Poster Conference Speakers Program Talks Posters Registration
Organizers
Meeting history Hotel Taxco Travel Info Pictures
The XXXVI
edition of the Winter Meeting on Statistical Physics
will take place in
The XXXVI edition of the Winter Meeting on
Statistical Physics will take place in
This event is the most important meeting on
statistical physics in
Speakers (click on name for avaibable titles and abstracts)
Home
1.- Jan Sengers (Institute
for Physical Science and Technology - University of Maryland, USA)
2.- Elisabeth
Schöll-Paschinger (Institut für Experimentalphysik der Universität Wien,
Austria)
3.-
Agustí Perez-Madrid (Departament de Física
Fonamental, Universitat de Barcelona, Spain)
4.- Nitant Kenkre (University of New Mexico, USA)
5.- Tomás Alarcón (Mathematical Institute, University of Oxford, England)
6.-
Emmanuel Trizac (Laboratoire de Physique
Théorique et Modèles Statistiques, Université de Paris-Sud, France)
7.- Peter Vekilov (Department of Chemical and Biomolecular
Engineering, University of Houston, USA)
8.-
Fernando Oliveira
(Insituto de Física e Centro Internacional de Física da Matéria
Condensada, Universidade de Brasilia, Brazil)
(NOTE: Due to
problems with mexican visa, Profr. Oliveira is not coming to the conference this
time).
9.- Jure Dobnikar (Jozef
Stefan Institute, Ljubljana, Slovenia)
10.-
Jesús Santana Solano (Cinvestav-Monterrey, Mexico)
11.-
Moisés Santillán Zerón (Cinvestav-Monterrey, Mexico)
12.- Minerva
González Melchor (Universidad Autónoma de Puebla, Mexico)
13.- Orlando Guzmán (Universidad Autónoma Metropolitana-Iztapalapa,
Mexico)
14.- Hernán Larralde (Centro de Ciencias Físicas,
Mexico)
15.- Victor Romero Rochín (Instituto de Física - UNAM,
Mexico)
16.- Jaime Ruiz García (Instituto de Física-UASLP,
Mexico)
Program Home
Tuesday 9 |
Wednesday 10 |
Thursday 11 |
Friday 12 |
|
7:00 – 9:00 |
|
Breakfast |
Breakfast |
Breakfast |
8:45 – 9:00 |
|
Opening ceremony |
|
|
9:00 – 10:00 |
|
|||
10:00 – 11:00 |
|
|||
11:00 – 11:30 |
|
Coffee / Posters
|
Coffee / Posters |
Coffee / Posters
|
11:30 – 12:30 |
|
To be announced |
||
12:30 – 13:30 |
|
|||
13:30 – 14:30 |
|
|
||
14:30 – 16:00 |
|
Lunch |
Lunch |
Lunch |
16:00 – 17:00 |
Registration |
Organizing meeting |
|
|
17:00 – 18:00 |
Registration |
Free |
|
|
18:00 – 18:30 |
Coffee |
Afternoon |
|
|
18:30 – 19:30 |
|
|
||
19:15 – 20:15 |
Welcome cocktail |
|
|
|
20:00 |
Dinner |
Dinner |
Dinner |
|
Talks Home
Thermal Fluctuations in Nonequilibrium Thermodynamics
Jan V. Sengers
Institute for Physical
Science and Technology, University of Maryland, College Park, MD, U.S.A.
The lecture will address the
following three principles concerning fluctuations in fluids and fluid mixtures
that are in not in thermodynamic equilibrium:
1. The principle of local
thermodynamic equilibrium in nonequilibrium thermodynamics is valid for the
thermodynamic properties, but not for the fluctuations of these properties.
2. Fluctuations in fluids in
stationary nonequilibrium states are always long ranged, even far away from any hydrodynamic
instability.
3. Traditional hydrodynamic
instability analysis does not yield a correct
description of fluctuations
near instabilities.
These principles will be illustrated by theoretical and experimental studies of fluctuations in liquid and liquid mixtures subjected to a stationary temperature gradient.
A Self-Consistent Liquid-State Theory
Elisabeth
Schöll-Paschinger
Institut für
Experimentalphysik der Universität Wien, Austria
I will present the self-consistent Ornstein-Zernike
approximation (SCOZA), an advanced microscopic liquid-state theory that was
developed by Hoye and Stell and is known to give remarkably accurate results
for the liquid-vapour coexistence curves of simple fluids and remains
successful even in the critical region. After introducing the theoretical
concept, I will discuss several applications of this theory to various discrete
and continuum systems. Hard-core Yukawa fluids, Ise-Sogami fluids, fullerenes,
and square well fluids will be studied in detail. Furthermore, I will present
the phase behavior of systems with explicitly density-dependent potentials that
exhibit the phenomenon of double criticality. The accuracy of the SCOZA for binary symmetric fluid
mixtures, which show a much richer phase behavior, will be demonstrated by
comparison with Monte Carlo simulations.
Finally, I discuss possible extensions of the theory to soft-core
fluids.
On the Law of Increase of Entropy for
Nonequilibrium Systems
Departament
de Física Fonamental, Universitat de Barcelona, Spain
In this contribution we prove
that the nonequilibrium entropy of an N-body isolated system possesses a lower
bound and therefoere can not decrease and the entropy production should be
non-negative. Under the assumption of a smooth full phase-space distribution
function we define the nonequilibrium entropy as a functional of the set of
reduced distribution functions (distribution vector). As an application we
obtain a generalization of the BGK (Bhatnagar-Gross-Krook) relaxational model
in addition to the Boltzmann kinetic equation. We also establish the relation
between our theory and Clausius' formulation of the second law.
Patterns,
Confinement of Random Walkers, and Wavefront Propagation in Population Dynamics
V. M. Kenkre
Consortium of the Americas
for Interdisciplinary Science, University of New Mexico, Albuquerque, NM 87131,
USA
Recent work carried out in our group in the description of random walks and wavefront propagation in the subject of mathematical ecology will be presented. Specifically three issues will be discussed: patterns that arise as a result of spatially nonlocal competition interactions, effect of confinement on measurements of motion parameters, and transient effects in wavefront propagation from nonlinear population dynamics equations. The work is supported by the NSF, the NIH and DARPA.
Multiphysics Biological Modelling
Tomás Alarcón
Mathematical Institute,
University of Oxford, England
As advances in biological
sciences occur, it becomes clearer that a thorough understanding of biological
phenomena will require theoretical, quantitative frameworks. However the
complexity of such processes poses an extraordinary challenge to physical
scientists. The multiscale nature of biological processes in which phenomena
occuring at time and spatial scales ranging from tissue to gene are strongly
coupled overcomes most of the traditional modelling approaches and, therefore,
new ones are needed. An attempt to fill this gap consists of formulating
multiphysics models. In these models, each scale of interest is analysed in
terms of the different physical description. These different models are
eventually integrated in one single model which couple them all. In this talk,
I will introduce and motivate from a biological point of view this type of
model and give some examples of applications in the study of the growth and
treatment of solid tumours.
From
Painleve classification to Manning counter-ion condensation : new results for
the physical properties of bio-polymers
Emmanuel Trizac
Laboratoire de Physique
Théorique et Modèles Statistiques, Université de Paris-Sud, France
Onsager-Manning condensation
is a manifestation of the long range character of the Coulombic potential in 2D
geometry. This phenomenon is the cornerstone of our understanding of
bio-polymers. Beyond a charge density threshold, counterions
"condensate" onto the charged polymer. With salt (added electrolyte),
which is the experimentally relevant situation, the phenomenon is more complex
and has received little attention. We will show that recent mathematical
advances allow to obtain analytical results in a large range of salt content.
We will in particular discuss the implications of this work for the Coulombic
elasticity of bio-polymers through their persistence length.
Many-body interactions in colloidal systems
Jure Dobnikar
Jožef Stefan Institute, Jamova 39, 1000 Ljubljana
The colloid-colloid interactions in charge stabilized colloidal
suspensions are mediated via microions (electrolyte) and are therefore
inherently many-body in nature and simplified descriptions in terms of
pairwise additive effective interactions are not always appropriate. In recent
years a number of experimental and theoretical studies showed that
understanding the many-body effects is essential for complete understanding of
colloidal interactions.
I will present our numerical studies based on solving the nonlinear
Poisson-Boltzmann equation in three dimensions.
The method has been applied to study the following problems:
·
Coupling the Poisson-Boltzmann solver to the Brownian dynamics
simulations, we have studied the solid-liquid phase transition and showed that
many body interactions lead to a macroscopic effect, i.e., the deviation of the
melting line from the predictions based on the pairwise additive interactions.
·
Three-body interactions have been directly measured (experimentally) and
calculated and a qualitative agreement has been obtained.
·
The forces on each colloid in a system of 6000 colloids have been
evaluated by solving the nonlinear Poisson-Boltzmann equation and compared to
the sum of the effective forces derived from the cell model and Jellium model
approximations. A reasonable agreement has been observed, again with deviations
only explainable by many-body interactions.
The elastic constants have
been measured and numerically calculated in 3-D colloidal fcc crystals and the
Cauchy relation has been shown to be violated, which is a fingerprint of non
pairwise additive potentials.
