170 research outputs found
One year OSIRHYS IV project synthesis: mechanical behaviour of 700 bar type iv high pressure vessel code qualification.
International audienceIn this paper we present results of the OSIRHYS IV French project which aims to develop andvalidate models and methods for composite high pressure design and optimization withbehavior uncertainties knowledge. Models of the five partners of this project are presentedand burst simulation results are compared for three test temperatures (-40°C, 15°C and85°C)
Optimisation et identification intégrée à la corrélation d'images de paramètres de lois élastoplastiques
L'identification de paramètres d'une loi élastique et de deux lois de comportement élasto- plastique à écrouissage cinématique intégrée à la corrélation d'images (CINI) est menée sur une éprouvette biaxiale cruciforme. La géométrie est optimisée spécifiquement pour l'identification d'une loi élastique linéaire. Cette optimisation s'exprime dans le formalisme de la mesure des champs de déplacement et considère l'ensemble de l'essai depuis l'acquisition d'images et la me- sure d'efforts jusqu'à l'estimation des paramètres constitutifs. Par conséquent, l'ensemble des incertitudes existantes est pris en compte dans la définition du protocole expérimental.Integrated digital image correlation (IDIC) is applied to identify the constitutive parameters of an elastic and two elastoplastic laws with kinematic hardening. An experiment is conducted on a cruciform specimen in a biaxial setup. The geometry of the specimen is optimized to allow for the least uncertainty in the identification of parameters of linear elastic law. The optimization takes into account the complete experimental and identification processes. Thus, full field measurements, direct numerical simulations and identification procedures accounting for uncertainties, all contribute at their best to the resulting experimental protocol.
Spatially Correlated Cluster Populations in the Outer Disk of NGC 3184
We use deep (~27.5 mag V-band point-source limiting magnitude) V- and U-band
LBT imaging to study the outer disk (beyond the optical radius R_25) of the
non-interacting, face-on spiral galaxy NGC 3184 (D = 11.1 Mpc; R_25 = 11.1 kpc)
and find that this outer disk contains >1000 objects (or marginally-resolved
'knots') resembling star clusters with masses ~10^2 - 10^4 M_sun and ages up to
~1 Gyr. We find statistically significant numbers of these cluster-like knots
extending to ~1.4 R_25, with the redder knots outnumbering bluer at the largest
radii. We measure clustering among knots and find significant correlation to
galactocentric radii of 1.5 R_25 for knot separations <1 kpc. The effective
integrated surface brightness of this outer disk cluster population ranges from
30 - 32 mag arcsec^-2 in V. We compare the HI extent to that of the correlated
knots and find that the clusters extend at least to the damped Lyman-alpha
threshold of HI column density (2e20 cm^-2; 1.62 R_25). The blue knots are
correlated with HI spiral structure to 1.5 R_25, while the red knots may be
correlated with the outer fringes of the HI disk to 1.7 R_25. These results
suggest that outer disks are well-populated, common, and long-lasting features
of many nearby disk galaxies.Comment: Accepted for publication in The Astrophysical Journal. 12 pages, 10
figure
The EFIGI catalogue of 4458 nearby galaxies with detailed morphology
Accepted for publication in Astronomy and Astrophysics, 27 pages, 7 tables, 32 colour figures. Data available at http://www.efigi.orgInternational audienceNow that large databases of resolved galaxy images are provided by modern imaging surveys, advanced morphological studies can be envisioned, urging for well defined calibration samples. We present the EFIGI catalogue, a multiwavelength database specifically designed for a dense sampling of all Hubble types. The catalogue merges data from standard surveys and catalogues (Principal Galaxy Catalogue, Sloan Digital Sky Survey, Value-Added Galaxy Catalogue, HyperLeda, and the NASA Extragalactic Database) and provides detailed morphological information. Imaging data are obtained from the SDSS DR4 in the u, g, r, i, and z bands for a sample of 4458 PGC galaxies, whereas photometric and spectroscopic data are obtained from the SDSS DR5 catalogue. Point-Spread Function models are derived in all five bands. Composite colour images of all objects are visually examined by a group of astronomers, and galaxies are staged along the Hubble sequence and classified according to 16 morphological attributes describing their structure, texture, as well as environment and appearance on a five-level scale. The EFIGI Hubble sequence shows remarkable agreement with the RC3 Revised Hubble Sequence. The main characteristics and reliability of the catalogue are examined, including photometric completeness, type mix, systematic trends and correlations. The final EFIGI database is a large sub-sample of the local Universe, with a dense sampling of Sd, Sdm, Sm and Im types compared to magnitude-limited catalogues. We estimate the photometric catalogue to be more than ~ 80% complete for galaxies with 10 < g < 14. More than 99.5% of EFIGI galaxies have a known redshift in the HyperLeda and NED databases
