共查询到20条相似文献,搜索用时 656 毫秒
1.
S. Spezia L. Curcio A. Fiasconaro N. Pizzolato D. Valenti B. Spagnolo P. Lo Bue E. Peri S. Colazza 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):453-458
We investigate the role of the noise in the mating behavior between individuals of Nezara viridula (L.), by analyzing the temporal and spectral features of the non-pulsed type female calling song emitted by single individuals.We
have measured the threshold level for the signal detection, by performing experiments with the calling signal at different
intensities and analyzing the insect response by directionality tests performed on a group of male individuals. By using a
sub-threshold signal and an acoustic Gaussian noise source, we have investigated the insect response for different levels
of noise, finding behavioral activation for suitable noise intensities. In particular, the percentage of insects which react
to the sub-threshold signal, shows a non-monotonic behavior, characterized by the presence of a maximum, for increasing levels
of the noise intensity. This constructive interplay between external noise and calling signal is the signature of the non-dynamical
stochastic resonance phenomenon. Finally, we describe the behavioral activation statistics by a soft threshold model which
shows stochastic resonance. We find that the maximum of the ensemble average of the input-output cross-correlation occurs
at a value of the noise intensity very close to that for which the behavioral response has a maximum. 相似文献
2.
We present a study of the dynamics of single polymers colliding with molecular obstacles using Molecular-dynamics simulations.
In concert with these simulations we present a generalized polymer-obstacle collision model which is applicable to a number
of collision scenarios. The work focusses on three specific problems: i) a polymer driven by an external force colliding with
a fixed microscopic post; ii) a polymer driven by a (plug-like) fluid flow colliding with a fixed microscopic post; and iii)
a polymer driven by an external force colliding with a free polymer. In all three cases, we present a study of the length-dependent
dynamics of the polymers involved. The simulation results are compared with calculations based on our generalized collision
model. The generalized model yields analytical results in the first two instances (cases i) and ii)), while in the polymer-polymer
collision example (case iii)) we obtain a series solution for the system dynamics. For the case of a polymer-polymer collision
we find that a distinct V-shaped state exists as seen in experimental systems, though normally associated with collisions
with multiple polymers. We suggest that this V-shaped state occurs due to an effective hydrodynamic counter flow generated
by a net translational motion of the two-chain system. 相似文献
3.
D. Valenti G. Augello B. Spagnolo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):443-451
We analyze the dynamics of the FitzHugh-Nagumo (FHN) model in the presence of colored noise and a periodic signal. Two cases
are considered: (i) the dynamics of the membrane potential is affected by the noise, (ii) the slow dynamics of the recovery
variable is subject to noise. We investigate the role of the colored noise on the neuron dynamics by the mean response time
(MRT) of the neuron. We find meaningful modifications of the resonant activation (RA) and noise enhanced stability (NES) phenomena
due to the correlation time of the noise. For strongly correlated noise we observe suppression of NES effect and persistence
of RA phenomenon, with an efficiency enhancement of the neuronal response. Finally we show that the self-correlation of the
colored noise causes a reduction of the effective noise intensity, which appears as a rescaling of the fluctuations affecting
the FHN system. 相似文献
4.
Verhulst model with Lévy white noise excitation 总被引:1,自引:0,他引:1
A. A. Dubkov B. Spagnolo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):361-367
The transient dynamics of the Verhulst model perturbed by arbitrary non-Gaussian white noise is investigated. Based on the
infinitely divisible distribution of the Lévy process we study the nonlinear relaxation of the population density for three
cases of white non-Gaussian noise: (i) shot noise; (ii) noise with a probability density of increments expressed in terms
of Gamma function; and (iii) Cauchy stable noise. We obtain exact results for the probability distribution of the population
density in all cases, and for Cauchy stable noise the exact expression of the nonlinear relaxation time is derived. Moreover
starting from an initial delta function distribution, we find a transition induced by the multiplicative Lévy noise, from
a trimodal probability distribution to a bimodal probability distribution in asymptotics. Finally we find a nonmonotonic behavior
of the nonlinear relaxation time as a function of the Cauchy stable noise intensity. 相似文献
5.
