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1.
We use large-scale Monte Carlo simulations to test scaling theories for the electrostatic persistence length l
e of isolated, uniformly charged polymers with Debye-Hückel intrachain interactions in the limit where the screening length
κ-1 exceeds the intrinsic persistence length of the chains. Our simulations cover a significantly larger part of the parameter
space than previous studies. We observe no significant deviations from the prediction l
e∝κ-2 by Khokhlov and Khachaturian which is based on applying the Odijk-Skolnick-Fixman theories of electrostatic bending rigidity
and electrostatically excluded volume to the stretched de Gennes-Pincus-Velasco-Brochard polyelectrolyte blob chain. A linear
or sublinear dependence of the persistence length on the screening length can be ruled out. We show that previous results
pointing into this direction are due to a combination of excluded-volume and finite chain length effects. The paper emphasizes
the role of scaling arguments in the development of useful representations for experimental and simulation data.
Received 12 February 2002 相似文献
2.
Roger M Guenoun P Muller F Belloni L Delsanti M 《The European physical journal. E, Soft matter》2002,9(4):313-326
The concentration profiles of monomers and counterions in star-branched polyelectrolyte micelles are calculated through Monte
Carlo simulations, using the freely jointed chain model. We have investigated the onset of different regimes corresponding
to the spherical and Manning condensation of counterions as a function of the strength of the Coulomb coupling. The Monte
Carlo results are in fair agreement with the predictions of Self-Consistent-Field analytical models. We have simulated a real
system of diblock copolymer micelles of (sodium-polystyrene-sulfonate)(NaPSS)-(polyethylene-propylene)(PEP) with f = 54 hydrophilic branches of N = 251 monomers at room temperature in salt-free solution. The calculated form factor compares nicely with our neutron scattering
data.
Received 18 July 2002 and Received in final form 11 October 2002
RID="a"
ID="a"e-mail: roger@drecam.saclay.cea.fr 相似文献
3.
Monte Carlo simulations are used to study the non-uniform equilibrium charge distribution along a single annealed polyelectrolyte
chain under θ solvent conditions and with added salt. Within a range of the order of the Debye length charge accumulates at
chain ends while a slight charge depletion appears in the central part of the chain. The simulation results are compared with
theoretical predictions recently given by Castelnovo et al. In the parameter range where the theory can be applied we find almost perfect quantitative agreement.
Received 7 March 2002 and Received in final form 28 May 2002 相似文献
4.
G. Migliorini N. Lee V. Rostiashvili T.A. Vilgis 《The European physical journal. E, Soft matter》2001,6(3):259-270
We study the properties of polyelectrolyte chains under different solvent conditions, using a variational technique. The free
energy and the conformational properties of a polyelectrolyte chain are studied by minimizing the free energy FN, depending on N(N - 1)/2 trial probabilities that characterize the conformation of the chain. The Gaussian approximation is considered for
a ring of length 24 < N < 28 and for an open chain of length 50 < N < 200 in poor- and theta-solvent conditions, including a Coulomb repulsion between the monomers. In theta-solvent conditions
the blob size is measured and found in agreement with scaling theory, including charge depletion effects, expected for the
case of an open chain. In poor-solvent conditions, a globule instability, driven by electrostatic repulsion, is observed.
We notice also inhomogeneous behavior of the monomer-monomer correlation function, reminiscence of necklace formation in poor-solvent
polyelectrolyte solutions. A global phase diagram in terms of solvent quality and inverse Bjerrum length is presented.
Received 7 June 2001 and Received in final form 17 October 2001 相似文献
5.
In a SANS experiment, we have directly determined for the first time the conformation of hyaluronan, a model semirigid polyelectrolyte. At high ionic strength, this is completely possible, where the scattered intensity crosses over (when decreasing q) from a q(-1) rod variation to a q(-2) and, where fitting to the "wormlike" chain model gives the backbone, intrinsic, persistence length: L0 = 86.5 A. At low ionic strength, we can safely check that the measured persistence length appears increased by at least the amount predicted by Odijk for the electrostatic contribution, L(e) (approximately kappa(-2), square of the Debye screening length). However, the intensity at the lowest q is not only due to the single chain, since it crosses over from a q(-1) to a q(-4) variation, characteristic of polymer associations. 相似文献
6.
