Thermal decomposition of ammonium metavanadate
- Authors: Stewart, Brian Victor
- Date: 1972
- Subjects: Decomposition (Chemistry) , Solids -- Thermal properties , Ammonia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4503 , http://hdl.handle.net/10962/d1013274
- Description: The isothermal, endothermic, stepwise decomposition of ammonium metavanadate (AMV) in inert (argon or nitrogen), oxidising (air or oxygen) and reducing (ammonia) atmospheres as well as under high vacuum (pressure < IOn bar) conditions has been investigated. The reverse reaction, the isothermal recombination of V₂ 0₅ with ammonia and water vapour has also been investigated. The decomposition and recombination reactions were followed by continuously recording the mass loss of the sample with time using a Cahn R.G. Automatic Electrobalance. This enabled small samples ( ~ lOmg) to be used and consequently any self cooling of the sample during the decomposition was minimized. The intermediates and final products formed have been characterized by chemical analysis, X-ray powder diffraction studies, infrared spectroscopy and the mass loss involved in their formation. The changes in the physical properties of the samples during decomposition and recombination have been investigated by surface area measurements (using the BET method and krypton adsorption) and eIectron microscopy. Values for the enthalpy changes involved in the decomposition have been obtained by differential scanning calorimetry. The stoichiometry of the isothermal decomposition of ammonium metavanadate, under the various conditions of surrounding atmosphere has been discussed. Except for the later stages of the decomposition in ammonia, the results correspond well to the gradual reduction of the ratio of "(NH₄)₂ 0" to "V₂0₅" units from the original 1:1 ratio in ammonium metavanadate to pure "V₂0₅" with ammonia and water being evolved throughout the decomposition in the mole ratio of 2:1. The final product of the decomposition in vacuum, argon and air is "V₂0₅" and in ammonia, below 360°, V0₂. The kinetic parameters for each of the stages of the decomposition of AMV in each of the atmospheres studied have been determined. The mechanism of the first stage of the decomposition under the different conditions of surrounding atmosphere has been discussed from both the kinetic and the thermodynamic points of view. The absolute reaction rate theory has been applied to the decomposition in inert atmospheres enabling the formulae of the activated complexes formed during each stage to be calculated. It has also been shown that the detailed atomic movements occurring during the first stage of the decomposition in ammonia can be predicted from a knowledge of the stoichiometry of the reaction and of the detailed crystal structures of the starting and product materials. The kinetics and mechanism of the recombination of "V₂0₅" with ammonia and water vapour to form AMV have also been discussed in detail.
- Full Text:
- Date Issued: 1972
- Authors: Stewart, Brian Victor
- Date: 1972
- Subjects: Decomposition (Chemistry) , Solids -- Thermal properties , Ammonia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4503 , http://hdl.handle.net/10962/d1013274
- Description: The isothermal, endothermic, stepwise decomposition of ammonium metavanadate (AMV) in inert (argon or nitrogen), oxidising (air or oxygen) and reducing (ammonia) atmospheres as well as under high vacuum (pressure < IOn bar) conditions has been investigated. The reverse reaction, the isothermal recombination of V₂ 0₅ with ammonia and water vapour has also been investigated. The decomposition and recombination reactions were followed by continuously recording the mass loss of the sample with time using a Cahn R.G. Automatic Electrobalance. This enabled small samples ( ~ lOmg) to be used and consequently any self cooling of the sample during the decomposition was minimized. The intermediates and final products formed have been characterized by chemical analysis, X-ray powder diffraction studies, infrared spectroscopy and the mass loss involved in their formation. The changes in the physical properties of the samples during decomposition and recombination have been investigated by surface area measurements (using the BET method and krypton adsorption) and eIectron microscopy. Values for the enthalpy changes involved in the decomposition have been obtained by differential scanning calorimetry. The stoichiometry of the isothermal decomposition of ammonium metavanadate, under the various conditions of surrounding atmosphere has been discussed. Except for the later stages of the decomposition in ammonia, the results correspond well to the gradual reduction of the ratio of "(NH₄)₂ 0" to "V₂0₅" units from the original 1:1 ratio in ammonium metavanadate to pure "V₂0₅" with ammonia and water being evolved throughout the decomposition in the mole ratio of 2:1. The final product of the decomposition in vacuum, argon and air is "V₂0₅" and in ammonia, below 360°, V0₂. The kinetic parameters for each of the stages of the decomposition of AMV in each of the atmospheres studied have been determined. The mechanism of the first stage of the decomposition under the different conditions of surrounding atmosphere has been discussed from both the kinetic and the thermodynamic points of view. The absolute reaction rate theory has been applied to the decomposition in inert atmospheres enabling the formulae of the activated complexes formed during each stage to be calculated. It has also been shown that the detailed atomic movements occurring during the first stage of the decomposition in ammonia can be predicted from a knowledge of the stoichiometry of the reaction and of the detailed crystal structures of the starting and product materials. The kinetics and mechanism of the recombination of "V₂0₅" with ammonia and water vapour to form AMV have also been discussed in detail.
- Full Text:
- Date Issued: 1972
A comparison of attitudes toward intensive competition among high school pupils
- Authors: Potgieter, Justus R
- Date: 1971
- Subjects: Competition (Psychology) in adolescence Competition (Psychology) Interpersonal relations Motivation (Psychology)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1930 , http://hdl.handle.net/10962/d1007604
- Description: From Preface: As a teacher with experience in competitive sport, the author became interested in the topic of athletic competition when joining the staff of an all-boys' school. The competitive aspect of sport at such a school can make quite an impression on an inexperienced teacher. The question then arose; Is this competitive atmosphere universal? Is this type of competition acceptable and desirable in our schools? Being a teacher of Physical Education as well as other subjects and also being actively involved in the coaching of senior sports teams the author regarded himself suitably qualified to investigate the matter of athletic competition in our schools.
- Full Text:
- Date Issued: 1971
- Authors: Potgieter, Justus R
- Date: 1971
- Subjects: Competition (Psychology) in adolescence Competition (Psychology) Interpersonal relations Motivation (Psychology)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1930 , http://hdl.handle.net/10962/d1007604
- Description: From Preface: As a teacher with experience in competitive sport, the author became interested in the topic of athletic competition when joining the staff of an all-boys' school. The competitive aspect of sport at such a school can make quite an impression on an inexperienced teacher. The question then arose; Is this competitive atmosphere universal? Is this type of competition acceptable and desirable in our schools? Being a teacher of Physical Education as well as other subjects and also being actively involved in the coaching of senior sports teams the author regarded himself suitably qualified to investigate the matter of athletic competition in our schools.
