1,405 research outputs found
Inertial waves and modes excited by the libration of a rotating cube
We report experimental measurements of the flow in a cubic container
submitted to a longitudinal libration, i.e. a rotation modulated in time.
Velocity fields in a vertical and a horizontal plane are measured in the
librating frame using a corotating particle image velocimetry system. When the
libration frequency is smaller than twice the mean rotation rate
, inertial waves can propagate in the interior of the fluid. At
arbitrary excitation frequencies , the oscillating flow
shows two contributions: (i) a basic flow induced by the libration motion, and
(ii) inertial wave beams propagating obliquely upward and downward from the
horizontal edges of the cube. In addition to these two contributions, inertial
modes may also be excited at some specific resonant frequencies. We
characterize in particular the resonance of the mode of lowest order compatible
with the symmetries of the forcing, noted [2,1,+]. By comparing the measured
flow fields to the expected inviscid inertial modes computed numerically
[L.R.M. Maas, Fluid Dyn. Res. \textbf{33}, 373 (2003)], we show that only a
subset of inertial modes, matching the symmetries of the forcing, can be
excited by the libration.Comment: Phys. Fluids (in press
H.E.S.S. discovery of very-high-energy gamma-ray emission of PKS 1440-389
Blazars are the most abundant class of known extragalactic very-high-energy
(VHE, E>100 GeV) gamma-ray sources. However, one of the biggest difficulties in
investigating their VHE emission resides in their limited number, since less
than 60 of them are known by now. In this contribution we report on H.E.S.S.
observations of the BL Lac object PKS 1440-389. This source has been selected
as target for H.E.S.S. based on its high-energy gamma-ray properties measured
by Fermi-LAT. The extrapolation of this bright, hard-spectrum gamma-ray blazar
into the VHE regime made a detection on a relatively short time scale very
likely, despite its uncertain redshift. H.E.S.S. observations were carried out
with the 4-telescope array from February to May 2012 and resulted in a clear
detection of the source. Contemporaneous multi-wavelength data are used to
construct the spectral energy distribution of PKS 1440-389 which can be
described by a simple one-zone synchrotron-self Compton model.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherland
Optical-NIR spectroscopy of the puzzling gamma-ray source 3FGL 1603.9-4903/PMN J1603-4904 with X-shooter
The Fermi/LAT instrument has detected about two thousands Extragalactic High
Energy (E > 100 MeV) gamma-ray sources. One of the brightest is 3FGL
1603.9-4903, associated to the radio source PMN J1603-4904. Its nature is not
yet clear, it could be either a very peculiar BL Lac or a CSO (Compact
Symmetric Object) radio source, considered as the early stage of a radio
galaxy. The latter, if confirmed, would be the first detection in gamma-rays
for this class of objects. Recently a redshift z=0.18 +/- 0.01 has been claimed
on the basis of the detection of a single X-ray line at 5.44 +/- 0.05 keV
interpreted as a 6.4 keV (rest frame) fluorescent line. We aim to investigate
the nature of 3FGL 1603.9-4903/PMN J1603-4904 using optical to NIR
spectroscopy. We observed PMN J1603-4904 with the UV-NIR VLT/X-shooter
spectrograph for two hours. We extracted spectra in the VIS and NIR range that
we calibrated in flux and corrected for telluric absorption and we
systematically searched for absorption and emission features. The source was
detected starting from ~6300 Ang down to 24000 Ang with an intensity comparable
to the one of its 2MASS counterpart and a mostly featureless spectrum. The
continuum lacks absorption features and thus is non-stellar in origin and
likely non-thermal. On top of this spectrum we detected three emission lines
that we interpret as the Halpha-[NII] complex, the [SII] 6716,6731 doublet and
the [SIII] 9530 line, obtaining a redshift estimate of z= 0.2321 +/- 0.0004.
The equivalent width of the Halpha-[NII] complex implies that PMN J1603-4904
does not follow the observational definition of BL Lac, the line ratios suggest
that a LINER/Seyfert nucleus is powering the emission. This new redshift
measurement implies that the X-ray line previously detected should be
interpreted as a 6.7 keV line which is very peculiar.Comment: Published in Astronomy and Astrophysic
Apologiste et franc-tireur : étude du style de Péguy dans Un nouveau théologien, M. Fernand Laudet
A kinematical analysis of NGC 2992
We present long slit spectroscopy for the [OIII] and H wavelength
ranges along nine different position angles for the Sa Seyfert 1.9 galaxy NGC
2992. Double profiles are present in several regions, suggesting that the gas
is not simply following galaxy rotation. A simple kinematical model, which
takes into account circular rotation together with a constant radial outflow,
seems to be a good approximation to account for the observed kinematics.Comment: Accepted for publication in Astronomy & Astrophysic
La mise en scĂšne de la conversion des pasteurs au temps de lâĂ©dit de Nantes
En parallĂšle au mouvement de conversion dâecclĂ©siastiques vers le protestantisme qui existe aux XVIe et XVIIe siĂšcles et qui se prolonge au-delĂ , des pasteurs se convertissent au catholicisme durant la mĂȘme pĂ©riode, mĂȘme si ce mouvement sâaccroĂźt dans les annĂ©es qui prĂ©cĂšdent ou qui suivent la RĂ©vocation de lâĂ©dit de Nantes. Que ces conversions soient pour des raisons politiques, thĂ©ologiques ou plus personnelles, elles sâaccompagnent de la volontĂ© des autoritĂ©s politiques et catholiques de les mettre en avant pour quâelles servent dâexemples auprĂšs de leurs anciens coreligionnaires et tout particuliĂšrement auprĂšs des pasteurs des Ăglises rĂ©formĂ©es .