Search for non-standard neutrino interactions with 10 years of ANTARES data
Non-standard interactions of neutrinos arising in many theories beyond the Standard Model can significantly alter matter effects in atmospheric neutrino propagation through the Earth. In this paper, a search for deviations from the prediction of the standard 3-flavour atmospheric neutrino oscillations using the data taken by the ANTARES neutrino telescope is presented. Ten years of atmospheric neutrino data collected from 2007 to 2016, with reconstructed energies in the range from ~16 GeV to 100 GeV, have been analysed. A log-likelihood ratio test of the dimensionless coefficients eµt and ett-eµµ does not provide clear evidence of deviations from standard interactions. For normal neutrino mass ordering, the combined fit of both coefficients yields a value 1.7s away from the null result. However, the 68% and 95% confidence level intervals for eµt and ett-eµµ, respectively, contain the null value. Best fit values, one standard deviation errors and bounds at the 90% confidence level for these coefficients are given for both normal and inverted mass orderings. The constraint on eµt is among the most stringent to date and it further restrains the strength of possible non-standard interactions in the µ-t sector.Postprint (published version
MoMaF : The Mock Map Facility
We present the Mock Map Facility, a powerful tool to generate mock catalogues
or images from semi-analytically post-processed snapshots of cosmological
N-body simulations. The paper describes in detail an efficient technique to
create such mocks from the GALICS semi-analytic model, providing the reader
with an accurate quantification of the artifacts it introduces at every step.
We show that replication effects introduce a negative bias on the clustering
signal -- typically peaking at less than 10 percent around the correlation
length. We also thoroughly discuss how the clustering signal is affected by
finite volume effects, and show that it vanishes at scales larger than about a
tenth of the simulation box size. For the purpose of analysing our method, we
show that number counts and redshift distributions obtained with GALICS and
MOMAF compare well to K-band observations and to the 2dFGRS. Given finite
volume effects, we also show that the model can reproduce the APM angular
correlation function. The MOMAF results discussed here are made publicly
available to the astronomical community through a public database. Moreover, a
user-friendly Web interface (http://galics.iap.fr) allows any user to recover
her/his own favourite galaxy samples through simple SQL queries. The
flexibility of this tool should permit a variety of uses ranging from extensive
comparisons between real observations and those predicted by hierarchical
models of galaxy formation, to the preparation of observing strategies for deep
surveys and tests of data processing pipelines.Comment: 19 pages, 15 Figs, significantly modified version now accepted for
publication in MNRAS. High-resolution version available at
http://galics.cosmologie.fr/papers/momaf.ps.g
The Multi-Epoch Nearby Cluster Survey: type Ia supernova rate measurement in z~0.1 clusters and the late-time delay time distribution
We describe the Multi-Epoch Nearby Cluster Survey (MENeaCS), designed to
measure the cluster Type Ia supernova (SN Ia) rate in a sample of 57 X-ray
selected galaxy clusters, with redshifts of 0.05 < z < 0.15. Utilizing our real
time analysis pipeline, we spectroscopically confirmed twenty-three cluster SN
Ia, four of which were intracluster events. Using our deep CFHT/Megacam
imaging, we measured total stellar luminosities in each of our galaxy clusters,
and we performed detailed supernova detection efficiency simulations. Bringing
these ingredients together, we measure an overall cluster SN Ia rate within
R_{200} (1 Mpc) of 0.042^{+0.012}_{-0.010}^{+0.010}_{-0.008} SNuM
(0.049^{+0.016}_{-0.014}^{+0.005}_{-0.004} SNuM) and a SN Ia rate within red
sequence galaxies of 0.041^{+0.015}_{-0.015}^{+0.005}_{-0.010} SNuM
(0.041^{+0.019}_{-0.015}^{+0.005}_{-0.004} SNuM). The red sequence SN Ia rate
is consistent with published rates in early type/elliptical galaxies in the
`field'. Using our red sequence SN Ia rate, and other cluster SNe measurements
in early type galaxies up to , we derive the late time (>2 Gyr) delay
time distribution (DTD) of SN Ia assuming a cluster early type galaxy star
formation epoch of z_f=3. Assuming a power law form for the DTD, \Psi(t)\propto
t^s, we find s=-1.62\pm0.54. This result is consistent with predictions for the
double degenerate SN Ia progenitor scenario (s\sim-1), and is also in line with
recent calculations for the double detonation explosion mechanism (s\sim-2).
