Auto-model based computer simulation of Plateau-Rayleigh instability of mixtures of immiscible liquids

The classic theory to derive the characteristic Rayleigh wavelength, i.e., the distance between neighbouring droplets into which an originally cylindrical liquid body disintegrates, as a consequence of Rayleigh instability, is analysed in terms of the phenomenon of self-organization due to the mechanism of ‘fastest forming instability’. The paper aims at simulating this self-organization with Monte Carlo dynamics while accounting spatial interactions in lattices of Markov Random Fields that enable also modelling of Plateau-Rayleigh instability of instable mixtures of dispersed immiscible liquids. The Hammersley and Clifford theorem, concerning the general form of energy function, belonging to Markov Random Fields, is introduced for detailed classification of a simple model used for computer simulation. The relevant Auto-model, with Kawasaki dynamics, is chosen to investigate the liquid jet and the instability of the liquid’s cylindrical film. The computer-simulated outputs show encouraging agreement with the classic analytical predictions on main features of the Rayleigh instability. The model is also used as a foundation stone for developing a simple analytical approach for the estimation of Rayleigh wavelength of jets and cylindrical films, composed of instable mixtures of immiscible liquids. Qualitatively, the theory agrees with both computer simulation and experiment.     

Avoided level crossing μSR of organic free radicals

Several aspects of the ALC-μSR technique of muonated organic free radicals in liquids, including the effects of chemical dynamics and T₁-processes are discussed.     

Ion sweeping in conducting dielectric materials

Conductivity-related low-frequency dielectric losses frequently obscure loss peaks arising from dipole relaxations in dielectric materials. The application of moderately large electrical fields to ion containing liquids and solids in combination with temperature cycling enables one to reduce the contribution of conductivity to dielectric loss spectra significantly. Details of this electrical cleaning method are given. Its application is demonstrated and discussed for a diverse array of materials ranging from polymeric and small-molecule supercooled liquids to hydrated proteins and ice-like crystals. The suppression of conductivity-related losses allows one to gain insights into the low-frequency dynamics of such materials. The mobility of the ionic impurities at the base temperature and at the ‘cleaning’ temperature are briefly discussed.     

Mode-coupling theory of the glass transition for colloidal liquids in slit geometry

ABSTRACT

We provide a detailed derivation of the mode-coupling equations for a colloidal liquid confined by two parallel smooth walls. We introduce irreducible memory kernels for the different relaxation channels thereby extending the projection operator technique to colloidal liquids in slit geometry. Investigating both the collective dynamics as well as the tagged-particle motion, we prove that the mode-coupling functional assumes the same form as in the Newtonian case corroborating the universality of the glass-transition singularity with respect to the microscopic dynamics.     

Translational light scattering in simple liquids

Summary A short review of translational light scattering of simple liquids is reported. The microscopic cross-section is compared with the equivalent expression for neutron scattering experiments (Van Hove, 1954). A survey of the fundamental experiments is reported and the possible application to the study of the dynamics of simple dense systems is analysed. The relevant approximations are critically discussed and the limits of the technique are established. The review mainly deals with classical or almost classical liquids, but also some extensions to quantum systems are considered. paper presented at the workshop ?Highlights on Simple Liquids?, held in Turin at ISI on 1–3 May 1989.     

Confined viscous liquids: Interfacial <Emphasis Type="Italic">versus</Emphasis> finite size effects

Confining a supercooled liquid to spaces of several nanometer in diameter can lead to dramatic changes in the relaxation dynamics of the material. In many cases, the effect is reported as a confinement induced shift of the glass transition temperature T_g. Both positive and negative values for ΔT _g have been observed and the length scale of the confining geometry is considered the main variable. We review the dynamics of glass-forming liquids in both hard and soft confinement of <10 nm spaces, with focus on results from solvation dynamics experiments. It is shown that the interface is instrumental in determinig the dynamics, giving rise to reaxation time gradients across the cooperativity length scale of the liquid. Depending on the interfacial conditions, dynamics can become faster or slower for the same liquid, same size of confinement, and identical experimental technique used. No indications of true finite size effects are observed, and the pore or droplet size is relevant only indirectly through the relative number of molecules near the surface.     

