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861.
Navarro O Marion N Mei J Nolan SP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(19):5142-5148
The use of second-generation [(NHC)Pd(R-allyl)Cl] complexes for Suzuki-Miyaura and Buchwald-Hartwig cross-coupling reactions involving heteroaromatic halides at room temperature is reported. The first examples of room temperature Suzuki-Miyaura cross-coupling of deactivated aryl chlorides with alkenyl boronic acids are also disclosed. Terminal substitution at the allyl moiety of the palladium complex facilitates its activation at room temperature leading to very active catalytic species enabling the present catalytic transformations to be performed rapidly using very mild reaction conditions. Catalyst loadings can be as low as 10 ppm for the Buchwald-Hartwig aryl amination and 50 ppm for the Suzuki-Miyaura reaction. 相似文献
862.
Guardiola R Kornilov O Navarro J Peter Toennies J 《The Journal of chemical physics》2006,124(8):084307
The ground-state energies and the radial and pair distribution functions of neutral 4He clusters are systematically calculated by the diffusion Monte Carlo method in steps of one 4He atom from 3 to 50 atoms. In addition the chemical potential and the low-lying excitation levels of each cluster are determined with high precision. These calculations reveal that the "magic numbers" observed in experimental 4He cluster size distributions, measured for free jet gas expansions by nondestructive matter-wave diffraction, are not caused by enhanced stabilities. Instead they are explained in terms of an enhanced growth due to sharp peaks in the equilibrium concentrations in the early part of the expansion. These peaks appear at cluster sizes which can just accommodate one more additional stable excitation. The good agreement with experiment provides not only experimental confirmation of the energy level and the chemical potential calculations, but also evidence for a new mechanism which can lead to magic numbers in cluster size distributions. By accounting for the falloff of the radial density distributions at the surface and a size-dependent surface tension, the energy levels are demonstrated to be consistent with a modified Rayleigh model of surface excitations. The compressibility coefficient of these small clusters is found to be one order of magnitude smaller than the bulk compressibility. 相似文献
863.
Augusto Rivera Mauricio Maldonado Jaime Ríos-Motta Miguel Angel Navarro Diego González-Salas 《Tetrahedron letters》2010,51(1):102-104
A one-pot good-yielding synthesis of 1-(alcoxymethyl)-1H-benzimidazoles and 1-((1H-benzimidazol-1-yl)methyl)-1H-benzotriazole from N1,N2-bis((1H-benzotriazol-1-yl)methyl)benzene-1,2-diamine (3) and alcohols is described. The synthesis of 3 from macrocyclic aminal 6H,13H-5:12,7:14-dimethanedibenzo-[d,i][1,3,6,8]tetraazecine (DMDBTA, 1) and benzotriazole is also described. Both these methods are simple, isolation of the products from the reaction mixtures is easy, and the yields are good. 相似文献
864.
L. Paussa N. C. Rosero‐Navarro F. Andreatta Y. Castro A. Duran M. Aparicio L. Fedrizzi 《Surface and interface analysis : SIA》2010,42(4):299-305
Aluminium alloys such as AA2024 are susceptible to severe corrosion attack in aggressive solutions (e.g. chlorides). Conversion coatings, like chromate, or rare earth conversion coatings are usually applied in order to improve corrosion behaviour of aluminium alloys. Methacrylate‐based hybrid films deposited with sol–gel technique might be an alternative to conversion coatings. Barrier properties, paint adhesion and possibly self‐healing ability are important aspects for replacement of chromate‐based pre‐treatments. This work evaluates the behaviour of cerium as corrosion inhibitor in methacrylate silane‐based hybrid films containing SiO2 nano‐particles on AA2024. Hybrid films were deposited on aluminium alloy AA2024 by means of dip‐coating technique. Two different types of coating were applied: a non‐inhibited film consisting of two layers (non‐inhibited system) and a similar film doped with cerium nitrate in an intermediate layer (inhibited system). The film thickness was 5 µm for the non‐inhibited system and 8 µm for the inhibited system. Film morphology and composition were investigated by means of GDOES (glow discharge optical emission spectroscopy). Moreover, GDOES qualitative composition profiles were recorded in order to investigate Ce content in the hybrid films as a function of immersion time in 0.05 M NaCl solution. The electrochemical behaviour of the hybrid films was studied in the same electrolyte by means of EIS technique (electrochemical impedance spectroscopy). Electrochemical measurements provide evidence that the inhibited system containing cerium displays recovery of electrochemical properties. This behaviour is not observed for the non‐inhibited coating. GDOES measurements provide evidence that the behaviour of inhibited system can be related to migration of Ce species to the substrate/coating interface. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
865.
Several classical theorems on character degrees are revisited from the point of view of the real characters.
The research of the first two authors is partially supported by the Spanish Ministerio de Educación y Ciencia (MTM2004-06067-C02-01).
The third author gratefully acknowledges the support of the NSF (grant DMS-0600967) 相似文献
866.
If G has a nilpotent normal p-complement and V is a finite, faithful and completely reducible G-module of characteristic p, we prove that there exist ${v_1, v_2 \in V}If G has a nilpotent normal p-complement and V is a finite, faithful and completely reducible G-module of characteristic p, we prove that there exist v1, v2 ? V{v_1, v_2 \in V} such that CG(v1)?CG(v2) = P{{\bf C}_{G}{(v_1)}\cap {\bf C}_{G}{(v_2)} = P} , where P ? Sylp(G){P \in {\rm Syl}_p(G)} . We hence deduce that, if the normal p-complement K is nontrivial, there exists v ? CV(P){v \in {\bf C}_{V}(P)} such that |K : C
K
(v)|2 > |K|. 相似文献
867.
Let (X, d) be a compact metric and 0 < α < 1. The space Lip α (X) of Hölder functions of order α is the Banach space of all functions ? from X into \(\mathbb{K}\) such that ∥?∥ = max{∥?∥∞, L(?)} < ∞, where is the Hölder seminorm of ?. The closed subspace of functions ? such that is denoted by lip α (X). We determine the form of all bijective linear maps from lip α (X) onto lip α (Y) that preserve the Hölder seminorm.
相似文献
$L(f) = sup\{ \left| {f(x) - f(y)} \right|/d^\alpha (x,y):x,y \in X, x \ne y\} $
$\mathop {\lim }\limits_{d(x,y) \to 0} \left| {f(x) - f(y)} \right|/d^\alpha (x,y) = 0$
868.
We predict the formation of optically trapped, metal-dielectric nanoparticle clusters above photonic crystal microcavities. We determine the conditions on particle size and position for a gold particle to be trapped above the microcavity. We then show that strong field redistribution and enhancement near the trapped gold nanoparticle results in secondary trapping sites for a pair of dielectric nanoparticles. 相似文献
869.
Batail L. Davesne D. Péru S. Becker P. Pastore A. Navarro J. 《The European Physical Journal A - Hadrons and Nuclei》2023,59(9):1-14
The European Physical Journal A - Much of astrophysics is fueled by nuclear physics with observables, such as energy output and elements produced, that are heavily dependent on the masses of the... 相似文献
870.
Sanhueza Luis Garrido Karla Celis Freddy García Macarena Cáceres Cesar Moczko Ewa Díaz Ramiro J. Aguirre María García Camilo 《Journal of Solid State Electrochemistry》2023,27(6):1511-1521
Journal of Solid State Electrochemistry - Screen-printed electrodes (SPEs) have the advantage of being considered electrochemical cells that can be implemented in portable sensor applications. With... 相似文献