Structure of the Vesicular Stomatitis Virus N0-P Complex

Replication of non-segmented negative-strand RNA viruses requires the continuous supply of the nucleoprotein (N) in the form of a complex with the phosphoprotein (P). Here, we present the structural characterization of a soluble, heterodimeric complex between a variant of vesicular stomatitis virus N lacking its 21 N-terminal residues (NΔ21) and a peptide of 60 amino acids (P60) encompassing the molecular recognition element (MoRE) of P that binds RNA-free N (N0). The complex crystallized in a decameric circular form, which was solved at 3.0 Å resolution, reveals how the MoRE folds upon binding to N and competes with RNA binding and N polymerization. Small-angle X-ray scattering experiment and NMR spectroscopy on the soluble complex confirms the binding of the MoRE and indicates that its flanking regions remain flexible in the complex. The structure of this complex also suggests a mechanism for the initiation of viral RNA synthesis

Identification of Ammonium Salts on Comet 67P/C-G Surface from Infrared VIRTIS/Rosetta Data Based on Laboratory Experiments. Implications and Perspectives

The nucleus of comet 67P/Churyumov-Gerasimenko exhibits a broad spectral reflectance feature around 3.2 $\mu$m, which is omnipresent in all spectra of the surface, and whose attribution has remained elusive since its discovery. Based on laboratory experiments, we have shown that most of this absorption feature is due to ammonium (NH4+) salts mixed with the dark surface material. The depth of the band is compatible with semi-volatile ammonium salts being a major reservoir of nitrogen in the comet, which could dominate over refractory organic matter and volatile species. These salts may thus represent the long-sought reservoir of nitrogen in comets, possibly bringing their nitrogen-to-carbon ratio in agreement with the solar value. Moreover, the reflectance spectra of several asteroids are compatible with the presence of NH4+ salts at their surfaces. The presence of such salts, and other NH4+-bearing compounds on asteroids, comets, and possibly in proto-stellar environments, suggests that NH4+ may be a tracer of the incorporation and transformation of nitrogen in ices, minerals and organics, at different phases of the formation of the Solar System

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/)

Local topography effects on the surface temperatures on Mars - Application to the case of Recurring Slope Lineae (RSL)

International audienceRecurring Slope Lineae (RSL) are dark linear recurrent features which incrementally lengthen and fade each year on Martian slopes. Their activity during warmest seasons rises the question of modern martian water related process. To investigate this question, this study focuses on the thermal context of slopes hosting RSL. The paper presents a numerical study of surface and subsurface temperatures at high spatial resolution (1 m/pix) of three well-described RSL sites: Palikir Crater, Coprates Chasma and Rauna Crater. We then compare our local thermal simulations to quantitative measurements of the length and timing of RSL lengthening and fading in these three sites. We underline that RSL sites surface temperatures are poorly correlated with RSL morphology's changes. Indeed, lineae lengthening occurs while surface temperature are under the melting point of pure water (273 K) for at least two sites: Coprates Chasma and Rauna Crater, for two different sets of surface physical properties. We also highlight the significant differences in temperature range while lengthening occurs for all the sites, from ~220 K in Coprates Chasma site to a maximum of ~300 K in Palikir Crater. RSL are sometimes associated with signals in topography, involving significant heating variations of the surface, which can yield to the formation of local winds. Facing the thermal inconsistency between wet triggering processes and RSL reported activity, we suggest that RSL are more probably dry processes

Spatially Resolved Thermal Infrared Observations of Uranus and Neptune from the ESO Very Large Telescope in September, 2006: Unexpected Meridional Distribution and Possible Zonal Variability of Upper Tropospheric and Stratospheric

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Predicted Antenna Temperatures Measured by REX/New Horizons During The Pluto’s FlybyProbing the sub-surface in Microwave

International audienceThe Pluto dwarf planet was observed in details in July 2015 by the New Horizons spacecraft (NASA) during a close-targeted flyby which reavealed surprising and fascinating landscapes with a variety of albedo and chemical composition over the surface. During the flyby, the REX microwave instrument was activated in order to measure the antenna temperature while the beam crossed Pluto’s surface. In particular, 3 scans were performed, the first two during few tens of seconds when both the day and night side of Pluto were observed, including the South pole ; and the last one during an occultation with Earth. We present here predited antenna temperatures considering the known and assumed variations of thermal and electrical properties of the Pluto’s sub-surface.. Each scan allow to observe thermal radiation at 4.2 cm wavelength of the surface and subsurface of Pluto, at different locations (latitudes / longitudes). Using a seasonnal thermal model that considers the measured Bond albedo and type of ice, we have modeled the Brightness temperatures that were measured by REX, for different amount of porosity (or thermal inertia). This modeling uses a seasonally-forced thermal model and an emissivity model in the case of circular polarized observations. An antenna temperature if then retrieved assuming a beam pattern for REX. We present here how the antenna temperatures vary with the porosity of the ices obseved

Spatially Resolved Thermal Infrared Observations of Uranus and Neptune from the ESO Very Large Telescope in September, 2006: Unexpected Meridional Distribution and Possible Zonal Variability of Upper Tropospheric and Stratospheric

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Spatially Resolved Thermal Infrared Observations of Uranus and Neptune from the ESO Very Large Telescope in September, 2006: Unexpected Meridional Distribution and Possible Zonal Variability of Upper Tropospheric and Stratospheric

International audienc

Thermal, dielectric and structural properties of Enceladus' leading face

International audienceThe Cassini RADAR was initially designed to examine the surface of Titan through the veil of its optically-opaque atmosphere. However, it is occasionally used to observe airless Saturn's moons from long range and, less frequently, during targeted flybys. In particular, the 16th targeted encounter of Enceladus (Nov. 6, 2011, flyby E16) was dedicated to the RADAR instrument which then acquired data for over 4 hours. This paper focuses on the mid-resolution (0.1-0.6REnceladus) and low-resolution polarized data (0.6-1.0REnceladus) collected during the E16 flyby in the radiometry mode of the RADAR, mainly on the leading side of the moon.In its passive mode, the RADAR records the thermal emission at 2-cm wavelength from, likely, the first meters of an icy surface. Ries and Janssen (2015) first analyzed the E16 mid-resolution radiometry observation and reported on a large-scale emissivity anomaly, possibly associated with the seemingly young tectonized Leading Hemisphere Terrain mapped by Crow-Willard and Pappalardo (2015). With the goal of further investigating the extension of the anomaly region and providing constrains on the thermal, dielectric and structural properties of Enceladus' near surface, we have re-examined this dataset as well as observations acquired in two orthogonal polarizations with the help of a thermal model. This thermal model accounts for both diurnal and seasonal variations of the incident flux, including eclipses which is of importance for the E16 observations partially occurred during a solar eclipse by Saturn.Preliminary results suggest that the average thermal inertia of the near surface of Enceladus' leading face is relatively low, as low as 40 Jm-2K-1s-1/2 . This value does not depart much from the one inferred from measurements in the IR suggesting that the surface of Enceladus is covered by a very porous regolith, at least a few meters thick. In agreement, with this interpretation, the degree of volume scattering (i.e., high-order scattering by voids/heterogeneities in the subsurface) was found to be high, especially in the anomaly region where it is of same order of magnitude of the anomalously radar-bright terrains on Titan (Janssen et al., 2011)