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Structural and magnetic properties and superconductivity in Ba(Fe{sub 1-x}TM{sub x}){sub 2}As{sub 2}

Description: We studied the effects on structural and magnetic phase transitions and the emergence of superconductivity in transition metal substituted BaFe{sub 2}As{sub 2}. We grew four series of Ba(Fe{sub 1-x}TM{sub x}){sub 2}As{sub 2} (TM=Ru, Mn, Co+Cr and Co+Mn) and characterized them by crystallographic, magnetic and transport measurements. We also subjected Ba(Fe{sub 1-x}Cr{sub x}){sub 2}As{sub 2} and Ba(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} to heat treatment to explore what changes might be induced.
Date: July 23, 2012
Creator: Thaler, Alexander
Partner: UNT Libraries Government Documents Department
open access

THE APPLICATION OF SINGLE PARTICLE AEROSOL MASS SPECTROMETRY FOR THE DETECTION AND IDENTIFICATION OF HIGH EXPLOSIVES AND CHEMICAL WARFARE AGENTS

Description: Single Particle Aerosol Mass Spectrometry (SPAMS) was evaluated as a real-time detection technique for single particles of high explosives. Dual-polarity time-of-flight mass spectra were obtained for samples of 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazinane (RDX), and pentaerythritol tetranitrate (PETN); peaks indicative of each compound were identified. Composite explosives, Comp B, Semtex 1A, and Semtex 1H were also analyzed, and peaks due to the explosive components of each sam… more
Date: October 23, 2006
Creator: Martin, A
Partner: UNT Libraries Government Documents Department
open access

Solidification process in melt spun Nd-Fe-B type magnets

Description: A generalized solidification model has been developed based on a systematic investigation on the microstructure of melt spun Nd-Fe-B alloys. Melt spinning was conducted on initial stoichiometric and TiC added Nd{sub 2}Fe{sub 14}B (2-14-1) compositions to produce under, optimally and over quenched microstructures. Microstructural characterization was carried out by TEM, SEM, Optical microscopy, XRD, DTA, VSM and DC SQUID techniques. By taking the dendritic breakup during recalescence into consid… more
Date: February 23, 1998
Creator: Li, C.
Partner: UNT Libraries Government Documents Department
open access

Search for B to rho/omega gamma decays at BaBar

Description: The authors present the results of the search for the decays B{sup 0/{+-}} {yields} {rho}{sup 0/{+-}}{gamma} (previously observed) and B{sup 0} {yields} {omega}{gamma} (for which currently only an upper limit exists). Together with B {yields} K*{gamma} decays, B {yields} ({rho}/{omega}){gamma} allow us to measure the ratio of CKM-matrix elements |V{sub td}/V{sub ts}|. The analysis is based on the full BABAR dataset of 424.35 fb{sup -1} corresponding to 465 million B{bar B} pairs, and makes heav… more
Date: September 23, 2008
Creator: Piatenko, Timofei & /SLAC, /Caltech
Partner: UNT Libraries Government Documents Department
open access

Straddle-packer determination of the vertical distribution of hydraulic properties in the Snake River Plain Aquifer at well USGS-44, Idaho Chemical Processing Plant, INEL

Description: Many of the monitor wells that penetrate the upper portion of the Snake River Plain aquifer at the Idaho National Engineering Laboratory (INEL) are open over large intervals that include multiple water-bearing zones. Most of these wells are equipped with dedicated submersible pumps. Water of varying quality from different water-bearing zones is mixed within the wells. The hydrologic properties of individual water bearing zones are difficult to determine. Water quality and water-level data on or… more
Date: September 23, 1994
Creator: Monks, J. I.
Partner: UNT Libraries Government Documents Department
open access

Quantum groups, roots of unity and particles on quantized Anti-de Sitter space

Description: Quantum groups in general and the quantum Anti-de Sitter group U{sub q}(so(2,3)) in particular are studied from the point of view of quantum field theory. The author shows that if q is a suitable root of unity, there exist finite-dimensional, unitary representations corresponding to essentially all the classical one-particle representations with (half) integer spin, with the same structure at low energies as in the classical case. In the massless case for spin {ge} 1, {open_quotes}naive{close_q… more
Date: May 23, 1997
Creator: Steinacker, H.
Partner: UNT Libraries Government Documents Department
open access

Fission of Gold With 112-Mev C{sup 12} Ions: A Yield-Mass and Charge- Distribution Study

