Laboratory studies on a spherically curved Bragg spectrometer for cosmic X-ray spectroscopy

A spherical array of twenty LiF 200 crystals was built to test the performances of a freestanding, self-focussing spherical crystal cosmic X-ray spectrometer. Measurements presently available show that the size of the image for a point source at infinite distance would be 3 mm (FWHM) along the focalisation axis and 2.1 mm (FWHM) along the dispersion axis. The mosaic spread on individual crystals is less than 0.1 degree. A slightly systematic deviation from the ideal bending (0.1 degree) is observed at the edges of most crystals and this appears to be the major limitation to spectrometer performance

Identification d'un réseau hydrométrique pour le suivi des modifications climatiques dans la province de Québec

Depuis une dizaine d'années, la communauté scientifique s'est beaucoup intéressée à l'hypothèse d'un réchauffement à l'échelle planétaire. De nombreuses études ont porté sur l'analyse de ces modifications climatiques éventuelles ainsi que sur la modélisation de leurs impacts sur les ressources en eau. Cependant, malgré l'attention croissante que reçoit le sujet des modifications climatiques, très peu de travail a été accompli pour mettre en place des réseaux de mesure spécialement conçus pour l'étude des modifications climatiques et leurs impacts sur les ressources en eau, et pour créer des bases de données adaptées à cet objectif. Cette tâche est encore plus nécessaire dans le cadre des réductions budgétaires auxquelles sont soumis les réseaux hydrométriques dans certains pays développés. Cet article présente les bases d'une étude dont l'objectif est la conception d'un réseau hydrométrique pour le suivi des modifications climatiques dans la province de Québec, Canada. Le but est d'identifier, afin de les conserver, les stations de jaugeage les plus adéquates pour accomplir cette tâche. L'article présente aussi une brève revue des types de modifications climatiques qui peuvent être observés et de certains tests qui existent pour leur détection et leur quantification. Une procédure bayésienne de détection des sauts de la moyenne a été sélectionnée sur la base de ses avantages théoriques, et appliquée aux séries de données des stations retenues au Québec.The 1980s and 1990s contained most of the warmest years since the beginning of worldwide temperature recording nearly 140 years ago. Widely accepted estimates project that the earth's average temperature might increase by about 2°C over the next 100 years. It is also expected that, as a result of global warming, the frequency and intensity of floods and droughts may change. However, despite the increasing attention that the issue of climate change receives, there has been little effort to develop a systematic approach for the collection of relevant data, and to establish observational networks specifically designed for the analysis of climate variability and change and their impact on hydrologic regimes and water resources in general. This task is particularly important given the major network reductions that result from recent cutbacks in the funding of monitoring programs in Canada and other countries. This paper presents the results of a rigorous study that was carried out recently, and aimed at establishing a hydrometric network for the study of the attributes of climate change and variability across the province of Quebec (Canada) and their impact on water resources. The approach is based on identifying and maintaining stations that can help provide an understanding of the physical processes within the hydrological cycle and account for climate variations across the province. This network will be of fundamental importance in establishing scientific evidence of the magnitude and direction of possible shifts in climate patterns across the province. These aspects are of global significance and must be considered during the rationalization of monitoring networks. The results of the application of this procedure to the hydrometric network of the province of Quebec are presented. The paper presents also a brief review of the various types of non-stationarities that can be observed in hydrologic data series, and some of the current approaches that can be used for the detection of these non-stationarities. Several statistical tests and procedures have been proposed in the literature for the analysis of the characteristics of data samples and for hypothesis testing, for various types of non-stationarity. A Bayesian procedure, proposed by Lee and Heghinian (1977) and generalized by Bernier (1994), for the detection of shifts in the mean of hydrological and meteorological time-series is selected based on its theoretical advantages (Faucher et al., 1997). The procedure is then applied for the analysis of all streamflow series of selected stations in the province of Quebec with the objective of extracting information on possible climatic changes. Results indicate the presence of significant non-stationarities for a number of the series analyzed. For five stations, the most probable date for the shift in the mean level falls in the period 1983-1985. Recommandations are made for future research activities

Bayesian Joint Detection-Estimation of cerebral vasoreactivity from ASL fMRI data

