Problème de la motorisation d'un véhicule électrique, 1ère partie

National audienceCet article, en 2 parties, est issu d'une conférence donnée en 1994 (club EEA). Il pose le problème de la motorisation des véhicules électriques à l'échelle du système. Toute la chaîne de traction est prise en compte en intégrant les moteurs électriques, les convertisseurs électroniques de puissance et les réducteurs éventuels. Les solutions mono-moteurs et multi-moteurs sont évaluées. Les effets d'échelle sur le fractionnement des moteurs et sur les effets de grandes vitesses sont également analysés

Problème de la motorisation d'un véhicule électrique, 2ème partie

National audienceCet article, en 2 parties, est issu d'une conférence donnée en 1994 (club EEA). Il pose le problème de la motorisation des véhicules électriques à l'échelle du système. Toute la chaîne de traction est prise en compte en intégrant les moteurs électriques, les convertisseurs électroniques de puissance et les réducteurs éventuels. Les solutions mono-moteurs et multi-moteurs sont évaluées. Les effets d'échelle sur le fractionnement des moteurs et sur les effets de grandes vitesses sont également analysés

Les tenseurs de contraintes électromagnétiques

Dans les dispositifs électromagnétiques, le Tenseur de Maxwell est communément utilisé pour le calcul de la force globale qui s'exerce sur les pièces mobiles comme par exemple le noyau d'un électroaimant ou le rotor d'un moteur électrique. Ce Tenseur est aussi utilisé pour définir les forces de surface qui s'exercent sur les discontinuités matérielles (interfaces et surfaces de matériaux). La littérature mentionne en outre l'existence de plusieurs Tenseurs des contraintes électromagnétiques qui vérifient les mêmes propriétés que celui de Maxwell [1] : les Tenseurs proposés par Minkowski (1908), Einstein & Laud (1908), et, Abraham (1909-10). Ces différentes expressions du Tenseur des contraintes électromagnétiques interrogent sur sa genèse, sa définition et sur sa forme générale. Dans cette communication, nous présentons tout d'abord le Tenseur de Maxwell communément utilisé en génie électrique ainsi que ceux de Minkowski, Einstein & Laud, et, Abraham. Dans un deuxième temps, nous nous intéressons à l'introduction du Tenseur des contraintes électromagnétiques à partir de la force et du couple de volume d'origine électromagnétique. Nous nous basons pour cela sur la 'Pill-box method' et sur le Principe des Puissances Virtuelles appliqué à l'électromagnétisme [1][2]. Nous donnons la forme générale du Tenseur des contraintes électromagnétiques obtenu. Enfin, nous explorons les libertés offertes par cette nouvelle forme pour adopter une expression qui donne une contrainte électromagnétique 'plus douce' que par le Tenseur de Maxwell. Les avantages de ce nouveau Tenseur sont de conduire à un calcul numérique plus précis de la force et du couple globale et, par conséquent, de faciliter le traitement numérique des couplages globaux entre électromagnétisme et mécanique. [1] C. Eringen & G. A. Maugin, Electrodynamics of Continua I et II, Springer-Verlag, 1990. [2] G.A. Maugin, The method of virtual power in continua mechanics: Application to coupled fields, Acta Mechanica 35, (1980)

Problème de la motorisation d'un véhicule électrique

National audienceCet article pose le problème de la motorisation des véhicules électriques à l'échelle du système. Toute la chaîne de traction est prise en compte en intégrant les moteurs électriques, les convertisseurs électroniques de puissance et les réducteurs éventuels. Les solutions mono-moteurs et multi-moteurs sont évaluées. Les effets d'échelle sur le fractionnement des moteurs et sur les effets de grandes vitesses sont également analysés

Species-specific contribution of volumetric growth and tissue convergence to posterior body elongation in vertebrates.

Posterior body elongation is a widespread mechanism propelling the generation of the metazoan body plan. The posterior growth model predicts that a posterior growth zone generates sufficient tissue volume to elongate the posterior body. However, there are energy supply-related differences between vertebrates in the degree to which growth occurs concomitantly with embryogenesis. By applying a multi-scalar morphometric analysis in zebrafish embryos, we show that posterior body elongation is generated by an influx of cells from lateral regions, by convergence-extension of cells as they exit the tailbud, and finally by a late volumetric growth in the spinal cord and notochord. Importantly, the unsegmented region does not generate additional tissue volume. Fibroblast growth factor inhibition blocks tissue convergence rather than volumetric growth, showing that a conserved molecular mechanism can control convergent morphogenesis through different cell behaviours. Finally, via a comparative morphometric analysis in lamprey, dogfish, zebrafish and mouse, we propose that elongation via posterior volumetric growth is linked to increased energy supply and is associated with an overall increase in volumetric growth and elongation.Jean-François Nicolas, Estelle Hirsinger: Core funding from the Institut Pasteur and Agence Nationale de la Recherche (ANR-10-BLAN-121801 DEVPROCESS). Estelle Hirsinger and Sylvie Mazan are from the Centre National de la Recherche Scientifique (CNRS). Benjamin Steventon was funded by the Agence Nationale de la Recherche (ANR- 10-BLAN-121801 DEVPROCESS), then a Roux fellowship (Institut Pasteur) then an AFM-Téléthon fellowship (number 16829).This is the author accepted manuscript. The final version is available from The Company of Biologists via http://dx.doi.org/10.1242/dev.12637

csal1 Is Controlled by a Combination of FGF and Wnt Signals in Developing Limb Buds