Physicochemical mechanisms of sickle cell anemia
Peter Vekilov
Department of Chemical and
Biomolecular Engineering, University of Houston, USA
Sickle cell anemia is a
debilitating genetic disease, which affects hundreds of thousands babies born
each year worldwide. Its primary pathogenic event is the polymerization of a
mutant, sickle cell, hemoglobin (HbS) and this is one of a line of diseases
(Alzheimer's, Huntington's, prion, etc.) in which nucleation initiates
pathophysiology. We show that the
homogeneous nucleation of HbS polymers follows a two-step mechanism with
metastable dense liquid clusters serving as precursor to the to the ordered
nuclei of the HbS polymer. The
evidence comes from data on: the rates of fiber nucleation and growth, and
nucleation delay times; the interaction of fibers with polarized light; and
mesoscopic metastable HbS clusters in solution. The presence of a precursor in
the HbS nucleation mechanism potentially allows low-concentration solution
components to strongly affect the nucleation kinetics. The variations of these
concentrations in patients might account for the high variability of the
disease in genetically identical patients. In addition, these components can
potentially be utilized for control of HbS polymerization and treatment of the
disease.
Direct Measurement of Colloidal Particle
Rotation and Field Dependence in Alternating Current Electrohydrodynamic Flows
Jesús Santana Solano
Cinvestav-Monterrey,
Mexico
We have measured the
influence of both applied alernating
current (AC) field strenght and frequency on the electrohydrodynamic
(EH) flows present in colloidal systems near an electrode surface. The effect
of the flows is visualized by the rotation of the colloids, fluorescently
labeled by a novel technique involving EH-driven aggregation of smaller tracer
colloids to the surface of the larger colloids. Our results shows an E^2
dependence of these flows, consistent with an induced charge mechanism for
effective colloidal interactions. We have also observed a crossover in
frequency that suggests a change in the origin of the induced charge,
consistent with predictions from available theory. The EH flows appear to be
hydrodynamically screened inside clusters, as evidenced by the lack of rotation
of interior colloids and the cluster-size independent rotation rate of colloids
on the boundary.
Jesus Santana-Solano, David
T. Wu, and David W. M. Marr, Langmuir, 2006, 22, 5932-5936.
Origin of Bistability in the Lactose Operon
Moisés Santillán
Cinvestav-Monterrey,
Mexico
Multistability is an emergent
dynamic property that has been
invoked to explain multiple co-existing biological states. In this, work we
investigate the origin of bistability in the lac operon. To do this, we
develop a mathematical model for
the regulatory pathway in this system and compare the model predictions with
the experimental results of Ozbudak et al. (Nature 427, 737-740, 2004), in
which a non-metabolizable inducer was employed. We investigate the effect of
lactose metabolism using this model, and show that it greatly modifies the
bistable region in the external lactose (Le) vs. external glucose (Ge)
parameter space. The model also predicts that lactose metabolism can cause
bistability to disappear for very
low Ge. We have also carried out stochastic numerical simulations of the model,
for several values of Ge and
Le, to analyze the effects of
intrinsic noise due to small numbers of regulatory molecules. Our results
indicate that bistability is an efficient way to guarantee that E. coli
consumes glucose and lactose in the most efficient possible way. Namely, the lac operon is induced only when there is almost no
glucose in the growing medium, but
if Le is high, the operon induction level increases abruptly when the
bacterial culture is virtually depleted of glucose. We demonstrate that
this behavior could not be
obtained without bistability if the stability of the induced and uninduced
states is to be preserved. Finally, we wish to point out that the present
methods and results may be useful to study the emergence of multistability in
biological systems other than the lac operon.
Electrostatic Interactions in Dissipative Particle Dynamics
Minerva González-Melchor
Universidad
Autónoma de Puebla, Mexico
A new proposal to calculate
electrostatic interactions in dissipative particle dynamics is presented. These
interactions are calculated using the Ewald Sums method combined with charge distributions
on DPD particles. The method is applied to study bulk electrolytes and
polyelectrolyte/surfactant solutions. This proposal is also applied to
calculate the radius of gyration of a polyelectrolyte in a salt solution. The
radius of gyration shows good agreement with the trend found in static light
scattering experiments.
Liquid
crystal-based biosensors:
principles, simulations, and experiments
Orlando Guzmán
Departamento de Física, UAM-Iztapalapa
A thin film of liquid crystal can be used to detect
subtle changes on the interfaces that confine it. By careful control over interfacial chemistry and
topography, one can build LC-based biosensors. Typically, polarized light patterns are used to signal the
detection of adsorbed analyte. In this talk we will: (a) describe recent
experimental LC-based biosensors and discuss the principles for their
operation, (b) show that, by using multiple methods, computer simulation has
provided insights about the observed
patterns and the dynamical behavior of the LC, and (c) present a way to enhance the
sensitivity of these devices by quantifying the gradual modification of a
surface, as a function of concentration of analyte, in terms of the liquid
crystal’s anchoring energy.
Hernán Larralde, Centro de Ciencias Físicas, Mexico
Out of equilibrium systems
are characterized by the presence of fluxes. This is obvious in time dependent
systems, but it is also the case in non equilibrium steady states, which are
ditinguished from equilibrium by the fact that there is a non zero mean flux of
some quantity through the system. The above statement requires the recognition
that fluxes are stochastic variables and, perhaps, that their statistics beyond
the mean, can provide insight into the description of out of equilibrium
phenomena. Indeed, from Onsager to the fluctuation theorem, there has been a
great deal of work trying to relate the statistics of flux to entropy
production. In this talk I will present results from ongoing research on the
statistical properties of mass, energy and coupled fluxes in some simple
stochastic systems.
Glasses and
Deformed Crystals: Equilibrium States?
Victor
Romero-Rochín
Instituto de Física, UNAM, México
It is an accepted fact that
glasses and deformed crystals are not states of equilibrium; they are assumed
to be metaestable states. Without challenging directly such an assertion but
based on the experimental evidence that those states may be extremely long
lived, and thus be considered for those times as "stable", we present
a consistent thermodynamic theory (based on well known results of the theory of
elasticity) that can describe those solid states. We make a description of the
equilibrium states by means of the metric or strain tensor and the pressure
tensor of the body. We discuss our results aided by Molecular Dynamics
Simulation of a Lennard-Jones system.
Trapping and Condensing DNA at the
Air/Water Interface
Jaime Ruiz García,
Instituto de Física, Universidad Autónoma de San Luis Potosí, Álvaro Obregón
64, San Luis Potosí, Mexico.
DNA is a highly charged
polyelectrolite and as such it is considered to be completely soluble in pure
water. Surprisingly, we found that DNA can be trapped at the air/water
interface and does not go back into a pure water subphase. We show that DNA is
trapped in a minimum energy at the interface, much bigger that KT, that does
not permit its return to the bulk. Once at the interface, DNA molecules
condense to form different two-dimensional mesostructures such as foams, giant
rings, disks and rods at low density. This condensation occurs without the
presence of multivalent cationic ions, as it is required in bulk, for example
in condensing DNA toroids. However, we show that monovalent and divalent
cations do not change this behavior, but trivalent cations does. At high
density, the molecules form a remarkable monomolecular network. At the
interface, DNA is only partially immersed in water, which originates that the
chains get only partially charged, but the charges are of the same sign. Therefore,
this can be considered another case of like-charge attraction, similar to those
found in colloids trapped at the air/water interface. However, the origin of
the attractive part of the interaction potential is unknown. In addition, we
found that DNA at the air/water interface can form 2D smectic-like domains tens
of microns in size. Both, the DNA monomolecular networks and the smectic-like
domains are interesting from theoretical and application standpoints.
Posters
Home
1.- A comparative study of the complex
transcription-factor gene regulatory networks of E. coli and S. cerevisiae
L. Guzmán-Vargas1, Moisés Santillán2,3 and Albert
Díaz-Guilera4
1)
Unidad Profesional interdisciplinaria en
Ingeniería y Tecnologías Avanzadas, Instituto Politécnico Nacional, Av. IPN No.
2580, México D.F. 07340, México
2)
Centro de Investigaci_on y Estudios
Avazados del IPN, Unidad Monterrey, Av. Cerro de las Mitras No. 2565, Col.
Obispado, 064060, Monterrey, Nuevo Le_on, M_exico.
3) Centre for Nonlinear Dynamics
in Physiology and Medicine, McGill University, McIntyre Medical Sciences
Building, 655 Promenade Sir William Osler, H3G1Y6 Montreal QC, Canada.
4) Dept. Física Fonamental, Facultat de Física, Universitat de Barcelona, Diagonal 647, 08028 Barcelona, Spain.
In this work we
present a comparative analysis of two dfferent transcriptional regulatory
networks: one for the bacterium Escherichia coli, and one for the budding yeast
Saccharomyces cerevisiae. First, we measure several network properties for the
bipartite networks (with unidirectional links from the transcription factors to
the regulated genes), as well as for the networks projected to the
transcription factors and to the regulated genes. These measurements include
the clustering coefficient, the degree distribution, and a coefficient
measuring to what degree the nodes with most links in the network are connected
among them. Later, we construct random networks with the same degree
distributions as those of E. coli and S. cerevisiae, and carry out the same
measurements to compare with the original networks. Finally, we tested network
robustness by subjecting the original and randomized networks to removal of the
most connected nodes, and evaluating the changes.
2.- Test of an
universality ansatz fo the contact values of the radial distribution functions
of hard-spheres mixtures near a hard wall
Mariano López de Haro1, Santos B. Yuste2 and
Andrés Santos2
1.- Centro de Investigación
en Energía, UNAM, Temixco, Morelos 62580, Mexico.
