120 research outputs found
Long-time dynamics of Rouse-Zimm polymers in dilute solutions with hydrodynamic memory
The dynamics of flexible polymers in dilute solutions is studied taking into
account the hydrodynamic memory, as a consequence of fluid inertia. As distinct
from the Rouse-Zimm (RZ) theory, the Boussinesq friction force acts on the
monomers (beads) instead of the Stokes force, and the motion of the solvent is
governed by the nonstationary Navier-Stokes equations. The obtained generalized
RZ equation is solved approximately. It is shown that the time correlation
functions describing the polymer motion essentially differ from those in the RZ
model. The mean-square displacement (MSD) of the polymer coil is at short times
\~ t^2 (instead of ~ t). At long times the MSD contains additional (to the
Einstein term) contributions, the leading of which is ~ t^(1/2). The relaxation
of the internal normal modes of the polymer differs from the traditional
exponential decay. It is displayed in the long-time tails of their correlation
functions, the longest-lived being ~ t^(-3/2) in the Rouse limit and t^(-5/2)
in the Zimm case, when the hydrodynamic interaction is strong. It is discussed
that the found peculiarities, in particular an effectively slower diffusion of
the polymer coil, should be observable in dynamic scattering experiments.Comment: 6 page
Preliminary results of the Cerenkov EAS flashes the Crimean Astrophysical Observatory
The facility designed for the study of angular resolution of light in the extensive air showers EAS flashes is described. The threshold energy of the facility is about 3 x 10 to the 12h power eV. The data on the angular distribution of light in a flash and the ratio of the flux in the UV and visual region as a function of the distance to the axis of a shower are given. Obtained results are compared to the published computations
The effectiveness of physical activity in cardiorehabilitation
The review shows that the molecular mechanisms initiated by physical exertion underlie the multifactorial influence of the latter on the function of the cardiovascular system and the course of cardiac diseases. Exercise is an important component of the therapeutic treatment in patients with cardiovascular diseases, which is confirmed by the results of a metaanalysis that included 63 studies that were associated with various forms of aerobic exercise of different intensity (from 50 to 95 % VO2) for 1 to 47 months, which showed that exercise-based CR improves cardiovascular function. Knowledge of the molecular basis of the impact of physical activity makes it possible to use biochemical markers to assess the effectiveness of rehabilitation programs
On solving Schwinger-Dyson equations for non-Abelian gauge theory
A method for solving Schwinger-Dyson equations for the Green function
generating functional of non-Abelian gauge theory is proposed. The method is
based on an approximation of Schwinger-Dyson equations by exactly soluble
equations. For the SU(2) model the first step equations of the iteration scheme
are solved which define a gauge field propagator. Apart from the usual
perturbative solution, a non-perturbative solution is found which corresponds
to the spontaneous symmetry breaking and obeys infrared finite behaviour of the
propagator.Comment: 12 pages, Plain LaTeX, no figures, extended and revised version
published in Journal of Physics
Phenomenological features of mortality and morbidity dynamics in Tomsk versus heliogeophysical activity
The influence of heliogeophysical activity on the morbidity and mortality of the population in Tomsk is studied epidemiologically on the basis of regional data. The biological effectiveness of heliogeophysical factors selected on the basis of the Karhunen–Loeve method from epidemiological data on the morbidity and mortality in Tomsk in 1990–2008 is estimated. An analysis of the impact of variations in heliogeophysical activity on morbidity and mortality (according to the International Statistical Classification of Diseases and Related Health, ICD-10) showed the existence of common factors within different nosological classes that reliably correlate with the major components of variations in characteristic indices of heliogeophysical activity
Hydrodynamic interactions and Brownian forces in colloidal suspensions: Coarse-graining over time and length-scales
We describe in detail how to implement a coarse-grained hybrid Molecular
Dynamics and Stochastic Rotation Dynamics simulation technique that captures
the combined effects of Brownian and hydrodynamic forces in colloidal
suspensions. The importance of carefully tuning the simulation parameters to
correctly resolve the multiple time and length-scales of this problem is
emphasized. We systematically analyze how our coarse-graining scheme resolves
dimensionless hydrodynamic numbers such as the Reynolds number, the Schmidt
number, the Mach number, the Knudsen number, and the Peclet number. The many
Brownian and hydrodynamic time-scales can be telescoped together to maximize
computational efficiency while still correctly resolving the physically
relevant physical processes. We also show how to control a number of numerical
artifacts, such as finite size effects and solvent induced attractive depletion
interactions. When all these considerations are properly taken into account,
the measured colloidal velocity auto-correlation functions and related self
diffusion and friction coefficients compare quantitatively with theoretical
calculations. By contrast, these calculations demonstrate that, notwithstanding
its seductive simplicity, the basic Langevin equation does a remarkably poor
job of capturing the decay rate of the velocity auto-correlation function in
the colloidal regime, strongly underestimating it at short times and strongly
overestimating it at long times. Finally, we discuss in detail how to map the
parameters of our method onto physical systems, and from this extract more
general lessons that may be relevant for other coarse-graining schemes such as
Lattice Boltzmann or Dissipative Particle Dynamics.Comment: 31 pages, 14 figure
Brownian oscillators driven by correlated noise in a moving trap
Brownian oscillator, i.e. a micron-sized or smaller particle trapped in a
thermally fluctuating environment is studied. The confining harmonic potential
can move with a constant velocity. As distinct from the standard Langevin
theory, the chaotic force driving the particle is correlated in time. The
dynamics of the particle is described by the generalized Langevin equation with
the inertial term, a coloured noise force, and a memory integral. We consider
two kinds of the memory in the system. The first one corresponds to the
exponentially correlated noise in a weakly viscoelastic fluid and in the second
case the memory naturally arises within the Navier-Stokes hydrodynamics. Exact
analytical solutions are obtained in both the cases using a simple and
effective method not applied so far in this kind of problems.Comment: Presented at the 17th International Conference Applied Physics of
Condensed Matter (APCOM 2011), Novy Smokovec, High Tatras, Slovakia, June 22
- 24, 201
Meson vacuum phenomenology in a three-flavor linear sigma model with (axial-)vector mesons
We study scalar, pseudoscalar, vector, and axial-vector mesons with
non-strange and strange quantum numbers in the framework of a linear sigma
model with global chiral symmetry. We perform a
global fit of meson masses, decay widths, as well as decay amplitudes. The
quality of the fit is, for a hadronic model that does not consider
isospin-breaking effects, surprisingly good. We also investigate the question
whether the scalar states lie below or above 1 GeV and find the
scalar states above 1 GeV to be preferred as states. Additionally,
we also describe the axial-vector resonances as states.Comment: 29 pages, 4 figures, 3 tables. v2 is the updated version after
referee remarks (dilaton field discussed, a new figure added
Chromomagnetic Catalysis of Color Superconductivity in a (2+1)-dimensional NJL Model
The influence of a constant uniform external chromomagnetic field on the
formation of color superconductivity has been investigated. The consideration
was performed in the framework of a (2+1)-dimensional Nambu--Jona-Lasinio model
with two different four-fermionic structures responsible for condensates. In particular, it was shown that there exists a
critical value of the external chromomagnetic field such that at
a nonvanishing diquark condensate is dynamically created (the so-called
chromomagnetic catalysis effect of color superconductivity). Moreover, external
chromomagnetic fields may in some cases enhance the diquark condensate of color
superconductivity.Comment: 32 pages, 2 figures, revte
- …