Bibliography : pages 211-267. / This thesis describes two aspects of the various scientific approaches to the study of urolithiasis. In the first instance, the theory, development and results of three quantitative analytical procedures are described while in the second, crystallization experiments in a rotary evaporator are presented. Of the different methods of quantitative X-ray powder diffraction analyses, the 'internal standard method' and a microanalytical technique were identified as being potentially the two most useful procedures for the quantitative analysis of urinary calculi. 'Reference intensity ratios' for 6 major stone phases were determined and were used in the analysis of 20 calculi by the 'internal standard method'. It is concluded that the attainment of accurate results using this procedure is not easily achieved because of problems such as the unavailability of standards which realistically mimic stone composition, sample preparation, overlap of reflections from sample components and standards and the requirement of 'infinitely thick' specimens ( > 250 mg). For the microanalytical technique, micro-quantities of 10 calculi from the original 20 were deposited on silver filters and were quantitatively analysed using both, the attenuation of the Ag peak and the separately measured absorption coefficients μ*· Inductively coupled plasma atomic emission spectroscopic (ICP-AES) methods were also investigated, developed and used in this study. Various procedures for the digestion of calculi were tested and a mixture of HNO₃ and HClO₄ was eventually found to be the most successful. The major elements Ca, Mg, and Pin 41 calculi were-determined. For the determination of trace elements, a new microwave-assisted digestion procedure was developed and used for the digestion of 100 calculi. Thereafter the major elements Ca, Mg and P together with the minor and trace elements Al, Cu, Fe, K, Li, Mn, Mo, Na, Pb, S, Sr and Zn in all 100 stones were simultaneously determined. The data so obtained were subjected to 3 types of statistical analyses involving direct correlations, scatter plots and a relatively new multivariate analysis of logarithmic data known as a 'covariance biplot'. Several interesting correlations were obtained. Fluoride concentrations in two stone collections - 20 calculi from India and 42 from South Africa - were determined using a fluoride-ion sensitive electrode and the HNO₃/HClO₄ digestion procedure used for the ICP study. Direct measurement of fluoride proved unsuccessful thereby necessitating the investigation and development of a diffusion technique. Using this method the fluoride content of both collections was determined. A series of crystallization experiments involving a standard reference artificial urine was carried out in a rotary evaporator. The effect of pH and urine composition was studied by varying the former and by including certain components (uric acid, urea, creatinine, MgO, methylene blue, chondroitin sulphate A, fluoride) in the reference solution. Crystals formed in these experiments were subjected to qualitative and semi-quantitative X-ray powder diffraction analyses. Scanning electron microscopy of several deposits was also carried out. Similar deposits to those observed in calculi were obtained with the fast evaporator. The results presented suggest that this system provides a simple, yet very useful means for studying the crystallization characteristics of urine solutions. The quantitative analytical procedures described in detail in this thesis can serve as model techniques for other workers involved in stone research. Together with other approaches such as the crystallization experiments discussed, these procedures can lead to a better understanding of the aetiological processes which govern stone formation.

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Includes bibliographical references. / The primary aim of this thesis is to establish a computer model of the chemical elements in seawater and to use this model to gain insight into the chemical processes controlling dissolution, precipitation, redox levels and coordinative interactions in surface seawater. In order to accomplish this task a relatively extensive database consisting of about 580 complexation equilibria arising from 32 inorganic and 10 organic components has been set up. Constants have been selected from critical compilations. Included in these equilibria are solubility products for the formation of potential solids, redox reactions and interactions with the atmospheric gases carbon dioxide and oxygen.

The field of organic electronics is currently receiving a great deal of attention from theoretical and experimental chemists, physicists and material scientists, especially regarding energy transport and optical behavior. The conventional understanding of photophysical and transport processes in organic aggregates, films and crystals is based on the Frenkel exciton model. However, despite its success, the Frenkel model cannot properly account for several important properties of aggregates of highly polarizable chromophores, such as the charge-transfer character of the ground and excited states (and their associated dipole moments) which can change in response to intermolecular interactions. The essential state model (ESM) is investigated as an alternative to the Frenkel exciton model for understanding absorption and emission in aggregates of polar and high-polarizable chromophores. Polar and high-polarizable chromophores consist of donor and acceptor components linked by a c-conjugated bridge. In thiswork, the ESM is expanded to include local vibronic coupling via an Holsteinstyle Hamiltonian. Emphasis is placed on the divergences from the conventional Kasha model which is based on the Frenkel exciton Hamiltonian and is commonly used to understand the relationship between molecular packing and photophysical properties. Divergences between the current approach and the Kasha model are thoroughly explored for the DA dimers in the weak and strong intermolecular coupling limits. Vibronic signatures which reveal information about molecular packing are compared to those derived from Frenkel exciton theory Specific applications include Davydov splitting in covalently bonded squaraine (DAD) complexes and the general photophysical response of dimers of DA chromophores such as merocyanines dyes. / Chemistry

Potential energy surfaces describing bimolecular collisions sensitively depend on the chemical functionality and the relative orientation of colliding partners, thus defining the accessibly reactive and nonreactive pathways. Herein, we investigate the peculiar product outcomes arising from Jahn-Teller distortion of the nitric oxide and methane complex (NO-CH4). We have reported an in-depth spectroscopic and dynamics study of NO-CH4 by utilizing conformation-specific and action spectroscopy, as well as velocity map imaging, to understand the fundamental dissociative mechanisms at play. Ultimately, we have gained information about how the Jahn Teller effect possibly impacts the potential product energy transfer pathways. There is a translationally slow pathway that arises from effective vibration-vibration energy transfer into the 2v4 mode of methane, which occurs on a fast timescale (<2.5 ps). In addition, there is translationally fast pathway that arises from NO and CH4 being able to sample more of their respective energy space, leading to rotational broadening and a slow dissociative timescale (>2.5 ps). The distinctly varied product outcomes provide important experimental signatures of a Jahn Teller distorted equilibrium geometry and the ranging effects it can have.

Acrylic paint is a modern artistic material made of colored pigment and polymeric binder. Acrylic binder requires fundamental study at the molecular level to understand its physical properties for purposes of art conservation and general polymer chemistry. The research presented in this thesis uses single-sided nuclear magnetic resonance (NMR) as a non-invasive and non-destructive way to measure relaxation and self-diffusion, which provide insight to molecular mobility and physical properties of proton-containing samples. Specifically, this study relies on T2 relaxation to gain insight to regions within acrylic paint with different molecular mobilities. In both dry and wet paint, relaxometry data revealed two relaxation behaviors, each representing a region with unique binder mobility. Furthermore, the effect of pigment concentration on relaxation behavior of wet paint suggested molecules in acrylic binder undergo chemical exchange between these regions with differing mobilities. The characterization of local molecular environments in acrylic paint provides a foundation for future studies of acrylic polymers and contributes fundamental knowledge about the chemistry of acrylic paints to support their long-term preservation.

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