24 research outputs found
GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy
We propose to perform a continuously scanning all-sky survey from 200 keV to 80 MeV achieving a sensitivity which is better by a factor of 40 or more compared to the previous missions in this energy range (COMPTEL, INTEGRAL; see Fig. 1). The Gamma-Ray Imaging, Polarimetry and Spectroscopy (âGRIPSâ) mission addresses fundamental questions in ESAâs Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS has its focus on the evolving, vio-lent Universe, exploring a unique energy window. We propose to investigate Îł-ray bursts and blazars, the mechanisms behind supernova explosions, nucleosynthesis and spallation, the enigmatic origin of positrons in our Galaxy, and the nature of radiation processes and particle acceleration in extreme cosmic sources including pulsars and magnetars. The natural energy scale for these non-thermal processes is of the order of MeV. Although they can be partially and indirectly studied us-ing other methods, only the proposed GRIPS measurements will provide direct access to their primary photons. GRIPS will be a driver for the study of transient sources in the era of neutrino and gravitational wave observatories such as Ice-CUBE and LISA, establishing a new type of diagnostics in relativistic and nuclear astrophysics. This will support extrapolations to investigate star formation, galaxy evolution, and black hole formation at high redshifts
X-ray Spectral Survey with XMM--Newton of a Complete Sample of Nearby Seyfert Galaxies
Results obtained from an X-ray spectral survey of nearby Seyfert galaxies
using XMM--Newton are reported. The sample was optically selected, well
defined, complete in B mag, and distance limited: it consists of the nearest
(D<22 Mpc) 27 Seyfert galaxies (9 of type 1, 18 of type 2) taken from the Ho et
al. (1997) sample. This is one of the largest atlases of hard X-ray spectra of
low-L active galaxies ever assembled. All nuclear sources except two Sey 2s are
detected between 2-10 keV, half for the first time ever, and average spectra
are obtained for all of them. Nuclear luminosities reach values down to 10**38
erg/s. The shape of the distribution of X-ray parameters is affected by the
presence of Compton-thick objects (> 30% among type 2s). The latter have been
identified either directly from their intense FeK line and flat X-ray spectra,
or indirectly with flux diagnostic diagrams which use isotropic indicators.
After taking into account these highly absorbed sources, we find that (i) the
intrinsic X-ray spectral properties (i.e., spectral shapes and luminosities
above 2 keV) are consistent between type 1 and type 2 Sey, as expected from
``unified models'', (ii) Sey galaxies as a whole are distributed fairly
continuously over the entire range of Nh, between 10**20 and 10**25 cm**-2, and
(iii) while Sey 1s tend to have lower Nh and Sey 2s tend to have the highest,
we find 30% and 10% exceptions, respectively. Overall the sample well
represents the average intrinsic X-ray spectral properties of nearby AGN,
including a proper estimate of the distribution of their absorbing columns.
Finally, we conclude that, with the exception of a few cases, the present study
agrees with predictions of unified models of Sey galaxies, and extends their
validity down to very low luminosities.Comment: 23 pages, 4 tables, 4 figures, 2 Appendices with 27 source spectra
and notes, to be published in the Astronomy & Astrophysics Journa
GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy
We propose to perform a continuously scanning all-sky survey from 200 keV to
80 MeV achieving a sensitivity which is better by a factor of 40 or more
compared to the previous missions in this energy range. The Gamma-Ray Imaging,
Polarimetry and Spectroscopy (GRIPS) mission addresses fundamental questions in
ESA's Cosmic Vision plan. Among the major themes of the strategic plan, GRIPS
has its focus on the evolving, violent Universe, exploring a unique energy
window. We propose to investigate -ray bursts and blazars, the
mechanisms behind supernova explosions, nucleosynthesis and spallation, the
enigmatic origin of positrons in our Galaxy, and the nature of radiation
processes and particle acceleration in extreme cosmic sources including pulsars
and magnetars. The natural energy scale for these non-thermal processes is of
the order of MeV. Although they can be partially and indirectly studied using
other methods, only the proposed GRIPS measurements will provide direct access
to their primary photons. GRIPS will be a driver for the study of transient
sources in the era of neutrino and gravitational wave observatories such as
IceCUBE and LISA, establishing a new type of diagnostics in relativistic and
nuclear astrophysics. This will support extrapolations to investigate star
formation, galaxy evolution, and black hole formation at high redshifts.Comment: to appear in Exp. Astron., special vol. on M3-Call of ESA's Cosmic
Vision 2010; 25 p., 25 figs; see also www.grips-mission.e
C-13 NMR-STUDY OF POLY[(S)-5-METHYL-1-HEPTENE] AND POLY(1-HEPTENE) PREPARED BY ZIEGLER-NATTA CATALYST
Isotactic homopolymers of high optical purity (S)-5-methyl-1-heptene and of 1-heptene have been prepared and studied by 13C n.m.r. The tacticity degree evaluation of the polymers was performed on the basis of skeletal methine or methylene carbon atoms resonances in terms of diads. Conformational properties of both polymers have been investigated and discussed on the basis of n.m.r. dynamic parameters
13C n.m.r. study of poly[(S)-5-methyl-1-heptene] and poly(1-heptene) prepared by Ziegler-Natta catalyst
Nuclear Resonances: The Quest for Large Column Densities and a New Tool
Nuclear physics offers us a powerful tool: using nuclear resonance absorption lines to infer the physical conditions in astrophysical settings which are otherwise diffcult to deduce. Present-day technology provides an increase in sensitivity over previous gamma-ray missions large enough to utilize this tool for the ïŹrst time. The most exciting promise is to measure gamma-ray bursts from the ïŹrst star(s) at redshifts 20â60, but also active galactic nuclei are promising targets
Ătudes pharmacogĂ©nĂ©tiques du polymorphisme Ile655Val du gĂšne her-2 dans le cancer du sein mĂ©tastatique traitĂ© par HerceptinÂź
ANGERS-BU MĂ©decine-Pharmacie (490072105) / SudocSudocFranceF