Single macromolecules can now be isolated and characterized experimentally using techniques such as optical tweezers and videomicroscopy. An interesting and important single-molecule problem is that of the dynamics of a polymer chain tethered to a solid surface and subjected to a shear flow. An experimental study of such a system was reported by Doyle et al. (Phys. Rev. Lett. 84, 4769 (2000)), and their results showed a surprising recirculating motion of the DNA chain. We explore this problem using molecular dynamics computer simulations with explicit hydrodynamic interactions. The dynamical properties of a Freely Jointed Chain (FJC) with Finitely Extensible Nonlinear Elastic (FENE) links are examined in similar conditions (i.e., confined between two surfaces and in the presence of a Poiseuille flow). We see the remarkable cyclic polymer motion observed experimentally, and we show that a simple cross-correlation function can be used to measure the corresponding period of motion. We also propose a new empirical equation relating the magnitude of the shear flow to the amount of chain deformation, an equation that appears to apply for both weak and strong flows. Finally, we report on packing effects near the molecularly flat wall, an associated chain-sticking phenomenon, and the impact of the chain hydrodynamic drag on the local fluid flow. 相似文献
6.
We study the phenomenon of stochastic resonance on
small-world networks consisting of bistable genetic regulatory units,
whereby the external subthreshold periodic forcing is introduced as a
pacemaker trying to impose its rhythm on the whole network through the
single unit to which it is introduced. Without the addition of additive
spatiotemporal noise, however, the whole network remains forever trapped in
one of the two stable steady states of the local dynamics. We show that the
correlation between the frequency of subthreshold pacemaker activity and the
response of the network is resonantly dependent on the intensity of additive
noise. The reported pacemaker driven stochastic resonance depends
significantly on the asymmetry of the two potential wells characterizing the
bistable dynamics, which can be tuned via a single system parameter. In
particular, we show that the ratio between the clustering coefficient and
the characteristic path length is a suitable quantity defining the ability
of a small-world network to facilitate the outreach of the pacemaker-emitted
subthreshold rhythm, but only if the asymmetry between the potentials is
practically negligible. In case of substantially asymmetric potentials the
impact of the small-world topology is less profound and cannot warrant an
enhancement of stochastic resonance by units that are located far from the
pacemaker. 相似文献
7.
A. Fiasconaro W. Ebeling E. Gudowska-Nowak 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):403-414
We give an overview over recent studies on the model of Active Brownian Motion (ABM) coupled to reservoirs providing free
energy which may be converted into kinetic energy of motion. First, we present an introduction to a general concept of active
Brownian particles which are capable to take up energy from the source and transform part of it in order to perform various
activities. In the second part of our presentation we consider applications of ABM to ratchet systems with different forms
of differentiable potentials. Both analytical and numerical evaluations are discussed for three cases of sinusoidal, staircaselike
and Mateos ratchet potentials, also with the additional loads modelled by tilted potential structure. In addition, stochastic
character of the kinetics is investigated by considering perturbation by Gaussian white noise which is shown to be responsible
for driving the directionality of the asymptotic flux in the ratchet. This stochastically driven directionality effect is visualized as a strong nonmonotonic dependence of the statistics of the right versus left trajectories of motion
leading to a net current of particles. Possible applications of the ratchet systems to molecular motors are also briefly discussed. 相似文献
8.
Hideo Hasegawa 《Physica A》2008,387(12):2697-2718
We have discussed the dynamics of Langevin model subjected to colored noise, by using the functional-integral method (FIM) combined with equations of motion for mean and variance of the state variable. Two sets of colored noise have been investigated: (a) one additive and one multiplicative colored noise, and (b) one additive and two multiplicative colored noise. The case (b) is examined with relevance to a recent controversy on the stationary subthreshold voltage distribution of an integrate-and-fire model including stochastic excitatory and inhibitory synapses and a noisy input. We have studied the stationary probability distribution and dynamical responses to time-dependent (pulse and sinusoidal) inputs of the linear Langevin model. Model calculations have shown that results of the FIM are in good agreement with those of direct simulations (DSs). A comparison is made among various approximate analytic solutions such as the universal colored noise approximation (UCNA). It has been pointed out that dynamical responses to pulse and sinusoidal inputs calculated by the UCNA are rather different from those of DS and the FIM, although they yield the same stationary distribution. 相似文献
9.
