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On Subexponentials, Synthetic Connectives, and Multi-level Delimited Control
No full textInternational audienceWe construct a partially-ordered hierarchy of delimited control operators similar to those of the CPS hierarchy of Danvy and Filinski. However, instead of relying on nested CPS translations, these operators are directly interpreted in linear logic extended with subexponentials (i.e., multiple pairs of ! and ?). We construct an independent proof theory for a fragment of this logic based on the principle of focusing. It is then shown that the new constraints placed on the permutation of cuts correspond to multiple levels of delimited control
Proof Outlines as Proof Certificates: A System Description
No full textInternational audienceWe apply the foundational proof certificate (FPC) framework to the problem of designing high-level outlines of proofs. The FPC framework provides a means to formally define and check a wide range of proof evidence. A focused proof system is central to this framework and such a proof system provides an interesting approach to proof reconstruction during the process of proof checking (relying on an underlying logic programming implementation). Here, we illustrate how the FPC framework can be used to design proof outlines and then to exploit proof checkers as a means for expanding outlines into fully detailed proofs. In order to validate this approach to proof outlines, we have built the ACheck system that allows us to take a sequence of theorems and apply the proof outline " do the obvious induction and close the proof using previously proved lemmas "
Defining the meaning of TPTP formatted proofs
No full textInternational audienceThe TPTP library is one of the leading problem libraries in the automated theorem proving community. Over time, support was added for problems beyond those in first-order clausal form. TPTP has also been augmented with support for various proof formats output by theorem provers. Such proofs can also be maintained in the TSTP proof library. In this paper we propose an extension of this framework to support the semantic specification of the inference rules used in proofs
ROS Detection and Quantification with Lanthanide-Based Nanosensors
No full textInternational audienceReactive oxygen species (ROS), in particular hydrogen peroxide (H2O2), are produced as secondary cellular messengers involved in a variety of signaling pathways. Detecting ROS concentration in cells and in living organisms is particularly important because ROS oxidative stress plays a complex role in multiple pathologies: inflammatory processes, neurodegenerative diseases, and cancer. We first report on an europium-based H2O2 sensor (Y0.6Eu0.4VO4) that shows red, oxidant-dependant, reversible luminescence modulation used in cells in culture
Divide and conquer in ABC: Expectation-Progagation algorithms for likelihood-free inference
No full textTo appear in the forthcoming Handbook of Approximate Bayesian Computation (ABC), edited by S. Sisson, L. Fan, and M. BeaumontABC algorithms are notoriously expensive in computing time, as they require simulating many complete artificial datasets from the model. We advocate in this paper a "divide and conquer" approach to ABC, where we split the likelihood into n factors, and combine in some way n "local" ABC approximations of each factor. This has two advantages: (a) such an approach is typically much faster than standard ABC and (b) it makes it possible to use local summary statistics (i.e. summary statistics that depend only on the data-points that correspond to a single factor), rather than global summary statistics (that depend on the complete dataset). This greatly alleviates the bias introduced by summary statistics, and even removes it entirely in situations where local summary statistics are simply the identity function.We focus on EP (Expectation-Propagation), a convenient and powerful way to combine n local approximations into a global approximation. Compared to the EP- ABC approach of Barthelm\'e and Chopin (2014), we present two variations, one based on the parallel EP algorithm of Cseke and Heskes (2011), which has the advantage of being implementable on a parallel architecture, and one version which bridges the gap between standard EP and parallel EP. We illustrate our approach with an expensive application of ABC, namely inference on spatial extremes
Développement d’un laser XUV collisionnel à plasma OFI ultrabref et intense
