UNT Theses and Dissertations - 50 Matching Results

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A Quenchofluorometric Study of Polycyclic Aromatic Hydrocarbons in Molecularly Organized Media

Description: Detection, identification and separation of polycyclic aromatic compounds in environmental samples are of extreme importance since many of these compounds are well known for their potential carcinogenic and/or mutagenic activities. Selective quenching of molecular fluorescence can be utilized effectively to analyze mixtures containing different polycyclic aromatic hydrocarbons. Molecularly organized assemblies are used widely in detection and separation of these compounds mainly because of less… more
Date: May 1998
Creator: Pandey, Siddharth
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Partner: UNT Libraries
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Raman and NMR Investigation of Molecular Reorientation and Internal Rotation in Liquids

Description: Molecular rotational motions are known to influence both Raman scattering of light and nuclear spin relaxation. Therefore, the application of Raman bandshape analysis and NMR relaxation time measurements to probe molecular dynamics in liquids will provide us with a deeper understanding of the dynamical behavior and structure of molecules in the liquid phase. Presented here are (i) studies of molecular reorientation of acetonitrile in the neat liquid phase and in solution by Raman bandshape ana… more
Date: December 1991
Creator: Yuan, Peng
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Selectivity Failure in the Chemical Vapor Deposition of Tungsten

Description: Tungsten metal is used as an electrical conductor in many modern microelectronic devices. One of the primary motivations for its use is that it can be deposited in thin films by chemical vapor deposition (CVD). CVD is a process whereby a thin film is deposited on a solid substrate by the reaction of a gas-phase molecular precursor. In the case of tungsten chemical vapor deposition (W-CVD) this precursor is commonly tungsten hexafluoride (WF6) which reacts with an appropriate reductant to yield … more
Date: August 1994
Creator: Cheek, Roger W. (Roger Warren)
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Partner: UNT Libraries
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Solid State Diffusion Kinetics of Intermetallic Compound Formation in Composite Solder

Description: The Sn/Pb eutectic alloy system is the most widely used joining material in the electronics industry. In this application, the solder acts as both an electrical and mechanical connection within and among the different packaging levels in an electronic device. Recent advances in packaging technologies, however, driven by the desire for miniaturization and increased circuit speed, result in severe operating conditions for the solder connection. In an effort to improve its mechanical integrity, me… more
Date: May 1993
Creator: Sees, Jennifer A. (Jennifer Anne)
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Solution Studies of ⁶Li Enriched Organolithium Compounds Using New NMR Techniques

Description: With the values of 6Li T1 measured and the literature values of J(13C-6Li) for these compounds, three new 13C NMR techniques are developed for the analysis of organolithium compounds. Modifications to the spectrometer are discussed, as well as calibrations of the 6Li decoupler channel needed to set up these new experiments. The theoretical development of each technique is presented, as well as data from their verification, using organolithium compounds of known structure. Once qualified, the ne… more
Date: May 1990
Creator: Ellington, Donald H. (Donald Howard)
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Solution Studies of the Structures and Stability of Mixed Lithium Alkoxide/Alkvllithium Aggregates

Description: New one- and two-dimensional NMR techniques were used to elucidate the solution structures of these complex mixtures. The system, lithium tert-butoxide/tert-butyllithium, was studied as a model system with O/Li ratios varying from 0/1 to 1/1. It was found that at low O/Li ratios, a single mixed tetrameric aggregate was formed. At higher O/Li ratios, mixed hexameric species were formed. Two other systems, lithium isopropoxide/iso-propyllithium and lithium n-propoxide/n-propyllithium were also st… more
Date: December 1992
Creator: DeLong, George T. (George Thomas)
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Partner: UNT Libraries
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Solvent and Ionic Complexes of the Calix[6]arenes

Description: One of the more attractive attributes of calixarenes is their wide variety of possible conformations and hence cavity shapes. However, the flexibility that allows this long-range benefit gives rise to major synthetic challenges when working with the larger members of the family. O-alkylations have proven to be the most widely employed synthetic routes to "functionalization" of the calixarenes, and these have shown a dependence upon both solvent and the metal ions present. Surprisingly, there ha… more
Date: December 1997
Creator: Wolfgong, William J.
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Spectrofluorometric and Solubility Studies of Polycyclic Aromatic Hydrocarbons in Hydrogen Bonded Binary Solvent Mixtures

