The Dwarf Spheroidal Companions to M31: WFPC2 Observations of Andromeda I

Images have been obtained with the Hubble Space Telescope WFPC2 camera of Andromeda I, a dwarf spheroidal (dSph) galaxy that lies in the outer halo of M31. The resulting color-magnitude diagrams reveal for the first time the morphology of the horizontal branch in this system. We find that, in a similar fashion to many of the galactic dSph companions, the horizontal branch (HB) of And~I is predominantly red. Combined with the metal abundance of this dSph, this red HB morphology indicates that And I can be classified as a ``second parameter'' system in the outer halo of M31. This result then supports the hypothesis that the outer halo of M31 formed in the same extended chaotic manner as is postulated for the outer halo of the Galaxy.Comment: 26 pages using aas2pp4.sty, including 2 tables and 7 figures, to be published in AJ. Figure 1 is in gif form. To include in main ps file, use xv to create a ps file called Da_Costa.fig1.ps and uncomment appropriate lines in .tex fil

Pesquisa sobre o Ensino de Música em Escolas Públicas Municipais do Litoral do Rio Grande do Sul

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Vectorisation paramétrée des données textuelles

International audienceAutomatic processing of textual data enables users to analyze semi-automatically and on a large scale the data. This analysis is based on two successive processes: (i) representation of texts, (ii) gathering of textual data (clustering). The software described in this paper focuses on the first step of the process by offering expert a parameterized representation of textual data

TiO2/clay as a heterogeneous catalyst in photocatalytic/photochemical oxidation of anionic reactive blue 19

AbstractA TiO2-coated Tunisian clay (TiO2–clay) was synthesized by a typical impregnation method. The physicochemical characterization points to a successful impregnation of titania on the clay surface. The activity of this structured catalyst was studied in the photocatalytic/photochemical oxidation of anionic reactive blue 19 (RB 19). The effect of UVA and solar irradiation (UV-solar) was studied at room temperature. TiO2–clay demonstrated an effective degradation of RB 19 under both types of irradiation. Moreover, in this study, the effects of various oxidants such as hydrogen peroxide (H2O2), potassium peroxodisulfate (K2S2O8) and sodium carbonate (Na2CO3) were thoroughly investigated. H2O2 was a promising oxidant for promoting RB 19 degradation under UVA. The kinetics of discoloration of RB 19 followed a pseudo-first-order rate law. We can remark that 20min of UV irradiation was enough to achieve 100% discoloration of the aqueous solution. However, under UV–Vis, HPLC and chemical oxygen demand measurements indicated, that a longer reaction time (of around 45min) was required for achieving the complete dye mineralization. The findings clearly demonstrated the applicability of this TiO2/clay catalyst for the photocatalytic oxidation of RB 19

Structural features of pyrocarbon atomistic models constructed from transmission electron microscopy images

International audienceWe report on atomistic models of laminar pyrocarbons constructed using a combination of 2D high resolution transmission electron microscopy (HRTEM) lattice fringe image analysis, 3D image synthesis and atomistic simulated annealing. In a first step, the effectiveness of the method and the convergence of the models with respect to the quench rate are checked on small systems. Then, the nanostructural features of large fully carbonaceous atomistic models obtained from the HRTEM images of a rough laminar pyrocarbon, asprepared and after partial graphitization, are discussed. Both models show a very pronounced sp2 character (≥ 97%), essentially made of hexagonal rings (≥ 88%) and pentagonal and heptagonal rings in similar amounts (≈ 6%). The latter mostly form pentagon-heptagon pairs or networks of line defects between misoriented hexagonal domains. Numerous pairs of screw dislocations, connecting different graphene domains, are also observed while edge dislocations with unsaturated carbon atoms are almost absent. The models are validated with respect to experimental pair distribution functions, showing excellent agreement

Behavior assessment of asymmetrical building with concrete damage plasticity (CDP) under seismic load

According to the research conducted, the asymmetric multi-storey buildings are complex and suffer from severe damage caused by increased torsional response. This paper addresses the behavior assessment of setback building with irregularity in the plan under severe seismic event such as Kobe earthquake. Using three-dimensional model, the structure is subjected to seismic waves in the three directions through ground accelerations. Nonlinear dynamic procedures have been used by means time-history analysis method. The mechanical model describes physical nonlinear behavior with damage and plasticity showing the regions of cracking propagation, mainly the columns-beams connections and the whole column as well, corroborating the weak column and strong beam concept. The slabs did not present significant failures despite indicating damage regions on the borders of the first floors

Prédiction de la structure et des propriétés de pyrocarbones à partir d'une reconstruction à l'échelle atomique

National audienceNous présentons ici une approche originale permettant de construire des modèles à l'échelle atomique de matériaux nanotexturés à partir de leurs images de Microscopie Electronique en Transmission à Haute Résolution (HRTEM). Partant d'une image HRTEM filtrée à hautes et basses fréquences (a), un ensemble de descripteurs statistiques est collecté puis imposé à une synthèse d'image 3D aléatoire (b). Cette dernière est ensuite utilisée comme champ de potentiel attirant les atomes sur les franges lors d'une simulation de trempe d'un liquide de carbone par dynamique moléculaire (c). Une simulation d'image HRTEM à partir du matériau virtuel obtenu permet de valider la qualité de la reconstruction (d). Nous présentons en détail cette méthode ainsi que la structure et les propriétés mécaniques calculées pour des pyrocarbones laminaires rugueux, tels que préparés et traités thermiquement

Atomistic models of pyrolytic carbons obtained with the IGAR method

International audienceThis study aims at obtaining atomistic representations of these RL and ReL pyCs and at describing their nano-texture/structure. We will first describe some improvements in the IGAR method. Then, the nature of defects in these materials, in terms of non-hexagonal rings and screw dislocations, as well as their hydrogen atoms contents and locations, will be thoroughly compared and discussed. These models will also be validated against experimental HRTEM images and pair distribution functions (PDF) (and structure factors) obtained from neutron diffraction