Fluctuations are known to radically alter the behaviour of reaction-diffusion systems. Below a certain upper critical dimension d_c , this effect results in the breakdown of traditional approaches, such as mean field rate equations. In this thesis we tackle this fluctuation problem by employing systematic field theoretic/renormalisation group methods, which enable perturbative calculations to be made below d_c. We first consider a steady state reaction front formed in the two species irreversible reaction A + B → Ø. In one dimension we demonstrate that there are two components to the front - one an intrinsic width, and one caused by the ability of the centre of the front to wander. We make theoretical predictions for the shapes of these components, which are found to be in good agreement with our one dimensional simulations. In higher dimensions, where the intrinsic component dominates, we also make calculations for its asymptotic profile. Furthermore, fluctuation effects lead to a prediction of asymptotic power law tails in the intrinsic front in all dimensions. This effect causes high enough order spatial moments of a time dependent reaction front to exhibit multiscaling. The second system we consider is a time dependent multispecies reaction-diffusion system with three competing reactions A+A → Ø, B + B → Ø, and A + B → Ø, starting with homogeneous initial conditions. Using our field theoretic formalism we calculate the asymptotic density decay rates for the two species for d ≤ d_c. These calculations are compared with other approximate methods, such as the Smoluchowski approach, and also with previous simulations and exact results.

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The ability of Pyrolysis-GC/MS analytical system---developed earlier to study the mechanism of Maillard reaction---was further enhanced to include chemical ionization, tandem mass spectrometry and a sample pre-concentration trap essential to detect minor components. Furthermore, the sample delivery during Py-GC/MS analysis was optimized and its relevance to the study of aqueous Maillard model systems was also characterized. The results of these investigations have indicated that the use of higher values of carrier gas flow rates or high constant pressures, during Py-GC/MS analysis can increase the total number of peaks and total area counts of the pyrograms. The influence of the reaction phase on the mechanism of formation of Maillard products was studied by comparison of 13C-label incorporation patterns of the common products formed in model systems consisting of labeled glycine and D-glucoses subjected to both pyrolysis and heating in aqueous solutions. Although pyrolysis reaction produced higher number of products, however, the major pathways of formation of variety of important Maillard products followed the same mechanism under both pyrolytic and aqueous systems. Furthermore, the advantages of the optimized system, were demonstrated both in the investigation of the mechanism of Maillard reaction, using L-serine and L-threonine as model systems and in the study of formation of Maillard generated carcinogens and chemical markers. Analyses of the pyrolysis products of [13C-1], [13C-2] and [13C-3] labeled L-serines and L-threonines have indicated the presence of three initial degradation pathways. Decarboxylation followed by deamination; a retro-aldol reaction and dehydration followed by isomerization, deamination and hydrolysis leading to the formation of pyruvic and 2-ketobutanoic acids. Interestingly, the amino carbonyl interaction between the resulting pyruvic acid and the aminoethanol can lead to the formation of an Amadori product i

<p>Includes Bibliographical references (leaves 83- 94).Forty-three male athymic nude mice were implanted with human vaginal mucosal cysts under general anaesthesia with Ketamine [25mg/kg] and Medetomidine [0.5mg/kg]. Cysts in 37 mice were recovered after 9 weeks of growth. twenty three cyst linings had retained the original structure of the vaginal epithelium. No marked deifference was present between the thickness of 9 week old linings and donor vaginal epithelium. The contaminants isolated from the skin of mice before implantation were mainly normal commercals of healthy experimental animals. There was no distinct difference in the number of cases with intact cyst formation between the terramycin/vitamin cocktaik group. The frequency of poor wound healing and/ or murine epidermis ingrowth was three times higher in animals stitched with silk sutures that in those cases where nylon sutures were used.</p>

Thesis (M.App.Sc.)--University of South Australia, 1995.