Libro de resúmenes y programa(definitivo) - Universidad de Sevilla

Fenómenos de transporte a todas
las escalas
Quinto encuentro de la red española de física de sistemas fuera del
equilibrio

PROGRAMA:
Hora Miércoles 7
9:30-10:00 RECEPCIÓN
10:00-10:40 CAFÉ
10:40-11:30 MARINI
11:30-12:10 GARCIMARTIN
12:10-12:50 DOMINGUEZ
13:00-15:00 COMIDA
15:00-15:50 KURCHAN
15:50-16:30 VEGA
16:30-17:00 CAFÉ
17:00-17:40 PUERTAS
17:40-18:20 SANCHEZ
Hora Jueves 8 Viernes 9
9:30-10:20 VAN ROIJ VAN DER MEER
10:20-10:50 CAFÉ CAFÉ
10:50-11:30 SCAGLIARINI HURTADO
11:30-12:10 PLATERO HITA
12:10-12:50 PRADOS ABAD
13:00-15:00 COMIDA COMIDA
15:00-15:40 VILAR
15:40-16:20 RUIZ-MONTERO
16:20-17:00 CEBRIÁN
17:00-17:30 CAFÉ
21:00 CENA
La cena será en el restaurante Porta Rossa en la Calle Arenal 5.

Acceso Wi-Fi:
Red: ReInUS
Usuario: redespfe5
Password: sev79mar&

Resúmenes

Diffusion and reactions in biologically motivated problems
E. Abad
Centro Universitario de Mérida, Avda. Santa Teresa de Jornet, 38, E-06080 Mérida
S. B. Yuste
Dpto. de Física, Universidad de Extremadura, Av. Elvas s/n, 06071 Badajoz
K. Lindenberg
Department of Chemistry and Biochemistry, and BioCircuits Institute, University of CaliforniaSan
Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, USA
In this contribution we review some recent results from stochastic models for transport properties
in three biologically motivated problems. The first problem concerns the calculation of
conductance properties of ion channels via a master equation approach. We study the case of
a narrow channel with monoionic conduction and set up a 1D rate model where ions overcome
large energy barriers by hopping between neighbouring energy minima. We compute the hopping
rates in terms of first passage times and splitting probabilities for the underlying generalized
Kramers problem [1]. Within this framework we are able to compute conductance properties for
the gramicidin A channel in terms of a single adjustable parameter (the equilibrium ion entry rate).
We obtain good fits to experimental curves by tuning this parameter within a physiologically acceptable
range. Next, we consider transport in a ratchet model providing an idealized description
of the motion of motor proteins along microtubuli. More specifically, we study the overdamped
motion of a Brownian particle in a 1D periodic potential whose amplitude fluctuates between two
states under the action of coloured noise [2]. The latter aims to mimic memory effects arising
from ATP hydrolysis -the driving force responsible for the protein motion along the microtubule-.
We compute the particle flux as a function of temperature and the autocorrelation time of the
coloured noise. We find that the results are very sensitive to the specific details of the potential
geometry, and in many cases we observe flux reversals when varying the typical system parameters
Finally, we address the problem of morphogen gradient formation by extending the classical
1D synthesis-diffusion-degradation (SSD) model to account for the possibility of anomalous subdiffusion
[3]. The resulting reaction-subdiffusion equation contains a Riemann-Liouville fractional
derivative which accounts for memory effects arising from anomalous transport. When solved using
the proper boundary conditions, our equation gives morphogen concentration profiles which
strongly differ from those yielded by the SSD model. We discuss the possible relevance of the
above results for biological systems.
[1] E.Abad, J. Reingruber, and M.S.P. Sansom, On a novel rate theory for transport in narrow
ion channels and its application to flux optimization via geometric effects, J. Chem. Phys. 130,
085101 (2009).
[2] E. Abad and A. Mielke, Brownian motion in periodic fluctuating potentials, Ann. Physik 7
(1998), 9-23.
[3] S.B. Yuste, E. Abad and K. Lindenberg, Reaction-subdiffusion model for morphogen gradient
formation, Phys. Rev. E 82, 061123 (2010).

