La prégnance de la dégradation de l’environnement par l’homme doit nous amener à envisager de profonds changements de nos modes de vie, de mobilité, de production et de consommation pour aller vers une humanité plus harmonieuse avec l’environnement. La finalité de la technologie peut servir la résilience écologique.Ainsi, l’avènement d’applications permettant d’envisager un covoiturage dynamique apporterait deux effets bénéfiques à la réduction de la pollution : l’un, lié à une décroissance de la consommation de carburant via l’optimisation du remplissage des véhicules et, l’autre, lié à la diminution du nombre d’automobiles en ville grâce à leur partage.Nous présentons l’embryon d’une application de carsharing reposant sur un algorithme génétique hermaphrodite (actuellement accessible sur github) en espérant pouvoir fédérer des développeurs libres sur le projet

Electromagnetic coils are ubiquitously used in the modern world in motors, antennas, etc. In many applications (magnetic field coil calibration and nuclear magnetic resonance spectroscopy and imaging) there is a strong need for a homogeneous magnetic field. In this paper, we propose a simple modelling based on serial Fourier decomposition allowing the determination of the electrical conductor distribution to make the magnetic field homogeneous. The method is valid both for plane and axisymmetric geometries. The method allows the retrieval of the classical configurations of saddle coil for the plane geometry and Helmholtz coil for the axisymmetric one. The method is generalized for any number of electrical conductors and brings the perspective of new homogeneous magnetic resonance imaging (MRI) coil configuration.

Nuclear Magnetic Resonance spectroscopy and imaging can be classified as inductive techniques working in the near- to far-field regimes. We investigate an alternative capacitive detection with the use of micrometer sized probes positioned at sub wavelength distances of the sample in order to characterize and model evanescent electromagnetic fields originating from NMR phenomenon. We report that in this experimental configuration the available NMR signal is one order of magnitude larger and follows an exponential decay inversely proportional to the size of the emitters. Those investigations open a new road to a better understanding of the evanescent waves component in NMR with the opportunity to perform localized spectroscopy and imaging.

Ce document présente une séance de travaux pratiques de caractérisation d'un magnétomètre à induction haute performance destinée aux étudiants de M2 OSAE de l'Observatoire de Meudon. Ce TP se déroule sur une journée et nécessite du matériel spécifique (bobines Helmholtz, analyseur de spectre).Le TP a pour but de comparer deux modes de fonctionnement du magnétomètre inductif permettant de s'affranchir de la résonance: la contre-réaction de flux et l'amplification en courant. Le TP permet de réaliser des caractérisations en champ magnétique et donner un cadre concret à des caractérisations de bruit.

The performance of induction magnetometers, in terms of resolution, depends both on the induction sensor and the electronic circuit. To investigate accurately the sensor noise sources, an induction sensor, made of a ferrite ferromagnetic core, is combined with a dedicated low voltage and current noise preamplifier, designed in CMOS 0.35 µm technology. A modelling of the contribution of the ferromagnetic core to the noise through the complex permeability formalism is performed. Its comparison with experimental measurements highlight another possible source for the dominating noise near the resonance.

Nuclear magnetic resonance imaging (NMRI) is a powerful tool for biological investigations. Nevertheless, the imaging resolution performance results in the combination of the magnetic field (B0) and the antenna efficiency. This latter one results in a compromise between the size of the sample, the location of the region of interest and the homogeneity requirement. In the context of spinal cord imaging on mice, a ribbon solenoid coil is used to enhance the efficiency of the MRI experiment. This paper details the calculation of the local magnetization contribution to the induced voltage of MRI coils. The modeling is illustrated on ribbon solenoid antennas used in emitter–receiver mode for the study. The analytical model, which takes into account the emitting mode, the receiving step and the imaging sequence, is compared to the measurement performed on a 9.4 T VARIAN MRI apparatus. The efficiency of the antenna, in terms of signal to noise ratio, is significantly enhanced with respect to a commercial quadrature volumic antenna, given a significant advantage for the study of spinal cord injuries.

Spinal cord injury (SCI) is a debilitating neuropathology with no effective treatment. Magnetic resonance imaging (MRI) technology is the only method used to assess the impact of an injury on the structure and function of the human spinal cord. Moreover, in pre-clinical SCI research, MRI is a non-invasive method with great translational potential since it provides relevant longitudinal assessment of anatomical and structural alterations induced by an injury. It is only recently that MRI techniques have been effectively used for the follow-up of SCI in rodents. However, the vast majority of these studies have been carried out on rats and when conducted in mice, the contusion injury model was predominantly chosen. Due to the remarkable potential of transgenic mice for studying the pathophysiology of SCI, we examined the use of both in and ex vivo 1H-MRI (9.4 T) in two severities of the mouse SCI (hemisection and over-hemisection) and documented their correlation with histological assessments. We demonstrated that a clear distinction between the two injury severities is possible using in and ex vivo 1H-MRI and that ex vivo MR images closely correlate with histology. Moreover, tissue modifications at a remote location from the lesion epicenter were identified by conventional ex vivo MRI analysis. Therefore, in vivo MRI has the potential to accurately identify in mice the progression of tissue alterations induced by SCI and is successfully implemented by ex vivo MRI examination. This combination of in and ex vivo MRI follow-up associated with histopathological assessment provides a valuable approach for further studies intended to evaluate therapeutic strategies on SCI.