Searcharxiv⌕ Search

arXiv subjects

Arik Yochelis

Publications and source records attributed to Arik Yochelis.

34 records · Page 2Linked to original sources
arXiv2018

Molding the asymmetry of localized frequency-locking waves by a generalized forcing and implications to the inner ear

Frequency locking to an external forcing frequency is a {well} known phenomenon. In the auditory system, it results in a localized traveling wave, the shape of which is essential for efficient discrimination between incoming frequencies. An amplitude equation approach is used to show that the shape of the localized traveling wave depends crucially on the relative strength of additive vs. parametric forcing components; the stronger the parametric forcing the more asymmetric the response profile and the sharper the traveling-wave front. The analysis captures the empirically observed regions of linear and nonlinear responses and highlights the significance of parametric forcing mechanisms in shaping the resonant response in the inner ear.

nlin.PS↗
arXiv2018

Catalytic membrane reactor model as a laboratory for pattern emergence in reaction-diffusion-advection media

Reaction-diffusion-advection media on semi-infinite domains are important in chemical, biological and ecological applications, yet remain a challenge for pattern formation theory. To demonstrate the rich emergence of nonlinear traveling waves and stationary periodic states, we review results obtained using a membrane reactor as a case model. Such solutions coexist in overlapping parameter regimes and their temporal stability is determined by the boundary conditions (periodic vs. mixed) which either preserve or destroy the translational symmetry, i.e., selection mechanisms under realistic Danckwerts boundary conditions. A brief outlook is given at the end.

nlin.PS↗
arXiv2017

From solvent free to dilute electrolytes: Essential components for a continuum theory

The increasing number of experimental observations on highly concentrated electrolytes and ionic liquids show qualitative features that are distinct from dilute or moderately concentrated electrolytes, such as self-assembly, multiple-time relaxation, and under-screening, which all impact the emergence of fluid/solid interfaces, and transport in these systems. Since these phenomena are not captured by existing mean field models of electrolytes, there is a paramount need for a continuum framework for highly concentrated electrolytes and ionic liquids. In this work, we present a self-consistent spatiotemporal framework for a ternary composition that comprises ions and solvent employing free energy that consists of short and long range interactions, together with a dissipation mechanism via Onsagers' relations. We show that the model can describe multiple bulk and interfacial morphologies at steady-state. Thus, the dynamic processes in the emergence of distinct morphologies become equally as important as the interactions that are specified in the equilibrium-free energy. The model equations not only provide insights to transport mechanisms beyond the Stokes-Einstein-Smoluchowski relations but also enables to qualitative recovery in the full range (three distinct regions) of non-monotonic electrical screening length that has been recently observed in experiments using organic solvent to dilute ionic liquids.

physics.chem-ph↗
arXiv2017

Comb-like Turing patterns embedded in Hopf oscillations: Spatially localized states outside the 2:1 frequency locked region

A generic distinct mechanism for the emergence of spatially localized states embedded in an oscillatory background is demonstrated by using 2:1 frequency locking oscillatory system. The localization is of Turing type and appears in two space dimensions as a comb-like state in either $π$ phase shifted Hopf oscillations or inside a spiral core. Specifically, the localized states appear in absence of the well known flip-flop dynamics (associated with collapsed homoclinic snaking) that is known to arise in the vicinity of Hopf-Turing bifurcation in one space dimension. Derivation and analysis of three Hopf-Turing amplitude equations in two space dimensions reveals a local dynamics pinning mechanism for Hopf fronts, which in turn allows the emergence of perpendicular (to the Hopf front) Turing states. The results are shown to agree well with the comb-like core size that forms inside spiral waves. In the context of 2:1 resonance, these localized states form outside the 2:1 resonance region and thus extend the frequency locking domain for spatially extended media, such as periodically driven Belousov-Zhabotinsky chemical reactions. Implications to chlorite-iodide-malonic-acid and shaken granular media are also addressed.

nlin.PS↗
arXiv2017

Mean field approach to first and second order phase transitions in ionic liquids

Ionic liquids are solvent-free electrolytes, some of which possess an intriguing self-assembly property. Using a mean-field framework (based on Onsager's relations) we show that bulk nano-structures arise via type-I and II phase transitions (PT), which directly affect the electrical double layer (EDL) structure. Ginzburg-Landau equation is derived and PT are related to temperature, potential and interactions. The type-I PT occurs for geometrically dissimilar anion/cation ratio and, surprisingly, is induced by perturbations on order of thermal fluctuations. Finally, we compare the insights with the decaying charge layers within the EDL, as widely observed in experiments.

