In free-standing smectic films, layers near the surfaces of the film often contain molecules tilted away from the layer normal, while in the bulk of the film the magnitude of the tilt decays exponentially with distance from the surface. We have identified the detailed molecular tilt orientations in the surface layers of films for one antiferroelectric liquid crystal compound. A series of five surface structures exists with different nonplanar tilt arrangements for each structure. The molecular orientations in the surface layers evolve with temperature. The polarization of the film also evolves with temperature, corresponding to the tilt arrangements. Using ellipsometric data, we reconstruct the changes in the magnitude and azimuthal direction of the tilt as functions of temperature. We have also studied films of several different thicknesses. We present a phase diagram for the five surface structures showing the dependence on temperature and film thickness.

We consider the thermally activated fragmentation of a homopolymer chain. In our simple model the dynamics of the intact chain is a Rouse one until a bond breaks and bond breakdown is considered as a first passage problem over a barrier to an absorbing boundary. Using the framework of the Wilemski-Fixman approximation we calculate activation times of individual bonds for free and grafted chains. We show that these times crucially depend on the length of the chain and the location of the bond yielding a minimum at the free chain ends. Theoretical findings are qualitatively confirmed by Brownian dynamics simulations.

Publication statistics are ubiquitous in the ratings of scientific achievement, with citation counts and paper tallies factoring into an individual’s consideration for postdoctoral positions, junior faculty, and tenure. Citation statistics are designed to quantify individual career achievement, both at the level of a single publication, and over an individual’s entire career. While some academic careers are defined by a few significant papers (possibly out of many), other academic careers are defined by the cumulative contribution made by the author’s publications to the body of science. Several metrics have been formulated to quantify an individual’s publication career, yet none of these metrics account for the collaboration group size, and the time dependence of citation counts. In this paper we normalize publication metrics in order to achieve a universal framework for analyzing and comparing scientific achievement across both time and discipline. We study the publication careers of individual authors over the 50-year period 1958–2008 within six high-impact journals: CELL, the New England Journal of Medicine (NEJM), Nature, the Proceedings of the National Academy of Science (PNAS), Physical Review Letters (PRL), and Science. Using the normalized metrics (i) “citation shares” to quantify scientific success, and (ii) “paper shares” to quantify scientific productivity, we compare the career achievement of individual authors within each journal, where each journal represents a local arena for competition. We uncover quantifiable statistical regularity in the probability density function of scientific achievement in all journals analyzed, which suggests that a fundamental driving force underlying scientific achievement is the competitive nature of scientific advancement.

Cooperation has been widely studied when an individual strategy is adopted against all coplayers. In this context, some extra mechanisms, such as punishment, reward, memory, and network reciprocity must be introduced in order to keep cooperators alive. Here, we adopt a different point of view. We study the adoption of different strategies against different opponents instead of adoption of the same strategy against all of them. In the context of the prisoner dilemma, we consider an evolutionary process in which strategies that provide more benefits are imitated and the players replace the strategy used in one of the interactions furnishing the worst payoff. Individuals are set in a well-mixed population, so that network reciprocity effect is excluded and both synchronous and asynchronous updates are analyzed. As a consequence of the replacement rule, we show that mutual cooperation is never destroyed and the initial fraction of mutual cooperation is a lower bound for the level of cooperation. We show by simulation and mean-field analysis that (i) cooperation dominates for synchronous update and (ii) only the initial mutual cooperation is maintained for asynchronous update. As a side effect of the replacement rule, an “implicit punishment” mechanism comes up in a way that exploitations are always neutralized providing evolutionary stability for cooperation.

An algorithm inspired by Genome sequencing is proposed which “reconstructs” a single long trajectory of a dynamical system from many short trajectories. This procedure is useful in situations when many data sets are available but each is insufficiently long to apply a meaningful analysis directly. The algorithm is applied to the Rössler and Lorenz dynamical systems as well as to experimental data taken from the Belousov-Zhabotinskii chemical reaction. Topological information was reliably extracted from each system and geometrical and dynamical measures were computed.

We study the nearest-neighbor distributions of the $k$-body embedded ensembles of random matrices for $n$ bosons distributed over two-degenerate single-particle states. This ensemble, as a function of $k$, displays a transition from harmonic-oscillator behavior $\left(k=1\right)$ to random-matrix-type behavior $\left(k=n\right)$. We show that a large and robust quasidegeneracy is present for a wide interval of values of $k$ when the ensemble is time-reversal invariant. These quasidegenerate levels are Shnirelman doublets which appear due to the integrability and time-reversal invariance of the underlying classical systems. We present results related to the frequency in the spectrum of these degenerate levels in terms of $k$ and discuss the statistical properties of the splittings of these doublets.

