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981.
V. V. Sobolev A. I. Kalugin V. Val. Sobolev S. V. Smirnov 《Physics of the Solid State》2002,44(5):870-879
The complete sets of 12 fundamental optical functions for fluorite crystals in the range 5–39 eV and corundum crystals in the range 2–30 eV are determined from the experimental and theoretical spectra known for certain of these functions. The main features and generalities of these functions are revealed. A theoretical analysis of the optical spectra obtained is performed using the known theoretical band diagrams and the spectra of ?2. 相似文献
982.
Albert Avinyó Joan Solà-Morales Marta València 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2003,17(4):919-936
In this paper we present and analyze two new algorithms
to construct a smooth diffeomorphism of a domain with prescribed
jacobian function. The first one is free from any restriction on
the boundary, while the second one produces a diffeomorphism that
coincides with the identity map on the boundary of the domain.
Both are based on the solution of an initial value problem for the
linear heat equation, and the second also uses solutions of the
Stokes system of Fluid Mechanics. 相似文献
983.
984.
Kévin Cocq Nathalie Saffon‐Merceron Yannick Coppel Corentin Poidevin Valérie Maraval Remi Chauvin 《Angewandte Chemie (International ed. in English)》2016,55(48):15133-15136
A ring carbo‐mer of naphthalene, C32Ar8 (Ar=p‐n‐pentylphenyl), has been obtained as a stable blue chromophore, after a 19‐step synthetic route involving methods inspired from those used in the synthesis of carbo‐benzenes, or specifically devised for the present target, like a double Sonogashira‐type coupling reaction. The last step is a SnCl2/HCl‐mediated reduction of a decaoxy‐carbo‐decalin, which is prepared through successive [8+10] macrocyclization steps. Two carbo‐benzene references are also described, C18Ar6 and o‐C18Ar4(C≡C‐SiiPr3)2. The carbo‐naphthalene bicycle is locally aromatic according to structural and magnetic criteria, as revealed by strong diatropic ring current effects on the deshielding of 1H nuclei of the Ar groups and on the negative value of the DFT‐calculated NICS at the center of the C18 rings (?12.8 ppm). The stability and aromaticity of this smallest fused molecular fragment of α‐graphyne allows prediction of the same properties for the carbon allotrope itself. 相似文献
985.
N. B. Kondrashova A. S. Starostin V. A. Val’tsifer V. Ya. Mitrofanov S. A. Uporov E. Bormashenko 《Russian Journal of Applied Chemistry》2016,89(12):1960-1968
Ways to obtain Fe2O3–SiO2 iron-containing silica composites with organized mesoporous structure (MCM-41) and large specific surface area (up to 1476 m2 g–1) were considered. The influence exerted by the method used to synthesize the materials on their structure, texture characteristics, particle size, and magnetic properties were studied. The aggregative stability of samples was examined. It was shown that treatment of the resulting composites with compounds from the chlorosilane group affects their hydrophobic properties. 相似文献
986.
The purpose of our work is to illustrate that, by using a simple optical method (phenomenon of caustics) it is possible to locate, near the crack tip, the boundaries of the plastic zone for a cracked body. In this Note, we show that, through numerical simulations, in the case of a ductile SEN specimen, loaded in mode I and following a loading history, the appearance and development of the plastic zone involves irreversible topological changes in the vicinity of the crack tip, made obvious by caustics shape variations. To cite this article: O. Pop et al., C. R. Mecanique 332 (2004). 相似文献
987.
Linking molecular models with ion mobility experiments. Illustration with a rigid nucleic acid structure
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Valentina D'Atri Massimiliano Porrini Frédéric Rosu Valérie Gabelica 《Journal of mass spectrometry : JMS》2015,50(5):ii-ii
Ion mobility spectrometry experiments allow the mass spectrometrist to determine an ion's rotationally averaged collision cross section ΩEXP. Molecular modelling is used to visualize what ion three‐dimensional structure(s) is(are) compatible with the experiment. The collision cross sections of candidate molecular models have to be calculated, and the resulting ΩCALC are compared with the experimental data. Researchers who want to apply this strategy to a new type of molecule face many questions: (1) What experimental error is associated with ΩEXP determination, and how to estimate it (in particular when using a calibration for traveling wave ion guides)? (2) How to generate plausible 3D models in the gas phase? (3) Different collision cross section calculation models exist, which have been developed for other analytes than mine. Which one(s) can I apply to my systems? To apply ion mobility spectrometry to nucleic acid structural characterization, we explored each of these questions using a rigid structure which we know is preserved in the gas phase: the tetramolecular G‐quadruplex [dTGGGGT]4, and we will present these detailed investigation in this tutorial. © 2015 The Authors. Journal of Mass Spectrometry published by John Wiley & Sons Ltd. 相似文献
988.
