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Sum Frequency Generation Vibrational Spectroscopy Studies on ModelPeptide Adsorption at the Hydrophobic Solid-Water and HydrophilicSolid-Water Interfaces

Description: Sum frequency generation (SFG) vibrational spectroscopy has been used to study the interfacial structure of several polypeptides and amino acids adsorbed to hydrophobic and hydrophilic surfaces under a variety of experimental conditions. Peptide sequence, peptide chain length, peptide hydrophobicity, peptide side-chain type, surface hydrophobicity, and solution ionic strength all affect an adsorbed peptide's interfacial structure. Herein, it is demonstrated that with the choice of simple, model… more
Date: December 19, 2007
Creator: York, Roger L.
Partner: UNT Libraries Government Documents Department
open access

High-Pressure Catalytic Reactions of C6 Hydrocarbons on PlatinumSingle-Crystals and nanoparticles: A Sum Frequency Generation VibrationalSpectroscopic and Kinetic Study

Description: Catalytic reactions of cyclohexene, benzene, n-hexane, 2-methylpentane, 3-methylpentane, and 1-hexene on platinum catalysts were monitored in situ via sum frequency generation (SFG) vibrational spectroscopy and gas chromatography (GC). SFG is a surface specific vibrational spectroscopic tool capable of monitoring submonolayer coverages under reaction conditions without gas-phase interference. SFG was used to identify the surface intermediates present during catalytic processes on Pt(111) and Pt… more
Date: December 19, 2007
Creator: Bratlie, Kaitlin
Partner: UNT Libraries Government Documents Department
open access

X-ray resonant magnetic scattering investigations of hexagonal multiferroics RMnO3 (R = Dy, Ho, Er)

Description: Electricity and magnetism were unified into a common subject by James Clerk Maxwell in the nineteenth century yielding the electromagnetic theory. Four equations govern the dynamics of electric charges and magnetic fields, commonly known as Maxwell's equations. Maxwell's equations demonstrate that an accelerated charged particle can produce magnetic fields and a time varying magnetic field can induce a voltage - thereby linking the two phenomena. However, in solids, electric and magnetic orderi… more
Date: December 19, 2009
Creator: Nandi, Shibabrata
Partner: UNT Libraries Government Documents Department
open access

Considering value of information when using CFD in design

Description: This thesis presents an approach to find lower resolution CFD models that can accurately lead a designer to a correct decision at a lower computational cost. High-fidelity CFD models often contain too much information and come at a higher computational cost, limiting the designs a designer can test and how much optimization can be performed on the design. Lower model resolution is commonly used to reduce computational time. However there are no clear guidelines on how much model accuracy is req… more
Date: December 19, 2009
Creator: Misra, John Satprim
Partner: UNT Libraries Government Documents Department
open access

Evaluation of bisphenol E cyanate ester for the resin-injection repair of advanced composites

Description: This thesis is a compilation of a general introduction and literature review that ties together the subsequent chapters which consist of two journal articles that have yet to be submitted for publication. The overall topic relates to the evaluation and application of a new class of cyanate ester resin with unique properties that lend it applicable to use as a resin for injection repair of high glass transition temperature polymer matrix composites. The first article (Chapter 2) details the eval… more
Date: December 19, 2009
Creator: Lio, Wilber Yaote
Partner: UNT Libraries Government Documents Department
open access

Solvation!

Description: This dissertation consists of two closely related parts: theory development and coding of correlation effects in a model potential for solvation, and study of solvent effects on chemical reactions and processes. The effective fragment potential (EFP) method has been re-parameterized, using density functional theory (DFT), more specifically, the B3LYP functional. The DFT based EFP method includes short-range correlation effects; hence it is a first step in incorporating the treatment of correlat… more
Date: December 19, 2004
Creator: Adamovic, Ivana
Partner: UNT Libraries Government Documents Department
open access

Oxidation Behavior and Chlorination Treatment to Improve Oxidation Resistance of Nb-Mo-Si-B Alloys

Description: This thesis is written in an alternate format. The thesis is composed of a general introduction, two original manuscripts, and a general conclusion. References cited within each chapter are given at the end of each chapter. The general introduction starts with the driving force behind this research, and gives an overview of previous work on boron doped molybdenum silicides, Nb/Nb{sub 5}Si{sub 3} composites, boron modified niobium silicides and molybdenum niobium silicides. Chapter 2 focuses on … more
Date: December 19, 2004
Creator: Behrani, Vikas
Partner: UNT Libraries Government Documents Department
open access

New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

Description: The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I{sub 2}, ICl, PhSeCl, PhSCl and p-O{sub 2}NC{sub 6}H{sub 4}SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This meth… more
Date: December 19, 2004
Creator: Huang, Qinhua
Partner: UNT Libraries Government Documents Department
open access

