On a class of pseudo-differential operators in IRⁿ
- Authors: Matjila, D M
- Date: 1988
- Subjects: Pseudodifferential operators Operator theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5392 , http://hdl.handle.net/10962/d1001981
- Description: The class of pseudo-differential operators with symbols from Sm (superscript) po̧̧ (subscipt)(Ωx IRⁿ) has been extensively studied.The main assumption which characterises this class of symbols is that a(x,Ȩ) є Sm (superscript)po̧̧ (subscipt)(Ωx IRⁿ) should have a polynomial growth in the Ȩ variable only. The x-variable is controlled on compact subsets of Ω. A polynomial growth in both the x and Ȩ variables on a C°°(lR²ⁿ) function a(x,Ȩ) gives rise to a different class of symbols and a corresponding class of operators. In this work, such symbols and the action of the operators on the functional spaces S(lRⁿ) , S'(lRⁿ) and the Sobolev spaces Qs (superscript) (lRⁿ) (s є lRⁿ) are studied. A study of the calculus (i.e. transposes, adjoints and compositions) and the functional analysis of these operators is done with special attention to L-boundedness and compactness. The class of hypoelliptic pseudo-differential operators in IRⁿ is introduced as a subclass of those considered earlier.These operators possess the property that they allow a pseudo- inverse or parametrix. In conclusion. the spectral theory of these operators is considered. Since a general spectral theory would be beyond the scope of this work, only some special cases of the pseudo-differential operators in IRⁿ are considered. A few applications of this spectral theory are discussed
- Full Text:
- Authors: Matjila, D M
- Date: 1988
- Subjects: Pseudodifferential operators Operator theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5392 , http://hdl.handle.net/10962/d1001981
- Description: The class of pseudo-differential operators with symbols from Sm (superscript) po̧̧ (subscipt)(Ωx IRⁿ) has been extensively studied.The main assumption which characterises this class of symbols is that a(x,Ȩ) є Sm (superscript)po̧̧ (subscipt)(Ωx IRⁿ) should have a polynomial growth in the Ȩ variable only. The x-variable is controlled on compact subsets of Ω. A polynomial growth in both the x and Ȩ variables on a C°°(lR²ⁿ) function a(x,Ȩ) gives rise to a different class of symbols and a corresponding class of operators. In this work, such symbols and the action of the operators on the functional spaces S(lRⁿ) , S'(lRⁿ) and the Sobolev spaces Qs (superscript) (lRⁿ) (s є lRⁿ) are studied. A study of the calculus (i.e. transposes, adjoints and compositions) and the functional analysis of these operators is done with special attention to L-boundedness and compactness. The class of hypoelliptic pseudo-differential operators in IRⁿ is introduced as a subclass of those considered earlier.These operators possess the property that they allow a pseudo- inverse or parametrix. In conclusion. the spectral theory of these operators is considered. Since a general spectral theory would be beyond the scope of this work, only some special cases of the pseudo-differential operators in IRⁿ are considered. A few applications of this spectral theory are discussed
- Full Text:
Oor die kortkuns van John Miles
- Authors: De Beer, Marésa
- Date: 1988
- Subjects: Miles, John, 1938- -- Criticism and interpretation
- Language: Afrikaans
- Type: text , Thesis , Masters , MA
- Identifier: vital:3569 , http://hdl.handle.net/10962/d1002092
- Description: This thesis involves intensive analyses of some of the short-short stories in John Miles's Liefs nie op straat nie, in order to reveal the narrative strategies employed in each. In other words, it is geared to "the rules that govern ... textual actualization and, consequently, those rules that govern the way literary discourse functions as communication" (Riffaterre 1983: 158). Subsequently, attention is given to the interrelationship among the texts, the way in which they act upon one another and interact with the title of the volume, in order to establish the function of such relations. The following texts are analysed in consecutive chapters: "Lucy", "Lappies, kan jy my hoor, Lappies?", "Voorgevoel", "Dom Nakkie, my Dom Nakkie" and "Wie het nog Dom Nakkie gesien?", "Hy staan by die deur en hy klop", "Gustav gaan speel", and "Liefs nie op straat nie". In a concluding chapter the implications of the title are discussed with reference to all the texts in the volume, including those not analysed individually. It is concluded that, on the one hand, the expectations raised by the title are ironicized because the title is never "completed" explicitly, and because that which, by implication, should not be seen in public ("op straat"), is specifically situated in the street and scrutinized in close-up. But on the other hand the title also evokes a peculiar mentality present in all the texts, either in the narrators, or in the characters, or in both. The discussion of "Lucy" is focussed mainly on the contrast and interaction between the world of the child and that of the adult and on the way in which this interaction is actualized within the text through the contrast in the experience of time, the use of "mémoire involontaire", "durée" and the contrasts between (and overlapping of) narrative perspective and focalization. In respect of "Lappies, kan jy my hoor, Lappies?" special attention is paid to similarities and contrasts between this text and the traditional suspense story, notably the way in which conventional techniques are employed to create suspense, as well as to generate an entire subtext which eventually "relocates" the text on the niveau of the murderer's psychological dilemma. In discussing "Voorgevoel" emphasis is not placed primarily on what is conveyed by the narrator, but on the way in which his intentions are subverted both by the window pane through which he is looking and by the narration as such. In this way he is foregrounded and revealed as narrator, just as the text is foregrounded and revealed as literature, with the emphasis, in both cases, not only on their defence mechanisms but also on their impotence. "Dom Nakkie, my Dom Nakkie" and "Wie het nog Dom Nakkie gesien?" are grouped together in one chapter in order to illuminate the interaction between the two narratives in the first text, as well as the interaction between the two texts. Ultimately, they may be seen as three narratives juxtaposed through irony and relativism. The "triumph" of the "preferably not in public" mentality, both in the text and in society, is also illustrated by the interaction between the three narratives. In chapter, 5, in which "Hy staan by die deur en hy klop" is discussed, attention is focussed on the ironic function of the Biblical references, the contrast between Jan and the rest of society, and the way in which the "climax" is located within the Iserian "blank" in the text, so that the entire process of decoding is based on a filling in of that "blank" and its implications. "Gustav gaan speel" is based loosely on Barthes's lexia model, in order to determine the signifying process in the text, and also to demonstrate the way in which the text presupposes rereading. In the discussion of the title text it is revealed how the text is centered in the basic dichotomy between the narrator-as-writer and the journalist, and the way in which this polarity is relativized by the text as such. The text is demonstrated to be the credo of the volume as a whole as well as of the fiction of the Seventies in Afrikaans.
- Full Text:
- Authors: De Beer, Marésa
- Date: 1988
- Subjects: Miles, John, 1938- -- Criticism and interpretation
- Language: Afrikaans
- Type: text , Thesis , Masters , MA
- Identifier: vital:3569 , http://hdl.handle.net/10962/d1002092
- Description: This thesis involves intensive analyses of some of the short-short stories in John Miles's Liefs nie op straat nie, in order to reveal the narrative strategies employed in each. In other words, it is geared to "the rules that govern ... textual actualization and, consequently, those rules that govern the way literary discourse functions as communication" (Riffaterre 1983: 158). Subsequently, attention is given to the interrelationship among the texts, the way in which they act upon one another and interact with the title of the volume, in order to establish the function of such relations. The following texts are analysed in consecutive chapters: "Lucy", "Lappies, kan jy my hoor, Lappies?", "Voorgevoel", "Dom Nakkie, my Dom Nakkie" and "Wie het nog Dom Nakkie gesien?", "Hy staan by die deur en hy klop", "Gustav gaan speel", and "Liefs nie op straat nie". In a concluding chapter the implications of the title are discussed with reference to all the texts in the volume, including those not analysed individually. It is concluded that, on the one hand, the expectations raised by the title are ironicized because the title is never "completed" explicitly, and because that which, by implication, should not be seen in public ("op straat"), is specifically situated in the street and scrutinized in close-up. But on the other hand the title also evokes a peculiar mentality present in all the texts, either in the narrators, or in the characters, or in both. The discussion of "Lucy" is focussed mainly on the contrast and interaction between the world of the child and that of the adult and on the way in which this interaction is actualized within the text through the contrast in the experience of time, the use of "mémoire involontaire", "durée" and the contrasts between (and overlapping of) narrative perspective and focalization. In respect of "Lappies, kan jy my hoor, Lappies?" special attention is paid to similarities and contrasts between this text and the traditional suspense story, notably the way in which conventional techniques are employed to create suspense, as well as to generate an entire subtext which eventually "relocates" the text on the niveau of the murderer's psychological dilemma. In discussing "Voorgevoel" emphasis is not placed primarily on what is conveyed by the narrator, but on the way in which his intentions are subverted both by the window pane through which he is looking and by the narration as such. In this way he is foregrounded and revealed as narrator, just as the text is foregrounded and revealed as literature, with the emphasis, in both cases, not only on their defence mechanisms but also on their impotence. "Dom Nakkie, my Dom Nakkie" and "Wie het nog Dom Nakkie gesien?" are grouped together in one chapter in order to illuminate the interaction between the two narratives in the first text, as well as the interaction between the two texts. Ultimately, they may be seen as three narratives juxtaposed through irony and relativism. The "triumph" of the "preferably not in public" mentality, both in the text and in society, is also illustrated by the interaction between the three narratives. In chapter, 5, in which "Hy staan by die deur en hy klop" is discussed, attention is focussed on the ironic function of the Biblical references, the contrast between Jan and the rest of society, and the way in which the "climax" is located within the Iserian "blank" in the text, so that the entire process of decoding is based on a filling in of that "blank" and its implications. "Gustav gaan speel" is based loosely on Barthes's lexia model, in order to determine the signifying process in the text, and also to demonstrate the way in which the text presupposes rereading. In the discussion of the title text it is revealed how the text is centered in the basic dichotomy between the narrator-as-writer and the journalist, and the way in which this polarity is relativized by the text as such. The text is demonstrated to be the credo of the volume as a whole as well as of the fiction of the Seventies in Afrikaans.
