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211.
Yves Jeannin 《Comptes Rendus Chimie》2004,7(12):1235-1240
A novel vacant heteropolytungstate of skeleton X2W21 derived from the polytungstate [H6X2W22O76]8– (X = Sb,Bi). Five heteropolytungstates Na8[H6Sb2W21O73]·16.5 H2O, Na8[H6Sb2W21O73]·19 H2O, Na8[H6Bi2W21O73]·16.5 H2O, Li2Na6[H6Sb2W22O76]·14.5 H2O, and Na5[H7Sb2NiW21O73(H2O)3]·20 H2O were prepared and studied by X-ray diffraction. The values of isotropic temperature factors of the external tungsten atom and of its three terminal oxygen atoms were compared to those of same-type atoms, firstly of the same polytungstate, and secondly inside this five-compound family. This analysis led to the conclusion that the vacant assembly X2W21O73 (X = Sb,Bi) does exist and that the vacancy may be filled up with a first row transition metal such as nickel. To cite this article: Y. Jeannin, C. R. Chimie 7 (2004). 相似文献
212.
We exhibit infinite, solvable, virtually abelian groups with a fixed number of generators, having arbitrarily large balls
consisting of torsion elements. We also provide a sequence of 3-generator non-virtually nilpotent polycyclic groups of algebraic
entropy tending to zero. All these examples are obtained by taking appropriate quotients of finitely presented groups mapping
onto the first Grigorchuk group.
Received: 3 August 2005 相似文献
213.
In one space dimension we address the homogenization of the spectral problem for a singularly perturbed diffusion equation
in a periodic medium. Denoting by ε the period, the diffusion coefficient is scaled as ε2. The domain is made of two purely periodic media separated by an interface. Depending on the connection between the two cell
spectral equations, three different situations arise when ε goes to zero. First, there is a global homogenized problem as
in the case without an interface. Second, the limit is made of two homogenized problems with a Dirichlet boundary condition
on the interface. Third, there is an exponential localization near the interface of the first eigenfunction.
Received: January 10, 2001; in final form: July 9, 2001?Published online: June 11, 2002 相似文献
214.
Nieder B Buus S Cazals Y Scharf B 《The Journal of the Acoustical Society of America》2007,122(1):35-37
The induced reduction in the loudness (ILR) of a weaker tone caused by a preceding stronger tone was measured with both tones in the same ear (ipsilateral ILR) and also in opposite ears (contralateral ILR). The two tones were always equal in duration and were presented repeatedly over several minutes. When the tone duration was 200 ms, for 24 listeners the loudness reduction averaged 11 dB under ipsilateral ILR and 6 dB under contralateral ILR. When the duration was 5 ms, ILR was 8 dB whether ipsilateral or contralateral. For each duration, ipsilateral and contralateral ILR were strongly correlated (r around 0.80). 相似文献
215.
Bi W Pagneux V Lafarge D Aurégan Y 《The Journal of the Acoustical Society of America》2007,122(1):280-290
An efficient method is proposed for modeling time harmonic acoustic propagation in a nonuniform lined duct without flow. The lining impedance is axially segmented uniform, but varies circumferentially. The sound pressure is expanded in term of rigid duct modes and an additional function that carries the information about the impedance boundary. The rigid duct modes and the additional function are known a priori so that calculations of the true liner modes, which are difficult, are avoided. By matching the pressure and axial velocity at the interface between different uniform segments, scattering matrices are obtained for each individual segment; these are then combined to construct a global scattering matrix for multiple segments. The present method is an improvement of the multimodal propagation method, developed in a previous paper [Bi et al., J. Sound Vib. 289, 1091-1111 (2006)]. The radial rate of convergence is improved from O(n(-2)), where n is the radial mode indices, to O(n(-4)). It is numerically shown that using the present method, acoustic propagation in the nonuniform lined intake of an aeroengine can be calculated by a personal computer for dimensionless frequency K up to 80, approaching the third blade passing frequency of turbofan noise. 相似文献
216.
