Hétérogéneités du manteau et origine des basaltes des Marquises (Polynésie)

Les auteurs discutent les connaissances bibliographiques concernant les hétérogénéités isotopiques du manteau et les processus les engendrant. Par l'étude conjointe des isotopes et des traces ils abordent la genèse des basaltes des Marquises. Leurs caractéristiques géochimiques suggèrent un modèle d'interaction de magmas d'origine profonde avec le manteau supérieur appauvri. Puisqu'elles sont très différentes de celles des basaltes des îles Hawaii, les auteurs supposent que l'on peut proposer plusieurs modèles pour la genèse du volcanisme intraplaque océanique

Design and sizing of electromagnetic linear actuators for valve applications

International audienceIn this paper, various structures of linear motion actuators are described. These structures have been studied in order to drive the valves of a car motor. According to general specifications, a description of the design and sizing of variable reluctance or permanent magnet devices is given. The main qualities of each structure are enhanced

OPTIMISATION OF A DRIVE SYSTEM AND ITS EPICYCLIC GEAR SET

International audienceThis paper describes the design of a drive consisting of a DC motor, a speed reducer, a lead screw transformation system, a power converter and its associated DC source. The objective is to reduce the mass of the system. Indeed, the volume and weight optimisation of an electrical drive is an important issue for embedded applications. Here, we present an analytical model of the system in a specific application and afterwards an optimisation of the motor and speed reducer main dimensions and the battery voltage in order to reduce the weight

Multi objective optimisation of an electromagnetic valve actuator

International audienceThis paper is about a modelling and an optimisation of an electromechanical drive system. The device consists of a DC source, a power converter, a linear actuator and its load. The aim of the system is to drive a load along a linear displacement. The two main objectives are to reduce the actuator volume and the copper losses, which are contrary objectives. Here, we present an analytical modelling of the system and afterwards an optimisation of the linear actuator main dimensions in order to carry out the previous objectives

Substratum géologique et partage des terres dans le sud du Tchad Région des lacs de Léré et de Tréné et réserve de faune de Binder Nayri

National audienceÀ travers une analyse du substratum géologique et de l'occupation du sol dans unerégion sahélo-soudanienne au sud du Tchad : le massif du Mayo-Kébbi (carte 1), nousproposons de montrer :– quels sont les liens entre la nature du substratum géologique (socle et formationssuperficielles) et les paysages ;– comment se répartissent les ressources naturelles entre les paysages et comment seréalise le partage entre les zones fortement anthropisées et les zones naturelles dédiéesà une réserve de faune.Basée sur une analyse de terrain spatialisée (cartographie géologique et pédologique,enquête villageoise...), complétée par des éléments de bibliographie, la méthode faitégalement appel aux outils de télédétection pour la mise à jour de la carte d'occupationdu sol. La compilation globale aboutit à une meilleure compréhension de l’organisationdes paysages

Relationships between components of blood pressure and cardiovascular events in patients with stable coronary artery disease and hypertension

Observational studies have shown a J-shaped relationship between diastolic blood pressure (BP) and cardiovascular events in hypertensive patients with coronary artery disease. We investigated whether the increased risk associated with low diastolic BP reflects elevated pulse pressure (PP). In 22 672 hypertensive patients with coronary artery disease from the CLARIFY registry (Prospective Observational Longitudinal Registry of Patients With Stable Coronary Artery Disease), followed for a median of 5.0 years, BP was measured annually and averaged. The relationships between PP and diastolic BP, alone or combined, and the primary composite outcome (cardiovascular death or myocardial infarction) were analyzed using multivariable Cox proportional hazards models. Adjusted hazard ratios for the primary outcome were 1.62 (95% confidence interval [CI], 1.40–1.87), 1.00 (ref), 1.07 (95% CI, 0.94–1.21), 1.54 (95% CI, 1.32–1.79), and 2.34 (95% CI, 1.95–2.81) for PP<45, 45 to 54 (reference), 55 to 64, 65 to 74, and ≥75 mm Hg, respectively, and 1.50 (95% CI, 1.31–1.72), 1.00 (reference), and 1.58 (95% CI, 1.42–1.77) for diastolic BPs of <70, 70 to 79 (ref), and ≥80 mm Hg, respectively. In a cross-classification analysis between diastolic BP and PP, the relationship between diastolic BP and the primary outcome remained J-shaped when the analysis was restricted to patients with the lowest-risk PP (45–64 mm Hg), with adjusted hazard ratios of 1.53 (95% CI, 1.27–1.83), 1.00 (ref), and 1.54 (95% CI, 1.34–1.75) in the <70, 70 to 79 (reference), and ≥80 mm Hg subgroups, respectively. The J-shaped relationship between diastolic BP and cardiovascular events in hypertensive patients with coronary artery disease persists in patients within the lowest-risk PP range and is therefore unlikely to be solely the consequence of an increased PP reflecting advanced vascular disease