2.- Departamento de Física,
Universidad de Extremadura, Badajoz, E-06071, Spain.
Recent Monte Carlo simulation
results for the contact values of polydisperse hard-sphere mixtures at a hard
planar wall are considered in the light of a universality assumption made in
approximate theoretical approaches. It is found that the data seem to fulfill
the universality ansatz reasonably well, thus opening up the possibility of
inferring properties of complicated systems from the study of simpler ones.
3.- Structural Properties of a Seven-Dimensional
Hard-Sphere Fluid
Miguel Robles1, Mariano López de Haro1
and Andrés Santos2
(1)
Centro de Investigación
en Energía, UNAM, Temixco, Morelos 62580, Mexico.
(2)
Departamento de Física,
Universidad de Extremadura, E-06071 Badajos, Spain.
The direct correlation function and the
(static) structure factor for a seven-dimensional hard-sphere fluid are
considered. Analytical results for these quantities are derived within the
Percus-Yevick approximation.
4.- Monte Carlo Simulations of the Liquid-Vapour Interface of
Lennard-Jones Diatomics for the Direct Determination of the Interfacial Tension
using the Test-Area Method
José Guillermo Sampayo-Hernández, Erich A. Müller and George Jackson
Department of Chemical Engineering, Imperial College London, South
Kensington Campus, London SW7 2AZ, UK
We have performed Metropolis constant volume Monte-Carlo simulation
(MC-NVT) to examine the vapour-liquid interface of systems of diatomic
Lennard-Jones molecules. The recently developed test-area method (TA) [Gloor et al., J. Chem. Phys., 123, 134703 (2005)] is used to
determine the interfacial tension; the TA method involves a thermodynamic (free
energy perturbation) route to the tension rather than the more common
mechanical (virial) relation of Kirkwood and Buff. Simulation data is reported
for diatomics with different bond lengths L
where the site-site Lennard-Jones potential is spherically truncated (ST) at 6s. Bond lengths of, 0.505, 0.6, 0.63, 0.67, 0.793 and 1.0 are examined. The
surface tension obtained with the TA method for the Lennard-Jones diatomics
with
are compared
with values obtained with the mechanical relation. The simulated vapour-liquid
interfacial tensions for systems with values of the parameters chosen to
represent real fluids (e.g., nitrogen and ethane) are satisfactory agreement
with the experimental data. The density profiles, saturation densities in the
vapour and liquid phases, and the interfacial thickness are also obtained for
each system showing a good
agreement with previously published results where available.
5.- Behavior and Characterisation of Liquid Crystals
Phases: a Molecular Dynamics Simulation Study
Enrique Cañeda Guzmán, José Antonio Moreno Razo and
Enrique Díaz Herrera
Departamento
de Física, Universidad Autónoma Metropolitana Iztapalapa, Mexico.
In this study we report
results of Molecular Dynamics simulation of liquid crystals for ellipsoidal
shape particles using a Gay-Berne (GB) potential. The phase diagram is
calculated with parameters GB (k = 3; k’ = 5; m = 1; n = 3), it had been
discussed a little in the literature and is of interest to study the
orientacional behavior of the equilibrio liquid-crystal in the coexistence at
low temperature. We give a detailed discussion of the structure of the liquid
crystalline phases exhibited by ellipsoidal shaped mesogenic molecules. On the
other hand, results of molecular dynamics simulations for binary mixtures of
fuids confined Lennard-Jones type are presented, like initial stage in the
development of a numerical code, in a future work we would study in more detail
the effect of confinement of these systems, that has been few discussed. We
will extend these study to binary liquid crystal mixtures.
6.- De la mariposa de Hofstadter a la de Fibonacci
Gerardo García Naumis and Francisco J. López
Rodríguez
Instituto de Física, UNAM.
Apartado POstal 20-364, 01000, México D.F., México.
En este trabajo se muestra
que es posible escribir los potenciales ergódicos que resultan de considerar el
movimiento de un electrón en una red bajo un campo magnético o en un cuasicristal, como un potencial genérico
de tipo trigonométrico. De este modo, las propiedades de conducción y el
espectro de energías de ambos sistemas pueden estudiarse mediante las funciones
de correlación estadística del potencial, observandose una transición de
estados extendidos a críticos (fractales). Como resultaod, el presente trabajo
plantea la posibilidad de construir motores cuánticos de tipo matraca usando
campos magnéticos modulados en el espacio.
7.- Title not
available
José Antonio Climent
Hernández
Facultad de Ciencias, UNAM.
(Circuito interior S/N Facultad de Ciencias, Edificio de Ciencias Experimentales
y Docencia "Tlahuizcalpan".
Analysis of the Cox, Ross & Rubinstein y Black & Scholes methods
to develop an information system to value American and European Call and Put
option prices on American dollar and the state of the contracts until their
maturity. This development is performed in terms of a Fokker-Plank equation
using the Itô and Stratonovich calculus.
8.- Microrheology of viscoelastic fluids containing
light scattering inclusions
Catalina Haro-Pérez1, Efrén
Andablo-Reyes1, Pedro Díaz-Leyva1, and José Luis
Arauz-Lara1,2
(1)
Instituto de Física "Manuel Sandoval Vallarta", Universidad
Autónoma de San Luis Potosí,
Álvaro Obregón 64, 78000 San Luis Potosí, México
(2)
Departamento de Física, CINVESTAV, Avenida IPN 2508, Colonia Zacatenco, 07360 México D. F., México.
The microrheology of
viscoelastic fluids containing inclusions with high scattering power is
measured by depolarized dynamic light scattering (DDLS) from optically anisotropic spherical
colloidal probes. The anisotropy of the probes allows us to measure both their
translational and the rotational mean squared displacements simultaneously,
whereas DDLS allows us to suppress the light scattered from the inclusions. The
storage and loss moduli are determined from both mean squared displacements and
the results compared with mechanical measurements.
9.- Polarization-Diffusion Effect on the Dispersion of
N- and alpha- Dielectric Relaxation Modes
S. I. Hernández and L. F. del Castillo
Instituto
de Investigaciones en Materiales, Universidad Nacional Autónoma de México, P.O
Box 70-360, 04510 México, D.F., Mexico
In this work, the
contribution of polarization diffusion on the dispersion of the electric
susceptibility in polymeric materials, that exhibits normal (N-) relaxation at
low frequencies and segmental or alpha relaxation at high frequencies, is
studied. Polarization diffusion is locally established when the viscoelastic
relaxation couples to the relaxation of a dipolar system. In order to formulate
this diffusion process, it was proposed a physical description based on a
system of two coupled equations to express the viscoelastic and dielectric
relaxations, and the coupling between them is introduced by considering spatial
inhomogeneities. The complex polarization-diffusion coefficient and the wave
number as frequency function are obtained considering two parameters, which
were evaluated considering a diffusive model for the N- and alpha dielectric
modes respectively, for two polymeric systems.
10.- Structure
and Diffusion of Colloidal Dumbbells
Andrés García-Castillo and José Luis Arauz-Lara
Instituto de Física,
Universidad Autónoma de San Luis Potosí, San Luis Potosí, SLP, México
The static structure and diffusion of colloidal dumbbells in water,
confined in quasi-two-dimensional geometries is measured by optical microscopy.
Colloidal dumbbells are fabricated by inducing colloidal aggregation followed
by sintering. The particles are confined between two parallel plates in order
to form a quasi-two-dimensional system. Measurements of the structure of the
suspension and the mean squared displacements, rotational and translational of
the particles are presented.
11.- Thermodynamical Formalism of symbolic systems: An
application to DNA sequence of Phage fX174
José Rubén Luévano
Departamento
de Ciencias Básicas, Universidad Autónoma Metropolitana-Azcapotzalco, 02200
México, DF, México.
In this work we give a
straightforward application of thermodynamical formalism to DNA sequence of the
bacteriophage fX174. That DNA sequence was the first one
decoded, and its simplicity allows us to test the applicability of our
thermodynamic approach. We introduce a formal canonical partition
function, hence we compute the free energy and the generalized entropies.
Also, we compute the Lempel-Ziv complexity of the symbolic system induced by
the corresponding genetic sequence.
12.- Combining Rules for Mixtures of Elongated
Molecules
José Alfredo González-Calderón and Fernando del Río
Apartado
Postal 55-534, México 0934, Distrito Federal, México.
We show that Approximate
Non-Conformal (ANC) theory is reliable for describing the mixed second virial
coefficient of mixtures of elongated molecules (n-alkanes) and also mixtures of
elongated with quasi-spherical molecules.
We analyzed systems with low dipole moments molecules such as n-methane,
n-ethane,...., and n-octane, together with Ar, N2, and O2. The research was
done using Lorentz-Berthelot, Fender-Halsey-Lorentz and Kong combining rules.
Whe show that Lorentz-Berthelot combining rules are appropiate for describing
the experimental data of second virial coefficient of the mixture while the
other do not represent correctly the data when the mixture has components of very different sizes or energies.
13.- Optimised Equation of State of Square-Well Fluids
of Variable Range
Rodolfo EspÃíndola-Heredia and Fernando del Río
Apartado
Postal 55-534, México 0934, Distrito Federal, México.
