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201.
Xavier Pannecoucke Alain Van Dorsselaer Bang Luu 《Journal of mass spectrometry : JMS》1992,27(2):140-144
Negative-ion fast atom bombardment mass spectra of five compounds resulting from combinations between oxysterols and nucleoside analogues linked by phosphodiester bonds are presented and interpreted. This method seems to be the most appropriate for elucidating the structure of these complex, labile and non-volatile phosphate-containing molecules which exhibit important antitumour and/or immunosuppressive activities. 相似文献
202.
203.
Xavier Fradera Jordi Poater Sílvia Simon Miquel Duran Miquel Solà 《Theoretical chemistry accounts》2002,108(4):214-224
This article presents an overview of recent advances in the study of electron pairing through the use of localization and
delocalization indices obtained from double integration over atomic basins of the exchange–correlation density in the framework
of the atoms-in-molecules theory. These localization and delocalization indices describe the intra- and interatomic distribution
of the electron pairs in a molecule. The main results of the application of these second-order indices to the analysis of
molecular structure and chemical reactivity are briefly reviewed. It is shown that localization and delocalization indices
represent a powerful tool to describe the electron-pair structure of molecules, which, in turn, provides deeper insight into
relevant chemical phenomena such as electron correlation effects and the formation of localized α, β electron pairs.
Received: 8 April 2002 / Accepted: 26 June 2002 / Published online: 6 September 2002
Acknowledgements. Financial help was furnished by the Spanish DGES projects no. PB98-0457-C02-01 and BQU2002-04112-C02-02. J.P. thanks the
Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for benefiting from a doctoral
fellowship, no. 2000FI-00582. M.S. is indebted to the Departament d'Universitats, Recerca i Societat de la Informació of the
Generalitat de Catalunya for financial support through the Distinguished University Research Promotion, 2001. We also thank
the Centre de Supercomputació de Catalunya for providing us with computing facilities.
Correspondence to: M. Solà e-mail: miquel.sola@udg.es 相似文献
204.
We consider numerical methods for the incompressible Reynolds averaged Navier–Stokes equations discretized by finite difference
techniques on non-staggered grids in body-fitted coordinates. A segregated approach is used to solve the pressure–velocity
coupling problem. Several iterative pressure linear solvers including Krylov subspace and multigrid methods and their combination
have been developed to compare the efficiency of each method and to design a robust solver. Three-dimensional numerical experiments
carried out on scalar and vector machines and performed on different fluid flow problems show that a combination of multigrid
and Krylov subspace methods is a robust and efficient pressure solver.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
205.
Palladium catalyzed coupling of tertiary allylic alcohols (having five, ten or fifteen carbon atoms) with 2-iodophenols or hydroquinones furnishes the corresponding 2,2-disubstituted chromenes (2H-1-benzopyrans) and chromen-6-ols. 相似文献
206.
Xavier Gerbaux Armand Hadni M. Tazawa 《International Journal of Infrared and Millimeter Waves》1997,18(9):1611-1635
The different technical approaches are considered mostly to compare the accuracy attainable in microwaves to Far IR where
new resonant tchniques have been developped. It is possible to use the fringes of the observed spectra to get directly the
London penetration length. However in the present state of the Art there is more accuracy to use a two-fluid model with at
least one Mid-IR oscillator, and a strategy is possible to fit separately the different parameters. The different results
are reviewed and compared to the microwaves data. There is a good accordance, except perhaps for the power law-giving the
concentration of quasiparticles in the superconductive phase. For a thin film of YBCO devoid of grain-boundaries (no twins),
a θ4 law is found instead of a θ1.5 law for an ordinary film. It should be highly valuable that both microwaves and Far-IR data should be taken on the same sample.
presented at the 22nd International Conference on Infrared and Millimeter Waves, July 20–25, 1997, Wintergreen, Virginia 22958
USA. 相似文献
207.
We develop and analyse NeumannNeumann methods for hpfinite-element approximations of scalar elliptic problems ongeometrically refined boundary layer meshes in three dimensions.These are meshes that are highly anisotropic where the aspectratio typically grows exponentially with the polynomial degree.The condition number of our preconditioners is shown to be independentof the aspect ratio of the mesh and of potentially large jumpsof the coefficients. In addition, it only grows polylogarithmicallywith the polynomial degree, as in the case of p approximationson shape-regular meshes. This work generalizes our previousone on two-dimensional problems in Toselli & Vasseur (2003a,submitted to Numerische Mathematik, 2003c to appear in Comput.Methods Appl. Mech. Engng.) and the estimates derived here canbe employed to prove condition number bounds for certain typesof FETI methods. 相似文献
208.
209.
Optical properties of silver and gold semi-continuous films near the percolation threshold are investigated by scanning near field optical microscopy (SNOM) operating in the collection/transmission mode. The electromagnetic enhanced fields, due to plasmon-polariton localizations, are observed and the intensity distribution is shown to present high intensity variations that increase with the wavelength. The local fields are also demonstrated to be polarization dependent. The intensity distribution is investigated as function of the incident wavelength both for gold and silver films. The calculated probability distribution function (PDF) exhibits an exponential decay for large enhancement factors and is proved to be wavelength dependent. 相似文献
210.
The macroscopic response of a cracked solid subjected to drying is investigated within the framework of micromechanics. The originality of this contribution lies in the fact that the variations of the aspect ratios of cracks induced by the capillary pressure increase are accounted for. When the initial aspect ratio is small enough, it is shown that neglecting the geometrical changes yields an erroneous prediction of the sign of the macroscopic volume strain rate. To cite this article: X. Chateau et al., C. R. Mecanique 331 (2003). 相似文献