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The limit of strength and toughness of steel

Description: The ideal structural steel combines high strength with high fracture toughness. This dissertation discusses the governing principles of strength and toughness, along with the approaches that can be used to improve these properties and the inherent limits to how strong and tough a steel can be.
Date: December 17, 2001
Creator: Guo, Zhen
Partner: UNT Libraries Government Documents Department
open access

Tuning the Superconducting Properties of Magnesium Diboride

Description: This work is presented in the following order: A review of the relevant physics and discussion of theoretical predictions for a two gap superconducting compound is given in chapter 2. Chapter 3 provides a review of the basic properties of MgB{sub 2}. Details of sample synthesis and characterization are given in chapter 4. Chapter 5 presents normal state and superconducting properties of Mg(B{sub 1-x}C{sub x}){sub 2} wires. Attempts to increase critical current densities in filaments via titaniu… more
Date: December 17, 2005
Creator: Wilke, Rudeger Heinrich Theoderich
Partner: UNT Libraries Government Documents Department
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Reduction of Solvent Effect in Reverse Phase Gradient Elution LC-ICP-MS

Description: Quantification in liquid chromatography (LC) is becoming very important as more researchers are using LC, not as an analytical tool itself, but as a sample introduction system for other analytical instruments. The ability of LC instrumentation to quickly separate a wide variety of compounds makes it ideal for analysis of complex mixtures. For elemental speciation, LC is joined with inductively coupled plasma mass spectrometry (ICP-MS) to separate and detect metal-containing, organic compounds i… more
Date: December 17, 2005
Creator: Sullivan, Patrick Allen
Partner: UNT Libraries Government Documents Department
open access

Cool Cluster Correctly Correlated

Description: Atomic clusters are unique objects, which occupy an intermediate position between atoms and condensed matter systems. For a long time it was thought that physical and chemical properties of atomic dusters monotonically change with increasing size of the cluster from a single atom to a condensed matter system. However, recently it has become clear that many properties of atomic clusters can change drastically with the size of the clusters. Because physical and chemical properties of clusters can… more
Date: December 17, 2005
Creator: Varganov, Sergey Aleksandrovich
Partner: UNT Libraries Government Documents Department
open access

Exploration of Simple Analytical Approaches for Rapid Detection of Pathogenic Bacteria

Description: Many of the current methods for pathogenic bacterial detection require long sample-preparation and analysis time, as well as complex instrumentation. This dissertation explores simple analytical approaches (e.g., flow cytometry and diffuse reflectance spectroscopy) that may be applied towards ideal requirements of a microbial detection system, through method and instrumentation development, and by the creation and characterization of immunosensing platforms. This dissertation is organized into … more
Date: December 17, 2005
Creator: Rahman, Salma
Partner: UNT Libraries Government Documents Department
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Theoretical Studies of Pb on Si(111) and Si(100), Global Search for H-Passivated Si Nanowires, and Construction of highly Localized Quasiatomic Minimal Basis Orbitals for Mo

Description: Metal on semiconductor surfaces has been the topic of intense studies due to its technological applications. As nano-devices shrink in size, the conventional understanding of electronic devices are no longer applicable as quantum effects start to play an important role in the behavior of the devices. At the same time, when structures are approaching atomic scale, the precise fabrication by lithographic techniques, for example, are not even applicable. Very often, the fabrication of regular stru… more
Date: December 17, 2005
Creator: Chan, Tzu-Liang
Partner: UNT Libraries Government Documents Department
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Transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates: Catalysts for asymmetric olefin hydroamination and acceptorless alcohol decarbonylation

Description: The research presented and discussed in this dissertation involves the synthesis of transition metal complexes of oxazolinylboranes and cyclopentadienyl-bis(oxazolinyl)borates, and their application in catalytic enantioselective olefin hydroamination and acceptorless alcohol decarbonylation. Neutral oxazolinylboranes are excellent synthetic intermediates for preparing new borate ligands and also developing organometallic complexes. Achiral and optically active bis(oxazolinyl)phenylboranes are s… more
Date: December 17, 2012
Creator: Manna, Kuntal
Partner: UNT Libraries Government Documents Department
open access

A High-Energy, Ultrashort-Pulse X-Ray System for the Dynamic Study of Heavy, Dense Materials

Description: Thomson-scattering based x-ray radiation sources, in which a laser beam is scattered off a relativistic electron beam resulting in a high-energy x-ray beam, are currently being developed by several groups around the world to enable studies of dynamic material properties which require temporal resolution on the order of tens of femtoseconds to tens of picoseconds. These sources offer pulses that are shorter than available from synchrotrons, more tunable than available from so-called Ka sources, … more
Date: September 17, 2004
Creator: Gibson, D J
Partner: UNT Libraries Government Documents Department
open access

Experiential Education in Groundwater Hydrology: Bridging the Technical-Policy-Populace Gap Final Report

