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991.
J.-J. Didisheim K. Yvon D. Shaltiel P. Fischer P. Bujard E. Walker 《Solid State Communications》1979,32(11):1087-1090
A neutron diffraction analysis at room temperature of ZrV2D4·5 has been made. The deuterium atoms are found to occupy two types of tetrahedral interstices in the metal atom host structure. One is formed by 1 Zr and 3 V atoms and has an occupancy of 39%, whereas the other one is formed by 2 Zr and 2 V atoms, having an occupancy of 25%. Together these interstices can be considered as forming a three-dimensional infinite network of diffusion paths which is similar to that observed in the deuterated hexagonal Laves-phase ZrMn2D3. The adjacent D atom sites in this network are about 1.3 åA apart and the average Zr-D and V-D distances are 2.10 and 1.77 åA, respectively. 相似文献
992.
B.Y. Oh M. Pratap G. Sionakides G.A. Smith J. Whitmore R.J. Miller J.J. Phelan P.F. Schultz L. Voyvodic R.J. Walker E.W. Anderson H.B. Crawley A. Firestone W.J. Kernan F. Ogino D.L. Parker D.G. Hill M. Kazuno F. Svrcek 《Nuclear Physics B》1976,116(1):13-27
Semi-inclusive π? cross sections in 200 and 300 GeV/c pp interactions are presented and compared with lower energy data. In the target fragmentation region the data are compared to the hypothesis of semi-inclusive KNO scaling. The energy and charge multiplicity dependences of the semi-inclusive cross sections in the central region are studied and a simple parametrization of the semi-inclusive density function is described. 相似文献
993.
994.
995.
R. E. London T. E. Walker T. W. Whaley N. A. Matwiyoff 《Magnetic resonance in chemistry : MRC》1977,9(10):598-600
15N n.m.r. spectra of [13C-2, 3-15N2-guanidino]arginine and [13C, 15N2] urea were obtained in D2O and H2O at a variety of pH values both with and without proton decoupling. The effects of the proton exchange rate are readily observable in the proton coupled 15N spectra. When the guanidino group is deprotonated (pK = 12.5), the terminal nitrogens give a single resonance 6.6 ppm downfield of the protonated species, indicating a rapid tautomeric exchange. The observed NH and CN couplings are compared with calculated values, and good agreement is found for 1J(CN) using a Blizzard–Santry type calculation. The ramifications of the proton exchange on 15N n.m.r. spectra of amino acids and peptides are discussed. 相似文献
996.
997.
Summary This paper treats periodic fluid transients in liquid metals contained in constant-area rectangular ducts with uniform, transverse, applied magnetic fields and with insulating walls parallel to the magnetic field and perfectly conducting walls perpendicular to it. The magnetic Reynolds and Mach numbers are assumed to be small, and the Reynolds number is assumed to be large. First, asymptotic solutions are obtained for small values of the interaction parameter and then approximate solutions are obtained for arbitrary values of the interaction parameter using a Galerkin method with modified Fourier series.
Résumé Cet article traite des ondes de compression périodiques dans un métal liquide contenu dans une conduite rectangulaire à section rectangulaire constante, à laquelle un champ magnétique transverse et uniforme est appliqué et dont deux parois sont isolantes et parallèles au champ magnétique, les deux autres étant parfaitement conductrices. On admet que le nombre magnétique de Reynolds et le nombre de Mach sont petits et que le nombre de Reynolds est grand. Quand le nombre d'intéraction est petit, les solutions seront asymptotiques et quand le nombre d'intéraction est arbitrarire, on trouvera les solutions approximatives par la méthode de Galerkin avec les series modifiées de Fourier.相似文献
998.
We report on real-time, time-gated, direct imaging through scattering media with an attenuation of 14 mean-free paths by use of third-harmonic generation in the eye-safe and telecommunication-compatible near-IR spectral region (1550 nm). 相似文献
999.
We compare the cladding patterns present in grating structures fabricated with an ultrafast laser and a phase mask with a cw beam interference model. We find that the observed patterns agree well with the model results for picosecond pulses; however, for femtosecond pulses, we show that the full bandwidth and the pulsed nature of the sources must be considered because the pattern can be affected by group-velocity walk-off. An interesting consequence of order walk-off is the possibility of pure two-beam interference generation with a phase mask in the femtosecond pulse regime. 相似文献
1000.
Walker O Varadan R Fushman D 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,168(2):336-345
We present a computer program ROTDIF for efficient determination of a complete rotational diffusion tensor of a molecule from NMR relaxation data. The derivation of the rotational diffusion tensor in the case of a fully anisotropic model is based on a six-dimensional search, which could be very time consuming, particularly if a grid search in the Euler angle space is involved. Here, we use an efficient Levenberg-Marquardt algorithm combined with Monte Carlo generation of initial guesses. The result is a dramatic, up to 50-fold improvement in the computational efficiency over the previous approaches. This method is demonstrated on a computer-generated and real protein systems. We also address the issue of sensitivity of the diffusion tensor determination from (15)N relaxation measurements to experimental errors in the relaxation rates and discuss possible artifacts from applying higher-symmetry tensor model and how to recognize them. 相似文献