共查询到20条相似文献,搜索用时 21 毫秒
1.
Motivated by numerous X-ray scattering studies of lamellar phases with membrane proteins, amphiphilic peptides, polymers,
or other inclusions, we have determined the modifications of the classical Caillé law for a smectic phase as a function of
the nature and concentration of inclusions added to it. Besides a fundamental interest on the behavior of fluctuating systems
with inclusions, a precise characterization of the action of a given protein on a lipid membrane (anchoring, swelling, stiffening
...) is of direct biological interest and could be probed by way of X-ray measurements. As a first step we consider three
different couplings involving local pinching (or swelling), stiffening or curvature of the membrane. In the first two cases
we predict that independent inclusions induce a simple renormalization of the bending and compression moduli of the smectic
phase. The X-ray experiments may also be used to probe correlations between inclusions. Finally we show that asymmetric coupling
(such as a local curvature of the membrane) results in a modification of the usual Caillé law.
Received 10 March 2000 and Received in final form 30 August 2000 相似文献
2.
The effect of rigid inclusions on the phase behavior of a film containing a mixture of lipid molecules is investigated. In
the proposed model, the inclusion-induced deformation of the film, and the resulting energy cost are strongly dependent upon
the spontaneous curvature of the mixed film. The spontaneous curvature is in turn strongly influenced by the composition of
film. This coupling between the film composition and the energy per inclusion leads to a lateral modulation of the composition,
which follows the local curvature of the membrane. In particular, it is shown that inclusions may induce a global phase separation
in a film which would otherwise be homogeneously mixed. The mixed film is then composed of patches of different average composition,
separated by the inclusions. This process may be of relevance to explain some aspects of lipid-protein association in biological
membranes.
Received 8 April 1999 and Received in final form 4 October 1999 相似文献
3.
S. Roux J.F. Muzy A. Arneodo 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):301-322
Swirling turbulent flows display intermittent pressure drops associated with intense vorticity filaments. Using the wavelet
transform modulus maxima representation of pressure fluctuations, we propose a method of characterizing these pressure drop
events from their time-scale properties. This method allows us to discriminate fluctuations induced by just formed (young)
as well as by burst (old) filaments from background pressure fluctuations. The statistical characteristics of these filaments
(core size, waiting time) are analyzed in details and compared with previously reported experimental and numerical findings.
Their intermittent occurrence is found to be governed by a pure Poisson's law, the hallmark of independent events. Then we
apply the wavelet transform modulus maxima (WTMM) method to the background pressure fluctuations. This study reveals that,
once removed all the filaments, the “multifractal” nature of pressure fluctuations still persists. This is a clear indication
that the statistical contribution of the filaments is not important enough to account for the intermittency phenomenon in
turbulents flows.
Received 27 July 1998 and Received in final form 23 November 1998 相似文献
4.
Slow dynamics of density fluctuations near the colloidal glass transition is discussed from a new viewpoint by numerically
solving a nonlinear stochastic diffusion equation for the density fluctuations recently proposed by one of the present authors
(MT). The effects of spatial heterogeneities on the dynamics of density fluctuations are then investigated in an equilibrium
system. The spatial heterogeneities are generated by the nonlinear density fluctuations, while in a nonequilibrium system
they are described by a nonlinear deterministic equation for the average number density. The dynamics of equilibrium density
fluctuations is thus shown to be quite different from that of nonequilibrium ones, leading to a logarithmic decay followed
by less distinct α- and β-relaxation processes.
Received 9 March 2002 and Received in final form 19 September 2002 相似文献
5.
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
6.
Y. Marandet H. Capes L. Godbert-Mouret M. Koubiti J. Rosato R. Stamm 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(2):247-260
In this work we investigate the influence of low
frequency turbulence on Doppler spectral line shapes in magnetized
plasmas. Low frequency refers here to fluctuations whose typical
time scale is much larger than those characterizing the atomic
processes, such as radiative decay, collisions and charge exchange.
This ordering is in particular relevant for drift wave turbulence,
ubiquitous in edge plasmas of fusion devices. Turbulent fluctuations
are found to affect line shapes through both the spatial and time
averages introduced by the measurement process. The profile is
expressed in terms of the fluid fields describing the plasma.
Assuming the spectrometer acquisition time to be much larger than
the turbulent time scale, an ordering generally fulfilled in
experiments, allows to develop a statistical formalism. We proceed
by successively investigating the effects of density, fluid velocity
and temperature fluctuations on the Doppler profile of a spectral
line emitted by a charge exchange population of neutrals. Line
shapes, and especially line wings are found to be affected by ion
temperature or fluid velocity fluctuations, and can in some cases
exhibit a power-law behavior. These effects are shown to be
measurable with existing techniques, and their interpretation in
each particular case would rely on already existing tools. From a
fundamental point of view, this study gives some insights in the
appearance of non-Boltzmann statistics, such as Lévy statistics,
when dealing with averaged experimental data. 相似文献
7.
