Showing items 1 - 20 of 42

Your selections:

"The isolation and estimation of low molecular weight N-nitrosamines in biological materials"

- Du Plessis, Leo Stephen

  • Authors: Du Plessis, Leo Stephen
  • Date: 1973
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:21176 , http://hdl.handle.net/10962/6750
  • Description: Summary: Low molecular weight N-nitrosamines were detected by ultraviolet, infrared, nuclear magnetic resonance, mass spectral, thin-layer chromatographic and gas liquid chromatographic means. A method for the estimation of dimethylnitrosamine, diethylnitrosamine, ethal-n-propylnitrosamine and di-n-propylnitrosamine has been developed. The method involves the isolation of the nitrosamines in an aqueous distillate by freeze-drying. After extraction of the nitrosamines from the aqueous distillate by means of dichloromethane, their separation and quantitative estimation are achieved by gas liquid chromatography of the extract. The procedure can be extended down to the ppb range. Dimethylnitrosamine was isolated from an extract of Solanum incanum and identified by gas liquid chromatography on four different columns, infrared and nuclear magnetic resonance spectroscopy.
  • Full Text:

'n Evaluering van onderwysvoorsienings en onderwysfasiliteite in die Karoo-distrikte Aberdeen, Graaff-Reinet, Jansenville-Klipplaat en Murraysburg vir die hoofbevolkingsgroepe Blank, Kleurling en Bantoe

- Dreyer, J N

A contribution to the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa

- Bruton, Michael N

  • Authors: Bruton, Michael N
  • Date: 1973
  • Subjects: Cichlids , Tilapia , Mozambique tilapia
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5839 , http://hdl.handle.net/10962/d1009950 , Cichlids , Tilapia , Mozambique tilapia
  • Description: An account is given of some aspects of the biology of Tilapia mossambica Peters in Lake Sibaya, South Africa. Previous work on Tilapia in Lake Sibaya is reviewed. Apart from brief gillnet surveys, which recorded the species' presence, no research on T. mossambica had been performed at Lake Sibaya before the two-year study of Minshull who collected data on food preferences, depth distribution of juveniles and breeding biology of adults. The main physiographical features of the lake are outlined. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1-7 m deep. Adult fishes (over 8 cm SL) are usually absent from water deeper than 12 m and shallower than 0.5 m, whereas juveniles may occur at all depths, and fry only in very shallow water. T. mossambica inhabits the littoral in the warm and transition periods (August to April) but moves into deep water in the cool season (May to July). Exposed and sheltered shallow areas are utilised for different purposes by adult fishes, the former for nesting, and the latter for feeding and mouth-brooding. Habitat selection by males was governed by nest site selection. Habitat Nests were most common in sheltered, sparsely vegetated littoral and sublittoral areas, but also present in well-vegetated sheltered areas. Breeding females preferred sheltered littoral areas but ventured onto the terrace to release the young. Juvenile and fry T. mossambica inhabited shallow exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour of T. mossambica is described, and integrated with data on T. mossambica from other systems. The breeding season spans seven months. Shoaling takes place in shallow water probably as a means of protection. T. mossambica is an omnivorous feeder relying largely on diatoms. The main predator is probably the barbel Clarias gariepinus, but avian predators may be more important. A method whereby the time of formation of rings on the scales of T. mossambica is described. The fishes were found to reach maturity after one year at a length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 14 cm (females) and 17 cm (males). The maximum final size was about 24 cm SL. An estimate of the standing crop for fishes in the littoral and subiittoral areas of the eastern and southern shores of the south basin is given. The data were derived from a mark and recapture The biology of T. mossambica in Lake Sibaya as revealed by the present study is discussed with reference to data on the same and similar species in other systems. The utilis ation of the available resources in the lake by T. mossambica is commented upon, and reference is made to the significance of stunting, and the import ance of the retention of generalised characters for the successful habitation of the cyclically-renewed habitat of the littoral. Precocious breeding in T. mossambica is regarded as a functional adaptation which increases the proportion of fishes small enough to utilise the rich food resources in shallow water.
  • Full Text:

