9,886 research outputs found
Phase Separation of Multi-Component Bose-Einstein Condensates of Trapped Atoms and Molecules with a Homonuclear Feshbach Resonance
We investigate phase separation of Bose-Einstein condensates (BECs) of
two-component atoms and one-component molecules with a homonuclear Feshbach
resonance. We develop a full model for dilute atomic and molecular gases
including correlation of the Feshbach resonance and all kinds of interparticle
interactions, and numerically calculate order parameters of the BECs in
spherical harmonic oscillator traps at zero temperature with the Bogoliubov's
classical field approximation. As a result, we find out that the Feshbach
resonance can induce two types of phase separation. The actual phase structures
and density profiles of the trapped gases are predicted in the whole parameter
region, from the atom dominant regime to the molecule dominant regime. We focus
on the role of the molecules in the phase separation. Especially in the atom
dominant regime, the role of the molecules is described through effective
interactions derived from our model. Furthermore we show that a perturbative
and semi-classical limit of our model reproduces the conventional atomic BEC
(single-channel) model.Comment: 11pages, 4 figure
Invariance Violation Extends the Cosmic Ray Horizon ?
We postulate in the present paper that the energy-momentum relation is
modified for very high energy particles to violate Lorentz invariance and the
speed of photon is changed from the light velocity c. The violation effect is
amplified, in a sensitive way to detection, through the modified kinematical
constraints on the conservation of energy and momentum, in the absorption
process of gamma-rays colliding against photons of longer wavelengths and
converting into an electron-positron pair. For gamma-rays of energies higher
than 10 TeV, the minimum energy of the soft photons for the reaction and then
the absorption mean free path of gamma-rays are altered by orders of magnitude
from the ones conventionally estimated. Consideration is similarly applied to
high energy cosmic ray protons. The consequences may require the standard
assumptions on the maximum distance that very high energy radiation can travel
from to be revised.Comment: 14 pages, 1 figure, to be published in Ap J Letter
Behavioral and cardiopulmonary effects of dexmedetomidine alone and in combination with butorphanol, methadone, morphine or tramadol in conscious sheep
Objective:
To compare cardiopulmonary and sedative effects following administration of dexmedetomidine alone or with butorphanol, methadone, morphine or tramadol in healthy sheep.
Study design:
Randomized crossover study.
Animals:
Six Santa InĂȘs sheep, five females, one male, aged 12â28 months and weighing 40.1 ± 6.2 kg.
Methods:
Sheep were assigned treatments of dexmedetomidine (0.005 mg kgâ1; D); D and butorphanol (0.15 mg kgâ1; DB); D and methadone (0.5 mg kgâ1; DM); D and morphine (0.5 mg kgâ1; DMO); or D and tramadol (5.0 mg kgâ1; DT). All drugs were administered intravenously with at least 7 days between each treatment. Rectal temperature, heart rate (HR), respiratory rate (fR), invasive arterial pressure, blood gases and electrolytes were measured prior to administration of drugs (baseline, T0) and every 15 minutes following drug administration for 120 minutes (T15âT120). Sedation was scored by three observers blinded to treatment.
Results:
HR decreased in all treatments and fR decreased in DM at T30 and DMO at T30 and T45. PaCO2 was increased in D, DB and DM compared with baseline, and PaO2 decreased in D at T15 and T45; in DB at T15 to T75; in DM at T15 to T60; in DMO at T15; and in DT at T15, T30 and T75. There was a decrease in temperature in D, DB and DM. An increased pH was measured in D at all time points and in DT at T30âT120. inline image and base excess were increased in all treatments compared with baseline. There were no statistical differences in sedation scores.
