Towards Quantitative Void Fraction Measurement With an Eddy Current Flowmeter for Fourth Generation Sodium Cooled Fast Reactors: A Simplified Model

We propose an experimental methodology for the purpose of quantitative void fraction measurements in fourth generation Sodium cooled fast reactors with a standard Eddy Current Flow Meter (ECFM) sensor. The methodology consists of using the technique of ellipse fit and correlate the fluctuations in the angle of inclination of this ellipse with the void fraction. This methodology is applied in this paper to an ideal configuration of periodic grooves on solid aluminium cylinder with various volumic fractions. The effects of physical parameters such as coil excitation frequency, coil current and motion have been studied. The first results show that ECFM is sensitive to void fractions between 0.3% and 6.9%. It further demonstrates that the response to void fraction is insensitive to the mean velocity of the two-phase medium

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/)

Analyse rétrospective sur 103 prescriptions de PPSB en cas d'accident hémorragique ou de situation d'urgence sous AVK (un audit ciblé confronté aux recommandations 2008 de la HAS)

Les recommandations de la HAS publiées en 2008, portant sur la prise en charge des accidents hémorragiques graves sous AVK et la prévention des accidents hémorragiques en cas de chirurgie ou de gestes urgents chez des malades sous AVK, fixent des objectifs précis aux urgentistes. Notre travail rétrospectif, effectué au service des urgences adultes et à l'UHCD du pôle urgences, a évalué 103 prescriptions de PPSB dont 69 administrations pour des accidents hémorragiques et 34 administrations prophylactiques. L'analyse des prescriptions de PPSB a retenu que les 69 accidents hémorragiques répondaient aux critères de gravité retenus par la HAS pour justifier une réversion en urgence de l'effet des AVK, soit 100 % d'indications justifiées. Chez 49 des 69 patients (71%), les urgentistes ont precrits de manière précise la posologie recommandée de PPSB. Concernant les prescriptions de vitamine K, elles ont été effectuées 57 fois (83%) mais eulement 40 fois (58%) à la posologie attendue de 10 mg et dans 17 cas (25%) à une posologie non conforme. Dans 12 cas (17%), l'administration de vitamine K n'a pas été effectuée. En croisant les co-administrations de PPSB et de vitamine K, les prescriptions respectent strictement les recommandations dans 41% des cas (28 patients). 46 malades (67%) ont eu un 1er contrôle de l'INR dont 36 dans le délai attendu de 30 minutes post réversion. Dans seulement 19 cas, les urgentistes ont prescrits l'INR recommandé 6 heures après l'administration de vitamine K. Ainsi le taux de conformité du suivi de l'INR après réversion est de seulement 13%. Dans le groupe des 34 malades ayant reçu du PPSB à titre prophylactique, 33 cas (96%) justifiaient la réversion de l'effet des AVK. 25 fois la posologie de PPSB était conforme aux recommandations (75%). Chez 23 patients la co-prescription de vitamine K était indiquée et réalisée 12 fois (35%), alors que seulement 4 (12%) des 11 malades qui ne nécessitaient pas vitamine K n'en ont pas eu de manière effective. Ainsi l'indication de la vitamine K était respectée dans 47% des cas. L'iNR a été contrôlé dans les délais impartis respectivement de 30 minutes après l'administration de PPSB chez seulement 12 patients (35%) et de 6 heures après la vitamine K chez 19 malades (56%). A la lecture de ces résultats, on note que les urgentistes du CHU de Clermont-Ferrand se sont bien appropriés les recommandations 2008 de la HAS en terme de définition des critères de gravité des hémorragies sous AVK et d'indication de réversion en urgence de l'effet des AVK. SI les posologies prescrites de PPSB sont conformes aux attentes plus de 7 fois sur 10, la bonne prescription concomitante de vitamine K ne concerne qu'un peu plus de la moitié des malades et le suivi de l'INR post réversion reste insuffisant.CLERMONT FD-BCIU-Santé (631132104) / SudocSudocFranceF

Traitement par la protéine C activée (évaluation de l'efficacité et de la tolérance chez 37 patients de réanimation chirurgicale)

