defined as the number of juveniles per unit space reared through to the grow-out stage per unit time. The model predicted that maximum productivity would be achieved at a stocking density of 10,000 juveniles/m2. The results have shown that H. midae can be successfully weaned on an artificial diet, as the growth on the diet was not significantly different to growth obtained on diatoms. Long-term growth trials are needed to confirm these results. The importance of standardized experiments on the nutritional requirements and digestibility of abalone was emphasized. The importance of improved artificial diets, optimal culture conditions, as well as the application of biotechnological techniques to further abalone aquaculture was highlighted.
- Full Text:
- Date Issued: 1994
Ecology of the ichthyofauna in three temporarily open/closed estuaries on the Natal coast
- Authors: Harrison, Trevor D
- Date: 1994
- Subjects: Estuarine ecology -- South Africa -- KwaZulu-Natal , Estuarine animals -- South Africa -- Swartkops River Estuary , Fishes -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5269 , http://hdl.handle.net/10962/d1005113 , Estuarine ecology -- South Africa -- KwaZulu-Natal , Estuarine animals -- South Africa -- Swartkops River Estuary , Fishes -- South Africa -- KwaZulu-Natal
- Description: The ichthyofauna of three small Natal estuaries, the Mhlanga, Damba and Zotsha was sampled over a period of two years. A total of 68 kinds of fishes representing 24 families, 39 genera and 56 species were captured during this study. Forty seven kinds of fishes were recorded in the Mhlanga of which Gilchristella aestuaria,Oreochromis mossambicus, Valamugil cunnesius, Valamugil sp. and juvenile mugilids numerically dominated. In terms of biomass, O. mossambicus, V. cunnesius, Liza alata, Myxus capensis and Mugil cephalus dominated the ichthyofauna of the Mhlanga. In the Damba, 24 kinds of fishes were recorded. The most abundant fishes captured were Glossogobius callidus, M. capensis and O. mossambicus. M. capensis, M. cephalus, O. mossambicus and G. callidus dominated the fish biomass captured in the Damba. A total of 56 kinds of fishes were recorded in the Zotsha during this study. The ichthyofauna of the Zotsha was numerically dominated by juvenile mugilids, G. aestuaria, O. mossambicus, Rhabdosargus holubi, Terapon jarbua, Ambassis productus and G. callidus. The species which dominated the fish biomass in the Zotsha were O. mossambicus, L. alata, Valamugil robustus, Valamugil buchanani, M. capensis, M. cephalus and V. cunnesius. Classifying the species captured according to whether they were resident estuarine species, freshwater species, estuarine-dependent marine species and marine species revealed that the first three groups were all well represented in the systems. The only system in which marine species made any significant contribution to the ichthyofauna was the Zotsha. Oreochromis mossambicus was the dominant freshwater species in all three estuaries during this study. Gilchristella aestuaria and Glossogobius callidus were the principal estuarine species in the Mhlanga and the Damba respectively. Both G. aestuaria and G. callidus were the dominant estuarine species captured in the Zotsha. The principal estuarine-dependent marine fishes captured in the Mhlanga were V. cunnesius, Valamugil sp., juvenile mugilids, M. capensis, M. cephalus and L. alata. In the Damba, M. capensis and M. cephalus were the dominant estuarine-dependent marine species and in the Zotsha juvenile mugilids, R. holubi, T. jarbua, A . productus, M. capensis, V. cunnesius, V. robustus, M. cephalus and L. alata predominated. The results of this study indicate that the estuaries are dominated at different periods by different assemblages of fishes. This is linked to the spawning and migration patterns of the various species as well as the hydrological regime of each estuary. During the winter these systems are normally closed with relatively deep waters and high food resource and habitat availability. Freshwater and estuarine species mainly inhabit the upper reaches of the systems while estuarine-dependent marine species mainly occupy the middle and lower reaches and dominate the fish community. When these systems open with the onset of the spring/summer rains, adult and sub-adult estuarine-dependent marine species emigrate to the marine environment and juveniles begin recruiting into the systems. Spring is also the peak breeding period of resident estuarine and freshwater species, resulting in an increase in the contribution of these fishes to the overall population during this period. When closed estuaries open many of them drain and this results in the fishes concentrating in the lower reaches of the system where moderate water depths are present, thus further contributing to an increase in the proportion of freshwater and estuarine species in this region. The breaching of closed estuaries also results in a slump in food resources and habitat availability. Competition and possible increased vulnerability to avian predation (due to the shallow nature of the systems), may contribute to a decrease in the proportion of estuarine and freshwater species in summer. The prolonged spawning and recruitment of 0+ juveniles of estuarine-dependent marine species results in an increase in the proportion of these fishes present in the estuaries during summer. In autumn, these systems normally close, water levels rise and available food resources and habitat increase. This allows the redistribution of freshwater and estuarine species upstream, leaving estuarine-dependent marine species to dominate the middle and lower reaches. Although temporarily open/closed estuaries along the Natal coast may not be as diverse as permanently open estuaries in terms of their ichthyofauna, their importance must not be underestimated since by providing a continuous sequence of sheltered habitats along the coast they may contribute significantly to the viability of estuarine-dependent marine fish stocks.
