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Photodissociation and charge transfer dynamics of negative ions studied with femtosecond photoelectron spectroscopy

Description: This dissertation presents studies aimed at understanding the potential energy surfaces and dynamics of isolated negative ions, and the effects of solvent on each. Although negative ions play important roles in atmospheric and solution phase chemistry, to a large extent the ground and excited state potential energy surfaces of gas phase negative ions are poorly characterized, and solvent effects even less well understood. In an effort to fill this gap, the author's coworkers and the author have… more
Date: December 17, 1999
Creator: Zanni, Martin T.
Partner: UNT Libraries Government Documents Department
open access

Anion photoelectron spectroscopy of radicals and clusters

Description: Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying {sup 2}{Sigma} and {sup 2}{Pi} states of C{sub 2n}H (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree o… more
Date: December 16, 1999
Creator: Travis, Taylor R.
Partner: UNT Libraries Government Documents Department
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Growth of a Au-Ni-Sn intermetallic compound on the solder-substrate interface after aging

Description: Au/Ni metallization has become increasingly common in microelectronic packaging when Cu pads are joined with Pb-Sn solder. The outermost Au layer serves to protect the pad from corrosion and oxidation and the Ni layer provides a diffusion barrier to inhibit detrimental growth of Cu-Sn intermetallics. As a result of reflowing eutectic Pb-Sn on top of Au/Ni metallization, the as-solidified joints have AuSn{sub 4} precipitates distributed throughout the bulk of the solder joint, and Ni{sub 3}Sn{su… more
Date: December 16, 1999
Creator: Minor, Andrew M. & Morris, J. W., Jr.
Partner: UNT Libraries Government Documents Department
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Photodissociation spectroscopy and dynamics of free radicals, clusters, and ions

Description: The photodissociation spectroscopy and dynamics of free radicals and ions is studied to characterize the dissociative electronic states in these species. To accomplish this, a special method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with the technique of fast beam photofragment translational spectroscopy. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic s… more
Date: December 16, 1999
Creator: Hyeon, Choi
Partner: UNT Libraries Government Documents Department
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X-ray absorption spectroscopy on the calcium cofactor to the manganese cluster in photosynthetic oxygen evolution

Description: Along with Mn, calcium and chloride ions are necessary cofactors for oxygen evolution in Photosystem II (PS II). To further test and verify whether Ca is close to the Mn cluster, the authors substituted strontium for Ca and probed from the Sr point of view for any nearby Mn. The extended X-ray absorption fine structure (EXAFS) of Sr-reactivated PS II indicates major differences between the intact and NH{sub 2}OH-treated samples. In intact samples, the Fourier transform of the Sr EXAFS shows a F… more
Date: December 16, 1999
Creator: Cinco, Roehl M.
Partner: UNT Libraries Government Documents Department
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Effects of processing conditions and ambient environment on the microstructure and fracture strength of copper/niobium/copper interlayer joints for alumina

Description: Partial transient liquid phase (PTLP) bonding is a technique which can be used to join ceramics with metals and is used to form niobium-based joints for alumina. The principal advantage to PTLP bonding is that it enables refractory joints to be fabricated at temperatures below those typically required by solid state diffusion bonding. A thorough review of the important parameters (chemical compatibility, thermal expansion match, sufficient wettability of the liquid phase on the solid phases) in… more
Date: December 15, 1999
Creator: Marks, Robert Alan
Partner: UNT Libraries Government Documents Department
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Characterization of electrical resistivity as a function of temperature in the Mo-Si-B system

Description: Measurements of electrical resistivity as a function of temperature from 25 to 1,500 C were conducted on polycrystalline samples in the Mo-Si-B system. Single phase, or nearly single phase, samples were prepared for the following phases: Mo{sub 3}Si, Mo{sub 5}SiB{sub 2}, Mo{sub 5}Si{sub 3}B{sub x}, MoB, MoSi{sub 2}, and Mo{sub 5}Si{sub 3}. Thesis materials all exhibit resistivity values within a narrow range(4--22 x 10{sup {minus}7}{Omega}-m), and the low magnitude suggests these materials are … more
Date: December 10, 1999
Creator: Beckman, Sarah E.
Partner: UNT Libraries Government Documents Department
open access

Development and evaluation of high resolution quadrupole mass analyzer and an inductively coupled plasma-Mach disk

