1,551 research outputs found
Finite-size effects in intracellular microrheology
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.Comment: 6 pages 2 figures. To appear in the Journal of Chemical Physic
Potenciando el aprendizaje proactivo con ILIAS&WebQuest: aprendiendo a paralelizar algoritmos con GPUs
Arquitectura de Computadores es una asignatura
troncal de segundo ciclo de la titulación de IngenierÃa
de Telecomunicación (P.E. 2004) de la Universidad
de Jaén, que desde el curso académico 2009/10
cuenta con una metodologÃa de aprendizaje proactivo
para motivar al alumno en la realización de las
prácticas. En concreto, se ha abordado la enseñanza
de la materia de paralelización de algoritmos haciendo
uso de GPUs de tarjetas gráficas convencionales.
Además, se ha dado soporte telemático al profesorado
y alumnado de la asignatura mediante el uso de
plataformas web de e-learning como ILIAS y otras
como WebQuest. Por último, en este trabajo se presentan
algunos de los resultados alcanzados con esta
experiencia.Peer Reviewe
Mesoscopic non-equilibrium thermodynamics approach to non-Debye dielectric relaxation
Mesoscopic non-equilibrium thermodynamics is used to formulate a model
describing non-homogeneous and non-Debye dielectric relaxation. The model is
presented in terms of a Fokker-Planck equation for the probability distribution
of non-interacting polar molecules in contact with a heat bath and in the
presence of an external time-dependent electric field. Memory effects are
introduced in the Fokker-Planck description through integral relations
containing memory kernels, which in turn are used to establish a connection
with fractional Fokker-Planck descriptions. The model is developed in terms of
the evolution equations for the first two moments of the distribution function.
These equations are solved by following a perturbative method from which the
expressions for the complex susceptibilities are obtained as a functions of the
frequency and the wave number. Different memory kernels are considered and used
to compare with experiments of dielectric relaxation in glassy systems. For the
case of Cole-Cole relaxation, we infer the distribution of relaxation times and
its relation with an effective distribution of dipolar moments that can be
attributed to different segmental motions of the polymer chains in a melt.Comment: 33 pages, 6 figure
The transition to irreversibility in sheared suspensions: An analysis based on a mesoscopic entropy production
We study the shear-induced diffusion effect and the transition to
irreversibility in suspensions under oscillatory shear flow by performing an
analysis of the entropy production associated to the motion of the particles.
We show that the Onsager coupling between different contributions to the
entropy production is responsible for the scaling of the mean square
displacement on particle diameter and applied strain. We also show that the
shear-induced effective diffusion coefficient depends on the volume fraction
and use Lattice-Boltzmann simulations to characterize the effect through the
power spectrum of particle positions for different Reynolds numbers and volume
fractions. Our study gives a thermodynamic explanation of the the transition to
irreversibility through a pertinent analysis of the second law of
thermodynamics.Comment: 17 pages, 3 figures, paper submitted tp phys rev
Compressibility and structural stability of ultra-incompressible bimetallic interstitial carbides and nitrides
We have investigated by means of high-pressure x-ray diffraction the
structural stability of Pd2Mo3N, Ni2Mo3C0.52N0.48, Co3Mo3C0.62N0.38, and
Fe3Mo3C. We have found that they remain stable in their ambient-pressure cubic
phase at least up to 48 GPa. All of them have a bulk modulus larger than 330
GPa, being the least compressible material Fe3Mo3C, B0 = 374(3) GPa. In
addition, apparently a reduction of compressibility is detected as the carbon
content increased. The equation of state for each material is determined. A
comparison with other refractory materials indicates that interstitial nitrides
and carbides behave as ultra-incompressible materials.Comment: 14 pages, 3 figures, 1 tabl
Reinforced SIL-1 micromembranes integrated on chip: APPLICATION to CO2 separation
A novel 4-step microfabrication process is proposed in this work to prepare arrays of c-oriented silicalite (SIL-1) micromembranes on customized silicon nitride (Si3Nx) microsieves. The arrays are integrated on chip and their overall porosity values can be tuned from 1.6% to 19.9%. A low stress Si3Nx microfabricated sieve has been used as support to reinforce via mechanical interlocking and to reduce the effects of the residual stress during membrane processing. The secondary hydrothermal growth over the Si3Nx microsieves also changes the SIL-1 chemistry, improving its affinity towards CO2 adsorption. As a result, the SIL-1/Si3Nx micromembranes integrated on chip facilitate the preferential permeation of CO2 in CO2/H2 mixtures, showing a maximum CO2/H2 separation factor of 16.9 and a CO2 permeance of 8.2×10-7 mol m-2 s-1 Pa-1 at ambient conditions
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