Les oxoborates de calcium et de terres rares (TR) Ca4TRO(BO3)3. Une nouvelle famille de matériaux à fonctions multiples pour l'optique : croissance cristalline, propriétés non linéaires et laser

The aim of this work is to study a new family of non linear compounds Ca4REO(BO3)3 (where RE is set for lanthanide or yttrium). The second order non linear properties for the GdCOB (Ca4GdO(BO3)3) and YCOB (Ca4YO(BO3)3) compounds were characterised. These materials favorably compare with commercialised non linear borates such as LBO and BBO. Crystal growth was performed by using the Czochralski method, allowing large size single crystals (diameter 50 mm and length 100 to 120 mm) with good optical quality. Moreover crystals are totally unsensitive to moisture. Luminescent lanthanide ions (neodymium or ytterbium) can be inserted in the non linear matrix and single crystals were grown by the Czocralski method. The study of the optical properties leads to demonstrate the laser effect under titanium sapphire or laser diode pumping in the infrared range (around 1060 nm) for the neodymium and ytterbium doped GdCOB and for the neodymium doped YCOB. Finally, non linear properties and laser effect can be combined and give rise to blue or green continuous visible laser sources, by self frequency doubling or self sum frequency. The obtained performances together with availability of large size crystal can lead to the realisation of microchip lasers.L'objet de ce mémoire est l'étude d'une nouvelle famille de matériaux pour l'optique non linéaire Ca4TRO(BO3)3 (où TR désigne les lanthanides ou l'yttrium). Les propriétés non linéaires d'ordre 2 pour les composés GdCOB (Ca4GdO(BO3)3) et YCOB (Ca4YO(BO3)3) ont été caractérisées. Elles sont comparables à celles des borates non linéaires commercialisés (BBO, LBO). La croissance par la technique Czochralski de ces matériaux permet leur élaboration sous forme de monocristaux de grandes dimensions (diamètre 50 mm, longueur 100 à 120 mm) et de bonne qualité optique. De plus ces composés sont non hygroscopiques. Des ions lanthanides luminescents (néodyme ou ytterbium) ont été insérés dans ces matrices et des monocristaux ont été élaborés. L'étude des propriétés optiques de ces matériaux a conduit à la mise en évidence de l'effet laser dans l'infrarouge (vers 1060 nm) pour la matrice GdCOB dopée par l'ion Nd3+ ou Yb3+ et pour la matrice YCOB dopée par l'ion Nd3+ aussi bien en pompage par laser saphir dopé au titane qu'en pompage par diode laser. Enfin, nous avons pu combiner les propriétés laser et non linéaires dans ces matériaux afin de réaliser des sources laser continues visibles (bleues et vertes) par utodoublage de fréquence ou autosomme de fréquences. Les performances obtenues alliées à la possibilités de croissance en grandes dimensions ouvrent la voie à la fabrication collective de microlaser

Aide à la prise en charge des dyspnées aiguës aux urgences de l'hôpital de Remiremont grace au dosage du BNP par la méthode Triage® (étude prospective et rétrospective sur 51 patients)

STRASBOURG-Medecine (674822101) / SudocSudocFranceF

Chromium isotopic homogeneity between the Moon, the Earth, and enstatite chondrites

International audienceAmong the elements exhibiting non-mass dependent isotopic variations in meteorites, chromium (Cr) has been central in arguing for an isotopic homogeneity between the Earth and the Moon, thus questioning physical models of Moon formation. However, the Cr isotopic composition of the Moon relies on two samples only, which define an average value that is slightly different from the terrestrial standard. Here, by determining the Cr isotopic composition of 17 lunar, 9 terrestrial and 5 enstatite chondrite samples, we reassess the isotopic similarity between these different planetary bodies, and provide the first robust estimate for the Moon. In average, terrestrial and enstatite samples show similar ε 54 Cr. On the other hand, lunar samples show variables excesses of 53 Cr and 54 Cr compared to terrestrial and enstatite chondrites samples with correlated ε 53 Cr and ε 54 Cr (per 10,000 deviation of the 53 Cr/ 52 Cr and 54 Cr/ 52 Cr ratios normalized to the 50 Cr/ 52 Cr ratio from the NIST SRM 3112a Cr standard). Unlike previous suggestions, we show for the first time that cosmic irradiation can 2 affect significantly the Cr isotopic composition of lunar materials. Moreover, we also suggest that rather than spallation reactions, neutron capture effects are the dominant process controlling the Cr isotope composition of lunar igneous rocks. This is supported by the correlation between ε 53 Cr and ε 54 Cr, and 150 Sm/ 152 Sm ratios. After correction of these effects, the average ε 54 Cr of the Moon is indistinguishable from the terrestrial and enstatite chondrite materials reinforcing the idea of an Earth-Moon-Enstatite chondrite system homogeneity. This is compatible with the most recent scenarios of Moon formation suggesting an efficient physical homogenization after a high-energy impact on a fast spinning Earth, and/or with an impactor originating from the same reservoir in the inner proto-planetary disk as the Earth and enstatite chondrites and having similar composition