Resolución de la ecuación cinética en superredes semiconductoras
mediante métodos de partículas y diferencias finitas.
Elena Cebrian
Departamento de Matemáticas y Computación. Universidad de Burgos.
Mariano Alvaro, Manuel Carretero y Luis L.Bonilla
G. Millán Institute of Fluid Dynamics, Nanosciencce and Industrial Mathematics, Universidad Carlos
III de Madrid, Avenida de la Universidad 30, 28911 Leganés
Las superredes semiconductoras son cristales artificiales unidimensionales formados por crecimiento
epitaxial de capas pertenecientes a semiconductores diferentes [4]. Fueron ideadas por
Esaki y Tsu [6] para obtener oscilaciones de Bloch. La banda de conducción de la superred es
una sucesión periódica de barreras y pozos. Cuando se aplica una diferencia de potencial entre
los contactos, es posible obtener oscilaciones estables de la corriente [4], causadas por pulsos
del campo eléctrico originados en el cátodo que se mueven hasta desaparecer por ánodo y son
similares a las del efecto Gunn (GHz) aunque diferentes a las de Bloch (THz) [7]. Las oscilaciones
tipo Gunn han sido observadas en experimentos con superredes GaAs/AlAs desde 1996
y son la base de los dispositivos con oscilaciones rápidas.
El transporte de electrones en una minibanda de la superred puede ser descrito por una
ecuación cinética acoplada a la ecuación de Poisson [3]. El operador de colisión puede ser simplificado
mediante un término tipo Bhatnagar-Gross-Krook (BGK) [2]. La relación de dispersión
entre las minibandas de energía y los momentos es periódica debido a la relación entre la velocidad
de difusión de los electrones y el campo eléctrico, el cual tiene un valor máximo [4]. Entonces
la velocidad de difusión decrece cuando el campo crece para valores grandes del campo
(movilidad diferencial negativa). Esto da lugar a las oscilaciones autosostenidas tipo Gunn de la
corriente cuando se toman condiciones de contorno apropiadas [4].
Bonilla y otros [1,3] han derivado la ecuación de convección-difusión no lineal del campo
eléctrico a partir del modelo cinético acoplado a la ecuación de Poisson con término de colisión
tipo BGK, usando un método perturbativo tipo Chapman Enskog en el límite hiperbólico en el cual
el operador de colisión es del mismo orden que el término que contiene al campo eléctrico y domina
al resto de los términos. Entonces las oscilaciones autosostenidas de la corriente se obtienen
resolviendo numéricamente las ecuaciones de convección-difusión con condiciones de contorno
apropiadas. En esta presentación se muestra cómo se ha abordado la resoluci’on numérica del
modelo cinético semiclásico usando por un lado el método de partículas ponderado [5] y por otro
un método de diferencias finitas. Con ambos métodos se han obtenido prácticamente los mismos
resultados, los cuales son muy similares a los obtenidos con la ecuación hidrodin’amica.
[1] M. Alvaro, M. Carretero, L. L. Bonilla. Numerical method for hydrodynamic modulation
equations describing Bloch oscillations in semiconductor superlattices (prepint).
[2] P.L. Bhatnagar, E.P. Gross, M. Krook, Phys. Rev. 94 (1954) 511-525.
[3] L.L. Bonilla, R. Escobedo, A. Perales, Phys. Rev. B 68 (2003) 241304(R) (4 pages).
[4] L.L. Bonilla, H.T. Grahn, Rep. Prog. Phys. 68 (2005) 577-683.
[5] E. Cebrin, L.L.Bonilla and A.Carpio, J. Comput. Phys. (228), 7689-7705 (2009).
[6] L. Esaki and R. Tsu, IBM J. Res. Develop. 14, 61-65 (1970).
[7] H. Kroemer, Pages 20-98. John Wiley, N. Y. 1972.

From gravitational colapse to spinodal decomposition
Alvaro Domínguez
Física Teórica, Universidad de Sevilla, Apdo. de Correos 1065, Sevilla 41080, Spain
Colloidal monolayers (colloidal particles trapped at the interface between two fluids) are a
faithful experimental realization of a two-dimensional fluid, for which reason they have attracted
much interest during the last years. The interaction between particles under generic conditions
can be dominated by the capillary forces due to the deformation of the fluid interface. The large
difference between the effective interaction range (∼millimeters) and the typical interparticle separation
(∼micrometers) is particularly interesting. Together with the dependence of the capillary
force on separation, this characteristic confers the system features of both a self–gravitating fluid
as well as of a van der Waals fluid.
We have studied a mean-field dynamical model for this system. We present the results of theoretical
calculations and N-body simulations for the instability of an initially homogeneous particle
distribution, paying special attention to the crossover of the evolution from “gravitational collapse”
to “spinodal decomposition”.

