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Calculation Of Change-Changing Cross Sections Of IONS Or Atoms Colliding With Fast IONS Using The Classical Trajectory Method

Description: Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental … more
Date: October 10, 2008
Creator: Kaganovich, I. D., Shnidman, Ariel, Mebane, Harrison, Davidson, R.C.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Chemical imaging of biological materials by NanoSIMS using isotopic and elemental labels

Description: The NanoSIMS 50 combines unprecedented spatial resolution (as good as 50 nm) with ultra-high sensitivity (minimum detection limit of {approx}200 atoms). The NanoSIMS 50 incorporates an array of detectors, enabling simultaneous collection of 5 species originating from the same sputtered volume of a sample. The primary ion beam (Cs{sup +} or O{sup -}) can be scanned across the sample to produce quantitative secondary ion images. This capability for multiple isotope imaging with high spatial resol… more
Date: April 10, 2006
Creator: Weber, P K; Fallon, S J; Pett-Ridge, J; Ghosal, S & Hutcheon, I D
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Characterization of chemical bonding in low-k dielectric materialsfor interconnect isolation: a xas and eels study

Description: The use of low dielectric constant materials in the on-chipinterconnect process reduces interconnect delay, power dissipation andcrosstalk noise. To achieve the requirements of the ITRS for 2007-2009minimal sidewall damage from etch, ash or cleans is required. In chemicalvapor deposited (CVD) organo-silicate glass (OSG) which are used asintermetal dielectric (IMD) materials the substitution of oxygen in SiO2by methyl groups (-CH3) reduces the permittivity significantly (from 4.0in SiO2 to 2.6-3… more
Date: April 10, 2006
Creator: Hoffmann, P.; Schmeisser, D.; Engelmann, H. J.; Zschech, E.; Stegmann, H.; Himpsel, F. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Enhancing Carbon Fixation by Metabolic Engineering: A Model System of Complex Network Modulation

Description: In the first two years of this research we focused on the development of a DNA microarray for transcriptional studies in the photosynthetic organism Synechocystis and the elucidation of the metabolic pathway for biopolymer synthesis in this organism. In addition we also advanced the molecular biological tools for metabolic engineering of biopolymer synthesis in Synechocystis and initiated a series of physiological studies for the elucidation of the carbon fixing pathways and basic central carbo… more
Date: April 10, 2008
Creator: Stephanopoulos, Dr. Gregory
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Spatial distribution of average charge state and deposition rate in high power impulse magnetron sputtering of copper

Description: The spatial distribution of copper ions and atoms in high power impulse magnetron sputtering (HIPIMS) discharges was determined by (i) measuring the ion current to electrostatic probes and (ii) measuring the film thickness by profilometry. A set of electrostatic and collection probes were placed at different angular positions and distances from the target surface. The angular distribution of the deposition rate and the average charge state of the copper species (including ions and neutrals) wer… more
Date: May 10, 2008
Creator: Anders, Andre; Horwat, David & Anders, Andre
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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EXAFS Measurements of Laser-Shocked V and Ti and Crystal Phase Transformation in Ti

Description: Extended X-Ray Absorption Fine Structure (EXAFS), using a laser-imploded target as a source, can yield the properties of laser-shocked metals on a nanosecond time scale. EXAFS measurements of vanadium shocked to {approx}0.4 Mbar yield the compression and temperature in good agreement with hydrodynamic simulations and shock-speed measurements. In laser-shocked titanium at the same pressure, the EXAFS modulation damping is much higher than warranted by the predicted temperature increase. This is … more
Date: March 10, 2004
Creator: Yaakobi, B.; Meyerhofer, D. D.; Boehly, T. R.; Rehr, J. J.; Remington, B. A.; Allen, P. G. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Spectroscopic studies of hydrogen collisions

Description: Low energy collisions involving neutral excited states of hydrogen are being studied with vacuum ultraviolet spectroscopy. Atomic hydrogen is generated by focusing an energetic pulse of ArF, KrF, or YAG laser light into a cell of molecular hydrogen, where a plasma is created near the focal point. The H{sub 2} molecules in and near this region are dissociated, and the cooling atomic hydrogen gas is examined with laser and dispersive optical spectroscopy. In related experiments, we are also inves… more
Date: December 10, 1991
Creator: Kielkopf, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Measurement of fragmentation and functionalization pathways in the multistep heterogeneous oxidation of organic aerosol