Cocco S Marko JF Monasson R Sarkar A Yan J 《The European physical journal. E, Soft matter》2003,10(3):249-263
The elastic response of flexible polymers made of elements which can be either folded or unfolded, having different lengths
in these two states, is discussed. These situations are common for biopolymers as a result of folding interactions intrinsic
to the monomers, or as a result of binding of other smaller molecules along the polymer length. Using simple flexible-chain
models, we show that even when the energy ε associated with maintaining the folded state is comparable to k
B
T, the elastic response of such a chain can mimic usual polymer linear elasticity, but with a force scale enhanced above that
expected from the flexibility of the chain backbone. We discuss recent experiments on single-stranded DNA, chromatin fiber
and double-stranded DNA with proteins weakly absorbed along its length which show this effect. Effects of polymer semiflexiblity
and torsional stiffness relevant to experiments on proteins binding to dsDNA are analyzed. We finally discuss the competition
between electrostatic self-repulsion and folding interactions responsible for the complex elastic response of single-stranded
DNA.
Received 7 August 2002 and Received in final form 7 March 2003 / Published online: 15 April 2003
RID="a"
ID="a"e-mail: jmarko@uic.edu 相似文献
7.
Equilibrium structures of planar polyelectrolyte brushes formed by grafted chains carrying charges of opposite sign are examined
by employing mean-field lattice theory. Two brushes of different architecture are considered: one formed by grafted diblock
copolymers with oppositely charged blocks and the other being a mixed brush composed of oppositely charged homopolymers. The
systems display nontrivial intrinsically inhomogeneous brush structures originating from the chain connectivity and the electrostatic
interaction among the segments. In addition, a coexistence of stretched and coiled chains inside the brush is observed. The
influence of the charges of the blocks, the relative length of the oppositely charged blocks, and the ionic strength of the
solution on the brush inhomogeneity and structural differences between the two types of brushes are discussed.
Received 14 March 2001 and Received in final form 18 June 2001 相似文献
8.
G. De Smedt C. Godrèche J.M. Luck 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(2):215-225
We consider a ferromagnetic Ising chain evolving under Kawasaki dynamics at zero temperature. We investigate the statistics
of the blocking time, as well as various characteristics of the metastable configurations reached by the system, including
the statistics of the final energy, the spin correlations, and the distribution of domain sizes. Results of extensive numerical
simulations are compared with analytical predictions made for the a priori ensemble of all blocked configurations with equal weights. Qualitative differences are found, e.g. in the domain sizes, which are found to be neither statistically independent nor exponentially distributed.
Received 24 October 2002 / Received in final form 13 January 2003 Published online 1st April 2003
RID="a"
ID="a"e-mail: luck@spht.saclay.cea.fr
RID="b"
ID="b"URA 2306 of CNRS 相似文献
9.
V.S. Gerdjikov A. Kyuldjiev G. Marmo G. Vilasi 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):177-181
We consider generalizations of the standard Hamiltonian dynamics to complex dynamical variables and introduce the notions
of real Hamiltonian form in analogy with the notion of real forms for a simple Lie algebra. Thus to each real Hamiltonian
system we are able to relate several nonequivalent ones. On the example of the complex Toda chain we demonstrate how starting
from a known integrable Hamiltonian system (e.g. the Toda chain) one can complexify it and then project onto different real forms.
Received 18 October 2001 / Received in final form 24 May 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: gerjikov@inrne.bas.bg 相似文献
10.
Castelnovo M Bowles RK Reiss H Gelbart WM 《The European physical journal. E, Soft matter》2003,10(2):191-197
We consider the problem of inserting a stiff chain into a colloidal suspension of particles that interact with it through
excluded volume forces. The free energy of insertion is associated with the work of creating a cavity devoid of colloid and
sufficiently large to accommodate the chain. The corresponding work per unit length is the force that resists the entry of
the chain into the colloidal suspension. In the case of a hard sphere fluid, this work can be calculated straightforwardly
within the scaled particle theory; for solutions of flexible polymers, on the other hand, we employ simple scaling arguments.