Group 4 Metalloporphyrin diolato Complexes and Catalytic Application of Metalloporphyrins and Related Transition Metal Complexes

Description: In this work, the first examples of group 4 metalloporphyrin 1,2-diolato complexes were synthesized through a number of strategies. In general, treatment of imido metalloporphyrin complexes, (TTP)M=NR, (M = Ti, Zr, Hf), with vicinal diols led to the formation of a series of diolato complexes. Alternatively, the chelating pinacolate complexes could be prepared by metathesis of (TTP)MCl{sub 2} (M = Ti, Hf) with disodium pinacolate. These complexes were found to undergo C-C cleavage reactions to p… more
Date: December 19, 2004
Creator: Du, Guodong
Partner: UNT Libraries Government Documents Department
open access

Hole Burning Imaging Studies of Cancerous and Analogous Normal Ovarian Tissues Utilizing Organelle Specific Dyes

Description: Presented in this dissertation is the successful demonstration that nonphotochemical hole burning (NPWB) imaging can be used to study in vitro tissue cellular systems for discerning differences in cellular ultrastructures due to cancer development. This has been accomplished with the surgically removed cancerous ovarian and analogous normal peritoneal tissues from the same patient and the application of a fluorescent mitochondrion specific dye, Molecular Probe MitoFluor Far Red 680 (MF680), com… more
Date: December 19, 2004
Creator: Matsuzaki, Satoshi
Partner: UNT Libraries Government Documents Department
open access

Solidification at the High and Low Rate Extreme

Description: The microstructures formed upon solidification are strongly influenced by the imposed growth rates on an alloy system. Depending on the characteristics of the solidification process, a wide range of growth rates is accessible. The prevailing solidification mechanisms, and thus the final microstructure of the alloy, are governed by these imposed growth rates. At the high rate extreme, for instance, one can have access to novel microstructures that are unattainable at low growth rates. While the … more
Date: December 19, 2004
Creator: Meco, Halim
Partner: UNT Libraries Government Documents Department
open access

A Performance Comparison of Tree and Ring Topologies in Distributed System

Description: A distributed system is a collection of computers that are connected via a communication network. Distributed systems have become commonplace due to the wide availability of low-cost, high performance computers and network devices. However, the management infrastructure often does not scale well when distributed systems get very large. Some of the considerations in building a distributed system are the choice of the network topology and the method used to construct the distributed system so as … more
Date: December 19, 2005
Creator: Huang, Min
Partner: UNT Libraries Government Documents Department
open access

Fabrication of Ceramic Layer-by-Layer Infrared Wavelength Photonic Band Gap Crystals

Description: Photonic band gap (PBG) crystals, also known as photonic crystals, are periodic dielectric structures which form a photonic band gap that prohibit the propagation of electromagnetic (EM) waves of certain frequencies at any incident angles. Photonic crystals have several potential applications including zero-threshold semiconductor lasers, the inhibition of spontaneous emission, dielectric mirrors, and wavelength filters. If defect states are introduced in the crystals, light can be guided from … more
Date: December 19, 2004
Creator: Kang, Henry Hao-Chuan
Partner: UNT Libraries Government Documents Department
open access

Benchmarking: More Aspects of High Performance Computing

Description: The original HPL algorithm makes the assumption that all data can be fit entirely in the main memory. This assumption will obviously give a good performance due to the absence of disk I/O. However, not all applications can fit their entire data in memory. These applications which require a fair amount of I/O to move data to and from main memory and secondary storage, are more indicative of usage of an Massively Parallel Processor (MPP) System. Given this scenario a well designed I/O architectur… more
Date: December 19, 2004
Creator: Ravindrudu, Rahul
Partner: UNT Libraries Government Documents Department
open access

Coupling Temperature Control with Electrochemically Modulated Liquid Chromatography: Fundamental Aspects and Applications

Description: The primary focus of the doctoral research presented herein has been the integration of temperature control into electrochemically modulated liquid chromatography (EMLC). The combination of temperature control and the tunable characteristics of carbonaceous EMLC stationary phases have been invaluable in deciphering the subtleties of the retention mechanism. The effects of temperature and E{sub app} on the retention of several naphthalene disulfonates were therefore examined by the van' Hoff rel… more
Date: December 19, 2004
Creator: Ponton, Lisa M.
Partner: UNT Libraries Government Documents Department
open access

Morphological Control of Multifunctional Mesoporous Silica Nanomaterials for Catalysis Applications

