4,172 research outputs found
La participation populaire aux grands projets d'infrastructure lancés par les pouvoirs publics
Wall effects on pressure fluctuations in turbulent channel flow
The purpose of the present paper is to study the influence of wall-echo on
pressure fluctuations , and on statistical correlations containing ,
{\em viz} redistribution , pressure diffusion , and
velocity/pressure-gradient . We extend the usual analysis of
turbulent correlations containing pressure fluctuations in wall-bounded
\tsc{dns} computations [Kim J.: {\em J. Fluid Mech.} {\bf 205} (1989)
421--451], separating not only into rapid and slow
parts [Chou P.Y.: {\em Quart. Appl. Math.} {\bf 3} (1945)
38--54], but further into volume ( and
) and surface (wall-echo;
and ) terms. An algorithm, based on a Green's function
approach, is developed to compute the above splittings for various correlations
containing pressure fluctuations (redistribution, pressure diffusion,
velocity/pressure-gradient), in fully developed turbulent plane channel flow.
This exact analysis confirms previous results based on a method-of-images
approximation [Manceau R., Wang M., Laurence D.: {\em J. Fluid Mech.} {\bf 438}
(2001) 307--338] showing that, at the wall, and
are usually of the same sign and approximately equal. The above
results are then used to study the contribution of each mechanism on the
pressure correlations in low Reynolds-number plane channel flow, and to discuss
standard second-moment-closure modelling practices
Tentative detection of ethylene glycol toward W51/e2 and G34.3+0.2
How complex organic - and potentially prebiotic - molecules are formed in
regions of low- and high-mass star-formation remains a central question in
astrochemistry. In particular, with just a few sources studied in detail, it is
unclear what role environment plays in complex molecule formation. In this
light, a comparison of relative abundances of related species between sources
might be useful to explain observed differences. We seek to measure the
relative abundance between three important complex organic molecules, ethylene
glycol ((CHOH)), glycolaldehyde (CHOHCHO) and methyl formate
(HCOOCH), toward high-mass protostars and thereby provide additional
constraints on their formation pathways. We use IRAM 30-m single dish
observations of the three species toward two high-mass star-forming regions -
W51/e2 and G34.3+0.2 - and report a tentative detection of (CH2OH)2 toward both
sources. Assuming that (CHOH), CHOHCHO and HCOOCH spatially
coexist, relative abundance ratios, HCOOCH/(CHOH), of 31 and 35 are
derived for G34.3+0.2 and W51/e2, respectively. CHOHCHO is not detected,
but the data provide lower limits to the HCOOCH/CHOHCHO abundance
ratios of 193 for G34.3+0.2 and 550 for W51/e2. A comparison of these
results to measurements from various sources in the literature indicates that
the source luminosities may be correlated with the HCOOCH/(CHOH)
and HCOOCH/CHOHCHO ratios. This apparent correlation may be a
consequence of the relative timescales each source spend at different
temperatures-ranges in their evolution. Furthermore, we obtain lower limits to
the ratio of (CHOH)/CH2OHCHO for G34.3+0.2 (6) and W51/e2
(16). This result confirms that a high (CHOH)/CHOHCHO
abundance ratio is not a specific property of comets, as previously speculated.Comment: Accepted for publication by A&
Radiation environment along the INTEGRAL orbit measured with the IREM monitor
The INTEGRAL Radiation Environment Monitor (IREM) is a payload supporting
instrument on board the INTEGRAL satellite. The monitor continually measures
electron and proton fluxes along the orbit and provides this information to the
spacecraft on board data handler. The mission alert system broadcasts it to the
payload instruments enabling them to react accordingly to the current radiation
level. Additionally, the IREM conducts its autonomous research mapping the
Earth radiation environment for the space weather program. Its scientific data
are available for further analysis almost without delay.Comment: 5 pages, 7 figures, accepted for publication in A+A letter
HCOOCH3 as a probe of temperature and structure of Orion-KL
We studied the O-bearing molecule HCOOCH3 to characterize the physical
conditions of the different molecular source components in Orion-KL. We
identify 28 methyl formate emission peaks throughout the 50" field of
observations. The two strongest peaks are in the Compact Ridge (MF1) and in the
SouthWest of the Hot Core (MF2). Spectral confusion is still prevailing as half
of the expected transitions are blended over the region. Assuming that the
transitions are thermalized, we derive the temperature at the five main
emission peaks. At the MF1 position we find a temperature of 80K in a 1.8"x0.8"
beam size and 120K on a larger scale (3.6" x2.2"), suggesting an external
source of heating, whereas the temperature is about 130K at the MF2 position on
both scales. Transitions of HCOOCH3 in vt=1 are detected as well and the good
agreement of the positions on the rotational diagrams between the vt=0 and the
vt=1 transitions suggests a similar temperature. The velocity of the gas is
between 7.5 and 8.0km/s depending on the positions and column density peaks
vary from 1.6x10^16 to 1.6x10^17cm^-2. A second velocity component is observed
around 9-10 km/s in a North-South structure stretching from the Compact Ridge
up to the BN object; this component is warmer at the MF1 peak. The two other
C2H4O2 isomers are not detected and the derived upper limit for the column
density is <3x10^14cm^-2 for glycolaldehyde and <2x10^15cm^-2 for acetic acid.
