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Coupling of the 4f Electrons in Lanthanide Molecules

Description: (C5Me5)2LnOTf where Ln = La, Ce, Sm, Gd, and Yb have been synthesized and these derivatives are good starting materials for the synthesis of (C5Me5)2LnX derivatives. (C5Me5)2Ln(2,2'-bipyridine), where Ln = La, Ce, Sm, and Gd, along with several methylated bipyridine analogues have been synthesized and their magnetic moments have been measured as a function of temperature. In lanthanum, cerium, and gadolinium complexes the bipyridine ligand ligand is unequivocally the radical anion, and the obse… more
Date: September 12, 2008
Creator: Kazhdan, Daniel
Partner: UNT Libraries Government Documents Department
open access

A Search for Direct CP Violation in Two-Body Cabibbo-Suppressed Decays of Neutral Charmed Mesons

Description: Presented are the results of a search for direct CP violation in Cabibbo-suppressed decays of D{sup 0} to two charged daughters. The analysis described was performed on {approx}230 fb{sup -1} of the BABAR data sample, recorded at the Stanford Linear Accelerator Center and using the PEP-II electron storage rings. We measure CP asymmetries for decay to the KK and {pi}{pi} final states, as well as for the branching ratio, and develop a new technique for tagging-efficiency correction using the Cabi… more
Date: November 12, 2007
Creator: Flacco, Christian Julienne & /UC, Santa Cruz
Partner: UNT Libraries Government Documents Department
open access

Ultrafast Control of Magnetism in Ferromagnetic Semiconductors via Photoexcited Transient Carriers

Description: The field of spintronics offers perspectives for seamless integration of coupled and inter-tunable electrical and magnetic properties in a single device. For integration of the spin degree of freedom with current electronic technology, new semiconductors are needed that show electrically-tunable magnetic properties at room temperature and above. Dilute magnetic semiconductors derived from III-V compounds, like GaMnAs and InMnAs, show coupled and tunable magnetic, transport, and optical properti… more
Date: December 12, 2008
Creator: Cotoros, Ingrid A.
Partner: UNT Libraries Government Documents Department
open access

One- and two-dimensional infrared spectroscopic studies of solution-phase homogeneous catalysis and spin-forbidden reactions

Description: Understanding chemical reactions requires the knowledge of the elementary steps of breaking and making bonds, and often a variety of experimental techniques are needed to achieve this goal. The initial steps occur on the femto- through picosecond time-scales, requiring the use of ultrafast spectroscopic methods, while the rate-limiting steps often occur more slowly, requiring alternative techniques. Ultrafast one and two-dimensional infrared and step-scan FTIR spectroscopies are used to investi… more
Date: December 12, 2008
Creator: Sawyer, Karma Rae
Partner: UNT Libraries Government Documents Department
open access

New Synthetic Methods for Hypericum Natural Products

Description: Organic chemistry has served as a solid foundation for interdisciplinary research areas, such as molecular biology and medicinal chemistry. An understanding of the biological activities and structural elucidations of natural products can lead to the development of clinically valuable therapeutic options. The advancements of modern synthetic methodologies allow for more elaborate and concise natural product syntheses. The theme of this study centers on the synthesis of natural products with part… more
Date: December 12, 2006
Creator: Jeon, Insik
Partner: UNT Libraries Government Documents Department
open access

Phase Transformation in Cast Superaustenitic Stainless Steels

Description: Superaustenitic stainless steels constitute a group of Fe-based alloys that are compositionally balanced to have a purely austenitic matrix and exhibit favorable pitting and crevice corrosion resistant properties and mechanical strength. However, intermetallic precipitates such as sigma and Laves can form during casting or exposure to high-temperature processing, which degrade the corrosion and mechanical properties of the material. The goal of this study was to accurately characterize the soli… more
Date: December 12, 2006
Creator: Phillips, Nathaniel Steven Lee
Partner: UNT Libraries Government Documents Department
open access

Novel Aryne Chemistry in Organic Synthesis

Description: Arynes are among the most intensively studied systems in chemistry. However, many aspects of the chemistry of these reactive intermediates are not well understood yet and their use as reagents in synthetic organic chemistry has been somewhat limited, due to the harsh conditions needed to generate arynes and the often uncontrolled reactivity exhibited by these species. Recently, o-silylaryl triflates, which can generate the corresponding arynes under very mild reaction conditions, have been foun… more
Date: December 12, 2006
Creator: Liu, Zhijian
Partner: UNT Libraries Government Documents Department
open access

High Pressure Scanning Tunneling Microscopy and High PressureX-ray Photoemission Spectroscopy Studies of Adsorbate Structure,Composition and Mobility during Catalytic Reactions on A Model SingleCrystal

Description: Our research focuses on taking advantage of the ability of scanning tunneling microscopy (STM) to operate at high-temperatures and high-pressures while still providing real-time atomic resolution images. We also utilize high-pressure x-ray photoelectron spectroscopy (HPXPS) to monitor systems under identical conditions thus giving us chemical information to compare and contrast with the structural and dynamic data provided by STM.
Date: May 12, 2006
Creator: Montano, M. O.
Partner: UNT Libraries Government Documents Department
open access