- Full Text:
- Date Issued: 1994
- Authors: Harrison, Trevor D
- Date: 1994
- Subjects: Estuarine ecology -- South Africa -- KwaZulu-Natal , Estuarine animals -- South Africa -- Swartkops River Estuary , Fishes -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5269 , http://hdl.handle.net/10962/d1005113 , Estuarine ecology -- South Africa -- KwaZulu-Natal , Estuarine animals -- South Africa -- Swartkops River Estuary , Fishes -- South Africa -- KwaZulu-Natal
- Description: The ichthyofauna of three small Natal estuaries, the Mhlanga, Damba and Zotsha was sampled over a period of two years. A total of 68 kinds of fishes representing 24 families, 39 genera and 56 species were captured during this study. Forty seven kinds of fishes were recorded in the Mhlanga of which Gilchristella aestuaria,Oreochromis mossambicus, Valamugil cunnesius, Valamugil sp. and juvenile mugilids numerically dominated. In terms of biomass, O. mossambicus, V. cunnesius, Liza alata, Myxus capensis and Mugil cephalus dominated the ichthyofauna of the Mhlanga. In the Damba, 24 kinds of fishes were recorded. The most abundant fishes captured were Glossogobius callidus, M. capensis and O. mossambicus. M. capensis, M. cephalus, O. mossambicus and G. callidus dominated the fish biomass captured in the Damba. A total of 56 kinds of fishes were recorded in the Zotsha during this study. The ichthyofauna of the Zotsha was numerically dominated by juvenile mugilids, G. aestuaria, O. mossambicus, Rhabdosargus holubi, Terapon jarbua, Ambassis productus and G. callidus. The species which dominated the fish biomass in the Zotsha were O. mossambicus, L. alata, Valamugil robustus, Valamugil buchanani, M. capensis, M. cephalus and V. cunnesius. Classifying the species captured according to whether they were resident estuarine species, freshwater species, estuarine-dependent marine species and marine species revealed that the first three groups were all well represented in the systems. The only system in which marine species made any significant contribution to the ichthyofauna was the Zotsha. Oreochromis mossambicus was the dominant freshwater species in all three estuaries during this study. Gilchristella aestuaria and Glossogobius callidus were the principal estuarine species in the Mhlanga and the Damba respectively. Both G. aestuaria and G. callidus were the dominant estuarine species captured in the Zotsha. The principal estuarine-dependent marine fishes captured in the Mhlanga were V. cunnesius, Valamugil sp., juvenile mugilids, M. capensis, M. cephalus and L. alata. In the Damba, M. capensis and M. cephalus were the dominant estuarine-dependent marine species and in the Zotsha juvenile mugilids, R. holubi, T. jarbua, A . productus, M. capensis, V. cunnesius, V. robustus, M. cephalus and L. alata predominated. The results of this study indicate that the estuaries are dominated at different periods by different assemblages of fishes. This is linked to the spawning and migration patterns of the various species as well as the hydrological regime of each estuary. During the winter these systems are normally closed with relatively deep waters and high food resource and habitat availability. Freshwater and estuarine species mainly inhabit the upper reaches of the systems while estuarine-dependent marine species mainly occupy the middle and lower reaches and dominate the fish community. When these systems open with the onset of the spring/summer rains, adult and sub-adult estuarine-dependent marine species emigrate to the marine environment and juveniles begin recruiting into the systems. Spring is also the peak breeding period of resident estuarine and freshwater species, resulting in an increase in the contribution of these fishes to the overall population during this period. When closed estuaries open many of them drain and this results in the fishes concentrating in the lower reaches of the system where moderate water depths are present, thus further contributing to an increase in the proportion of freshwater and estuarine species in this region. The breaching of closed estuaries also results in a slump in food resources and habitat availability. Competition and possible increased vulnerability to avian predation (due to the shallow nature of the systems), may contribute to a decrease in the proportion of estuarine and freshwater species in summer. The prolonged spawning and recruitment of 0+ juveniles of estuarine-dependent marine species results in an increase in the proportion of these fishes present in the estuaries during summer. In autumn, these systems normally close, water levels rise and available food resources and habitat increase. This allows the redistribution of freshwater and estuarine species upstream, leaving estuarine-dependent marine species to dominate the middle and lower reaches. Although temporarily open/closed estuaries along the Natal coast may not be as diverse as permanently open estuaries in terms of their ichthyofauna, their importance must not be underestimated since by providing a continuous sequence of sheltered habitats along the coast they may contribute significantly to the viability of estuarine-dependent marine fish stocks.
- Full Text:
- Date Issued: 1994
Gold-bearing volcanic breccia complexes related to carboniferous-permian magmatism, North Queensland, Australia
- Authors: Mujdrica, Stefan
- Date: 1994
- Subjects: Gold mines and mining -- Australia -- Queensland , Gold ores -- Geology -- Australia -- Queensland
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4965 , http://hdl.handle.net/10962/d1005577 , Gold mines and mining -- Australia -- Queensland , Gold ores -- Geology -- Australia -- Queensland
- Description: Gold-bearing volcanic breccia complexes are the major sources of gold in the Tasman Fold Belt System in north Queensland. The Tasman Fold Belt System represents the site of continental accretion as a series of island-arcs and intra-arc basins with accompanying thick sedimentation, volcanism, plutonism, tectonism and mineralisation. In north Queensland, the fold belt system comprises the Hodgkinson-Broken River Fold Belt, Thomson Fold Belt, New England Fold Belt and the Georgetown Inlier. The most numerous ore deposits are associated with calc-alkaline volcanics and granitoid intrusivesof the transitional tectonic stage of the fold belt system. The formation and subsequent gold mineralisation of volcanic breccia complexes are related to Permo-Carboniferous magmatism within the Thomson Fold Belt and Georgetown Inlier. The two most important producing areas are at Mount Leyshon and Kidston mines, which are high tonnage, low-grade gold deposits. The Mount Leyshon breccia complex was emplaced along the contact between CambroOrdovician metasedimentary and metavolcanic rocks, and Ordovician-Devonian I-type granitoids of the Lolworth-Ravenswood Block. The Kidston breccia complex is located on a major lithological contact between the Early to Middle Proterozoic . Einasleigh Metamorphics and the Silurian-Devonian Oak River Granodiorite. The principal hosts to the gold mineralisation at the Mount Leyshon and Kidston deposits, are breccia pipes associated with several episodes of porphyry intrusives. The goldbearing magmatic-hydrothermal and phreatomagmatic breccias post-date the development of a porphyry-type protore. The magmatic-hydrothermal breccias were initially emplaced without the involvement of meteoric-hydrothermal fluids, within a closed system. Later magma impulses reached higher levels in the cooled upper magma chamber, where meteoric water invaded the fracture system. This produced an explosive emplacement of phreatomagmatic breccias, as seen at Mount Leyshon. Widespread sericitisation and pyrite mineralisation are common, with cavity fill, disseminated and fracturelveincontrolled gold and base metal sulphides. The Kidston and Mount Leyshon breccia complexes have hydrothermal alteration and mineralisation characteristics of the 'Lowell-Guilbert Model'. However, the argillic zone is generally not well defined. The gold travelled as chloride complexes with the hydrothermal fluids before being deposited into cavities and fractures of the breccias. Later stage epithermal deposits formed at the top of the breccia complexes that were dominantly quartz-adularia-sericite-type. The erosion, collapse and further intrusion of later porphyry phases allowed the upper parts of the breccia complexes to mix with the lower hydrothermal systems. Exploration for gold-related volcanic breccia complexes is directed at identifying hydrothermal alteration. This is followed by detailed ground studies including geological, mineralogical, petrological and geochemical work, with the idea of constructing a 'model' that can be tested with subsequent subsurface work (e.g. drilling). Geomorphology, remote sensing, geochemistry, geophysics, petrology, isotopes and fluid inclusions are recommended exploration techniques for the search of gold-bearing volcanic breccia complexes. Spectral remote sensing has especially become an important tool for the detection of hydrothermal alteration. Clay and iron minerals of the altered rock, within the breccia complexes, have distinctive spectral characteristics that can be recognisable in multispectral images from the Landsat thematic mapper. The best combination of bands, when using TM remote sensing for hydrothermally altered rock, are 3/5/7 or 4/5/7. The breccia complexes have exploration signatures represented as topographic highs, emplaced within major structural weaknesses, associated I-type granitic batholiths, early potassic alteration with overprint of sericitic alteration, and an associated radiometric high and magnetic low. The exploration for gold-bearing volcanic breccia complex deposits cannot be disregarded, because of the numerous occurrences that are now the major gold producers in north Queensland.
