The design and construction of a recording spectrometer for the measurement of fluorescence excitation spectra in the vacuum ultra-violet region
- Authors: Davidson, A T
- Date: 1963
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21177 , http://hdl.handle.net/10962/6761
- Description: Summary: A recording spectrometer for the measurement of fluorescence excitation spectra in the visible and ultra-violet regions of the spectrum is described. A direct method of modulating the hydrogen light source of the spectrograph is presented, whereby the discharge is driven by an A.C. power oscillator. The use of tuned amplifiers in the detecting unit is investigated as a means of eliminating the D.C. component of the dark current. Aspects of the modulation method are discussed. Fluorescence and energy transfer in aromatic hydrocarbon is discussed with particular regard to anthracene. Some absorption, fluorescence, excitation and reflection spectra of anthracene obtained by previous workers are presented9 together with Tables listing the wavelengths of principal maxima for the above spectra published in the literature. Features of the excitation spectrum of anthracene are discussed and are related to its absorption and fluorescence spectra. The role of surface effects, defects and impurities are discussed in relation to the fluorescence of anthracene. The method of A.C. detection was unable to resolve the excitation spectrum of anthracene due to the high noise level associated with the method. However, peaks in the ultra-violet region of the hydrogen molecular spectrum were recorded at a modulation frequency of 400 Kc/sec. The noise level is explained and ways of improving the signal to noise ratio of the A.C. detection system are suggested. It is concluded that D.C. detection is a simpler and more direct way of measuring excitation spectra. No modulated signals were detected when the hydrogen discharge was excited at 6·5 Mc/sec. Signals were recorded at modulation frequencies of 400 Kc/sec . The degree of modulation at 400 Kc/sec. increased with decrease in the pressure of the hydrogen discharge.
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The development of a method for the determination of microgram amounts of magnesium by atomic absorption
- Authors: Taylor, John Douglas
- Date: 1963
- Subjects: Atomic absorption spectroscopy -- Instruments , Magnesium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4507 , http://hdl.handle.net/10962/d1013344
- Description: This thesis includes a description of modifications of the Hilger atomic absorption apparatus, which was used for most of the work. These modifications were restricted to the atomiser and burner, which were replaced by a modified "Eel" flame. photometer atomiser-burner and resulted in improved sensitivity and instrumental stability for the atomic absorption of magnesium. A comparison of the performance of this unit with that of the unmodified Hilger apparatus is given. A "Handigas" butane-propane mixture)-air flame was used for most of this work, but a coal-gas-air flame was also studied and found to give slightly greater sensitivity. The method was found to be subject to interference from many elements. Strontium salts, employed as releasing agents to overcome the effect of other elements, were not completely effective as milligram amounts of several elements interfered even when strontium was present. Among the more serious interfering elements are: aluminium, iron, manganese and zirconium (less than 20 p.p.m. interfere); the alkali and alkaline earth metal salts (more than 200-500 p.p.m. interfere); phosphate (more than 100 p.p.m. P₂0₅ uranium (more than 4,000 p.p.m.); arsenate and vanadate. An attempt is made to explain the mechanism of some of these interfering effects. A combination of strontium salt and acetyl acetone was found to over-come the effects of small amounts of several elements that form complexes with acetyl acetone (e.g. iron and aluminium) far more effectively than strontium alone. Larger amounts of many interfering elements are removed by a solvent extraction procedure employing acetyl acetone and chloroform. Elements which cannot be removed by this means may be separated by anion-exchange, volatilisation, electrolysis or precipitation. A spiking technique, which compensates JT/GB for the effects of small amounts of interfering elements, is described and enables many samples to be analysed without prior separations. The method described has good sensitivity (the limit of determination is approximately 1 microgram of magnesium in 50 ml. of solution). It has been applied to the analysis of clay samples, iron ore, limestone and uranium metal, oxides and processing solutions. The coefficient of variation of the method was determined using two clay samples and results of 2.0 and 4.6 percent, at magnesium oxide concentrations of 0.65 and 0.22 percent respectively, wore obtained. The speed of the method compares favourably with others described for the determination of microgram amounts of magnesium, but increases if large amounts of interfering elements are present.