While some of the signaling molecules that govern establishment of the limb axis have been characterized, little is known about the downstream effector genes that interpret these signals. In Drosophila, the spalt gene is involved in cell fate determination and pattern formation in different tissues. We have cloned a chick homologue of Drosophila spalt, which we have termed csal1, and this study focuses on the regulation of csal1 expression in the limb bud. csal1 is expressed in limb buds from HH 17 to 26, in both the apical ectodermal ridge and the distal mesenchyme. Signals from the apical ridge are essential for csal1 expression, while the dorsal ectoderm is required for csal1 expression at a distance from the ridge. Our data indicate that both FGF and Wnt signals are required for the regulation of csal1 expression in the limb. Mutations in the human homologue of csal1, termed Hsal1/SALL1, result in a condition known as Townes–Brocks syndrome (TBS), which is characterized by preaxial polydactyly. The developmental expression of csal1 together with the digit phenotype in TBS patients suggests that csal1 may play a role in some aspects of distal patterning

Magnetic-Field Induced Strains in Ferromagnetic Shape Memory Alloy Ni55Mn23Ga22 Deposited by RF-Magnetron Sputtering

1.5mm–Ni55Mn23Ga22 ferromagnetic thin films were deposited onto silicon substrates and silicon single beam cantilever using radio-frequency magnetron sputtering. As-deposited sample and heat-treated thin films were studied on their silicon substrates and peeled off to determine the influence of the stress. Post-heat treatment process allows at the films to achieve the shape memory effect (SME). Vibrating sample magnetometer (VSM) and deflection measurement of the sample annealed at 873 K during 36 ks exhibit ferromagnetic martensitic structure with a typical SME response to the magnetic field induced strains which match the values of the bulk material

Novel intronic microRNA represses zebrafish myf5 promoter activity through silencing dickkopf-3 gene

A strong, negative cis-element located at the first intron +502/+835 (I300) of zebrafish myf5 has been reported. To elucidate the molecular mechanism underlying this repression network, we microinjected zebrafish single-cell embryos with I300 RNA, resulting in the dramatic reduction of luciferase activity driven by the myf5 promoter. Within this I300 segment, we identified an intronic microRNA (miR-In300) located at +609/+632 and found that it was more highly expressed in the older mature somites than those newly formed, which negatively correlated with the distribution of zebrafish myf5 transcripts. We proved that miR-In300 suppressed the transcription of myf5 through abolishing myf5 promoter activity, and we subsequently identified the long isoform of the Dickkopf-3 gene (dkk3) as the target gene of miR-In300. We further found that injection of the dkk3-morpholinos (MOs) resulted in downregulation of myf5 transcripts in somites, whereas co-injection of myf5 mRNA with dkk3-MO1 enabled rescue of the defects induced by dkk3-MO1 alone. Finally, injection of miR-In300-MO enhanced both myf5 transcripts in somites and the level of Dkk3 protein in zebrafish embryos. Based on these findings, we concluded that miR-In300 binds to its target gene dkk3, which inhibits the translation of dkk3 mRNA and, in turn, suppresses zebrafish myf5 promoter activity

The role of chick Ebf genes in the mediolateral patterning of the somites

This study was conducted to check whether the three chick Early B-cell Factor (Ebf) genes, particularly cEbf1, would be targets for Shh and Bmp signals during somites mediolateral (ML) patterning. Tissue manipulations and gain and loss of function experiments for Shh and Bmp4 were performed and the results revealed that cEbf1 expression was initiated in the cranial presomitic mesoderm by low dose of Bmp4 from the lateral mesoderm and maintained in the ventromedial part of the epithelial somite and the medial sclerotome by Shh from the notochord; while cEbf2/3 expression was induced and maintained by Bmp4 and inhibited by high dose of Shh. To determine whether Ebf1 plays a role in somite patterning, transfection of a dominant-negative construct was carried out; this showed suppression of cPax1 expression in the medial sclerotome and upregulation and medial expansion of cEbf3 and cPax3 expression in sclerotome and dermomyotome, respectively, suggesting that Ebf1 is important for ML patterning. Thus, it is possible that low doses of Bmp4 set up Ebf1 expression which, together with Shh from the notochord, leads to establishment of the medial sclerotome and suppression of lateral identities. These data also conclude that Bmp4 is required in both the medial and lateral domain of the somitic mesoderm to keep the ML identity of the sclerotome through maintenance of cEbf gene expression. These striking findings are novel and give a new insight on the role of Bmp4 on mediolateral patterning of somites

Shh Signaling from the Nucleus Pulposus Is Required for the Postnatal Growth and Differentiation of the Mouse Intervertebral Disc

Intervertebral discs (IVD) are essential components of the vertebral column. They maintain separation, and provide shock absorbing buffers, between adjacent vertebrae, while also allowing movements between them. Each IVD consists of a central semi-liquid nucleus pulposus (NP) surrounded by a multi-layered fibrocartilagenous annulus fibrosus (AF). Although the IVDs grow and differentiate after birth along with the vertebral column, little is known about the mechanism of this. Understanding the signals that control normal IVD growth and differentiation would also provide potential therapies for degenerative disc disease, which is the major cause of lower back pain and affects a large proportion of the population. In this work, we show that during postnatal growth of the mouse, Sonic hedgehog (Shh) signaling from the NP cells controls many aspects of growth and differentiation of both the NP cells themselves and of the surrounding AF, and that it acts, at least partly, by regulating other signaling pathways in the NP and AF. Recent studies have shown that the NP cells arise from the embryonic notochord, which acts as a major signaling center in the embryo. This work shows that this notochord-derived tissue continues to carry out a major signaling function in the postnatal body and that the IVDs are signaling centers, in addition to their already known functions in the mechanics of vertebral column function