A dielectric and spectroscopic study of molecular association in solutions of alcohols
- Authors: Campbell, Colin
- Date: 1975
- Subjects: Alcohols , Dielectrics , Spectrum analysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4454 , http://hdl.handle.net/10962/d1010424
- Description: This study is concerned with the association characteristics of solutions of alcohols in some non-polar solvents. The permittivities at 2 MHz and 25°C for solutions of the straight chain octanols in cyclohexane, carbon tetrachloride and benzene have been examined over the entire solute concentration range, with particular attention -1 being paid to the range below 0.1 molℓ⁻¹ By applying the Kirkwood- Fröhlich equation to these data, the apparent dipole moments of the alcohols as a function of concentration have been evaluated. These concentration dependencies have been correlated with infrared absorption results on the same systems to provide information on the sizes and configurations of the proposed hydrogen bonded multimers. It is concluded that, at very low solute concentrations, the alcohol molecules exist as monomers; but with increasing concentration, two types of hydrogen bonded multimers are formed, the first (at low concentrations) being of high dipole moment and the second (at higher concentrations) being of low dipole moment. At high concentrations, the molecules associate to form a three-dimensional network. Attempts have been made to determine equilibrium parameters for molecular models which are consistent with the qualitative understanding of the association behaviour. These parameters were obtained by applying least-squares, curve-fitting techniques to the low concentration permittivity data. A similar investigation has been conducted on solutions of 2,3,4-trimethyl-3-pentanol in the same solvents. The steric hindrance around the hydroxyl group of this alcohol modifies the association behaviour so that a three-dimensional network does not form at high solute concentrations. Proton magnetic resonance chemical shifts for the hydroxyl proton of this alcohol in carbon tetrachloride solutions have been measured. Attempts have also been made to determine equilibrium parameters which describe formation of the hydrogen bonded multimers. To extend this study to include solutes other than octanols, similar experiments have been conducted on solutions of t-butanol in hexadecane, a system which has recently been investigated by other workers using different experimental techniques. The association behaviour of this system is qualitatively similar to that of the straight-chain octanols. The combination of permittivity and infrared measurements, although proving extremely powerful in interpreting the association characteristics of dilute alcohol solutions, is less adequate at high solute concentrations. Attention was therefore directed towards dielectric relaxation and viscosity studies to investigate concentrated solutions. The relaxation times at 20°C of the low frequency dispersion have been measured for solutions of 1-propanol, 1-butanol, 1-hexanol, 1-octanol and 1-decanol in cyclohexane using time domain reflectometry techniques. Similar measurements have also been made on solutions of 1-butanol and 1-octanol in carbon tetrachloride and in benzene. The concentration dependence of the viscosities of certain of these systems has also been examined in an independent study. The ratio of the dielectric relaxation time to the viscosity, the "reduced relaxation time", is qualitatively similar for each system studied. This similarity leads to an explanation of the molecular process responsible for the low frequency dispersion in terms of the proximity of the hydroxyl groups in concentrated alcohol solutions and the fraction of the groups which are not involved in hydrogen bonding.
