Abstract and lifelike experimental games
- Authors: Colman, Andrew Michael
- Date: 1980
- Subjects: Game theory Social psychology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3137 , http://hdl.handle.net/10962/d1006958
- Description: The theory of games seems to me to provide the most promising alternative to the traditional theories of social behaviour. Gaming modelS are inherently social in character (an individual's strategy choice in a game cannot even be properly defined without reference to at least one other individual) and they represent a radical departure from the "social stimulus - individual response" approach. They sean, furthermore, to be the only models which can adequately conceptualize an important (and large) class of social behaviours which arise from deliberate free choice. (From preface)
- Full Text:
- Date Issued: 1980
- Authors: Colman, Andrew Michael
- Date: 1980
- Subjects: Game theory Social psychology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3137 , http://hdl.handle.net/10962/d1006958
- Description: The theory of games seems to me to provide the most promising alternative to the traditional theories of social behaviour. Gaming modelS are inherently social in character (an individual's strategy choice in a game cannot even be properly defined without reference to at least one other individual) and they represent a radical departure from the "social stimulus - individual response" approach. They sean, furthermore, to be the only models which can adequately conceptualize an important (and large) class of social behaviours which arise from deliberate free choice. (From preface)
- Full Text:
- Date Issued: 1980
Bacteriophage growth on stationary phase achromabacter strains
- Authors: Robb, Susan Mary
- Date: 1980
- Subjects: Bacteriophages , Strains and stresses
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4125 , http://hdl.handle.net/10962/d1014131
- Description: Achromobacter w.t. and strain 14 both support phage α3a growth in stationary phase, but unlike the w.t. strain, exponential phase cultures of strain 14 block phage development. A standard method was developed for determining phage growth in stationary phase cultures. Lyophilised cells were used to eliminate variations due to the unstable phenotype of Achromobacter strain 14 cells. Phage α3a growth in stationary phase was characterized by a long and variable latent period of 6 to 9 h and an increased burst size of 709 p.f.u. per cell as compared with 153 p.f.u. per cell in exponential wild type cells. During the latent period the infected cells were very sensitive to changes in growth conditions and in particular, dilution. Pre-conditioning of the bacterial cells by allowing them to stand for 24 h after shaking for 3 days was an important aspect of the stationary phase phage growth system. Cells which had been allowed to stand retained the ability to be infected and to support phage growth for at least 16 days. Shaking cultures gradually lost the ability to support phage growth but the phage could persist in the host cell for 10 days until removal from shaking when the lytic cycle could proceed after allowing the cultures to stand. In comparison the latent period and burst size in Achromobacter w.t. stationary phase cells were reduced to less than 2 h and less than 200 respectively. Stationary phase cultures differed physiologically and morphologically depending on the aeration conditions. In comparison with non-aerated standing cultures, vigorously aerated cultures showed a decrease in viability, RNA synthesis, membrane transport, intracellular ATP levels, UV resistance and heat resistance but had markedly higher protein synthesis levels. Aerated cells were small non-motile rods which did not support phage growth. They developed into large motile rods under conditions of limited aeration and were able to propagate phage. It was proposed that changes in the host control mechanisms for macromolecular synthesis may be instrumental in either blocking or permitting phage development. A spontaneous mutant of Achromobacter strain 14 (14x) which liberated phage and was resistant to superinfection was isolated. The phage-host relationship was unstable and similar to the phage carrier state. The liberated phage were able to grow in exponential strain 14 cells. It was proposed that strain 14 was a defective lysogen and that an immunity phase shift model may account for the differential phage growth in exponential and stationary phase cells. Host transcriptional control appears to be implicated in control of phage development in exponential and stationary phase cells. Achromobacter Lp only supported phage in exponential phase but a rifampicin resistant mutant of this strain was able to propagate phage in stationary phase. In vitro RNA synthesis assays showed that the rifampicin resistance was caused by an alteration in the RNA polymerase. Preliminary experiments to determine intracellular phage macromolecular synthesis were carried out using exponential Achromobacter w.t. cells which had been irradiated with UV prior to infection. In irradiated cells, infection with phage resulted in stimulation of DNA synthesis but no stimulation of protein synthesis. Phage production was drastically reduced in cells which had been treated with very low UV doses. It was proposed that α3a development may rely heavily on host cell functions which are destroyed by UV. Achromobacter mutants with defective leucine transport systems were isolated. Mutants which lost the leucine uptake system completely were totally resistant to phage infection and were unable to adsorb phage α3a. This is the first report to implicate an amino-acid transport system in phage adsorption.
- Full Text:
- Date Issued: 1980
- Authors: Robb, Susan Mary
- Date: 1980
- Subjects: Bacteriophages , Strains and stresses
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4125 , http://hdl.handle.net/10962/d1014131
- Description: Achromobacter w.t. and strain 14 both support phage α3a growth in stationary phase, but unlike the w.t. strain, exponential phase cultures of strain 14 block phage development. A standard method was developed for determining phage growth in stationary phase cultures. Lyophilised cells were used to eliminate variations due to the unstable phenotype of Achromobacter strain 14 cells. Phage α3a growth in stationary phase was characterized by a long and variable latent period of 6 to 9 h and an increased burst size of 709 p.f.u. per cell as compared with 153 p.f.u. per cell in exponential wild type cells. During the latent period the infected cells were very sensitive to changes in growth conditions and in particular, dilution. Pre-conditioning of the bacterial cells by allowing them to stand for 24 h after shaking for 3 days was an important aspect of the stationary phase phage growth system. Cells which had been allowed to stand retained the ability to be infected and to support phage growth for at least 16 days. Shaking cultures gradually lost the ability to support phage growth but the phage could persist in the host cell for 10 days until removal from shaking when the lytic cycle could proceed after allowing the cultures to stand. In comparison the latent period and burst size in Achromobacter w.t. stationary phase cells were reduced to less than 2 h and less than 200 respectively. Stationary phase cultures differed physiologically and morphologically depending on the aeration conditions. In comparison with non-aerated standing cultures, vigorously aerated cultures showed a decrease in viability, RNA synthesis, membrane transport, intracellular ATP levels, UV resistance and heat resistance but had markedly higher protein synthesis levels. Aerated cells were small non-motile rods which did not support phage growth. They developed into large motile rods under conditions of limited aeration and were able to propagate phage. It was proposed that changes in the host control mechanisms for macromolecular synthesis may be instrumental in either blocking or permitting phage development. A spontaneous mutant of Achromobacter strain 14 (14x) which liberated phage and was resistant to superinfection was isolated. The phage-host relationship was unstable and similar to the phage carrier state. The liberated phage were able to grow in exponential strain 14 cells. It was proposed that strain 14 was a defective lysogen and that an immunity phase shift model may account for the differential phage growth in exponential and stationary phase cells. Host transcriptional control appears to be implicated in control of phage development in exponential and stationary phase cells. Achromobacter Lp only supported phage in exponential phase but a rifampicin resistant mutant of this strain was able to propagate phage in stationary phase. In vitro RNA synthesis assays showed that the rifampicin resistance was caused by an alteration in the RNA polymerase. Preliminary experiments to determine intracellular phage macromolecular synthesis were carried out using exponential Achromobacter w.t. cells which had been irradiated with UV prior to infection. In irradiated cells, infection with phage resulted in stimulation of DNA synthesis but no stimulation of protein synthesis. Phage production was drastically reduced in cells which had been treated with very low UV doses. It was proposed that α3a development may rely heavily on host cell functions which are destroyed by UV. Achromobacter mutants with defective leucine transport systems were isolated. Mutants which lost the leucine uptake system completely were totally resistant to phage infection and were unable to adsorb phage α3a. This is the first report to implicate an amino-acid transport system in phage adsorption.