- Full Text:
Organisational structures for effective geography teaching in selected medium and large primary schools
- Authors: Kaschula, Nathaniel Ronald
- Date: 1988
- Subjects: Geography -- Study and teaching (Elementary) -- South Africa Education, Primary -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1859 , http://hdl.handle.net/10962/d1004552
- Description: Effective teaching is determined by a host of factors, not least of which is the educational guidance given to the teacher. This guidance should come about through an effecctively designed support structure initiated by the school principal as part of his management strategy. Very little has been written on this topic, particularly with reference to primary schools. In the past, geography teachers were trained, appointed to a school and expected to get on with their teaching. However, present-day teachers, in order to be effective educators, require in-service training. This should occur In a variety of ways and on a continuous basis, because teaching is an on-going business and not a job to be learned once and for always. This thesis investigates the organisational structures that exist for the teaching of geography in selected medium and large primary schools in the Eastern Cape. The author found that principals used either a subject head or standard head model. In large primary schools a subject head model was preferred i.e. a specialist geography teacher was responslble for developing the subject vertically from standard 2 to 5. The opposite was true in medium-sized schools. Principals of these schools preferred to delegate responsibility to a standard head. It was the duty ot the standard head, usually a generalist teacher without specific training in geography, to develop geography horizontally among, for example, all the standard 3 pupils. The role played by key members of a primary schools' instructional leadership team, namely the principal, subject head, and the standard head are examined in detail. The author offers justification why geography should be included In the primary curriculum. It is his contention that geography contributes to a child's general education, develops basic geographical skills, extends general mental abilities and fosters positive attitudes towards other people with whom he shares this world. A management model is proposed for principals, flexible enough for application in all schools. It is designed to ensure that teachers continue growing professionaIIy within the structure of a small group. There is no best way to organise the teaching of geography because each school has its own unique resources which should be optimally utilised in order to bring about learning. The professional development of geography teachers is possible because someone competent in geographical education should assume leadership of the qroup. This will enable ideas to be shared, plans made and strategies implemented in an eftort to improve teacher-competence through an efficiently organised geography department. In the final chapter conclusions are drawn and a recommendatlon is made for primary school principals to Implement an organlsatlonal model for the teaching of geography. A choice may be made from three models, namely a standard head, subject head or a comblnation of both models. It Is within the parameters of one of these structures that the subject can be properly managed, for example, field-trips planned, teaching aids purchased, envlronmental educatlon programmes designed, teaching strategies discussed and examinat(ons set. Thls view is supported by Cawood and GIbbon's (1980) empirical evidence. They found that good educatlonal leadership fosters effective teaching in schools.
- Full Text:
- Authors: Kaschula, Nathaniel Ronald
- Date: 1988
- Subjects: Geography -- Study and teaching (Elementary) -- South Africa Education, Primary -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1859 , http://hdl.handle.net/10962/d1004552
- Description: Effective teaching is determined by a host of factors, not least of which is the educational guidance given to the teacher. This guidance should come about through an effecctively designed support structure initiated by the school principal as part of his management strategy. Very little has been written on this topic, particularly with reference to primary schools. In the past, geography teachers were trained, appointed to a school and expected to get on with their teaching. However, present-day teachers, in order to be effective educators, require in-service training. This should occur In a variety of ways and on a continuous basis, because teaching is an on-going business and not a job to be learned once and for always. This thesis investigates the organisational structures that exist for the teaching of geography in selected medium and large primary schools in the Eastern Cape. The author found that principals used either a subject head or standard head model. In large primary schools a subject head model was preferred i.e. a specialist geography teacher was responslble for developing the subject vertically from standard 2 to 5. The opposite was true in medium-sized schools. Principals of these schools preferred to delegate responsibility to a standard head. It was the duty ot the standard head, usually a generalist teacher without specific training in geography, to develop geography horizontally among, for example, all the standard 3 pupils. The role played by key members of a primary schools' instructional leadership team, namely the principal, subject head, and the standard head are examined in detail. The author offers justification why geography should be included In the primary curriculum. It is his contention that geography contributes to a child's general education, develops basic geographical skills, extends general mental abilities and fosters positive attitudes towards other people with whom he shares this world. A management model is proposed for principals, flexible enough for application in all schools. It is designed to ensure that teachers continue growing professionaIIy within the structure of a small group. There is no best way to organise the teaching of geography because each school has its own unique resources which should be optimally utilised in order to bring about learning. The professional development of geography teachers is possible because someone competent in geographical education should assume leadership of the qroup. This will enable ideas to be shared, plans made and strategies implemented in an eftort to improve teacher-competence through an efficiently organised geography department. In the final chapter conclusions are drawn and a recommendatlon is made for primary school principals to Implement an organlsatlonal model for the teaching of geography. A choice may be made from three models, namely a standard head, subject head or a comblnation of both models. It Is within the parameters of one of these structures that the subject can be properly managed, for example, field-trips planned, teaching aids purchased, envlronmental educatlon programmes designed, teaching strategies discussed and examinat(ons set. Thls view is supported by Cawood and GIbbon's (1980) empirical evidence. They found that good educatlonal leadership fosters effective teaching in schools.
- Full Text:
People's education - An Examination of the Concept
- Centre for Adult and Continuing Education (CACE)
- Authors: Centre for Adult and Continuing Education (CACE)
- Date: 1988
- Subjects: Centre for Adult and Continuing Education (CACE)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/168796 , vital:41648
- Description: This research report sets out to examine the concept of People’s Education in South Africa from December 1985, when the call for People’s Education was first made, to September 19877“It is the result of a preliminary six month research project which set out to lay the basis for a long term study of international perspectives on People’s Education. The researcher experienced the difficulties associated with doing contemporary research in a charged political environment. Several of the potential interviewees were either in detention or ‘on the run’ because of their commitment to People’s Education. The contemporary nature of the research focus also meant that the sources of relevant printed materials were limited and dispersed. The study demonstrates that People’s Education is concerned with more than responding to ‘the education crisis'. In addition, it is attempting to address the problem of a future education system in a post-apartheid society. As adult educators we are excited by the challenges that People’s Education offers. It is one of the first times in South Africa that ‘lifelong education ’ is on the agenda where education in the school is seen as only one aspect of necessary education provision. Adult Education at the workplace, in voluntary associations, in political movements, in the home, is seen as integral to the educational process both in the period of social transformation and in a future, post-apartheid society. This study has confirmed that People’s Education cannot be ignored. People’s Education has achieved what many previous investigations into education have not achieved; it has involved a wide range of grassroots people in the debates around the future of South African education. It is an ongoing process. As Ken Hartshorne is quoted as saying : "Both the debate on and the process leading to post-apartheid education are well underway; they are loaded with complexities, uncertainties and risks, because they are taking place in an unstable and unresolved vortex which changes from day to day, from place to place." I would like to acknowledge the assistance of colleagues who played an important role in the process of the study : Professor Owen van den Berg who was very helpful in the setting up of the project, and Mr Brian O’Connell who assisted with the conceptualisation and ongoing discussion of the project. In addition, his critical reading of the draft of this report provided many invaluable suggestions. Thanks are also due to our colleagues at UWC and elsewhere who took time to read the draft paper and offered constructive criticisms.
- Full Text:
- Authors: Centre for Adult and Continuing Education (CACE)
- Date: 1988
- Subjects: Centre for Adult and Continuing Education (CACE)
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/168796 , vital:41648
- Description: This research report sets out to examine the concept of People’s Education in South Africa from December 1985, when the call for People’s Education was first made, to September 19877“It is the result of a preliminary six month research project which set out to lay the basis for a long term study of international perspectives on People’s Education. The researcher experienced the difficulties associated with doing contemporary research in a charged political environment. Several of the potential interviewees were either in detention or ‘on the run’ because of their commitment to People’s Education. The contemporary nature of the research focus also meant that the sources of relevant printed materials were limited and dispersed. The study demonstrates that People’s Education is concerned with more than responding to ‘the education crisis'. In addition, it is attempting to address the problem of a future education system in a post-apartheid society. As adult educators we are excited by the challenges that People’s Education offers. It is one of the first times in South Africa that ‘lifelong education ’ is on the agenda where education in the school is seen as only one aspect of necessary education provision. Adult Education at the workplace, in voluntary associations, in political movements, in the home, is seen as integral to the educational process both in the period of social transformation and in a future, post-apartheid society. This study has confirmed that People’s Education cannot be ignored. People’s Education has achieved what many previous investigations into education have not achieved; it has involved a wide range of grassroots people in the debates around the future of South African education. It is an ongoing process. As Ken Hartshorne is quoted as saying : "Both the debate on and the process leading to post-apartheid education are well underway; they are loaded with complexities, uncertainties and risks, because they are taking place in an unstable and unresolved vortex which changes from day to day, from place to place." I would like to acknowledge the assistance of colleagues who played an important role in the process of the study : Professor Owen van den Berg who was very helpful in the setting up of the project, and Mr Brian O’Connell who assisted with the conceptualisation and ongoing discussion of the project. In addition, his critical reading of the draft of this report provided many invaluable suggestions. Thanks are also due to our colleagues at UWC and elsewhere who took time to read the draft paper and offered constructive criticisms.
