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Structure and Dynamics of Phosphate Glasses: From Ultra- to Orthophosphate Composition

Description: The short- and intermediate-range order as well as atomic dynamics in various phosphate glasses were investigated using neutron diffraction and inelastic scattering. The 3-D network of corner-sharing PO{sub 4} tetrahedra in g-P{sub 2}O{sub 5} is highly unstable and hygroscopic. Depolymerization of the network to chain-like structure and eventually to unconnected PO{sub 4} units by incorporating alkali, alkali-earth or transition-metal modifiers is clearly evident in the structure factor S(Q) in… more
Date: July 14, 1997
Creator: Loong, C. K.; Price, D. L.; Sales, B. C. & Boatner, L. A.
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Partner: UNT Libraries Government Documents Department
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Two-Dimensional Anisotropy in a Layered Metallic Antiferromagnet RE{sub 1-x}Sr{sub x}MnO{sub 3} with x approx.1/2

Description: Some RE{sub 1-x}Sr{sub x}MnO{sub 3} (RE=Nd,Pr) systems with x {approximately} 1/2 exhibit an A-type anti-ferromagnetic (AFM) structure instead of the expectged CE-type magnetic structure. This can be understood as being a consequence of the increase of the band width (W). These A-type magnetic systems also show salient features in their crystal structures. We proposed a two dimensional anisotropy of the transport as well as the magnetic properties for the A-type AFM structure and we show that w… more
Date: July 1, 1997
Creator: Kawano, H.; Yoshizawa, H.; Fernandez-Baca, J. A.; Tomioka, Y. & Kuwahara, H.
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Partner: UNT Libraries Government Documents Department
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Excitations of the Transversely Polarized Spin Density Waves in Chromium

Description: Inelastic neutron scattering measurements across the TSDW satellites of chromium were performed at {Delta}E=5,20meV, both under zero field and 5T magnetic field. Analysis concerning the transverse magnetic excitations (T{sub 1},T{sub 2}) and the longitudinal magnetic excitations (L) indicates that T{sub 1} and L are equally intense while T{sub 2} dominates and becomes more so at higher energies.
Date: July 15, 1997
Creator: Lee, W. T.; Werner, S. A.; Fernandez-Baca, J. A. & Fishman, R. S.
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Partner: UNT Libraries Government Documents Department
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Neutron scattering characterization of pure and rare-earth modified zirconia catalysis.

Description: The combined application of neutron powder diffraction, small angle neutron scattering and neutron inelastic scattering has led to improved understanding of the crystal phases, defect structure, microstructure and hydroxyl/water dynamics in pure and lanthanide-modified zirconia catalysts. Powder diffraction experiments quantified the degree of stabilization and provided evidence for static, oxygen vacancy-induced atomic displacements in stabilized zirconia. Quantitative assessment of Bragg peak… more
Date: November 18, 1997
Creator: Loong, C.-K.; Ozawa, M.; Richardson, J. W., Jr.; Suzuki, S. & Thiyagarajan, P.
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Partner: UNT Libraries Government Documents Department
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Integrated nuclear techniques to detect illicit materials

Description: This paper discusses the problem of detecting explosives in the context of an object being transported for illicit purposes. The author emphasizes that technologies developed for this particular application have payoffs in many related problem areas. The author discusses nuclear techniques which can be applied to this detection problem. These include: x-ray imaging; neutronic interrogation; inelastic neutron scattering; fieldable neutron generators. He discusses work which has been done on the … more
Date: October 1, 1997
Creator: DeVolpi, A.
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Partner: UNT Libraries Government Documents Department
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LO phonons in La{sub 1.85}Sr{sub .15}CuO{sub 4}

