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Transcription-induced domains form the elementary constraining building blocks of bacterial chromosomes
No full textInternational audienceTranscription generates local topological and mechanical constraints on the DNA fiber, leading to the generation of supercoiled chromosome domains in bacteria. However, the global impact of transcription on chromosome organization remains elusive, as the scale of genes and operons in bacteria remains well below the resolution of chromosomal contact maps generated using Hi-C (~5–10 kb). Here we combined sub-kb Hi-C contact maps and chromosome engineering to visualize individual transcriptional units. We show that transcriptional units form discrete three-dimensional transcription-induced domains that impose mechanical and topological constraints on their neighboring sequences at larger scales, modifying their localization and dynamics. These results show that transcriptional domains constitute primary building blocks of bacterial chromosome folding and locally impose structural and dynamic constraints
2D seismic wave propagation using the distributional finite-difference method: further developments and potential for global seismology
No full textInternational audienceWe present a time-domain distributional finite-difference scheme based on the Lebedev staggered grid for the numerical simulation of wave propagation in acoustic and elastic media. The central aspect of the proposed method is the representation of the stresses and displacements with different sets of B-splines functions organized according to the staggered grid. The distributional finite-difference approach allows domain-decomposition, heterogeneity of the medium, curvilinear mesh, anisotropy, non-conformal interfaces, discontinuous grid, and fluid-solid interfaces. Numerical examples show that the proposed scheme is suitable to model wave propagation through the Earth, where sharp interfaces separate large, relatively homogeneous layers. A few domains or elements are sufficient to represent the Earth’s internal structure without relying on advanced meshing techniques. We compare seismograms obtained with the proposed scheme and the spectral element method, and we show that our approach offers superior accuracy, reduced memory usage, and comparable efficiency
Non-collinear magnetism driven by a hidden multipolar order in PrO2
No full textInternational audienceStandard microscopic approach to magnetic orders is based on assuming a Heisenberg form for inter-atomic exchange interactions. These interactions are considered as the driving force for the ordering transition with magnetic moments serving as the primary order parameter. Any higher-rank multipoles appearing simultaneously with such magnetic order are typically treated as auxiliary order parameters rather than a principal cause of the transition. In this study, we show that these traditional assumptions are violated in the case of PrO 2. Evaluating a full set of Pr-Pr superexchange interactions from a first-principles many-body technique we find that its unusual non-collinear 2k magnetic structure stems from high-rank multipolar interactions, and that the corresponding contribution of the Heisenberg interactions is negligible. The observed magnetic order in PrO 2 is thus auxiliary to high-rank "hidden" multipoles. Within this picture we consistently account for previously unexplained experimental observations like the magnitude of exchange splitting and the evolution of magnetic structure in external field. Our findings challenge the standard paradigm of observable magnetic moments being the driving force for magnetic transitions
Simple predictors of in superconducting cuprates reveal role of interactions between effective Wannier orbitals in the 3-band model
No full textInternational audienceAt optimal doping, different cuprate compounds can exhibit vastly different critical temperatures for superconductivity (), ranging from about 20 K to about 135 K. The precise properties of the lattice that determine the magnitude of the are currently unknown. In this paper, we investigate the dependence of the optimal doping on the parameters of the Emery () model for the CuO planes in the cuprates. We show that the best scaling is obtained not with the parameters of the model written in the real (-orbital) space, but rather written in the space of effective Wannier orbitals. In this basis, one obtains a model of three sublattices coupled through all possible 4-point interactions. We identify multiple predictor variables that fit the experimental to about K and that depend on the coupling constants in the transformed Hamiltonian
Quand les marges prennent le pouvoir éditorial – les rubriques humoristiques de Shinseinen –
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Izumi Shikibu 和泉式部 et Sone no Yoshitada 曽禰好忠 Deux poètes en marge de la cour impériale japonaise à l’époque de Heian (794-1185)
No full textInternational audienceLa Cour japonaise de l’époque de Heian constitue un milieu privilégié réunissant l’élite sociale et culturelle du Japon de l’époque. Il est pourtant possible d’y trouver des individus marginalisés ou marginaux. Nous nous intéresserons ainsi aux cas de deux poètes : Sone no Yoshitada (930 ?-987 ?) et Izumi Shikibu (v.970- ?), dame de cour dont l’écriture est marquée par l’influence de Yoshitada. Malgré leur marginalisation, ces deux aristocrates ont continué à pratiquer la poésie waka, activité pourtant sociale et régie par des règles laissant à première vue peu de place à l’originalité. Nous étudierons ici au travers d’exemples de poèmes de ces deux auteurs l’articulation entre marginalité, originalité et pratique littéraire collective voire institutionnalisée
Records From a Disappearing Temple : A Note on the “King and Queen” in the Painted Gallery at Kuh-i Khwaja