- Full Text:
- Date Issued: 1994
- Authors: Mujdrica, Stefan
- Date: 1994
- Subjects: Gold mines and mining -- Australia -- Queensland , Gold ores -- Geology -- Australia -- Queensland
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4965 , http://hdl.handle.net/10962/d1005577 , Gold mines and mining -- Australia -- Queensland , Gold ores -- Geology -- Australia -- Queensland
- Description: Gold-bearing volcanic breccia complexes are the major sources of gold in the Tasman Fold Belt System in north Queensland. The Tasman Fold Belt System represents the site of continental accretion as a series of island-arcs and intra-arc basins with accompanying thick sedimentation, volcanism, plutonism, tectonism and mineralisation. In north Queensland, the fold belt system comprises the Hodgkinson-Broken River Fold Belt, Thomson Fold Belt, New England Fold Belt and the Georgetown Inlier. The most numerous ore deposits are associated with calc-alkaline volcanics and granitoid intrusivesof the transitional tectonic stage of the fold belt system. The formation and subsequent gold mineralisation of volcanic breccia complexes are related to Permo-Carboniferous magmatism within the Thomson Fold Belt and Georgetown Inlier. The two most important producing areas are at Mount Leyshon and Kidston mines, which are high tonnage, low-grade gold deposits. The Mount Leyshon breccia complex was emplaced along the contact between CambroOrdovician metasedimentary and metavolcanic rocks, and Ordovician-Devonian I-type granitoids of the Lolworth-Ravenswood Block. The Kidston breccia complex is located on a major lithological contact between the Early to Middle Proterozoic . Einasleigh Metamorphics and the Silurian-Devonian Oak River Granodiorite. The principal hosts to the gold mineralisation at the Mount Leyshon and Kidston deposits, are breccia pipes associated with several episodes of porphyry intrusives. The goldbearing magmatic-hydrothermal and phreatomagmatic breccias post-date the development of a porphyry-type protore. The magmatic-hydrothermal breccias were initially emplaced without the involvement of meteoric-hydrothermal fluids, within a closed system. Later magma impulses reached higher levels in the cooled upper magma chamber, where meteoric water invaded the fracture system. This produced an explosive emplacement of phreatomagmatic breccias, as seen at Mount Leyshon. Widespread sericitisation and pyrite mineralisation are common, with cavity fill, disseminated and fracturelveincontrolled gold and base metal sulphides. The Kidston and Mount Leyshon breccia complexes have hydrothermal alteration and mineralisation characteristics of the 'Lowell-Guilbert Model'. However, the argillic zone is generally not well defined. The gold travelled as chloride complexes with the hydrothermal fluids before being deposited into cavities and fractures of the breccias. Later stage epithermal deposits formed at the top of the breccia complexes that were dominantly quartz-adularia-sericite-type. The erosion, collapse and further intrusion of later porphyry phases allowed the upper parts of the breccia complexes to mix with the lower hydrothermal systems. Exploration for gold-related volcanic breccia complexes is directed at identifying hydrothermal alteration. This is followed by detailed ground studies including geological, mineralogical, petrological and geochemical work, with the idea of constructing a 'model' that can be tested with subsequent subsurface work (e.g. drilling). Geomorphology, remote sensing, geochemistry, geophysics, petrology, isotopes and fluid inclusions are recommended exploration techniques for the search of gold-bearing volcanic breccia complexes. Spectral remote sensing has especially become an important tool for the detection of hydrothermal alteration. Clay and iron minerals of the altered rock, within the breccia complexes, have distinctive spectral characteristics that can be recognisable in multispectral images from the Landsat thematic mapper. The best combination of bands, when using TM remote sensing for hydrothermally altered rock, are 3/5/7 or 4/5/7. The breccia complexes have exploration signatures represented as topographic highs, emplaced within major structural weaknesses, associated I-type granitic batholiths, early potassic alteration with overprint of sericitic alteration, and an associated radiometric high and magnetic low. The exploration for gold-bearing volcanic breccia complex deposits cannot be disregarded, because of the numerous occurrences that are now the major gold producers in north Queensland.
- Full Text:
- Date Issued: 1994
Metabolic responses to in vitro zinc supplementation
- Authors: Steel, Helen Carolyn
- Date: 1994
- Subjects: Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4040 , http://hdl.handle.net/10962/d1004101 , Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Description: The present study was carried out to determine the effects and possible mechanism of action of zinc supplementation on the in vitro growth of malignant murine melanoma (B16) and non-malignant monkey kidney (LLCMK) cells. Cell culture studies showed that zinc supplementation significantly inhibited B16 growth at all the concentrations studied (1, 3, 5 and lOμg/ml). Zinc was also found to inhibit the growth of the LLCMK cells, although to a lesser extent than the B16 cells. Possible evidence of mobilisation of the essential fatty acids from the membrane phospholipid stores was noted in both cell types. This effect was, however, greater in the B16 cells. Δ⁶-desaturase activity was found to be significantly lower in the B16 cells than in the LLCMK cells (p ≥ 0.05). Zinc supplementation resulted in an increase in the enzymes activity in the LLCMK cells and, at high concentrations, in the B16 cells. An estimation of elongase and Δ⁶-desaturase activity with zinc supplementation indicated that zinc had little or no effect on the activity of these enzymes. B16 cells were found to have higher levels of free radicals than the LLCMK cells. Zinc supplementation resulted in increased free radical formation in the B16 cells, while no effect was observed in the LLCMK cells. Lipid peroxidation increased in both cell types with increased zinc concentrations. The observed effect of zinc supplementation on cell growth may involve these elevated levels of lipid peroxides. CycIo-oxygenase activity was found to be greater in the B16 cells than the LLCMK cells. The activity of the enzyme increased with higher concentrations of zinc (lOμg/ml) in both cell types. Prostaglandin E, levels were found to be lower in the B16 cells compared to the LLCMK cells. The levels of prostaglandin E, in both cell types appeared to be dependent on the levels of the polyunsaturated fatty acid precursors to the prostaglandins. Zinc was found to inhibit the activity of the enzyme adenylate cyclase in both cell types. The cAMP levels in the LLCMK cells were also found to decrease with zinc supplementation. In the case of the B16 cells, cAMP levels increased at low concentrations of zinc despite a decrease in adenyl ate cyclase activity, suggesting a possible inhibition of cAMP phosphodiesterase activity at these concentrations of zinc. It is concluded that although zinc supplementation does have an effect on cell growth, this effect is not mediated through the activation of adenylate cyclase by the prostaglandins resulting in elevated levels of cAMP. A possible mechanism involving lipid peroxidation is proposed.