- Full Text:
- Date Issued: 1971
A contribution to the biology of warthog (Phacochoerus africanus, Gmelin) in the Sengwa region of Rhodesia
- Authors: Cumming, D H M
- Date: 1971
- Subjects: Warthog Warthog -- Physiology Warthog -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5843 , http://hdl.handle.net/10962/d1010740
- Description: To the AmaZulu a warthog is "inhlovudawana" or "little elephant"; to arrogant hunters it is the "poor man's rhinoceros"; to some writers of encyclopaediae it is a "grotesque and hideous beast"; to stockmen it has long been a carrier of diseases. Injury was added to insult with the discovery that the blood of these self-assured, often comical and certainly engaging animals supports the greater proportion of tsetse flies in the African savannas. Their significance as the primary hosts of Glossina morsitans Westw., the vectors of tryanosomiasis, justified an extended field study of warthog biology. This thesis reports four years of field work on warthogs, together with complementary observations of hand-reared warthogs (and their offspring) which roamed freely in the vicinity of the remote field station on which I live. The Sengwa Research Project, of which this study forms a part, was initiated in 1965 to study relationships between game animals and tsetse flies. One of the main problems investigated in the Sengwa Project is that of "host encounter" (Glasgow, 1961, Bursell, 1970) and how the distribution, abundance and behaviour of game animals may affect their availability to hungry tsetse flies. I have, accordingly, been concerned with discovering how warthog are dispersed in the Sengwa area and have attempted to gain some understanding of the factors, both environmental and social, which may affect or govern their dispersion and possibly population number. Intro. p. 1.
- Full Text:
- Date Issued: 1971
- Authors: Cumming, D H M
- Date: 1971
- Subjects: Warthog Warthog -- Physiology Warthog -- Ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5843 , http://hdl.handle.net/10962/d1010740
- Description: To the AmaZulu a warthog is "inhlovudawana" or "little elephant"; to arrogant hunters it is the "poor man's rhinoceros"; to some writers of encyclopaediae it is a "grotesque and hideous beast"; to stockmen it has long been a carrier of diseases. Injury was added to insult with the discovery that the blood of these self-assured, often comical and certainly engaging animals supports the greater proportion of tsetse flies in the African savannas. Their significance as the primary hosts of Glossina morsitans Westw., the vectors of tryanosomiasis, justified an extended field study of warthog biology. This thesis reports four years of field work on warthogs, together with complementary observations of hand-reared warthogs (and their offspring) which roamed freely in the vicinity of the remote field station on which I live. The Sengwa Research Project, of which this study forms a part, was initiated in 1965 to study relationships between game animals and tsetse flies. One of the main problems investigated in the Sengwa Project is that of "host encounter" (Glasgow, 1961, Bursell, 1970) and how the distribution, abundance and behaviour of game animals may affect their availability to hungry tsetse flies. I have, accordingly, been concerned with discovering how warthog are dispersed in the Sengwa area and have attempted to gain some understanding of the factors, both environmental and social, which may affect or govern their dispersion and possibly population number. Intro. p. 1.
- Full Text:
- Date Issued: 1971
An investigation into religious instruction in state high schools in the Cape Province
- Authors: Penny, Alan Joseph
- Date: 1971
- Subjects: Religious education -- South Africa -- Cape of Good Hope Religious education of teenagers
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1933 , http://hdl.handle.net/10962/d1007641
- Description: From Preface: The question of religious instruction in Cape Schools first aroused my interest when I was subjected to anything but religious tnstruction during my own high school years. My desire to enquire into the whole position of religious instruction in the high school curriculum grew out of an essay on the role of religion in the education of the child which I wrote whilst reading for the B.Ed. degree. As background, I read Harold Loukes' classic Teenage Religion, and from then onwards, I felt that it was necessary to undertake an investigation of this kind in the Cape Province. My aim was not only prompted out of a desire to expose what I already knew to be an educationally and religiously unsound and unhealthy state of affairs, but more deeply because I, although an ignorant amateur in theology, am aware that too often the traditional religious foundations, poorly built by unintelligent teaching, are shaken, if not destroyed, by scientific discovery and material advancement.
- Full Text:
- Date Issued: 1971
- Authors: Penny, Alan Joseph
- Date: 1971
- Subjects: Religious education -- South Africa -- Cape of Good Hope Religious education of teenagers
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1933 , http://hdl.handle.net/10962/d1007641
- Description: From Preface: The question of religious instruction in Cape Schools first aroused my interest when I was subjected to anything but religious tnstruction during my own high school years. My desire to enquire into the whole position of religious instruction in the high school curriculum grew out of an essay on the role of religion in the education of the child which I wrote whilst reading for the B.Ed. degree. As background, I read Harold Loukes' classic Teenage Religion, and from then onwards, I felt that it was necessary to undertake an investigation of this kind in the Cape Province. My aim was not only prompted out of a desire to expose what I already knew to be an educationally and religiously unsound and unhealthy state of affairs, but more deeply because I, although an ignorant amateur in theology, am aware that too often the traditional religious foundations, poorly built by unintelligent teaching, are shaken, if not destroyed, by scientific discovery and material advancement.
- Full Text:
- Date Issued: 1971
An investigation into the sensory mechanisms underlying the two point threshold, with particular reference to the practice effect
- Authors: Gradwell, Peter Bertram
- Date: 1971
- Subjects: Sensorimotor integration , Perceptual-motor learning
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3209 , http://hdl.handle.net/10962/d1012085 , Sensorimotor integration , Perceptual-motor learning
- Description: The two point threshold was studied extensively by the psychophysical experimenters of the last century. More recent formulations in signal detection theory have suggested that the statements of these workers about absolute thresholds should be viewed with caution. This study investigates the two point threshold in the light of these formulations, and has two main aims :- (1) To state and deal with the problem of relating a limitation in perceptual ability, such as that which is represented by the two point threshold, to the receptor organisation of the body. (2) To demonstrate a practice effect on the two point threshold, and to consider this in the light of (1) above. To fulfil these two aims, a model of the neural mechanisms underlying the discrimination of two points applied to the skin is proposed, and this is able to accommodate what is known of the two point threshold. Although the model is simple it explicitly accounts for size transfer and the practice effect, and provides some clues as to the type of neural mechanism capable of producing them. The practice effect is demonstrated experimentally, and the results are then referred to the model proposed. The physiology of an organism sets the limits for its behaviour. 'The first aim is thus an important one, in that it considers a specific case of this general problem. And secondly, the practice effect on the two point threshold is typical of a number of fairly simple "learning" phenomena, which are part of the psychologists' study of learning.
