			Home About us Contact

Ionic Fluxes (ionic + flux)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Mathematical modeling for the ionic inclusion process inside conducting polymer-based thin-films

POLYMER ENGINEERING & SCIENCE, Issue 11 2008
Saptarshi Majumdar
Ionic inclusion inside thin conducting polymer (CP) film is a major and common feature for actuator as well as membrane-based drug release. In this study, an electro-active polymeric thin-film system has been conceptualized. PNP-electro-neutrality (Poisson,Nernst, Planck) based modeling framework with customized boundary conditions is used to depict the electrochemical phenomena. In dynamic model, kinetics of probable redox reactions is included along with electro-migration and diffusion terms in the overall PNP framework. At steady state, interfacial voltage seems to hold the critically important role, while ionic migration and reaction kinetics play very crucial roles in determining the dynamics of such systems. The validated model predicts that lowering in the standard potential of the polymeric electrode accelerates the process of ionic ingress. Higher ionic flux is obtained using slower voltage scan. Variation of diffusivity shows the large spectrum of relatively unexplored dynamics for such electro-active thin-film-based system. The significance is in designing actuator- or membrane-based controlled molecular release systems. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source]

Mechanistic hypotheses for nonsynaptic epileptiform activity induction and its transition from the interictal to ictal state,Computational simulation

EPILEPSIA, Issue 11 2008
Antônio-Carlos G. De Almeida
Summary Purpose:, The aim of this work is to study, by means of computational simulations, the induction and sustaining of nonsynaptic epileptiform activity. Methods:, The computational model consists of a network of cellular bodies of neurons and glial cells connected to a three-dimensional (3D) network of juxtaposed extracellular compartments. The extracellular electrodiffusion calculation was used to simulate the extracellular potential. Each cellular body was represented in terms of the transmembrane ionic transports (Na+/K+ pumps, ionic channels, and cotransport mechanisms), the intercellular electrodiffusion through gap-junctions, and the neuronal interaction by electric field and the variation of cellular volume. Results:, The computational model allows simulating the nonsynaptic epileptiform activity and the extracellular potential captured the main feature of the experimental measurements. The simulations of the concomitant ionic fluxes and concentrations can be used to propose the basic mechanisms involved in the induction and sustaining of the activities. Discussion:, The simulations suggest: The bursting induction is mediated by the Cl, Nernst potential overcoming the transmembrane potential in response to the extracellular [K+] increase. The burst onset is characterized by a critical point defined by the instant when the Na+ influx through its permeable ionic channels overcomes the Na+/K+ pump electrogenic current. The burst finalization is defined by another critical point, when the electrogenic current of the Na+/K+ pump overcomes its influx through the channels. [source]

Ionic/Electronic Hybrid Materials Integrated in a Synaptic Transistor with Signal Processing and Learning Functions

ADVANCED MATERIALS, Issue 22 2010
Qianxi Lai
A synaptic transistor is fabricated by integrating ionic/electronic hybrid materials to emulate biological synapses with spike signal processing, learning, and memory functions. A potential spike generates transient ionic fluxes in a polymer layer in the transistor gate, triggering an excitatory postsynaptic current in the transistor drain. Temporally correlated pre- and post-synaptic spikes modify ions stored in the polymer, resulting in the nonvolatile modification of the transistor with spike-timing-dependent plasticity. [source]

The Effects of Surface Waviness and Length on Electrokinetic Transport in Wavy Capillary

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2006
Noor Quddus
Abstract An electrokinetic model for a wavy capillary has been developed. Poisson-Nernst-Planck and Navier-Stokes equations constitute the model that governs fluid and ionic fluxes and electric potential distribution inside the capillary. In the present paper, a finite wavy cylindrical capillary with a large reservoir at both capillary ends is analyzed using finite element method. The model is used primarily to examine the influence of capillary surface waviness on the electrokinetic transport behaviours. Different frequencies and amplitudes of the wavy surface are considered to investigate the influence of surface waviness on electrokinetic transport. Fluctuations in potential and ionic concentration distribution increase with the increase in either amplitude or frequency of the capillary surface waviness. However, for higher frequencies the fluctuation diminishes for all surface waviness amplitudes. It is observed that for any irregularity in the capillary surface results in higher salt rejection. Salt rejection is found to be dependent on capillary axial length as well as flow velocity. A critical Peclet number, beyond which salt rejection attains a constant steady value, dictates maximum salt rejection. On a mis au point un modèle électrocinétique pour un capillaire onduleux. Les équations de Poisson-Nernst-Planck et de Navier-Stokes constituent le modèle qui gouverne le fluide et les flux ioniques ainsi que la distribution de potentiel électrique dans le capillaire. Dans le présent article, on analyse par la méthode des éléments finis un capillaire cylindrique onduleux fini possédant un grand réservoir aux deux extrémités du capillaire. Le modèle sert principalement à examiner l'influence de l'ondulation de la surface capillaire sur les comportements de transport électrocinétiques. On prend en compte différentes fréquences et amplitudes de la surface onduleuse pour étudier l'influence de l'ondulation de surface sur le transport électrocinétique. Les fluctuations dans la distribution de concentration potentielle et ionique augmentent l'amplitude ou la fréquence d'ondulation de surface capillaire. Toutefois, pour des fréquences plus élevées, la fluctuation diminue pour toutes les amplitudes d'ondulation de surface. On a observé que toute irrégularité dans la surface capillaire entraîne un plus grand rejet de sel. On a trouvé que le rejet de sel était dépendant de la longueur axiale de capillaire ainsi que de la vitesse d'écoulement. Un nombre de Peclet critique, au-delà duquel le rejet de sel atteint une valeur stable constante, dicte le rejet de sel maximum. [source]