Physical Review E最新文献

Debris flows often exhibit coherent wave structures-shocklike roll waves on steeper slopes and weaker, more sinusoidal dispersive pulses on gentler slopes. Coarse-rich heads raise basal resistance, whereas fines-rich tails lower it; in gentle reaches, small-amplitude pulses can locally transport momentum across low-resistance segments. We focus on this gentle-slope, long-wave, low-amplitude regime, where the base-flow Froude number is order unity. In this limit, we obtain a Korteweg-de Vries (KdV) reduction from depth-averaged balances with frictional (Coulomb) and viscous-plastic basal options, using a curvature-type internal normal-stress closure in the long-wave small-k regime. Multiple-scale analysis yields effective nonlinear and dispersive coefficients. We also introduce a practical nonlinearity diagnostic that can be computed from observed crest speeds and flow thicknesses. When laboratory-frame crest celerity is available, we estimate an effective quadratic coefficient from the KdV speed-amplitude relation and report its ratio to the shallow-water reference. When only a depth-averaged first-surge speed and thickness are available, we use the same construction to form a velocity-based proxy and note its bias near zero. A Froude-slope diagram organizes published cases into a steep-slope roll-wave domain and a gentle-slope corridor where KdV pulses are admissible. Numerical solutions of the full depth-averaged model produce cnoidal and solitary waves that agree with the reduced KdV predictions within this corridor. We regard dispersive pulses as a regime-specific complement to roll-wave dynamics, offering a condition-dependent contribution to mobility on gentle reaches rather than a universal explanation for long runout.

We consider the phase transition induced by compressing a self-avoiding walk in a slab where the walk is attached to both walls of the slab in two and three dimensions, and the resulting phase once the polymer is compressed. The process of moving between a stretched situation where the walls pull apart to a compressed scenario is a phase transition with some similarities to that induced by pulling and pushing the end of the polymer. However, there are key differences in that the compressed state is expected to behave like a lower dimensional system, which is not the case when the force pushes only on the end point of the polymer. We use scaling arguments to predict the exponents both associated with the phase transition and in the compressed state and find good agreement with Monte Carlo simulations.

People's opinions evolve through social interactions, and their social networks evolve as their opinions change. In this paper, we generalize bounded-confidence models of opinion dynamics by incorporating neighborhood effects. In our neighborhood bounded-confidence models (NBCMs), interacting agents are influenced both by each other's opinions and by the opinions of the agents in each other's neighborhoods (through so-called "transitive influence"). We extend our NBCMs to adaptive network models that incorporate "transitive homophily", with agents rewiring to connect preferentially to agents whose mean neighbor opinions are close to their own opinions. We numerically simulate an asynchronously updating adaptive NBCM on a variety of networks, and we explore how its opinion dynamics and structural properties change as we adjust the relative importances of dyadic and transitive influence. We observe that the transitive influence of neighborhoods can play an important role in shaping the qualitative features of opinion dynamics.

Thermodynamic uncertainty relations reveal a fundamental trade-off between the precision of a trajectory observable and entropy production, where the uncertainty of the observable is quantified by its variance. In information theory, Shannon entropy is a common measure of uncertainty. However, a clear quantitative relationship between the Shannon entropy of an observable and the entropy production in stochastic thermodynamics remains to be established. In this study, we show that an uncertainty relation can be formulated in terms of the Shannon entropy of an observable and the entropy production. We introduce symmetry entropy, an entropy measure that quantifies the symmetry of the observable distribution, and demonstrate that a greater asymmetry in the observable distribution requires higher entropy production. Specifically, we establish that the sum of the entropy production and the symmetry entropy cannot be less than ln2. As a corollary, we also prove that the sum of the entropy production and the Shannon entropy of the observable is no less than ln2. As an application, we demonstrate our relation in the diffusion decision model, revealing a fundamental trade-off between decision accuracy and entropy production in stochastic decision-making processes.

Using molecular dynamics, this study investigates the local elastic properties of transverse shear deformation of lipid membranes. The analysis demonstrates that transverse shear deformation induces anisotropy in the local stress profile of the lipid bilayer, a phenomenon attributed to the Poynting effect. By analyzing the relationship between transverse shear stress and the induced anisotropy, the local transverse shear modulus is determined. From the local transverse shear modulus, several integral elastic parameters can be derived, including the monolayer tilt modulus, tilt-curvature coupling modulus, and curvature gradient modulus. The calculated tilt modulus values show good agreement with results from an independent analysis of lipid director fluctuations.

