Fast Approximation of EEG Forward Problem and Application to Tissue Conductivity Estimation

Bioelectric source analysis in the human brain from scalp electroencephalography (EEG) signals is sensitive to the conductivity of the different head tissues. Conductivity values are subject dependent, so non-invasive methods for conductivity estimation are necessary to fine tune the EEG models. To do so, the EEG forward problem solution (so-called lead field matrix) must be computed for a large number of conductivity configurations. Computing one lead field requires a matrix inversion which is computationally intensive for realistic head models. Thus, the required time for computing a large number of lead fields can become impractical. In this work, we propose to approximate the lead field matrix for a set of conductivity configurations, using the exact solution only for a small set of basis points in the conductivity space. Our approach accelerates the computing time, while controlling the approximation error. Our method is tested for brain and skull conductivity estimation , with simulated and measured EEG data, corresponding to evoked somato-sensory potentials. This test demonstrates that the used approximation does not introduce any bias and runs significantly faster than if exact lead field were to be computed.Comment: Copyright (c) 2019 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to [email protected]

Voltammetric behavior of triethylamine trihydrofluoride and anisole in acetonitrile as a first approach of studies for electro-fluorination of some adducts

This work focuses on kinetic studies of anisole and triethylamine trihydrofluoride (fluorinating agent) on platinum electrode and acetonitrile as solvent, in order to get a better understanding of their anodic behavior. Results show that both compounds can be oxidized and some kinetic parameters are calculated: the diffusion coefficient within the working media, the anodic electronic transfer coefficient and the apparent intrinsic heterogeneous electronic transfer constant. An unusual variation of these parameters occurs within the chosen reaction conditions, particularly by varying the triethylaminetrihydrofluoride concentration. Preliminary experiments for anodic fluorination of dimethoxy ethane (DME) and anisole were carried out and even if results show a possible electrofluorination for the DME (classically used as solvent), there is no fluorination of anisole when electrochemical microreactor was used

Une histoire du Viking Metal (1970-2014). Contribution à l'étude de l'imaginaire nordique

Au détour de lieux de sociabilité metal (forums de discussions, bars ou salles de concerts), les « discussions de comptoirs » d’amateurs, expliquant avec passion que : telle formation est du hard rock et non du heavy metal, telle autre du « black » et non « death », une troisième du « folk » et non « viking » sont légions. Cette réflexion entend donc établir une histoire d’un sous-genre particulier. L’approche de l’histoire culturelle s’effectue par les représentations d’un groupe social. Articulé autour de deux parties, diachronique et synchronique, ce projet analyse donc, de 1970 à nos jours, l’utilisation de l’imaginaire nordique dans la musique metal. Il s’inscrit donc dans une histoire plus large du hard rock où l’angle choisi est celui de la marge. Comment se caractérise l’imaginaire nordique dans la musique metal ? Comment définir le viking metal ? Quelle est son histoire et quels sont les moments de rupture ? Qui sont les acteurs principaux de ce phénomène culturel ? Pourquoi les musiciens puisent leur inspiration dans le passé ? Qu’est-ce que cet usage du passé nous apprend sur le temps présent ? En quoi les différents acteurs participent à la construction de l’imaginaire nordique ? À travers cinq chapitres, nous tâcherons de répondre à l’ensemble de ces questions

Aerial-Ground collaborative sensing: Third-Person view for teleoperation

Rapid deployment and operation are key requirements in time critical application, such as Search and Rescue (SaR). Efficiently teleoperated ground robots can support first-responders in such situations. However, first-person view teleoperation is sub-optimal in difficult terrains, while a third-person perspective can drastically increase teleoperation performance. Here, we propose a Micro Aerial Vehicle (MAV)-based system that can autonomously provide third-person perspective to ground robots. While our approach is based on local visual servoing, it further leverages the global localization of several ground robots to seamlessly transfer between these ground robots in GPS-denied environments. Therewith one MAV can support multiple ground robots on a demand basis. Furthermore, our system enables different visual detection regimes, and enhanced operability, and return-home functionality. We evaluate our system in real-world SaR scenarios.Comment: Accepted for publication in 2018 IEEE International Symposium on Safety, Security and Rescue Robotics (SSRR