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Coordination chemistry of two heavy metals: I, Ligand preferences in lead(II) complexation, toward the development of therapeutic agents for lead poisoning: II, Plutonium solubility and speciation relevant to the environment

Description: The coordination chemistry and solution behavior of the toxic ions lead(II) and plutonium(IV, V, VI) have been investigated. The ligand pK{sub a}s and ligand-lead(II) stability constants of one hydroxamic acid and four thiohydroaxamic acids were determined. Solution thermodynamic results indicate that thiohydroxamic acids are more acidic and slightly better lead chelators than hydroxamates, e.g., N-methylthioaceto-hydroxamic acid, pK{sub a} = 5.94, log{beta}{sub 120} = 10.92; acetohydroxamic ac… more
Date: November 1, 1993
Creator: Neu, M. P.
Partner: UNT Libraries Government Documents Department
open access

Aging effects on the microstructure, surface characteristics and wettability of Cu pretinned with Sn-Pb solders

Description: This study investigates effects of aging in air and argon at 170 C on Cu coupons which were pretinned with 75Sn-25Pb, 8Sn-92Pb, and 5Sn-95Pb solders. Coatings were applied using electroplating or hot dipping techniques. The coating thickness was controlled between 3 to 3{mu}m and the specimens were aged for 0 hours, 2 hours, 24 hours and 2 weeks. Wetting balance tests were used to evaluate the wettability of the test specimens. Microstructural development was evaluated using X-ray diffraction, … more
Date: November 1, 1993
Creator: Linch, H. S.
Partner: UNT Libraries Government Documents Department
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Microstructural development and mechanical behavior of eutectic bismuth-tin and eutectic indium-tin in response to high temperature deformation

Description: The mechanical behavior and microstructure of eutectic Bi-Sn and In-Sn solders were studied in parallel in order to better understand high temperature deformation of these alloys. Bi-Sn solder joints were made with Cu substrates, and In-Sn joints were made with either Cu or Ni substrates. The as-cast microstructure of Bi-Sn is complex regular, with the two eutectic phases interconnected in complicated patterns. The as-cast microstructure of In-Sn depends on the substrate. In-Sn on Cu has a non-… more
Date: November 1, 1993
Creator: Goldstein, J. L. F.
Partner: UNT Libraries Government Documents Department
open access

Ion-assisted laser deposition of intermediate layers for YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin film growth on polycrystalline and amorphous substrates

Description: The growth of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) high-temperature superconductor thin films has largely been limited to deposition on single-crystal substrates to date. In order to expand the range of potential applications, growth on polycrystalline and amorphous substrates is desirable. In particular, the deposition of YBCO thin films with high critical current densities on polycrystalline metal alloys would allow the manufacture of superconducting tapes. However, it is shown that it … more
Date: November 1, 1993
Creator: Reade, R. P.
Partner: UNT Libraries Government Documents Department
open access

Properties of W + jet events in proton-antiproton collisions at 1.8 TeV

Description: W boson + QCD Jet events, produced in 1.8 TeV proton-antiproton collisions and measured by the Collider Detector at Fermilab (CDF), were used to measure the center-of-mass production angle of the W + jet system, and were also used to place limits on the production of excited quark states. The center-of-mass production angular distribution agrees well with leading order and next-to-leading order QCD predictions. Excited quark states were searched for in the reaction q + g {yields} q* {yields} q … more
Date: November 22, 1993
Creator: Drucker, R. B.
Partner: UNT Libraries Government Documents Department
open access

Modern integral equation techniques for quantum reactive scattering theory

Description: Rigorous calculations of cross sections and rate constants for elementary gas phase chemical reactions are performed for comparison with experiment, to ensure that our picture of the chemical reaction is complete. We focus on the H/D+H{sub 2} {yields} H{sub 2}/DH + H reaction, and use the time independent integral equation technique in quantum reactive scattering theory. We examine the sensitivity of H+H{sub 2} state resolved integral cross sections {sigma}{sub v{prime}j{prime},vj}(E) for the t… more
Date: November 1, 1993
Creator: Auerbach, S. M.
Partner: UNT Libraries Government Documents Department
open access

Laser-material interactions: A study of laser energy coupling with solids

Description: This study of laser-light interactions with solid materials ranges from low-temperature heating to explosive, plasma-forming reactions. Contained are four works concerning laser-energy coupling: laser (i) heating and (ii) melting monitored using a mirage effect technique, (iii) the mechanical stress-power generated during high-powered laser ablation, and (iv) plasma-shielding. First, a photothermal deflection (PTD) technique is presented for monitoring heat transfer during modulated laser heati… more
Date: November 1, 1993
Creator: Shannon, M. A.
Partner: UNT Libraries Government Documents Department
open access