Description: Dispersion of the highest energy LO phonons in La{sup 1.85}Sr{sub .15}CuO{sub 4} was studied by neutron inelastic scattering. At T = 10 K the dispersion along (h, 0, 0) is anomalous forming dispersion branches with a discontinuity at h = 1/4. A possible relation of this anomaly to the spin-charge stripes with be discussed.
Date: November 1, 1997
Creator: Egami, T.; Petrov, Y.; McQueeney, R.J.; Petrov, Y.; Yethiraj, M.; Shirane, G. et al.
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Partner: UNT Libraries Government Documents Department
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Excess cross-sections at the electroweak scale in the sextet quark {open_quotes}standard model{close_quotes}

Description: If dynamical electroweak symmetry breaking is due to a flavor doublet of color sextet quarks, enhanced electroweak scale QCD instanton interactions may produce a large top mass, raise the {eta}{sub 6} axion mass, and also explain the excesses in the DIS cross-section at HERA and jet cross-sections at the Tevatron.
Date: June 30, 1997
Creator: White, A.R.
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Partner: UNT Libraries Government Documents Department
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The Pomeron beyond BFKL

Description: Conformally invariant reggeon interactions derived from t-channel unitarity are discussed and progress towards understanding the {open_quotes}physical Pomeron{close_quotes}, via massless quark reggeon interactions, is briefly out-lined.
Date: May 12, 1997
Creator: White, A. R.
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Partner: UNT Libraries Government Documents Department
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The performance of neutron scattering spectrometers at a long-pulse spallation source

Description: In this document the author considers the performance of a long pulse spallation source for those neutron scattering experiments that are usually performed with a monochromatic beam at a continuous wave (CW) source such as a nuclear reactor. The first conclusion drawn is that comparison of the performance of neutron scattering spectrometers at CW and pulsed sources is simpler for long-pulsed sources than it is for the short-pulse variety. Even though detailed instrument design and assessment wi… more
Date: June 1, 1997
Creator: Pynn, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Magnetic Excitation of CuGeO{sub 3} under Applied Pressure

Description: Magnetic excitations of the spin-Peierls compound CuGeO{sub 3} under applied pressure of 2 GPa have been studied. The dispersion along the chain direction up to zone boundary has been obtained. The spin-Peierls gap energy increases to 4.2 meV and the zone boundary energy decreases to 14.1 meV. The pressure dependence of dispersion relation can be interpreted by the increase of the next-nearest-neighbor intra-chain interaction under applied pressure causing the increase of both the spin-Peierls … more
Date: July 31, 1997
Creator: Nishi, M.; Kakurai, K.; Fujii, Y.; Yethiraj, M.; Tennant, D. A.; Nagler, S. E. et al.
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Partner: UNT Libraries Government Documents Department
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Neutron study of fracton excitations in percolating antiferromagnets

Description: The authors report the results of an inelastic neutron scattering experiment on nearly-percolating Heisenberg antiferromagnets (RbMn{sub c}Mg{sub 1{minus}o}F{sub 3}), in which the Mn concentrations (C = 0.31, 0.34 and 0.39) are very close to the percolation threshold (c{sub p} = 0.312). A broad peak superimposed on Ising-cluster excitations was observed throughout the Brillouin zone. The intensity of a broad peak increased on approaching the percolation threshold. The origin of this broad peak … more
Date: June 27, 1997
Creator: Ikeda, H.; Takahashi, M.; Fernandez-Baca, J. A. & Nicklow, R. M.
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Partner: UNT Libraries Government Documents Department
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Inelastic neutron scattering study of the (O{sub 4}H{sub 4}) substitution in garnet

Description: Inelastic scattering data have been collected at incident neutron energies of 50, 150, 300 and 600 meV for hydrogarnet [Sr{sub 3}Al{sub 2}(O{sub 4}H{sub 4}){sub 3}], a model compound for silicate hydrogarents found in the Earth`s crust and mantle. The vibrational spectrum is characterized by a relatively sharp O-H stretch at {approximately}460 meV, which is consistent with the weak O...H bond ({approximately}2.65 {angstrom}) and other complex features in the 20-100 meV region. The mode assignme… more
Date: July 14, 1997
Creator: Lager, G. A.; Nipko, J. C. & Loong, C. K.
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Partner: UNT Libraries Government Documents Department
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Pseudogap and Incommensurate Magnetic Fluctuations in YBa{sub 2}Cu{sub 3}O{sub 6.6}

