27 research outputs found

    The ^4He trimer as an Efimov system

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    We review the results obtained in the last four decades which demonstrate the Efimov nature of the 4^4He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal devoted to Efimov physic

    Learning Brightness Transfer Functions for the Joint Recovery of Illumination Changes and Optical Flow

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    The increasing importance of outdoor applications such as driver assistance systems or video surveillance tasks has recently triggered the development of optical flow methods that aim at performing robustly under uncontrolled illumination. Most of these methods are based on patch-based features such as the normalized cross correlation, the census transform or the rank transform. They achieve their robustness by locally discarding both absolute brightness and contrast. In this paper, we follow an alternative strategy: Instead of discarding potentially important image information, we propose a novel variational model that jointly estimates both illumination changes and optical flow. The key idea is to parametrize the illumination changes in terms of basis functions that are learned from training data. While such basis functions allow for a meaningful representation of illumination effects, they also help to distinguish real illumination changes from motion-induced brightness variations if supplemented by additional smoothness constraints. Experiments on the KITTI benchmark show the clear benefits of our approach. They do not only demonstrate that it is possible to obtain meaningful basis functions, they also show state-of-the-art results for robust optical flow estimation. Document type: Part of book or chapter of boo

    Can wood density be efficiently selected at early stage in maritime pine (Pinus pinaster Ait.)?

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    La croissance et la rectitude du tronc sont les deux principaux critères de sélection dans le programme d'amélioration génétique du pin maritime en France. Cette étude a pour objectif d'évaluer la possibilité de sélectionner la densité du bois au stade juvénile. Plus de 1 900 arbres, provenant de trois tests, ont été analysés par microdensitométrie. Des gains génétiques relatifs élevés ont été mis en évidence pour la densité du bois au stade adulte (3 à 9 %). Les estimations de la densité réalisées aux stades adulte et juvénile étant bien corrélées, l'efficacité relative de la sélection atteint environ 80 % à l'âge de 12 ans. Les mesures de densité par rayons X ne sont pas envisageables à grande échelle dans le cadre d'un programme d'amélioration, ainsi nous avons évalué l'efficacité de l'utilisation du Résistographe, une méthode indirecte pour estimer la densité du bois sur arbres debout. Des corrélations élevées ont été mises en évidence entre les données obtenues avec le Résistographe et celles obtenues par microdensitométrie (R2 = 0.93 avec les données familiales). Il semble donc possible d'intégrer la densité du bois, estimée avec le Résistographe, comme nouveau critère de sélection dans notre programme d'amélioration.Growth and stem straightness are the two main selection criteria in the French maritime pine breeding programme. In this contribution, our objective was to study the possibility of selecting for wood density assessed at an early stage. We measured X-ray wood density, in three progeny tests, on more than 1 900 breast high increment cores. High relative expected genetic gain (from 3 to 9%) was found for wood density at mature stage. Juvenile and adult wood density estimations were well-correlated; the relative efficiency of early selection reached about 80% at 12 years old. As it would not be realistic to use the X-ray densitometer at an operational scale in a breeding programme, we tested the efficiency of using the Resistograph, an indirect method to assess wood density on live trees. High correlation between the Resistograph and density data (R2 = 0.93 on familial data) was found, suggesting that wood density through Resistograph assessment could be soon integrated as a new selection criterion in our breeding programme

    Are maternal smoking and stress during pregnancy related to ADHD symptoms in children?

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    Background:  There are some indications that maternal lifestyle during pregnancy (smoking and stress) contributes to symptoms of ADHD in children. We prospectively studied whether prenatal exposure to maternal smoking and/or stress is associated with ADHD symptoms and diagnostic criteria (according to DSM-IV) in 7-year-olds. Methods:  Nulliparous Scandinavian women were consecutively recruited at their first prenatal health care visit and assessments of smoking and stress were collected at gestational weeks 10, 12, 20, 28, 32, and 36. Children were followed up at 7 years old. We obtained full data for 72% of the sample: ADHD symptoms were rated by 74% of mothers (n = 290) and 96% of eligible teachers (n = 208). Attrition analyses showed no differences on key variables between participants and non-participants at follow-up. Results:  Results of multiple regression analyses showed prenatal exposure to smoking (β = .16, p < .01) and stress (β = .18, p < .01) were independently associated with later symptoms of ADHD. Results of logistic regression analyses showed that fulfillment of the diagnostic criteria for ADHD was related to exposure to prenatal stress (β = .68, p < .01) especially in boys. The results were not confounded by sociodemographic factors or birth outcomes. Conclusions:  This study provides evidence that prenatal exposure to stress and smoking is independently associated with later symptoms of ADHD in human children, particularly for boys. Because stress and smoking are relatively common during pregnancy, and yet preventable, these results are of public health significance
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