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Positron lifetimes in solids from first principles calculations

Description: We present a first principles method for calculating positron lifetimes in solids, based on self-consistent calculations using the Linear Muffin-Tin Orbital method. Local density approximations are used for both electron-electron and electron-positron interactions. Results are presented for a variety of elemental metals and vacancies to demonstrate the reliability of this approach. Theoretical calculations of positron lifetimes can be used to interpret experimental data. As an examples of this,… more
Date: August 7, 1991
Creator: Sterne, P. A.; O'Brien, J. C.; Howell, R. H. & Kaiser, J. H.
Partner: UNT Libraries Government Documents Department
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Improvements in the weldability of a superconductor sheath material

Description: This paper investigates the effects of chemistry and heat treatment variation on the 4-K tensile properties of A-286, a candidate sheath material for force-cooled superconductors. Currently, full use of A-286 and similar superalloys is limited by the observed low yield and ultimate tensile strengths in the welded and aged condition. The low strength is shown to be associated with the formation of precipitate-free zones as a result of alloying-element segregation during weld pool solidification.… more
Date: August 7, 1985
Creator: Summers, L.T. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department
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Creep of 304 LN and 316 L stainless steels at cryogenic temperatures

Description: Creep behavior of Type 304 LN plate and 316 L shielded-metal-arc (SMA)-deposited stainless weld metal was investigated at 4/sup 0/K. Testing was performed at constant load in a creep machine with a cryostat designed for long-term stability. Both transient and steady-state creep were observed during tests lasting over 2000 hours. Steady-state creep rates were much greater than expected from extrapolations of 300-K creep data. Creep rates on the order of 10/sup -10/ s/sup -1/ were observed at str… more
Date: August 7, 1985
Creator: Roth, L. D.; Manhardt, A. E.; Dalder, E. N. C. & Kershaw, R. P., Jr.
Partner: UNT Libraries Government Documents Department
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X-ray spectroscopic study of the charge state and local orderingof room-temperature ferromagnetic Mn oped ZnO

Description: The charge state and local ordering of Mn doped into a pulsed laser deposited single-phase thin film of ZnO are investigated by using X-ray absorption spectroscopy at the O K-, Mn K- and L-edges, and X-ray emission spectroscopy at the O K- and Mn L-edge. This film is found to be ferromagnetic at room temperature. EXAFS measurement shows that Mn{sup 2+} replaces Zn site in tetrahedral symmetry, and there is no evidence for either metallic Mn or MnO in the film. Upon Mn doping, the top of O 2p va… more
Date: August 7, 2007
Creator: Guo, J.-H.; Gupta, Amita; Sharma, Parmanand; Rao, K.V.; Marcus,M.A.; Dong, C.L. et al.
Partner: UNT Libraries Government Documents Department
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Ultrafast gigantic photo-response in (EDO-TTF)2PF6 initiated by 10-fs laser pulses

Description: We photo-exited a charge-ordered organic salt (EDO-TTF)2PF6 with sub-10-fs optical pulses. The photo-induced metallic phase appeared within 80-fs after pumping, characterized by large changes in reflectivity (DELTA R/R~0.8) followed by strong coherent phonon modulation
Date: August 7, 2006
Creator: Schoenlein, Robert William; Itatani, Jiro; Rini, Matteo; Cavalleri, Andrea; Onda, Ken; Ishikawa, Tadahiko et al.
Partner: UNT Libraries Government Documents Department
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Insulator-to-metal transition induced by mid-IR vibrational excitation in a magnetoresistive manganite

Description: Selective vibrational excitation of insulating Pr0.7Ca0.3MnO3 at 17 ?m triggers a transition to a metallic state. A four order of magnitude drop of the sample resistivity and ultrafast, nanosecond-lived reflectivity changes are observed
Date: August 7, 2006
Creator: Schoenlein, Robert William; Rini, Matteo; Itatani, Jiro; Tomioka, Yasuhide; Tokura, Yoshinori; Schoenlein, Robert W. et al.
Partner: UNT Libraries Government Documents Department
open access

