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Reducing the Computational Cost of Ab Initio Methods

Description: In recent years, advances in computer technology combined with new ab initio computational methods have allowed for dramatic improvement in the prediction of energetic properties. Unfortunately, even with these advances, the extensive computational cost, in terms of computer time, memory, and disk space of the sophisticated methods required to achieve chemical accuracy - defined as 1 kcal/mol from reliable experimental data effectively - limits the size of molecules [i.e. less than 10-15 non-h… more
Date: August 2008
Creator: Mintz, Benjamin
Partner: UNT Libraries
open access

Reduction Pathways in Cyclopentadienyl Rhenium Dicarbonyl Dibromide Deriviatives and Indenyl Rhenium Tricarbonyl: Synthesis, Structure, and Reactivity of Anionic Cyclopentadienyl Rhenium Complexes. Ring Attack vs. Metal-Halogen Exchange

Description: The reactions of diagonal and lateral Cp'Re(CO)2Br2 (where Cp' = n5-C5H5, n5-C5Me5) and (n5-CgH7)Re(CO)3 with reducing agents have been examined. Hydride reduction at -78 °C is observed to occur at the Cp ring in both CpRe(CO)2Br2 isomers, affording a thermally unstable [(n4 -C5Hg)Re(CO)2Br2]- complex. The product of hydride ring attack has been characterized by low-temperature IR and 1H NMR measurements in addition to 13C NOE and heteronuclear 2D NMR measurements. Reaction of lateral CpRe(CO)2… more
Date: December 1989
Creator: Lee, Sang Woo, 1952-
Partner: UNT Libraries
open access

Reductive Functionalization of 3D Metal-Methyl Complexes and Characterization of a Novel Dinitrogen Dicopper (I) Complex

Description: Reductive functionalization of methyl ligands by 3d metal catalysts and two possible side reactions has been studied. Selective oxidation of methane, which is the primary component of natural gas, to methanol (a more easily transportable liquid) using organometallic catalysis, has become more important due to the abundance of domestic natural gas. In this regard, reductive functionalization (RF) of methyl ligands in [M(diimine)2(CH3)(Cl)] (M: VII (d3) through CuII (d9)) complexes, has been stud… more
Date: May 2017
Creator: Fallah, Hengameh
Partner: UNT Libraries
open access

Regioselective Coupling Reactions of Diiodophenol Derivatives

Description: Palladium catalyzed reactions of derivatives of 2,4-diiodophenol are explored. Coupling reactions with a series of terminal alkynes and formylation are found to be efficient and regioselective. Coupling with stananne reagents and alkenes do not work. The nature of the oxygen protecting group is critical. The phytotoxic natural product, Eutypine, is synthesized by using regioselective formylation and alkyne coupling. An approach to the plant antimicrobial compound Plicatin B is examined.
Date: December 1994
Creator: Ji, Jianhua
Partner: UNT Libraries
open access

The Regulation of HMG-CoA Reductase by Enzyme-Lipid Interactions

Description: The temperature-dependent catalytic activity of rat liver 3-hydroxy-3 -methylglutaryl coenzyme A reductase (HMG-CoA reductase) displays the nonlinear Arrhenius behavior characteristic of many membrane-bound enzymes. A two-conformer equilibrium model has been developed to characterize this behavior. In the model, HMG-CoA reductase undergoes a conformational change from a low specific activity to a high specific activity form. This conformation change is apparently driven by a temperature-depende… more
Date: May 1981
Creator: Smith, Vana L.
Partner: UNT Libraries
open access

Regulation of Pyridine Nucleotide Metabolism in Saccharomyces cerevisiae

Description: The levels of total nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), and their redox states were determined as the function of growth in S. cerevisiae. Cells growing in a medium containing 0.8% glucose exhibit two phases of exponential growth, utilizing glucose and ethanol, respectively. The NAD pool is 50% reduced during both stages of growth while the NADP pool is 67% reduced in glucose growth and 48% reduced in ethanol growth. The NAD/NADP ratio… more
Date: May 1976
Creator: Ting, Haung-yu
Partner: UNT Libraries
open access

