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Calculations of the rate of thermal dissociation of air behind normal shock waves at Mach numbers of 10, 12, and 14

Description: Report presenting the rate equation for the dissociation of air, based on simple-collision theory, and the numerical values of the factors that enter it. The rate equation and conservation equations for a flowing dissociating gas are solved for the conditions behind normal shock waves at Mach numbers of 10, 12, and 14. Results regarding the adjustment of translation, rotation, and vibration and adjustment of dissociation are provided.
Date: April 1956
Creator: Wood, George P.
Partner: UNT Libraries Government Documents Department

Distorted Time Perception as an Underlying Factor of Psychosis Proneness and Dissociation

Description: Distortions in the perception of time historically have been associated with dissociation and psychosis in clinical populations. However, the relations among dissociation, psychosis, and time perception in sub-clinical populations have not been investigated. In the present study, college undergraduates scoring either normally or deviantly high on the Per-Mag were given a Dissociative Experiences Scale (DES) and a computerized time-estimation/production task. Participants scoring high on the Per-Mag obtained higher scores on the DES than participants scoring low on the Per- Mag. Per-Mag scores also correlated positively with DES scores across 608 total participants screened. The relation between dissociative and psychotic symptomatology is discussed considering dichotomous versus continuous conceptualizations of psychopathology. The effects of intelligence, social desirability, malingering, gender, and post-traumatic stress on the measures used are also discussed.
Date: August 1995
Creator: Koehler, Gregory C. (Gregory Charles)
Partner: UNT Libraries

A SURFACE CRYSTALLOGRAPHY STUDY BY DYNAMICAL LEED OF THE (sqrt3xsqrt3)R30o CO STRUCTURE ON THE Rh(111) CRYSTAL SURFACE

Description: The atomic positions of the Rh(111) + ({radical}3 x {radical}3)R30{sup o} CO and CO{sub 2} surfaces are analyzed by dynamical LEED. The Rh(111) + ({radical}3 x {radical}3)R30{sup o} CO and CO{sub 2} systems produce identical I-V curves, confirming the dissociation of CO{sub 2} to CO on this surface. The adsorbed CO is found to stand perpendicular to the surface with the carbon end down at an atop site (that is, terminally bonded). The CO overlayer spacings are d{sub RhC} = 1.95 {+-} 0.1 {angstrom} and d{sub CD} = 1.07 {+-} 0.1 {angstrom}. This geometry yields a Zanazzi-Jona R-factor of 0.40 and a Pendry R-factor of 0.50.
Date: September 1, 1980
Creator: Koestner, R.J.; Van Hove, M.A. & Somorjai, G.A.
Partner: UNT Libraries Government Documents Department

Autocatalytic water dissociation on Cu(110) at near ambient conditions

Description: Autocatalytic dissociation of water on the Cu(110) metal surface is demonstrated based on X-ray photoelectron spectroscopy studies carried out in-situ under near ambient conditions of water vapor pressure (1 Torr) and temperature (275-520 K). The autocatalytic reaction is explained as the result of the strong hydrogen-bond in the H{sub 2}O-OH complex of the dissociated final state, which lowers the water dissociation barrier according to the Broensted-Evans-Polanyi relations. A simple chemical bonding picture is presented which predicts autocatalytic water dissociation to be a general phenomenon on metal surfaces.
Date: May 16, 2007
Creator: Mulleregan, Alice; Andersson, Klas; Ketteler, Guido; Bluhm, Hendrik; Yamamoto, Susumu; Ogasawara, Hirohito et al.
Partner: UNT Libraries Government Documents Department

Dissociative-recombination product states and the dissociation energy D<sub>0</sub> of Ne<sub>2</sub><sup>+</sup>

Description: Final product states of Ne<sub>2</sub><sup>+</sup> dissociative recombination were studied using time-of-flight spectroscopy to determine the kinetic energies released. The dissociative recombination occurred in a sustained discharge in the presence of a variable magnetic field and discharge voltage, at pressures of 5-15 mTorr. Under different conditions various excited states were observed ranging from the lowest 3<i>s</i> metastable states to higher Rydbcrg states within 0.000 54 eV of the dissociation limit. From their narrow widths, it is deduced that these higher states arose from Ne<sub>2</sub><sup>+</sup> ions with subthermal energies. From two of these narrow distributions, we obtain an improved value for the dissociation limit D<sub>0</sub>(Ne<sub>2</sub><sup>+</sup>)= 1.26±0.02 eV.
Date: February 28, 1998
Creator: Hardy, K. A.; Peterson, J. R.; Ramos, G. & Sheldon, J. W.
Partner: UNT Libraries Government Documents Department