Chaos and its implications

Starting with the very definition of chaos, we demonstrate that the study of chaos is not an abstract one but can lead to some useful practical applications. With the advent of some powerful mathematical techniques and with the availability of fast computers, it is now possible to study the fascinating phenomena of chaos — the subject which is truly interdisciplinary. The essential role played by fractals, strange attractors, Poincare maps, etc., in the study of chaotic dynamics, is briefly discussed. Phenomena of self-organization, coherence in chaos and control of chaos in plasmas is highlighted.     

On the dynamics of polymers in dense systems – Results of neutron spin echo spectroscopy

One of the basic problems in the dynamics of polymers concerns the importance of geometrical or topological interactions which are directly related to the large scale molecular structures. In the famous reptation model these constraints are pictured in terms of a tube of localization following the average chain profile and confining the chain motion to the curve‐linear tube. Recently studying the dynamic structure factor of a single labeled chain in a polymer melt by means of neutron spin echo spectroscopy (NSE) led to a direct observation of these tube constraints. Here I shall summarize these neutron spin echo experiments. I shall address the NSE technique, present results on the entropy driven segmental chain dynamics, discuss the dynamics of single chains in the melt where the chain length is increased through the transition to “reptation” dynamics and display NSE measurements on long chain systems which revealed the molecular existence of the entanglement distance. Their magnitudes agree very well with tube diameters derived from dynamical mechanical measurements on the basis of the reptation model proving thereby the basic assumption of this Nobel Price winning concept. This revised version was published online in August 2006 with corrections to the Cover Date.     

Self-organization and supramolecular chemistry of protein films from the nano-to the macroscale

Experimental data obtained with optical, polarization, scanning electron, and confocal laser microscopes reveal a previously unknown supramolecular modification of protein self-organization (“protos”). This modification arises upon condensation in the open nonequilibrium water-protein system. The process gives rise to the liquid crystal phase of nanostructured eddylike protos films epitaxially growing on the nano-and macrolevels. The model of protein spontaneous self-organization allows one to visualize and study the nonlinear dynamics of condensation and self-organization of protein films with a supramolecular configuration on the nano-and macroscale under abiotic and biotic conditions. This model may help in creating an atlas for protein identification, as well as for diagnostics of pathogenic processes in the living organism that disturb protein self-organization.     

Universal behavior of shear viscosity near the freezing point

The dynamics of liquids above the freezing point is studied. It is demonstrated that the available experimental data on shear viscosity of simple liquids can be described in the framework of the so-called weak crystallization theory. The theory predicts that, in the main approximation, shear viscosity is proportional to the (T/T _*−1)^−3/2, where T _* is the temperature close to the freezing temperature. This prediction is in good agreement with experimental data for many substances.     

Universal behavior of shear viscosity near the freezing point

The dynamics of liquids above the freezing point is studied. It is demonstrated that the available experimental data on shear viscosity of simple liquids can be described in the framework of the so-called weak crystallization theory. The theory predicts that, in the main approximation, shear viscosity is proportional to the (T/T _*−1)^−3/2, where T _* is the temperature close to the freezing temperature. This prediction is in good agreement with experimental data for many substances. The text was submitted by the author in English.     

Pressure-induced change in the relaxation dynamics of glycerol

Glycerol is one of the best studied and most widely used glass-forming liquids; however, its dynamic properties are still under discussion. The dielectric spectra of glycerol are studied in detail over wide ranges of temperatures and pressures up to 4.5 GPa. Starting from the pressures of 2–3 GPa, qualitative change in the dynamics of structural relaxation processes in glycerol has been revealed. It is accompanied by the appearance of secondary relaxation and a change in the asymptotic behavior of the pressure dependence of the fragility. The relation between the parameters for different relaxation mechanisms is analyzed.     

