322 research outputs found
Jet Tomography of Hot and Cold Nuclear Matter
Medium modification of parton fragmentation functions induced by multiple
scattering and gluon bremsstrahlung is shown to describe the recent HERMES data
in deeply inelastic scattering (DIS) very well, providing the first evidence of
-dependence of the modification. The energy loss is found to be
GeV/fm for a 10-GeV quark in a nucleus. Including
the effect of expansion, analysis of the spectra in central
collisions at GeV yields an averaged energy loss equivalent to
GeV/fm in a static medium. Predictions for central
collisions at GeV are also given.Comment: 4 pages in RevTex with 3 ps figures, final version published in Phys.
Rev. Letter
A study on the anomaly of over ratios in collisions with jet quenching
The ratios of at large transverse momentum in central
collisions at RHIC are studied in the framework of jet quenching based on a
next-to-leading order pQCD parton model. It is shown that theoretical
calculations with a gluon energy loss larger than the quark energy loss will
naturally lead to a smaller ratios at large transverse momentum in
collisions than those in collisions at the same energy. Scenarios
with equal energy losses for gluons and quarks and a strong jet conversion are
both explored and it is demonstrated in both scenarios ratios at high
in central collisions are enhanced and the calculated ratios of
protons over pions approach to the experimental measurements. However, in the latter scenario is found to fit data better than that in the
former scenario.Comment: 20 pages, 13 figures; revised version; accepted for publication in
Journal of Physics
Parton Energy Loss with Detailed Balance
Stimulated gluon emission and thermal absorption in addition to induced
radiation are considered for an energetic parton propagating inside a quark-
gluon plasma. In the presence of thermal gluons, stimulated emission reduces
while absorption increases the parton's energy. The net effect is a reduction
of the parton energy loss. Though decreasing asymptotically as with the
parton energy, the relative reduction is found to be important for intermediate
energies. The modified energy dependence of the energy loss will affect the
shape of suppression of moderately high hadrons due to jet quenching in
high-energy heavy-ion collisions.Comment: 4 pages in RevTex with 1 postscript figure. Some typos are corrected
and new comments are adde
The Plasmon in Hot Theory
We study the 2-loop resummed propagator in hot theory. The
propagator has a cut along the whole real axis in the complex energy plane, but
for small , the spectral density is sharply peaked around the plasmon. The
dispersion relation and the width of the plasmon are calculated at zero {\em
and} finite momentum. At large momenta the spectral width vanishes, and the
plasmon looses its collectivity and behaves like a non-interacting free
particle.Comment: REVTeX, 30 pages, 8 uuencoded ps-figure
The RAVE-on Catalog of Stellar Atmospheric Parameters and Chemical Abundances for Chemo-dynamic Studies in the Gaia Era
The orbits, atmospheric parameters, chemical abundances, and ages of
individual stars in the Milky Way provide the most comprehensive illustration
of galaxy formation available. The Tycho-Gaia Astrometric Solution (TGAS) will
deliver astrometric parameters for the largest ever sample of Milky Way stars,
though its full potential cannot be realized without the addition of
complementary spectroscopy. Among existing spectroscopic surveys, the RAdial
Velocity Experiment (RAVE) has the largest overlap with TGAS (200,000
stars). We present a data-driven re-analysis of 520,781 RAVE spectra using The
Cannon. For red giants, we build our model using high-fidelity APOGEE stellar
parameters and abundances for stars that overlap with RAVE. For main-sequence
and sub-giant stars, our model uses stellar parameters from the K2/EPIC. We
derive and validate effective temperature , surface gravity
, and chemical abundances of up to seven elements (O, Mg, Al, Si, Ca,
Fe, Ni). We report a total of 1,685,851 elemental abundances with a typical
precision of 0.07 dex, a substantial improvement over previous RAVE data
releases. The synthesis of RAVE-on and TGAS is the most powerful data set for
chemo-dynamic analyses of the Milky Way ever produced
<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues â a realisation of the Tycho-Gaia Astrometric Solution (TGAS) â and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of âŒ3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yrâ1 for the proper motions. A systematic component of âŒ0.3 mas should be added to the parallax uncertainties. For the subset of âŒ94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yrâ1. For the secondary astrometric data set, the typical uncertainty of the positions is âŒ10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to âŒ0.03 mag over the magnitude range 5 to 20.7.
Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data
The American Astronomical Society, find out more The Institute of Physics, find out more The Sixth Data Release of the Radial Velocity Experiment (Rave). II. Stellar Atmospheric Parameters, Chemical Abundances, and Distances
We present part 2 of the 6th and final Data Release (DR6 or FDR) of the Radial Velocity Experiment (RAVE), a magnitude-limited (9<I<12) spectroscopic survey of Galactic stars randomly selected in the southern hemisphere. The RAVE medium-resolution spectra (R~7500) cover the Ca-triplet region (8410-8795A) and span the complete time frame from the start of RAVE observations on 12 April 2003 to their completion on 4 April 2013. In the second of two publications, we present the data products derived from 518387 observations of 451783 unique stars using a suite of advanced reduction pipelines focussing on stellar atmospheric parameters, in particular purely spectroscopically derived stellar atmospheric parameters (Teff, log(g), and the overall metallicity), enhanced stellar atmospheric parameters inferred via a Bayesian pipeline using Gaia DR2 astrometric priors, and asteroseismically calibrated stellar atmospheric parameters for giant stars based on asteroseismic observations for 699 K2 stars. In addition, we provide abundances of the elements Fe, Al, and Ni, as well as an overall [alpha/Fe] ratio obtained using a new pipeline based on the GAUGUIN optimization method that is able to deal with variable signal-to-noise ratios. The RAVE DR6 catalogs are cross matched with relevant astrometric and photometric catalogs, and are complemented by orbital parameters and effective temperatures based on the infrared flux method. The data can be accessed via the RAVE Web site (http://rave-survey.org) or the Vizier database
The sixth data release of the Radial Velocity Experiment (RAVE) -- II:stellar atmospheric parameters, chemical abundances and distances
We present part 2 of the 6th and final Data Release (DR6 or FDR) of the
Radial Velocity Experiment (RAVE), a magnitude-limited (9<I<12) spectroscopic
survey of Galactic stars randomly selected in the southern hemisphere. The RAVE
medium-resolution spectra (R~7500) cover the Ca-triplet region (8410-8795A) and
span the complete time frame from the start of RAVE observations on 12 April
2003 to their completion on 4 April 2013. In the second of two publications, we
present the data products derived from 518387 observations of 451783 unique
stars using a suite of advanced reduction pipelines focussing on stellar
atmospheric parameters, in particular purely spectroscopically derived stellar
atmospheric parameters (Teff, log(g), and the overall metallicity), enhanced
stellar atmospheric parameters inferred via a Bayesian pipeline using Gaia DR2
astrometric priors, and asteroseismically calibrated stellar atmospheric
parameters for giant stars based on asteroseismic observations for 699 K2
stars. In addition, we provide abundances of the elements Fe, Al, and Ni, as
well as an overall [alpha/Fe] ratio obtained using a new pipeline based on the
GAUGUIN optimization method that is able to deal with variable signal-to-noise
ratios. The RAVE DR6 catalogs are cross matched with relevant astrometric and
photometric catalogs, and are complemented by orbital parameters and effective
temperatures based on the infrared flux method. The data can be accessed via
the RAVE Web site (http://rave-survey.org) or the Vizier database.Comment: 65 pages, 33 figures, accepted for publication to A
The Radial Velocity Experiment (RAVE): Fifth Data Release
Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is the fifth data release from a magnitude-limited (9< I < 12) survey of stars randomly selected in the southern hemisphere. The RAVE medium-resolution spectra () covering the Ca-triplet region (8410-8795\AA) span the complete time frame from the start of RAVE observations in 2003 to their completion in 2013. Radial velocities from 520,781 spectra of 457,588 unique stars are presented, of which 255,922 stellar observations have parallaxes and proper motions from the Tycho-Gaia astrometric solution (TGAS) in Gaia DR1. For our main DR5 catalog, stellar parameters (effective temperature, surface gravity, and overall metallicity) are computed using the RAVE DR4 stellar pipeline, but calibrated using recent K2 Campaign 1 seismic gravities and Gaia benchmark stars, as well as results obtained from high-resolution studies. Also included are temperatures from the Infrared Flux Method, and we provide a catalogue of red giant stars in the dereddened color interval (0.50,0.85) for which the gravities were calibrated based only on seismology. Further data products for sub-samples of the RAVE stars include individual abundances for Mg, Al, Si, Ca, Ti, Fe, and Ni, and distances found using isochrones. Each RAVE spectrum is complemented by an error spectrum, which has been used to determine uncertainties on the parameters. The data can be accessed via the RAVE Web site or the Vizier database
Aurora kinases are expressed in medullary thyroid carcinoma (MTC) and their inhibition suppresses in vitro growth and tumorigenicity of the MTC derived cell line TT
International audienceBACKGROUND: The Aurora kinase family members, Aurora-A, -B and -C, are involved in the regulation of mitosis, and alterations in their expression are associated with cell malignant transformation. To date no information on the expression of these proteins in medullary thyroid carcinoma (MTC) are available. We here investigated the expression of the Aurora kinases in human MTC tissues and their potential use as therapeutic targets. METHODS: The expression of the Aurora kinases in 26 MTC tissues at different TNM stages was analyzed at the mRNA level by quantitative RT-PCR. We then evaluated the effects of the Aurora kinase inhibitor MK-0457 on the MTC derived TT cell line proliferation, apoptosis, soft agar colony formation, cell cycle and ploidy. RESULTS: The results showed the absence of correlation between tumor tissue levels of any Aurora kinase and tumor stage indicating the lack of prognostic value for these proteins. Treatment with MK-0457 inhibited TT cell proliferation in a time- and dose-dependent manner with IC50 = 49.8 ± 6.6 nM, as well as Aurora kinases phosphorylation of substrates relevant to the mitotic progression. Time-lapse experiments demonstrated that MK-0457-treated cells entered mitosis but were unable to complete it. Cytofluorimetric analysis confirmed that MK-0457 induced accumulation of cells with ℠4N DNA content without inducing apoptosis. Finally, MK-0457 prevented the capability of the TT cells to form colonies in soft agar. CONCLUSIONS: We demonstrate that Aurora kinases inhibition hampered growth and tumorigenicity of TT cells, suggesting its potential therapeutic value for MTC treatment
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