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Observation by flow sup 1 H NMR and dimerization kinetics and products of reactive ortho-quinodimethanes and benzocyclobutadiene

Description: The reactive o-quinodimethanes, 1,2-dimethylene-1,2-dihydronaphthalene (9) and o-xylylene (1) were observed by flow {sup 1}H NMR spectroscopy at room temperature. The {sup 1}H NMR spectrum of 9 was obtained in the absence of precursor and dimers. However, the {sup 1}H NMR spectrum of the more reactive 1, generated in a similar manner from (o-((trimethylsilyl)methyl)benzyl)trimethylammonium iodide (5.) could be obtained only in the presence of its stable (4 + 2) and (4 + 4) dimers. The dimerizat… more
Date: September 21, 1990
Creator: Fischer, David
Partner: UNT Libraries Government Documents Department
open access

Magnetic and thermal properties of high Tc superconductors

Description: Measurements of the normal state magnetic susceptibility {chi}(T) of YBa{sub 2}Cu{sub 3}O{sub 7}, Bi{sub 1.8}Pb{sub 0.2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}, and Bi{sub 2{minus}x}Pb{sub x}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+{delta}} (x = 0.2 and 0.25) were carried out. All {chi}(T) data show negative curvature below {approximately}2{Tc}. The data for YBa{sub 2}Cu{sub 3}O{sub 7} are in excellent agreement with a new calculation of the superconducting fluctuation diamagnetism. From the analysis, … more
Date: September 21, 1990
Creator: Lee, Wonchoon
Partner: UNT Libraries Government Documents Department
open access

A Search for Thermal Isomerization of Olefins to Carbenes: Thermal Generations of the Silicon-Nitrogen Double Bond

Description: The first part of this thesis will search for the thermal isomerization of olefins to carbenes which is predicted to be a high energy process by calculations and has only been observed in a few strained olefins. The possibility of thermal isomerization of simple olefins to carbenes will be explored. Substitution of a silyl group on the double bond of an olefin allows a potential intermediate which has a {beta}-radical to the silyl group during the cis-trans isomerization. The effects of a trime… more
Date: September 21, 1990
Creator: Zhang, Xianping
Partner: UNT Libraries Government Documents Department
open access

Physical metallurgy and magnetic behavior of Cd stabilized bcc (beta)Gd alloys

Description: As a continuation of the research on bcc Gd-Mg alloy system by Herchenroeder and Gschneidner, the metastable bcc Gd-Cd alloys were studied with the emphasis on their metallurgical and magnetic properties. An essentially single phase alloy could be retained for Cd concentrations from 15 at. % Cd to 19 at. % Cd, which is in the vicinity of the eutectoid composition of {beta}Gd in the Gd-Cd system. The lattice constants obtained for these alloys were used to determine the lattice constant of pure … more
Date: September 21, 1990
Creator: Tang. Jinke
Partner: UNT Libraries Government Documents Department
open access

A reciprocal space approach for locating symmetry elements in Patterson superposition maps

Description: A method for determining the location and possible existence of symmetry elements in Patterson superposition maps has been developed. A comparison of the original superposition map and a superposition map operated on by the symmetry element gives possible translations to the location of the symmetry element. A reciprocal space approach using structure factor-like quantities obtained from the Fourier transform of the superposition function is then used to determine the best'' location of the sym… more
Date: September 21, 1990
Creator: Hendrixson, Ton
Partner: UNT Libraries Government Documents Department
open access

Electrical Resistivity of Some Zintl Phase and the Precursors

Description: Resistivity measurements have been performed for electric characterization of the compounds Ba{sub 5}Sb{sub 3} and Ba{sub 5}Sb{sub 3}Cl, both with the Mn{sub 5}Si{sub 3} structure type, along with Ca{sub 5}Bi{sub 3} and Ca{sub 5}Bi{sub 3}F, both with the {beta}-Yb{sub 5}Sb{sub 3} structure type. These measurements were taken as a function of temperature using the four probe method on pressed polycrystalline pellets of the compounds. A sealed apparatus was developed for containing these air-sens… more
Date: September 21, 1990
Creator: Wolfe, Larry
Partner: UNT Libraries Government Documents Department
open access

High-resolution angle-resolved photoemission studies of high Tc superconductor Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8

Description: An angle-resolved photoemission study of the normal and superconducting states in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} was performed. Measurements in the normal state show bands dispersing through the Fermi level from at least 350 meV below E{sub F}. The Fermi level crossings are consistant with local-density band calculation, including a point calculated to be of Bi-O character. Additional measurements were made where bands crossed the Fermi level between 100 and 250K, along with measurements… more
Date: September 21, 1990
Creator: Liu, Rong
Partner: UNT Libraries Government Documents Department
open access

