Quasi-equilibrium State Research Articles

The status of isochrony in the formation and evolution of self-gravitating systems

In the potential theory, isochrony was introduced by Michel H\'enon in 1959 to characterize astrophysical observations of some globular clusters. Today, Michel Henon's isochrone potential is mainly used for his integrable property in numerical simulations, but is generally not really known. In a recent paper [29], we have presented new fundamental and theoretical results about isochrony that have particular importance in self-gravitating dynamics and which are detailed in this paper. In particular, new characterization of the isochrone state has been proposed which are investigated in order to analyze the product of the fast relaxation of a self-gravitating system. The general paradigm consists in considering that this product is a lowered isothermal sphere (King Model). By a detailed numerical study we show that this paradigm fails when the isochrone model succeeds in reproducing the quasi-equilibrium state obtained just after fast relaxation.

Orbital-dependent electron dynamics in Fe-pnictide superconductors

We report on orbital-dependent quasiparticle dynamics in EuFe$_2$As$_2$, a parent compound of Fe-based superconductors and a novel way to experimentally identify this behavior, using time- and angle-resolved photoelectron spectroscopy across the spin density wave transition. We observe two different relaxation time scales for photo-excited d$_x$$_z$/d$_y$$_z$ and d$_x$$_y$ electrons. While d$_x$$_z$/d$_y$$_z$ electrons relax faster through the electron-electron scattering channel, showing an itinerant character, d$_x$$_y$ electrons form a quasi-equilibrium state with the lattice due to their localized character, and the state decays slowly. Our findings suggest that electron correlation in Fe-pnictides is an important property, which should be taken into careful account when describing the electronic properties of both parent and electron-doped compounds, and therefore establish a strong connection with cuprates.

Observing the Laboratory Interaction of Undertow and Nonlinear Wave Motion over Barred and Nonbarred Beaches to Determine Beach Profile Evolution in the Surf Zone

ABSTRACT Choi, J.; Roh, M., and Hwang, H., 2018. Observing the laboratory interaction of undertow and nonlinear wave motion over barred and nonbarred beaches to determine beach profile evolution in the surf zone. A vertically two-dimensional laboratory experiment was performed with a movable bed to investigate the interaction of undertow and sawtooth-shaped nonlinear wave motion over the cross-shore evolution of barred (storm) and nonbarred (normal) beach profiles. The bottom elevations, free-surface motion, and flow velocity were measured under regular wave conditions, excluding infragravity waves, over a movable bed. The observations were conducted in the surf zone during alternate repeats of the two wave conditions until each quasiequilibrium state was reached. From the net sediment transport of the observation area, it was shown that the storm case was in an erosion state and that the normal case was in an accretion state. The measurements confirmed that the strong undertow, which is a dominant factor...

A Dynamic Model in the Labor Market: Reasons of Imbalances at the Transition Stage of the Economy

The aim of this work is the formalization of the model of coordination of interests of employers and owners of human capital in the labor market in high-tech industries of the national economy in the conditions of transformation of the national economy. Research conducted by the authors proved that the structure of costs of reproduction of human capital and the requirements for human potential have their own distinct features that should be considered in the specification of the economic model of value creation of human capital in these sectors. Authors propose an improved method of balancing interaction of economic interests of subjects of the labor market: employee and employer. The model reveals the mechanism of formation of the equilibrium value of human capital based on the cost approach and the income approach in modeling supply and demand in the labor market in high-tech industries. The model allows to estimate a quasi-equilibrium state of the labor market in high-tech industries with emerging trends in this market in the country as a whole. The study provides valuable analytical information required to implement science-based economic decisions in the management of human resources and their transformation into human capital, which in turn will improve the efficiency of realization of innovation potential of the company as the subject of the high-tech industry of national economy.At the level of state governance model allows to monitor the mismatches in the labor market that allows to develop actions to minimize their negative impacts on the national economy.

Quasi-Equilibria and Polarization Transfer Between Adjacent and Remote Spins: 1H-13C CP MAS Kinetics in Glycine.

