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201.
Descamp P Holon F Ballesta L Guilbert A Guillot M Boissery P Raimondino V Deter J 《Marine pollution bulletin》2011,62(2):284-292
Posidonia oceanica is an endemic seagrass from the Mediterranean Sea. It is an indicator of water quality and of the ecological state of coastal ecosystems. The aim of this paper is to test acoustic telemetry for monitoring the position of P. oceanica meadow limits with varied types. After evaluating the accuracy of the system, we present results from a spatiotemporal survey of P. oceanica meadows on nine sites located on the French coast. The method has been demonstrated to be highly efficient for high precision underwater mapping regardless of meadow type, with 1 cm accuracy for a distance of 40 m between the base and the pointer. A temporal survey led at Cerbere-Banyuls shows a weak global progression of 4 m2 (progression of 26 m2 - regression of 22 m2) between 2006 and 2010. Finally, we discuss the cost and efficiency of this method, and wether it should be generalized for further studies. 相似文献
202.
Nicholas Deichmann John Clinton Stephan Husen Benjamin Edwards Florian Haslinger Donat Fäh Domenico Giardini Philipp Kästli Urs Kradolfer Stefan Wiemer 《Swiss Journal of Geoscience》2011,104(3):537-547
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during
2010. During this period, 407 earthquakes and 85 quarry blasts were detected and located in the region under consideration.
With a total of only 19 events with ML ≥ 2.5, the seismic activity in the year 2010 was below the average over the previous 35 years. The two most noteworthy earthquakes
were the ML 3.4 Barrhorn event near Sankt Niklaus (VS) and the ML 3.0 event of Feldkirch, both of which produced shaking of intensity IV. 相似文献
203.
Florian Perez Claude Mügler Philippe Jean-Baptiste Jean Luc Charlou 《Computational Geosciences》2013,17(2):217-237
We present a new numerical tool developed in the Cast3M software framework to model hydrothermal circulation. Thermodynamic properties of one-phase pure water are calculated from the International Association for the Properties of Water and Steam formulation. This new numerical tool is validated on several test cases of convection in closed-top and open-top boxes. Simulations of hydrothermal circulation in a homogeneous-permeability porous medium also give results in good agreement with already published simulations. This new numerical tool is used to construct a geometric and physical conceptual model of the Rainbow vent site at 36°14′N on the Mid-Atlantic Ridge. Several configurations are discussed, showing that high temperatures and high mass fluxes measured at the Rainbow site cannot be modeled with hydrothermal circulation in a homogeneous-permeability porous medium. These high values require the presence of a fault or a preferential pathway right below the venting site. We propose and discuss a two-dimensional single-pass model that allows us to simulate both high temperatures and high mass fluxes. This modeling of the hydrothermal circulation at the Rainbow site constitutes the first but necessary step to understand the origin of high concentrations of hydrogen issued from this ultramafic-hosted vent field. 相似文献
204.
Tobias Diehl Nicholas Deichmann John Clinton Stephan Husen Toni Kraft Katrin Plenkers Benjamin Edwards Carlo Cauzzi Clotaire Michel Philipp Kästli Stefan Wiemer Florian Haslinger Donat Fäh Urs Kradolfer Jochen Woessner 《Swiss Journal of Geoscience》2013,106(3):543-558
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2012. During this period, 497 earthquakes and 88 quarry blasts were detected and located in the region under consideration. With a total of only 13 events with ML ≥ 2.5, the seismic activity in the year 2012 was far below the average over the previous 37 years. Most noteworthy were the earthquake sequence of Filisur (GR) in January with two events of ML 3.3 and 3.5, the ML 4.2 and ML 3.5 earthquakes at a depth of 32 km below Zug in February and the ML 3.6 event near Vallorcine in October. The epicentral intensity of the ML 4.2 event close to Zug was IV, with a maximum intensity of V reached in a few areas, probably due to site amplification effects. 相似文献
205.