From the 223GHz continuum map, we identify several dust clumps with associated
gas masses in the range 0.8 to 5.8Msun. Assuming that the HCOOCH3 is spatially
distributed as the dust, we find relative abundances of HCOOCH3 in the range
<0.1x10^-8 to 5.2x10^-8. We suggest a relation between the methyl formate
distribution and shocks as traced by 2.12 mum H2 emission.Comment: Accepted for publication in A&
Evidence for DCO+ as a probe of ionization in the warm disk surface
In this Letter we model the chemistry of DCO in protoplanetary disks.
We find that the overall distribution of the DCO abundance is
qualitatively similar to that of CO but is dominated by thin layer located at
the inner disk surface. To understand its distribution, we investigate the
different key gas-phase deuteration pathways that can lead to the formation of
DCO. Our analysis shows that the recent update in the exothermicity of
the reaction involving CHD as a parent molecule of DCO favors
deuterium fractionation in warmer conditions. As a result the formation of
DCO is enhanced in the inner warm surface layers of the disk where X-ray
ionization occurs. Our analysis points out that DCO is not a reliable
tracer of the CO snow line as previously suggested. We thus predict that
DCO is a tracer of active deuterium and in particular X-ray ionization of
the inner disk.Comment: Accepted for publication in the Astrophysical Journal Letters (ApJL).
11 pages, 5 figure
Le tabagisme chez les écoliers en Valais: 2002-2010
Introduction: Le tabagisme est une cause majeure de maladies et de décès dans la population en Valais. Près d'un valaisan sur trois et une valaisanne sur quatre sont fumeurs. L'initiation au tabagisme a lieu le plus souvent à l'adolescence. Il est dès lors important de connaître les habitudes tabagiques des écoliers valaisans. Méthodes: Tous les quatre ans, le Valais et les autres cantons suisses participent à l'enquête Health Behaviour in School aged Chidren (HBSC), qui est réalisée dans plus de 40 pays sous l'égide de l'Organisation mondiale de la santé. L'objectif est de récolter et d'analyser des données pertinentes sur les comportements de santé des écoliers de 11 à 15 ans, et notamment sur le tabagisme. L'enquête HBSC 2010 a été menée dans 71 classes auprès de 1'198 écoliers en Valais. Les données ont été récoltées par questionnaire. Résultats: De nombreux écoliers valaisans de 11-15 ans ont déjà fumé au moins une fois dans leur vie. Alors que très peu d'écoliers sont des fumeurs quotidiens avant l'âge de 14 ans, près d'un écolier sur six (17% des garçons et des filles) affirme fumer quotidiennement à 15 ans. Entre 2002 et 2010, les proportions d'écoliers ayant fumé au moins une fois ou fumant quotidiennement ont diminué. Les écoliers de 14-15 ans fumant régulièrement (au moins une fois par semaine) rapportent avoir acheté le plus souvent eux mêmes leurs cigarettes ou se les êtres procurées auprès de connaissances. 42% des écoliers et 44% des écolières ont au moins leur mère, leur père ou un de leurs frères et soeurs qui fument. Conclusions et perspectives : Le tabagisme est fréquent dans la population valaisanne, et ce dès l'adolescence. La prévalence du tabagisme a légèrement diminué chez les écoliers entre 2002 et 2010. Toutefois, l'augmentation marquée de l'initiation tabagique entre 11 et 15 ans et la prévalence importante des fumeurs quotidiens parmi les écoliers de 15 ans confirment que la prévention du tabagisme est nécessaire dès le plus jeune âge. L'accessibilité des écoliers au tabac devrait être évaluée et des mesures devraient être renforcées pour la diminuer
States of quantum systems and their liftings
Let H(1), H(2) be complex Hilbert spaces, H be their Hilbert tensor product
and let tr2 be the operator of taking the partial trace of trace class
operators in H with respect to the space H(2). The operation tr2 maps states in
H (i.e. positive trace class operators in H with trace equal to one) into
states in H(1). In this paper we give the full description of mappings that are
linear right inverse to tr2. More precisely, we prove that any affine mapping
F(W) of the convex set of states in H(1) into the states in H that is right
inverse to tr2 is given by the tensor product of W with some state D in H(2).
In addition we investigate a representation of the quantum mechanical state
space by probability measures on the set of pure states and a representation --
used in the theory of stochastic Schroedinger equations -- by probability
measures on the Hilbert space. We prove that there are no affine mappings from
the state space of quantum mechanics into these spaces of probability measures.Comment: 14 page
Beam test results of 3D fine-grained scintillator detector prototype for a T2K ND280 neutrino active target
An upgrade of the long baseline neutrino experiment T2K near detector ND280
is currently being developed with the goal to reduce systematic uncertainties
in the prediction of number of events at the far detector Super-Kamiokande. The
upgrade program includes the design and construction of a new highly granular
fully active scintillator detector with 3D WLS fiber readout as a neutrino
target. The detector of about in size and a mass
of 2.2~tons will be assembled from about plastic
scintillator cubes of . Each cube is read out by three
orthogonal Kuraray Y11 Wave Length Shifting (WLS) fibers threaded through the
detector. A detector prototype made of 125 cubes was assembled and tested in a
charged particle test beam at CERN in the fall of 2017. This paper presents the
results obtained on the light yield and timing as well as on the optical
cross-talk between the cubes.Comment: 5 pages, 8 figure
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