Description: It is well recognized that half the countries in the world will face significant fresh water shortages in the next 20 years, due largely to growing populations and increased agricultural and industrial demands (Gleick, 1997). These shortages will significantly limit economic growth, decrease the quality of life and human health for billions of people, and could potentially lead to violence and conflict over securing scarce supplies of water. In the Middle East, groundwater represents an importa… more
Date: July 17, 2003
Creator: Tompson, A. F. B.; Maxwell, R. M.; Richardson, J. H.; El Sha'r, W. A.; Rihani, J. F. F.; El-Naser, H. et al.
Partner: UNT Libraries Government Documents Department
open access

Length-Limited Data Transformation and Compression

Description: Scientific computation is used for the simulation of increasingly complex phenomena, and generates data sets of ever increasing size, often on the order of terabytes. All of this data creates difficulties. Several problems that have been identified are (1) the inability to effectively handle the massive amounts of data created, (2) the inability to get the data off the computer and into storage fast enough, and (3) the inability of a remote user to easily obtain a rendered image of the data res… more
Date: May 17, 2005
Creator: Senecal, J G
Partner: UNT Libraries Government Documents Department
open access

Structural Investigations of Surfaces and Orientation-SpecificPhenomena in Nanocrystals and Their Assemblies

Description: Studies of colloidal nanocrystals and their assemblies are presented. Two of these studies concern the atomic-level structural characterization of the surfaces, interfaces, and interiors present in II-VI semiconductor nanorods. The third study investigates the crystallographic arrangement of cobalt nanocrystals in self-assembled aggregates. Crystallographically-aligned assemblies of colloidal CdSe nanorods are examined with linearly-polarized Se-EXAFS spectroscopy, which probes bonding along di… more
Date: June 17, 2006
Creator: Aruguete, Deborah Michiko
Partner: UNT Libraries Government Documents Department
open access

Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

Description: In the last two decades, the field of nanoscience andnanotechnology has witnessed tremendous advancement in the synthesis andapplication of group II-VI colloidal nanocrystals. The synthesis based onhigh temperature decomposition of organometallic precursors has becomeone of the most successful methods of making group II-VI colloidalnanocrystals. This methodis first demonstrated by Bawendi and coworkersin 1993 to prepare cadmium chalcogenide colloidal quantum dots and laterextended by others to … more
Date: May 17, 2007
Creator: Liu, Haitao
Partner: UNT Libraries Government Documents Department
open access

Chip-Scale Bioassays Based on Surface-Enhanced Raman Scattering: Fundamentals and Applications

Description: This work explores the development and application of chip-scale bioassays based on surface-enhanced Raman scattering (SERS) for high throughput and high sensitivity analysis of biomolecules. The size effect of gold nanoparticles on the intensity of SERS is first presented. A sandwich immunoassay was performed using Raman-labeled immunogold nanoparticles with various sizes. The SERS responses were correlated to particle densities, which were obtained by atomic force microscopy (AFM). The respon… more
Date: December 17, 2005
Creator: Park, Hye-Young
Partner: UNT Libraries Government Documents Department
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Synthesis and Characterization of Stimuli Responsive Block Copolymers, Self-Assembly Behavior and Applications

Description: The central theme of this thesis work is to develop new block copolymer materials for biomedical applications. While there are many reports of stimuli-responsive amphiphilic [19-21] and crosslinked hydrogel materials [22], the development of an in situ gel forming, pH responsive pentablock copolymer is a novel contribution to the field, Figure 1.1 is a sketch of an ABCBA pentablock copolymer. The A blocks are cationic tertiary amine methacrylates blocked to a central Pluronic F127 triblock copo… more
Date: December 17, 2005
Creator: Determan, Michael Duane
Partner: UNT Libraries Government Documents Department
open access

Single-Molecule Imaging of DNAs with Sticky Ends at Water/Fused Silica Interface

Description: Total internal reflection fluorescence microscopy (TIRFM) was used to study intermolecular interactions of DNAs with unpaired (sticky) ends of different lengths at water/fused silica interface at the single-molecule level. Evanescent field residence time, linear velocity and adsorption/desorption frequency were measured in a microchannel for individual DNA molecules from T7, Lambda, and PSP3 phages at various pH values. The longest residence times and the highest adsorption/desorption frequenci… more
Date: December 17, 2005
Creator: Isailovic, Slavica
Partner: UNT Libraries Government Documents Department
open access

Two-dimensional nuclear magnetic resonance of quadrupolar systems

Description: This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to … more
Date: September 17, 1997
Creator: Wang, Shuanhu
Partner: UNT Libraries Government Documents Department
open access

Fundamental studies of supported bimetallic catalysts by NMR spectroscopy

Description: Various hydrogenation reactions on transition metals are important commercially whereas certain hydrogenolysis reactions are useful from fundamental point of view. Understanding the hydrogen mobility and kinetics of adsorption-desorption of hydrogen is important in understanding the mechanisms of such reactions involving hydrogen. The kinetics of hydrogen chemisorption was studied by means of selective excitation NMR on silica supported Pt, Rh and Pt-Rh catalysts. The activation energy of hydro… more
Date: October 17, 1996
Creator: Savargaonkar, N.
Partner: UNT Libraries Government Documents Department
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Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

Description: This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have… more
Date: December 17, 1999
Creator: Zanni, Martin T.
Partner: UNT Libraries Government Documents Department
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