No full textInternational audienceThis article reexamines a wall painting discovered in 1925 and 1929 by Ernst Herzfeld in the Painted Gallery of the great Parthian-Sasanian temple complex at Kuh-i Khwaja in Iran (Sistan-Baluchestan province). The painting subsequently disappeared and today it can be studied only from Herzfeld’s photographs (hardly usable), sketch, and watercolors, kept at the Smithsonian’s National Museum of Asian Art. It shows a royal or aristocratic couple standing in a schematic architectural setting. No interpretation has so far been attempted. It is proposed that the couple is standing at the entrance of a fire chamber (such as the real one that exists at the back of the temple) and that the man holds a written scroll (already identified as such by Herzfeld according to a scribbled note), which probably contains a deed of endowment. The costumes are Sasanian but not royal Sasanian, while the type of the woman’s crown is documented in Kidarite-Hephtalite Bactria. A date is proposed in the fourth or fifth century. The man could belong to the vassal dynasty of the Sagānshāhs or be a later Sasanian governor
Modèles d'impuretés quantiques dissipatifs
No full textThis thesis focuses on the study of dissipative quantum impurity models. Quantum impurity models describe a localized quantum system, known as the impurity, that interacts with a large quantum bath, enabling the exploration of essential phenomena such as the Kondo effect in magnetic impurities and the transport properties in quantum dots. An intriguing extension of these models is the exploration of the interplay between strong correlations and dissipation. Dissipation, often described by the Lindblad master equation in its Markovian limit, introduces challenges and opportunities as it interacts with coherent many-body effects. In this thesis, we want to investigate the non-equilibrium dynamics of quantum impurity systems influenced by both strong correlations and dissipation across four main parts. We begin by developing numerical methods, specifically a diagrammatic Monte Carlo technique, to analyze the real-time dynamics of dissipative quantum impurity models. Our findings demonstrate that local Markovian dissipation enhances the convergence of Monte Carlo sampling by constraining the process to a reduced subspace of diagrams. This effectively mitigates the sign problem and facilitates the exploration of longer time scales compared to conventional unitary approaches. In the second part, we derive a self-consistent dynamical map using the Non-Crossing Approximation to study the long-term behavior of dissipative quantum impurity models. This method effectively resums diagrams into a self-consistent Dyson equation, capturing essential non-Markovian environmental effects, including the Kondo effect. In a third part, we examine the relationship between Kondo physics and Markovian dissipation by investigating an interacting quantum dot coupled to a metallic bath under continuous charge monitoring. We identify a crossover from Kondo screening to the Quantum Zeno effect, effectively described by a non-Hermitian Kondo model in the weak dissipation regime. Finally, the last part explores the effects of particle losses on the Kondo effect and the Kondo-Zeno crossover. Preliminary results indicate that while single-particle losses reduce many-body effects, two-body losses introduce intriguing phenomena, such as spin decay and hints of the Kondo-Zeno crossover, along with an unusual spectral function exhibiting a low-frequency lineshape.Cette thèse porte sur l’étude des modèles d’impureté quantique dissipatifs. Les modèles d’impureté quantique décrivent un système quantique localisé, appelé impureté, qui interagit avec un réservoir quantique, permettant d’explorer des phénomènes essentiels tels que l’effet Kondo dans les impuretés magnétiques et les propriétés de transport. Une extension intéressante de ces modèles consiste à explorer l’interaction entre les fortes corrélations et la dissipation. La dissipation, souvent décrite par l’équation maîtresse de Lindblad dans sa limite Markovienne, présente des défis et des opportunités en interagissant avec les effets cohérents à N-corps. Dans cette thèse, nous cherchons à étudier les dynamiques hors équilibre des systèmes d’impureté quantique influencés à la fois par les fortes corrélations et la dissipation. Nous commençons par développer des méthodes numériques, notamment une technique de Monte Carlo diagrammatique, pour analyser la dynamique en temps réel des modèles d’impureté quantique dissipatifs. Nos résultats montrent que la dissipation Markovienne locale améliore la convergence de l’échantillonnage Monte Carlo en restreignant le processus à un sous-espace réduit de diagrammes. Cela permet de réduire efficacement le problème de signe et facilite l’exploration de plus longues échelles de temps par rapport aux approches unitaires usuelles. Dans la deuxième partie, nous dérivons une carte dynamique auto-cohérente en utilisant l’Approximation Sans Croisement (NCA) pour étudier le comportement à long temps des modèles d’impureté quantique dissipatifs. Cette méthode résume efficacement les diagrammes dans une équation de Dyson auto-cohérente, capturant des effets environnementaux non-markoviens essentiels, y compris l’effet Kondo. Dans la troisième partie, nous examinons la relation entre la physique de Kondo et la dissipation markovienne en étudiant une boîte quantique interactive couplée à un réservoir métallique sous une surveillance continue de sa charge. Nous mettons en évidence un crossover entre le régime de Kondo et l’effet Zeno quantique, modélisé par un Kondo non hermitien, qui montre la robustesse de l’effet Kondo sous faible dissipation. Enfin, la dernière partie explore les effets des pertes de particules sur l’effet Kondo et la transition Kondo-Zeno. Les résultats préliminaires indiquent que, bien que les pertes d’une seule particule réduisent significativement les effets collectifs à N-corps, les pertes à deux corps introduisent des phénomènes intrigants, tels qu’une décroissance du spin et des indices de la transition Kondo-Zeno, ainsi qu’une fonction spectrale inhabituelle présentant une forme de ligne à basse fréquence
Archéologie trans-himalayenne : mouvements de populations et interactions matérielles, de la préhistoire à la période bouddhique: Programme de recherche pluriannuel du Centre de Recherches sur les Civilisations de l'Asie Orientale (CRCAO)
No full texthttps://www.crcao.fr/recherche/archeologie-trans-himalayenne-mouvements-de-populations-et-interactions-materielles-de-la-prehistoire-a-la-periode-bouddhique