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1.
A general expression for the cooperative diffusion constant of weakly charged gels is derived as a function of the thermodynamic
parameters such as polyelectrolyte concentration, salt concentration, ionic strength, and the degree of crosslinking. In the
low concentration range it decreases with the monomer concentration.
Received: 30 January 1998 / Revised: 4 May 1998 / Accepted: 6 May 1998 相似文献
2.
T. Charitat B. Fourcade 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):333-336
An o-ring takes spontaneously the shape of a chair when strong enough torsion is applied in its tangent plane. This state
is metastable, since work has to be done on the o-ring to return to the circular shape. We show that this metastable state
exists in a Hamiltonian where curvature and torsion are coupled via an intrinsic curvature term. If the o-ring is constrained to be planar (2d case), this metastable state displays a kink-anti-kink
pair. This state is metastable if the ratio is less than , where C and A are the torsion and the bending elastic constants [#!landau!#]. In three dimensions, our variational approach shows that
. This model can be generalized to the case where the bend is induced by a concentration field which follows the variations
of the curvature.
Received: 27 August 1997 / Revised: 23 October 1997 / Accepted: 12 November 1997 相似文献
3.
M. Ben Amar P.P. da Silva N. Limodin A. Langlois M. Brazovskaia C. Even I.V. Chikina P. Pieranski 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):197-202
Catenoid-shaped smectic films are spanned between two coaxial circular frames separated by a distance H. It is shown that there exists a critical height H* such that below it two shapes of the catenoid are possible. The stability of these two shapes is analysed in terms of their
vibrations. The spectrum of eigenfrequencies is calculated as a function of the catenoid height. It is shown that the frequency
of the fundamental mode is real for the stable shape and imaginary for the other shape. Experimental study of vibrational
eigenmodes performed on stable SCE4 films confirms this theoretical prediction.
Received: 25 November 1997 / Received in final form: 30 January 1998 / Accepted: 9 March 1998 相似文献
4.
E. Del Gado L. de Arcangelis A. Coniglio 《The European physical journal. E, Soft matter》2000,2(4):359-365
Within a recently introduced model based on the bond-fluctuation dynamics, we study the viscoelastic behaviour of a polymer
solution at the gelation threshold. We here present the results of the numerical simulation of the model on a cubic lattice:
the percolation transition, the diffusion properties and the time autocorrelation functions have been studied. From both the
diffusion coefficients and the relaxation times critical behaviour a critical exponent k for the viscosity coefficient has been extracted: the two results are comparable within the errors giving , in close agreement with the Rouse model prediction and with some experimental results. In the critical region below the
transition threshold the time autocorrelation functions show a long-time tail which is well fitted by a stretched exponential
decay.
Received 20 December 1999 and Received in final form 18 February 2000 相似文献
5.
de Arcangelis L Del Gado E Coniglio A 《The European physical journal. E, Soft matter》2002,9(3):277-282
We study the viscoelastic properties and the relaxation process in a gelling system by means of a minimal statistical-mechanics
model. The model is based on percolation and bond fluctuation dynamics. The values for the critical exponents of the viscosity
and elasticity agree with a part of the experimental observations and of the theoretical predictions. The obtained relaxation
patterns well reproduce the behaviour observed in different gelling systems.
Received 10 March 2002 and Received in final form 30 April 2002 相似文献
6.
This paper proposes simple models of polymer networks with sliding junctions for molecular simulation and reports the main results obtained by Brownian dynamics on the elastic properties of networks with tri-functional sliding junctions. The stress-strain relation for isotropic swelling and uniaxial deformation are obtained and compared with those of the conventional chemical gels. We find that mobility and distribution of sliding junctions along the polymer chains drastically change with deformation, and lead to new profiles of the stress. We also find that sliding junctions aggregate by deformation, resulting in the decrease in the number of elastically effective chains. 相似文献
7.
D. Lopez J.-M. Guenet 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(3):405-411
We report on the preparation conditions and the characterization by calorimetry and small-angle neutron scattering of a molecular
composite material obtained via the heterogeneous nucleation of the fibrils of a thermoreversible gel. This physical process
allows encapsulation of monomolecular filaments of a self-assembling bicopper complex into nanosized polymer fibrils. Due
to the existence of 1-D arrangements of copper atoms, this material may possess unusual magnetic properties (spin ladders).
Received 20 January 1999 and Received in final form 14 May 1999 相似文献
8.