The 1H-13C CP MAS kinetic curves were measured in glycine powder sample at the MAS rates of 7, 10, and 12 kHz. Each experimental curve contained up to 1000 equidistant points over the whole contact time range of 10 μs - 10 ms. The CP kinetic data for CH2 group, i.e., for the system containing adjacent 1H-13C spin pairs with a definite dominant dipolar coupling can be described in the frame of the isotropic spin-diffusion approach. The local order parameter ⟨ S⟩ ≈ 1.0, determined as the ratio of the measured dipolar 1H-13C coupling constant and the calculated static dipolar coupling constant, is very close to the values deduced in series of other amino acids. The strong narrow peaks observed in the spin coupling spectrum at multiples of the MAS frequency can be considered as the confirmation that the periodic quasi-equilibrium state can appear also in the powder samples. The anisotropic spin-diffusion approach improved by the introducing of the thermal equilibration in the proton bath is the most proper model to describe the CP kinetics in the system containing remote spins. Very realistic values of the spin-cluster size ( N) have been obtained without any constraint on the flow of the nonlinear curve fitting. The finite values of N ≤ 4 means that CP transfer is located within one glycine molecule.

Electromechanics of polarized cell growth

One of the most challenging questions in cell and developmental biology is how molecular signals are translated into mechanical forces that ultimately drive cell growth and motility. Despite an impressive body of literature demonstrating the importance of cytoskeletal and motor proteins as well as osmotic stresses for cell developmental mechanics, a host of dissenting evidence strongly suggests that these factors per se cannot explain growth mechanics even at the level of a single tip-growing cell. The present study addresses this issue by exploring fundamental interrelations between electrical and mechanical fields operating in cells. In the first instance, we employ a simplified but instructive model of a quiescent cell to demonstrate that even in a quasi-equilibrium state, ion transport processes are conditioned principally by mechanical tenets. Then we inquire into the electromechanical conjugacy in growing pollen tubes as biologically relevant and physically tractable developmental systems owing to their extensively characterized growth-associated ionic fluxes and strikingly polarized growth and morphology. A comprehensive analysis of the multifold stress pattern in the growing apices of pollen tubes suggests that tip-focused ionic fluxes passing through the polyelectrolyte-rich apical cytoplasm give rise to electrokinetic flows that actualize otherwise isotropic intracellular turgor into anisotropic stress field. The stress anisotropy can be then imparted from the apical cytoplasm to the abutting frontal cell wall to induce its local extension and directional cell growth. Converging lines of evidence explored in the concluding sections attest that tip-focused ionic fluxes and associated interfacial transport phenomena are not specific for pollen tubes but are also employed by a vast variety of algal, plant, fungal and animal cells, rendering their cytoplasmic stress fields essentially anisotropic and ultimately instrumental in cell shaping, growth and motility.

Dynamics of viscoelastic filaments based on Onsager principle

When a polymer solution is uniaxially stretched and held fixed at both ends, the solution quickly separates into droplets connected by strings and takes the beads-on-string structure. The string then becomes thinner by capillary forces. Here we develop a theoretical framework on viscoelastic fluids based on Onsager principle, and apply it to the dynamics of viscoelastic filaments. We show that the beads-on-string structure is a thermodynamic quasi-equilibrium state, and derive an equation for the coexistence condition in the pseudo-equilibrium state. Using the condition, we solve the evolution equation analytically and show that the string radius and the tensile stress vary exponentially as predicted by the classical theory of Entov and Hinch [J. Non-Newtonian Fluid Mech. 72, 31 (1997)], but the prefactor for the tensile stress is different from their theory and agrees with the numerical solutions of Clasen et al. [J. Fluid Mech. 556, 283 (2006)].

Quasi-steady radiation of sound from turbulent sonic ergoregions

Sonic Hawking radiation has recently been observed in dilute Bose–Einstein condensates (BECs), but it remains an open question whether this landmark achievement of atomic physics can lead to new insights into the effects on Hawking radiation of nonlinear back-reaction and new short-distance physics, as was originally hoped by Unruh when he introduced the sonic analogy. Furthermore, studies of sonic analog black holes have until now concentrated on (1+1)-dimensional scenarios, but Unruh’s sonic analogy for curved spacetime is only valid in more than one spatial dimension. We therefore model the evolution of a (2+1)-dimensional sonic black hole in a dilute BEC, over a long enough time to let the initial Corley–Jacobson instabilities saturate in vortex production and give way to a long-lived quasi-stationary state. In this quasi-equilibrium state we find the initial laminar ergoregion replaced by a turbulent zone that steadily radiates sound, but with a non-thermal power spectrum.