Cette communication a donc pour objectif de montrer comment lâĂglise catholique cherche Ă mettre en scĂšne ces conversions et Ă les faire connaĂźtre lors de manifestations publiques et quels supports sont utilisĂ©s pour toucher le public visĂ©. Thierry Wanegffelen sâest intĂ©ressĂ© Ă cette question pour le XVIe siĂšcle . Il a soulignĂ© le fait « quâune cĂ©rĂ©monie dâabjuration vise Ă conforter le sentiment de lâunitĂ© de lâĂglise du Christ ». Il faut cependant distinguer deux principales catĂ©gories dâabjurations. Il existe tout dâabord celles au cours desquelles les protestants abjurent en masse sur une courte pĂ©riode de quelques jours, voire de plusieurs mois â câest le cas lors de la « saison de la Saint-BarthĂ©lemy, pendant les dragonnades du Poitou de 1681, ou dans les mois qui prĂ©cĂšdent et suivent la RĂ©vocation de lâĂ©dit de Nantes, il nâest gĂ©nĂ©ralement demandĂ© quâune simple renonciation à « lâhĂ©rĂ©sie de Calvin ». En revanche, si lâon excepte ces pĂ©riodes particuliĂšres, la cĂ©rĂ©monie dâabjuration donne lieu Ă un rituel plus Ă©laborĂ© qui prend encore plus dâimportance lorsque le converti sâavĂšre un personnage important, un pasteur par exemple. Ce sont ces cĂ©rĂ©monies qui vont nous intĂ©resser.
Naturellement rĂ©cits de conversions et ouvrages de controverses constituent lâessentiel des sources utilisĂ©es , mais aussi les actes des synodes provinciaux ou nationaux afin de pouvoir Ă©tudier comment la conversion de tel ou tel pasteur est annoncĂ©e. Des exemples seront pris sur lâensemble du XVIIe siĂšcle afin dâenvisager certaines Ă©volutions aussi bien du cĂŽtĂ© catholique que du cĂŽtĂ© rĂ©formĂ©. Deux principaux aspects peuvent ĂȘtre envisagĂ©s : tout dâabord je partirai dâun cas prĂ©cis de conversion de pasteurs, pour permettre, dans un second temps, une comparaison avec dâautres exemples
SST-GATE: A dual mirror telescope for the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) will be the world's first open
observatory for very high energy gamma-rays. Around a hundred telescopes of
different sizes will be used to detect the Cherenkov light that results from
gamma-ray induced air showers in the atmosphere. Amongst them, a large number
of Small Size Telescopes (SST), with a diameter of about 4 m, will assure an
unprecedented coverage of the high energy end of the electromagnetic spectrum
(above ~1TeV to beyond 100 TeV) and will open up a new window on the
non-thermal sky. Several concepts for the SST design are currently being
investigated with the aim of combining a large field of view (~9 degrees) with
a good resolution of the shower images, as well as minimizing costs. These
include a Davies-Cotton configuration with a Geiger-mode avalanche photodiode
(GAPD) based camera, as pioneered by FACT, and a novel and as yet untested
design based on the Schwarzschild-Couder configuration, which uses a secondary
mirror to reduce the plate-scale and to allow for a wide field of view with a
light-weight camera, e.g. using GAPDs or multi-anode photomultipliers. One
objective of the GATE (Gamma-ray Telescope Elements) programme is to build one
of the first Schwarzschild-Couder prototypes and to evaluate its performance.
The construction of the SST-GATE prototype on the campus of the Paris
Observatory in Meudon is under way. We report on the current status of the
project and provide details of the opto-mechanical design of the prototype, the
development of its control software, and simulations of its expected
performance.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223
Assessing Latrine Use in Rural India: A Cross-Sectional Study Comparing Reported Use and Passive Latrine Use Monitors.
Although large-scale programs, like India's Total Sanitation Campaign (TSC), have improved latrine coverage in rural settings, evidence suggests that actual use is suboptimal. However, the reliability of methods to assess latrine use is uncertain. We assessed the reliability of reported use, the standard method, by comparing survey-based responses against passive latrine use monitors (PLUMs) through a cross-sectional study among 292 households in 25 villages in rural Odisha, India, which recently received individual household latrines under the TSC. PLUMs were installed for 2 weeks and householders responded to surveys about their latrine use behavior. Reported use was compared with PLUM results using Bland-Altman (BA) plots and concordance statistics. Reported use was higher than corresponding PLUM-recorded events across the range of comparisons. The mean reported "usual" daily events per household (7.09, 95% confidence interval [CI] = 6.51, 7.68) was nearly twice that of the PLUM-recorded daily average (3.62, 95% CI = 3.29, 3.94). There was poor agreement between "usual" daily latrine use and the average daily PLUM-recorded events (Ïc = 0.331, 95% CI = 0.242, 0.427). Moderate agreement (Ïc = 0.598, 95% CI = 0.497, 0.683) was obtained when comparing daily reported use during the previous 48 hours with the average daily PLUM count. Reported latrine use, though already suggesting suboptimal adoption, likely exaggerates the actual level of uptake of latrines constructed under the program. Where reliance on self-reports is used, survey questions should focus on the 48 hours prior to the date of the survey rather than asking about "usual" latrine use behavior
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