150 research outputs found
Jules Verne 2.0, renewal of a large wind tunnel facility
International audienceThe paper aims at showing the evolution of methods to design a large wind tunnel. The current Jules Verne facility was designed with a scale model of the wind tunnel which enabled hot wire local wind speed measurements. The new facility is designed according a numerical modelling approach which parameters were validated by PIV measurements in the reduced scale physical model
Séance spécialisée : géodynamique des bassins océaniques et des marges continentales
Une morphologie de fonds sous-marins bathyaux comportant des indurations liées à des dépôts ferro-manganésifères inclus dans des sédiments hémipélagiques peu ou pas cimentés a été découverte sur une ride volcanique tertiaire au large de la Nouvelle-Calédonie (SW Pacifique). Elle semble être en relation avec des circulations hydrothermales au travers de la couverture sédimentaire pendant l'activité volcanique miocène de la ride des Loyauté. (Résumé d'auteur
Calibration of the Spectrometer aboard the INTEGRAL satellite
SPI, the Spectrometer on board the ESA INTEGRAL satellite, to be launched in
October 2002, will study the gamma-ray sky in the 20 keV to 8 MeV energy band
with a spectral resolution of 2 keV for photons of 1 MeV, thanks to its 19
germanium detectors spanning an active area of 500 cm2. A coded mask imaging
technique provides a 2 deg angular resolution. The 16 deg field of view is
defined by an active BGO veto shield, furthermore used for background
rejection. In April 2001 the flight model of SPI underwent a one-month
calibration campaign at CEA in Bruy\`eres le Ch\^atel using low intensity
radioactive sources and the CEA accelerator for homogeneity measurements and
high intensity radioactive sources for imaging performance measurements. After
integration of all scientific payloads (the spectrometer SPI, the imager IBIS
and the monitors JEM-X and OMC) on the INTEGRAL satellite, a cross-calibration
campaign has been performed at the ESA center in Noordwijk. A set of sources
has been placed in the field of view of the different instruments in order to
compare their performances and determine their mutual influence. Some of those
sources had already been used in Bruy\`eres during the SPI standalone test. For
the lowest energy band calibration an X-ray generator has been used. We report
on the scientific goals of this calibration activity, and present the
measurements performed as well as some preliminary results.Comment: 12 pages, 19 figures, Published in Proceedings of SPIE conference,
24-28 August 2002, Waikoloa, Hawaii, US
SPI/INTEGRAL in-flight performance
The SPI instrument has been launched on-board the INTEGRAL observatory on
October 17, 2002. SPI is a spectrometer devoted to the sky observation in the
20 keV-8 MeV energy range using 19 germanium detectors. The performance of the
cryogenic system is nominal and allows to cool the 19 kg of germanium down to
85 K with a comfortable margin. The energy resolution of the whole camera is
2.5 keV at 1.1 MeV. This resolution degrades with time due to particle
irradiation in space. We show that the annealing process allows the recovery of
the initial performance. The anticoincidence shield works as expected, with a
low threshold at 75 keV, reducing the GeD background by a factor of 20. The
digital front-end electronics system allows the perfect alignement in time of
all the signals as well as the optimisation of the dead time (12%). We
demonstrate that SPI is able to map regions as complex as the galactic plane.