Chromium isotope evidence in ejecta deposits for the nature of Paleoproterozoic impactors

International audienceNon-mass dependent chromium isotopic signatures have been successfully used to determine the presence and identification of extra-terrestrial materials in terrestrial impact rocks. Paleoproterozoic spherule layers from Greenland (Graensesø) and Russia (Zaonega), as well as some distal ejecta deposits (Lake Superior region) from the Sudbury impact (1,849±0.3 Ma) event, have been analyzed for their Cr isotope compositions. Our results suggest that 1) these distal ejecta deposits are all of impact origin, 2) the Graensesø and Zaonega spherule layers contain a distinct carbonaceous chondrite component, and are possibly related to the same impact event, which could be Vredefort (2,023±4 Ma) or another not yet identified large impact event 2 from that of similar age, and 3) the Sudbury ejecta record a complex meteoritic signature, which is different from the Graensesø and Zaonega spherule layers, and could indicate the impact of a heterogeneous chondritic body

Theoretical and Experimental Investigations of a Diode-Pumped Quasi-Three-Level Laser: The Yb3+-Doped Ca4GdO(BO3)3 (Yb : GdCOB) Laser

International audienc

Efficient, tunable, zero-line-diode-pumped, continuous-wave Yb3+:Ca4LnO(BO3)3 (Ln=Gd,Y) lasers at room temperature, application to miniature lasers

International audienceWe demonstrate an efficient cw 976-nm-diode-pumped Yb31:Ca4GdO(BO3)3 laser. At room temperature we obtained 814 mW of power with a slope efficiency of 77% and a small-signal gain per round trip of 1.67. We also demonstrate that the Yb31:Ca4LnO(BO3)3 (Ln 5 Gd, Y) crystals are suitable for a plano-plano microchiptype cavity. With this microlaser we have obtained an average power of 300 mW, which corresponds to an optical-optical conversion efficiency of 27

Generation of 90-fs pulse from a modelocked diode-pumped Yb3+:Ca4GdO(BO3)3 laser

A diode-pumped Yb31:Ca4GdO_BO3_3 (Yb:GdCOB) laser generating 90-fs pulses at a center wavelength of 1045 nm is demonstrated. This is, to our knowledge, the shortest pulse duration obtained from an ytterbium laser with a crystalline host. This laser is mode locked with a high-finesse semiconductor saturable-absorber mirror and emits 40 mW of average power at a repetition rate of 100 MH

Efficient and tunable continuous-wave diode-pumped Yb3+:Ca4GdO(BO3)3 laser

International audienceA Yb31:Ca4GdO(BO3)3 (Yb:GdCOB) crystal has been diode pumped for the first time to our knowledge. We obtained 47.5% slope efficiency at 6 °C, producing 191 mW of power at 1050 nm, with a 2.4% output coupler. Temperature does not significantly affect the laser performance: At room temperature we still obtained 180mWof power for the same cavity. We achieved tunability of the Yb:GdCOB laser from 1035 to 1088 nm with a 1.7% output coupler and 100-nm tunability with a low-transmission output coupling (T 5 0.03%

Contamination of soil by copper affects the dynamics, diversity, and activity of soil bacterial communities involved in wheat decomposition and carbon storage.

5 pagesInternational audienceA soil microcosm experiment was conducted to evaluate the influence of copper contamination on the dynamics and diversity of bacterial communities actively involved in wheat residue decomposition. In the presence of copper, a higher level of CO(2) release was observed, which did not arise from greater wheat decomposition but from a higher level of stimulation of soil organic matter mineralization (known as the priming effect). Such functional modifications may be related to significant modifications in the diversity of active bacterial populations characterized using the DNA stable-isotope probing approach