Description: The purpose of this dissertation is to investigate the behavior of polycyclic aromatic hydrocarbons (PAHs) in binary solvent systems and determine and/or develop predictive mathematical expressions for describing solutions in which hydrogen-bonding occurs.
Date: May 1997
Creator: Powell, Joyce R., 1968-
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Spectroscopic Properties of Polycyclic Aromatic Compounds

Description: The fluorescence spectrum of many polycyclic aromatic compounds (PACs) depends upon solvent polarity. The emission spectrum of PAC monomers consists of several major vibronic bands labeled I, II, etc., in progressive order. Emission intensity enhancement of select bands is observed in polar solvents.
Date: May 1994
Creator: Tucker, Sheryl A. (Sheryl Ann)
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Partner: UNT Libraries
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Stereoselective Solid-State NaBH₄ Reduction of 1-Methylpentacyclo[5.4.0.0²,⁶.0³,¹⁰,0⁵,⁹]undecane-8, 11-Dione, Synthesis and Chemistry of Strained Alkenes, and Chemical and Microbial Synthesis of Racemic and Optically Active (S)-4-Hydroxy-2-Cyclohexenone

Description: Part I. Reduction of the 1-methylpentacyclo [5.4.0.0²,⁶.0³,¹⁰,0⁵,⁹]undecane-8, 11-dione (9) with solid NaBH₄ resulted in highly stereoselective reduction of both C=O groups in the substrate, thereby affording the corresponding endo-8, endo-11-diol (11a). The configuration of 11a was established unequivocally by converting 11a into the corresponding cyclic thiocarbonate ester, 12. Part II. Z-1,2-Di(1'-adamantyl)ethene (14) was synthesized with a high degree of stereoselectively in four steps (Sc… more
Date: August 1995
Creator: Xing, Dongxia
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Structural Elucidation of tert-Butyllithium/Lithium Alkoxide and Lithium Hydride/Lithium Alkoxide Mixed Aggregates

Description: The effects of lithium alkoxides on the rates of reactions and on the structures of a series of tert-butyllithium/lithium alkoxide mixed aggregates were studied, where the alkoxides were iso-butoxide, tert-butoxide and menthoxide. It was found that their effects depend not only on their amount present, but also on their steric bulk. The tert-butyllithium/lithium alkoxide mixed aggregates were exposed to UV light or heat to form lithium hydride/lithium alkoxide mixed aggregates. The aggregation… more
Date: December 1997
Creator: Nguyen, Hanh D.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Studies of Solvent Displacement from Solvated Metal Carbonyl Complexes of Chromium, Molybdenum, and Tungsten

Description: Flash photolysis techniques were applied to studies of solvent displacement by Lewis bases (L) from solvated metal carbonyl complexes of Cr, Mo, and W. On the basis of extensive studies of the reaction rate laws, activation parameters , and linear-free-energy-relationships, it was concluded that the mechanisms of solvent displacement reactions depend on the electronic and steric properties of the solvents and L, as well as the identities of the metal atoms. The strengths of solvent-metal bondin… more
Date: August 1990
Creator: Zhang, Shulin
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A Study of the Processing Properties of Hard-Particle Reinforced Composite Solders

Description: The microstructural, mechanical and thermal properties of various composite solder formulations were investigated. Special interest was given in observing the processing properties, microstructural characteristics, fatigue behavior, tensile strength, and the effect of environmental ageing on the composite solder formulations. The solderability parameters wetting and speed of soldering, reflow temperature, and the thermal stability of the resulting composite solder were also examined.
Date: May 1994
Creator: Calderon, Jose Guadalupe
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Substitution Chemistry of Ruthenium Clusters with the Diphosphine Ligands: 4,5-Bis(Diphenylphosphino)-4-Cyclo-Penten-1,3-Dione (bpcd), (Z)-Ph₂PCH=CHPP₂ and 3,4-Bis(Diphenylphosphino)-5-Methoxy-2(5H)-Furanone (bmf)

