WZ Sagittae as a DQ Herculis star

We argue that quiescent WZ Sge is a rapidly spinning magnetic rotator in which most of the matter transfered from the secondary is ejected from the system. Assuming that the observed 27.87 s oscillation period is due to the spinning white dwarf we propose that the other observed principal period of 28.96 s is a beat due to reprocessing of the rotating white dwarf beam on plasma blobs in Keplerian rotation at the outer disc rim. The weaker, transient, 29.69 s period is identified as a beat with the Keplerian period of the magnetosphere. WZ Sge evolves through a cycle of spin-up and spin-down phases. During the spin-down phase it is a DQ Her star, during the spin-up phase it should be a ER UMa star.Comment: 8 pages, 5 figures; accepted for publication in MNRA

Assessment of standard coil positioning in transcranial magnetic stimulation in depression

International audienceTranscranial magnetic stimulation (TMS) is a non-invasive technique used in the treatment of major depression. Meta-analyses have shown that it is more efficient than a placebo and that its efficacy is enhanced by the optimum tuning of stimulation parameters. However, the stimulation target, the dorsolateral prefrontal cortex (DLPFC), is still located using an inaccurate method. In this study, a neuronavigation system was used to perform a comprehensive quantification of target localization errors. We identified and quantified 3 sources of error in the standard method: cap repositioning, interexpert variability in coil positioning and distance between the stimulated point and the expected target. For cap repositioning, the standard deviation was lower than 5 mm in the 3 axes. For interexpert variability in coil positioning, the spatial dispersion of the points was higher than 10 mm in 2 of the 3 axes. For interindividual anatomical variability, the distance between the actual “reference” DLPFC and its standard determination was greater than 20 mm for 54% of the subjects, while one subject out of eleven was correctly targeted which means 10 mm or less from the reference. Results showed that interindividual anatomical variability and interexpert variability were the two main sources of error using the standard method. Results demonstrate that a neuronavigation system is mandatory to conduct reproducible and reliable studies

Une plateforme logicielle de neurochirurgie assistée par l'image

National audienc

An anthropomorphic polyvinyl alcohol brain phantom based on Colin27 for use in multimodal imaging

International audienceIn this paper, the method for the creation of an anatomically and mechanically realistic brain phantom from polyvinyl alcohol cryogel (PVA-C) is proposed for validation of image processing methods such as segmentation, reconstruction, registration, and denoising. PVA-C is material widely used in medical imaging phantoms because of its mechanical similarities to soft tissues. The phantom was cast in a mold designed using the left hemisphere of the Colin27 brain dataset [C. Holmes et al., "Enhancement of MR images using registration for signal averaging," J. Comput. Assist. Tomogr. 22(2), 324 (1998)]. Marker spheres and inflatable catheters were also implanted to enable good registration comparisons and to simulate tissue deformation, respectively. The phantom contained deep sulci, a complete insular region, and an anatomically accurate left ventricle. It was found to provide good contrast in triple modality imaging, consisting of computed tomography, ultrasound, and magnetic resonance imaging. Multiple sets of multimodal data were acquired from this phantom. The methods for building the anatomically accurate, multimodality phantom were described in this work. All multimodal data are made available freely to the image processing community (http://pvabrain.inria.fr). We believe the phantom images could allow for the validation and further aid in the development of novel medical image processing techniques

La Bourgogne : dynamiques spatiales et environnement

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MICCAI 2010 Poster : An Anthropomorphic Polyvinyl Alcohol Triple-Modality Brain Phantom based on Colin27

<p>We propose a method for the creation of an anatomically and mechanically realistic brain phantom from polyvinyl alcohol cryogel (PVA-C) for validation of image processing methods for segmentation, reconstruction, registration, and denoising. PVA-C is material widely used in medical imaging phantoms for its mechanical similarities to soft tissues. The phantom was cast in a mold designed using the left hemiphere of the Colin27 brain dataset [Holmes et al. 1998] and contains deep sulci, a complete insular region, and an anatomically accurate left ventricle. Marker spheres and inflatable catheters were also implanted to enable good registration and simulate tissue deformation, respectively. The phantom was designed for triple modality imaging, giving good contrast images in computed tomography, ultrasound, and magnetic resonance imaging. Multimodal data acquired from this phantom are made freely available to the image processing community (http://pvabrain.inria.fr) and will aid in the validation and further development of medical image processing techniques.</p

L’eau au service des territoires ? Entre valorisation et instrumentalisation

Longtemps dominé par une volonté de maîtrise, incarnée par la construction d’ouvrages techniques, le rapport à l’eau de maints acteurs s’est progressivement inversé depuis les années 1970 sous l’influence du poids des considérations environnementales et de la reconnaissance de limites dans les interventions humaines. Cette évolution s’est manifestée dans divers domaines allant de la gestion des eaux pluviales à celle du risque d’inondation ou encore dans le domaine de l’aménagement et de la gestion des cours d’eau, qu’on s’efforce désormais de ménager voire de renaturer. L’eau s’impose alors comme une véritable « ressource territoriale », au point de devenir parfois une figure centrale de tout projet territorial qu’il s’agisse d’esthétique, de paysage, d’écologie ou de nourrir un imaginaire, une sensibilité et une poétique. Cette mise en avant de l’eau et des espaces de l’eau participe aussi d’une démarche de marketing territorial. Pour autant, derrière un apparent consensus, la valorisation de l’eau dans les projets territoriaux n’est pas dénuée d’ambiguïtés reflétant les conceptions différentes, potentiellement concurrentes et contradictoires, qui se déploient à propos des milieux aquatiques. Faut-il mettre à distance l’eau et tenter de la maîtriser via des aménagements structurels ? Faut-il s’en rapprocher et s’efforcer de vivre avec en tissant de nouvelles proximités spatiales et sociales, ainsi que de nouvelles formes de valorisation économique ou écologique ? Les réponses à ces questions ont varié au fil du temps. Mais aujourd’hui, les multiples liens tissés avec l’eau représentent une opportunité pour penser un aménagement au gré de l’eau et non contre elle ou sans elle. Les articles de ce numéro offrent un éventail d’analyses à différentes échelles de cette mise en service de l’eau dans les projets territoriaux, pour certains en s’appuyant sur des cas d’étude localisés dans l’espace sud-ouest européen, pour d’autres hors de cette aire géographique, permettant ainsi d’identifier de grandes tendances qui manifestement dépassent les singularités géographiques locales ou régionales. Deux articles complètent ce numéro thématique. Le premier présente les associations foncières pastorales qui, au-delà de leur origine montagnarde, pourraient être des outils précieux de gestion collective du foncier privé. Le second article reste dans les Pyrénées mais pour y discuter certains choix de mobilité opérés dans des territoires de faible densité