Influence of NH4NO3 Formation on the NOx Reduction Pathways over Vanadium-based Catalyst under Diesel Exhaust Conditions

Nitrates are often deposited on the pipe wall and catalyst surface in the SCR system, so the NOx removing efficiency and catalytic activity are also reduced and limited at low exhaust temperatures. According to working characteristics and exhaust conditions of Diesel engine, a NH3−NO/NO2−SCR reaction model including NOx reduction, NH4NO3 formation and decomposition pathways was proposed in this paper, and the influence of NH4NO3 on the NOx reduction pathways and low-temperature catalytic activity was studied using the described model. As an important intermediate product of NOx reduction at low temperatures, NH4NO3 formation rate is strongly dependent on the apparent rate of SCR reaction. Since NH4NO3 formation reaction is enhanced in the presence of H2O, and its decomposition is controlled by the exhaust temperature, both reactions can proceed into a quasi-equilibrium state at high temperatures.

The NUIST Earth System Model (NESM) version 3: description and preliminary evaluation

Abstract. The Nanjing University of Information Science and Technology Earth System Model version 3 (NESM v3) has been developed, aiming to provide a numerical modeling platform for cross-disciplinary Earth system studies, project future Earth climate and environment changes, and conduct subseasonal-to-seasonal prediction. While the previous model version NESM v1 simulates the internal modes of climate variability well, it has no vegetation dynamics and suffers considerable radiative energy imbalance at the top of the atmosphere and surface, resulting in large biases in the global mean surface air temperature, which limits its utility to simulate past and project future climate changes. The NESM v3 has upgraded atmospheric and land surface model components and improved physical parameterization and conservation of coupling variables. Here we describe the new version's basic features and how the major improvements were made. We demonstrate the v3 model's fidelity and suitability to address global climate variability and change issues. The 500-year preindustrial (PI) experiment shows negligible trends in the net heat flux at the top of atmosphere and the Earth surface. Consistently, the simulated global mean surface air temperature, land surface temperature, and sea surface temperature (SST) are all in a quasi-equilibrium state. The conservation of global water is demonstrated by the stable evolution of the global mean precipitation, sea surface salinity (SSS), and sea water salinity. The sea ice extents (SIEs), as a major indication of high-latitude climate, also maintain a balanced state. The simulated spatial patterns of the energy states, SST, precipitation, and SSS fields are realistic, but the model suffers from a cold bias in the North Atlantic, a warm bias in the Southern Ocean, and associated deficient Antarctic sea ice area, as well as a delicate sign of the double ITCZ syndrome. The estimated radiative forcing of quadrupling carbon dioxide is about 7.24 W m−2, yielding a climate sensitivity feedback parameter of −0.98 W m−2 K−1, and the equilibrium climate sensitivity is 3.69 K. The transient climate response from the 1 % yr−1 CO2 (1pctCO2) increase experiment is 2.16 K. The model's performance on internal modes and responses to external forcing during the historical period will be documented in an accompanying paper.

Performance Evaluation of High-Resolution Land Data Assimilation System (HRLDAS) Over Indian Region

The present study evaluates the skill of a High-Resolution Land Data Assimilation System (HRLDAS) in simulating soil moisture (SM), soil temperature (ST) and sensible heat flux (SHF) for the Indian region (5°–39°N; 60°–100°E). The HRLDAS framework uses uncoupled Noah Land Surface Model (LSM) that integrates near-surface atmospheric parameters and land surface parameters from observations and analysis for the period January 2001–October 2013 at 20 km spatial resolution. The HRLDAS takes about 1 year to reach its quasi-equilibrium state for clay soil. The HRLDAS simulated ST and SM reasonably agree with the in situ observations. The simulated ST shows a negative bias in the monsoon season over the Gujarat, Mandla, and Kharagpur. The SM is under-estimated and the under-estimation increases with soil depth at Kharagpur, India. The negative bias in TRMM precipitation forcing causes under-estimation of SM. The simulated SM shown higher saturation point than observations. The daytime SHF has positive bias during the pre-monsoon, monsoon seasons and agrees well with observations in the post-monsoon season at Ranchi, India. The Noah 1D sensitivity experiments revealed that there is a need to revisit soil field capacity and porosity parameter for improving the skill of the HRLDAS.

