Correlated atomic motions in Pd79Si21 alloy glass observed by inelastic pulsed neutron scattering

The dynamical structure factor, , for Pd₇₉Si₂₁ alloy glass was measured with a fine Q and ω resolution by inelastic neutron scattering using the chopper spectrometer, MARI, installed at the ISIS facility, Rutherford Appleton Laboratory. Fine structure is clearly observed in over the dynamic range

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, which indicates the existence of well defined modes caused by correlated atomic motions even in the disordered structure of metallic alloy glasses.     

Atomic K-vacancy production with 3 GeV carbon ions

We report measurements of K-vacancy production cross sections for 3 GeV¹² C ions on targets ranging from Ti to Pb. The cross sections lie below values from PWBA, BEA, and relativistically modified PWBA and BEA theories.     

New limits on D0 (1.865) production in proton-nucleus collisions at 400 GeV/c

We present final results of a sensitive search for new particles in π^±K^? effective mass spectra observed in proton-nucleus collisions at 400 GeV/c. We establish a limit for D⁰ (1.865) production B_π⁺π^? dσ/dy < 360 nb/nucleon at y_cm^≈ ?0.4. For D?⁰ → π^?K⁺ the limit is 290 nb/nucleon.     

Characterization of organic arsenic compounds in bivalves

Water-soluble arsenic compounds were extracted with methanol/water (1:1, v/v) from various species of bivalves and also from certified reference materials (NIES No. 6, mussel tissue, and NBS 1566, oyster tissue). The extracts were analyzed with a high-performance liquid chromatograph combined with an inductively coupled argon plasma mass spectrometer serving as an arsenic-specific detector. A certified reference material (NIES No. 6) was used to check the reproducibility of the analysis. The relative standard deviations (RSDs) of the peak area of major arsenic compounds among repeated measurements (n = 6) on the same extrct were less than 3.3%, indicating good reproducibility of the technique. The RSDs of some peaks among measurements of independent extracts, on the other hand, were more than 10%, possibly reflecting the heterogeneity of the sample in terms of the chemical species under the present experimental conditions. In many of the samples analyzed in the present study, two arsenic-containing ribofuranosides were detected in addition to arsenobetaine. A compound bearing a glycerophosphoryl glycerol moiety was dominant in such cases. Interestingly, a bivalve living in an estuary (Corbicula japonica) did not contain a detectable amount of arsenobetaine though it had arsenic-containing ribofuranosides. The distribution of arsenic species in the various parts of a clam (Meretrix lusoria) and a mussel (Mytilus coruscum) was also analyzed.     

Structural investigation of sodium borate glasses and melts by Raman spectroscopy. III. Relation between the rearrangement of super-structures and the properties of glass

The structure of the intermediate range order (IRO) of sodium borate glasses and melts were quantitatively investigated by the analysis of high-temperature Raman scattering spectra. Raman bands at the middle frequency region of 700-950 cm⁻¹ were normalized using the bands at high frequency spectra and their intensities were compared among the spectra collected from the melts with different composition at various temperature. Bands at 805, 780, 750 and 720 cm⁻¹ were focused and their intensity changes were quantified. The exceeds of temperature over the glass transition temperature did not necessarily cause the decrease of all the band intensities. At Na₂O<15 mol%, 805 cm⁻¹ band was the most sensitive to temperature, while at 15<Na₂O<30, it was switched to 780 cm⁻¹ band and 805 cm⁻¹ band became insensitive. When Na₂O concentration exceeded 30 mol%, 750 and 720 cm⁻¹ bands were decreased with temperature. Accompanying the previous analysis on the structures of short range-order (SRO) of boron atoms [J. Non-Cryst. Solids, in this issue], some models of the structural rearrangement along with temperature were proposed. The combination of the obtained structural informations of IRO and SRO was found to explain the mechanisms causing various characteristic properties of borate glasses and melts, especially immiscibility and boron oxide anomaly of thermal expansion coefficient from the microscopic and dynamic points of view of the vitrification process in melt.