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<p> This thesis is concerned with the cooperative growth problem of the discontinuous precipitation reaction. Previous theories are examined, and the kinetic details of a model, which assumes the existence of a metastable monotectoid reaction and the adherence & local equilibrium, are derived. As with other attempt to describe the parameters of duplex growth situations we cannot find a unique relation between the rate of growth and the lamellar spacing. The various optimal or variational procedures used to remove this degree of freedom are considered. The Cu-In system is subject to quantitative experimental study, and the extent of interference of the concurrent general precipitation reaction is determined. Finally the kinetic data and auxiliary information are used to test the various theories. </p> / Thesis / Doctor of Philosophy (PhD)

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This research focuses on experimental investigations of the drying and bending properties of wood flakes. Three species (southern yellow pine, sweetgum, and yellow-poplar) were tested. Experiments on flake drying and effect of flake properties (cutting direction and dimension) and an external factor (temperature) were used to evaluate the flake drying process. Drying experiments were conducted using a convection oven. Bending properties of dried flakes were also measured. Modulus of elasticity (MOE), modulus of rupture (MOR), and strength at proportional limit (SPL) of flakes were measured based on Methods of Testing Small Clear Specimens of Timber (ASTM D143-94) using a miniature material tester. The drying curve was characterized by a second-order/quadratic equation. This equation was then differentiated to get the drying rate curve. Observation on drying and drying rate curves revealed that the rate of moisture loss consists of two falling rate periods; no constant rate drying period was observed. First falling rate drying period is controlled by convective heat transfer. Bound water diffusion controls the second falling rate drying period. Species, cutting direction, dimension, and temperature were found to have significant effect on drying rate of wood flakes. Southern yellow pine has the fastest drying rate followed by sweetgum then yellow-poplar. Differences in drying rate between species were attributed to differences in specific gravity and other factors. Radially-cut specimens have a slower drying rate than tangentially-cut specimens. There were also significant differences in drying rate between the four different flake dimensions. Thickness was found to be the more sensitive parameter in terms of dimensions. As expected, drying temperature also had highly significant effect on drying rate. An increasing trend in drying rate was observed as drying temperature increased. Simulation of flake drying using a numerical model yielded a different result. Simulated flake drying has two drying periods: a constant rate and falling rate. Moisture of the flake decreases constantly and surface temperature increases rapidly to boiling point and remains there in the constant rate drying period. During the falling rate period, rate of moisture transport is limited by the ability of water to diffuse through wood and flake temperature starts to rise. Bending properties were found to vary between and within the three species. Southern yellow pine had the lowest bending stiffness and strength followed by sweetgum while yellow-poplar had the highest bending properties. Radially-cut specimens were found to have lower MOE, MOR, and SPL than tangentially-cut specimens. Drying temperature was also found to have a significant effect on bending stiffness and strength. A decreasing trend in bending properties was observed when drying temperature was increased. / Ph. D.

Parkinson's disease (PD) is a chronic, progressive disorder of the central nervous system that affects approximately 1.5 million Americans. One of the principal pathological features of PD is dopamine deficiency in the substantia nigra of the brain. A key enzyme that has been associated with the neurodegeneration seen in PD is monoamine oxidase-B (MAO-B). Several inhibitors of this enzyme have resulted in neuroprotection in the mouse model of PD. One such compound is 7-nitroindazole (1). This thesis describes the synthesis and MAO activity of several indazolyl and benzimidazolyl prodrugs that are designed to release an enzyme inhibitor in the affected brain area. These studies have provided information regarding the nucleophilic aromatic substitutions of the ambident nucleophiles under consideration. We have also discovered a compound that releases the enzyme inhibitor upon bioactivation by MAO. These results as well as a MPTP mouse study with the aforementioned compound are detailed within. / Master of Science

In many experiments, surfactant adsorption and desorption at solid-liquid interfaces is found to be quite slow, considering that surfactants are small molecules. Attenuated total reflectance Fourier transform infrared spectroscopy was used to study the adsorption, desorption, and exchange of tetradecyltrimethylammonium bromide (C₁₄TABr) at the silicon oxide surface. The exchange of surfactant was monitored using protonated and perdeuterated C₁₄TABr. The data show that exchange of C₁₄TABr between the surface and the bulk solution is very fast, complete exchange occurs in less than 10 seconds. A simple exchange model suggests that the disassociation rate constant of a single monomer is no less than 1 s^-1, which is ~ 10⁴ times slower than monomer exchange in bulk solutions. The actual exchange rate may be greater than observed in the present work due to transport phenomena. The rates of exchange are similar at concentrations above and below the critical micellar concentration. Adsorption is similarly rapid, but under some circumstances there is a small residue of surfactant that is slow to desorb. Desorption experiments utilizing KBr solutions of high and low ionic strength show that two thirds of each adsorbed micelle is held by hydrophobic association, and the other third is electrostatically bound. Adsorption, desorption, and exchange experiments at temperatures of 11&deg;C above and 8&deg;C below the Krafft temperature (14.4&deg;C) show similar kinetics. / Master of Science