Sawitree Saengkaew Tawatchai Charinpanitkul Hathaichanok Vanisri Wiwut Tanthapanichakoon Yves Biscos Nicolas Garcia Gérard Lavergne Loïc Mees Gérard Gouesbet Gérard Grehan 《Experiments in fluids》2007,43(4):595-601
The rainbow refractrometry, under its different configurations (classical and global), is an attractive technique to extract
information from droplets in evaporation such as diameter and temperature. Recently a new processing strategy has been developed
which increases dramatically the size and refractive index measurements accuracy for homogeneous droplets. Nevertheless, for
mono component as well as for multicomponent droplets, the presence of temperature and/or of concentration gradients induce
the presence of a gradient of refractive index which affects the interpretation of the recorded signals. In this publication,
the effect of radial gradient on rainbow measurements with a high accuracy never reached previously is quantified. 相似文献
217.
Targeting the Two Oncogenic Functional Sites of the HPV E6 Oncoprotein with a High‐Affinity Bivalent Ligand
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218.
Diselenophosphate‐Induced Conversion of an Achiral [Cu20H11{S2P(OiPr)2}9] into a Chiral [Cu20H11{Se2P(OiPr)2}9] Polyhydrido Nanocluster
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Dr. Rajendra S. Dhayal Jian‐Hong Liao Dr. Xiaoping Wang Dr. Yu‐Chiao Liu Dr. Ming‐His Chiang Dr. Samia Kahlal Prof. Jean‐Yves Saillard Prof. C. W. Liu 《Angewandte Chemie (International ed. in English)》2015,54(46):13604-13608
A polyhydrido copper nanocluster, [Cu20H11{Se2P(OiPr)2}9] ( 2H ), which exhibits an intrinsically chiral inorganic core of C3 symmetry, was synthesized from achiral [Cu20H11{S2P(OiPr)2}9] ( 1H ) of C3h symmetry by a ligand‐exchange method. The structure has a distorted cuboctahedral Cu13 core, two triangular faces of which are capped along the C3 axis, one by a Cu6 cupola and the other by a single Cu atom. The Cu20 framework is further stabilized by 9 diselenophosphate and 11 hydride ligands. The number of hydride, phosphorus, and selenium resonances and their splitting patterns in multinuclear NMR spectra of 2H indicate that the chiral Cu20H11 core retains its C3 symmetry in solution. The 11 hydride ligands were located by neutron diffraction experiments and shown to be capping μ3‐H and interstitial μ5‐H ligands (in square‐pyramidal and trigonal‐bipyramidal cavities), as supported by DFT calculations on [Cu20H11(Se2PH2)9] ( 2H′ ) as a simplified model. 相似文献
219.
220.
[Cu32(H)20{S2P(OiPr)2}12]: The Largest Number of Hydrides Recorded in a Molecular Nanocluster by Neutron Diffraction
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Dr. Rajendra S. Dhayal Jian‐Hong Liao Dr. Samia Kahlal Dr. Xiaoping Wang Dr. Yu‐Chiao Liu Dr. Ming‐Hsi Chiang Prof. Werner E. van Zyl Prof. Jean‐Yves Saillard Prof. C. W. Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(23):8369-8374
An air‐ and moisture‐stable nanoscale polyhydrido copper cluster [Cu32(H)20{S2P(OiPr)2}12] ( 1H ) was synthesized and structurally characterized. The molecular structure of 1H exhibits a hexacapped pseudo‐rhombohedral core of 14 Cu atoms sandwiched between two nestlike triangular cupola fragments of (2×9) Cu atoms in an elongated triangular gyrobicupola polyhedron. The discrete Cu32 cluster is stabilized by 12 dithiophosphate ligands and a record number of 20 hydride ligands, which were found by high‐resolution neutron diffraction to exhibit tri‐, tetra‐, and pentacoordinated hydrides in capping and interstitial modes. This result was further supported by a density functional theory investigation on the simplified model [Cu32(H)20(S2PH2)12]. 相似文献