Conclusions and clinical relevance:
The combination of dexmedetomidine with butorphanol, methadone, morphine or tramadol resulted in similar changes in cardiopulmonary function and did not improve sedation when compared with dexmedetomidine alone
High energy electrons beyond 100 GEV observed by emulsion chamber
Much efforts have been expended to observe the spectrum of electrons in the high energy region with large area emulsion chambers exposed at balloon altitudes, and now 15 electrons beyond 1 TeV have been observed. The observed integral flux at 1 TeV is (3.24 + or - 0.87)x10(-5)/sq m sec sr. The statistics of the data around a few hundred GeV are also improving by using new shower detecting films of high sensitivity. The astrophysical significance of the observed spectrum are discussed for the propagation of electrons based on the leaky box and the nested leaky box model
Dominance of a single topological sector in gauge theory on non-commutative geometry
We demonstrate a striking effect of non-commutative (NC) geometry on
topological properties of gauge theory by Monte Carlo simulations. We study 2d
U(1) NC gauge theory for various boundary conditions using a new finite-matrix
formulation proposed recently. We find that a single topological sector
dictated by the boundary condition dominates in the continuum limit. This is in
sharp contrast to the results in commutative space-time based on lattice gauge
theory, where all topological sectors appear with certain weights in the
continuum limit. We discuss possible implications of this effect in the context
of string theory compactifications and in field theory contexts.Comment: 16 pages, 27 figures, typos correcte
Resonant Cyclotron Radiation Transfer Model Fits to Spectra from Gamma-Ray Burst GRB870303
We demonstrate that models of resonant cyclotron radiation transfer in a
strong field (i.e. cyclotron scattering) can account for spectral lines seen at
two epochs, denoted S1 and S2, in the Ginga data for GRB870303. Using a
generalized version of the Monte Carlo code of Wang et al. (1988,1989b), we
model line formation by injecting continuum photons into a static
plane-parallel slab of electrons threaded by a strong neutron star magnetic
field (~ 10^12 G) which may be oriented at an arbitrary angle relative to the
slab normal. We examine two source geometries, which we denote "1-0" and "1-1,"
with the numbers representing the relative electron column densities above and
below the continuum photon source plane. We compare azimuthally symmetric
models, i.e. models in which the magnetic field is parallel to the slab normal,
with models having more general magnetic field orientations. If the bursting
source has a simple dipole field, these two model classes represent line
formation at the magnetic pole, or elsewhere on the stellar surface. We find
that the data of S1 and S2, considered individually, are consistent with both
geometries, and with all magnetic field orientations, with the exception that
the S1 data clearly favor line formation away from a polar cap in the 1-1
geometry, with the best-fit model placing the line-forming region at the
magnetic equator. Within both geometries, fits to the combined (S1+S2) data
marginally favor models which feature equatorial line formation, and in which
the observer's orientation with respect to the slab changes between the two
epochs. We interpret this change as being due to neutron star rotation, and we
place limits on the rotation period.Comment: LaTeX2e (aastex.cls included); 45 pages text, 17 figures (on 21
pages); accepted by ApJ (to be published 1 Nov 1999, v. 525
Detection of a Hard Tail in the X-ray Spectrum of the Z Source GX 349+2
We present the results of a BeppoSAX observation of the Z source GX 349+2
covering the energy range 0.1-200 keV. The presence of flares in the light
curve indicates that the source was in the flaring branch during the BeppoSAX
observation. We accumulated energy spectra separately for the non-flaring
intervals and the flares. In both cases the continuum is well described by a
soft blackbody ( keV) and a Comptonized spectrum
corresponding to an electron temperature of keV, optical depth
(for a spherical geometry), and seed photon temperature of keV. All temperatures tend to increase during the flares. In the
non-flaring emission a hard tail dominates the spectrum above 30 keV. This can
be fit by a power law with photon index , contributing of the
total source luminosity over the BeppoSAX energy range. A comparison with hard
tails detected in some soft states of black hole binaries suggests that a
similar mechanism could originate these components in black hole and neutron
star systems.Comment: 15 pages, including 8 figures, to appear in Ap
The molecular basis of host specialization in bean pathovars of Pseudomonas syringae
Biotrophic phytopathogens are typically limited to their
adapted host range. In recent decades, investigations have
teased apart the general molecular basis of intraspecific
variation for innate immunity of plants, typically involving
receptor proteins that enable perception of pathogen-associated
molecular patterns or avirulence elicitors from the
pathogen as triggers for defense induction. However, general
consensus concerning evolutionary and molecular factors
that alter host range across closely related phytopathogen
isolates has been more elusive. Here, through genome
comparisons and genetic manipulations, we investigate the
underlying mechanisms that structure host range across
closely related strains of Pseudomonas syringae isolated
from different legume hosts. Although type III secretionindependent
virulence factors are conserved across these
three strains, we find that the presence of two genes encoding
type III effectors (hopC1 and hopM1) and the absence
of another (avrB2) potentially contribute to host range differences
between pathovars glycinea and phaseolicola.
These findings reinforce the idea that a complex genetic
basis underlies host range evolution in plant pathogens.
This complexity is present even in hostâmicrobe interactions
featuring relatively little divergence among both hosts
and their adapted pathogens
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