Réalisation d'un système d'émission-réception 4 canaux dédié au cerveau de rat pour un système RM à 7T

International audienceUn système ainsi qu'une bobine d'émission-réception ont été réalisés pour un système RM à 7 T. Ce système d'émission-réception 4 canaux permet de créer un champ magnétique RF B1+ polarisé circulairement. La combinaison constructive des phases des 4 canaux a été démontrée par des images RM

Two Origins for the Gene Encoding α-Isopropylmalate Synthase in Fungi

BACKGROUND: The biosynthesis of leucine is a biochemical pathway common to prokaryotes, plants and fungi, but absent from humans and animals. The pathway is a proposed target for antimicrobial therapy. METHODOLOGY/PRINCIPAL FINDINGS: Here we identified the leuA gene encoding alpha-isopropylmalate synthase in the zygomycete fungus Phycomyces blakesleeanus using a genetic mapping approach with crosses between wild type and leucine auxotrophic strains. To confirm the function of the gene, Phycomyces leuA was used to complement the auxotrophic phenotype exhibited by mutation of the leu3+ gene of the ascomycete fungus Schizosaccharomyces pombe. Phylogenetic analysis revealed that the leuA gene in Phycomyces, other zygomycetes, and the chytrids is more closely related to homologs in plants and photosynthetic bacteria than ascomycetes or basidiomycetes, and suggests that the Dikarya have acquired the gene more recently. CONCLUSIONS/SIGNIFICANCE: The identification of leuA in Phycomyces adds to the growing body of evidence that some primary metabolic pathways or parts of them have arisen multiple times during the evolution of fungi, probably through horizontal gene transfer events

Biomechanical Liver characterization through Magnetic Resonance Elastography

International audienc

Biomechanical Liver characterization through Magnetic Resonance Elastography

International audienc

Dispersion-managed electrical transmission lines

International audienceWe examine the ability of electrical pulses to execute a highly stable propagation in a special electrical network made of concatenated pieces of discrete electrical lines with alternately positive and negative signs of the second-order dispersion. We show that such networks, called dispersion-managed electrical lines, induce a pulse breathing phenomenon, that is a dynamical behaviour with alternate regimes of pulse broadening and compression. This breathing phenomenon, which prevents the pulse from broadening without bounds during propagation in the network is the most appealing feature of the technique of dispersion management developed in the last decade in the area of optical communications. Meanwhile, we show that the benefit of using dispersion management in ETLs is strongly mitigated by the third-order dispersion and the losses at the junction points between adjacent pieces of line. These come into play as major factors of impairment for the pulse robustness with a much stronger impact than in dispersion-managed optical transmission lines

Solitons à gestion de dispersion et solitons de cut-off dans les lignes électriques non linéaires

La première partie de cette thèse est consacrée à une étude numérique de la technique de la gestion de dispersion sur un système de lignes électriques discrètes et non linéaires. L'utilisation des lignes passe-bas et passe-bande induit une respiration impulsionnelle caractéristique des solitons à gestion de dispersion. Cependant ces systèmes de lignes électriques se révèlent être particulièrement sensibles aux effets de la dispersion d'ordre 3 et d'adaptation d'impédance. La deuxième partie de cette thèse concerne la supra-transmission et la bistabilite non linéaire au-delà de la fréquence de coupure d'une ligne électrique passe-bas non linéaire. Nous développons une théorie qui permet de prédire les amplitudes seuils déclenchant la supra-transmission et la génération de solitons de cut-off dans le cas d'une ligne longue, et la bistabilité avec hystérésis pour une ligne courte. Les résultats de cette théorie sont confirmés numériquement et expérimentalement sur des lignes longues de 200 et 18 cellules.The first part of this thesis is devoted to a numerical study of dispersion management in a discrete nonlinear electrical transmission line. A system composed of a low-pass and band pass line induces a pulse breathing typical of dispersion managed solitons. However this system is shown to be particularly prone to third order dispersion and impedance mismatch. The second part of this thesis concerns supra-transmission and nonlinear bistability above the cut-off frequency of a nonlinear low-pass electrical line. We develop a theory which predicts the amplitude thresholds triggering supra-transmission and cut-off soliton generation in the case of a long line, and Bistability with hysteresis in a short line. The results of this theory are confirmed numerically and experimentally on lines consisting of 200 and 18 cells.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Dispersion-managed electrical transmission lines

International audienceWe examine the ability of electrical pulses to execute a highly stable propagation in a special electrical network made of concatenated pieces of discrete electrical lines with alternately positive and negative signs of the second-order dispersion. We show that such networks, called dispersion-managed electrical lines, induce a pulse breathing phenomenon, that is a dynamical behaviour with alternate regimes of pulse broadening and compression. This breathing phenomenon, which prevents the pulse from broadening without bounds during propagation in the network is the most appealing feature of the technique of dispersion management developed in the last decade in the area of optical communications. Meanwhile, we show that the benefit of using dispersion management in ETLs is strongly mitigated by the third-order dispersion and the losses at the junction points between adjacent pieces of line. These come into play as major factors of impairment for the pulse robustness with a much stronger impact than in dispersion-managed optical transmission lines

Dispersion-managed electrical transmission lines

International audienceWe examine the ability of electrical pulses to execute a highly stable propagation in a special electrical network made of concatenated pieces of discrete electrical lines with alternately positive and negative signs of the second-order dispersion. We show that such networks, called dispersion-managed electrical lines, induce a pulse breathing phenomenon, that is a dynamical behaviour with alternate regimes of pulse broadening and compression. This breathing phenomenon, which prevents the pulse from broadening without bounds during propagation in the network is the most appealing feature of the technique of dispersion management developed in the last decade in the area of optical communications. Meanwhile, we show that the benefit of using dispersion management in ETLs is strongly mitigated by the third order dispersion and the losses at the junction points between adjacent pieces of line. These come into play as major factors of impairment for the pulse robustness with a much stronger impact than in dispersion-managed optical transmission lines

Dispersion-managed electrical transmission lines

International audienceWe examine the ability of electrical pulses to execute a highly stable propagation in a special electrical network made of concatenated pieces of discrete electrical lines with alternately positive and negative signs of the second-order dispersion. We show that such networks, called dispersion-managed electrical lines, induce a pulse breathing phenomenon, that is a dynamical behaviour with alternate regimes of pulse broadening and compression. This breathing phenomenon, which prevents the pulse from broadening without bounds during propagation in the network is the most appealing feature of the technique of dispersion management developed in the last decade in the area of optical communications. Meanwhile, we show that the benefit of using dispersion management in ETLs is strongly mitigated by the third order dispersion and the losses at the junction points between adjacent pieces of line. These come into play as major factors of impairment for the pulse robustness with a much stronger impact than in dispersion-managed optical transmission lines

Experimental observation of the generation of cutoff solitons in a discrete LC nonlinear electrical line

International audienceWe address the problem of supratransmission of waves in a discrete nonlinear system, driven at one end by a periodic excitation at a frequency lying above the phonon band edge. In an experimental electrical transmission line made of 200 inductance-capacitance LC cells, we establish the existence of a voltage threshold for a supratransmission enabling the generation and propagation of cut-off solitons within the line. The decisive role of modulational instability in the onset and development of the process of generation of cut-off solitons is clearly highlighted. The phenomenon of dissipation is identified as being particularly harmful for the soliton generation, but we show that its impact can be managed by a proper choice of the amplitude of the voltage excitation of the system