A Reinvestigation of the Kinetics and Mechanism of Ligand Exchange in Mu-(2,2,8,8-Tetramethyl-3, 7-Dithianonane)-Decacarbonylditungsten(0)

Description: This student is interested in reinvestigating the kinetics and mechanism of the bridged compound in l,2-dichloroethane with triisopropyl phosphite and in finding the reasons why the values of competition ratio k₋₂ /k₃ in this reaction are so large.
Date: August 1988
Creator: Liao, Jing-Piin
Partner: UNT Libraries

The Revival of Electrochemistry: Electrochemical Deposition of Metals in Semiconductor Related Research

Description: Adherent Cu films were electrodeposited onto polycrystalline W foils from purged solutions of 0.05 M CuSO4 in H2SO4 supporting electrolyte and 0.025 M CuCO3∙Cu(OH)2 in 0.32 M H3BO3 and corresponding HBF4 supporting electrolyte, both at pH = 1. Films were deposited under constant potential conditions at voltages between -0.6 V and -0.2 V versus Ag/AgCl. All films produced by pulses of 10 s duration were visible to the eye, copper colored, and survived a crude test called "the Scotch tape test… more
Access: Restricted to the UNT Community Members at a UNT Libraries Location.
Date: August 2005
Creator: Wang, Chen
Partner: UNT Libraries
open access

Selective Lipid Absorption

Description: An experiment was designed to study in the same animal any preferential absorption of a free fatty acid in the presence of a triglyceride of the same fatty acid. Rats were administered a mixture of free fatty acid and its triglyceride labeled with carbon-13 and carbon-14 respectively. Each isotope in the fed lipid and in the lipid recovered from the gastrointestinal tract was measured. The isotope effect, if any, was studied by administering a mixture of palmitic acid-1-C13 and palmitic acid-1-… more
Date: January 1960
Creator: Marcia, John Albion
Partner: UNT Libraries
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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)
Partner: UNT Libraries
open access

Self-assembly Polymeric Nanoparticles Composed of Polymers Crosslinked with Transition Metals for Use in Drug Delivery

Description: A major drawback of chemotherapy is the lack of selectively leading to damage in healthy tissue, which results in severe acute side effects to cancer patients. The use of nanoparticles as a drug delivery system has emerged as novel strategy to overcome the barriers of immunogenic response, controlled release of therapeutic, and targeting the toxicity only to cancerous cells. In this study, polymeric nanoparticles composed of transition metals and particles derived from natural biopolymers hav… more
Date: December 2015
Creator: Nguyen, Duong Thuy
Partner: UNT Libraries
open access

Self-diffusion of Pb210 and Cl36 in Molten PbCl2-KCl Mixtures in the Region of the Compound 2PbCl2-KCl

Description: The specific goal of the investigation was the measurement, as a function of temperature, of the self-diffusion coefficients of Pb210 and Cl36 in PbCl2-KCl compositions in the region of the first compound, and to calculate from these data the activation energy necessary for the diffusion of these ions.
Date: June 1960
Creator: Tidwell, Troy Haskell
Partner: UNT Libraries
open access

Semiconducting Aromatic Boron Carbide Films for Neutron Detection and Photovoltaic Applications

Description: Semiconducting aromatic-boron carbide composite/alloyed films formed by plasma enhanced chemical vapor deposition from carborane and aromatic precursors have been demonstrated to be excellent detectors for thermal neutrons because of the large 10B cross section. The electronic properties of these films derived from XPS show that the properties of boron carbide can be tuned by co-deposition of aromatic compounds and carborane. Aromatic doping results in narrower indirect band gaps (1.1 - 1.7 eV … more
Date: December 2019
Creator: Oyelade, Adeola O
Partner: UNT Libraries
open access

Sensitization of Lanthanides and Organic-Based Phosphorescence via Energy Transfer and Heavy-Atom Effects

Description: The major topics discussed are the phosphorescence sensitization in the lanthanides via energy transfer and in the organics by heavy atom effects. The f-f transitions in lanthanides are parity forbidden and have weak molar extinction coefficients. Upon complexation with the ligand, ttrpy (4'-p-Tolyl-[2,2':6',2"]-terpyridine) the absorption takes place through the ligand and the excitation is transferred to the lanthanides, which in turn emit. This process is known as "sensitized luminescence." … more
Date: May 2010
Creator: Arvapally, Ravi K.
Partner: UNT Libraries
open access

