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Collision-induced dissociation reactions and pulsed field ionization photoelectron

Description: This report summarized the four parts of the research study and describes the general conclusions. Individual chapters have been removed for separate processing. The chapter titles are: A study of the dissociation of CH{sub 3}SH{sup +} by collisional activation: Observation of non-statistical behavior; High resolution vacuum ultraviolet pulsed field ionization photoelectron band for OCS{sup +}(X{sup 2}{Pi}): An experimental and theoretical study; Rotationally resolved pulsed field ionization ph… more
Date: February 12, 1999
Creator: Stimson, S.
Partner: UNT Libraries Government Documents Department
open access

Optically detected magnetic resonance studies on {pi}-conjugate polymers and novel carbon allotropes

Description: This report describes the following: introduction to photoluminescence detected magnetic resonance (PLDMR); introduction to {pi}-conjugated systems; PLDMR measurements on poly(p-phenylene)-type ladder polymers; PLMDR measurements on poly(p-phenylene ethylene); and PLDMR measurements on C{sub 70}, polythiophene, poly(p-phenylene vinylene) and Dan-40. Appendices to this report describe: Operation of ODMR (optically detected magnetic resonance) spectrometer; ODMR system parameters; and Special pur… more
Date: February 12, 1999
Creator: Partee, J.
Partner: UNT Libraries Government Documents Department
open access

Syntheses and studies of organosilicon compounds

Description: The syntheses of polycarbosilanes and polysilanes as silicon carbide ceramic precursors have been active research areas in the Barton Research Group. In this thesis, the work is focused on the preparation of polycarbosilanes and polysilanes as stoichiometric silicon carbide precursor polymers. The syntheses of the precursor polymers are discussed and the conversions of these precursors to silicon carbide via pyrolysis are reported. The XRD pattern and elemental analyses of the resulting silicon… more
Date: February 12, 1999
Creator: Xie, R.
Partner: UNT Libraries Government Documents Department
open access

Single- and multi-photon ionization studies of organosulfur species

Description: Accurate ionization energies (IE`s) for molecular species are used for prediction of chemical reactivity and are of fundamental importance to chemists. The IE of a gaseous molecule can be determined routinely in a photoionization or a photoelectron experiment. IE determinations made in conventional photoionization and photoelectron studies have uncertainties in the range of 3--100 meV (25--250 cm{sup {minus}1}). In the past decade, the most exciting development in the field of photoionization a… more
Date: February 12, 1999
Creator: Cheung, Y. S.
Partner: UNT Libraries Government Documents Department
open access

Capillary electrophoretic study of individual exocytotic events in single mast cells

Description: The peak profile of individual degranulation events from the on-column release of serotonin from single rat peritoneal mast cells (RPMCs) was monitored using capillary electrophoresis with laser-induced native fluorescence detection (CE-LINF). Serotonin, an important biogenic amine, is contained in granules (0.25 fL) within RPMCs and is extruded by a process termed exocytosis. The secretagogue, Polymyxin B sulfate, was used as the CE running buffer after injection of a single RPMC into the sepa… more
Date: February 12, 1999
Creator: Ho, A.M.W.
Partner: UNT Libraries Government Documents Department
open access

Capillary electrophoresis separation of neutral organic compounds, pharmaceutical drugs, proteins and peptides, enantiomers, and anions

Description: Addition of a novel anionic surfactant, namely lauryl polyoxyethylene sulfate, to an aqueous-acetonitrile electrolyte makes it possible to separate nonionic organic compounds by capillary electrophoresis. Separation is based on differences in the association between analytes and the surfactant. Highly hydrophobic compounds such as polyaromatic hydrocarbons are well separated by this new surfactant. Migration times of analytes can be readily changed over an unusually large range by varying the a… more
Date: February 12, 1999
Creator: Ding, W.L.
Partner: UNT Libraries Government Documents Department
open access

LiV{sub 2}O{sub 4}: A heavy fermion transition metal oxide

Description: The format of this dissertation is as follows. In the remainder of Chapter 1, brief introductions and reviews are given to the topics of frustration, heavy fermions and spinels including the precedent work of LiV{sub 2}O{sub 4}. In Chapter 2, as a general overview of this work the important publication in Physical Review Letters by the author of this dissertation and collaborators regarding the discovery of the heavy fermion behavior in LiV{sub 2}O{sub 4} is introduced [removed for separate pro… more
Date: February 12, 1999
Creator: Kondo, Shinichiro
Partner: UNT Libraries Government Documents Department
open access