Equation of State measurements of hydrogen isotopes on Nova

Description: High intensity lasers can be used to perform measurements of materials at extremely high pressures if certain experimental issues can be overcome. We have addressed those issues and used the Nova laser to shock-compress liquid deuterium and obtain measurements of density and pressure on the principal Hugoniot at pressures from 300 kbar to more than 2 Mbar. The data are compared with a number of equation of state models. The data indicate that the effect of molecular dissociation of the deuterium into a monatomic phase may have a significant impact on the equation of state near 1 Mbar.
Date: November 1, 1997
Creator: Collins, G. W., LLNL
Partner: UNT Libraries Government Documents Department

Three-Body Breakup Dynamics in Dissociative Recombination

Description: Using the CRYRing Facility in Stockholm Coupled with an MCP-CCD detector, and a differential stopping foil, we have determined dynamic parameters in the three-body dissociative recombination of H<sub>2</sub>O<sup>+</sup>. These include the distribution between the O(<sup>3</sup>P) and O(<sup>1</sup>D) channels, the distribution of H atom recoil energies in the O(<sup>3</sup>P) channel and the distribution of angles between the two departing H atoms.
Date: June 16, 1999
Creator: Al-Khalili, A.; Datz, S.; Derkatch, A.; Larsson, M.; Rosén, S.; Shi, W. et al.
Partner: UNT Libraries Government Documents Department

Effect of Dissociation on Exhaust-Nozzle Performance

Description: Memorandum presenting net jet thrusts for stoichiometric hydrocarbon-air, hydrogen-air and pentaborane-air mixtures for equilibrium and frozen expansion in the exhaust nozzle at flight Mach numbers up to 10. Examinations of the dissociation products involved and the energies associated with them, for the hydrocarbon- and hydrogen-air mixtures indicated that a major portion of the dissociation energy for the hydrocarbon mixture is involved in the carbon monoxide molecule.
Date: June 11, 1958
Creator: Reynolds, T. W.
Partner: UNT Libraries Government Documents Department

The Breathing Orbital Valence Bond Method in Diffusion Monte Carlo: C-H Bond Dissociation ofAcetylene

Description: This study explores the use of breathing orbital valence bond (BOVB) trial wave functions for diffusion Monte Carlo (DMC). The approach is applied to the computation of the carbon-hydrogen (C-H) bond dissociation energy (BDE) of acetylene. DMC with BOVB trial wave functions yields a C-H BDE of 132.4 {+-} 0.9 kcal/mol, which is in excellent accord with the recommended experimental value of 132.8 {+-} 0.7 kcal/mol. These values are to be compared with DMC results obtained with single determinant trial wave functions, using Hartree-Fock orbitals (137.5 {+-} 0.5 kcal/mol) and local spin density (LDA) Kohn-Sham orbitals (135.6 {+-} 0.5 kcal/mol).
Date: May 30, 2008
Creator: Domin, D.; Braida, Benoit & Lester Jr., William A.
Partner: UNT Libraries Government Documents Department

Real time in situ detection of organic nitrates in atmospheric aerosols

Description: A new field instrument is described that quantifies total particle phase organic nitrates. The instrument is based on the thermal dissociation laser induced fluorescence (TD-LIF) method that thermally converts nitrates to NO2 which is then detected by LIF. This instrument is unique in its ability to provide fast sensitive measurements of particle phase organic nitrates, without interference from inorganic nitrate. Here we use it to quantify organic nitrates in SOA generated from high-NOx photooxidation of limonene, a-pinene, D-3-carene, and tridecane. In these experiments the organic nitrate moiety is observed to be 6-15percent of the total SOA mass, depending on the organic precursor.
Date: June 11, 2010
Creator: Rollins, Andrew W.; Smith, Jared D.; Wilson, Kevin R. & Cohen, Ronald C.
Partner: UNT Libraries Government Documents Department

Three-body breakup in dissociative electron attachment to the water molecule

Description: We report the results of {\em ab initio} calculations on dissociative electron attachment (DEA) to water that demonstrate the importance of including three-body breakup in the dissociation dynamics. While three-body breakup is ubiquitous in the analogous process of dissociative recombination, its importance in low-energy dissociative electron attachment to a polyatomic target has not previously been quantified. Our calculations, along with our earlier studies of DEA into two-body channels, indicate that three-body breakup is a major component of the observed O- cross section. The local complex potential model provides a generally accurate picture of the experimentallyobserved features in this system, reproducing some quantitatively, others qualitatively, and one not at all.
Date: August 28, 2008
Creator: Haxton, Daniel J.; Rescigno, Thomas N. & McCurdy, C. William
Partner: UNT Libraries Government Documents Department

