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The Effect of Oxygen Contamination on the Amorphous Structure of Thermally Sprayed Coatings of Cu47Ti33Zr11Ni8Si1

Description: this research has shown that it is possible to deposit coatings of gas atomized Cu{sub 47}Ti{sub 33}Zr{sub 11}Ni{sub 8}Si{sub 1} powders containing various levels of oxygen contamination using plasma arc spray methods. The structure of the coating was found to depend primarily on the spray environment, with an argon atmosphere producing the most amorphous samples for a given starting powder. The oxygen content of the coatings reflected the relative levels of the oxygen contamination in the star… more
Date: May 27, 2002
Creator: Besser, Matthew Frank
Partner: UNT Libraries Government Documents Department
open access

Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

Description: The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles … more
Date: June 27, 2002
Creator: Harnisch, Jennifer Anne
Partner: UNT Libraries Government Documents Department
open access

Modeling of Photonic Band Gap Crystals and Applications

Description: In this work, the authors have undertaken a theoretical approach to the complex problem of modeling the flow of electromagnetic waves in photonic crystals. The focus is to address the feasibility of using the exciting phenomena of photonic gaps (PBG) in actual applications. The authors start by providing analytical derivations of the computational electromagnetic methods used in their work. They also present a detailed explanation of the physics underlying each approach, as well as a comparativ… more
Date: August 27, 2002
Creator: El-Kady, Ihab Fathy
Partner: UNT Libraries Government Documents Department
open access

Organusulfur Catalysis With Reduced Molybdenum Sulfides Containing the Mo6S8 Cluster

Description: Industrial synthesis of sulfur-containing organic chemicals basically focuses on the broad categories of mercaptans (thiols), alkylsulfides (thioethers), polysulfides, and thiophenes. Of the organo-sulfur compounds produced, by far the most important in terms of quantities produced is methyl mercaptan (methanethiol or MeSH), which is produced mainly for the downstream production of methionine and methanesulfonyl chloride. Higher thiols are also used in the manufacture of rubber and plastics as … more
Date: August 27, 2002
Creator: Paskach, Thomas Jay
Partner: UNT Libraries Government Documents Department
open access

Analysis of Gd5(Si2Ge2) Microstructure and Phase Transition

Description: With the recent discovery of the giant magnetocaloric effect and the beginning of extensive research on the properties of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, a necessity has developed for a better understanding of the microstructure and crystal structure of this family of rare earth compounds with startling phenomenological properties. The aim of this research is to characterize the microstructure of the Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}, with X {approx_equal} 2 and its phase change by… more
Date: June 27, 2002
Creator: Meyers, John Scott
Partner: UNT Libraries Government Documents Department
open access

Length Scale Correlations of Cellular Microstructures in Directionally Solidified Binary System

Description: In a cellular array, a range of primary spacing is found to be stable under given growth conditions. Since a strong coupling of solute field exists between the neighboring cells, primary spacing variation should also influence other microstructure features such as cell shape and cell length. The existence of multiple solutions is examined in this study both theoretically as well as experimentally. A theoretical model is developed that identifies and relates four important microstructural length… more
Date: June 27, 2002
Creator: Shen, Yunxue
Partner: UNT Libraries Government Documents Department
open access

Bioanalytical Applications of Fluorescence Line-Narrowing and Non-Line-Narrowing Spectroscopy Interfaced with Capillary Electrophoresis and High-Performance Liquid Chromatography

Description: Capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) are widely used analytical separation techniques with many applications in chemical, biochemical, and biomedical sciences. Conventional analyte identification in these techniques is based on retention/migration times of standards; requiring a high degree of reproducibility, availability of reliable standards, and absence of coelution. From this, several new information-rich detection methods (also known as hyphenat… more
Date: June 27, 2002
Creator: Roberts, Kenneth Paul
Partner: UNT Libraries Government Documents Department
open access

Nitric Oxide in Astrocyte-Neuron Signaling

Description: Astrocytes, a subtype of glial cell, have recently been shown to exhibit Ca{sup 2+} elevations in response to neurotransmitters. A Ca{sup 2+} elevation can propagate to adjacent astrocytes as a Ca{sup 2+} wave, which allows an astrocyte to communicate with its neighbors. Additionally, glutamate can be released from astrocytes via a Ca{sup 2+}-dependent mechanism, thus modulating neuronal activity and synaptic transmission. In this dissertation, the author investigated the roles of another endog… more
Date: June 27, 2002
Creator: Li, Nianzhen
Partner: UNT Libraries Government Documents Department
open access