A critical study of the chansons of the Chatelain de Couci (end of the XIIth to beginning of the XIIIth Century)

- Salter, Christina

  • Authors: Salter, Christina
  • Date: 1973
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:21144 , http://hdl.handle.net/10962/6563
  • Full Text:

A physico-chemical investigation of refractory hard metals

- Philip, Hamish Ian

  • Authors: Philip, Hamish Ian
  • Date: 1973
  • Subjects: Refractory materials Heat resistant alloys
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4441 , http://hdl.handle.net/10962/d1007630
  • Description: In this investigation, the resistivity of vanadium nitride at elevated temperatures has been measured using a resistance bridge based on the Dauphinée/Mooser (1955) chopper system. In general, an almost linear increase of resistivity with temperature was observed for VN, but at certain temperatures, deviations from linearity (anomalies) were observed, these have been classified into three types. Attempts have been made to correlate the anomalous behaviour and temperature coefficients of resistivity with the ambient atmospheres and with the impurities, (especially oxygen), stoichiotmetry and density of this material. Oxygen and excess nitrogen appear to be electron donors in their effects on VN and result in a decrease in the slope of resistivity vs temperature curves. Oxygen and excess nitrogen also appear to increase the overall resistivity due to an increase in defect concentration. No effects due to the ambient atmosphere have been observed in the case of hot-pressed samples. lndicating that reaction can only occur if the reacting gases can reach the interior of the samples.
  • Full Text:

A structural investigation of the sulphated polysaccharide from Aeodes ulvoidea Schmitz

- Allsobrook, Anthony John Robert

  • Authors: Allsobrook, Anthony John Robert
  • Date: 1973
  • Subjects: Red algae -- Composition Polysaccharides
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4437 , http://hdl.handle.net/10962/d1007482
  • Description: Aeodes ulvoidea, a red seaweed of the Grateloupiaceae, yielded a highly sulphated polysaccharide which was shown to contain D- and L-galactose, 4-0-methy-L-galactose, 2-0-methyl - D- and L-galactose and 6-0-methyl-D-galactose, together with chromatographic traces of xylose and mannose. The sulphate was not labile to alkali, but it was largely removed with methanolic hydrogen chloride. Periodate oxidation of the polysaccharide, methylation of the de sulphated polysaccharide, and investigation of fifteen oligosaccharides from partial hydrolysis and acetolysis studies of the polysaccharide, indicate that (a) the polysaccharide is composed of a backbone of D-galactose residues which are 1,3- and 1,4-linked (b) at least some regions of alternating structure do occur (c) the 2-0-methylgalactose is linked through the 4-position (d) the 4-0-methyl-L-galactose is present as single unit side chains glycosidically linked to the galactose backbone at position 6, and (e) most of the 6-0-methyl-D-galactose is linked to the 4-position of 2-0-methyl-D-galactose.
  • Full Text:

A study of Jewish identification and commitment in Johannesburg

- Dubb, Allie A

  • Authors: Dubb, Allie A
  • Date: 1973
  • Subjects: Jews -- South Africa -- Johannesburg Johannesburg (South Africa) -- Social conditions
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3362 , http://hdl.handle.net/10962/d1011564
  • Description: The present study is an investigation of the nature and extent of Jewish identification and commitment in the Johannesburg Jewish Community. Jewish identification is defined as the attitudes and behaviour through which Jews express their identity with each other and with the Jewish group. It is conceived as comprising several dimensions - structural, cultural, religious, etc . - each of which may be assessed in terms of attitudes and/or behaviour. The aim of the study is, in the first place to describe the various dimensions of Jewish identification and to discover relations between them, and between them and other variables. Fieldwork consisted in the administration of a schedule, lasting about an hour, by trained interviewers to a quota sample of Johannesburg Jews. The schedule comprised questions relating to behaviour, attitudes and personal particulars. These data were augmented by several intensive interviews and by interviewers' observations. The final sample consisted of 286 men and women, in almost equal proportions, who had answered affirmatively the initial question, "Are you Jewish?" Five hypotheses were postulated, mainly on the basis of the findings of several previous studies in the United States. Briefly, it was postulated: firstly, that Jews would tend to identify through their attitudes to a greater extent than through actual behaviour; secondly that the area in which identification on the behavioural level was most likely to be manifested, was in patterns of social relations; thirdly, that observance of religious rituals was primarily a manifestation of identification rather than religious commitment ; fourthly; that there was some conflict between the desire to maintain the group and the feeling that barriers between ethnic groups should be minimal; and, finally , that the boundaries of the .Jewish community could be defined most adequately in terms of the relevance to community membership to the allocation of roles rather than in cultural terms. The first hypothesis had to be partially rejected; the remaining four were confirmed by the data. The study comprises eleven Chapters: in the first four, the problem is defined, hypotheses stated and research and sampling methods discussed; in Chapter Five, the demographic background is described, and in Chapters Six to Ten the findings relating to the various dimensions are presented and the hypotheses tested. In the final Chapter, the hypotheses and various specific findings are discussed in relation to their wider theoretical implications, as well as to their possibilities for further research and practical applications.
  • Full Text:

A study of the ecology, behaviour and systematics of Tockus Hornbills

- Kemp, Alan Charles

A study of the tragedy of Coriolanus by William Shakespeare

- Knox, Catherine Mary

  • Authors: Knox, Catherine Mary
  • Date: 1973
  • Subjects: Shakespeare, William, 1564-1616 -- Coriolanus , Shakespeare, William, 1564-1616 -- Criticism and interpretation
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2304 , http://hdl.handle.net/10962/d1012642 , Shakespeare, William, 1564-1616 -- Coriolanus , Shakespeare, William, 1564-1616 -- Criticism and interpretation
  • Description: It would be difficult to prove conclusively that Shakespeare was not invited or requested to write a play based on the popular story of Coriolanus. J.M. Robertson concretises this possibility with an intriguing thesis that the play was in fact rewritten from an original by Chapman. The story, he argues, would have had a far greater appeal to Chapman with his consuming interest in the heroic age of Classical antiquity, than to Shakespeare. Further, it is likely, he says, that Chapman was familiar with Alexandre Hardy 's Coriolan which, it is generally accepted, Shakespeare was not, hence the startling similarities in some of the two plays' deviations from their common source. This is hardly a more satisfactory explanation than the kind of airy alternative that disposes of the mystery by saying the source material is such that it would invite any dramatist to make similar changes. Chap. 1
  • Full Text:

A triangle of forces : language, religion and politics : inaugural lecture delivered at Rhodes University

- Smuts, J. (Johannes)

  • Authors: Smuts, J. (Johannes)
  • Date: 1973
  • Subjects: Sociolinguistics
  • Language: English
  • Type: Text
  • Identifier: vital:669 , http://hdl.handle.net/10962/d1020738
  • Description: Inaugural lecture delivered at Rhodes University , Rhodes University Libraries (Digitisation)
  • Full Text:

Aloe alooides, Eastern Transvaal

- Findlay, Dick

Aloe distans, Saldanha Bay

- Findlay, Dick

Aloe lutescens, Northern Transvaal

- Findlay, Dick

An analysis of the transport infrastructure of the Cape Midlands and Karroo regions

- Staude, G E

An enquiry into some present-day attitudes in art education and their relationship to the current alienation of artist from society

