1,828 research outputs found
A new nearby pulsar wind nebula overlapping the RX J0852.0-4622 supernova remnant
Energetic pulsars can be embedded in a nebula of relativistic leptons which
is powered by the dissipation of the rotational energy of the pulsar. The
object PSR J0855-4644 is an energetic and fast-spinning pulsar (Edot =
1.1x10^36 erg/s, P=65 ms) discovered near the South-East rim of the supernova
remnant (SNR) RX J0852.0-4622 (aka Vela Jr) by the Parkes multibeam survey. The
position of the pulsar is in spatial coincidence with an enhancement in X-rays
and TeV gamma-rays, which could be due to its putative pulsar wind nebula
(PWN).
The purpose of this study is to search for diffuse non-thermal X-ray emission
around PSR J0855-4644 to test for the presence of a PWN and to estimate the
distance to the pulsar. An X-ray observation was carried out with the
XMM-Newton satellite to constrain the properties of the pulsar and its nebula.
The absorption column density derived in X-rays from the pulsar and from
different regions of the rim of the SNR was compared with the absorption
derived from the atomic (HI) and molecular (12CO) gas distribution along the
corresponding lines of sight to estimate the distance of the pulsar and of the
SNR.
The observation has revealed the X-ray counterpart of the pulsar together
with surrounding extended emission thus confirming the existence of a PWN. The
comparison of column densities provided an upper limit to the distance of the
pulsar PSR J0855-4644 and the SNR RX J0852.0-4622 (d<900 pc). Although both
objects are at compatible distances, we rule out that the pulsar and the SNR
are associated. With this revised distance, PSR J0855-4644 is the second most
energetic pulsar, after the Vela pulsar, within a radius of 1 kpc and could
therefore contribute to the local cosmic-ray e-/e+ spectrum.Comment: 10 pages, 9 Figures. Accepted for publication in A&
Historical tsunami database for France and its overseas territories
A search and analysis of a large number of historical documents has made it possible: (i) to discover so-far unknown tsunamis that have hit the French coasts during the last centuries, and (ii) conversely, to disprove the tsunami nature of several events referred to in recent catalogues. This information has been structured into a database and also made available as a website (<a ref="http://www.tsunamis.f/" target="_blank">http://www.tsunamis.fr</a>) that is accessible in French, English and Spanish. So far 60 genuine ("true") tsunamis have been described (with their dates, causes, oceans/seas, places observed, number of waves, flood and ebb distances, run-up, and intensities) and referenced against contemporary sources. Digitized documents are accessible online. In addition, so as to avoid confusion, tsunamis revealed as "false" or "doubtful" have been compiled into a second catalogue. <br><br> Both the database and the website are updated annually corresponding to the state of knowledge, so as to take into account newly discovered historical references and the occurrence of new tsunamis on the coasts of France and many of its overseas territories: Guadeloupe, Martinique, French Guiana, New Caledonia, Réunion, and Mayotte
L0 Confirmation with fast, Tsa based tracking in the T-stations
A fast tracking algorithm to confirm the high L0 trigger objects with tracks from the T-stations is presented. The L0 trigger candidate is used to define a search window to a potential track. Using this, a seeded track search is performed. The track finding algorithm is based on the \textit{TsaSeeding} algorithm~\cite{bib:Tsa}. The efficiency to confirm a true L0 trigger signal is around 96\%, the momentum can be measured up to =3\%
L-Convex Polyominoes are Recognizable in Real Time by 2D Cellular Automata
A polyomino is said to be L-convex if any two of its cells are connected by a
4-connected inner path that changes direction at most once. The 2-dimensional
language representing such polyominoes has been recently proved to be
recognizable by tiling systems by S. Brocchi, A. Frosini, R. Pinzani and S.
Rinaldi. In an attempt to compare recognition power of tiling systems and
cellular automata, we have proved that this language can be recognized by
2-dimensional cellular automata working on the von Neumann neighborhood in real
time.
