Livrable D3.3 of the PERSEE project : 2D coding tools

49Livrable D3.3 du projet ANR PERSEECe rapport a été réalisé dans le cadre du projet ANR PERSEE (n° ANR-09-BLAN-0170). Exactement il correspond au livrable D3.3 du projet. Son titre : 2D coding tool

Using Quad‐Pol and Single‐Pol RADARSAT‐2 Data for Monitoring Cold Alpine and Outlet Antarctic Glaciers

International audienceThis paper presents some applications of the Maximum Likelihood (ML) texture tracking on displacement estimation of some alpine and antarctic glaciers surfaces. This method is adapted to the statistical characteristic of the new High Resolution (HR) Polarimetric SAR (Pol- SAR) data. The ML texture tracking method is firstly reminded and a statistical model of HR PolSAR data is explained. The main part of this paper is focused on the application of this method on glaciers monitoring. Three different glaciers have been chosen to test the algorithm: a cold alpine glacier, a temperate alpine glacier and an outlet antarctic glacier. The accuracy and limits of the method are highlighted in each case and results application is discussed

Livrable D3.4 of the PERSEE project : 2D coding tools final report

Livrable D3.4 du projet ANR PERSEECe rapport a été réalisé dans le cadre du projet ANR PERSEE (n° ANR-09-BLAN-0170). Exactement il correspond au livrable D3.4 du projet. Son titre : 2D coding tools final repor

Spatial and temporal distributions of surface mass balance between Concordia and Vostok stations, Antarctica, from combined radar and ice core data: first results and detailed error analysis

Results from ground-penetrating radar (GPR) measurements and shallow ice cores carried out during a scientific traverse between Dome Concordia (DC) and Vostok stations are presented in order to infer both spatial and temporal characteristics of snow accumulation over the East Antarctic Plateau. Spatially continuous accumulation rates along the traverse are computed from the identification of three equally spaced radar reflections spanning about the last 600 years. Accurate dating of these internal reflection horizons (IRHs) is obtained from a depth-age relationship derived from volcanic horizons and bomb testing fallouts on a DC ice core and shows a very good consistency when tested against extra ice cores drilled along the radar profile. Accumulation rates are then inferred by accounting for density profiles down to each IRH. For the latter purpose, a careful error analysis showed that using a single and more accurate density profile along a DC core provided more reliable results than trying to include the potential spatial variability in density from extra (but less accurate) ice cores distributed along the profile. The most striking feature is an accumulation pattern that remains constant through time with persistent gradients such as a marked decrease from 26 mm w.e. yr(-1) at DC to 20 mm w.e. yr(-1) at the south-west end of the profile over the last 234 years on average (with a similar decrease from 25 to 19 mm w.e. yr(-1) over the last 592 years). As for the time dependency, despite an overall consistency with similar measurements carried out along the main East Antarctic divides, interpreting possible trends remains difficult. Indeed, error bars in our measurements are still too large to unambiguously infer an apparent time increase in accumulation rate. For the proposed absolute values, maximum margins of error are in the range 4 mm w.e. yr(-1) (last 234 years) to 2 mm w.e. yr(-1) (last 592 years), a decrease with depth mainly resulting from the time-averaging when computing accumulation rates

Livrable D5.2 of the PERSEE project : 2D/3D Codec architecture

Livrable D5.2 du projet ANR PERSEECe rapport a été réalisé dans le cadre du projet ANR PERSEE (n° ANR-09-BLAN-0170). Exactement il correspond au livrable D5.2 du projet. Son titre : 2D/3D Codec architectur

Retrieval of snow properties from the Sentinel-3 Ocean and Land Colour Instrument

The Sentinel Application Platform (SNAP) architecture facilitates Earth Observation data processing. In this work, we present results from a new Snow Processor for SNAP. We also describe physical principles behind the developed snow property retrieval technique based on the analysis of Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A/B measurements over clean and polluted snow fields. Using OLCI spectral reflectance measurements in the range 400–1020 nm, we derived important snow properties such as spectral and broadband albedo, snow specific surface area, snow extent and grain size on a spatial grid of 300 m. The algorithm also incorporated cloud screening and atmospheric correction procedures over snow surfaces. We present validation results using ground measurements from Antarctica, the Greenland ice sheet and the French Alps. We find the spectral albedo retrieved with accuracy of better than 3% on average, making our retrievals sufficient for a variety of applications. Broadband albedo is retrieved with the average accuracy of about 5% over snow. Therefore, the uncertainties of satellite retrievals are close to experimental errors of ground measurements. The retrieved surface grain size shows good agreement with ground observations. Snow specific surface area observations are also consistent with our OLCI retrievals. We present snow albedo and grain size mapping over the inland ice sheet of Greenland for areas including dry snow, melted/melting snow and impurity rich bare ice. The algorithm can be applied to OLCI Sentinel-3 measurements providing an opportunity for creation of long-term snow property records essential for climate monitoring and data assimilation studies—especially in the Arctic region, where we face rapid environmental changes including reduction of snow/ice extent and, therefore, planetary albedo.publishedVersio

Statistical study of the prompt-fission γ -ray spectrum for U 238 (n, f) in the fast-neutron region STATISTICAL STUDY of the PROMPT-FISSION ... L. QI et al.

