[Todos] Fwd: CHARLA IFLYSIB: Martes 14/5, 11.00hs - 'Anomalous diffusion, fractional diffusion equation, and electrical impedance response of complex fluids' & 'A simple model of ac hopping surface conductivity in ionic liquids'

Jue Mayo 9 11:17:02 -03 2019

-------- Mensaje original -------- 

 		ASUNTO:
 		CHARLA IFLYSIB: Martes 14/5, 11.00hs - 'Anomalous diffusion,
fractional diffusion equation, and electrical impedance response of
complex fluids' & 'A simple model of ac hopping surface conductivity in
ionic liquids'

 		FECHA:
 		2019-05-09 11:06

 		REMITENTE:
 		Charlas Iflysib <charlas.iflysib en gmail.com>

 		DESTINATARIO:
 		Charlas Iflysib <charlas-iflysib en googlegroups.com>,
academic en fcaglp.unlp.edu.ar, fcnym en museo.fcnym.unlp.edu.ar,
info en ciop.unlp.edu.ar, internet en biol.unlp.edu.ar, scyt en frlp.utn.edu.ar,
secre2 en fisica.unlp.edu.ar, secre en biol.unlp.edu.ar,
secre en mate.unlp.edu.ar, secretaria en inifta.unlp.edu.ar

LOS ESPERAMOS CON CAFÉ 15 MINUTOS ANTES DE LA CHARLA EN EL LOBBY DEL
INSTITUTO.

Charla doble del IFLYSIB (las charlas serán más breves de lo habitual)

MARTES 14/5, 11:00HS. 
LUGAR: IFLYSIB (59 #789, LA PLATA) 

TÍTULO:   _ANOMALOUS DIFFUSION, FRACTIONAL DIFFUSION EQUATION, AND
ELECTRICAL IMPEDANCE RESPONSE OF COMPLEX FLUIDS_

EXPOSITOR:  _LUIZ ROBERTO EVANGELISTA_
Departamento de Fı́sica, Universidade Estadual de Maringá. Maringá,
Paraná, Brazil.

RESUMEN: 
Anomalous diffusion problems constitute a fast growing field of research
in several areas of physics, biology, ecology, geophysics, and many
others [1]. The fact that the time dependence of the mean squared
displacement is nonlinear, i.e., <(z - <z>)²> ∝ tγ, with γ≠1, is a
noteworthy characteristic of an anomalous diffusion. This non-Brownian
behaviour can be found in a wide variety of scenarios [2,3], and is
usually related to the non-Markovian characteristics of the systems such
as memory effects, fractality, and interactions. To face the high
complexity of the behaviours of these systems, several formalisms have
been considered, among which are of particular importance the extensions
of the diffusion equation such as the fractional diffusion equations
[4-7]. In this talk, we discuss a series of mathematical problems
connected with the solution of fractional diffusion equation and
fractional diffusion equation of distributed order for the mobile ions
coupled to the Poisson's equation for the electrical potential in the
bulk, subjected to boundary conditions that are stated by means of very
general expressions. These expressions constitute boundary conditions
that embody, in particular, the usual kinetic equation for describing
the adsorption-desorption process at the electrodes, but can be also
expressed in terms of a temporal kernel that can be judiciously chosen
to cover scenarios which are not suitably described within the usual
framework of blocking electrodes. The predictions of a few of these
models have been recently compared with experimental data relevant to
typical liquid-crystalline samples [3] providing evidence that the
diffusion process of the ions in these electrolytic cells is anomalous
and the mechanisms of these processes may be connected to the surface
effects that induce an anomalous process on the bulk [8]. Some general
perspectives of applications of the general theoretical framework
presented in this talk are revisited, pointing towards new directions of
the research with fractional calculus in physical, chemical, and
biological contexts. 

References:
[1] A. Pekalsi and K. Znajd-Weron (eds), Anomalous Diffusion: From
Basics to Apllications, Lecture Notes in Physics, (Springer, Berlin,
1999).
[2] P. A. Santoro, J. L. de Paula. E. K. Lenzi, and L. R. Evangelista,
Anomalous diffusion governed by a fractional diffusion equation and the
electrical response of an electrolytic cell, J. Chem. Phys. 135, 114704
(2011).
[3] F. Ciuchi, A. Mazzulla, N. Scaramuzza, E. K. Lenzi, and L. R.
Evangelista, Fractional Diffusion Equation and the Electrical Impedance:
Experimental Evidence in Liquid-Crystalline Cells, J. Phys. Chem. C 116,
8773 (2012).
[4] J. Bisquert, Fractional Diffusion in the Multiple-Trapping Regime
and Revision of the Equivalence with the Continuous-Time Random Walk,
Phys. Rev. Lett. 91, 010602 (2003).
[5] E. K. Lenzi, L. R. Evangelista, and G. Barbero, Fractional Diffusion
Equation and Impedance Spectroscopy of Electrolytic Cells, J. Phys.
Chem. B 113, 11371 (2009).
[6] J. R. Macdonald, L. R. Evangelista, E. K. Lenzi, and G. Barbero,
Comparison of Impedance Spectroscopy Expressions and Responses of
Alternate Anomalous Poisson-Nernst-Planck Diffusion Equations for
Finite-Length Situations, J. Phys. Chem. C 115, 7648 (2011).
[7] L. R. Evangelista, E. K. Lenzi, G. Barbero, and J. R. Macdonald,
Anomalous diffusion and memory effects on the impedance spectroscopy for
finite-length situations, J. Phys.: Condensed Matter 23, 485005 (2011).
[8] E. K. Lenzi, R. S. Zola, H. V. Ribeiro, D. S. Vieira, F. Ciuchi, A.
Mazzulla, N. Scaramuzza, and L. R. Evangelista, Ion Motion in
Electrolytic Cells: Anomalous Diffusion Evidences, J. Phys. Chem. B 121,
2882 (2017).

TÍTULO:   _A SIMPLE MODEL OF AC HOPPING SURFACE CONDUCTIVITY IN IONIC
LIQUIDS_ 

Expositor:  _Giovanni Barbero_
Dipartimento di Scienza Applicata del Politecnico di Torino. Torino,
Italia.  

RESUMEN:  
The boundary conditions proposed to discuss the charge exchange taking
place in an ionic liquid in contact with non-blocking electrode are
reconsidered in a dynamical situation. Assuming that the bulk density
variation of the ionic density depends linearly on the surface value of
the ionic current density, the frequency dependence of the
phenomenological parameter is determined. The analysis has been
performed in the framework where the relaxation times are smaller than a
maximum relaxation time τMs, and that the response function is
independent on the value of the relaxation time. By means of simple
physical consideration, an expression for the surface conductivity
describing the ionic charge exchange at the electrode is obtained.
According to our calculations, its frequency dependence is similar to
that predicted for the electric conductivity in disordered material when
the mechanism is of hopping time. From measurements of impedance
spectroscopy, by the best fit of the experimental data, the temperature
dependence of the hopping time, of the dc surface conductivity, and of
the diffusion coefficient are derived. They are in good agreement with
the theoretical predictions obtained by means of the random distribution
of surface energy barrier. 
  -- 
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