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The influence of temperature in the ecology of the intermediate host snails of Schistosoma and Fasciola (Trematoda) in southern Rhodesia
- Authors: Shiff, Clive Julian
- Date: 1963
- Subjects: Schistosoma , Schistosomiasis , Fasciola , Snails -- Zimbabwe , Trematoda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5881 , http://hdl.handle.net/10962/d1013208
- Description: The influence of temperature on the bionomics of Bulinus (Physopsis) globosus, Biomphalaria pfeifferi and Lymnaea natalensis has been studied both in the laboratory under controlled conditions and in the field under normal seasonal influences. Field studies were carried out in two different localities, one a semi-permanent pond and the other a temporary waterbody. For this purpose a sampling implement was developed. The results show the seasonal progression of these populations both with respect to estimated numbers and the size distribution of the snails. The rate of actual increase at different seasons was calculated for the three species where the data were sufficient. In the laboratory the snails were maintained at various temperatures, other conditions being kept standard. Daily records of mortality and fecundity of various cohorts reared from the egg stage enabled the compilation of life tables fof the speciesand from these data were calcualted the intrinsic rate of natural increase and other parameters. Effects of crowding in aquaria were studied. From the data obtained in the laboratory it was possible to predict the distribution and population potential for each species for snail of various environmental conditions. These predictions were, in fact, confirmed by field observation.
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The place of geometry in university mathematics : inaugural lecture delivered at Rhodes University
- Authors: Cruise, S E
- Date: 1963
- Language: English
- Type: Text
- Identifier: vital:612 , http://hdl.handle.net/10962/d1020681
- Description: Inaugural lecture delivered at Rhodes University. , Rhodes University Libraries (Digitisation)
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The role of the artist in society as seen in the novels of Henry James
- Authors: Middleton, D F
- Date: 1963
- Subjects: James, Henry, 1843-1916 , Journalists as artists , Art and society , Fiction -- History and criticism -- 19th century
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2305 , http://hdl.handle.net/10962/d1012874
- Description: Henry James (1843-1916) is a curious and, by his own choice, enigmatic figure. We have a great many dates, a few letters, and little else. James's fragment of autobiography, vast as it is; is strangely unrevealing. There is a wealth of impressions as one would expect from such a writer but precious little about the man. Henry James was chary of describing his personal feelings - so much so that some doubted his ability to have any strong emotions. His autobiography, interesting as it is, is pure observation, memories of people, places and impressions, all marvellously sensitive, but little personal feeling. Intro., p. 1.
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Vere deus vere homo: a critical assessment of Christological discourse concluding with a brief appraisal of selected Christological hymns
- Authors: Gamley, Anthony M
- Date: 1963
- Subjects: Jesus Christ -- History of doctrines Hymns, English Theology, Doctrinal Barth, Karl., 1886-1968
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1253 , http://hdl.handle.net/10962/d1011938
- Description: "We preach Christ crucified, a stumbling-block to Jews and folly to Gentiles". In so writing, St. Paul stated in its briefest form the scandal of the Christian faith. To human reason it is nonsense to suppose that a man who grew up and lived like other men, and who ultimately died on a cross, could at the same time be the Son of God, equal to God, eternal like God, and Creator of the world with Him. Contrary to the painfully-evolved and carefully formulated conclusion reached by philosophers, that God is one, and diametrically opposed to the monotheistic divine revelation given to Israel, the belief that Jesus was Son of God and equal to His Father seemed; when it was first postulated, to imply some kind of flaw in the indivisibility of God. Men were being asked to believe that they could see God incarnate, that is, in a being of flesh and blood. Yet all our faith hovers around this precise point.
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