Search for B0 to K*+ K*-

Description: The authors report the results of a search for the decay B{sup 0} {yields} K*{sup +}K*{sup -} with a sample of 454 {+-} 5 million B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the Stanford Linear Accelerator Center. They obtain an upper limit at the 90% confidence level on the branching fraction for {Beta}(B{sup 0} {yields} K*{sup +}K*{sup -}) < 2.0 x 10{sup -6}, assuming the decay is fully longitudinally polarized.
Date: August 7, 2008
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department
open access

The Effects of Various Conductive Additive and Polymeric Binder Contents on the Performance of a Lithium-ion Composite

Description: Fundamental electrochemical methods, cell performance tests, and physical characterization tests such as electron microscopy were used to study the effects of levels of the inert materials (acetylene black (AB), a nano-conductive additive, and polyvinylidene difluoride (PVDF), a polymer binder) on the power performance of lithium-ion composite cathodes. The electronic conductivity of the AB/PVDF composites at different compositions was measured with a four-point probe direct current method. The… more
Date: August 7, 2008
Creator: Stevenson, Cynthia; Liu, G.; Zheng, H.; Kim, S.; Deng, Y.; Minor, A.M. et al.
Partner: UNT Libraries Government Documents Department
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1,2-HOIQO--A highly versatile 1,2-HOPO analog

Description: A cyclic, bidentate hydroxamic acid binding unit based on an isoquinoline scaffold has been utilized for the synthesis of a hexadentate tripodal ligand based on the TREN backbone. This prototype for a new class of multidentate chelators forms mononuclear iron(III) complexes and one-dimensional coordination polymers with lanthanide(III) cations. The latter has been determined by single crystal X-ray analysis of the cerium species. The solid state structure in the monoclinic space group P2{sub 1}… more
Date: August 7, 2006
Creator: Seitz, Michael; Pluth, Michael D. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department
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Measurement of CP-Violating Asymmetries in the B0->K+K-Ks Dalitz Plot

Description: The authors present a preliminary measurement of CP-violation parameters in the decay B{sup 0} {yields} K{sup +}K{sup -}K{sub S}{sup 0}, using approximately 465 million B{bar B} events collected by the BABAR detector at SLAC. Reconstructing the neutral kaon as K{sub S}{sup 0} {yields} {pi}{sup +}{pi}{sup -} or K{sub S}{sup 0} {yields} {pi}{sup 0}{pi}{sup 0}, they analyze the Dalitz plot distribution and measure fractions to intermediate states. They extract CP parameters from the asymmetries in… more
Date: August 7, 2008
Creator: Kim, H
Partner: UNT Libraries Government Documents Department
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Temperature sensitivity of Cu K(alpha) imaging efficiency using a spherical Bragg reflecting crystal

Description: The Vulcan laser facility at the Rutherford Appleton Laboratory was used to study the interaction of a 75 J 10 ps, high intensity laser beam with low-mass solid, Cu targets. Two instruments were fielded as diagnostics of the Cu K-shell emission from the targets: A single photon counting CCD spectrometer provided the absolute K{sub {alpha}} yield and a spherically bent Bragg crystal recorded 2D monochromatic images with a spatial resolution of 10 {micro}m. Due to the shifting and broadening of t… more
Date: August 7, 2006
Creator: Akli, K. U.; Key, M. H.; Chung, H. K.; Hansen, S. B.; Freeman, R. R.; Chen, M. H. et al.
Partner: UNT Libraries Government Documents Department
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PARAMETRIC EFFECTS OF ANTI-FOAM COMPOSITION, SIMULANT PROPERTIES AND NOBLE METALS ON THE GAS HOLDUP AND RELEASE OF A NON-NEWTONIAN WASTE SLURRY SIMULANT

Description: Gas holdup tests were performed in bench-scale and small-scale mechanically-agitated mixing systems at the Savannah River National Laboratory (SRNL) for a simulant of waste from the Hanford Tank 241-AZ-101. These featured additions of DOW Corning Q2-3183A anti-foam agent. Results indicated that this anti-foam agent (AFA) increased gas holdup in the waste simulant by about a factor of four and, counter-intuitively, that the holdup increased as the non-newtonian simulant shear strength decreased … more
Date: August 7, 2008
Creator: Guerrero, H; Charles Crawford, C & Mark Fowley, M
Partner: UNT Libraries Government Documents Department
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Proton hexality from an anomalous flavor U(1) and neutrino masses--Linking to the string scale