- Full Text:
Perceptions of, and attitudes towards, varieties of English in the Cape Peninsula, with particular reference to the ʾcoloured communityʾ
- Authors: Wood, Tahir Muhammed
- Date: 1988
- Subjects: English language -- South Africa -- Cape of Good Hope , English language -- Variation , Sociolinguistics -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:2336 , http://hdl.handle.net/10962/d1002018
- Description: This study set out to analyse the concept of the ʾcoloured communityʾ and to describe the linguistic phenomena associated with it. It was found that the community was characterized by division and an overt rejection of 'coloured' identity. A satisfactory definition of the community could only be arrived at by exploring social psychological and anthropological concepts, particularly that of the social network, and a covert identification was postulated. This in turn was used to explain the linguistic phenomena which were found to be associated with the community. The latter included a vernacular dialect consisting of non-standard Afrikaans blended with English, as well as a stratification of particular items in the English spoken by community members . This stratification was analysed in terms of the social distribution of the items, enabling comparisons to be made with the English spoken by ʾwhitesʾ. A fieldwork study was embarked on with the intention of discovering the nature of the perceptions of, and attitudes towards, the idiolects of certain speakers. These idiolects were considered to be typical and representative of the forms of English normally encountered in the Cape Peninsula, and were described in terms of the co-occurrences of linguistic items which they contained. Tape recordings of the speech of this group of speakers were presented in a series of controlled experiments to subjects from various class and community backgrounds who were required to respond by completing questionnaires. It was found that those lects which contained items and co-occurrences of items peculiar to 'coloured' speakers were associated with lower status than those containing items and co-occurrences of items peculiar to 'white' speakers. Attitudes towards speakers were found to be more complex and depended upon the styles and paralanguage behaviours of the speakers, as well as accent, and also the psychological dispositions of the subjects who participated
- Full Text:
- Authors: Wood, Tahir Muhammed
- Date: 1988
- Subjects: English language -- South Africa -- Cape of Good Hope , English language -- Variation , Sociolinguistics -- South Africa
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:2336 , http://hdl.handle.net/10962/d1002018
- Description: This study set out to analyse the concept of the ʾcoloured communityʾ and to describe the linguistic phenomena associated with it. It was found that the community was characterized by division and an overt rejection of 'coloured' identity. A satisfactory definition of the community could only be arrived at by exploring social psychological and anthropological concepts, particularly that of the social network, and a covert identification was postulated. This in turn was used to explain the linguistic phenomena which were found to be associated with the community. The latter included a vernacular dialect consisting of non-standard Afrikaans blended with English, as well as a stratification of particular items in the English spoken by community members . This stratification was analysed in terms of the social distribution of the items, enabling comparisons to be made with the English spoken by ʾwhitesʾ. A fieldwork study was embarked on with the intention of discovering the nature of the perceptions of, and attitudes towards, the idiolects of certain speakers. These idiolects were considered to be typical and representative of the forms of English normally encountered in the Cape Peninsula, and were described in terms of the co-occurrences of linguistic items which they contained. Tape recordings of the speech of this group of speakers were presented in a series of controlled experiments to subjects from various class and community backgrounds who were required to respond by completing questionnaires. It was found that those lects which contained items and co-occurrences of items peculiar to 'coloured' speakers were associated with lower status than those containing items and co-occurrences of items peculiar to 'white' speakers. Attitudes towards speakers were found to be more complex and depended upon the styles and paralanguage behaviours of the speakers, as well as accent, and also the psychological dispositions of the subjects who participated
- Full Text:
Petrology and geochemistry of the lower group chromitites and host rocks on the farm Zandspruit 168 JP, Western Bushveld Complex
- Authors: Botha, Michael James
- Date: 1988
- Subjects: Petrology -- Africa, Southern , Geochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4905 , http://hdl.handle.net/10962/d1001565
- Description: The eight Lower Group chromitite layers of the Ruighoek Pyroxenite in the area west of the Pilanesberg (LGl - LG7), on the farm Zandspruit 168 JP, were sampled in borehole cores drilled through the succession. The stratigraphic succession faIls within Cameron's (980) units B to E of the Critical Zone. The lowermost layer of the Lower Group, the LG 1 chromitite, is located some 440 metres below the MG 2 (Middle Group) chromitite layer, above which the first appearance of cumulus plagioclase in the Complex is seen. By convention, this horizon is designated the top of the Ruighoek Pyroxenite in the Western Bushveld Complex. Homogeneous units of chromite-bearing orthopyroxenite (bronzitite), exhibiting inconspicuous layering defined in terms of variations in orthopyroxene grain-size host all but one of the Lower Group layers; the LG 4 chromitite layer is exposed within an olivine-rich subunit 23 metres in thickness (C₃ subunit). The cumulative thickness of chromitite is 2,92 metres or 0,8 per cent of the studied section, which is 381 metres in thickness. Minimum and maximum thicknesses of the LGl - LG7 layers exposed in drill core are 17 and 81 centimetres, respectively, with minor chromitite layers ranging between 2 and 5 centimetres in thickness. Weighted mean Cr₂0₃ contents of units B to E vary between 1,17 and 3,22 per cent, with the latter estimate representative of the D₂ subunit which hosts the LG 6 chromitite layer. The LG 6 is correlated with the Steelpoort layer of the Eastern Bushveld Complex, and varies between 76 and 81 centimetres in thickness under a large portion of the farm Zandspruit. An undisturbed succession striking N15°E and dipping 12 - 15°E is depicted within the studied area, which is bounded on the eastern side by the north-striking Frank fault. Major folding of the layered succession is evident to the north of the area, where the layering adjacent to the trace of the fault dips 35° to the southwest. Particular attention is paid in the present study to (a) the nature of chromitite layers and their host rocks, (b) the contrast between the mineral chemistry of weakly disseminated chromite and grains within massive ore layers, (c) concentrations of Cr, V, Ni, Co, Sc and Ti in orthopyroxene in relation to stratigraphic height, and levels of Sr, Ba and Zr associated with hypothetically pure, intercumulus plagioclase feldspar, and (d) possible mechanisms which induce crystallization of chromitite layers containing 50 per cent Cr₂0₃ from magma with a Cr content of less than 1 000 ppm. Electron microprobe studies of chromite in relation to mineralogical and textural environment clearly reveal that (a) the proportions of Cr and Al cations are linked to paragenesis: higher Al/Cr ratios characterize olivine-bearing domains, whereas grains intergrown with plagioclase feldspar exhibit low AI/Cr ratios, and (b) Al contents rise with a decline in Mg/(Mg + Fe²⁺) from high values to a value of 0,450, then decrease with a further decline in Mg/(Mg + Fe²⁺). The paragenetically later trend is emphasized in a large population of chromite grains which escaped early encapsulation in orthopyroxene crystals and continued to grow in the environment of intercumulus plagioclase. Within-and between-sample compositional variation of grains in silicate-rich domains is modelled in terms of in situ growth increments, diffusive homogenization of zonal structures, and residence time within interstitial melt. Fractionation trends, as measured by Mg/(Mg + Fe²⁺) ratios in whole-rock and/or microprobe studies of orthopyroxene, are reversed in relation to stratigraphic height towards the top of the B unit and in the overlying C unit. These data are supported, for example, by lower vanadium contents and higher Ni/Sc ratios in hypothetically pure orthopyroxene. Small olivine crystals in chromite-rich domains are enriched in Ni relative to coarse-grained olivine in adjacent dunite: a feature attributed to early isolation of primocrysts from magma in the former case, and in situ equilibration between olivine crystals and Ni-depleted residual melt in the latter case . Similarly, rising Ni contents and Mg/(Mg + Fe²⁺) ratios of orthopyroxene with increasing stratigraphic height in the footwall of the LG 6 chromitite layer, linked to a progressive decline in orthopyroxene grain-size, are effects which may arise out of early separation of interstitial melt from orthopyroxene cumulates. A model is thus proposed which (a) links the thickness of chromitite layers to the vertical separation between successive layers or the thickness of fine-grained orthopyroxenite in the footwall, (b) ascribes copious nucleation of chromite to liquid mixing of this footwall derived, Cr - depleted contaminant with influxes of hot, primitive magma, and (c) tenders the notion that the present modal proportion of mesostasis in the footwall of a chromitite layer serves as a reciprocal measure of the volume of fractionated exudate
