Dynamical System Description of the Solar Radiation Pressure and j2 Phase Space for End-Of-life Design and Frozen Orbit Design

n this work we review the effect of solar radiation pressure on the eccentricity of circumterrestrial orbits, perturbed also by the oblateness of the Earth. We compute the equilibrium points of a reduced system of equations describing the time evolution of the eccentricity, the longitude of the ascending node and the argument of pericenter, and their linear stability. This analysis is the basis for understanding how the phase space is organized in terms of central and hyperbolic orbits. The role of the initial phase with respect to the Sun and of the magnitude of the inclination evolution is also examined. The results follow previous investigations performed by the authors, providing a more complete picture of the whole dynamics, that can be applied to design convenient end-of-life strategies for small satellites equipped with a solar sail or to determine quasi stable Sun-following orbits for satellites swarms

D028 L’expression des gènes PAI-1, tPA et uPA est fortement régulée pendant la différenciation des cellules souches embryonnaires en myocytes et adipocytes

PAI-1 est l’inhibiteur physiologique des activateurs du plasminogène uPA et tPA et inhibe le complexe formé entre uPA et son récepteur, et par voie de conséquence, entre la vitronectine et l’intégrine alphav beta3. PAI-1 est impliqué dans l’adhésion et la migration des cellules endothéliales, dans la différenciation adipocytaire et dans la réponse à l’insuline; in vivo, il facilite la thrombose, la fibrose et le remodelage tissulaire. Des taux élevés circulants de PAI-1 représentent un biomarqueur de l’obésité centrale et sont un facteur pronostic du diabète de type 2. Les propriétés biologiques de PAI-1 ont conduit à l’hypothèse que PAI-1 serait impliqué directement dans le développement du tissu adipeux. Notre objectif est d’évaluer les rôles spécifiques des gènes PAI-1, uPA et tPA dans les mécanismes moléculaires de la différenciation des cellules souches embryonnaires (cellules ES) de souris dans différents lignages.Indétectables à l’état indifférencié, les expressions de PAI-1, uPA et tPA et les activités enzymatiques uPA et tPA sont fortement régulées durant la différenciation des cellules ES. Les activités uPA et tPA sont rapidement augmentées durant la phase précoce de détermination du processus, sans expression détectable de PAI-1. Puis, l’expression de PAI-1 augmente progressivement dans les surnageants de culture des cellules bien différenciées, corrélant avec une inhibition concomittante des activités uPA et tPA. Des expériences d’immunohistochimie montrent que PAI-1 est exprimé à la fois dans les myotubes et dans les adipocytes matures.Le rôle potentiel de ces régulations successives est analysé par la construction de lignées de cellules ES surexprimant le cDNA de PAI- 1 dès l’état indifférencié. Les effets d’une surexpression ectopique de PAI-1 à différent temps pendant la différenciation des cellules ES sont recherchés.De plus, le traitement précoce des cellules ES en différenciation par l’amiloride, inhibiteur spécifique d’uPA, provoque une diminution de la myogénèse et une augmentation de la différenciation adipocytaire. Par contre ces effets ne sont pas retrouvés en traitant les cellules par l’EACA, inhibiteur de la plasmine ou le DMA, un dérivé inactif de l’amiloride

Ventilator-associated pneumonia in patients with covid-19: A systematic review and meta-analysis

The aim of this systematic review and meta-analysis was to estimate the pooled occurrence of ventilator-associated pneumonia (VAP) among patients admitted to an intensive care unit with COVID-19 and mortality of those who developed VAP. We performed a systematic search on PubMed, EMBASE and Web of Science from inception to 2nd March 2021 for nonrandomized studies specifically addressing VAP in adult patients with COVID-19 and reporting data on at least one primary outcome of interest. Random effect single-arm meta-analysis was performed for the occurrence of VAP and mortality (at the longest follow up) and ICU length of stay. Twenty studies were included in the systematic review and meta-analysis, for a total of 2611 patients with at least one episode of VAP. The pooled estimated occurrence of VAP was of 45.4% (95% C.I. 37.8–53.2%; 2611/5593 patients; I2 = 96%). The pooled estimated occurrence of mortality was 42.7% (95% C.I. 34–51.7%; 371/946 patients; I2 = 82%). The estimated summary estimated metric mean ICU LOS was 28.58 days (95% C.I. 21.4–35.8; I2 = 98%). Sensitivity analysis showed that patients with COVID-19 may have a higher risk of developing VAP than patients without COVID-19 (OR 3.24; 95% C.I. 2.2–4.7; P = 0.015; I2 = 67.7%; five studies with a comparison group)

Ocean acidification impairs vermetid reef recruitment.

Vermetids form reefs in sub-tropical and warm-temperate waters that protect coasts from erosion, regulate sediment transport and accumulation, serve as carbon sinks and provide habitat for other species. The gastropods that form these reefs brood encapsulated larvae; they are threatened by rapid environmental changes since their ability to disperse is very limited. We used transplant experiments along a natural CO2 gradient to assess ocean acidification effects on the reef-building gastropod Dendropoma petraeum. We found that although D. petraeum were able to reproduce and brood at elevated levels of CO2, recruitment success was adversely affected. Long-term exposure to acidified conditions predicted for the year 2100 and beyond caused shell dissolution and a significant increase in shell Mg content. Unless CO2 emissions are reduced and conservation measures taken, our results suggest these reefs are in danger of extinction within this century, with significant ecological and socioeconomic ramifications for coastal systems

Saturated high-repetition-rate 18.9-nm tabletop laser in nickel-like molybdenum

Includes bibliographical references (page 167).We report saturated operation of an 18.9-nm laser at 5-Hz repetition rate. An amplification with a gain-length product GL of 15.5 is obtained in the 4d 1S0―4p 1P1 laser line of Ni-like Mo in plasmas heated at grazing incidence with ~1-J pulses of 8.1-ps duration from a tabletop laser system. Lasing is obtained over a broad range of time delays and pumping conditions. We also measure a GL of 13.5 in the 22.6-nm transition of the same ion. The results are of interest for numerous applications requiring high-repetition-rate lasers at wavelengths below 20 nm