Victoria Shushakova Edwin R. Fuller Jr. Florian Heidelbach David Mainprice Siegfried Siegesmund 《Environmental Earth Sciences》2013,69(4):1281-1297
Thermoelastic behavior of different marble types was analyzed using computational modeling and experimental measurements. Eight marble samples with different composition, grain size, grain boundary geometry, and texture were investigated. Calcitic and dolomitic marbles were considered. The average grain size varies from 75 μm to 1.75 mm; grain boundary geometry differs from nearly equigranular straight grain boundaries to inequigranular-interlobate grain boundaries. Four typical marble texture types were observed by EBSD measurements: weak texture; strong texture; girdle texture and high-temperature texture. These crystallographic orientations were used in conjunction with microstructure-based finite element analysis to compute the thermoelastic responses of marble upon heating. Microstructural response maps highlight regions and conditions in the marble fabric that are susceptible to degradation phenomena. This behavior was compared to the measured thermal expansion behavior, which shows increasing residual strains upon repetitive heating–cooling cycles. The thermal expansion behavior as a function of temperature changes can be classified into four categories: (a) isotropic thermal expansion with small or no residual strain; (b) anisotropic thermal expansion with small or no residual strain; (c) isotropic thermal expansion with a residual strain; and (d) anisotropic thermal expansion with residual strain. Thermal expansion coefficients were calculated for both simulated and experimental data and also modeled from the texture using the MTEX software. Fabric parameters control the amount and directional dependence of the thermal expansion. Marbles with strong texture show higher directional dependence of the thermal expansion coefficients and have smaller microstructural values of the maximum principal stress and strain energy density, the main precursors of microcracking throughout the marble fabric. In contrast, marbles with weak texture show isotropic thermal expansion behavior, have a higher propensity to microcracking, and exhibit higher values of maximum principal stress and strain energy density. Good agreement between the experimental and computational results is observed, demonstrating that microstructure-based finite-element simulations are an excellent tool for elucidating influences of rock fabric on thermoelastic behavior. 相似文献
206.
Manuel Calvo-Rathert Ángel Carrancho Florian Stark Juan José Villalaín Mimi Hill 《Quaternary Research》2012,77(2):326-330
This study tests if burnt soils and sediments can provide reliable records of geomagnetic field strength at the time of burning by carrying out an experiment to reproduce the prehistoric use of fire on a clayish soil substratum. Rock magnetic experiments showed that in the upper 0–1 cm of the central part of the burnt surface, remanence is a thermoremanent magnetization carried by single-domain magnetite and that samples are thermally stable. Fourteen specimens from that area were subjected to paleointensity experiments with the Coe method (1967). An intensity of 42.9 ± 5.7 μT was estimated below 440°C, whereas at higher temperatures magneto-mineralogical alterations were observed. Corresponding successful microwave intensity determinations from two specimens gave a mean value of 47.6 μT. Both results are in reasonable agreement with the expected field value of 45.2 μT. Burnt soils of archeological fires thus have the potential to record accurately the paleofield strength and may be useful targets for archeointensity investigations. Coincident results obtained from two different paleointensity determination methods support this conclusion. 相似文献
207.
Thomas Kalbacher Jens-Olaf Delfs Haibing Shao Wenqing Wang Marc Walther Luis Samaniego Christoph Schneider Rohini Kumar Andreas Musolff Florian Centler Feng Sun Anke Hildebrandt Rudolf Liedl Dietrich Borchardt Peter Krebs Olaf Kolditz 《Environmental Earth Sciences》2012,65(5):1367-1380
Numerical modeling of interacting flow and transport processes between different hydrological compartments, such as the atmosphere/land surface/vegetation/soil/groundwater systems, is essential for understanding the comprehensive processes, especially if quantity and quality of water resources are in acute danger, like e.g. in semi-arid areas and regions with environmental contaminations. The computational models used for system and scenario analysis in the framework of an integrated water resources management are rapidly developing instruments. In particular, advances in computational mathematics have revolutionized the variety and the nature of the problems that can be addressed by environmental scientists and engineers. It is certainly true that for each hydro-compartment, there exists many excellent simulation codes, but traditionally their development has been isolated within the different disciplines. A new generation of coupled tools based on the profound scientific background is needed for integrated modeling of hydrosystems. The objective of the IWAS-ToolBox is to develop innovative methods to combine and extend existing modeling software to address coupled processes in the hydrosphere, especially for the analysis of hydrological systems in sensitive regions. This involves, e.g. the provision of models for the prediction of water availability, water quality and/or the ecological situation under changing natural and socio-economic boundary conditions such as climate change, land use or population growth in the future. 相似文献
208.
