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Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri
No full textInternational audienceContext. The latest evolutionary phases of low- and intermediate-mass stars are characterized by complex physical processes like turbulence, convection, stellar pulsations, magnetic fields, condensation of solid particles, and the formation of massive outflows that inject freshly produced heavy elements and dust particles into the interstellar medium.Aims. By investigating individual objects in detail, we wish to analyze and disentangle the effects of the interrelated physical processes on the structure of the wind-forming regions around them.Methods. We use the Northern Extended Millimeter Array to obtain spatially and spectrally resolved observations of the semi-regular asymptotic giant branch (AGB) star RS Cancri and apply detailed 3D reconstruction modeling and local thermodynamic equilibrium radiative transfer calculations in order to shed light on the morpho-kinematic structure of its inner, wind-forming environment.Results. We detect 32 lines of 13 molecules and isotopologs (CO, SiO, SO, SO2, H2O, HCN, PN), including several transitions from vibrationally excited states. HCN, H13CN, and millimeter vibrationally excited H2O, SO, 34SO, SO2, and PN are detected for the first time in RS Cnc. Evidence for rotation is seen in HCN, SO, SO2, and SiO(v = 1). From CO and SiO channel maps, we find an inner, equatorial density enhancement, and a bipolar outflow structure with a mass-loss rate of 1 × 10−7 M⊙yr−1 for the equatorial region and of 2 × 10−7 M⊙yr−1 for the polar outflows. The 12CO/13CO ratio is measured to be ~20 on average, 24 ± 2 in the polar outflows and 19 ± 3 in the equatorial region. We do not find direct evidence of a companion that might explain this kind of kinematic structure, and explore the possibility that a magnetic field might be the cause of it. The innermost molecular gas is influenced by stellar pulsation and possibly by convective cells that leave their imprint on broad wings of certain molecular lines, such as SiO and SO.Conclusions. RS Cnc is one of the few nearby, low-mass-loss-rate, oxygen-rich AGB stars with a wind displaying both an equatorial disk and bipolar outflows. Its orientation with respect to the line of sight is particularly favorable for a reliable study of its morpho-kinematics. Nevertheless, the mechanism causing early spherical symmetry breaking remains uncertain, calling for additional high spatial- and spectral-resolution observations of the emission of different molecules in different transitions, along with more thorough investigation of the coupling among the different physical processes at play
Fused microwave and ultrasonic breast imaging within the framework of a joint variational Bayesian approximation
No full textInternational audienceEarly diagnosis of breast tumors can in principle be achieved by jointly running electromagnetic and acoustic probings, more precisely Microwave (MW) and ultrasound (US). Indeed, such modalities are non-invasive, non-ionizing, low-cost, and proceed without registration for free pending breasts, not like other joint modalities that impose compression. Because of the strongly-contrasted electromagnetic parameters of breast constituents, MW yields high-contrast images of low resolution, and the converse with the US since faced with weakly refracting elements. The key benefit is the common breast structure, and fusion should produce images with both high contrast and resolution. A Bayesian formalism is chosen, and an unsupervised Joint Variational Bayesian Approximation or JVBA is developed. In it, edges hidden variables and hyper-parameters are automatically tuned along with the optimization. The mathematics is detailed in a general setting of fusion, then one proposes imaging of realistic MRI-derived breast slices. A wealth of numerical simulations from noisy single-frequency MW and multiple-frequency US data preserved from inverse crime yields means (i.e., breast maps) and variances of the unknown electromagnetic and acoustic parameter distributions as probabilistic realizations, evolutions of hyper-parameters, as well as global indicators of accuracy. Comparisons with a joint edge-preserving contrast source inversion (JCSI-EP) developed earlier in a deterministic framework illustrate the methodology
Rapport de recherche : UPE2A ULIS - analyse du processus d'institutionnalisation d'un dispositif scolaire expérimental
No full textOn the European Knowledge of Sanskrit
No full textLecture delivered in Hangchou Buddhist Academy (20.10.2018, revised January 2022
Droit canonique médiéval et droits fondamentaux modernes: une comparaison historique
No full textInternational audienceCet article vise à apporter un point de vue nouveau sur le fonctionnement des droits fondamentaux dans les systèmes juridiques modernes, au moyen d’une analogie historique. Le problème de départ est celui de l’interprétation de notre situation historique, en tant que celle-ci est saturée par les idéaux jumeaux du constitutionnalisme et de l’État de droit. Aujourd’hui, la position par défaut des juristes est qu’il est souhaitable qu’une riche gamme de droits soient garantis aux niveaux constitutionnel et conventionnel, et placés sous la protection d’organes spécifiques. Le paradigme des droits est pour ainsi dire le bain culturel dans lequel baignent les étudiants depuis une trentaine d’années. La comparaison proposée vise précisément à rendre un peu de relief et d’étrangeté à ce moment historique dans lequel nous sommes plongés, en rapprochant deux époques lointaines. La première est l’époque dite « classique » du droit canonique, qui s’étend de la fin du XIe siècle au début du XIVe siècle. Durant cette période en effet, sous l’action puissante et continue de la papauté romaine, un droit d’essence religieuse a transformé en profondeur et unifié les droits des royaumes européens. Le second terme de la comparaison est la période d’enracinement et de diffusion progressive de l’État de droit en Europe à partir de la fin de la Seconde Guerre mondiale, jusqu’à son triomphe au tournant du millénaire. Il s’agit ainsi de rapprocher deux époques séparées l’une de l’autre par sept à neuf