- Full Text:
- Date Issued: 1971
- Authors: Gradwell, Peter Bertram
- Date: 1971
- Subjects: Sensorimotor integration , Perceptual-motor learning
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3209 , http://hdl.handle.net/10962/d1012085 , Sensorimotor integration , Perceptual-motor learning
- Description: The two point threshold was studied extensively by the psychophysical experimenters of the last century. More recent formulations in signal detection theory have suggested that the statements of these workers about absolute thresholds should be viewed with caution. This study investigates the two point threshold in the light of these formulations, and has two main aims :- (1) To state and deal with the problem of relating a limitation in perceptual ability, such as that which is represented by the two point threshold, to the receptor organisation of the body. (2) To demonstrate a practice effect on the two point threshold, and to consider this in the light of (1) above. To fulfil these two aims, a model of the neural mechanisms underlying the discrimination of two points applied to the skin is proposed, and this is able to accommodate what is known of the two point threshold. Although the model is simple it explicitly accounts for size transfer and the practice effect, and provides some clues as to the type of neural mechanism capable of producing them. The practice effect is demonstrated experimentally, and the results are then referred to the model proposed. The physiology of an organism sets the limits for its behaviour. 'The first aim is thus an important one, in that it considers a specific case of this general problem. And secondly, the practice effect on the two point threshold is typical of a number of fairly simple "learning" phenomena, which are part of the psychologists' study of learning.
- Full Text:
- Date Issued: 1971
Creative processes in young children
- Authors: Styles, Irene Mavis
- Date: 1971
- Subjects: Creative ability in children , Creative thinking
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3244 , http://hdl.handle.net/10962/d1013327
- Description: Enthusiasm for developing creativity in the individual has been remarkably widespread - at least in America - over the past twenty-five years or so. The armed services, the arts and sciences, educational institutions, businesses and industries are recognising to a greater and greater extent, the urgent necessity of developing this relatively neglected aspect of people is personalities. Their reasons differ, of course, and usually the welfare of the individual himself is not the main concern. This is perhaps fortunate, as advances made on philanthropic grounds alone have never progressed very rapidly. In business and industry, new ideas are urgently needed for survival - this was especially evident after World War II which was, in the end, really a battle of ideas. The importance of this implication has not decreased with distance in time from that conflagration, indeed, individuals in the armed services are probably the people most deeply involved in and the most concerned with the problem of developing creative thought. "We are in a mortal struggle for the survival of our way of life", writes Guilford. "The need (for developing creativity) is a national crisis" says Anderson*. Intro., p. 1.
- Full Text:
- Date Issued: 1971
- Authors: Styles, Irene Mavis
- Date: 1971
- Subjects: Creative ability in children , Creative thinking
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3244 , http://hdl.handle.net/10962/d1013327
- Description: Enthusiasm for developing creativity in the individual has been remarkably widespread - at least in America - over the past twenty-five years or so. The armed services, the arts and sciences, educational institutions, businesses and industries are recognising to a greater and greater extent, the urgent necessity of developing this relatively neglected aspect of people is personalities. Their reasons differ, of course, and usually the welfare of the individual himself is not the main concern. This is perhaps fortunate, as advances made on philanthropic grounds alone have never progressed very rapidly. In business and industry, new ideas are urgently needed for survival - this was especially evident after World War II which was, in the end, really a battle of ideas. The importance of this implication has not decreased with distance in time from that conflagration, indeed, individuals in the armed services are probably the people most deeply involved in and the most concerned with the problem of developing creative thought. "We are in a mortal struggle for the survival of our way of life", writes Guilford. "The need (for developing creativity) is a national crisis" says Anderson*. Intro., p. 1.
- Full Text:
- Date Issued: 1971
Developmental studies of certain South African Ascostromatic ascomycetes
- Authors: Tim, Stephen K-M
- Date: 1971
- Subjects: Fungi -- Parasites Ascomycetes Pyrenomycetes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4245 , http://hdl.handle.net/10962/d1007289
- Description: From General Introduction: Toward the last half of the nineteenth century, the structure and mode of development of the ascocarp has aroused much interest. De Bary (1887) recognised the fruiting bodies of the Ascomycetes as 'compound sporophores' made up of interwoven hyphae or of pseudoparenchyma consisting of a peripheral layer separate from an inner tissue. These fruiting bodies included the discocarp or apothecium, the pyrenocarp or perithecium and the cleistocarp or cleistothecium. The name, Pyrenomycetes, has been variously applied to a group of Ascomycetes but mainly to the perithecial types, inclusive of the true perithecia and the loculate forms. The perithecium itself was described as a 'cup-shaped discomycetous' sporocarp with margins incurved to form a pyriform structure (de Bary, 1887). The presence or absence of a stroma had been long considered as a basis for the separation of the major groups of the Ascomycetes. Separation on these grounds was found unacceptable as it grouped together clearly unrelated species or separated related ones. As the subdivisions of the pyrenomycetous Ascomycetes are dependent upon the morphological features of the ascocarp, it would be pertinent to discuss the following: a) The Stroma. b) The various forms of ascocarp which mayor may not be associated with such a stroma. i) Perithecia: free or immersed in a stroma. ii) Uni- or multiloculate stromata. c) The centrum, the details associated with the centrum and the use of these details in the taxonomy of the pyrenomycetes.
- Full Text:
- Date Issued: 1971
- Authors: Tim, Stephen K-M
- Date: 1971
- Subjects: Fungi -- Parasites Ascomycetes Pyrenomycetes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4245 , http://hdl.handle.net/10962/d1007289
- Description: From General Introduction: Toward the last half of the nineteenth century, the structure and mode of development of the ascocarp has aroused much interest. De Bary (1887) recognised the fruiting bodies of the Ascomycetes as 'compound sporophores' made up of interwoven hyphae or of pseudoparenchyma consisting of a peripheral layer separate from an inner tissue. These fruiting bodies included the discocarp or apothecium, the pyrenocarp or perithecium and the cleistocarp or cleistothecium. The name, Pyrenomycetes, has been variously applied to a group of Ascomycetes but mainly to the perithecial types, inclusive of the true perithecia and the loculate forms. The perithecium itself was described as a 'cup-shaped discomycetous' sporocarp with margins incurved to form a pyriform structure (de Bary, 1887). The presence or absence of a stroma had been long considered as a basis for the separation of the major groups of the Ascomycetes. Separation on these grounds was found unacceptable as it grouped together clearly unrelated species or separated related ones. As the subdivisions of the pyrenomycetous Ascomycetes are dependent upon the morphological features of the ascocarp, it would be pertinent to discuss the following: a) The Stroma. b) The various forms of ascocarp which mayor may not be associated with such a stroma. i) Perithecia: free or immersed in a stroma. ii) Uni- or multiloculate stromata. c) The centrum, the details associated with the centrum and the use of these details in the taxonomy of the pyrenomycetes.
