Self-excited dust-density waves are experimentally studied in a dusty plasma under microgravity. Two types of waves are observed: a mode inside the dust volume propagating in the direction of the ion flow and another mode propagating obliquely at the boundary between the dusty plasma and the space charge sheath. The dominance of oblique modes can be described in the frame of a fluid model. It is shown that the results fom the fluid model agree remarkably well with a kinetic electrostatic model of Rosenberg [J. Vac. Sci. Technol. A 14, 631 (1996)]. In the experiment, the instability is quenched by increasing the gas pressure or decreasing the dust density. The critical pressure and dust density are well described by the models.

We report on nonequilibrium molecular dynamics (NEMD) simulation results on the color conductivity of fluids confined in cylindrical nanopores. Because conventional NEMD methods are restricted to fields several orders of magnitude stronger than those accessible by experiment, these methods have provided access so far only to the response of the fluid under far-from-equilibrium conditions. Using the transient-time correlation function formalism, we show how NEMD simulations can be extended to study the conductivity of a model liquid confined in a cylindrical nanopore and subjected to an arbitrarily low (and realistic) field. Our results provide a full picture of the dependence of conductivity on the applied field and on the effective diameter of the nanopore. They also demonstrate that the conductivity steadily increases—up to twice the value evaluated for the bulk—as the effective radius of the pore decreases.

Using Langevin simulations, we find that simple “generic” bead-and-spring homopolymer chains in a sufficiently bad solvent spontaneously develop helical order during the process of collapsing from an initially stretched conformation. The helix formation is initiated by the unstable modes of the straight chain, which drive the system towards a long-lived metastable transient state. The effect is most pronounced if hydrodynamic interactions are screened.

A two-dimensional square-lattice model for the formation of secondary structures in proteins, the hydrogen-bonding model, is extended to include the effects of solvent quality. This is achieved by allowing configuration-dependent nearest-neighbor interactions. The phase diagram is presented and found to have a much richer variety of phases than either the pure hydrogen-bonding self-avoiding walk model or the standard $\Theta$-point model.

By introducing three well-defined dimensionless numbers, we establish the link between the scale dilatation method able to estimate master (i.e., unique) singular behaviors of the one-component fluid subclass and the universal crossover functions recently estimated [Garrabos and Bervillier, Phys. Rev. E 74, 021113 (2006)] from the bounded results of the massive renormalization scheme applied to the ${\Phi }_d^4\left(n\right)$ model of scalar order parameter $(n=1)$ and three dimensions $(d=3)$, representative of the Ising-like universality class. The master (i.e., rescaled) crossover functions are then able to fit the singular behaviors of any one-component fluid without adjustable parameter, using only one critical energy scale factor, one critical length scale factor, and two dimensionless asymptotic scale factors, which characterize the fluid critical interaction cell at its liquid-gas critical point. An additional adjustable parameter accounts for quantum effects in light fluids at the critical temperature. The effective extension of the thermal field range along the critical isochore where the master crossover functions seems to be valid corresponds to a correlation length greater than three times the effective range of the microscopic short-range molecular interaction.

Continuous-time quantum walks with long-range steps $R^{-\gamma }$ ($R$ being the distance between sites) on a discrete line behave in similar ways for all $\gamma \ge 2$. This is in contrast to classical random walks, which for $\gamma >3$ belong to a different universality class than for $\gamma \le 3$. We show that the average probabilities to be at the initial site after time $t$ as well as the mean square displacements are of the same functional form for quantum walks with $\gamma =2$, $4$, and with nearest neighbor steps. We interpolate this result to arbitrary $\gamma \ge 2$.

A correlated random walk approach to diffusion is applied to the disordered nonoverlapping Lorentz gas. By invoking the Lu-Torquato theory for chord-length distributions in random media [J. Chem. Phys. 98, 6472 (1993)], an analytic expression for the diffusion constant in arbitrary number of dimensions $d$ is obtained. The result corresponds to an Enskog-like correction to the Boltzmann prediction, being exact in the dilute limit, and better or nearly exact in comparison to renormalized kinetic theory predictions for all allowed densities in $d=2,3$. Extensive numerical simulations were also performed to elucidate the role of the approximations involved.

