DISCO: a Spatio-Spectral Recombiner for Pupil Remapping Interferometry

Pupil-remapping is a new high-dynamic range imaging technique that has recently demonstrated feasibility on sky. The current prototypes present however deceiving limiting magnitude, restricting the current use to the brightest stars in the sky. We propose to combine pupil-remapping with spatio-spectral encoding, a technique first applied to the VEGA/CHARA interferometer. The result is an instrument proposal, called "Dividing Interferometer for Stars Characterizations and Observations" (DISCO). The idea is to take profit of wavelength multiplexing when using a spectrograph in order to pack as much as possible the available information, yet providing a potential boost of 1.5 magnitude if used in existing prototypes. We detail in this paper the potential of such a concept.Comment: Improving the performances of current optical interferometers \& future designs, France (2013

Gene expression profile of androgen modulated genes in the murine fetal developing lung

<p>Abstract</p> <p>Background</p> <p>Accumulating evidences suggest that sex affects lung development. Indeed, a higher incidence of respiratory distress syndrome is observed in male compared to female preterm neonates at comparable developmental stage and experimental studies demonstrated an androgen-related delay in male lung maturation. However, the precise mechanisms underlying these deleterious effects of androgens in lung maturation are only partially understood.</p> <p>Methods</p> <p>To build up a better understanding of the effect of androgens on lung development, we analyzed by microarrays the expression of genes showing a sexual difference and those modulated by androgens. Lungs of murine fetuses resulting from a timely mating window of 1 hour were studied at gestational day 17 (GD17) and GD18, corresponding to the period of surge of surfactant production. Using injections of the antiandrogen flutamide to pregnant mice, we hunted for genes in fetal lungs which are transcriptionally modulated by androgens.</p> <p>Results</p> <p>Results revealed that 1844 genes were expressed with a sexual difference at GD17 and 833 at GD18. Many genes were significantly modulated by flutamide: 1597 at GD17 and 1775 at GD18. Datasets were analyzed by using in silico tools for reconstruction of cellular pathways. Between GD17 and GD18, male lungs showed an intensive transcriptional activity of proliferative pathways along with the onset of lung differentiation. Among the genes showing a sex difference or an antiandrogen modulation of their expression, we specifically identified androgen receptor interacting genes, surfactant related genes in particularly those involved in the pathway leading to phospholipid synthesis, and several genes of lung development regulator pathways. Among these latter, some genes related to Shh, FGF, TGF-beta, BMP, and Wnt signaling are modulated by sex and/or antiandrogen treatment.</p> <p>Conclusion</p> <p>Our results show clearly that there is a real delay in lung maturation between male and female in this period, the latter pursuing already lung maturation while the proper is not yet fully engaged in the differentiation processes at GD17. In addition, this study provides a list of genes which are under the control of androgens within the lung at the moment of surge of surfactant production in murine fetal lung.</p

Defects Location Estimation Using Multiscale Thermal Finite Element Method

The Selective Laser Melting (SLM) process is the subject of numerous researches for a few decades. Manufactured parts experience very high heating and cooling rates along the laser beam path and suffer an extensive range of temperatures. These high heating and cooling rates can lead to defects such as cracks, distortions, and porosities. These defects are driven by the thermal history, related to several factors such as scanning strategy, surrounding powder insulation, parts geometry, number of parts to be manufactured, recoating time, etc. All these factors need to be considered to precisely simulate the thermal history. In this study, a multiscale thermal approach has been developed and applied to a study case. Most of the thermal history aspects are covered using five temporal and spatial scales FEM model. The overall thermal history and future improvements for simulating a full build plate in reasonable computational time are discussed

Numerical modelling of parts distortion and beam supports breakage during selective laser melting (SLM) additive manufacturing

The Selective Laser Melting (SLM) process has been progressively endorsed as an industrial manufacturing technique to produce high value-added components. However, one of the main obstacles to its wide application is the uncertainty regard- ing the successful completion of the manufacturing process. Mechanical stresses are generated and accumulated during the process, which may lead to the parts warping and cracking. Support structures may also detach from the part but it is not certain that these cracks conduct to the manufacturing failure. The process simulations currently available do not consider the cracking of the supports and the ongoing part’s deflection. The aim of this study is to investigate cone supports fracture behaviour comparing the results from a numerical model and the manufacturing of an industrial part. A model using 1D-beam elements to mesh the supports has been developed to consider the damage of the supports, their breakage and the ongoing deflection. Some numerical convergence issues are identified and solutions are proposed. Specific experimental set-ups are developed to characterise the behaviour of the supports individually and as a group. Significant improvements are denoted while injecting the measured characteristics within the model. Some key parameters of the supports damage behaviour are identified. It is shown that the supports mechanical characteristics are significantly different from the parts due to their manufacturing conditions and environment. Also, limitations regarding the characterisation of the supports as well as strong numerical convergence issues brought by multiple supports cracking are discussed

Fresnel diffraction in an interferometer: application to MATISSE

While doing optical study in an instrument similar to the interferometers dedicated to the Very Large Telescope (VLT), we have to take care of the pupil and focus conjugations. Modules with artificial sources are designed to simulate the stellar beams, in terms of collimation and pupil location. They constitute alignment and calibration tools. In this paper, we present such a module in which the pupil mask is not located in a collimated beam thus introducing Fresnel diffraction. We study the instrumental contrast taking into account the spatial coherence of the source, and the pupil diffraction. The considered example is MATISSE, but this study can apply to any other instrument concerned with Fresnel diffraction.Comment: 8 pages- to appear in Proceedings of SPIE Astronomical Telescopes and Instrumentation 201