Description: We devise minimalistic gauged U(1)_X Froggatt-Nielsen models which at low-energy give rise to the recently suggested discrete gauge Z_6 symmetry, proton hexality, thus stabilizing the proton. Assuming three generations of right-handed neutrinos, with the proper choice of X-charges, we obtain viable neutrino masses. Furthermore, we find scenarios such that no X-charged hidden sector superfields are needed, which from a bottom-up perspective allows the calculation of g_string, g_X and G_SM's … more
Date: August 7, 2007
Creator: Murayama, Hitoshi; Dreiner, Herbi K.; Luhn, Christoph; Murayama, Hitoshi & Thormeiere, Marc
Partner: UNT Libraries Government Documents Department
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The Role of Collinear Photons In the Rare Decay B to X_s ell ell

Description: We review the phenomenology of the rare decay {bar B} {yields} X{sub s}{ell}{sup +}{ell}{sup -}. We present the results of a detailed phenomenological analysis and discuss the role of the decay in the search for new physics at present and future colliders. Moreover, we extensively elaborate on the size of electromagnetic logarithms ln(m{sub b}{sup 2}/m{sub {ell}}{sup 2}) in view of experimental cuts. We point out the differences in the analyses of BaBar and Belle and give suggestions on how to … more
Date: August 7, 2008
Creator: Huber, T.; Hurth, T. & Lunghi, E.
Partner: UNT Libraries Government Documents Department
open access

The Equilibrium Length of High-Current Bunches in Electron Storage Rings

Description: An equilibrium theory of the length of intense electron bunches circulating in a storage ring is presented. The consequence of electrical interaction with various resonant structures is expressed in terms of quadratures over the impedance of the structures, and impedance functions for a variety of elements are evaluated. It is shown that elements having resonances at high frequency can, above transition, cause bunches to increase in length with increasing current. The parametric dependence of t… more
Date: August 7, 1970
Creator: Pellegrini, C. & Sessler, A. M.
Partner: UNT Libraries Government Documents Department
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ANALYTICAL METHOD FOR MEASURING TOTAL PROTIUM AND TOTAL DEUTERIUM IN A GAS MIXTURE CONTAINING H2, D2,AND HD VIA GAS CHAROMATOGRAPHY

Description: The most common analytical method of identifying and quantifying non-radioactive isotopic species of hydrogen is mass spectrometry. A low mass, high resolution mass spectrometer with adequate sensitivity and stability to identify and quantify hydrogen isotopes in the low ppm range is an expensive, complex instrument. A new analytical technique has been developed that measures both total protium (H) and total deuterium (D) in a gas mixture containing H{sub 2}, D{sub 2}, and HD using an inexpensi… more
Date: August 7, 2007
Creator: Sessions, H
Partner: UNT Libraries Government Documents Department
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Picosecond x-ray absorption spectroscopy of photochemical transient species in solution

Description: A photoinduced Fe(II) spin crossover reaction in solution is studied with ultrafast x-ray absorption spectroscopy. The iron-nitrogen bond lengthens by 0.21+-0.03 Angstrom in the high-spin transient excited state relative to the ground state.
Date: August 7, 2006
Creator: Schoenlein, Robert William; Khalil, Munira; Marcus, Matthew A.; Smeigh, Amanda L.; McCusker, James K.; Chong, Henry H.W. et al.
Partner: UNT Libraries Government Documents Department
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New Observables In the Decay Mode \bar B_d \-->\bar K^{0*} \ell^+ \ell^-

Description: We discuss the large set of observables available from the angular distributions of the decay {bar B}{sub d} {yields} {bar K}*{sup 0}{ell}{sup +}{ell}{sup -}. We present a NLO analysis of all observables based on the QCD factorization approach in the low-dilepton mass region and an estimate of {Lambda}/m{sub b} corrections. Moreover, we discuss their sensitivity to new physics. We explore the experimental sensitivities at LHCb (10 fb{sup -1}) and SuperLHCb (100 fb{sup -1}) based on a full-angul… more
Date: August 7, 2008
Creator: Egede, U.; /Imperial Coll., London; Hurth, T.; /SLAC, /CERN; Matias, J.; Ramon, M. et al.
Partner: UNT Libraries Government Documents Department
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Measurement of Semileptonic B Decays Into Orbitally-Excited Charm Mesons