- Full Text:
- Date Issued: 1994
- Authors: Steel, Helen Carolyn
- Date: 1994
- Subjects: Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4040 , http://hdl.handle.net/10962/d1004101 , Zinc in the body , Zinc -- Physiological effect , Cancer -- Research
- Description: The present study was carried out to determine the effects and possible mechanism of action of zinc supplementation on the in vitro growth of malignant murine melanoma (B16) and non-malignant monkey kidney (LLCMK) cells. Cell culture studies showed that zinc supplementation significantly inhibited B16 growth at all the concentrations studied (1, 3, 5 and lOμg/ml). Zinc was also found to inhibit the growth of the LLCMK cells, although to a lesser extent than the B16 cells. Possible evidence of mobilisation of the essential fatty acids from the membrane phospholipid stores was noted in both cell types. This effect was, however, greater in the B16 cells. Δ⁶-desaturase activity was found to be significantly lower in the B16 cells than in the LLCMK cells (p ≥ 0.05). Zinc supplementation resulted in an increase in the enzymes activity in the LLCMK cells and, at high concentrations, in the B16 cells. An estimation of elongase and Δ⁶-desaturase activity with zinc supplementation indicated that zinc had little or no effect on the activity of these enzymes. B16 cells were found to have higher levels of free radicals than the LLCMK cells. Zinc supplementation resulted in increased free radical formation in the B16 cells, while no effect was observed in the LLCMK cells. Lipid peroxidation increased in both cell types with increased zinc concentrations. The observed effect of zinc supplementation on cell growth may involve these elevated levels of lipid peroxides. CycIo-oxygenase activity was found to be greater in the B16 cells than the LLCMK cells. The activity of the enzyme increased with higher concentrations of zinc (lOμg/ml) in both cell types. Prostaglandin E, levels were found to be lower in the B16 cells compared to the LLCMK cells. The levels of prostaglandin E, in both cell types appeared to be dependent on the levels of the polyunsaturated fatty acid precursors to the prostaglandins. Zinc was found to inhibit the activity of the enzyme adenylate cyclase in both cell types. The cAMP levels in the LLCMK cells were also found to decrease with zinc supplementation. In the case of the B16 cells, cAMP levels increased at low concentrations of zinc despite a decrease in adenyl ate cyclase activity, suggesting a possible inhibition of cAMP phosphodiesterase activity at these concentrations of zinc. It is concluded that although zinc supplementation does have an effect on cell growth, this effect is not mediated through the activation of adenylate cyclase by the prostaglandins resulting in elevated levels of cAMP. A possible mechanism involving lipid peroxidation is proposed.
- Full Text:
- Date Issued: 1994
Parallel implementation of a virtual reality system on a transputer architecture
- Authors: Bangay, Shaun Douglas
- Date: 1994 , 2012-10-11
- Subjects: Virtual reality , Computer simulation , Transputers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4668 , http://hdl.handle.net/10962/d1006687 , Virtual reality , Computer simulation , Transputers
- Description: A Virtual Reality is a computer model of an environment, actual or imagined, presented to a user in as realistic a fashion as possible. Stereo goggles may be used to provide the user with a view of the modelled environment from within the environment, while a data-glove is used to interact with the environment. To simulate reality on a computer, the machine has to produce realistic images rapidly. Such a requirement usually necessitates expensive equipment. This thesis presents an implementation of a virtual reality system on a transputer architecture. The system is general, and is intended to provide support for the development of various virtual environments. The three main components of the system are the output device drivers, the input device drivers, and the virtual world kernel. This last component is responsible for the simulation of the virtual world. The rendering system is described in detail. Various methods for implementing the components of the graphics pipeline are discussed. These are then generalised to make use of the facilities provided by the transputer processor for parallel processing. A number of different decomposition techniques are implemented and compared. The emphasis in this section is on the speed at which the world can be rendered, and the interaction latency involved. In the best case, where almost linear speedup is obtained, a world containing over 250 polygons is rendered at 32 frames/second. The bandwidth of the transputer links is the major factor limiting speedup. A description is given of an input device driver which makes use of a powerglove. Techniques for overcoming the limitations of this device, and for interacting with the virtual world, are discussed. The virtual world kernel is designed to make extensive use of the parallel processing facilities provided by transputers. It is capable of providing support for mUltiple worlds concurrently, and for multiple users interacting with these worlds. Two applications are described that were successfully implemented using this system. The design of the system is compared with other recently developed virtual reality systems. Features that are common or advantageous in each of the systems are discussed. The system described in this thesis compares favourably, particularly in its use of parallel processors. , KMBT_223
- Full Text:
- Date Issued: 1994
- Authors: Bangay, Shaun Douglas
- Date: 1994 , 2012-10-11
- Subjects: Virtual reality , Computer simulation , Transputers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4668 , http://hdl.handle.net/10962/d1006687 , Virtual reality , Computer simulation , Transputers
- Description: A Virtual Reality is a computer model of an environment, actual or imagined, presented to a user in as realistic a fashion as possible. Stereo goggles may be used to provide the user with a view of the modelled environment from within the environment, while a data-glove is used to interact with the environment. To simulate reality on a computer, the machine has to produce realistic images rapidly. Such a requirement usually necessitates expensive equipment. This thesis presents an implementation of a virtual reality system on a transputer architecture. The system is general, and is intended to provide support for the development of various virtual environments. The three main components of the system are the output device drivers, the input device drivers, and the virtual world kernel. This last component is responsible for the simulation of the virtual world. The rendering system is described in detail. Various methods for implementing the components of the graphics pipeline are discussed. These are then generalised to make use of the facilities provided by the transputer processor for parallel processing. A number of different decomposition techniques are implemented and compared. The emphasis in this section is on the speed at which the world can be rendered, and the interaction latency involved. In the best case, where almost linear speedup is obtained, a world containing over 250 polygons is rendered at 32 frames/second. The bandwidth of the transputer links is the major factor limiting speedup. A description is given of an input device driver which makes use of a powerglove. Techniques for overcoming the limitations of this device, and for interacting with the virtual world, are discussed. The virtual world kernel is designed to make extensive use of the parallel processing facilities provided by transputers. It is capable of providing support for mUltiple worlds concurrently, and for multiple users interacting with these worlds. Two applications are described that were successfully implemented using this system. The design of the system is compared with other recently developed virtual reality systems. Features that are common or advantageous in each of the systems are discussed. The system described in this thesis compares favourably, particularly in its use of parallel processors. , KMBT_223
- Full Text:
- Date Issued: 1994
Pollution caused by mine dumps and its control
- Chikusa, Chimwemwe Mainsfield
- Authors: Chikusa, Chimwemwe Mainsfield
- Date: 1994
- Subjects: Pollution , Pollution -- Law and legislation -- South Africa , Mineral industries -- Waste disposal , Slimes (Mining)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4991 , http://hdl.handle.net/10962/d1005603 , Pollution , Pollution -- Law and legislation -- South Africa , Mineral industries -- Waste disposal , Slimes (Mining)
- Description: All mine dumps are a point source of either physical, chemical or both forms of pollution. Physical pollution includes the physical site coverage of the dump, slumping of parts of the dams and dust that may originate from it (air pollution). Chemical pollution from, or related to the mine dumps include the dominant acid drainage (which contains heavy metals), radioactivity, electromagnetic radiation, noise and chemicals released from the mineral processing stage. In one way or the other, exposure to these pollution forms is detrimental to the human health and his environment. It is this fact that urges the public, government and the responsible mining companies to find ways of monitoring the pollution and stopping it, preferably at the source. Where it can not be stopped, techniques of reducing it, or containing it have been, and are still being developed. Personal protection is the priority. Pollution exposure to the general public is minimised as much as possible. Pollution control techniques that employ less expensive, natural, self-sustaining elements suitable for the environment such as wetlands and vegetation are recommended. The artificial short term and often expensive alternatives are of secondary priority. However, choice of which technique to use is based on the merit of each problem, knowing that chemicals act faster but are effective for a short period as compared to the natural systems. Pollution management is the critical part of the whole process. This involves decision making on courses of action and financial allocation on the part of both the polluter and the monitoring department/agent. The ability to effectively manage pollution programmes is achieved these days with the aid of computers. It is emphasised that pollution control should be handled in an integrated, multi-disciplinary approach manner. This is because pollution is a question of life and death, hence every individual remains accountable to it. Keeping the public and the concerned parties educated, informed and welcoming their concerns on the environmental issues related to the mine dumps generated in a mining venture is essential in the modern days of environmental public awareness, or otherwise face the public lath.