B. Rohwedder 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(2):255-260
Fringe shapes in a multiple-beam de Broglie-wave interferometer based on the atomic Kapitza-Dirac effect are studied. An all-optical
implementation of such a device is proposed. A realization in the time-domain, using Bose-Einstein condensates released from
a trap, seems viable within the present state of the art.
Received 5 April 2000 and Received in final form 14 July 2000 相似文献
8.
A.K. Chattopadhyay 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):567-576
We study the dynamics of a growing crystalline facet where the growth mechanism is controlled by the geometry of the local
curvature. A continuum model, in (2+1) dimensions, is developed in analogy with the Kardar-Parisi-Zhang (KPZ) model is considered
for the purpose. Following standard coarse graining procedures, it is shown that in the large time, long distance limit, the
continuum model predicts a curvature independent KPZ phase, thereby suppressing all explicit effects of curvature and local
pinning in the system, in the “perturbative” limit. A direct numerical integration of this growth equation, in 1+1 dimensions,
supports this observation below a critical parametric range, above which generic instabilities, in the form of isolated pillared
structures lead to deviations from standard scaling behaviour. Possibilities of controlling this instability by introducing
statistically “irrelevant" (in the sense of renormalisation groups) higher ordered nonlinearities have also been discussed.
Received 23 April 2002 / Received in final form 24 July 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: akc@mpipks-dresden.mpg.de 相似文献
9.
Adsorption of polymers anchored to membranes 总被引:2,自引:0,他引:2
M. Breidenich R.R. Netz R. Lipowsky 《The European physical journal. E, Soft matter》2001,5(4):403-414
Polymers, which are attached to a membrane at one of their ends, exert an entropic pressure, which curves the membrane away
from the polymers. It is shown that adsorption which arises from a short-ranged potential between the polymer and the membrane
has a large influence on the curvature of the membrane, leading to a decrease of the entropically induced curvature. If one
ignores the finite size of the anchor segment, the polymer-induced curvature does not change sign and vanishes in the limit
of strong adsorption and a pure contact potential. If one includes the finite size of the anchor segment, the membrane bends
towards the polymer for sufficiently strong adsorption.
Received 20 October 2000 相似文献
10.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):423-431
Several examples of photon entanglement are studied in the Q representation of quantum optics. In particular, the entangled states produced in parametric downconversion are studied in
detail, and we determine the conditions for the violation of Bell's inequality. Our approach shows that photon entanglement
is related to the existence of correlations between the quantum fluctuations of the electromagnetic field associated to different
modes.
Received 10 August 2002 / Received in final form 7 November 2002 Published online 4 February 2003 相似文献
11.
M. Hoyuelos G.-L. Oppo P. Colet M. San Miguel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):441-451
We analyze the quantum fluctuations of the degenerate optical parametric oscillator close to an instability for the formation
of a square pattern. While strong correlations between the fluctuations of the signal modes emitted at the critical wave number
and with opposite wave vector are present both below and above threshold, no features signaling the square character of the
pattern forming above threshold have been identified below threshold in the spatio-temporal second-order coherence. We also
explore in which regimes a reduced few mode model gives meaningful results.
Received 17 September 2002 / Received in final form 11 November 2002 Published online 26 February 2003 相似文献
12.
J.-M. Courty A. Heidmann M. Pinard 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(3):399-408
Thermal noise of a mirror can be reduced by cold damping. The displacement is measured with a high-finesse cavity and controlled
with the radiation pressure of a modulated light beam. We establish the general quantum limits of noise in cold damping mechanisms
and we show that the optomechanical system allows to reach these limits. Displacement noise can be arbitrarily reduced in
a narrow frequency band. In a wide-band analysis we show that thermal fluctuations are reduced as with classical damping whereas
quantum zero-point fluctuations are left unchanged. The only limit of cold damping is then due to zero-point energy of the
mirror.
Received 1st August 2001 and Received in final form 12 October 2001 相似文献
13.
I. Rabbiosi A.J. Scroggie G.-L. Oppo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):453-459
Quantum fluctuations of the signal field are shown to induce packed arrays of cavity solitons in a degenerate optical parametric
oscillator above threshold in the limit of large pump finesse relative to the signal finesse. The cavity solitons in the array
are formed by locked domain walls, and lead to a highly correlated quantum structure. The effect of the quantum fluctuations
is non-trivial since the arrays of cavity solitons have a far less stable than other stable solutions and disappear with decreasing
pump finesse. The transition from disorder to order due to quantum noise is also discussed.
Received 20 September 2002 / Received in final form 28 November 2002 Published online 11 February 2003 相似文献
14.
F. Levi A. Godone J. Vanier S. Micalizio G. Modugno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(1):53-59
The paper is concerned with the line shapes of resonance phenomena observed in Coherent Population Trapping (CPT) applied
to alkali atoms in a cell containing a buffer gas. Significant asymmetries and departures from a Lorentzian shape have been
observed in connection with the measurement of dark lines and CPT maser emission profiles. Measurements are reported as a
function of the power and frequency tuning of the laser used to create the CPT phenomenon. The paper reports on different
experimental conditions and a comparison between theory and experiments is made for the cases of cesium and rubidium in a
buffer gas.
