5,161 research outputs found
Observations of the upper troposphere and lower stratosphere using the urbana coherent-scatter radar
The Urbana coherent-scatter radar was used to observe the upper troposphere and lower stratosphere, and 134 hours of data were collected. Horizontal wind measurements show good agreement with balloon-measured winds. Gravity waves were frequently observed, and were enhanced during convective activity. Updrafts and downdrafts were observed within thunderstorms. Power returns are related to hydrostatic stability, and changes in echo specularity are shown
Chromosome mapping: radiation hybrid data and stochastic spin models
This work approaches human chromosome mapping by developing algorithms for
ordering markers associated with radiation hybrid data. Motivated by recent
work of Boehnke et al. [1], we formulate the ordering problem by developing
stochastic spin models to search for minimum-break marker configurations. As a
particular application, the methods developed are applied to 14 human
chromosome-21 markers tested by Cox et al. [2]. The methods generate
configurations consistent with the best found by others. Additionally, we find
that the set of low-lying configurations is described by a Markov-like ordering
probability distribution. The distribution displays cluster correlations
reflecting closely linked loci.Comment: 26 Pages, uuencoded LaTex, Submitted to Phys. Rev. E,
[email protected], [email protected]
Photoassociation dynamics in a Bose-Einstein condensate
A dynamical many body theory of single color photoassociation in a
Bose-Einstein condensate is presented. The theory describes the time evolution
of a condensed atomic ensemble under the influence of an arbitrarily varying
near resonant laser pulse, which strongly modifies the binary scattering
properties. In particular, when considering situations with rapid variations
and high light intensities the approach described in this article leads, in a
consistent way, beyond standard mean field techniques. This allows to address
the question of limits to the photoassociation rate due to many body effects
which has caused extensive discussions in the recent past. Both, the possible
loss rate of condensate atoms and the amount of stable ground state molecules
achievable within a certain time are found to be stronger limited than
according to mean field theory. By systematically treating the dynamics of the
connected Green's function for pair correlations the resonantly driven
population of the excited molecular state as well as scattering into the
continuum of non-condensed atomic states are taken into account. A detailed
analysis of the low energy stationary scattering properties of two atoms
modified by the near resonant photoassociation laser, in particular of the
dressed state spectrum of the relative motion prepares for the analysis of the
many body dynamics. The consequences of the finite lifetime of the resonantly
coupled bound state are discussed in the two body as well as in the many body
context. Extending the two body description to scattering in a tight trap
reveals the modifications to the near resonant adiabatic dressed levels caused
by the decay of the excited molecular state.Comment: 27 pages revtex, 16 figure
Oral History with Dr. Sylvia Goss & Dr. Willie Goss
The Cultural Research & Engagement Fellows (CREF) Program at Mississippi State University explores the social and cultural dimensions of food systems, food access, land in majority-Black, historically agrarian rural communities by engaging youth at the nexus of food access, farming, and culture. The CREF program is made possible by a grant from the Office of Research & Economic Development (ORED) and the Office of Institutional Diversity and Inclusion (OIDI) at Mississippi State University
The neutral gas in the environs of the Geminga gamma-ray pulsar
We present a high-resolution (24 arcsec) study of the HI interstellar gas
distribution around the radio-quiet neutron star Geminga. Based on Very Large
Array (VLA) and MPIfR Effelsberg telescope data, we analyzed a 40' x 40' field
around Geminga. These observations have revealed the presence of a neutral gas
shell, 0.4 pc in radius, with an associated HI mass of 0.8 Msun, which
surrounds Geminga at a radial velocity compatible with the kinematical distance
of the neutron star. In addition, morphological agreement is observed between
the internal face of the HI shell and the brightest structure of Geminga's tail
observed in X-rays.We explore the possibility that this morphological agreement
is the result of a physical association.Comment: One tarfile including a Latex file (7 pages) and two figures. Paper
accepted for publication in Advances in Space Research; typos corrected;
changes in section Results and Discussion after referee's suggestions. S.
Johnston's affilation correcte
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