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821.
Sylvain S. Bosquain Antoine Dorcier Paul J. Dyson Mikael Erlandsson Luca Gonsalvi Gábor Laurenczy Maurizio Peruzzini 《应用有机金属化学》2007,21(11):947-951
The water‐soluble ruthenium(II) complexes [Cp′RuX(PTA)2]Y and [CpRuCl(PPh3)(mPTA)]OTf (Cp′ = Cp, Cp*, X = Cl and Y = nil; or X = MeCN and Y = PF6; PTA = 1,3,5‐triaza‐7‐phosphaadamantane; mPTA = 1‐methyl‐1,3,5‐triaza‐7‐phosphaadamantane) were used as catalyst precursors for the hydrogenation of CO2 and bicarbonate in aqueous solutions, in the absence of amines or other additives, under relatively mild conditions (100 bar H2, 30–80 °C), with moderate activities. Kinetic studies showed that the hydrogenation of HCO3? proceeds without an induction period, and that the rate strongly depends on the pH of the reaction medium. High‐pressure multinuclear NMR spectroscopy revealed that the ruthenium(II) chloride precursors are quantitatively converted into the corresponding hydrides under H2 pressure. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
822.
Luca Fabbri 《International Journal of Theoretical Physics》2013,52(2):634-643
We study Dirac field equations coupled to electrodynamics with metric and torsion fields: we discuss how special spinorial solutions are incompatible with torsion; eventually these results will be used to sketch a discussion on the problem of renormalizability of point-like particles. 相似文献
823.
A Palladium‐Catalyzed Carbonylation Approach to Eight‐Membered Lactam Derivatives with Antitumor Activity 下载免费PDF全文
Dr. Raffaella Mancuso Dr. Dnyaneshwar S. Raut Dr. Nadia Marino Dr. Giorgio De Luca Dr. Cinzia Giordano Prof. Dr. Stefania Catalano Dr. Ines Barone Prof. Dr. Sebastiano Andò Prof. Dr. Bartolo Gabriele 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):3053-3064
The reactivity of 2‐(2‐alkynylphenoxy)anilines under PdI2/KI‐catalyzed oxidative carbonylation conditions has been studied. Although a different reaction pathway could have been operating, N‐palladation followed by CO insertion was the favored pathway with all substrates tested, including those containing an internal or terminal triple bond. This led to the formation of a carbamoylpalladium species, the fate of which, as predicted by theoretical calculations, strongly depended on the nature of the substituent on the triple bond. In particular, 8‐endo‐dig cyclization preferentially occurred when the triple bond was terminal, leading to the formation of carbonylated ζ‐lactam derivatives, the structures of which have been confirmed by XRD analysis. These novel medium‐sized heterocyclic compounds showed antitumor activity against both estrogen receptor‐positive (MCF‐7) and triple negative (MDA‐MB‐231) breast cancer cell lines. In particular, ζ‐lactam 3 j′ may represent a novel and promising antitumor agent because biological tests clearly demonstrate that this compound significantly reduces cell viability and motility in both MCF‐7 and MDA‐MB‐231 breast cancer cell lines, without affecting normal breast epithelial cell viability. 相似文献
824.
Valerio B. Di Marco Luca Raveane Annalisa Dean Pietro Traldi 《Rapid communications in mass spectrometry : RCM》2010,24(7):868-874
Electrospray ionization mass spectrometry (ESI‐MS) is very often employed to study metal/ligand equilibria in aqueous solution. However, the ionization process can introduce perturbations which affect the speciation results in an unpredictable way. It is necessary to identify these perturbations in order to correctly interpret the ESI‐MS speciation results. Aluminium(III)/1,6‐dimethyl‐4‐hydroxy‐3‐pyridinecarboxylate (DQ716) aqueous solutions at various pH were analysed by ESI‐MS, and speciation results were compared with those obtained by equilibrium techniques. Differences observed were both qualitative and quantitative. The ESI‐MS spectral changes due to different settings of the following instrumental parameters were analyzed: the solution flow rate (FS), the nebulizer gas flow rate (FG), the potential applied at the entrance capillary (EC), and the temperature of the drying gas (TG). The effects produced by FS and EC on the spectra strongly suggest the key role of surface activity in determining the relative fraction of the ions reaching the detector. The experimental effects of FS and TG were interpreted considering the presence of at least two reactions in the gas phase and a dimerization occurring in the droplets. These perturbations cannot be generalized because they appear to be chemical system‐related and instrument‐dependent. Therefore, the identification of perturbations is a required task for any metal‐ligand equilibrium study performed by ESI‐MS. Our results indicate that perturbations can be identified by evaluating the effects produced in the spectra by a change of instrumental parameters. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
825.
