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Horizon causality from holographic scattering in asymptotically dS
No full textInternational audienceIn the AdS/CFT correspondence, direct scattering in the bulk may not have a local boundary analog. A nonlocal implementation on the boundary requires mutual information. This statement is formalized by the connected wedge theorem, which can be proven using general relativity within AdS but also by applying quantum information theory on the boundary, suggesting that the theorem applies to any holographic duality. We examine scattering within the static patch of asymptotically dS spacetime, which is conjectured to be described by a quantum theory on the stretched horizon in static patch holography. We prove that causality on the horizon should be induced from null infinities to maintain consistency with the theorem. Specifically, signals propagating in the static patch are associated with local operators at . Our results suggest a novel connection between static patch holography and the dS/CFT correspondence
Reactions of aliphatic terminal alkynes with Ti(OiPr)4/BuLi: selectivity, kinetic aspects, and a new tetramerisation process
No full textInternational audienceThe reactions of terminal aliphatic alkynes with Ti(OiPr)4/nBuLi or Ti(OiPr)4/sBuLi were investigated. Thesesubstrates were transformed more slowly than previously studied 1-aryl acetylene compounds and mixturesof products were generally obtained. This allowed the rate constants of the elementary steps involved to beevaluated. One substrate was shown to undergo cyclotrimerisation with high regioselectivity in favour of the1,2,4 adduct. Furthermore, an unprecedented tetramerisation process was uncovered
On the relative packing densities of pistachios and pistachio shells
No full text3 pages, 4 figuresInternational audienceGiven an appetizer bowl full of N pistachios, what is the optimal size of the container -neither too small, nor too big -needed for accommodating the resulting 2N non-edible pistachio shells? Performing a simple experiment we find that, provided the shells are densely packed, such container needs only be slightly more than half (≈ 0.57) that of the original pistachio bowl. If loosely packed this number increases to ≈ 0.73. Our results are discussed in light of existing literature on packing ellipsoids and spherical shells.</div
Modèles mathématiques pour la radiologie interventionnelle personnalisée : Application au traitement du cancer
No full textThe integration of computer vision into Image-Guided interventions has the potential to change our medical practice. This work lays some bricks for the future of autonomous interventions in our specific field regarding cancer patients, addressing key components necessary for its realization.We first explore the transformative impact of AI on the physical abilities of interventional radiologists. We emphasize the need to navigate technical and ethical challenges. Interdisciplinary collaboration and robust evaluation processes are highlighted as essential for the safe integration of AI into clinical practiceWe then propose an organ agnostic method for detecting focal anomalies on volumetric cross-sectional imaging. Leveraging the Large Diffeomorphic Deformation Metric Mapping (LDDMM) framework, this approach showcases enhanced object reconstruction and precise lesion localization. In the same framework, we propose a classifier, where patient selection presents unique challenges due to the complex benefice/risk ratios.To go beyond images, clinical data from tumor DNA analysis is integrated into a prospective study specifically conducted for this work. Generative Adversarial Networks (GAN) and Modelling Atlases Using the Markov Chain Monte Carlo - Stochastic Approximation Expectation-Maximization (MCMC-SAEM) Algorithms are used to predict patient trajectories. This approach enables the exploration of new trajectories, enhancing our understanding of disease progression and treatment response in relationship of circulating tumor DNA.Lastly, we explore advanced visualization techniques for in vivo and ex vivo 3D vasculature. We propose a planar representation of undescribed anatomy, offering a promising avenue for further exploration and understanding.Together, these sections offer solutions to parts of the realization of autonomous interventions in our field.Les méthodes statistiques contemporaines ont le potentiel de changer la pratique médicale au sein même de nos blocs de radiologie interventionnelle. Ce travail pose quelques jalons pour l'avenir des interventions autonomes dans notre domaine spécifique avec pour fil conducteur la prise en charge des patients atteints de cancer.Nous explorons d'abord l'impact transformateur de l'IA sur les capacités physiques des radiologues interventionnels. A terme, l’autonomie au bloc passera par la robotisation et l’analyse d’images produites en direct. L’intégration de la vision au geste permettra d’avancer vers ce bloc autonome.Nous proposons ensuite une méthode de détection d’anomalies ne dépendant pas de l’organe exploré à partir d’une imagerie en coupe. En exploitant le cadre du Large Diffeomorphic Deformation Metric Mapping (LDDMM), cette approche met en valeur une reconstruction d'objet améliorée et une segmentation de la lésion. Dans le même cadre, nous proposons un classificateur, permettant d’établir une nouvelle lecture de la sélection des patients avant l’intervention.Afin d’aller au-delà des images, des données cliniques issues de l'analyse de l'ADN tumoral circulant sont intégrées dans une étude prospective spécifiquement menée pour ce travail. Des réseaux antagonistes génératifs (GAN) et des algorithmes d'approximation stochastique (MCMC-SAEM) sont utilisés pour prédire les trajectoires des patients. Cette approche permet d'explorer de nouvelles trajectoires, améliorant notre compréhension de la progression de la maladie et de la réponse au traitement en relation avec l'ADN tumoral circulant.Enfin, nous explorons des techniques de visualisation avancée pour l’anatomie vasculaire 3D in vivo et ex vivo. Nous proposons une représentation planaire de l'anatomie, offrant des possibilités en termes de navigation et de classification de l’arbre vasculaire.Ensemble, ces sections offrent des solutions à certains défis menant vers la réalisation d'interventions autonomes guidées par l’image
Distribution and morphology of non-persistent contrail and persistent contrail formation areas in ERA5