International audienceAlthough the study of cerebral vasoreactivity using fMRI is mainly conducted through the BOLD fMRI modality, owing to its relatively high signal-to-noise ratio (SNR), ASL fMRI provides a more interpretable measure of cerebral vasoreactivity than BOLD fMRI. Still, ASL suffers from a low SNR and is hampered by a large amount of physiological noise. The current contribution aims at improving the re- covery of the vasoreactive component from the ASL signal. To this end, a Bayesian hierarchical model is proposed, enabling the recovery of per- fusion levels as well as fitting their dynamics. On a single-subject ASL real data set involving perfusion changes induced by hypercapnia, the approach is compared with a classical GLM-based analysis. A better goodness-of-fit is achieved, especially in the transitions between baseline and hypercapnia periods. Also, perfusion levels are recovered with higher sensitivity and show a better contrast between gray- and white matter

Near-to mid-IR spectral purity transfer with a tunable frequency comb: methanol frequency metrology over a record frequency span

We report the development and operation of a frequency-comb-assisted high-resolution mid-infrared molecular spectrometer combining high spectral purity, SI-traceability, wide tunability and high sensitivity. An optical frequency comb is used to transfer the spectral purity of a SI-traceable 1.54 $\mu$m metrology-grade frequency reference to a 10.3 $\mu$m quantum cascade laser (QCL). The near-infrared reference is operated at the French time/frequency metrology institute, calibrated there to primary frequency standards, and transferred to Laboratoire de Physique des Lasers via the REFIMEVE fiber network. The QCL exhibits a sub-10 --15 frequency stability from 0.1 to 10 s and its frequency is traceable to the SI with a total uncertainty better than 4 x 10 --14 after 1-s averaging time. We have developed the instrumentation allowing comb modes to be continuously tuned over 9 GHz resulting in a QCL of record spectral purity uninterruptedly tunable at the precision of the reference over an unprecedented span of 1.4 GHz. We have used our apparatus to conduct sub-Doppler spectroscopy of methanol in a multi-pass cell, demonstrating state-of-art frequency uncertainties down to the few kilohertz level. We have observed weak intensity resonances unreported so far, resolved subtle doublets never seen before and brought to light discrepancies with the HITRAN database. This demonstrates the potential of our apparatus for probing subtle internal molecular processes, building accurate spectroscopic models of polyatomic molecules of atmospheric or astrophysical interest, and carrying out precise spectroscopic tests of fundamental physics

Synthesis and structure determination via ultra-fast electron diffraction of the new microporous zeolitic germanosilicate ITQ-62

