From night bustle to printed quietness

Des del punt de vista d'un científic, la comunicació científica entre col·legues significa la possibilitat de reconeixement dels postulats que es desprenen de la seva recerca, és la ciència de dia, la quietud de la ciència impresa. Però hi ha una altra ciència, la de nit, que comporta tota la part creativa i emotiva de la ciència.For the scientist, science communication between colleagues entails the possibility to make research known, which is day science. But there is another science, night science, which involves the creative and emotional part of science

Detection of Jovian seismic waves: a new probe of its interior structure

Knowledge of Jupiter's deep interior would provide unique constraints on the formation of the Solar System. Measurement of its core mass and global composition would shed light on whether the planet formed by accretion or by direct gravitational collapse. At present, the inner structure of Jupiter is poorly constrained and seismology, which consists of identifying acoustic eigenmodes, offers a way to directly measure its deep sound speed profile, and thus its physical properties. Seismology of Jupiter has been considered since the mid 1970s, but hitherto the various attempts to detect global modes led, at best, to ambiguous results. We report the detection of global modes of Jupiter, based on radial velocity measurements performed with the SYMPA Fourier spectro-imager. The global seismic parameters that we measure include the frequency of maximum amplitude 1213+/-50 \mu Hz, the mean large frequency spacing between radial harmonics 155.3+/-2.2 \mu Hz and the mode maximum amplitude 49 (-10/+8) cm/s, all values that are consistent with current models of Jupiter. This result opens the way to the investigation of the inner structure of the Solar System's giant planets based on seismology techniques.Comment: Accepted in Astronomy & Astrophysics (8 pages, 9 figures

Looking for the order of a system of arbitrary ordinary differential equations. De investigando ordine systematis aequationum differentialium vulgarium cujuscunque

English translation of a posthumous paper in Latin of C.G.J. Jacobi: Journal für die reine und angewandte Mathematik, 64 , 4, 297-320, Berlin, Georg Reimer, 1865.International audienceThis paper was edited by S. Cohn and C.W. Borchardt from posthumous manuscripts of C.G.J. Jacobi. The various canonical forms that a given system ordinary differential equations may take are considered. Looking for the order of the system, without using a normal form, is reduced to a problem of inequalities: the affectation problem. A new type of formulas, the truncated determinants, is introduced. The non vanishing of this quantity means that the order will be equal to the value H , solution of this in- equalities problem, which is obtained by an algorithm similar to Harold Kuhn's Hungarian metho

The reduction to normal form of a non-normal system of differential equations. De aequationum differentialium systemate non normali ad formam normalem revocando

English translation of a posthumous manuscript in Latin first published in Vorlesungen über Dynamik von C.G.J. Jacobi nebstes fünf hinterlassenen Abhandlungen desselben, A. Clesch ed., Berlin, Georg Reimer, 1866.International audienceThis paper was edited by Sigismund Cohn, C.W. Borchardt and A. Clebsch from posthumous manuscripts of C.G.J. Jacobi. The solution of the following problem: "to transform a square table of m^2 numbers by adding minimal numbers l_i to each horizontal row, in such a way that it possess m transversal maxima", determines the order and the shortest normal form reduction of he system: the equations u_i = 0 must be respectively diff erentiated l_i times. One also determines the number of di fferentiations of each equation of the given system needed to produce the differential equations necessary to reduce the proposed system to a single equation

