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

Study of the scientific potential of a three 40 cm Telescopes Interferometer at Dome C

Recent site testing (see: http://www-luan.unice.fr/Concordiastro/indexantartic.html) has shown that Dome C in Antarctica might have a high potential for stellar interferometry if some solutions related to the surface atmospheric layer are found. A demonstrator interferometer could be envisioned in order to fully qualify the site and prepare the future development of a large array. We analyse the performances of a prototype interferometer for Dome C made with 3 telescopes of 40 cm diameter. It assumes classical Michelson recombination. The most recent atmospheric and environmental conditions measured at Dome C are considered (see K. Agabi "First whole atmosphere night-time seeing measurements at Dome C, Antarctica"). We also study the possible science reachable with such a demonstrator. Especially we evaluate that even such small aperture interferometer could allow the detection and low resolution spectroscopy of the most favourable pegaside planets.Comment: 6 pages, 5 figures, conferences SPIE, 0rlando, 200

Reaction Kinetics of CO and CO2_{2}Methanation over Nickel

Methanation of both CO and CO2 with electrolysis-sourced hydrogen is a key step in power-to-gas technologies with nickel as the most prominent catalyst. Here, a detailed, thermodynamically consistent reaction mechanism for the methanation reactions of CO and CO$_{2}$ over Ni-based catalysts is presented. This microkinetic model is based on the mean-field approximation and comprises 42 reactions among 19 species. The model was developed based on experiments from a number of studies in powder and monolith catalysts. These are numerically reproduced by flow field simulations coupled with the kinetic scheme. The reaction mechanism features multiple paths for the conversion of CO and CO$_{2}$ into CH$_{4}$, including a carbide pathway and direct hydrogenation of CO$_{2}$ on the surface. The model developed describes the methanation process adequately over a wide range of temperatures, catalyst loadings, support materials, and reactant ratios. Hence, it can serve as a microkinetic basis for reaction engineering and up-scaling purposes

SYMPA, a dedicated instrument for Jovian Seismology. II. Real performance and first results

Context. Due to its great mass and its rapid formation, Jupiter has played a crucial role in shaping the Solar System. The knowledge of its internal structure would strongly constrain the solar system formation mechanism. Seismology is the most efficient way to probe directly the internal structure of giant planets. Aims. SYMPA is the first instrument dedicated to the observations of free oscillations of Jupiter. Principles and theoretical performance have been presented in paper I. This second paper describes the data processing method, the real instrumental performance and presents the first results of a Jovian observation run, lead in 2005 at Teide Observatory. Methods. SYMPA is a Fourier transform spectrometer which works at fixed optical path difference. It produces Doppler shift maps of the observed object. Velocity amplitude of Jupiter's oscillations is expected below 60 cm/s. Results Despite light technical defects, the instrument demonstrated to work correctly, being limited only by photon noise, after a careful analysis. A noise level of about 12 cm/s has been reached on a 10-night observation run, with 21 % duty cycle, which is 5 time better than previous similar observations. However, no signal from Jupiter is clearly highlighted.Comment: 13 pages, 26 figure

La génération de 68 et le passé des pères : entre accusation et identification inconsciente ?

Dans le contexte de la Vergangenheitsbewältigung, les événements de 68 sont généralement considérés comme un moment de rupture important, marquant la fin d’une longue période de refoulement collectif et individuel. On s’accorde à dire que c’est, entre autres, grâce à l’insistance de la génération de 68 que la chape de plomb qui pesait sur le passé nazi de l’Allemagne commence à se fissurer. Toutefois, depuis un certain temps, le regard sur le rôle que les soixante-huitards ont joué dans la prise de conscience historique commence à changer. La sincérité de leur révolte, soupçonnée de relever d’un désir d’identification inavoué et d’un rejet d’affinités sous-jacentes, est contestée. Ces remises en question politique, générationnelle et scientifique ainsi que l’actuelle tendance à l’auto-critique de la part d’anciens soixante-huitards sont analysées dans notre contribution. Dans ce contexte, l’étude du roman Ein unsichtbares Land (Un pays invisible) d’un ancien acteur du mouvement étudiant, Stephan Wackwitz, permet de mieux comprendre la relation complexe qu’entretient la deuxième génération d’après-guerre avec le IIIe Reich et ceux qui l’ont vécu.Die Ereignisse von 68, die im Kontext der Vergangenheitsbewältigung üblicherweise als ein entscheidender Bruch wahrgenommen werden, bedeuten das Ende einer langen Periode kollektiver und individueller Verdrängung. Es ist, so die allgemeine Annahme, zu einem nicht unbedeutenden Teil dem Insistieren der 68er zu verdanken, dass das bleierne Schweigen, das auf der nationalsozialistischen Vergangenheit Deutschlands lastete, gebrochen wurde. Seit einiger Zeit scheint sich jedoch die Einschätzung der 68er und ihrer Einflussnahme auf das historische Bewusstsein zu ändern. Die Authentizität ihrer Revolte, die im Verdacht steht, einer unbewussten Identifikation und der Abwehr unterschwelliger Affinitäten zu gehorchen, wird in Frage gestellt. Diese politische, generationsbedingte oder auch wissenschaftliche Hinterfragung sowie die aktuelle Tendenz zur Selbstkritik seitens ehemaliger 68er werden im vorliegenden Beitrag untersucht. Literarisch ausgeführt wird letztere im Roman Ein unsichtbares Land von Stephan Wackwitz, einem ehemaligen Vertreter der Studentenbewegung, der das komplexe Verhältnis der 68er zum Dritten Reich und zur Kriegsgeneration beleuchtet