Description: The authors present a study of B decays into semileptonic final states containing charged and neutral D{sub 1}(2420) and D*{sub 2}(2460). The analysis is based on a data sample of 208 fb{sup -1} collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. With a simultaneous fit to four different decay chains, the semileptonic branching fractions are extracted from measurements of the mass difference {Delta}m = m(D**)-m(D) distributions. Pr… more
Date: August 7, 2008
Creator: Aubert, Bernard; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
Partner: UNT Libraries Government Documents Department
open access

NMR structure of the N-terminal domain of the replication initiator protein DnaA

Description: DnaA is an essential component in the initiation of bacterial chromosomal replication. DnaA binds to a series of 9 base pair repeats leading to oligomerization, recruitment of the DnaBC helicase, and the assembly of the replication fork machinery. The structure of the N-terminal domain (residues 1-100) of DnaA from Mycoplasma genitalium was determined by NMR spectroscopy. The backbone r.m.s.d. for the first 86 residues was 0.6 +/- 0.2 Angstrom based on 742 NOE, 50 hydrogen bond, 46 backbone ang… more
Date: August 7, 2007
Creator: Wemmer, David E.; Lowery, Thomas J.; Pelton, Jeffrey G.; Chandonia, John-Marc; Kim, Rosalind; Yokota, Hisao et al.
Partner: UNT Libraries Government Documents Department
open access

Search for B+ Meson Decay to a1+ K*0

Description: We present the preliminary result of a search for the decay B{sup {+-}} {yields} a{sub 1}{sup {+-}} K*{sup 0}. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 465 million B{bar B} pairs produced in e{sup +}e{sup -} annihilation at the {Upsilon}(4S) energy. The result for the branching fraction is: {Beta}(B{sup +} {yields} a{sub 1}{sup +}K*{sup 0}) x {Beta}(a{sub 1}{sup +} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup +}) = (0.7{sub -0.4-0.7}{sup +0.5+0… more
Date: August 7, 2008
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department
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Impact of Carbon Structure and Morphology on the ElectrochemicalPerformance of LiFePO4/C Composites

Description: The electrochemical performance of LiFePO{sub 4}/C composites in lithium cells is closely correlated to pressed pellet conductivities measured by AC impedance methods. These composite conductivities are a strong function not only of the amount of carbon, but of its structure and distribution. Ideally, the amount of carbon in composites should be minimal (less than about 2 wt. %) so as not to decrease the energy density unduly. This is particularly important for plug-in hybrid electric vehicle a… more
Date: August 7, 2007
Creator: Doeff, Marca M.; Wilcox, James D.; Yu, Rong; Aumentado, Albert; Marcinek, Marek & Kostecki, Robert
Partner: UNT Libraries Government Documents Department
open access

A Measurement of CP Asymmetry in b->sgamma Using a Sum ofExclusive Final States

Description: We perform a measurement of the CP asymmetry in b {yields} s{gamma} decays using a sample of 383 x 10{sup 6} B{bar B} events collected by the BABAR detector at the PEP-II asymmetric B factory. We reconstruct sixteen flavor-specific B decay modes containing a high-energy photon and a hadronic system X{sub s} containing an s quark. We measure the CP asymmetry to be -0.011 {+-} 0.030(stat) {+-} 0.014(syst) for a photon energy threshold at 1.6 GeV and the hadronic system mass between 0.6 and 2.8 Ge… more
Date: August 7, 2008
Creator: Zao, M
Partner: UNT Libraries Government Documents Department
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The Effects of Halo Assembly Bias on Self-Calibration in Galaxy Cluster Surveys

Description: Self-calibration techniques for analyzing galaxy cluster counts utilize the abundance and the clustering amplitude of dark matter halos. These properties simultaneously constrain cosmological parameters and the cluster observable-mass relation. It was recently discovered that the clustering amplitude of halos depends not only on the halo mass, but also on various secondary variables, such as the halo formation time and the concentration; these dependences are collectively termed 'assembly bias'… more
Date: August 7, 2008
Creator: Wu, Hao-Yi; Rozo, Eduardo & Wechsler, Risa H.
Partner: UNT Libraries Government Documents Department
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