La perception de la Guerre de Sécession dans la presse québécoise, 1861-1865

La décennie 1860-1870 a été d'une grande importance pour le Québec, autant au niveau politique qu'économique ou social. Au cours de ces années critiques la Confédération canadienne prend forme, Confédération dont les structures influencent le Québec pour l'avenir. Les discussions qui ont mené à la Confédération canadienne ont été d'autant plus délicates qu'au sud des colonies britanniques se déroulait un cas exemplaire de rapports difficiles entre différents paliers de gouvernement: la guerre de Sécession. Forcément, pour un libéral ou un conservateur, pour un francophone ou un anglophone, l'orientation adoptée face au projet de Confédération canadienne sera influencée au moins en partie par ce conflit et les enseignements que l'on croit pouvoir en tirer. Les États-Unis se sont-ils effondrés en raison de la domination d'une section sur l'autre ? Ou alors, en raison d'une autorité centrale trop faible ou trop forte ? Ces interrogations, les leaders politiques se les posent avec acuité puisque nombre des éléments de la situation américaine sont transférables au futur Canada : populations s'estimant différentes, différences économiques considérables, méfiance entre les différentes régions...Or, si des éléments sont transférables, d'autres ne le sont pas. En effet, la guerre de Sécession comporte une charge idéologique qui n'a pas d'équivalent direct au Canada : démocratie démagogique d'un côté, l'esclavage de l'autre, qui sont autant de traits que les partisans du Sud ou du Nord attribuent à l'adversaire.Le présent mémoire explore la représentation que les futurs Québécois, anglophones ou francophones, eurent de ce conflit. Cette perception est analysée par le biais de la presse, soit les journaux d'allégeance conservatrice The Morning Chronicle et La Minerve, ainsi que les journaux libéraux Le Pays et The Montreal Witness. La conclusion essentielle est que l'allégeance politique de tel ou tel journal prime sur toutes autres considérations dans les prises de position face à la guerre de Sécession : il y a une grande unité de ton entre le Chronicle et La Minerve, et une animosité absolue entre Le Pays et cette même Minerve, même si ces deux derniers jours sont francophones. De même, Le Pays et le Witness ont en gros la même orientation, et ce même Witness est en opposition avec le Chronicle. L'importance capitale de l'allégeance politique fait que l'analyse de la guerre de Sécession elle-même passe souvent au second plan dans la couverture de cet événement par ces journaux, couverture qui sert plutôt de prétexte pour commenter la politique canadienne

3-D Magnetotelluric Investigations for geothermal exploration in Martinique (Lesser Antilles). Characteristic Deep Resistivity Structures, and Shallow Resistivity Distribution Matching Heliborne TEM Results

Within the framework of a global French program oriented towards the development of renewable energies, Martinique Island (Lesser Antilles, France) has been extensively investigated (from 2012 to 2013) through an integrated multi-methods approach, with the aim to define precisely the potential geothermal ressources, previously highlighted (Sanjuan et al., 2003). Amongst the common investigation methods deployed, we carried out three magnetotelluric (MT) surveys located above three of the most promising geothermal fields of Martinique, namely the Anses d'Arlet, the Montagne Pel{\'e}e and the Pitons du Carbet prospects. A total of about 100 MT stations were acquired showing single or multi-dimensional behaviors and static shift effects. After processing data with remote reference, 3-D MT inversions of the four complex elements of MT impedance tensor without pre-static-shift correction, have been performed for each sector, providing three 3-D resistivity models down to about 12 to 30 km depth. The sea coast effect has been taken into account in the 3-D inversion through generation of a 3-D resistivity model including the bathymetry around Martinique from the coast up to a distance of 200 km. The forward response of the model is used to calculate coast effect coefficients that are applied to the calculated MT response during the 3-D inversion process for comparison with the observed data. 3-D resistivity models of each sector, which are inherited from different geological history, show 3-D resistivity distribution and specificities related to its volcanological history. In particular, the geothermal field related to the Montagne Pel{\'e}e strato-volcano, is characterized by a quasi ubiquitous conductive layer and quite monotonic typical resistivity distribution making interpretation difficult in terms of geothermal targets. At the opposite, the resistivity distribution of Anse d'Arlet area is radically different and geothermal target is thought to be connected to a not so deep resistive intrusion elongated along a main structural axis. Beside these interesting deep structures, we demonstrate, after analyzing the results of the recent heliborne TEM survey covering the whole Martinique, that surface resistivity distribution obtained from 3-D inversion reproduce faithfully the resistivity distribution observed by TEM. In spite of a very different sampling scale, this comparison illustrates the ability of 3-D MT inversion to take into account and reproduce static shift effects in the sub-surface resistivity distribution.Comment: Wordl Geothermal Congress 2015, Apr 2015, Melbourne, Australi