Self-organization of the critical state in a two-dimensional multijunction SQUID under closed boundary conditions

A model of a closed system with self-organization is presented. This is a simplified model of a multijunction SQUID in an ac magnetic field. In our closed system, a self-organized critical state is realized on account of the fact that current dumping, which gives rise to self-organization in open systems, is replaced here by a fundamentally different mechanism — annihilation of the currents. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 2, 119–125 (25 January 1999)     

Belowground feedbacks as drivers of spatial self-organization and community assembly

Vegetation patterning in water-limited and other resource-limited ecosystems highlights spatial self-organization processes as potentially key drivers of community assembly. These processes provide insight into predictable landscape-level relationships between organisms and their abiotic environment in the form of regular and irregular patterns of biota and resources. However, two aspects have largely been overlooked; the roles played by plant – soil-biota feedbacks and allelopathy in spatial self-organization, and their potential contribution, along with plant-resource feedbacks, to community assembly through spatial self-organization. Here, we expand the drivers of spatial self-organization from a focus on plant-resource feedbacks to include plant – soil-biota feedbacks and allelopathy, and integrate concepts of nonlinear physics and community ecology to generate a new hypothesis. According to this hypothesis, below-ground processes can affect community assemblages through two types of spatial self-organization, global and local. The former occurs simultaneously across whole ecosystems, leading to self-organized patterns of biota, allelochemicals and resources, and niche partitioning. The latter occurs locally in ecotones, and determines ecotone structure and motion, invasion dynamics, and species coexistence. Studies of the two forms of spatial self-organization are important for understanding the organization of plant communities in drier climates which are likely to involve spatial patterning or re-patterning. Such studies are also important for developing new practices of ecosystem management, based on local manipulations at ecotones, to slow invasion dynamics or induce transitions from transitive to intransitive networks of interspecific interactions which increase species diversity.     

Aspects of the self-organization of carbonaceous conducting nanostructures during electroforming of a metal-insulator-metal open sandwich structure with a nanometer-size insulating gap

Experimental results are presented on the electroforming of a nanometer-size MIM (metal-insulator-metal) diode with a carbonaceous active medium. The diode is in the form of an MIM sandwich structure which is open on one face and has a nanometer-size insulating gap. Measurements of its current-voltage characteristics are made which reflect processes of self-organization and self-forming of carbonaceous conducting nanostructures in the insulating gap. It is shown that the properties of such a circuit element differ greatly from those of a conventional MIM diode. These differences can be explained if it is taken into account that a thin insulating layer is built in, in series with the carbonaceous conducting medium growing in the insulating gap. The data obtained indicate that the carbonaceous structure is of nanometer size in all three spatial dimensions. The models that have been developed to represent this structure correspond well with the experimental results, in particular the spatiotemporal self-organization in this system. Zh. Tekh. Fiz. 68, 85–93 (November 1998)     

Simulations of the flipping images and microparameters of molecular orientations in liquids according to the molecule string model

The relaxation dynamics of liquids is one of the fundamental problems in liquid physics,and it is also one of the key issues to understand the glass transition mechanism.It will undoubtedly provide enlightenment on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied.In this paper,we first give five microparameters to describe the individual molecular string(MS) relaxation based on the dynamical Hamiltonian of the MS model,and then simulate the images of individual MS ensemble,and at the same time calculate the parameters of the equilibrium state.The results show that the main molecular orientation flipping image in liquids(including supercooled liquid) is similar to the random walk.In addition,two pairs of the parameters are equal,and one can be ignored compared with the other.This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of the general Glauber type,and the computer simulation time of interaction MS relaxation.Moreover,the conclusion is of reference significance for solving and simulating the multi-state MS model.     

Contrast-enhanced photothermal imaging for the evaluation of thermal transport parameters of liquids

In this article, we discuss the application of a baseline-suppressed, contrast-enhanced laser photothermal imager as a sensitive effusivity sensor for liquids, for the first time. We analyze the sources of errors associated with a conventional phase-comparison technique for evaluating the thermal transport parameters of liquids as a function of the pump power. Weak signal at lower powers and convection currents at higher powers are found to be the principal agencies deteriorating the sensitivity. Enhanced sensitivity has been achieved by using lower pump power and a signal baseline-suppressing common-mode-rejection-demodulation technique. The strength of thermoelastic vibration is small due to the low linear thermal expansion coefficient of the silicon nitride plate, which is the optical absorber. The approach has been extended for analyzing the effusivity modification of a water–methanol mixture as a function of methanol volume. The method is capable of detecting less than 1% change in effusivity for the mixture, which is 300–400% enhancement compared to the capability of conventional phase comparison. PACS 78.20.Nv; 81.70.Cv     

