Avant-propos et introduction

Présentation des problématiques et des articles contenus dans le livre "La Chasse. Pratiques sociales et symboliques", de Boccard, 2006

Estimation de facteurs de Bayes entre modèles dynamiques non linéaires à espace d'état

aeres : ACLInternational audienceLes modèles non linéaires à espace d'état sont utilisés de façon croissante pour représenter de nombreux systèmes dynamiques stochastiques et pour les contrôler. De nouveaux outils de filtrage particulaire sont maintenant disponibles pour l'identification de ces modèles. Il n'en va pas de même pour le problème de leur sélection statistique car les vraisemblances associées sont le plus souvent non accessibles et d'estimation difficile. Ceci exclut a priori les critères classiques de comparaison de modèles de type Akaïke et compromet l'utilisation des méthodes performantes basées sur l'estimation d'un facteur de Bayes par simulations MCMC. Cette Note propose un estimateur convergent non paramétrique d'un facteur de Bayes pour ces modèles, comme application directe de ces nouveaux filtres particulaires. The use of nonlinear state space models in the study and control of stochastic dynamic systems is regularly growing. With the new generation of particle filters, efficient filtering methods are now available for the identification of these models. However their statistical selection is still an open problem because of the frequent nonaccessibility of the related likelihoods and the intricate estimation of the latter. This rules out all the usual model comparison information criteria as Akaïke's and unfavour also the efficient methods relying on Bayes factor estimation by MCMC simulations

Universal conductance fluctuations in epitaxial GaMnAs ferromagnets: structural and spin disorder

Mesoscopic transport measurements reveal a large effective phase coherence length in epitaxial GaMnAs ferromagnets, contrary to usual 3d-metal ferromagnets. Universal conductance fluctuations of single nanowires are compared for epilayers with a tailored anisotropy. At large magnetic fields, quantum interferences are due to structural disorder only, and an unusual behavior related to hole-induced ferromagnetism is evidenced, for both quantum interferences and decoherence. At small fields, phase coherence is shown to persist down to zero field, even in presence of magnons, and an additional spin disorder contribution to quantum interferences is observed under domain walls nucleation.Comment: 15 pages, 4 figure

Structures d'egalisation cyclique EQMM

Les techniques classiques d'égalisation des signaux numériques modulés supposent que le signal utile reçu est perturbé par un bruit de nature stationnaire. Or, il s'avère souvent que les perturbations proviennent d'autres modulations numériques (brouillage lié à l'accès multiple dans un réseau ou brouilleurs de rythme symbole quelconque). Le bruit est alors polycyclostationnaire. Dans ce papier, nous développons de nouvelles structures d'égalisation suivant le critère EQMM utilisant cette propriété. Après de brefs rappels sur la cyclostationnarité et le filtrage cyclique, les nouvelles structures d'égaliseurs linéaire et à décision dans la boucle sont présentées. Enfin, par simulations, leurs performances en TEB sont comparées à celles des structures classiques

Long-term assessment of the thermal stability of sodium nitrate-urea eutectic phase change material

The eutectic mixture formed by urea and sodium nitrate can be an interesting candidate for use as a phase change material for thermal energy storage in space heating and domestic hot water applications. It shows a melting point of 85 °C, a melting enthalpy of 172 J/g and a price around 0.9 €/kg. However, the thermal stability of the mixture is a great concern for this application. A preliminary evaluation of the thermal stability was performed and previously reported by the authors. It consisted of an accelerated thermal cycling test with 210 thermal cycles and the material showed a stable behavior. Nevertheless, the long-term stability of urea in the liquid state at temperatures below 100 °C is uncertain and requires a specific study. The main objective of the present work is to evaluate the long-term thermal stability of the mixture when it is exposed to long periods of use under conditions representative of actual applications, by means of analyzing the thermal and compositional behavior of samples remaining at 100 °C for several periods up to one year. A methodology is proposed, which intends to isolate the thermal degradation phenomenon from others, such as phase segregation, supercooling, and polymorphism, that can be introduced by thermal-cycling. It also aims to be more representative of the actual application than the accelerated thermal cycling approach.The authors would like to acknowledge the Ramon Areces Foundation for funding and the Spanish Ministry of Science, Innovation and Universities (MICINN) through the Sweet-TES research project (RTI2018-099557-B-C22). The author Laura Quant wants to thank the financial support of the University of the Basque Country UPV/EHU, through the Personnel Research Training Program to carry out PhD thesis in cotutelle between the University of the Basque country and the Universit ' e de Pau et des Pays de l'Adour (2016 call). Research efforts in this field are also coordinated through the IEA ES Annex 33/SHC Task 58. Finally, the authors greatly thank the technical and human support provided by SGiker of UPV/EHU; especially to Aitor Larranaga, Mamen Sampedro and Alfredo Sarmiento for their valued help

