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11.
Neutron diffraction techniques used in the study of the structural characteristics of liquid water under ambient conditions are reviewed, showing the way that developments in the experimental and analytic procedures have led to improvements in the extracted results. The three partial pair correlation functions (OH, HH and OO) can be isolated from a set of diffraction measurements with varying hydrogen/deuterium isotopic composition. Although isotopic substitution is used routinely in many other investigations there are particular difficulties with hydrogenous systems due to the high incoherent scattering from hydrogen and the possibility that the H/D substitution is not a true isomorphic replacement. These features are discussed in some detail to analyse the systematic errors and the precision of the final results. An additional aspect of the comparison of data taken by different groups concerns the use of either reactor or pulsed neutron methods. Studies using the Orphee reactor with an over-determined set of five datasets are considered in detail, using analytic correction procedures based on the Powles formalism. Various consistency checks are applied to the data such that smoothing or iteration routines are not required. Two independent sets of the OD and DD pair correlation functions are obtained and are compared with the latest results from Soper et al. The small discrepancies between the various datasets are discussed in terms of propagating systematic errors and also possible variations from H/D equivalence. The relevance of the new results for the interpretation and modelling of ambient water structure are presented and the review ends with a brief comment on likely future developments that incorporate additional experimental information. 相似文献
12.
We study the differential equation tu′(t) + Au(t) = f(t), 0 < t < ∞, in Banach spaces. We obtain existence and uniqueness theorems for the solutions as well as regularity properties in suitable interpolation spaces. 相似文献
13.
F. Bergsma J. Dorenbosch C. Nieuwenhuis J. V. Allaby U. Amaldi G. Barbiellini A. Capone Y. Eisenberg W. Flegel M. Jonker L. Lanceri M. Metcalf J. Panman D. Perret-Gallix R. Plunkett C. Santoni K. Winter I. Abt J. Aspiazu F. W. Büsser H. Daumann P. D. Gall T. Hebbeker F. Niebergall P. Schütt P. Stähelin P. Gorbunov E. Grigoriev V. Kaftanov V. Khovansky A. Rosanov L. Barone B. Borgia M. Diemoz U. Dore F. Ferroni E. Longo L. Luminari P. Monacelli F. de Notaristefani E. Valente CHARM Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,40(2):171-192
We present here the final results of experiments searching for neutrino oscillations, carried out by the CHARM Collaboration. The data — taking took place in 1983. The first experiment was performed by exposing two detectors simultaneously to the CERN PS low energyv µ beam. In the second experiment the full CHARM detector was exposed to the wide-band horn-focusedv µ beam of the CERN SPS. Complete details of the experiments and data reduction are presented. No statistically significant signals for neutrino oscillations were observed. Our 90% CL limits in the appearance experiment (v µ→v e ) exclude Δm 2≧0.19 eV2 for complete mixing (sin22θ=1), and sin22θ≧0.008 for the region Δm 2≧30 eV2. These results, and the limits observed for (v µ→v x ) (disappearance of (v µ), are in agreement with those of most other experiments but exclude part of the region previously reported as a possible indication ofv µ→v e oscillations. 相似文献
14.
J.C. Dore 《Journal of Molecular Liquids》1984,28(2):87-93
A brief review is made of methods used to determine the conformation of molecules by diffraction methods. Studies of various simple molecules (e.g. N2, P4, CC?4) show little change of form between the vapour and condensed phases. More recent work on hydrogen-bonded liquids indicates that there is a substantial stretch in the intra-molecular OH(D) bond. Although little data is currently available the results seem to indicate that this effect is systematic for associated species and relates to the strength of the hydrogen bond. The prospects for a more detailed study using the improved flux levels of new X-ray and neutron sources are also examined. 相似文献
15.
P. Dore L. Nencini G. Birnbaum 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,30(3):245-254
The translational-rotational absorption spectrum of normal H2 has been measured from 80 to 900 cm?1 at seven temperatures from 77.4 to 298 K. These results have been accurately fitted by a three-parameter line-shape function, thereby providing a reliable way of predicting the absorption of H2 anywhere in this frequency and temperature region. 相似文献
16.
S. AL-Harran M. Baubillier I.J. Bloodworth G.J. Bossen A. Burns J.N. Carney G.F. Cox U. Dore Ph. Gavillet J.B. Kinson K. Knudson F. Levy P.F. Loverre H. McCann M.J. MacDermott P.J. Negus B. Oh R. Zitoun 《Nuclear Physics B》1981,191(1):26-38
We present results for the hypercharge exchange reaction K?p→f' λ from a high statistics experiment at 8.25 GeV/c using the CERN 2m HBC. The total and differential cross sections have been measured; the polarisation of the Λ hyperon and the f' density matrix elements have been calculated as functions of momentum transfer. We also present detailed information on the relative strength of the natural and unnatural parity exchange contributions to the production mechanism. 相似文献
17.
Neutrino beams obtained from proton accelerators were first operated in 1962. Since then, neutrino beams have been intensively used in particle physics and evolved in many different ways. We describe the characteristics of various neutrino beams, relating them to the historical development of the physics studies and discoveries. We also discuss some of the ideas still under consideration for future neutrino beams.
相似文献18.
Giovanni Buffa Dr. Luca Dore Prof. Francesca Tinti Dr. Markus Meuwly Prof. 《Chemphyschem》2008,9(15):2237-2244
An experimental and theoretical study of pressure broadening and pressure shift of HCO+ rotational lines perturbed by collisions with He is presented. Results are reported from measurements at 88 K for the lines j=4←3, 5←4 and 6←5 with frequencies ranging from 0.35 to 0.54 THz. Using a new CCSD(T)/aug‐cc‐pVQZ potential energy surface for the He–HCO+ interaction, the collisional line shape parameters are studied from fully quantum and semiclassical calculations. Results from the quantum treatment are in satisfactory agreement with experiments whereas the semiclassical approach can lead to appreciable differences. A study of the dependence of line width Γ and shift s as a function of the translational energy shows the presence of quantum oscillations. Calculations on a previous Hartree–Fock‐based potential energy surface lead to quite similar results for the collisional line shape parameters. Using a simplified version of the potential morphing method it is found that the line width Γ is particularly sensitive to the long‐range part of the potential energy surface. This also explains the success of the first line‐broadening calculations which date back to the 1950s. 相似文献
19.
Micro‐Raman measurements were performed on two Etruscan polychromes on architectural terracotta panels now on display at the Villa Giulia Etruscan Museum in Rome. These painted panels, dated from 530 to 520 B .C ., are of particular interest because of the unusual presence of green and blue layers. Etruscans in the Archaic Age indeed mainly used white, red, and black colours for painted terracotta panels. Raman spectra allowed the analytical identification of green (malachite) and blue (Egyptian blue) pigments employed by Etruscans for this kind of artistic production. This finding provides evidence for a larger use of malachite and Egyptian blue, previously well documented only in Etruscan wall paintings. The use of different pigments to obtain different colour tones has been also observed. Egyptian blue is indeed mixed with malachite to obtain different green tones, and a black pigment seems to have been applied over the Egyptian blue layer to obtain a dark blue tone. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
20.
Future contributions to Journal of Chemical Crystallography 相似文献