cond-mat.soft↗
arXiv2016

Frequency locking in auditory hair cells: Distinguishing between additive and parametric forcing

The auditory system displays remarkable sensitivity and frequency discrimination, attributes shown to rely on an amplification process that involves a mechanical as well as a biochemical response. Models that display proximity to an oscillatory onset (a.k.a. Hopf bifurcation) exhibit a resonant response to distinct frequencies of incoming sound, and can explain many features of the amplification phenomenology. To understand the dynamics of this resonance, frequency locking is examined in a system near the Hopf bifurcation and subject to two types of driving forces: additive and parametric. Derivation of a universal amplitude equation that contains both forcing terms enables a study of their relative impact on the hair cell response. In the parametric case, although the resonant solutions are 1:1 frequency locked, they show the coexistence of solutions obeying a phase shift of $π$, a feature typical of the 2:1 resonance. Different characteristics are predicted for the transition from unlocked to locked solutions, leading to smooth or abrupt dynamics in response to different types of forcing. The theoretical framework provides a more realistic model of the auditory system, which incorporates a direct modulation of the internal control parameter by an applied drive. The results presented here can be generalized to many other media, including Faraday waves, chemical reactions, and nonlinear optics, which are known to exhibit resonant behavior.

nlin.PS↗
arXiv2016

Spatially localized self-assembly driven by electrically charged phase separation

Self-assembly driven by phase separation coupled to Coulombic interactions is fundamental to a wide range of applications, examples of which include soft matter lithography via di-block copolymers, membrane design using polyelectrolytes, and renewable energy applications based on complex nano-materials, such as ionic liquids. The most common mean field framework for these problems is the non-local Cahn-Hilliard (a.k.a. Ohta-Kawasaki) framework. In this work, we study the emergence of spatially localized states in both the classical and the extended Ohta-Kawasaki model. The latter also accounts for: (i) asymmetries in long-range Coulomb interactions that are manifested by differences in the dielectric response, and (ii) asymmetric short-range interactions that correspond to differences in the chemical potential between two materials phases. It is shown that in one space dimension (1D) there is a multiplicity of coexisting localized solutions, which organize in the homoclinic snaking structure, bearing similarity to dissipative systems. In addition, an analysis of 2D extension is performed and distinct instability mechanisms (related to extended and localized modes) of localized stripes are discussed with respect to model parameters and domain size. Finally, implications to localized hexagonal patterns are also made. The insights provide an efficient mechanistic framework to design and control localized self-assembly that might be a plausible strategy for low cost of nano electronic applications, i.e., a rather simple nano scale fabrication of isolated morphologies.

math.AP↗
arXiv2015

Theory of phase separation and polarization for dissociated ionic liquids

Room temperature ionic liquids are attractive to numerous applications and particularly, to renewable energy devices. As solvent free electrolytes, they demonstrate a paramount connection between the material morphology and Coulombic interactions: unlike dilute electrolytes, the electrode/RTIL interface is a product of both electrode polarization and spatiotemporal bulk properties. Yet, theoretical studies have dealt almost exclusively with independent models of morphology and electrokinetics. In this work, we develop a novel Cahn-Hilliard-Poisson type mean-field framework that couples morphological evolution with electrokinetic phenomena. Linear analysis of the model shows that spatially periodic patterns form via a finite wavenumber instability, a property that cannot arise in the currently used Fermi-Poisson-Nernst-Planck equations. Numerical simulations in above one-space dimension, demonstrate that while labyrinthine type patterns develop in the bulk, stripe patterns emerge near charged surfaces. The results qualitatively agree with empirical observations and thus, provide a physically consistent methodology to incorporate phase separation properties into an electrochemical framework.

physics.chem-ph↗
arXiv2009

Principal bifurcations and symmetries in the emergence of reaction-diffusion-advection patterns on finite domains