- Full Text:
- Date Issued: 1980
Christian joy
- Authors: Williams, Denis Ivor
- Date: 1980
- Subjects: Joy -- Religious aspects -- Christianity Christian life
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1212 , http://hdl.handle.net/10962/d1001541
- Description: Christian joy is identified by linguistic and symbolic, experiential and psychological studies, and by a study of its opposite, sorrow. The final and most comprehensive approach is Biblical and theological. Here, through Judaism and Christianity, the genesis and fulfilment of Christian joy is examined, in life and the gifts of God, in hope, and in union with God. It is defined as "a gift of God's Holy Spirit as man becomes one with Christ in love." Five hypotheses are evaluated and confirmed: - 1. God is perfect joy, 2. God is the source and end of all Christian joy, 3. Jesus Christ is both the most joyful and the most sorrowful of men, 4. The Christian participates in the joy and sorrow of Jesus Christ, 5. Christian joy is eschatological in nature. The need is stressed for a fuller understanding and expression of Christian joy, which is seen as the complement of Christian love, and as a distinguishing characteristic of Christians, because of its primary intentional and ultimate satisfactory nature
- Full Text:
- Date Issued: 1980
- Authors: Williams, Denis Ivor
- Date: 1980
- Subjects: Joy -- Religious aspects -- Christianity Christian life
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1212 , http://hdl.handle.net/10962/d1001541
- Description: Christian joy is identified by linguistic and symbolic, experiential and psychological studies, and by a study of its opposite, sorrow. The final and most comprehensive approach is Biblical and theological. Here, through Judaism and Christianity, the genesis and fulfilment of Christian joy is examined, in life and the gifts of God, in hope, and in union with God. It is defined as "a gift of God's Holy Spirit as man becomes one with Christ in love." Five hypotheses are evaluated and confirmed: - 1. God is perfect joy, 2. God is the source and end of all Christian joy, 3. Jesus Christ is both the most joyful and the most sorrowful of men, 4. The Christian participates in the joy and sorrow of Jesus Christ, 5. Christian joy is eschatological in nature. The need is stressed for a fuller understanding and expression of Christian joy, which is seen as the complement of Christian love, and as a distinguishing characteristic of Christians, because of its primary intentional and ultimate satisfactory nature
- Full Text:
- Date Issued: 1980
Genetic studies and physiological responses to ultraviolet radiation in the Bacteroides fragilis group
- Authors: Jones, David Todman
- Date: 1980
- Subjects: Bacteroides Ultraviolet radiation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4072 , http://hdl.handle.net/10962/d1007047
- Description: The contents of this thesis have been divided into 2 parts . The first part deals with genetic studies carried out on 36 strains belonging to the Bacteroides fragilis group. A number of mutants were isolated from several of the strains. A notable feature of the methods used was the low yield of mutants obtained and the marked sensitivity of these organisms to the mutagenic agents. Variations in colonial morphology was found to be a common feature amongst these organisms. In a few strains this phenomenon was clearly visible, in the remainder it was much weaker, and often could only be seen with the aid of a microscope . Colonial variation was found to be due to the ability of a proporti on of the cells to pruduce capsules or slime layers. The variants were found to segregate at high frequency and different growth conditions were found to have little effect on the segregation frequency or capsule formation . A number of phages specific for B. fragilis and B. t hetaiotaomicron were isol ated. All these phages were virulent and attempts to induce lysogenic phages were unsuccesful . The use of these phages in attempts to obtain transduction proved unsuccessful. A phage carrier state was found to occur in the majority of the phage-host cell systems, which seemed to be due to the presence of phage-resistant encapsulated cells in the population. Bacteriocins were produced by about half the strains, these inhibited the growth of a high proportion of the 36 strains tested. The bacteriocins were released into the growth media at the end of the growth period in the 2 bacteriocins tested. A link between the mode of action of one bacteriocin and rifampicin-resistance was investigated. All the bacter iocins tested were found to be inactive against some rifampicin-resistant mutants of a susceptible strain, suggesting a common mode of action. The presence of capsules in some cells appeared to confer bacteriocin-resistance on these variants. The second part of the thesis deals with a study of the physiological responses of a single strain of B.fragilis to ultraviolet radiation. This strain was found to be more sensitive to ultraviolet radiation under aerobic conditions. The amount of pyrimidine dimers formed after irradiation under anaerobic and aerobic conditions, was not found to differ significantly, indicating that the increase in sensitivity under aerobic conditions was not due to an increase in DNA damage. The use of repair inhibitors and the survival characteristics indicate that this difference was due to decreased repair capabilities under aerobic conditions. Liquid holding recovery in B.fragiZis was found to occur under aerobic conditions . This process was brought about by excision repair and appeared to be due to a decrease in repair efficiency under aerobic conditions. Under anaerobic conditions, where full repair capabilities were present, liquid holding recovery was inhibited. Both minimal medium recovery and fluence dependent filament formation were found to occur in irradiated B.fragiZis cells. The survival kinetics of a number of irradiated B.fragiZis phages were determined and a number of phage reactivation processes were investigated. Little or no host cell reactivation appeared to occur in the strains investigated, however, some ultraviolet reactivation and multiplicity reactivation was found to occur, but only under anaerobic conditions. Photoreactivation was found to be absent in this organism, but an excision repair system was present . The excision repair system was partially characterized and was found to resemble short patch excision repair in E.coli. Evidence was found which suggested that a second mode of repair which was sensitive to oxygen, also occurred in this strain. This repair system which appeared to be responsible for error-prone repair, and the systems which were responsible for ultraviolet reactivation and multiplicity reactivation, seemed to be dependent on a recombination function' which was inhibited by oxygen. The significance of this finding for future genetic studies was discussed.
- Full Text:
- Date Issued: 1980
- Authors: Jones, David Todman
- Date: 1980
- Subjects: Bacteroides Ultraviolet radiation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4072 , http://hdl.handle.net/10962/d1007047
- Description: The contents of this thesis have been divided into 2 parts . The first part deals with genetic studies carried out on 36 strains belonging to the Bacteroides fragilis group. A number of mutants were isolated from several of the strains. A notable feature of the methods used was the low yield of mutants obtained and the marked sensitivity of these organisms to the mutagenic agents. Variations in colonial morphology was found to be a common feature amongst these organisms. In a few strains this phenomenon was clearly visible, in the remainder it was much weaker, and often could only be seen with the aid of a microscope . Colonial variation was found to be due to the ability of a proporti on of the cells to pruduce capsules or slime layers. The variants were found to segregate at high frequency and different growth conditions were found to have little effect on the segregation frequency or capsule formation . A number of phages specific for B. fragilis and B. t hetaiotaomicron were isol ated. All these phages were virulent and attempts to induce lysogenic phages were unsuccesful . The use of these phages in attempts to obtain transduction proved unsuccessful. A phage carrier state was found to occur in the majority of the phage-host cell systems, which seemed to be due to the presence of phage-resistant encapsulated cells in the population. Bacteriocins were produced by about half the strains, these inhibited the growth of a high proportion of the 36 strains tested. The bacteriocins were released into the growth media at the end of the growth period in the 2 bacteriocins tested. A link between the mode of action of one bacteriocin and rifampicin-resistance was investigated. All the bacter iocins tested were found to be inactive against some rifampicin-resistant mutants of a susceptible strain, suggesting a common mode of action. The presence of capsules in some cells appeared to confer bacteriocin-resistance on these variants. The second part of the thesis deals with a study of the physiological responses of a single strain of B.fragilis to ultraviolet radiation. This strain was found to be more sensitive to ultraviolet radiation under aerobic conditions. The amount of pyrimidine dimers formed after irradiation under anaerobic and aerobic conditions, was not found to differ significantly, indicating that the increase in sensitivity under aerobic conditions was not due to an increase in DNA damage. The use of repair inhibitors and the survival characteristics indicate that this difference was due to decreased repair capabilities under aerobic conditions. Liquid holding recovery in B.fragiZis was found to occur under aerobic conditions . This process was brought about by excision repair and appeared to be due to a decrease in repair efficiency under aerobic conditions. Under anaerobic conditions, where full repair capabilities were present, liquid holding recovery was inhibited. Both minimal medium recovery and fluence dependent filament formation were found to occur in irradiated B.fragiZis cells. The survival kinetics of a number of irradiated B.fragiZis phages were determined and a number of phage reactivation processes were investigated. Little or no host cell reactivation appeared to occur in the strains investigated, however, some ultraviolet reactivation and multiplicity reactivation was found to occur, but only under anaerobic conditions. Photoreactivation was found to be absent in this organism, but an excision repair system was present . The excision repair system was partially characterized and was found to resemble short patch excision repair in E.coli. Evidence was found which suggested that a second mode of repair which was sensitive to oxygen, also occurred in this strain. This repair system which appeared to be responsible for error-prone repair, and the systems which were responsible for ultraviolet reactivation and multiplicity reactivation, seemed to be dependent on a recombination function' which was inhibited by oxygen. The significance of this finding for future genetic studies was discussed.
- Full Text:
- Date Issued: 1980
Interaction and transaction : a study of conciliar behaviour in a Black South African township
- Authors: De Jongh, Michael
- Date: 1980
- Subjects: Social interaction -- South Africa -- Port Elizabeth , Black people -- South Africa -- Politics and government , Local government -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2118 , http://hdl.handle.net/10962/d1009437
- Description: The recent history of Africa is one of rapid chance. This process is still continuing and even accelerating. The peoples of Africa are being drawn from a subsistence way of life to a money economy and, more often than not, from a rural to an urban environment. South Africa is no exception to this pattern. In fact, as the most developed country on the continent it is in the front-line of this transformation. Various facets of this problem have held the attention of anthropologists world-wide. Southern Africa specifically has produced some of the earliest urban studies (Hellman, 1948), as well as some of the classical contributions to the field (Mitchell, 1956, 1960, 1966, 1969, 1970; Epstein, 1958; Mayer, 1961, "(1971), 1962; Pauw, 1963). Complex as the urban problems are, anthropologists have obviously not been alone in this field. Workers from many disciplines have been and still are required to contribute to the understanding of the process or urbanization as well as the urban process. Partly for this reason no attempt has been made in the present study to illuminate all the varied facets of the urban field. In general, the focus has been on the urban process and more specifically, on part of a local-level political system. Thus only a limited problem has been selected for analysis.
- Full Text:
- Date Issued: 1980
- Authors: De Jongh, Michael
- Date: 1980
- Subjects: Social interaction -- South Africa -- Port Elizabeth , Black people -- South Africa -- Politics and government , Local government -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2118 , http://hdl.handle.net/10962/d1009437
- Description: The recent history of Africa is one of rapid chance. This process is still continuing and even accelerating. The peoples of Africa are being drawn from a subsistence way of life to a money economy and, more often than not, from a rural to an urban environment. South Africa is no exception to this pattern. In fact, as the most developed country on the continent it is in the front-line of this transformation. Various facets of this problem have held the attention of anthropologists world-wide. Southern Africa specifically has produced some of the earliest urban studies (Hellman, 1948), as well as some of the classical contributions to the field (Mitchell, 1956, 1960, 1966, 1969, 1970; Epstein, 1958; Mayer, 1961, "(1971), 1962; Pauw, 1963). Complex as the urban problems are, anthropologists have obviously not been alone in this field. Workers from many disciplines have been and still are required to contribute to the understanding of the process or urbanization as well as the urban process. Partly for this reason no attempt has been made in the present study to illuminate all the varied facets of the urban field. In general, the focus has been on the urban process and more specifically, on part of a local-level political system. Thus only a limited problem has been selected for analysis.
- Full Text:
- Date Issued: 1980
Some aspects of an ethological study of the aculeate wasps and the bees of a karroid area in the vicinity of Grahamstown, South Africa
- Authors: Gess, Friedrich Wolfgang
- Date: 1980
- Subjects: Wasps -- South Africa Bees -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5834 , http://hdl.handle.net/10962/d1009445
- Description: From introduction: The present study is the first attempt in southern Africa to consider an entire community of aculeate wasps and bees and their interactions with their environment as manifested by their ethology. As far as the author has been able to ascertain it is in fact the most comprehensive of its kind to have been undertaken anywhere, the only similar but more restricted account of this nature being that of Evans (1970) which is mainly concerned with fossorial species and their associates.