Reactions of the excited state of polypyridyl chromium(III) ion

Description: There has been much recent interest in the photochemistry and photophysics of transition metal polypyridine complexes due to the possibility of their use in solar energy conversion systems. The excited state of these compounds are known to undergo useful electron transfer and energy transfer reactions. This work attempts to elucidate the mechanism of the quenching of *CrL{sub 3}{sup 3+} (where L = 2,2{prime}-bipyridine, 4,4{prime}-dimethyl-2,2{prime}-bipyridine, 1,10-phenanthroline, 5-chloro-1,… more
Date: September 21, 1990
Creator: Steffan, Carl
Partner: UNT Libraries Government Documents Department
open access

Fundamental Investigations of Supported Monometallic and Bimetallic Catalysts by Proton Magnetic Resonance Spectroscopy

Description: Proton magnetic resonance spectroscopy, or nuclear magnetic resonance (NMR) of hydrogen, has been applied to investigate silica-supported Group VIII monometallic and Group VIII-Group IB bimetallic catalysts and alumina- and silica-supported platinum-rhenium bimetallic catalysts. Two adsorbed states of hydrogen, i.e., irreversible and reversible hydrogen, on the surfaces of monometallic Ru, Pt, and Cu particles and bimetallic Ru-Group Ib, Pt-Group Ib, and Pt-Re particles were observed directly v… more
Date: September 21, 1990
Creator: Wu, Xi
Partner: UNT Libraries Government Documents Department
open access

Electrocatalysis of Anodic and Cathodic Oxygen-Transfer Reactions

Description: The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO{sub 3}{sup {minus}}) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO{sub 3}{sup {minus}} to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO{sub 3}{sup {minus}} to produce an adsorbed product. An electrocatalyt… more
Date: September 21, 1990
Creator: Wels, Brian R.
Partner: UNT Libraries Government Documents Department
open access

Exclusive neutral strange particle production from double Pomeron exchange produced by proton-proton interactions at radical s = 62 GeV

Description: Data are presented for the first time on exclusive Pomeron-Pomeron interactions which produce a neutral strange and neutral antistrange particle pair in a central system X. In this paper, the system, X, is identified as one of the following neutral combinations; K{sub s}{sup 0}K{sub s}{sup 0}, K{sub s}{sup 0}K{sup {plus minus}}{pi}{sup {minus plus}}, {Lambda}{sup 0}{bar {Lambda}}{sup 0}, {Lambda}{sup 0}{bar {Lambda}}{sup 0}*. These data were obtained in proton-proton collisions at {radical}s = … more
Date: September 21, 1990
Creator: Skeens, John
Partner: UNT Libraries Government Documents Department
open access

Platinum(II) complexes as spectroscopic probes for biomolecules

Description: The use of platinum(II) complexes as tags and probes for biomolecules is indeed advantageous for their reactivities can be selective for certain purposes through an interplay of mild reaction conditions and of the ligands bound to the platinum. The use of {sup 195}Pt NMR as a method of detecting platinum and its interactions with biomolecules was carried out with the simplest model of platinum(II) tagging to proteins. Variable-temperature {sup 195}Pt NMR spectroscopy proved useful in studying t… more
Date: September 21, 1990
Creator: Ratilla, Eva
Partner: UNT Libraries Government Documents Department
open access

Target Visualization at the National Ignition Facility

Description: As the National Ignition Facility continues its campaign to achieve ignition, new methods and tools will be required to measure the quality of the targets used to achieve this goal. Techniques have been developed to measure target surface features using a phase-shifting diffraction interferometer and Leica Microsystems confocal microscope. Using these techniques we are able to produce a detailed view of the shell surface, which in turn allows us to refine target manufacturing and cleaning proce… more
Date: November 21, 2011
Creator: Potter, D
Partner: UNT Libraries Government Documents Department
open access

Charge Transfer and Support Effects in Heterogeneous Catalysis

Description: The kinetic, electronic and spectroscopic properties of two‐dimensional oxide‐supported catalysts were investigated in order to understand the role of charge transfer in catalysis. Pt/TiO{sub 2} nanodiodes were fabricated and used as catalysts for hydrogen oxidation. During the reaction, the current through the diode, as well as its I‐V curve, were monitored, while gas chromatography was used to measure the reaction rate. The current and the turnover rate were found to have the same temperature… more
Date: December 21, 2011
Creator: Hervier, Antoine
Partner: UNT Libraries Government Documents Department
open access

Cellular membrane trafficking of mesoporous silica nanoparticles

Description: This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the e… more
Date: June 21, 2012
Creator: Fang, I-Ju
Partner: UNT Libraries Government Documents Department
open access

A Voltage Controlled Oscillator for a Phase-Locked Loop Frequency Synthesizer in a Silicon-on-Sapphire Process

Description: Engineers from a government-owned engineering and manufacturing facility were contracted by government-owned research laboratory to design and build an S-band telemetry transmitter using Radio Frequency Integrated Circuit (RFIC) technology packaged in a Low-Temperature Co-fired Ceramic (LTCC) Multi-Chip Module. The integrated circuit technology chosen for the Phase-Locked Loop Frequency Synthesizer portion of the telemetry transmitter was a 0.25 um CMOS process that utilizes a sapphire substrat… more
Date: May 21, 2009
Creator: Garrison, Sean
Partner: UNT Libraries Government Documents Department
open access