- Full Text:
- Date Issued: 1971
Die utopie und der deutsche utopische roman seit 1939
- Krueger, Gustav Adolf Ludwig Werner
- Authors: Krueger, Gustav Adolf Ludwig Werner
- Date: 1971
- Subjects: German fiction -- 20th century , German literature -- History and criticism
- Language: German
- Type: Thesis , Masters , MA
- Identifier: vital:3631 , http://hdl.handle.net/10962/d1012711 , German fiction -- 20th century , German literature -- History and criticism
- Description: Wie bei jeder wissenschaftlichen Untersuchung stellt sich auch hier, bei einer Arbeit über den utopischen Roman, die Frage nach einer Begriffsbestimmung. In diesem Fall geht es um eine genaue Umreissung der Begriffe "Utopie", "Staatsroman", "Utopischer Roman" oder auch "Utopia-Roman", vorausgesetzt, dass man diese Begriffe überhaupt als Gattungsbezeichnungen zu benutzen gewillt ist. Intro., p. 1.
- Full Text:
- Date Issued: 1971
- Authors: Krueger, Gustav Adolf Ludwig Werner
- Date: 1971
- Subjects: German fiction -- 20th century , German literature -- History and criticism
- Language: German
- Type: Thesis , Masters , MA
- Identifier: vital:3631 , http://hdl.handle.net/10962/d1012711 , German fiction -- 20th century , German literature -- History and criticism
- Description: Wie bei jeder wissenschaftlichen Untersuchung stellt sich auch hier, bei einer Arbeit über den utopischen Roman, die Frage nach einer Begriffsbestimmung. In diesem Fall geht es um eine genaue Umreissung der Begriffe "Utopie", "Staatsroman", "Utopischer Roman" oder auch "Utopia-Roman", vorausgesetzt, dass man diese Begriffe überhaupt als Gattungsbezeichnungen zu benutzen gewillt ist. Intro., p. 1.
- Full Text:
- Date Issued: 1971
Ecological studies on the non-parasitic larval stages of some tick species in the Eastern Cape Province of South Africa (Acarina : ixodidae)
- Londt, Jason G. H. (Jason Gilbert Hayden), 1943-
- Authors: Londt, Jason G. H. (Jason Gilbert Hayden), 1943-
- Date: 1971
- Subjects: Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5862 , http://hdl.handle.net/10962/d1012777 , Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Description: "Ticks have already been studied in our country and abroad. Progress in the field of taxonomy has probably been the most rapid and has culminated in a large number of papers and excellent monographs, but much more remains to be done. To produce an overall picture of the factors influencing the behaviour of the tick under natural conditions, studies have to be conducted on tick ecology and experimental physiology. We still have a lack of knowledge of host specificity, the selection of feeding sites on hosts and the nature of resistance to attacks by ticks. Because of the varied habits of different species of ticks, the first essential prerequisite is an adequate knowledge of their biology." (Jansen 1969). The above words sum up the position of research on ticks in southern Africa at the present time.
- Full Text:
- Date Issued: 1971
- Authors: Londt, Jason G. H. (Jason Gilbert Hayden), 1943-
- Date: 1971
- Subjects: Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5862 , http://hdl.handle.net/10962/d1012777 , Ticks -- Ecology -- South Africa -- Eastern Cape , Ixodidae -- Ecology -- South Africa -- Eastern Cape
- Description: "Ticks have already been studied in our country and abroad. Progress in the field of taxonomy has probably been the most rapid and has culminated in a large number of papers and excellent monographs, but much more remains to be done. To produce an overall picture of the factors influencing the behaviour of the tick under natural conditions, studies have to be conducted on tick ecology and experimental physiology. We still have a lack of knowledge of host specificity, the selection of feeding sites on hosts and the nature of resistance to attacks by ticks. Because of the varied habits of different species of ticks, the first essential prerequisite is an adequate knowledge of their biology." (Jansen 1969). The above words sum up the position of research on ticks in southern Africa at the present time.
- Full Text:
- Date Issued: 1971
Effects of vigilance decrement on the recognition of embedded figures
- Authors: Daniel, Robert David
- Date: 1971
- Subjects: Perception -- Testing , Cognitive psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3202 , http://hdl.handle.net/10962/d1010961
- Description: Field independence was described by Witkin et al (1962) as the ability to separate an item perceived from its context. Here most experiments have used visually presented material where the subject was shown a simple geometrical figure and then a complex one containing the simple figure as part of it: the subject's task was to find and point out where the simple figure was hidden. Recent work has suggested that the skills involved in Witkin's tests might be associated with particular cultural backgrounds. This extension of Witkin's theory of field independence by Wober linked visual phenomena with those of a social and maturational nature: the ability to separate visual items from their context was shown to be aligned with the development of a sense of personal identity ; the person was considered to be an item set in a context or social field, be it family or society around him: an individual, depending on the way he was socialized as a child, may perceive the world analytically, if he did he was labelled field independent, if not he was field dependent. Intro. p.1.
- Full Text:
- Date Issued: 1971
- Authors: Daniel, Robert David
- Date: 1971
- Subjects: Perception -- Testing , Cognitive psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3202 , http://hdl.handle.net/10962/d1010961
- Description: Field independence was described by Witkin et al (1962) as the ability to separate an item perceived from its context. Here most experiments have used visually presented material where the subject was shown a simple geometrical figure and then a complex one containing the simple figure as part of it: the subject's task was to find and point out where the simple figure was hidden. Recent work has suggested that the skills involved in Witkin's tests might be associated with particular cultural backgrounds. This extension of Witkin's theory of field independence by Wober linked visual phenomena with those of a social and maturational nature: the ability to separate visual items from their context was shown to be aligned with the development of a sense of personal identity ; the person was considered to be an item set in a context or social field, be it family or society around him: an individual, depending on the way he was socialized as a child, may perceive the world analytically, if he did he was labelled field independent, if not he was field dependent. Intro. p.1.
