High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)

(abridged) A complete census of planetary systems around a volume-limited sample of solar-type stars (FGK dwarfs) in the Solar neighborhood with uniform sensitivity down to Earth-mass planets within their Habitable Zones out to several AUs would be a major milestone in extrasolar planets astrophysics. This fundamental goal can be achieved with a mission concept such as NEAT - the Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne extremely-high-precision astrometric measurements sufficient to detect dynamical effects due to orbiting planets of mass even lower than Earth's around the nearest stars. Such a survey mission would provide the actual planetary masses and the full orbital geometry for all the components of the detected planetary systems down to the Earth-mass limit. The NEAT performance limits can be achieved by carrying out differential astrometry between the targets and a set of suitable reference stars in the field. The NEAT instrument design consists of an off-axis parabola single-mirror telescope, a detector with a large field of view made of small movable CCDs located around a fixed central CCD, and an interferometric calibration system originating from metrology fibers located at the primary mirror. The proposed mission architecture relies on the use of two satellites operating at L2 for 5 years, flying in formation and offering a capability of more than 20,000 reconfigurations (alternative option uses deployable boom). The NEAT primary science program will encompass an astrometric survey of our 200 closest F-, G- and K-type stellar neighbors, with an average of 50 visits. The remaining time might be allocated to improve the characterization of the architecture of selected planetary systems around nearby targets of specific interest (low-mass stars, young stars, etc.) discovered by Gaia, ground-based high-precision radial-velocity surveys.Comment: Accepted for publication in Experimental Astronomy. The full member list of the NEAT proposal and the news about the project are available at http://neat.obs.ujf-grenoble.fr. The final publication is available at http://www.springerlink.co

Laser-induced cell printing: a versatile tool for applications in biology

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Laser-Induced printing of stem cells: a powerful tool for biological applications

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High repetition rate laser-induced prinitng of biopolymers: time-resolvestudy of multiple jet dynamics

International audienceLaser-induced forward transfer (LIFT) is a versatile, non-contact, high-resolution laser direct writing technique that offers promising solutions in various fields of application. Our work is focused on the use of this technique to create organized 2D/3D arrangements of biomaterials and living cells to create in vitro biomodels for applications in tissue engineering or regenerative medicine.LIFT is a two-part printing method using laser-matter interaction to transfer tiny amounts of material from a thin donor film to a receptor substrate, both separated by a few hundreds of micrometres. A short laser pulse induces the formation of a jet propagating perpendicularly to the donor substrate. The bio-ink previously spread as a thin film on this donor substrate is thus collected as a micrometer-sized droplet on the receiver. In order to precisely control the amount and the location of the deposited material, it is necessary to investigate carefully the jetting dynamics as a function of various parameters including the laser fluence and the rheological properties of the bioink. In this study, we used time-resolved fast imaging to investigate the hydrodynamics of the transfer of successive jets at high pulse repetition rate.The set up being currently use is composed of a high-frequency laser (12ps, 60KHz) coupled with a fast-writing scanner that allows us to print large quantities of materials in extremely short times. Successive pulses are focused on a bioink-coated donor substrate and the transfer material is imaged with a shadowgraphic technique using a delayed nanosecond flash. With this technique we can record precise moment of the dynamic and accurately decompose the ejection mechanism. We present here our investigations on the jet dynamics as a function of the rheological properties of the bioink, the irradiation fluence, the distance and time between each individual jet…Understanding and controlling these dynamics will allow us to improve the quality and reproducibility of the prints. It will also help us to estimate the ideal donor-receiver distance in order to minimize the mechanical impact of the deposition process on the cells contained in the bio-ink

Optimization of the laser-induced forwatd transfer process for the printing of living cells

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Combination of two laser processes for the creation of relevant bio-models for therapeutical applications

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Assessment of laser-synthesized Si nanoparticle effects on myoblast motility, proliferation and differentiation: towards potential tissue engineering applications

International audienceDue to their biocompatibility and biodegradability and their unique structural and physicochemical properties, laser-synthesized silicon nanoparticles (Si-NPs) are one of the nanomaterials which have been most studied as potential theragnostic tools for non-invasive therapeutic modalities. However, their ability to modulate cell behavior and to promote proliferation and differentiation is still very little investigated or unknown. In this work, ultrapure ligand free Si-NPs of 50 ± 11.5 nm were prepared by femtosecond (fs) laser ablation in liquid. After showing the ability of Si-NPs to be internalized by murine C2C12 myoblasts, the cytotoxicity of the Si-NPs on these cells was evaluated at concentrations ranging from 14 to 224 μg mL−1. Based on these findings, three concentrations of 14, 28 and 56 μg mL−1 were thus considered to study the effect on myoblast differentiation, proliferation and motility at the molecular and phenotypical levels. It was demonstrated that up to 28 μg mL−1, the Si-NPs are able to promote the proliferation of myoblasts and their subsequent differentiation. Scratch tests were also performed revealing the positive Si-NP effect on cellular motility at 14 and 28 μg mL−1. Finally, gene expression analysis confirmed the ability of Si-NPs to promote proliferation, differentiation and motility of myoblasts even at very low concentration. This work opens up novel exciting prospects for Si-NPs made by the laser process as innovative tools for skeletal muscle tissue engineering in view of developing novel therapeutic protocols for regenerative medicine

A measure of the size of the magnetospheric accretion region in TW Hydrae

International audienceStars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate the disk close to the corotation radius, at which the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that hydrogen emission (a well known tracer of accretion activity) mostly comes from a region a few milliarcseconds across, usually located within the dust sublimation radius1-3. The origin of the hydrogen emission could be the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that Brackett γ (Brγ) emission is spatially resolved rules out the possibility that most of the emission comes from the magnetosphere4-6 because the weak magnetic fields (some tenths of a gauss) detected in these sources7,8 result in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. The small angular size of the magnetosphere (a few tenths of a milliarcsecond), however, along with the presence of winds9,10 make the interpretation of the observations challenging. Here we report optical long-baseline interferometric observations that spatially resolve the inner disk of the T Tauri star TW Hydrae. We find that the near-infrared hydrogen emission comes from a region approximately 3.5 stellar radii across. This region is within the continuum dusty disk emitting region (7 stellar radii across) and also within the corotation radius, which is twice as big. This indicates that the hydrogen emission originates in the accretion columns (funnel flows of matter accreting onto the star), as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (more than one astronomical unit)