I.C.E.: a Transportable Atomic Inertial Sensor for Test in Microgravity

We present our the construction of an atom interferometer for inertial sensing in microgravity, as part of the I.C.E. (\textit{Interf\'{e}rom\'{e}trie Coh\'{e}rente pour l'Espace}) collaboration. On-board laser systems have been developed based on fibre-optic components, which are insensitive to mechanical vibrations and acoustic noise, have sub-MHz linewidth, and remain frequency stabilised for weeks at a time. A compact, transportable vacuum system has been built, and used for laser cooling and magneto-optical trapping. We will use a mixture of quantum degenerate gases, bosonic $^{87}$Rb and fermionic $^{40}$K, in order to find the optimal conditions for precision and sensitivity of inertial measurements. Microgravity will be realised in parabolic flights lasting up to 20s in an Airbus. We show that the factors limiting the sensitivity of a long-interrogation-time atomic inertial sensor are the phase noise in reference frequency generation for Raman-pulse atomic beam-splitters and acceleration fluctuations during free fall

Small-scale study of Debris-Flows Interactions with a Lateral Debris Basin and Crossings: The Manival Torrent case study

Small-scale models are useful tools to study the interactions between debris flows and structures and channels. Small-scale modelling of debris flows remains however complicated because of the complex rheology and scaling challenges of these geophysical processes. An on-going study of a debris basin and the downstream channel where two fords and a bridge are located is presented in this extended abstract. The studied torrent is the Manival catchment, located near Grenoble in France. We present the catchment features, the scientific questions studied, some preliminary calibration results describing the mixtures used to model debris flows as well as results from three debris-flood and two debris-flow runs. In essence, the model highlighted that the structure enable a large share of the bedload transport to pass downstream. Debris flows can be more or equally trapped depending on their rheology which controls the surges dynamics and the deposition slope in the debris basin

The PP2A inhibitor I2PP2A is essential for sister chromatid segregation in oocyte meiosis II.

Haploid gametes are generated through two consecutive meiotic divisions, with the segregation of chromosome pairs in meiosis I and sister chromatids in meiosis II. Separase-mediated stepwise removal of cohesion, first from chromosome arms and later from the centromere region, is a prerequisite for maintaining sister chromatids together until their separation in meiosis II [1]. In all model organisms, centromeric cohesin is protected from separase-dependent removal in meiosis I through the activity of PP2A-B56 phosphatase, which is recruited to centromeres by shugoshin/MEI-S332 (Sgo) [2-5]. How this protection of centromeric cohesin is removed in meiosis II is not entirely clear; we find that all the PP2A subunits remain colocalized with the cohesin subunit Rec8 at the centromere of metaphase II chromosomes. Here, we show that sister chromatid separation in oocytes depends on a PP2A inhibitor, namely I2PP2A. I2PP2A colocalizes with the PP2A enzyme at centromeres at metaphase II, independently of bipolar attachment. When I2PP2A is depleted, sister chromatids fail to segregate during meiosis II. Our findings demonstrate that in oocytes I2PP2A is essential for faithful sister chromatid segregation by mediating deprotection of centromeric cohesin in meiosis II

Long-distance frequency dissemination with a resolution of 10-17

We use a new technique to disseminate microwave reference signals along ordinary optical fiber. The fractional frequency resolution of a link of 86 km in length is 10-17 for a one day integration time, a resolution higher than the stability of the best microwave or optical clocks. We use the link to compare the microwave reference and a CO2/OsO4 frequency standard that stabilizes a femtosecond laser frequency comb. This demonstrates a resolution of 3.10-14 at 1 s. An upper value of the instability introduced by the femtosecond laser-based synthesizer is estimated as 1.10-14 at 1 s

BRG1-SWI/SNF-dependent regulation of the Wt1 transcriptional landscape mediates epicardial activity during heart development and disease

Epicardium-derived cells (EPDCs) contribute cardiovascular cell types during development and in adulthood respond to Thymosin \u3b24 (T\u3b24) and myocardial infarction (MI) by reactivating a fetal gene programme to promote neovascularization and cardiomyogenesis. The mechanism for epicardial gene (re-)activation remains elusive. Here we reveal that BRG1, the essential ATPase subunit of the SWI/SNF chromatin-remodelling complex, is required for expression of Wilms' tumour 1 (Wt1), fetal EPDC activation and subsequent differentiation into coronary smooth muscle, and restores Wt1 activity upon MI. BRG1 physically interacts with T\u3b24 and is recruited by CCAAT/enhancer-binding protein \u3b2 (C/EBP\u3b2) to discrete regulatory elements in the Wt1 locus. BRG1-T\u3b24 co-operative binding promotes optimal transcription of Wt1 as the master regulator of embryonic EPDCs. Moreover, chromatin immunoprecipitation-sequencing reveals BRG1 binding at further key loci suggesting SWI/SNF activity across the fetal epicardial gene programme. These findings reveal essential functions for chromatin-remodelling in the activation of EPDCs during cardiovascular development and repair

Camera Localization by Single View Query Using One Circular Target

21st Scandinavian Conference, SCIA 2019, Norrköping, Sweden, June 11–13, 2019, ProceedingsInternational audienceWe are concerned with the problem of computing the pose of a (so-called query) camera, from the sole contour of a circular marker in a single view, assuming that we have at one's disposal a set of reference views seeing circular markers, from which the full camera pose and calibration have been precisely estimated. In the calibrated case, regarding the query image alone, there is also a twofold ambiguity in the pose as well as an unknown rotation in the supporting plane of the marker that cannot be fixed. The key idea of this paper is to show that with the additional information of one pair of matched points in both query and reference views, an exact solution for the query pose can be obtained. In order to answer the question whether a given reference view corresponds to the query view, another pair of matched points in both views is then necessary. With multiple matched point pairs, it is possible to deploy a RANSAC-based scheme to assess accurately the best configuration while maintaining robustness to mismatched point pairs. This method shows some promising results especially when the set of point correspondences contains a lot of outliers (erroneous matches)