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- Date Issued: 1975
Interactions between steroidal anti-inflammatory agents and collagen
- Authors: Kanfer, Isadore
- Date: 1975
- Subjects: Anti-inflammatory agents Collagen
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3849 , http://hdl.handle.net/10962/d1012620
- Description: Much research has been done on the formation of fibrils from solutions of soluble collagen in vitro in order to gain some knowledge of the mechanisms which may occur in vivo. The in vitro formation of fibres from solutions of collagen has been shown to be extremely sensitive to the nature of the solution environment and the presence of added chemical compounds, and thus constitutes an interesting system for the study of collagen-small molecule inter actions. The present study is concerned with the effects of various corticosteroid drugs, used medicinally as anti-inflammatory agents, on collagen in solution. As these corticosteroids are administered to reduce inflammation in conditions such as rheumatoid arthritis and a host of other pathological conditions in which collagen is implicated, this work has been undertaken in order to establish and charac teri ze any binding mechanisms which may be involved. Furthermore, the corticosteroid drugs available commercially in pure form as the free base or as the water-soluble ester salts offer an interesting range of structural and stereochemical variants for the study of their reaction with a complex and biologically important protein molecule such as collagen. A great deal of research on drug- protein interactions (Goldstein, 1949; Meyer and Guttman, 1968a) and more specifically, steroid-protein interactions have been reported over the years (Daughaday, 1959; Sandberg et al., 1966; Villee and Engel, 1961; Westphal , 1971). Comprehensive reports, however, on steroid-collagen interactions in vitro are conspicuously absent from modern scientific literature although relatively superficial accounts have been published (Menczel and Maibach, 1972; Eik-Nes et al., 1954). Although work involving the above has appeared relating specifically to the effects of steroids on collagen biosynthesis both in vivo and in vitro there have been minimal accounts of steroid-collagen interactions tailored to characterize the binding at the molecular level. The effect of corticosteroids on the metabolism of connective tissue has also received special attention (Asboe-Hansen, 1959; Kivirikko, 1953; Nakagawa and Tsurufuji, 1972). Recently, Uitto et al. (1972) reported the effects of several anti-inflammatory corticosteroids on collagen biosynthesis in vitro, whilst Aalto and Kulonen (1972) reported the effects of several antirheumatic drugs on the synthesis of collagen and other proteins in vitro. The interactions between collagen and certain drugs has also been briefly reviewed (Chvapil, 1967). Much data also exists on the binding of a wide range of small molecules and ions with serum albumin (Steinhardt and Reynolds, 1969; Scatchard, 1949; Klotz, 1950). Serum albumin, being specialized for a very general transport function and apparently designed for the purpose of combining with a large range of small molecules, has a proportion of possible reactive sites 'buried' within the molecule itself because of its folded conformation. In addition, serum albumin shows a high degree of cooperative binding in contrast to collagen. The latter molecule, with its larger molecular size and weight is specialized for a biologically structural function and has a higher proportion of possible reactive sites which appear relatively more accessible to ligands. A study of the interactions between corticosteroids and collagen thus provides the opportunity to investigate a protein which is very different from the much studied serum albumin. Because of the limited information available regarding the interaction of steroid drugs and collagen at the molecular level, studies of this nature are relevant to the understanding of the mode of action of steroid compounds which are such an important group of therapeutic substances used in modern medicine.
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- Date Issued: 1975
Accident liability and primary process thinking : a study in ego psychology
- Authors: Nell, Oelrich
- Date: 1975
- Subjects: Automobile drivers -- Psychology , Ego (Psychology) , Traffic safety -- South Africa -- Psychological aspects , Liability for traffic accidents -- South Africa , Traffic accidents -- South Africa -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3220 , http://hdl.handle.net/10962/d1012950
- Description: Serious efforts must be made to combat the high accident rate on the roads in the Republic of South Africa. The same spirit which exists in the field of medicine when there are evidences that an epidemic is beginning to take its toll, must come into being amongst those who are concerned with traffic and its problems. The public itself needs to become more aware of road safety. Many associations and institutions have been created to assist with the inculcation of the road safety ideal. The National Road Safety Council, which creates opportunities for investigation into aspects of road safety must continue to expand its sphere of influence. The research project contained on the following pages represents an attempt to contribute to the human factor in traffic safety, particularly by making a closer study of the driver of the motor vehicle. The writer is concerned with the carnage that is caused by road accidents. His previous study of personality and particularly of the projective techniques of assessment has prompted a consideration of the problem.