Venus wind map at cloud top level with the MTR/THEMIS visible spectrometer. I. Instrumental performance and first results

Solar light gets scattered at cloud top level in Venus' atmosphere, in the visible range, which corresponds to the altitude of 67 km. We present Doppler velocity measurements performed with the high resolution spectrometer MTR of the Solar telescope THEMIS (Teide Observatory, Canary Island) on the sodium D2 solar line (5890 \AA). Observations lasted only 49 min because of cloudy weather. However, we could assess the instrumental velocity sensitivity, 31 m/s per pixel of 1 arcsec, and give a value of the amplitude of zonal wind at equator at 151 +/- 16 m/s.Comment: 17 pages, 12 figure

Écriture de la ville et poétique du mensonge – l’espace urbain chez Flaubert et Balzac

Cette contribution étudie comment la littérature de la grande ville s’attache à découvrir derrière le visage trompeur et mensonger du paysage urbain une vérité cachée et une promesse de connaissance. Elle s’intéresse d’abord à l’œuvre de Balzac, où les protagonistes doivent déchiffrer la ville dans sa complexité sociale et érotique afin de connaître sa vérité et pouvoir ainsi prétendre au pouvoir mondain et sexuel. L’étude de Ferragus, roman parisien d’amour et d’espionnage, met en évidence le jeu de miroirs entre vérité et mensonge constitutif de la littérature urbaine. Sont ensuite analysés les textes de Flaubert (L’Éducation sentimentale et Madame Bovary) qui rompent avec les codes de la littérature urbaine. On y assiste à une mise en question radicale de l’espace urbain comme lieu de véracité. La ville devient alors synonyme de tromperie et engendre un texte qui déforme la vérité et illustre le décalage entre émotion et expression – constitutif de la notion de mensonge telle que nous la comprenons – et cela au niveau scénarique, narratologie et sémiotique.Im folgenden Beitrag soll untersucht werden, wie die Großstadtliteratur darauf abzielt, hinter der trügerischen Fassade der fiktiven oder realen Stadtlandschaft eine verborgene Wahrheit und das Versprechen einer Erkenntnis aufzuspüren. Es wird zunächst gezeigt, wie Balzac die Protagonisten der Comédie humaine dazu anhält, die Stadt in ihrer sozialen und erotischen Komplexität zu entziffern, um die in ihr verborgene Wahrheit zu erkennen, und sich so gesellschaftliche und sexuelle Macht anzueignen. Die Untersuchung des Pariser Liebes- und Spionageromans Ferragus macht deutlich, welche grundlegende Rolle das Wechselspiel zwischen Wahrheit und Lüge für die Stadtliteratur spielt. Anschließend wird an Texten Flauberts (L’Éducation sentimentale und Madame Bovary) nachgewiesen, wie diese mit den traditionellen Codes des Großstadtromans brechen, indem die Stadt zum Synonym für Lüge wird. Die Flaubertschen Romane inszenieren systematisch die für das Konzept der Lüge konstitutive Diskrepanz zwischen Gefühl und Ausdruck, und zwar auf szenarischer, narratologischer und semiotischer Ebene.We would like to show in our contribution how urban literature aims at discovering a hidden truth and the promise of knowledge behind the illusionary and deceitful appearance of the city. We will firstly analyse Balzac’s oeuvre in which the protagonists have to decipher the city in its social and erotic complexity in order to attain political and sexual power. Our study of Ferragus, a Parisian novel of love and betrayal, will show the delusionary mirror interplay between truth and lie that is at the very heart of urban poetics. We will then study two novels by Flaubert (Sentimental Education and Madame Bovary), which reinvent the codes of urban literature. They radically challenge the idea of the city revealing some sort of truth. With Flaubert, urban space becomes synonymous with illusion and generates a text that, on a narrative and semiotic level, illustrates the discrepancy between emotion and expression that constitutes the definition of lie as we understand it