Etude des paramètres d'un modèle de génération de signaux EEG intracérébraux : synchronisation, conductivité cérébrale et surface corticale

- La stéréo-électroencéphalographie (SEEG) permet d'enregistrer l'activité électrique cérébrale en profondeur (électrodes intracérébrales, signaux EEG de profondeur). Ce travail est centré sur l'étude des relations qui existent entre les dynamiques qui s'expriment dans les signaux SEEG et l'organisation spatio-temporelle des sources neuronales à l'origine de ces signaux. Ce problème est abordé au travers d'un modèle réaliste de génération des signaux SEEG à partir d'un champ de dipôles correspondant à une source néocorticale étendue formée par un ensemble de populations de neurones interconnectées. Les résultats montrent que le modèle est capable de générer des signaux comparables à des signaux SEEG réels enregistrés lors de processus épileptiques (pointes épileptiques). Les signaux simulés permettent alors d'interpréter les signaux réels par rapport aux problèmes liés à la source (surface, synchronisation des populations de neurones) et au milieu (conductivité)

Absolute and high precision 3 degrees of freedom position sensor

We present a compact 3 degrees of freedom (dof) (X-Y-θz) absolute position sensor offering a sub-micrometric resolution. The travelling range is 15x15mm2 (translations) and ±180° (rotation), with an absolute precision better than 10μm over the whole travelling range and of less than 1μm of resolution (0.02° for rotation). The position acquisition frequency is 10Hz. The sensor is composed of a CCD camera chip, a silicon target with a pattern of holes constituting a digital code and a luminescent polymer sheet to light the holes. The reading of the pattern code is performed by image processing

Modèle de génération simultanée des signaux EEG de surface et de profondeur

Ce travail porte sur l'interprétation des signaux électroencéphalographiques (EEG) et stéréo-électroencéphalographiques (SEEG) acquis chez des patients épileptiques candidats à la chirurgie. Cette question est abordée au travers d'une modélisation réaliste des signaux EEG et SEEG, qui repose sur une représentation physiologiquement pertinente des sources de l'activité cérébrale associant un modèle biophysique de sources dipolaires et un modèle biomathématique de populations neuronales. Les signaux induits sur les capteurs de surface et de profondeur sont ensuite obtenus par la résolution du problème direct dans le volume conducteur de la tête. Le modèle complet permet d'étudier les relations existant entre la configuration spatio-temporelle des sources d'activité et les propriétés des signaux observés en surface et en profondeur

The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases

The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article

Toward compliant and structural optimization of a compliant rotation reducer mechanism

This paper presents a Compliant Rotational Reducer Mechanism (CRRM), under development in the context of a space project. The CRRM is optimized using structural and flexural topology optimization for respectively, the structural and flexure problems. With respect to the structural optimization, a mass reduction of 20 % and a shift of the lowest undesirable eigenfrequency from 400 to 1000 Hz was obtained. For the flexural optimization, a Rotational Center Constraint (RCC) and a Floating Structure Modal Objective Function (FSMOF) are introduced. The FSMOF allows to impose a desired eigenmode of a mechanism. The RCC and FSMOF are applied to generate a flexure pivot with eigenmodes of a typical flexure pivot. Finally, these results are integrated into a novel version of the CRRM

Development and integration of high straightness flexure guiding mechanisms dedicated to the METAS watt balance Mark II

There is a firm will in the metrology community to redefine the kilogram in the International System of units by linking it to a fundamental physical constant. The watt balance is a promising way to link the mass unit to the Planck constant h. At the Federal Institute of Metrology METAS a second watt balance experiment is under development. A decisive part of the METAS Mark II watt balance is the mechanical linear guiding system. The present paper discusses the development and the metrological characteristics of two guiding systems that were conceived by the Laboratoire de Systemes Robotiques of EPFL and built using flexure mechanical elements. Integration in the new setup is also described

Design of the new METAS watt balance experiment Mark II

The kilogram is the last unit of the international system of units (SI) still based on a material artefact, the international prototype of the kilogram (IPK). The comparisons made in the last hundred years have clearly revealed a long-term relative drift between the IPK and the official copies kept under similar conditions at the Bureau International des Poids et Mesures. A promising route towards a new definition of the kilogram based on a fundamental constant is represented by the watt balance experiment which links the mass unit to the Planck constant h. For more than ten years, the Federal Institute of Metrology METAS has been actively working in the conception and development of a watt balance experiment. This paper describes the new design of the Mark II METAS watt balance. The metrological characteristics of the different components of the experiment are described and discussed