核子与核力决定的核形状(英文)

讨论了最近提出的作为量子多体系统重要潜在机制之一的量子自组织,原子核无疑是最好的实例。由于原子核内核子的单粒子和集体运动共存,它们的相互制约决定了核结构。集体模式因其驱动力,如使椭球形变的四极力及其阻力达到平衡形成,而单粒子能量就是产生阻力的一种根源。当存在较大单粒子能隙时,相关的集体运动更易受到阻碍。因此,一般认为,单粒子运动和集体运动是相互对抗的"天敌"。然而,由于核力的多样和复杂性,单极相互作用使单粒子能量改变也能减小其对集体运动的阻碍而加强集体模式,该现象将通过Zr同位素实例加以说明。这就导致了量子自组织的产生:单粒子能量由两种量子液体（质子和中子）和控制阻力的单极相互作用自组织。于是,不同于朗道费米液体理论的结论,原子核不一定像填装了自由核子的刚性瓶。Ⅱ型壳演化即是包含跨准幻壳能隙激发的直观实例。在重核中,量子自组织因其轨道和核子数更多而更为重要。We discuss the quantum self-organization introduced recently as one of the major underlying mechanisms of the quantum many-body systems. Atomic nuclei are actually a good example, because two types of the motion of nucleons, single-particle states and collective modes, interplay in determining their structure. The collective mode appears as a consequence of the balance between the effect of the mode-driving force (e.g., quadrupole force for the ellipsoidal deformation) and the resistance power against it. The single-particle energies are one of the sources to bring about such resistance power:a coherent collective motion is more hindered by larger spacings between relevant single particle states. Thus, the single-particle state and the collective mode are "enemies" against each other in the usual understanding. However, the nuclear forces are rich and complicated enough so as to enhance relevant collective mode by reducing the resistance power by changing single-particle energies for each eigenstate through monopole interactions. This will be demonstrated with the concrete example taken from Zr isotopes. In this way, the quantum self-organization occurs:single-particle energies can be self-organized by (i) two quantum liquids, e.g., protons and neutrons, (ii) monopole interaction (to control resistance). Thus, atomic nuclei are not necessarily like simple rigid vases containing almost free nucleons, in contrast to the naïve Fermi liquid picture a la Landau. Type Ⅱ shell evolution is considered to be a simple visible case involving excitations across a (sub)magic gap. The quantum self-organization becomes more important in heavier nuclei where the number of active orbits and the number of active nucleons are larger.     

Simulations of the flipping images and microparameters of molecular orientations in liquids according to molecule string model

The relaxation dynamics of liquids is one of the fundamental problems in liquid physics, and it is also one of the key issues to understand the glass transition mechanism. It will undoubtedly give enlightenments on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied. In this paper, we first give five microparameters to describe the individual molecular string (MS) relaxation based on the dynamical Hamiltonian of the MS model, and then simulate the images of individual MS ensemble, at the same time calculate the parameters of the equilibrium state. The results show that the main molecular orientation flipping image in liquids (including supercooled liquid) is similar to the random walk. In addition, two pairs of the parameters are equal, and one can be ignored compared with the other. This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of general Glauber type, and the computer simulation time of interaction MS relaxation. Moreover, the conclusion has no doubt of the reference significance for solving and simulating the multi-state MS model.     

Physicsʼ insights into pedestrian motion and crowd dynamics: Reply to comments on “The emergence of design in pedestrian dynamic: Locomotion,self-organization,walking paths and constructal law”

Pedestrians? world is not a static one, but rather one which is constantly in flux. The pedestrian dynamics is subject to a wide range of influences and displays an interesting phenomenology. Along with collective self-organization phenomena (e.g., streams of people, rivers of people, collective synchronization), there are also a multitude of applications in the context of crowd management, design of pedestrian facilities and urban planning. Here, I address comments from the discussants of my review paper from the viewpoint of elementary physics laws paying particular attention to the self-organization phenomena in crowds.