Bootstrap and permutation tests of independence for point processes

Motivated by a neuroscience question about synchrony detection in spike train analysis, we deal with the independence testing problem for point processes. We introduce non-parametric test statistics, which are rescaled general $U$-statistics, whose corresponding critical values are constructed from bootstrap and randomization/permutation approaches, making as few assumptions as possible on the underlying distribution of the point processes. We derive general consistency results for the bootstrap and for the permutation w.r.t. to Wasserstein's metric, which induce weak convergence as well as convergence of second order moments. The obtained bootstrap or permutation independence tests are thus proved to be asymptotically of the prescribed size, and to be consistent against any reasonable alternative. A simulation study is performed to illustrate the derived theoretical results, and to compare the performance of our new tests with existing ones in the neuroscientific literature

Surrogate data methods based on a shuffling of the trials for synchrony detection: the centering issue

International audienceWe investigate several distribution-free dependence detection procedures, all based on a shuffling of the trials, from a statistical point of view. The mathematical justification of such procedures lies in the bootstrap principle and its approximation properties. In particular, we show that such a shuffling has mainly to be done on centered quantities-that is, quantities with zero mean under independence-to construct correct p-values, meaning that the corresponding tests control their false positive (FP) rate. Thanks to this study, we introduce a method, named permutation UE, which consists of a multiple testing procedure based on permutation of experimental trials and delayed coincidence count. Each involved single test of this procedure achieves the prescribed level, so that the corresponding multiple testing procedure controls the false discovery rate (FDR), and this with as few assumptions as possible on the underneath distribution, except independence and identical distribution across trials. The mathematical meaning of this assumption is discussed, and it is in particular argued that it does not mean what is commonly referred in neuroscience to as cross-trials stationarity. Some simulations show, moreover, that permutation UE outperforms the trial-shuffling of Pipa and Grün ( 2003 ) and the MTGAUE method of Tuleau-Malot et al. ( 2014 ) in terms of single levels and FDR, for a comparable amount of false negatives. Application to real data is also provided

Ab initio effective rotational Hamiltonians - A comparative study

40 pages dont 6 tablesInternational audienceTwo independent methods to obtain ab initio effective rotational Hamiltonians have been implemented recently. The first one is based on a generalization of perturbation theory to non-commutative rings, the other one on contact transformation techniques. In principle, both methods are able to give rotational Hamiltonians including centrugal distortion effects of arbitrary high orders. These methods are compared for the first time in this article with regard to calculations of the rotational levels of methane vibrational ground state

Douleurs induites en radiologie d'urgence : intérêt du MEOPA

Introduction : la douleur est un motif fréquent de consultation aux urgences dont la considération et la prise en charge ont été développée à partir de la fin des années 90 sous l’impulsion initiale de directives nationales. Cependant malgré l’émergence de nouveaux concepts comme la prise en charge des douleurs liées aux soins ou la lutte contre l’oligo-analgésie, force est de constater un essoufflement de cette thématique depuis le 3ème et dernier plan douleur de 2010.Le service des urgences adultes est un axe majeur pourvoyeur de douleurs induites. Ce travail de thèse propose d’évaluer la prise en charge de celle-ci par un protocole d’administration MEOPA® jusqu’en salle de radiographie.Objectif : évaluer les bénéfices d’un protocole de prise en charge des douleurs induites par MEOPA® en radiologie dans le service des urgences adultes du centre hospitalo- universitaire de la Timone chez les patients de 15 à 60 ans présentant un traumatisme isolé de membre.Méthodes : étude observationnelle prospective réalisée de avril 2018 à février 2019 aux urgences adultes de l’Hôpital de la Timone chez les patients de 15 à 60 ans nécessitant une radiographie pour un traumatisme isolé de membre et bénéficiant d’un protocole d’administration de MEOPA® dès le premier contact médical.Les résultats étaient recueillis par questionnaires à destination des patients, des soignants et des manipulateurs d’électroradiologie médicale (M.E.M).Un questionnaire avant-après mise en place du protocole évaluait le ressentit des M.E.M.Résultats : 79 patients ont été inclus. La douleur moyenne évaluée par l’EN était initialement de 6,46 ±1,77 puis de 3,77 ± 2,42 en salle de radiographie soit une diminution de 2,69 ± 2,22.78% des patients étaient satisfait de l’utilisation du MEOPA® et dans 85% des cas les M.E.M ont observés un bénéfice à l’utilisation du MEOPA®.Le MEOPA® est bien accepté par les patients qui dans 46% ont ressentis des effets secondaires minimes ou modérés tous réversibles sans entrainer d’arrêt prématuré.Les analyses secondaires ont permis de mettre en évidence des difficultés techniques pour le personnel soignant quant au transport du patient avec une bouteille de MEOPA®.Conclusion : la réalisation de radiographies chez les patients traumatisés aux urgences adultes est source de douleurs induites. Un protocole de prise en charge par MEOPA® permet une réduction de ces douleurs dues aux manipulations. Cependant les contraintes liées à son encombrement nécessitent de nouvelles études afin de trouver la solution la plus adaptée

Diffusion en milieux nanométriques confinés (application à l'exocytose de neurotransmetteurs et à la communication moléculaire dans les dendrimères redox)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Reactive Leidenfrost droplets

International audienceWe experimentally investigate the reactivity of Leidenfrost droplets with their supporting substrates. Several organic liquids are put into contact with a copper substrate heated above their Leidenfrost temperature. As the liquid evaporates, the gaseous flow cleans the superficial copper oxide formed at the substrate surface and the reaction maintains a native copper spot below the evaporating droplet. The copper spot can reach several times the droplet size for the most reactive organic compounds. This study shows an interesting coupling between the physics of the Leidenfrost effect and the mechanics of reactive flows. Different applications are proposed such as drop motion tracking and vapor flow monitoring

Study of the thrust–drag balance with a swimming robotic fish

International audienceA robotic fish is used to test the validity of a simplification made in the context of fish locomotion. With this artificial aquatic swimmer, we verify that the momentum equation results from a simple balance between a thrust and a drag that can be treated independently in the small amplitude regime. The thrust produced by the flexible robot is proportional to A 2 f 2 , where A and f are the respective tail-beat amplitude and oscillation frequency, irrespective of whether or not f coincides with the resonant frequency of the fish. The drag is proportional to U 2 0 , where U 0 is the swimming velocity. These three physical quantities set the value of the Strouhal number in this regime. For larger amplitudes, we found that the drag coefficient is not constant but increases quadratically with the fin amplitude. As a consequence, the achieved locomotion velocity decreases, or the Strouhal number increases, as a function of the fin amplitude. Published by AIP Publishing. https://doi