HAL-UNICE
Not a member yet
30584 research outputs found
Sort by
Transport gap engineering by contact geometry in graphene nanoribbons: Experimental and theoretical studies on artificial materials
No full textInternational audienceElectron transport in small graphene nanoribbons is studied by microwave emulation experiments and tight-binding calculations. In particular, it is investigated under which conditions a transport gap can be observed. Our experiments provide evidence that armchair ribbons of width 3m+2 with integer m are metallic and otherwise semiconducting, whereas zigzag ribbons are metallic independent of their width. The contact geometry, defining to which atoms at the ribbon edges the source and drain leads are attached, has strong effects on the transport. If leads are attached only to the inner atoms of zigzag edges, broad transport gaps can be observed in all armchair ribbons as well as in rhomboid-shaped zigzag ribbons. All experimental results agree qualitatively with tight-binding calculations using the nonequilibrium Green's function method
L'accrochage scolaire des jeunes confiés à une famille d'accueil : une réussite atypique au regard des parcours de vie
No full textFew research works have focussed on the academic achievement of children in foster care families. When the issue is investigated, it is mainly through the analysis of school difficulties and academic underachievement but rarely through academic success although some foster care children manage to do well at school and to carry on studying until they reach the equivalent of at least A-levels. To understand the underlying reasons behind this success, we will explore the question of corporate parenting in foster families, and how this new environment that is “offered” to the child can redistribute the cards of social determinism. Based on the analysis of forty face-to-face interviews with children who were in foster care, we identify some protective factors that will enable them to persevere in school despite adverse life conditions. We study the relationships between foster care children, their foster families, and their social workers, particularly with regards to the way they approach education. The foster care system in some instances allows children to develop strong bonds with an emotional figure, in the eyes of whom education is important, which seems to influence the academic trajectory of children in foster care.Peu de recherches se sont intéressées à la scolarité des enfants confiés à une famille d’accueil. A de rares exceptions près, quand la scolarité est abordée dans les études, elle est analysée sous le versant des difficultés scolaires et de l’échec scolaire mais rarement en termes de réussite. Or, certains enfants confiés à une famille d’accueil s’accrochent à l’école et persévèrent dans leur scolarité jusqu’à l’obtention d’un niveau scolaire équivalent au moins au baccalauréat. Afin de comprendre les raisons de cet accrochage scolaire, nous interrogeons la question de la suppléance familiale en famille d’accueil et comment ce nouvel environnement « offert » à l’enfant redistribue les cartes du déterminisme social. Grâce aux témoignages de quarante personnes (jeunes et familles d’accueil), nous analysons les facteurs de protection qui permettent à ces jeunes de poursuivre leur scolarité malgré la présence de facteurs de risque dans leur parcours de vie. Nous étudions les rapports entre l’enfant confié, sa famille d’accueil et ses éducateurs notamment concernant la façon de gérer la question scolaire. L’accueil familial permet dans certains cas, à certains jeunes, de développer des liens forts avec une figure affective aux yeux de laquelle la scolarité est importante ce qui semble influencer la trajectoire scolaire des jeunes confiés
Students Living As Couples in Tunisia : Between Legal Marriage and New Forms of Secret Unions
No full textInternational audienc
Plans d'expériences à remplissage d'espace minimax et maximin : quelques propriétés et méthodes de construction
No full textInternational audienceA few properties of minimax and maximin optimal designs in a compact subset of R^d are presented, and connections with other space-filling constructions are indicated. Several methods are given for the evaluation of the minimax-distance (or dispersion) criterion for a given n-point design. Various optimisation methods are proposed and their limitations, in particular in terms of dimension d, are indicated. A large majority of the results presented are not new, but their collection in a single document containing a respectable bibliography will hopefully be useful to the reader.Cet article présente quelques propriétés de plans d'expériences minimax et maximin optimaux dans un compact de R^d , ainsi que leur relations avec d'autres plans " à remplissage d'espace ". Plusieurs méthodes sont indiquées pour l'évaluation du critère de distance minimax (ou dispersion) pour un plan donné à n points. Diverses méthodes d'optimisation sont proposées et leurs limitations sont indiquées, en particulier en terme de dimension d. La grande majorité des résultats présentés ne sont pas nouveaux, mais nous espérons que le lecteur trouvera utile de les voir réunis dans un seul document accompagné d'une bibliographie conséquente
Modification of Flight and Locomotion Performances, Respiratory Metabolism,and Transcriptome Expression in the Lady Beetle Harmonia axyridis through Sublethal Pesticide Exposure
No full textBiological control is usually used in combination with chemical control for practical agricultural applications. Thus, the influence of insecticides on the natural predators used for biological control should be investigated for integrated pest management. The ladybird Harmonia axyridis is an effective predator on aphids and coccids. Beta-cypermethrin is a broad-spectrum insecticide used worldwide for controlling insect pests. H. axyridis is becoming increasingly threatened by this insecticide. Here, we investigated the effect of a sublethal dose of beta-cypermethrin on flight, locomotion, respiration, and detoxification system of H. axyridis. After exposure to beta-cypermethrin, succinic female adults flew more times, longer distances, and during longer time periods. Exposure to a sublethal dose of beta-cypermethrin also promoted an increase in walking rate, walking distance, walking duration, and also an increase in respiratory quotient and respiratory rate. To investigate the effects of beta-cypermethrin on H. axyridis detoxification