Gas atomization processing of tin and silicon modified LaNi{sub 5} for nickel-metal hydride battery applications

Description: Numerous researchers have studied the relevant material properties of so-called AB{sub 5} alloys for battery applications. These studies involved LaNi{sub 5} substituted alloys which were prepared using conventional cast and crush alloying techniques. While valuable to the understanding of metal hydride effects, the previous work nearly ignored the potential for alternative direct powder production methods, like high pressure gas atomization (HPGA). Thus, there is a need to understand the relat… more
Date: February 12, 1999
Creator: Ting, J.
Partner: UNT Libraries Government Documents Department
open access

Chiral separation of pharmaceutical compounds using electrochemically modulated liquid chromatography (EMLC)

Description: This research explores the application of a new technique, termed electrochemically modulated liquid chromatography (EMLC), to the chiral separations of pharmaceutical compounds. The introduction section provides a literature review of the technique and its applications, as well as brief overview of the research described in each of the next two chapters. Chapter 2 investigates the EMLC-based enantiomeric separation of a group of chiral benzodiazepines with {beta}-cyclodextrin as a chiral mobil… more
Date: February 12, 1999
Creator: Wang, S.
Partner: UNT Libraries Government Documents Department
open access

Structure sensitive adsorption of hydrogen on ruthenium and ruthenium-silver catalysts supported on silica

Description: Supported metal catalysts typically consist of particles with sizes less than 10 nm, and because of the small crystallite size, low coordination number sites (edges and corners) represent a significant fraction of all surface sites. Furthermore, it has been demonstrated that adsorption rates can be much greater at these low coordination sites than on basal plane sites. What has not been generally appreciated, however, is that preferential adsorption at edge and corner sites may explain the mech… more
Date: February 12, 1999
Creator: Kumar, N.
Partner: UNT Libraries Government Documents Department
open access

The analysis of aqueous mixtures using liquid chromatography-electrospray mass spectrometry

Description: The focus of this dissertation is the use of chromatographic methods coupled with electrospray mass spectrometry (ES-MS) for the determination of both organic and inorganic compounds in aqueous solutions. The combination of liquid chromatography (LC) methods and ES-MS offers one of the foremost methods for determining compounds in complex aqueous solutions. In this work, LC-ES-MS methods are devised using ion exclusion chromatography, reversed phase chromatography, and ion exchange chromatograp… more
Date: February 12, 1999
Creator: Johnson, S.
Partner: UNT Libraries Government Documents Department
open access

Calibration of laser ablation inductively coupled plasma mass spectrometry using dried solution aerosols for the quantitative analysis of solid samples

Description: Inductively coupled plasma mass spectrometry (ICP-MS) has become the method of choice for elemental and isotopic analysis. Several factors contribute to its success. Modern instruments are capable of routine analysis at part per trillion levels with relative detection limits in part per quadrillion levels. Sensitivities in these instruments can be as high as 200 million counts per second per part per million with linear dynamic ranges up to eight orders of magnitude. With standards for only a f… more
Date: February 12, 1999
Creator: Leach, J.
Partner: UNT Libraries Government Documents Department
open access

A study of surface diffusion with the scanning tunneling microscope from fluctuations of the tunneling current

Description: The transport of atoms or molecules over surfaces has been an important area of study for several decades now, with its progress generally limited by the available experimental techniques to characterize the phenomena. A number of methods have been developed over the years to measure surface diffusion yet only very few systems have been characterized to this day mainly due to the physical limitations inherent in these available methods. Even the STM with its astonishing atomically-resolved imag… more
Date: January 12, 1996
Creator: Manuel, L.
Partner: UNT Libraries Government Documents Department
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Surface structures of Al-Pd-Mn and Al-Cu-Fe icosahedral quasicrystals

Description: In this dissertation, the author reports on the surface structure of i-Al-Pd-Mn twofold, threefold, fivefold and i-Al-Cu-Fe fivefold surfaces. The LEED studies indicate the existence of two distinct stages in the regrowth of all four surfaces after Ar{sup +} sputtering. In the first stage, upon annealing at relatively low temperature: 500K--800K (depending on different surfaces), a cubic phase appears. The cubic LEED patterns transform irreversibly to unreconstructed quasicrystalline patterns u… more
Date: February 12, 1999
Creator: Shen, Z.
Partner: UNT Libraries Government Documents Department
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