- Full Text:
- Date Issued: 1971
Extractives of Leonotis and Euryops species
- Authors: Eagle, G A
- Date: 1971
- Subjects: Stereochemistry Leonotis -- Analysis Euryops -- Analysis Botanical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4465 , http://hdl.handle.net/10962/d1011610
- Description: The isolation and structure determination of dubiin and leonitin, two new diterpenoid acetates from Leonotis dubia and Leonotis leonitis respectively, are discussed. The compounds are diterpenoids of the labdane type and are closely related to marrubiin. The proposed structures are based on chemical and spectral evidence. Dubiin, C₂₂H₃₀0₆̕ contains a tertiary hydroxy- group, a furan ring and a ó-lactone while leonitin, C₂₂H₃₀0₇̕ is a γ - dilactone. at C-20. Both compounds are unusual in being oxygenated The extraction of three Euryops species and the isolation of euryopsol, C₂₂H₃₀0₄̕̕ are also described. A furanoeremophilane structure containing three hydroxy- groups, one of which is at a bridgehead position, is proposed. Euryopsol is the first furanoeremophilanoid with a substituent attached at C-IO
- Full Text:
- Date Issued: 1971
- Authors: Eagle, G A
- Date: 1971
- Subjects: Stereochemistry Leonotis -- Analysis Euryops -- Analysis Botanical chemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4465 , http://hdl.handle.net/10962/d1011610
- Description: The isolation and structure determination of dubiin and leonitin, two new diterpenoid acetates from Leonotis dubia and Leonotis leonitis respectively, are discussed. The compounds are diterpenoids of the labdane type and are closely related to marrubiin. The proposed structures are based on chemical and spectral evidence. Dubiin, C₂₂H₃₀0₆̕ contains a tertiary hydroxy- group, a furan ring and a ó-lactone while leonitin, C₂₂H₃₀0₇̕ is a γ - dilactone. at C-20. Both compounds are unusual in being oxygenated The extraction of three Euryops species and the isolation of euryopsol, C₂₂H₃₀0₄̕̕ are also described. A furanoeremophilane structure containing three hydroxy- groups, one of which is at a bridgehead position, is proposed. Euryopsol is the first furanoeremophilanoid with a substituent attached at C-IO
- Full Text:
- Date Issued: 1971
In community in Christ: a study of theological setting of the sacraments in the New Testament
- Authors: Moore, Basil S
- Date: 1971
- Subjects: Sacraments Sacraments (Liturgy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1240 , http://hdl.handle.net/10962/d1007688
- Description: Introduction: Neville Clark has rightly warned against the attempt to approach the theology of the sacraments from a broad and general definition of a 'sacrament' from which we 'read off' a Christian doctrine of the sacraments without paying due regard to the biblical statements. Such an approach could not but obscure the essential differences between the sacraments, and the fact that they stem from historical roots. On the other hand, the specialist treatment of the sacraments which begins by making a detailed analysis of the biblical material fails to do justice to the wholeness of biblical theology and tends to treat the sacraments in isolation not only from each other but also from other aspects of Christian theology with which they are inalienably connected. Bearing in mind the difficulties inherent in both of these approaches, a fresh and more systematic approach is required.
- Full Text:
- Date Issued: 1971
- Authors: Moore, Basil S
- Date: 1971
- Subjects: Sacraments Sacraments (Liturgy)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1240 , http://hdl.handle.net/10962/d1007688
- Description: Introduction: Neville Clark has rightly warned against the attempt to approach the theology of the sacraments from a broad and general definition of a 'sacrament' from which we 'read off' a Christian doctrine of the sacraments without paying due regard to the biblical statements. Such an approach could not but obscure the essential differences between the sacraments, and the fact that they stem from historical roots. On the other hand, the specialist treatment of the sacraments which begins by making a detailed analysis of the biblical material fails to do justice to the wholeness of biblical theology and tends to treat the sacraments in isolation not only from each other but also from other aspects of Christian theology with which they are inalienably connected. Bearing in mind the difficulties inherent in both of these approaches, a fresh and more systematic approach is required.
- Full Text:
- Date Issued: 1971
Ironie en ek : aspekte van die ironie as struktuurfaktor in die romanwerke van Marnix Gijsen
- Authors: Steyn, Karin
- Date: 1971
- Subjects: Irony in literature , Gijsen, Marnix, 1899-1984 -- Criticism and interpretation , Dutch fiction -- 20th Century
- Language: Afrikaans
- Type: Thesis , Masters , MA
- Identifier: vital:3635 , http://hdl.handle.net/10962/d1013287
- Description: From Nawoord, p. 182. Ironie word in Gijsen se oeuvre nie alleenlik op 'n besondere wyse gebruik as 'n vorm van spel met woorde ter versiering of tot vermaak van die leser nie, maar irornie vorm ook 'n allerbelangrikste aspek van die struktuur van sy verhale. Gijsen "gebruik" nie in die eerste plaas ironie om die een of ander doel te bereik nie. Sy werke is ironies, en 'n begrip van die ironiese struktuur is in elke verhaal essensieel vir "n begrip van die verhaal self.
- Full Text:
- Date Issued: 1971
- Authors: Steyn, Karin
- Date: 1971
- Subjects: Irony in literature , Gijsen, Marnix, 1899-1984 -- Criticism and interpretation , Dutch fiction -- 20th Century
- Language: Afrikaans
- Type: Thesis , Masters , MA
- Identifier: vital:3635 , http://hdl.handle.net/10962/d1013287
- Description: From Nawoord, p. 182. Ironie word in Gijsen se oeuvre nie alleenlik op 'n besondere wyse gebruik as 'n vorm van spel met woorde ter versiering of tot vermaak van die leser nie, maar irornie vorm ook 'n allerbelangrikste aspek van die struktuur van sy verhale. Gijsen "gebruik" nie in die eerste plaas ironie om die een of ander doel te bereik nie. Sy werke is ironies, en 'n begrip van die ironiese struktuur is in elke verhaal essensieel vir "n begrip van die verhaal self.
- Full Text:
- Date Issued: 1971
Proton conduction in organic solids
- Authors: Chan-Henry, Robert Yatshein
- Date: 1971
- Subjects: Electrolytes -- Conductivity , Protons , Organic conductors , Organic solid state chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4446 , http://hdl.handle.net/10962/d1007729 , Electrolytes -- Conductivity , Protons , Organic conductors , Organic solid state chemistry
- Description: Dielectric, d. c. conductivity and electrolysis measurements have been made principally on solid imidazole and urea. Electrode effects, especially the development of a suitable protode, and techniques for detecting mobile protons in solids were pursued. The dielectric data have been correlated with the d. c. results. A mechanism for extrinsic proton conduction in urea has been proposed.