The anisotropy of the hot-electron velocity distribution in ultra-high-intensity laser produced plasma was studied with x-ray polarization spectroscopy using multilayer planar targets including x-ray emission tracer in the middle layer. This measurement serves as a diagnostic for hot-electron transport from the laser-plasma interaction region to the overdense region where drastic changes in the isotropy of the electron velocity distribution are observed. These polarization degrees are consistent with analysis of a three-dimensional polarization spectroscopy model coupled with particle-in-cell simulations. Electron velocity distribution in the underdense region is affected by the electric field of the laser and that in the overdense region becomes wider with increase in the tracer depth. A full-angular spread in the overdense region of $22.4{°}_{-2.4}^{+5.4}$ was obtained from the measured polarization degree.

We derive a fully relativistic form factor for Thomson scattering in unmagnetized plasmas valid to all orders in the normalized electron velocity, $\stackrel{⃑}{\beta }=\stackrel{⃑}{v}/c$. The form factor is compared to a previously derived expression where the lowest order electron velocity, $\stackrel{⃑}{\beta }$, corrections are included [J. Sheffield, Plasma Scattering of Electromagnetic Radiation (Academic Press, New York, 1975)]. The $\stackrel{⃑}{\beta }$ expansion approach is sufficient for electrostatic waves with small phase velocities such as ion-acoustic waves, but for electron-plasma waves the phase velocities can be near luminal. At high phase velocities, the electron motion acquires relativistic corrections including effective electron mass, relative motion of the electrons and electromagnetic wave, and polarization rotation. These relativistic corrections alter the scattered emission of thermal plasma waves, which manifest as changes in both the peak power and width of the observed Thomson-scattered spectra.

In this paper, we theoretically investigate the propagation properties of probe and mixing fields in a quantum well waveguide. This waveguide is driven by two strong control (pumping and coupling) fields and a weak probe field. Under appropriate parameters condition, the electron spin coherence can suppress the absorption and enhance the nonlinear susceptibilities of the probe (or mixing) field. This study reveals that probe (or mixing) field can form soliton pairs and propagate in the quantum well waveguide with slow group velocity. We also study the soliton collision and dynamics evolution. The results show that the propagation of soliton can be strongly modified by the electron spin coherence.

Although partition functions of finite-size systems are always analytic, and hence have no poles, they can be expressed in many cases as series containing terms with poles. Here we show that such poles can be related to linear branches of the entropy, expressed in the thermodynamic limit as a function of the energy per particle. We also show that these poles can be used to determine whether the entropy is nonconcave or has linear parts, which is something that cannot be done with the sole knowledge of the thermodynamic free energy derived from the partition function. We discuss applications for equilibrium systems having first-order phase transitions.

Equations describing the evolution of particles, solitons, or localized structures, driven by a zero-average, periodic, external force, and invariant under time reversal and a half-period time shift, exhibit a ratchet current when the driving force breaks these symmetries. The biharmonic force $f\left(t\right)={ϵ}_1\text{cos}\left(q\omega t+{\varphi }_1\right)+{ϵ}_2\text{cos}\left(p\omega t+{\varphi }_2\right)$ does it for almost any choice of ${\varphi }_1$ and ${\varphi }_2$, provided $p$ and $q$ are two coprime integers such that $p+q$ is odd. It has been widely observed, in experiments in semiconductors, in Josephson junctions, photonic crystals, etc., as well as in simulations, that the ratchet current induced by this force has the shape $v\propto {ϵ}_1^p{ϵ}_2^q\text{cos}\left(p{\varphi }_1-q{\varphi }_2+{\theta }_0\right)$ for small amplitudes, where ${\theta }_0$ depends on the damping (${\theta }_0=\pi /2$ if there is no damping, and ${\theta }_0=0$ for overdamped systems). We rigorously prove that this precise shape can be obtained solely from the broken symmetries of the system and is independent of the details of the equation describing the system.

Monte Carlo simulations have been used to study the phase diagrams for square Ising-lattice-gas models with two- and three-body interactions for values of interaction parameters in a range that has not been previously considered. We find unexpected qualitative differences as compared with predictions made on general grounds.

The satisfiability of a class of random Boolean equations named massive algebraic system septated to linear and nonlinear subproblems is studied in this paper. On one hand, the correlation between the magnetization of generators and the clustering of solutions of the linear subproblem is investigated by analyzing the Gaussian elimination process. On the other hand, the characteristics of maximal elements of solutions of the nonlinear subproblem are studied by introducing the partial order among solutions. Based on the algebraic characteristics of these two subproblems, the upper and lower bounds of satisfiability threshold of massive algebraic system are obtained by unit-clause propagation and leaf-removal process, and coincide as the ratio of nonlinear equations $q>0.739$ in which analytical values of the satisfiability threshold can be derived. Furthermore, a complete algorithm with heuristic decimation is proposed to observe the approximation of the satisfiability threshold, which performs more efficiently than the classical ones.