Received 3 March 2000 and Received in final form 10 April 2000 相似文献
15.
R. Rangel E. Medina 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):101-109
We give a detailed picture of the mesoscopic conductance fluctuations in the deep insulating regime (DIR) within the Nguyen,
Spivak and Shklovskii model in the unitary and symplectic ensembles. Slutski's theorem is invoked to rigorously state the
ergodic problem for conductance fluctuations in the DIR, in contrast with previous studies. A weakly decaying behavior of
the log-conductance correlation function, even weaker when spin-orbit scatterers are included, is established on the relevant
field scale of the model. Such a slow decay implies that the stochastic process, defined by the fluctuations of the log-conductance,
is non-ergodic in the mean square sense in the ensembles with the reported symmetries. The results can be interpreted in terms
of the effective number of samples within the available magnetic scale. Using the replica approach, we derive the strong localisation
counterparts of the well known 'cooperon' and 'diffuson' which permit analyzing quantitatively the decaying behavior of the
correlation function and reveal its symmetry related properties in agreement with the numerical results.
Received 11 April 2002 / Received in final form 27 August 2002 Published online 19 November 2002 相似文献
16.
I.M. Mladenov 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):327-330
The general shape equation describing the forms of vesicles is a highly nonlinear partial differential equation for which
only a few explicit solutions are known. These solvable cases are briefly reviewed and a new analytical solution which represents
the class of the constant mean curvature surfaces is described. Pearling states of the tubular fluid membranes can be explained
as a continuous deformation preserving membrane mean curvature.
Received 2 February 2002 / Received in final form 4 February 2002 Published online 2 October 2002
RID="a"
ID="a"e-mail: mladenov@obzor.bio21.bas.bg 相似文献
17.
Y. Jiang O. Jedrkiewicz S. Minardi P. DiTrapani A. Mosset E. Lantz F. Devaux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):521-526
The pixel by pixel calibration of a scientific CCD camera allows Poissonian statistics of the spatial fluctuations of an uniform
enlightening to be retrieved in the full range of the camera dynamic. The procedure works efficiently for thermal as well
as for laser sources, provided that the wavelength and the coherence properties of the source are chosen in order to avoid
the formation of equal thickness fringes in the chip (etaloning effect). Calibration allows also the comparison at the shot
noise level of images recorded at different places on the chip.
Received 9 September 2002 / Received in final form 16 October 2002 Published online 21 January 2003 相似文献
18.
B. Božič V. Heinrich S. Svetina B. Žekš 《The European physical journal. E, Soft matter》2001,6(1):91-98
Shapes of nearly cylindrical sections of axisymmetric phospholipid membranes are studied theoretically. Describing the shape
of such sections by their deviation from a reference cylinder, the well-established shape equation for axisymmetric bilayer
membranes is expanded in terms of this deviation, and it is then solved analytically. The phase diagram shows the resulting
stationary shapes as functions of system parameters and external conditions, i.e., the pressure difference across the membrane, the membrane tension, the difference between the tensions of the two monolayers,
and the axial force acting on the vesicle. The accuracy of the approximate analytical solution is demonstrated by comparison
with numerical results. The obtained analytical solution allows to extend the analysis to include shapes where numerical methods
have failed.
Received 27 September 2000 and Received in final form 26 March 2001 相似文献
19.
A simplified version of the model by Elser and Joseph for the process of growth of an entropically stabilized, two-dimensional
quasicrystal with no dynamics in the bulk, is proposed. The phason fluctuations are modeled by a scalar field on a periodic
lattice. The choice of the master equation for the growth is restricted by the requirement that its detailed balance solution
describes the equilibrium fluctuations of the field with a quadratic Hamiltonian. The model is parametrized by the chemical
potential bias and the microscopic surface tension coefficient . The phase diagram of the system on the plane (, ) shows several distinct regimes of growth, separated by relatively narrow transition zones. Within the regions corresponding
to these regimes, the phason fluctuations do not depend on and . Analytic expressions for the spectra of phason fluctuations are obtained and confirmed by numerical simulation.
Received 30 June 2000 相似文献
20.
The spatial confinement of a fluctuation spectrum leads to forces at the confining boundaries. While electromagnetic (EM)
fluctuations lead to the well-known dispersion forces, the acoustic analogy has widely been neglected. We show that the strength
of the forces resulting from confined acoustic modes may be of the same order of magnitude as van der Waals forces. Additionally,
the predicted scaling behavior is identical to the non-retarded case of the EM fluctuations. Our results suggest that dewetting
experiments using polymer films are strongly influenced by the acoustic dispersion forces.
Received 5 March 2002 and Received in final form 21 May 2002 相似文献