- Full Text:
- Authors: Botha, Michael James
- Date: 1988
- Subjects: Petrology -- Africa, Southern , Geochemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4905 , http://hdl.handle.net/10962/d1001565
- Description: The eight Lower Group chromitite layers of the Ruighoek Pyroxenite in the area west of the Pilanesberg (LGl - LG7), on the farm Zandspruit 168 JP, were sampled in borehole cores drilled through the succession. The stratigraphic succession faIls within Cameron's (980) units B to E of the Critical Zone. The lowermost layer of the Lower Group, the LG 1 chromitite, is located some 440 metres below the MG 2 (Middle Group) chromitite layer, above which the first appearance of cumulus plagioclase in the Complex is seen. By convention, this horizon is designated the top of the Ruighoek Pyroxenite in the Western Bushveld Complex. Homogeneous units of chromite-bearing orthopyroxenite (bronzitite), exhibiting inconspicuous layering defined in terms of variations in orthopyroxene grain-size host all but one of the Lower Group layers; the LG 4 chromitite layer is exposed within an olivine-rich subunit 23 metres in thickness (C₃ subunit). The cumulative thickness of chromitite is 2,92 metres or 0,8 per cent of the studied section, which is 381 metres in thickness. Minimum and maximum thicknesses of the LGl - LG7 layers exposed in drill core are 17 and 81 centimetres, respectively, with minor chromitite layers ranging between 2 and 5 centimetres in thickness. Weighted mean Cr₂0₃ contents of units B to E vary between 1,17 and 3,22 per cent, with the latter estimate representative of the D₂ subunit which hosts the LG 6 chromitite layer. The LG 6 is correlated with the Steelpoort layer of the Eastern Bushveld Complex, and varies between 76 and 81 centimetres in thickness under a large portion of the farm Zandspruit. An undisturbed succession striking N15°E and dipping 12 - 15°E is depicted within the studied area, which is bounded on the eastern side by the north-striking Frank fault. Major folding of the layered succession is evident to the north of the area, where the layering adjacent to the trace of the fault dips 35° to the southwest. Particular attention is paid in the present study to (a) the nature of chromitite layers and their host rocks, (b) the contrast between the mineral chemistry of weakly disseminated chromite and grains within massive ore layers, (c) concentrations of Cr, V, Ni, Co, Sc and Ti in orthopyroxene in relation to stratigraphic height, and levels of Sr, Ba and Zr associated with hypothetically pure, intercumulus plagioclase feldspar, and (d) possible mechanisms which induce crystallization of chromitite layers containing 50 per cent Cr₂0₃ from magma with a Cr content of less than 1 000 ppm. Electron microprobe studies of chromite in relation to mineralogical and textural environment clearly reveal that (a) the proportions of Cr and Al cations are linked to paragenesis: higher Al/Cr ratios characterize olivine-bearing domains, whereas grains intergrown with plagioclase feldspar exhibit low AI/Cr ratios, and (b) Al contents rise with a decline in Mg/(Mg + Fe²⁺) from high values to a value of 0,450, then decrease with a further decline in Mg/(Mg + Fe²⁺). The paragenetically later trend is emphasized in a large population of chromite grains which escaped early encapsulation in orthopyroxene crystals and continued to grow in the environment of intercumulus plagioclase. Within-and between-sample compositional variation of grains in silicate-rich domains is modelled in terms of in situ growth increments, diffusive homogenization of zonal structures, and residence time within interstitial melt. Fractionation trends, as measured by Mg/(Mg + Fe²⁺) ratios in whole-rock and/or microprobe studies of orthopyroxene, are reversed in relation to stratigraphic height towards the top of the B unit and in the overlying C unit. These data are supported, for example, by lower vanadium contents and higher Ni/Sc ratios in hypothetically pure orthopyroxene. Small olivine crystals in chromite-rich domains are enriched in Ni relative to coarse-grained olivine in adjacent dunite: a feature attributed to early isolation of primocrysts from magma in the former case, and in situ equilibration between olivine crystals and Ni-depleted residual melt in the latter case . Similarly, rising Ni contents and Mg/(Mg + Fe²⁺) ratios of orthopyroxene with increasing stratigraphic height in the footwall of the LG 6 chromitite layer, linked to a progressive decline in orthopyroxene grain-size, are effects which may arise out of early separation of interstitial melt from orthopyroxene cumulates. A model is thus proposed which (a) links the thickness of chromitite layers to the vertical separation between successive layers or the thickness of fine-grained orthopyroxenite in the footwall, (b) ascribes copious nucleation of chromite to liquid mixing of this footwall derived, Cr - depleted contaminant with influxes of hot, primitive magma, and (c) tenders the notion that the present modal proportion of mesostasis in the footwall of a chromitite layer serves as a reciprocal measure of the volume of fractionated exudate
- Full Text:
Phenylpropanolamine : analytical and pharmacokinetic studies using high-performance liquid chromatography
- Authors: Scherzinger, Sabine Hilda
- Date: 1988
- Subjects: Phenylpropanolamine , Pharmacokinetics , High performance liquid chromatography
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: vital:3811 , http://hdl.handle.net/10962/d1004528
- Description: Phenylpropanolamine (PPA), a synthetic sympathomimetic amine structurally related to ephedrine has been widely used over t he past 40 years as a nasal decongestant and appetite suppressant. It has been the focus of much controversy concerning the efficacy of the drug in its use as an anorectic agent, and due to the side effects caused by the higher doses of PPA required for appetite suppression. Although extensively used, there is little information concerning the determination of PPA in biological fluids and on the pharmacokinetics of this drug. An adaptation of a published high-performance liquid chromatographic (HPLC) assay for PPA in serum and urine using U.V. detection at 210 nm is presented. PPA was separated in the reversed phase mode. The method has a limit of sensitivity of 5.0 ng/mL and 10.0 ng/mL in serum and urine respectively. Serum concentration data following a single 25 mg dose of phenylpropanolamine in human volunteers demonstrate the application of the analytical method for bioavailability and pharmacokinetic studies. After the administration of 25 mg, 50 mg or 100 mg PPA.HCl solutions to 5 human volunteers, a dose proportionality study demonstrated that PPA appears to exhibit linear kinetics. Linear one body compartment kinetics were assumed and the wagner-Nelson method used to transform in vivo serum data to absorption plots. The serum data were fitted to a model using nonlinear regression techniques to characterize the pharmacokinetic processes of PPA. The absorption of phenylpropanolamine appears to be discontinuous and the drug seems to favour a two body compartment model. The pharmacokinetic parameters obtained from a steady state study using multiple dosing of PPA.HCl solutions compared with those found from previous studies after the administration of sustained-release formulations. A plasma protein binding study using equilibrium dialysis demonstrated that PPA is not highly protein bound in the blood.
- Full Text:
- Authors: Scherzinger, Sabine Hilda
- Date: 1988
- Subjects: Phenylpropanolamine , Pharmacokinetics , High performance liquid chromatography
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: vital:3811 , http://hdl.handle.net/10962/d1004528
- Description: Phenylpropanolamine (PPA), a synthetic sympathomimetic amine structurally related to ephedrine has been widely used over t he past 40 years as a nasal decongestant and appetite suppressant. It has been the focus of much controversy concerning the efficacy of the drug in its use as an anorectic agent, and due to the side effects caused by the higher doses of PPA required for appetite suppression. Although extensively used, there is little information concerning the determination of PPA in biological fluids and on the pharmacokinetics of this drug. An adaptation of a published high-performance liquid chromatographic (HPLC) assay for PPA in serum and urine using U.V. detection at 210 nm is presented. PPA was separated in the reversed phase mode. The method has a limit of sensitivity of 5.0 ng/mL and 10.0 ng/mL in serum and urine respectively. Serum concentration data following a single 25 mg dose of phenylpropanolamine in human volunteers demonstrate the application of the analytical method for bioavailability and pharmacokinetic studies. After the administration of 25 mg, 50 mg or 100 mg PPA.HCl solutions to 5 human volunteers, a dose proportionality study demonstrated that PPA appears to exhibit linear kinetics. Linear one body compartment kinetics were assumed and the wagner-Nelson method used to transform in vivo serum data to absorption plots. The serum data were fitted to a model using nonlinear regression techniques to characterize the pharmacokinetic processes of PPA. The absorption of phenylpropanolamine appears to be discontinuous and the drug seems to favour a two body compartment model. The pharmacokinetic parameters obtained from a steady state study using multiple dosing of PPA.HCl solutions compared with those found from previous studies after the administration of sustained-release formulations. A plasma protein binding study using equilibrium dialysis demonstrated that PPA is not highly protein bound in the blood.