Description: Unpolarized inelastic neutron scattering is used to study the temperature and wave vector dependence of the dynamical magnetic susceptibility, {xi}`` (q,{omega}), of a well characterized single crystal YBa{sub 2}Cu{sub 3}O{sub 6.6} (T{sub c} = 62.7 K). We find that a pseudogap opens in the spin fluctuation spectrum at temperatures well above T{sub c}. We speculate that the appearance of the low frequency incommensurate fluctuations is associated with the opening of the pseudogap. To within the … more
Date: July 24, 1997
Creator: Dai, P., Mook, H.A.,
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Partner: UNT Libraries Government Documents Department
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Analytical techniques for instrument design -- Matrix methods

Description: The authors take the traditional Cooper-Nathans approach, as has been applied for many years for steady-state triple-axis spectrometers, and consider its generalization to other inelastic scattering spectrometers. This involves a number of simple manipulations of exponentials of quadratic forms. In particular, they discuss a toolbox of matrix manipulations that can be performed on the 6-dimensional Cooper-Nathans matrix. They show how these tools can be combined to solve a number of important p… more
Date: December 31, 1997
Creator: Robinson, R.A.
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Partner: UNT Libraries Government Documents Department
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Magnetic excitations in (VO)HPO{sub 4}{center_dot}{1/2}H{sub 2}O

Description: The magnetic excitations of an antiferromagnetic spin dimer system, (VO)HPO{sub 4}{center_dot}{1/2}H{sub 2}O, are examined using inelastic neutron scattering. A dispersionless mode is found, consistent with expectations for a dimer excitation. The intensity variation of the mode reveals a V{sup 4+} - V{sup 4+} dimer separation of 4.43{angstrom}, almost 50% larger than the originally expected length.
Date: July 11, 1997
Creator: Garrett, A. W.; Nagler, S. E. & Tennant, D. A.
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Partner: UNT Libraries Government Documents Department
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Precision Measurements of {sup 56}Fe Cross Sections for the 847-keV Gamma Transition

Description: At the First Research Coordination Meeting of the IAEA/NDS CRP on Measurement, Calculation and Evaluation of Photon Production Data an experiment to measure with high precision the cross sections of the production of the 847-keV gamma ray due to inelastic neutron scattering with iron was proposed and discussed. The main justification for the proposed improved precision was the need for improved calculations of radiation transport through thick iron components of nuclear reactors. Present evalua… more
Date: December 31, 1997
Creator: Dickens, J.K.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Photon-neutrino interactions

Description: The cross sections for the processes {gamma}{nu} {yields} {gamma}{gamma} {yields} {nu}{anti {nu}} are calculated with the aid of an effective Lagrangian derived from the Standard model. These cross sections are shown to be much larger than the elastic cross section {sigma}({gamma}{nu} {yields} {gamma}{nu}) for photon energies {omega} {ge} 1 keV. Possible astrophysical implications are discussed.
Date: December 1, 1997
Creator: Dicus, D.A. & Repko, W.W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Spin Dynamics of the Reentrant Spin Glass Fe{sub 0.7}A1{sub 0.3}

Description: Inelastic neutron scattering experiments are reported to study magnetic excitations in a single crystal of the reentrant spin glass Fe(0.7)Al(0.3) near the (111) Bragg peak. In the ferromagnetic phase, the magnetic excitation spectrum is separated in two areas: at low q, spin waves are propagating and at higher q, the response is quasielastic-like. In the spin glass phase, the response is always quasielastic.
Date: December 31, 1997
Creator: Raymond, S.; Bao, W.; Shapiro, S.M. & Motoya, K.
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Partner: UNT Libraries Government Documents Department
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Constant Q measurements of collective modes in Mg{sub 70}Zn{sub 30} glass