Structure, ionic Conductivity and mobile Carrier Density in Fast Ionic Conducting Chalcogenide Glasses

Description: This thesis consists of six sections. The first section gives the basic research background on the ionic conduction mechanism in glass, polarization in the glass, and the method of determining the mobile carrier density in glass. The proposed work is also included in this section. The second section is a paper that characterizes the structure of MI + M{sub 2}S + (0.1 Ga{sub 2}S{sub 3} + 0.9 GeS{sub 2}) (M = Li, Na, K and Cs) glasses using Raman and IR spectroscopy. Since the ionic radius plays … more
Date: December 12, 2006
Creator: Yao, Wenlong
Partner: UNT Libraries Government Documents Department
open access

Ion Deflection for Final Optics in Laser Inertial Fusion Power Plants

Description: Left unprotected, both transmissive and reflective final optics in a laser-driven inertial fusion power plant would quickly fail from melting, pulsed thermal stress, or degradation of optical properties as a result of ion implantation. One potential option for mitigating this threat is to magnetically deflect the ions such that they are directed to a robust energy dump. In this paper we detail integrated studies that have been carried out to assess the viability of this approach for protecting … more
Date: December 12, 2005
Creator: Abbott, R P
Partner: UNT Libraries Government Documents Department
open access

Rational Ligand Design for U(VI) and Pu(IV)

Description: Nuclear power is an attractive alternative to hydrocarbon-based energy production at a time when moving away from carbon-producing processes is widely accepted as a significant developmental need. Hence, the radioactive actinide power sources for this industry are necessarily becoming more widespread, which is accompanied by the increased risk of exposure to both biological and environmental systems. This, in turn, requires the development of technology designed to remove such radioactive threa… more
Date: August 12, 2009
Creator: Szigethy, Geza
Partner: UNT Libraries Government Documents Department
open access

Protein Structure Recognition: From Eigenvector Analysis to Structural Threading Method

Description: In this work, they try to understand the protein folding problem using pair-wise hydrophobic interaction as the dominant interaction for the protein folding process. They found a strong correlation between amino acid sequences and the corresponding native structure of the protein. Some applications of this correlation were discussed in this dissertation include the domain partition and a new structural threading method as well as the performance of this method in the CASP5 competition. In the f… more
Date: December 12, 2003
Creator: Cao, Haibo
Partner: UNT Libraries Government Documents Department
open access

Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic Semiconductors

Description: Organic electronic materials are a new class of emerging materials. Organic light emitting devices (OLEDs) are the most promising candidates for future flat panel display technologies. The photophysical characterization is the basic research step one must follow to understand this new class of materials and devices. The light emission properties are closely related to the transport properties of these materials. The objective of this dissertation is to probe the relation between transport and p… more
Date: December 12, 2003
Creator: Kim, Chang-Hwan
Partner: UNT Libraries Government Documents Department
open access

Organogermanium Chemistry: Germacyclobutanes and digermane Additions to Acetylenes

Description: This dissertation comprises two main research projects. The first project, presented in Chapter 1, involves the synthesis and thermochemistry of germacyclobutanes (germetanes). Four new germetanes (spirodigermetane, diallylgermetane, dichlorogermetane, and germacyclobutane) have been synthesized using a modified di-Grignard synthesis. Diallylgermetane is shown to be a useful starting material for obtaining other germetanes, particularly the parent germetane, germacyclobutane. The gas-phase ther… more
Date: December 12, 2003
Creator: Chubb, Andrew Michael
Partner: UNT Libraries Government Documents Department
open access

Probing Properties of Glassy Water and Other Liquids with Site Selective Spectroscopies

Description: The standard non-photochemical hole burning (NPHB) mechanism, which involves phonon-assisted tunneling in the electronically excited state, was originally proposed to explain the light-induced frequency change of chemically stable molecules in glassy solids at liquid helium temperatures by this research group more than two decades ago. The NPHB mechanism was then further elucidated and the concept of intrinsic to glass configurational relaxation processes as pre-mediating step to the hole burni… more
Date: August 12, 2005
Creator: Dang, Nhan Chuong
Partner: UNT Libraries Government Documents Department
open access

Thermal Properties of Starch From New Corn Lines as Impacted by Environment and During Line Development

Description: The objectives of this research were to further characterize exotic by adapted corn inbreds by studying the impact of environment on their starch thermal properties, and investigating the development of starch thermal properties during kernel maturation by using differential scanning calorimetry (DSC). A method to expedite identification of unusual starch thermal traits was investigated by examining five corn kernels at a time, instead of one kernel, which the previous screening methods used. C… more
Date: December 12, 2003
Creator: Lenihan, Elizabeth M.
Partner: UNT Libraries Government Documents Department
open access

Organic Light-Emitting Devices (OLEDS) and Their Optically Detected Magnetic Resonance (ODMR)