No full textCollisionally-pumped “OFI” plasma-based soft X-ray lasers are achieved by focusing an ultra-intense infrared laser pulse into a gas. The resulting laser-plasma interaction allows the generation of a plasma column in population inversion, made of multi-charged ions and energetic electrons. We are interested in the emission from the 3d94dJ=0 → 3d94pJ=1 atomic transition of krypton IX (Nickel-like) at 32.8 nm. When this plasma is seeded by an external high-harmonic source, the resulting emission exhibits excellent spatial properties, while demonstrating a significantly higher photon yield at the relevant wavelength.Although being compact and exhibiting numerous attractive characteristics, collisional plasma-based X-ray lasers face limitations intrinsic to their pumping scheme. Indeed, they used to deliver quite long pulses (a few picosecond), thus limiting the scope of applications. The main focus of this thesis has been associated with the implementation of an original technique aimed at achieving 100 fs-range duration of emission by quenching the plasma amplifier gain lifetime through collisional over-ionization (Collisional Ionization Gating). This required operating at very high electron densities (about 1020 cm-3), which involved the implementation of optical waveguiding techniques. The “seeded regime” has been used to sample the ultrafast gain lifetime of such a plasma amplifier. A time-dependent Maxwell-Bloch code allowed describing the ultrashort amplification dynamics and deriving a final soft X-ray pulse duration. The method additionally allows a larger photon yield per shot (14 µJ), thus promising a nearly three orders of magnitude surge in soft X-ray pulse intensity compared to previous performances. Another important focus of this thesis dealt with the implementation of a circularly polarized plasma-based X-ray laser. Such source allows the study of dichroism, magnetization dynamics in matter or chiral domains in biology. The source has been demonstrated by seeding a krypton IX plasma amplifier with a resonant circularly polarized high-harmonic signal. In agreement with experimental measurements, our Maxwell-Bloch numerical model confirms the conservation of the high-harmonic polarization over amplification in the plasma and the efficiency of the scheme, which paves the way for prospective single-shot measurements.Les lasers XUV collisionnels dit « OFI » sont réalisés en focalisant une impulsion laser infrarouge ultra-intense dans un milieu gazeux. L’interaction qui en résulte permet la génération d’une colonne de plasma en inversion de population, constituée d’ions multi-chargés et d’électrons énergétiques. Nous nous intéressons à l’emission de la transition 3d94dJ=0 → 3d94pJ=1 du krypton IX (nickeloïde) à 32,8 nm. Lorsque ce plasma amplificateur est injecté par une source harmonique externe, l’émission résultante montre d’excellentes propriétés spatiales tout en offrant, à la longueur d’onde considérée, un nombre de photons bien supérieur. Bien que compacts et démontrant d’excellentes propriétés spatiales, les lasers XUV collisionnels font face à des limites inhérentes à leur schéma de pompage. En effet, ceux-ci produisaient jusqu’ici des impulsions relativement longues (quelques picosecondes), limitant ainsi le champ d’applications. L’axe majeur de cette thèse a consisté à repousser cette limite afin d’atteindre une durée d’émission de l’ordre de la centaine de femtosecondes, en mettant en œuvre une « fenêtre temporelle sur le gain » de l’amplificateur plasma par sur-ionisation collisionnelle (Collisional Ionization Gating). Ceci est rendu possible en opérant à des densités électroniques très élevées (autour de 1020 cm-3), ce qui nécessite l’utilisation de techniques de guidage optique. Le régime d’injection d’harmoniques a été utilisé pour sonder la dynamique temporelle du gain d’un tel amplificateur plasma. Un modèle numérique Maxwell-Bloch à dépendance temporelle nous a permis de décrire cette dynamique d’amplification et d’en extraire une durée d’émission XUV. D’autre part, la méthode permet également la génération d’un plus grand nombre de photons par tir (jusqu’à 14 µJ), offrant ainsi une augmentation de l’intensité des impulsions XUV émises de près de trois ordres de grandeurs par rapport aux performances précédentes.Un autre axe important de la thèse a consisté en la réalisation d’un laser XUV polarisé circulairement. De telles sources permettent l’étude des propriétés dichroïques de la matière, de la dynamique de domaines magnétiques de matériaux ou de la structure chirale d’échantillons biologiques. La source a été réalisée avec succès en amplifiant une source harmonique résonante et polarisée circulairement par un plasma de Krypton IX. Conformément aux mesures expérimentales, notre modèle numérique Maxwell-Bloch confirme la conservation de l’état de polarisation des harmoniques au cours de l’amplification ainsi que l’efficacité du schéma de génération, ce qui ouvre ainsi la voie vers l’acquisition de mesures en un seul tir