Description: Fission prcduct cross sections were measured radiochemically and mass- spectrometrically for gold bombsrded with 112-Mev C/sup 12/ ions. Cross sections for 43 nuclides were measured for elements from nickel to barium. Thirty-six yields are either primary fission product yields (independent yields) or were corrected (with less than 25% correction) so as to represent independent yields. The independent yields were empirically systematized and a yield-mass curve was constructed. The yield-mass cur… more
Date: May 23, 1960
Creator: Blann, H. M.
Partner: UNT Libraries Government Documents Department
open access

Intense Ion Beam for Warm Dense Matter Physics

Description: The Neutralized Drift Compression Experiment (NDCX) at Lawrence Berkeley National Laboratory is exploring the physical limits of compression and focusing of ion beams for heating material to warm dense matter (WDM) and fusion ignition conditions. The NDCX is a beam transport experiment with several components at a scale comparable to an inertial fusion energy driver. The NDCX is an accelerator which consists of a low-emittance ion source, high-current injector, solenoid matching section, induct… more
Date: May 23, 2008
Creator: Coleman, Joshua Eugene
Partner: UNT Libraries Government Documents Department
open access

Synthesis and characterization of novel group VI metal (Mo, W) nitride and oxide compounds

Description: Investigations into the preparation of tungsten nitrides have involved the synthesis of molecular precursors, and their conversion to tungsten nitrides at relatively low temperatures. Two interesting molecular precursors, [WNCl{sub 3}{center_dot}NCCH{sub 3}]{sub 4} and WN(N{sub 3}){sub 3}{center_dot}xNCCH{sub 3}, have been prepared and characterized. The molecular structure of the first consists of a W{sub 4}N{sub 4} tetrameric core with multiple and single W-N bonds arranged in an alternating … more
Date: February 23, 1998
Creator: Zhang, Z.
Partner: UNT Libraries Government Documents Department
open access

Solidification analysis of a centrifugal atomizer using the Al-32.7wt.% Cu alloy

Description: A centrifugal atomizer (spinning disk variety) was designed and constructed for the production of spherical metal powders, 100--1,000 microns in diameter in an inert atmosphere. Initial atomization experiments revealed the need for a better understanding of how the liquid metal was atomized and how the liquid droplets solidified. To investigate particle atomization, Ag was atomized in air and the process recorded on high-speed film. To investigate particle solidification, Al-32.7 wt.% Cu was at… more
Date: February 23, 1998
Creator: Osborne, M.G.
Partner: UNT Libraries Government Documents Department
open access

Interfacial characterization and analytical applications of chemically-modified surfaces

Description: The goal of this work is to explore several new strategies and approaches to the surface modification and the microscopic characterization of interfaces in the areas mainly targeting sensor technologies that are of interest to environmental control or monitoring, and scanning probe microscopies techniques that can monitor interfacial chemical reactions in real time. Centered on the main theme, four specific topics are presented as four chapters in this dissertation following the general introdu… more
Date: February 23, 1998
Creator: Wang, J.
Partner: UNT Libraries Government Documents Department
open access

Neutron Capture and the Production of 60-Fe in Stellar Environments

Description: The observation of gamma rays associated with the decay of {sup 26}Al and {sup 60}Fe can provide important information regarding ongoing nucleosynthesis in our galaxy. The half-lives of these radioisotopes (7.2 x 10{sup 5} y and 1.5 x 10{sup 6} y, respectively) are long compared to the interval between synthesis events such as supernovae, so they build up in a steady state in the interstellar medium (centered on the galactic plane, where massive stars reside), yet short enough that gamma radiat… more
Date: August 23, 2005
Creator: Kelley, K
Partner: UNT Libraries Government Documents Department
open access

Adsorbate structures and catalytic reactions studied in the torrpressure range by scanning tunneling microscopy

Description: High-pressure, high-temperature scanning tunneling microscopy (HPHTSTM) was used to study adsorbate structures and reactions on single crystal model catalytic systems. Studies of the automobile catalytic converter reaction [CO + NO {yields} 1/2 N{sub 2} + CO{sub 2}] on Rh(111) and ethylene hydrogenation [C{sub 2}H{sub 4} + H{sub 2} {yields} C{sub 2}H{sub 6}] on Rh(111) and Pt(111) elucidated information on adsorbate structures in equilibrium with high-pressure gas and the relationship of atomic… more
Date: May 23, 2003
Creator: Hwang, Kevin Shao-Lin
Partner: UNT Libraries Government Documents Department
open access

Quantum harmonic Brownian motion in a general environment: A modified phase-space approach

Description: After extensive investigations over three decades, the linear-coupling model and its equivalents have become the standard microscopic models for quantum harmonic Brownian motion, in which a harmonically bound Brownian particle is coupled to a quantum dissipative heat bath of general type modeled by infinitely many harmonic oscillators. The dynamics of these models have been studied by many authors using the quantum Langevin equation, the path-integral approach, quasi-probability distribution fu… more
Date: June 23, 1993
Creator: Yeh, L.
Partner: UNT Libraries Government Documents Department
open access