- Full Text:
Poems That Doubt
- Authors: Cornwell, Gareth D N
- Date: 1988
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/460154 , vital:75896 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_464
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
- Authors: Cornwell, Gareth D N
- Date: 1988
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/460154 , vital:75896 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_464
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
Polymerized serum albumin beads for use as slow-release adjuvants
- Martin, Michelle Elizabeth Denny
- Authors: Martin, Michelle Elizabeth Denny
- Date: 1988
- Subjects: Serum albumin , Antigens , Vaccines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3879 , http://hdl.handle.net/10962/d1001613
- Description: Experimental vaccines have been made by covalently bonding virus particles into polymerized rabbit serum albumin beads. Using Nodamura virus as a model antigen, these model vaccines induced specific humoral antibody production, comparable with that achieved using Freund's adjuvants. Virus specific antibodies were also induced when Nodamura virus was covalently attached to the bead surface using different crosslinkers. However, when poliovirus type 2 (Sabin strain) was polymerized into beads, the levels of neutralizing antibodies were insignificant compared with control aqueous vaccines. The synthetic immunostimulator, muramyl dipeptide, was included with bead vaccines in an attempt to potentiate the immune response. Immunostimulation is achieved by a slow release of antigen coinciding with the gradual breakdown of bead structure.
- Full Text:
- Authors: Martin, Michelle Elizabeth Denny
- Date: 1988
- Subjects: Serum albumin , Antigens , Vaccines
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3879 , http://hdl.handle.net/10962/d1001613
- Description: Experimental vaccines have been made by covalently bonding virus particles into polymerized rabbit serum albumin beads. Using Nodamura virus as a model antigen, these model vaccines induced specific humoral antibody production, comparable with that achieved using Freund's adjuvants. Virus specific antibodies were also induced when Nodamura virus was covalently attached to the bead surface using different crosslinkers. However, when poliovirus type 2 (Sabin strain) was polymerized into beads, the levels of neutralizing antibodies were insignificant compared with control aqueous vaccines. The synthetic immunostimulator, muramyl dipeptide, was included with bead vaccines in an attempt to potentiate the immune response. Immunostimulation is achieved by a slow release of antigen coinciding with the gradual breakdown of bead structure.
- Full Text:
Potency ranking of two new topical corticosteroid creams containing 0.1% desonide or 0.05% halometasone utilizing the human skin-blanching assay
- Meyer, Eric, Smith, Eric W, Haigh, John M, Kanfer, Isadore
- Authors: Meyer, Eric , Smith, Eric W , Haigh, John M , Kanfer, Isadore
- Date: 1988
- Language: English
- Type: Article
- Identifier: vital:6400 , http://hdl.handle.net/10962/d1006327
- Description: The human blanching assay was used to assess the potency of two new proprietary corticosteroid creams. The blanching abilities of 0.1% desonide cream and 0.05% halometasone cream were evaluated relative to the blanching elicited by 0.05% clobetasol 17-propionate cream, 0.1% betamethasone 17-valerate cream and 0.05% clobetasone 17-butyrate cream. The results of the trial indicated that the 0.1% desonide cream falls into the potent group of topical corticosteroid preparations and the 0.05% halomethasone cream falls into the moderately potent group.
- Full Text:
- Authors: Meyer, Eric , Smith, Eric W , Haigh, John M , Kanfer, Isadore
- Date: 1988
- Language: English
- Type: Article
- Identifier: vital:6400 , http://hdl.handle.net/10962/d1006327
- Description: The human blanching assay was used to assess the potency of two new proprietary corticosteroid creams. The blanching abilities of 0.1% desonide cream and 0.05% halometasone cream were evaluated relative to the blanching elicited by 0.05% clobetasol 17-propionate cream, 0.1% betamethasone 17-valerate cream and 0.05% clobetasone 17-butyrate cream. The results of the trial indicated that the 0.1% desonide cream falls into the potent group of topical corticosteroid preparations and the 0.05% halomethasone cream falls into the moderately potent group.
- Full Text:
Reading Thomas Merton
- Authors: Wylie, Dan
- Date: 1988
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/460491 , vital:75942 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_464
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
- Authors: Wylie, Dan
- Date: 1988
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/460491 , vital:75942 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_464
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
Rhodes University Graduation Ceremony 1988
- Authors: Rhodes University
- Date: 1988
- Language: English
- Type: text
- Identifier: vital:8122 , http://hdl.handle.net/10962/d1005705
- Description: Rhodes University Graduation Ceremonies on Friday, 8 April 1988 at 8 p.m. [and] on Friday, 9 April 1988 at 10 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday; 7 May 1988 at 11.30 a.m. in the Guild Theatre.
- Full Text:
- Authors: Rhodes University
- Date: 1988
- Language: English
- Type: text
- Identifier: vital:8122 , http://hdl.handle.net/10962/d1005705
- Description: Rhodes University Graduation Ceremonies on Friday, 8 April 1988 at 8 p.m. [and] on Friday, 9 April 1988 at 10 a.m. in the 1820 Settlers National Monument. , Rhodes University East London Graduation Ceremony Saturday; 7 May 1988 at 11.30 a.m. in the Guild Theatre.
- Full Text:
Sequence in the mathematics syllabus : an investigation of the Senior Secondary Mathematics Syllabus (July 1984) of the Cape Education Department attempting to reconcile the demands of the strictly mathematical order and the developmental needs of pupils, modified by the mathematical potential of the electronic calculator : some teaching strategies resulting from new influences in the syllabus
- Authors: Breetzke, Peter Roland
- Date: 1988
- Subjects: Mathematics -- Study and teaching (Secondary) -- South Africa , Calculators , Mathematics -- South Africa -- Outlines, syllabi, etc.
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1364 , http://hdl.handle.net/10962/d1001430
- Description: This study was motivated by the latest revision of the mathematics syllabuses of the Cape Education Department. The most important changes to content in the Senior Secondary Mathematics Syllabus (July 1984) are the introduction of calculus and linear programming, the substitution of a section on analytical geometry for vector algebra and the recall of the remainder and factor theorems. The way in which these changes were introduced left the task of integrating them into the teaching process in the hands of individual teachers. This is a task of extreme importance. If one's classroom practice is to simply plough one's way through the syllabus, one loses many opportunities to make the study of mathematics meaningful and worthwhile. Accepting the view of the spiral nature of the curriculum where one returns to concepts and procedures at increasing levels of sophistication, one needs to identify the position of topics in this spiral and to trace their conceptual foundations. Analytical geometry is in particular need of this treatment. Similarly there are many opportunities for preparing for the introduction of calculus. If the teaching of calculus is left until the last moments of the Standard 10 year without proper groundwork, the pupil will be left with little time to develop an understanding of the concepts involved. It is the advent of calculators which presents the greatest challenge to mathematics education. We ignore this challenge to the detriment of our teaching. Taken seriously calculators have the potential to exert a radical influence on the content of curricula and examinations. They bring into question the time we spend on teaching arithmetic algorithms and the priority given to algebraic manipulation. Numercial methods gain new prominence. Calculators can even breathe new life into the existing curriculum. Their computing power can be harnessed not only to carry out specific calculations but also to introduce new topics and for concept reinforcement. The purpose of this study has been to bring about a proper integration of the new sections into the existing syllabus and to give some instances of how the calculator can become an integral part of the teaching/learning process
- Full Text:
- Authors: Breetzke, Peter Roland
- Date: 1988
- Subjects: Mathematics -- Study and teaching (Secondary) -- South Africa , Calculators , Mathematics -- South Africa -- Outlines, syllabi, etc.
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1364 , http://hdl.handle.net/10962/d1001430
- Description: This study was motivated by the latest revision of the mathematics syllabuses of the Cape Education Department. The most important changes to content in the Senior Secondary Mathematics Syllabus (July 1984) are the introduction of calculus and linear programming, the substitution of a section on analytical geometry for vector algebra and the recall of the remainder and factor theorems. The way in which these changes were introduced left the task of integrating them into the teaching process in the hands of individual teachers. This is a task of extreme importance. If one's classroom practice is to simply plough one's way through the syllabus, one loses many opportunities to make the study of mathematics meaningful and worthwhile. Accepting the view of the spiral nature of the curriculum where one returns to concepts and procedures at increasing levels of sophistication, one needs to identify the position of topics in this spiral and to trace their conceptual foundations. Analytical geometry is in particular need of this treatment. Similarly there are many opportunities for preparing for the introduction of calculus. If the teaching of calculus is left until the last moments of the Standard 10 year without proper groundwork, the pupil will be left with little time to develop an understanding of the concepts involved. It is the advent of calculators which presents the greatest challenge to mathematics education. We ignore this challenge to the detriment of our teaching. Taken seriously calculators have the potential to exert a radical influence on the content of curricula and examinations. They bring into question the time we spend on teaching arithmetic algorithms and the priority given to algebraic manipulation. Numercial methods gain new prominence. Calculators can even breathe new life into the existing curriculum. Their computing power can be harnessed not only to carry out specific calculations but also to introduce new topics and for concept reinforcement. The purpose of this study has been to bring about a proper integration of the new sections into the existing syllabus and to give some instances of how the calculator can become an integral part of the teaching/learning process
- Full Text:
Shakespeare and the bomber pilot: A reply to Colin Gardner
- Authors: Wright, Laurence
- Date: 1988
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/455734 , vital:75452 , https://hdl.handle.net/10520/AJA1011582X_59
- Description: I want to start at what may seem an unfair distance from the kind of view Colin Gardner has put forward. Early in 1947 the date is signifi-cant-a group of science students at Cambridge asked that some lec-tures on English Literature be organised for their special benefit. TR Henn responded and versions of his lectures were later published as The Apple and the Spectroscope (1951). In the book, Henn records the reaction of one of his students to Macbeth's speech at 1.7. 16-25: Be-sides, this Duncan Hath borne his faculties so meek, hath been So clear in his great office, that his virtues Will plead like angels, trumpet-tongu'd against The deep damnation of his taking off; And pity, like a naked new-born babe, Striding the blast, or heaven's cherubin, hors'd U pan the sightless couriers of the air, Shall blow the horrid deed in every eye, That tears shall drown the wind.
