Simulations of magnetized multiphase galactic disk regulated by supernovae explosions

What exactly controls star formation in the Galaxy remains controversial. In particular, the role of feedback and magnetic field are still partially understood. We investigate the role played by supernovae feedback and magnetic field onto the star formation and the structure of the Galactic disk. We perform numerical simulations of the turbulent, magnetized, self-gravitating, multi-phase, supernovae regulated ISM within a 1 kpc stratified box. We implemented various schemes for the supernovae. This goes from a random distribution at a fixed rate to distributions for which the supernovae are spatially and temporally correlated to the formation of stars. To study the influence of magnetic field on star formation, we perform both hydrodynamical and magneto-hydrodynamical simulations. We find that supernovae feedback has a drastic influence on the galactic evolution. The supernovae distribution is playing a very significant role. When the supernovae are not correlated with star formation events, they do not modify significantly the very high star formation rate obtained without feedback. When the supernovae follow the accretion, the star formation rate can be reduced by a factor up to 30. Magnetic field is also playing a significant role. It reduces the star formation rate by a factor up to 2-3 and reduces the number of collapse sites by a factor of about 2. The exact correlation between the supernovae and the dense gas appears to have significant consequences on the galactic disk evolution and the star formation. This implies that small scale studies are necessary to understand and quantify the feedback efficiency. Magnetic field does influence the star formation at galactic scales by reducing the star formation rate and the number of star formation sites.Comment: to be published in A&

Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate

In diffuse interstellar clouds the chemistry that leads to the formation of the oxygen bearing ions OH+, H2O+, and H3O+ begins with the ionization of atomic hydrogen by cosmic rays, and continues through subsequent hydrogen abstraction reactions involving H2. Given these reaction pathways, the observed abundances of these molecules are useful in constraining both the total cosmic-ray ionization rate of atomic hydrogen (zeta_H) and molecular hydrogen fraction, f(H2). We present observations targeting transitions of OH+, H2O+, and H3O+ made with the Herschel Space Observatory along 20 Galactic sight lines toward bright submillimeter continuum sources. Both OH+ and H2O+ are detected in absorption in multiple velocity components along every sight line, but H3O+ is only detected along 7 sight lines. From the molecular abundances we compute f(H2) in multiple distinct components along each line of sight, and find a Gaussian distribution with mean and standard deviation 0.042+-0.018. This confirms previous findings that OH+ and H2O+ primarily reside in gas with low H2 fractions. We also infer zeta_H throughout our sample, and find a log-normal distribution with mean log(zeta_H)=-15.75, (zeta_H=1.78x10^-16 s^-1), and standard deviation 0.29 for gas within the Galactic disk, but outside of the Galactic center. This is in good agreement with the mean and distribution of cosmic-ray ionization rates previously inferred from H3+ observations. Ionization rates in the Galactic center tend to be 10--100 times larger than found in the Galactic disk, also in accord with prior studies.Comment: 76 pages, 25 figures, 6 tables; accepted for publication in Ap

Catholics, Curses, and Cousins in a Cracker Box

In a small sitting room of a mortuary in a rural Missouri town, the author considers the life of her recently departed cousin. Having shared a family home early in their childhood, and despite similar upbringing, their lives had ultimately diverged, with him choosing a path that many would consider self-destructive and bound to lead to an early death. Contemplating the circumstances of her cousin\u27s death, the author falls into ruminations on their childhood, family, and common experiences they shared during those early years. Considering the disparate paths their lives ultimately took, the author questions the influence of nature versus nurture in determining their life choices. She questions common thinking that the life lived most productively is the most successful. The memoir provides no decisive answer to either question; makes no attempt to do so. But the occasion of the memorial service opens a wellspring of memories of her cousin and his brother and sisters, and the early life they shared with the author and her sister in their most formative years. In this personal memoir, the author recounts experiences of her childhood in a South St. Louis neighborhood where she, her mother, father, and sister shared a two-family flat with her dad\u27s brother and his family. Their home was a bastion of fundamental Protestant Christianity in a neighborhood of Catholic characters who provided social education for the cousins beyond anything they ever learned in Sunday school. The memoir offers the reader a slice-of-life taste of a more innocent time: an age when children still played outdoors instead of in front of video games; when families - moms, dads, grandparents, aunts, uncles, and the children - all gathered on porches with cool, sweet lemonade on hot summer nights, and passed down stories with language more colorful and entertaining than any television program could have offered. And, remembering these years, the author identifies influences contributing to her love of writing and the role it has played in her life