- Rodger, John Neil

  • Authors: Rodger, John Neil
  • Date: 1973
  • Language: English
  • Type: Thesis , Masters , MFA
  • Identifier: vital:21146 , http://hdl.handle.net/10962/6574
  • Description: From Introduction: "We can't teach these kids anything, man, they are so pure and unspoiled. Anything we show them or any discipline we impose upon them will only corrupt their purity. It's best if they just stay home and do their own thing”. "If your instructor says he knows what art is, watch out.” These two statements, the first by an instructor at a prominent New York art school, the second by one of America's respected critics, are the sort of talk one might expect to hear at any gathering of the avent-garde . To hear them said in and about the art school puts things in a different light. They are indicative -of the sort of thing that is preached and practised by a sufficient proportion of the art- educational force in the Western world to constitute a crisis unparalleled in the entire history of art education. Unopposed, such views must rapidly spell death for the institution. They must also, if they reached the proportions their authors appear to hope for, ensure a universal visual illiteracy unequalled in any other age. Of course statements like this, archly delivered by the very people who would suffer the most immediate loss at their implementation, are not at all true reflections of the whole state of art education in our time, or those people would simply not be in a position to make them. There are a great many people in the profession who would wholeheartedly reject such statements, and this faction is by no means confined to the older members.
  • Full Text:

An investigation of the determinants of the spatial characteristics of figure placements

- Edwards, David J A

  • Authors: Edwards, David J A
  • Date: 1973
  • Subjects: Characters and characteristics , Psychology, Applied , Cross-cultural studies
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3205 , http://hdl.handle.net/10962/d1011739 , Characters and characteristics , Psychology, Applied , Cross-cultural studies
  • Description: The doll placement technique is a projective instrument which yields objective measures from which inferences may be drawn. Subjects place pairs of dolls to represent social encounters described to them by the experimenter. When the dolls have been placed, the distance between them and the angles at which they stand can serve as a source of information either about the personality of the placer or about the way in which he perceives the relationship between the interactors represented. Most experimental work employing figure placements has used flat felt figures which subjects have mounted on a flannel graph. This method limits an investigator to one dependent variable, the inter-figure distance. However if three dimensional dolls are placed three dependent measures can be derived from a placement, one of distance and two of orientation. It has been demonstrated that a reliable correlation exists between the spatial relations between figures placed by a person and the spatial relationships between real interactors. The theoretical analysis of the determinants of interpersonal distance and orientation in social encounters which has been worked out by students of non-verbal behaviour is therefore able to serve as a basis for the interpretation of the spatial characteristics of doll placements. Previous work with the doll placement technique has concentrated on the distance between dolls. The present study explored the determinants of figure orientations. Firstly an analysis was made of the types of orientation pattern that can occur when two persons are involved in a social encounter. Secondly, an experiment was performed which was designed to explore whether asymmetry in an orientation pattern might act as a cue to determine how individual figures in a pair were perceived. Thirdly, two doll placement studies were performed which were designed to investigate the conditions giving rise to asymmetrical orientation patterns and the determinants of direct and indirect orientations. The confidence or anxiety attributed to an interactor represented by a figure proved to be a major determinant of its spatial position. The results of the study indicate that the use of the angle measures in the analysis of doll placements considerably enhances the value of the technique. It is argued that the doll placement method could be profitably employed both as a clinical instrument and as a research tool for cross-cultural psychology.
  • Full Text:

Aspects of the biology of aestivation in Bulinus (Physopsis) africanus (Krauss) (Gastropoda, Pulmonata)

- Heeg, J. (Jan)