- Full Text:
- Authors: Wright, Laurence
- Date: 1988
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/455734 , vital:75452 , https://hdl.handle.net/10520/AJA1011582X_59
- Description: I want to start at what may seem an unfair distance from the kind of view Colin Gardner has put forward. Early in 1947 the date is signifi-cant-a group of science students at Cambridge asked that some lec-tures on English Literature be organised for their special benefit. TR Henn responded and versions of his lectures were later published as The Apple and the Spectroscope (1951). In the book, Henn records the reaction of one of his students to Macbeth's speech at 1.7. 16-25: Be-sides, this Duncan Hath borne his faculties so meek, hath been So clear in his great office, that his virtues Will plead like angels, trumpet-tongu'd against The deep damnation of his taking off; And pity, like a naked new-born babe, Striding the blast, or heaven's cherubin, hors'd U pan the sightless couriers of the air, Shall blow the horrid deed in every eye, That tears shall drown the wind.
- Full Text:
Skills for building organisation
- LACOM
- Authors: LACOM
- Date: 1988
- Subjects: LACOM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/137138 , vital:37491
- Description: Getting and carrying out mandates is one of the most important duties of a shop steward. This booklet has been prepared to help shop stewards carry out this duty. In a democratic organisation the job of a representative is to represent other people's views and wishes - to carry out the mandate of the people who elected them. For the people to feel that this is happening they must be able to know what their representatives are doing and saying. They can only know this if they get report-backs from their representatives on what they have been doing. The representatives on their own cannot make decisions for the people. People must be able to discipline representatives who don't represent their views.
- Full Text:
- Authors: LACOM
- Date: 1988
- Subjects: LACOM
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/137138 , vital:37491
- Description: Getting and carrying out mandates is one of the most important duties of a shop steward. This booklet has been prepared to help shop stewards carry out this duty. In a democratic organisation the job of a representative is to represent other people's views and wishes - to carry out the mandate of the people who elected them. For the people to feel that this is happening they must be able to know what their representatives are doing and saying. They can only know this if they get report-backs from their representatives on what they have been doing. The representatives on their own cannot make decisions for the people. People must be able to discipline representatives who don't represent their views.
- Full Text:
Structural studies on some capsular antigens from escherichia coli and klebsiella
- Authors: Anderson, Andrew Nixon
- Date: 1988
- Subjects: Escherichia , Klebsiella , Antigens
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3730 , http://hdl.handle.net/10962/d1001469
- Description: A review of the structural studies of bacterial capsular polysaccharides (K-antigens) from Escherichia coli and Klebsiella, and of the trends in modern chemical and instrumental techniques available for the analysis of carbohydrate material is presented. The structural elucidations of the capsular polysaccharides from E. coli K37 and K55, and Klebsiella K39 are reported with comments on the novelty and possible immunological significance of the structures. The usefulness of the bacteriophage degradation technique has been emphasized using the polysaccharides from E. coli K55, and Klebsiella K30 and K39 to demonstrate the scope of the reaction
- Full Text:
- Authors: Anderson, Andrew Nixon
- Date: 1988
- Subjects: Escherichia , Klebsiella , Antigens
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3730 , http://hdl.handle.net/10962/d1001469
- Description: A review of the structural studies of bacterial capsular polysaccharides (K-antigens) from Escherichia coli and Klebsiella, and of the trends in modern chemical and instrumental techniques available for the analysis of carbohydrate material is presented. The structural elucidations of the capsular polysaccharides from E. coli K37 and K55, and Klebsiella K39 are reported with comments on the novelty and possible immunological significance of the structures. The usefulness of the bacteriophage degradation technique has been emphasized using the polysaccharides from E. coli K55, and Klebsiella K30 and K39 to demonstrate the scope of the reaction
- Full Text:
Studies on zooplankton feeding ecology and resource utilization in a sub-tropical hypertrophic impoundment (Hartbeespoort Dam, South Africa)
- Authors: Jarvis, Andrew Charles
- Date: 1988
- Subjects: Freshwater zooplankton -- Ecology -- South Africa Freshwater zooplankton -- Tropics -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5624 , http://hdl.handle.net/10962/d1004600
- Description: Various aspects of the feeding ecology of zooplankton are described for hypertrophic Hartbeespoort Dam, where the phytoplankton is dominated by the cyanophyte Microcystis. The study considers zooplankton succession, community grazing rates, and speciesspecific filtration rates on Microaystis colonies and natural bacterioplankton. Seasonal abundance of the main herbivorous zooplankton between 1981 and 1986 is described both in respect of biomass and specific densities. In situ community grazing rates were measured from January 1983 to March 1985 using 14C-Iabelled Chlorella . Zooplankton succession and community grazing rates are examined in relation to food quantity and quality. Experiments measuring species-specific filtration rates on labelled Chlorella and Microcystis colony fractions revealed low filtration rates for small-bodied cladoceran species on cyanophyte colonies. Daphnia fed significantly on Microcystis colonies up to 60-100 ).μm but Daphnia filtration rates on Chlorella were suppressed by ~707. during the mid-summer increase in Microcystis abundance. Filtration rates of small cladoceran species were not suppressed by MicpocystisJ which was not an important food resource . Cladoceran filtration rate:body length models were developed for Chlorella and Microcystis colony fractions as food. Multiple regression models explained variance in filtration rates on these foods as a function of body length, food type and size, grazer species and temperature (in order of significance). Inclusion of food quality factors such as cyanophyte colony size seems justified in models of plankton feeding in eutrophic or hypertrophic lakes. Methods for in situ measurement of zooplankton filtration rates on 'H-thymidine-Iabelled natural bacteria were improved for use under hypertrophic conditions, and associated isotope-adsorption errors were measured. Community, species-specific and length-specific filtration rates on bacterioplankton were measured (late-spring to late-summer 1986-87) . Ceriodaphnia exhibited no preference for bacteria or Chlorella. Other cladocerans preferred the algal food . Algal/bacterial selectivity coefficients of the zooplankton community revealed an increased algal preference following the mid-summer shift to phytoplankton dominance by largely inedible Microcystis. This implies that bacterioplankton is not an important food resource for the summer cladoceran community. Estimates of the contribution of bacterial carbon to the daily zooplankton carbon requirements are low. The implications of all results are discussed in relation to seasonal succession, the clear-water phase', and biomanipulation in this hypertrophic reservoir.
- Full Text:
- Authors: Jarvis, Andrew Charles
- Date: 1988
- Subjects: Freshwater zooplankton -- Ecology -- South Africa Freshwater zooplankton -- Tropics -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5624 , http://hdl.handle.net/10962/d1004600
- Description: Various aspects of the feeding ecology of zooplankton are described for hypertrophic Hartbeespoort Dam, where the phytoplankton is dominated by the cyanophyte Microcystis. The study considers zooplankton succession, community grazing rates, and speciesspecific filtration rates on Microaystis colonies and natural bacterioplankton. Seasonal abundance of the main herbivorous zooplankton between 1981 and 1986 is described both in respect of biomass and specific densities. In situ community grazing rates were measured from January 1983 to March 1985 using 14C-Iabelled Chlorella . Zooplankton succession and community grazing rates are examined in relation to food quantity and quality. Experiments measuring species-specific filtration rates on labelled Chlorella and Microcystis colony fractions revealed low filtration rates for small-bodied cladoceran species on cyanophyte colonies. Daphnia fed significantly on Microcystis colonies up to 60-100 ).μm but Daphnia filtration rates on Chlorella were suppressed by ~707. during the mid-summer increase in Microcystis abundance. Filtration rates of small cladoceran species were not suppressed by MicpocystisJ which was not an important food resource . Cladoceran filtration rate:body length models were developed for Chlorella and Microcystis colony fractions as food. Multiple regression models explained variance in filtration rates on these foods as a function of body length, food type and size, grazer species and temperature (in order of significance). Inclusion of food quality factors such as cyanophyte colony size seems justified in models of plankton feeding in eutrophic or hypertrophic lakes. Methods for in situ measurement of zooplankton filtration rates on 'H-thymidine-Iabelled natural bacteria were improved for use under hypertrophic conditions, and associated isotope-adsorption errors were measured. Community, species-specific and length-specific filtration rates on bacterioplankton were measured (late-spring to late-summer 1986-87) . Ceriodaphnia exhibited no preference for bacteria or Chlorella. Other cladocerans preferred the algal food . Algal/bacterial selectivity coefficients of the zooplankton community revealed an increased algal preference following the mid-summer shift to phytoplankton dominance by largely inedible Microcystis. This implies that bacterioplankton is not an important food resource for the summer cladoceran community. Estimates of the contribution of bacterial carbon to the daily zooplankton carbon requirements are low. The implications of all results are discussed in relation to seasonal succession, the clear-water phase', and biomanipulation in this hypertrophic reservoir.