Neutron scattering studies of the RENi{sub 2}B{sub 2}C (RE = Lu, Y, Ho, Er): Lattice dynamics

Description: The first chapter gives a brief overview of the system discussed in this dissertation. Chapters 2--5 and Appendix B of this dissertation consist of papers that are published, or have been submitted, which show experimental data regarding the phonon softening of LuNi{sub 2}B{sub 2}C. These papers have been removed and processed separately. Chapter 6 will contain a summary of the conclusions up to date. Appendix A will consist of a brief derivation of {chi}(q) which is talked about in the introdu… more
Date: February 23, 1998
Creator: Bullock, M.
Partner: UNT Libraries Government Documents Department
open access

Photodissociation dynamics of polyatomic molecules

Description: This report consists of five studies as follows: A laser photofragmentation time-of-flight mass spectrometric study of acetophenone at 193 and 248 nm; A 193 nm laser photofragmentation time-of-flight mass spectrometric study of dimethylsulfoxide; 193 nm laser photofragmentation time-of-flight mass spectrometric study of HSCH{sub 2}CH{sub 2}SH; Thiophene biradical decay of the primary laser photofragmentation product at 193 nm; and Scattering cross sections for O({sup 3}P)[SO(X,{sup 3}{Sigma}{su… more
Date: February 23, 1998
Creator: Zhao, H.
Partner: UNT Libraries Government Documents Department
open access

An Orifice Plate Pulse Column for Liquid-Liquid Extraction

Description: A study was made of the performance of an orifice plate pulse column which is essentially a spray column containing internal constrictions in the form of orifices. The chemical system studied was acetic acid-waterhexone, and the variables considered were pulse frequency, throughput, phase continuity, and direction of solute transfer. For comparison purposes, several runs were made with a conventional spray column. Curves are presented showing the effect of the column variables on the column eff… more
Date: August 23, 1954
Creator: O'Brien, D. C.
Partner: UNT Libraries Government Documents Department
open access

The structure-property relationships of powder processed Fe-Al-Si alloys

Description: Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties … more
Date: February 23, 1998
Creator: Prichard, P.D.
Partner: UNT Libraries Government Documents Department
open access

Experimental Studies of Laser-Induced Breakdown in Transparent Dielectrics

Description: The mechanisms by which transparent dielectrics damage when exposed to high power laser radiation has been of scientific and technological interest since the invention of the laser. In this work, a set of three experiments are presented which provide insight into the damage initiation mechanisms and the processes involved in laser-induced damage. Using an OPO (optical parametric oscillator) laser, we have measured the damage thresholds of deuterated potassium dihydrogen phosphate (DKDP) from th… more
Date: September 23, 2003
Creator: Carr, C W
Partner: UNT Libraries Government Documents Department
open access

New methods and materials for solid phase extraction and high performance liquid chromatography

Description: This paper describes methods for solid phase extraction and high performance liquid chromatography (HPLC). The following are described: Effects of Resin Sulfonation on the Retention of Polar Organic Compounds in Solid Phase Extraction; Ion-Chromatographic Separation of Alkali Metals In Non-Aqueous Solvents; Cation-Exchange Chromatography in Non-Aqueous Solvents; and Silicalite As a Stationary Phase For HPLC.
Date: April 23, 1996
Creator: Dumont, P.J.
Partner: UNT Libraries Government Documents Department
open access

Stability of eutectic interface during directional solidification

Description: Directional solidification of eutectic alloys shows different types of eutectic morphologies. These include lamellar, rod, oscillating and tilting modes. The growth of these morphologies occurs with a macroscopically planar interface. However, under certain conditions, the planar eutectic front becomes unstable and gives rise to a cellular or a dendritic structure. This instability leads to the cellular/dendritic structure of either a primary phase or a two-phase structure. The objective of thi… more
Date: April 23, 1996
Creator: Han, S.H.
Partner: UNT Libraries Government Documents Department
open access

Deciphering the details of RNA aminoglycoside interactions: from atomistic models to biotechnological applications

Description: A detailed study was done of the neomycin-B RNA aptamer for determining its selectivity and binding ability to both neomycin– and kanamycin-class aminoglycosides. A novel method to increase drug concentrations in cells for more efficiently killing is described. To test the method, a bacterial model system was adopted and several small RNA molecules interacting with aminoglycosides were cloned downstream of T7 RNA polymerase promoter in an expression vector. Then, the growth analysis of E. coli … more
Date: July 23, 2012
Creator: Ilgu, Muslum
Partner: UNT Libraries Government Documents Department
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