Philippe Petit

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We report the discovery of a medium-strength (∼0.5 kG) magnetic field on the young, massive star τ Sco (B0.2 V), which becomes the third-hottest magnetic star known. Circularly polarized Zeeman signatures are clearly detected in observations collected mostly with the ESPaDOnS spectropolarimeter, recently installed on the 3.6-m Canada–France–Hawaii(More)
– Samples of single-wall carbon nanotubes containing tubes with an " armchair " wrapping have been produced and exhibit metallic behavior with an intrinsic resistivity which increases approximately linearly with temperature over a wide temperature range. Here we study the coupling of the conduction electrons to long-wavelength torsional shape fluctuations,(More)
We describe the operation of a cold atom clock in reduced gravity. We have recorded the cesium hyperfine resonance signal at a frequency near 9.2 GHz in the ∼ 10 −2 g gravity environment produced by jet plane parabolic flights. With a resonance width of 7 Hz, the device operated in a regime which is not accessible on earth. In the much lower gravity level(More)
This paper presents a new automatic technique for the seg-mentation of the rib cage on CT images. Motivated by a usage scenario in the context of large, heterogeneous databases of CT-images, we introduce two shape descriptors to be used in conjunction with a Random Forests (RF) classifier. These de-scriptors were specifically designed to address the(More)
From observations collected with the ESPaDOnS spectropolarimeter, we report the discovery of magnetic fields at the surface of the mildly accreting classical T Tauri star (cTTS) V2129 Oph. Zeeman signatures are detected, both in photospheric lines and in the emission lines formed at the base of the accretion funnels linking the disc to the protostar, and(More)
We present in this paper the first results of a spectropolarimetric analysis of a small sample (∼ 20) of active stars ranging from spectral type M0 to M8, which are either fully-convective or possess a very small radiative core. This study aims at providing new constraints on dynamo processes in fully-convective stars. The present paper focuses on 5 stars(More)
Hexahedral elements with a single integration point have been the solid elements of choice to represent organs in human finite element models for impact. While those elements have been known to be efficient in terms of stability and computational cost, they are difficult to generate and meshing represents a significant part of a model development time. The(More)
Context. The chemically peculiar HgMn stars are a class of Bp stars which have historically been found to be both non-magnetic and non-variable. Remarkably, it has recently been demonstrated that the bright, well-studied HgMn star α And exhibits clear Hg ii line profile variations indicative of a non-uniform surface distribution of this element. Aims. With(More)
We investigate the magnetic geometry of the active G8 dwarf ξ Bootis A, from spec-tropolarimetric observations obtained in 2003 with the MuSiCoSéchelle spectropo-larimeter at the Télescope Bernard Lyot (Observatoire du Pic du Midi, France). We repeatedly detect a photospheric magnetic field, with periodic variations consistent with rotational modulation.(More)