Le TGV-Atlantique : entre récession et concurrence

Le TGV véhicule bien des images. Train des Parisiens ou de la décentralisation ? Vitesse démocratisée ou tarifs élevés ? Train d'affaires ou service public ? Le TGV transporte d'abord des voyageurs. Qui sont-ils ? Que font-ils ? Quelles sont leurs spécificités par rapport aux voyageurs utilisant un autre moyen de transports ? Sont-ils différents de ceux qui voyageaient avant sa mise en service ? En d'autres termes, quelles transformations de la mobilité tant professionnelle que personnelle peuvent-elles être reliées à la mise en service du TGV ?Pour répondre à ces questions, une enquête coordonnée sur les trois modes de transport (autoroute, avion, train) a été réalisée à l'initiative de l'Observatoire Economique et Statistique des Transports par le Laboratoire d'Economie des Transport en 1989 et en 1993 autour du TGV-Atlantique. Cette enquête, intervenue juste avant et quatre ans après la mise en service du TGV-Atlantique, a permis de recueillir 18.000 questionnaires portant sur l'ensemble des parcours Province-Paris concernés par la nouvelle offre. Cette synthèse des résultats permet de mieux comprendre comment les déplacement professionnels, les déplacements domicile-travail, les déplacements personnels ainsi que les relations entre l'Ile-de-France et les principales agglomérations de la façade atlantique de la France se sont modifiées à la faveur de la mise en service du TGV-A.TGV-Atlantique ; transport ferroviaire ; transport à grande vitesse ; choix du mode de transport ; déplacement domicile-travail; mobilité professionnelle ; déplacement personnel ; enquête ; étude avant-après

150 ans d’humanitaire, vus du CICR… et d’ailleurs

En 2013, le Comité international de la Croix-Rouge fêtait ses 150 ans, tout comme le fera un an plus tard la Croix-Rouge française. Et en 2019, la Revue internationale de la Croix-Rouge en fera autant. Trois occasions de revenir sur le numéro spécial que cette dernière a publié en 2012 – CICR : 150 ans d’action humanitaire – en nous arrêtant sur deux contributions : celle de Paul Bouvier (« Soin humanitaire et petites choses dans des lieux déshumanisés », p. 359-373) et celle de Rony Brauman ..

Fast multilinear Singular Values Decomposition for higher-order Hankel tensors

International audienceThe Higher-Order Singular Value Decomposition (HOSVD) is a possible generalization of the Singular Value Decomposition (SVD) to tensors, which have been successfully applied in various domains. Unfortunately, this decomposition is computationally demanding. Indeed, the HOSVD of a Nth- order tensor involves the computation of the SVD of N matrices. Previous works have shown that it is possible to reduce the complexity of HOSVD for third-order structured tensors. These methods exploit the columns redundancy, which is present in the mode of structured tensors, especially in Hankel tensors. In this paper, we propose to extend these results to fourth order Hankel tensor. We propose two ways to extend Hankel structure to fourth order tensors. For these two types of tensors, a method to build a reordered mode is proposed, which highlights the column redundancy and we derive a fast algorithm to compute their HOSVD. Finally we show the benefit of our algorithms in terms of complexity

Upper critical field of CeCoIn5

We present a detailed analysis of the upper critical field for CeCoIn5 under high pressure. We show that, consistently with other measurements, this system shows a decoupling between maximum of the superconducting transition temperature Tc and maximum pairing strength. This puts forward CeCoIn5 as an important paradigm for this class of unconventional, strongly correlated superconductors.Comment: 15 pages, 5 figures, author version, published in New J. Phy

Electrochemical attachment of a conjugated amino-ferrocifen complex onto carbon and metal surfaces

International audienceThe attachment of a pi-conjugated amino-ferrocifen complex was electrochemically achieved either by direct oxidation of the amino group or via the oxidation of the ferrocene moiety. In the first case, the modification consists in oxidizing, at +0.70V/SCE, the amino moiety to its radical cation, which upon deprotonation from the amino group, yields all aminyl radical that may add onto the electrode surface. Alternatively, it is demonstrated that the amine moiety can be indirectly oxidized through an intramolecular electron transfer from the amino moiety to the ferrocenyl group after oxidation of the ferrocene part at +0.40 V. This can occur thanks to the conjugated pi system of the complex. More importantly. it is demonstrated that the covalent attachment of the complex can be achieved on glassy carbon, gold, and platinum surfaces whatever the approach used. The possible mechanisms for the covalent attachment are discussed. Interestingly, it is also shown that the amino-ferrocene compound adsorbs very well likely via pi stacking between grafted and non-grafted molecules. Nevertheless, the adsorbed molecules could be easily removed after passing the electrode in an ultrasonic bath. The electrode coverage was determined under various conditions by integration of the corresponding voltammograms. (C) 2008 Elsevier B.V. All rights reserved

Passive microrheology as a useful tool for milk gel analyses

Passive microrheology based on Diffusing Wave Spectroscopy (DWS) [1,2] is presented as a straightforward tool for the analysis of milk gel preparation. Diffusing Wave Spectroscopy consists of analysing the interferential images of light, which is backscattered by the sample. This so called speckles images, which are detected by a CCD camera, change in time due to the Brownian motion of the particles that scatter the light. The variation of the images as a function of time can be directly correlated to the viscoelastic properties of the sample. As it is an optical method, it is perfectly adapted to study the weak gels of milk products. Nowadays, milk gels such as yogurts or chees have attracted lots of interest due to its growing market. The milk properties, such as pH, calcium content and protein content are very important and change significantly the cheese properties. This work shows how passive microrheology can be used to follow up the milk gel formation with exact gel time determination. Gel time was determined by a new rescaling method, namely Time-Cure Superposition (TCS) [3,4]. This data processing determines the gel point according to the Winter-Chambon criterion [5]. Moreover, the viscoelastic properties of the preparation can be compared according to parameters, such as the protein enrichment, calcium ion addition or others. Results were compared to other instruments (texturometers, rheometer, Optigraph®, etc.). References: [1] D. A. Weitz et al., in Dynamic Light Scattering, W. Brown (Ed.) (Oxford Univ. Press, New York (1993), Chap. 16. [2] D. J. Pine et al., Phys. Rev. Lett. 1988, 60, 1434. [3] T. H. Larsen, E. M. Furst, Phys. Rev. Letters, 2008, 100, 14600 [4] K. M. Schultz, E. M. Furst, Soft Matter, 2012, 8, 6198 [5] H. H. Winter, F. Chambon, J. Rheology 1986, 30, 364-38