A optimised equation of state
(EOS) of particles interacting with a square-well (SW) potential of variable
width 1.1 < λ < 3.0 is presented. The equation was built following the
perturbation procedure used in previous EOS. The SW perturbation terms were calculated up to fourth order
by MC simulation of hard-sphere systems and comparated for consistency in the
thermodinamic limit with the internal energy of the SW fluid obtained by NVT
Monte Carlo simulations. Internal energies, pressures, chemical potentials and
specific heats agree with results of simulations and compare farvourably with
those of recent SW EOS.
14.- Prediction of Excess Properties and Phase
Equilibrium in Liquids Mixtures from Effective Potentials
Benjamín Ibarra-Tandi and Fernando del Río
Apartado
Postal 55-534, México 0934, Distrito Federal, México.
We calculate thermodynamic
properties of mixtures using the Approximate Non-Conformal, ANC, theory of
fluids. This theory introduces a family of intermolecular potentials
characterized by the usual molecular parameters for size δm and energy ε,
plus an extra parameter, account for the profile of the potential: The softness
s. We predict excess volumes and vapour-liquid coexistence of mixtures of Ar,
Kr and other simple liquids at low temperatures. Very good agreement with
experiment is obtained by using the ANC interactions, previously determined
from gas-phase properties, supplemented with a two-body effective term that
models the Axilrod-Teller-Muto three-body potential.
15.- Virial coefficients and effective potentials of
linear molecules
Adrián Rocha-Ichante and Fernando del Río
Apartado
Postal 55-534, México 0934, Distrito Federal, México.
We test the applicability of the ANC theory to a diversity of
nonspherical model molecules: Non-Spherical Square Wells (NSSW) and
Non-Spherical Kihara (NSK). Effective volumes, virial coefficients are
calculated analytically. Effective potentials are also determined explicitly
for all cases. As a main qualitative results it is found that molecules look
harder when they are more elongated. This behaviour has been observed in
n-alkanes and perfluoro-alkanes.
16.- Motion in washboard potentials: Dimer versus
monomer
E. Heinsalu and M. Patriarca
Institute of Theoretical
Physics, Faculty of Chemistry and Physics, Tartu University, Tähe 4, 51010 Tartu, Estonia
We study the system of two interacting particles forming a dimer and
moving in a one-dimensional periodic potential. The system is under the
influence of a constant external force and the interaction between the
particles is assumed to be harmonic. We study the diffusive motion and the
mobility of the dimer in the parameter space of the system. The results are
compared to those of a monomer.
17.- Recent results on fractional diffusion in space-
and time-periodic force-fields
E. Heinsalu, M. Patriarca, I. Goychuk, G. Schmid and P. Hänggi,
Institute of Theoretical
Physics, Faculty of Chemistry and Physics, Tartu University, Tähe 4, 51010
Tartu, Estonia
Recent novel results on fractional diffusion are presented. Anomalous
transport is investigated within the framework of the fractional Fokker-Planck
equation (FFPE) and the underlying continuous time random walk (CTRW). Our
research addresses both, the time-independent as well as the time-dependent
force fields. In the first case, we derive from FFPE some intriguing results
for anomalous transport and anomalous diffusion in washboard and periodic potentials [1,2,3]. The results
are confirmed by stochastic simulations of the underlying CTRW. Considering the
time-dependent fields, we present new features for anomalous transport under
the influence of a time-periodic symmetric dichotomous force. Our results prove
that the standard FFPE in time-dependent fields is flawed. The results are,
however, consistent with a modified version of the FFPE, which can be derived
rigorously for this particular case under study.
[1] I. Goychuk, E. Heinsalu, M. Patriarca, G. Schmid, and P. Hänggi,
Current and universal scaling in anomalous transport, Phys. Rev. E *73*, 020101
(2006), Rapid Communication.
[2] E. Heinsalu, M.
Patriarca, I. Goychuk, G. Schmid, and P. Hänggi, Fractional Fokker-Planck
dynamics: Numerical algorithm and simulations, Phys. Rev. E *73*, 046133
(2006).
[3] E. Heinsalu, M.
Patriarca, I. Goychuk, and P. Hänggi, Fractional diffusion in periodic
potentials, J. Phys. – Condensed Matter (2007), in press,
[arXiv:cond-mat/0604269]
18.- Finite-size effects in microrheology
I. Santamaria-Holek and J.M. Rubi
We propose a model to explain finite-size effects in intracellular microrheology
observed in experiments. The constrained dynamics of the particles in the
intracellular medium, treated as a viscoelastic medium, is described by means
of a diffusion equation in which interactions of the particles with the
cytoskeleton are modelled by a harmonic force. The model reproduces the
observed power-law behavior of the mean-square displacement in which the
exponent depends on the ratio between particle-to-cytoskeleton-network sizes.
19.- Phases obtained by shear in a solution of flexible
cylindrical micelles
Jorge Delgado1, Pavlik Lettinga2 and Rolando
Castillo1
(1) Instituto de Física at
UNAM, Mexico and (2) Forschungszentrum Jülich, Germany.
Semidilute and dilute regimes
of viscoelastic CTAB/NaSal systems are studied under stationary and
non-stationary shear flow conditions. In the diluted regime, we could observe
and explain the formation of shear-induced structures (SIS) from fast strain
thixotropic loops that decouple the stress coming from non-deforming material
(the solvent) and the stress coming from SIS formation. Furthermore, the
maximum quantity of SIS at every shear rate is obtained from ramping-down
curves. These curves are independent of the deformation history and can be
related with a typical time of SIS formation. In contrast with the dilute
regime, where SIS span the fluid; in the semidilute regime the formation of
bands in the fluid is common. Using different rheometers and from flow velocity
profiles, we obtained the flow properties of different bands in the fluid. We
can describe a real interface between bands and an initial hydrodynamic nature
of stress oscillations under stationary flow conditions. We found that stress
oscillations, typical from a coupling between concentration and flow, are
associated with a single band in the fluid.
Finally we discuss the idea
of a phase transition under shear in the semidilute regime.
20.- Purification and characterization of multi-wall
carbon nanotubes produced by chemical vapor deposition (CVD) method
J.L. Hernández-López,1 E.R. Alvizo-Páez,1
J. Ruiz-García1, J.M. Romo-Herrera,2 M. Terrones2
and H. Terrones2
(1)
Instituto de Física, Departamento de Fisicoquímica y Física Estadística, Dr.
Manuel Nava Martínez No. 6, Zona Universitaria, Universidad Autónoma de San
Luis Potosí, San Luis Potosí, 78290 México.
(2)
Instituto Potosino de Investigación Científica y Tecnológica, A.C., Camino a la
Presa San José s/n, Lomas 4ª
Sección, San Luis Potosí, 78231 México.
A purification procedure for
multi-wall carbon nanotubes (MWCNTs) and nitrogen-containing carbon nanotubes
(CNx MWCNTs) is presented in this work. The methodology incorporates
a hydrothermal/ultrasonic treatment along with other treatments such as
extraction of polyaromatic compounds, dissolution of metal particles and
mechanical separations by means of isopycnic centrifugation based-techniques.
The effects of each treatment in the purification process are also discussed by
characterizing the intermediate products using SEM, STEM, XRD,
DRFTIR-spectroscopy and TGA.
21.- Morphology Transitions in
Langmuir Monolayer Domains
Andrea Gutiérrez-Campos, Karen Volke and Rolando
Castillo
Instituto
de Física, UNAM.
In recent experiments, morphology transitions in
Langmuir monolayer domains have been observed. In the present work related to
my PhD research investigation, the mechanisms behind such morphology
transitions will be studied. In the first part, pattern formation and growth
from fluid to condensed phases will be studied for four different monolayers:
Nervonic Acid, DODA, Methyl Palmitate and DMPE. With an appropriate Langmuir
trough and a Brewster angle microscope (BAM), we will observe morphology
transitions and relate them to a possible orientation change of the
amphiphillic chains. This orientation change is related to the anisotropy in
line tension of the interface between condensed and fluid phases. In the second
part of this work, we will formulate a hydrodynamic model to understand the
domain growth analyzing the interface instability. Finally, we propose an
experimental setup which will allow us to trap one single monolayer domain with
the aid of PMMA microspheres attached to the domains, using optical tweezers.
With this experimental setup, we will be able to modify the thermodynamic
variables involved in the morphology transitions and with the BAM we will
observe the domain evolution.
22.- Concept of Caging in the Freezing of Hard Disk
Adrián Huerta1, Andrij Trokhymchuk and Douglas Henderson
(1)
Departamento de Física No lineal del Instituto de Ciencias Físicas, UNAM.
As density in the system of hard disks
progressively increases towards freezing transition, the number of nearest
neighbors of each disk saturates at the level of six neighbors and system as
whole shows enhanced tendency for hexagonal ordering. An unoccupied area, that
still is in disposal, is distributed uniformly over the entire system that
results in the interparticle gap width of ~0.152¦Ò . This value of the gap
correlates well with the estimates using independent sources from the
literature. In the present report we show that hexagonal ordering with spacing
of 0.152¦Ò initiates the caging of the central particle by the alternative
nearest-neighbors and can be crucial in the understanding of the freezing
transition in a hard-disk system.
23.- A Molecular Dynamics Study of Interfacial
Behavior of Discotic Molecules
Cienega Cacerez Octavio, J Antonio Moreno-Razo and
E. Díaz-Herrera
Universidad
Autónomoa Metropolitana Iztapalapa, Av. San Rafael Atlixco 186, Colonia
Vicentina, C.P. 09340, México D.F., México.