Reducción de atascos mediante obstáculos.
Angel Garcimartín, Iker Zuriguel y Alvaro Janda
Departamento de Física y Matemática Aplicada Facultad de Ciencias Universidad de Navarra
31080 Pamplona, Spain
Presentamos resultados experimentales sobre el efecto que provoca un obstáculo colocado
justo antes de la salida de un silo. Si la posición de este obstáculo es la adecuada, hemos
encontrado que se puede reducir la probabilidad de atasco en un factor 100. Sorprendentemente,
el flujo medio no varía apreciablemente. Por mediciones indirectas podemos concluir que la causa
de este fenómeno es la reduccin de la presin en la zona que queda entre el orificio de salida y el
obstáculo (figura). Tambin se presentará un experimento en ciernes para probar si este mismo
método es eficaz con seres vivos.
[1] I. Zuriguel, A. Janda, A. Garcimartín, C. Lozano, R. Arévalo and D. Maza, Silo Clogging
Reduction by the Presence of an Obstacle, Phys. Rev. Lett. 107 (2011), 278001.

Correlaciones espaciales en problemas de reacción-difusión
con el algoritmo de Gillespie
Jorge Luis Hita y José M. Ortiz de Zárate
Universidad Complutense
Recientemente hemos iniciado un programa para simular, utilizando el algoritmo de Gillespie,
problemas de reacción-difusión isotermos en una dimensión espacial. Pretendemos estudiar
numéricamente las correlaciones estadísticas de las fluctuaciones de la concentración en
distintos puntos espaciales; con el objetivo último de verificar que son de corto alcance si las
reacciones químicas (procesos cinéticos) estn en equilibrio y que son de largo alcance si las
reacciones químicas están fuera del equilibrio.
Presentaremos algunos de los resultados más relevantes que hemos obtenido hasta ahora.
Primero en sistemas homogéneos (sin difusión y, por consiguiente, con concentración espacialmente
uniforme) estudiaremos el número de partículas N necesarias para que la distribución de
probabilidad de las fluctuaciones en la concentración, debidas al carácter estocstico del proceso
cinético, pueda considerarse gaussiana. Una convergencia óptima a una gaussiana se consigue
con pocos cientos de partículas, como se demuestra con un test de percentiles. La varianza σ
obtenida de estas simulaciones coincide con las predicciones de la system-size expansion de
van Kampen.
También presentaremos resultados obtenidos de simular la difusión (1D) con una adaptación
del algoritmo de Gillespie recientemente propuesta para este fin. Como era de esperar, las
distribuciones de probabilidad de las fluctuaciones son gaussianas con varianza dada por la raíz
cuadrada del número medio de partículas por sitio. El siguiente paso será combinar difusión y
reacciones químicas.

Spontaneous Symmetry Breaking at the Fluctuating Level
Pablo I. Hurtado and Pedro L. Garrido
Departamento de Electromagnetismo y Física de la Materia, and Instituto Carlos I de Física
Teórica y Computacional, Universidad de Granada, Granada 18071, Spain
Phase transitions not allowed in equilibrium steady states may happen however at the fluctuating
level. We observe for the first time this striking and general phenomenon measuring
current fluctuations in an isolated diffusive system. While small fluctuations result from the sum
of weakly-correlated local events, for currents above a critical threshold the system self-organizes
into a coherent traveling wave which facilitates the current deviation by gathering energy in a localized
packet, thus breaking translation invariance. This results in Gaussian statistics for small
fluctuations but non-Gaussian tails above the critical current. Our observations, which agree with
predictions derived from hydrodynamic fluctuation theory, strongly suggest that rare events are
generically associated with coherent, self-organized patterns which enhance their probability.
[1] P.I. Hurtado and P.L. Garrido, Phys. Rev. Lett. 107, 180601 (2011).