826.
F De Luca E De Vita G H Raza C Casieri 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,139(1):126-131
The transverse relaxation time in the rotating frame T2rho is proposed as an effective parameter to get specific contrast in solid state imaging. Several peculiarities make T2rho an interesting candidate to map dynamics and structure in solids: the effect of the secular spin interaction can be controlled by the experimenter and therefore the relaxation associated with the nonsecular terms, which is particularly sensitive to very slow dynamics, can be observed. In this paper we present preliminary results obtained on polymers and prove the capability of the MARF Imaging, enhanced by a filter based on rotary echo refocusing, to produce images of solids contrasted by T2rho. 相似文献
827.
Balancing Neumann-Neumann preconditioners for mixed approximations of heterogeneous problems in linear elasticity 总被引:2,自引:0,他引:2
Paulo?Goldfeld Luca F.?Pavarino Olof B.?WidlundEmail author 《Numerische Mathematik》2003,95(2):283-324
Summary. Balancing Neumann-Neumann methods are extented to mixed formulations of the linear elasticity system with discontinuous coefficients, discretized with mixed finite or spectral elements with discontinuous pressures. These domain decomposition methods implicitly eliminate the degrees of freedom associated with the interior of each subdomain and solve iteratively the resulting saddle point Schur complement using a hybrid preconditioner based on a coarse mixed elasticity problem and local mixed elasticity problems with natural and essential boundary conditions. A polylogarithmic bound in the local number of degrees of freedom is proven for the condition number of the preconditioned operator in the constant coefficient case. Parallel and serial numerical experiments confirm the theoretical results, indicate that they still hold for systems with discontinuous coefficients, and show that our algorithm is scalable, parallel, and robust with respect to material heterogeneities. The results on heterogeneous general problems are also supported in part by our theory.
Mathematics Subject Classification (1991):65N55, 65N30, 65N35, 65F10, 65Y05This work was supported by a scholarship of CNPq, of the Ministry for Science and Technology of Brazil, under process 201205/97-1. The work was developed in part at MCS/ANL-DOE, under a Givens Research Associate appointment in Summer 2001.This work was supported in part by the National Science Foundation under Grant NSF-CCR-9732208 and in part by MIUR.This work was supported in part by the National Science Foundation under Grants qNSF-CCR-9732208, and in part by the U.S. Department of Energy under contracts DE-FC02-01ER25482 and DE-FG02-92ER25127. 相似文献
828.
Eckhard?M.?S.?HitzerEmail author Luca?Redaelli 《Advances in Applied Clifford Algebras》2003,13(2):157-181
Conventional illustrations of the rich elementary relations and physical applications of geometric algebra are helpful, but
restricted in communicating full generality and time dependence. The main restrictions are one special perspective in each
graph and the static character of such illustrations. Several attempts have been made to overcome such restrictions. But up
till now very little animated and fully interactive, free, instant access, online material is available.
This report presents therefore a set of over 90 newly developed (freely online accessible [1]) JAVA applets. These applets
range from the elementary concepts of vector, bivector, outer product and rotations to triangle relationships, oscillations
and polarized waves. A special group of 21 applets illustrates three geometrically different approaches to the representation
of conics; and even more ways to describe ellipses. Next Clifford’s famous circle chain theorem is illustrated. Finally geometric
applications important for crystallography and structural mechanics give a glimpse of the vast potential for applied mathematics.
The interactive geometry software Cinderella [2] was used for creating these applets. The interactive features of many of
the applets invite the user to freely explore by a few mouse clicks as many different special cases and perspectives as he
likes. This is of great help in “visualizing” geometry encoded by geometric algebra. 相似文献
829.
The Sagnac time delay and the corresponding Sagnac phase shift, for relativistic matter and electromagnetic beams counter-propagating in a rotating interferometer, are deduced on the ground of relativistic kinematics. This purely kinematical approach allows to explain the universality of the effect, namely the fact that the Sagnac time difference does not depend on the physical nature of the interfering beams. The only prime requirement is that the counter-propagating beams have the same velocity with respect to any Einstein synchronized local co-moving inertial frame. 相似文献
830.
Bernardi L Cerè V Femoni C Pollicino S Ricci A 《The Journal of organic chemistry》2003,68(8):3348-3351
Oxime ethers derived from 2-pyridinecarboxaldehyde and glyoxylic acid can be effectively allylated in water with five differently functionalized allylic bromides promoted by indium. When the metal is positioned in close proximity of flanking heteroatomic centers, chelation by In is indeed operative and affects both reactivity and stereochemistry. Stereochemical assignments in the addition products were based on X-ray crystallographic measurements and spectral correlations. 相似文献