Paris: The slightly altered, slightly metamorphosed CM that bridges the gap between CMs and Cos

A fresh, 1.3 kilo stone was found in Paris. It is a CM chondrite with metal, Fe-sulfide, FeS-rich PCPs and relict mesostasis and is ~3.0 ± 0.1. Petrographic and oxygen isotope evidence indicates that it has affinities with the CO chondrites

The geochemistry of gem opals as evidence of their origin

International audienceSeventy-seven gem opals from ten countries were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) through a dilution process, in order to establish the nature of the impurities. The results are correlated to the mode of formation and physical properties and are instrumental in establishing the geographical origin of a gem opal. The geochemistry of an opal is shown to be dependant mostly on the host rock, at least for examples from Mexico and Brazil, even if modified by weathering processes. In order of decreasing concentration, the main impurities present are Al, Ca, Fe, K, Na, and Mg (more than 500 ppm). Other noticeable elements in lesser amounts are Ba, followed by Zr, Sr, Rb, U, and Pb. For the first time, geochemistry helps to discriminate some varieties of opals. The Ba content, as well as the chondritenormalized REE pattern, are the keys to separating sedimentary opals (BaN110 ppm, Eu and Ce anomalies) from volcanic opals (Bab110 ppm, no Eu or Ce anomaly). The Ca content, and to a lesser extent that of Mg, Al, K and Nb, helps to distinguish gem opals from different volcanic environments. The limited range of concentrations for all elements in precious (play-of-color) compared to common opals, indicates that this variety must have very specific, or more restricted, conditions of formation. We tentatively interpreted the presence of impurities in terms of crystallochemistry, even if opal is a poorly crystallized or amorphous material. The main replacement is the substitution of Si4+ by Al3+ and Fe3+. The induced charge imbalance is compensated chiefly by Ca2+, Mg2+, Mn2+, Ba2+, K+, and Na+. In terms of origin of color, greater concentrations of iron induce darker colors (from yellow to "chocolate brown"). This element inhibits luminescence for concentrations above 1000 ppm, whereas already a low content in U (=1 ppm) induces a green luminescence

Design of a nitrogen-implanted titanium-based superelastic alloy with optimized properties for biomedical applications

International audienceIn this study, a superelastic Ni-free Ti-based biomedical alloy was treated in surface by the implantation of nitrogen ions for the first time. The N-implanted surface was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and secondary ion mass spectroscopy, and the superficial mechanical properties were evaluated by nano-indentation and by ball-on-disk tribological tests. To investigate the biocompatibility, the corrosion resistance of the N-implanted Ti alloy was evaluated in simulated body fluids (SBF) complemented by in-vitro cytocompatibility tests on human fetal osteoblasts. After implantation, surface analysis methods revealed the formation of a titanium-based nitride on the substrate surface. Consequently, an increase in superficial hardness and a significant reduction of friction coefficient were observed compared to the non-implanted sample. Also, a better corrosion resistance and a significant decrease in ion release rates have been obtained. Cell culture experiments indicated that the cytocompatibility of the N-implanted Ti alloy was superior to that of the corresponding non-treated sample. Thus, this new functional N-implanted titanium-based superelastic alloy presents the optimized properties that are required for various medical devices: superelasticity, high superficial mechanical properties, high corrosion resistance and excellent cytocompatibility

The Red Radio Ring: a gravitationally lensed hyperluminous infrared radio galaxy at z=2.553 discovered through the citizen science project SpaceWarps

We report the discovery of a gravitationally lensed hyperluminous infrared galaxy (intrinsic LIR≈1013 L⊙) with strong radio emission (intrinsic L1.4 GHz≈1025WHz−1) at z=2.553. The source was identified in the citizen science project SpaceWarpsthrough the visual inspection of tens of thousands of iJKs colour composite images of luminous red galaxies (LRGs), groups and clusters of galaxies and quasars. Appearing as a partial Einstein ring (re≈3 arcsec) around an LRG at z=0.2, the galaxy is extremely bright in the sub-millimetre for a cosmological source, with the thermal dust emission approaching 1 Jy at peak. The redshift of the lensed galaxy is determined through the detection of the CO(3→2) molecular emission line with the Large Millimetre Telescope's Redshift Search Receiver and through [O iii] and Hα line detections in the near-infrared from Subaru/Infrared Camera and Spectrograph. We have resolved the radio emission with high-resolution (300-400 mas) eMERLIN L-band and Very Large Array C-band imaging. These observations are used in combination with the near-infrared imaging to construct a lens model, which indicates a lensing magnification of μ≈10. The source reconstruction appears to support a radio morphology comprised of a compact (<250 pc) core and more extended component, perhaps indicative of an active nucleus and jet or lob