Inequalities that generalize the second law.
Jorge Kurchan
CNRS, Francia
Some fifteen years ago, Jarzynski proved a very general and elementary equality, form which
a form of the Second Principle follows immediately. More recently, Hatano and Sasa showed that
one may generalize this to systems whose dynamics is by construction non-equilibrium even in
the stationary regime; such as, for example, a bar with a potential difference at the ends. The
problem with this generalization of the Second Law is that it requires the precise knowledge of the
probability distribution in every stationary nonequilibrium configuration, and, more seriously, that
the inequality obtained may be in some cases empty. We have been studying alternative versions
of the Second Law, which may potentially be used in most cases, and which in addition suggest a
variational principle for the distribution function.

Dynamics of Fluids in Nanospaces
Umberto Marini Bettolo Marconi, Camerino
In this contribution we review some recent results from stochastic models for transport properties
in three biologically motivated problems. The first problem concerns the calculation of
conductance properties of ion channels via a master equation approach. We study the case of
a narrow channel with monoionic conduction and set up a 1D rate model where ions overcome
large energy barriers by hopping between neighbouring energy minima. We compute the hopping
rates in terms of first passage times and splitting probabilities for the underlying generalized
Kramers problem [1]. Within this framework we are able to compute conductance properties for
the gramicidin A channel in terms of a single adjustable parameter (the equilibrium ion entry rate).
We obtain good fits to experimental curves by tuning this parameter within a physiologically acceptable
range. Next, we consider transport in a ratchet model providing an idealized description
of the motion of motor proteins along microtubuli. More specifically, we study the overdamped
motion of a Brownian particle in a 1D periodic potential whose amplitude fluctuates between two
states under the action of coloured noise [2]. The latter aims to mimic memory effects arising
from ATP hydrolysis -the driving force responsible for the protein motion along the microtubule-.
We compute the particle flux as a function of temperature and the autocorrelation time of the
coloured noise. We find that the results are very sensitive to the specific details of the potential
geometry, and in many cases we observe flux reversals when varying the typical system parameters
Finally, we address the problem of morphogen gradient formation by extending the classical
1D synthesis-diffusion-degradation (SSD) model to account for the possibility of anomalous subdiffusion
[3]. The resulting reaction-subdiffusion equation contains a Riemann-Liouville fractional
derivative which accounts for memory effects arising from anomalous transport. When solved using
the proper boundary conditions, our equation gives morphogen concentration profiles which
strongly differ from those yielded by the SSD model. We discuss the possible relevance of the
above results for biological systems. References [1] E.Abad, J. Reingruber, and M.S.P. Sansom,
On a novel rate theory for transport in narrow ion channels and its application to flux optimization
via geometric effects, J. Chem. Phys. 130, 085101 (2009). [2] E. Abad and A. Mielke, Brownian
motion in periodic fluctuating potentials, Ann. Physik 7 (1998), 9-23. [3] S.B. Yuste, E. Abad and
K. Lindenberg, Reaction-subdiffusion model for morphogen gradient formation, Phys. Rev. E 82,
061123 (2010).

Coherent dynamics of electrons in ac driven quantum dot arrays
G. Platero
Instituto de Ciencia de Materiales (CSIC) Cantoblanco , Madrid , Spain.
A powerful method of manipulating the coherent dynamics of quantum particles is to control
the phase of their tunnelling. We will show how such phases can be produced in two distinct and
complementary ways. We have considered the dynamics of two interacting electrons hopping on
a quasi onedimensional lattice with a nontrivial topology, threaded by a uniform magnetic flux, and
study the effect of adding a time periodic ac electric field. We will show that the dynamical phases
produced by the driving field can combine with the familiar AharonovBohm phases arising from
the magnetic flux to give precise control over the dynamics and localization of the particles, even
in the presence of strong particle interactions [1]. Recent electron spin resonance experiments
measure coherent spin rotations of one single electron, a fundamental ingredient for quantum
operations. We will show how it is possible to manipulate electron charge and spin dynamics in
double and triple quantum dots by means of ac magnetic fields. We demonstrate that by tuning
the the field intensity, frequency and the phase difference between the fields within each dot,
charge localization can be achieved. Furthermore, ac magnetic fields are also able to induce spin
locking, i.e., to freeze the electronic spin, at certain field parameters and symmetry configurations
[2]. Spin Blockade has been measured in transport experiments through double quantum dots.
We will discuss the effect of ac magnetic fields on spin blockade and we will show that ac magnetic
fields can not only remove spin blockade , but also restore it due to collective rotations of the
two spins. at certain parameters of the field [3].
[1] C.E. Creffield and G. Platero, Phys. Rev. Lett. 105, 086804 (2010).
[2] A. Gómez-León and G. Platero, Phys. Rev. B, 84, 121310(R) (2011).
[3] M. Busl et al., Phys. Rev. B, 81, 121306(R) (2010); R. Sánchez et al., Phys. Rev. B ,77,
165312 (2008).