Modèle mathématique à bilan d'énergie du changement climatique
No full textThe goal of this study is to build a global reduced-complexity model of coupled climate-economy-biosphere interactions, which uses the minimum number of variables and equations needed to capture the fundamental mechanisms involved and can thus help clarify the role of the different mechanisms and parameters. The Coupled Climate-Economy-Biosphere (CoCEB) model takes an integrated assessment approach to simulating global change. While many integrated assessment models treat abatement costs merely as an unproductive loss of income, the study considered abatement activities also as an investment in overall energy efficiency of the economy and decrease of overall carbon intensity of the energy system. The study shows that these efforts help to abate climate change and lead to positive effects in economic growth. Due to the fact that integrated assessment models in the literature mainly focus on mitigation in the energy sector and consider emissions from land-use as exogenous, the global climate-economy-biosphere (CoCEB) model was extended by adding a biomass equation and the related exchanges of CO2 and used to investigate the relationship between the effects of using carbon capture and storage (CCS) and deforestation control, and the economy growth rate. These measures are found to reduce the impacts of climate change and positively affect the economy growth. These results remain nevertheless sensitive to the formulation of CCS costs while those for deforestation control were less sensitive. The model developed brings together and summarizes information from diverse estimates of climate change mitigation measures and their associated costs, and allows comparing them in a coherent way.Dans cet étude, un modèle de complexité réduite des interactions et rétroactions du système couplé climat-économie-biosphère est construit avec le minimum de variables et d'équations nécessaires. Le Coupled Climate-Economy-Biosphere (CoCEB) est un modèle d’évaluation intégrée (IAM pour Integrated assessment model) du changement globale. Alors que beaucoup IAM traitent les coûts de réduction des émissions (abattement) simplement comme une perte non productive de revenu, cet étude considère également les activités d’abattement comme un investissement dans l'efficacité énergétique globale de l'économie et dans la diminution de l’ « intensité carbone » du système énergétique. L’étude montre que ces efforts aident à l’abattement du changement climatique et ont un effet positif sur l’économie. La plupart des IAM actuels se concentrent principalement sur le secteur énergétique pour les mesures d’abattement, et ne tiennent compte des émissions provenant de l'utilisation des terres que comme un forçage exogène. Le CoCEB a donc été étendu en ajoutant une équation pour la biomasse ses échanges de carbone. Cela permet d’étudier les aspects économiques de la séquestration de carbone du au contrôle du déboisement dans les forêts, et aussi à l’application généralisée des technologies de capture et stockage du carbone (CCS). L’étude confirme que ces mesures réduisent l’impact du changement climatique sur la croissance économique, mais ces résultats restent très dépendants des grandes incertitudes sur le cout des CCS et du contrôle de la deforestation. Ce modèle est un cadre formel qui représente de façon simple les différents éléments du système couplé et leurs interactions, il rassemble les différentes estimations des coûts afférents aux mesures de mitigation et permet de les comparer de façon cohérente
Modelling mode choice within couples
No full textWe analyze couples mode choice, with an application in Paris region. When spouses’ commuting decisions are assumed to be independent – the standard assumption – the model poorly reproduces intra-household decisions. We set up a model of joint decision, which provides more plausible results and exhibits a greater predictive power. We estimate the determinants of the bargaining power (spouses’ age, nationality, type of job contract, tenure status and number of children) using a collective model. To control remaining endogeneity issues, we finally model the joint choice of car ownership and mode choice. Values of time are computed for driving alone and together
