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991.
992.
A stable suspension of nanoparticles is generally achieved by modifying the surface properties of the nanoparticles using a surfactant. This is to create a surface charge on the nanoparticles which prevents them from forming aggregates. This phenomenon is very sensitive to changes in the local environment. Conventional optical tweezers though capable of trapping sub-micrometer particles are not known to trap single nanoparticles. However, the stability and dynamics of a suspension of nanoparticles can be probed through the changes in the fluctuations of an optically trapped microsphere that has been added to the suspension. Adding microspheres to the nanoparticle suspension can affect the stability depending on the surface charges the microparticles themselves have. The study reports here on the variation of the dynamics of suspended nanoparticles, which have a positive surface charge, when silica microspheres, which are negatively surface charged, are added to the suspension. With the addition of silica beads, there is agglomeration of the nanoparticles. The dynamics of these agglomerated structures are then probed by measuring the Brownian fluctuations of an optically trapped silica bead. These results are in sharp contrast to those of earlier studies carried out with suspensions of identical nanoparticles but with negative surface charge. 相似文献
993.
994.
In this article, we study the role of defects in the quasistatic evolution of a martensitic phase boundary. The formulation of the model gives rise to a nonlocal free boundary problem, for which we present an implicit finite-time discretization. For an approximate model, assuming a nearly flat interface, we show that the phase boundary exhibits a sick-slip behavior in the presence of a heterogeneous environment, thus leading to a transition from viscous kinetics to rate-independent behavior. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
995.
Reaction of N-(2′-hydroxyphenyl)benzaldimines (abbreviated in general as H2L-R, where R stands for the para-substituent in the benzaldehyde fragment and H stands for the dissociable hydrogen atoms) with [Ru(PPh3)2(CO)2Cl2] affords a family of organoruthenium complexes of the type [Ru(PPh3)2(CO)(L-R)] where the N-(2′-hydroxyphenyl)benzaldimine ligand is coordinated to the metal center as tridentate C,N,O-donor. Structure of a representative complex has been determined by X-ray crystallography. All the [Ru(PPh3)2(CO)(L-R)] complexes are diamagnetic, and show characteristic 1H NMR signals and moderately intense MLCT transitions in the visible region. Cyclic voltammetry of the [Ru(PPh3)2(CO)(L-R)] complexes shows a reversible Ru(II)–Ru(III) oxidation within 0.38–0.68 V versus SCE, followed by an irreversible oxidation of the coordinated benzaldimine ligand within 1.09–1.27 V versus SCE. An irreversible reduction of the coordinated benzaldimine ligand is also observed near −1.1 V versus SCE. Potential of the Ru(II)–Ru(III) oxidation is observed to be sensitive to the nature of para-substituent R. 相似文献
996.
Reaction of α-amino acids (HL) with [Ru(PPh3)3Cl2] in the presence of a base afforded a family of complexes of type [Ru(PPh3)2(L)2]. These complexes are diamagnetic (low-spin d6, S=0) and show ligand-field transitions in the visible region. 1H and 31P NMR spectra of the complexes indicate the presence of C2 symmetry. Cyclic voltammetry on the [Ru(PPh3)2(L)2] complexes show a reversible ruthenium(II)–ruthenium(III) oxidation in the range 0.30–0.42 V vs. SCE. An irreversible ruthenium(III)–ruthenium(IV) oxidation is also displayed by two complexes near 1.5 V vs. SCE. 相似文献
997.
Nonlinear Dynamics - Whenever a disease emerges, awareness in susceptibles prompts them to take preventive measures, which influence individuals’ behaviors. Therefore, we present and analyze... 相似文献
998.
We have developed a new approach to computing the collision boundary of a collection of obstacles grown by a convex robot. The essential idea of this approach involves first representing the robot as a set sum of line segments and triangles. The process of growing the obstacles by the robot can then be viewed as a sequence of steps where each step involves growing the partial grown collection of obstacles by a line segment or a triangle. A fast algorithm has been presented to solve this problem. 相似文献
999.
Isaac V. Chenchiah Kaushik Bhattacharya 《Archive for Rational Mechanics and Analysis》2008,187(3):409-479
The elastic energy of a multiphase solid is a function of its microstructure. Determining the infimum of the energy of such
a solid and characterizing the associated optimal microstructures is an important problem that arises in the modeling of the
shape memory effect, microstructure evolution, and optimal design. Mathematically, the problem is to determine the relaxation
under fixed phase fraction of a multiwell energy. This paper addresses two such problems in the geometrically linear setting.
First, in two dimensions, we compute the relaxation under fixed phase fraction for a two-well elastic energy with arbitrary
elastic moduli and transformation strains, and provide a characterization of the optimal microstructures and the associated
strain. Second, in three dimensions, we compute the relaxation under fixed phase fraction for a two-well elastic energy when
either (1) both elastic moduli are isotropic, or (2) the elastic moduli are well ordered and the smaller elastic modulus is
isotropic. In both cases we impose no restrictions on the transformation strains. We provide a characterization of the optimal
microstructures and the associated strain. We also compute a lower bound that is optimal except possibly in one regime when
either (1) both elastic moduli are cubic, or (2) the elastic moduli are well ordered and the smaller elastic modulus is cubic;
for moduli with arbitrary symmetry we obtain a lower bound that is sometimes optimal. In all these cases we impose no restrictions
on the transformation strains and whenever the bound is optimal we provide a characterization of the optimal microstructures
and the associated strain. In both two and three dimensions the quasiconvex envelope of the energy can be obtained by minimizing
over the phase fraction. We also characterize optimal microstructures under applied stress. 相似文献
1000.