362 research outputs found

### Two-Channel Totally Asymmetric Simple Exclusion Processes

Totally asymmetric simple exclusion processes, consisting of two coupled
parallel lattice chains with particles interacting with hard-core exclusion and
moving along the channels and between them, are considered. In the limit of
strong coupling between the channels, the particle currents, density profiles
and a phase diagram are calculated exactly by mapping the system into an
effective one-channel totally asymmetric exclusion model. For intermediate
couplings, a simple approximate theory, that describes the particle dynamics in
vertical clusters of two corresponding parallel sites exactly and neglects the
correlations between different vertical clusters, is developed. It is found
that, similarly to the case of one-channel totally asymmetric simple exclusion
processes, there are three stationary state phases, although the phase
boundaries and stationary properties strongly depend on inter-channel coupling.
An extensive computer Monte Carlo simulations fully support the theoretical
predictions.Comment: 13 pages, 10 figure

### Boundary-induced phase transitions in traffic flow

Boundary-induced phase transitions are one of the surprising phenomena
appearing in nonequilibrium systems. These transitions have been found in
driven systems, especially the asymmetric simple exclusion process. However, so
far no direct observations of this phenomenon in real systems exists. Here we
present evidence for the appearance of such a nonequilibrium phase transition
in traffic flow occurring on highways in the vicinity of on- and off-ramps.
Measurements on a German motorway close to Cologne show a first-order
nonequilibrium phase transition between a free-flow phase and a congested
phase. It is induced by the interplay of density waves (caused by an on-ramp)
and a shock wave moving on the motorway. The full phase diagram, including the
effect of off-ramps, is explored using computer simulations and suggests means
to optimize the capacity of a traffic network.Comment: 5 figures, revte

### Steady-state selection in driven diffusive systems with open boundaries

We investigate the stationary states of one-dimensional driven diffusive
systems, coupled to boundary reservoirs with fixed particle densities. We argue
that the generic phase diagram is governed by an extremal principle for the
macroscopic current irrespective of the local dynamics. In particular, we
predict a minimal current phase for systems with local minimum in the
current--density relation. This phase is explained by a dynamical phenomenon,
the branching and coalescence of shocks, Monte-Carlo simulations confirm the
theoretical scenario.Comment: 6 pages, 5 figure

### Changes of gas metabolism, gas homeostasis and tissue respiration in rats during prolonged hypokinesia

The oxygen uptake and tissue gas homeostasis of restrained albinic rats remained relatively constant during a 60 day experiment. The gas metabolism in some tissues changed, and O2 consumption increased in the liver and decreased in the myocardium. Capacity for physical work was reduced by five times. Hypokinesia for 60 days resulted in a delay in the animals growth

### Benzofurocaine: effects on experimental periodontitis, anti-diabetic activity and molecular mechanisms of action

A promising compound for the treatment of inflammatory periodontal diseases is benzofuracaine (BFC). BFC has pronounced anti-inflammatory, analgesic, reparative, hypoglycemic and other effects. Objective: To assess the influence of benzofuracaine on experimental periodontitis and to study its antidiabetic activity and molecular mechanisms of actio

### Changes of the body functions during long-term hypokinesia

Prolonged hypokinesis (100-170 days) studied in 2000 rats kept in cages limiting their mobility provoked considerable changes in the gaseous and energetic metabolism: an elevation of the total gaseous metabolism and of the rate of O2 requirement by the muscles (in the late periods of hypokinesis) and a change in the intensity of tissue respiration of the liver and myocardium. There also proved to be a reduction in the level of phosphorylation and separation of oxidative phosphorylation in the myocardium, liver, and partially in the skeletal muscle. Prolonged hypokinesia led to changes in tissue metabolism: a disturbance of development of the animals, a marked delay and an increase in the weight of the organism and the muscular system, and disturbances of the mineral and protein metabolism. Prolonged hypokinesis also lead to exhaustion of the hypothalamus-hypophysis-adrenal cortex system

### Lattice Statistics in Three Dimensions: Exact Solution of Layered Dimer and Layered Domain Wall Models

Exact analyses are given for two three-dimensional lattice systems: A system
of close-packed dimers placed in layers of honeycomb lattices and a layered
triangular-lattice interacting domain wall model, both with nontrivial
interlayer interactions. We show that both models are equivalent to a 5-vertex
model on the square lattice with interlayer vertex-vertex interactions. Using
the method of Bethe ansatz, a closed-form expression for the free energy is
obtained and analyzed. We deduce the exact phase diagram and determine the
nature of the phase transitions as a function of the strength of the interlayer
interaction.Comment: 22 pages in Revtex, 6 PS files, submitted to PR

### Dynamic Singularities in Cooperative Exclusion

We investigate cooperative exclusion, in which the particle velocity can be
an increasing function of the density. Within a hydrodynamic theory, an initial
density upsteps and downsteps can evolve into: (a) shock waves, (b) continuous
compression or rarefaction waves, or (c) a mixture of shocks and continuous
waves. These unusual phenomena arise because of an inflection point in the
current versus density relation. This anomaly leads to a group velocity that
can either be an increasing or a decreasing function of the density on either
side of these wave singularities.Comment: 4 pages, 4 figures, 2 column revtex 4-1 format; version 2:
substantially rewritten and put in IOP format, mail results unchanged;
version 3: minor changes, final version for publication in JSTA

### Power spectra of TASEPs with a localized slow site

The totally asymmetric simple exclusion process (TASEP) with a localized
defect is revisited in this article with attention paid to the power spectra of
the particle occupancy N(t). Intrigued by the oscillatory behaviors in the
power spectra of an ordinary TASEP in high/low density phase(HD/LD) observed by
Adams et al. (2007 Phys. Rev. Lett. 99 020601), we introduce a single slow site
with hopping rate q<1 to the system. As the power spectrum contains
time-correlation information of the particle occupancy of the system, we are
particularly interested in how the defect affects fluctuation in particle
number of the left and right subsystems as well as that of the entire system.
Exploiting Monte Carlo simulations, we observe the disappearance of
oscillations when the defect is located at the center of the system. When the
defect is off center, oscillations are restored. To explore the origin of such
phenomenon, we use a linearized Langevin equation to calculate the power
spectrum for the sublattices and the whole lattice. We provide insights into
the interactions between the sublattices coupled through the defect site for
both simulation and analytical results.Comment: 16 pages, 6 figures; v2: Minor revision

### Theoretical Investigation of Totally Asymmetric Exclusion Processes on Lattices with Junctions

Totally asymmetric simple exclusion processes on lattices with junctions,
where particles interact with hard-core exclusion and move on parallel lattice
branches that at the junction combine into a single lattice segment, are
investigated. A simple approximate theory, that treats the correlations around
the junction position in a mean-field fashion, is developed in order to
calculate stationary particle currents, density profiles and a phase diagram.
It is shown that there are three possible stationary phases depending on the
state of each of the lattice branch. At first-order phase boundaries, where the
density correlations are important, a modified phenomenological domain-wall
theory, that accounts for correlations, is introduced. Extensive Monte Carlo
computer simulations are performed to investigate the system, and it is found
that they are in excellent agreement with theoretical predictions.Comment: 16 pages, 7 figure

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