New circumstellar dust component in oxygen rich environments

Spectra of oxygen rich stars in the IRAS low-resolution spectra (LRS) catalog were found to display two distinct classes of curcumstellar excess emission. The first group has the normal silicate with emission peaking at 10 and 18 microns. The second group has an emission spectrum peaking at 13 and 20 microns. There are also spectra with a mixture of the above types. Generally the continuum temperature associated with the second group is much warmer than that associated with the normal silicate group. Laboratory spectra are compared with the new excess which associates the emission with a class of materials represented by hydrated aluminates and silicates. Possible interpretations include equilibrium condensation sequences and peculiar metal abundance ratios

Carbon stars with alpha-C:H emission

Many carbon stars in the IRS low resolution spectra (LRS) catalog were found which display emission spectra that compare favorable with the absorption spectrum of alpha-C:H. These stars have largely been classified as 4X in the LRS which has led to their interpretation by others in terms of displaying a mixture of the UIRF's 8.6 micron band and SiC at 11.5 microns. It was also found that many of these stars have a spectral upturn at 20+ microns which resembles the MgS band seen in carbon stars and planetary nebulae. It was concluded that this group of carbon stars will evolve into planetary nebulae like NGC 7027 and IC 418. In the presence of hard ultraviolet radiation the UIRF's will light up and be displayed as narrow emission bands on top of the broad alpha-C:H emission bands

Localisation, traduction et diversité sociolinguistique en Afrique sub-saharienne : stratégies et perspectives

Pour les langues d’Afrique sub-saharienne, localisation et traduction interviennent dans un double jeu de contraintes linguistiques et sociolinguistiques et font face à deux tendances parfois conflictuelles : la mondialisation, d’une part, et les politiques déclarées de promotion de la diversité linguistique, d’autre part. En nous focalisant sur les pratiques s’appuyant sur les technologies de l’information, à la fois outils de la localisation et de la traduction en langues africaines et moyens de développement de celles-ci, nous présenterons les problèmes liés à ces activités et exposerons comment ces activités s’organisent et se déploient dans le contexte actuel. Nous ferons état de la présence des langues africaines sub-sahariennes dans les environnements numériques et proposerons une analyse de la dynamique de la traduction où s’articulent des processus et des pratiques qui agissent selon deux axes, l’un de facilitation et l’autre de complexification.Localization and translation for languages of sub-Saharan Africa are done within a double set of linguistic and sociolinguistic constraints, and they face two often conflicting trends, on the one hand globalization, and on the other hand the declared policies of promotion of language diversity. I will focus on the area of information technologies, which are both the tools for localization and translation in African languages and the means for developing them. I will present the problems encountered in translation and localization activities, and how these activities develop in the present context. I will review the presence of African languages in digital environments and propose an analysis of the dynamics of translation in which processes and practices interact along two axes, facilitation and complexification

At what stress level is the central Indian Ocean lithosphere buckling?

Internal contrasts in strength are responsible for lithospheric buckling. These are quantified by comparing the Indian Ocean data to two-dimensional visco-elasto-plastic numerical models where the material properties depend on temperature and pressure. The central Indian Basin is known for its intraplate seismicity and long wavelength undulations of the sea floor and associated gravity signatures. To simulate the amplitudes of undulations that reach 1 km within about 11 Ma of compression and 60 km of shortening, the required mean yield strength of the lithosphere is 400 MPa. If either a hydrostatic fluid pressure is considered in the crust or a mechanical decoupling at the depth of the Moho, small crustal wavelengths are superimposed on the long wavelength deformation, in agreement with observations. It is then possible to match the alternative indication that buckling commenced only 4 Ma ago, with a total amount of shortening of 30 km, and with a required yield strength of 200 MPa. About 10% of homogeneous thickening accompanies buckling. Taking into account variable thermal conductivity demonstrates that a change in the geotherm is sufficient to increase buckling amplitudes by 10% within 5 Ma

Régionalisation de l'effet fondateur au Québec

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

The 11 Micron Emissions of Cabon Stars

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing CIO resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this 11.9 micron emission feature to the 11.3 micron feature

Une bibliothèque Art déco

La bibliothèque Carnegie, véritable joyau de l’architecture Art déco, fait aujourd’hui la fierté de Reims. Depuis son inauguration en 1928, les brochures touristiques n’ont cessé d’attirer l’attention sur la majesté de ses dimensions et le luxe de ses décors. En même temps, le bâtiment a toujours suscité un vif intérêt chez les architectes et les bibliothécaires, intérêt relayé dans la presse spécialisée et toujours vivace aujourd’hui. Il faut dire que cette bibliothèque a parfaitement su rép..

The 11 Micron Emissions of Carbon Stars

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing C/O resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this 11.9 micron emission feature to the 11.3 micron feature