The Gay-Berne potential
anisotropic of interaction has been employed extensively in simulation studies
of rod-like liquid-crystals. However, the potential can be used also to study discotic
liquid crystals, that is, compounds whose molecules are flattened or
disc-shaped. Here we used a suitable parametrization for Gay-Berne discs with
GB(k=0.345 k’=0.2 m=1 n=2) for pure
systems. We report results of computacional simulations of molecular dynamics
in the ensemble NPT and NVT for a system of 2000
particles. We calculated the phase diagram of this system and studied the
behavior of the interface tension like function of the temperature for the
coexistence curve. We calculated the pair radial distribution function g(r) and
the orientational G(r) like part of the structural information of the
homogeneus (Isotropic, Nematic, Columnar).
24.- Structure and Dynamics of Interacting Brownian
Particles in One-Dimensional Channels on Periodic Laser-Fields
Salvador Herrera-Velarde and Ramón Castañeda-Priego
Instituto
de Física, Universidad de Guanajuato, Loma del Bosque 103, Col. Loma del
Campestre, 37150 León, Guanajuato, México.
We systematically study both
structural and dynamic properties of one-dimensional charged colloids on
periodic laser-fields by means of browian dynamics and Monte Carlo computer
simulations, as well as by integral equations theory. The latter one, which is
solved within the Rogers-Young approximation, describes quantitatively the
structure in the fluid phase without applied laser-field. In such case, we find
that the structure of the suspension possesses basically the properties shown
by two- and three- dimensional open systems, i.e., the characteristic length
scale of the system is given by the mean interparticle distance. We also find
that the mean-square displacement (MSD), W(t), shows the typical
crossover from normal diffusion at short-times to sub-diffusion at long-times
in which W(t) ~ t1/2, as theoretically predicted for
colloidal and atomic systems. Nevertheless, when the laser-field is activated,
a competition between its periodicity and the natural length scale of the
suspension is observed and therefore a gradual structural transition is found.
Moreover, at small potential strengths the MSD preserves its well-known
sub-diffusive behaviour. However, at higher potential strengths the colloids
are, on average, placed at the laser-potential minima, but one can also observe
particle configurations in which two colloids are closer or further than the
distance between two consecutive minima. Thus, the dynamics of the system is
determined by the collective diffusion of such particle distributions along the
channel modifying the t1/2 diffusion law at long times.
25.- Directing the Spectroscopies States of CdS
Nanoparticles by Chemical Surface Modification
M. Quintana1, F. Méndez2 and
E. Pérez1
(1)
IF-Universidad Autónoma
de San Luis Potosí, Manuel Nava 6, Zona Universitaria, CP 78290, San Luis
Potosí, SLP.
(2)
Universidad Autónoma Metropolitana-Iztapalapa,
México DF
Size-tunable optical
properties in nanoscales derive primarily from the physical size and shape of
the materials. In II-VI semiconductor nanoparticles the size-tuning is
attributed to the confinement of the exciton in a nanocrystal significantly
smaller than the bulk exciton. That interest the chemist because excitons can
be engineered in a material according to structure. Interesting spectroscopic
properties are governing by the size, including the band gap and the exciton
binding energy which are often minuscules in bulk materials, and are greatly
accentuated in nanometer sized materials. In this work we present a surface
chemical modification of CdS nanoparticles by different Lewis bases. The
spectroscopy studies reveal details of the collective excited states that
capture and redistributed the excitation causing a blue shift and fluorescence
enhancement depending on the adsorbed molecules. The experimental results are
explained by a theoretical DFT calculation.
26.- Study of the
dynamic of Brownian non spherical particles
José Guillermo Méndez Bermúdeza, Minerva
González Melchora, Iván Santamaría Holekb
a Instituto de Física “Luis
Rivera Terrazas” BUAP. C.P. 72570. Av. San Claudio y 18 sur, San Manuel.
Puebla, México.
b Facultad de Ciencias,
Universidad Nacional Autónoma de México, Circuito exterior de Ciudad
Universitaria, 04510 DF, México
In this work we analize the
behavior of non-spherical particles inmersed in a heat bath at temperatura T.
This system execute translational an rotacional Brownian motion. This study is
being carried out with theory and computer simulation. In the theorical study
we use the mesoscopic non equilibrium thermodynamics, base on the existente of
local equilibrium in phase space. For this case, we derive the equation of
state. In the second part, we use the Gay-Berne potencial to model the
interaction of non spherical particles. The translational and rotacional
equations of motion are solved numerically using the Leap-Frog algorithm. The implementation
of this part of the work is in progress.
27.- The approximate entropy as a measure of the
complexity in time series
A. Ramírez-Rojas
Área
de Física de Procesos Irreversibles Departamento de Ciencias
Básicas,
Universidad Autónoma Metropolitana-Azcapotzalco, 02200, México.
The approximate entropy
(ApEn) was introduced by Pincus [1] to quantify the creation of information in
a time series. A low value of the entropy indicates that the time series is
deterministic; a high value indicates complexity. We calculate the ApEn for an
electroseismic time series and, we observed an important decreasing behavior of
the ApEn, indicating low complexity of the signal a few hours before a great
earthquake. In fact, we consider that this methodology could be a good
estimator in order to describe the complexity of a time series. Particularly
ApEn seems to be as a possible indicator precursory behaviour before of a great
seism.
1. S. M. Pincus. Approximate
entropy as a measure of system complexity.
Proc.
Natl. Acad. Sci. USA. 88, 2297 - 2301, 1991.
28.- Metastability in the kinetic Ising model
David P. Sanders, Hernan Larralde & Francois
Leyvraz
Insituto
de Ciencias Fisicas, Universidad Nacional Autónoma de México,
Apartado
postal 48-3, C.P. 62551, Cuernavaca, Morelos, Mexico
Many physical systems have
metastable states, i.e. states far from equilibrium, where a system remains for
a long time before a sudden decay to equilibrium occurs. We sketch a theory
[1,2] describing metastable states in
Markov processes, assuming that the evolution operator has a small
eigenvalue, i.e. a long time-scale. The corresponding eigenvector contains
information about the structure of the metastable state.
We test this theory
numerically [2] in the kinetic Ising model, i.e. the standard Ising model
(spins on a lattice modelling a ferromagnet) with external field and Metropolis
spin-flip dynamics, finding very good agreement. In particular, we use the
Wang-Landau algorithm to show that the coarse-grained metastable distribution
is proportional to the equilibrium distribution, as has commonly been assumed,
and that the coarse-grained eigenvectors contain information about free
energies, hysteresis loops, and the probability of reaching the metastable and
equilibrium states from given initial conditions.
[1] H. Larralde and F.
Leyvraz (2005), Metastability for Markov processes with detailed balance, Phys.
Rev. Lett. 94, 160201.
29.- Computational studies of dilute systems with
electrostatic interactions between particles
Edgar Nuñez Rojas and Hector Dominguez Castro
Instituto
de Investigaciones en Materiales, UNAM, Circuito exterior s/n. México, D. F.,
C. P. 04500
In this work Dynamic
Molecular simulations of dilute systems of particles electrostatically charged were carried out using the Soft
Primitive Model. Simulations were
performed at diferent desinsities within a given interval of temperatures.
After, temperature was set up and simulations were carried out varying density of
the system. In some of these systems, it was noticed the formation of aggregate
structures with different number of particles; such systems are being studied
to determine the main factors involved in its aggregation. Electrostatic system
shows a metastable behaviour when temperature varies within the interval of
temperature chosen. Results showed that there is a region within the interval
of density chosen in which the cluster formation shows a metastable behaviour.
On the other hand, after this region electrostatic system shows an homogeneous
behaviour without formation of aggregate structures.
30.- Rheology and Micro-rheology of slow relaxing
fluids
Julian M. Galvan-Miyoshi and Rolando Castillo
We have studied the rheology
and microrheology behavior of a microemulsion made of hexadecyltrimethylammonium
bromide (CTAB) / sodium salicylate (NaSal)/ water, which forms very long and
flexible cylindrical worm-micelles. The viscoelastic behavior of this mixtures
depends on the CTAB molar concentration, on the molecular ratio between CTAB
and NaSal, R=[NaSal]/[CTAB], and on temperature. We have probed the
viscoelastic properties of the mixture with a light scattering technique
(diffusion wave spectroscopy), through measuring the average motion of
microspheres dispersed in the microemulsion. We obtained G'(w) and G''(w),
prior obtaining the mean square displacement of the microspheres, showing that
the microemulsion is a Maxwellian fluid at low frequencies. We obtained the Cole-Cole diagram and
the Maxwell fluid constants. Also, measurements of the intensity correlation
function were made on the polyacrylamide gel during the sol-gel transition.
Results shows a plateau appearing and growing as the gel is forming.
31.- Atomic Force Microscopy images of Lyotropic
Lamellar Phases
C. Garza , L. T. Thieghi and R. Castillo
Instituto
de Física. UNAM P.O. Box. 20-364, D.F. México, 01000,
México.
For the very first time,
atomic force microscope images of lamellar phases were observed combined with a
freeze fracture technique that does not involve the use of replicas. Samples
are rapidly frozen, fractured, and scanned directly with atomic force
microscopy, at liquid nitrogen temperature and in high vacuum. This procedure
can be used to investigate micro-structured liquids. The lamellar phases in
AOT/water and in C12E5/water systems were used to asses this new technique. Our
observations were compared with X-ray diffraction measurements and with other
freeze fracture methods reported in the literature. Our results show that this
technique is useful to image lyotropic lamellar phases and the estimated
lamellar periodicities are consistent with those obtained by X-ray diffraction.
