4,935 research outputs found
Response to Comment on "Pairing and Phase Separation in a Polarized Fermi Gas"
Zwierlein and Ketterle rely on subjective arguments and fail to recognize
important differences in physical parameters between our experiment and theirs.
We stand by the conclusions of our original report
Measurement of the Hyperfine Structure and Isotope Shifts of the 3s23p2 3P2 to 3s3p3 3Do3 Transition in Silicon
The hyperfine structure and isotope shifts of the 3s23p2 3P2 to 3s3p3 3Do3
transition in silicon have been measured. The transition at 221.7 nm was
studied by laser induced fluorescence in an atomic Si beam. For 29Si, the
hyperfine A constant for the 3s23p2 3P2 level was determined to be -160.1+-1.3
MHz (1 sigma error), and the A constant for the 3s3p3 3Do3 level is -532.9+-0.6
MHz. This is the first time that these constants were measured. The isotope
shifts (relative to the abundant isotope 28Si) of the transition were
determined to be 1753.3+-1.1 MHz for 29Si and 3359.9+-0.6 MHz for 30Si. This is
an improvement by about two orders of magnitude over a previous measurement.
From these results we are able to predict the hyperfine structure and isotope
shift of the radioactive 31Si atom, which is of interest in building a scalable
quantum computer
The infrared morphology of galactic centers
Initial results are presented of a program to map the centers of galaxies in the mid-infrared using the NASA-MSFC 20 pixel bolometer array. Maps at 10.8 micrometer of the galaxies NGC 5236 (M82), NGC 1808, NGC 4536, and NGC 4527 reveal complex emitting regions ranging in size from 500 pc to 2 kpc. The infrared spatial distributions generally resemble those in the visible and radio. In all cases a large fraction of the IRAS 12 micrometer flux originates in spatial structures prominent in the maps
Environmental, developmental, and genetic factors controlling root system architecture
A better understanding of the development and architecture of roots is essential to develop strategies to increase crop yield and optimize agricultural land use. Roots control nutrient and water uptake, provide anchoring and mechanical support and can serve as important storage organs. Root growth and development is under tight genetic control and modulated by developmental cues including plant hormones and the environment. This review focuses on root architecture and its diversity and the role of environment, nutrient, and water as well as plant hormones and their interactions in shaping root architecture
On formal verification of arithmetic-based cryptographic primitives
Cryptographic primitives are fundamental for information security: they are
used as basic components for cryptographic protocols or public-key
cryptosystems. In many cases, their security proofs consist in showing that
they are reducible to computationally hard problems. Those reductions can be
subtle and tedious, and thus not easily checkable. On top of the proof
assistant Coq, we had implemented in previous work a toolbox for writing and
checking game-based security proofs of cryptographic primitives. In this paper
we describe its extension with number-theoretic capabilities so that it is now
possible to write and check arithmetic-based cryptographic primitives in our
toolbox. We illustrate our work by machine checking the game-based proofs of
unpredictability of the pseudo-random bit generator of Blum, Blum and Shub, and
semantic security of the public-key cryptographic scheme of Goldwasser and
Micali.Comment: 13 page
The SXI telescope on board EXIST: scientific performances
The SXI telescope is one of the three instruments on board EXIST, a
multiwavelength observatory in charge of performing a global survey of the sky
in hard X-rays searching for Supermassive Black Holes. One of the primary
objectives of EXIST is also to study with unprecedented sensitivity the most
unknown high energy sources in the Universe, like high redshift GRBs, which
will be pointed promptly by the Spacecraft by autonomous trigger based on hard
X-ray localization on board. The recent addition of a soft X-ray telescope to
the EXIST payload complement, with an effective area of ~950 cm2 in the energy
band 0.2-3 keV and extended response up to 10 keV will allow to make broadband
studies from 0.1 to 600 keV. In particular, investigations of the spectra
components and states of AGNs and monitoring of variability of sources, study
of the prompt and afterglow emission of GRBs since the early phases, which will
help to constrain the emission models and finally, help the identification of
sources in the EXIST hard X-ray survey and the characterization of the
transient events detected. SXI will also perform surveys: a scanning survey
with sky coverage of about 2pi and limiting flux of 5x10^{-14}cgs plus other
serendipitous. We give an overview of the SXI scientific performance and also
describe the status of its design emphasizing how it has been derived by the
scientific requirements.Comment: 9 pages, 6 figures, to be published in Proc. of SPIE, vol 7435-11,
200
Library of medium-resolution fiber optic echelle spectra of F, G, K, and M field dwarfs to giants stars
We present a library of Penn State Fiber Optic Echelle (FOE) observations of
a sample of field stars with spectral types F to M and luminosity classes V to
I. The spectral coverage is from 3800 AA to 10000 AA with nominal a resolving
power 12000. These spectra include many of the spectral lines most widely used
as optical and near-infrared indicators of chromospheric activity such as the
Balmer lines (H_alpha, H_beta), Ca II H & K, Mg I b triplet, Na I D_{1} and
D_{2}, He I D_{3}, and Ca II IRT lines. There are also a large number of
photospheric lines, which can also be affected by chromospheric activity, and
temperature sensitive photospheric features such as TiO bands. The spectra have
been compiled with the goal of providing a set of standards observed at medium
resolution. We have extensively used such data for the study of active
chromosphere stars by applying a spectral subtraction technique. However, the
data set presented here can also be utilized in a wide variety of ways ranging
from radial velocity templates to study of variable stars and stellar
population synthesis. This library can also be used for spectral classification
purposes and determination of atmospheric parameters (T_eff, log{g}, [Fe/H]). A
digital version of all the fully reduced spectra is available via ftp and the
World Wide Web (WWW) in FITS format.Comment: Latex file with 17 pages, 4 figures. Full postscript (text and
figures) available at http://www.ucm.es/info/Astrof/fgkmsl/FOEfgkmsl.html To
be published in ApJ
Wide-angle elastic scattering and color randomization
Baryon-baryon elastic scattering is considered in the independent scattering
(Landshoff) mechanism. It is suggested that for scattering at moderate
energies, direct and interchange quark channels contribute with equal color
coefficients because the quark color is randomized by soft gluon exchange
during the hadronization stage. With this assumption, it is shown that the
ratio of cross sections at CM angle
decreases from a high energy value of R_{\pbar p / pp} \approx 1/2.7, down to
R_{\pbar p / pp} \approx 1/28, compatible with experimental data at moderate
energies. This sizable fall in the ratio seems to be characteristic of the
Landshoff mechanism, in which changes at the quark level have a strong effect
precisely because the hadronic process occurs via multiple quark scatterings.
The effect of color randomization on the angular distribution of proton-proton
elastic scattering and the cross section ratio is also discussed.Comment: 18 pages, latex2e, 4 uuencoded figures, include
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