Large Fluctuations in Driven Dissipative Media
A. Prados and A. Lasanta
Física Teórica, Universidad de Sevilla, Apdo. de Correos 1065, Sevilla 41080, Spain
Pablo I. Hurtado
Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Granada 18071,
Spain
We analyze the fluctuations of the dissipated energy in a simple and general model where
dissipation, diffusion and driving are the key ingredients. The full dissipation distribution, which
follows from hydrodynamic fluctuation theory, shows non-Gaussian tails and no negative branch,
thus violating the fluctuation theorem as expected from the irreversibility of the dynamics. It exhibits
simple scaling forms in the weak- and strong-dissipation limits, with large fluctuations favored
in the former case but strongly suppressed in the latter. The typical path associated to a
given dissipation fluctuation is also analyzed in detail. Our results, confirmed in extensive simulations,
strongly support the validity of hydrodynamic fluctuation theory to describe fluctuating
behavior in driven dissipative media.
[1] A. Prados, A. Lasanta and P. I. Hurtado, Phys. Rev. Lett. 107, 140601 (2011)

Comparison of different forcings in active microheology
in colloids
Antonio M. Puertas
Group of Complex Fluids Physics, Departamento de Fısica Aplicada
Universidad de Almería, 04120 Almería (SPAIN)
Whereas pasive microrheology in colloids is based solely on the observation of single particle
motion, in active microrheology, colloidal tracers experience external forces and their behaviour
is observed. In both cases, the complex microscopic mechanical behaviour is measured and a
connection with bulk quantities is usually sought. I will present here simulations of active microrhelogy
in a dense system of hard colloids where one particle is dragged through the system. The
tracer is dragged i) with a constant external force, (the velocity fluctuates) ii) at a constant speed
(with a fluctuating force) or iii) held in a harmonic trap moving at constant speed. The friction
coefficient is measured using the linear relationship between the (average) drag force and the
(average) velocity, in the stationary regime. Different results are obtained in the three different
cases, providing distinct aspects of the microscopic dynamics of the system. Larger friction coefficients
are measured at constant velocity as the tracer must open its way through the system,
and agree with the case of the harmonic trap at low velocities. On the other hand, small friction
coefficients are obtained when the particle is dragged at a constant force, and agree with the
harmonic trap at large velocities. Interestingly, a yield ”stress” is observed in the constant force
case, giving an estimate of the strength of the cage of neighbours. In all cases, comparison is
made with theoretical results based on a low density theory [Phys. Fluids 17, 073101 (2005)].

Temperature anisotropy in granular fluids
Maria J. Ruiz-Montero and J. Javier Brey
Física Teórica. Universidad de Sevilla
One of the consequences of inelasticity in granular mixtures is that the energy equipartition
required in equilibrium systems is not verified. The granular temperatures of the components of
the mixture, defined from the average kinetic energy of each species are not equal. This feature
was pointed out many years ago [1], and a systematic study of it has been carried out in the last
years.
Once established that the partial temperatures are different, some questions arise: should they
be incorporated to the set of variables needed to identify the macroscopic state of the mixture? If
the answer is negative, are the partial temperatures determined by the usual set of hydrodynamic
fields and the properties of the particles? In this work we will study the steady state of a vibrated
granular mixture in the presence of gravity in the low density limit, and we will show that the
macroscopic state in the bulk of the system is defined by intensive variables that do not include
the partial temperatures of the system. Also, the local cooling rates of each of the components
will be investigated, and the accuracy of the expression obtained assuming a local homogeneous
cooling state distribution [2] of the gas will be analyzed by comparing it with computer simulations
of the system.
[1] J.T. Jenkins and F. Mancini, J. Appl. Mech. Vol. 35, 27 (1987).
[2] V. Garzo and J.W. Dufty, Phys. Rev. E Vol. 60, 5706 (1999).