- Full Text:
- Date Issued: 1980
- Authors: Gess, Friedrich Wolfgang
- Date: 1980
- Subjects: Wasps -- South Africa Bees -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5834 , http://hdl.handle.net/10962/d1009445
- Description: From introduction: The present study is the first attempt in southern Africa to consider an entire community of aculeate wasps and bees and their interactions with their environment as manifested by their ethology. As far as the author has been able to ascertain it is in fact the most comprehensive of its kind to have been undertaken anywhere, the only similar but more restricted account of this nature being that of Evans (1970) which is mainly concerned with fossorial species and their associates.
- Full Text:
- Date Issued: 1980
Synthesis and reactions of sugar chlorosulphates
- Authors: Naidoo, Nadasen Thargarajan
- Date: 1980
- Subjects: Sugar -- Synthesis , Chemical reactions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3734 , http://hdl.handle.net/10962/d1001522
- Description: Sugar chlorosulphates of furanoid and pyranoid derivatives bearing chlorosulphonyloxy groups at primary and secondary positions, were synthesized and examined mainly with a view to determine their extent of reactivity in terms of nucleophilic substitution reactions, especially with azide. Inversion of configuration occurred at reactive chiral centres, whereas intermediate azidosulphonyloxy derivatives (azidosulphates) were formed via S-Cℓ bond fission of the chlorosulphonyloxy group at less reactive primary or secondary centres, e.g. 1,2:3,4-diO̲isopropyl idene-α-D-galactopyranose 6-azidosulphate, 1,2-O̲isopropylidenea- D-xylofuranose 3-azidosulphate and 1,2:5,6-di-O̲-isopropyl idene-α-Dglucofuranose 3-azidosulphate. 1,2:3,4-Di-O̲-isopropylidene-α-Dgalactopyranose 6-azidosulphate ultimately afforded the 6-azidodeoxy derivative probably by an SN2 mechanism. Some SNi characteristics were,however, evident when substitution occurred at a reactive primary centre (e.g. methyl 2,3,4-tri-O̲-methyla- D-glucopyranoside 6-chlorosulphate), as the 6-azidodeoxy derivative obtained, appeared to be contaminated with a trace amount of the corresponding 6-chlorodeoxy sugar, which had presumably formed via an internal SNi mechanism, while no intermediate azidosulphonyloxy derivative was isolated. In another study, the reaction pathways for the synthesis of benzylated chlorodeoxy sugars having potential biological properties as exemplified by the multivalent drug, tribenoside, were also investigated
- Full Text:
- Date Issued: 1980
- Authors: Naidoo, Nadasen Thargarajan
- Date: 1980
- Subjects: Sugar -- Synthesis , Chemical reactions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3734 , http://hdl.handle.net/10962/d1001522
- Description: Sugar chlorosulphates of furanoid and pyranoid derivatives bearing chlorosulphonyloxy groups at primary and secondary positions, were synthesized and examined mainly with a view to determine their extent of reactivity in terms of nucleophilic substitution reactions, especially with azide. Inversion of configuration occurred at reactive chiral centres, whereas intermediate azidosulphonyloxy derivatives (azidosulphates) were formed via S-Cℓ bond fission of the chlorosulphonyloxy group at less reactive primary or secondary centres, e.g. 1,2:3,4-diO̲isopropyl idene-α-D-galactopyranose 6-azidosulphate, 1,2-O̲isopropylidenea- D-xylofuranose 3-azidosulphate and 1,2:5,6-di-O̲-isopropyl idene-α-Dglucofuranose 3-azidosulphate. 1,2:3,4-Di-O̲-isopropylidene-α-Dgalactopyranose 6-azidosulphate ultimately afforded the 6-azidodeoxy derivative probably by an SN2 mechanism. Some SNi characteristics were,however, evident when substitution occurred at a reactive primary centre (e.g. methyl 2,3,4-tri-O̲-methyla- D-glucopyranoside 6-chlorosulphate), as the 6-azidodeoxy derivative obtained, appeared to be contaminated with a trace amount of the corresponding 6-chlorodeoxy sugar, which had presumably formed via an internal SNi mechanism, while no intermediate azidosulphonyloxy derivative was isolated. In another study, the reaction pathways for the synthesis of benzylated chlorodeoxy sugars having potential biological properties as exemplified by the multivalent drug, tribenoside, were also investigated
- Full Text:
- Date Issued: 1980
Systematics and biogeography of the redfin Barbus species (Pisces : Cyprinidae) from Southern Africa
- Authors: Skelton, Paul Harvey
- Date: 1980
- Subjects: Barbus Cyprinidae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5211 , http://hdl.handle.net/10962/d1004776
- Description: Resumé: This study deals with the systematics and biogeography of a group of minnowlike Barbus species which, as adults, are characterized by bright red fins. The species are found in the coastal rivers of the fold belt region of the southern and south-western Cape Province. A closely related species, Oreodaimon quathlambae, inhabits certain high altitude streams of the Drakensberg mountains. Traditional methods were employed to revise the taxonomy of the species. Characters studied included morphometric and meristic measurements, and several qualitative anatomical features, several of which were studied in these species for the first time. A new species, Barbus erubescens Skelton, was described during the course of the study (Appendix 3). The taxonomic status of other species are endorsed or revised (B.afer and B.asper). Each species is redescribed and figured. The complete osteology of one redfin species, B.burchelli, is described and illustrated. Comparisons are made with all other redfin species and various osteological characters of systematic value are discussed. The phylogeny of the redfins is studied using Hennigian methods. Comparative data from other southern African Barbus species and pertinent literature were used to determine and evaluate synapomorphic characters and character sequences. The redfins sensu lato are shown to be diphyletic. Barbus calidus Barnard and B.erubescens were found to be sister species not closely related to the other redfin species. Oreodaimon quathlambae (Barnard) is shown to be monophyletic with the second redfin lineage. Barbus burgi Boulenger is placed as the plesiomorph sister species in this lineage and consecutive dichotomies derive Barbus burchelli (Smith); Barbus afer Peters, and Barbus asper Boulenger; Barbus phlegethon Barnard; Barbus tenuis Barnard and Oreodaimon quathlambae. The classification of the redfins is reviewed in the light of their phylogeny and recommendations for an infonnal hierarchy are made. The generic status of each lineage is considered and a new genus, Pseudobarbus, erected for all the redfin species except B.calidus and B.erubescens, but including O. quathlambae. The distributions of redfin species are recorded. A hypothesis is given to explain this distribution, based on a comparison of distribution patterns of a number of plant and animal species and a consideration of the geological and geographical history of southern Africa. Vicariance is suggested to be the major factor which influenced redfin distribution. A theory of dispersal explains the distribution of P.tenuis. The biogeography suggests the redfins are relatively ancient (possibly Miocene?) southern African fishes. Suggestions are made on future studies on the redfins. Attention is drawn to possible implications of the redfin study on systematic study of southern African freshwater fishes.
- Full Text:
- Date Issued: 1980
Systematics and biogeography of the redfin Barbus species (Pisces : Cyprinidae) from Southern Africa
- Authors: Skelton, Paul Harvey
- Date: 1980
- Subjects: Barbus Cyprinidae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5211 , http://hdl.handle.net/10962/d1004776
- Description: Resumé: This study deals with the systematics and biogeography of a group of minnowlike Barbus species which, as adults, are characterized by bright red fins. The species are found in the coastal rivers of the fold belt region of the southern and south-western Cape Province. A closely related species, Oreodaimon quathlambae, inhabits certain high altitude streams of the Drakensberg mountains. Traditional methods were employed to revise the taxonomy of the species. Characters studied included morphometric and meristic measurements, and several qualitative anatomical features, several of which were studied in these species for the first time. A new species, Barbus erubescens Skelton, was described during the course of the study (Appendix 3). The taxonomic status of other species are endorsed or revised (B.afer and B.asper). Each species is redescribed and figured. The complete osteology of one redfin species, B.burchelli, is described and illustrated. Comparisons are made with all other redfin species and various osteological characters of systematic value are discussed. The phylogeny of the redfins is studied using Hennigian methods. Comparative data from other southern African Barbus species and pertinent literature were used to determine and evaluate synapomorphic characters and character sequences. The redfins sensu lato are shown to be diphyletic. Barbus calidus Barnard and B.erubescens were found to be sister species not closely related to the other redfin species. Oreodaimon quathlambae (Barnard) is shown to be monophyletic with the second redfin lineage. Barbus burgi Boulenger is placed as the plesiomorph sister species in this lineage and consecutive dichotomies derive Barbus burchelli (Smith); Barbus afer Peters, and Barbus asper Boulenger; Barbus phlegethon Barnard; Barbus tenuis Barnard and Oreodaimon quathlambae. The classification of the redfins is reviewed in the light of their phylogeny and recommendations for an infonnal hierarchy are made. The generic status of each lineage is considered and a new genus, Pseudobarbus, erected for all the redfin species except B.calidus and B.erubescens, but including O. quathlambae. The distributions of redfin species are recorded. A hypothesis is given to explain this distribution, based on a comparison of distribution patterns of a number of plant and animal species and a consideration of the geological and geographical history of southern Africa. Vicariance is suggested to be the major factor which influenced redfin distribution. A theory of dispersal explains the distribution of P.tenuis. The biogeography suggests the redfins are relatively ancient (possibly Miocene?) southern African fishes. Suggestions are made on future studies on the redfins. Attention is drawn to possible implications of the redfin study on systematic study of southern African freshwater fishes.
