Five decades of terrestrial and freshwater research at Ny-Ålesund, Svalbard

For more than five decades, research has been conducted at Ny-Ålesund, in Svalbard, Norway, to understand the structure and functioning of High-Arctic ecosystems and the profound impacts on them of environmental change. Terrestrial, freshwater, glacial and marine ecosystems are accessible year-round from Ny-Ålesund, providing unique opportunities for interdisciplinary observational and experimental studies along physical, chemical, hydrological and climatic gradients. Here, we synthesize terrestrial and freshwater research at Ny-Ålesund and review current knowledge of biodiversity patterns, species population dynamics and interactions, ecosystem processes, biogeochemical cycles and anthropogenic impacts. There is now strong evidence of past and ongoing biotic changes caused by climate change, including negative effects on populations of many taxa and impacts of rain-on-snow events across multiple trophic levels. While species-level characteristics and responses are well understood for macro-organisms, major knowledge gaps exist for microbes, invertebrates and ecosystem-level processes. In order to fill current knowledge gaps, we recommend (1) maintaining monitoring efforts, while establishing a long-term ecosystem-based monitoring programme; (2) gaining a mechanistic understanding of environmental change impacts on processes and linkages in food webs; (3) identifying trophic interactions and cascades across ecosystems; and (4) integrating long-term data on microbial, invertebrate and freshwater communities, along with measurements of carbon and nutrient fluxes among soils, atmosphere, freshwaters and the marine environment. The synthesis here shows that the Ny-Ålesund study system has the characteristics needed to fill these gaps in knowledge, thereby enhancing our understanding of High-Arctic ecosystems and their responses to environmental variability and change

Application of optical methods to investigate the non-linear asymmetric behavior of ceramics exhibiting large strain to rupture by four-points bending test

International audienceLarge strain to rupture behavior is essential, for refractory materials, to improve their thermal shock resistance. The non-linear comportment under loading of specific developed ceramics associated to their type of microstructure (micro-cracked) leads to the possibility to increase their strain-to-rupture level. Aluminum titanate (AT: Al 2TiO 5) ceramics are one of these materials and are characterized by a mechanical behavior strongly dependent on their microstructure. Indeed, this behavior can vary from a fragile one to a large non-linear one according to the degree of microcracking present within the material. The paper here presented is devoted to the study of this nonlinear behavior thanks to four-points bending test associated with digital image correlation technique to determine kinematics fields. Results highlight the asymmetric character of the mechanical behavior of a microcracked aluminum titanate. A comparison between the Young moduli and fracture strength obtained using conventional and ones identified by digital image correlation will be don

Surface Oxidation Issues in CO Oxidation on Pd70Au30(110)

International audienc

CO oxidation on bimetallic catalytic surfaces studied by ambient-pressure X-ray photoelectron spectroscopy

National @ ATARI+EEH:FCAInternational audienceCO oxidation on bimetallic catalytic surfaces studied by ambient-pressure X-ray photoelectron spectroscopyM.A. Languille1,§, E. Ehret1, H.C. Lee2, C.K. Jeong2, T. Ryo3, H. Kondoh3, Y. Jugnet1, J.C. Bertolini1, Z. Liu4, G Olivieri5, F. Bournel5, J.J. Gallet5, B.S. Mun2 and F.J. Cadete Santos Aires11Institut de Recherches sur la Catalyse et l’Environnement de Lyon (UMR 5256 CNRS/Univ. Lyon 1), 2, Av. Albert Einstein. 69626-Villeurbanne cedex. France.2Department of Physics and Photon Science, School of Physics and Chemistry, Ertl Center for Electrochemistry and Catalysis, Gwangju Institute of Science and Technology. Korea.3Department of Chemistry, Keio University, Yokohama 223-8522. Japan.4Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720. USA.5Laboratoire de Chimie Physique – Matière et Rayonnement (UMR 7614 CNRS/Univ. P. & M. Curie). 11, Rue Pierre et Marie Curie. 75231 Paris Cedex 05. France.§ present address : Centre de Recherches sur la Conservation des Collections (USR3224 CRC), Muséum National d’Histoire Naturelle. 36, Rue Geoffroy Saint-Hilaire – CP 21. 75005-Paris. France.ABSTRACTEven though the study of gaseous molecules has been tackled since the early days of X-ray photoelectron spectroscopy (XPS)1,2, a new design and the use of synchrotron facilities, as (tunable) X-ray sources, has increased the interest of using ambient (or near-ambient) pressure XPS (AP-XPS or NAP-XPS)3-5 to study solid gas/solid and liquid/solid interfaces. This is particularly true when you want to access chemical and electronic properties of catalytic surfaces in realistic reaction conditions (variable P, T).We are interested in the study of bimetallic catalytic surfaces and their chemical/electronic surface properties during the oxidation of carbon monoxide. Indeed, the low temperature catalytic oxidation of carbon monoxide to carbon dioxide is an important reaction used in several areas and in particular for removing the CO traces from the H2 combustible for fuel cell applications. Pt and Au are well known catalysts for the CO oxidation reaction, however on both metals the oxygen dissociation remains the rate determining step. Alloying Pt or Au with a second metal, that facilitates the oxygen activation while keeping free sites for CO adsorption on the surface, appears as an effective way to improve the catalytic performances of these two metals. Based on the performance of real catalysts (bimetallic nanoparticles supported on oxides), we have thus chosen to study by (N)AP-XPS two surfaces : Pt3Sn(111) (with two surface terminations - (2x2) and (√3x√3) depending on the annealing temperature)6 and Pd70Au30(110). REFERENCES1. K. Siegbahn, C. Nordling, G. Johannson, J. Hedman, P.F. Heden, K. Hamrin, U. Gelius, T. Bergmark, L.O. Werme, R. Manne, Y. Baer, ESCA Applied to Free Molecules, Amsterdam, London: North Holland, 1969.2.H. Siegbahn, K. Siegbahn, J. Electron Spectrosc. Relat. Phenom 2, 319-325 (1973).3.D.F. Ogletree, H. Bluhm, G. Lebedev, C. Fadley, Z. Hussain, M. Salmeron, Rev. Sci. Instr. 73, 3872-3877 (2002).4. M. Salmeron, R. Schlögl, Surf. Sci. Reports 63,169-199 (2008).5. M.E. Grass, P.G. Karlsson, F. Aksoy, M. Lundqvist, B. Wannberg, B.S. Mun, Z. Hussain, Z. Liu, Rev. Sci. Instr. 81, 053106 (2010).6. Y. Jugnet, D. Loffreda, C. Dupont, F. Delbecq, E. Ehret, F.J. Cadete Santos Aires, B.S. Mun, F. Aksoy Akgul, Z. Liu, J. Phys. Chem. Lett. 3, 3707-3714 (2012)

Orbital and millennial Antarctic climate variability over the past 800,000 years

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, 800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records