32.- Polystyrene Nanoparticles Covered with a
Thermically Cross-linked PAH/PAA Film
Rosa Mayela Romero-Gómez1, Ma. de
Lourdes González-González2, Ferdinando Tristán3, Elías Pérez2
(1)Facultad
de Ciencias, (2)Instituto de Física, (3)Centro de Investigación y Estudios de
Posgrado, Universidad Autónoma de San Luis Potosí, San Luis Potosí, S.L.P.,
México
Polyelectrolyte
Layer-by-Layer (LbL) self-assembling is a well known method used to obtain very
thin films on different surfaces based on the adsorption of the polymers by
coulombic forces. This work is focused on the surface of negatively charged
polystyrene [PS] colloidal particles. These colloidal particles are covered by
a self-assembled film made with five bilayers of two weak polyelectrolytes:
positive poly(allyl amine) [PAH] and negative poly(acrylic acid) [PAA]. In
order to maximize their adsorption on the colloidal particles PAH is adsorbed
on the surface using a pH value of 4 while the PAA is adsorbed at pH value of
7.5. Once the self-assembled film was formed on the PS colloidal particles,
they are heated above 120 ºC to allow the cross-linking of the film. PS
particles are characterized through all the process using Attenuated Total
Reflectance Fourier Transform Infrared Spectroscopy [ATR-FTIR], Atomic Force
Microscopy [AFM] and Dynamic Light Scattering [DLS].
33.- A markovian model for the G-protein
voltage-sensitive modulation of N-type calcium channels
Santiago
Rebolledo-Antúnez and David García-Díaz
Departamento de Fisiología, Facultad de
Medicina, Universidad Nacional Autónoma de México, Av. Universidad 3000 México D.F.
04510, México
Neurotransmitters
modulate N-type calcium channels via G protein-coupled receptors in both
voltage-sensitive and insensitive modes. It has been suggested that
voltage-sensitive modulation modifies gating of these channels involving changes
at the level of voltage-sensitive transitions before the channel opens. Eyring
theory implies that the rate
constants for these transitions must consist of two components: one, is
voltage-sensitive (with charge transferring) and the other, is voltage-insensitive
(enthalpic and entropic factors). In this work we present a markovian model for
the gating kinetics of the G-protein
voltage-sensitive modulation of N-type calcium channels. This model
suggests that this type of modulation occurs in the voltage-insensitive
component at the rate constant transitions level where there is not charge
transferring.
34.- Parametric adjustment of a model of coherent
scattering of light to the optical reflectance of a flat surface with adsorbed
particles
F. Alarcón-Oseguera2, M.-C. Peña-Gomar1,
Augusto García2, Francisco Castillo3 and E. Pérez3
(1)
Facultad de Ciencias Físico-Matemáticas de la Universidad Michoacana de San
Nicolás de Hidalgo, Edificio B, Ciudad Universitaria, C.P. 58030, Morelia,
Michoacán, México.
(2) Centro de Ciencias Aplicadas y Desarrollo
Tecnológico, Universidad Nacional Autónoma de México, Ciudad Universitaria,
A.P. 70-168, México D.F. 04510.
(3)
Instituto de Física, Universidad Autónoma de San Luis Potosí, Alvaro Obregón
64, C.P. 78000, San Luis Potosí, SLP, México.
In order to obtain the
parameters and limits of a theoretical model of the reflectance produced by
particles adsorbed in a flat surface an adjustment methodology is designed in
where the experimental datas are taken into account. The quality of the fitting
is moderate by a c2 distribution. The adjustment is essentially, a method of least square
that is solved by Newton-Raphson, where the matrix is inverted by singular
values decomposition. This method allows a careful analysis of the fit
parameters and it allows us to have criteria to validate the theoretical model.
35.- Statics and dynamics properties of a neutral complex made by a
polymer and two spheres
A. Vargas-Calderón, N.
Bagatella-Flores
Facultad de Física e Inteligencia Artificial, Universidad Veracruzana
Our
main motivation is a biological
system made by the nucleosome, which is the smallest entity of the chromatine
and consist in a DNA chain and the
histone, being it a octamer proteins and a linker protein. The DNA chain attach
the histone almost two turns, and then attach other histone.
In this work
we want to investigate the
equilibrium configuration and the statics and dynamic properties of complex
made by a polymer chain with two spheres via Brownian Molecular Dynamics
simulations. We are looking for the equilibrium configuration of the complex
made by the chain and the two spheres in which its energy is minimized. We ask
which equilibrium configuration is preffered, to be the two big spheres
together or separated, together in
the middle of the chain or in one end, which end. For other hand, since the length
chain is longer than the persistence length of the chain, we expect to see big
loops, from them we want to count its size and preffered position to appear. We
expect to see small loops but they must desapear faster because they cost big
energy.
For the
dynamic properties we need to determine the mean square displacement of the
center monomer attatched to each sphere, then it is possible determine the
resulting diffusion coefficient of each central monomer as a function of
friction coefficient, chain length, persistence length lp and absortion energy ka. From this information we can describe the
motion mechanism of the chain, which could be any of two situations, sliding or reptating (attach or detach
monomers).
36.- Statics and dynamics properties of a set of polymers
J.H. Zamora-Navarrete, N.
Bagatella-Flores
Facultad de Física e Inteligencia Artificial, Universidad
Veracruzana
Our main
motivation is a biological system like DNA, which is a chain with negative charge
polyelectrolyte. The human cell contains more than two meters of DNA packaged
into the molecules of dimensions from 5 to 20 micrometers of diameter. Then the
chromosomic molecules of DNA are thousand of times larger than the nuclear
diameter, for that reason the DNA must be packaged in a very efficient way, in order to protect the genetic
information, along the cellular cycle. In the present work, using Brownian
Molecular Dynamics simulation we want to understand the static and dynamic
properties of a set of short polymers. Their equilibrium configuration as a
function of their persistence length, those must be toroidal, bundle or
globular configuration, and should looks like DNA real configurations.
37.- Polymeric
Phase Diagrams
N. Bagatella-Flores,*,1
S.A. Orozco-Fuentes1, Z. Dominguez2
1Facultad de Física e Inteligencia Artificial, Universidad Veracruzana,
Apartado Postal 475. Xalapa, Veracruz., MEXICO
2Unidad de Servicios de Apoyo en Resolucion Analitica, Universidad Veracruzana.,
Apartado Postal 575, Xalapa, Ver., MEXICO
We investigate
the equilibrium configurations and the dynamic and static properties of a
polymer chain via Brownian Molecular Dynamics simulations. We start by
calculating the dynamics of the polymer in one and three dimensions.
Specifically, we determine the mean square displacement of the center of mass
and the resulting diffusion coefficient of the chain as a function of friction
coefficient, chain length, and persistence length. We observe that the
diffusion value for a chain with fixed number of monomers and friction
coefficient is almost the same in one or three dimensions. Our results
reproduce the Einstein relation. Since the polymer is at equilibrium
configuration in which its energy is minimized, the chain moves as a whole
object, and the position of the center of mass is almost invariant with respect
to the positions of all the monomers of the chain. Thus, we do not observe any
noticeable change in the diffusion coefficient as a function of the persistence
length. We also establish the dependence of the equilibrium configuration with
respect to the chain length and the persistence length. From the equilibrium
configurations we extract the length and position distribution of thermally
excited loop defects. Finally, a polymeric phase diagram is obtained for a polymer
in three dimensions as a function of the chain length.
Registration
Home
2007
Meeting Registration fees (in mexican pesos,
including registration, lodging and meals*)
Early registration (before November 30) |
Late registration (after November 30) |
|
Reduced fee for
students presenting poster (sharing double
room) |
$3,000.00 + 15 % IVA (si requiere factura) |
$3,300.00 $1,650.00 (becados) +
15 % IVA (si requiere factura) |
Regular participant (sharing double room) |
$5,000.00 + 15 % IVA (si requiere factura) |
$5,600.00 + 15 % IVA (si requiere factura) |
Regular participant (single room) |
$6,300.00 + 15 % IVA (si requiere factura) |
$6,800.00 + 15 % IVA (si requiere factura) |
Accompanying person (sharing room) |
$2,700.00 + 15 % IVA (si requiere factura) |
$3,000.00 + 15 % IVA (si requiere factura) |
* The fee includes meals from dinner on Tuesday the 9th to
lunch on Friday the 12th January.
Payments
should be deposited in the following bank account
(Please send a copy of your bank receipt by
e-mail to Ramón Castañeda Priego e-mail: wmsp@fisica.ugto.mx):
Bank |
Banamex,
S. A. |
Office |
0349 |
Account
number |
1866151
(payments in Mexican pesos) 934534-7
(payments in USD) |
Account owner |
Sociedad
Mexicana de Física, A. C. |
Bank
code |
|
Bank Address |
Av.
Paseos del Pedregal 110 Col.
Jardines del Pedregal 01900
México, D. F. |
Standard
bank code for electronic transferences |
002180034918661519 (transferences in Mexican pesos) 002180034993453470
(transferences in USD) |
Purpose
of payment |
WMSP05 |
NOTAS IMPORTANTES PARA
PARTICIPANTES MEXICANOS:
·
Si requieren recibo con RFC, a las cuotas
siguientes agréguese IVA. El precio a cubrir entonces, es la cuota de la tabla
más el IVA.