Description: The chemistry of transition metal clusters has been a fast developing area of organometallic research in recent years. Compared to mononuclear metal complexes, polynuclear clusters offer more opportunities to study cooperative effects and electron reservoir properties between contiguous metal centers, in addition to functioning as storehouses for the release of catalytically active small fragments capable of exhibiting heterosite subtrate activation. Theoretically, metal clusters are intermedia… more
Date: May 1997
Creator: Shen, Huafeng
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Substitution Chemistry of the Cobalt Complexes [Co₂(CO)₆(PhC≡CR) (R=Ph, H) and PhCCo₃(CO)₉] with the Diphosphine Ligands [Bis(diphenylphosphino)maleic Anhydride (BMA) and (Z)-Ph₂PCH=CHPPh₂]. Reversible Chelate-to-Bridge Diphosphine Ligand Exchange, Phosphorus-Carbon Bond Cleavage and Phosphorus-Carbon Bond Formation

Description: The tricobalt cluster PhCCo3(CO)9 (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in the presence of added Me3NO to give the diphosphine-substituted cluster PhCCo3(CO)7(bma) (2). Cluster 2 is unstable in solution, readily losing CO to afford Co3(CO)6[(μ2-η2/η1-C(Ph)C=C(PPh2)C(O)OC(O)](μ2-PPh2) (3) as the sole observed product. VT-31P NMR measurements on cluster 2 indicate that the bma ligand functions as both a chelating and a bridging ligand. At … more
Date: December 1994
Creator: Yang, Kaiyuan
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Sulfur-induced Corrosion at Metal and Oxide Surfaces and Interfaces

Description: Sulfur adsorbed on metallic and oxide surfaces, whether originating from gaseous environments or segregating as an impurity to metallic interfaces, is linked to the deterioration of alloy performance. This research dealt with investigations on the interactions between sulfur and iron or iron alloy metallic and oxide surfaces under ultrahigh vacuum conditions. Sulfur was either intentionally dosed from a H2S source on an atomically clean metal surface, or segregated out as an impurity from the b… more
Date: August 1997
Creator: Cabibil, Hyacinth (Hyacinth Liesl)
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Surface and Interfacial Studies of Metal-Organic Chemical Vapor Deposition of Copper

Description: The nucleation and successful growth of copper (Cu) thin films on diffusion barrier/adhesion promoter substrates during metal-organic chemical vapor deposition (MOCVD) are strongly dependent on the initial Cu precursor-substrate chemistry and surface conditions such as organic contamination and oxidation. This research focuses on the interactions of bis(1,1,1,5,5,5-hexafluoroacetylacetonato)copper(II), [Cu(hfac)2], with polycrystalline tantalum (Ta) and polycrystalline as well as epitaxial tita… more
Date: December 1997
Creator: Nuesca, Guillermo M.
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The Synthesis and Chemistry of Polyciclic Cage Compounds

Description: Chapter I describes the synthesis of a trishomocubyl helical tubuland diol and some aspects of its inclusion chemistry. Thus, all three isomers of 4,7-dimethylpentacyclo[6.3.0.0^2,6.0^3,10.0^5,9]undecane-4,7-diol have been prepared and their X-ray structures have been determined. The syn,syn-isomer crystallizes in a double-stranded hydrogen-bonded lattice, while anti,syn-isomer forms a hydrogen-bonded layer lattice. In contrast, the anti,anti-isomer is a new member of the helical tubuland diol … more
Date: December 1994
Creator: Wang, Yanjun
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Synthesis and Study of Bioactive Compounds: I. Pyrethroids; II. Glutathione Derivatives

Description: Part I: In the first study of pyrethroids, twenty-one novel pyrethroid esters bearing strong electron-withdrawing groups (e.g., halomethylketo and nitro groups) in the double bond side chain of the cyclopropane acid moiety have been synthesized and evaluated for insect toxicity. Rather than the usually employed Wittig reaction for these syntheses, the novel pyrethroid acid moieties were prepared by amino acidcatalyzed Knoevenagel condensations under mild conditions. In the second study of pyre… more
Date: May 1995
Creator: Chyan, Ming-Kuan
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Thermodynamic and Structural Studies of Layered Double Hydroxides

Description: The preparation of layered double hydroxides via titration with sodium hydroxide was thoroughly investigated for a number of M(II)/M(III) combinations. These titration curves were examined and used to calculate nominal solubility product constants and other thermodynamic quantities for the various LDH chloride systems.
Date: May 1998
Creator: Boclair, Joseph W. (Joseph Walter)
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Partner: UNT Libraries
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