[EN] Here, we present the synthesis and structure determination of the new zeolite ITQ-62. Its structure was determined via ultra-fast electron diffraction tomography and refined using powder XRD data of the calcined material. This new zeolite contains a tridirectional channel system of highly distorted 8-rings, as well as a monodirectional 12-ring channel system.The authors gratefully acknowledge financial support from the Spanish Government (MAT2015-71842-P and MAT2015-71261-R MINECO/FEDER and Severo Ochoa SEV-2016-0683). The authors thank ALBA Light Source for beam allocation at the beamline MSPD, and specially thank the Electron Microscopy Service of the Universitat Politecnica de Valencia. Finally, the authors thank Dr Alejandro Vidal and Dr Teresa Blasco for helping in the NMR data discussion.Bieseki, L.; Simancas Coloma, R.; Jorda Moret, JL.; Bereciartua-Pérez, PJ.; Cantin Sanz, A.; Simancas-Coloma, J.; Pergher, SB.... (2018). Synthesis and structure determination via ultra-fast electron diffraction of the new microporous zeolitic germanosilicate ITQ-62. Chemical Communications. 54(17):2122-2125. https://doi.org/10.1039/c7cc09240gS212221255417Barrer, R. M., & Denny, P. J. (1961). 201. Hydrothermal chemistry of the silicates. Part IX. Nitrogenous aluminosilicates. Journal of the Chemical Society (Resumed), 971. doi:10.1039/jr9610000971Kerr, G. T. (1966). Chemistry of Crystalline Aluminosilicates. II. The Synthesis and Properties of Zeolite ZK-4. Inorganic Chemistry, 5(9), 1537-1539. doi:10.1021/ic50043a015Burton, A. W., & Zones, S. I. (2007). Organic Molecules in Zeolite Synthesis: Their Preparation and Structure-Directing Effects. Introduction to Zeolite Science and Practice, 137-179. doi:10.1016/s0167-2991(07)80793-2Zones, S. I., Nakagawa, Y., Lee, G. S., Chen, C. Y., & Yuen, L. T. (1998). Searching for new high silica zeolites through a synergy of organic templates and novel inorganic conditions. Microporous and Mesoporous Materials, 21(4-6), 199-211. doi:10.1016/s1387-1811(98)00011-0Burton, A. W., Zones, S. I., & Elomari, S. (2005). The chemistry of phase selectivity in the synthesis of high-silica zeolites. Current Opinion in Colloid & Interface Science, 10(5-6), 211-219. doi:10.1016/j.cocis.2005.08.005Moliner, M., Rey, F., & Corma, A. (2013). Towards the Rational Design of Efficient Organic Structure-Directing Agents for Zeolite Synthesis. Angewandte Chemie International Edition, 52(52), 13880-13889. doi:10.1002/anie.201304713Park, G. T., Jo, D., Ahn, N. H., Cho, J., & Hong, S. B. (2017). Synthesis and Structural Characterization of a CHA-type AlPO4 Molecular Sieve with Penta-Coordinated Framework Aluminum Atoms. Inorganic Chemistry, 56(14), 8504-8512. doi:10.1021/acs.inorgchem.7b01194Dorset, D. L., Strohmaier, K. G., Kliewer, C. E., Corma, A., Díaz-Cabañas, M. J., Rey, F., & Gilmore, C. J. (2008). Crystal Structure of ITQ-26, a 3D Framework with Extra-Large Pores. Chemistry of Materials, 20(16), 5325-5331. doi:10.1021/cm801126tDorset, D. L., Kennedy, G. J., Strohmaier, K. G., Diaz-Cabañas, M. J., Rey, F., & Corma, A. (2006). P-Derived Organic Cations as Structure-Directing Agents:  Synthesis of a High-Silica Zeolite (ITQ-27) with a Two-Dimensional 12-Ring Channel System. Journal of the American Chemical Society, 128(27), 8862-8867. doi:10.1021/ja061206oJo, D., Ryu, T., Park, G. T., Kim, P. S., Kim, C. H., Nam, I.-S., & Hong, S. B. (2016). Synthesis of High-Silica LTA and UFI Zeolites and NH3–SCR Performance of Their Copper-Exchanged Form. ACS Catalysis, 6(4), 2443-2447. doi:10.1021/acscatal.6b00489Miller, M. A., Moscoso, J. G., Koster, S. C., Gatter, M. G., & Lewis, G. J. (2007). Synthesis and characterization of the 12-ring zeolites UZM-4 (BPH) and UZM-22 (MEI) via the charge density mismatch approach in the Choline-Li2O-SrO-Al2O3-SiO2 system. Studies in Surface Science and Catalysis, 347-354. doi:10.1016/s0167-2991(07)80859-7Simancas, R., Jordá, J. L., Rey, F., Corma, A., Cantín, A., Peral, I., & Popescu, C. (2014). A New Microporous Zeolitic Silicoborate (ITQ-52) with Interconnected Small and Medium Pores. Journal of the American Chemical Society, 136(9), 3342-3345. doi:10.1021/ja411915cSimancas, R., Dari, D., Velamazan, N., Navarro, M. T., Cantin, A., Jorda, J. L., … Rey, F. (2010). Modular Organic Structure-Directing Agents for the Synthesis of Zeolites. Science, 330(6008), 1219-1222. doi:10.1126/science.1196240Martinez-Franco, R., Moliner, M., Yun, Y., Sun, J., Wan, W., Zou, X., & Corma, A. (2013). Synthesis of an extra-large molecular sieve using proton sponges as organic structure-directing agents. Proceedings of the National Academy