Digital Commons Network^™

The Scattering Of Gas Phase Molecules Andvan Der Waals Clusters From Surfaces, John Norman Beauregard

Doctoral Dissertations

The interaction of gas phase species with surfaces plays an important role in a myriad of processes such as heterogeneous catalysis, corrosion and the etching of semiconductor surfaces in the microelectronics industry. Thus, the study of gas-surface interactions has become a field of intense research. In this dissertation, we present the results of a computational study of the scattering of gas phase molecules and van der Waals clusters from surfaces. We have used molecular dynamics calculations which allow for the examination of the microscopic details of gas-surface scattering.

In this work we study four distinct systems. In Chapter I the …

Fiber Optic Chemical Sensors Based On Polymer Swelling And Shrinking, Ming Qi Bai

Doctoral Dissertations

Fiber optic chemical sensors based on the polymer bead swelling and shrinking have been evaluated and improved. The sensing element is a crosslinked polymer bead which swells or shrinks as a function of analyte. The change in bead size is coupled to the movement of a small mirror in front of two optical fibers. One fiber conducts light from a LED source to the mirror, the other fiber collects reflected light and carries it to a photomultiplier tube which serves as the detector. Changes in mirror position change the amount of light reflected into the collection fiber.

The variation in …

Regulation Of The Yeast Transcriptional Activator Adr1, W James Cook

Doctoral Dissertations

Glucose repression of the ADH2 gene from Saccharomyces cerevisiae is mediated by the abundance and activity of the transcriptional activator ADR1. The focus of this dissertation is to characterize the mechanisms by which glucose controls the ability of ADR1 to activate ADH2 transcription.

Glucose results in a two-fold decrease in the steady state levels of ADR1 mRNA. This glucose-dependent reduction in steady state ADR1 mRNA was shown to be due to an increased rate of ADR1 mRNA degradation. The unusually long, 510 nucleotide 5$\sp\prime$ untranslated region of the ADR1 mRNA appeared to mediate this glucose-dependent ADR1 mRNA decay.

To better …

Equilibrium Electrophoresis: Results From The Second Prototype, David Barton Hayes

Doctoral Dissertations

Equilibrium electrophoresis is a new method that determines the apparent charge on macroions. The theory of equilibrium electrophoresis is summarized. The second generation device is described. Apparent charges, at various ionic strengths, measured by equilibrium electrophoresis are reported for pd(A)$\sb{20},$ pd(T)$\sb{20},$ pd(A)$\sb{20}$ $\cdot$ pd(T)$\sb{20},$ cytochrome c from horse heart, TA lysozyme mutant, TA(119/135) charge mutated lysozyme, and EDTA. The apparent charge of plasmid pBR322 from electrophoretic mobility and sedimentation velocity is reported. The results are compared to those expected according to the Record-Manning counterion condensation theory and the Debye-Huckel shielding theory. The apparent charges of the two ss DNA samples …

I Asymmetric Photochemistry Ii Exploratory And Mechanistic Studies On The Triplet Sensitized Vapor Phase Photochemistry Of Allenes Iii Developments In The Synthesis Of Strained Cyclic Cumulenes, William Calvin Shakespeare

Doctoral Dissertations

The development and implementation of a new chiral triplet sensitizer derived from 1,1$\sp\prime$-binaphthol is described. Irradiation of 1,3-diphenylallene (16) in the presence of 4,5,6,7-tetrahydro-dinaphtho(2,1-g:1$\sp\prime,2\sp\prime$-i) (1,6) dioxecine (10) resulted in 0.66% optical induction. Irradiation of 1,3-cyclooctadiene (17) in the presence of 10 resulted in 11.3% optical induction. The singlet state of 10 could be effectively quenched by higher diene concentration, substantially reducing the optical yield. Irradiation of trans-1,2-diphenyl-cyclopropane (1) in the presence of 10 resulted in very low optical yields.