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- Date Issued: 1975
Studies on the biology and ecology of Amblyomma Herbraem Koch, 1844 and other tick species (Ixodidae) of the Eastern Cape
- Authors: Norval, R A I
- Date: 1975
- Subjects: Ticks -- South Africa -- Eastern Cape , Ixodidae -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5871 , http://hdl.handle.net/10962/d1012968
- Description: Tick borne diseases of livestock are among the most important factors which have retarded economic development in many parts of Africa. Modification of the environment due to the expansion of agriculture into previously undeveloped areas, together with the introduction of livestock, has disturbed the natural balance which existed between ticks and indigenous hosts. Many tick species have adapted to domestic stock, and in some instances have spread over large areas which were previously uninfested. A number of tick species which are parasitic on domestic stock, eg. Amblyomma hebraeum Koch, 1844, Boophilus decoloratus (Koch, 1844), Rhipicephalus evertsi Neumann, 1897 and Rhipicephalus appendiculatus Netunann, 1901, are vectors of pathogenic micro-organisms. Unlike indigenous hosts however, domestic stock have no innate immunity to tickborne diseases. Intro., p. 1.
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- Date Issued: 1975
A contribution to the understanding of the ethology of the cichlids of Southern Africa
- Authors: Ribbink, Anthony J
- Date: 1975
- Subjects: Cichlids -- Africa, Southern , Fishes -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5889 , http://hdl.handle.net/10962/d1013369
- Description: Allopatric populations of Pseudocrenilabrus philander were found to differ in male breeding coloration. These colours are described and attention is drawn to the possibility that male coloration might prevent population hybridisation. Behaviour of the allopatric populations was studied in the laboratory. The execution of behaviour patterns of the various populations was found to be indistinguishable, and very similar to that of Haplochromis. Behaviour of P. philander was recorded in three morphologically different natural water bodies. Diurnal activities were found to follow a set rhythm. Though P. philander was shown to have adapted to a variety of habitats they retained their behavioural Components in an unchanged form. Field and laboratory observations are used to propose a behavioural mechanism for the natural regulation of population density. Although aggression between conspecific territorial Sarot herodon mossambicus habituated so that neighbours could live close to one another, it was found that P.philander are intolerant of their neighbours and are consequently forced apart. Though the execution of behaviour patterns was apparently identical for all populations of P. philander, field observations indicated that the frequency of performance differed. An experimental procedure was established to quantitatively compare the behaviour of various populations. As a result of comparative and choice chamber investigations, it is suggested that one of the four populations of P. philander would be unlikely to hybridise with the others if they were to become sympatric. These popUlations would be kept apart because of colour and behavioural differences. Differences of egg-size, fry-size, developmental and interbrood periods were also found, providing further evidence of incipient speciation. Evolutionary divergence of the allopatric populations of P. philander is discussed against a background of geological and geographical evidence. Consideration is given to the role of male coloration, ethological barriers and the importance of ethological differences to taxonomy. Behavioural evidence suggests that P. philander has closer affinities with the haplochromids than was initially realised. It is concluded that the clinal populations of P. philander should not be taxonomically separated, and it is argued that it would be premature to give the Kuruman population an elevated taxonomic status.
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- Date Issued: 1975
From Frontier to Midlands : a history of the Graaff-Reinet district, 1786-1910
- Authors: Smith, Kenneth Wyndham
- Date: 1975
- Subjects: Graaff-Reinet (South Africa) -- History , South Africa -- Economic conditions -- History , South Africa -- Politics and government -- History , Frontier and pioneer life -- Graaff-Reinet
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2615 , http://hdl.handle.net/10962/d1013242
- Description: The study of local history in South Africa is still in its infancy and has not been accorded the same recognition as elsewhere. There is no convenient manual to guide the would-be local historian of the Cape. There are few models that provide an insight into the main problems encountered by the local historian of a Cape community. In such local histories as exist, attention has been focussed predominantly on the foundation and physical growth of towns, the naming of streets, the establishment of schools and hospitals. Many of these accounts were written for publicity purposes or to commemorate the founding of towns. Although there is no history of the Dutch Reformed Church in Graaff-Reinet, the history of local congregations of the Dutch Reformed Church has generally been well covered in the form of Gedenkboeke and other studies. These frequently have a particular relevance as many towns such as Burgersdorp and Colesberg were founded as a result of the initiative of the church. Preface.