Description: By definition a plasma is an electrically conducting gaseous mixture containing a significant concentration of cations and electrons. The Inductively Coupled Plasma (ICP) is an electrodeless discharge in a gas at atmospheric pressure. This discharge is an excellent one for vaporizing, atomizing, and ionizing elements. The early development of the ICP began in 1942 by Babat and then by Reed in the early 1960s. This was then followed by the pioneering work of Fassel and coworkers in the late 1960… more
Date: December 10, 1999
Creator: Amad, Ma'an Hazem
Partner: UNT Libraries Government Documents Department
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Electrochemical and scanning probe microscopic characterization of spontaneously adsorbed organothiolate monolayers at gold

Description: This dissertation presented several results which add to the general knowledge base regarding organothiolates monolayer spontaneously adsorbed at gold films. Common to the body of this work is the use of voltammetric reductive resorption and variants of scanning probe microscopy to gain insight into the nature of the monolayer formation process as well as the resulting interface. The most significant result from this work is the success of using friction force microscopy to discriminate the end… more
Date: December 10, 1999
Creator: Wong, Sze-Shun Season
Partner: UNT Libraries Government Documents Department
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Fast methods for analysis of neurotransmitters from single cell and monitoring their releases in central nervous system by capillary electrophoresis, fluorescence microscopy and luminescence imaging

Description: Fast methods for separation and detection of important neurotransmitters and the releases in central nervous system (CNS) were developed. Enzyme based immunoassay combined with capillary electrophoresis was used to analyze the contents of amino acid neurotransmitters from single neuron cells. The release of amino acid neurotransmitters from neuron cultures was monitored by laser induced fluorescence imaging method. The release and signal transduction of adenosine triphosphate (ATP) in CNS was s… more
Date: December 10, 1999
Creator: Wang, Ziqiang
Partner: UNT Libraries Government Documents Department
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Liquid metal extraction of Nd from NdFeB magnet scrap

Description: This research involves using molten magnesium (Mg) to remove neodymium (Nd) from NdFeB magnet scrap by diffusion. The results show that liquid metal extraction of Nd may be a viable and inexpensive method for recovering the expensive rare earth element Nd for use in Mg castings.
Date: December 10, 1999
Creator: Xu, Yanchen
Partner: UNT Libraries Government Documents Department
open access

Wave propagation in ordered, disordered, and nonlinear photonic band gap materials

Description: Photonic band gap materials are artificial dielectric structures that give the promise of molding and controlling the flow of optical light the same way semiconductors mold and control the electric current flow. In this dissertation the author studied two areas of photonic band gap materials. The first area is focused on the properties of one-dimensional PBG materials doped with Kerr-type nonlinear material, while, the second area is focused on the mechanisms responsible for the gap formation a… more
Date: December 10, 1999
Creator: Lidorikis, Elefterios
Partner: UNT Libraries Government Documents Department
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High-resolution spectroscopic diagnostics of very high-temperature plasmas in the hard x-ray regime

Description: Motivated by the need for establishing a reliable database useful for the application of x-ray spectroscopic tools for the diagnostic of very high temperature plasmas, high-resolution crystal spectrometer measurements have been performed investigating the characteristic K-shell radiation of highly charged krypton and xenon. The measurements, which have been performed at the Electron-Beam-Ion-Trap (EBIT) facility of the Lawrence Livermore National Laboratory, include the investigation of the n =… more
Date: December 6, 1999
Creator: Widmann, K
Partner: UNT Libraries Government Documents Department
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Adhesion/Diffusion Barrier Layers for Copper Integration: Carbon-Silicon Polymer Films and Tantalum Substrates

Description: The Semiconductor Industry Association (SIA) has identified the integration of copper (Cu) with low-dielectric-constant (low-k) materials as a critical goal for future interconnect architectures. A fundamental understanding of the chemical interaction of Cu with various substrates, including diffusion barriers and adhesion promoters, is essential to achieve this goal. The objective of this research is to develop novel organic polymers as Cu/low-k interfacial layers and to investigate popular ba… more
Date: December 1999
Creator: Chen, Li
Partner: UNT Libraries

The Afro-British Slave Narrative: The Rhetoric of Freedom in the Kairos of Abolition

Description: The dissertation argues that the development of the British abolition movement was based on the abolitionists' perception that their actions were kairotic; they attempted to shape their own kairos by taking temporal events and reinterpreting them to construct a kairotic process that led to a perceived fulfillment: abolition. Thus, the dissertation examines the rhetorical strategies used by white abolitionists to construct an abolitionist kairos that was designed to produce salvation for white B… more
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: December 1999
Creator: Evans, Dennis F.
Partner: UNT Libraries
open access

An Analysis of the Ability of an Instrument to Measure Quality of Library Service and Library Success

Description: This study consisted of an examination of how service quality should be measured within libraries and how library service quality relates to library success. A modified version of the SERVQUAL instrument was evaluated to determine how effectively it measures library service quality. Instruments designed to measure information center success and information system success were evaluated to determine how effectively they measure library success and how they relate to SERVQUAL. A model of library … more
Date: December 1999
Creator: Landrum, Hollis T.
Partner: UNT Libraries

'...and one of time.': A Composition for Full Orchestra with Narration

Description: ‘...and one of time.' is a reinterpretation of a small musical moment from Philip Glass' opera, Einstein on the Beach, centered around the phrase "Berne, Switzerland 1905." This reinterpretation is realized through the use of several different compositional techniques including spectral composition, micropolyphony and dodecaphony, as well as the application of extra-musical models developed by Alan Lightman, John Gardner, Italo Calvino and Albert Einstein.
Access: Restricted to UNT Community Members. Login required if off-campus.
Date: December 1999
Creator: Rinker, John Thomas
Partner: UNT Libraries
open access

Asleep in the Arms of God

Description: A work of creative fiction in the form of a short novel, Asleep in the Arms of God is a limited-omniscient and omniscient narrative describing the experiences of a man named Wafer Roberts, born in Jack County, Texas, in 1900. The novel spans the years from 1900 to 1925, and moves from the Keechi Valley of North Texas, to Fort Worth and then France during World War One, and back again to the Keechi Valley. The dissertation opens with a preface, which examines the form of the novel, and regional … more
Date: December 1999
Creator: Clay, Kevin M.
Partner: UNT Libraries
open access

Benchmarks in American Higher Education: Selected Approaches for Distance Education Copyright and Intellectual Property Policies

Description: An evaluation of American higher education distance education programs was conducted to explore how they approach intellectual property, copyright and information sharing/antitrust policy concerns for Internet-based programs. An evaluation of the current status of distance education and Internet-based training in higher education was conducted through a pilot study that included a random sample of 223 accredited institutions. Seventy-seven institutions responded to a survey, of which there were… more
Date: December 1999
Creator: Smith, Kenneth D.
Partner: UNT Libraries
open access

Cassette Systems for Creating Intergeneric Hybrid ATCases

Description: Cassette systems for creating intergeneric hybrid ATCases were constructed. An MluI restriction enzyme site was introduced at the carbamoylphosphate binding site within the pyrB genes of both Pseudomonas putida and Escherichia coli. Two hybrids, E. coli pyrB polar domain fused with P. putida pyrB equatorial domain and P. putida pyrB polar domain fused with E. coli pyrB equatorial domain, are possible. The intergeneric E. coli-P. putida hybrid pyrB gene was constructed and found to encode an a… more
Date: December 1999
Creator: Simpson, Luci N.
Partner: UNT Libraries

Chemotactic Response of Lumbricus terrestris Coelomocytes to Larval and Adult Stages of Rhabditis pellio

Description: Experiments were performed to assess the suitability of Rhabditis pellio, a nematode found in earthworms, as a challenge organism for use in development of a biomarker assay to determine the potential of chemicals to suppress the immunocompetence of the non-specific immune system. To accomplish this goal, information on the life cycle of R. pellio was determined; including effects of incubation time and temperature on growth rates; along with information on the immune response elicited in the e… more
Access: Restricted to the UNT Community Members at a UNT Libraries Location.
Date: December 1999
Creator: Medrano, Jennifer Centurion
Partner: UNT Libraries
open access

Classification of Toolmark Surfaces on Zipper Teeth

Description: This study proposes the classification of the toolmark under the heads of zipper teeth as a subclass characteristic as outlined by the Association of Firearm and Toolmark Examiners (AFTE). Two separate cases in which zipper teeth were found at crime scenes prompted this study. Brass zipper teeth manufactured by YKK were taken from 20 pairs of jeans and studied using a Reichert comparison microscope at 4X power. Photographs were taken and over 750 comparisons made. It was found that the toolmark… more
Date: December 1999
Creator: Jacobsen, Dawn
Partner: UNT Libraries
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