The role of European National Forest Inventories for international forestry reporting

International audienceAbstractKey messageDespite agreements on definitions, the national data provided for international reporting are lacking comparability. To address this limitation the European National Forest Inventory Network has established criteria to harmonise definitions and to provide tools to transform national data into internationally comparable data.ContextForest reporting presents a series of challenges for countries, owing to diverse processes at international level such as the Global Forest Resources Assessment (FRA), Convention on Biological Diversity, United Nations Framework Convention on Climate Change and its Kyoto Protocol. Further challenges are faced at European level with Forest Europe and policy needs.AimsThe aim of this paper is to provide a comprehensive review of the national and international forest reporting processes and of the role of the National Forest Inventories (NFIs) and the long-associated challenges resulting from a lack of comparability in definitions used. In addition, there is a discussion on the role of the European National Forest Inventory Network (ENFIN) as a facilitator for enhancing harmonization and comparability of national data and the ancillary information required to monitor European forestry-related policies.MethodsNFIs take part to international reporting processes as providers of information. They are correspondent to the FRA process, and then they know very well the context of harmonization. Participating in the ENFIN research projects, NFIs, and particularly authors, conducted a screening exercise on harmonization status at European and World level.ResultsThis review article is a synthesis of the main findings of the abovementioned screening exercise. It highlights the main gaps in terms of comparability of result in international reporting. Thanks to ENFIN harmonization research project, it gives same ways of working as a possible benchmark for the rest of the world.ConclusionBased on the international reporting exercises, their interactions, and impacts on new forestry policy requirements, the need for a strengthened harmonization process can clearly be demonstrated. Due to European policy needs, research work within ENFIN has been initiated to develop tools for building comparable results at international level. This work is an important benchmark particularly for countries outside Europe from which to base future harmonization work

Microevents produced by gas migration and expulsion at the seabed: A study based on sea bottom recordings from the Sea of Marmara

International audienceDifferent types of 4-component ocean bottom seismometers (OBS) were deployed for variable durations ranging from 1 week to about 4 months in 2007, over soft sediments covering the seafloor of the Tekirdag Basin (western part of the Sea of Marmara, Turkey). Non-seismic microevents were recorded by the geophones, but generally not by the hydrophones, except when the hydrophone is located less than a few tens of centimetres above the seafloor. The microevents are characterized by short durations of less than 0.8 s, by frequencies ranging between 4 and 30 Hz, and by highly variable amplitudes. In addition, no correlation between OBSs was observed, except for two OBSs, located 10 m apart. Interestingly, a swarm of ∼400 very similar microevents (based on principal component analysis) was recorded in less than one day by an OBS located in the close vicinity of an active, gas-prone fault cutting through the upper sedimentary layers. The presence of gas in superficial sediments, together with analogies with laboratory experiments, suggest that gas migration followed by the collapse of fluid-filled cavities or conduits could be the source of the observed microevents. This work shows that OBSs may provide valuable information to improve our understanding of natural degassing processes from the seafloor