Cholesteric droplets accompanied by a topological defect are studied in free standing smectic $C^{\ast }$ films. We observed a transition between two droplet-defect configurations with the defect in the film and on the droplet boundary. We found that the distance between the droplet surface and the topological defect decreases continuously with increasing temperature and above a certain critical temperature the defect jumps to the droplet boundary. We relate this stepwise change in the defect position to the change in the anchoring on the droplet boundary. This transformation leads to a decrease in the interparticle distances in self-organized chains from droplets. Our simple theory allows us to estimate the value of the anchoring energy.

We present results for unforced polymer translocation from simulations using Langevin dynamics in two dimensions (2D) to four dimensions and stochastic rotation dynamics supporting hydrodynamic modes in three dimensions (3D). We compare our results to forced translocation and a simplified model where the polymer escapes from an infinite pore. The simple model shows that the scaling behavior of unforced translocation is independent of the dimension of the side to which the polymer is translocating. We find that, unlike its forced counterpart, unforced translocation dynamics is insensitive to pore design. Hydrodynamics is seen to markedly speed up the unforced translocation process but not to affect the scaling relations. Average mean-squared displacement shows scaling with average transition time in unforced but not in forced translocation. The waiting-time distribution in unforced translocation follows closely Poissonian distribution. Our measured transfer probabilities align well with those obtained from an equilibrium theory in 3D, but somewhat worse in 2D, where a polymer’s relaxation toward equilibrium with respect to its translocation time is slower. Consequently, in stark contrast to forced translocation, unforced translocation is seen to remain close to equilibrium and shows clear universality.

THz spectroscopy is used to investigate the dynamics of the globular protein hen egg white lysozyme under varying hydration and temperature conditions. An analysis of the experimental spectra has revealed that the amount of solvent in the hydration shell has a strong influence on the low-frequency protein conformational dynamics and also the arrangement of hydrogen bonds in the protein secondary structure. Furthermore at a hydration level $>0.2$ we identify collective backbone fluctuations in the protein secondary structure that are not present at low hydration. It is possible that these solvent induced modes are important for the biological function of the protein.

We argue that the transition to turbulence is controlled by large amplitude events that follow extreme distribution theory. The theory suggests an explanation for recent observations of the turbulent state lifetime which exhibit superexponential scaling behavior with Reynolds number.

Zero-lag synchronization (ZLS) between two chaotic systems coupled by a portion of their signal is achieved for restricted ratios between the delays of the self-feedback and the mutual coupling. We extend this scenario to the case of a set of multiple self-feedbacks $\left\{N_{d_i}\right\}$ and a set of multiple mutual couplings $\left\{N_{c_j}\right\}$. We demonstrate both analytically and numerically that ZLS can be achieved when $\sum l_i{N}_{d_i}+\sum m_j{N}_{c_j}=0$, where $l_i,m_j∊\mathbb{Z}$. Results which were mainly derived for Bernoulli maps and exemplified with simulations of the Lang-Kobayashi differential equations, indicate that ZLS can be achieved for a continuous range of mutual coupling delay. This phenomenon has an important implication in the possible use of ZLS in communication networks.

The behavior of the average velocity for a classical particle in the one-dimensional Fermi accelerator model under sawtooth external force is considered. For elastic collisions, it is known that the average velocity of the particle grows unlimitedly because of the discontinuities of the derivative of the moving wall’s position with respect to time. However, and contrary to what was expected to be observed, the introduction of a friction force generated from a slip of a body against a rough surface leads to a boundary separating different regions of the phase space that yields the particle to either experience unlimited energy growth or suppression of Fermi acceleration. The Fermi acceleration is described by using scaling arguments. The formalism presented can be extended to two-dimensional time-dependent billiards as well as to higher-order mappings.

The stability of a water layer of uniform thickness held in a two-dimensional container of finite or semi-infinite extent is examined using linear stability theory. The liquid-vapor interface can be heated both through the liquid and through the vapor, as previously experimentally reported. The need to introduce a heat transfer coefficient is eliminated by introducing statistical rate theory (SRT) to predict the evaporation flux. There are no fitting or undefined parameters in the expression for the evaporation flux. The energy transport is parametrized in terms of the evaporation number, $E_{ev}$, that for a given experimental circumstance can be predicted. The critical Marangoni number for the finite, ${\text{Ma}}_{cf}$, and for the semi-infinite system, ${\text{Ma}}_{c\infty }$, can be quantitatively predicted. Experiments in which water evaporated from a stainless-steel funnel and from a polymethyl methacrylate (PMMA) funnel into its vapor have been previously reported. Marangoni convection was observed in the experiments that used the stainless-steel funnel but not with the PMMA funnel even though the Marangoni number for the PMMA funnel was more than $27000$. The SRT-based stability theory indicates that the critical value of the Marangoni number for the experiments with the PMMA funnel was greater than the experimental value of the Marangoni number in each case; thus, no Marangoni convection was predicted to result from an instability. The observed convection with the stainless-steel funnel resulted from a temperature gradient imposed along the interface.