Effect of a Nanodisperse Graphite on the Viscoelastic Properties of Polyvinyl Chloride

In the absence of segregation of nanodisperse graphite particles, obtained by electrolysis as a new filler of polyvinyl chloride (PVC), the viscoelastic phenomena dependent on the structural changes of a composite are investigated. The shear modulus and the volume compressibility caused by deviations of elements of the structure from the quasi-equilibrium state under the action of ultrasonic vibrations (ω = 0.4·106 0.4 · 10 s–1) are calculated at filler concentrations 0 ≤ φ ≤ 10.0 vol.% and temperatures 298 K ≤ T ≤ (Tg + 10) K. It is shown that the volume density of internal energy depends on the expectation time for the transition of structural elements through the energy barrier, the dynamic viscosity of the material, and temperature. The results of calculations serve as the basis for producing PVC systems with controllable of properties.

Mass Ejection from the Remnant of a Binary Neutron Star Merger: Viscous-radiation Hydrodynamics Study

Abstract We perform long-term general relativistic neutrino radiation hydrodynamics simulations (in axisymmetry) for a massive neutron star (MNS) surrounded by a torus, which is a canonical remnant formed after the binary neutron star merger. We take into account the effects of viscosity, which is likely to arise in the merger remnant due to magnetohydrodynamical turbulence. The viscous effect plays key roles for the mass ejection from the remnant in two phases of the evolution. In the first t ≲ 10 ms, a differential rotation state of the MNS is changed to a rigidly rotating state. A shock wave caused by the variation of its quasi-equilibrium state induces significant mass ejection of mass ∼(0.5–2.0) for the α-viscosity parameter of 0.01–0.04. For the longer-term evolution with ∼0.1–10 s, a significant fraction of the torus material is ejected. We find that the total mass of the viscosity-driven ejecta ( ) could dominate over that of the dynamical ejecta ( ). The electron fraction, Y e , of the ejecta is always high enough (Y e ≳ 0.25) that this post-merger ejecta is lanthanide-poor; hence, the opacity of the ejecta is likely to be ∼10–100 times lower than that of the dynamical ejecta. This indicates that the electromagnetic signal from the ejecta would be rapidly evolving, bright, and blue if it is observed from a small viewing angle (≲45°) for which the effect of the dynamical ejecta is minor.

Do cells sense time by number of divisions?

Can the cell’s perception of time be expressed through the length of the shortest telomere? To address this question, we analyze an asymmetric random walk that models telomere length for each division that can decrease by a fixed length a or, if recognized by a polymerase, it increases by a fixed length b ≫ a. Our analysis of the model reveals two phases, first, a determinist drift of the length toward a quasi-equilibrium state, and second, persistence of the length near an attracting state for the majority of divisions. The measure of stability of the latter phase is the expected number of divisions at the attractor (”lifetime”) prior to crossing a threshold T that model senescence. Using numerical simulations, we further study the distribution of times for the shortest telomere to reach the threshold T. We conclude that the telomerase regulates telomere stability by creating an effective potential barrier that separates statistically the arrival time of the shortest from the next shortest to T. The present model explains how random telomere dynamics underlies the extension of cell survival time.

Ion-ion dynamic structure factor, acoustic modes, and equation of state of two-temperature warm dense aluminum.

The ion-ion dynamical structure factor and the equation of state of warm dense aluminum in a two-temperature quasiequilibrium state, with the electron temperature higher than the ion temperature, are investigated using molecular-dynamics simulations based on ion-ion pair potentials constructed from a neutral pseudoatom model. Such pair potentials based on density functional theory are parameter-free and depend directly on the electron temperature and indirectly on the ion temperature, enabling efficient computation of two-temperature properties. Comparison with ab initio simulations and with other average-atom calculations for equilibrium aluminum shows good agreement, justifying a study of quasiequilibrium situations. Analyzing the van Hove function, we find that ion-ion correlations vanish in a time significantly smaller than the electron-ion relaxation time so that dynamical properties have a physical meaning for the quasiequilibrium state. A significant increase in the speed of sound is predicted from the modification of the dispersion relation of the ion acoustic mode as the electron temperature is increased. The two-temperature equation of state including the free energy, internal energy, and pressure is also presented.