T. Dauxois P. Holdsworth S. Ruffo 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(4):659-667
It is well known that long-range interactions pose serious problems for the formulation of statistical mechanics. We show
in this paper that ensemble equivalence is violated in a simple mean-field model of N fully coupled classical rotators with repulsive interaction (antiferromagnetic XY model). While in the canonical ensemble the rotators are randomly dispersed over all angles, in the microcanonical ensemble a bi-cluster of rotators separated by angle , forms in the low energy limit. We attribute this behavior to the extreme degeneracy of the ground state. We obtain empirically
an analytical formula for the probability density function for the angle made by the rotator, which compares extremely well
with numerical data and should become exact in the zero energy limit. At low energy, in the presence of the bi-cluster, an
extensive amount of energy is located in the single harmonic mode, with the result that the energy temperature relation is
modified. Although still linear, , it has the slope , instead of the canonical value .
Received 1 February 2000 相似文献
9.
M. Geoghegan F. Boué G. Bacri A. Menelle D.G. Bucknall 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(1):83-96
We have used neutron reflectometry to measure interfacial widths between two polystyrene films, where either one or both films
are crosslinked. The observed interfacial width between two networks is larger than the size expected for “dangling ends”,
which suggests motion of heterogeneous regions of the networks. In the case when one of the networks is replaced by a linear
polymer, the interfacial profile can be asymmetric with a diffusion “front” of linear polymer penetrating the network to a
length scale of up to 200 ?. In the case of a more densely crosslinked network and a high molecular weight linear polymer
the interface is symmetric implying negligible penetration.
Received: 4 December 1996 / Revised: 13 October 1997 / Accepted: 23 December 1997 相似文献
10.
V. Lesturgeon T. Nicolai D. Durand 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(1):71-82
Free radical co-polymerization of methyl methacrylate (MMA) and ethyl glycol dimethyl metacrylate (EGDMA) was investigated
in solution at different molar ratios R = [EGDMA]/[MMA] between 0 and 0.05. Initially mainly linear PMMA was formed with weight average molar mass 7.5 g/mol independent of R. At larger reaction extents branched polymers were formed and the systems gelled. The scattering intensity rose initially
with the reaction extent, but reached a plateau value at larger reaction extents. The plateau value increased strongly with
R. Dynamic light scattering showed the appearance of a slow relaxation not observed in linear PMMA solutions. The data can
be interpreted by assuming that the excess scattering originates from the branching points and relaxes through self diffusion
of the branched particles. The results agree with predictions of the percolation model for gelation and Rouse dynamics. Viscosity
measurements corroborate this interpretation. Measurements on a progressively diluted sample quenched close to the gel point
again showed quantitative agreement with the percolation model for gelation.
Received 11 May 1998 and Received in final form 22 October 1998 相似文献
11.
R. Salazar A.R. Plastino R. Toral 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):679-688
We introduce a new nonextensive entropic measure that grows like , where N is the size of the system under consideration. This kind of nonextensivity arises in a natural way in some N-body systems endowed with long-range interactions described by interparticle potentials. The power law (weakly nonextensive) behavior exhibited by is intermediate between (1) the linear (extensive) regime characterizing the standard Boltzmann-Gibbs entropy and (2) the
exponential law (strongly nonextensive) behavior associated with the Tsallis generalized q-entropies. The functional is parametrized by the real number in such a way that the standard logarithmic entropy is recovered when . We study the mathematical properties of the new entropy, showing that the basic requirements for a well behaved entropy
functional are verified, i.e., possesses the usual properties of positivity, equiprobability, concavity and irreversibility and verifies Khinchin axioms
except the one related to additivity since is nonextensive. For , the entropy becomes superadditive in the thermodynamic limit. The present formalism is illustrated by a numerical study of the thermodynamic
scaling laws of a ferromagnetic Ising model with long-range interactions.
Received 24 May 2000 相似文献
12.
F. Büyükkiliç D. Demirhan 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):705-711
In this paper, the particles of quantum gases, that is, bosons and fermions are regarded as g-ons which obey fractional exclusion statistics. With this point of departure the thermostatistical relations concerning the
Bose and Fermi systems are unified under the g-on formulation where a fractal approach is adopted. The fractal inspired entropy, the partition function, distribution function,
the thermodynamics potential and the total number of g-ons have been found for a grand canonical g-on system. It is shown that from the g-on formulation; by a suitable choice of the parameters of the nonextensivity q, the parameter of the fractional exclusion statistics g, nonextensive Tsallis as well as extensive (q=1) standard thermostatistical relations of the Bose and Fermi systems are recovered.
Received 17 September 1999 相似文献
13.
We present a field-theoretic Renormalization Group (RG) analysis of the statistical mechanics of long flexible, screened polyelectrolyte
chains (Debye-Hückel chains) in polar solvents where the screening length is of the order of the chain size. A systematic
analysis of the resulting field theory shows that the system is one with two length-scales requiring the calculation of scaling functions as well as exponents to fully describe its physical behaviour. This means that care
must be taken to understand the interplay of the length-scales. Using the RG we identify the relevant scaling variables and
explicitly calculate the scaling behaviour of the end-to-end distance for single chains. In addition we consider the many-chain
system and calculate the scaling behaviour of the osmotic pressure of a dilute solution of chains.