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- Date Issued: 1975
The African press in South Africa
- Authors: St Leger, Frederick York
- Date: 1975
- Subjects: Press -- South Africa -- History Ethnic press -- South Africa -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3328 , http://hdl.handle.net/10962/d1003116
- Description: In a plural society, riven by deep conflict, as is South Africa, where however the Press retains a considerable measure of freedom to contribute to the political process it is the political role which is of the greatest significance rather than, for example, the reflection by the Press of social values or the internal organisation of the Press as a social system. Although it is, of course, hardly possible completely to ignore these other aspects in any institutional study.
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- Date Issued: 1975
Paradoks as poësie: 'n ondersoek na enkele aspekte van die poësie van Breyten Breytenbach
- Authors: Van der Merwe, Anna Maria
- Date: 1975
- Subjects: Breytenbach, Breyten -- Criticism and interpretation
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3636 , http://hdl.handle.net/10962/d1013302
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- Date Issued: 1975
The population dynamics of an indigenous Psyllid Acizzia Russellae (Homoptera: Psyllidae )with special reference to the influence of the host plant Acacia Karroo
- Authors: Webb, John Warren
- Date: 1975
- Subjects: Homoptera , Jumping plant-lice , Insect populations , Insects -- Ecology , Acacia -- Karroo
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5894 , http://hdl.handle.net/10962/d1013415
- Description: The biology and ecology of an indigenous, non-pest insect on an indigenous host plant were investigated. The study includes a taxonomic description of this new species, an account of its general biology, monitoring of the seasonal fluctuations in numbers of the psyllid and its hymenopterous parasitoids, and a study of various aspects of the host plant, including nitrogen levels, water stress, leaf hardness, and the effect of cutting, in relation to spatial and temporal differences in insect population numbers. Natural enemies, inter- and intra-specific competition had very little determining influence on the population numbers of the psyllid. Temperature and humidity had little direct effect, but may have influenced the population dynamics via its effects on the host plant. Seasonal patterns in psyllid numbers followed fluctuations in nitrogen levels; statistically valid correlations were obtained between leaf nitrogen and psyllid numbers on individual trees at various times. These findings were supported by the results of preliminary laboratory experiments employing different fertilizer treatments. No effect of water stress or leaf hardness was clearly discerned. Cutting of trees altered the characteristics of the subsequent regenerative growth so as to allow massive psyllid infestations to develop, thus showing the tremendous importance of the host plant in determining population levels in this insect. Preliminary investigations of the nature and mechanism of this effect were conducted, and its significance is discussed. The relevance of these findings to modern concepts of regulation in insect populations and to principles of pest management is discussed.
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- Date Issued: 1975
Studies on achromobacter iophagus and other collagenolytic hide bacteria
- Authors: Welton, Richard Leslie
- Date: 1975
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21099 , http://hdl.handle.net/10962/6367
- Description: From Introduction: Collagenases are enzymes capable of specifically attacking the native collagen helix under non-denaturing conditions at physiological conditions of pH, temperature and salt concentration. They are active only on collagen or its breakdown products and are without effect on any other fibrous or globular protein. In the laboratory, collagenases are used in investigations of the biosynthesis of collagen and for structural and immunochemical studies of collagens and collagen-like proteins; also they are proving their worth as agents for facilitating tissue transplantation and for cell-dispersion in tissue cultures . Established clinical applications of collagenases include the treatment of burns and dermal lesions; in addition they are being evaluated as agents for the removal of undesirable tissues such as herniated intervertebral discs and the sloughs resulting from cryogenic or cauterizing procedures. Moreover, as human collagenases are implicated in various pathological disorders involving connective tissue degradation, the roles played by these collagenases are being investigated in the hope of finding ways to arrest, control or treat the diseases.
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- Date Issued: 1975