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Resonant light scattering by a slab of ultracold atoms
No full textA gas of ultracold atoms probed with laser light is a nearly-ideal experimental realization of a medium of resonant point-like scatterers, a key problem from condensed matter to biology or photonics. Yet, several recent experiments have reported large discrepancies with theory. In this work, we measure the complex transmission through a slab of ultracold two-level atoms with an interferometric technique. We find good agreement with first-principles simulations of mutually-coupled, laser-driven dipoles, and provide an explanation for the discrepancies in earlier measurements
Mechanical regulation of substrate adhesion and de-adhesion drives a cell-contractile wave during Drosophila tissue morphogenesis
No full textInternational audienceDuring morphogenesis, mechanical forces induce large-scale deformations; yet, how forces emerge from cellular contractility and adhesion is unclear. In Drosophila embryos, a tissue-scale wave of actomyosin contractility coupled with adhesion to the surrounding vitelline membrane drives polarized tissue invagination. We show that this process emerges subcellularly from the mechanical coupling between myosin II activation and sequential adhesion/de-adhesion to the vitelline membrane. At the wavefront, integrin clusters anchor the actin cortex to the vitelline membrane and promote activation of myosin II, which in turn enhances adhesion in a positive feedback. Following cell detachment, cortex contraction and advective flow amplify myosin II. Prolonged contact with the vitelline membrane prolongs the integrin-myosin II feedback, increases integrin adhesion, and thus slows down cell detachment and wave propagation. The angle of cell detachment depends on adhesion strength and sets the tensile forces required for detachment. Thus, we document how the interplay between subcellular mechanochemical feedback and geometry drives tissue morphogenesis
Recueil : Droit international public: Avec les traités européens
No full textInternational audienceCe recueil a pour but de rendre aisément accessibles les textes les plus importants pour la pratique du droit international public en vigueur en Suisse. Il comprend aussi bien les textes majeurs de droit international public général que différents textes de droit international public spécial notamment dans les domaines du droit international des droits de l’homme, du droit international économique, du droit international de la santé, du droit international de l’environnement, du droit du désarmement et de la sécurité internationale, du droit international humanitaire et du droit européen de la protection des données, ainsi que des éléments de droit suisse pertinents pour la mise en œuvre du droit international public dans l’ordre juridique interne. Cette sélection de textes fait du recueil le compagnon idéal tant d’un cours d’introduction au droit international public que de cours plus avancés. Compact et d’utilisation facile, le recueil est un ouvrage de référence qui ne devrait manquer sur le bureau d’aucun juriste amené à appliquer le droit international public
L'Archi-Elixir Secret des Essences Perlées, appelé Miroir Illuminant la Quintessence (sNying thig gsang ba’i yang bcud snying po gsal ba’i me long zhes bya ba)
No full textIncreased evolutionary rate in the Z-chromosome of sympatric and allopatric species of Morpho butterflies
No full textInternational audienceDivergent evolution of genomes among closely related species is shaped by both neutral processes and ecological forces, such as local adaptation and reinforcement. These factors can drive accelerated evolution of sex chromosomes relative to autosomes. Comparative genomic analyses between allopatric and sympatric species with overlapping or divergent ecological niches offer insights into reinforcement and ecological specialization on genome evolution. In the butterfly genus Morpho, several species coexist in sympatry, with specialization across forest strata and temporal niches. We analyzed the genomes of eight Morpho species, along with previously published genomes of three others, to compare chromosomal rearrangements and signs of positive selection in the Z chromosome vs autosomes. We found extensive chromosomal rearrangements in Z chromosome, particularly in sympatric species with similar ecological niches, suggesting a role for inversions in restricting gene flow at a postzygotic level. Z-linked genes also exhibited significantly higher dN/dS ratios than autosomal genes across the genus, with pronounced differences in closely related species living in sympatry. Additionally, we examined the evolution of eight circadian clock genes, detecting positive selection in Period, located on the Z chromosome. Our findings suggest that the Z chromosome evolves more rapidly than autosomes, particularly among closely related species, raising questions about its role in pre- and post-zygotic isolation mechanisms
Les Instructions Complémentaires appelées Guirlande des Avis (Khrid rgyab lung gi phreng ba)
No full textSimulability of non-classical continuous-variable quantum circuits
No full textInternational audienceIn continuous-variable quantum computation, identifying key elements that enable a quantum computational advantage is a long-standing issue. Starting from the standard results on the necessity of Wigner negativity, we develop a comprehensive and versatile framework that not only enables the identification of a potential quantum computational advantage, but also allows to pinpoint the contribution of each quantum gate in achieving this objective. As such, it can be straightforwardly applied to current continuous-variables quantum circuits, while also constraining the tolerable amount of losses above which any potential quantum advantage can be ruled out. We use -ordered quasiprobability distributions on phase-space to capture the non-classical features in the protocol, and focus our model entirely on the ordering parameter . This allows us to highlight the resourcefulness and robustness to loss of a universal set of unitary gates comprising three distinct Gaussian gates, and a fourth one, the cubic gate, providing important insight on the role of non-Gaussianity
Realization of an atomic quantum Hall system in four dimensions
No full textInternational audienceModern condensed matter physics relies on the concept of topology to classify matter, from quantum Hall systems to topological insulators. Engineered systems, benefiting from synthetic dimensions, can potentially give access to topological states predicted in dimensions D > 3. We report the realization of an atomic quantum Hall system evolving in four dimensions (4D), with two spatial dimensions and two synthetic ones encoded in the large spin of dysprosium atoms. We measure the nontrivial topological index of the ground band through a full characterization of the nonlinear electromagnetic response and observe the associated anisotropic hyperedge modes. We also excite nonplanar cyclotron motion, in contrast to the planar orbits in D ≤ 3. Our work may enable the investigation of strongly correlated topological liquids in 4D, generalizing fractional quantum Hall states