A Hubble Space Telescope Survey for Resolved Companions of Planetary-Nebula Nuclei

We report results of an HST "snapshot" survey aimed at finding resolved binary companions of the central stars of Galactic planetary nebulae (PNe). Using WF/PC and WFPC2, we searched the fields of 113 PNe for stars whose close proximity to the central star suggests a physical association. We find 10 binary nuclei that are very likely to be physically associated, and another six that are possible binary associations. By correcting for interstellar extinction and placing the central stars' companions on the main sequence, we derive distances to the objects, and thereby significantly increase the number of PNe with reliable distances. Comparison of our derived distances with those obtained from various statistical methods shows that all of the latter have systematically overestimated the distances, by factors ranging up to a factor of two or more. We show that this error is most likely due to the fact that the properties of our PNe with binary nuclei are systematically different from those of PNe used heretofore to calibrate statistical methods. Specifically, our PNe tend to have lower surface brightnesses at the same physical radius than the traditional calibration objects. This difference may arise from a selection effect: the PNe in our survey are typically nearby, old nebulae, whereas most of the objects that calibrate statistical techniques are low-latitude, high-surface-brightness, and more distant nebulae. As a result, the statistical methods that seem to work well with samples of distant PNe, e.g., those in the Galactic bulge or external galaxies, may not be applicable to the more diverse population of local PNe.Comment: 37 text pages, 17 table pages, 9 figures. Accepted by Astronomical Journal for June 1999 issu

Nouveaux filtres optimisés pour la détection de lignes de crêtes

Cet article présente deux nouveaux filtres linéaires de détection de lignes de crêtes. La synthèse de ces filtres a été dictée par les besoins d'une application concrète relevant du domaine des agroéquipements. Le premier filtre a une structure similaire à celle du filtre de Ziou et s'implémente de manière récursive à l'ordre 2. Le second filtre est construit selon la méthodologie de Canny pour la détection optimale d'un contour de type « exponentielle-lissée » dont le profil a été confronté à des mesures expérimentales directement liées à l'application cible. L'implémentation récursive de ce filtre s'effectue à l'ordre 4. Les résultats obtenus pour la détection de contours sur une image de synthèse et sur des images réelles montrent la supériorité des filtres proposés par rapport au filtre de Ziou pour l'application visée. Le second filtre proposé procure les meilleurs résultats dans le cas d'images bruitées

Quantification de graisse pour la stéatose hépatique par spectroscopie proche infrarouge en réflectance diffuse

International audienc

Ways of preventing surgeon burnout.

In surgical practice, numerous sources of stress (stressors) are unpredictable, two examples being daily workload and postoperative complications. They may help to explain surgeon burnout, of which the prevalence (34 to 53%) has been the subject of many studies. That said, even though assessments are legion, recommended solutions have been few and far between, especially insofar as by nature and training, surgeons are disinclined to interest themselves in burnout, which they are prone to consider as something experienced by "others". The objective of this attempt at clarification is to identify in the literature the strategies put forward in view of avoiding surgeon burnout, and to assess the impact of this phenomenon not only on the surgeon's professional and personal entourage, but also on patient safety. Prevention-based strategies, many of them focused on modifiable stressors, will be detailed