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22122 research outputs found
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Histoire intellectuelle de la Chine: [résumé des cours et travaux : 2021-2022]
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Informatique et sciences numériques (chaire annuelle 2021-2022): [résumé des cours et travaux : 2021-2022]
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Spirosilanes Activate Gold(I)-Catalysts in Cycloisomerization and Intermolecular Reactions
No full textInternational audienceGold-catalyzed reactions have established as a powerful tool in organic synthesis, offering efficient pathways to construct diverse molecular structures and notably scaffolds with high complexity. Most processes rely on the use of LAuCl precatalysts, which are generally activated, i.e. cationized, by silver salts. In this work, we explore the role of silicon-based Lewis acids based such as spirosilane derivatives as alternative activators in lieu of silver salts. It was found that Martin spirosilanes mediate the activation of gold precatalysts, facilitating diverse cyclization and cycloisomerization reactions as well as intermolecular reactions.NMR studies and computational investigations suggest that no real cationization, i.e. formation of an ionic pair, takes place, but rather activation through weak interaction between silicon and the chlorine atom of LAuCl. This preserves the Au-Cl bond and ultimately enables the LAuCl complex to be recovered. On the same line, the LAuCl-silane interaction has also proven to be beneficial for asymmetric catalysis. This work significantly contributes to the expansion of gold-catalyzed transformations by opening up the prospect of a more sustainable gold catalysis. It also opens perspectives on the use of silicon-based Lewis acids as versatile cooperative agents in organometallic chemistry
The Healing Empire: Aromatic Oils, Unguents, and the Reception of Solomon in Byzantium: Aromatic Oils, Unguents, and the Reception of Solomon in Byzantium
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Mapping and explaining syntax errors with LRgrep
No full textInternational audienceLR parsers and generated parsers are often criticized for their perceived inability to produce good syntax error messages. Yet, we believe, this inability is not inherent to LR parsing or to the use of a parser generator. Instead, we claim, this perception is caused mainly by the lack of languages and tools that allow the problem of producing good syntax error messages to be addressed at a suitable level of abstraction.In this paper, we demonstrate how to use the LRgrep language and its compiler to construct good syntax error explanations for an LR parser. We focus on a toy language of arithmetic expressions, with global and local variable definitions, whose parser is built by the Menhir parser generator. The LRgrep tool helps us discover all of the error situations that this parser can encounter. The LRgrep language lets us describe each situation via a succinct pattern and provide code that constructs an explanation message for this situation. Our description of all error situations and messages fits in one page of LRgrep and OCaml code
GWTC-4.0: Constraints on the Cosmic Expansion Rate and Modified Gravitational-wave Propagation
No full textInternational audienceWe analyze data from 142 of the 218 gravitational-wave (GW) sources in the fourth LIGO-Virgo-KAGRA Collaboration (LVK) Gravitational-Wave Transient Catalog (GWTC-4.0) to estimate the Hubble constant jointly with the population properties of merging compact binaries. We measure the luminosity distance and redshifted masses of GW sources directly; in contrast, we infer GW source redshifts statistically through i) location of features in the compact object mass spectrum and merger rate evolution, and ii) identifying potential host galaxies in the GW localization volume. Probing the relationship between source luminosity distances and redshifts obtained in this way yields constraints on cosmological parameters. We also constrain parameterized deviations from general relativity which affect GW propagation, specifically those modifying the dependence of a GW signal on the source luminosity distance. Assuming our fiducial model for the source-frame mass distribution and using GW candidates detected up to the end of the fourth observing run (O4a), together with the GLADE+ all-sky galaxy catalog, we estimate km s Mpc. This value is reported as a median with 68.3% (90%) symmetric credible interval, and includes combination with the measurement from GW170817 and its electromagnetic counterpart. Using a parametrization of modified GW propagation in terms of the magnitude parameter , we estimate , where recovers the behavior of general relativity
Réformer l'écriture céleste: un transfert par occidentalisation de la cithare qin ?
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Du maître de sagesse à la figure canonique : la représentation de Confucius entre le IVe siècle av. n. è. et le Ier siècle de n. è.
No full textInternational audienceLa tradition lettrée chinoise présente Confucius (v. 551-479 av. n. è.) comme le maître par excellence, le désignant souvent par la simple appellation « Maître » (zi 子). Confucius revêt aussi le rôle de patriarche de la classe des lettrés-fonctionnaires, qui formait une sorte d’entité organique ayant assuré la cohésion politique, idéologique, spirituelle, culturelle et éducative de l’empire chinois pendant plus de deux millénaires. Néanmoins, de même que son enseignement fut constamment réinterprété à travers les âges, la représentation de Confucius dans la mémoire collective – loin d’être uniforme – ne cessa d’évoluer en fonction du contexte historique propre à chaque époque. La phase initiale dans la transformation du portrait du penseur se produisit durant les siècles qui précédèrent et suivirent l’avènement de l’empire en l’an 221 avant notre ère. Cette longue phase se divise en trois étapes. Dans un premier temps, plus d’un siècle après sa mort, Confucius était dépeint comme un maître qui, entouré de disciples, se mit en quête d’un souverain sage prêt à instaurer un gouvernement fondé sur la vertu. Dans un second temps, environ un siècle après la fondation impériale, le maître de sagesse fut alors décrit comme un « roi sans couronne », dont l’enseignement fut promu au rang de doctrine impériale officielle. Dans un dernier temps, aux alentours de l’ère chrétienne, une nouvelle image de Confucius se développa, avec l’instauration de son culte officiel qui s’accompagna de sa canonisation. Nous nous proposons d’examiner le processus d’évolution de la représentation de Confucius entre le IVe siècle avant notre ère et le Ier siècle de notre ère, suivant les circonstances politiques, sociales et culturelles spécifiques à chaque période. Notre analyse s’appuiera sur des données issues aussi bien de sources transmises que de sources exhumées textuelles et iconographiques, qui ont refait surface au cours des vingt dernières années