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The History of the Bill J. Priest Institute for Economic Development of the Dallas County Community College District

Description: The Bill J. Priest Institute for Economic Development is an entity created in the Dallas County Community College District to serve the community in workforce and economic development. The history of the Priest Institute over the last ten years parallels and illustrates the commitment of community colleges nationally to workforce and economic development. The history also reflects similar goals and trends within the state of Texas and, particularly, in the city of Dallas. The Priest Institute i… more
Date: April 1994
Creator: Hughes, Martha
Partner: UNT Libraries
open access

Mental Status, Intellectual, and Mood States Associated with Environmental Illness Patients

Description: The purpose of the present study was to begin development of a psychological profile for environmentally ill patients. Existing psychiatric labels are unable to encompass these patients. Test scores were drawn from a pool of 89 patients whose environmental exposures were verified by the presence of toxins in the blood serum. A Mental Status Exam, a Wechsler Adult Intelligence Scale-Revised screen, and the Profile of Mood States were administered. Results indicate a primary pattern which is sign… more
Date: April 1991
Creator: Fincher, Cynthia Ellen
Partner: UNT Libraries
open access

The application of psoralens to the study of DNA structure, function and dynamics

Description: A series of six nitroxide spin-labeled psoralens were designed, synthesized and tested as probes for DNA dynamics. The synthesis of these spin-labeled psoralen derivatives and their photoreactivity with double-stranded DNA fragments is described. The spin labels (nitroxides) were demonstrated to survive the uv irradiation required to bind the probe to the target DNA. EPR spectra of the photobound spin-labels indicate that they do not wobble with respect to the DNA on the time-scales investigate… more
Date: April 1, 1991
Creator: Spielmann, P. H.
Partner: UNT Libraries Government Documents Department
open access

The effect of rhenium, sulfur and alumina on the conversion of hydrocarbons over platinum single crystals: Surface science and catalytic studies

Description: Conversion reactions of hydrocarbons over Pt-Re model catalyst surfaces modified by sulfur and alumina have been studied. A plasma deposition source has been developed to deposit Pt, Re, and Al on metal substrates variable coverage in ultrahigh vacuum without excessive heating. Conversion of n-hexane was performed over the Re-covered Pt and Pt-covered Re surfaces. The presence of the second metal increased hydrogenolysis activity of both Pt-Re surfaces. Addition of sulfur on the model Catalyst … more
Date: April 1, 1992
Creator: Kim, C.
Partner: UNT Libraries Government Documents Department
open access

Electromagnetic dissociation of {sup 238}U in heavy-ion collisions at 120 MeV/A

Description: This thesis describes a measurement of the heavy-ion induced electromagnetic dissociation of a 120 MeV/A {sup 238}U beam incident on five targets: {sup 9}Be, {sup 27}Al, {sup nat}Cu, {sup nat}Ag, and {sup nat}U. Electromagnetic dissociation at this beam energy is essentially a two step process involving the excitation of a giant resonance followed by particle decay. At 120 MeV/A there is predicted to be a significant contribution of the giant quadrupole resonance to the EMD cross sections. The … more
Date: April 1, 1991
Creator: Justice, M. L.
Partner: UNT Libraries Government Documents Department
open access

A calorimetric measurement of the strong coupling constant in electron-positron annihilation at a center-of-mass energy of 91.6 GeV

Description: In this work, a measurement of the strong coupling constant {alpha}{sub s} in e{sup +}e{sup {minus}} annihilation at a center-of-mass energy of 91.6 GeV is presented. The measurement was performed with the SLD at the Stanford Linear Collider facility located at the Stanford Linear Accelerator Center in California. The procedure used consisted of measuring the rate of hard gluon radiation from the primary quarks in a sample of 9,878 hadronic events. After defining the asymptotic manifestation of… more
Date: April 1, 1994
Creator: Martirena, S. G.
Partner: UNT Libraries Government Documents Department
open access

High resolution electron diffraction analysis of structural changes associated with the photocycle of bacteriorhodopsin

Description: Changes in protein structure that occur during the formation of the M photointermediate of bacteriorhodopsin can be directly visualized by electron diffraction techniques. Samples containing a high percentage of the M intermediate were trapped by rapidly cooling the crystals with liquid nitrogen following illumination with filtered green light at 240K and 260K respectively. Difference Fourier projection maps for M minus bR at two temperatures and for M{sub 260K} minus M{sub 240K} are presented.… more
Date: April 1, 1994
Creator: Han, B.-G.
Partner: UNT Libraries Government Documents Department
open access

The crosswell electromagnetic response of layered media

Description: Crosswell electromagnetic measurements are a promising new geophysical technique for mapping subsurface electrical conductivity which can provide information about the subsurface distribution of water, oil or steam. In this work the fields from a low frequency vertical magnetic dipole have been examined from the specific point of view of their application to the determination of the conductivity of a layered medium. The source and the receiver were placed inside two separate boreholes. The rang… more
Date: April 1, 1994
Creator: Deszcz-Pan, M.
Partner: UNT Libraries Government Documents Department
open access