S. E. Mangioni H. S. Wio 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(1):67-73
We analyze the effect of a colored non Gaussian noise on a model of
a random walker moving along a ratchet potential. Such a model was
motivated by the transport properties of motor proteins, like
kinesin and myosin. Previous studies have been realized assuming
white noises. However, for real situations, in general we could
expect that those noises be correlated and non Gaussian. Among other
aspects, in addition to a maximum in the current as the noise
intensity is varied, we have also found another optimal value of the
current when departing from Gaussian behavior. We show the relevant
effects that arise when departing from Gaussian behavior,
particularly related to current's enhancement, and discuss its
relevance for both biological and technological situations. 相似文献
10.
The nano-friction phenomenon in a one-dimensional Frenkel-Kontorova (FK) model under Gaussian colored noise is investigated by using the molecular dynamic simulation method. The role of colored noise is analyzed through the inclusion of a stochastic force via a Langevin molecular dynamics method. Via the stochastic Runge-Kutta algorithm, the relationship between different parameter values of the Gaussian colored noise (the noise intensity and the correlation time) and the nano-friction phenomena such as hysteresis, the maximum static friction force is separately studied here. Similar results are obtained from the two geometrically opposed ideal cases: incommensurate and commensurate interfaces. It was found that the noise strongly influences the hysteresis and maximum static friction force and with an appropriate external driving force, the introduction of noise can accelerate the motion of the system, making the atoms escape from the substrate potential well more easily. Interestingly, suitable correlation time and noise intensity give rise to super-lubricity. It is noteworthy that the difference between the two circumstances lies in the fact that the effect of the noise is much stronger on triggering the motion of the FK model for the commensurate interface than that for the incommensurate interface. 相似文献
11.
We discuss how the effective parameters characterising averaged motion in nonlinear systems are affected by noise (random fluctuations). In this approach to stochastic dynamics, the stochastic system is replaced by its deterministic equivalent but with noise-dependent parameters. We show that it can help to resolve certain paradoxes and that it has a utility extending far beyond its usual application in passing from the microscopic equations of motion to the macroscopic ones. As illustrative examples, we consider the diode-capacitor circuit, a Brownian ratchet, and a generic stochastic resonance system. In the latter two cases we calculate for the first time their effective parameters of averaged motion as functions of noise intensity. We speculate that many other stochastic problems can be treated in a similar way.
PACS: 05.10.Gg, 05.40.-a, 05.40.Jc 相似文献
12.
13.
L. R. Nie D. C. Mei 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(4):475-481
The properties of the underdamped Josephson junction subjected to
colored noises were investigated with large and small phase
difference (φ). For the case of the large φ, we found
numerically that: (i) the probability distribution function of
φ exhibits monostability → bistability → monostability
transitions as the autocorrelation rate (λ) of a colored
noise increases; (ii) in the bistability region the multiplicative
noise drives the phase difference to turn over periodically; (iii)
the slope K of the linear response of the junction potential
difference (〈V 〉) can be somewhat reduced by means of tuning an
optimal λ; (iv) the amplitude of φ in response to
external sinusoidal signals changes with λ. For the case of
small φ, after deriving the analytical expressions of the
potential difference amplitude (〈V 〉max) and the K in the
presence of a dichotomous noise, we found nonmonotonic behavior of
〈V 〉max and the slope K as a function of λ. 相似文献
14.
D. Valenti L. Schimansky-Geier X. Sailer B. Spagnolo 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(1-2):199-203
The dynamics of a spatially extended system of two competing
species in the presence of two noise sources is studied. A
correlated dichotomous noise acts on the interaction parameter and
a multiplicative white noise affects directly the dynamics of the
two species. To describe the spatial distribution of the species
we use a model based on Lotka-Volterra (LV) equations. By writing
them in a mean field form, the corresponding moment equations for
the species concentrations are obtained in Gaussian approximation.
In this formalism the system dynamics is analyzed for different
values of the multiplicative noise intensity. Finally by comparing
these results with those obtained by direct simulations of the
time discrete version of LV equations, that is coupled map lattice
(CML) model, we conclude that the anticorrelated oscillations of
the species densities are strictly related to non-overlapping
spatial patterns. 相似文献
15.
Coarse-grained molecular dynamics simulations combined with milestoning method are used to study the stochastic process of polymer chain translocation though a nanopore. We find that the scalings for polymer translocation process (the chain is initialized with the first monomer in the nanopore) and for polymer escape process (the chain is initialized with the middle monomer in the nanopore) are different. The translocation process is mainly controlled by the entropic barrier, while the polymer escape process is driven by the effective force due to free energy difference. 相似文献
16.