- Full Text:
- Date Issued: 1980
The meaning of becoming and being a member of a small and structured religious group
- Authors: Stones, Christopher R
- Date: 1980
- Subjects: Religious communities -- South Africa Jesus People -- South Africa -- Johannesburg Hare Krishnas -- South Africa -- Johannesburg Divine Light Mission Seminarians -- South Africa -- Pretoria Catholic theological seminaries -- South Africa Phenomenological psychology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3101 , http://hdl.handle.net/10962/d1004381
- Description: The concern of this investigation is with the meaning of becoming as well as being a member of one of four specific small and structured religious communities. Three of these religious groups - the Jesus People, the Hare Krishna Devotees and the Maharaj Ji Premies - are considered to be nonconformist in terms of the life-style, value-system and theology each adopts within the mainstream social and theological ethos, while the fourth group - a sample of Catholic Seminarians - like the other groups is a small community with a structured life-style, but its life-style and value-system is not necessarily non-conformist. These groups are all to be found, amongst other places, in Johannesburg, apart from the Catholic Priests, all of whom were living in a seminary in Pretoria. All the members of these religious communities - both men and women - who were interviewed were Caucasian, their educational standard ranged from pre-matric through to university graduate status, and the overall average age of the 9rouP members was 24 years - the youngest subject was aged 17 while the oldest was 31 years of age. Rather than a meas~rement orientated procedure, a phenomenologically inspired methodological procedure was used to explicitate the data. It is argued that a descriptive phenomenological perspective is more appropriate for the elucidation of meaning-structures, especially with reference to the present inquiry, than would be a quantitative, measurement and mathematical treatment of the subject matter with which this thesis is concerned. The results are best summarized by stating that, although the explication revealed that the four groups are distinctly different in certain aspects of the meaning-structures of the individuals' becoming and being members of a group, there are nonetheless marked similarities between the groups in other aspects of the explicitated data.
- Full Text:
- Date Issued: 1980
- Authors: Stones, Christopher R
- Date: 1980
- Subjects: Religious communities -- South Africa Jesus People -- South Africa -- Johannesburg Hare Krishnas -- South Africa -- Johannesburg Divine Light Mission Seminarians -- South Africa -- Pretoria Catholic theological seminaries -- South Africa Phenomenological psychology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3101 , http://hdl.handle.net/10962/d1004381
- Description: The concern of this investigation is with the meaning of becoming as well as being a member of one of four specific small and structured religious communities. Three of these religious groups - the Jesus People, the Hare Krishna Devotees and the Maharaj Ji Premies - are considered to be nonconformist in terms of the life-style, value-system and theology each adopts within the mainstream social and theological ethos, while the fourth group - a sample of Catholic Seminarians - like the other groups is a small community with a structured life-style, but its life-style and value-system is not necessarily non-conformist. These groups are all to be found, amongst other places, in Johannesburg, apart from the Catholic Priests, all of whom were living in a seminary in Pretoria. All the members of these religious communities - both men and women - who were interviewed were Caucasian, their educational standard ranged from pre-matric through to university graduate status, and the overall average age of the 9rouP members was 24 years - the youngest subject was aged 17 while the oldest was 31 years of age. Rather than a meas~rement orientated procedure, a phenomenologically inspired methodological procedure was used to explicitate the data. It is argued that a descriptive phenomenological perspective is more appropriate for the elucidation of meaning-structures, especially with reference to the present inquiry, than would be a quantitative, measurement and mathematical treatment of the subject matter with which this thesis is concerned. The results are best summarized by stating that, although the explication revealed that the four groups are distinctly different in certain aspects of the meaning-structures of the individuals' becoming and being members of a group, there are nonetheless marked similarities between the groups in other aspects of the explicitated data.
- Full Text:
- Date Issued: 1980
The relationship of academic aptitude and study habits to academic success : a study of first year students' experience of academic life with specific reference to the University of Fort Hare
- Authors: Penny, Alan Joseph
- Date: 1980
- Subjects: Academic achievement , Student adjustment -- South Africa , College students, Black -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1379 , http://hdl.handle.net/10962/d1001445
- Description: Any enquiry follows some incident which has prompted the question that leads to the enquiry. This study was prompted by a review of the 1974 first year examination results at the University of Fort Hare. The average percentage pass rate for that year was 59.3%. The cynic may remark that this is no different to the first year pass rate at white South African universities (cf. Erens and Louw, 1978), but when it is realised that students entering Fort Hare, or any other black university for that matter, are a highly select group, these figures have more Impact. The consequences of failure in terms of the wastage of human potential are immense (cf. Auerbach, 1977) but are more critical when this occurs, as It does, "... in a society which is competitive rather than co-operative, where people are for ever being classified according to what they have rather than that they can contribute and where competition plus classification inevitably breeds fears." Bligh (1978). A review of the first year examination results for the five years from 1971 revealed an average pass rate of 55.5% and for 1976, 1977 and 1978 a marked decline to 39.32%. For the earlier period, Downing (1977) found that 19.69% of students completed their degree courses In the minimum number of years. For the latter period (1976 to 1978) this has dropped to 16.3%, which, with the figure for the earlier period, suggests that whilst the failure rate may be highest at the end of the first year, in subsequent years it is also high. In this respect Fort Hare differs from white universities where about 75% of students complete their degrees in minimum time (cf. Erens and Louw, 1978)
- Full Text:
- Date Issued: 1980
- Authors: Penny, Alan Joseph
- Date: 1980
- Subjects: Academic achievement , Student adjustment -- South Africa , College students, Black -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1379 , http://hdl.handle.net/10962/d1001445
- Description: Any enquiry follows some incident which has prompted the question that leads to the enquiry. This study was prompted by a review of the 1974 first year examination results at the University of Fort Hare. The average percentage pass rate for that year was 59.3%. The cynic may remark that this is no different to the first year pass rate at white South African universities (cf. Erens and Louw, 1978), but when it is realised that students entering Fort Hare, or any other black university for that matter, are a highly select group, these figures have more Impact. The consequences of failure in terms of the wastage of human potential are immense (cf. Auerbach, 1977) but are more critical when this occurs, as It does, "... in a society which is competitive rather than co-operative, where people are for ever being classified according to what they have rather than that they can contribute and where competition plus classification inevitably breeds fears." Bligh (1978). A review of the first year examination results for the five years from 1971 revealed an average pass rate of 55.5% and for 1976, 1977 and 1978 a marked decline to 39.32%. For the earlier period, Downing (1977) found that 19.69% of students completed their degree courses In the minimum number of years. For the latter period (1976 to 1978) this has dropped to 16.3%, which, with the figure for the earlier period, suggests that whilst the failure rate may be highest at the end of the first year, in subsequent years it is also high. In this respect Fort Hare differs from white universities where about 75% of students complete their degrees in minimum time (cf. Erens and Louw, 1978)
- Full Text:
- Date Issued: 1980
'n Studie van die houding en gesindheid teenoor spesiale onderwys soos geopenbaar deur 'n groep ouers van spesiale klas-leerlinge in Oos-Kaapland
- Bouwer, Jeremia Cornelius Esias
- Authors: Bouwer, Jeremia Cornelius Esias
- Date: 1979
- Subjects: Special education -- South Africa -- Eastern Cape
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1361 , http://hdl.handle.net/10962/d1001427
- Description: Die weerstand wat ouers soms teen Spesiale Onderwys bied, kan stremmend inwerk op leerlinge. Om insig in die gesindheid van ouers van Spesiale Klas-Ieerlinge te verkry, is 'n gewysigde vorm van die Thurston Sentence Completion Form gebruik. Die vorms is deur ouers van leerlinge in 'n aantal Spesiale Klasse in Oos-Kaapland voltooi en die response is in positiewe en negatiewe reaksies ingedeel. Ook is elke item ontleed. Daar is tot die gevolgtrekking gekom dat die meeste ouers tog weI positief ingesteld is teenoor Spesiale Onderwys en inderdaad erkenning verleen aan die werk wat in die klasse gedoen word. Die behoefte aan 'n nouer skakeling tussen die betrokke ouers en die skole het duidelik na vore gekom
- Full Text:
- Date Issued: 1979
- Authors: Bouwer, Jeremia Cornelius Esias
- Date: 1979
- Subjects: Special education -- South Africa -- Eastern Cape
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1361 , http://hdl.handle.net/10962/d1001427
- Description: Die weerstand wat ouers soms teen Spesiale Onderwys bied, kan stremmend inwerk op leerlinge. Om insig in die gesindheid van ouers van Spesiale Klas-Ieerlinge te verkry, is 'n gewysigde vorm van die Thurston Sentence Completion Form gebruik. Die vorms is deur ouers van leerlinge in 'n aantal Spesiale Klasse in Oos-Kaapland voltooi en die response is in positiewe en negatiewe reaksies ingedeel. Ook is elke item ontleed. Daar is tot die gevolgtrekking gekom dat die meeste ouers tog weI positief ingesteld is teenoor Spesiale Onderwys en inderdaad erkenning verleen aan die werk wat in die klasse gedoen word. Die behoefte aan 'n nouer skakeling tussen die betrokke ouers en die skole het duidelik na vore gekom
- Full Text:
- Date Issued: 1979
A comparison of the performance of selected conceptual models of the rainfall-runoff process in semi-arid catchments near Grahamstown
- Authors: Roberts, Peter J T
- Date: 1979
- Subjects: Runoff , Rainfall , South Africa , Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4798 , http://hdl.handle.net/10962/d1001898
- Description: A comparison of the performance of selected conceptual models of the rainfall-runoff process forms the central theme of this study and the comparison was conducted with three major objectives in mind. The first objective was to develop a conceptual model that could be used by practising hydrologists for the refinement and extension of historical streamflow records. The major requirements of the model were that it should be simple in structure and easy to operate and yet be flexible in terms of complexity of structure and input requirements as well as producing output at a level of accuracy that is competitive with that of the more complex models presently available. A comparison of the performance of the required model with that of other models formed an integral part of the development process. The second objective of the comparative study was to contribute to current knowledge of the criteria used in the selection of a suitable model for a particular application. There are, at present, no reliable guidelines to assist the hydrologist in selecting a suitable model from the wide range of models available and a comparative study would indicate the merits of various forms of model structure. The third objective is associated with the problems that arise when no streamflow data are available for model calibration. One approach is to calibrate the model in a nearby gauged catchment that the hydrologist regards as being 'hydrologically similar' and transferring the model parameter values to the ungauged catchment. Little is known about the feasibility of this parameter transfer process or about the choice of a model for such an application. The third objective was to test the feasibility of the parameter transfer process and to make use of the comparison of model performance to determine the model characteristics that are most suitable for the purpose
- Full Text:
- Date Issued: 1979
- Authors: Roberts, Peter J T
- Date: 1979