of Sciences, 110(10), 3749-3754. doi:10.1073/pnas.1220733110Choi, M., Na, K., Kim, J., Sakamoto, Y., Terasaki, O., & Ryoo, R. (2009). Stable single-unit-cell nanosheets of zeolite MFI as active and long-lived catalysts. Nature, 461(7261), 246-249. doi:10.1038/nature08288Zones, S. I., & Davis, M. E. (1996). Zeolite materials: recent discoveries and future prospects. Current Opinion in Solid State and Materials Science, 1(1), 107-117. doi:10.1016/s1359-0286(96)80018-0Bellussi, G., Carati, A., & Millini, R. (2010). Industrial Potential of Zeolites. Zeolites and Catalysis, 449-491. doi:10.1002/9783527630295.ch16Zones, S. I. (2011). Translating new materials discoveries in zeolite research to commercial manufacture. Microporous and Mesoporous Materials, 144(1-3), 1-8. doi:10.1016/j.micromeso.2011.03.039Olsbye, U., Svelle, S., Bjørgen, M., Beato, P., Janssens, T. V. W., Joensen, F., … Lillerud, K. P. (2012). Conversion of Methanol to Hydrocarbons: How Zeolite Cavity and Pore Size Controls Product Selectivity. Angewandte Chemie International Edition, 51(24), 5810-5831. doi:10.1002/anie.201103657Korhonen, S. T., Fickel, D. W., Lobo, R. F., Weckhuysen, B. M., & Beale, A. M. (2011). Isolated Cu2+ions: active sites for selective catalytic reduction of NO. Chem. Commun., 47(2), 800-802. doi:10.1039/c0cc04218hMoliner, M., Franch, C., Palomares, E., Grill, M., & Corma, A. (2012). Cu–SSZ-39, an active and hydrothermally stable catalyst for the selective catalytic reduction of NOx. Chemical Communications, 48(66), 8264. doi:10.1039/c2cc33992gBereciartua, P. J., Cantín, Á., Corma, A., Jordá, J. L., Palomino, M., Rey, F., … Casty, G. L. (2017). Control of zeolite framework flexibility and pore topology for separation of ethane and ethylene. Science, 358(6366), 1068-1071. doi:10.1126/science.aao0092Dodin, M., Paillaud, J.-L., Lorgouilloux, Y., Caullet, P., Elkaïm, E., & Bats, N. (2010). A Zeolitic Material with a Three-Dimensional Pore System Formed by Straight 12- and 10-Ring Channels Synthesized with an Imidazolium Derivative as Structure-Directing Agent. Journal of the American Chemical Society, 132(30), 10221-10223. doi:10.1021/ja103648kPaillaud, J.-L. (2004). Extra-Large-Pore Zeolites with Two-Dimensional Channels Formed by 14 and 12 Rings. Science, 304(5673), 990-992. doi:10.1126/science.1098242Lorgouilloux, Y., Dodin, M., Paillaud, J.-L., Caullet, P., Michelin, L., Josien, L., … Bats, N. (2009). IM-16: A new microporous germanosilicate with a novel framework topology containing d4r and mtw composite building units. Journal of Solid State Chemistry, 182(3), 622-629. doi:10.1016/j.jssc.2008.12.002Earl, D. J., Burton, A. W., Rea, T., Ong, K., Deem, M. W., Hwang, S.-J., & Zones, S. I. (2008). Synthesis and Monte Carlo Structure Determination of SSZ-77: A New Zeolite Topology. The Journal of Physical Chemistry C, 112(24), 9099-9105. doi:10.1021/jp7116856Tang, L., Shi, L., Bonneau, C., Sun, J., Yue, H., Ojuva, A., … Zou, X. (2008). A zeolite family with chiral and achiral structures built from the same building layer. Nature Materials, 7(5), 381-385. doi:10.1038/nmat2169Corma, A., Navarro, M. T., Rey, F., Rius, J., & Valencia, S. (2001). Pure Polymorph C of Zeolite Beta Synthesized by Using Framework Isomorphous Substitution as a Structure-Directing Mechanism. Angewandte Chemie International Edition, 40(12), 2277-2280. doi:10.1002/1521-3773(20010618)40:123.0.co;2-oYun, Y., Hernández, M., Wan, W., Zou, X., Jordá, J. L., Cantín, A., … Corma, A. (2015). The first zeolite with a tri-directional extra-large 14-ring pore system derived using a phosphonium-based organic molecule. Chemical Communications, 51(36), 7602-7605. doi:10.1039/c4cc10317cJiang, J., Yun, Y., Zou, X., Jorda, J. L., & Corma, A. (2015). ITQ-54: a multi-dimensional extra-large pore zeolite with 20 × 14 × 12-ring channels. Chemical Science, 6(1), 480-485. doi:10.1039/c4sc02577fHernández-Rodríguez, M., Jordá, J. L., Rey, F., & Corma, A. (2012). Synthesis and Structure Determination of a New Microporous Zeolite with Large Cavities Connected by Small Pores. Journal of the American Chemical Society, 134(32), 13232-13235. doi:10.1021/ja306013kJiang, J., Jorda, J. L., Diaz-Cabanas, M. J., Yu, J., & Corma, A. (2010). The Synthesis of an Extra-Large-Pore Zeolite with Double Three-Ring Building Units and a Low Framework Density. Angewandte Chemie International Edition, 49(29), 4986-4988. doi:10.1002/anie.201001506Blasco, T., Corma, A., Díaz-Cabañas, M. J., Rey, F., Vidal-Moya, J. A., & Zicovich-Wilson, C. M. (2002). Preferential Location of Ge in the Double Four-Membered Ring Units of ITQ-7 Zeolite. The Journal of Physical