A numerical exploration of Miranda's dynamical history

The Uranian satellite Miranda presents a high inclination (4.338{\deg}) and evidences of resurfacing. It is accepted since 20 years (e.g. Tittemore and Wisdom 1989, Malhotra and Dermott 1990) that this inclination is due to the past trapping into the 3:1 resonance with Umbriel. These last years there is a renewal of interest for the Uranian system since the Hubble Space Telescope permitted the detection of an inner system of rings and small embedded satellites, their dynamics being of course ruled by the main satellites. For this reason, we here propose to revisit the long-term dynamics of Miranda, using modern tools like intensive computing facilities and new chaos indicators (MEGNO and frequency map analysis). As in the previous studies, we find the resonance responsible for the inclination of Miranda and the secondary resonances associated, likely to have stopped the rise of Miranda's inclination at 4.5{\deg}. Moreover, we get other trajectories in which this inclination reaches 7{\deg}. We also propose an analytical study of the secondary resonances associated, based on the study by Moons and Henrard (1993).Comment: 14 pages, 8 figure

Analysis of the evolution of space debris through a synthetic population

Space debris are all man-made objects orbiting the Earth which no longer serve a useful function. Space debris have increased substantially in the last decades and can be counted in millions. This paper deals with the idea of the creation of a synthetic population of space debris, which preserves as accurate as possible the characteristics of the real one. All the individuals of the synthetic population will be propagated by powerful numerical integrators, becoming into an excellent tool for global predictions or simulations, useful for the future ADR actions, and for the location of parking orbits

MTG-Link: filling gaps in draft genome assemblies with linked read data

National audienceDe novo genome assembly is a challenging task, especially for large non-model organism genomes. Low sequence coverage, genomic repeats and heterozygosity often create ambiguities in the assembly, and result in undefined sequences between contigs called "gaps". Hence, filling gaps in draft genomes has become a natural sub-problem of many de novo genome assembly projects. Even though there are several tools for closing gaps, to our knowledge none uses the long-range information of the linked read data. Linked read technologies have a great potential for filling gaps in draft genomes as they provide long-range information while maintaining the power and accuracy of short-read sequencing. In this work, we present MTG-Link, a novel gap-filling tool dedicated to linked read data. Taking advantage of the barcode information contained in the linked read dataset, a subsample of reads is first selected for each gap. These reads are then locally assembled and the resulting gap-filled sequences are automatically evaluated. We validated our approach on a real 10X genomics linked read dataset, on a set of simulated gaps, and showed that the read subsampling step of MTG-Link enables to get better gap assemblies in a time/memory efficient manner. We also applied MTG-Link on individual genomes of a mimetic butterfly (Heliconius numata), where it significantly improved the contiguity of a 1.3 Mb locus of biological interest. MTG-Link is freely available at https://github.com/anne-gcd/MTG-Link

Elliptical micropillars for efficient generation and detection of coherent acoustic phonons

Coherent acoustic phonon generation and detection assisted by optical resonances are at the core of efficient optophononic transduction processes. However, when dealing with a single optical resonance, the optimum generation and detection conditions take place at different laser wavelengths, i.e. different detunings from the cavity mode. In this work, we theoretically propose and experimentally demonstrate the use of elliptical micropillars to reach these conditions simultaneously at a single wavelength. Elliptical micropillar optophononic resonators present two optical modes with orthogonal polarizations at different wavelengths. By employing a cross-polarized scheme pump-probe experiment, we exploit the mode splitting and couple the pump beam to one mode while the probe is detuned from the other one. In this way, at a particular micropillar ellipticity, both phonon generation and detection processes are enhanced. We report an enhancement of a factor of ~3.1 when comparing the signals from elliptical and circular micropillars. Our findings constitute a step forward in tailoring the light-matter interaction for more efficient ultrahigh-frequency optophononic devices.Comment: 10 pages, 5 figure

Differentiation of human induced pluripotent stem cells towards notochordal-like cells: the role of tissue source