The mechanism by which triplet excited state allenes react in the vapor phase is investigated through both theory and experiment. Benzene …

Reaction Of Nickel With Soils And Goethite: Equilibrium And Kinetic Studies, Ahmed Ali Mehadi

Doctoral Dissertations

Reaction of nickel with soil B horizons under various ionic strengths, pH and temperature conditions was conducted using a batch kinetics method. The forward and reverse apparent rate constants were determined using computer simulation techniques. Thermodynamic parameters were calculated from the rate constants. Increase in soil pH and temperature increased the sorption of nickel, while increase in ionic strength decreased nickel sorption. The reactions were all spontaneous with negative standard free energies ($\Delta$G$\sp\circ$); soils having higher nickel sorption capacity were more negative. The free energy decreased with increase in pH. The enthalpy ($\Delta$H$\sp\circ$) and entropy ($\Delta$S$\sp\circ$) for the reactions were …

Studies Of Rotationally Inelastic Collisions In Argon + Hydrogen Fluoride, James J C Barrett

Doctoral Dissertations

In this dissertation we examine rotationally inelastic collisions involving an atom plus a diatom. We concentrate specifically on the Ar + HF system. In these investigations we employ a number of theoretical methods, including classical trajectories, quantum close-coupled calculations and semiclassical methods, to examine the differential cross sections in Ar + HF. We also investigate the effects of various "sudden" approximations on the scattering dynamics and the limitations of these approximations.

Through this work we were able to identify a new quantum feature in rotationally inelastic scattering. By studying the time evolution of transition amplitudes (rather than probabilities) we are …

The Association Properties Of Retroviral Integration Protein, Jacqueline Lei Coleman

Doctoral Dissertations

Retroviral Integration Protein (IN) has been shown to be both necessary and sufficient for the integration of reverse transcribed retroviral DNA into the host cell DNA. It has been demonstrated that self-association is required for proper function, yet little is known about the thermodynamic properties of this association. Analytical ultracentrifugation was used to determine the stoichiometries and free energies ($\Delta$G) of IN self association under various physical conditions. The best fit model of association in all glycerol-free conditions studied was a reversible monomer-dimer-tetramer. The addition of glycerol at concentrations of 8% (vol/vol) or greater significantly enhances the monomer-dimer formation so …

Coordination Chemistry Of Polyphosphoxane Rings, Xiaoyong Sun

Doctoral Dissertations

Substitution of triphosphoxane rings on metal complexes containing labile ligands, M(CO)$\sb4$NBD and $\rm MX\sb2L\sb2$ (X = Cl, Br, I; L = DME, THF, NBD) and thermal reactions of bis(dialkylamino)phosphine oxides with metal hexacarbonyls yielded the tri-, tetra-, and pentaphosphoxane ring complexes cis-$\rm M(CO)\sb4\lbrack R\sb2NPO\rbrack\sb3,$ cis-$\rm M(CO)\sb4\lbrack R\sb2NPO\rbrack\sb4,$ cis-$\rm M\sb2(CO)\sb8\lbrack R\sb2NPO\rbrack\sb4,$ cis-$\rm M\sb2(CO)\sb7\lbrack R\sb2NPO\rbrack\sb5,$ cis-$\rm MX\sb2\lbrack R\sb2NPO\rbrack\sb4,$ and cis-$\rm MX\sb2\lbrack R\sb2NPO\rbrack\sb5$ as the isolated products. The P$\sb4$O$\sb4$ rings in metal tetraphosphoxane complexes appear in six coordination modes including the 1,3-chelating, 1,5-chelating boat-boat, boat-chair conformation, 1,3,5,7-chelating boat-boat cage mode, twist-boat mode, and 1,3,5-tridentate mode bridging two metals. A novel Ni(O)-cage complex $\rm …

Kinetics And Mechanism Of Iron Oxidation In Apoferritin, Shujun Sun

Doctoral Dissertations

The enzymatic activity of horse spleen apoferritin in iron(II) oxidation was examined using microelectrode oximetry. The reaction exhibits saturation kinetics with respect to both Fe$\sp{2+}$ and O$\sb2$. The kinetics are discussed in terms of two mechanisms, one involving monomeric and the other dimeric iron protein complexes. In both instances Fe$\sp{2+}$ oxidation occurs in 1-electron steps. At increments of 50 Fe$\sp{2+}$/protein or less, all of the iron is oxidized via the protein ferroxidase site(s), independent of the amount of core already present. The results of these studies emphasize the role of the protein shell in all phases of core growth.

A …