Pattern formation mechanisms of a reaction-diffusion-advection system, with one diffusivity, differential advection, and (Robin) boundary conditions of Danckwerts type, are being studied. Pattern selection requires mapping the domains of coexistence and stability of propagating or stationary nonuniform solutions, which for the general case of far from instability onsets, is conducted using spatial dynamics and numerical continuations. The selection is determined by the boundary conditions which either preserve or destroy the translational symmetry of the model. Accordingly, we explain the criterion and the properties of stationary periodic states if the system is bounded and show that propagation of nonlinear waves (including solitary) against the advective flow corresponds to coexisting family that emerges nonlinearly from a distinct oscillatory Hopf instability. Consequently, the resulting pattern selection is qualitatively different from the symmetric finite wavenumber Turing or Hopf instabilities.

nlin.PS↗
arXiv2009

Drifting solitary waves in a reaction-diffusion medium with differential advection

Propagation of solitary waves in the presence of autocatalysis, diffusion, and symmetry breaking (differential) advection, is being studied. The focus is on drifting (propagating with advection) pulses that form via a convective instability at lower reaction rates of the autocatalytic activator, i.e. the advective flow overcomes the fast excitation and induces a drifting fluid type behavior. Using spatial dynamics analysis of a minimal case model, we present the properties and the organization of such pulses. The insights underly a general understanding of localized transport in simple reaction-diffusion-advection models and thus provide a background to potential chemical and biological applications.

nlin.PS↗
arXiv2008

Generation of finite wave trains in excitable media

Spatiotemporal control of excitable media is of paramount importance in the development of new applications, ranging from biology to physics. To this end we identify and describe a qualitative property of excitable media that enables us to generate a sequence of traveling pulses of any desired length, using a one-time initial stimulus. The wave trains are produced by a transient pacemaker generated by a one-time suitably tailored spatially localized finite amplitude stimulus, and belong to a family of fast pulse trains. A second family, of slow pulse trains, is also present. The latter are created through a clumping instability of a traveling wave state (in an excitable regime) and are inaccessible to single localized stimuli of the type we use. The results indicate that the presence of a large multiplicity of stable, accessible, multi-pulse states is a general property of simple models of excitable media.

nlin.PS↗
arXiv2008

Front motion and localized states in an asymmetric bistable activator-inhibitor system with saturation

We study the spatiotemporal properties of coherent states (peaks, holes, and fronts) in a bistable activator-inhibitor system that exhibits biochemical saturated autocatalysis, and in which fronts do not preserve spatial parity symmetry. Using the Gierer-Meinhardt prototype model, we find the conditions in which two distinct pinning regions are formed. The first pinning type is known in the context of variational systems while the second is structurally different due to the presence of a heteroclinic bifurcation between two uniform states. The bifurcation also separates the parameter regions of counterpropagating fronts, leading in turn to the growth or contraction of activator domains. These phenomena expand the range of pattern formation theory and its biomedical applications: activator domain retraction suggests potential therapeutic strategies for patterned pathologies, such as cardiovascular calcification.

nlin.PS↗
arXiv2005

Droplet motion driven by surface freezing or melting: A mesoscopic hydrodynamic approach

A fluid droplet may exhibit self-propelled motion by modifying the wetting properties of the substrate. We propose a novel model for droplet propagation upon a terraced landscape of ordered layers formed as a result of surface freezing driven by the contact angle dependence on the terrace thickness. Simultaneous melting or freezing of the terrace edge results in a joint droplet-terrace motion. The model is tested numerically and compared to experimental observations on long-chain alkane system in the vicinity of the surface melting point.

physics.flu-dyn↗
arXiv2005

Thin films of van der Waals fluid: From interface interactions to wetting transitions

We present a theoretical study of wetting phenomena and interactions between liquid-vapor interfaces based on the density functional theory. The focus is mostly on the impact of long-range van der Waals interactions both within the fluid and between the fluid and substrate. For the latter, we consider two models-hard wall and soft wall approximations-differing by the role of steric effects and leading to a qualitatively different character of phase transitions. We compute numerically the disjoining and conjoining potentials (which are important dynamically for spreading, spinodal dewetting, and coarsening in thin films, as well as resolution of interfacial singularities), and loci of intermediate and complete wetting transitions as functions of the Hamaker constant and temperature. We find that taking into account short-range interactions is essential for the description of wetting transitions in the soft wall limit. We derive an analytical form of the disjoining potential and analyze it in the context of the complete, frustrated and partial wetting.

physics.chem-ph↗