The most recent calculations of the single degenerate scenario delay time
distribution predicts an order of magnitude drop off in SN Ia rate \sim 6-7 Gyr
after stellar formation, and the observed cluster rates cannot rule this out.Comment: 35 pages, 14 figures, ApJ accepte
The UV-Optical Color Dependence of Galaxy Clustering in the Local Universe
We measure the UV-optical color dependence of galaxy clustering in the local
universe. Using the clean separation of the red and blue sequences made
possible by the NUV - r color-magnitude diagram, we segregate the galaxies into
red, blue and intermediate "green" classes. We explore the clustering as a
function of this segregation by removing the dependence on luminosity and by
excluding edge-on galaxies as a means of a non-model dependent veto of highly
extincted galaxies. We find that \xi (r_p, \pi) for both red and green galaxies
shows strong redshift space distortion on small scales -- the "finger-of-God"
effect, with green galaxies having a lower amplitude than is seen for the red
sequence, and the blue sequence showing almost no distortion. On large scales,
\xi (r_p, \pi) for all three samples show the effect of large-scale streaming
from coherent infall. On scales 1 Mpc/h < r_p < 10 Mpc/h, the projected
auto-correlation function w_p(r_p) for red and green galaxies fits a power-law
with slope \gamma ~ 1.93 and amplitude r_0 ~ 7.5 and 5.3, compared with \gamma
~ 1.75 and r_0 ~ 3.9 Mpc/h for blue sequence galaxies. Compared to the
clustering of a fiducial L* galaxy, the red, green, and blue have a relative
bias of 1.5, 1.1, and 0.9 respectively. The w_p(r_p) for blue galaxies display
an increase in convexity at ~ 1 Mpc/h, with an excess of large scale
clustering. Our results suggest that the majority of blue galaxies are likely
central galaxies in less massive halos, while red and green galaxies have
larger satellite fractions, and preferentially reside in virialized structures.
If blue sequence galaxies migrate to the red sequence via processes like
mergers or quenching that take them through the green valley, such a
transformation may be accompanied by a change in environment in addition to any
change in luminosity and color.Comment: accepted by MNRA
Star Cluster Populations in the Outer Disks of Nearby Galaxies
We present a Large Binocular Telescope (LBT) imaging study that characterizes
the star cluster component of nearby galaxy outer disks (beyond the optical
radius R_25). Expanding on the pilot project of Herbert-Fort et al. (2009), we
present deep (~ 27.5 mag V-band point-source limiting magnitude) U- and V-band
imaging of six galaxies: IC 4182, NGC 3351, NGC 4736, NGC 4826, NGC 5474, and
NGC 6503. We find that the outer disk of each galaxy is populated with
marginally-resolved star clusters with masses ~10^3 M_sun and ages up to ~ 1
Gyr (masses and ages are limited by the depth of our imaging and uncertainties
are large given how photometry can be strongly affected by the presence or
absence of a few stars in such low mass systems), and that they are typically
found out to at least 2 R_25 but sometimes as far as 3 to 4 R_25- even beyond
the apparent HI disk. The mean rate of cluster formation for 1 R_25<= R <=
1.5R_25 is at least one every ~2.5 Myr and the clusters are spatially
correlated with the HI, most strongly with higher density gas near the
periphery of the optical disk and with lower density neutral gas at the HI disk
periphery. We hypothesize that the clusters near the edge of the optical disk
are formed in the extension of spiral structure from the inner disk and are a
fairly consistent phenomenon and that the clusters formed at the periphery of
the HI disk are the result of accretion episodes.Comment: 23 pages, accepted for publication in Ap
A Tale of Two Oxidation States: Bacterial Colonization of Arsenic-Rich Environments
Microbial biotransformations have a major impact on contamination by toxic elements, which threatens public health in developing and industrial countries. Finding a means of preserving natural environments—including ground and surface waters—from arsenic constitutes a major challenge facing modern society. Although this metalloid is ubiquitous on Earth, thus far no bacterium thriving in arsenic-contaminated environments has been fully characterized. In-depth exploration of the genome of the β-proteobacterium Herminiimonas arsenicoxydans with regard to physiology, genetics, and proteomics, revealed that it possesses heretofore unsuspected mechanisms for coping with arsenic. Aside from multiple biochemical processes such as arsenic oxidation, reduction, and efflux, H. arsenicoxydans also exhibits positive chemotaxis and motility towards arsenic and metalloid scavenging by exopolysaccharides. These observations demonstrate the existence of a novel strategy to efficiently colonize arsenic-rich environments, which extends beyond oxidoreduction reactions. Such a microbial mechanism of detoxification, which is possibly exploitable for bioremediation applications of contaminated sites, may have played a crucial role in the occupation of ancient ecological niches on earth
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