5,599 research outputs found
Effect of shape anisotropy on transport in a 2-dimensional computational model: Numerical simulations showing experimental features observed in biomembranes
We propose a 2-d computational model-system comprising a mixture of spheres
and the objects of some other shapes, interacting via the Lennard-Jones
potential. We propose a reliable and efficient numerical algorithm to obtain
void statistics. The void distribution, in turn, determines the selective
permeability across the system and bears a remarkable similarity with features
reported in certain biological experiments.Comment: 1 tex file, 2 sty files and 5 figures. To appear in Proc. of StatPhys
conference held in Calcutta, Physica A 199
Bianchi Type I Magnetofluid Cosmological Models with Variable Cosmological Constant Revisited
The behaviour of magnetic field in anisotropic Bianchi type I cosmological
model for bulk viscous distribution is investigated. The distribution consists
of an electrically neutral viscous fluid with an infinite electrical
conductivity. It is assumed that the component of shear tensor
is proportional to expansion () and the coefficient of
bulk viscosity is assumed to be a power function of mass density. Some physical
and geometrical aspects of the models are also discussed in presence and also
in absence of the magnetic field.Comment: 13 page
Bianchi Type-II String Cosmological Models in Normal Gauge for Lyra's Manifold with Constant Deceleration Parameter
The present study deals with a spatially homogeneous and anisotropic
Bianchi-II cosmological models representing massive strings in normal gauge for
Lyra's manifold by applying the variation law for generalized Hubble's
parameter that yields a constant value of deceleration parameter. The variation
law for Hubble's parameter generates two types of solutions for the average
scale factor, one is of power-law type and other is of the exponential form.
Using these two forms, Einstein's modified field equations are solved
separately that correspond to expanding singular and non-singular models of the
universe respectively. The energy-momentum tensor for such string as formulated
by Letelier (1983) is used to construct massive string cosmological models for
which we assume that the expansion () in the model is proportional to
the component of the shear tensor . This
condition leads to , where A, B and C are the metric coefficients
and m is proportionality constant. Our models are in accelerating phase which
is consistent to the recent observations. It has been found that the
displacement vector behaves like cosmological term in the
normal gauge treatment and the solutions are consistent with recent
observations of SNe Ia. It has been found that massive strings dominate in the
decelerating universe whereas strings dominate in the accelerating universe.
Some physical and geometric behaviour of these models are also discussed.Comment: 24 pages, 10 figure
Intrinsic carrier mobility of multi-layered MoS field-effect transistors on SiO
By fabricating and characterizing multi-layered MoS-based field-effect
transistors (FETs) in a four terminal configuration, we demonstrate that the
two terminal-configurations tend to underestimate the carrier mobility
due to the Schottky barriers at the contacts. For a back-gated two-terminal
configuration we observe mobilities as high as 125 cmVs which
is considerably smaller than 306.5 cmVs as extracted from the
same device when using a four-terminal configuration. This indicates that the
intrinsic mobility of MoS on SiO is significantly larger than the
values previously reported, and provides a quantitative method to evaluate the
charge transport through the contacts.Comment: 8 pages, 5 figures, typos fixed, and references update
Dynamic critical behavior of failure and plastic deformation in the random fiber bundle model
The random fiber bundle (RFB) model, with the strength of the fibers
distributed uniformly within a finite interval, is studied under the assumption
of global load sharing among all unbroken fibers of the bundle. At any fixed
value of the applied stress (load per fiber initially present in the bundle),
the fraction of fibers that remain unbroken at successive time steps is shown
to follow simple recurrence relations. The model is found to have stable fixed
point for applied stress in the range 0 and 1; beyond which total failure of
the bundle takes place discontinuously. The dynamic critical behavior near this
failure point has been studied for this model analysing the recurrence
relations. We also investigated the finite size scaling behavior. At the
critical point one finds strict power law decay (with time t) of the fraction
of unbroken fibers. The avalanche size distribution for this mean-field
dynamics of failure has been studied. The elastic response of the RFB model has
also been studied analytically for a specific probability distribution of fiber
strengths, where the bundle shows plastic behavior before complete failure,
following an initial linear response.Comment: 13 pages, 5 figures, extensively revised and accepted for publication
in Phys. Rev.
Probability distribution of residence-times of grains in sandpile models
We show that the probability distribution of the residence-times of sand
grains in sandpile models, in the scaling limit, can be expressed in terms of
the survival probability of a single diffusing particle in a medium with
absorbing boundaries and space-dependent jump rates. The scaling function for
the probability distribution of residence times is non-universal, and depends
on the probability distribution according to which grains are added at
different sites. We determine this function exactly for the 1-dimensional
sandpile when grains are added randomly only at the ends. For sandpiles with
grains are added everywhere with equal probability, in any dimension and of
arbitrary shape, we prove that, in the scaling limit, the probability that the
residence time greater than t is exp(-t/M), where M is the average mass of the
pile in the steady state. We also study finite-size corrections to this
function.Comment: 8 pages, 5 figures, extra file delete
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