We study the diffusion phenomena on the negatively curved surface made up of congruent heptagons. Unlike the usual two-dimensional plane, this structure makes the boundary increase exponentially with the distance from the center, and hence the displacement of a classical random walker increases linearly in time. The diffusion of a quantum particle put on the heptagonal lattice is also studied in the framework of the tight-binding model Hamiltonian, and we again find the linear diffusion like the classical random walk. A comparison with diffusion on complex networks is also made.

We study the dynamics of a trapped, charged Brownian particle in the presence of a time-dependent magnetic field. We calculate work distributions for different time-dependent protocols numerically. In our problem, thermodynamic work is related to variation of the vector potential with time as opposed to the earlier studies where the work is related to time variation of the potentials, a quantity that depends only on the coordinates of the particle. Using the Jarzynski and the Crooks equalities, we show that the free energy of the particle is independent of the magnetic field, thus complementing the Bohr–van Leeuwen theorem. We also show that our system exhibits a parametric resonance in a certain parameter space.

We present a measure of local information transfer, derived from an existing averaged information-theoretical measure, namely, transfer entropy. Local transfer entropy is used to produce profiles of the information transfer into each spatiotemporal point in a complex system. These spatiotemporal profiles are useful not only as an analytical tool, but also allow explicit investigation of different parameter settings and forms of the transfer entropy metric itself. As an example, local transfer entropy is applied to cellular automata, where it is demonstrated to be a useful method of filtering for coherent structure. More importantly, local transfer entropy provides the first quantitative evidence for the long-held conjecture that the emergent traveling coherent structures known as particles (both gliders and domain walls, which have analogs in many physical processes) are the dominant information transfer agents in cellular automata.

The unstable plastic flow of an $\mathrm{AlMg}$ alloy, associated with the Portevin-Le Chatelier effect, was studied near the lower strain-rate boundary of instability using multifractal analysis. Self-similarity of deformation curves, indicating long-range time correlations of stress serrations, was detected within the strain-rate range where serrations are commonly ascribed to the occurrence of uncorrelated deformation bands. The deformation curves display a wide range of shapes that are characterized by different groupings of serrations. Multifractal analysis provides a method to quantify the observed complexity and compare it to known Portevin–Le Chatelier effect regimes. The measurement noise effect on the multifractal spectra determined from experimental data was mimicked by superposing multifractal Cantor sets with random noise. Such tests using standard multifractal data sets justify the separation of self-similar and random components of the serrated deformation curves. Furthermore, these results shed light on the general problem of the effect of experimental noise on the apparent multifractal properties of physical fractals.

We describe the mechanism of destabilization in a chain of identical coupled oscillators. Along with the transition from stationary to oscillatory behavior of the single oscillator, the network undergoes a complicated bifurcation scenario including the coexistence of multiple periodic orbits with different frequencies, spatial patterns, and modulation instabilities. This scenario, which is similar to the well-known Eckhaus scenario in spatially extended systems, occurs here also in the case of purely convective unidirectional coupling, and hence it cannot be explained as a simple discretization of its spatially continuous counterpart. Although the number of coexisting periodic orbits grows with the number of oscillators, we are able to treat this problem independently of the actual size of the network by investigating the limiting equations for the related spectral problems.

Recent investigations in nonlinear sciences show that not only hyperbolic but also mixed dynamical systems may exhibit exponential relaxation in the chaotic regime. The relaxation rates, which lead the decay of probability distributions and correlation functions, are related to the classical evolution resolvent (Perron-Frobenius operator) pole logarithm, the so-called Pollicott-Ruelle resonances. In this Brief Report, the leading Pollicott-Ruelle resonances are calculated analytically for a general class of area-preserving maps. Besides the leading resonances related to the diffusive modes of momentum dynamics (slow rate), we also calculate the leading faster rate, related to the angular correlations. The analytical results are compared to the existing results in the literature.

We investigated the nonequilibrium phase transition of the conserved lattice gas model in one dimension using two update methods: i.e., the sequential update and the parallel update. We measured the critical indices of $\theta$, $\beta$, ${\nu }_{\parallel }$, and ${\nu }_{\perp }$ and found that, for a parallel update, the exponents were delicately influenced by the hopping rule of active particles. When the hopping rule was designed to be symmetric, the results were found to be consistent with those of the sequential update. The exponents we obtained were precisely the same as the corresponding results of a recently presented lattice model of two species of particles with a conserved field in one dimension, in contrast with the authors’ claim. We also found that one of the scaling relations known for absorbing phase transition is violated.