Yes / The main objective of this research is to investigate solid-state destabilization mechanism and kinetics of the model cocrystal caffeine : malonic acid (CA:MO) in presence of oxalic acid (OX) as a structural competitor. Competitive destabilization of CA:MO and subsequent formation of CA:OX takes place at temperatures significantly below its melting point. Destabilization mechanism was found to be mediated by sublimation of both CA:MO and OX. During CA:MO destabilization, free CA could not be detected and direct transformation to CA:OX cocrystal was observed. The destabilization kinetics follow Prout-Tompkins nucleation and crystal growth model with activation energy of 133.91 kJ/mol and subsequent CA:OX growth kinetic follow Ginstling – Brounshtien diffusion model with activation energy of kJ/mol.

Density functional theory (DFT), a powerful toolbox, can unveil chemical transformations in detail. This dissertation focuses on exploring catalytic puzzles, deciphering experimental results, and occasionally, reevaluating conventional concepts. In the first problem, a combination of DFT and kinetic studies uncovers the hidden role of borane in directed borylation reactions catalyzed by iridium complex. Borane, initially considered a side product, is revealed to be an autocatalyst. Chiral catalysts are pivotal for achieving asymmetric molecular construction. However, when the chirality center in the catalyst changes with each turnover, what impact does this have? In our second investigation, we delved into a thorough mechanistic study of enantiomeric selectivity during ruthenium complex-catalyzed hydroarylation. This study leads to a reevaluation and refinement of our concepts of asymmetric induction, specifically tailored to dynamic chirality. A series of six Ni(II) complexes featuring N-heterocyclic carbene (NHC) ligands demonstrate photocatalytic CO2 reduction to CO. Remarkably, these complexes retain their activity even in the absence of a photosensitizer, exhibiting self-sensitized photocatalytic capabilities. Our investigation involved ultrafast transient absorption spectroscopy (TAS) experiments and computational studies to provide a deeper understanding of these catalytic activities. Throughout my PhD journey at Mississippi State University, I engaged in diverse research areas within the chemistry department. The final chapter presents a series of chemistry problems encountered in the Hand Lab, where the application of DFT offers insightful solutions. These problems emerged from discussions and collaborations among graduate students, reflecting the spirit of teamwork and collective problem-solving in the department: 1. Understanding electronic structure of FAVE polymer (Smith lab); 2. Explaining the unexpected isomerization of RhCl(3-Si,Si,P) complex (Montiel lab); 3. Understanding stable dinitrogen pincer abnormal CCCPt(N2) complex (Hollis lab) and 4. Characterization of Ni tripodal PE (E = Si, Ge) complexes and studies on the hydroboration mechanism (Montiel lab)

An investigation of the temperature response and corresponding lesion growth resulting from in vivo interstitial laser photocoagulation was performed in order to test the applicability of Arrhenius theory. The irradiations were performed in vivo in rabbit muscle for various exposures at 1.0W using an 805 nm diode laser source coupled to an optical fibre with a pre-charred tip, thereby forcing it to function as a point heat source. Temperature responses were measured using a five-microthermocouple array along a range of radial distances from the point heat source. Each temperature profile was fitted with a curve predicted by the Weinbaum-Jiji bioheat transfer equation. The lesions were resected 48 hours after irradiation and the boundary of thermal damage resulting in necrosis was determined histologically. Numerical integration of the Arrhenius integral using temperature-time data at the lesion boundary produced corresponding activation energy and pre-exponential factor pairs (Ea , a) consistent with reported values for various other endpoints and tissue types. As well, theoretical predictions of the lesion growth from Arrhenius theory agreed well with experimental results. However, the thermal parameters, which are generally assumed to be constant when solving the bioheat transfer equation, were found to vary with radial distance from the source, presumably due to a dependence on temperature. / Thesis / Master of Science (MS)