How to Simulate the Surface of a Cometary Nucleus for Public Science Demonstrations

International audienceTo celebrate and appropriately illustrate the rendezvous of the European Rosetta spacecraft with comet 67P/Churyumov– Gerasimenko and the landing of Philae on the surface of the comet’s nucleus on 12 November 2014, the French science museum Palais de la Découverte developed and presented a new and original demonstration. The experiment simulates the behaviour of a cometary surface in a vacuum and shows the formation of jet-like features. We explain here how to prepare an analogue to cometary material from porous ices and carbon, how to approximately reproduce the cometary environment at low pressure, temperature and solar illumination, and how to present the experiment at a public science demonstration

Friction Mediates Scission of Tubular Membranes Scaffolded by BAR Proteins

International audienceMembrane scission is essential for intracellular trafficking. While BAR domain proteins such as endophilin have been reported in dynamin-independent scission of tubular membrane necks, the cutting mechanism has yet to be deciphered. Here, we combine a theoretical model, in vitro, and in vivo experiments revealing how protein scaffolds may cut tubular membranes. We demonstrate that the protein scaffold bound to the underlying tube creates a frictional barrier for lipid diffusion; tube elongation thus builds local membrane tension until the membrane undergoes scission through lysis. We call this mechanism friction-driven scission (FDS). In cells, motors pull tubes, particularly during endocytosis. Through reconstitution, we show that motors not only can pull out and extend protein-scaffolded tubes but also can cut them by FDS. FDS is generic, operating even in the absence of amphipathic helices in the BAR domain, and could in principle apply to any high-friction protein and membrane assembly

Pathogenic variants in THSD4, encoding the ADAMTS-like 6 protein, predispose to inherited thoracic aortic aneurysm

Purpose Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening disease with often unrecognized inherited forms. We sought to identify novel pathogenic variants associated with autosomal dominant inheritance of TAAD. Methods We analyzed exome sequencing data from 35 French TAAD families and performed next-generation sequencing capture panel of genes in 1114 unrelated TAAD patients. Functional effects of pathogenic variants identified were validated in cell, tissue, and mouse models. Results We identified five functional variants inTHSD4of which two heterozygous variants lead to a premature termination codon.THSD4encodes ADAMTSL6 (member of the ADAMTS/L superfamily), a microfibril-associated protein that promotes fibrillin-1 matrix assembly. TheTHSD4variants studied lead to haploinsufficiency or impaired assembly of fibrillin-1 microfibrils.Thsd4(+/-)mice showed progressive dilation of the thoracic aorta. Histologic examination of aortic samples from a patient carrying aTHSD4variant and fromThsd4(+/-)mice, revealed typical medial degeneration and diffuse disruption of extracellular matrix. Conclusion These findings highlight the role of ADAMTSL6 in aortic physiology and TAAD pathogenesis. They will improve TAAD management and help develop new targeted therapies

The COBRAT project (Coupled Observations from Balloon Related to Asim and Taranis)

International audienceWithin a few years the TARANIS (Tool for the Analysis of RAdiations from lightNIngs and Sprites) mission from CNES and the ASIM (Atmosphere-Space Interactions Monitor) from ESA will be operating in space. They are dedicated to the study of TLEs and TGFs and their potential consequences. Both phenomena are observed above thunderstorms and are supposed to be generated in the altitude range [10 km - 80 km]. Accordingly, coordinated measurements from balloons (in the vicinity of the generation regions) will be needed to identify unambiguously the generation mechanisms and the importance of the atmospheric effects. The aim of the COBRAT (Coupled Observations from Balloon Related to Asim and Taranis) project is to maximize the scientific return of the TARANIS and ASIM missions. It is based on the development and the operation of Zero Pressure Balloons (ZPB) that can reside in the middle stratosphere (altitudes in the 20-40 km range) above stormy areas for more than one week and can carry heavy poly-instrumented gondolas (up to 150 kg). We present and discuss the strategy adopted by the COBRAT project

The COBRAT project (Coupled Observations from Balloon Related to Asim and Taranis)