STRASBOURG-Medecine (674822101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Quand les associations remplacent l'Etat ? n° 163 Revue française d'administration publique

National audienceDu projet de Big Society de David Cameron en Grande Bretagne, aux Social impact bonds aux Etats-‑Unis ou à quelques expériences communautaires au Québec, le projet d’un remplacement des pouvoirs publics par les associations pour l’exercice de certaines missions a été mis à l’ordre du jour. Dans quelle mesure cette tendance est également perceptible dans le cas français ? Ce dossier thématique présente tout d’abord un tour d’horizon des expériences dans certains pays étrangers qui met en évidence le brouillage de frontières avec le secteur privé lucratif. L’évolution de l’encadrement des associations à travers la redistribution des formes de financement ou les modalités d’encadrement par les activités de conseil de gestion est ensuite abordée. Des études de cas dans des secteurs contrastés comme le périscolaire, la protection de la nature et l’accompagnement des handicapés permettent enfin de faire ressortir de nouvelles lignes de partage entre initiatives associatives et commande publique. Ces exemples font également apparaître une diversification des formes d’emploi et de nouvelles articulations entre travail salarié et bénévole, de même que de nouveaux principes de justification de l’action publique. Ce qui en ressort de manière globale n’est pas tant une logique de substitution qu’un jeu de désengagements et de réengagements de l’État vis-à‑vis des associations

La recomposition des relations entre l'Etat et les associations : désengagements et réengagements

National audienceDu projet de Big Society de David Cameron en Grande Bretagne, aux Social impact bonds aux Etats-‑Unis ou à quelques expériences communautaires au Québec, le projet d’un remplacement des pouvoirs publics par les associations pour l’exercice de certaines missions a été mis à l’ordre du jour. Dans quelle mesure cette tendance est également perceptible dans le cas français ? Ce dossier thématique présente tout d’abord un tour d’horizon des expériences dans certains pays étrangers qui met en évidence le brouillage de frontières avec le secteur privé lucratif. L’évolution de l’encadrement des associations à travers la redistribution des formes de financement ou les modalités d’encadrement par les activités de conseil de gestion est ensuite abordée. Des études de cas dans des secteurs contrastés comme le périscolaire, la protection de la nature et l’accompagnement des handicapés permettent enfin de faire ressortir de nouvelles lignes de partage entre initiatives associatives et commande publique. Ces exemples font également apparaître une diversification des formes d’emploi et de nouvelles articulations entre travail salarié et bénévole, de même que de nouveaux principes de justification de l’action publique. Ce qui en ressort de manière globale n’est pas tant une logique de substitution qu’un jeu de désengagements et de réengagements de l’État vis-à‑vis des associations

Acoustic techniques for SFR continuous monitoring - Illustration with the continuous characterisation of a bubble cloud

International audienceFeedback on the operation of French sodium fast reactors (SFR) revealed the necessity to improve continuous monitoring, particularly in terms of the primary system instrumentation. Among others, research and development is performed in order to characterise the continuous presence of microbubbles in the primary liquid sodium.A water-air bench has been experimented as the first step of the industrial development of acoustical techniques. The generated bubble cloud characteristics are very similar to the reactor case (bubble radiuses and void fractions).Non-linear acoustic methods have been investigated to determine the histogram of bubble radiuses. Our work involved using the non-linear data resulting from the mixing of two frequencies. Sweeping at low frequency makes it possible to determine the non-linear resonance of the bubbles present. Then the non-linear mixing with a high-imagery frequency is used to build the bubble radius histograms. In addition to this method, measurement of the low-frequency acoustic velocity using a Helmholtz resonator is proposed to determine the void fraction. Future industrial prospects for this work look promisin

