15,007 research outputs found
Reduction and analysis of data from OGO-4 experiment 15 Final report, 1 Nov. 1969 - 30 Nov. 1970
Procedures for processing atmospheric composition data obtained through use of sweeping quadrupole mass spectrometer on OGO-4 satellit
Perturbations to observed ambient neutral densities due to presence of an Orbiting Geophysical Observatory
Perturbations in density of ions and neutral particles in upper atmosphere due to OG
Bounds on the electromagnetic interactions of excited spin-3/2 leptons
We discuss possible deviations from QED produced by a virtual excited
spin-3/2 lepton in the reaction . Data recorded
by the OPAL Collaboration at a c.m. energy are used to
establish bounds on the nonstandard-lepton mass and coupling strengths.Comment: Latex, 5 pages, 7 ps figures. To be published in Phys. Rev.
Stellar Chemical Abundances: In Pursuit of the Highest Achievable Precision
The achievable level of precision on photospheric abundances of stars is a
major limiting factor on investigations of exoplanet host star characteristics,
the chemical histories of star clusters, and the evolution of the Milky Way and
other galaxies. While model-induced errors can be minimized through the
differential analysis of spectrally similar stars, the maximum achievable
precision of this technique has been debated. As a test, we derive differential
abundances of 19 elements from high-quality asteroid-reflected solar spectra
taken using a variety of instruments and conditions. We treat the solar spectra
as being from unknown stars and use the resulting differential abundances,
which are expected to be zero, as a diagnostic of the error in our
measurements. Our results indicate that the relative resolution of the target
and reference spectra is a major consideration, with use of different
instruments to obtain the two spectra leading to errors up to 0.04 dex. Use of
the same instrument at different epochs for the two spectra has a much smaller
effect (~0.007 dex). The asteroid used to obtain the solar standard also has a
negligible effect (~0.006 dex). Assuming that systematic errors from the
stellar model atmospheres have been minimized, as in the case of solar twins,
we confirm that differential chemical abundances can be obtained at sub-0.01
dex precision with due care in the observations, data reduction and abundance
analysis.Comment: Accepted for publication in ApJ; 13 pages, 6 figures, 7 table
Phonon-assisted and phonon-free radiative transitions in sulfur-doped GaAs diffused junctions
In the course of electroluminescence studies of GaAs junctions we investigated the emission spectra of sulfur-doped zinc-diffused diodes. The peaks in the spectra correspond to three main transitions and their associated phonon emission satellites
Induced Lorentz-violating terms at finite temperature
We study the radiatively induced Lorentz-violating terms at finite
temperature, namely, the higher-derivative term and the Chern-Simons term.
These terms are induced by integrating out the fermions coupled to the
coefficient . The calculation of the resulting expressions is
performed by using the derivative expansion and the Matsubara formalism. The
Chern-Simons terms is nonzero only at finite temperature, whereas the
higher-derivative term is finite at zero temperature, however, it goes to zero
as the temperature grows to infinity. We also obtain a higher-derivative
Chern-Simons term, nevertheless, it vanishes asymptotically.Comment: 12 pages, 4 figures, revtex4; v2: EPL versio
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