Description: In this study the Neutron Brillouin Scattering technique has been used to measure longitudinal excitations in a magnesium-zinc glass at momentum transfers within the first pseudo-Brillouin zone. The measurements were performed at room temperature and constant momentum transfer, which enables the data to be readily and reliably compared with theory. The experimental results taken down to Q = 6.2 nm{sup {minus}1} and E = 27 meV show a 5 meV downward shift in the dispersion energy of the longitudi… more
Date: November 1, 1997
Creator: Benmore, C.J.; Sweeney, S.; Robinson, R.A.; Egelstaff, P.A. & Suck, J.B.
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Partner: UNT Libraries Government Documents Department
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Back-scattering channel-cut high-resolution monochromator for inelastic x-ray scattering

Description: We report on a design and on some experimental results for the performance of a new high energy resolution monochromator. It is a large channel-cut Si crystal with a 197 mm separation between the two faces designed to operate in a near-backscattering regime. The device was tested as a second monochromator on Sector 3 of the Synchrotron Radiation Instrumentation Collaborative Access Team (SRI-CAT) at the Advanced Photon Source using the Si(777) reflection at a photon energy of 13.84 keV. The sam… more
Date: August 1, 1997
Creator: Kushnir, V. I.; Abbamonte, P. M.; Macrander, A. T. & Schwoerer-Boehning, M.
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Partner: UNT Libraries Government Documents Department
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The spin and flavor content of intrinsic sea quarks

Description: The intrinsic quark-antiquark pairs generated by the minimal energy nonperturbative meson-baryon fluctuations in the nucleon sea provide a consistent framework for understanding a number of empirical anomalies observed in the deep inelastic quark-parton structure of nucleons: the flavor asymmetry of the nucleon sea implied by the violation of Gottfried sum rule, the proton spin problem implied by the violation of the Ellis-Jaffe sum rule, and the outstanding conflict between two different deter… more
Date: July 1, 1997
Creator: Bo-Qiang Ma & Brodsky, S.J.
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Partner: UNT Libraries Government Documents Department
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Phonon and magnetic excitations in neodymium pentaphosphate

Description: The structure of NdP{sub 5}O{sub 14} consists of cross-linked double chains of corner-sharing PO{sub 4} tetrahedra extending parallel to the crystallographic a-axis. Each Nd atom is coordinated by 8 oxygen atoms. The NdO{sub 8} polyhedra are isolated from each other and share no common oxygen atoms. High-gain and long-lifetime laser action had been reported in NdP{sub 5}O{sub 14} crystals. The neutron excitation spectra reveal a one-phonon density of states extended to about 180 meV with severa… more
Date: July 14, 1997
Creator: Loong, C. K.; Nipko, J. C.; Goodman, G. L.; Wang, J. Y. & Liu, Y. G.
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Partner: UNT Libraries Government Documents Department
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From HERA to the Tevatron: A scaling law in hard diffraction

Description: Results on hard diffraction from CDF are reviewed and compared with predictions based on the diffractive structure function of the proton measured in deep inelastic scattering at HERA. The predictions are generally larger than the measured rates by a factor of {approximately} 6, suggesting a breakdown of conventional factorization. Correct predictions are obtained by scaling the rapidity gap probability distribution of the diffractive structure function to the total integrated gap probability. … more
Date: December 4, 1997
Creator: Goulianos, K. & CDF
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Partner: UNT Libraries Government Documents Department
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Low energy magnetic fluctuations in the TSDW phase of chromium

Description: A polarized neutron study of chromium carried out in a field of 6T applied to a single-domain single-Q crystal indicates that the inelastic intensity observed close to the transverse spin density wave (TSDW) satellite positions (1 {+-} {delta}, 0,0) does not behave as expected for spin-wave scattering. In particular, the signal corresponds to magnetization fluctuations of almost equal magnitude both parallel and perpendicular to the ordered moments in the TSDW phase.
Date: December 1, 1997
Creator: Azuah, R.T.; Kulda, J.; Pynn, R. & Stirling, W.G.
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Partner: UNT Libraries Government Documents Department
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