New studies on scattering properties of different kinds of soot and carbon-black

International audienceNew polarization and brightness curves as a function of scattering angle are studied at λ=632.8 and 543.5 nm using PROGRA2 instruments (Propriétés Optiques des Grains Astronomiques et Atmosphériques) for four different kinds of soot and for two samples of carbon-black levitating in the cloud. The soot samples are also studied on the deposited surface. Two of the soot samples are issued from incomplete combustion of Toluene liquid solvent under two different combustion conditions. Two others are issued from a solid polymer. Polymethyl Methacrylate or PMMA under two different combustion conditions. These new studies are done using new more sensitive cameras than previous ones, allowing darker agglomerates to be detected

Scattering properties of sands. 2. Results for sands from different origins

International audienceMineral sand is a major component of aerosols in the atmosphere. It is necessary to have a laboratory database to interpret the remote sensing measurements of light scattered by such grains. For this purpose, the PROGRA2 experiment is dedicated to the retrieval of polarization and brightness phase curves, in the visible wavelength domain, of various grains that can be found in Earth's atmosphere and in space. The measurements of the scattered light by levitating clouds of grains are conducted at two wavelengths, 632.8 and 543.5 nm, with PROGRA2-VIS. Large grains (at least tens of micrometers) are studied in microgravity conditions during parabolic flights; smaller (micrometer-sized) grains are lifted by an air draught in ground-based conditions. The PROGRA2-SURF instrument allows measurements on the grains deposited on a plane surface, at the same wavelengths. New data for the scattering properties are presented for sands of various origins, including fine clay. The polarimetric phase curves for levitating grains are close to each other for all the samples (except for black sands); small discrepancies are mainly due to grains' light absorption differences. The polarization curves for levitating grains differ strongly from those of deposited grains (dry or wet). In particular, these curves can be used to interpret remote sensing measurements to distinguish between grains at ground and grains transported by wind

Observation of a very large and persistent mode of desert dust in African air masses transported over the Mediterranean Sea with drifting balloons

International audienceThe objective of this study was to document in situ the particle size distribution of desert dust particles during their long-range transport in the free troposphere, with a particular focus on the coarse size fraction that dominates the mass flux. The basic idea was to deploy a specifically designed optical particle counter/sizer named LOAC (Light Optical Aerosol Counter/sizer) under drifting balloons in order to minimize isokinetic sampling problems. Boundary-layer pressurized balloons (BLBPs) were launched on alert in the western Mediterranean basin in the framework of the Chemistry and Aerosol Mediterranean Experiment (ChArMEx) field campaigns, allowing us to perform original quasi-Lagrangian monitoring of desert dust aerosols over the sea. We illustrate tests and validations of LOAC measurements performed to qualify the instrument that include comparisons with concurrent aircraft and tethered balloon measurements, and remote sensing measurements including an AERONET sun-photometer, and a ground-based and the CALIOP lidar systems. As many as 10 LOAC flights were successfully conducted, mainly from Minorca Isl., Spain, during 4 Saharan dust transport events, with BLPBs drifting at altitudes between 2.0 and 3.3 km above sea level. The longest flight exceeded 700 km and lasted more than 25 h. Aerosol optical depths in the balloon vicinity did not exceed about 0.4 but the presence of turbid dust layers was confirmed thanks to dual scattering angle measurements by LOAC allowing the identification of dust particles. LOAC data from BLBPs could generally be fitted by a 3-mode lognormal distribution at roughly 0.2, 4 and 30 µm in modal diameter. Up to about 0.0001 dust particles per cubic cm larger than 40 µm are reported and no significant evolution of the size distribution was observed during the flights whereas we were expecting to observe gravitational sedimentation of the largest particle size fraction. We also flown LOAC under meteorological sounding balloons during those events to document the dust vertical distribution. Shorter integration time limits the sensitivity to large particles but their presence was confirmed in dust layers. Large particle were also occasionally observed during routine LOAC soundings at Aire-sur-l'Adour in southwestern France. The presence and persistence of a 'giant' mode at about 30 µm in diameter even after several days of transport contradicts calculations of particles sedimentation velocity. From an indirect evidence of the presence of charged particles derived from the LOAC measurements, we speculate that electrical forces might counteract gravitational settling of the coarse particles. More details can be found in the ChArMEx Special Issue (https://www.atmos-chem-phys.net/special_issue334.html; see Renard et al. papers)