- Full Text:
- Date Issued: 1971
- Authors: Chan-Henry, Robert Yatshein
- Date: 1971
- Subjects: Electrolytes -- Conductivity , Protons , Organic conductors , Organic solid state chemistry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4446 , http://hdl.handle.net/10962/d1007729 , Electrolytes -- Conductivity , Protons , Organic conductors , Organic solid state chemistry
- Description: Dielectric, d. c. conductivity and electrolysis measurements have been made principally on solid imidazole and urea. Electrode effects, especially the development of a suitable protode, and techniques for detecting mobile protons in solids were pursued. The dielectric data have been correlated with the d. c. results. A mechanism for extrinsic proton conduction in urea has been proposed.
- Full Text:
- Date Issued: 1971
Some aspects of the effect of temperature on the respiratory and cardiac activities of the Cichlid Teleost Tilapia mossambica
- Authors: Josman, V
- Date: 1971
- Subjects: Fishes -- Effect of temperature on , Cichlids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5859 , http://hdl.handle.net/10962/d1012613
- Description: The importance of the cichlid teleost Tilapia mossambica as a protein source, coupled with its remarkable adaptability, has resulted in its introduction into many water systems throughout the tropical, sub-tropical and even temperate regions of the world. However, its successful exploitation of these waters is dependent very largely upon the value of minimum temperatures and their duration. For e.g. Long et al (1961) has drawn attention to the tremendous mortalities of T. mossambica that occur in shallow water bodies during the precipitous temperature decreases that accompany the winter monsoons in Vietnam and other eastern countries, even at temperatures as high as 14 or 16º C. Coehe (1967) does not recommend stocking with T. mossambica where temperatures are not above 14º C all the time. Ailanson et al (1962) conclude, after an experimental study, that low temperatures (13º C or lower) in South African highveld dams in winter are certainly an important factor in the extensive mortalities of T. mossambica that have been reported from these dams. Jubb (1961) also reports that this species is often killed during a severe winter in Rhodesia. Intro., p.1.
- Full Text:
- Date Issued: 1971
- Authors: Josman, V
- Date: 1971
- Subjects: Fishes -- Effect of temperature on , Cichlids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5859 , http://hdl.handle.net/10962/d1012613
- Description: The importance of the cichlid teleost Tilapia mossambica as a protein source, coupled with its remarkable adaptability, has resulted in its introduction into many water systems throughout the tropical, sub-tropical and even temperate regions of the world. However, its successful exploitation of these waters is dependent very largely upon the value of minimum temperatures and their duration. For e.g. Long et al (1961) has drawn attention to the tremendous mortalities of T. mossambica that occur in shallow water bodies during the precipitous temperature decreases that accompany the winter monsoons in Vietnam and other eastern countries, even at temperatures as high as 14 or 16º C. Coehe (1967) does not recommend stocking with T. mossambica where temperatures are not above 14º C all the time. Ailanson et al (1962) conclude, after an experimental study, that low temperatures (13º C or lower) in South African highveld dams in winter are certainly an important factor in the extensive mortalities of T. mossambica that have been reported from these dams. Jubb (1961) also reports that this species is often killed during a severe winter in Rhodesia. Intro., p.1.
- Full Text:
- Date Issued: 1971
Some aspects of the mission policy and practice of the Church of the Province of South Africa in Ovamboland, 1924-1960
- Authors: Mallory, Charles Shannon
- Date: 1971
- Subjects: Church of the Province of Southern Africa -- Namibia -- Owambo
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:1232 , http://hdl.handle.net/10962/d1007312 , Church of the Province of Southern Africa -- Namibia -- Owambo
- Description: This thesis is a study that was originally inspired by the question, "What does it mean to be a Christian in rural Africa today?" While the Church needs to ask this question everywhere in the world, from experience the writer believes it is especially germane to the non-Western cultures of Africa and Asia. That experience is drawn from eight years' work among the Kwanyama tribe of Ovambos in the Ovamboland Anglican Mission. Hence, this study is confined to one rural African tribe as it came under 46 years' influence of one Christian denomination.
- Full Text:
- Date Issued: 1971
- Authors: Mallory, Charles Shannon
- Date: 1971
- Subjects: Church of the Province of Southern Africa -- Namibia -- Owambo
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:1232 , http://hdl.handle.net/10962/d1007312 , Church of the Province of Southern Africa -- Namibia -- Owambo
- Description: This thesis is a study that was originally inspired by the question, "What does it mean to be a Christian in rural Africa today?" While the Church needs to ask this question everywhere in the world, from experience the writer believes it is especially germane to the non-Western cultures of Africa and Asia. That experience is drawn from eight years' work among the Kwanyama tribe of Ovambos in the Ovamboland Anglican Mission. Hence, this study is confined to one rural African tribe as it came under 46 years' influence of one Christian denomination.
- Full Text:
- Date Issued: 1971
The Birds' River dolerite complex
- Authors: Booth, P W K
- Date: 1971
- Subjects: Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5043 , http://hdl.handle.net/10962/d1007664 , Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Description: A plug-like intrusion of Karroo dolerite, near Dordrecht in the Eastern Cape of the Republic, is described. Field mapping with the, aid of aerial photographs has revealed that the contact of the intrusion, for the most part, dips very steeply outwards. In the south- eastern and eastern areas, however, sheet- or sill-like forms appear to be given off from the main intrusion. In plan view the intrusion is roughly oval shaped, its longer axis being aligned in a north-westerly direction. Its surface area measures approximately 60 square kilometres (24 square miles). A large number of xenoliths composed exclusively of Stormberg sediments, pyroclastic rocks and minor lavas, are to be found cropping out within the dolerite intrusion. These xenoliths, many of which occur in positions far above or below their normal stratigraphic elevation, are extremely variable in size - the largest having an area of approximately 15 square kilometres (6 square miles). The xenoliths represent fragments of the original "roof" of sediments and pyroclastics which have collapsed into and been engulfed by the dolerite magma. This type of dolerite intrusion is known as a "belljar" intrusion. A superficial classification of the dolerites, based chiefly on textural and certain mineralogical features, is presented. In the area surrounding the main intrusion are a number of dolerite dikes and sheets. The youngest phase of igneous activity is represented by the Dragon's Back dike, which cuts across the complex in a north-westerly direction. Several veining phenomena, as well as an interesting variety of metamorphic and metasomatic rocks, are associated with the main dolerite intrusion. Six diatremes are situated in the vicinity of the intrusion. Pyroclastic rocks are represented by a variety of types, and are to be found outside the area of the intrusion, and as xenoliths within it. A tentative interpretation of the mechanism of formation of the intrusion, which appears to be related to volcanic activity and cauldron subsidence, is presented.