- Subjects: Runoff , Rainfall , South Africa , Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4798 , http://hdl.handle.net/10962/d1001898
- Description: A comparison of the performance of selected conceptual models of the rainfall-runoff process forms the central theme of this study and the comparison was conducted with three major objectives in mind. The first objective was to develop a conceptual model that could be used by practising hydrologists for the refinement and extension of historical streamflow records. The major requirements of the model were that it should be simple in structure and easy to operate and yet be flexible in terms of complexity of structure and input requirements as well as producing output at a level of accuracy that is competitive with that of the more complex models presently available. A comparison of the performance of the required model with that of other models formed an integral part of the development process. The second objective of the comparative study was to contribute to current knowledge of the criteria used in the selection of a suitable model for a particular application. There are, at present, no reliable guidelines to assist the hydrologist in selecting a suitable model from the wide range of models available and a comparative study would indicate the merits of various forms of model structure. The third objective is associated with the problems that arise when no streamflow data are available for model calibration. One approach is to calibrate the model in a nearby gauged catchment that the hydrologist regards as being 'hydrologically similar' and transferring the model parameter values to the ungauged catchment. Little is known about the feasibility of this parameter transfer process or about the choice of a model for such an application. The third objective was to test the feasibility of the parameter transfer process and to make use of the comparison of model performance to determine the model characteristics that are most suitable for the purpose
- Full Text:
- Date Issued: 1979
A history of the growth and development of the Seventh-Day Adventist Church in Southern Africa, 1920-1960
- Thompson, Ronald Charles Lloyd
- Authors: Thompson, Ronald Charles Lloyd
- Date: 1979
- Subjects: Seventh-Day Adventists -- South Africa -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1231 , http://hdl.handle.net/10962/d1007294
- Description: From Introduction: The most natural divisions of time for this historical survey of the growth and development of the Seventh-day Adventist Church in Southern Africa fall into three periods: (1) from 1920, when the African Division of Seventh-day Adventists was organized, to 1931, when it was reorganized under the name Southern African Division; (2) from 1931 to 1945, covering the period years of the Great Depression and Second world War; (3) from 1946 to 1960, the post-war. Attention is given in Chapter I to a certain phase of church development because the church had emerged at the highest level of Adventist organization, i.e. a Division. Although the first group of Adventists adopted the simplest form of organization in 1892 known as the South African Conference, the church was small and little known. The church at Division level therefore embarked on a programme of orientation and adaptation to gain recognition and make itself known everywhere. Closely allied to this was organization. Chapter II defines the organization of the church and explains how it was financed. The history of its organization and reorganization is also traced. Chapters III and IV deal with an era of expansion during the twenties in the establishment of missions, medical missions and training institutions, while new mission fields were entered and old mission fields were further developed. Chapters V and VI continue to trace the development of missions, mission fields, medical missions, and training institutions together with important changes in the medical and educational work. Further reorganization and new developments in the European church and African church are also outlined. The great emphasis on expansion and the development of institutions finally reached a point whereby "institutionalism" overtook "evangelism". Chapter VII discusses this problem and what was done to try and arrest it. Thus the history of the church is brought to an interesting turning point and climax in Part Two. Chapter VIII breaks from the common run of growth and development in missions, medical missions and institutions and traces the development of the principles and practice of the Adventist Church. The Southern African Division set itself the objective of full maturity in the establishment of a self-supporting, self-governing and self- propagating church in Africa. The history of these principles are covered together with the principles governing the reception of government grants-in-aid. Chapter IX deals with the analysis and development of the three-fold ministry of teaching, preaching and healing. These chapters in Part Three do not constitute a conclusion but simply give further insights in the growth and development of the church .
- Full Text:
- Date Issued: 1979
- Authors: Thompson, Ronald Charles Lloyd
- Date: 1979
- Subjects: Seventh-Day Adventists -- South Africa -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1231 , http://hdl.handle.net/10962/d1007294
- Description: From Introduction: The most natural divisions of time for this historical survey of the growth and development of the Seventh-day Adventist Church in Southern Africa fall into three periods: (1) from 1920, when the African Division of Seventh-day Adventists was organized, to 1931, when it was reorganized under the name Southern African Division; (2) from 1931 to 1945, covering the period years of the Great Depression and Second world War; (3) from 1946 to 1960, the post-war. Attention is given in Chapter I to a certain phase of church development because the church had emerged at the highest level of Adventist organization, i.e. a Division. Although the first group of Adventists adopted the simplest form of organization in 1892 known as the South African Conference, the church was small and little known. The church at Division level therefore embarked on a programme of orientation and adaptation to gain recognition and make itself known everywhere. Closely allied to this was organization. Chapter II defines the organization of the church and explains how it was financed. The history of its organization and reorganization is also traced. Chapters III and IV deal with an era of expansion during the twenties in the establishment of missions, medical missions and training institutions, while new mission fields were entered and old mission fields were further developed. Chapters V and VI continue to trace the development of missions, mission fields, medical missions, and training institutions together with important changes in the medical and educational work. Further reorganization and new developments in the European church and African church are also outlined. The great emphasis on expansion and the development of institutions finally reached a point whereby "institutionalism" overtook "evangelism". Chapter VII discusses this problem and what was done to try and arrest it. Thus the history of the church is brought to an interesting turning point and climax in Part Two. Chapter VIII breaks from the common run of growth and development in missions, medical missions and institutions and traces the development of the principles and practice of the Adventist Church. The Southern African Division set itself the objective of full maturity in the establishment of a self-supporting, self-governing and self- propagating church in Africa. The history of these principles are covered together with the principles governing the reception of government grants-in-aid. Chapter IX deals with the analysis and development of the three-fold ministry of teaching, preaching and healing. These chapters in Part Three do not constitute a conclusion but simply give further insights in the growth and development of the church .
- Full Text:
- Date Issued: 1979
A mineralogical investigation of co-existing iron-titanium oxides from various igneous rocks with special reference to some South African titaniferous iron ores
- Authors: Reynolds, Ivan Melvin
- Date: 1979
- Subjects: Igneous rocks Mineralogy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4926 , http://hdl.handle.net/10962/d1004589
- Description: Part I consists of a detailied review of the available literature on the Fe- Ti oxides and their solid solution relationships. Particular attention is glven to the microstructures exhibited by these oxides and the hypotheses put forward to explain them. These data are synthesised and models are presented in which the microstructural developments in titaniferous magnetites amd ilmenites are explained in terms of current ideas on the influence of oxygen fugacity, exsolution mechanisms and crystal chemistry. These models have direct application to the microintergrowths observed in the naturally occurring Fe-Ti oxides from a wide range of igneous rocks. The available data on the minor and trace element chemistry of the Fe-Ti oxides are reviewed with particular reference to their variation in these minerals from different host rocks. The behaviour of the Fe-Ti oxides during secondary oxidation is discussed with particular reference to the oxidation of titaniferous magnetite and the weathering of ilmenite. The results of a mineralogical investigation into the co-existing Fe-Ti oxides from a range of igneous rocks including kimberlites, gabbros, dolerites, diabases, syenites, granophyres, granites and pegmatites are presented in Part 2 together with data on the ilmenites present in certain Eastern Cape beach sands. The kimberlite ilmenites are chemically distinct and can be readily distinguished on the basis of their relatively high MgO, Fe₂0₃ and Cr₂O₃ contents. They can also be distinguished from ilmenites from other igneous rocks on the basis of unit cell dimensions, d-spacings, reflectivities and micro-indentation hardness. The ilmenites from a wide range of basic to granitic igneous rocks exhibit a limited compositional range in which the MnO content appears to increase with increasing Si0₂ content. Relatively insensitive indirectly determined parameters such as unit cell dimensions, reflectivities and micro-indentation hardnesses cannot be used to distinguish between the ilmenites from the different rock types in these classes. The titaniferous magnetites exhibit progressively decreasing Ti0₂ contents from a maximum in the basic igneous rocks to a minimum in the granitic types. The titaniferous magnetite typically exhibits varying degrees of deuteric alteration, while the microstructures developed can be interpreted 1n terms of the models presented in Part 1. Part 3 represents an extension of Part 2 and deals with a mineralogical investigation of the titaniferous iron ores in five South African basic intrusions. The Bushveld and Kaffirskraal ores consist of multi-phase titaniferous magnetite grains containing crystallographically oriented ilmenite, ulvospinel and pleonaste microintergrowths. Minor coarser-grained ilmenite is also present. The Usushwana ores are texturally similar but contain abundant lamellar ilmenite in place of the ulvospinel. The primary features are well preserved in the unmetamorphosed Bushveld and Kaffirskraal ores. The Usushwana ores have been slightly metamorphosed resulting in the extensive replacement of the titaniferous magnetites by sphene and chlorite aggregates. The ores from these three complexes cannot be beneficiated by conventional ore-dressing techniques and require direct metallurgical treatment for the recovery of Fe, Ti0₂ and V₂O₅. The metamorphosed Mambula and Rooiwater ores have been recrystallised to a varying degrees and consist of multi-phase titaniferous magnetite grains containing modified ilmenite and pleonaste microintergrowths. These modified microstructures differ from those encountered in titaniferous magnetites from unmetnmorphosed basic rocks and their degree of modification can be related to the degree of met amorphism. Variable amounts of coarse granular ilmenite are also present and their development is related to the metamorphic grade and degree of recrystallisation. These ores can be partially beneficiated to yield ilmenite- and lower-Ti0₂ magnetite concentrates in which V₂O₅ contents of the magnetic fractions are higher than those of the original ores. The Trompsburg ores differ from those of the other complexes in that they are Mg-rich and are characterised by the presence of abundant olivine. The titaniferous magnetites typically exhibit well-defined ulvospinel cloth textures and are often surrounded by small amounts of graphite. They show evidence of a variety of extensive late-stage alteration features. The ores from the five investigated complexes are compared with similar ores from the Bushveld Complex. The ores from each complex can be readily distinguished on the basis of their chemical compositions and textural relationships. These features can be related to their crystallisation his tories and, in some cases, to post-crystallisation processes. The microstructural evolution of the ores from each complex is interpreted in terms of the models developed in Part I.