Description: The competition between the addition of polar, oxygen-containing functional groups (functionalization) and the cleavage of C-C bonds (fragmentation) has a governing influence on the change in volatility of organic species upon atmospheric oxidation, and hence on the loading of tropospheric organic aerosol. However the branching between these two channels is generally poorly constrained for oxidized organics. Here we determine functionalization/fragmentation branching ratios for organics spannin… more
Date: March 10, 2009
Creator: Kroll, Jesse H.; Smith, Jared D.; Che, Dung L.; Kessler, Sean H.; Worsnop, Douglas R. & Wilson, Kevin R.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Gas-phase energies of actinide oxides -- an assessment of neutral and cationic monoxides and dioxides from thorium to curium

Description: An assessment of the gas-phase energetics of neutral and singly and doubly charged cationic actinide monoxides and dioxides of thorium, protactinium, uranium, neptunium, plutonium, americium, and curium is presented. A consistent set of metal-oxygen bond dissociation enthalpies, ionization energies, and enthalpies of formation, including new or revised values, is proposed, mainly based on recent experimental data and on correlations with the electronic energetics of the atoms or cations and wit… more
Date: August 10, 2009
Creator: Marcalo, Joaquim & Gibson, John K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A Measurement of the Rate of Muon Capture in Hydrogen Gas andDetermination of the Proton's Induced Pseudoscalar Coupling gP

Description: This dissertation describes a measurement of the rate ofnuclear muon capture by the proton, performed by the MuCap Collaborationusing a new technique based on a time projection chamber operating inultraclean, deuterium-depleted hydrogen gas at room temperature and 1 MPapressure. The hydrogen target's low gas density of 1 percent compared toliquid hydrogen is key to avoiding uncertainties that arise from theformation of muonic molecules. The capture rate was obtained from thedifference between t… more
Date: July 10, 2007
Creator: Banks, Thomas Ira
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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First principles simulation of a superionic phase of hydrogen fluoride (HF) at high pressures and temperatures

Description: The authors have conducted Ab initio molecular dynamics simulations of hydrogen fluoride (HF) at pressures of 5-66 GPa along the 900 K isotherm. They predict a superionic phase at 33 GPa, where the fluorine atoms are fixed in a bcc lattice while the hydrogen atoms diffuse rapidly with a diffusion constant of between 2 x 10{sup -5} and 5 x 10{sup -5} cm{sup 2}/s. They find that a transformation from asymmetric to symmetric hydrogen bonding occurs in HF at 66 GPa and 900 K. With superionic HF the… more
Date: April 10, 2006
Creator: Goldman, N & Fried, L E
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Local structure and vibrational properties of alpha-Pu, alpha-Uand the alpha-U charge density wave

Description: The local atomic environment and vibrational properties of atoms in monoclinic pure {alpha}-plutonium as well as orthorhombic pure a-uranium and its low-temperature charge-density-wave (CDW) modulation are examined by extended x-ray absorption fine structure spectroscopy (EXAFS). Pu L{sub III}-edge and U L{sub III}-edge EXAFS data measured at low temperatures verify the crystal structures of {alpha}-U and {alpha}-Pu samples previously determined by x-ray diffraction and neutron scattering. Deby… more
Date: August 10, 2004
Creator: Nelson, E. J.; Allen, P. G.; Blobaum, K. J. M.; Wall, M. A. & Booth, C. H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Spectroscopic studies of hydrogen collisions. Progress report

Description: Low energy collisions involving neutral excited states of hydrogen are being studied with vacuum ultraviolet spectroscopy. Atomic hydrogen is generated by focusing an energetic pulse of ArF, KrF, or YAG laser light into a cell of molecular hydrogen, where a plasma is created near the focal point. The H{sub 2} molecules in and near this region are dissociated, and the cooling atomic hydrogen gas is examined with laser and dispersive optical spectroscopy. In related experiments, we are also inves… more
Date: December 10, 1991
Creator: Kielkopf, J.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Combustion-related studies using weakly-bonded complexes

Description: Objectives are to study binary complexes involving molecular oxygen and the photoinitiated reactions, and to study species involving oxygen atoms and small molecules and simple hydrocarbons. Attempts were made to produce O({sup 3}P) in a jet by photodissociation of NO{sub 2} and to cluster it with HCl. A new pulsed jet vacuum system with greater sensitivity is being constructed. The IR spectrum of O{sub 2}DCl complex was measured.
Date: April 10, 1990
Creator: Beaudet, R. A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Local Structure and Vibrational Properties of alpha-Pu, alpha-U, and the alpha-U Charge Density Wave

