3,393 research outputs found
Localized states and interaction induced delocalization in Bose gases with quenched disorder
Very diluted Bose gas placed into a disordered environment falls into a
fragmented localized state. At some critical density the repulsion between
particles overcomes the disorder. The gas transits into a coherent superfluid
state. In this article the geometrical and energetic characteristics of the
localized state at zero temperature and the critical density at which the
quantum phase transition from the localized to the superfluid state proceeds
are found.Comment: 17 pages, 5 figur
Microlensing of the Lensed Quasar SDSS0924+0219
We analyze V, I and H band HST images and two seasons of R-band monitoring
data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that
image D is a point-source image of the quasar at the center of its host galaxy.
We can easily track the host galaxy of the quasar close to image D because
microlensing has provided a natural coronograph that suppresses the flux of the
quasar image by roughly an order of magnitude. We observe low amplitude,
uncorrelated variability between the four quasar images due to microlensing,
but no correlated variations that could be used to measure a time delay. Monte
Carlo models of the microlensing variability provide estimates of the mean
stellar mass in the lens galaxy (0.02 Msun < M < 1.0 Msun), the accretion disk
size (the disk temperature is 5 x 10^4 K at 3.0 x 10^14 cm < rs < 1.4 x 10^15
cm), and the black hole mass (2.0 x 10^7 Msun < MBH \eta_{0.1}^{-1/2}
(L/LE)^{1/2} < 3.3 x 10^8 Msun), all at 68% confidence. The black hole mass
estimate based on microlensing is consistent with an estimate of MBH = 7.3 +-
2.4 x 10^7 Msun from the MgII emission line width. If we extrapolate the
best-fitting light curve models into the future, we expect the the flux of
images A and B to remain relatively stable and images C and D to brighten. In
particular, we estimate that image D has a roughly 12% probability of
brightening by a factor of two during the next year and a 45% probability of
brightening by an order of magnitude over the next decade.Comment: v.2 incorporates referee's comments and corrects two errors in the
original manuscript. 28 pages, 10 figures, published in Ap
HAT-P-55b: A Hot Jupiter Transiting a Sun-like Star
We report the discovery of a new transiting extrasolar planet, HAT-P-55b. The
planet orbits a V = 13.207 +/- 0.039 sun-like star with a mass of 1.013 +/-
0.037 solar masses, a radius of 1.011 +/- 0.036 solar radii and a metallicity
of -0.03 +/- 0.08. The planet itself is a typical hot Jupiter with a period of
3.5852467 +/- 0.0000064 days, a mass of 0.582 +/- 0.056 Jupiter masses and a
radius of 1.182 +/- 0.055 Jupiter radii. This discovery adds to the increasing
sample of transiting planets with measured bulk densities, which is needed to
put constraints on models of planetary structure and formation theories.Comment: 7 pages, 4 figures, accepted for publication in PAS
Simultaneous Estimation of Time Delays and Quasar Structure
We expand our Bayesian Monte Carlo method for analyzing the light curves of
gravitationally lensed quasars to simultaneously estimate time delays and
quasar structure including their mutual uncertainties. We apply the method to
HE1104-1805 and QJ0158-4325, two doubly-imaged quasars with microlensing and
intrinsic variability on comparable time scales. For HE1104-1805 the resulting
time delay of (Delta t_AB) = t_A - t_B = 162.2 -5.9/+6.3 days and accretion
disk size estimate of log(r_s/cm) = 15.7 -0.5/+0.4 at 0.2 micron in the rest
frame are consistent with earlier estimates but suggest that existing methods
for estimating time delays in the presence of microlensing underestimate the
uncertainties. We are unable to measure a time delay for QJ0158-4325, but the
accretion disk size is log(r_s/cm) = 14.9 +/- 0.3 at 0.3 micron in the rest
frame.Comment: 21 pages, 6 figures, submitted to Ap
Thermodynamics of a Bose-Einstein Condensate with Weak Disorder
We consider the thermodynamics of a homogeneous superfluid dilute Bose gas in
the presence of weak quenched disorder. Following the zero-temperature approach
of Huang and Meng, we diagonalize the Hamiltonian of a dilute Bose gas in an
external random delta-correlated potential by means of a Bogoliubov
transformation. We extend this approach to finite temperature by combining the
Popov and the many-body T-matrix approximations. This approach permits us to
include the quasi-particle interactions within this temperature range. We
derive the disorder-induced shifts of the Bose-Einstein critical temperature
and of the temperature for the onset of superfluidity by approaching the
transition points from below, i.e., from the superfluid phase. Our results lead
to a phase diagram consistent with that of the finite-temperature theory of