Rectification métrique de l'image d'un marqueur à contour circulaire à partir d'une caméra calibrée par défaut

International audienceDes marqueurs plans spécialisés (par exemple, le bleam de la société Ubleam) offrent aujourd'hui de nombreuses applications industrielles en permettant notamment à un opérateur de localiser et d'identifier un équipement dans un environnement de travail. Un des enjeux actuels est de pouvoir à la fois réduire la taille des marqueurs et d'accroître la distance d'acquisition. La rectification métrique de l'image d'un marqueur plan est une tâche nécessaire dans n'importe quelle application de ce type. Une nouvelle méthode de calcul des paramètres d'une telle rectification à partir d'un marqueur à contour circulaire est proposée dans cet article. Dans les méthodes existantes, ce calcul nécessite en général la connaissance supplémentaire soient des paramètres de calibrage, soit de l'image d'un autre cercle coplanaire. Nous contribution consiste à proposer l'utilisation d'un seul cercle en introduisant des paramètres de caméra "par défaut" avec l'idée d'utiliser les incertitudes sur ces connaissances afin de réduire l'espace de recherche de solutions. Nous montrons qu'avec l'image du contour d'un marqueur circulaire dont la résolution est "suffisamment" grande dans l'image, il est possible d'obtenir une précision de rectification qui soit équivalente à celle obtenue avec un calibrage hors ligne précis de la caméra (obtenu avec OpenCV). En dessous d'une certaine résolution, on obtient des précisions identiques que l'on prenne un calibrage par défaut ou un calibrage hors ligne

Pose estimation of a single circle using default intrinsic calibration

International audienceCircular markers are planar markers which offer great performances for detection and pose estimation. For an uncalibrated camera with an unknown focal length, the images of at least two coplanar circles are generally required to recover their poses and their supporting plane. Unfortunately, detecting more than one ellipse in the image is tricky and time-consuming, especially regarding concentric circles. On the other hand, when the camera is calibrated, the pose of one circle can be computed with its image alone but the solution is twofold and can hardly be disambiguated. Our contribution is to put beyond this limit by dealing with the uncalibrated case of a camera seeing one circle and highlighting geometric configuration where the ambiguity can be analysed. We propose a new problem formulation that enables to show how to detect geometric configurations in which the ambiguity can be removed. Furthermore, we introduce the notion of default camera intrinsics and show, empirically, the surprising observation that very approximate calibration leads to a circle pose estimation which gives accurate results in reprojection for augmented reality

Évaluation de la durabilité de différentes formes d’organisation de l’agriculture : adaptation de la méthode IDEA à l’hévéaculture familiale en Thaïlande

International audienceWith increasing concerns on the sustainability of agricultural systems, many tools have been developed to assess farm sustainability. The main objective of this study was to assess and compare the sustainability of different forms of family farm organization. A second objective was to test the relevance of the IDEA method (Indicateurs de Durabilité des Exploitations Agricoles or Farm Sustainability Indicators) to compare tree-crop-based family farms in tropical areas. Percentages of sustainability were calculated based on individual interviews conducted with 25 rubber farmers representing three different types of farm (typology based on the labor used for farming activities), using three scales and 10 components. The socio-territorial scale was the weak point of the rubber farms. In contrast, the economic scale was relatively the best asset on all farms. The factor that most differentiated the three types of farm was the agro-ecological scale followed by the socio-territorial scale. The economic scale did not discriminate. Moreover, only the diversity of production and efficiency components showed a notable difference between the different types of farm. Overall, the three types of farm with contrasting forms of farm organization were not much different in terms of sustainability performance. Family business farms with managerial family labor appeared to be the least sustainable. Thus, as family business farms are becoming more and more important in Thai agriculture, if these results are confirmed on a broader scale, this represents an issue for the sustainability of the Thai rubber sector that would require government intervention.Les préoccupations croissantes concernant la durabilité des systèmes agricoles ont conduit au développement de nombreux outils pour l’évaluer. L’objectif principal de cette étude était d’évaluer et comparer la durabilité de différentes formes d’organisation de l’agriculture familiale. Un deuxième objectif était de tester la pertinence de la méthode IDEA (Indicateurs de Durabilité des Exploitations Agricoles) pour comparer des exploitations familiales à base de plantes pérennes en zone tropicale. À partir d’entretiens individuels conduits avec 25 planteurs d’hévéa représentant trois types d’exploitations agricoles (typologie basée sur le travail mobilisé pour les activités agricoles), des pourcentages de durabilité ont été calculés sur trois échelles et 10 composantes. L’échelle socio-territoriale était le point faible des exploitations hévéicoles. À l’inverse, l’échelle économique était le point fort pour toutes les exploitations. L’échelle agro-écologique est celle qui discriminait le mieux les trois types d’exploitations, suivie par l’échelle socio-territoriale. L’échelle économique n’était pas discriminante. De plus, les seules composantes présentant des différences entre les trois types d’exploitation étaient la diversité des productions et l’efficience des exploitations. Les trois types d’exploitation représentant des formes contrastées d’organisation de la production agricole ne sont finalement pas apparus très différents en termes de durabilité. Les exploitations familiales patronales avec la famille seulement impliquée dans la gestion seraient les moins durables. Pourtant, les exploitations patronales occupent une place croissante dans l’agriculture en Thaïlande. Si ces résultats sont confirmés à plus grande échelle, cela représente un problème pour la durabilité de l’hévéaculture en Thaïlande qui demanderait une intervention du gouvernement