39,652 research outputs found
Heat Fluctuations in Brownian Transducers
Heat fluctuation probability distribution function in Brownian transducers
operating between two heat reservoirs is studied. We find, both analytically
and numerically, that the recently proposed Fluctuation Theorem for Heat
Exchange [C. Jarzynski and D. K. Wojcik, Phys. Rev. Lett. 92, 230602 (2004)]
has to be modified when the coupling mechanism between both baths is
considered. We also extend such relation when external work is present. Our
work fixes the domain of applicability of the theorem in more realistic
operating systems.Comment: Comments are welcom
Nonintegrable Schrodinger Discrete Breathers
In an extensive numerical investigation of nonintegrable translational motion
of discrete breathers in nonlinear Schrodinger lattices, we have used a
regularized Newton algorithm to continue these solutions from the limit of the
integrable Ablowitz-Ladik lattice. These solutions are shown to be a
superposition of a localized moving core and an excited extended state
(background) to which the localized moving pulse is spatially asymptotic. The
background is a linear combination of small amplitude nonlinear resonant plane
waves and it plays an essential role in the energy balance governing the
translational motion of the localized core. Perturbative collective variable
theory predictions are critically analyzed in the light of the numerical
results.Comment: 42 pages, 28 figures. to be published in CHAOS (December 2004
Tracing out the Northern Tidal Stream of the Sagittarius Dwarf Spheoridal Galaxy
The main aim of this paper is to report two new detections of tidal debris in
the northern stream of the Sagittarius dwarf galaxy located at 45 arcdeg and 55
arcdeg from the center of galaxy. Our observational approach is based on deep
color-magnitude diagrams, that provides accurate distances, surface brightness
and the properties of stellar population of the studied region of this tidal
stream. The derived distances for these tidal debris wraps are 45 kpc and 54
kpc respectively.We also confirm these detections with numerical simulations of
the Sagittarius dwarf plus the Milky Way. The model reproduces the present
position and velocity of the Sagittarius main body and presents a long tidal
stream formed by tidal interaction with the Milky Way potential. This model is
also in good agreement with the available observations of the Sagittarius tidal
stream. We also present a method for estimating the shape of the Milky Way halo
potential using numerical simulations. From our simulations we obtain an
oblateness of the Milky Way dark halo potential of 0.85, using the current
database of distances and radial velocities of the Sagittarius tidal stream.
The color-magnitude diagram of the apocenter of Sagittarius shows that this
region of the stream shares the complex star formation history observed in the
main body of the galaxy. We present the first evidence for a gradient in the
stellar population along the stream, possibly correlated with its different
pericenter passages. (abridged)Comment: 43 pages (including 15 figures; for high resolution color figures,
please contact [email protected]). Submitted to Ap
3He-rich SEP Events Observed by STEREO-A
Using the SIT (Suprathermal Ion Telescope) instrument on STEREO-A we have
examined the abundance of the rare isotope 3He during the rising activity phase
of solar cycle 24 between January 2010 and December 2011. We have identified
six solar energetic particle (SEP) events with enormous abundance enhancements
of 3He (3He/4He >1). The events were short lasting, typically ~0.5-1 day and
most of them occurred in association with high-speed solar wind streams and
corotating interaction regions. With one exception the events were not
associated with ~100 keV solar electron intensity increases. The events showed
also enhanced NeS/O and Fe/O ratios. The solar images indicate that the events
were generally associated with the active regions located near a coronal hole.Comment: accepted for publication in AIP Conference Proceedings for
'Thirteenth International Solar Wind Conference
Molecular Realism in Default Models for Information Theories of Hydrophobic Effects
This letter considers several physical arguments about contributions to
hydrophobic hydration of inert gases, constructs default models to test them
within information theories, and gives information theory predictions using
those default models with moment information drawn from simulation of liquid
water. Tested physical features include: packing or steric effects, the role of
attractive forces that lower the solvent pressure, and the roughly tetrahedral
coordination of water molecules in liquid water. Packing effects (hard sphere
default model) and packing effects plus attractive forces (Lennard-Jones
default model) are ineffective in improving the prediction of hydrophobic
hydration free energies of inert gases over the previously used Gibbs and flat
default models. However, a conceptually simple cluster Poisson model that
incorporates tetrahedral coordination structure in the default model is one of
the better performers for these predictions. These results provide a partial
rationalization of the remarkable performance of the flat default model with
two moments in previous applications. The cluster Poisson default model thus
will be the subject of further refinement.Comment: 5 pages including 3 figure
- âŠ