Chemistry B, 106(10), 2634-2642. doi:10.1021/jp013302bMoliner, M., Willhammar, T., Wan, W., González, J., Rey, F., Jorda, J. L., … Corma, A. (2012). Synthesis Design and Structure of a Multipore Zeolite with Interconnected 12- and 10-MR Channels. Journal of the American Chemical Society, 134(14), 6473-6478. doi:10.1021/ja301082nCorma, A., Diaz-Cabanas, M. J., Jorda, J. L., Rey, F., Sastre, G., & Strohmaier, K. G. (2008). A Zeolitic Structure (ITQ-34) with Connected 9- and 10-Ring Channels Obtained with Phosphonium Cations as Structure Directing Agents. Journal of the American Chemical Society, 130(49), 16482-16483. doi:10.1021/ja806903cCorma, A., Díaz-Cabañas, M. J., Jordá, J. L., Martínez, C., & Moliner, M. (2006). High-throughput synthesis and catalytic properties of a molecular sieve with 18- and 10-member rings. Nature, 443(7113), 842-845. doi:10.1038/nature05238Sun, J., Bonneau, C., Cantín, Á., Corma, A., Díaz-Cabañas, M. J., Moliner, M., … Zou, X. (2009). The ITQ-37 mesoporous chiral zeolite. Nature, 458(7242), 1154-1157. doi:10.1038/nature07957Corma, A., Rey, F., Valencia, S., Jordá, J. L., & Rius, J. (2003). A zeolite with interconnected 8-, 10- and 12-ring pores and its unique catalytic selectivity. Nature Materials, 2(7), 493-497. doi:10.1038/nmat921Werner, P. E., Eriksson, L., & Westdahl, M. (1985). TREOR, a semi-exhaustive trial-and-error powder indexing program for all symmetries. Journal of Applied Crystallography, 18(5), 367-370. doi:10.1107/s0021889885010512Simancas, J., Simancas, R., Bereciartua, P. J., Jorda, J. L., Rey, F., Corma, A., … Mugnaioli, E. (2016). Ultrafast Electron Diffraction Tomography for Structure Determination of the New Zeolite ITQ-58. Journal of the American Chemical Society, 138(32), 10116-10119. doi:10.1021/jacs.6b06394Kolb, U., Mugnaioli, E., & Gorelik, T. E. (2011). Automated electron diffraction tomography - a new tool for nano crystal structure analysis. Crystal Research and Technology, 46(6), 542-554. doi:10.1002/crat.201100036Grosse-Kunstleve, R. W., McCusker, L. B., & Baerlocher, C. (1999). Zeolite structure determination from powder diffraction data: applications of theFOCUSmethod. Journal of Applied Crystallography, 32(3), 536-542. doi:10.1107/s0021889899003453R. Bialek , KRIBER. Crystallographic computation program , ETH Zurich Institut fur Kristallographie , Zurich, Switzerland , 1991Ch. Baerlocher , A.Hepp and W. M.Meier , DLS-76. Distance least squares refinement program , ETH Zurich Institut fur Kristallographie , Zurich, Switzerland , 1977Fauth, F., Peral, I., Popescu, C., & Knapp, M. (2013). The new Material Science Powder Diffraction beamline at ALBA Synchrotron. Powder Diffraction, 28(S2), S360-S370. doi:10.1017/s0885715613000900Peral, I., McKinlay, J., Knapp, M., & Ferrer, S. (2011). Design and construction of multicrystal analyser detectors using Rowland circles: application to MAD26 at ALBA. Journal of Synchrotron Radiation, 18(6), 842-850. doi:10.1107/s090904951103152

Aerogel Waveplates

Optical transmission measurements were made on 98% porosity silica aerogel samples under various degrees of uniaxial strain. Uniaxially compressed aerogels exhibit large birefringence, proportional to the amount of compression, up to the 15% strain studied. The birefringence is mostly reversible and reproducible through multiple compression-decompression cycles. Our study demonstrates that uniaxially strained high porosity aerogels can be used as tunable waveplates in a broad spectral range.Comment: 7 pages, 4 figures, submitted to Optics Expres

Systematically missing confounders in individual participant data meta-analysis of observational cohort studies.

One difficulty in performing meta-analyses of observational cohort studies is that the availability of confounders may vary between cohorts, so that some cohorts provide fully adjusted analyses while others only provide partially adjusted analyses. Commonly, analyses of the association between an exposure and disease either are restricted to cohorts with full confounder information, or use all cohorts but do not fully adjust for confounding. We propose using a bivariate random-effects meta-analysis model to use information from all available cohorts while still adjusting for all the potential confounders. Our method uses both the fully adjusted and the partially adjusted estimated effects in the cohorts with full confounder information, together with an estimate of their within-cohort correlation. The method is applied to estimate the association between fibrinogen level and coronary heart disease incidence using data from 154,012 participants in 31 cohort