Description: The local atomic environment and vibrational properties of atoms in monoclinic pure {alpha}-plutonium as well as orthorhombic pure {alpha}-uranium and its low-temperature charge-density-wave (CDW) modulation are examined by extended x-ray absorption fine structure spectroscopy (EXAFS). Pu L{sub III}-edge and U L{sub III}-edge EXAFS data measured at low temperatures verify the crystal structures of {alpha}-U and {alpha}-Pu samples previously determined by x-ray diffraction and neutron scattering… more
Date: August 10, 2004
Creator: Nelson, E J; Allen, P G; Blobaum, K M; Wall, M A & Booth, C H
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Nuclear Fuel Leasing, Recycling and proliferation: Modeling a Global View

Description: On February 11, 2004, U.S. President George W. Bush, in a speech to the National Defense University stated: ''The world must create a safe, orderly system to field civilian nuclear plants without adding to the danger of weapons proliferation. The world's leading nuclear exporters should ensure that states have reliable access at reasonable cost to fuel for civilian reactors, so long as those states renounce enrichment and reprocessing. Enrichment and reprocessing are not necessary for nations s… more
Date: March 10, 2004
Creator: Crozat, M P; Choi, J; Reis, V H & Hill, R
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Measuring the Effect of Fuel Structures and Blend Distribution on Diesel Emissions Using Isotope Tracing

Description: Carbon atoms occupying specific positions within fuel molecules can be labeled and followed in emissions. Renewable bio-derived fuels possess a natural uniform carbon-14 ({sup 14}C) tracer several orders of magnitude above petroleum-derived fuels. These fuels can be used to specify sources of carbon in particulate matter (PM) or other emissions. Differences in emissions from variations in the distribution of a fuel component within a blend can also be measured. Using Accelerator Mass Spectromet… more
Date: February 10, 2004
Creator: Cheng, A. S.; Mueller, C. J.; Buchholz, B. A. & Dibble, R. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Mechanism of GEMS formation

Description: GEMS (glass with embedded metal and sulfides) in interplanetary dust particles (IDPs) were examined using 200 keV analytical transmission electron microscopy. The morphologies and crystallography of embedded relict grains reveal that GEMS are pseudomorphs formed by irradiation processing of crystals free-floating in space. Some GEMS retain a compositional and morphological ''memory'' of the crystal from which they formed. Pseudomorphism rules out condensation, annealing, flash heating, or shock… more
Date: March 10, 2004
Creator: Bradley, J P & Dai, Z R
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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A coarse-grained model for PETN crystals

Description: Using the energetic material Pentaerythritol Tetranitrate (PETN) as a specific example of molecular crystal, we describe the development of a simple coarse-graining procedure by grouping several atoms or whole functional groups into single charge-neutral beads. As compared to fully atomistic calculations the coarse-grained model speeds up simulations by more than two orders of magnitude. Yet, by adjusting only two parameters in the coarse-grained interaction, the model accurately predicts the l… more
Date: February 10, 2006
Creator: Gee, R.; Wu, C. & Maiti, A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The Catalysis of Nuclear Reactions by mu Mesons

Description: In the course of a recent experiment involving the stopping of negative K mesons in a 10-inch liquid hydrogen bubble chamber, an interesting new reaction was observed to take place. The chamber is traversed by many more negative {mu} mesons than K mesons, so that in the last 75,000 photographs, approximately 2500 {mu}{sup -} decays at rest have been observed. In the same pictures, several hundred {pi}{sup -} mesons have been observed to disappear at rest, presumably by one of the ''Panofsky rea… more
Date: December 10, 1956
Creator: Alvarez, L. W.; Bradner, H.; Crawford, F. S., Jr.; Crawford, J. A.; Falk-Vairant, P.; Good, M. L. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Ultrafast terahertz probes of transient conducting and insulating phases in an electron-hole gas

Description: Many-body systems in nature exhibit complexity and self-organization arising from seemingly simple laws. The long-range Coulomb interaction between electrical charges generates a plethora of bound states in matter, ranging from the hydrogen atom to complex biochemical structures. Semiconductors form an ideal laboratory for studying many-body interactions of quasi-particles among themselves and with lattice vibrations and light. Oppositely charged electron and hole quasi-particles can coexist in… more
Date: April 10, 2003
Creator: Kaindl, Robert A.; Carnahan, Marc A.; Hagele, Daniel; Lovenich, Reinhold & Chemla, Daniel S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Prediction of the Thermal Conductivity of Fused Salts

Description: A method for predicting thermal conductivities of fused salts and salt mixtures at their melting points was developed. It allows for the atomic or lattice portion arising from the short-range order present in liquids, and the ionic portion arising from a drift of ions and subsequent energy transfer between the atoms. (J.R.D.)
Date: August 10, 1956
Creator: Gambill, W. R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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