INTRODUCTION: Notochordal cells (NCs) are linked to a healthy intervertebral disc (IVD), and they are considered an exciting target for cell-based therapy. However, NCs are scarcely available as they are lost early in life, and attempts at in vivoexpansion have failed because NCs lose their specific phenotype. The production of Notochordal-like cells (NLCs) from human induced pluripotent stem cells (iPSCs) is a viable alternative. However, current attempts have been challenged by the low differentiation efficiency into the NC lineage. Therefore, the aim of this study was to build on the tissue-specific epigenetic memory of hiPSCs derived from IVD progenitor cells (TIE2+-cells) to improve hiPSC differentiation towards mature, matrix-producing NLCs. METHODS: hiPSCs were generated from TIE2⁺ cells of three adult donors. As a comparison, donormatched minimally invasive peripheral blood mononuclear (PBM) cell-derived iPSCs were used. Firstly, the iPSCs were differentiated into mesendodermal progenitors by Wnt pathway activation (N2B27 medium + 3µM CHIR99021)¹. Thereafter, the cells were further driven towards the NClineage by transfection with synthetic NOTO mRNA¹ and further matured using a 3D pellet culture in discogenic medium containing 10ng/mL TGF-β1. Read-out parameters included cell morphology, gene and protein expression and matrix deposition. RESULTS: Both TIE2⁺ and PBM cell-derived hiPSC showed successful differentiation towards mesendodermal progenitor cells following Wnt activation on day 2, indicated by the cells moving out of the colonies after CHIR stimulation. Accordingly, a decreased gene expression of pluripotency markers (OCT4, SOX2, NANOG), and upregulation of Wnt-target genes (LEF1, NODAL) and mesendodermal markers (TBXT, FOXA2, TBX6) was observed compared to mTESR1 controls. This was confirmed by immuno-stains for FOXA2 and TBXT. At day 3, we confirmed a 9-fold increase in NOTO mRNA levels after transfection in all donor lines. At day 28, the appearance of vacuolated NLCs was observed in both TIE2⁺ and PBM cell-derived pellet cultures confirming successful commitment towards the NC-lineage. Interestingly, while DMMB-assay detected GAG deposition in both lines, a significant increase in GAG content was seen in the TIE2⁺ cell-derived pellets. DISCUSSION & CONCLUSIONS: Tissue-specific TIE2⁺ cell-derived iPSCs may allow for an improved iPSNLC differentiation efficiency, indicated by the increased potency for deposition of GAG-rich matrix. Detailed analysis of the phenotypic markers and matrix deposited at the end of the 28 day maturation is ongoing to further document the phenotype of these iPS-NLCs. Delineating which epigenetic features are retained after reprogramming of these two cell lines, could shed light on the differences in their differentiation capacity. REFERENCES: ¹Colombier et al., 202

Spodoptera frugiperda (Lepidoptera: Noctuidae) host-plant variants: two host strains or two distinct species?

International audienceThe moth Spodoptera frugiperda is a well-known pest of crops throughout the Americas, which consists of two strains adapted to different host-plants: the first feeds preferentially on corn, cotton and sorghum whereas the second is more associated with rice and several pasture grasses. Though morphologically indistinguishable, they exhibit differences in their mating behavior, pheromone compositions, and show development variability according to the host-plant. Though the latter suggest that both strains are different species, this issue is still highly controversial because hybrids naturally occur in the wild, not to mention the discrepancies among published results concerning mating success between the two strains. In order to clarify the status of the two host-plant strains of S. frugiperda, we analyze features that possibly reflect the level of post-zygotic isolation: (1) first generation (F1) hybrid lethality and sterility; (2) patterns of meiotic segregation of hybrids in reciprocal second generation (F2), as compared to the meiosis of the two parental strains. We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny. Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field. Altogether these results provide additional evidence in favor of a sibling species status for the two strains

Histoire des bibliothécaires

Le Centre de recherche en histoire du livre a souhaité redynamiser le domaine scientifique de l\u27histoire des bibliothèques. Avec ce colloque consacré à l\u27histoire des bibliothécaires, il aborde l\u27une des composantes essentielles d\u27une histoire des bibliothèques qui, paradoxalement, n\u27avait jamais retenu l\u27attention des historiens, tant en France qu\u27à l\u27étranger. Le colloque couvre la période du Moyen Âge à aujourd\u27hui, et est construit dans une perspective directe d\u27histoire comparée. Il se compose de trois parties : 1. Bibliothèque religieuse, bibliothèque savante, bibliothèque nationale 2. Bibliothécaires des Lumières 3. Figures de la modernit

La communication littéraire et ses outils : écrits publics, écrits privés

À partir d’exemples portant sur divers types d’écrits (dictionnaire, journal, roman, correspondance), cet ouvrage interroge les formes de la communication littéraire dans les sphères publique et privée. Le Congrès national des sociétés historiques et scientifiques rassemble chaque année universitaires, membres de sociétés savantes et jeunes chercheurs. Ce recueil est issu de travaux présentés lors du 139e Congrès sur le thème « Langages et communication »