Flavanone (2,3-dihydro-2-phenyl-4H-benzopyran-4-one) and a series of 4'- and 7-halogeno derivatives were prepared from the corresponding 2'-hydroxychalcones [1-(2-hydroxyphenyl)-3-phenyl-2-propen-l-ones], which, in turn, were synthesized by aldol condensation of substituted 2'-hydroxacetophenones with various benzaldehydes. A series of 2,3-dihydro-2-phenyl-l,4-benzoxazepin-5(4H)-ones were prepared by ring expansion of the corresponding flavanones, via the Schmidt reaction, using trimethylsilylazide and trifluoroacetic acid. A series of tetrazoles {2,3-dihydro-2-phenyl-tetrazolo[1,5-d]-1,4-benzoxazepines} were also isolated as by-products of the Schmidt reaction. Flavanone oxime was synthesized for use in Beckmann reactions, and its molecular structure was determined by x-ray crystallography. Attempts to prepare 1,4-benzoxazepinone or its 1,5-analogue via Beckmann rearrangement of flavanone oxime, with polyphosphoric acid or phosphorus pentachloride catalysts, however, were unsuccessful. Several methods for introducing Δ²-unsaturation into the benzoxazepinone system were also examined. High resolution ¹H n.m.r., computer modelling, and molecular mechanics techniques were used to determine the conformations of the heterocycles of the benzoxazepinones and tetrazoles and results are compared with earlier studies in this field. Certain trends in the fragmentation patterns were observed in the low resolution mass spectra of the benzoxazepinones and tetrazoles, and high resolution mass spectrometric data were used to explore the major fragmentation patterns of these compounds.

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.

No description available.

Observations from a broad range of astrophysical scales have forced us to the realization that the well understood matter comprising the stars and galaxies we see around us accounts for only a small fraction of the total mass of the Universe. An amount roughly five times larger exist in the form of dark matter about which we have virtually no direct evidence apart from its large scale gravitational effects. It is also known that the largest contribution to the energy density of the universe is the dark energy, a negative pressure form of energy which will not be dealt with here. I will present a candidate for the dark matter which is based completely in known physics and which presents several possible observational signatures. In this model the dark matter is composed of dense nuggets of baryonic matter and antimatter in a colour superconducting state. If these object are sufficiently massive their low number density will make them effectively dark in the sense that collisions with visible matter become infrequent. This work presents the basics of dark matter as a colour superconductor and then uses the physical properties of the quark nuggets to extract observational consequences. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The presence of inhomogeneities in semiconductor materials used to fabricate solar cell devices may result in spatial non uniformities in the device properties which may affect current generation in these devices. Besides, current reducing defects such as inclusions, local shunts and optical blockages may be introduced during the various device manufacturing processes which may adversely affect the performance and overall efficiency of solar cells. Diagnostic techniques are therefore needed to identify these defects so as to improve the production technology. This thesis presents the Light Beam Induced Current (LBIC) technique for mapping spatial non uniformities in solar cell devices. The LBIC is a non destructive characterisation technique that uses a focused light beam to raster scan a solar cell surface as the photo-generated current is recorded as a function of position to generate a photo-response map. The technique was used to obtain photoresponse maps for a mc-Si, Back contact Back junction (BC-BJ) silicon solar cell and the InGaP/InGaAs/Ge concentrating triple junction (CTJ) solar cell from which various local current reducing defects were mapped. A reflection signal detector was incorporated into the LBIC measurement system to enable us distinguish between optical blockages on the cell surface and current reducing defects within the solar cell devices. By dynamically biasing the solar cell devices, the electrical activity of the identified defects was investigated and also point-by-point current-voltage (I-V) characteristics were obtained. An interval division algorithm was applied to the measured point-by-point I-V characteristics to extract device and performance parameters from which device and performance parameter uniformity of the devices were mapped. Dark and full cell solar illumination I-V characteristics were also measured to extract device parameters. Analysis of extracted parameters revealed differences between extracted dark and illuminated device parameters which was attributed to departure from the superposition principle due to non-linearity of the semiconductor device equations with respect to carrier concentration. An investigation into the effect of illumination intensity on the I-V parameters of a spot illuminated BC-BJ Si solar cell showed a linear increase and a logarithmic increase of the short circuit current and open circuit voltage respectively with intensity while the series resistance decreased with intensity, which was attributed to increase in conductivity of the active layer. The ideality factor and saturation current were observed to increase while the shunt resistance initially increased before decreasing at higher intensity levels. Under monochromatic illumination, the photo-response of the BC-BJ Si cell was higher at 785nm than at 445nm due to low absorption coefficient of Si for longer wavelength radiations, resulting in carrier generation within the bulk, where there is a higher probability of carriers being collected at the p-n junction before they recombine. Under solar illumination, as the spectral content was altered using long pass colour filters with cut off wavelengths of 610nm and 1000nm, the performance parameters were observed to decrease and this was mainly due to decrease in intensity. For the CTJ solar cell, however, blocking of radiations below 610nm resulted in current mismatch that severely degraded the short circuit current (Isc). The current mismatch affected the extracted device and performance parameters. With a 1000nm long pass filter, a dark I-V was obtained since only the bottom Ge subcell was activated.