In order
to register, please send an e-mail to Ramón Castañeda Priego wmsp@fisica.ugto.mx
with the following information (see example at the end of this page):
Poster contribution (yes or not). In the case
that you have a poster contribution, please include title, authors, addresses and
abstract, exactly in the same form you want it to appear in the program of the
meeting. Please underline the name of the exponent.
Program of the XXXV
Winter Meeting (2006) (The 2007 program
will be anounced soon) Home
Tuesday 10 |
Wednesday 11 |
Thursday 12 |
Friday 13 |
|
7:00 – 9:00 |
|
Breakfast |
Breakfast |
Breakfast |
8:45 – 9:00 |
|
Opening ceremony |
|
|
9:00 – 10:00 |
|
|||
10:00 – 11:00 |
|
|||
11:00 – 11:30 |
|
Coffee/Posters |
Coffee/Posters |
Coffee/Posters |
11:30 – 12:30 |
|
|||
12:30 – 13:30 |
|
|||
13:30 – 14:00 |
|
Organizing meeting |
|
|
14:00 – 16:00 |
|
Lunch |
Lunch |
Lunch |
16:00 – 17:00 |
Registration |
|
|
|
17:00 – 18:00 |
Registration |
Free |
|
|
18:00 – 18:30 |
Coffee |
Afternoon |
|
|
18:30 – 19:30 |
|
|
||
19:15 – 20:15 |
Welcome cocktail |
|
|
|
20:00 |
Dinner |
Dinner |
Dinner |
|
The XXXVI edition
of the Winter Meeting on Statistical Physics will take place in the Hotel Monte Taxco.
If you need to
spend the night in
Organizers
Home
The XXXVI edition of the Winter Meeting on Statistical Physics is organized by
Miguel Mayorga Rojas, Departamento de Física, Facultad de Ciencias, Universidad
Autónoma del Estado de México, Av. Instituto Literario 100, 50000 Toluca,
Estado de México, Mexico. Tel (722) 2 96 55 56, Fax (722) 2 96 55 56, e-mail:
mmr@uaemex.mx.
Amir Maldonado Arce, Departamento de Física, Universidad de Sonora,
Rosales y Luis Encinas s/n, Apdo Postal 1626, 83000 Hermosillo, Sonora, Mexico.
Tel (662) 2 59 21 08, Fax (662) 2 59 21 09, e-mail: maldona@fisica.uson.mx.
Ramón Castañeda Priego, Instituto de Física, Universidad de Guanajuato, Lomas
del Bosque 103, Lomas del Campestre, 37150 León, Guanajuato, Mexico. Tel (477)
7 88 51 00 ext 8432, e-mail: ramoncp@fisica.ugto.mx. http://www.ifug.ugto.mx/~ramoncp/.
Iván Santamaría Holek, Departamento de Física, Facultad de Ciencias,
Universidad Nacional Autónoma de México, 04510, México, DF, Mexico. E-mail: ivan@graef.fciencias.unam.mx.
View from Hotel
Monte
One would never
expect to find a town in such a precarious setting, but the reason is obvious:
silver. Hernán Cortés was constantly on the alert for rumours of gold and
silver, hoping to discover mines so that he could please his king by enriching
the coffers of
SIGHTSEEING IN
Plaza Borda: This small plaza
in the centre of town is a photographer’s delight – the epitome of what one
imagines the perfect Mexican square should look like. It is tiny (there isn’t
much room to spare in Taxco), but as pretty as can be with shade trees, the
typical bandstand, and whitewashed buildings with tiled roofs and wrought-iron
balconies everywhere you look.
Santa Prisca
Church: One would never dream of finding such an incredibly beautiful church as
Santa Prisca tucked away in a small mining town, but then most towns didn’t
have such a wealthy benefactor as José de la Borda. When the word trickled to
Europe that silver had been found in the New Word, a Frenchman by the name of
José de la Borda packed his bags and rushed (as fast as you could rush in the
18th century) to Mexico to make his fortune. Finding nothing, he was
about to give up and head for home, when his horse slipped and exposed a rich
vein of silver. To thank God for this miracle, Borda built the Santa Prisca
church, where his son Manuel became priest. No expense was spared and the
church is a jewel. Its twin bell towers and ornate dome have become a landmark
of
Shopping: It seems every
building has its silver shop. You cannot go more than a few steps before
finding another one (at last count there were more than 200). Many sell silver
items at the same price and in similar style to those found in resort shops
throughout
Silver museum: Just across from
Santa Prisca is a silver museum run by a local silversmith. At first glance it
seems more like a shop, but what is interesting is that on exhibit are
award-winning pieces of jewellery. It is fascinating to see the superb designs
and craftsmanship in these lovely pieces of art.
SIGHTSEEING
OUTSIDE OF
Cuernavaca’s main
plaza is faced by several Colonial buildings including the Palacio de Cortés
and the Palacio de Gobierno, but the Colonial style in the area of the plaza is
not pristine since modern buildings managed to slip in before architectural
controls were put in place.
Cuernavaca’s
Cathedral is within a walled complex of churches that includes not only the 16th-century
cathedral, but also the 18th-century Templo de la Tercera Orden de
The Spanish king
bequeathed 30 cities to Cortés, including
The Robert Brady
museum, housed in a lovely Colonial home that was owned by Robert Brady,
contains over 1,300 diverse pieces of his art. Brady, born in the backwaters of
Malinalco: Located west of
There are only a
few buildings at the site, the most impressive being an amazing pyramid/temple
cut out of the solid rock face. One climbs the pyramid steps and enters the
temple through the open mouth of a massive serpent that serves as the entryway
to a round, inner chamber. This dark inner room may have been used for secret
initiation ceremonies or military rites. Its central altar and semicircular
bench are decorated with sculptured stone images of eagles and jaguars. Other
buildings in this hilltop complex are thought to have been meeting halls,
chambers for ritual events, and storage facilities.
In the modern
village below the fortress-like site is an early (1537) Augustinian monastery
and church built of cut stone carried down from the archaeological site of
Malinalco. This early fortress-church has an interesting open chapel with the
Stations of the Cross placed around its large enclosed courtyard.
Xochicalco: To the south of
The elite precinct
built on top of the hill is one of the most recently excavated parts of the
site. In this section of the city are found the large storage rooms, ball courts,
palaces, and temples of the rulers of Xochicalco. This well-protected precinct
was situated to take advantage of the beautiful views across the valley and the
cooling breezes during the hot summer months. It was heavily fortified with
thick fortress-like walls, ramps, and defendable staircases. These massive
fortifications can be seen from far across the valley and clearly controlled
access to the site.
The commoners
lived in the lower sections of the city where a number of large temple
complexes, pyramids, and buildings are found. Here, on an artificially levelled
hill, one of the largest ball courts in
The site, like
several others of the same time period, appears to have been inhabited or at
least strongly influenced by several different contemporary cultures. Most
obvious is the Mayan influence, which is clearly seen in the elaborate
decoration of the
SOME TOURISTIC
LINKS TO
http://www.mexperience.com/guide/colonial/taxco.htm
http://www.floramex.com/li-history_of_silver_in_taxco.htm
http://www.guerrero.gob.mx/dominios/turismo/taxco/historia.htm
(Spanish)
http://www.tourbymexico.com/guerrero/taxco/taxco.htm
http://www.otherroads.com/taxco.htm
http://www.virtualmex.com/taxco.htm
http://www.visitmexico.com/destinations/r_pac/s_gur/d_txc
http://www.surf-mexico.com/states/Guerrero/Taxco/taxco.htm
http://digthatcrazyfarout.com/taxco
http://www.sanbachs.net/cgi-bin/mexico/mexico2.cgi/City=TAX
http://www.mexperience.com/inmexico/photos/7taxco.htm
http://perso.club-internet.fr/gjoachim/taxco.htm
(French)
http://www.mexonline.com/taxco.htm
Travel
Info
Home
By plane:
You have to fly to
Please be aware
that the airlines can be full occupied at the end and at the beginning of the
year, and that it is therefore important to reserve a flight with time.
By bus:
You have to take a
bus to
By car:
You have to drive
to
Pictures
Home
Some pictures of
XXXV
Winter Meeting on Statistical Physics
Taxco,
January 10 - 13, 2006
Speakers: Gonzalo Ares de Parga (Mexico), Mauricio Carbajal Tinoco (Mexico), Claudio Cerdeiriña Alvarez (Spain), H.H. von Grünberg (Austria), George Jackson (England), Ernesto Hernández Zapata (Mexico), Charles M. Knobler (USA), Ger Koper (The Netherlands), Magdaleno Medina Noyola (Mexico), Iván Ortega Blake (Mexico), M. Quintana (Mexico), Jose Manuel Romero-Enrique (Spain), Margarida Telo da Gama (Portugal), Martin Schoen (Germany), Roberto Zenit (Mexico).