Although the construction uses a characterization of L-convex polyominoes
that is similar to the one used for tiling systems, the real time constraint
which has no equivalent in terms of tilings requires the use of techniques that
are specific to cellular automata
Current-induced two-level fluctuations in pseudo spin-valves (Co/Cu/Co) nanostructures
Two-level fluctuations of the magnetization state of pseudo spin-valve
pillars Co(10 nm)/Cu(10 nm)/Co(30 nm) embedded in electrodeposited nanowires
(~40 nm in diameter, 6000 nm in length) are triggered by spin-polarized
currents of 10^7 A/cm^2 at room temperature. The statistical properties of the
residence times in the parallel and antiparallel magnetization states reveal
two effects with qualitatively different dependences on current intensity. The
current appears to have the effect of a field determined as the bias field
required to equalize these times. The bias field changes sign when the current
polarity is reversed. At this field, the effect of a current density of 10^7
A/cm^2 is to lower the mean time for switching down to the microsecond range.
This effect is independent of the sign of the current and is interpreted in
terms of an effective temperature for the magnetization.Comment: 4 pages, 5 figures, revised version, to be published in Phys. Rev.
Let
Effect of deflector aerator on stepped spillway flow
Systematic physical model tests are performed on a stepped spillway equipped with a bottom aerator at the beginning of the stepped part. A deflector is used to issue a jet in order to initiate air entrainment into the flow. A horizontal slot located in the vertical face of the first step allows for air supply underneath the flow. The cavity subpressure was measured to ensure optimal aerator performance, namely atmospheric pressure conditions. The air discharge entrained below the jet is measured to derive the aerator air entrainment coefficient. The local air concentrations are spatially measured downstream of the aerator at regularly spaced profiles, allowing the investigation of air transport and detrainment as well as the average and bottom air concentrations. The present paper focuses on the resulting spatial distribution of air concentration for five deflector geometries. The chute angle, step height, approach flow Froude number and approach flow depth were kept constant, so that the differences occur mostly on the jet length and air entrainment coefficient. The flow depth and the air concentration rapidly converge towards quasi-uniform flow values downstream of the aerator
Measurements of three-dimensional glenoid erosion when planning the prosthetic replacement of osteoarthritic shoulders.
The three-dimensional (3D) correction of glenoid erosion is critical to the long-term success of total shoulder replacement (TSR). In order to characterise the 3D morphology of eroded glenoid surfaces, we looked for a set of morphological parameters useful for TSR planning. We defined a scapular coordinates system based on non-eroded bony landmarks. The maximum glenoid version was measured and specified in 3D by its orientation angle. Medialisation was considered relative to the spino-glenoid notch. We analysed regular CT scans of 19 normal (N) and 86 osteoarthritic (OA) scapulae. When the maximum version of OA shoulders was higher than 10°, the orientation was not only posterior, but extended in postero-superior (35%), postero-inferior (6%) and anterior sectors (4%). The medialisation of the glenoid was higher in OA than normal shoulders. The orientation angle of maximum version appeared as a critical parameter to specify the glenoid shape in 3D. It will be very useful in planning the best position for the glenoid in TSR
SPI Measurements of the Diffuse Galactic Hard X-ray Continuum
INTEGRAL Spectrometer SPI data from the first year of the Galactic Centre
Deep Exposure has been analysed for the diffuse continuum from the Galactic
ridge. A new catalogue of sources from the INTEGRAL Imager IBIS has been used
to account for their contribution to the celestial signal. Apparently diffuse
emission is detected at a level ~10% of the total source flux. A comparison of
the spectrum of diffuse emission with that from an analysis of IBIS data alone
shows that they are consistent. The question of the contribution of unresolved
sources to this ridge emission is still open.Comment: Proceedings of the 5th INTEGRAL Workshop, Munich 16-20 February 2004.
ESA SP-552. Reference to Terrier et al. (2004) updated to include astro-ph
versio
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