Micropolar fluid theory, an extension of classical Newtonian fluid dynamics, incorporates angular velocities and rotational inertias and has long been a foundational framework for describing granular flows. We propose a macroscopic model of granular matter based on micropolar fluid dynamics, which incorporates internal rotations, couple stresses, and broken parity through odd viscosity. Our framework extends traditional micropolar theory to describe chiral granular flows driven far from equilibrium, where energy is continuously injected and dissipated. In particular, we focus on steady states and explicitly neglect energy conservation, reflecting the dissipative nature of granular systems maintained in nonequilibrium by external forcing. Within this setup, we study the lift force experienced by a test bead embedded in a compressible, parity-breaking granular flow. We analyze how odd viscosity and microrotation modify the transverse forces, using both analytical results in the linearized Stokes regime and nonlinear finite-element simulations. Our results demonstrate that micropolar fluids provide a physically consistent and symmetry-informed continuum description of chiral granular matter, capable of capturing lift forces that emerge uniquely from odd transport effects.

It has been shown that poly(3-hexylthiophene) (P3HT) dissolved in chloroform (CHCl_{3}) undergoes efficient aggregation with permanent polaron formation when submitted to phototreatment mediated by visible pulsed radiation. Although the need for pulsed radiation has been addressed, the role of CHCl_{3} in the aggregation process and permanent polaron formation has been elusive. Here we show that CHCl_{3} is a major player in photoaggregated products because it undergoes dissociation into hydrogen chloride (HCl) when submitted to high-energy radiation. HCl is a strong acid and binds to the P3HT thiophene ring, establishing a required p-doped structure rich in counter ions that stabilize the polarons. UV-Vis absorption, photoluminescence, and Raman modes provide spectroscopic fingerprints, indicating that the planarization of polymeric chains occurs and that such planarization is maintained by the permanent polarons formed throughout the structure when they are present. We also show that methanol (MeOH) in an acidic environment works as a facilitator that enhances the efficiency of the polymeric doping process, polaron formation, and controllability of the aggregates' character.

This study introduces an approach to extend the Keller and Skalak (KS) theory by integrating the modified Riemann-Liouville fractional derivative. Our focus is on investigating the transition of red blood cells from flipping to stationary motion within shear flows. Expanding upon the predictions outlined by KS regarding flipping periods and alignment with flow, our research aims to delve deeper into this transition process, which remains largely unexplored experimentally. The rationale for employing fractional derivatives stems from their capacity to capture memory effects and nonlocal interactions, thus providing a more nuanced modeling framework for complex particle dynamics.

Identifying the universality class of critical active phase transitions has been the subject of recent interest and controversy. Resolving these controversies will require robust numerical investigations to determine whether active critical exponents point to novel universality classes or are consistent with established ones. Here, we conduct large-scale computer simulations and a finite-size scaling analysis of the motility-induced phase separation (MIPS) of active Brownian hard spheres in three dimensions (3D), finding that the static and dynamic critical exponents all closely match those of the 3D Ising universality class with a conserved scalar order parameter. This finding is corroborated by a fluctuating hydrodynamic description of the critical dynamics of the order parameter field which flows to the Wilson-Fisher fixed point in three dimensions. Our work suggests that 3D MIPS and likely the entire phase diagram of active Brownian hard spheres is similar to that of molecular passive fluids despite the absence of Boltzmann statistics.

Individual bacterial cells grow and divide stochastically. Yet they maintain their characteristic sizes across generations within a tightly controlled range. What rules ensure intergenerational stochastic homeostasis of individual cell sizes? Valuable clues have emerged from high-precision long-term tracking of individual statistically identical Caulobacter crescentus cells as reported by Joshi et al. [bioRxiv (2023)]10.1101/2023.01.18.524627 and Ziegler et al. [Mol. Biol. Cell 35, ar78 (2024)1059-152410.1091/mbc.E23-11-0452]: Intergenerational cell-size homeostasis is an inherently stochastic phenomenon, follows Markovian or memory-free dynamics, and cells obey an intergenerational scaling law, which governs the stochastic map characterizing generational sequences of cell sizes. These observed emergent simplicities serve as essential building blocks of the data-informed principled theoretical framework we develop here. Our exact analytic fitting-parameter-free results for the predicted intergenerational stochastic map governing the precision kinematics of cell-size homeostasis are remarkably well borne out by experimental data, including extant published data on other microorganisms, Escherichia coli and Bacillus subtilis. Furthermore, our framework naturally yields the general exact and analytic condition that is necessary and sufficient to ensure that stochastic homeostasis can be achieved and maintained. Significantly, this condition is more stringent than the known heuristic result from quasideterministic frameworks. In turn, the fully stochastic treatment we present here extends and updates extant frameworks and highlights the inherently stochastic behaviors of individual cells in homeostasis.