In this thesis mass spectral and chromatographic techniques were developed and applied to identify and characterise numerous novel platinum(II) and (IV) compounds designed as anticancer agents. In a novel method for the synthesis of cis-oxalato(trans- -1,2- cyclohexanediamine)platinum(II) or oxaliplatin these techniques could be applied to differentiate between the molecular complex and the autoionised analogue (viz. Ptdach2 2+Ptox2 2-). In another novel synthetic method for the same compound the ligand exchange reactions at various temperatures could be investigated and kinetic curves obtained served to illuminate the chemistry involved, indicating the role of small amounts of water in the essentially non-aqueous solvent systems dmf and isoamyl alcohol respectively. These allowed ligand exchange without resulting in hydrolyses even up to 85°C. The ionisation rate of divalent platinum halide complexes was determined for various amine ligands as well as N-S chelate ligands. A comparison of these could suggest why N-S complexes have poor anticancer action. Ionisation was not only studied for neutral molecular species but also for monocationic ones. Relationships could be found with stereochemical aspects of the chelates used. By investigating results of EV-CAD studies thermodynamic data could be obtained which indicated that bond strength decreases from chloro to iodo analogues although extent of ionisation in aqueous solution, i.e kinetic stability, is the reverse. Products formed by the reaction of NO2 gas with Platinum(II) compounds could be identified and separated which greatly contributed to the understanding of the chemistry involved in the formation of mononitro platinum(IV) complexes. Some of these proved to have exceptional anticancer properties. Studies of the interaction of thiol containing biomolecules were performed as a function of time. The results contributed to the understanding of the action of the anticancer agents.

The spark spectra of zinc have been photographed in the region between 990 Å and 2590 Å using a condensed spark in helium as source. Exposures were taken using a Hilger large quartz prism spectrograph and a 3 meter normal incidence vacuum grating spectrograph of local design. Of 1000 lines measured, some 228 were classified in the spectra Zn I, Zn II, and Zn III on the basis of square arrays constructed using energy levels from Moore's "Atomic Energy levels," volume II (1952). Also, 67 lines were classified in the third spark spectrum of zinc, Zn IV, enabling assignment of relative energies to 8 even levels belonging to the configuration 3d⁸ 4s and to 27 odd levels belonging to the configuration 3d⁸ 4p, In addition, use was made of 25 lines measured by Bloch and Bloch (1936) in the region below 500 Å in determination of the ground state 3d⁹²D. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A sensitive, wide or narrow band, solid state spectrometer operating at a wavelength of 0.85 cm has been built which is described in detail. The spectrometer is of the crystal detector reflection-cavity-in-magic-Tee-bridge type and can operate from room down to liquid helium temperatures. The cavity Is excited In the TE₁₁₁ mode and the magnetic field modulated at 140 cps. Both large and small field modulations are incorporated for scope presentation of line width varying from about 0.5 to 500 gauss. Signals from single crystals of copper sulphate pentahydrate and polycrystalline 1-1-diphenyl-2-picryl hydrazyl (DPPH) have been obtained. From the latter, a sensitivity limit of about 10⁻⁸ gram is obtained at room temperature for a bandwidth of 1 cps indicating a sensitivity of the order of 10⁻¹¹ gram at 4.2° K. Various methods of improvement were discussed in order to reach the ultimate sensitivity. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

[No abstract submitted] / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Due to the many crystallographic and spectroscopic anomalies found in investigations of amides, polyamides, and imides, succinimide suggested itself as an interesting compound for spectral investigations. The spectrum of solid succinimide ( KBr pellet ) was recorded in the range 4000 - 250 cm⁻¹, whereas the spectra of vapour, single crystal, and solutions of succinimide in a variety of solvents and at varying concentrations, were obtained in the region 4000 - 250 cm⁻¹. For the recording of vapour spectra, and for the growth of thin sections of single crystals, special apparatus and techniques were devised and are described in detail. N - d - succinimide, N - h - succinimide - d₄, N - d succinimide - d₄, and various related compounds were also investigated. The absorption bands of succinimide have been assigned by comparison with spectra of related compounds and by studying association phenomena and isotope substitution effects. An PG matrix treatment has been undertaken and agreement between calculated and observed frequencies is good when only a minimum number of interaction constants are employed. The anomalous behaviour of succinimide in the Amide II and Amide III regions has been explained by the assumption of a dimer, as has the 3080 cm⁻¹ band. Solution studies indicate that the dimer exist even in moderately concentrated solution. / Science, Faculty of / Chemistry, Department of / Graduate