117 research outputs found
Effective Dissipation and Turbulence in Spectrally Truncated Euler Flows
A new transient regime in the relaxation towards absolute equilibrium of the
conservative and time-reversible 3-D Euler equation with high-wavenumber
spectral truncation is characterized. Large-scale dissipative effects, caused
by the thermalized modes that spontaneously appear between a transition
wavenumber and the maximum wavenumber, are calculated using fluctuation
dissipation relations. The large-scale dynamics is found to be similar to that
of high-Reynolds number Navier-Stokes equations and thus to obey (at least
approximately) Kolmogorov scaling.Comment: 4 pages, 5 figures new version with only 4 figures; title changed;
manuscript changed; accepted by PR
Fokker-Planck type equations for a simple gas and for a semi-relativistic Brownian motion from a relativistic kinetic theory
A covariant Fokker-Planck type equation for a simple gas and an equation for
the Brownian motion are derived from a relativistic kinetic theory based on the
Boltzmann equation. For the simple gas the dynamic friction four-vector and the
diffusion tensor are identified and written in terms of integrals which take
into account the collision processes. In the case of Brownian motion, the
Brownian particles are considered as non-relativistic whereas the background
gas behaves as a relativistic gas. A general expression for the
semi-relativistic viscous friction coefficient is obtained and the particular
case of constant differential cross-section is analyzed for which the
non-relativistic and ultra relativistic limiting cases are calculated.Comment: To appear in PR
Nonlocal observables and lightcone-averaging in relativistic thermodynamics
The unification of relativity and thermodynamics has been a subject of
considerable debate over the last 100 years. The reasons for this are twofold:
(i) Thermodynamic variables are nonlocal quantities and, thus, single out a
preferred class of hyperplanes in spacetime. (ii) There exist different,
seemingly equally plausible ways of defining heat and work in relativistic
systems. These ambiguities led, for example, to various proposals for the
Lorentz transformation law of temperature. Traditional 'isochronous'
formulations of relativistic thermodynamics are neither theoretically
satisfactory nor experimentally feasible. Here, we demonstrate how these
deficiencies can be resolved by defining thermodynamic quantities with respect
to the backward-lightcone of an observation event. This approach yields novel,
testable predictions and allows for a straightforward-extension of
thermodynamics to General Relativity. Our theoretical considerations are
illustrated through three-dimensional relativistic many-body simulations.Comment: typos in Eqs. (12) and (14) corrected, minor additions in the tex
Matching stationary spacetimes
Using the quasi-Maxwell formalism, we derive the necessary and sufficient
conditions for the matching of two stationary spacetimes along a stationary
timelike hypersurface, expressed in terms of the gravitational and
gravitomagnetic fields and the 2-dimensional matching surface on the space
manifold. We prove existence and uniqueness results to the matching problem for
stationary perfect fluid spacetimes with spherical, planar, hyperbolic and
cylindrical symmetry. Finally, we find an explicit interior for the cylindrical
analogue of the NUT spacetime.Comment: 13 pages; v2: references added, typos corrected, matches final
published version; v3: statement about higher genus stars corrected,
reference added; v4: footnote 3 made more precis
Stationary Cylindrical Anisotropic Fluid
We present the whole set of equations with regularity and matching conditions
required for the description of physically meaningful stationary cylindrically
symmmetric distributions of matter, smoothly matched to Lewis vacuum spacetime.
A specific example is given. The electric and magnetic parts of the Weyl tensor
are calculated, and it is shown that purely electric solutions are necessarily
static. Then, it is shown that no conformally flat stationary cylindrical fluid
exits, satisfying regularity and matching conditions.Comment: 17 pages Latex. To appear in Gen.Rel.Gra
Improved Holographic QCD
We provide a review to holographic models based on Einstein-dilaton gravity
with a potential in 5 dimensions. Such theories, for a judicious choice of
potential are very close to the physics of large-N YM theory both at zero and
finite temperature. The zero temperature glueball spectra as well as their
finite temperature thermodynamic functions compare well with lattice data. The
model can be used to calculate transport coefficients, like bulk viscosity, the
drag force and jet quenching parameters, relevant for the physics of the
Quark-Gluon Plasma.Comment: LatEX, 65 pages, 28 figures, 9 Tables. Based on lectures given at
several Schools. To appear in the proceedinds of the 5th Aegean School
(Milos, Greece
Determination of eye irritation potential of low-irritant products: comparison of in vitro results with the in vivo draize rabbit test
A Reassessment of the in vitro total protein content determination (TPC) with SIRC and 3T3 cells for the evaluation of the ocular irritation potential of shampoos: comparison with the in vivo Draize rabbit test
Toxic effect in the lungs of rats after inhalation exposure to benzalkonium chloride
Background: Benzalkonium chloride (BAC) is a quaternary ammonium compound (QAC) toxic to microorganisms. Inhalation is one of the major possible routes of human exposure to BAC. Materials and Methods: Experiments were performed on female Wistar rats. The rats were exposed to aerosol of BAC water solution at the target concentration of 0 (control group) and 35 mg/m3 for 5 days (6 h/day) and, after a 2-week interval, the animals were challenged (day 21) with BAC aerosol at the target concentration of 0 (control group) and 35 mg/m3 for 6 h. Results: Compared to the controls, the animals exposed to BAC aerosol were characterized by lower food intake and their body weight was significantly smaller. As regards BAC-exposed group, a significant increase was noted in relative lung mass, total protein concentration, and MIP-2 in BALF both directly after the termination of the exposure and 18 h afterwards. Significantly higher IL-6 and IgE concentrations in BALF and a decrease in the CC16 concentration in BALF were found in the exposed group immediately after the exposure. The leukocyte count in BALF was significantly higher in the animals exposed to BAC aerosol compared to the controls. In the lungs of rats exposed to BAC the following effects were observed: minimal perivascular, interstitial edema, focal aggregates of alveolar macrophages, interstitial mononuclear cell infiltrations, thickened alveolar septa and marginal lipoproteinosis. Conclusion: Inhalation of BAC induced a strong inflammatory response and a damage to the blood-air barrier. Reduced concentrations of CC16, which is an immunosuppressive and anti-inflammatory protein, in combination with increased IgE concentrations in BALF may be indicative of the immuno-inflammatory response in the animals exposed to BAC aerosol by inhalation. Histopathological examinations of tissue samples from the BAC-exposed rats revealed a number of pathological changes found only in the lungs
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