Gas-phase oxygen abundances and radial metallicity gradients in the two nearby spiral galaxies NGC7793 and NGC4945

Gas-phase abundances in HII regions of two spiral galaxies, NGC7793 and NGC4945, have been studied to determine their radial metallicity gradients. We used the strong-line method to derive oxygen abundances from spectra acquired with GMOS-S, the multi-object spectrograph on the 8m- Gemini South telescope. We found that NGC7793 has a well-defined gas-phase radial oxygen gradient of -0.321 $\pm$ 0.112 dex R$_{\rm 25}^{-1}$ (or -0.054 $\pm$ 0.019 dex kpc$^{-1}$) in the galactocentric range 0.17$<$R$_{\rm G}$/R$_{\rm 25}$ $<$ 0.82, not dissimilar from gradients calculated with direct abundance methods in galaxies of similar mass and morphology. We also determined a shallow radial oxygen gradient in NGC4945, -0.253 $\pm$ 0.149 dex R$_{\rm 25}^{-1}$ (or -0.019 $\pm$ 0.011 dex kpc$^{-1}$) for 0.04$<$R$_{\rm G}$/R$_{\rm 25}$ $<$ 0.51, where the larger relative uncertainty derives mostly from the larger inclination of this galaxy. NGC7793 and NGC4945 have been selected for this study because they are similar, in mass and morphology, to M33 and the Milky Way, respectively. Since at zeroth order we expect the radial metallicity gradients to depend on mass and galaxy type, we compared our galaxies in the framework of radial metallicity models best suited for M33 and the Galaxy. We found a good agreement between M33 and NGC7793, pointing toward similar evolution for the two galaxies. We notice instead differences between NGC4945 and the radial metallicity gradient model that best fits the Milky Way. We found that these differences are likely related to the presence of an AGN combined with a bar in the central regions of NGC4945, and to its interacting environment.Comment: ApJ, in pres

The radial metallicity gradient and the history of elemental enrichment in M81 through emission-line probes

We present a new set of weak-line abundances of HII regions in M81, based on Gemini Multi-Object Spectrograph (GMOS) observations. The aim is to derive plasma and abundance analysis for a sizable set of emission-line targets to study the galactic chemical contents in the framework of galactic metallicity gradients. We used the weak-line abundance approach by deriving electron density and temperatures for several HII regions in M81. Gradient analysis is based on oxygen abundances.Together with a set of HII region abundances determined similarly by us with Multi-Mirror Telescope (MMT) spectra, the new data yield to a radial oxygen gradient of -0.088$\pm$0.013 dex kpc$^{-1}$, which is steeper than the metallicity gradient obtained for planetary nebulae (-0.044$\pm$0.007 dex kpc$^{-1}$). This result could be interpreted as gradient evolution with time: Models of galactic evolution with inside-out disk formation associated to pre-enriched gas infall would produce such difference of gradients, although stellar migration effects would also induce a difference in the metallicity gradients between the old and young populations. By comparing the M81 metallicity gradients with those of other spiral galaxies, all consistently derived from weak-line analysis, we can infer that similar gradient difference is common among spirals. The metallicity gradient slopes for HII regions and PNe seem to be steeper in M81 than in other galactic disks, which is likely due to the fact that M81 belongs to a galaxy group. We also found that M81 has experienced an average oxygen enrichment of 0.14$\pm$0.08 dex in the spatial domain defined by the observations. Our data are compatible with a break in the radial oxygen gradient slope around R$_{25}$ as inferred by other authors both in M81 and in other galaxies.Comment: Astronomy and Astrophysics, in pres

The New Spectatorship. Hacia una relación dinámica entre el espectador y la obra / The New Spectatorship. Towards a Dynamic Relationship between Viewer and Artwork

La base de este ensayo visual es la obra de Luc Huijbregts, que fue mostrada en la sala de exposiciones “Espacio de Arte” en La Casa del Siglo XV de Segovia (España) durante el verano de 2007. El espectador se encuentra a sí mismo en un espacio-proceso que desmantela la distancia convencional que le separa de la obra de arte. Al entrar en la exposición, un lienzo de Nisa Goiburu, integra todo el entorno “profano”. Más adelante, el espectador llega a una serie de obras tridimensionales. Mediante el uso del suelo como base, invitan a su participación activa, contrariamente a lo que sucede con los pedestales convencionales. El espectador no queda confinado a un espacio inferior. Fotografías de Marie-Christine NoëlThe New Spectatorship. Towards a Dynamic Relationship between Viewer and ArtworkThe foundation of this visual essay is the work of Luc Huijbregts, displayed at the showroom “Espacio de Arte” at La Casa del Siglo XV in Segovia (Spain) during the summer of 2007. The viewer finds himself in a process which dismantles the conventional distance separating him from the artwork. As he enters the exhibit, a canvas on display integrates its “profane” surroundings. Further along, the viewer comes to a series of threedimensional works. By using the floor as a base, they invite his participation instead of precluding it, as would a conventional pedestal: the viewer is no longer confined to a lower space. Photographs by Marie-Christine Noë