Received 16 December 1999 and Received in final form 13 December 2000 相似文献
14.
L. Samson I. Ippolito G.G. Batrouni J. Lemaitre 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):377-385
We report on experiments studying the statistical properties of the motion of balls on a bumpy surface. This motion is found
to be diffusive. In the direction of the mean flow, the coefficient of diffusion is found to attain a constant value, independent
of the size of the ball and the inclination angle. The diffusion transverse to the mean flow is characterized by a coefficient
which decreases with the inclination of the plane, and scales with the size of moving ball.
Received: 13 March 1997 / Revised: 10 December 1997 / Accepted: 17 February 1998 相似文献
15.
T. Lachhab C. Weill 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(1):59-69
Mechanical properties of packings of deformable spheres of polyelectrolyte gel are studied experimentally. These particles
are plunged into a brine. They have the property to swell and shrink when the concentration of salt of the solution is varied.
An oedometric compression is performed imposing cycles of deformation at constant speed and constant salinity Cs. Under many different conditions, we study the laws of deformation relating the macroscopic compression force F, to the macroscopic strain . We find empirical non linear relations of the type . The values of this exponent m are discussed and compared to the results of measurements on a single sphere compressed on
a plane as well as to the results of experiments and simulations on dry model granular assemblies. The swelling and deswelling
properties of the spheres are used to perform isotropic compression tests. In this situation we determine the relation between
the force at equilibrium and the macroscopic strain . The results are compared with those obtained in the oedometric compression tests.
Received 27 January 1998 相似文献
16.
P. Bhattacharyya 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):247-252
Dynamic properties of a one-dimensional probabilistic cellular automaton are studied by Monte Carlo simulation near a critical
point which marks a second-order phase transition from an active state to an effectively unique absorbing state. Values obtained
for the dynamic critical exponents indicate that the transition belongs to the universality class of directed percolation.
Finally the model is compared with a previously studied one to show that a difference in the nature of the absorbing states
places them in different universality classes.
Received: 6 February 1998 / Revised and Accepted: 17 February 1998 相似文献
17.
K. Urayama S. Kohjiya 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(1):75-78
The stress-elongation relations at large deformations for the polymer network chains with randomcoiled and supercoiled conformations are investigated
using the polysiloxane networks with high elongations at break far over 10. Supercoil is the conformation of network chains
in deswollen polymer networks which are made by removing solvent from the networks crosslinked in solutions at low polymer
concentrations. The validity of the scaling concept of Pincus blob for the mechanical response of a polymer chain is experimentally
confirmed for the network composed of randomcoiled chains. The analysis of the stress- relations for the deswollen networks comprised of supercoiled chains on the basis of the Pincus blob concept suggests that
supercoil is a much more contracted conformation relative to randomcoil.
Received: 25 August 1997 / Received in final form: 13 October 1997 / Accepted: 22 January 1998 相似文献
18.
W. Zippold R. Kühn H. Horner 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):531-537
We investigate the non-equilibrium dynamics of spherical spin models with two-spin interactions. For the exactly solvable
models of the d-dimensional spherical ferromagnet and the spherical Sherrington-Kirkpatrick (SK) model the asymptotic dynamics
has for large times and large waiting times the same formal structure. In the limit of large waiting times we find in both
models an intermediate time scale, scaling as a power of the waiting time with an exponent smaller than one, and thus separating
the time-translation-invariant short-time dynamics from the aging regime. It is this time scale on which the fluctuation-dissipation
theorem is violated. Aging in these models is similar to that observed in spin glasses at the level of correlation functions,
but different at the level of response functions, and thus different at the level of experimentally accessible quantities
like thermoremanent magnetization.
Received 22 April 1999 相似文献
19.
T. Huillet A. Porzio M. Ben Alaya 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(1):147-158
This work emphasizes the special role played by max-semistable and log-max-semistable distributions as relevant statistical models of various observable and “internal” variables in Physics. Some of their remarkable
properties (chiefly self-similarity) are displayed in some detail. One of their characteristic features is a log-periodic variation of the scale parameter which
appears in the stable extreme value distributions.
Received 29 November 1999 and Received in final form 24 March 2000 相似文献
20.
B. Ratajska-Gadomska W. Gadomski 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(2):281-288
Herewith we report on the measurements of the time evolution of the fluorescence yield and the Rayleigh scattering, performed
during the gelation process in the following solutions: gelatin in water, gelatin in a heavy water and agarose in water. Our
results provide the experimental evidence of the universal power law, resulting from the percolation theory, which expresses
the dependence of the fluorescence yield on the number of intermolecular bonds created during the sol-gel transition. The
values of universal critical exponents present in this law are found to have the same values for all investigated materials.
Received 4 May 2000 相似文献