- Full Text:
- Date Issued: 1971
- Authors: Booth, P W K
- Date: 1971
- Subjects: Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5043 , http://hdl.handle.net/10962/d1007664 , Diabase , Diabase -- South Africa -- Cape of Good Hope -- Dordrecht. , Igneous rocks -- South Africa
- Description: A plug-like intrusion of Karroo dolerite, near Dordrecht in the Eastern Cape of the Republic, is described. Field mapping with the, aid of aerial photographs has revealed that the contact of the intrusion, for the most part, dips very steeply outwards. In the south- eastern and eastern areas, however, sheet- or sill-like forms appear to be given off from the main intrusion. In plan view the intrusion is roughly oval shaped, its longer axis being aligned in a north-westerly direction. Its surface area measures approximately 60 square kilometres (24 square miles). A large number of xenoliths composed exclusively of Stormberg sediments, pyroclastic rocks and minor lavas, are to be found cropping out within the dolerite intrusion. These xenoliths, many of which occur in positions far above or below their normal stratigraphic elevation, are extremely variable in size - the largest having an area of approximately 15 square kilometres (6 square miles). The xenoliths represent fragments of the original "roof" of sediments and pyroclastics which have collapsed into and been engulfed by the dolerite magma. This type of dolerite intrusion is known as a "belljar" intrusion. A superficial classification of the dolerites, based chiefly on textural and certain mineralogical features, is presented. In the area surrounding the main intrusion are a number of dolerite dikes and sheets. The youngest phase of igneous activity is represented by the Dragon's Back dike, which cuts across the complex in a north-westerly direction. Several veining phenomena, as well as an interesting variety of metamorphic and metasomatic rocks, are associated with the main dolerite intrusion. Six diatremes are situated in the vicinity of the intrusion. Pyroclastic rocks are represented by a variety of types, and are to be found outside the area of the intrusion, and as xenoliths within it. A tentative interpretation of the mechanism of formation of the intrusion, which appears to be related to volcanic activity and cauldron subsidence, is presented.
- Full Text:
- Date Issued: 1971
The contribution of F. D. Maurice to the nineteenth century discussion of the atonement in Britain
- Authors: Richardson, Robert Neville
- Date: 1971
- Subjects: Maurice, Frederick Denison, 1805-1872 Atonement -- History of doctrines -- 19th century Atonement -- Great Britain -- 19th century
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1235 , http://hdl.handle.net/10962/d1007485
- Description: From Introduction: Frederick Denison Maurice is generally remembered in connection with the rise of Christian Socialism. That his activities in this Movement were the most important aspect of his career is doubtful. ... Maurice's fundamental theological principles were: first, the idea of unity - unity in the Godhead, "Unity in Trinity", and unity among men in the human family; secondly, the Fatherhood of God - a Fatherhood which had at its heart the principle of sacrificial love. The events of Maurice's life proved to be fertile ground for the growth of these convictions. It was these convictions which shaped his whole understanding of the Atonement. Davies (3) points out that, in his teaching on the Atonement, Maurice turned away from the Western and Augustinian insistence that the basis of man's relationship to God was the Fall, and held, with the theolo Gians of the Eastern Church, that Christ's redemption of man is best understood as a restoration of man's relationship to God in Creation.
- Full Text:
- Date Issued: 1971
- Authors: Richardson, Robert Neville
- Date: 1971
- Subjects: Maurice, Frederick Denison, 1805-1872 Atonement -- History of doctrines -- 19th century Atonement -- Great Britain -- 19th century
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1235 , http://hdl.handle.net/10962/d1007485
- Description: From Introduction: Frederick Denison Maurice is generally remembered in connection with the rise of Christian Socialism. That his activities in this Movement were the most important aspect of his career is doubtful. ... Maurice's fundamental theological principles were: first, the idea of unity - unity in the Godhead, "Unity in Trinity", and unity among men in the human family; secondly, the Fatherhood of God - a Fatherhood which had at its heart the principle of sacrificial love. The events of Maurice's life proved to be fertile ground for the growth of these convictions. It was these convictions which shaped his whole understanding of the Atonement. Davies (3) points out that, in his teaching on the Atonement, Maurice turned away from the Western and Augustinian insistence that the basis of man's relationship to God was the Fall, and held, with the theolo Gians of the Eastern Church, that Christ's redemption of man is best understood as a restoration of man's relationship to God in Creation.
- Full Text:
- Date Issued: 1971
The contribution of F.D. Maurice to the Christian Socialist Movement of 1848-1954
- Authors: Steel, Ronald Luke
- Date: 1971
- Subjects: Maurice, Frederick Denison, 1805-1872 , Christian Socialist Movement
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1275 , http://hdl.handle.net/10962/d1013270
- Description: Maurice was a man who solicited both keen support and bitter opposition, both during his life time and after. It is only within the last twenty or thirty years that his true worth has begun to be recognised and appreciated. The aim of the thesis is to show that his contribution to the Christian Socialist Movement was an invaluable one. Chapter two describes the working-class conditions and their causes during the first half of the nineteenth century, as well as the role the Church played in social improvement. Chapter three deals with Chartism and the European Revolutions of 1848, and the effect of the Revolutions on Chartism. Chapter four gives an account of the man F.D. Maurice, as well as some of his thoughts and aims. Chapter five is a detailed account of Maurice's contribution to Christian Socialism, showing that he was not the 'practical' leader, and emphasising the importance of his theological beliefs in governing what to do. Intro. p. 1.
- Full Text:
- Date Issued: 1971
- Authors: Steel, Ronald Luke
- Date: 1971
- Subjects: Maurice, Frederick Denison, 1805-1872 , Christian Socialist Movement
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1275 , http://hdl.handle.net/10962/d1013270
- Description: Maurice was a man who solicited both keen support and bitter opposition, both during his life time and after. It is only within the last twenty or thirty years that his true worth has begun to be recognised and appreciated. The aim of the thesis is to show that his contribution to the Christian Socialist Movement was an invaluable one. Chapter two describes the working-class conditions and their causes during the first half of the nineteenth century, as well as the role the Church played in social improvement. Chapter three deals with Chartism and the European Revolutions of 1848, and the effect of the Revolutions on Chartism. Chapter four gives an account of the man F.D. Maurice, as well as some of his thoughts and aims. Chapter five is a detailed account of Maurice's contribution to Christian Socialism, showing that he was not the 'practical' leader, and emphasising the importance of his theological beliefs in governing what to do. Intro. p. 1.