Hypokalemic rhabdomyolysis: a rare manifestation of primary aldosteronism

Rhabdomyolysis is a rare presentation of hypokalemia, although muscle weakness is a well-known manifestation of hypokalemia. Primary aldosteronism is characterized by hypertension, suppressed plasma renin activity, increased aldosterone excretion and hypokalemia with metabolic alkalosis. Rhabdomyolysis is not common in primary aldosteronism. We present here a 40-year-old woman presenting with rhabdomyolysis accompanied by severe hypokalemia as heralding symptom of primary aldosteronism

Diffusion limit of langevin pdf models in weakly inhomogeneous turbulence

In this work, we discuss the modelling of transport in Langevin probability density function (PDF) models used to predict turbulent flows. Our focus is on the diffusion limit of these models, i.e. when advection and dissipation are the only active physical processes. In this limit, we show that Langevin PDF models allow for an asymptotic expansion in terms of the ratio of the integral length to the mean gradient length. The main contribution of this expansion yields an evolution of the turbulent kinetic energy equivalent to that given by a k-epsilon model. In particular, the transport of kinetic energy is given by a gradient diffusion term. Interestingly, the identification between PDF and k-epsilon models raises a number of questions concerning the way turbulent transport is closed in PDF models. In order to validate the asymptotic solution, several numerical simulations are performed.Dans cet article, nous abordons la question de la modélisation du transport turbulent dans les modèles de turbulence basés sur les fonctions de densité de probabilité (PDF). Nous étudions la limite diffusive de ces modèles obtenue lorsque l'advection et la dissipation sont les seuls processus physiques actifs. Dans cette limite, nous montrons que les modèles PDF donnent lieu à un développement asymptotique selon un petit paramètre correspondant au rapport de l'échelle intégrale sur l'échelle du gradient moyen. La contribution principale de ce développement s'identifie avec un modèle k-epsilon classique. En particulier, le transport de l'énergie turbulente est donné par une diffusion en premier gradient. L'identification entre modèle k-epsilon et modèle PDF permet de soulever un certain nombre de questions sur la manière dont le transport est modélisé dans les approches PDF. La solution asymptotique est validée par des simulations numériques réalisées à l'aide d'un code Monte Carlo mais aussi d'un code déterministe

Semaine d'Etude Mathématiques et Entreprises 4 : Planification optimale de production d'énergie sous contraintes technologiques

Ce papier est une synthèse de notre travail de recherche durant la quatrième SEME (Semaine d'Etudes pour les Mathématiques en Entreprise), à l'Institut Henri Poincaré. L'objectif était de trouver une méthode pour approcher au mieux une courbe de consommation d'énergie anticipée sous des contraintes technologiques (par exemple le fait que les machines mettent du temps à changer de niveau de productivité, ou mettent parfois un temps incompressible minimal à se relancer si elles ont arrêté de produire. Nous proposons deux approches complémentaires : la première est inspirée de la théorie du contrôle optimal et la seconde s'appuie sur l'analyse convexe

Peroxynitrite activates the NLRP3 inflammasome cascade in SOD1(G93A) mouse model of amyotrophic lateral sclerosis

Neuroinflammation, characterized by the appearance of reactive microglial and astroglial cells, is one of the several pathogenic mechanisms of amyotrophic lateral sclerosis (ALS), a fast-progressing and fatal neurodegenerative disease. Cerebrospinal fluid and spinal cord of ALS patients and SOD1 mutant mice show high concentrations of IL-1β. This interleukin, expressed as an inactive precursor, undergoes a proteolytic maturation by caspase1, whose activation, in turn, depends on inflammasomes. Whether and how inflammasome is activated in ALS models is still to be clarified. The mechanism of inflammasome activation was studied in murine microglial cells overexpressing hSOD1(G93A) and verified in the spinal cord of hSOD1(G93A) mice. Murine microglial hSOD1(G93A) cells express all the inflammasome components and LPS activates caspase1 leading to an increase in the secretion of IL-1β. By activating NF-κB, LPS increases ROS and NO levels that spontaneously react to form peroxynitrite, thus leading to protein nitration. Reduction in peroxynitrite levels results in a decrease in caspase1 activity. Protein nitration and caspase1 activity are concomitantly increased in the spinal cord of pre-symptomatic SOD1(G93A) mice. Oxidative/nitrosative stress induces peroxynitrite formation that may be a key trigger of caspase1/inflammasome activation. Peroxynitrite formation may play a critical role in inflammasome activation and might be exploited as potential therapeutic target for ALS

Quantification of Small Non-Coding RNAs Allows an Accurate Comparison of miRNA Expression Profiles

MicroRNAs (miRNAs) are highly conserved ∼22-mer RNA molecules, encoded by plants and animals that regulate the expression of genes binding to the 3′-UTR of specific target mRNAs. The amount of miRNAs in a total RNA sample depends on the recovery efficiency that may be significantly affected by the different purification methods employed. Traditional approaches may be inefficient at recovering small RNAs, and common spectrophotometric determination is not adequate to quantify selectively these low molecular weight (LMW) species from total RNA samples. Here, we describe the use of qualitative and quantitative lab-on-a-chip tools for the analysis of these LMW RNA species. Our data emphasize the close correlation of LMW RNAs with the expression levels of some miRNAs. We therefore applied our result to the comparison of some miRNA expression profiles in different tissues. Finally, the methods we used in this paper allowed us to analyze the efficiency of extraction protocols, to study the small (but significant) differences among various preparations and to allow a proper comparison of some miRNA expression profiles in various tissues