Mutual influence of supernovae and molecular clouds

Context. Molecular clouds are known to be turbulent and strongly affected by stellar feedback. Moreover, stellar feedback is believed to drive turbulence at large scales in galaxies. Aims. We study the role played by supernovae in molecular clouds and the influence of the magnetic field on this process. Methods. We performed three-dimensional numerical simulations of supernova explosions, in and near turbulent self-gravitating molecular clouds. In order to study the influence of the magnetic field, we performed both hydrodynamical and magnetohydrodynamical simulations. We also ran a series of simple uniform density medium simulations and developed a simple analytical model. Results. We find that the total amount of momentum that is delivered during supernova explosions typically varies by a factor of about 2, even when the gas density changes by 3 orders of magnitude. However, the amount of momentum delivered to the dense gas varies by almost a factor of 10 if the supernova explodes within or outside the molecular cloud. The magnetic field has little influence on the total amount of momentum injected by the supernova explosions but increases the momentum injected into the dense gas. Conclusions. Supernovae that explode inside molecular clouds remove a significant fraction of the cloud mass. Supernovae that explode outside have a limited influence on the cloud. It is thus essential to know sufficiently well the correlation between supernovae and the surrounding dense material in order to know whether supernovae can regulate star formation effectively.Comment: 12 pages, 14 figures, to be published in A&

A filtered database search algorithm for endogenous serum protein carbonyl modifications in a mouse model of inflammation

During inflammation, the resulting oxidative stress can damage surrounding host tissue, forming protein-carbonyls. The SJL mouse is an experimental animal model used to assess in vivo toxicological responses to reactive oxygen and nitrogen species from inflammation. The goals of this study were to identify the major serum proteins modified with a carbonyl functionality and to identify the types of carbonyl adducts. To select for carbonyl-modified proteins, serum proteins were reacted with an aldehyde reactive probe that biotinylated the carbonyl modification. Modified proteins were enriched by avidin affinity and identified by two-dimensional liquid chromatography tandem MS. To identify the carbonyl modification, tryptic peptides from serum proteins were subjected to avidin affinity and the enriched modified peptides were analyzed by liquid chromatography tandem MS. It was noted that the aldehyde reactive probe tag created tag-specific fragment ions and neutral losses, and these extra features in the mass spectra inhibited identification of the modified peptides by database searching. To enhance the identification of carbonyl-modified peptides, a program was written that used the tag-specific fragment ions as a fingerprint (in silico filter program) and filtered the mass spectrometry data to highlight only modified peptides. A de novo-like database search algorithm was written (biotin peptide identification program) to identify the carbonyl-modified peptides. Although written specifically for our experiments, this software can be adapted to other modification and enrichment systems. Using these routines, a number of lipid peroxidation-derived protein carbonyls and direct side-chain oxidation proteins carbonyls were identified in SJL mouse serum.National Institutes of Health (U.S.) (NCI Program Project Grant CA26731)Massachusetts Institute of Technology. Center for Environmental Health Sciences (NIEHS grant P30 ES002109

L’apprentissage transfrontalier France/Allemagne, à l’aune de l’action publique locale alsacienne

L’article aborde les systèmes d’apprentissage français et allemand, à l’aune des politiques publiques alsaciennes, et plus particulièrement « l’apprentissage transfrontalier ». Sont analysées les représentations et les pratiques des acteurs locaux, français et allemands, impliqués dans le dispositif. À l’intersection de débats nationaux et européens autour de l’apprentissage, la politique transfrontalière de formation professionnelle révèle ainsi comment la comparaison est mobilisée par l’action publique. In fine, il ressort que, malgré la mobilisation des pouvoirs publics, l’apprentissage transfrontalier demeure un parcours d’exception.This article approaches apprenticeship in France and Germany through the analyse of local public policies in Alsace (France), and especially the program of “cross-border apprenticeship”. Local French and German stakeholders’ practices and representations will be analysed, in order to examine to what extend the comparison between both national systems shapes public action. Indeed, cross-border vocational training policy is at the intersection of discourses and tools from local, national and European levels of public action. It appears that, despite the mobilization of public stakeholders, cross-border apprenticeship remains an unusual experience.Anhand einer soziologischen Analyse von Lokalpolitik im Elsass (Frankreich) – bzw. des Programms der „Grenzüberschreitenden Ausbildung“, bietet dieser Artikel einen Einblick in das französische und deutsche Ausbildungssystem. Die nationale und die europäische Debatte verknüpfend, zeigt die grenzüberschreitende Berufsbildungspolitik, wie öffentliche Stakeholder den Vergleich in ihren Praktiken und Repräsentationen mobilisieren. Es zeigt sich, dass trotz des Engagements der Behörden die grenzüberschreitende Ausbildung ein Ausnahmeweg bleibt.El artículo analiza los sistemas de aprendizaje francés y alemán, a la luz de las políticas públicas en Alsacia, y más particularmente el « aprendizaje transfronterizo ». Se analizan las representaciones y prácticas de los actores locales, franceses y alemanes, involucrados en el dispositivo. En la intersección de los debates nacionales y europeos en torno al aprendizaje, la política de formación profesional transfronteriza revela así cómo la acción pública utiliza la comparación. Finalmente, se observa que, a pesar de la movilización de los poderes públicos, el aprendizaje transfronterizo sigue siendo un itinerario fuera de lo común

Influence de la rétroaction des étoiles sur la structure du milieu interstellaire à l'échelle galactique