International audienceWithin a few years the TARANIS (Tool for the Analysis of RAdiations from lightNIngs and Sprites) mission from CNES and the ASIM (Atmosphere-Space Interactions Monitor) from ESA will be operating in space. They are dedicated to the study of TLEs and TGFs and their potential consequences. Both phenomena are observed above thunderstorms and are supposed to be generated in the altitude range [10 km - 80 km]. Accordingly, coordinated measurements from balloons (in the vicinity of the generation regions) will be needed to identify unambiguously the generation mechanisms and the importance of the atmospheric effects. The aim of the COBRAT (Coupled Observations from Balloon Related to Asim and Taranis) project is to maximize the scientific return of the TARANIS and ASIM missions. It is based on the development and the operation of Zero Pressure Balloons (ZPB) that can reside in the middle stratosphere (altitudes in the 20-40 km range) above stormy areas for more than one week and can carry heavy poly-instrumented gondolas (up to 150 kg). We present and discuss the strategy adopted by the COBRAT project

Contribution à la caractérisation des propriétés optiques des sables et des suies atmosphériques avec les instruments PROGRA2

Des nouvelles courbes de polarisation et de radiances en fonction de l angle de diffusion sont étudiées à _ = 632,8 nm et 543,5 nm en utilisant des instruments PROGRA2 (Propriétés Optiques des GRains Astronomiques et Atmosphériques) pour différents types d'échantillons de suie et de noir de carbone en lévitation dans l air et déposés sur une surface. Les échantillons de suie sont produits dans des conditions de combustion différentes, affectant ainsi leurs propriétés morphologiques. Un générateur de suie a été également utilisé pour étudier des suies jeunes émises par la combustion du propane. Une comparaison des propriétés optiques entre les suies en lévitation et déposées sur une surface a été discutée. Enfin, ces courbes sont comparées à celles produites par différents types de sable. Les amplitudes de polarisation produites par la suie diffèrent en fonction du diamètre des particules primaires et de la distribution en taille. Ces courbes seules sont donc insuffisantes pour estimer la nature des agglomérats solides qui pourraient être détectés par des mesures à distance dans la stratosphère. D'autre part les courbes de radiance produites par ces échantillons montrent un comportement différent de celles produites par les échantillons de sable et par la poussière interplanétaire. Il est donc important lors de l'interprétation des mesures stratosphériques de combiner les courbes de radiances avec les courbes de polarisation pour déterminer la nature des agglomérats et de fournir des informations sur la nature de suie détectée telle que la taille des particules primaires ainsi que la distribution en taille.New polarization and brightness curves as function of scattering angle are studied at _= 632.8 nm and 543.5 nm using PROGRA2 instruments (Propriétés Optiques des Grains Astronomiques et Atmosphériques) for different kinds of soot samples and carbon-black samples levitating in a cloud and deposited on a surface. The soot samples are generated under different combustion conditions, thus affecting their optical properties. A soot generator was also used to study fresh samples issued from propane combustion. A comparison between soot levitating on a cloud and deposited on surface was discussed. Finally these curves are compared to those produced by different kind of sand. The amplitudes of polarization produced by soot differ significantly depending on the primary particle diameter and on size distribution. These curves alone are then not sufficient to estimate the nature of the solid agglomerates that could be detected by remote measurements in the stratosphere. On the other hand the curves of brightness produced by these samples show a behavior different from those produced by the sand samples and that produced by interplanetary dust. It is therefore important in the interpretation of stratospheric measurements to combine the brightness with the polarization curves to identify the nature of the agglomerates and to provide information on the nature of soot detected as the primary particle diameter and size distribution.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF

Etude des propriétés physiques des aérosols de la moyenne et haute atmosphère à partir d'une nouvelle analyse des observations du GOMOS-ENVISAT pour la période 2002-2006