ISOLEUCYL-tRNA SYNTHETASE OF E. coli B. A RAPID KINETIC INVESTIGATION OF THE L-ISOLEUCINE ACTIVATING REACTION

Description: We have investigated the preequilibrium kinetics of the L-isoleucine activation reaction catalyzed by Ile-tRNA synthetase in the presence of a fluorescent reporter group, 2-p-toluidinylnaphthalene-6-sulfonate, using the stopped-flow technique. It is found that of all the reactants involved, L-isoleucine binds slowest to the enzyme, apparently in a two-step process. The kinetics of the reaction are invariant in the presence of co-reactants, whereas the kinetics for ATP are drastically changed in the presence of Mg{sup 2+} ions. The formation of enzyme bound L-isoleucyl {approx} AMP is conveniently followed at dilute concentrations. The value for the rate constant of formation was determined to be 135 sec{sup -1} and of the reverse process to be 670 sec{sup -1} at pH 8.0 25 C. These values are considerably higher than the rate constant 15 sec{sup -1} of the dissociation reaction for L-isoleucine. The value of the kinetically defined equilibrium constant between the ternary Michaelis-Menten complex and the ternary enzyme-product complex indicates that, at equilibrium, the Michaelis-Menten complex is favored. The effect of temperature has been determined, and a tentative interpretation of the thermodynamic parameters is offered. The zero standard enthalpy and positive entropy for binding of L-isoleucine is consistent with hydrophobic interactions, whereas the enzyme-ligand complexes for ATP and pyrophosphate might be stabilized by hydrogen-bonds and ion-ion interactions. The equilibrium constant of formation of the ternary enzyme-product complex from the Michaelis-Menten complex does not increase significantly with temperature. The types of kinetic pathways have been restricted to the alternative of a random mechanism or an ordered sequential mechanism in which L-iso-leucine binds first. We believe that the mechanism is random.
Date: May 1, 1972
Creator: Holler, E. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department

Melting Sequence of Quarkonia

Description: In this talk I discuss what we can learn about quarkonium dissociation from lattice-potential based models, and summarize the current understanding of lattice data on quarkonium.
Date: April 5, 2008
Creator: Mocsy,A.
Partner: UNT Libraries Government Documents Department

Fragmentation pathwaysfor selected electronic states of theacetylene dication

Description: Coincident measurement of the Auger electron and fragmention momenta emitted after carbon core-level photoionization of acetylenehas yielded new understanding of how the dication fragments. Ab initiocalculations and experimental data, including body-frame Auger angulardistributions, are used to identify the parent electronic states andtogether yield a comprehensive map of the dissociation pathways whichinclude surface crossings and barriers to direct dissociation. The Augerangular distributions show evidence of core-holelocalization.
Date: December 18, 2007
Creator: Osipov, Timur; Rescigno, Thomas N.; Weber, Thorsten; Miyabe,Shungo; Jahnke, T.; Alnaser, A. et al.
Partner: UNT Libraries Government Documents Department

Evidence for CO Dissociation on Rhodium Surfaces

Description: Carbon monoxide adsorbs molecularly on rhodium surfaces at 300K, but if the rhodium samples are heated in the presence of carbon monoxide, there is evidence for carbon-oxygen bond breaking at step and/or defect sites. The effects of step and defect site density, subsurface oxygen concentration, and oxygen dissolution into the rhodium lattice on CO dissociation are discussed.
Date: June 1, 1980
Creator: Castner, D. G.; Dubois, L. H.; Sexton, B. A. & Somorjai, G. A.
Partner: UNT Libraries Government Documents Department

Decisive role of the energetics of dissociation products in the adsorption of water on O/Ru(0001)

Description: Using density-functional theory they found that, depending on coverage, coadsorbed oxygen can act both as a promoter and as an inhibitor of the dissociation of water on Ru(0001), the transition between these two behaviors occurring at (0.2 M). The key factor that determines this transition is the adsorption energy of the reaction products, OH in particular. The chemistry of this coadsorbed system is dictated by the effective coordination of the Ru atoms that participate in the bonding of the different species. In particular, they observed that a low coverage of oxygen increases the adsorption energy of the OH fraction on the Ru surface. This surprising extra stabilization of the OH with the coadsorption of oxygen can be understood in the context of the metallic bonding and could well correspond to a general trend for the coadsorption of electronegative species on metallic surfaces.
Date: October 15, 2008
Creator: Cabrera-Sanfelix, Pepa; Arnau, Andres; Mugarza, Aitor; Shimizu, Tomoko K.; Salmeron, Miquel & Sánchez-Portal, Daniel
Partner: UNT Libraries Government Documents Department