University of Grenoble

About: University of Grenoble is a education organization based out in Saint-Martin-d'Hères, France. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 25658 authors who have published 45143 publications receiving 909760 citations.

The Mechanism of Selenate Adsorption on Goethite and Hydrous Ferric Oxide

Abstract: EXAFS spectroscopy has been used to investigate the structure of selenate surface complexes sorbed on dry and wet goethite and hydrous ferric oxide. It is shown that selenate oxyanions always form inner-sphere surface complexes on both sorbents regardless of the hydration state. Selenate, like phosphate and selenite, forms binuclear bridging complexes on (hk0) planes with two singly coordinated A-type OH groups. Furthermore evidence is provided for the attachment of selenate oxyanions on (001) planes by the sharing of edges with Fe octahedra. Selenite and arsenate appear to form the same types of surface complexes as selenate at the surface of goethite and hydrous ferric oxide. It is likely that this sorption mechanism is operative for other anions including phosphate and sulfate. A consequence of this study is the conclusion that the crystallographic planes of Fe oxides (hk0 and 001) do not appear to selectivity bond either cations or anions, at least at high surface coverage.

Measuring the misfit between seismograms using an optimal transport distance: application to full waveform inversion

Abstract: Full waveform inversion using the conventional L2 distance to measure the misfit between seismograms is known to suffer from cycle skipping. An alternative strategy is proposed in this study, based on a measure of the misfit computed with an optimal transport distance. This measure allows to account for the lateral coherency of events within the seismograms, instead of considering each seismic trace independently, as is done generally in full waveform inversion. The computation of this optimal transport distance relies on a particular mathematical formulation allowing for the non-conservation of the total energy between seismograms. The numerical solution of the optimal transport problem is performed using proximal splitting techniques. Three synthetic case studies are investigated using this strategy: the Marmousi 2 model, the BP 2004 salt model, and the Chevron 2014 benchmark data. The results emphasize interesting properties of the optimal transport distance. The associated misfit function is less prone to cycle skipping. A workflow is designed to reconstruct accurately the salt structures in the BP 2004 model, starting from an initial model containing no information about these structures. A high-resolution P-wave velocity estimation is built from the Chevron 2014 benchmark data, following a frequency continuation strategy. This estimation explains accurately the data. Using the same workflow, full waveform inversion based on the L2 distance converges towards a local minimum. These results yield encouraging perspectives regarding the use of the optimal transport distance for full waveform inversion: the sensitivity to the accuracy of the initial model is reduced, the reconstruction of complex salt structure is made possible, the method is robust to noise, and the interpretation of seismic data dominated by reflections is enhanced.

The 2019 surface acoustic waves roadmap

Abstract: Today, Surface Acoustic Waves (SAWs) and Bulk Acoustic Waves (BAW) are already two of the very few phononic technologies of industrial relevance and can been found in a myriad of devices employing these nanoscale earthquakes on a chip. Acoustic radio frequency filters, for instance, are integral parts of wireless devices. SAWs in particular find applications in life sciences and microfluidics for sensing and mixing of tiny amounts of liquids. In addition to these continuously growing number of applications, SAWs are ideally suited to probe and control elementary excitations in condensed matter at the limit of single quantum excitations. Even collective excitations, classical or quantum, or integrated optomechanical are nowadays coherently interfaced by SAWs. This wide, highly diverse, interdisciplinary and continuously expanding spectrum literally unites advanced sensing and manipulation applications. Remarkably, SAW technology is inherently multiscale and span from single atomic or nanoscopic units up even to the millimeter scale. The aim of this roadmap article is to present a snapshot of the present state of Surface Acoustic Wave science and technology in 2019 and provide an opinion on the challenges and opportunities that the future holds from a group of renown experts covering the interdisciplinary key areas, ranging from fundamental quantum effects to practical applications of acoustic devices in life science.

EUCAARI ion spectrometer measurements at 12 European sites – analysis of new particle formation events

Abstract: We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range ∼1-42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1-30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale. © Author(s) 2010.