The forces computed in these ways are shown, for nanometer chain and colloid diameters, to be of the order of tens of pN for solution volume fractions of a few tenths. These magnitudes are argued to be important for biophysical processes such
as the ejection of DNA from viral capsids into the cell cytoplasm.
Received 18 December 2002 Published online: 16 April 2003
RID="a"
ID="a"e-mail: castel@chem.ucla.edu
RID="b"
ID="b"Present address: Courant Institute of Mathematical Sciences, NYU, New York, New York 10012, USA 相似文献
11.
J.E. Amaro M.B. Barbaro J.A. Caballero T.W. Donnelly A. Molinari 《The European Physical Journal A - Hadrons and Nuclei》2002,15(4):421-427
The impact of Hartree-Fock correlations on the nuclear momentum distribution is studied in a fully relativistic one-boson-exchange
model. Hartree-Fock equations are exactly solved to first order in the coupling constants. The renormalization of the Dirac
spinors in the medium is shown to affect the momentum distribution, as opposed to what happens in the non-relativistic case.
The unitarity of the model is shown to be preserved by the present renormalization procedure.
Received: 7 June 2002 / Accepted: 24 September 2002 / Published online: 10 December 2002
RID="a"
ID="a"e-mail: juan@nucle.us.es
Communicated by G. Orlandini 相似文献
12.
The Coherent Potential Approximation (CPA) self-consistent equation is calculated for a binary disordered chain introducing
a simple transformation. The transformation reduces the CPA equation to a cubic polynomial whose complex roots are related
to the Green function and their relation to the complex Lyapunov exponent is also established. This solution fruitfully captures
essential aspects of the well-known anomalous scaling behaviors in a different and advantageous way. It is found that the
anomalous behavior is strongly effected by the nature of these roots. A small disorder expansion is carried out for comparison
with the previous weak disorder calculations. We found that the CPA reproduced the anomalous behavior of the exact calculations.
Received 22 April 2002 Published online 1st October 2002
RID="a"
ID="a"e-mail: avgin@bornova.ege.edu.tr 相似文献
13.
R. Dandoloff A. Saxena 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):265-267
For a spin-polarized electron gas on an elastic cylinder in an external axial magnetic field and an axial electric field we
find that the corresponding Euler-Lagrange equation is the double sine-Gordon (DSG) equation with an exact 2π-skyrmion solution.
The DSG skyrmion is stabilized, without Coulomb repulsion, by the curvature of the cylinder. It adopts a characteristic length
ξ which is smaller than the radius of the cylinder. For an elastic cylinder this mismatch of length scales causes a deformation
of the cylinder in the region of the skyrmion.
Received 23 October 2001 / Received in final form 8 March 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: rossen.dandoloff@ptm.u-cergy.fr 相似文献
14.
The ground- and first-excited states of magnetopolarons in two-dimensional quantum dots for all coupling strengths 总被引:2,自引:0,他引:2
B.S. Kandemir T. Altanhan 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):227-232
The ground- and first-excited state energies of a magnetopolaron in a two dimensional parabolic quantum dot are studied within
a variational calculation for all coupling strength. The Lee-Low-Pines-Huybrecht variational technique that is developed previously
for all coupling strength has been extented for polarons in a magnetic field. The dependence of the polaronic correction on
the magnetic field and the confinement length is investigated. The polarization potential and the renormalized cyclotron masses
as a function of electron-phonon coupling strength and the strength of both confinement potential and magnetic field are also
studied within the same approach.
Received 16 December 2002 / Received in final form 14 April 2003 Published online 4 June 2003
RID="a"
ID="a"e-mail: kandemir@science.ankara.edu.tr 相似文献
15.
V. Baru J. Haidenbauer C. Hanhart J.A. Niskanen 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):437-446
We present a new parameterization of the trinucleon wave function. As a novel feature a separable parameterization for the
complete wave function is given. In this way any calculation that considers two-body currents only is largely simplified.