Development of Novel Polymeric Materials for Gene Therapy and pH-Sensitive Drug Delivery: Modeling, Synthesis, Characterization, and Analysis

Description: The underlying theme of this thesis is the use of polymeric materials in bioapplications. Chapters 2-5 either develop a fundamental understanding of current materials used for bioapplications or establish protocols and procedures used in characterizing and synthesizing novel materials. In chapters 6 and 7 these principles and procedures are applied to the development of materials to be used for gene therapy and drug delivery. Chapter one is an introduction to the ideas that will be necessary to… more
Date: August 27, 2002
Creator: Anderson, Brian Curtis
Partner: UNT Libraries Government Documents Department
open access

Magnetic X-Ray Scattering Study of GdCo2Ge2 and NdCo2Ge2

Description: The results of magnetic x-ray resonant exchange scattering (XRES) experiments are important to the development of an understanding of magnetic interactions in materials. The advantages of high Q resolution, polarization analysis, and the ability to study many different types of materials make it a vital tool in the field of condensed matter physics. Though the concept of XRES was put forth by Platzman and Tzoar in 1970, the technique did not gain much attention until the work of Gibbs and McWha… more
Date: August 27, 2002
Creator: Good, William
Partner: UNT Libraries Government Documents Department
open access

The Theory of Random Laser Systems

Description: Studies of random laser systems are a new direction with promising potential applications and theoretical interest. The research is based on the theories of localization and laser physics. So far, the research shows that there are random lasing modes inside the systems which is quite different from the common laser systems. From the properties of the random lasing modes, they can understand the phenomena observed in the experiments, such as multi-peak and anisotropic spectrum, lasing mode numbe… more
Date: June 27, 2002
Creator: Jiang, Xunya
Partner: UNT Libraries Government Documents Department
open access

Nonphotochemical Hole-Burning Studies of Energy Transfer Dynamics in Antenna Complexes of Photosynthetic Bacteria

Description: This thesis contains the candidate's original work on excitonic structure and energy transfer dynamics of two bacterial antenna complexes as studied using spectral hole-burning spectroscopy. The general introduction is divided into two chapters (1 and 2). Chapter 1 provides background material on photosynthesis and bacterial antenna complexes with emphasis on the two bacterial antenna systems related to the thesis research. Chapter 2 reviews the underlying principles and mechanism of persistent… more
Date: June 27, 2002
Creator: Matsuzaki, Satoshi
Partner: UNT Libraries Government Documents Department
open access

Radiative transitions in InGaN quantum-well structures

Description: InGaN based light emitting devices demonstrate excellent luminescence properties and have great potential in lighting applications. Though these devices are already being produced on an industrial scale, the nature of their radiative transition is still not well understood. In particular, the role of the huge (>1MV/cm), built-in electric field in these transitions is still under debate. The luminescence characteristics of InGaN quantum well structures were investigated as a function of excit… more
Date: June 27, 2002
Creator: Shapiro, Noad Asaf
Partner: UNT Libraries Government Documents Department
open access

Nonphotochemical Hole-Burning Imaging Studies of in vitro Carcinoma and Normal Cells Utilizing a Mitochondrial Specific Dye

Description: Low temperature Nonphotochemical Hole Burning (NPHB) Spectroscopy of the dye rhodamine 800 (MF680) was applied for the purpose of discerning differences between cultured normal and carcinoma ovarian surface epithelial (OSE) cells. Both the cell lines were developed and characterized at the Mayo Clinic (Rochester, MN), with the normal cell line having been transfected with a strain of temperature sensitive Simian Virus 40 Large T Antigen (SV40) for the purpose of extending the life of the cell c… more
Date: June 27, 2002
Creator: Walsh, Richard Joseph
Partner: UNT Libraries Government Documents Department
open access

Implementation of MPICH on Top of MP{_}Lite

Description: The goal of this thesis is to develop a new Channel Interface device for the MPICH Implementation of the MPI (Message Passing Interface) standard using MP{_}Lite. MP{_}Lite is a lightweight message-passing library that is not a full MPI implementation, but offers high performance MPICH (Message Passing Interface CHameleon) is a full implementation of the MPI standard that has the p4 library as the underlying communication device for TCP/IP networks. By integrating MP{_}Lite as a Channel Interfa… more
Date: June 27, 2002
Creator: Selvarajan, Shoba
Partner: UNT Libraries Government Documents Department
open access

Imaging Catalytic Surfaces by Multiplexed Capillary Electrophoresis With Absorption Detection