Behavior of the particle transport coefficients near the density limit in MTX

Description: The perturbed particle transport coefficients were determined for a range of plasma conditions in the Alcator C tokamak, a component of the Microwave Tokamak Experiment (MTX), from analysis of density perturbations created in gas modulation experiments. Density measurements from a 15 chord far-infrared interferometer were sufficiently detailed to allow radial profiles of the transport coefficients to be resolved. Gas modulation experiments were carried out on plasmas over a range of relatively … more
Date: April 1, 1993
Creator: Marinak, M. M.
Partner: UNT Libraries Government Documents Department
open access

Independent verification and validation of large software requirement specification databases

Description: To enhance quality, an independent verification and validation (IV&V) review is conducted as software requirements are defined. Requirements are inspected for consistency and completeness. IV&V strives to detect defects early in the software development life cycle and to prevent problems before they occur. The IV&V review process of a massive software requirements specification, the Reserve Component Automation System (RCAS) Functional Description (FD) is explored. Analysis of the RCAS FD error… more
Date: April 1, 1992
Creator: Twitchell, K. E.
Partner: UNT Libraries Government Documents Department
open access

Electronic and structural properties of metallic microclusters

Description: The first part of this thesis presents a first-order pseudopotential calculation at T=O of the total energy of small sodium clusters of size N<800. The calculation is based on a local-pseudopotential scheme and local-density correlation and exchange. A temperature-size (T-N) phase-diagram is then derived using the T=O results and Lindemann`s criterion for melting. The phase-diagram contains three regions of stability: (1) a liquid (jellium) phase at temperatures above the melting line T{sub M}(… more
Date: April 1, 1992
Creator: Maiti, A.
Partner: UNT Libraries Government Documents Department
open access

Crossed molecular beam studies of atmospheric chemical reaction dynamics

Description: The dynamics of several elementary chemical reactions that are important in atmospheric chemistry are investigated. The reactive scattering of ground state chlorine or bromine atoms with ozone molecules and ground state chlorine atoms with nitrogen dioxide molecules is studied using a crossed molecular beams apparatus with a rotatable mass spectrometer detector. The Cl + O{sub 3} {yields} ClO + O{sub 2} reaction has been studied at four collision energies ranging from 6 kcal/mole to 32 kcal/mol… more
Date: April 1, 1993
Creator: Zhang, Jingsong
Partner: UNT Libraries Government Documents Department
open access

Small catalytic RNA: Structure, function and application

Description: We have utilized a combination of photochemical cross-linking techniques and site-directed mutagenesis to obtain secondary and tertiary structure information for the self-cleaving, self-ligating subsequence of RNA from the negative strand of Satellite Tobacco Ringspot Virus. We have found that the helical regions fold about a hinge to promoting four different possible tertiary interactions, creating a molecular of similar shape to a paperclip. A model suggesting that the ``paperclip`` and ``ham… more
Date: April 1, 1991
Creator: Monforte, J. A.
Partner: UNT Libraries Government Documents Department
open access

The microstructural mechanism of electromigration failure in narrow interconnects of Al alloys

Description: This thesis reports a study of the mechanism of electromigration failure in Al-2Cu-1Si thin-film conducting lines on Si. Samples were patterned from 0.5 {mu}m thick vapor-deposited films with various mean grain sizes (G), and had lines widths (W) of 1.3, 2, 4 and 6 {mu}m. The lines were aged at various conditions to change the Cu-precipitate distribution and were tested to failure at T = 225{degrees}C and j = 2.5 {times} 10{sup 6} A/cm{sup 2}. Some samples were tested over a range of substrate … more
Date: April 1, 1993
Creator: Kim, Choongun
Partner: UNT Libraries Government Documents Department
open access

Support minimized inversion of acoustic and elastic wave scattering

Description: This report discusses the following topics on support minimized inversion of acoustic and elastic wave scattering: Minimum support inversion; forward modelling of elastodynamic wave scattering; minimum support linearized acoustic inversion; support minimized nonlinear acoustic inversion without absolute phase; and support minimized nonlinear elastic inversion.
Date: April 24, 1994
Creator: Safaeinili, A.
Partner: UNT Libraries Government Documents Department
open access

The mechanism of the oligomerization of thiophene-based para-quinodimethanes

Description: For the last decade, the Trahanovsky research group has focused on the study of various reactive molecules such as o-quinodimethanes (o-QDM`s) and p-quinodimethanes (p-QDM`s) derived from benzene, furan, and thiophene. These types of molecules are reactive and dimerize or polymerize at room temperature. One of the group`s interests is to understand the dimerization mechanism of these molecules. Paper 1 describes the preparation and dimerization product analyses of 2-ethylidene-5-methylene-2,5-d… more
Date: April 24, 1994
Creator: Wang, Yili
Partner: UNT Libraries Government Documents Department
open access

The analysis and minimization of oxygen contamination in the powder processing of molybdenum disilicide