In Situ Wettability Characterization of Chemically Heterogeneous Surfaces Probed by Ionic Liquid Contact Angle in Vacuum: Pentacene on Single-Crystal SrTiO3(001)

Intrinsic surface wettability of pentacene thin films with different island coverages grown on single-crystal SrTiO3(001) was investigated by an in situ contact angle measurement in a high vacuum using ionic liquid as a probe fluid. The contact angle at the quasi-equilibrium state, which was measured at a certain time after its fast decay depending on the liquid viscosity, increased with the deposition amount of pentacene and saturated when the surface was fully covered with pentacene islands. The observed island coverage dependence of the in situ contact angle was well-fitted by a three-component Cassie equation composed of surface areas of not only the bare substrate and island pentacene but also adsorbed pentacene. The importance of the in situ contact angle measurement was confirmed by the result of an air exposure experiment, where the contact angle took almost irrelevant values to the integral coverage of pentacene, suggesting the significant effects of airborne contaminants on the surface wettability.

Crystallization of supercooled liquid and amorphous silicene

Crystallization under isothermal condition of supercooled liquid and amorphous silicene (a-silicene) models has been studied via molecular dynamics (MD) simulation with Stillinger-Weber (SW) interaction potential. Supercooled liquid and a-silicene models containing 104 atoms are obtained via the rapid solidification process from the melt. At each given temperature below and above Tg, models are annealed from 5 ns up to 8 ns in order to investigate aging effect on two-dimensional structural arrangement of disordered Si-atoms. Time dependence of thermodynamic and structural quantities is analyzed including potential energy, radial distribution function (RDF), coordination number, buckling degree, ring and bond-angle distribution. We find that 2D-crystallization of supercooled liquid and a-silicene exhibits a first-order behavior. Time-temperature-transformation (TTT) diagram exhibits a commonly nose-shape by analyzing a wide temperature range from supercooled liquid to amorphous state. High critical cooling rates of a-silicene are found indicating low glass-formation ability of the system. Thermodynamic properties of crystallization of silicenes attained after-aging are studied in details and we clarify a novel scenario of crystallization. A homogenous tendency of natural quenched-in nucleation atoms aggregate into larger clusters in 2D Si supercooled liquid sheet. Consequently, a polycrystalline layer of silicene is developed with decent low-numbered chain defects as grain boundary. In contrast, crystallization of a-silicene shows a partial crystallization behavior: Crystal clusters are found to exhibit a heterogeneous growth in models obtained below Tg. Crystal formed from a-silicene is a quasi-equilibrium state with a large number of defects still existed in models after a long relaxing time.

Effect of a Nonstationary Electric Current on the Oxide Melt–Gas Phase System

The influence of a nonstationary electric current on an oxide melt is studied. A nonstationary energy action is found to change the microstructure of a liquid system and to promote unlikely chemical reactions between an oxide melt and gas components. The division of the gas-phase components into oxidizing and reducing gases becomes rather conventional. It is found that stable application of an electric current can bring the system to a quasi-equilibrium state, which can retard the development of a chemical reaction, and the chemical reaction during the process can generate an electric current.

Diagnose the Earth

The earth is sick and the present work explains how it gets ill and how serious the decease is. It is shown that the illness originates in over dense population since present population is 7.6 billion while 1.3 billion is the breakeven point of the earth for CO2 metabolism and 6.7 billion is the upper limit to maintain a quasi-equilibrium state for the metabolism. More and more greenhouse gases emit into atmosphere from underground and undersea, and warming up process is accelerated. Utilization of clean energy cannot save the earth, but to pray a little ice age coming soon. What humanity can and should do is to use zero-emitted coal power and change the fertility rate to negative.

Non-Equilibrium Evaporation/Condensation Model

A new mathematical model for non-equilibrium evaporation/condensation including boiling effect is proposed. A simplified differential-algebraic system of equations is obtained. A code to solve numerically this differential-algebraic system has been developed. It is designed to solve both systems of equations with and without the boiling effect. Numerical calculations of ammonia–water systems with various initial conditions, which correspond to evaporation and/or condensation of both components, have been performed. It is shown that, although the system evolves quickly towards a quasi-equilibrium state, it is necessary to use a non-equilibrium evaporation model to calculate accurately the evaporation/condensation rates, and consequently all the other dependent variables.