To demonstrate this we calculate the π3He scattering length in chiral-perturbation theory. We find reasonable agreement with experimental values inferred from data
on level shifts in pionic 3He bound states. The relevance of the π-triton system for an alternative determination of the πN scattering lengths is discussed.
Received: 12 August 2002 / Accepted: 25 November 2002 / Published online: 25 February 2003
RID="a"
ID="a"e-mail: c.hanhart@fz.juelich.de
Communicated by V. Vento 相似文献
16.
V.S. Gerdjikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):237-241
We compare the Hamiltonian properties of the N-soliton solutions of the NLSE in the adiabatic approximation and show how it matches the Hamiltonian formulation for the
complex Toda chain which describes the adiabatic N-soliton interactions.
Received 21 October 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: gerjikov@inrne.bas.bg 相似文献
17.
We study the quark mass expansion of the magnetic moments of the nucleon in a chiral effective field theory including nucleons,
pions and delta-resonances as explicit degrees of freedom. We point out that the usual power counting applied so far to this
problem misses important quark mass structures generated via an intermediate isovector M1 nucleon-delta transition. We propose a modified power counting and compare the resulting chiral extrapolation function to
available (quenched) lattice data. The extrapolation is found to work surprisingly well, given that the lattice data result
from rather large quark masses. Our calculation raises the hope that extrapolations of lattice data utilizing chiral effective
field theory might be applicable over a wider range in quark masses than previously thought, and we discuss some open questions
in this context. Furthermore, we observe that within the current lattice data uncertainties the extrapolations presented here
are consistent with the Padé fit ansatz introduced by the Adelaide group a few years ago.
Received: 23 April 2002 / Accepted: 18 July 2002 / Published online: 17 December 2002
RID="c"
ID="c"e-mail: themmert@physik.tu-muenchen.de
RID="d"
ID="d"e-mail: weise@ect.it
Communicated by A. Sch?fer 相似文献
18.
Hong-yi Fan J. Chen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(3):437-442
Based on the newly constructed Einstein, Podolsky and Rosen (EPR) entangled state representation we introduce macroscopic
classical functions associated with atomic coherent state τ with angular momentum value j. These functions are proportional to the ordinary one-variable Hermite polynomials of order 2j. The corresponding Wigner quasiprobability function for τ in phase space is also derived which turns out to be a two-variable Hermite polynomial H
2j, 2j. In so doing, a new classical-quantum correspondence scheme for angular momentum system is established.
Received 7 August 2002 / Received in final form 14 December 2002 Published online 24 April 2003
RID="a"
ID="a"Work supported by the National Natural Science Foundation of China under grant 10175057.
RID="b"
ID="b"e-mail: fhym@sjtu.edu.en 相似文献
19.
R. Capovilla C. Chryssomalakos J. Guven 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):163-166
We examine the equilibria of a rigid loop in the plane, characterized by an energy functional quadratic in the curvature,
subject to the constraints of fixed length and fixed enclosed area. Whereas the only non self-intersecting equilibrium corresponding
to the fixed length constraint is the circle, the area constraint gives rise to distinct equilibria labeled by an integer.
These configurations exhibit self-intersections and bifurcations as the area is reduced. In addition, not only can the Euler-Lagrange
equation be integrated to provide a quadrature for the curvature but the embedding itself can be expressed as a local function
of the curvature. Perturbations connecting equilibria are shown to satisfy a first order ODE which is readily solved. Analytical
expressions for the energy as a function of the area are obtained in the limiting regimes.
Received 18 October 2001 / Received in final form 31 May 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: capo@fis.cinvestav.mx
RID="b"
ID="b"e-mail: chryss@nuclecu.unam.mx
RID="c"
ID="c"e-mail: jemal@nuclecu.unam.mx 相似文献
20.
N.A. Orr 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):109-113
Clustering is a relatively widespread phenomenom which takes on many guises across the nuclear landscape. Selected topics
concerning the study of halo systems and clustering in light, neutron-rich nuclei are discussed here through illustrative
examples taken from the Be isotopic chain. The production and detection of multineutron clusters is also briefly presented.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: orr@caelav.in2p3.fr 相似文献