Description: I found an efficient method to control the morphology of the organically monofunctionalized mesoporous silica materials by introducing different types of organoalkoxysilanes in a base-catalyzed co-condensation reaction. The monofunctionalized materials exhibit different particle morphologies relative to the pure MCM-41 material. The concentration dependence of the morphology is a critical factor to determine the final particle shape. A proposed mechanism of the shape evolution is also offered. … more
Date: December 19, 2004
Creator: Huh, Seong
Partner: UNT Libraries Government Documents Department
open access

Development of Chiral LC-MS Methods for small Molecules and Their Applications in the Analysis of Enantiomeric Composition and Pharmacokinetic Studies

Description: The purpose of this research was to develop sensitive LC-MS methods for enantiomeric separation and detection, and then apply these methods for determination of enantiomeric composition and for the study of pharmacokinetic and pharmacodynamic properties of a chiral nutraceutical. Our first study, evaluated the use of reverse phase and polar organic mode for chiral LC-API/MS method development. Reverse phase methods containing high water were found to decrease ionization efficiency in electrospr… more
Date: December 19, 2004
Creator: Desai, Meera Jay
Partner: UNT Libraries Government Documents Department
open access

Microstructural Development in Al-Si Powder During Rapid Solidification

Description: Powder metallurgy has become an increasingly important form of metal processing because of its ability to produce materials with superior mechanical properties. These properties are due in part to the unique and often desirable microstructures which arise as a result of the extreme levels of undercooling achieved, especially in the finest size powder, and the subsequent rapid solidification which occurs. A better understanding of the fundamental processes of nucleation and growth is required to… more
Date: December 19, 2004
Creator: Genau, Amber Lynn
Partner: UNT Libraries Government Documents Department
open access

Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd5(SixGe1-x)4

Description: Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} for x 0 {approx} 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material pr… more
Date: December 19, 2004
Creator: Han, Mangui
Partner: UNT Libraries Government Documents Department
open access

Performance Study and Dynamic Optimization Design for Thread Pool Systems

Description: Thread pools have been widely used by many multithreaded applications. However, the determination of the pool size according to the application behavior still remains problematic. To automate this process, in this thesis we have developed a set of performance metrics for quantitatively analyzing thread pool performance. For our experiments, we built a thread pool system which provides a general framework for thread pool research. Based on this simulation environment, we studied the performance … more
Date: December 19, 2004
Creator: Xu, Dongping
Partner: UNT Libraries Government Documents Department
open access

Quantum Chemistry, and Eclectic Mix: From Silicon Carbide to Size Consistency

Description: Chemistry is a field of great breadth and variety. It is this diversity that makes for both an interesting and challenging field. My interests have spanned three major areas of theoretical chemistry: applications, method development, and method evaluation. The topics presented in this thesis are as follows: (1) a multi-reference study of the geometries and relative energies of four atom silicon carbide clusters in the gas phase; (2) the reaction of acetylene on the Si(100)-(2x1) surface; (3) an… more
Date: December 19, 2004
Creator: Rintelman, Jamie Marie
Partner: UNT Libraries Government Documents Department
open access

Gas Sensors Based on Ceramic p-n Heterocontacts

Description: Ceramic p-n heterocontacts based on CuO/ZnO were successfully synthesized and a systematic study of their hydrogen sensitivity was conducted. The sensitivity and response rates of CuO/ZnO sensors were studied utilizing current-voltage, current-time, and impedance spectroscopy measurements. The heterocontacts showed well-defined rectifying characteristics and were observed to detect hydrogen via both dc and ac measurements. Surface coverage data were derived from current-time measurements which … more
Date: December 19, 2004
Creator: Aygun, Seymen Murat
Partner: UNT Libraries Government Documents Department
open access

The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles

Description: Metal matrix composites (MMC), especially Al matrix composites, received a lot of attention during many years of research because of their promise for the development of automotive and aerospace materials with improved properties and performance, such as lighter weight and better structural properties, improved thermal conductivity and wear resistance. In order to make the MMC materials more viable in various applications, current research efforts on the MMCs should continue to focus on two imp… more
Date: December 19, 2004
Creator: Tang, Fei
Partner: UNT Libraries Government Documents Department
open access

Photoemission Study of the Rare Earth Intermetallic Compounds: RNi2Ge2 (R=Eu, Gd)

Description: EuNi{sub 2}Ge{sub 2} and GdNi{sub 2}Ge{sub 2} are two members of the RT{sub 2}X{sub 2} (R = rare earth, T = transition metal and X = Si, Ge) family of intermetallic compounds, which has been studied since the early 1980s. These ternary rare-earth intermetallic compounds with the tetragonal ThCr{sub 2}Si{sub 2} structure are known for their wide variety of magnetic properties, Extensive studies of the RT{sub 2}X{sub 2} series can be found in Refs [ 1,2,3]. The magnetic properties of the rare-ear… more
Date: December 19, 2004
Creator: Park, Jongik
Partner: UNT Libraries Government Documents Department
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