Stability of directed transport and molecular separation in a symmetric channel is analyzed. The original mechanism is based on harmonic spatial oscillations of the channel, under which the system exhibits multiple regimes of a directed transport. The particles may be forced to move with different velocities and directions as the amplitude and/or frequency of the oscillations are adjusted to a proper resonance. The advantage of this mechanism in contrast to the ratchet systems is that the average particle velocity is larger than the velocity of the growing of the width of the particle spatial distribution. We have studied the stability of the directed transport with regard to random impacts to the channel parameters and oscillation frequency. Here we present the results of the simulations which show that the ability of the combined longitudinally and transversally vibrating randomized dynamic channel to perform directed molecular transport remains resilient to quite intensive random channel structure fluctuations $(50–60\%)$ and relatively strong random impacts to its oscillations $(15–20\%)$.

Glassy dynamics was investigated for thin films of atactic polystyrene by complex electric capacitance measurements using dielectric relaxation spectroscopy. During the isothermal aging process the real part of the electric capacitance increased with time, whereas the imaginary part decreased with time. It follows that the aging time dependences of real and imaginary parts of the electric capacitance were primarily associated with change in volume (film thickness) and dielectric permittivity, respectively. Further, dielectric permittivity showed memory and rejuvenation effects in a similar manner to those observed for poly(methyl methacrylate) thin films. On the other hand, volume did not show a strong rejuvenation effect.

As an alloy surface evolves under capillary forces, differing mobilities of the individual components can lead to kinetic alloy decomposition at the surface. In this paper, we address the relaxation of nanoscale sinusoidal ripples on alloy surfaces by considering the effects of both surface and bulk diffusion. In the absence of bulk diffusion, we derive exact analytical expressions for relaxation rates and identify two natural time scales that govern the relaxation dynamics. Bulk diffusion is shown to reduce kinetic surface segregation and enhance relaxation rates, owing to intermixing near the surface. Our results provide a quantitative framework for the interpretation of relaxation experiments on alloy surfaces.

The connection between the finite size of an evolving population and its dynamical behavior is examined through analytical and computational studies of a simple model of evolution. The infinite population limit of the model is shown to be governed by a special case of the quasispecies equations. A flat fitness landscape yields identical results for the dynamics of infinite and finite populations. On the other hand, a monotonically increasing fitness landscape shows “epochs” in the dynamics of finite populations that become more pronounced as the rate of mutation decreases. The details of the dynamics are profoundly different for any two simulation runs in that events arising from the stochastic noise in the pseudorandom number sequence are amplified. As the population size is increased or, equivalently, the mutation rate is increased, these epochs become smaller but do not entirely disappear.

In order to investigate the protein folding-unfolding process, dynamic light scattering (DLS) and atomic force microscopy (AFM) imaging were used to study two fragments of the muscle cardiac protein $\beta$-connectin, also known as titin. Both fragments belong to the $I$ band of the sarcomer, and they are composed of four domains from $I_{27}$ to $I_{30}$ (tetramer) and eight domains from $I_{27}$ to $I_{34}$ (octamer). DLS measurements provide the size of both fragments as a function of temperature from 20 up to 86 °C, and show a thermal denaturation due to temperature increase. AFM imaging of both fragments in the native state reveals a homogeneous and uniform distribution of comparable structures. The DLS and AFM techniques turn out to be complementary for size measurements of the fragments and fragment aggregates. An unexpected result is that the octamer folds into a smaller structure than the tetramer and the unfolded octamer is also smaller than the unfolded tetramer. This feature seems related to the significance of the hydrophobic interactions between domains of the fragment. The longer the fragment, the more easily the hydrophobic parts of the domains interact with each other. The fragment aggregation behavior, in particular conditions, is also revealed by both DLS and AFM as a process that is parallel to the folding-unfolding transition.

Entropy production for a system outside the thermodynamic limit is formulated using Hill’s nanothermodynamics, in which a macroscopic ensemble of such systems is considered. The external influence of the environment on the average nanosystem is connected to irreversible work with an explicit formula based on the Jarzynski equality. The entropy production retains its usual form as a sum of products of fluxes and forces and Onsager’s symmetry principle is proven to hold for the average nanosystem, if it is assumed to be valid for the macroscopic ensemble, by two methods. The first one provides expressions that relate the coefficients of the two systems. The second gives a general condition for a system under an external force to preserve Onsager’s symmetry.