Approche méthodologique pour intégrer des scénarios de végétation forestière tenant compte des changements climatiques dans la prédiction des méthodes de restauration minière sous climat humide au Québec

La restauration des parcs à résidus générateurs de drainage minier acide (DMA) constitue un défi environnemental important pour l’industrie minière. Au Québec, différentes techniques de contrôle du DMA provenant de parcs à résidus sont utilisées pour empêcher la contamination de l’environnement, parmi lesquelles on retrouve les recouvrements d’ingénierie appelés barrières à l’oxygène (Bussière et al., 2003; Aubertin et al., 2016; Bussière et Guittonny, 2020). Dans le contexte de restauration de sites miniers, l’objectif est de mettre en place un recouvrement permettant de contrôler la contamination et pouvant supporter une végétation pérenne qui s’intègre bien à l’environnement du site (MEND, 2014). Cependant, la végétation peut affecter le bilan hydrique, les propriétés des matériaux des barrières à l’oxygène et, par le fait même, leur performance (MEND, 2014; Guittonny et al., 2018). À ce jour, les caractéristiques à long terme de la végétation forestière qui s’installera sur les parcs à résidus restaurés sont encore mal connues et nécessitent de prendre en compte l’influence des changements climatiques (CC) sur l’évolution des écosystèmes. En effet, les CC conduisent à une redistribution généralisée des espèces à l’échelle planétaire (IPCC, 2014; Bonebrake et al., 2018). Un changement des conditions climatiques pourrait entraîner un changement dans la distribution des espèces d’arbres et dans la composition des forêts. Les conditions climatiques ont déjà changé et affectent déjà la distribution de certaines espèces d’arbres au Canada (Williamson et al., 2009; Price et al., 2013; Berteaux et al., 2014; Ressources naturelles Canada, 2017). Le climat existant dans une région où une espèce vit et se reproduit se trouvera vraisemblablement ailleurs dans l’avenir (McKenney et al., 2007; Berteaux et al., 2014; Sittaro et al., 2017). Le présent rapport vise à proposer une approche méthodologique pour la prise en compte de l’influence de la végétation forestière sur la performance à long terme des barrières à l’oxygène sur base des scénarios de végétation sous CC au Québec. En amont de ce rapport, une revue de littérature sur les changements d’aire de répartition des essences clés de la forêt feuillue et boréale, en réponse aux CC, a été réalisée (Botula et al., 2019). Celle-ci a permis d’identifier la composition de la végétation qui sera présente de manière plausible d’ici 2100 pour deux sites miniers : l’un en activité, la mine Westwood en Abitibi, et l’autre abandonné, le site Lorraine au Témiscamingue. En se basant sur ces travaux, des scénarios de végétation d’ici 2100 seront proposés dans ce rapport pour les deux sites, ainsi que des gammes de valeurs correspondantes pour les paramètres de végétation à intégrer aux modèles numériques hydrogéologiques utilisés pour la prédiction de la performance des barrières à l’oxygène. Les résultats présentés ici pourront aider les partenaires miniers à déterminer si l’évolution de la végétation sur leurs sites suite aux CC affectera la performance à long terme des méthodes de restauration utilisées, et si des mesures de gestion de cette végétation devront être mises en place. Ce rapport est divisé en trois chapitres et se termine par une conclusion et des suggestions : le premier chapitre est une synthèse des connaissances en lien avec les effets des CC sur la distribution des essences clés de la forêt feuillue et boréale au Québec; le deuxième chapitre est une synthèse des connaissances en lien avec l’influence de la végétation forestière sur la performance des barrières à l’oxygène au Québec; le troisième chapitre est une analyse qualitative de l’influence des CC sur les paramètres de la végétation utilisés pour évaluer la performance des barrières à l’oxygène avec application à deux sites miniers : Westwood et Lorraine

Study of the atmospheric refraction in a single mode instrument - Application to AMBER/VLTI

International audienceThis paper presents a study of the atmospheric refraction and its effect on the light coupling efficiency in an instrument using single-mode optical fibers. We show the analytical approach which allowed us to assess the need to correct the refraction in J- and H-bands while observing with an 8-m Unit Telescope. We then developed numerical simulations to go further in calculations. The hypotheses on the instrumental characteristics are those of AMBER (Astronomical Multi BEam combineR), the near infrared focal beam combiner of the Very Large Telescope Interferometric mode (VLTI), but most of the conclusions can be generalized to other single-mode instruments. We used the software package caos (Code for Adaptive Optics Systems) to take into account the atmospheric turbulence effect after correction by the ESO system MACAO (Multi-Application Curvature Adaptive Optics). The opto-mechanical study and design of the system correcting the atmospheric refraction on AMBER is then detailed. We showed that the atmospheric refraction becomes predominant over the atmospheric turbulence for some zenith angles z and spectral conditions: for z larger than 30° in J-band for example. The study of the optical system showed that it allows to achieve the required instrumental performance in terms of throughput in J- and H-bands. First observations in J-band of a bright star, alpha Cir star, at more than 30° from zenith clearly showed the gain to control the atmospheric refraction in a single mode instrument, and validated the operating law