Specificities of exosome versus small ectosome secretion revealed by live intracellular tracking of CD63 and CD9.

Despite their roles in intercellular communications, the different populations of extracellular vesicles (EVs) and their secretion mechanisms are not fully characterized: how and to what extent EVs form as intraluminal vesicles of endocytic compartments (exosomes), or at the plasma membrane (PM) (ectosomes) remains unclear. Here we follow intracellular trafficking of the EV markers CD9 and CD63 from the endoplasmic reticulum to their residency compartment, respectively PM and late endosomes. We observe transient co-localization at both places, before they finally segregate. CD9 and a mutant CD63 stabilized at the PM are more abundantly released in EVs than CD63. Thus, in HeLa cells, ectosomes are more prominent than exosomes. By comparative proteomic analysis and differential response to neutralization of endosomal pH, we identify a few surface proteins likely specific of either exosomes (LAMP1) or ectosomes (BSG, SLC3A2). Our work sets the path for molecular and functional discrimination of exosomes and small ectosomes in any cell type

The extreme physical properties of the CoRoT-7b super-Earth

International audience► Here, we discuss the extreme physical properties possible for the first characterized rocky super-Earth, CoRoT-7b ( = 1.58 , = 5.7 ). ► We make the working hypothesis that the planet is rocky with no volatiles in its atmosphere, and derive the physical properties that result. ► The dayside is very hot (2500 K at the sub-stellar point) while the nightside is very cold (∼ 50 K). The sub-stellar point is as hot as the tungsten filament of an incandescent bulb, resulting in the melting and distillation of silicate rocks and the formation of a lava ocean. ► These possible features of CoRoT-7b should be common to many small and hot planets, including Kepler-10b. They define a new class of objects that we propose to name ''Lava-ocean planets''

The habitability of Proxima Centauri b II. Possible climates and observability

International audienceRadial velocity monitoring has found the signature of a $M \sin i = 1.3$~M$_\oplus$ planet located within the Habitable Zone of Proxima Centauri, (Anglada-Escud\'e et al. 2016). Despite a hotter past and an active host star the planet Proxima~b could have retained enough volatiles to sustain surface habitability (Ribas et al. 2016). Here we use a 3D Global Climate Model to simulate Proxima b's atmosphere and water cycle for its two likely rotation modes (1:1 and 3:2 resonances) while varying the unconstrained surface water inventory and atmospheric greenhouse effect. We find that a broad range of atmospheric compositions can allow surface liquid water. On a tidally-locked planet with a surface water inventory larger than 0.6 Earth ocean, liquid water is always present, at least in the substellar region. Liquid water covers the whole planet for CO$_2$ partial pressures $\gtrsim 1$~bar. For smaller water inventories, water can be trapped on the night side, forming either glaciers or lakes, depending on the amount of greenhouse gases. With a non-synchronous rotation, a minimum CO$_2$ pressure is required to avoid falling into a completely frozen snowball state if water is abundant. If the planet is dryer, $\sim$0.5~bar of CO$_2$ would suffice to prevent the trapping of any arbitrary small water inventory into polar ice caps. More generally, any low-obliquity planet within the classical habitable zone of its star should be in one of the climate regimes discussed here. We use our GCM to produce reflection/emission spectra and phase curves. We find that atmospheric characterization will be possible by direct imaging with forthcoming large telescopes thanks to an angular separation of $7 \lambda/D$ at 1~$\mu$m (with the E-ELT) and a contrast of $\sim 10^{-7}$. The magnitude of the planet will allow for high-resolution spectroscopy and the search for molecular signatures

DEPOTS ELECTROLYTIQUES DE ZINC EN MILIEU CHLORURE CONCENTRE ET EN PRESENCE DE POLYMERES (MECANISMES D'ELECTROCRISTALLISATION ET DE CORROSION)

PARIS-BIUSJ-Thèses (751052125) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Composite profiles and membranes tensegrity panels

The development of the "non standard" architecture, mainly based on curved surfaces using rigid frames combined with cladding panels, emphasizes on new needs. A lightweight innovative solution has been developed to provide adaptable flat or curved cladding panels fixed on the supporting structure, with thermal insulation and possible prefabrication. The panels are realized with an association of tensile membranes and a woven structure of prestressed composite profiles. They are designed on the principle of tensegrity and provide both properties of flexibility and rigidity. Mechanical studies have been performed to determine the relationships between the panel shape and its initial stresses ("form control" and "force control" strategies) and a FEM analysis allows identifying the behavior in association with experimental testing on a prototype system. In parallel, thermal studies have been initiated to evaluate the performance of this double membrane panel

Characterization of rocky exoplanets from their infrared phase curve

International audienceDuring the last few years, observations have yielded an abundant population of short-period planets under 15 Earth masses. Among those, hot terrestrial exoplanets represent a key population to study the survival of dense atmospheres close to their parent star. Thermal emission from exoplanets orbiting low-mass stars will be observable with the next generation of infrared telescopes, in particular the JWST. In order to constrain planetary and atmospheric properties, we have developed models to simulate the variation of the infrared emission along the path of the orbit (IR phase curve) for both airless planets and planets with dense atmospheres. Here, we focus on airless planets and present preliminary results on the influence of orbital elements, planet rotation, surface properties and observation geometry. Then, using simulated noisy phase curves, we test the retrieval of planets' properties and identify the degeneracies

Non-linear structured population dynamics with co-variates

Co-variates are incorporated into a general model of non-linear structured population dynamics. The proof of the existence and uniqueness of the solutions results from those of a special set, the invariance envelope. It is also valid in presence of state constraints, and solutions need only to have a closed graph (instead of being weakly differentiable as requested in semi-group theory). Moreover, this invariance envelope provides a simple way to build the solutions, either explicitly in the linear exogenous case, or algo-rithmically in the non-linear case, both with co-variates. The case of age-structured systems and a model of demographic transition are discussed for illustration.Lotka-McKendrick, Viability theory Communicated by S. Tuljapurkar,

Measuring the albedo, inclination and radius of nontransiting terrestrial exoplanets

The photometric signal we receive from a star hosting a planet is modulated by the variation of the planet signal with its orbital phase. Future telescopes (JWST and EChO) will have the capability to measure thermal phase curves of exoplanets including hot rocky planets in transiting and nontransiting configurations. We model the thermal emission of a synchronous rocky planet with no atmosphere and its apparent variation with the orbital phase for a given orbital inclination. We assume that the planet is detected by radial velocity. We simulate observed noisy phase curves and then apply a procedure to retrieve the radius and albedo of the planet and the inclination of the orbit