Asymmetric thermopower in mesoscopic transport
David Sánchez and Llorenç Serra
Institut de Física Interdisciplinar i de Sistemes Complexos IFISC (CSIC-UIB), E-07122 Palma de
Mallorca, Spain.
Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca, Spain
We consider a generic quantum conductor coupled to two electric terminals. Phase-coherent
transport is generated across the conductor when an electric or thermal gradient is applied to the
reservoirs. We investigate heat and charge transport under the influence of inelastic processes,
which are modeled using an additional reservoir acting as an ideal volgate and thermal probe.
We illustrate our method with an application to a ballistic chaotic cavity. We find within random
matrix theory that thermopower fluctuations disappear quickly as the probe mode number
increases [1].
Importantly, we find that, upon elimination of the probe, the two-terminal Seebeck coefficient
shows an asymmetry when an applied magnetic field reverses its direction. This asymmetry effect
is revealed in the presence of incoherent scattering only. Furthermore, the asymmetry effect is of
higher order in a Sommerfeld expansion [1]. We believe that our results are relevant to quantify
the efficiency of thermoelectric nanodevices in the presence of dephasing.
[1] D. Sánchez and Ll. Serra, Phys. Rev. B 84, 201307(R) (2011).

Self-assembly and flocking in active colloidal suspensions
Andrea Scagliarini and Ignacio Pagonabarraga
Departament de Física Fonamental Universitat de Barcelona
Active fluids, such as suspensions of self-propelled particles or of cytoskeletal filaments and
molecular motors, are a fascinating example of soft matter displaying non-trivial collective behaviours
which representing issues in non-equilibrium statistical physics [1].
Moreover, the recent development of techniques to assemble miniaturized devices has led to
an ever-growing interest for micro- and nano- scale engines that can perform autonomous motion
[2] (”microrobots”), as, for instance, self-phoretic colloids, for which the propulsion is induced
by the generation of a chemical species in a reaction (locally) catalyzed at the particle surface
[3,4]. In our simulations colloids are described as resolved finite size particles, interacting with a
concentration field according to a coarse-grained model [5].
We have tested the numerical implementation against exact results on the chemotactic behaviour
of an isolated particle as well as on the self-propulsion mechanism. Our study on suspensions
of several particles suggests the existence of a non-equilibrium transition from a flocking
state to the formation of fractal-like aggregates, at changing a parameter accounting for the
particle-”fuel” chemical affinity [6].
[1] S. Ramaswamy, Annu. Rev. Condes. Matter Phys. 1, 323 (2010).
[2] R. Dreyfus et al, Nature 437, 862 (2005).
[3] W.E. Paxton et al, J. Am. Chem. Soc. 126, 13424 (2004).
[4] J.R. Howse et al, Phys. Rev. Lett. 99, 048102 (2007).
[5] R. Golestanian et al, Phys. Rev. Lett. 94, 220801 (2005).
[6] A. Scagliarini and I. Pagonabarraga, in preparation (2012).

Harvesting ”blue” energy by reversibly mixing river- and sea
water.
René van Roij
Utrecht University, Holanda
The mixing of fresh river water and salty sea water is an irreversible process, in which about
2 kJ of (free) energy is dissipated with every liter of river water that flows into the sea, i.e. the
equivalent of a waterfall of 200m. In this talk we will discuss how this energy can be harvested.
After a general introduction we will focus on Brogioli’s recently developed capacitive device [1],
which cyclicly charges and discharges nanoporous electrodes immersed in sea- and river water,
respectively, such that the expansion and compression of the electrostatic double layer in fresh
and salty water is exploited. We will show that Brogioli’s device can be seen as an analogue of a
Stirling heat engine, and we propose a modification to construct the most efficient ”blue engine”
based on a Carnot-like cycle [2]. The blue engine running in reverse-mode is a desalination device,
yielding separated fresh and salty water from brackish water at the expense of energy input;
the heat-engine analogue is a fridge [2]. Interestingly, the potential of the porous electrodes in the
device are as high as 500mV, exceeding the thermal voltage ( 25mV) by far, such that ordinary
Poisson-Boltzmann (PB) theory breaks down, even for monovalent ions in water. The Stern layer
and other ion-specific effects become relevant in this regime. We will discuss an extension of PB
theory in which the ”polarisability holes” due to the poorly polarisable ions compared to water are
taken into account, giving good agreement with experimental measurements of differential capacities
[3].
[1] D. Brogioli, Phys. Rev. Lett. 103, 058501 (2009).
[2] N. Boon and R. van Roij, Mol. Phys. 109, 1229 (2011).
[3] M. Hatlo, R. van Roij and L. Lue, Europhys. Lett. 97, 28010 (2012).