Difluorenyl carbo‐Benzenes: Synthesis,Electronic Structure,and Two‐Photon Absorption Properties of Hydrocarbon Quadrupolar Chromophores
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Dr. Iaroslav Baglai Manuel de Anda‐Villa Rodrigo M. Barba‐Barba Corentin Poidevin Dr. Gabriel Ramos‐Ortíz Dr. Valérie Maraval Dr. Christine Lepetit Dr. Nathalie Saffon‐Merceron Dr. José‐Luis Maldonado Prof. Dr. Remi Chauvin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):14186-14195
The synthesis, crystal and electronic structures, and one‐ and two‐photon absorption properties of two quadrupolar fluorenyl‐substituted tetraphenyl carbo‐benzenes are described. These all‐hydrocarbon chromophores, differing in the nature of the linkers between the fluorenyl substituents and the carbo‐benzene core (C?C bonds for 3 a , C?C?C?C expanders for 3 b ), exhibit quasi–superimposable one‐photon absorption (1PA) spectra but different two‐photon absorption (2PA) cross‐sections σ2PA. Z‐scan measurements (under NIR femtosecond excitation) indeed showed that the C?C expansion results in an approximately twofold increase in the σ2PA value, from 336 to 656 GM (1 GM=10?50 cm4 s molecule?1 photon?1) at λ=800 nm. The first excited states of Au and Ag symmetry accounting for 1PA and 2PA, respectively, were calculated at the TDDFT level of theory and used for sum‐over‐state estimations of σ2PA(λi), in which λi=2 hc/Ei, h is Planck’s constant, c is the speed of light, and Ei is the energy of the 2PA‐allowed transition. The calculated σ2PA values of 227 GM at 687 nm for 3 a and 349 GM at 708 nm for 3 b are in agreement with the Z‐scan results. 相似文献
989.
Adrian P. Sheppard Ji-Youn Arns Mark A. Knackstedt W. Val Pinczewski 《Transport in Porous Media》2005,59(2):155-173
Quasi-static rule-based network models used to calculate capillary dominated multi-phase transport properties in porous media employ equilibrium fluid saturation distributions which assume that pores are fully filled with a single bulk fluid with other fluids present only as wetting and/or spreading films. We show that for drainage dominated three-phase displacements in which a non-wetting fluid (gas) displaces a trapped intermediate fluid (residual oil) in the presence of a mobile wetting fluid (water) this assumption distorts the dynamics of three-phase displacements and results in significant volume errors for the intermediate fluid and erroneous calculations of intermediate fluid residual saturations, relative permeabilities and recoveries. The volume errors are associated with the double drainage mechanism which is responsible for the mobilization of waterflood residual oil. A simple modification of the double drainage mechanism is proposed which allows the presence of a relatively small number of partially filled pores and removes the oil volume errors. 相似文献
990.
Léa Falcoz-Vigne Yu Ogawa Sonia Molina-Boisseau Yoshiharu Nishiyama Valérie Meyer Michel Petit-Conil Karim Mazeau Laurent Heux 《Cellulose (London, England)》2017,24(9):3725-3739
The successive extraction and re-adsorption of a linear β-(1 → 4) xylan extracted from microfibrillated birch pulp was investigated using solid-state CP/MAS 13C NMR spectroscopy, specific surface area measurements, and atomistic molecular dynamics (MD) simulations. The NMR spectra confirmed that when in contact with cellulose after re-adsorption, the xylan molecules altered their conformation from the classical left-handed threefold structure found in the bulk to a different one, presumably a cellulose-like twofold system for quantities up to the equivalent amount of extracted xylan. Combining these observations with specific surface area measurements and the surface occupied by a xylosyl residue, it was possible to show that the re-adsorbed xylan in the modified conformation occurred only within the first adsorbed layer in direct interaction with the cellulose surface. It is only when an excess xylan was added and after full cellulose surface coverage, that the subsequent deposited layers took the classical threefold organization. Following the variation of xylan conformation in terms of sequential xylan addition allowed quantifying the surface of cellulose accessible for a tight adsorption of xylan, not only for microfibrillated birch cellulose, but for other samples as well. The MD simulations confirmed that xylan in threefold conformation had a weaker affinity for the cellulose surface than its twofold counterpart, thus supporting the hypothesis of the twofold conformation for xylan at the cellulose surface. The MD simulations also showed that in contact with cellulose, the adsorbed xylan was mainly organized as an extended molecular chain aligned parallel to the cellulose chain direction. 相似文献