- Full Text:
- Date Issued: 1979
- Authors: Reynolds, Ivan Melvin
- Date: 1979
- Subjects: Igneous rocks Mineralogy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4926 , http://hdl.handle.net/10962/d1004589
- Description: Part I consists of a detailied review of the available literature on the Fe- Ti oxides and their solid solution relationships. Particular attention is glven to the microstructures exhibited by these oxides and the hypotheses put forward to explain them. These data are synthesised and models are presented in which the microstructural developments in titaniferous magnetites amd ilmenites are explained in terms of current ideas on the influence of oxygen fugacity, exsolution mechanisms and crystal chemistry. These models have direct application to the microintergrowths observed in the naturally occurring Fe-Ti oxides from a wide range of igneous rocks. The available data on the minor and trace element chemistry of the Fe-Ti oxides are reviewed with particular reference to their variation in these minerals from different host rocks. The behaviour of the Fe-Ti oxides during secondary oxidation is discussed with particular reference to the oxidation of titaniferous magnetite and the weathering of ilmenite. The results of a mineralogical investigation into the co-existing Fe-Ti oxides from a range of igneous rocks including kimberlites, gabbros, dolerites, diabases, syenites, granophyres, granites and pegmatites are presented in Part 2 together with data on the ilmenites present in certain Eastern Cape beach sands. The kimberlite ilmenites are chemically distinct and can be readily distinguished on the basis of their relatively high MgO, Fe₂0₃ and Cr₂O₃ contents. They can also be distinguished from ilmenites from other igneous rocks on the basis of unit cell dimensions, d-spacings, reflectivities and micro-indentation hardness. The ilmenites from a wide range of basic to granitic igneous rocks exhibit a limited compositional range in which the MnO content appears to increase with increasing Si0₂ content. Relatively insensitive indirectly determined parameters such as unit cell dimensions, reflectivities and micro-indentation hardnesses cannot be used to distinguish between the ilmenites from the different rock types in these classes. The titaniferous magnetites exhibit progressively decreasing Ti0₂ contents from a maximum in the basic igneous rocks to a minimum in the granitic types. The titaniferous magnetite typically exhibits varying degrees of deuteric alteration, while the microstructures developed can be interpreted 1n terms of the models presented in Part 1. Part 3 represents an extension of Part 2 and deals with a mineralogical investigation of the titaniferous iron ores in five South African basic intrusions. The Bushveld and Kaffirskraal ores consist of multi-phase titaniferous magnetite grains containing crystallographically oriented ilmenite, ulvospinel and pleonaste microintergrowths. Minor coarser-grained ilmenite is also present. The Usushwana ores are texturally similar but contain abundant lamellar ilmenite in place of the ulvospinel. The primary features are well preserved in the unmetamorphosed Bushveld and Kaffirskraal ores. The Usushwana ores have been slightly metamorphosed resulting in the extensive replacement of the titaniferous magnetites by sphene and chlorite aggregates. The ores from these three complexes cannot be beneficiated by conventional ore-dressing techniques and require direct metallurgical treatment for the recovery of Fe, Ti0₂ and V₂O₅. The metamorphosed Mambula and Rooiwater ores have been recrystallised to a varying degrees and consist of multi-phase titaniferous magnetite grains containing modified ilmenite and pleonaste microintergrowths. These modified microstructures differ from those encountered in titaniferous magnetites from unmetnmorphosed basic rocks and their degree of modification can be related to the degree of met amorphism. Variable amounts of coarse granular ilmenite are also present and their development is related to the metamorphic grade and degree of recrystallisation. These ores can be partially beneficiated to yield ilmenite- and lower-Ti0₂ magnetite concentrates in which V₂O₅ contents of the magnetic fractions are higher than those of the original ores. The Trompsburg ores differ from those of the other complexes in that they are Mg-rich and are characterised by the presence of abundant olivine. The titaniferous magnetites typically exhibit well-defined ulvospinel cloth textures and are often surrounded by small amounts of graphite. They show evidence of a variety of extensive late-stage alteration features. The ores from the five investigated complexes are compared with similar ores from the Bushveld Complex. The ores from each complex can be readily distinguished on the basis of their chemical compositions and textural relationships. These features can be related to their crystallisation his tories and, in some cases, to post-crystallisation processes. The microstructural evolution of the ores from each complex is interpreted in terms of the models developed in Part I.
- Full Text:
- Date Issued: 1979
A study of the utilisation of East London harbour and its relative importance in the South African import and export trade, to 1975
- Authors: De Beer, David Petrus
- Date: 1979
- Subjects: Harbors -- South Africa -- East London , Exports -- South Africa -- East London , Imports -- South Africa -- East London , Export marketing -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:835 , http://hdl.handle.net/10962/d1013316
- Description: From Ch. 1: The object of this study is to consider the utilisation of East London Harbour and its relative importance in the South African import and export trade to 1975. The principal harbours of the Republic of South Africa are Table Bay (Cape TOwn), Algoa Bay (Port Elizabeth), Buffalo Harbour (East London) and Durban, and Walvis Bay in South West Africa. Small harbours suitable only for coastal shipping are Mossel Bay, Simonstown, Lamberts Bay, St. Helena Bay and Port Nolloth in the Republic and LUderitz in South West Africa. Two harbours, Saldanha Bay and Richards Bay are at present being built. The ports of the Republic of South Africa and South West Africa are owned by the Government, are constructed, controlled and operated by the South African Railways and Harbours Administration, under the direction of the Minister of Transport, and are managed by the General Manager, whose headquarters are in Johannesburg.
- Full Text:
- Date Issued: 1979
- Authors: De Beer, David Petrus
- Date: 1979
- Subjects: Harbors -- South Africa -- East London , Exports -- South Africa -- East London , Imports -- South Africa -- East London , Export marketing -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:835 , http://hdl.handle.net/10962/d1013316
- Description: From Ch. 1: The object of this study is to consider the utilisation of East London Harbour and its relative importance in the South African import and export trade to 1975. The principal harbours of the Republic of South Africa are Table Bay (Cape TOwn), Algoa Bay (Port Elizabeth), Buffalo Harbour (East London) and Durban, and Walvis Bay in South West Africa. Small harbours suitable only for coastal shipping are Mossel Bay, Simonstown, Lamberts Bay, St. Helena Bay and Port Nolloth in the Republic and LUderitz in South West Africa. Two harbours, Saldanha Bay and Richards Bay are at present being built. The ports of the Republic of South Africa and South West Africa are owned by the Government, are constructed, controlled and operated by the South African Railways and Harbours Administration, under the direction of the Minister of Transport, and are managed by the General Manager, whose headquarters are in Johannesburg.
- Full Text:
- Date Issued: 1979
Aspects of tradition and originality in the chamber music of Robert Schumann
- Authors: Lucia, Christine
- Date: 1979
- Subjects: Schumann, Robert, 1810-1856 Chamber music
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2628 , http://hdl.handle.net/10962/d1001973
- Full Text:
- Date Issued: 1979
- Authors: Lucia, Christine
- Date: 1979
- Subjects: Schumann, Robert, 1810-1856 Chamber music
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2628 , http://hdl.handle.net/10962/d1001973
- Full Text:
- Date Issued: 1979
Biology and systematics of some southern African myrmeleontoid insects (order Neuroptera)
- Authors: Mansell, Mervyn W
- Date: 1979
- Subjects: Ant lions -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5594 , http://hdl.handle.net/10962/d1002044
- Description: The biology of southern African Myrmeleontidae and Nemopteridae (Neuroptera, Myrmeleontoidea) was studied with special emphasis on the nemopterid subfamily Crocinae. The superfamily Myrmeleontoidea is considered to be a monophyletic group derived from ancestors similar to the family Nymphidae. The Myrmeleontidae and Nemopteridae are the most highly evolved families, and the Nemopteridae have a sistergroup relationship with the other four myrmeleontoid families. Within the Nemopteridae, the Crocinae are considered more advanced than the subfamily Nemopterinae. An account of previous work on the two families is presented: literature relating to the Myrmeleontidae is catalogued in appendix 2 and publications dealing with the Nemopteridae are surveyed in the text . Biological and morphological information derived from the immature stages as well as the adults was used in the systematic study of the two families. The geographical distribution and phylogeny of the Myrmeleontoidea is discussed with particular reference to the Myrmeleontidae and Nemopteridae. The Myrmeleontidae have a world wide distribution whilst the Nemopteridae are more restricted, being limited to the arid and semi-arid regions of the world. It is concluded that the two families originated on Gondwanaland, and their present distribution is explained on the basis of evidence provided by plate tectonics. In southern Africa, the Myrmeleontidae show two distributional trends: there is a distinct western fauna including many endemics and an eastern fauna which comprises taxa with a wide distribution in central and east Africa, extending their ranges into the eastern parts of the subregion. The Nemopteridae occur predominantly on the western side of the subcontinent and over 90% of the species are endemic to southern Africa. A systematic revision of the southern African Crocinae is presented and summarized in a set of illustrated keys to the adults and larvae. There are now ten known crocin species in four genera from the subregion, four species being described for the first time in this thesis. The larvae of all ten species and the eggs of seven, have been correlated with the adults and are described. Two crocin genera, Concroce and Thysanocroce, have larvae with short prothoraxes, whilst those in Laurhervasia and Tjederia are elongated. Larvae of the first two genera live in plant detritus under rocks and in crevices whereas larvae of the latter two genera inhabit small dusty caves. These findings on the Myrmeleontidae and Nemopteridae are discussed in the context of general systematic theory, phylogeny and zoogeography.
