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931.
Bert M. Weckhuysen Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(27):4910-4943
Catalytic solids in the spotlight : Detailed insight into the working principles of heterogeneous catalysts is essential for the design of improved or totally new ones. Such insight can be provided by making use of chemical imaging techniques, which yield spatiotemporal information about the workings of catalytic solids at different length scales: at the level of reactors, catalyst bodies, catalyst grains, and nanoparticles.
932.
Marie Sircoglou Maxime Mercy Nathalie Saffon Dr. Yannick Coppel Dr. Ghenwa Bouhadir Dr. Laurent Maron Dr. Didier Bourissou Dr. 《Angewandte Chemie (International ed. in English)》2009,48(19):3454-3457
Gallant exchange : Upon coordination of phosphanyl gallane ligands to AuCl, both neutral and zwitterionic complexes coexist. NMR spectroscopy provides direct evidence for the transfer of the chloride between gold and gallium in diphosphanyl gallane. The introduction of a third phosphanyl buttress allows the separation and structural characterization of the two coordination isomers (see picture; Au yellow, P red, Cl green, Ga blue).
933.
Bert Ungethüm Andreas Walte Wolf Münchmeyer Gerhard Matz 《International Journal for Ion Mobility Spectrometry》2009,12(4):131-137
Small concentrations of toxic compounds in atmospheric air have often to be measured selectively by portable equipment. Ion
mobility spectrometers are instruments used to monitor explosives, drugs and chemical warfare agents. First responders also
need to detect hazardous gases released in accidents while transporting them or in their production in chemical plants. Not
all toxic gases can be measured with the time of flight ion mobility spectrometer at concentrations required by safety standards
applied in workplace areas. The time of flight ion mobility spectrometer is based on an inlet membrane, an ionization region,
a shutter grid and the drift region with a detector in the drift tube. The separation of ions is due to the different mobility
of the ions when they are exposed to a weak electric field (E = 200…300 V/cm). High field asymmetric waveform spectrometry
or differential mobility spectrometry is a relative new ion mobility spectrometer technology. The separation is due to the
different mobilities of the ions in the high (E = 15000...30000 V/cm) and the weak electric fields. About 30 different toxic
industrial chemical compounds were analyzed with both systems under comparable conditions. For selected examples the detection
limits, the selectivity and the identification capabilities of the two systems for some of the main compounds will be discussed. 相似文献
934.
Bert Van Genechten Bart BergenDirk Vandepitte Wim Desmet 《Journal of computational physics》2010,229(18):6623-6643
The aim of the work presented in this paper is the numerical solution of low- and mid-frequency time-harmonic acoustic multiple-scattering problem. A novel so-called ‘multi-level’ modelling approach is proposed which is applicable to the study of a configuration of well separated obstacles of arbitrary shape on which any type of acoustic boundary condition can be applied. The generic character of the method is obtained by embedding the superposition principle for the multiple-scattering influence in a state-of-the-art acoustic modelling technique, the so-called Wave Based Method. The resulting approach successfully alleviates the geometrical limitations of the underlying Trefftz-based method and preserves the method’s computational efficiency, resulting in a generic multiple-scattering modelling framework with a superior computational efficiency in the low- as well as the mid-frequency range. Several numerical validation examples show that the proposed approach is as accurate as the classical single-scattering Wave Based Method and illustrate the computational efficiency as compared to Boundary Element Methods. 相似文献
935.
Bert Klumperman Eric T. A. van den Dungen Johan P. A. Heuts Michael J. Monteiro 《Macromolecular rapid communications》2010,31(21):1846-1862
The mechanistic interpretation of kinetic anomalies in reversible addition–fragmentation chain transfer (RAFT)‐mediated polymerization is critically reviewed. The main conclusion of this exercise is that available data do not allow model discrimination between the two prevailing mechanistic schemes, i.e., the slow fragmentation model and the intermediate radical termination model. However, assessment of the rate parameters reveals that the incompatibilities may not be as large as previously reported in literature. Dedicated kinetic studies on model compounds should be performed to shed further light on the seemingly incompatible data that currently exists in literature.
936.
Dust formation and growth in plasmas are in most cases continuous cyclic phenomena. We show that the growth of new dust generations takes place in a dust-free region, usually called a void, in the dust cloud. The three-step process of new dust generation is detailed thanks to the correlation between electrical, optical, and ex situ diagnostics. The strong inhomogeneity of both the plasma and the dust cloud during this process is underlined. 相似文献
937.
Zorko A Nellutla S van Tol J Brunel LC Bert F Duc F Trombe JC de Vries MA Harrison A Mendels P 《Physical review letters》2008,101(2):026405
We report the determination of the Dzyaloshinsky-Moriya interaction, the dominant magnetic anisotropy term in the kagome spin-1/2 compound ZnCu3(OH)6Cl2. Based on the analysis of the high-temperature electron spin resonance (ESR) spectra, we find its main component |Dz|=15(1) K to be perpendicular to the kagome planes. Through the temperature dependent ESR linewidth, we observe a building up of nearest-neighbor spin-spin correlations below approximately 150 K. 相似文献
938.
Maxime?Couderc Mircea?SofoneaEmail authorView authors OrcID profile 《Mediterranean Journal of Mathematics》2018,15(5):195
We consider a mathematical model which describes the equilibrium of an elastic body in contact with two obstacles. We derive its weak formulation which is in a form of an elliptic quasi-variational inequality for the displacement field. Then, under a smallness assumption, we establish the existence of a unique weak solution to the problem. We also study the dependence of the solution with respect to the data and prove a convergence result. Finally, we consider an optimization problem associated with the contact model for which we prove the existence of a minimizer and a convergence result, as well. 相似文献
939.
Grapinet M Udaltsov V Jacquot M Lacourt PA Dudley JM Larger L 《Chaos (Woodbury, N.Y.)》2008,18(1):013110
We describe experimental studies of the dynamical behavior of a recently proposed electro-optic discrete time nonlinear delay oscillator. With appropriate choice of the oscillator loop parameters and external forcing of the dynamics using a pulsed laser source, the system allows for the physical realization of a high dimensional mathematical nonlinear mapping. The dynamical features observed with this new class of discrete time delay oscillator differ significantly from those observed with similar continuous time nonlinear delay feedback oscillators and reveal the intrinsic discrete time nature of the dynamics. We also discuss specific applications to chaos communications using regularly clocked binary data. 相似文献
940.
Maxime Février 《Journal of Functional Analysis》2010,258(9):2983-3023
Free probabilistic considerations of type B first appeared in the paper of Biane, Goodman and Nica [P. Biane, F. Goodman, A. Nica, Non-crossing cumulants of type B, Trans. Amer. Math. Soc. 355 (2003) 2263-2303]. Recently, connections between type B and infinitesimal free probability were put into evidence by Belinschi and Shlyakhtenko [S.T. Belinschi, D. Shlyakhtenko, Free probability of type B: Analytic aspects and applications, preprint, 2009, available online at www.arxiv.org under reference arXiv:0903.2721]. The interplay between “type B” and “infinitesimal” is also the object of the present paper. We study infinitesimal freeness for a family of unital subalgebras A1,…,Ak in an infinitesimal noncommutative probability space (A,φ,φ′) and we introduce a concept of infinitesimal non-crossing cumulant functionals for (A,φ,φ′), obtained by taking a formal derivative in the formula for usual non-crossing cumulants. We prove that the infinitesimal freeness of A1,…,Ak is equivalent to a vanishing condition for mixed cumulants; this gives the infinitesimal counterpart for a theorem of Speicher from “usual” free probability. We show that the lattices NC(B)(n) of non-crossing partitions of type B appear in the combinatorial study of (A,φ,φ′), in the formulas for infinitesimal cumulants and when describing alternating products of infinitesimally free random variables. As an application of alternating free products, we observe the infinitesimal analogue for the well-known fact that freeness is preserved under compression with a free projection. As another application, we observe the infinitesimal analogue for a well-known procedure used to construct free families of free Poisson elements. Finally, we discuss situations when the freeness of A1,…,Ak in (A,φ) can be naturally upgraded to infinitesimal freeness in (A,φ,φ′), for a suitable choice of a “companion functional” . 相似文献