The obtained spectrum of the Crab nebula validates the present version of our
response matrix. The 3 sensitivity of the instrument at 1 MeV is 8
10phcmskeV for the continuum and 3
10phcms for narrow lines.Comment: 10 pages, 18 figures, accepted for publication in A&A (special
INTEGRAL volume
SPI: The spectrometer aboard INTEGRAL
SPI is a high spectral resolution gamma-ray telescope on board the ESA mission INTEGRAL (International Gamma Ray Astrophysics Laboratory). It consists of an array of 19 closely packed germanium detectors surrounded by an active anticoincidence shield of BGO. The imaging capabilities of the instrument are obtained with a tungsten coded aperture mask located 1.7 m from the Ge array. The fully coded field-of-view is 16º, the partially coded field of view amounts to 31º, and the angular resolution is 2.5º. The energy range extends from 20 keV to 8 MeV with a typical energy resolution of 2.5 keV at 1.3 MeV. Here we present the general concept of the instrument followed by a brief description of each of the main subsystems. INTEGRAL was successfully launched in October 2002 and SPI is functioning extremely well.Sanchez Martinez, Filomeno, [email protected]
Physical parameters of erupting Luminous Blue Variables: NGC 2363-V1 caught in the act
A quantitative study of the Luminous Blue Variable NGC 2363-V1 in the
Magellanic galaxy NGC 2366 (D = 3.44 Mpc) is presented, based on ultraviolet
and optical HST/STIS spectroscopy. Contemporary WFPC2 and WHT imaging reveals a
modest V-band brightness increase of ~ 0.2 mag per year between 1996 January
and 1997 November, reaching V=17.4 mag, corresponding to Mv=-10.4 mag.
Subsequently, V1 underwent a similar decrease in V-band brightness, together
with a UV brightening of 0.35 mag from 1997 November to 1999 November.
The optical spectrum of V1 is dominated by H emission lines, with Fe II, He I
and Na I also detected. In the ultraviolet, a forest of Fe absorption features
and numerous absorption lines typical of mid-B supergiants are observed. From a
spectral analysis with the non-LTE, line-blanketed code of Hillier & Miller
(1998), we derive stellar parameters of T*=11kK, R*=420Ro, log(L/Lo)=6.35
during 1997 November, and T*=13kK, R*=315Ro, log(L/Lo)=6.4 for 1999 July. The
wind properties of V1 are also exceptional, with Mdot ~ 4.4 x 10e-4 Mo/yr and
300 km/s, allowing for a clumped wind (filling factor = 0.3),
and assuming H/He ~ 4 by number.
The presence of Fe lines in the UV and optical spectrum of V1 permits an
estimate of the heavy elemental abundance of NGC 2363 from our spectral
synthesis. Although some deficiencies remain, allowance for charge exchange
reactions in our calculations supports a SMC-like metallicity, that has
previously been determined for NGC 2363 from nebular oxygen diagnostics.
Considering a variety of possible progenitor stars, V1 has definitely
undergone a giant eruption, with a substantial increase in stellar luminosity,
radius, and almost certainly mass-loss rate.Comment: 29 pages, 10 figures, Submitted to Ap
Dissecting quantitative trait variation in the resequencing era: complementarity of bi-parental, multi-parental and association panels
Quantitative trait loci (QTL) have been identified using traditional linkage mapping and positional cloning identified several QTLs. However linkage mapping is limited to the analysis of traits differing between two lines and the impact of the genetic background on QTL effect has been underlined. Genome-wide association studies (GWAs) were proposed to circumvent these limitations. In tomato, we have shown that GWAs is possible, using the admixed nature of cherry tomato genomes that reduces the impact of population structure. Nevertheless, GWAs success might be limited due to the low decay of linkage disequilibrium, which varies along the genome in this species. Multi-parent advanced generation intercross (MAGIC) populations offer an alternative to traditional linkage and GWAs by increasing the precision of QTL mapping. We have developed a MAGIC population by crossing eight tomato lines whose genomes were resequenced. We showed the potential of the MAGIC population when coupled with whole genome sequencing to detect candidate single nucleotide polymorphisms (SNPs) underlying the QTLs. QTLs for fruit quality traits were mapped and related to the variations detected at the genome sequence and expression levels. The advantages and limitations of the three types of population, in the context of the available genome sequence and resequencing facilities, are discussed.This work was supported by CEA-IG/CNG, by performing the DNA QC and providing access to INRA-EPGV to their Illumina Sequencing Platform. We acknowledge groups of Anne Boland (DNA and Cell Bank service) and Marie-Thérèse Bihoreau (Illumina HT Sequencing). The ANR MAGIC-Tom SNP project 09-GENM-109G and the European Solanaceae Integrated Project EUSOL (Food-CT-2006-016214) supported this work. LP was supported by a postdoctoral INRA fellowship, EA by an INRA PhD fellowship and JD by a grant from the Embassy of France in Thailand in Junior Research Fellowship Program 2014.Peer reviewe
INTEGRAL/SPI ground calibration
Three calibration campaigns of the spectrometer SPI have been performed
before launch in order to determine the instrument characteristics, such as the
effective detection area, the spectral resolution and the angular resolution.