A granular ratchet: Spontaneous symmetry breaking and
fluctuation theorems in a granular gas
Devaraj van der Meer, Peter Eshuis, Sylvain Joubaud, Ko van der Weele and Detlef Lohse.
Physics of Fluids group, University of Twente, The Netherlands.
We construct a ratchet of the Smoluchowski-Feynman type, consisting of four vanes that are
allowed to rotate freely in a vibrofluidized granular gas. The necessary out-of-equilibrium environment
is provided by the inelastically colliding grains, and the equally crucial symmetry breaking
by applying a soft coating to one side of each vane. The onset of the ratchet effect occurs at a
critical shaking strength via a smooth, continuous phase transition. For very strong shaking the
vanes interact actively with the gas and a convection roll develops, sustaining the rotation of the
vanes. From the experimental results we show that a steady state fluctuation relation holds for
the work injected to the system, and that its entropy production satisfies a detailed fluctuation theorem.
Surprisingly, we find that the above relations are satisfied even when a convection roll has
developed and there exists a strong coupling between the motion of the vanes and the granular
gas.

Properties of the segregation of a granular impurity under
Couette-Fourier flows
Francisco Vega Reyes, Vicente Garzó, Andrés Santos
Departamento de Física, Universidad de Extremadura, E-06071 Badajoz. Spain
We study in this work the segregation of a granular impurity under Couette-Fourier flow. Our
system consists of two sets (1,2) composed of identical inelastic hard spheres with low density,
each set being characterized by different size and mass. We also consider that each type of
binary collisions (1-1, 1-2, 2-2 particle collisions) is characterized by a different degree of inelasticity.
One of the sets is present in an almost negligible concentration compared to the other
set, and thus it can be considered as an ’impurity’ and the tracer limit for this species applies
[1]. Our granular spheres are enclosed between two infinite parallel walls that act as shear and
temperature sources. We consider that in general both walls are at different temperatures. We
obtain an exact numerical solution of the corresponding inelastic Boltzmann-Lorentz equation for
the granular impurity in this system (using the direct simulation Monte Carlo method, DSMC). Recently,
special cases of granular Couette-Fourier flows for a monocomponent granular gas have
been described in the same geometry. They may be called LTy and LTu classes because they
have linear temperature profiles: the first one, is linear vs. the space coordinate [2] whereas the
LTu class has a linear profile vs. flow velocity, and is also characterized by a constant heat flux
throughout the system [2]. We show that both special classes of flows also exist for the granular
impurity, with the same aforementioned properties. Moreover, we show that an impurity under LTy
and LTu Couette-Fourier flows, shows also the following hydrodynamic properties: 1) no diffusion
with respect to the granular gas (i.e., both species have the same flow velocity profiles); 3) the
ratio between both species temperatures is uniform in the system; 3) the pressure of the impurity
is non-uniform. Properties 2) and 3) imply that the impurity molar fraction is not uniform, i.e., the
impurity can segregate towards a specific region of the system. Property 1) implies that the segregation
theoretical criteria of the type of former works apply [3]. We analyze this problem for a
wide range of values of the relevant parameters of the problem, including also preliminary results
for more generic Couette-Fourier granular flows.
[1] J. J. Brey, N. Khalil, and J. W. Dufty, New J. Phys. 13, 055019 (2011).
[2] V. Garzó and F. Vega Reyes, Phys. Rev. E 79, 041303 (2009).
[3] F. Vega Reyes, V. Garzó and A. Santos, Steady base states for non-Newtonian granular
hydrodynamics, (2012), unpublished.
[4] F. Vega Reyes, A. Santos, and V. Garzó, Phys. Rev. Lett. 104, 028001 (2010).