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Text and context : an examination of the way in which John's prologue has been interpreted by selected writers : Origen, Luther and Bultmann
- Authors: Latham, Jonathan Cyril
- Date: 1988 , 2013-02-28
- Subjects: Bible -- John -- Criticism, interpretation etc.
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:1225 , http://hdl.handle.net/10962/d1004612 , Bible -- John -- Criticism, interpretation etc.
- Description: In chapter one of this work, as a preliminary to the formulation of the question that this thesis will attempt to answer, the changing understanding of the part played by the interpreter in the process of interpretation is discussed. This outline begins with the understanding of the role of the interpreter in liberal theology - where he is thought of as one who applies critical methods to the text in a detached and scientific way. After this the hermeneutic spiral is discussed - the formation of this model acknowledges to a greater degree the individual and human part played by the interpreter. This is followed by a brief examination of the most recent theories of interpretation in which meaning is regarded as residing not in the text but in the interpreter himself. The task of this thesis is to determine whether, as these recent theorists suggest, the reader creates meaning instead of reading out what somehow lies in the text itself. The task of this thesis is to ascertain, by studying the interpretationsof John's Prologue by Origen, Luther and Bultmann, whether the text does in fact operate as a series of sign-posts that pOint the interpreter to a destination within his own semantic universe. This may be determined by noting whether or not the contexts, i n the broadest sense, of these interpreters have played a formative part in their interpretations. contextual influences are regarded as existing wherever there is a procedure or meaning in the interpreter's commentary which one expe cts to find there as a result of one's knowledge of the interpreter's life and previous writings. Our research reveals that Orige n, Luther and Bultmann have produced three very different commentaries in which the common denominator is the formative influence of the interpreter's context. Each of these writers has produced an interpretation that is consistent, in both approach and theology, with their previous exegetical and theological thought. This indicates that contextual factors have played a significant part in determining their interpr etations of John 1 :1-18. It would appear that these interpreters have been led to find the meaning of John's Prologue not with reference to any new, unprecedented set of symbols, but with reference to their own, well-worn semantic universes. In the conclusion it is noted that this research appears to support what many modern theorists have said as to the locus of meaning in interpretation. In the conclusion it is also noted that many of the fears raised by these findings - that readers and writers, or speakers and hearers, may become so isolated and trapped in their own thought worlds that any real contact with the outside is impossible - may be groundless. These findings also point to a certain consistency between the interpreters and their communities. This refutes the fears as to the isolation and solitary development of the individual in that it points to a certain community or corporate aspect which plays a part in the development of the indivi dual's semantic universe . , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
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- Authors: Latham, Jonathan Cyril
- Date: 1988 , 2013-02-28
- Subjects: Bible -- John -- Criticism, interpretation etc.
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:1225 , http://hdl.handle.net/10962/d1004612 , Bible -- John -- Criticism, interpretation etc.
- Description: In chapter one of this work, as a preliminary to the formulation of the question that this thesis will attempt to answer, the changing understanding of the part played by the interpreter in the process of interpretation is discussed. This outline begins with the understanding of the role of the interpreter in liberal theology - where he is thought of as one who applies critical methods to the text in a detached and scientific way. After this the hermeneutic spiral is discussed - the formation of this model acknowledges to a greater degree the individual and human part played by the interpreter. This is followed by a brief examination of the most recent theories of interpretation in which meaning is regarded as residing not in the text but in the interpreter himself. The task of this thesis is to determine whether, as these recent theorists suggest, the reader creates meaning instead of reading out what somehow lies in the text itself. The task of this thesis is to ascertain, by studying the interpretationsof John's Prologue by Origen, Luther and Bultmann, whether the text does in fact operate as a series of sign-posts that pOint the interpreter to a destination within his own semantic universe. This may be determined by noting whether or not the contexts, i n the broadest sense, of these interpreters have played a formative part in their interpretations. contextual influences are regarded as existing wherever there is a procedure or meaning in the interpreter's commentary which one expe cts to find there as a result of one's knowledge of the interpreter's life and previous writings. Our research reveals that Orige n, Luther and Bultmann have produced three very different commentaries in which the common denominator is the formative influence of the interpreter's context. Each of these writers has produced an interpretation that is consistent, in both approach and theology, with their previous exegetical and theological thought. This indicates that contextual factors have played a significant part in determining their interpr etations of John 1 :1-18. It would appear that these interpreters have been led to find the meaning of John's Prologue not with reference to any new, unprecedented set of symbols, but with reference to their own, well-worn semantic universes. In the conclusion it is noted that this research appears to support what many modern theorists have said as to the locus of meaning in interpretation. In the conclusion it is also noted that many of the fears raised by these findings - that readers and writers, or speakers and hearers, may become so isolated and trapped in their own thought worlds that any real contact with the outside is impossible - may be groundless. These findings also point to a certain consistency between the interpreters and their communities. This refutes the fears as to the isolation and solitary development of the individual in that it points to a certain community or corporate aspect which plays a part in the development of the indivi dual's semantic universe . , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
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The Albania settlement of Griqualand West, 1866-1878
- Authors: Kurtz, June Margaret
- Date: 1988
- Subjects: Land settlement -- South Africa -- Cape of Good Hope , Albania (South Africa) , Griqualand West (South Africa) -- History
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2582 , http://hdl.handle.net/10962/d1004665 , Land settlement -- South Africa -- Cape of Good Hope , Albania (South Africa) , Griqualand West (South Africa) -- History
- Description: The history of the Albania Settlement of Griqualand West is examined from its beginnings in 1866 to its demise in 1878. Albania was very much a product of its time. Nineteenth century British colonial policy was basically expansionist, despite minor fluctuations caused by the various influences affecting it, such as the Free Trade and Mercantilist doctrines, social factors within Britain and events within the colonies themselves. From 1815 colonial settlements were fairly common in British territory, especially after Wakefield had provided a convincing theoretical framework for them. Within South Africa itself there are differing interpretations of what motivated British policy and of the role of the missionaries, while the changing political and economic landscape markedly affected Britain's decisions. British Government settlement schemes were undertaken mainly for social or military reasons, but there were also many settlements founded by land speculators. The economically depressed 1860s hit the Eastern Cape hard and this, combined with the transition to sheep farming, which created considerable land hunger, made the Albania scheme attractive to Eastern Cape farmers. The Griqua people led by Andries Waterboer had made a great effort to establish hegemony north of the Orange River, over the Sotho-Tswana and other Griqua chiefs. By 1866 the attempt had failed and Free State farmers were encroaching onto Nicholas Waterboer's lands. When Waterboer's agent, David Arnot, proposed the establishment of a settlement of Albany men to act as a "Wall of Flesh", Waterboer accepted the idea. Arnot's motivation was also land speculation in an area where diamonds were likely to push up land values. From its inception the settlement was dogged by quarrels, mainly over land, amongst the parties involved - the Griqua, brutally removed to make way for the settlers; the settlers, dissatisfied with the land tenure system and their administration; Arnot; the British and the encroaching Boer farmers . After the 1871 annexation of Griqualand West, into which Albania was absorbed, it took seven years, two Land Commissions, a Land Court and a special Land Claims Commissioner to sort out the tangled claims and bring order to the area and Albania's history to a close.
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- Authors: Kurtz, June Margaret
- Date: 1988
- Subjects: Land settlement -- South Africa -- Cape of Good Hope , Albania (South Africa) , Griqualand West (South Africa) -- History
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2582 , http://hdl.handle.net/10962/d1004665 , Land settlement -- South Africa -- Cape of Good Hope , Albania (South Africa) , Griqualand West (South Africa) -- History
- Description: The history of the Albania Settlement of Griqualand West is examined from its beginnings in 1866 to its demise in 1878. Albania was very much a product of its time. Nineteenth century British colonial policy was basically expansionist, despite minor fluctuations caused by the various influences affecting it, such as the Free Trade and Mercantilist doctrines, social factors within Britain and events within the colonies themselves. From 1815 colonial settlements were fairly common in British territory, especially after Wakefield had provided a convincing theoretical framework for them. Within South Africa itself there are differing interpretations of what motivated British policy and of the role of the missionaries, while the changing political and economic landscape markedly affected Britain's decisions. British Government settlement schemes were undertaken mainly for social or military reasons, but there were also many settlements founded by land speculators. The economically depressed 1860s hit the Eastern Cape hard and this, combined with the transition to sheep farming, which created considerable land hunger, made the Albania scheme attractive to Eastern Cape farmers. The Griqua people led by Andries Waterboer had made a great effort to establish hegemony north of the Orange River, over the Sotho-Tswana and other Griqua chiefs. By 1866 the attempt had failed and Free State farmers were encroaching onto Nicholas Waterboer's lands. When Waterboer's agent, David Arnot, proposed the establishment of a settlement of Albany men to act as a "Wall of Flesh", Waterboer accepted the idea. Arnot's motivation was also land speculation in an area where diamonds were likely to push up land values. From its inception the settlement was dogged by quarrels, mainly over land, amongst the parties involved - the Griqua, brutally removed to make way for the settlers; the settlers, dissatisfied with the land tenure system and their administration; Arnot; the British and the encroaching Boer farmers . After the 1871 annexation of Griqualand West, into which Albania was absorbed, it took seven years, two Land Commissions, a Land Court and a special Land Claims Commissioner to sort out the tangled claims and bring order to the area and Albania's history to a close.