E. V. Pankratova V. N. Belykh E. Mosekilde 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):529-536
The present paper examines the influence of the forcing frequency on the
response of a randomly perturbed Hodgkin-Huxley system in the realm
of suprathreshold amplitudes. Our results show that, in the presence
of noise, the choice of driving frequency can seriously affect the
precision of the external information transmission. At the same
level of noise the precision can either decrease or increase
depending on the driving frequency. We demonstrate that the
destructive influence of noise on the interspike interval can be
effectively reduced. That is, with driving signals in certain
frequency ranges, the system can show stable periodic spiking even
for relatively large noise intensities. Here, the most accurate
transmission of an external signal occurs. Outside these frequency
ranges, noise of the same intensity destroys the regularity of the
spike trains by suppressing the generation of some spikes. On the
other hand, we show that noise can have a reconstructive role for
certain driving frequencies. Here, increasing noise intensity
enhances the coherence of the neuronal response. 相似文献
17.
The effects of additive correlated noise, which is composed of common Gaussian white noise and local Gaussian colored noise, on a square lattice network locally modelled by the Rulkov map are studied. We focus on the ability of noise to induce pattern formation in a resonant manner. It is shown that local Gaussian colored noise is able to induce pattern formation, which is more coherent at some noise intensity or correlation time, so it is able to induce spatiotemporal coherence resonance in the network. When common Gaussian white noise is applied in addition, it is seen that the correlated noise can induce coherent spatial structures at some intermediate noise correlation, while this is not the case for smaller and larger noise intensities. The mechanism of the observed spatiotemporal coherence resonance is discussed. It is also found that the correlation time of local colored noise has no evident effect on the optimal value of the noise strength for spatiotemporal coherence resonance in the network. 相似文献
18.
The proposed algorithm is designed to enhance the line-detection stability in laser-stripe sensors. Despite their many features and capabilities, these sensors become unstable when measuring in dark or strongly-reflective environments. Ambiguous points within a camera image can appear on dark surfaces and be confused with noise when the laser-reflection intensity approaches noise level. Similar problems arise when strong reflections within the sensor image have intensities comparable to that of the laser. In these circumstances, it is difficult to determine the most probable point for the laser line. Hence, the proposed algorithm introduces a maximum a posteriori estimator, based on geometric Brownian motion, to provide a range estimate for the expected location of the reflected laser line. 相似文献
19.
Zurek S Kośmider M Drzewiński A van Leeuwen JM 《The European physical journal. E, Soft matter》2012,35(6):47-7
Voltage-driven polymer translocation is studied by means of a stochastic lattice model. The model incorporates voltage drop over the membrane as a bias in the hopping rate through the pore and exhibits the two main ingredients of the translocation process: driven motion through the pore and diffusive supply of chain length towards the pore on the cis-side and the drift away from the pore on the trans-side. The translocation time is either bias limited or diffusion limited. In the bias-limited regime the translocation time is inversely proportional to the voltage drop over the membrane. In the diffusion-limited regime the translocation time is independent of the applied voltage, but it is rather sensitive to the motion rules of the model. We find that the whole regime is well described by a single curve determined by the initial slope and the saturation value. The dependence of these parameters on the length of the chain, the motion rules and the repton statistics are established. Repulsion of reptons as well as the increase of chain length decrease the throughput of the polymer through the pore. As for free polymers, the inclusion of a mechanism for hernia creations/annihilations leads to the cross-over from Rouse-like behaviour to reptation. For the experimentally most relevant case (Rouse dynamics) the bimodal power law dependence of the translocation time on the chain length is found. 相似文献
20.
Y.-C. Lai K. Park L. Rajagopalan 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):65-70
We investigate a class of nonlinear wave equations subject to
periodic forcing and noise, and address the issue of energy optimization.
Numerically, we use a pseudo-spectral method to solve the nonlinear stochastic
partial differential equation and compute the energy of the system as a
function of the driving amplitude in the presence of noise.
In the fairly general setting where the system possesses two coexisting
states, one with low and another with high energy, noise can induce
intermittent switchings between the two states. A striking finding is that,
for fixed noise, the system energy can be optimized by the driving in a
form of resonance. The phenomenon can be explained by the Langevin dynamics
of particle motion in a double-well potential system with symmetry breaking.
The finding can have applications to small-size devices such as
microelectromechanical resonators and to waves in fluid and plasma. 相似文献