- Full Text:
- Date Issued: 1994
- Authors: Chikusa, Chimwemwe Mainsfield
- Date: 1994
- Subjects: Pollution , Pollution -- Law and legislation -- South Africa , Mineral industries -- Waste disposal , Slimes (Mining)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4991 , http://hdl.handle.net/10962/d1005603 , Pollution , Pollution -- Law and legislation -- South Africa , Mineral industries -- Waste disposal , Slimes (Mining)
- Description: All mine dumps are a point source of either physical, chemical or both forms of pollution. Physical pollution includes the physical site coverage of the dump, slumping of parts of the dams and dust that may originate from it (air pollution). Chemical pollution from, or related to the mine dumps include the dominant acid drainage (which contains heavy metals), radioactivity, electromagnetic radiation, noise and chemicals released from the mineral processing stage. In one way or the other, exposure to these pollution forms is detrimental to the human health and his environment. It is this fact that urges the public, government and the responsible mining companies to find ways of monitoring the pollution and stopping it, preferably at the source. Where it can not be stopped, techniques of reducing it, or containing it have been, and are still being developed. Personal protection is the priority. Pollution exposure to the general public is minimised as much as possible. Pollution control techniques that employ less expensive, natural, self-sustaining elements suitable for the environment such as wetlands and vegetation are recommended. The artificial short term and often expensive alternatives are of secondary priority. However, choice of which technique to use is based on the merit of each problem, knowing that chemicals act faster but are effective for a short period as compared to the natural systems. Pollution management is the critical part of the whole process. This involves decision making on courses of action and financial allocation on the part of both the polluter and the monitoring department/agent. The ability to effectively manage pollution programmes is achieved these days with the aid of computers. It is emphasised that pollution control should be handled in an integrated, multi-disciplinary approach manner. This is because pollution is a question of life and death, hence every individual remains accountable to it. Keeping the public and the concerned parties educated, informed and welcoming their concerns on the environmental issues related to the mine dumps generated in a mining venture is essential in the modern days of environmental public awareness, or otherwise face the public lath.
- Full Text:
- Date Issued: 1994
Reproductive biology of the Egyptian free-tailed bat, Tadarida Aegyptiaca
- Authors: Tsita, Johannes Ngoako
- Date: 1994
- Subjects: Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5754 , http://hdl.handle.net/10962/d1005442 , Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Description: The reproductive biology of Tadarida aegyptiaca was studied using specimens collected in the Cape Province of South Africa. The morphology of the reproductive tract of the species was generally similar to that of other molossids, however, the absence of Cowpers glands was unusual. Spermatogenesis began in February and spermatozoa were released to the cauda epididymis during August and September. Follicular development started in March and culminated with the appearance of Graafian follicles in July. Ovulation probably occurred in August and specimens were pregnant by September. Gestation length was estimated to be four to five months and a single young was born in December. The data suggest that T. aegyptiaca is monotocous and monoestrous.
- Full Text:
- Date Issued: 1994
- Authors: Tsita, Johannes Ngoako
- Date: 1994
- Subjects: Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5754 , http://hdl.handle.net/10962/d1005442 , Tadarida aegyptiaca -- Reproduction , Bats -- Reproduction
- Description: The reproductive biology of Tadarida aegyptiaca was studied using specimens collected in the Cape Province of South Africa. The morphology of the reproductive tract of the species was generally similar to that of other molossids, however, the absence of Cowpers glands was unusual. Spermatogenesis began in February and spermatozoa were released to the cauda epididymis during August and September. Follicular development started in March and culminated with the appearance of Graafian follicles in July. Ovulation probably occurred in August and specimens were pregnant by September. Gestation length was estimated to be four to five months and a single young was born in December. The data suggest that T. aegyptiaca is monotocous and monoestrous.
- Full Text:
- Date Issued: 1994
Static analysis of functional languages
- Authors: Mountjoy, Jon-Dean
- Date: 1994 , 2012-10-10
- Subjects: Functional programming languages
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4669 , http://hdl.handle.net/10962/d1006690 , Functional programming languages
- Description: Static analysis is the name given to a number of compile time analysis techniques used to automatically generate information which can lead to improvements in the execution performance of function languages. This thesis provides an introduction to these techniques and their implementation. The abstract interpretation framework is an example of a technique used to extract information from a program by providing the program with an alternate semantics and evaluating this program over a non-standard domain. The elements of this domain represent certain properties of interest. This framework is examined in detail, as well as various extensions and variants of it. The use of binary logical relations and program logics as alternative formulations of the framework , and partial equivalence relations as an extension to it, are also looked at. The projection analysis framework determines how much of a sub-expression can be evaluated by examining the context in which the expression is to be evaluated, and provides an elegant method for finding particular types of information from data structures. This is also examined. The most costly operation in implementing an analysis is the computation of fixed points. Methods developed to make this process more efficient are looked at. This leads to the final chapter which highlights the dependencies and relationships between the different frameworks and their mathematical disciplines. , KMBT_223
- Full Text:
- Date Issued: 1994
- Authors: Mountjoy, Jon-Dean
- Date: 1994 , 2012-10-10
- Subjects: Functional programming languages
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4669 , http://hdl.handle.net/10962/d1006690 , Functional programming languages
- Description: Static analysis is the name given to a number of compile time analysis techniques used to automatically generate information which can lead to improvements in the execution performance of function languages. This thesis provides an introduction to these techniques and their implementation. The abstract interpretation framework is an example of a technique used to extract information from a program by providing the program with an alternate semantics and evaluating this program over a non-standard domain. The elements of this domain represent certain properties of interest. This framework is examined in detail, as well as various extensions and variants of it. The use of binary logical relations and program logics as alternative formulations of the framework , and partial equivalence relations as an extension to it, are also looked at. The projection analysis framework determines how much of a sub-expression can be evaluated by examining the context in which the expression is to be evaluated, and provides an elegant method for finding particular types of information from data structures. This is also examined. The most costly operation in implementing an analysis is the computation of fixed points. Methods developed to make this process more efficient are looked at. This leads to the final chapter which highlights the dependencies and relationships between the different frameworks and their mathematical disciplines. , KMBT_223
- Full Text:
- Date Issued: 1994
Studies on the bioactivities of selected Eastern Cape seaweeds
- Authors: Carter, Anne Margaret
- Date: 1994
- Subjects: Marine algae -- South Africa -- Eastern Cape , Marine algae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4033 , http://hdl.handle.net/10962/d1004093 , Marine algae -- South Africa -- Eastern Cape , Marine algae
