390 research outputs found
Exact dynamics and decoherence of two cold bosons in a 1D harmonic trap
We study dynamics of two interacting ultra cold Bose atoms in a harmonic
oscillator potential in one spatial dimension. Making use of the exact solution
of the eigenvalue problem of a particle in the delta-like potential we study
time evolution of initially separable state of two particles. The corresponding
time dependent single particle density matrix is obtained and diagonalized and
single particle orbitals are found. This allows to study decoherence as well as
creation of entanglement during the dynamics. The evolution of the orbital
corresponding to the largest eigenvalue is then compared to the evolution
according to the Gross-Pitaevskii equation. We show that if initially the
center of mass and relative degrees of freedom are entangled then the
Gross-Pitaevskii equation fails to reproduce the exact dynamics and
entanglement is produced dynamically. We stress that predictions of our study
can be verified experimentally in an optical lattice in the low-tunneling
limit.Comment: 9 figures, 5 movies available on-lin
Evaluation of extralaryngeal diameters in senile individuals
The aim of the study was a morphometrical macroscopic evaluation of extralaryngeal
diameters in elderly people, according to its usefulness in ORL diagnostic
and operational methods.
Laryngeal preparations together with surrounding structures were taken from
cadavers of both sexes, aged 65 and over, about 24 hours after death. Clinically
important extralaryngeal diameters were collected using common morphometrical
methods. A few body features were also gathered. Computer statistical
methods were used in data assessment including basic statistics and linear correlations
between diameters, and between diameters and body features.
The data presented in the study may be very helpful in diagnostic methods’
evaluation. They may also help in: selection of the appropriate operational tool
size, choice of the most appropriate operational technique, preoperative preparations
and designing and building virtual models for physicians’ training
Quasicondensation reexamined
We study in detail the effect of quasicondensation. We show that this effect
is strictly related to dimensionality of the system. It is present in one
dimensional systems independently of interactions - exists in repulsive,
attractive or in non-interacting Bose gas in some range of temperatures below
characteristic temperature of the quantum degeneracy. Based on this observation
we analyze the quasicondensation in terms of a ratio of the two largest
eigenvalues of the single particle density matrix for the ideal gas. We show
that in the thermodynamic limit in higher dimensions the second largest
eigenvalue vanishes (as compared to the first one) with total number of
particles as whereas goes to zero only logarithmically in
one dimension. We also study the effect of quasicondensation for various
geometries of the system: from quasi-1D elongated one, through spherically
symmetric 3D case to quasi-2D pancake-like geometry
Evaluation of several methods used in anatomical investigations of the blood and lymphatic vessels
The aim of this review is to describe the advantages and limitations of several
methods used in anatomical investigations of intravisceral blood and lymphatic
networks. The microangiographic methods as well as corrosion methods are
described. In conclusion the authors confirmed that the most useful way for
exploration of the blood and lymphatic vessels is to prepare corrosion casts. This
paper focuses on the scanning electron microscopic examination of vascular
corrosion casts. This method allows the examination of the three-dimensional
organisation of vessels, including the blood and lymphatic capillaries. Imprints
of endothelial cell nuclei can be observed on the surface of the blood and lymphatic
vessels
Correlations in atomic systems: Diagnosing coherent superpositions
While investigating quantum correlations in atomic systems, we note that
single measurements contain information about these correlations. Using a
simple model of measurement -- analogous to the one used in quantum optics --
we show how to extract higher order correlation functions from individual
"phtotographs" of the atomic sample. As a possible application we apply the
method to detect a subtle phase coherence in mesoscopic superpostitions.Comment: 4 pages, 2 figures, provisionally accepted to Physical Review Letter
Dust in a Type Ia Supernova Progenitor: Spitzer Spectroscopy of Kepler's Supernova Remnant
Characterization of the relatively poorly-understood progenitor systems of
Type Ia supernovae is of great importance in astrophysics, particularly given
the important cosmological role that these supernovae play. Kepler's Supernova
Remnant, the result of a Type Ia supernova, shows evidence for an interaction
with a dense circumstellar medium (CSM), suggesting a single-degenerate
progenitor system. We present 7.5-38 m infrared (IR) spectra of the
remnant, obtained with the {\it Spitzer Space Telescope}, dominated by emission
from warm dust. Broad spectral features at 10 and 18 m, consistent with
various silicate particles, are seen throughout. These silicates were likely
formed in the stellar outflow from the progenitor system during the AGB stage
of evolution, and imply an oxygen-rich chemistry. In addition to silicate dust,
a second component, possibly carbonaceous dust, is necessary to account for the
short-wavelength IRS and IRAC data. This could imply a mixed chemistry in the
atmosphere of the progenitor system. However, non-spherical metallic iron
inclusions within silicate grains provide an alternative solution. Models of
collisionally-heated dust emission from fast shocks ( 1000 km s)
propagating into the CSM can reproduce the majority of the emission associated
with non-radiative filaments, where dust temperatures are K, but
fail to account for the highest temperatures detected, in excess of 150 K. We
find that slower shocks (a few hundred km s) into moderate density
material ( cm) are the only viable source of heating
for this hottest dust. We confirm the finding of an overall density gradient,
with densities in the north being an order of magnitude greater than those in
the south.Comment: Accepted by ApJ. 11 pages, 5 figures, 1 table. Produced using
emulateapj forma
Doming Modes and Dynamics of Model Heme Compounds
Synchrotron far-IR spectroscopy and density-functional calculations are used to characterize the low-frequency dynamics of model heme FeCO compounds. The “doming” vibrational mode in which the iron atom moves out of the porphyrin plane while the periphery of this ring moves in the opposite direction determines the reactivity of oxygen with this type of molecule in biological systems. Calculations of frequencies and absorption intensities and the measured pressure dependence of vibrational modes in the model compounds are used to identify the doming and related normal modes
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