Absolute determination of the effective area has been obtained from simulations
and measurements. At 1 MeV, the effective area is 65 cm^2 for a point source on
the optical axis, the spectral resolution ~2.3 keV. The angular resolution is
better than 2.5 deg and the source separation capability about 1 deg. Some
temperature dependant parameters will require permanent in-flight calibration.Comment: 9 pages, 12 figures, 2 tables. Accepted for publication in A&AL
(INTEGRAL Special issue
Combining ecophysiological modelling and quantitative trait locus analysis to identify key elementary processes underlying tomato fruit sugar concentration
A mechanistic model predicting the accumulation of tomato fruit sugars was developed in order (i) to dissect the relative influence of three underlying processes: assimilate supply (S), metabolic transformation of sugars into other compounds (M), and dilution by water uptake (D); and (ii) to estimate the genetic variability of S, M, and D. The latter was estimated in a population of 20 introgression lines derived from the introgression of a wild tomato species (Solanum chmielewskii) into S. lycopersicum, grown under two contrasted fruit load conditions. Low load systematically decreased D in the whole population, while S and M were targets of genotype×fruit load interactions. The sugar concentration positively correlated to S and D when the variation was due to genetic introgressions, while it positively correlated to S and M when the variation was due to changes in fruit load. Co-localizations between quantitative trait loci (QTLs) for sugar concentration and QTLs for S, M, and D allowed hypotheses to be proposed on the processes putatively involved at the QTLs. Among the five QTLs for sugar concentration, four co-localized with QTLs for S, M, and D with similar allele effects. Moreover, the processes underlying QTLs for sugar accumulation changed according to the fruit load condition. Finally, for some genotypes, the processes underlying sugar concentration compensated in such a way that they did not modify the sugar concentration. By uncoupling genetic from physiological relationships between processes, these results provide new insights into further understanding of tomato fruit sugar accumulation
PRISM (Polarized Radiation Imaging and Spectroscopy Mission): A White Paper on the Ultimate Polarimetric Spectro-Imaging of the Microwave and Far-Infrared Sky
PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to
ESA in response to the Call for White Papers for the definition of the L2 and
L3 Missions in the ESA Science Programme. PRISM would have two instruments: (1)
an imager with a 3.5m mirror (cooled to 4K for high performance in the
far-infrared---that is, in the Wien part of the CMB blackbody spectrum), and
(2) an Fourier Transform Spectrometer (FTS) somewhat like the COBE FIRAS
instrument but over three orders of magnitude more sensitive. Highlights of the
new science (beyond the obvious target of B-modes from gravity waves generated
during inflation) made possible by these two instruments working in tandem
include: (1) the ultimate galaxy cluster survey gathering 10e6 clusters
extending to large redshift and measuring their peculiar velocities and
temperatures (through the kSZ effect and relativistic corrections to the
classic y-distortion spectrum, respectively) (2) a detailed investigation into
the nature of the cosmic infrared background (CIB) consisting of at present
unresolved dusty high-z galaxies, where most of the star formation in the
universe took place, (3) searching for distortions from the perfect CMB
blackbody spectrum, which will probe a large number of otherwise inaccessible
effects (e.g., energy release through decaying dark matter, the primordial
power spectrum on very small scales where measurements today are impossible due
to erasure from Silk damping and contamination from non-linear cascading of
power from larger length scales). These are but a few of the highlights of the
new science that will be made possible with PRISM.Comment: 20 pages Late
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