- Description: In studies on the bioactivities of selected eastern Cape seaweeds, a suitable extraction solvent, namely methanol was used. The antimicrobial, antineoplastic and antiviral activities were investigated, and a seasonal comparison of antimicrobial activities as well as a scanning electron microscopic study were included. A number of algae were found to display significantly high antibacterial activities, of these, the two red algae Plocamium corallorhiza and Laurencia glomerata and the two brown algae Zonaria subarticulata and Ecklonia biruncinata showed the most potent broad spectrum antibacterial activity. L.glomerata and E.biruncinata were active against all five test bacteria, but were inactive against the yeast Candida albicans. C.albicans was the most resistant organism tested,~with only Peyssonelia capensis, f-corallorhiza and Ulva rigida inhibiting its growth. Of the 17 seaweeds tested, none showed any clear seasonal changes in antimicrobial activity. The microorganisms however did vary in their susceptibility to treatment. Staphylococcus aureus and the Micrococcus species were the most susceptible to treatment by the algal extracts, with the Gram positive endospore former, Bacillus subtilis and the two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa showing more resistance to treatment. C.albicans however was the most resistant organism. In the antineoplastic studies, the brown algae Z.subarticulata, E.biruncinata and Sargassum heterophyllum showed potent activity against both the normal, LLCMK, and cancerous, mouse melanoma-3S0 cells, reducing cell growth in each case. The green algae showed potent activity against the cancerous cells, lowering growth to 30% that of the normal cells. Normal cell growth was unaffected or was stimulated by the presence of these algal extracts. The red algae showed no antineoplastic activity. Representatives of each of the red, brown and green algae were used in the brine shrimp (Artemia salina) cytotoxicity study. None of the algae showed any toxicity towards the brine shrimp. In the antiviral studies against Polio Type 1, strain L-Sa, a reduction in virus infectivity was used as an indication of the presence of antiviral properties in the seaweeds tested. This was done by comparing the virus titres of algal-treated cells with those of untreated cells. Six of the algae tested displayed antiviral activity, these were the two Rhodophyceae Hypnea spicifera and L.glomerata, the two Phaeophyceae Dictyopteris macrocarpa and Dictyota naevosa, and the two Chlorophyceae U.rigida and Halimeda cuneata. Of these, D.naevosa showed particularly strong activity, recording a log reduction in virus titre of 4.
- Full Text:
- Date Issued: 1994
- Authors: Carter, Anne Margaret
- Date: 1994
- Subjects: Marine algae -- South Africa -- Eastern Cape , Marine algae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4033 , http://hdl.handle.net/10962/d1004093 , Marine algae -- South Africa -- Eastern Cape , Marine algae
- Description: In studies on the bioactivities of selected eastern Cape seaweeds, a suitable extraction solvent, namely methanol was used. The antimicrobial, antineoplastic and antiviral activities were investigated, and a seasonal comparison of antimicrobial activities as well as a scanning electron microscopic study were included. A number of algae were found to display significantly high antibacterial activities, of these, the two red algae Plocamium corallorhiza and Laurencia glomerata and the two brown algae Zonaria subarticulata and Ecklonia biruncinata showed the most potent broad spectrum antibacterial activity. L.glomerata and E.biruncinata were active against all five test bacteria, but were inactive against the yeast Candida albicans. C.albicans was the most resistant organism tested,~with only Peyssonelia capensis, f-corallorhiza and Ulva rigida inhibiting its growth. Of the 17 seaweeds tested, none showed any clear seasonal changes in antimicrobial activity. The microorganisms however did vary in their susceptibility to treatment. Staphylococcus aureus and the Micrococcus species were the most susceptible to treatment by the algal extracts, with the Gram positive endospore former, Bacillus subtilis and the two Gram negative bacteria Escherichia coli and Pseudomonas aeruginosa showing more resistance to treatment. C.albicans however was the most resistant organism. In the antineoplastic studies, the brown algae Z.subarticulata, E.biruncinata and Sargassum heterophyllum showed potent activity against both the normal, LLCMK, and cancerous, mouse melanoma-3S0 cells, reducing cell growth in each case. The green algae showed potent activity against the cancerous cells, lowering growth to 30% that of the normal cells. Normal cell growth was unaffected or was stimulated by the presence of these algal extracts. The red algae showed no antineoplastic activity. Representatives of each of the red, brown and green algae were used in the brine shrimp (Artemia salina) cytotoxicity study. None of the algae showed any toxicity towards the brine shrimp. In the antiviral studies against Polio Type 1, strain L-Sa, a reduction in virus infectivity was used as an indication of the presence of antiviral properties in the seaweeds tested. This was done by comparing the virus titres of algal-treated cells with those of untreated cells. Six of the algae tested displayed antiviral activity, these were the two Rhodophyceae Hypnea spicifera and L.glomerata, the two Phaeophyceae Dictyopteris macrocarpa and Dictyota naevosa, and the two Chlorophyceae U.rigida and Halimeda cuneata. Of these, D.naevosa showed particularly strong activity, recording a log reduction in virus titre of 4.
- Full Text:
- Date Issued: 1994
Surficial placer gold deposits
- Authors: Mann, P L
- Date: 1994
- Subjects: Gold mines and mining , Gold ores -- Geology , Placer deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5088 , http://hdl.handle.net/10962/d1018245
- Description: This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.
- Full Text:
- Date Issued: 1994
- Authors: Mann, P L
- Date: 1994
- Subjects: Gold mines and mining , Gold ores -- Geology , Placer deposits
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5088 , http://hdl.handle.net/10962/d1018245
- Description: This review summarises the factors which control the formation and distribution of surficial gold placer deposits. Regional tectonic and climatic conditions as well as gold source are considered. The characteristics of eluvial, alluvial, marine, glacial and fluvioglacial gold placer deposits are described. Particular attention is paid to the gold grains within these placers. These gold grains have a distinctive morphology and chemical composition which reflect the manner in which they were transported, deposited and concentrated within the placers. The knowledge of the processes which lead to the formation and location of surficial gold placers is then used to guide exploration and target potential deposits, which can then be evaluated.
- Full Text:
- Date Issued: 1994
Synthesis and conformational studies of indolizines
- Authors: George, Rosemary
- Date: 1994
- Subjects: Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4367 , http://hdl.handle.net/10962/d1005032 , Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Description: The present investigation has involved a kinetic and mechanistic study of the thermal cyclization of 3-acetoxy-3-(2-pyridyl)-2-methylenepropanoate esters and related compounds to 2-substituted indolizines. Substrates for the kinetic study were prepared via the Baylis-Hillmann reaction of pyridine-2-carboxaldehydes with acrylate esters, acrylonitrile and methyl vinyl ketone. The resulting hydroxy compounds were then acetylated to afford the acetoxy derivatives, thermal cyclization of which gave the corresponding 2-substituted indolizines. The cyclization reactions was followed using 'H NMR spectroscopy and were shown to follow firstorder kinetics. The influence of the various substituents on the observed first-order rate constants has been examined and variable temperature studies have permitted evaluation of activation parameters for the formation of methyl indolizine-2-carboxylate and ethyl indolizine-2-carboxylate. An alternative route to 2-substituted indolizines via halogenated derivatives was explored and several halogenated 2-pyridyl derivatives were synthesised and their thermal cyclization to indolizines was attempted. Novel 5-methylindolizine-2-carboxamides were prepared as part of this investigation and dynamic NMR spectroscopy was used to study internal rotation about the amide N-CO bond in these compounds.