Star formation, a fundamental process in astrophysics, remains only partially understood. Several processes are known to interact during all the steps over a large range of scales. It is therefore of highest importance to understand the dynamics of the interstellar medium, in which stars form. In particular, it is now well-known that the structure of the interstellar medium is strongly affected by feedback processes emanating from the stars that form in it. On the one hand this feedback limits the rate of formation of new stars, and on the other hand it is one of the main contributors to the shape and dynamics of galaxies: thickness of the disk, matter outflows, etc. This work aims to study numerically the dynamics of the interstellar medium, in order to highlight the impact of stellar feedback processes. The main process that will be studied is supernovae, being among the most energetic events in the interstellar medium. After the study and detailed modeling of the explosion of a single supernova inside a molecular cloud, a numerical model including star formation and supernova feedback will be presented and used in kiloparsec-scale simulations of a stratified galactic disk. An extension of this model will be suggested in order to take into account the ionizing radiation. It is indeed possible to regulate star formation with supernova feedback models, although the precise results strongly depend on the detailed scheme that is implemented. Using the most realistic-looking variant, high-resolution simulations are presented and studied. In particular, it is possible to extract properties of compressible and magnetized turbulence at the galactic scale: variation of the power spectra as a function of altitude, spontaneous alignment between velocity and magnetic field, antagonistic effect of stellar feedback onto this alignment, and structure formation.La formation des étoiles, processus fondamental en astrophysique, résiste toujours à la compréhension. En effet, de nombreux phénomènes interagissent durant les différentes étapes, et ce sur une large gamme d’échelles. Il est donc primordial de comprendre la dynamique du milieu interstellaire, dans lequel les étoiles se forment. En particulier, il est maintenant bien établi que la structure du milieu interstellaire est fortement impactée par des processus de rétroaction de la part des étoiles qui s’y forment. D’une part cette rétroaction limite le taux de formation de nouvelles étoiles, et d’autre part elle est l’un des contributeurs à la morphologie et la dynamique des galaxies : taille du disque, éjection de matière, etc. Ce travail de thèse propose d’étudier numériquement la dynamique du milieu interstellaire, de manière à mettre en évidence l’impact des processus de rétroaction. Le processus principal qui sera étudié est les supernovae, figurant parmi les évènements les plus énergétiques dans le milieu interstellaire. Après l’étude et la modélisation en détail de l’explosion d’une unique supernova dans nuage moléculaire, un modèle numérique incluant formation d’étoiles et rétroaction par supernovae sera présenté et mis en œuvre dans des simulations d’un disque galactique stratifié à l’échelle du kiloparsec. Une extension de ce modèle pour tenir compte du rayonnement ionisant sera proposée. Il est effectivement possible de réguler la formation d’étoiles à l’aide de modèles de rétroaction par les supernovae, mais les résultats précis dépendent de manière significative des détails du schéma mis en œuvre. En utilisant la variante apparaissant comme la plus réaliste, des simulations à haute résolution du milieu interstellaire sont présentées et étudiées. En particulier, il est possible de mettre en évidence des propriétés de la turbulence compressible et magnétisée à l’échelle galactique : variation des spectres de puissance en fonction de l’altitude, alignement spontané de la vitesse et du champ magnétique, effet antagoniste de la rétroaction sur cet alignement et formation de structures

Identités masculines, expression corporelle et éducation physique en France entre 1967 et 1985

Au cœur de la France des années 1970 marquée par une vague de bouleversements idéologiques et culturels, l’expression corporelle constitue une expérience novatrice et unique en Education Physique et Sportive (EPS) face à l’hégémonie du sport en EPS. Par son approche dérégulée, personnelle et émancipatrice, l’expression corporelle marque une rupture dans la gestion du corps des enfants scolarisés. Par son intermédiaire, les élèves ont ainsi accès à de nouvelles pratiques sollicitant le sensible et l’expressif. Cette conception de l’EPS bouleverse en outre la représentation de l’identité masculine de cette époque. Dominant, courageux, autoritaire et principalement reproduit par l’enseignement du sport, l’idéal masculin se trouve alors redéfini et remis en question. En dénonçant le caractère reproductif et inégalitaire du sport, les promoteurs de l’expression corporelle masculine visent non seulement à désacraliser le modèle patriarcal mais recherchent aussi l’émergence d’un nouvel idéal masculin, tourné vers plus d’émancipation et d’épanouissement. Au demeurant, les auteurs constatent l’émergence de nouvelles masculinités qu’ils qualifient de subordonnées voire marginalisées, et qui trouvent dans l’enseignement de l’expression corporelle un terrain inédit de prédilection. L’analyse exhaustive des revues professionnelles (Cahiers du GREC, Revue Esprit, Revue EP.S) et les entretiens de divers acteurs de l’expression corporelle (notamment JB. Bonange) permettent de mettre en évidence une prédominance des rapports sociaux de classe sur les rapports sociaux de genre, dans la mesure où l’expression corporelle émerge essentiellement en France dans les milieux favorisés tels que les universités, et ne parvient pas à se diffuser dans les milieux populaires, lieux de résistances d’une masculinité hégémonique traditionnelle