Pulse wave velocity distribution in a cohort study: from arterial stiffness to early vascular aging

BACKGROUND: By contrast with other southern European people, north Portuguese population registers an especially high prevalence of hypertension and stroke incidence. We designed a cohort study to identify individuals presenting accelerated and premature arterial aging in the Portuguese population. METHOD: Pulse wave velocity (PWV) was measured in randomly sampled population dwellers aged 18-96 years from northern Portugal, and used as a marker of early vascular aging (EVA). Of the 3038 individuals enrolled, 2542 completed the evaluation. RESULTS: Mean PWV value for the entire population was 8.4?m/s (men: 8.6?m/s; women: 8.2?m/s; P??10?m/s). Logistic regression models indicated gender differences concerning the risk of developing large artery damage, with women having the same odds of PWV above 10?m/s 10 years later than men. CONCLUSION: The population PWV values were higher than expected in a low cardiovascular risk area (Portugal). High prevalence rates of EVA and noteworthy large artery damage in young ages were found.Funded by the Life and Health Research Institute, Minho University, Guimarães, Portugal

Grey matter abnormalities in methcathinone abusers with a Parkinsonian syndrome

Funding Information: The study was supported by Grants GARNR9199 and GARLA0148P of the Estonian Science Foundation, and Grant No. 5.8.2 of the National Research Program of Latvia. Ricarda A L Menke is employed by the University of Oxford and her salary is funded by the Medical Research Council of the UK. Heidi Johansen-Berg is employed by the Universities of Oxford and Oslo, holds grants from the Wellcome Trust, National Institutes of Health Research, Education Endowment Foundation, Stroke Association, and Royalties from Elsevier. Charlotte J Stagg holds a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society. Ain?rs Stepens holds Grant No. 5.8.2 of the National Research Program of Latvia, which supported this study. Pille Taba holds Grant 9199 of the Estonian Science Foundation, which supported this study, is principal investigator of Grant 3.2.1001.11-0017 of the EU European Regional Development Fund, and participates in Grant IUT2-4 of the Estonian Research Council. Publisher Copyright: © 2016 The Authors. Brain and Behavior published by Wiley Periodicals, Inc. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.Background: A permanent Parkinsonian syndrome occurs in intravenous abusers of the designer psychostimulant methcathinone (ephedrone). It is attributed to deposition of contaminant manganese, as reflected by characteristic globus pallidus hyperintensity on T1-weighted MRI. Methods: We have investigated brain structure and function in methcathinone abusers (n = 12) compared to matched control subjects (n = 12) using T1-weighted structural and resting-state functional MRI. Results: Segmentation analysis revealed significant (p <.05) subcortical grey matter atrophy in methcathinone abusers within putamen and thalamus bilaterally, and the left caudate nucleus. The volume of the caudate nuclei correlated inversely with duration of methcathinone abuse. Voxel-based morphometry showed patients to have significant grey matter loss (p <.05) bilaterally in the putamina and caudate nucleus. Surface-based analysis demonstrated nine clusters of cerebral cortical thinning in methcathinone abusers, with relative sparing of prefrontal, parieto-occipital, and temporal regions. Resting-state functional MRI analysis showed increased functional connectivity within the motor network of patients (p <.05), particularly within the right primary motor cortex. Conclusion: Taken together, these results suggest that the manganese exposure associated with prolonged methcathinone abuse results in widespread structural and functional changes affecting both subcortical and cortical grey matter and their connections. Underlying the distinctive movement disorder caused by methcathinone abuse, there is a more widespread pattern of brain involvement than is evident from the hyperintensity restricted to the basal ganglia as shown by T1-weighted structural MRI.Peer reviewe