Description: A new technique for in situ imaging and screening heterogeneous catalysts by using multiplexed capillary electrophoresis with absorption detection was developed. By bundling the inlets of a large number of capillaries, an imaging probe can be created that can be used to sample products formed directly from a catalytic surface with high spatial resolution. In this work, they used surfaces made of platinum, iron or gold wires as model catalytic surfaces for imaging. Various shapes were recorded i… more
Date: August 27, 2002
Creator: Christodoulou, Michael
Partner: UNT Libraries Government Documents Department
open access

Remote Field Eddy Current Probes for the Detection of Stress Corrosion in Transmission Pipelines

Description: Magnetic flux leakage (MFL) is a technique used widely in non-destructive testing (NDT) of natural gas and petroleum transmission pipelines. This inspection method relies on magnetizing the pipe-wall in axial direction. The MFL inspection tool is equipped with an array of Hall sensors located around the circumference of the pipe, which registers the flux leakage caused by any defects present in the pipe-wall. Currently, the tool magnetizes the pipewall in axial direction making it largely insen… more
Date: August 27, 2002
Creator: Ivanov, Plamen Alexandroz
Partner: UNT Libraries Government Documents Department
open access

Hydrogen Storage Properties of Lithium Aluminohydride Modified by Dopants and Mechanochemistry

Description: Alkali metal aluminohydrides have high potential as solid hydrogen storage materials. They have been known for their irreversible dehydrogenation process below 100 atm until Bogdanovic et al succeeded in the re-hydrogenation of NaAlH{sub 4} below 70 atm. They achieved 4 wt.% H{sub 2} reversible capacity by doping NaAlH{sub 4} with Ti and/or Fe organo-metallic compounds as catalysts. This suggests that other alkali and, possibly alkaline earth metal aluminohydrides can be used for reversible hyd… more
Date: June 27, 2002
Creator: Hosokawa, Ketia
Partner: UNT Libraries Government Documents Department
open access

Pathway and Surface Mechanism Studies of 1,3-butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts

Description: The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9-14 m{sup 2}/g, and compositions were within the solid solution regime, i.e. below 15.0 mol % MoO{sub 3}/(MoO{sub 3} + V{sub 2}O{sub 5}). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V{sup +4} and were further reduced in 1,3-butadiene oxidati… more
Date: May 27, 2002
Creator: Schroeder, William David
Partner: UNT Libraries Government Documents Department
open access

Electrocatalytic Materials and Techniques for the Anodic Oxidation of Various Organic Compounds

Description: The focus of this thesis was first to characterize and improve the applicability of Fe(III) and Bi(V) doped PbO{sub 2} film electrodes for use in anodic O-transfer reactions of toxic and waste organic compounds, e.g. phenol, aniline, benzene, and naphthalene. Further, they investigated the use of alternative solution/electrode interfacial excitation techniques to enhance the performance of these electrodes for remediation and electrosynthetic applications. Finally, they have attempted to identi… more
Date: June 27, 2002
Creator: Treimer, Stephen Everett
Partner: UNT Libraries Government Documents Department
open access

Development of Novel Electrode Materials for the Electrocatalysis of Oxygen-Transfer and Hydrogen-Transfer Reactions

Description: Throughout this thesis, the fundamental aspects involved in the electrocatalysis of anodic O-transfer reactions and cathodic H-transfer reactions have been studied. The investigation into anodic O-transfer reactions at undoped and Fe(III)[doped MnO{sub 2} films] revealed that MnO{sub 2} film electrodes prepared by a cycling voltammetry deposition show improved response for DMSO oxidation at the film electrodes vs. the Au substrate. Doping of the MnO{sub 2} films with Fe(III) further enhanced el… more
Date: August 27, 2002
Creator: Simpson, Brett Kimball
Partner: UNT Libraries Government Documents Department
open access

High Throughput Sample Preparation and Analysis for DNA Sequencing, PCR and Combinatorial Screening of Catalysis Based on Capillary Array Technique

Description: Sample preparation has been one of the major bottlenecks for many high throughput analyses. The purpose of this research was to develop new sample preparation and integration approach for DNA sequencing, PCR based DNA analysis and combinatorial screening of homogeneous catalysis based on multiplexed capillary electrophoresis with laser induced fluorescence or imaging UV absorption detection. The author first introduced a method to integrate the front-end tasks to DNA capillary-array sequencers.… more
Date: May 27, 2002
Creator: Zhang, Yonghua
Partner: UNT Libraries Government Documents Department
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