L étude des aérosols de la stratosphère est primordiale pour modéliser précisément le bilan radiatif terrestre, et pour évaluer l influence des particules sur le cycle de destruction de l ozone. Depuis la découverte de la couche de Junge, ce domaine de recherche connaît différents décors, du plus important contenu en aérosols du dernier siècle après l éruption du Mont Pinatubo en 1991, à un rétablissement vers les faibles niveaux atteints dans les années 2000, qui permet l étude des particules autres que celles d origine volcanique. Cependant, à ce jour, le degré de connaissance est faible quant à la distribution spatiale et verticale de ces aérosols dans la moyenne et haute stratosphère. Leur détection présente plusieurs difficultés: les particules ont une grande variété d origines, compositions, tailles et formes, et leurs faibles épaisseurs optiques rendent indispensables des résultats précis. Un algorithme d inversion développé au LPC2E a été adapté à l analyse des données de niveau 1b de l instrument GOMOS à bord d ENVISAT, qui emploie la technique d occultation stellaire, et fournit une bonne (mais irrégulière) couverture géographique et temporelle des mesures; un critère de sélection est d ailleurs nécessaire du fait de l utilisation de sources lumineuses de propriétés différentes. La méthode mise au point est validée pour l étude de l extinction induite par les aérosols; une climatologie globale est alors établie pour la période allant d août 2002 à juillet 2006, et indique la présence permanente de particules dans l ensemble du globe, jusqu à environ 45 km d altitude. La variabilité temporelle de l extinction montre une augmentation progressive du contenu moyen depuis 2002 aux latitudes tropicales dans la basse stratosphère, et a permis d évaluer l effet de l oscillation quasi-biennale et d étudier d autres variations saisonnières. La dépendance spectrale permet de déduire certaines spécificités concernant la taille et la nature des aérosols, majoritairement des particules sulfatées, mais également des suies en provenance de la troposphère et des particules d origine interplanétaire.The study of stratospheric aerosols is crucial for modeling precisely the earth s radiative budget and because of their influence on ozone depletion. Since the discovery of Junge layer, this area of research has been through various situations: from the greatest volcanic upload of last century after Mount Pinatubo eruption in 1991, and slowly recovering to background levels reached in the 2000s, which allow the study of other than volcanic particles. However, the vertical and spatial distribution of these aerosols in the middle and high stratosphere is still poorly documented and not yet totally understood. Their detection presents many difficulties: the particles have a great variety of origins, compositions, shapes and sizes, and their low optical thicknesses make accurate results necessary. An inversion algorithm developed in the LPC2E has been adapted to the analysis of level 1b data from GOMOS instrument onboard ENVISAT. The star occultation technique leads to a good (but irregular) spatial and temporal sampling, and a data selection criteria allows the analysis of accurate results, which validation is led for the study of aerosol extinction. A global climatology is then established for the August 2002 to July 2006 period, and shows the permanent presence of aerosol particles around the globe, up to 45 km altitude. The temporal variability shows a progressive enhancement of the mean content from 2002 in the tropics, and was useful to study the influence of the quasi-biennial oscillation in the middle stratosphere, as well as some seasonal features. The study of the spectral dependence informs about the size and nature of the particles, mainly sulfate aerosols, but also soot coming from the troposphere and aerosols of extra-terrestrial origin.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF

A new global climatology of different types of aerosols in the stratosphere by GOMOS‐Envisat data treated with the LPC2E processor

International audienceA new global climatology of different types of aerosols in the stratosphere by GOMOS-Envisat data treated with the LPC2E processor • Local studies with balloon-borne instruments have detected the presence of solid particles (mainly soot) in the middle stratosphere free of volcanic aerosols (Renard et al, JGR, 113, D21303, 2008

High Resolution Mapping of PM2.5 Concentrations in Paris (France) Using Mobile Pollutrack Sensors Network in 2020

International audienceThere is a need for accurate monitoring of PM2.5 that adversely affects human health. Consequently, in addition to the monitoring performed by fixed microbalance instruments installed under legal obligation, we are proposing to deploy the Pollutrack network of mobile sensors within the city of Paris (France). The measurements are performed by mobile aerosol counters mounted on the roof of cars, providing a constant series of readings in the 0.3–10 µm size range that are then aggregated to identify areas of mass concentrations of pollution. The performance of the Pollutrack sensors has been established in ambient air in comparison with the microbalance measurement devices and with the Light Optical Aerosols Counter (LOAC) aerosol counter. A measurement uncertainty of about 5 µg. m−3 is obtained with absolute values from the Pollutrack measurements made at a given location. Instead of the current modelizations based on very few PM2.5 values, maps built from real measurements with a spatial resolution down to 100 m can now be produced each day for Paris, and potentially for specific times of the day, thanks to the high number of measurements achievable with the Pollutrack system (over 70,000 on weekdays). Interestingly, the global trend of PM2.5 content shows several significant pollution events in 2020 despite the COVID-19 crisis and the lockdown. The Pollutrack pollution maps recorded during different PM2.5 pollution conditions in the city frequently identified a strong spatial heterogeneity where the North and the East of Paris were more polluted than the west. These “hot spots” could be due to the city topology and its sensitivity to wind direction and intensity. These high-resolution maps will be crucial in creating evidence for the relevant authorities to respond appropriately to local sources of pollution and to improve the understanding of transportation of urban PM