6,983 research outputs found
Atom-molecule collisions in an optically trapped gas
Cold inelastic collisions between confined cesium (Cs) atoms and Cs
molecules are investigated inside a CO laser dipole trap. Inelastic
atom-molecule collisions can be observed and measured with a rate coefficient
of cm s, mainly independent of the
molecular ro-vibrational state populated. Lifetimes of purely atomic and
molecular samples are essentially limited by rest gas collisions. The pure
molecular trap lifetime ranges 0,3-1 s, four times smaller than the atomic one,
as is also observed in a pure magnetic trap. We give an estimation of the
inelastic molecule-molecule collision rate to be cm
s
Carbonation cell materials compatibility
Material test and evaluation program for compatibility of materials with alkaline and acid electrolyte environments of carbonation cell syste
Kondo Insulator description of spin state transition in FeSb2
The thermal expansion and heat capacity of FeSb2 at ambient pressure agrees
with a picture of a temperature induced spin state transition within the Fe
t_{2g} multiplet. However, high pressure powder diffraction data show no sign
of a structural phase transition up to 7GPa. A bulk modulus B=84(3)GPa has been
extracted and the temperature dependence of the Gruneisen parameter has been
determined. We discuss here the relevance of a Kondo insulator description for
this material.Comment: Physical Review B in press (2005
The sulfur cycle
Author Posting. © Oceanography Society, 2007. This article is posted here by permission of Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 20, 2 (2007): 117-123.The ocean represents a major reservoir
of sulfur on Earth, with large quantities
in the form of dissolved sulfate and
sedimentary minerals (e.g., gypsum
and pyrite). Sulfur occurs in a variety
of valence states, ranging from –2 (as
in sulfide and reduced organic sulfur)
to +6 (as in sulfate). Sulfate is the most
stable form of sulfur on today’s oxic
Earth; weathering and leaching of rocks
and sediments are its main sources to
the ocean. In addition, the reduced inorganic
forms of sulfur, with oxidation
states of –2 and 0 (as in elemental sulfur)
are quite common in anoxic environments,
with sulfur compounds of mixed
valence states (e.g., thiosulfate and polythionates)
produced transiently. The
natural release of volatile organic sulfur
compounds from the ocean, mainly as
dimethyl sulfide (DMS), transports sulfur
from the ocean to terrestrial regions,
and it also affects atmospheric chemistry
and the climate system. While
they remain very important, natural sulfur
emissions have currently been overtaken
by anthropogenic emissions, primarily
from the burning of fossil fuels.Preparation of this manuscript was partially
supported by National Science
Foundation grant OCE-0452333
and a fellowship from the Hanse-
Wissenschaftskolleg (http://www.
h-w-k.de) to SMS, National Science
Foundation grants OPP-0230497
and OPP-0083078 to RPK, as well as
the Research Center Ocean Margins
(RCOM) of the University of Bremen
(Germany) to HNSV (RCOM-Nr. 0476)
Augmented Reality in Astrophysics
Augmented Reality consists of merging live images with virtual layers of
information. The rapid growth in the popularity of smartphones and tablets over
recent years has provided a large base of potential users of Augmented Reality
technology, and virtual layers of information can now be attached to a wide
variety of physical objects. In this article, we explore the potential of
Augmented Reality for astrophysical research with two distinct experiments: (1)
Augmented Posters and (2) Augmented Articles. We demonstrate that the emerging
technology of Augmented Reality can already be used and implemented without
expert knowledge using currently available apps. Our experiments highlight the
potential of Augmented Reality to improve the communication of scientific
results in the field of astrophysics. We also present feedback gathered from
the Australian astrophysics community that reveals evidence of some interest in
this technology by astronomers who experimented with Augmented Posters. In
addition, we discuss possible future trends for Augmented Reality applications
in astrophysics, and explore the current limitations associated with the
technology. This Augmented Article, the first of its kind, is designed to allow
the reader to directly experiment with this technology.Comment: 15 pages, 11 figures. Accepted for publication in Ap&SS. The final
publication will be available at link.springer.co
Screening and Anti-Screening Effects in J/psi Production on Nuclei
The nuclear effects in J/psi hadro- and electroproduction on nuclei are
considered in framework of reggeon approach. It is shown that screening regime
which holds for electroproduction at x_F > 0.7 and for hadroproduction at x_F >
-(0.3-0.4) is changed with anti-screening regime for smaller x_F values.Comment: 6 pages, 6 figures. Small changes in wordin
Star clusters dynamics in a laboratory: electrons in an ultracold plasma
Electrons in a spherical ultracold quasineutral plasma at temperature in the
Kelvin range can be created by laser excitation of an ultra-cold laser cooled
atomic cloud. The dynamical behavior of the electrons is similar to the one
described by conventional models of stars clusters dynamics. The single mass
component, the spherical symmetry and no stars evolution are here accurate
assumptions. The analog of binary stars formations in the cluster case is
three-body recombination in Rydberg atoms in the plasma case with the same
Heggie's law: soft binaries get softer and hard binaries get harder. We
demonstrate that the evolution of such an ultracold plasma is dominated by
Fokker-Planck kinetics equations formally identical to the ones controlling the
evolution of a stars cluster. The Virial theorem leads to a link between the
plasma temperature and the ions and electrons numbers. The Fokker-Planck
equation is approximate using gaseous and fluid models. We found that the
electrons are in a Kramers-Michie-King's type quasi-equilibrium distribution as
stars in clusters. Knowing the electron distribution and using forced fast
electron extraction we are able to determine the plasma temperature knowing the
trapping potential depth.Comment: Submitted to MNRA
On the Solutions of the Lorentz-Dirac Equation
We discuss the unstable character of the solutions of the Lorentz-Dirac
equation and stress the need of methods like order reduction to derive a
physically acceptable equation of motion. The discussion is illustrated with
the paradigmatic example of the non-relativistic harmonic oscillator with
radiation reaction. We also illustrate removal of the noncasual
pre-acceleration with the introduction of a small correction in the
Lorentz-Dirac equation.Comment: 4 eps figs. to be published in GR
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