- Full Text:
- Date Issued: 1994
- Authors: George, Rosemary
- Date: 1994
- Subjects: Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4367 , http://hdl.handle.net/10962/d1005032 , Indole alkaloids -- Research , Organic compounds -- Synthesis , Chemistry, Organic
- Description: The present investigation has involved a kinetic and mechanistic study of the thermal cyclization of 3-acetoxy-3-(2-pyridyl)-2-methylenepropanoate esters and related compounds to 2-substituted indolizines. Substrates for the kinetic study were prepared via the Baylis-Hillmann reaction of pyridine-2-carboxaldehydes with acrylate esters, acrylonitrile and methyl vinyl ketone. The resulting hydroxy compounds were then acetylated to afford the acetoxy derivatives, thermal cyclization of which gave the corresponding 2-substituted indolizines. The cyclization reactions was followed using 'H NMR spectroscopy and were shown to follow firstorder kinetics. The influence of the various substituents on the observed first-order rate constants has been examined and variable temperature studies have permitted evaluation of activation parameters for the formation of methyl indolizine-2-carboxylate and ethyl indolizine-2-carboxylate. An alternative route to 2-substituted indolizines via halogenated derivatives was explored and several halogenated 2-pyridyl derivatives were synthesised and their thermal cyclization to indolizines was attempted. Novel 5-methylindolizine-2-carboxamides were prepared as part of this investigation and dynamic NMR spectroscopy was used to study internal rotation about the amide N-CO bond in these compounds.
- Full Text:
- Date Issued: 1994
The effect of appetite suppressants on pineal function
- Authors: Mchunu, Bongani Isaac
- Date: 1994
- Subjects: Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4038 , http://hdl.handle.net/10962/d1004098 , Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Description: The pineal gland has become the subject of considerable investigation as it provides a productive experimental model for studying circadian rhythms and regulation of end organs. In the rat, the pineal gland provides a convenient model for investigating the noradrenergic receptor system and the effects of various drugs on this system. The effect of appetite suppressants on the rat pineal gland function is described. Appetite suppressants increase melatonin synthesis in organ cultures of rat pineal glands. This effect appears to be mediated by noradrenaline acting on β-adrenoceptors on the pinealocyte membrane. When β-adrenoceptors are blocked, the appetite suppressant-induced rise in melatonin synthesis is prevented. Depletion of noradrenaline in sympathetic nerve terminals also prevented the appetite suppressant-induced rise in melatonin synthesis. Activation of β-adrenoceptors is followed by a rise in N-acetyltransferase activity via a cyclic adenosine monophosphate second messenger system. The effect of appetite suppressants on the activity of liver tryptophan pyrrolase was also investigated. The activity of this enzyme is an important determinant of tryptophan availability to the brain and consequently of brain serotonin levels. The results show that appetite suppressants inhibit both holoenzyme and total enzyme activities of tryptophan pyrrolase. This finding suggests that appetite suppressants may act by inhibiting tryptophan pyrrolase activity thereby increasing brain serotonin, a phenomenon known to be associated with anorexia. There are two possible mechanisms by which appetite suppressants inhibit tryptophan pyrrolase activity. Firstly, these agents, being drugs of dependence, may increase liver NADPH concentrations which inhibit pyrrolase activity. Secondly, appetite suppressants may act on the pineal gland to stimulate melatonin synthesis. Melatonin inhibits pyrrolase activity in a dose-dependent manner. This inhibition will elevate plasma tryptophan levels which result in a rise in brain serotonin synthesis. The present study suggests a possible relationship between the pineal gland and appetite centres in the hypothalamus. Melatonin may have a direct effect on appetite centres since food restriction is associated with an increased melatonin binding in the hypothalamus. If this possible relationship can be extended, melatonin can open new possibilities for the control of food intake and consequently, of pathological obesity.
- Full Text:
- Date Issued: 1994
- Authors: Mchunu, Bongani Isaac
- Date: 1994
- Subjects: Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4038 , http://hdl.handle.net/10962/d1004098 , Pineal gland -- Research , Pineal gland -- Secretions , Appetite depressants -- Physiological effect
- Description: The pineal gland has become the subject of considerable investigation as it provides a productive experimental model for studying circadian rhythms and regulation of end organs. In the rat, the pineal gland provides a convenient model for investigating the noradrenergic receptor system and the effects of various drugs on this system. The effect of appetite suppressants on the rat pineal gland function is described. Appetite suppressants increase melatonin synthesis in organ cultures of rat pineal glands. This effect appears to be mediated by noradrenaline acting on β-adrenoceptors on the pinealocyte membrane. When β-adrenoceptors are blocked, the appetite suppressant-induced rise in melatonin synthesis is prevented. Depletion of noradrenaline in sympathetic nerve terminals also prevented the appetite suppressant-induced rise in melatonin synthesis. Activation of β-adrenoceptors is followed by a rise in N-acetyltransferase activity via a cyclic adenosine monophosphate second messenger system. The effect of appetite suppressants on the activity of liver tryptophan pyrrolase was also investigated. The activity of this enzyme is an important determinant of tryptophan availability to the brain and consequently of brain serotonin levels. The results show that appetite suppressants inhibit both holoenzyme and total enzyme activities of tryptophan pyrrolase. This finding suggests that appetite suppressants may act by inhibiting tryptophan pyrrolase activity thereby increasing brain serotonin, a phenomenon known to be associated with anorexia. There are two possible mechanisms by which appetite suppressants inhibit tryptophan pyrrolase activity. Firstly, these agents, being drugs of dependence, may increase liver NADPH concentrations which inhibit pyrrolase activity. Secondly, appetite suppressants may act on the pineal gland to stimulate melatonin synthesis. Melatonin inhibits pyrrolase activity in a dose-dependent manner. This inhibition will elevate plasma tryptophan levels which result in a rise in brain serotonin synthesis. The present study suggests a possible relationship between the pineal gland and appetite centres in the hypothalamus. Melatonin may have a direct effect on appetite centres since food restriction is associated with an increased melatonin binding in the hypothalamus. If this possible relationship can be extended, melatonin can open new possibilities for the control of food intake and consequently, of pathological obesity.
- Full Text:
- Date Issued: 1994
The influence of the composition of mixed Karoo vegetation on the grazing habits of Merino and Dorper wethers
- Authors: Roux, Francis Augustus
- Date: 1994
- Subjects: Grazing -- South Africa -- Karoo , Sheep -- Feeding and feeds , Dorper sheep -- South Africa , Merino sheep -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4223 , http://hdl.handle.net/10962/d1003792 , Grazing -- South Africa -- Karoo , Sheep -- Feeding and feeds , Dorper sheep -- South Africa , Merino sheep -- South Africa
- Description: The primary objective of this research project was to determine whether area-selective grazing, by Dorper and Merino wethers, took place in small grazing camps as governed by differences in vegetal cover. The main research techniques employed were the descending-point method for the determination of botanical composition, sub-division of the camps into gridblocks to trace sheep movement in relation to vegetation patterning, fistulated animals to determine diet selection, the electronic theodolite for micro-topography, and few minor techniques. The result have shown that area- patch- and species selective grazing are prevalent in small grazing camps under "normal" stocking densities, and that different breeds of stock (Merino and Dorper sheep) have different grazing patterns and diet selection . Climax and sub-climax areas were those primarily select ed for grazing. There is little or no correlation between botanical composition and diet selected as per fistula ted animal. The average distances travelled by Dorpers and Merinos was 2 km / day and 3.1 km/day respectively. Plant phenology did not have a detectable influence in the choice of diet.