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The biology of Acia lineatifrons (Naude) (Homoptera : Cicadellidae) on grapevines in the Western Cape
- Authors: Marais, Elleunorah
- Date: 1988
- Subjects: Homoptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5597 , http://hdl.handle.net/10962/d1002047
- Description: The leafhopper, Acia lineatifrons (Naude) was identified as a pest on grapevines near Tulbagh in 1978 and has since been reported on grapevines all over the South Western Cape. A. lineatifrons causes browning of the leaves which often results in the shedding of the discoloured leaves. Heavy defoliation before harvest can result in sunburn damage to the grapes, whilst premature leaf loss after harvest adversely affects the ripening of the canes and the accumulation of reserves. This project was aimed at obtaining basic information on the biology and population dynamics of A. lineatifrons as well as to identify priorities for future research. This information is needed to develop a reliable crop-linked predictive model, methods for monitoring pest populations as well as to develop efficient short- and long-term control measures and pest management strategies. The life cycle of A. lineatifrons was studied in the laboratory. At 26°C the mean incubation period of the eggs was nine to eleven days, the mean developmental period for the five nymphal instars was 15 days and the minimum pre-oviposition period five to ten days. This adds up to a mean generation time of 29 to 36 days at 26°C. At 20°C the mean nymphal development period was 25 days, confirming the strong influence of temperature on the development rate. Fecundity was determined in the laboratory as the number of nymphs produced per female. The mean of 8,5 nymphs per female recorded at 26°C is very low compared to that of other leafhopper species (see Appendix 2). The low fecundity measured was most likely due to sub-optimal environmental conditions in the laboratory, a reduction in the suitability of the host plant under these conditions and handling of the females. The seasonal occurrence of A. lineatifrons on grapevines was studied over three seasons. It was found that the leafhoppers overwinter in the adult stage on indigenous Rubus spp, and that they enter the vineyard from the end of October until the beginning of November. Peak populations occurred between the middle of February and the end of March after which the population declined steadily towards the end of the season as the vine leaves were shed. The sex ratio of the overwintering population on R. chrysocarpus was heavily female biased, possibly due to differential mortality of the sexes. During the growing season the sex ratio was slightly male biased and reached equality on several occasions, both on the Rubus and on the grapevines. The movement of A. lineatifrons between the Rubus and the grapevines was investigated, but no evidence of a directional migration from the Rubus to the grapevines was found. Furthermore, no evidence was found to indicate that morphologically distinct short- and long-distance fliers, as found in Cicadulina species by Rose (1972b), exist in the A. lineatifrons population. Host preference tests also showed that adult leafhoppers apparently have no significant preference for grapevines to Rubus or vice versa. It seems, therefore, that the leafhoppers' move onto the grapevines at the beginning of the growing season is not prompted by a host preference. Chaboussou (1971) suggested that certain organic fungicides may cause leafhopper outbreaks because they affect the suitability of the vines as host plants and alter leafhopper fecundity. The effect of Mikal-M (active ingredient Fosetyl AL/Mancozeb), a systemic dithiocarbanate fungicide, on A. lineatifrons was investigated. Laboratory experiments showed no significant effect on fecundity and leaf analysis of potted vines treated with Mikal-M indicated no significant difference in total leaf nitrogen compared to untreated control plants. However, the field experiment on the effect of Mikal-M on the population build-up of the leafhopper showed that significantly more leafhoppers occurred on the vines treated with Mikal-M than on those treated with a conventional inorganic fungicide, copper oxychloride. In view of the far-reaching implications this can have on the viticultural industry, further research on the effects of organic fungicides on leafhopper populations is recommended to confirm the generality of these results so that recommendations regarding the use of these fungicides may be made. The question as to why A. lineatifrons became a pest only recently was raised. Three possibilities were considered, namely (1) that A. lineatifrons is a species of tropical origin which moved down the continent and became established in the Western Cape only recently, (2) that is has been in the Western Cape at least as long as the grapevines, but required prolonged exposure to establish itself on the new host and (3) that is has been on the vines for some time, but was noticed only recently when outbreaks occurred. These outbreaks could have been caused by the introduction of organic fungicides or the depletion of natural enemies by insecticides used to control other insects in the vineyards. Due to the lack of evidence this question could not be answered conclusively. Other research priorities that were established are the development of methods for damage assessment and monitoring of leafhopper populations, determining if A. lineatifrons can transmit grapevine virusses, the development of an economic threshold level and the identification of natural enemies of A. lineatifrons to enable the development of efficient pest management strategies (Summary, p. 63-65)
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- Authors: Marais, Elleunorah
- Date: 1988
- Subjects: Homoptera
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5597 , http://hdl.handle.net/10962/d1002047
- Description: The leafhopper, Acia lineatifrons (Naude) was identified as a pest on grapevines near Tulbagh in 1978 and has since been reported on grapevines all over the South Western Cape. A. lineatifrons causes browning of the leaves which often results in the shedding of the discoloured leaves. Heavy defoliation before harvest can result in sunburn damage to the grapes, whilst premature leaf loss after harvest adversely affects the ripening of the canes and the accumulation of reserves. This project was aimed at obtaining basic information on the biology and population dynamics of A. lineatifrons as well as to identify priorities for future research. This information is needed to develop a reliable crop-linked predictive model, methods for monitoring pest populations as well as to develop efficient short- and long-term control measures and pest management strategies. The life cycle of A. lineatifrons was studied in the laboratory. At 26°C the mean incubation period of the eggs was nine to eleven days, the mean developmental period for the five nymphal instars was 15 days and the minimum pre-oviposition period five to ten days. This adds up to a mean generation time of 29 to 36 days at 26°C. At 20°C the mean nymphal development period was 25 days, confirming the strong influence of temperature on the development rate. Fecundity was determined in the laboratory as the number of nymphs produced per female. The mean of 8,5 nymphs per female recorded at 26°C is very low compared to that of other leafhopper species (see Appendix 2). The low fecundity measured was most likely due to sub-optimal environmental conditions in the laboratory, a reduction in the suitability of the host plant under these conditions and handling of the females. The seasonal occurrence of A. lineatifrons on grapevines was studied over three seasons. It was found that the leafhoppers overwinter in the adult stage on indigenous Rubus spp, and that they enter the vineyard from the end of October until the beginning of November. Peak populations occurred between the middle of February and the end of March after which the population declined steadily towards the end of the season as the vine leaves were shed. The sex ratio of the overwintering population on R. chrysocarpus was heavily female biased, possibly due to differential mortality of the sexes. During the growing season the sex ratio was slightly male biased and reached equality on several occasions, both on the Rubus and on the grapevines. The movement of A. lineatifrons between the Rubus and the grapevines was investigated, but no evidence of a directional migration from the Rubus to the grapevines was found. Furthermore, no evidence was found to indicate that morphologically distinct short- and long-distance fliers, as found in Cicadulina species by Rose (1972b), exist in the A. lineatifrons population. Host preference tests also showed that adult leafhoppers apparently have no significant preference for grapevines to Rubus or vice versa. It seems, therefore, that the leafhoppers' move onto the grapevines at the beginning of the growing season is not prompted by a host preference. Chaboussou (1971) suggested that certain organic fungicides may cause leafhopper outbreaks because they affect the suitability of the vines as host plants and alter leafhopper fecundity. The effect of Mikal-M (active ingredient Fosetyl AL/Mancozeb), a systemic dithiocarbanate fungicide, on A. lineatifrons was investigated. Laboratory experiments showed no significant effect on fecundity and leaf analysis of potted vines treated with Mikal-M indicated no significant difference in total leaf nitrogen compared to untreated control plants. However, the field experiment on the effect of Mikal-M on the population build-up of the leafhopper showed that significantly more leafhoppers occurred on the vines treated with Mikal-M than on those treated with a conventional inorganic fungicide, copper oxychloride. In view of the far-reaching implications this can have on the viticultural industry, further research on the effects of organic fungicides on leafhopper populations is recommended to confirm the generality of these results so that recommendations regarding the use of these fungicides may be made. The question as to why A. lineatifrons became a pest only recently was raised. Three possibilities were considered, namely (1) that A. lineatifrons is a species of tropical origin which moved down the continent and became established in the Western Cape only recently, (2) that is has been in the Western Cape at least as long as the grapevines, but required prolonged exposure to establish itself on the new host and (3) that is has been on the vines for some time, but was noticed only recently when outbreaks occurred. These outbreaks could have been caused by the introduction of organic fungicides or the depletion of natural enemies by insecticides used to control other insects in the vineyards. Due to the lack of evidence this question could not be answered conclusively. Other research priorities that were established are the development of methods for damage assessment and monitoring of leafhopper populations, determining if A. lineatifrons can transmit grapevine virusses, the development of an economic threshold level and the identification of natural enemies of A. lineatifrons to enable the development of efficient pest management strategies (Summary, p. 63-65)
- Full Text: