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11.
We revisit the notion of renormalized charge, which is a concept of central importance in the field of highly charged colloidal or polyelectrolyte solutions. Working at the level of a linear Debye-Hückel-like theory only, we propose a versatile method to predict the saturated amount of charge renormalization, which is, however, a nonlinear effect arising at strong electrostatic coupling. The results are successfully tested against nonlinear Poisson-Boltzmann theory for polyions of various shapes (planar, cylindrical, and spherical), both in the infinite dilution limit or in confined geometry, with or without added electrolyte. Our approach, accurate for monovalent microions in solvents such as water, is finally confronted against experimental results on charged colloids and B-DNA solutions. 相似文献
12.
We show, using extensive molecular dynamics simulations, that the dynamics of the electric double layer (EDL) is very much dependent on the wettability of the charged surface on which the EDL develops. For a wetting surface, the dynamics, characterized by the so-called zeta potential, is mainly controlled by the electric properties of the surface, and our work provides a clear interpretation for the traditionally introduced immobile Stern layer. In contrast, the immobile layer disappears for nonwetting surfaces, and the zeta potential deduced from electrokinetic effects is considerably amplified by the existence of a slippage at the solid substrate. 相似文献
13.
In this paper, we consider the effect of cohesion on the stability of a granular heap and compute the maximum angle of stability of the heap as a function of the cohesion. We show that the stability is strongly affected by the dependence of the cohesion on the local pressure. In particular, this dependence is found to determine the localization of the failure plane. While for a constant adhesion force, slip occurs deep inside the heap, surface failure is obtained for a linear variation of the cohesion on the normal stress. Such a transition allows to interpret some recent experimental results on cohesive materials.Received: 6 May 2004, Published online: 29 June 2004PACS:
45.70.-n Granular systems - 61.43.Gt Powders, porous materials 相似文献
14.
Using molecular dynamics simulations, we show that a simple model of a glassy material exhibits the shear localization phenomenon observed in many complex fluids. At low shear rates, the system separates into a fluidized shear band and an unsheared part. The two bands are characterized by a very different dynamics probed by a local intermediate scattering function. Furthermore, a stick-slip motion is observed at very small shear rates. Our results, which open the possibility of exploring complex rheological behavior using simulations, are compared to recent experiments on various soft glasses. 相似文献
15.
Floquet S Ouali N Bocquet B Bernardinelli G Imbert D Bünzli JC Hopfgartner G Piguet C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(8):1860-1875
The segmental tris-tridentate ligand L7 reacts with stoichiometric quantities of Ln(III) (Ln=La-Lu) in acetonitrile to give the complexes [Ln(2)(L7)(3)](6+) and [Ln(3)(L7)(3)](9+). Formation constants point to negligible size-discriminating effects along the lanthanide series, but Scatchard plots suggest that the self-assembly of the trimetallic triple-stranded helicates [Ln(3)(L7)(3)](9+) is driven to completion by positive cooperativity, despite strong intermetallic electrostatic repulsions. Crystallization provides quantitatively [Ln(3)(L7)(3)](CF(3)SO(3))(9) (Ln=La, Eu, Gd, Tb, Lu) and the X-ray crystal structure of [Eu(3)(L7)(3)](CF(3)SO(3))(9).(CH(3)CN)(9).(H(2)O)(2) (Eu(3)C(216)H(226)N(48)O(35)F(27)S(9), triclinic, P1, Z=2) shows the three ligand strands wrapped around a pseudo-threefold axis defined by the three metal ions rigidly held at about 9 A. Each metal ion is coordinated by nine donor atoms in a pseudo-trigonal prismatic arrangement, but the existence of terminal carboxamide units in the ligand strands differentiates the electronic properties of the terminal and the central metallic sites. Photophysical data confirm that the three coordination sites possess comparable pseudo-trigonal symmetries in the solid state and in solution. High-resolution luminescence analyses evidence a low-lying LMCT state affecting the central EuN(9) site, so that multi-metal-centered luminescence is essentially dominated by the emission from the two terminal EuN(6)O(3) sites in [Eu(3)(L7)(3)](9+). New multicenter equations have been developed for investigating the solution structure of [Ln(3)(L7)(3)](9+) by paramagnetic NMR spectroscopy and linear correlations for Ln=Ce-Tb imply isostructurality for these larger lanthanides. NMR spectra point to the triple helical structure being maintained in solution, but an inversion of the magnitude of the second-rank crystal-field parameters, obtained by LIS analysis, for the LnN(6)O(3) and LnN(9) sites with respect to the parameters extracted for Eu(III) from luminescence data, suggests that the geometry of the central LnN(9) site is somewhat relaxed in solution. 相似文献
16.