Development of extreme ultraviolet and soft x-ray multilayer optics for scientific studies with femtosecond/attosecond sources

Description: The development of multilayer optics for extreme ultraviolet (EUV) radiation has led to advancements in many areas of science and technology, including materials studies, EUV lithography, water window microscopy, plasma imaging, and orbiting solar physics imaging. Recent developments in femtosecond and attosecond EUV pulse generation from sources such as high harmonic generation lasers, combined with the elemental and chemical specificity provided by EUV radiation, are opening new opportunities… more
Date: May 21, 2009
Creator: Aquila, Andrew Lee
Partner: UNT Libraries Government Documents Department
open access

On Decays of B Mesons to a Strange Meson and an Eta or Eta' Meson at Babar

Description: We describe studies of the decays of B mesons to final states {eta}K{sup *}(892), {eta}K{sup *}{sub 0}(S-wave), {eta}K{sup *}{sub 2}(1430), and {eta}'K based on data collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collier at the Stanford Linear Accelerator Center. We measure branching fractions and charge asymmetries for the decays B {yields} {eta}K{sup *}, where K{sup *} indicates a spin 0, 1, or 2 K{pi} system, making first observations of decays to final st… more
Date: April 21, 2009
Creator: Hirschauer, James Francis
Partner: UNT Libraries Government Documents Department
open access

Study of Rare B-Meson Decays Related to the CPObservable sin(2beta+gamma) at the BABAR Experiment

Description: This study reports the observation of the decays B{sup 0}{yields}D{sup (*)+}{sub S}{pi}{sup -} and B{sup 0}{yields}D{sup (*)-}K{sup +} in a sample of 230 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} events collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring, located at the Stanford Linear Accelerator Center. The branching fractions {beta}(B{sup 0} {yields} D{sup +}{sub S}{pi}{sup -}) = (1.3 {+-} 0.3 (stat) {+-} 0.2 (syst)) x 10{sup -5}, {beta}(B{sup 0}… more
Date: August 21, 2007
Creator: Orimoto, Toyoko Jennifer
Partner: UNT Libraries Government Documents Department
open access

Reconstruction of B- to D*0 e- anti_nu_e Decays and Determination of |Vcb|

Description: In this analysis the decay B- {yields} D*{sup 0}e{sup -}{bar {nu}}{sub e} is measured. The underlying data sampel consists of about 226 million B{bar B}-pairs accumulated on the {Upsilon}(4S) resonance by the BABAR detector at the asymmetric e{sup +}e{sup -} collider PEP-II. The reconstruction of the decay uses the channels D*{sup 0}{yields}D{sup 0}{pi}{sup 0}, D{sup 0} {yields} K{sup -}{pi}{sup +} and {pi}{sup 0} {yields} {gamma}{gamma}. The neutrino is not reconstructed. Since the rest frame … more
Date: August 21, 2007
Creator: Schubert, Jens
Partner: UNT Libraries Government Documents Department
open access

GaAs Blocked-Impurity-Band Detectors for Far-Infrared Astronomy

Description: High-purity and doped GaAs films have been grown by Liquid-phase epitaxy (LPE) for development of a blocked impurity band (BIB) detector for far-infrared radiation. The film growth process developed has resulted in the capability to grow GaAs with a net active impurity concentration below 1 x 10{sup 13} cm{sup -3}, ideal for the blocking layer of the BIB detector. The growth of n-type LPE GaAs films with donor concentrations below the metal-insulator transition, as required for the absorbing la… more
Date: December 21, 2004
Creator: Cardozo, Benjamin Lewin
Partner: UNT Libraries Government Documents Department
open access

Aspherical supernovae

Description: Although we know that many supernovae are aspherical, the exact nature of their geometry is undetermined. Because all the supernovae we observe are too distant to be resolved, the ejecta structure can't be directly imaged, and asymmetry must be inferred from signatures in the spectral features and polarization of the supernova light. The empirical interpretation of this data, however, is rather limited--to learn more about the detailed supernova geometry, theoretical modeling must been undertak… more
Date: May 21, 2004
Creator: Kasen, Daniel Nathan
Partner: UNT Libraries Government Documents Department
open access

Preliminary Testing of a Proportional Counter for Neutron Spectroscopy With Helium-3

Description: The He/sup 3/(n,p)T reaction can be utilized in a proportional counter for neutron-energy determination in the region 100 kev to 1 Mev. This has already been demonstrated and the reaction cross section in this energy region has been measured with a counter. For practical application of the counter as a spectrometer, such as in health physics work, it is desirable to increase the counter efficiency. A proportional counter utilizing an anticoincidence ring to reduce wall effect has been construct… more
Date: April 21, 1958
Creator: Green, J. N.
Partner: UNT Libraries Government Documents Department
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