Description: Problems with MoSi{sub 2} include low-temperature fracture toughness, high-temperature creep resistance, and ``pest`` phenomena. Oxygen introduced by powder processing may be the cause of some of these problems. This study led to the following conclusions: Supplied powders have significant oxygen present prior to processing (up to 2.5 %), in the form of silica on the surface. This oxygen contamination did not increase by exposure to air at room temperature. An improved powder processing method … more
Date: April 24, 1994
Creator: Shannon, K.
Partner: UNT Libraries Government Documents Department
open access

Topics in the structure of hadronic systems

Description: In this dissertation the author examines a variety of different problems in the physics of strongly-bound systems. Each is elucidated by a different standard method of analysis developed to probe the properties of such systems. He begins with an examination of the properties and consequences of the current algebra of weak currents in the limit of heavy quark spin-flavor symmetry. In particular, he examines the assumptions in the proof of the Ademollo-Gatto theorem in general and for spin-flavor… more
Date: April 1, 1994
Creator: Lebed, R. F.
Partner: UNT Libraries Government Documents Department
open access

Investigation of ultrafast photothermal surface expansion and diffusivity in GaAs via laser-induced dynamic gratings

Description: This thesis details the first direct ultrafast measurements of the dynamic thermal expansion of a surface and the temperature dependent surface thermal diffusivity using a two-color reflection transient grating technique. Studies were performed on p-type, n-type, and undoped GaAs(100) samples over a wide range of temperatures. By utilizing a 90 fs ultraviolet probe with visible excitation beams, the effects of interband saturation and carrier dynamics become negligible; thus lattice expansion d… more
Date: April 1, 1992
Creator: Pennington, D. M.
Partner: UNT Libraries Government Documents Department
open access

Chemical dynamics in time and energy space

Description: The development of a versatile picosecond ultraviolet/vacuum ultraviolet temporal spectrometer and its potential use for measuring internal energy redistribution in isolated molecules are described in detail. A detailed description of the double-pass Nd:YAG amplifier and the dye amplifiers is given with the pulse energies achieved in the visible, ultraviolet, and vacuum ultraviolet. The amplified visible pulses are shown to be of sub-picosecond duration and near transform limited. The instrumen… more
Date: April 1, 1993
Creator: Myers, J. D.
Partner: UNT Libraries Government Documents Department
open access

Flavor symmetries and fermion masses

Description: We introduce several ways in which approximate flavor symmetries act on fermions and which are consistent with observed fermion masses and mixings. Flavor changing interactions mediated by new scalars appear as a consequence of approximate flavor symmetries. We discuss the experimental limits on masses of the new scalars, and show that the masses can easily be of the order of weak scale. Some implications for neutrino physics are also discussed. Such flavor changing interactions would easily er… more
Date: April 1, 1994
Creator: Rasin, A.
Partner: UNT Libraries Government Documents Department
open access

Tris(Cyclopentadienyl)Uranium-t-Butyl: Synthesis, reactions, and mechanisms

Description: Compounds (RC{sub 5}H{sub 4}){sub 3}U(t-Bu) were prepared for R = H, Me, Et. Their decomposition products in aromatic solvents are consistent with a radical decomposition pathway induced by solvent-assisted U-C bond homolysis. NMR was used to study the reactions of (RC{sub 5}H{sub 4}){sub 3}UCl with t-BuLi (R = t-Bu, Me{sub 3}Si). Reactions of (MeC{sub 5}H{sub 4}){sub 3}U(t-Bu) with Lewis bases and fluorocarbons were studied. Analogous reaction chemistry between (RC{sub 5}H{sub 4}){sub 3}ThX sy… more
Date: April 1, 1993
Creator: Weydert, M.
Partner: UNT Libraries Government Documents Department
open access

Bacterially induced precipitation of CaCO{sub 3}: An example from studies of cyanobacterial mats. Final report

Description: Bacteria induce the precipitation of calcium carbonate in the laboratory and in nature by altering their chemical environment. Geologists are recognizing the possibility that bacterially induced precipitates may form significant mineral deposits, unfortunately, there are currently no sound criteria by which they can be recognized in recent sediments, or in the rock record. Cultures of aerobic and facultative bacteria from cyanobacterial mats on Andros Island, Bahamas, and Baffin Bay, Texas, ind… more
Date: April 30, 1990
Creator: Chafetz, H. S.
Partner: UNT Libraries Government Documents Department
open access

Triple-quantum filtered NMR imaging of sodium in the human brain

Description: In the past multiple-quantum filtered imaging of biexponential relaxation sodium-23 nuclei in the human brain has been limited by low signal to noise ratios; this thesis demonstrates that such imaging is feasible when using a modified gradient-selected triple-quantum filter at a repetition time which maximizes the signal to noise ratio. Nuclear magnetic resonance imaging of biexponential relaxation sodium-23 ({sup 23}Na) nuclei in the human brain may be useful for detecting ischemia, cancer, an… more
Date: April 1, 1993
Creator: Keltner, J. R.
Partner: UNT Libraries Government Documents Department
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