- Full Text:
- Date Issued: 1979
- Authors: Mansell, Mervyn W
- Date: 1979
- Subjects: Ant lions -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5594 , http://hdl.handle.net/10962/d1002044
- Description: The biology of southern African Myrmeleontidae and Nemopteridae (Neuroptera, Myrmeleontoidea) was studied with special emphasis on the nemopterid subfamily Crocinae. The superfamily Myrmeleontoidea is considered to be a monophyletic group derived from ancestors similar to the family Nymphidae. The Myrmeleontidae and Nemopteridae are the most highly evolved families, and the Nemopteridae have a sistergroup relationship with the other four myrmeleontoid families. Within the Nemopteridae, the Crocinae are considered more advanced than the subfamily Nemopterinae. An account of previous work on the two families is presented: literature relating to the Myrmeleontidae is catalogued in appendix 2 and publications dealing with the Nemopteridae are surveyed in the text . Biological and morphological information derived from the immature stages as well as the adults was used in the systematic study of the two families. The geographical distribution and phylogeny of the Myrmeleontoidea is discussed with particular reference to the Myrmeleontidae and Nemopteridae. The Myrmeleontidae have a world wide distribution whilst the Nemopteridae are more restricted, being limited to the arid and semi-arid regions of the world. It is concluded that the two families originated on Gondwanaland, and their present distribution is explained on the basis of evidence provided by plate tectonics. In southern Africa, the Myrmeleontidae show two distributional trends: there is a distinct western fauna including many endemics and an eastern fauna which comprises taxa with a wide distribution in central and east Africa, extending their ranges into the eastern parts of the subregion. The Nemopteridae occur predominantly on the western side of the subcontinent and over 90% of the species are endemic to southern Africa. A systematic revision of the southern African Crocinae is presented and summarized in a set of illustrated keys to the adults and larvae. There are now ten known crocin species in four genera from the subregion, four species being described for the first time in this thesis. The larvae of all ten species and the eggs of seven, have been correlated with the adults and are described. Two crocin genera, Concroce and Thysanocroce, have larvae with short prothoraxes, whilst those in Laurhervasia and Tjederia are elongated. Larvae of the first two genera live in plant detritus under rocks and in crevices whereas larvae of the latter two genera inhabit small dusty caves. These findings on the Myrmeleontidae and Nemopteridae are discussed in the context of general systematic theory, phylogeny and zoogeography.
- Full Text:
- Date Issued: 1979
Contributions to the theory of group rings
- Groenewald, Nicolas Johannes
- Authors: Groenewald, Nicolas Johannes
- Date: 1979
- Subjects: Group rings Group theory -- Mathematics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5391 , http://hdl.handle.net/10962/d1001980
- Description: Chapter 1 is a short review of the main results in some areas of the theory of group rings. In the first half of Chapter 2 we determine the ideal theoretic structure of the group ring RG where G is the direct product of a finite Abelian group and an ordered group with R a completely primary ring. Our choice of rings and groups entails that the study centres mainly on zero divisor ideals of group rings and hence it contributes in a small way to the zero divisor problem. We show that if R is a completely primary ring, then there exists a one-one correspondence of the prime zero divisor ideals in RG and RG¯, G finite cyclic of order n. If R is a ring with the property α, β € R, then αβ = 0 implies βα = 0, and S is an ordered semigroup, we show that if ∑α¡s¡ ∈ RS is a divisor of zero, then the coefficients α¡ belong to a zero divisor ideal in R. The converse is proved in the case where R is a commutative Noetherian ring. These results are applied to give an account of the zero divisors in the group ring over the direct product of a finite Abelian group and an ordered group with coefficients in a completely primary ring. In the second half of Chapter 2 we determine the units of the group ring RG where R is not necessarily commutative and G is an ordered group. If R is a ring such that if α, β € R and αβ = 0, then βα = 0, and if G is an ordered group, then we show that ∑αg(subscript)g is a unit in RG if and only if there exists ∑βh(subscript)h in RG such that∑αg(subscript)βg(subscript)-1 = 1 and αg(subscriptβh is nilpotent whenever GH≠1. We also show that if R is a ring with no nilpotent elements ≠0 and no idempotents ≠0,1, then RG has only trivial units. In this chapter we also consider strongly prime rings. We prove that RG is strongly prime if R is strongly prime and G is an unique product (u.p.) group. If H ⊲ G such that G/H is right ordered, then it is shown that RG is strongly prime if RH is strongly prime. In Chapter 3 results are derived to indicate the relations between certain classes of ideals in R and RG. If δ is a property of ideals defined for ideals in R and RG, then the "going up" condition holds for δ-ideals if Q being a δ-ideal in R implies that QG is a δ-ideal in RG. The "going down" condition is satisfied if P being a δ-ideal in RG implies that P∩ R is a δ-ideal in R. We proved that the "going up" and "going down" conditions are satisfied for prime ideals, ℓ-prime ideals, q-semiprime ideals and strongly prime ideals. These results are then applied to obtain certain relations between different radicals of the ring R and the group ring (semigroup ring) RG (RS). Similarly, results about the relation between the ideals and the radicals of the group rings RH and RG, where H is a central subgroup of G, are obtained. For the upper nil radical we prove that ⋃(RG) (RH) ⊆ RG, H a central subgroup of G, if G/H is an ordered group . If S is an ordered semigroup, however, then ⋃(RS) ⊆ ⋃(R)S for any ring R. In Chapter 4 we determine relations between various radicals in certain classes of group rings. In Section 4.3, as an extension of a result of Tan, we prove that P(R)G = P(RG) , R a ring with identity , if and only if the order of no finite normal subgroup of G is a zero divisor in R/P(R). If R is any ring with identity and H a normal subgroup of G such that G/H is an ordered group, we show that ⊓(RH)·RG = ⋃(RG) = ⊓(RG) , if ⋃(RH) is nilpotent. Similar results are obtained for the semigroup ring RS, S ordered. It is also shown if R is commutative and G finite of order n, then J(R)G = J(RG) if and only if n is not a zero divisor in R/J(R), J(R) being the Jacobson radical of R. For the Brown HcCoy radical we determine the following: If R is Brown McCoy semisimple or if R is a simple ring with identity, then B(RG) = (0), where G is a finitely generated torsion free Abelian group. In the last section we determine further relations between some of the previously defined radicals, in particular between P(R), U(R) and J(R). Among other results, the following relations between the abovementioned radicals are obtained: U(RS) = U(R)S = P(RS) = J(RS) where R is a left Goldie ring and S an ordered semigroup with unity
- Full Text:
- Date Issued: 1979
- Authors: Groenewald, Nicolas Johannes
- Date: 1979
- Subjects: Group rings Group theory -- Mathematics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5391 , http://hdl.handle.net/10962/d1001980
- Description: Chapter 1 is a short review of the main results in some areas of the theory of group rings. In the first half of Chapter 2 we determine the ideal theoretic structure of the group ring RG where G is the direct product of a finite Abelian group and an ordered group with R a completely primary ring. Our choice of rings and groups entails that the study centres mainly on zero divisor ideals of group rings and hence it contributes in a small way to the zero divisor problem. We show that if R is a completely primary ring, then there exists a one-one correspondence of the prime zero divisor ideals in RG and RG¯, G finite cyclic of order n. If R is a ring with the property α, β € R, then αβ = 0 implies βα = 0, and S is an ordered semigroup, we show that if ∑α¡s¡ ∈ RS is a divisor of zero, then the coefficients α¡ belong to a zero divisor ideal in R. The converse is proved in the case where R is a commutative Noetherian ring. These results are applied to give an account of the zero divisors in the group ring over the direct product of a finite Abelian group and an ordered group with coefficients in a completely primary ring. In the second half of Chapter 2 we determine the units of the group ring RG where R is not necessarily commutative and G is an ordered group. If R is a ring such that if α, β € R and αβ = 0, then βα = 0, and if G is an ordered group, then we show that ∑αg(subscript)g is a unit in RG if and only if there exists ∑βh(subscript)h in RG such that∑αg(subscript)βg(subscript)-1 = 1 and αg(subscriptβh is nilpotent whenever GH≠1. We also show that if R is a ring with no nilpotent elements ≠0 and no idempotents ≠0,1, then RG has only trivial units. In this chapter we also consider strongly prime rings. We prove that RG is strongly prime if R is strongly prime and G is an unique product (u.p.) group. If H ⊲ G such that G/H is right ordered, then it is shown that RG is strongly prime if RH is strongly prime. In Chapter 3 results are derived to indicate the relations between certain classes of ideals in R and RG. If δ is a property of ideals defined for ideals in R and RG, then the "going up" condition holds for δ-ideals if Q being a δ-ideal in R implies that QG is a δ-ideal in RG. The "going down" condition is satisfied if P being a δ-ideal in RG implies that P∩ R is a δ-ideal in R. We proved that the "going up" and "going down" conditions are satisfied for prime ideals, ℓ-prime ideals, q-semiprime ideals and strongly prime ideals. These results are then applied to obtain certain relations between different radicals of the ring R and the group ring (semigroup ring) RG (RS). Similarly, results about the relation between the ideals and the radicals of the group rings RH and RG, where H is a central subgroup of G, are obtained. For the upper nil radical we prove that ⋃(RG) (RH) ⊆ RG, H a central subgroup of G, if G/H is an ordered group . If S is an ordered semigroup, however, then ⋃(RS) ⊆ ⋃(R)S for any ring R. In Chapter 4 we determine relations between various radicals in certain classes of group rings. In Section 4.3, as an extension of a result of Tan, we prove that P(R)G = P(RG) , R a ring with identity , if and only if the order of no finite normal subgroup of G is a zero divisor in R/P(R). If R is any ring with identity and H a normal subgroup of G such that G/H is an ordered group, we show that ⊓(RH)·RG = ⋃(RG) = ⊓(RG) , if ⋃(RH) is nilpotent. Similar results are obtained for the semigroup ring RS, S ordered. It is also shown if R is commutative and G finite of order n, then J(R)G = J(RG) if and only if n is not a zero divisor in R/J(R), J(R) being the Jacobson radical of R. For the Brown HcCoy radical we determine the following: If R is Brown McCoy semisimple or if R is a simple ring with identity, then B(RG) = (0), where G is a finitely generated torsion free Abelian group. In the last section we determine further relations between some of the previously defined radicals, in particular between P(R), U(R) and J(R). Among other results, the following relations between the abovementioned radicals are obtained: U(RS) = U(R)S = P(RS) = J(RS) where R is a left Goldie ring and S an ordered semigroup with unity