Complex impedance spectra of polycrystalline samples (with grain size fractions ~5–63, 63–160 and 160–250 μm) and a single crystal sample (with orientation parallel to b), prepared from a natural megacryst augite, were measured in a piston cylinder apparatus at 10 kbar and 500–1,000°C and with a Solartron 1260 Impedance/Gain Phase analyzer over a frequency range of 0.1–106 Hz. The main charge carriers are attributed to small polarons, and the activation enthalpy is 83 ± 3 to 90 ± 3 kJ/mol. The measured electrical conductivity shows no difference between the polycrystalline and single crystal samples, suggesting independence of electrical conductivity on grain size given a change above ~5 μm. The electrical conductivity of augite is much higher than that of olivine, indicating that, if regionally enriched, augites may lead to zones of high electrical conductivity and electrical anisotropy in the deep lithosphere. 相似文献
209.
Robert Andritschke Andreas Zoglauer Gottfried Kanbach Peter F. Bloser Florian Schopper 《Experimental Astronomy》2005,20(1-3):395-403
MEGA, short for Medium Energy Gamma-ray Astronomy, is the development of a new technology telescope in the energy band 0.4--50\ MeV. The wide energy range of MEGA, which spans nuclear γ-ray lines and energetic continuum spectra, the large field of view, and the capacity for polarimetry enables unique investigations into cosmic nucleosynthesis, particle accelerators around compact objects, and explosive high-energy events. We describe the development and tests of a prototype detector. Results from laboratory tests using radioactive sources and from a beam test calibration are presented and an outlook of a potential space mission is sketched. 相似文献
210.
Florian Mermillod‐Blondin Jean‐Paul Gaudet Magali Grino Gaston Desrosiers Michel Creuz des Chtelliers 《水文研究》2003,17(4):779-794
The objective of this study was to measure the effects of invertebrates on the physical characteristics and microbial processes in hyporheic sediments. We investigated the impacts of an assemblage of three taxa (asellids, chironomid larvae, and tubificid worms) on sediment distribution, water fluxes, sediment organic carbon, biofilm (attached bacteria) characteristics, and O2, dissolved organic carbon NO3?, NO2?, and NH4+ concentrations in slow filtration sand–gravel columns. The results showed that invertebrates clearly modified the distribution of particles in the sediment column, probably because of the structures (tubes, macropores, and faecal pellets) produced by the three taxa in the sediment. Our assessment of water fluxes indicated that invertebrate activities led to an increase in the porosity of the sediment columns. In addition, aerobic (O2 consumption) and anaerobic (denitrification and fermentative decomposition of organic matter) microbial processes occurring in the sediment were stimulated in the presence of invertebrates. Finally, the present study demonstrates that invertebrates can act as ecosystem engineers in heterogeneous sediments that are under the influence of an advective flux of water. The solute residence time increased in columns containing the faunal assemblage. Micro‐organisms used more dissolved organic matter and nutrients in the presence of invertebrates because invertebrate activities increased the contact between the biofilm and water. We conclude that engineering by invertebrates in natural conditions modifies characteristics of the hyporheic zone and thereby enhances both the porosity of the sediment and the solute transport across the benthic interface. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献