siècles, afin de comparer deux dynamiques d’unification du droit en Europe. Ces deux dynamiques présentent en effet des traits communs frappants : elles sont en grande partie le produit de structures juridictionnelles spécialisées et transnationales ; et elles se sont opérées sous l’effet d’un droit d’une nature tout à fait originale – nature religieuse dans le cas médiéval, nature philosophique dans le cas contemporain, mais dans les deux cas, un droit d’une nature intensément moralisante. En outre, ces traits communs dessinent, au-delà des deux dynamiques d’unification du droit, les deux structures qui rendent ces dynamiques possibles. Il existe en effet dans les deux cas une division fondamentale du système normatif européen entre, d’une part, un droit que l’on qualifiera simplement de droit des principes, réceptacle des aspirations morales et spirituelles les plus hautes de l’époque, et d’autre part un droit technique et utilitaire (le droit civil au sens large) qui répond aux besoins organisationnels des sociétés européennes, au XIIe siècle comme aujourd’hui. Le fait le plus frappant est que dans les deux cas, droit canonique classique comme droits fondamentaux, le droit des principes est bien du droit, c’est-à-dire qu’il a une positivité qui lui est apportée par l’existence d’une sanction sous la forme d’un réseau d’institutions juridictionnelles qui lui sont dédiées. En dernière instance, donc, la comparaison historique proposée dans cet article consiste en une analogie structurale entre l’époque classique du droit canonique et l’époque contemporaine du constitutionnalisme et de l’État de droit. Elle vise à poser la question : l’Europe a-t-elle retrouvé, à travers la dynamique contemporaine de protection des droits fondamentaux, une structure fondamentale de son système normatif caractérisé par la division entre un droit (positif) des principes et un droit de l’utile, et par la transformation continue du second par le premier
The mathematical background of proving processes in discrete optimization - Exemplification with Research Situations for the Classrooms
No full textDiscrete mathematics brings interesting problems to teach and learn proof with accessible objects such as integers (arithmetic), graphs (modeling, order) or polyominoes (geometry). A lot of still open problems can be explained to a large public. The objects can be manipulated by simple dynamic operations (removing, adding, "gluing", contracting, splitting, decomposing, etc.). All these operations can be seen as tools for proving. This article particularly explores the field of "discrete optimization". A theoretical background is defined by taking two main axes into account: the epistemological analysis of discrete problems studied by contemporary researchers in discrete optimization and the design of adidactical situations for classrooms in the frame of the Theory of Didactical Situations. Two problems coming from ongoing research in discrete optimization (the Pentamino Exclusion and the Eight Queens problems) are developed. They underscore the learning potentialities of discrete mathematics and epistemological obstacles about proving processes. They emphasize the understanding of a necessary condition and a sufficient condition and problematize the difference between optimal and optimum. They provide proofs involving partitioning strategies, greedy algorithms but also primal-dual methods leading to the concept of duality. The way such problems can be implemented in the classrooms is described in a collaborative work between mathematicians and mathematics education researchers (Maths à Modeler Research Federation) through the Research Situations for the Classrooms
Extremely Broad Lyα Line Emission from the Molecular Intragroup Medium in Stephan’s Quintet: Evidence for a Turbulent Cascade in a Highly Clumpy Multiphase Medium?
No full textInternational audienceWe present Hubble Space Telescope Cosmic Origin Spectrograph (COS) UV line spectroscopy and integral-field unit (IFU) observations of the intragroup medium in Stephan's Quintet (SQ). SQ hosts a 30 kpc long shocked ridge triggered by a galaxy collision at a relative velocity of 1000 km s −1 , where large amounts of molecular gas coexist with a hot, X-ray-emitting, plasma. COS spectroscopy at five positions sampling the diverse environments of the SQ intragroup medium reveals very broad (≈2000 km s −1) Lyα line emission with complex line shapes. The Lyα line profiles are similar to or much broader than those of Hβ, [C II]157.7 μm, and CO (1-0) emission. The extreme breadth of the Lyα emission, compared with Hβ, implies resonance scattering within the observed structure. Scattering indicates that the neutral gas of the intragroup medium is clumpy, with a significant surface covering factor. We observe significant variations in the Lyα/Hβ flux ratio between positions and velocity components. From the mean line ratio averaged over positions and velocities, we estimate the effective escape fraction of Lyα photons to be ≈10%-30%. Remarkably, over more than four orders of magnitude in temperature, the powers radiated by X-rays, Lyα, H 2 , and [C II] are comparable within a factor of a few, assuming that the ratio of the Lyα to H 2 fluxes over the whole shocked intragroup medium stay in line with those observed at those five positions. Both shocks and mixing layers could contribute to the energy dissipation associated with a turbulent energy cascade. Our results may be relevant for the cooling of gas at high redshifts, where the metal content is lower than in this local system, and a high amplitude of turbulence is more common. Unified Astronomy Thesaurus concepts: Galaxy groups (597); Hickson compact group (729); Galaxy mergers (608); Galaxy interactions (600); Interacting galaxies (802); Intergalactic medium phases (814); Intergalactic medium (813); Cool intergalactic medium (303); Galaxy evolution (594); Galaxy processes (614); Galaxy quenching (2040); Interstellar dust (836
Des chercheurs pour former les enseignants aux démarches d'investigation: une analyse des difficultés rencontrées par le programme Savanturiers
No full textBrève histoire de la relégation des femmes en Guyane et en Nouvelle-Calédonie
No full textTexte publié dans un catalogue d'exposition