  • Authors: Heeg, J. (Jan)
  • Date: 1973
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:21054 , http://hdl.handle.net/10962/6178
  • Description: Aestivation, a period of dormancy during hot, dry conditions, is known to occur in both the Prosobranchia and the Pulmonata among freshwater Gastropoda. While there have been numerous accounts, mainly by field ecologists concerned with bilharziasis control, of the survival value of aestivation in the Gastropoda, little is known of its underlying physiological mechanisms. Results of investigations into the physiological basis of aestivation in the freshwater Prosobranchia, confined to the family Ampulariidae, have been conflicting, fundamental differences having been shown to exist between different species of the genus Pila . Only a single comprehensive study, that by von Brand and his coworkers on the planorbid snail Australorbis glabratus*, forms the basis of our knowledge of the aestivation process in the aquatic Pulmonata. In view of the conflicting results obtained in investigations on freshwater Prosobranchia, the general applicability of the findings for Australorbis glabratus to other freshwater Pulmonata was open to question. The present investigation on the planorbid snail Bulinus (Physopsis) afriaanus, a species known to be a successful aestivator, was prompted by the obvious need for a further comprehensive study on an aquatic pulmonate species . The results presented here show that aestivation in this species is a definite physiological state, characterised by a depression of the metabolic rate, which not only aids in husbanding the snails I metabolic resources. during the enforced starvation which must necessarily accompany aestivation, but also constitutes a form of resistance adaptation to the transient high temperatures which aestivating snails are bound to encounter. Loss of body water is shown to be important in initiating aestivation, but it is also the factor most likely to prove lethal during the course of aestivation. The results confirm and extend the earlier findings for Australorbis glabratus. The results are discussed in the context of our present knowledge of aestivation in other Gastropoda, both aquatic and terrestrial, and also in relation to other forms of resistance adaptation. As expected, the investigation raises more questions than it answers, thus directions for further research, arising out of the present findings, are suggested.
  • Full Text:

Aspects of the biology of Boophilus decoloratus (Koch, 1844) (Acarina : ixodidae)

- Londt, Jason G H (Jason Gilbert Hayden), 1943-

  • Authors: Londt, Jason G H (Jason Gilbert Hayden), 1943-
  • Date: 1973
  • Subjects: Ixodidae -- Development Ticks -- Development Boophilus -- Development
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5817 , http://hdl.handle.net/10962/d1007202
  • Description: 1. The external morphology of all stages in the life cycle of B. decoloratus is described with the aid of scanning electron micrographs. 2. The biological activities of B. decoloratus during its parasitic cycle are examined with special reference to the course of feeding of all stages, and to the influence of the pharate nymph and adult conditions in accelerating the completion of the cycle. 3. The pattern of dropping of replete females is considered in relation to their weight and their time of drop-off. 4. The adult male population structure is described. Two distinct weight groups are reported and the taxonomic significance of these is discussed. 5. The preoviposition period duration of B .decoloratus was studied under laboratory conditions and found to be temperature dependent and humidity independent. Female size, as implied by their engorged weights, influenced the duration of the oviposition period: ticks weighing less than 20 mg possessed longer preoviposition periods. 6. The preoviposition period of B.decoloratus females under fluctuating macroclimatic conditions was studied and found to be long in duration. The implications of this are discussed in relation to laboratory findings and the summer build-up of this species in nature. 7. The duration of the oviposition period of B. decoloratus and the number of eggs produced during this period were studied under laboratory and field conditions. Both these parameters were found to be temperature dependent and uninfluenced by humidity. The significance of a temperature dependent oviposition period is discussed. 8. The minimum amount of 'blood' required by female ticks for oviposition of eggs was found to be approximately 16 mg. under laboratory conditions. 9. The oviposition behaviour of B. decoloratus females has been described and the water relations of ovipositing and non-ovipositing females were examined and discussed . 10. The effects of handling female ticks during their oviposition period was studied and females which were handled were found to produce significantly fewer eggs. The significance of this is discussed. 11. During preliminary experiments on the incubation period of B. decoloratus it was found that the viability of eggs laid during the first half of the oviposlting period was greater than for eggs laid in the second half of the period. The critical temperature of the 'wax' coating of eggs was found to be 42⁰C while the critical humidity was approximately 70% R.H. (7,53 mmHg) at 26⁰C. The implications of these findings are discussed. 12. The development of eggs, traced throughout the incubation period by monitoring the build-up of guanine spectrophotometrically, was studied under different humidity conditions . Successful development was found to be dependent on the water content of the eggs at the time of laying. As eggs were also found to be unable to take up water vapour from the atmosphere this finding is important evidence to support the suggestion that the survival of the egg stage largely determines the spacial distribution of larvae in the field. 13. Results of work done at constant, alternating and naturally fluctuating temperatures and humidities demonstrated that the duration of the incubation period of B.decoloratus is temperature dependent and humidity independent. The significance of this is discussed in relation to the findings of previous workers and to the biology of the species. 14. Egg viability (percentage hatch) was found to be humidity dependent and temperature independent. The implications of these findings are discussed. 15. Some of the problems associated with the assessment of the effects of climatic conditions on ticks are discussed. Special reference has been made to the advocation of using saturation deficit instead of relative humidity as the parameter indicative of environmental humidity in any biological study involving fluctuating humidity conditions. 16. The problems associated with having three variables (e.g. temperature, saturation deficit and incubation period duration) are discussed and reasons given for why contour diagrams have been used in this investigation. 17. A model of the interactions between the main abiotic factors of the environment (temperature and humidity) and the biological parameters studied during the second part of this investigation is presented. 18. The effects of climatic conditions on the life cycle and distribution of B.decoloratus are discussed. Special reference has been made to the available evidence explaining the summer build-up in tick numbers known to occur in nature and the way in which the present findings have helped in an understanding of the spacial distribution of B.decoloratus in the field.
  • Full Text:

