A perspective from extinct radionuclides on a Young Stellar Object: The Sun and its accretion disk

Meteorites, which are remnants of solar system formation, provide a direct glimpse into the dynamics and evolution of a young stellar object (YSO), namely our Sun. Much of our knowledge about the astrophysical context of the birth of the Sun, the chronology of planetary growth from micrometer-sized dust to terrestrial planets, and the activity of the young Sun comes from the study of extinct radionuclides such as 26Al (t1/2 = 0.717 Myr). Here we review how the signatures of extinct radionuclides (short-lived isotopes that were present when the solar system formed and that have now decayed below detection level) in planetary materials influence the current paradigm of solar system formation. Particular attention is given to tying meteorite measurements to remote astronomical observations of YSOs and modeling efforts. Some extinct radionuclides were inherited from the long-term chemical evolution of the Galaxy, others were injected into the solar system by a nearby supernova, and some were produced by particle irradiation from the T-Tauri Sun. The chronology inferred from extinct radionuclides reveals that dust agglomeration to form centimeter-sized particles in the inner part of the disk was very rapid (<50 kyr), planetesimal formation started early and spanned several million years, planetary embryos (possibly like Mars) were formed in a few million years, and terrestrial planets (like Earth) completed their growths several tens of million years after the birth of the Sun.Comment: 49 pages, 9 figures, 1 table. Uncorrected preprin

Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Identification of Mycobacteria in Routine Clinical Practice

Background: Non-tuberculous mycobacteria recovered from respiratory tract specimens are emerging confounder organisms for the laboratory diagnosis of tuberculosis worldwide. There is an urgent need for new techniques to rapidly identify mycobacteria isolated in clinical practice. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) has previously been proven to effectively identify mycobacteria grown in high-concentration inocula from collections. However, a thorough evaluation of its use in routine laboratory practice has not been performed. Methodology: We set up an original protocol for the MALDI-TOF MS identification of heat-inactivated mycobacteria after dissociation in Tween-20, mechanical breaking of the cell wall and protein extraction with formic acid and acetonitrile. By applying this protocol to as few as 10 5 colony-forming units of reference isolates of Mycobacterium tuberculosis, Mycobacterium avium, and 20 other Mycobacterium species, we obtained species-specific mass spectra for the creation of a local database. Using this database, our protocol enabled the identification by MALDI-TOF MS of 87 M. tuberculosis, 25M. avium and 12 non-tuberculosis clinical isolates with identification scores $2 within 2.5 hours. Conclusions: Our data indicate that MALDI-TOF MS can be used as a first-line method for the routine identification of heatinactivated mycobacteria. MALDI-TOF MS is an attractive method for implementation in clinical microbiology laboratories i

Occurrence of noble metals in aluminum- and chromium- rich objects in ordinary chondrites and of baddeleyite (ZrO2) in a chromite inclusion

International audienc

Thème 1. Les nouvelles logiques des disparités spatiales, le rôle du tertiaire. Discussion sur les communications de P. George, B. Belloc, J. Dumas-R. Pierron

Pierron Robert, Elbaum Mireille, Noin Daniel, Levy M. L., Burgel Guy, Terrier Christophe, Jayet M., Laget Michel, George Pierre, Le Sage G., Pailhé Joël. Thème 1. Les nouvelles logiques des disparités spatiales, le rôle du tertiaire. Discussion sur les communications de P. George, B. Belloc, J. Dumas-R. Pierron . In: Espace, populations, sociétés, 1988-3. La population face à l'emploi - Population and work opportunities. pp. 467-469

Basaltic asteroids in the Near-Earth Objects population: a mineralogical analysis

7 pages.[Aims] We present reflectance spectra of three V-type Near-Earth Objects obtained at the 3.6 m Telescopio Nazionale Galileo and at the 2.5 m Nordic Optical Telescope covering the near-infrared and visible range, respectively. The range from 0.5 to 2.5 m, encompassing the 1 and 2 m pyroxene features, allows a mineralogical characterization of these asteroids.[Methods] A preliminary analysis using the classical methods has been applied to establish some constraints on the surface mineralogy of these objects. Then, the Modified Gaussian Method was applied to gain further insight on the possible mineral components present in the surface of the objects.[Results] The comparison between these basaltic asteroids in near Earth orbits and the achondrite basaltic meteorites shows a quite clear mineralogical link, corroborating the long-standing hypothesis of the Near-Earth Objects population as the immediate source of these meteorites.Peer reviewe