Separation and Characterization of Variant Forms of Phosphoglucose Isomerase: Purification and Structural Analysis of Active Site Peptides from Human and Rabbit Phosphoglucose Isomerase

Description: A method has been developed for the rapid, quantitative separation of normal and abnormal phosphoglucose isoemrase allozymes from individuals heterozygous for genetic variant forms of the enzyme. The method utilizes a substrate gradient elution of the enzyme from carboxymethyl Biogel and is far superior in terms of resolution and recovery to methods based on electrophoresis and isoelectric focusing. Four different genetic variant forms of the enzyme were isolated and subjected to a systematic c… more
Date: May 1980
Creator: Gibson, David R.
Partner: UNT Libraries
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Separation of Transition Metal Ions by HPLC, Using UV-VIS Detection

Description: HPLC has been used and can quickly determine several ions simultaneously. The method of determination described for transition metals [Cr(III), Fe(III), Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Mn(II)] and [Ca(II), Pb(II)] using HPLC with UV-VIS detection is better than the PAR complexation method commonly used. The effects of both eluent pH and detector wavelength were investigated. Results from using different pHs and wavelengths, optional analytical conditions for the separation of [Ni(II), C… more
Date: August 1987
Creator: Lien, Wan-Fu
Partner: UNT Libraries
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Silenes and Silenoids in the Chemistry of Cyclopentadienylsilanes

Description: Evidence is presented that apparent silene products obtained from the metalation of cyclopentadienyldimethyl - chlorosilane either with tert-butyl1ithium or with methylenetriphenylphosphorane actually arise from the metalated starting material, a silenoid, rather than from a silafulvene intermediate. Trimethylmethoxysi1ane is shown to be an effective trap for dimethylsilafulvene. A new dimethylsilafulvene precursor, bis(dimethylmethoxysi1yl) cyclopentadiene, which gives high yields of dimethyld… more
Date: August 1986
Creator: Rozell, James M. (James Morris)
Partner: UNT Libraries
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Silver(I) and Copper(I) Complexes from Homoleptic to Heteroleptic: Synthesis, Structure and Characterization

Description: A plethora of novel scientific phenomena and practical applications, such as solid-state molecular solar cells and other optoelectronic devices for energy harvesting and lighting technologies, have catalyzed us to synthesize novel compounds with tunable properties. Synthetic routes, single crystal structures, and spectral and materials properties are described. Reactions of Ag(I) and Cu(I) precursors with various types of ligands -- including the azolates, diimines, and diiphosphines -- lead to… more
Date: December 2018
Creator: Almotawa, Ruaa Mohammed
Partner: UNT Libraries
open access

Simultaneous Part-Per-Billion Determination of Sodium and Chloride Ions

Description: The method utilizes both cation and anion concentrator columns in parallel as a preconcentration system. The preconcentrator system is loaded using a reagent delivery module operated for a specific time at a preset flow rate. Total injection volumes of 2-5 ml are routinely used. Various chromatograms are discussed along with detailed information concerning detection limits for sodium and chloride, the system operating conditions, and the solutions to other pitfalls which have arisen during the … more
Date: August 1987
Creator: Gan, Din-Chung
Partner: UNT Libraries
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Sites of Reactivity During Ligand-Exchange Reactions in Octahedral Group VIB Metal Carbonyls

Description: The site of initial metal-carbonyl bond-breaking during ligand-exchange reactions in a series of octahedral metal carbonyls of the type (L2)M(CO)4 (M = Cr, Mo, W; L2 = diphos, phen, dipy) has been determined employing infrared spectroscopy and Fourier transform nuclear magnetic resonance spectroscopy. The results of this study reveal, for all metal carbonyl complexes of the type mentioned above, that loss of CO occurs exclusively at an axial position (cis to the bidentate ligand, I^)• The dynam… more
Date: December 1979
Creator: Asali, Khalil Jamil
Partner: UNT Libraries
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