Lopatin and Vinokur which was based on the replica method, and in which the
transition points were approached from above.Comment: 11 pages, 5 figure
Molecular targets of developmental exposure to bisphenol A in diabesity: a focus on endoderm-derived organs
Several studies associate foetal human exposure to bisphenol A (BPA) to metabolic/endocrine diseases, mainly diabesity. They describe the role of BPA in the disruption of pancreatic beta cell, adipocyte and hepatocyte functions. Indeed, the complexity of the diabesity phenotype is due to the involvement of different endoderm-derived organs, all targets of BPA. Here, we analyse this point delineating a picture of different mechanisms of BPA toxicity in endoderm-derived organs leading to diabesity. Moving from epidemiological data, we summarize the in vivo experimental data of the BPA effects on endoderm-derived organs (thyroid, pancreas, liver, gut, prostate and lung) after prenatal exposure. Mainly, we gather molecular data evidencing harmful effects at low-dose exposure, pointing to the risk to human health. Although the fragmentation of molecular data does not allow a clear conclusion to be drawn, the present work indicates that the developmental exposure to BPA represents a risk for endoderm-derived organs development as it deregulates the gene expression from the earliest developmental stages. A more systematic analysis of BPA impact on the transcriptomes of endoderm-derived organs is still missing. Here, we suggest in vitro toxicogenomics approaches as a tool for the identification of common mechanisms of BPA toxicity leading to the diabesity in organs having the same developmental origin
Molecular targets of developmental exposure to bisphenol A in diabesity: a focus on endoderm-derived organs
Several studies associate foetal human exposure to bisphenol A (BPA) to metabolic/endocrine diseases, mainly diabesity. They describe the role of BPA in the disruption of pancreatic beta cell, adipocyte and hepatocyte functions. Indeed, the complexity of the diabesity phenotype is due to the involvement of different endoderm-derived organs, all targets of BPA. Here, we analyse this point delineating a picture of different mechanisms of BPA toxicity in endoderm-derived organs leading to diabesity. Moving from epidemiological data, we summarize the in vivo experimental data of the BPA effects on endoderm-derived organs (thyroid, pancreas, liver, gut, prostate and lung) after prenatal exposure. Mainly, we gather molecular data evidencing harmful effects at low-dose exposure, pointing to the risk to human health. Although the fragmentation of molecular data does not allow a clear conclusion to be drawn, the present work indicates that the developmental exposure to BPA represents a risk for endoderm-derived organs development as it deregulates the gene expression from the earliest developmental stages. A more systematic analysis of BPA impact on the transcriptomes of endoderm-derived organs is still missing. Here, we suggest in vitro toxicogenomics approaches as a tool for the identification of common mechanisms of BPA toxicity leading to the diabesity in organs having the same developmental origin
An Explicit Framework for Interaction Nets
Interaction nets are a graphical formalism inspired by Linear Logic
proof-nets often used for studying higher order rewriting e.g. \Beta-reduction.
Traditional presentations of interaction nets are based on graph theory and
rely on elementary properties of graph theory. We give here a more explicit
presentation based on notions borrowed from Girard's Geometry of Interaction:
interaction nets are presented as partial permutations and a composition of
nets, the gluing, is derived from the execution formula. We then define
contexts and reduction as the context closure of rules. We prove strong
confluence of the reduction within our framework and show how interaction nets
can be viewed as the quotient of some generalized proof-nets
HAT-P-49b: A 1.7 M_J Planet Transiting a Bright 1.5 M_S F-Star
We report the discovery of the transiting extrasolar planet HAT-P-49b. The
planet transits the bright (V = 10.3) slightly evolved F-star HD 340099 with a
mass of 1.54M_S and a radius of 1.83 R_S. HAT-P-49b is orbiting one of the 25
brightest stars to host a transiting planet which makes this a favorable
candidate for detailed follow-up. This system is an especially strong target
for Rossiter- McLaughlin follow-up due to the fast rotation of the host star,
16 km/s. The planetary companion has a period of 2.6915 d, mass of 1.73 M_J and
radius of 1.41 R_J. The planetary characteristics are consistent with that of a
classical hot Jupiter but we note that this is the fourth most massive star to
host a transiting planet with both M_p and R_p well determined.Comment: Accepted to the Astronomical Journa
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