Multidimensional entropies for diagnosing Acute Myeloid Leukemia
from patient samples using flow cytometry data
Jose M. G. Vilar
Biophysics Unit (CSIC-UPV/EHU) and Department of Biochemistry and Molecular Biology, University
of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain; IKERBASQUE, Basque Foundation
for Science, 48011 Bilbao, Spain
Deciphering the basis of complex immunological diseases, such as leukemia, requires the
characterization of diverse cell subtypes through measurements of multiple factors at the singlecell
level. Rapid progress in this field depends critically not only on the appropriate experimental
techniques but also on the availability of computational tools able to tackle the inherent complexity
of the experimental data. I will present a new method to compare cell populations based on their
entropies along multidimensional landscapes constructed from the single-cell morphological and
molecular attributes of flow cytometry data. Applied to samples from peripheral blood and bone
marrow aspirate, this method accurately discriminates between Acute Myeloid Leukemia positive
patients and healthy donors.

Asistentes

Nombre Institución Email
Abad, Enrique. Universidad de Extremadura. eabad@unex.es
Alarcón, Francisco. Universidad de Barcelona. falarcon@ffn.ub.es
Alvaro, Mariano. Universidad Carlos III de
Madrid.
mariano.alvaro@uc3m.es
Aznar, María. Universidad de Barcelona. maznar@ffn.ub.es
Bettolo Marconi, Umberto
Marini.
Universitá di Camerino, Italia. umberto.marinibettolo@gmail.
com
Brey, Javier. Universidad de Sevilla. brey@us.es
Brito, Ricardo. Universidad Complutense de
Madrid.
brito@fis.ucm.es
Buzón, Vicente. Universidad de Sevilla. vbuzon@us.es
Carretero, Manuel. Universidad Carlos III de
Madrid.
manuel.carretero@uc3m.es
Cebrián de Barrio, Elena. Universidad de Burgos. elenac@ubu.es
Domínguez, Alvaro. Universidad de Sevilla. dominguez@us.es
García, Moises. Universidad de Extremadura. moises@unex.es
García de Soria, María
Isabel.
Universidad de Sevilla. gsoria@us.es
Garcimartín, Angel. Universidad de Navarra. angel@fisica.unav.es
Garzó, Vicente. Universidad de Extremadura. vicenteg@unex.es
González, Emilio. Universidad de Almería. vaentis@ual.es
Hita, Jorge Luis. Universidad Complutense de
Madrid.
jluis@estumail.ucm.es
Hurtado, Pablo. Universidad de Granada. phurtado@onsager.ugr.es
Khalil, Nagi. Universidad de Sevilla. nagi@us.es
Kurchan, Jorge. CNRS, Francia. jorge@pmmh.espci.fr
Lasanta, Antonio. Universidad de Sevilla. alasanta@us.es
Malgaretti, Paolo. Universidad de Barcelona. paoloindescai@gmail.com
Maynar, Pablo. Universidad de Sevilla. maynar@us.es

Ortiz de Zárate, José María. Universidad Complutense de
Madrid.
jmortizz@fis.ucm.es
Pagonabarraga, Ignacio. Universidad de Barcelona. ipagonabarraga@ub.edu
Platero, Gloria. ICMM-CSIC. gplatero@icmm.csic.es
Prados, Antonio. Universidad de Sevilla. prados@us.es
Puertas, Antonio M. Universidad de Almería. apuertas@ual.es
Rubí, Miguel. Universidad de Barcelona. mrubi@ub.edu
Ruiz, Miguel. Universidad de Sevilla miguelrg_2004@hotmail.com
Ruiz-Montero, María José. Universidad de Sevilla. majose@us.es
Sánchez, David. IFISC(UIB-CSIC). david.sanchez@uib.es
Santos, Andrés. Universidad de Extremadura. andres@unex.es
Scagliarini, Andrea. Universidad de Barcelona. ascagliarini@gmail.com
van der Meer, Devaraj. University of Twente, Holanda. d.vandermeer@utwente.nl
van Rooij, René. Utrecht University, Holanda. r.vanroij@uu.nl
Vega Reyes, Francisco. Universidad de Extremadura. fvega@unex.es
Vilar, José. Universidad del País Vasco. j.vilar@ikerbasque.org
Castrillo, Clara Universidad de Sevilla. claracastrillob@gmail.com