- Full Text:
- Date Issued: 1979
Dispersal of the cochineal insect Dactylopius Austrinus de Lotto (Homoptera : Dactylopiidae)
- Authors: Gunn, Brian Howard
- Date: 1979
- Subjects: Cochineal insect--South Africa , Cochineal insects , Biological control , Jointed cactus , South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5596 , http://hdl.handle.net/10962/d1002046
- Description: Dispersal of the cochineal insect Dactylopius austrinus De Lotto, introduced into South Africa in 1932 as a biological control agent against jointed cactus Opuntia aurantiaca Lindley, was investigated. Zimmermann et al. (l974) suggested that the apparent failure of this insect to control jointed cactus infestations is due to limited dispersal of the first instar nymphs (hereafter referred to as crawlers). Studies on crawler morphology have shown a clear sexual dimorphism in the pattern and development of filaments on the head, thorax and abdomen of male and female crawlers. This enabled differentiation between the sexes with respect to terminal velocities, behaviour and survival of crawlers which have shown that the crawlers, especially the females, are well adapted to dispersal. Long filaments on the head, thorax and abdomen of the female crawlers, that are restricted to dispersal in the crawler stage (as later instars are sessile) and a behaviour directed towards "take-off" enhance the potential for dispersal. The more sedentary males, with long filaments restricted to the abdomen, are able to disperse as winged adults. The principal factors influencing the timing of dispersal and number of crawlers blown from the host plant are wind and temperature; the latter determining the number of crawlers moving on the host plant. Dispersal is confined to the period between 06h00 and 20h00 and it was possible to correlate the pattern of crawler dispersal with wind patterns. The general equation of Taylor (1978) provided an adequate description of horizontal distribution of D.austrinus crawlers in all directions. Wind dispersal of the apterous crawlers is restricted by the low height of jointed cactus plants. Horizontal distribution is limited (generally less than 10 m) although a small proportion of crawlers carried vertically upwards by turbulence or convection currents are sufficiently hardy to survive long range displacement. It is suggested that the small size of the host plant will also reduce effective colonization as the canopy area provides a small target for the wind-blown crawlers. The limitation on dispersal due to the low height of the host plant suggested a system for artificially enhancing crawler dispersal from elevated towers in the field. Evaluation of this system confirmed that it would be practical to augment or introduce cochineal into jointed cactus infestations to enhance the biocontrol potential of this insect. This offers an alternative to chemical control, that has so far failed to control the spread of jointed cactus despite an intensive and expensive herbicide program
- Full Text:
- Date Issued: 1979
- Authors: Gunn, Brian Howard
- Date: 1979
- Subjects: Cochineal insect--South Africa , Cochineal insects , Biological control , Jointed cactus , South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5596 , http://hdl.handle.net/10962/d1002046
- Description: Dispersal of the cochineal insect Dactylopius austrinus De Lotto, introduced into South Africa in 1932 as a biological control agent against jointed cactus Opuntia aurantiaca Lindley, was investigated. Zimmermann et al. (l974) suggested that the apparent failure of this insect to control jointed cactus infestations is due to limited dispersal of the first instar nymphs (hereafter referred to as crawlers). Studies on crawler morphology have shown a clear sexual dimorphism in the pattern and development of filaments on the head, thorax and abdomen of male and female crawlers. This enabled differentiation between the sexes with respect to terminal velocities, behaviour and survival of crawlers which have shown that the crawlers, especially the females, are well adapted to dispersal. Long filaments on the head, thorax and abdomen of the female crawlers, that are restricted to dispersal in the crawler stage (as later instars are sessile) and a behaviour directed towards "take-off" enhance the potential for dispersal. The more sedentary males, with long filaments restricted to the abdomen, are able to disperse as winged adults. The principal factors influencing the timing of dispersal and number of crawlers blown from the host plant are wind and temperature; the latter determining the number of crawlers moving on the host plant. Dispersal is confined to the period between 06h00 and 20h00 and it was possible to correlate the pattern of crawler dispersal with wind patterns. The general equation of Taylor (1978) provided an adequate description of horizontal distribution of D.austrinus crawlers in all directions. Wind dispersal of the apterous crawlers is restricted by the low height of jointed cactus plants. Horizontal distribution is limited (generally less than 10 m) although a small proportion of crawlers carried vertically upwards by turbulence or convection currents are sufficiently hardy to survive long range displacement. It is suggested that the small size of the host plant will also reduce effective colonization as the canopy area provides a small target for the wind-blown crawlers. The limitation on dispersal due to the low height of the host plant suggested a system for artificially enhancing crawler dispersal from elevated towers in the field. Evaluation of this system confirmed that it would be practical to augment or introduce cochineal into jointed cactus infestations to enhance the biocontrol potential of this insect. This offers an alternative to chemical control, that has so far failed to control the spread of jointed cactus despite an intensive and expensive herbicide program
- Full Text:
- Date Issued: 1979
Hybridization studies within the genus Kluyveromyces van der Walt emend. van der Walt
- Authors: Johannsen, Elz̀bieta
- Date: 1979
- Subjects: Yeast fungi -- Biotechnology , Yeast fungi -- Genetics , Yeast fungi -- Hybridization
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4123 , http://hdl.handle.net/10962/d1013400
- Description: Hybridization studies based on the prototrophic selection technique, involving the use of auxotrophic mutants of strains of all accepted species of the genus Kluyveromyces, are reported. Two main groups of mutually interfertile taxa were established within the genus. The first group comprises Kluyveromyces bulgaricus, Kluyveromyces cicerisporus, Kluyveromyces dobzhanskii, Kluyveromyces drosophilarum, Kluyveromyces fragilis, Kluyveromyces lactis, Kluyveromyces marxianus, Kluyveromyces phaseolosporus, Kluyveromyces vanudenii and Kluyveromyces wikenii. The second group consists of Kluyveromyces dabzhanskii, Kluyveromyces drosophilarum, Kluyveromyces laotis, Kluyveromyces vanudenii and Kluyveromyces wiokerhamii. Hybrids were also detected in crosses involving Kluyveromyces drosophilarum and Kluyveromyces waltii as well as Kluyveromyces marxianus and Kluyveromyces thermotolerans. In terms of the concept of the biological species and in compliance with the requirements of the International Code of Botanical Nomenclature, taxa which hybridize with Kluyveromyces marxianus and form fertile recombinants at frequencies observed in intraspecific crosses, are accepted as varieties of Kluyveromyces marxianus. Hybridization was observed between Kluyveromyces marxianus var. lactis and the presumed imperfect forms of some Kluyveromyces species, namely Candida kefyr, Candida macedoniensis and Torulopsis sphaerica. Recombination was not detected in crosses involving Kluyveromyces marxianus var. marxianus and representatives of other yeast genera, i.e. Pichia, Saccharomyces, Torulaspora and Zygosaccharomyces. Conclusions regarding the relationship between members of the genus Kluyveromyces, reached on the basis of this investigation are compared with those reported by other workers, who based their investigations on phenotypic characteristics as well as on the determinations of mol % G+C and DNA-DNA homology studies.
- Full Text:
- Date Issued: 1979
- Authors: Johannsen, Elz̀bieta
- Date: 1979
- Subjects: Yeast fungi -- Biotechnology , Yeast fungi -- Genetics , Yeast fungi -- Hybridization
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4123 , http://hdl.handle.net/10962/d1013400
- Description: Hybridization studies based on the prototrophic selection technique, involving the use of auxotrophic mutants of strains of all accepted species of the genus Kluyveromyces, are reported. Two main groups of mutually interfertile taxa were established within the genus. The first group comprises Kluyveromyces bulgaricus, Kluyveromyces cicerisporus, Kluyveromyces dobzhanskii, Kluyveromyces drosophilarum, Kluyveromyces fragilis, Kluyveromyces lactis, Kluyveromyces marxianus, Kluyveromyces phaseolosporus, Kluyveromyces vanudenii and Kluyveromyces wikenii. The second group consists of Kluyveromyces dabzhanskii, Kluyveromyces drosophilarum, Kluyveromyces laotis, Kluyveromyces vanudenii and Kluyveromyces wiokerhamii. Hybrids were also detected in crosses involving Kluyveromyces drosophilarum and Kluyveromyces waltii as well as Kluyveromyces marxianus and Kluyveromyces thermotolerans. In terms of the concept of the biological species and in compliance with the requirements of the International Code of Botanical Nomenclature, taxa which hybridize with Kluyveromyces marxianus and form fertile recombinants at frequencies observed in intraspecific crosses, are accepted as varieties of Kluyveromyces marxianus. Hybridization was observed between Kluyveromyces marxianus var. lactis and the presumed imperfect forms of some Kluyveromyces species, namely Candida kefyr, Candida macedoniensis and Torulopsis sphaerica. Recombination was not detected in crosses involving Kluyveromyces marxianus var. marxianus and representatives of other yeast genera, i.e. Pichia, Saccharomyces, Torulaspora and Zygosaccharomyces. Conclusions regarding the relationship between members of the genus Kluyveromyces, reached on the basis of this investigation are compared with those reported by other workers, who based their investigations on phenotypic characteristics as well as on the determinations of mol % G+C and DNA-DNA homology studies.
- Full Text:
- Date Issued: 1979