Prompt-fission γ-ray spectra (PFGS) have been measured for the U238(n,f) reaction using fast neutrons produced by the LICORNE directional neutron source. Fission events were detected with an ionization chamber containing actinide samples placed in the neutron beam, and the coincident prompt-fission γ rays were measured using a number of LaBr3 scintillation detectors and a cluster of nine phoswich detectors from the PARIS array. Prompt-fission γ rays (PFGs) were discriminated from prompt-fission neutrons using the time-of-flight technique over distances of around 35 cm. PFG emission spectra were measured at two incident neutron energies of 1.9 and 4.8 MeV for U238(n,f) and also for Cf252(sf) as a reference. Spectral characteristics of PFG emission, such as mean γ multiplicity and average total γ-ray energy per fission, as well as the average γ-ray energy, were extracted. The sensitivity of these results to the width of the time window and the type of spectral unfolding procedure used to correct for the detector responses was studied. Iteration methods were found to be more stable in low-statistics data sets. The measured values at En=1.9MeV were found to be the mean γ multiplicity Mγ=6.54±0.19, total released energy per fission Eγ,tot=5.25±0.20 MeV, and the average γ-ray energy ϵγ=0.80±0.04 MeV. Under similar conditions, the values at En=4.8MeV were measured to be Mγ=7.31±0.46, Eγ,tot=6.18±0.65 MeV, and ϵγ=0.84±0.11 MeV

Copernicus Ocean State Report, issue 6

The 6th issue of the Copernicus OSR incorporates a large range of topics for the blue, white and green ocean for all European regional seas, and the global ocean over 1993–2020 with a special focus on 2020

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Producing substances and producing facts : dry process apparatus and chemical mechanics in France between 1850 and 1884

Une des branches de la chimie physique, la chimie physique des réactions, doit son développement à des recherches en voie sèche entre 1850 et les années 1880 prolongeant la mécanique chimique du début du XIXe siècle qui reposait principalement sur la chimie des sels. C’est l’objet de cette thèse. En mettant en œuvre une méthodologie basée sur l’étude des appareils de laboratoire en relation avec les idées, le contexte technique, les facteurs sociaux et les techniques de narration expérimentale, l’enjeu est aussi de contribuer à une épistémologie de l’expérience et du fait scientifique. L’analyse porte sur les recherches françaises en voie sèche, source de nombreux faits régulièrement cités dans des traités de chimie physique postérieurs à 1885. J’identifie deux périodes de production des faits : de 1850 à 1867, des faits nouveaux puis, de 1867 à 1884, des faits plus nombreux et plus standardisés organisés par des lois et des formalismes. Mon analyse montre comment les faits nouveaux sont le produit de collectifs techno-scientifiques regroupant des professeurs, des fabricants d’instruments et des industriels, avec d’une part, un collectif minéro-métallurgique de hautes températures et d’autre part des collectifs liés à la pharmaco-chimie. Les opérations de production de corps y jouent un rôle central. Les faits sont ensuite retravaillés dans le cadre d’une recherche de lois expérimentales par des groupes plus spécialisés puis pris en compte dans des réflexions théoriques plus larges. L’analyse de la dynamique de ces collectifs permet de comprendre finalement comment des voies particulières de recherche se rejoignent pour aboutir à la fin du siècle à la proposition de disciplines organisées, comme la chimie physique des réactions.The physical chemistry of reactions, one of the branches of physical chemistry, owes its development to researches in the dry process between 1850 and the 1880s extending the chemical mechanics of the early nineteenth century which was based mainly on salt chemistry. This is the subject of this PhD thesis. By implementing a methodology based on the study of laboratory apparatus in relation to ideas, technical context, social factors and experimental narrative techniques, the challenge is also to contribute to an epistemology of experience and scientific fact. The analysis focuses on French research in the dry process, the source of many facts regularly cited in physical chemistry treaties after 1885. Two periods of production of facts are identified in this thesis : a period of new facts from 1850 to 1867, then, from 1867 to 1884, a period with more numerous and standardized facts organized by laws and formalisms. My analysis shows how the new facts are the product of techno-scientific collectives bringing together professors, instrument manufacturers and industrialists, with, on one hand, a high temperatures mineral-metallurgical collective and, on the other hand, collectives linked to pharmaco-chemistry. Substances production plays a central role here. These facts are then reworked within the framework of an experimental laws research by more specialized groups, then, those facts are taken into account in broader theoretical reflections. The analysis of the dynamics of these collectives makes it finally possible to understand how particular research paths come together to end up at the end of the century with the proposal of organized disciplines such as the physical chemistry of reactions