15,543 research outputs found
Decoherence induced continuous pointer states
We investigate the reduced dynamics in the Markovian approximation of an
infinite quantum spin system linearly coupled to a phonon field at positive
temperature. The achieved diagonalization leads to a selection of the
continuous family of pointer states corresponding to a configuration space of
the one-dimensional Ising model. Such a family provides a mathematical
description of an apparatus with continuous readings.Comment: 8 page
Remote estimation of soil moisture
Two methods under consideration for making remote estimates of soil moisture involve measurements made in electromagnetic spectral region of 0.4 to 14.0 micrometers: (1) spectral reflectance, (2) soil temperature
Use of visible, near-infrared, and thermal infrared remote sensing to study soil moisture
Two methods are described which are used to estimate soil moisture remotely using the 0.4- to 14.0 micron wavelength region: (1) measurement of spectral reflectance, and (2) measurement of soil temperature. The reflectance method is based on observations which show that directional reflectance decreases as soil moisture increases for a given material. The soil temperature method is based on observations which show that differences between daytime and nighttime soil temperatures decrease as moisture content increases for a given material. In some circumstances, separate reflectance or temperature measurements yield ambiguous data, in which case these two methods may be combined to obtain a valid soil moisture determination. In this combined approach, reflectance is used to estimate low moisture levels; and thermal inertia (or thermal diffusivity) is used to estimate higher levels. The reflectance method appears promising for surface estimates of soil moisture, whereas the temperature method appears promising for estimates of near-subsurface (0 to 10 cm)
Nonnegative Feynman-Kac Kernels in Schr\"{o}dinger's Interpolation Problem
The existing formulations of the Schr\"{o}dinger interpolating dynamics,
which is constrained by the prescribed input-output statistics data, utilize
strictly positive Feynman-Kac kernels. This implies that the related Markov
diffusion processes admit vanishing probability densities only at the
boundaries of the spatial volume confining the process. We extend the framework
to encompass singular potentials and associated nonnegative Feynman-Kac-type
kernels. It allows to deal with general nonnegative solutions of the
Schr\"{o}dinger boundary data problem. The resulting stochastic processes are
capable of both developing and destroying nodes (zeros) of probability
densities in the course of their evolution.Comment: Latex file, 25 p
Constraining from X-ray properties of Clusters of Galaxies at high redshift
Properties of high redshift clusters are a fundamental source of information
for cosmology. It has been shown by Oukbir and Blanchard (1997) that the
combined knowledge of the redshift distribution of X-ray clusters of galaxies
and the luminosity-temperature correlation, , provides a powerful test
of the mean density of the Universe. In this paper, we address the question of
the possible evolution of this relation from an observational point of view and
its cosmological significance. We introduce a new indicator in order to measure
the evolution of the X-ray luminosity-temperature relation with redshift and
take advantage of the recent availability of temperature information for a
significant number of high and intermediate redshift X-ray clusters of
galaxies. From our analysis, we find a slightly positive evolution in the
relation. This implies a high value of the density parameter of
. However, because the selection of clusters included inour sample
is unknown, this can be considered only as a tentative result. A
well-controlled X-ray selected survey would provide a more robust answer. XMM
will be ideal for such a program.Comment: 10 pages, LaTeX, 4 figures,5 tables, accepted by A&
Time varying solar cycle protons program manual
Proton variations in earth radiation belt due to solar cycle - calculation program
STS-40 orbital acceleration research experiment flight results during a typical sleep period
The Orbital Acceleration Research Experiment (OARE), an electrostatic accelerometer package with complete on-orbit calibration capabilities, was flown for the first time aboard the Space Shuttle on STS-40. This is also the first time an accelerometer package with nano-g sensitivity and a calibration facility has flown aboard the Space Shuttle. The instrument is designed to measure and record the Space Shuttle aerodynamic acceleration environment from the free molecule flow regime through the rarified flow transition into the hypersonic continuum regime. Because of its sensitivity, the OARE instrument defects aerodynamic behavior of the Space Shuttle while in low-earth orbit. A 2-hour orbital time period on day seven of the mission, when the crew was asleep and other spacecraft activities were at a minimum, was examined. During the flight, a 'trimmed-mean' filter was used to produce high quality, low frequency data which was successfully stored aboard the Space Shuttle in the OARE data storage system. Initial review of the data indicated that, although the expected precision was achieved, some equipment problems occurred resulting in uncertain accuracy. An acceleration model which includes aerodynamic, gravity-gradient, and rotational effects was constructed and compared with flight data. Examination of the model with the flight data shows the instrument to be sensitive to all major expected low frequency acceleration phenomena; however, some erratic instrument bias behavior persists in two axes. In these axes, the OARE data can be made to match a comprehensive atmospheric-aerodynamic model by making bias adjustments and slight linear corrections for drift. The other axis does not exhibit these difficulties and gives good agreement with the acceleration model
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