The Red Radio Ring: a gravitationally lensed hyperluminous infrared radio galaxy at z = 2.553 discovered through the citizen science project SPACE WARPS

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We report the discovery of a gravitationally lensed hyperluminous infrared galaxy (intrinsic LIR ≈ 1013 L⊙) with strong radio emission (intrinsic L1.4 GHz ≈ 1025 W Hz−1) at z = 2.553. The source was identified in the citizen science project SPACE WARPS through the visual inspection of tens of thousands of iJKs colour composite images of luminous red galaxies (LRGs), groups and clusters of galaxies and quasars. Appearing as a partial Einstein ring (re ≈ 3 arcsec) around an LRG at z = 0.2, the galaxy is extremely bright in the sub-millimetre for a cosmological source, with the thermal dust emission approaching 1 Jy at peak. The redshift of the lensed galaxy is determined through the detection of the CO(3→2) molecular emission line with the Large Millimetre Telescope's Redshift Search Receiver and through [O III] and Hα line detections in the near-infrared from Subaru/Infrared Camera and Spectrograph. We have resolved the radio emission with high-resolution (300–400 mas) eMERLIN L-band and Very Large Array C-band imaging. These observations are used in combination with the near-infrared imaging to construct a lens model, which indicates a lensing magnification of μ ≈ 10. The source reconstruction appears to support a radio morphology comprised of a compact (<250 pc) core and more extended component, perhaps indicative of an active nucleus and jet or lobe.Peer reviewedFinal Published versio

The impact of human expert visual inspection on the discovery of strong gravitational lenses

We investigate the ability of human ’expert’ classifiers to identify strong gravitational lens candidates in Dark Energy Survey like imaging. We recruited a total of 55 people that completed more than 25% of the project. During the classification task, we present to the participants 1489 images. The sample contains a variety of data including lens simulations, real lenses, non-lens examples, and unlabeled data. We find that experts are extremely good at finding bright, well-resolved Einstein rings, whilst arcs with g-band signal-to-noise less than ∼25 or Einstein radii less than ∼1.2 times the seeing are rarely recovered. Very few non-lenses are scored highly. There is substantial variation in the performance of individual classifiers, but they do not appear to depend on the classifier’s experience, confidence or academic position. These variations can be mitigated with a team of 6 or more independent classifiers. Our results give confidence that humans are a reliable pruning step for lens candidates, providing pure and quantifiably complete samples for follow-up studies

Determination of hardness and elastic modulus inverse pole figures of a polycrystalline commercially pure titanium by coupling nanoindentation and EBSD techniques

International audienceNanoindentation and electron backscattered diffraction (EBSD) techniques were used to study the correlation between crystallographic orientations and mechanical properties of individual grains in CP-Ti polycrystalline samples. Therefore, a novel experimental protocol and a data analyses procedure have been implemented in order to obtain elastic modulus and hardness inverse pole figures (EIPF and HIPF). It has been demonstrated that the hardness varies significantly with orientation, and that the elastic modulus appears less sensitive than hardness to grain orientation

The geochemistry of opals as an evidence for their origin

International audienc

AGN photoionization of gas in companion galaxies as a probe of AGN radiation in time and direction

We consider active galactic nucleus (AGN) photoionization of gas in companion galaxies (cross-ionization) as a way to sample the intensity of AGN radiation in both direction and time, independent of the gas properties of the AGN host galaxies. From an initial set of 212 AGN+companion systems, identified with the help of Galaxy Zoo participants, we obtained long-slit optical spectra of 32 pairs that were a priori likely to show cross-ionization based on projected separation or angular extent of the companion. From emission-line ratios, 10 of these systems are candidates for cross-ionization, roughly the fraction expected if most AGNs have ionization cones with 70° opening angles. Among these, Was 49 remains the strongest nearby candidate. NGC 5278/9 and UGC 6081 are dual-AGN systems with tidal debris, complicating identification of cross-ionization. The two weak AGNs in the NGC 5278/9 system ionize gas filaments to a projected radius 14 kpc from each galaxy. In UGC 6081, an irregular high-ionization emission region encompasses both AGNs, extending more than 15 kpc from each. The observed AGN companion galaxies with and without signs of external AGN photoionization have similar distributions in estimated incident AGN flux, suggesting that geometry of escaping radiation or long-term variability controls this facet of the AGN environment. This parallels conclusions for luminous QSOs based on the proximity effect among Lyman α absorbers. In some galaxies, mismatch between spectroscopic classifications in the common BPT diagram and the intensity of weaker He II and [Ne V] emission lines highlights the limits of common classifications in low-metallicity environments