system, we analyzed the transcriptome of H. axyridis adults, focusing on genes related to detoxification systems. De novo assembly generated 65,509 unigenes with a mean length of 799 bp. From these genes, 26,020 unigenes (40.91% of all unigenes) exhibited clear homology to known genes in the NCBI non-redundant database. In addition, 10,402 unigenes were annotated in the Cluster of Orthologous Groups database, 12,088 unigenes were assigned to the Gene Ontology database and 12,269 unigenes were in the Kyoto Encyclopedia of Genes and Genome (KEGG) database. Exposure to beta-cypermethrin had significant effects on the transcriptome profile of H. axyridis adult. Based on uniquely mapped reads, 3,296 unigenes were differentially expressed, 868 unigenes were up-regulated and 2,248 unigenes were down-regulated. We identified differentially-expressed unigenes related to general detoxification systems in H. axyridis. This assembled, annotated transcriptome provides a valuable genomic resource for further understanding the molecular basis of detoxification mechanisms in H. axyridis
Comparative Validation of Polyp Detection Methods in Video Colonoscopy: Results from the MICCAI 2015 Endoscopic Vision Challenge
No full textInternational audienceColonoscopy is the gold standard for colon cancer screening though still some polyps are missed, thus preventing early disease detection and treatment. Several computational systems have been proposed to assist polyp detection during colonoscopy but so far without consistent evaluation. The lack of publicly available annotated databases has made it difficult to compare methods and to assess if they achieve performance levels acceptable for clinical use. The Automatic Polyp Detection sub-challenge, conducted as part of the Endoscopic Vision Challenge (http://endovis.grand-challenge.org) at the international conference on Medical Image Computing and Computer Assisted Intervention (MICCAI) in 2015, was an effort to address this need. In this paper, we report the results of this comparative evaluation of polyp detection methods, as well as describe additional experiments to further explore differences between methods. We define performance metrics and provide evaluation databases that allow comparison of multiple methodologies. Results show that convolutional neural networks (CNNs) are the state of the art. Nevertheless it is also demonstrated that combining different methodologies can lead to an improved overall performance
Les dynamiques électorales des droites radicales populistes en Europe
No full textCNRS, La lettre de l'InSHSLe succès électoral des partis de droite radicale populiste constitue un des phénomènes politiques les plus marquants en Europe depuis plus d’une quinzaine d’années. Ces formations occupent une place centrale dans la plupart des systèmes politiques de l’UE, qui témoigne de leur institutionnalisation et de la force des enjeux qui motivent leurs électorats
Wikiconflits : un corpus de discussions éditoriales conflictuelles du Wikipédia francophone
No full textInternational audienceSi Wikipédia (WP), qui fête aujourd'hui ses quinze ans, a donné lieu à de nombreuses études et projets de recherche qui ont permis de saisir différents aspects de son fonctionnement, de sa gouvernance ou encore des processus de réécriture à l'œuvre dans les articles, le projet encyclopédique a surtout été observé par les sciences sociales, et la question de l'écriture collaborative a été plutôt abordée du point de vue de la coopération (e.g. Viegas et al. 2004, Brandes & Lemer 2007, Kittur & Kraut 2008, Stvilia et al. 2008) que de celui de l'écriture, et des caractéristiques linguistiques et discursives particulières que le projet encyclopédique et son dispositif induisent. Le corpus Wikiconflits, qui est l'objet du présent article, a été développé pour pallier cette situation et encourager les études linguistiques sur le projet encyclopédique, du moins est ce l'une de nos ambitions.Wikiconflits s'articule ainsi autour des pages de discussion éditoriale associées aux articles encyclopédiques. Si le processus normal d'une édition d'article sur WP est collaboratif et constructif - c'est le cas de la grande majorité du WP anglophone, la coopération peut être plus ardue et entraîner des conflits éditoriaux. En tant que frontières de la discussion et la collaboration, les conflits nous semblent des objets particulièrement intéressants à aborder pour caractériser ce nouveau genre discursif de la page de discussion éditoriale et collaborative. Nous avons ainsi choisi de nous concentrer sur les articles ayant été le lieu de conflits, voire de guerres éditoriales.L'objectif du présent article est de présenter le corpus Wikiconflits, de ses principes de constitution à sa construction, en explicitant également les perspectives de recherche dans lesquelles nous souhaitons le mobiliser
Strong existence and uniqueness for stochastic differential equation with Hölder drift and degenerate noise
No full textInternational audienceIn this paper, we prove pathwise uniqueness for stochastic degenerate systems with a Hölder drift, for a Hölder exponent larger than the critical value 2/3. This work extends to the degenerate setting the earlier results obtained by Zvonkin, Veretennikov, Krylov and Röckner from non-degenerate to degenerate cases. The existence of a threshold for the Hölder exponent in the degenerate case may be understood as the price to pay to balance the degeneracy of the noise. Our proof relies on regularization properties of the associated PDE, which is degenerate in the current framework and is based on a parametrix method
Waveguide Photonic limiters based on topologically protected resonant modes
No full textInternational audienceWe propose a concept of chiral photonic limiters utilizing topologically protected localized midgap defect states in a photonic waveguide. The chiral symmetry alleviates the effects of structural imperfections and guarantees a high level of resonant transmission for low intensity radiation. At high intensity, the light-induced absorption can suppress the localized modes, along with the resonant transmission. In this case the entire photonic structure becomes highly reflective within a broad frequency range, thus increasing dramatically the damage threshold of the limiter. Here we demonstrate experimentally the loss-induced reflection principle of operation which is at the heart of reflective photonic limiters using a waveguide consisting of coupled dielectric microwave resonators