Elastic scattering of pions from tritium and {sup 3}He in the backward hemisphere in the region of the {Delta}{sub 33}(1232) resonance

Description: Several experiments have measured nominally-charge-symmetric scattering of pions from tritium ({sup 3}H) and {sup 3}He. These experiments have covered incident pion energies from 142 MeV to 295 MeV and scattering angles up to 110{degrees} in the laboratory. The results have been used to study charge-symmetry breaking and nuclear scattering systematics. In the work I have extended these measurements to angles near 180{degrees} for pion energies of 142 MeV, 180 MeV, 220 MeV, and 256 MeV, which br… more
Date: November 1, 1993
Creator: Matthews, S. K.
Partner: UNT Libraries Government Documents Department
open access

Measurement of the production cross section for W + {gamma} in the electron channel in {radical}s = 1.8 TeV {bar p}p collisions

Description: The production cross section times decay branching ratio for W{sub +{gamma}} in the electron decay channel in {radical}s = 1.8 TeV {bar p}-p collisions has been measured using W {yields} e{gamma} data sample obtained from the CDF 1988--1989 Tevatron collider run. For photons in the central region ({vert_bar}{eta}{sub {gamma}}{vert_bar} < 1.1) of the CDF detector with transverse energies E{sub T}{sup {gamma}} 5.0 GeV and lepton-photon angular separation {Delta}R{sub {ell}}{gamma} > 0.7, eight el… more
Date: November 1, 1993
Creator: Benjamin, D. P.
Partner: UNT Libraries Government Documents Department
open access

1: Redox chemistry of bimetallic fulvalene complexes; 2: Oligocyclopentadienyl complexes

Description: The electrochemistry of the heterobimetallic complexes (fulvalene)WFe(CO){sub 5} (30) and (fulvalene)WRu(CO){sub 5} (31) has been investigated. Compound 30 is reduced in two one-electron processes, and this behavior was exploited synthetically to prepare a tetranuclear dimer by selective metal reduction. Complex 31 displayed a distinction between the metals upon reoxidation of the dianion, allowing the formation of a dimer by selective metal anion oxidation. The redox behavior of 30 led to an i… more
Date: November 1, 1993
Creator: Brown, D. S.
Partner: UNT Libraries Government Documents Department
open access

Fast beam studies of free radical photodissociation

Description: The photodissociation of free radicals is studied in order to characterize the spectroscopy and dissociation dynamics of the dissociative electronic states in these species. To accomplish this, a novel method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with a highly complementary form of photofragment translational spectroscopy. The optical spectroscopy of transitions to dissociative states is determined by monitoring the total photof… more
Date: November 1, 1993
Creator: Cyr, D. R.
Partner: UNT Libraries Government Documents Department
open access

An investigation of DUA caching strategies for public key certificates

Description: Internet Privacy Enhanced Mail (PEM) provides security services to users of Internet electronic mail. PEM is designed with the intention that it will eventually obtain public key certificates from the X.500 directory service. However, such a capability is not present in most PEM implementations today. While the prevalent PEM implementation uses a public key certificate-based strategy, certificates are mostly distributed via e-mail exchanges, which raises several security and performance issues.… more
Date: November 1, 1993
Creator: Cheung, T. C.
Partner: UNT Libraries Government Documents Department
open access

Structures and related properties of helical, disulfide-stabilized peptides

Description: The three dimensional structure of several peptides were determined by NMR spectroscopy and distance geometry calculations. Each peptide formed a predictable, rigid structure, consisting of an {alpha}-helix, a {open_quotes}scaffold{close_quotes} region which packed along one face of the helix, and two disulfide bridges which covalently connect the helix and scaffold regions. The peptide Apa-M5 was designed to constrain the M5 peptide from MLCK in a helical geometry using the apamin disulfide sc… more
Date: November 1, 1993
Creator: Pagel, M. D.
Partner: UNT Libraries Government Documents Department
open access

Passive stabilization of MHD instabilities at high {beta}n in the HBT-EP Tokamak

Description: The HBT-EP Tokamak has been designed, built, and is now fully operational in the Columbia University Plasma Physics Laboratory. One of the primary purposes of this facility is to study the effects of a conducting wall on the MHD modes that lead up to plasma disruptions. Of particular interest are the types of instabilities that are driven by the kinetic pressure of the plasma, because these instabilities are believed to be responsible for the present limit to plasma {beta} with {beta} {proporti… more
Date: November 1, 1993
Creator: Gates, D. A.
Partner: UNT Libraries Government Documents Department
open access