Organizers: Héctor Domínguez,
Miguel A. Ojeda, Miguel Mayorga and Amir Maldonado
XXXIV
Winter Meeting on Statistical Physics
January 4-7, 2005
Speakers: Alberto Vela Amieva (Mexico), Santiago Lago (Spain), Dominique Langevin (France), Jean-Francois Dufreche (France), Stefan Klumpp (Germany), Carlos Fernández Tejero (Spain), Luis Fernando Rojas Ochoa (Germany), Eugenia Corvera Poiré (Mexico), Jan Dhont (Germany), Maximino Aldana (Mexico), Roland Roth (Germany), Mikko Karttunen (Finland), Ramón Castañeda Priego (Mexico), and Yuri Nahmad Molinari (Mexico).
Organizers: Ana Laura
Benavides, Héctor Domínguez, Miguel A. Ojeda, and J. M. Méndez Alcaraz.
XXXIII
Winter Meeting on Statistical Physics
Taxco, Guerrero, Mexico
January 6-9, 2004
Speakers:
Bernardo José Luis Arauz Lara (Mexico), José Campos Terán (Sweden), Andrés
Estrada Alexanders (Mexico), Angelina Rosario Guzmán Sánchez (Mexico), Volkhard
Helms (Germany), Maria Kilfoil (Canada), Kurt Kremer (Germany), Amir Maldonado
Arce (Mexico), Monica Moroni (Italy), Lorena Romero Salazar (Mexico), Iván
Santamaría Holek (Mexico), Francisco Sastre (Mexico), Catalina Stern (Mexico),
and Rosalío Rodríguez (Mexico).
Organizers:
Ana Laura Benavides, Eugenia Corvera Poiré, Jesús Antonio del Río, and José M.
Méndez A.
XXXII
Winter Meeting on Statistical Physics
Taxco, Guerrero, Mexico
January 7-10, 2003
Speakers:
Ana Laura Benavides Obregón (Mexico), E. G. D. Cohen (USA), María Eugenia
Costas (Mexico), Martín Chávez Páez (Mexico), Vincent Fleury (France), Seth
Fraden (USA), Vicente Garzó (Spain), José M. Méndez Alcaraz (Mexico), Raj
Rajagopalan (USA), Fernando del Río (Mexico), Carlos Santamarina (USA), Maria
Santore (USA), Andreas Schadschneider (Germany), Judith Celina Tánori Córdova
(Mexico), Carmen Varea (Mexico), and Lourdes Vega (Mexico).
Organizers:
Eugenia Corvera Poiré, José Luis Arauz Lara, and Jesús Antonio del Río.
XXX
Winter Meeting on Statistical Physics
January 2-5, 2001
Speakers: Katja Lindenberg (USA), Elías Pérez (Mexico), David Reichman (USA), Fernando del Río (Mexico), Robert Evans (England), Carmen Varea (Mexico), Nigel Wilding (England), Leonel Torres (Mexico), Jeremy Schofield (Canada), Jaime Ruiz García (Mexico), Fernando Bresme (England), Mauricio Carbajal Tinoco (Mexico), Keith Gubbins (USA), Héctor Domínguez Castro (Mexico), Enrique Velasco (Spain), and Paul Madden (England).
Organizers:
Víctor Romero Rochín, José Alejandre, and Alejandro Gil Villegas.
XXIV
Winter Meeting on Statistical Physics
Cuernavaca, Morelos, Mexico
January 3-6, 1995
Speakers:
D. Bonn (France), A. Ben-Shaul (Israel), J. A. Blackman (England), E. Corvera
(Canada), L. S. García-Colín (Mexico), J. M. J. van Leeuwen (Holland), T. C.
Lubenski (USA), P. A. Mello (Mexico), J. M. Méndez (Mexico), L. Meza (Mexico),
P. Pincus (USA), L. F. Rull (Spain), S. Sokolowski (Mexico), V. Talanquer
(Mexico-USA), C. Varea (Mexico), and D. Williamson (Mexico).
Organizers:
Miguel Costas, Rosalío Rodríguez, and Ana Laura Benavides.
XXIII
Winter Meeting on Statistical Physics
Cuernavaca,
Morelos, Mexico
January 9-12, 1994
Speakers: F. Aguilera (México),
D. Beysens (France), E. Braun (Mexico), J. A. del Río (México), B. C. Eu
(Canada), S. Godoy (Mexico), A. González (Mexico), C. Joslin (Canada), T. Keyes
(USA), D. Kivelson (USA), L. Lam (USA), M. López de Haro (México), R. Mountain
(USA), A. Robledo (Mexico), D. Schwartz (USA), C. M. Sorensen (USA), L. Torres
(Mexico), and L. Vicente (Mexico).
Organizers: Miguel Costas,
Rosalío Rodríguez, and Ana Laura Benavides.
XII
Winter Meeting on Statistical Physics
1983
Speakers: M. Alexanian
(Mexico), L. Blum (Puerto Rico), H. Ted Davis (USA), T. de la Selva (Mexico),
J. L. del Río (Mexico), D. Henderson (USA), J. Kestin (USA), A. Levelt-Sengers
(USA), M. Ley-Koo (Mexico), P. Lonngi (Mexico), G. Martínez Mekler (Mexico), E.
Piña (Mexico), P. Rossky (USA), J. Sengers (USA), C. Varea (Mexico), R. Velasco
(Mexico), and W. Wassam (USA).
Organizers:
XI
Winter Meeting on Statistical Physics
1982
Speakers: F. del Río
(Mexico), R. Dorfman (USA), L. García-Colín (Mexico), W. Hoover (USA), J.
Kincaid (USA), Ch. Knobler (USA), K. Lakatos-Lindenberg (USA), M. Medina
(Mexico), L. Mier y Terán (Mexico), J. Percus (USA), A. Robledo (Mexico), W. R.
Smith (Canada), G. Stell (USA), D. Thouless (USA), and P. G. Wolyness (USA).
X Winter
Meeting on Statistical Physics
1981
Speakers: A. Aguilar
(Mexico), E. G. D. Cohen (USA), H. Friedman (USA), K. Gubbins (USA), H.
Hasegawa (Japan), D. Henderson (USA), A. Isihara (USA), D. Kievelson (USA), M.
López de Haro (Mexico), S. Martínez Casas (Mexico), F. Stillinger (USA), B.
Widom (USA), and R. Zwanzig (USA).
IX
Winter Meeting on Statistical Physics
1980
Speakers: S. Godoy
(Mexico), F. Abraham (USA), F. del Río (Mexico), M. Lozada (Mexico), K. Freed
(USA), J. L. del Río (Mexico), E. G. D. Cohen (USA), D. Ayala (Mexico), A. Robledo
(Mexico), W. Schieve (USA), and J. Ross (USA).
VIII
Winter Meeting on Statistical Physics
1979
Speakers: J. Ross (USA), S.
Fujita (USA), D. Forster (USA), W. Steel (USA), L. Mier y Terán (Mexico), F.
Ramos (Mexico), G. Stell (USA), S. Larsen (USA), P. Lonngi (Mexico), M. Grmela
(Canada), I. McLure (England), E. Martina (Mexico), R. Watts (Australia), and
I. Procaccia (USA).
VII
Winter Meeting on Statistical Physics
1978
Speakers: B. J. Alder (USA), E. Blaisten (Mexico), E. Cota (Mexico), R. Levine (Israel), I. Oppenheim (USA), W. Brostow (Mexico), M. Berrondo (Mexico), S. Hsin Chen (USA), W. B. Streett (USA), and J. Lebowitz (USA).
VI
Winter Meeting on Statistical Physics
1977
Speakers: J. M. Deutch (USA), S. Goulart (Brazil), R. Griffiths (USA), m. Ley Koo (Mexico), D. Henderson (USA), W. Hoover (USA), A. Tsihara (USA), E. Lieb (USA), R. Rodríguez (Mexico), E. Stanley (USA), and H. Wiegel (Holland).
V Winter
Meeting on Statistical Physics
1976
Speakers: M. Alexanian
(Mexico), G. Chapela (Mexico), B. Chu (USA), M. de Llano (Mexico), K. Gubbins
(USA), D. A. McQuarrie (USA), R. Peralta (Mexico), A. Robledo (Mexico), J. S.
Rowlinson (USA), K. Wilson (USA), and R. Wilson (USA).
IV
Winter Meeting on Statistical Physics
1975
Speakers: D. Forster (USA),
L. García-Colín (Mexico), T. W. Leland (USA), E. Lieb (USA), J. Rodríguez A.
(Mexico), R. T. Rubin (USA), F. Prieto (Mexico), and M. A. Zendejas (Mexico).
III
Winter Meeting on Statistical Physics
1974
Speakers: J. Barojas
(Mexico), E. Braun (Mexico), E. G. D. Cohen (USA), S. Godoy (Mexico), L. G.
Gorostiza (Mexico), S. R. de Groot (Holland), E. Piña (Mexico), B. Widom (USA),
R. S. Wilson (USA), and H. E. de Witt (USA).
II
Winter Meeting on Statistical Physics
1973
Speakers: R. Alexander
(Mexico), E. Braun (Mexico), F. del Río (Mexico), J. L. Lebowitz (USA), P. A.
Mello (Mexico), R. D. Mountain (USA), R. S. Wilson (USA), and R. Zwanzig (USA).
I Winter
Meeting on Statistical Physics
Oaxtepec, Morelos, Mexico
1972
Speakers: E.
Braun (Mexico), S. Fujita (USA), M. S. Green (USA), S. Y. Larsen (USA), J. M.
H. Levelt-Sengers (USA), J. L. Lebowitz (USA), and J. Sengers (USA).
Organizers: L. García-Colín,
S. Larsen, F. del Río, and L. Mier y Terán.