- Full Text:
- Date Issued: 1971
The effects of organic perturbants on the structure of soluble collagen
- Authors: Hart, Geoffrey Joseph
- Date: 1971
- Subjects: Chemistry, Organic , Collagen
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3846 , http://hdl.handle.net/10962/d1012157 , Chemistry, Organic , Collagen
- Description: Organic solvents were used in the present study as a means of investigating the non-covalent interactions involved in the maintenance and pertubation of the three-dimensional structure of the collagen macromolecule in solution. The two main types of non-covalent interaction under consideration are hydrogen bond formation and hydrophobic effects. Elucidation of the relative importance of these factors in the maintenance of the solution structure of proteins is an area of intensive investigation and fundamental significance to biochemistry as a whole. During the past decade, considerable progress has been made towards a clearer understanding of the forces involved, and a number of different theoretical and experimental approaches have emerged. Until about 1960, hydrogen bonding was widely believed to be the dominant non-covalent interaction responsible for the maintenance of secondary and tertiary structure in many proteins. Subsequently, an increasingly important role for apolar (hydrophobic) effects was suggested by a number of authors, and at present there is no satisfactorily definitive interpretation of the available experimental evidence. The current work is based on a comparison of the effects of organic solvents on widely different substrates, namely collagen, cellulose, and the chromatographic reference material, catechin. The chromatographic mobility of catechin on cellulose may be regarded as a phenomenon which is mediated entirely by polar interaction mechanisms. The effects of various organic perturbants and of changing solvent/water ratios are readily interpreted on this basis. In the collagenous systems, however, certain results appear to require the introduction of concepts other than those relating exclusively to polar bonding affinities. The experimental evidence shows that there are cases where the enhancement of the polar interaction potential of solvent/water mixtures, in relation to catechin-cellulose systems, is accompanied by an apparent reduction of polar interaction potential of the same solvent/water mixtures with respect to soluble collagen. The anomaly outlined above will be discussed in terms of two fundamentally different theoretical assumptions. In the first of these, the mechanism of perturbant action in collagenous systems is regarded as essentially similar to that governing catechin-cellulose affinity patterns. Thus, interaction processes are all treated as polar phenomena, in which direct hydrophobic destabilization of the collagen triple helix plays no part. In an attempt to explain the effects of perturbants in both collagen and cellulose-containing systems in terms of the above assumption, two hypotheses are examined involving (1) direct polar interaction between perturbant molecules and functional groups of the protein; (2.) the possibility of an enhanced polar interaction potential of water molecules, due to lowering of the environmental dielectric constant when organic solvents are added to the systems. Within the other broad conceptual division, collagen and cellulose substrates are considered to respond in fundamentally different ways to the action of organic perturbants. As before, cellulose-catechin-solvent interactions are treated as entirely polar phenomena, and perturbant effects interpreted in terms of mechanisms such as direct solvation of the substrate, and the enhanced hydrogen bonding activity of water molecules. In contrast, perturbant lyotropic action with respect to soluble collagen i s viewed as the manifestation of a major contribution by hydrophobic interaction processes to macromolecular stability. Thus, solvents that competitively reduce the assumed entropic contribution to the stability of the collagen triple helix, are seen as potential destabilizers of the native state of the protein and inhibitors of the regeneration of co-operative structures during renaturation. Both of the above approaches are critically assessed in the light of the present work and the dominant trends apparent in the recent literature.
- Full Text:
- Date Issued: 1971
- Authors: Hart, Geoffrey Joseph
- Date: 1971
- Subjects: Chemistry, Organic , Collagen
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3846 , http://hdl.handle.net/10962/d1012157 , Chemistry, Organic , Collagen
- Description: Organic solvents were used in the present study as a means of investigating the non-covalent interactions involved in the maintenance and pertubation of the three-dimensional structure of the collagen macromolecule in solution. The two main types of non-covalent interaction under consideration are hydrogen bond formation and hydrophobic effects. Elucidation of the relative importance of these factors in the maintenance of the solution structure of proteins is an area of intensive investigation and fundamental significance to biochemistry as a whole. During the past decade, considerable progress has been made towards a clearer understanding of the forces involved, and a number of different theoretical and experimental approaches have emerged. Until about 1960, hydrogen bonding was widely believed to be the dominant non-covalent interaction responsible for the maintenance of secondary and tertiary structure in many proteins. Subsequently, an increasingly important role for apolar (hydrophobic) effects was suggested by a number of authors, and at present there is no satisfactorily definitive interpretation of the available experimental evidence. The current work is based on a comparison of the effects of organic solvents on widely different substrates, namely collagen, cellulose, and the chromatographic reference material, catechin. The chromatographic mobility of catechin on cellulose may be regarded as a phenomenon which is mediated entirely by polar interaction mechanisms. The effects of various organic perturbants and of changing solvent/water ratios are readily interpreted on this basis. In the collagenous systems, however, certain results appear to require the introduction of concepts other than those relating exclusively to polar bonding affinities. The experimental evidence shows that there are cases where the enhancement of the polar interaction potential of solvent/water mixtures, in relation to catechin-cellulose systems, is accompanied by an apparent reduction of polar interaction potential of the same solvent/water mixtures with respect to soluble collagen. The anomaly outlined above will be discussed in terms of two fundamentally different theoretical assumptions. In the first of these, the mechanism of perturbant action in collagenous systems is regarded as essentially similar to that governing catechin-cellulose affinity patterns. Thus, interaction processes are all treated as polar phenomena, in which direct hydrophobic destabilization of the collagen triple helix plays no part. In an attempt to explain the effects of perturbants in both collagen and cellulose-containing systems in terms of the above assumption, two hypotheses are examined involving (1) direct polar interaction between perturbant molecules and functional groups of the protein; (2.) the possibility of an enhanced polar interaction potential of water molecules, due to lowering of the environmental dielectric constant when organic solvents are added to the systems. Within the other broad conceptual division, collagen and cellulose substrates are considered to respond in fundamentally different ways to the action of organic perturbants. As before, cellulose-catechin-solvent interactions are treated as entirely polar phenomena, and perturbant effects interpreted in terms of mechanisms such as direct solvation of the substrate, and the enhanced hydrogen bonding activity of water molecules. In contrast, perturbant lyotropic action with respect to soluble collagen i s viewed as the manifestation of a major contribution by hydrophobic interaction processes to macromolecular stability. Thus, solvents that competitively reduce the assumed entropic contribution to the stability of the collagen triple helix, are seen as potential destabilizers of the native state of the protein and inhibitors of the regeneration of co-operative structures during renaturation. Both of the above approaches are critically assessed in the light of the present work and the dominant trends apparent in the recent literature.
- Full Text:
- Date Issued: 1971