- Full Text:
- Date Issued: 1994
- Authors: Roux, Francis Augustus
- Date: 1994
- Subjects: Grazing -- South Africa -- Karoo , Sheep -- Feeding and feeds , Dorper sheep -- South Africa , Merino sheep -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4223 , http://hdl.handle.net/10962/d1003792 , Grazing -- South Africa -- Karoo , Sheep -- Feeding and feeds , Dorper sheep -- South Africa , Merino sheep -- South Africa
- Description: The primary objective of this research project was to determine whether area-selective grazing, by Dorper and Merino wethers, took place in small grazing camps as governed by differences in vegetal cover. The main research techniques employed were the descending-point method for the determination of botanical composition, sub-division of the camps into gridblocks to trace sheep movement in relation to vegetation patterning, fistulated animals to determine diet selection, the electronic theodolite for micro-topography, and few minor techniques. The result have shown that area- patch- and species selective grazing are prevalent in small grazing camps under "normal" stocking densities, and that different breeds of stock (Merino and Dorper sheep) have different grazing patterns and diet selection . Climax and sub-climax areas were those primarily select ed for grazing. There is little or no correlation between botanical composition and diet selected as per fistula ted animal. The average distances travelled by Dorpers and Merinos was 2 km / day and 3.1 km/day respectively. Plant phenology did not have a detectable influence in the choice of diet.
- Full Text:
- Date Issued: 1994
The phytophagous insect community on the Veld Fig, Ficus Burtt-Davyi Hutch
- Authors: Ross, Sally Jane
- Date: 1994
- Subjects: Phytophagous insects -- South Africa , Phytophagous insects , Insect-plant relationships
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5739 , http://hdl.handle.net/10962/d1005425 , Phytophagous insects -- South Africa , Phytophagous insects , Insect-plant relationships
- Description: The quest for patterns in community organisation is a daunting task which may be made easier by concentrating on communities associated with a restricted range of resources and therefore of relative simplicity. Here, the phytophagous insect community on the African fig tree Ficus burtt-davyi Hutch. was studied in an attempt to gain some insight into the factors which influence the composition of insect herbivore communities at a very local level, on individual plants of one host species at a single location. The tree's phenological patterns were detennined, due to their relevance to herbivores, particularly those which are host-specific feeders. The trees exhibited inter-tree asynchrony and intra-tree synchrony in fruit crop initiation, whereas leaf production was synchronous both within and between trees. Sixteen frequently occurring phytophagous insect species fed on the 123 F. burtt-davyi trees in the study area over a period of one year. Factors with the potential to influence the composition of this community were investigated at levels of the whole community (species richness), the guild, and the individual species. At each 'level' the effects of the measured factors on fluctuations in community composition were investigated, both over time (i.e. temporally) and spatially from tree to tree. During the year the phytophage community was influenced largely by temperature, although rainfall and tree phenological changes did exert varying influences on the abundances of guilds and individual species. Tree to tree variation in species richness (and thus commensurately, in the frequencies of occurrence of guilds and individual species) was influenced primarily by tree architectural complexity. Architecturally more complex trees hosted a greater number of species, a relationship largely attributable to effects of passive sampling and within-tree microhabitat heterogeneity and/or the availability of living space. The distributions of the leaf and stem piercing species were strongly associated with the presence of ants and this relationship manifested itself within the community as a whole. The degree of isolation of trees had consequences for individual species and for overall species richness, with the numbers of species present decreasing as trees became more isolated. A detailed analysis of guild distributional patterns revealed that the most important influential factors were those also evident at the level of the whole community and that species within guilds were, on the whole, no more similar to one another with respect to their habitat preferences than species from different guilds. The grouping of species into functional units therefore threw no additional light on the way in which this community is organised. An analysis of possible interspecific interactions between all of the phytophagous species in the community revealed only positive associations, both between species within guilds and between those in different guilds. These were doubtless attributable to autocorrelation as a result of similar habitat preferences. Competition was therefore rejected as an organising force within the community.
- Full Text:
- Date Issued: 1994
- Authors: Ross, Sally Jane
- Date: 1994
- Subjects: Phytophagous insects -- South Africa , Phytophagous insects , Insect-plant relationships
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5739 , http://hdl.handle.net/10962/d1005425 , Phytophagous insects -- South Africa , Phytophagous insects , Insect-plant relationships
- Description: The quest for patterns in community organisation is a daunting task which may be made easier by concentrating on communities associated with a restricted range of resources and therefore of relative simplicity. Here, the phytophagous insect community on the African fig tree Ficus burtt-davyi Hutch. was studied in an attempt to gain some insight into the factors which influence the composition of insect herbivore communities at a very local level, on individual plants of one host species at a single location. The tree's phenological patterns were detennined, due to their relevance to herbivores, particularly those which are host-specific feeders. The trees exhibited inter-tree asynchrony and intra-tree synchrony in fruit crop initiation, whereas leaf production was synchronous both within and between trees. Sixteen frequently occurring phytophagous insect species fed on the 123 F. burtt-davyi trees in the study area over a period of one year. Factors with the potential to influence the composition of this community were investigated at levels of the whole community (species richness), the guild, and the individual species. At each 'level' the effects of the measured factors on fluctuations in community composition were investigated, both over time (i.e. temporally) and spatially from tree to tree. During the year the phytophage community was influenced largely by temperature, although rainfall and tree phenological changes did exert varying influences on the abundances of guilds and individual species. Tree to tree variation in species richness (and thus commensurately, in the frequencies of occurrence of guilds and individual species) was influenced primarily by tree architectural complexity. Architecturally more complex trees hosted a greater number of species, a relationship largely attributable to effects of passive sampling and within-tree microhabitat heterogeneity and/or the availability of living space. The distributions of the leaf and stem piercing species were strongly associated with the presence of ants and this relationship manifested itself within the community as a whole. The degree of isolation of trees had consequences for individual species and for overall species richness, with the numbers of species present decreasing as trees became more isolated. A detailed analysis of guild distributional patterns revealed that the most important influential factors were those also evident at the level of the whole community and that species within guilds were, on the whole, no more similar to one another with respect to their habitat preferences than species from different guilds. The grouping of species into functional units therefore threw no additional light on the way in which this community is organised. An analysis of possible interspecific interactions between all of the phytophagous species in the community revealed only positive associations, both between species within guilds and between those in different guilds. These were doubtless attributable to autocorrelation as a result of similar habitat preferences. Competition was therefore rejected as an organising force within the community.
- Full Text:
- Date Issued: 1994