[Todos] Fwd: Recordatorio: 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'

Lun Mayo 13 12:02:08 -03 2019

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

 		ASUNTO:
 		Recordatorio: 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:
 		2019-05-13 12:01

 		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. 

  -- 

COMISIÓN CHIFLY 
______________________________________________ 
  Si no estás interesado en recibir los avisos de las chiflys
escribinos.
------------ próxima parte ------------
Se ha borrado un adjunto en formato HTML...
URL: <http://mail.fisica.unlp.edu.ar/pipermail/todos/attachments/20190513/6903e4d5/attachment.html>