Computer simulation of martensitic transformations

Description: The characteristics of martensitic transformations in solids are largely determined by the elastic strain that develops as martensite particles grow and interact. To study the development of microstructure, a finite-element computer simulation model was constructed to mimic the transformation process. The transformation is athermal and simulated at each incremental step by transforming the cell which maximizes the decrease in the free energy. To determine the free energy change, the elastic ene… more
Date: November 1, 1993
Creator: Xu, Ping
Partner: UNT Libraries Government Documents Department
open access

Reaction {pi}N {yields} {pi}{pi}N near threshold

Description: The LAMPF E1179 experiment used the {pi}{sup 0} spectrometer and an array of charged particle range counters to detect and record {pi}{sup +}{pi}{sup 0}, {pi}{sup 0}p, and {pi}{sup +}{pi}{sup 0}p coincidences following the reaction {pi}{sup +}p {yields} {pi}{sup 0}{pi}{sup +}p near threshold. The total cross sections for single pion production were measured at the incident pion kinetic energies 190, 200, 220, 240, and 260 MeV. Absolute normalizations were fixed by measuring {pi}{sup +}p elastic… more
Date: November 1, 1993
Creator: Frlez, E.
Partner: UNT Libraries Government Documents Department
open access

A photon detector system for the search for the rare muon decay {mu} {yields} e{gamma}

Description: An innovative and state of the art pair spectrometer system to measure the photon component of {mu}{sup +} decay to obtain an improved branching ratio limit for the decay {mu} {yields} e{gamma} is investigated. Analysis algorithms are developed and an experimental inner bremsstrahlung spectrum is obtained and agrees well with Monte Carlo simulations. Background sources are investigated and found to be highly suppressed at various stages of acquisition and analysis.
Date: November 1, 1993
Creator: Van Ausdeln, L. A.
Partner: UNT Libraries Government Documents Department
open access

Application of semiclassical methods to reaction rate theory

Description: This work is concerned with the development of approximate methods to describe relatively large chemical systems. This effort has been divided into two primary directions: First, we have extended and applied a semiclassical transition state theory (SCTST) originally proposed by Miller to obtain microcanonical and canonical (thermal) rates for chemical reactions described by a nonseparable Hamiltonian, i.e. most reactions. Second, we have developed a method to describe the fluctuations of decay … more
Date: November 1, 1993
Creator: Hernandez, R.
Partner: UNT Libraries Government Documents Department
open access

Integrating Total Quality Management (TQM) and hazardous waste management

Description: The Resource Conservation and Recovery Act (RCRA) of 1976 and its subsequent amendments have had a dramatic impact on hazardous waste management for business and industry. The complexity of this law and the penalties for noncompliance have made it one of the most challenging regulatory programs undertaken by the Environmental Protection Agency (EPA). The fundamentals of RCRA include ``cradle to grave`` management of hazardous waste, covering generators, transporters, and treatment, storage, and… more
Date: November 1, 1993
Creator: Kirk, N.
Partner: UNT Libraries Government Documents Department
open access

The coordination and atom transfer chemistry of titanium porphyrin complexes

Description: Preparation, characterization, and reactivity of ({eta}{sup 2}- alkyne)(meso-tetratolylpoprphrinato)titanium(II) complexes are described, along with inetermetal oxygen atom transfer reactions involving Ti(IV) and Ti(III) porphyrin complexes. The {eta}{sup 2}- alkyne complexes are prepared by reaction of (TTP)TiCl{sub 2} with LiAlH{sub 4} in presence of alkyne. Structure of (OEP)Ti({eta}{sup 2}-Ph-C{triple_bond}C-Ph) (OEP=octaethylporphryin) was determined by XRD. The compounds undergo simple su… more
Date: November 5, 1993
Creator: Hays, J. A.
Partner: UNT Libraries Government Documents Department
open access

Trains and Transformations

Description: Thesis written by a student in the UNT Honors College discussing five of the author's experimental short stories.
Date: November 1993
Creator: Hadder, R. Neill
Partner: UNT Honors College
open access

On the implementation of error handling in dynamic interfaces to scientific codes

Description: With the advent of powerful workstations with windowing systems, the scientific community has become interested in user friendly interfaces as a means of promoting the distribution of scientific codes to colleagues. Distributing scientific codes to a wider audience can, however, be problematic because scientists, who are familiar with the problem being addressed but not aware of necessary operational details, are encouraged to use the codes. A more friendly environment that not only guides user… more
Date: November 1, 1993
Creator: Solomon, Cynthia Jean
Partner: UNT Libraries Government Documents Department
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