Description: Organic Light-Emitting Devices (OLEDs), both small molecular and polymeric have been studied extensively since the first efficient small molecule OLED was reported by Tang and VanSlyke in 1987. Burroughes' report on conjugated polymer-based OLEDs led to another track in OLED development. These developments have resulted in full color, highly efficient (up to {approx} 20% external efficiency 60 lm/W power efficiency for green emitters), and highly bright (> 140,000 Cd/m{sup 2} DC, {approx}2,0… more
Date: December 12, 2003
Creator: Li, Gang
Partner: UNT Libraries Government Documents Department
open access

Electromagnetic Wave Propagation in Two-Dimensional Photonic Crystals

Description: In this dissertation, they have undertaken the challenge to understand the unusual propagation properties of the photonic crystal (PC). The photonic crystal is a medium where the dielectric function is periodically modulated. These types of structures are characterized by bands and gaps. In other words, they are characterized by frequency regions where propagation is prohibited (gaps) and regions where propagation is allowed (bands). In this study they focus on two-dimensional photonic crystals… more
Date: December 12, 2003
Creator: Foteinopoulou, Stavroula
Partner: UNT Libraries Government Documents Department
open access

Quantification of Soil Physical Properties by Using X-Ray Computerized Tomography (CT) and Standard Laboratory (STD) Methods

Description: The implementation of x-ray computerized tomography (CT) on agricultural soils has been used in this research to quantify soil physical properties to be compared with standard laboratory (STD) methods. The overall research objective was to more accurately quantify soil physical properties for long-term management systems. Two field studies were conducted at Iowa State University's Northeast Research and Demonstration Farm near Nashua, IA using two different soil management strategies. The first… more
Date: December 12, 2003
Creator: Sanchez, Maria Ambert
Partner: UNT Libraries Government Documents Department
open access

Homogeneous Precipitation of Nickel Hydroxide Powders

Description: Precipitation and characterization of nickel hydroxide powders were investigated. A comprehensive precipitation model incorporating the metal ion hydrolysis, complexation and precipitation reactions was developed for the production of the powders with urea precipitation method. Model predictions on Ni{sup 2+} precipitation rate were confirmed with precipitation experiments carried out at 90 C. Experimental data and model predictions were in remarkable agreement. Uncertainty in the solubility pr… more
Date: December 12, 2003
Creator: Mavis, Bora
Partner: UNT Libraries Government Documents Department
open access

Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors

Description: Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer (< 10{sup 13} cm{sup -3}) approximately 1 mm thick grown on a heavily doped active layer ({approx} 10{sup 16} cm{sup -3}) approximately 20 mm thick. Epilayers were grown using liquid phase epitaxy (LPE) of germanium out of lead solution. The effects of the crystallographic orientation of the germanium substrate on LPE growth modes were explored. Growth was studied on substrates oriented by Laue x-ray diffrac… more
Date: May 12, 2001
Creator: Bandaru, Jordana
Partner: UNT Libraries Government Documents Department
open access

SPA-LEED Study of the Morphology and Nucleation of a Novel Growth Mode and the ''devil's staircase'' on Pb/Si(111)

Description: This thesis was developed to address the following questions for the Pb/Si(111) system: (1) Is it possible to control the nano-structure growth by changing the initial substrate; (2) is the nucleation theory applicable to the case of the 7-step growth mode; and (3) what phase or phases could be formed between coverage 6/5 ML and 4/3 ML? The first question was answered in chapter 2, different growth results were observed for different initial substrate, suggesting the possibility of controlling … more
Date: December 12, 2003
Creator: Yeh, Wang-Chi Vincent
Partner: UNT Libraries Government Documents Department
open access

Bioanalytical Applications of Real-Time ATP Imaging Via Bioluminescence

Description: The research discussed within involves the development of novel applications of real-time imaging of adenosine 5'-triphosphate (ATP). ATP was detected via bioluminescence and the firefly luciferase-catalyzed reaction of ATP and luciferin. The use of a microscope and an imaging detector allowed for spatially resolved quantitation of ATP release. Employing this method, applications in both biological and chemical systems were developed. First, the mechanism by which the compound 48/80 induces rel… more
Date: December 12, 2003
Creator: Gruenhagen, Jason Alan
Partner: UNT Libraries Government Documents Department
open access

Fission Multiplicity Detection with Temporal Gamma-Neutron Discrimination from Higher-Order Time Correlation Statistics

Description: The current practice of nondestructive assay (NDA) of fissile materials using neutrons is dominated by the {sup 3}He detector. This has been the case since the mid 1980s when Fission Multiplicity Detection (FMD) was replaced with thermal well counters and neutron multiplicity counting (NMC). The thermal well counters detect neutrons by neutron capture in the {sup 3}He detector subsequent to moderation. The process of detection requires from 30 to 60 {micro}s. As will be explained in Section 3.3… more
Date: November 12, 2002
Creator: Oberer, R.B.
Partner: UNT Libraries Government Documents Department
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