423 research outputs found
Computation of the Kolmogorov-Sinai entropy using statistitical mechanics: Application of an exchange Monte Carlo method
We propose a method for computing the Kolmogorov-Sinai (KS) entropy of
chaotic systems. In this method, the KS entropy is expressed as a statistical
average over the canonical ensemble for a Hamiltonian with many ground states.
This Hamiltonian is constructed directly from an evolution equation that
exhibits chaotic dynamics. As an example, we compute the KS entropy for a
chaotic repeller by evaluating the thermodynamic entropy of a system with many
ground states.Comment: 7 page
Effective temperature in nonequilibrium steady states of Langevin systems with a tilted periodic potential
We theoretically study Langevin systems with a tilted periodic potential. It
has been known that the ratio of the diffusion constant to the
differential mobility is not equal to the temperature of the environment
(multiplied by the Boltzmann constant), except in the linear response regime,
where the fluctuation dissipation theorem holds. In order to elucidate the
physical meaning of far from equilibrium, we analyze a modulated
system with a slowly varying potential. We derive a large scale description of
the probability density for the modulated system by use of a perturbation
method. The expressions we obtain show that plays the role of the
temperature in the large scale description of the system and that can
be determined directly in experiments, without measurements of the diffusion
constant and the differential mobility
The law of action and reaction for the effective force in a nonequilibrium colloidal system
We study a nonequilibrium Langevin many-body system containing two 'test'
particles and many 'background' particles. The test particles are spatially
confined by a harmonic potential, and the background particles are driven by an
external driving force. Employing numerical simulations of the model, we
formulate an effective description of the two test particles in a
nonequilibrium steady state. In particular, we investigate several different
definitions of the effective force acting between the test particles. We find
that the law of action and reaction does not hold for the total mechanical
force exerted by the background particles, but that it does hold for the
thermodynamic force defined operationally on the basis of an idea used to
extend the first law of thermodynamics to nonequilibrium steady states.Comment: 13 page
Verification of piezometric method for the observation of dissolved component and pressure head dynamics in a tidal flat groundwater
We carried out the verification of the piezometric method to observe concerning groundwater flow and solute transport under the unsteady state in the tidal flat. Especially, we considered whether solute moves and reacts instantaneously as pressure head changes in the tidal flat. The results of verification are summarized as follows, (1)The electric conductivity(EC) of water collected from the piezometer changed with the tidal fluctuation, and the variation was similar to that by buried EC sendor. Moreover, the variation accuracy increased by pulling out water in the piezometer just before water sampling. (2)The piezometric head (water table in the pipe) changed with the tidal fluctuation. Especially, it decreased with delaying during falling period of the tide level. This showed that pressure remained under the ground. (3)Our study corresponded to previous studies concerning between the groundwater and solute flux by the piezometric and catchment mass balance methods.Based on these results, we would apply this method to groundwater flow and solute dynamics in the tidal flat
Long range spatial correlation between two Brownian particles under external driving
We study the large distance behavior of a steady distribution of two Brownian
particles under external driving in a two-dimensional space. Employing a method
of perturbative system reduction, we analyze a Fokker-Planck equation that
describes the time evolution of the probability density for the two particles.
The expression we obtain shows that there exist a long range correlation
between the two particles, of type.Comment: 11 page
Ultrafiltration attenuates cardiopulmonary bypass–induced acute lung injury in a canine model of single-lung transplantation
ObjectiveThe purpose of this study was to investigate the effects of cardiopulmonary bypass and ultrafiltration on graft function in a canine single-lung transplantation model.MethodsFifteen left single-lung transplantations were done in weight-mismatched canine pairs. The animals were divided into 3 groups: group 1, in which transplantation was done without cardiopulmonary bypass; group 2, in which transplantation was done with cardiopulmonary bypass and in which the cardiopulmonary bypass flow was decreased slowly with controlled pulmonary artery pressure; and group 3, in which transplantation was done with cardiopulmonary bypass and ultrafiltration. Hemodynamic parameters and lung function were monitored for 6 hours after reperfusion. The grafts were harvested for histologic studies, myeloperoxidase assay, and real-time quantitive reverse transcription–polymerase chain reaction of mRNA encoding interleukin 6.ResultsThe hemodynamic parameters were similar among the 3 groups. In group 1 Pao2 and alveolar to arterial gradient for O2 levels were excellent throughout the 6-hour observation period, but in group 2 they progressively deteriorated. However, ultrafiltration significantly (P = .02) improved the Pao2 level in group 3. On histology, interstitial edema and polynuclear cell infiltration were most marked in group 2 and significantly worse than in groups 1 and 3. Myeloperoxidase assay and real-time quantitative reverse transcription–polymerase chain reaction showed increased myeloperoxidase activity and interleukin 6 gene expression in group 2 grafts compared with group 1 grafts. Myeloperoxidase activity and interleukin 6 gene expression were suppressed with ultrafiltration.ConclusionsCardiopulmonary bypass had negative effects on the graft, but ultrafiltration attenuated acute lung dysfunction by reducing the inflammatory response
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