Atmospheric ionization by precipitated electrons

- Wulff, Annemarie

  • Authors: Wulff, Annemarie
  • Date: 1973 , 2013-10-31
  • Subjects: Ionization , Electrons
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5503 , http://hdl.handle.net/10962/d1007229 , Ionization , Electrons
  • Description: From Introduction: Precipitation of energetic particl es into the upper atmosphere is known to cause aurora at high latitudes. Sanae is situated in the vicinity of the South Atlantic Geomagnetic Anomaly (Gledhill and Van Rooyen (1963)) where the magnetic field intensity is very low and it is felt that this phenomenon may enhance the loss of particles from the trapping zone into the upper atmosphere. Previous work at Rhodes has shown that it is extremely likely that particle precipitation could be the cause of some ionospheric effects at Sanae. Gledhill and Torr (1966) found that a "disturbed" ionosphere at Sanae was linked with "high" fluxes of precipitated electrons in the area conjugate to Sanae. Later papers by Gledhill, Torr and Torr (1967), and Torr and Torr (1967a, 1968a) established that electrons are precipitated over a large part of the earth's surface and this phenomenon is probably responsible for an average of about 30% of F-layer disturbances. The frequency of precipitation and corresponding disturbances is most pronounced in the South Atlantic Geomagnetic Anomaly . , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
  • Full Text:

Certain aspects of eroticism in twentieth century western painting

- Marais, Estelle

  • Authors: Marais, Estelle
  • Date: 1973
  • Subjects: Erotic art , Painting, Modern -- 20th century
  • Language: English
  • Type: Thesis , Masters , MFA
  • Identifier: vital:2486 , http://hdl.handle.net/10962/d1012833
  • Description: In this essay eroticism will be examined as it appears in some twentieth century representational styles. The decision to concentrate on the representational styles is based on the fact that eroticism is by nature incompatible with the non-representational or non-objective movements in art. This incompatibility is rooted in the knowledge that eroticism is intrinsically and fundamentally a human experience and could therefore find expression only in an art which is concerned with human experience, i.e. experiences which refer to man, his nature and his relation to Nature. It would be oversimplified and grossly inaccurate to equate the nonrepresentational with the abstract, abstraction being an element present in all art to a greater or lesser degree. However, when abstraction has reached the stage where it can define its aims, as, in the words of Kandinsky, "widening the separation between the domain of art and the domain of Nature", (Lake & Maillard: A Dictionary of Modern Painting, p. 1) then it may also approach the realm of the non-representational. When Michel Seupher states, "I call abstract art all art that does not recall or evoke reality", (Lake & Maillard: A Dictionary of Modern Painting, p. 136) abstract and nonrepresentational art becomes fused into an inseparable unity. Erotic expression will then be incompatible with this degree of abstraction. Intro., p. 1.
  • Full Text:
  • Disclaimer
  • Privacy
  • Copyright
  • Contact