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The Euler-Lagrange equation and optimal control: Preliminary results
No full textInternational audienceAlgebraically speaking, linear time-invariant (LTI) systems can be considered as modules. In this framework, controllability is translated as the freeness of the system module. Optimal control mainly relies on quadratic Lagrangians and the consideration of any basis of the system module leads to an open-loop control strategy via a linear Euler-Lagrange equation. In this approach, the endpoint is easily assignable and time horizon can be chosen to minimize the criterion. The loop is closed via an intelligent controller derived from modelfree control, which exhibits excellent performances concerning model mismatches and disturbances. The extension to nonlinear systems is briefly discussed
Attribution of the Extreme 2022 Summer Drought along the Yangtze River Valley in China Based on Detection and Attribution System of Chinese Academy of Sciences
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Soil Carbon-Concentration And Carbon-Climate Feedbacks In Cmip6 Earth System Models
No full textInternational audienceAchieving climate targets requires mitigation against climate change but also understanding of the response of land and ocean carbon systems. In this context, global soil carbon stocks and their response to environmental changes are key. This paper quantifies the global soil carbon feedbacks due to changes in atmospheric CO2, and the associated climate changes, for Earth system models (ESMs) in CMIP6. A standard approach is used to calculate carbon cycle feedbacks, defined here as soil carbon-concentration (βs) and carbon-climate (γs) feedback parameters, which are also broken down into processes which drive soil carbon change. The sensitivity to CO2 is shown to dominate soil carbon changes at least up to a doubling of atmospheric CO2. However, the sensitivity of soil carbon to climate change is found to become an increasingly important source of uncertainty under higher atmospheric CO2 concentrations
Earth Virtualization Engines (Eve)
No full textInternational audienceTo manage Earth in the Anthropocene, new tools, new institutions, and new forms of international cooperation will be required. Earth Virtualization Engines is proposed as an international federation of centers of excellence to empower all people to respond to the immense and urgent challenges posed by climate change
The delivery of water ice to the Martian surface by passive degassing
No full textInternational audiencePassive degassing, or volatile release from persistent, non-eruptive volcanic activity, may have contributed significantly to the Martian ice budget over the planet's history by providing a pathway for volatile species, such as water vapor, to outgas from the interior into the atmosphere and accumulate on the surface. Passive degassing from Martian volcanoes can result in ice accumulations in unusual locations (e.g., outside of the typical cold traps like the Tharsis Rise and polar ice caps). Such locally derived water could cover the volcanic source in an ice-rich veneer that may later serve as a source of ice for subsequent interactions between impactors or lava. Using the Laboratoire de Météorologie Dynamique Generic Planetary Climate Model, we model the spatial distribution of ice that results from passive degassing from five major Martian volcanic centers, Cerberus Fossae, Apollinaris Mons, Elysium Mons, Hadriacus Mons, and Pityusa Patera, and assess the sensitivity of these results to a range of volcanic, atmospheric, orbital, environmental, and numerical parameters. Previous studies have placed estimates on the amount of water released from volcanic outgassing (e.g., Carr, 1987; Craddock and Greeley, 2009; Grott et al., 2011; Carr and Head, 2015), but this is the first study to track the water released from specific volcanoes and to determine the spatial distribution of resulting ice deposits. We find that volcanic variables, such as mass flux and duration of degassing, primarily drive the thickness of volcanogenic ice fields –– higher mass fluxes create the thickest ice deposits (up to ∼210 mm around the volcanic center for a mass flux 106 kg s‑1) and durations of >6 months are required for ice to reach near-global distributions. Ice accumulation around the degassing source is maximized if the latitude of passive degassing occurs near the south pole (i.e., Pityusa Patera) due to its exposure to circulation patterns that promote ice deposition in that region. Changes in the season, dust visible optical depth, and eccentricity can also impact the thickness of ice, with ice accumulation around the volcanic source being maximized in the spring, with higher dust visible optical depths, and when the eccentricity is low, due to more favorable temperatures and atmospheric circulation. Variances in the obliquity can also influence ice fields by modulating which latitudes receive more surface ice accumulation. The amount of activated cloud condensation nuclei (CCN) in the atmosphere has a lesser impact on the thickness and spatial distribution of ice fields than other parameters, with lower amounts of CCN leading to narrower, but slightly thicker deposits compared to higher amounts of CCN. The mean surface pressure and longitude of perihelion both affect the timing of ice fields. The surface pressure influences how long water lingers in the atmosphere before depositing to the surface, while the longitude of perihelion controls the time of year in which the thickest ice deposits accumulate around the degassing source. Ice fields are highly sensitive to the model resolution. Higher model resolutions allow for a more detailed representation of physical processes, such as cloud formation and ice deposition, while lower resolution model runs provide a more approximate guide to the representation of these processes and may underestimate surface ice thicknesses around the degassing source. The thickest deposits of ice form around the source of passive degassing, but later migrates and restabilizes in cold traps after degassing has ceased, unless it is protected against sublimation by the deposition of dust or pyroclastic material. Assuming the ice is protected, recurrent episodes of passive degassing could have facilitated the gradual accumulation of ice deposits several meters thick over time