Gnida M Margulès L Cosléou J Bocquet R Demaison J Mkadmi EB Bürger H Harder H Mäder H 《Journal of Molecular Spectroscopy》2000,200(1):40-54
The present paper deals with the analysis of the microwave, millimeter-wave, and infrared spectra of (28)SiHF(3) in its ground, v(6) = 1 and v(4) = 1 excited states. The former was observed up to 1055 GHz leading to the determination of one octic centrifugal distortion constant, L(J) = -0.0749(55) μHz. Furthermore the interaction term ||h(3,GS) || = 1.1032(70) mHz has been fitted from splittings of six K = 3 lines. The excited states have been regarded as isolated ones. This enabled fits according the Q-, D-, and QD-reduction schemes proposed by E. I. Lobodenko, O. N. Sulakshina, V. I. Perevalov, and Vl. G. Tyuterev, (J. Mol. Spectrosc. 126, 159-170 (1987)) and further developed by J. K. G. Watson, C. Gerke, H. Harder, and K. Sarka, (J. Mol. Spectrosc. 187, 131-141 (1997)) and Harder (J. Mol. Spectrosc. 194, 145 (1999)). A multiple fit analysis was performed confirming the assumption that the excited states are not affected by intervibrational resonances. Finally the millimeter spectrum of (29)SiHF(3) and (30)SiHF(3) in their ground state was also measured up to 460 GHz and accurate rotational and centrifugal distortion parameters were derived. Copyright 2000 Academic Press. 相似文献
17.
N. Lyotard W. L. Shew L. Bocquet J.-F. Pinton 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):469-476
We make time resolved velocity measurements of steel
spheres in free fall through liquid using a continuous ultrasound
technique. We explore two different ways to induce large changes in
drag on the spheres: 1) a small quantity of viscoelastic polymer
added to water and 2) altering the surface of the sphere. Low
concentration polymer solutions and/or a pattern of grooves in the
sphere surface induce an early drag crisis, which may reduce drag by
more than 50% compared to smooth spheres in pure water. On
the other hand, random surface roughness and/or high concentration
polymer solutions reduce drag progressively and suppress the drag
crisis. We also present a qualititative argument which ties the
drag reduction observed in low concentration polymer solutions to
the Weissenberg number and normal stress difference. 相似文献
18.
A. Ignatov V. Bellini J.P. Bocquet M. Capogni M. Casano A. D’Angelo J.-P. Didelez A. Fantini G. Gervino B. Girolami A. Giusa M. Guidal V. Kouznetsov A. Lapik A. Lleres A. Mushkarenkov L. Nicoletti D. Rebreyend N. Rudnev G. Russo M.-L. Sperduto M.-C. Sutera 《Progress in Particle and Nuclear Physics》2008,61(1):253-259
New experimental approach to study meson photoproduction in nuclei is discussed. It is based on the measurement of the recoil nucleon as a tagger for identification of the initial step of reaction. Propagation of mesons and nucleons within a nucleus is described by the Intra-Nuclear Cascade (INC) model. Simulations and preliminary experimental data for the deuteron target obtained at GRAAL are presented. 相似文献
19.
F. Hindle G. Mouret S. Eliet M. Guinet A. Cuisset R. Bocquet T. Yasui D. Rovera 《Applied physics. B, Lasers and optics》2011,104(4):763-768
The generation of cw-THz radiation by photomixing is particularly suited to the high resolution spectroscopy of gases; nevertheless,
until recently, it has suffered from a lack of frequency metrology. Frequency combs are a powerful tool that can transfer
microwave frequency standards to optical frequencies and a single comb has permitted accurate (10−8) THz frequency synthesis with a limited tuning range. A THz synthesizer composed of three extended cavity laser diodes phase
locked to a frequency comb has been constructed and its utility for high resolution gas phase spectroscopy demonstrated. The
third laser diode allows a larger tuning range of up to 300 MHz to be achieved without the need for large frequency excursions,
while the frequency comb provides a versatile link to be established from any traceable microwave frequency standard. The
use of a single frequency comb as a reference for all of the cw-lasers eliminates the dependency of synthesized frequency
on the carrier envelope offset frequency. This greatly simplifies the frequency comb stabilization requirements and leads
to a reduced instrument complexity. 相似文献
20.
Eli Sutter Peter Albrecht Bin Wang Marie-Laure Bocquet Lijun Wu Yimei Zhu Peter Sutter 《Surface science》2011,605(17-18):1676-1684
Ru nanoclusters self-assemble over macroscopic sample areas during vapor deposition of Ru on monolayer graphene (MLG) on Ru(0001). The Ru nanoclusters form arrays with a mean lateral cluster diameter of ~ 20 Å, cluster heights of 1 or 2 ML, and a size distribution that remains nearly constant with increasing coverage. Combined scanning tunneling microscopy and density functional theory (DFT) show that the clusters are templated by the MLG/Ru(0001) moiré unit cell and identify the preferred binding site of the clusters as the low fcc region of the moiré. Cross-sectional transmission electron microscopy (TEM) and high-resolution TEM contrast simulations experimentally demonstrate that the interaction of the Ru clusters with the underlying MLG/Ru(0001) leads to a local lifting of the graphene layer of the template. DFT calculations confirm this mechanism of interaction of the Ru clusters with the strongly coupled MLG/Ru(0001). Weakening of the graphene-support coupling via oxygen intercalation is shown to have a major effect on the assembly of Ru nanocluster arrays. With a preferred binding site lacking on decoupled graphene, the Ru nanoclusters grow significantly larger, and clusters with 1 to 4 ML height can coexist. 相似文献