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Peierls substitution and Hall motion in exotic Carroll dynamics
No full textInternational audienceThe particle with first-order dynamics proposed by Dunne, Jackiw and Trugenberger (DJT) to justify the "Peierls substitution" is obtained by reduction from both of two-parameter centrally extended Galilean and Carroll systems. In the latter case the extension parameters and generate non-commutativity of the coordinates resp. behave as an internal magnetic field. The position and momentum follow uncoupled anomalous Hall motions. Consistently with partial immobility, one of the Carroll boost generators is broken but the other remains a symmetry. Switching off , the immobility of unextended Carroll particles is recovered. The Carroll system is dual to an uncharged anyon on the horizon of a black hole which exhibits the spin-Hall effect
Eċg wæs iren, átertánum fáh: Le damas d'assemblage en Alsace et l'Europe Centrale
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Experimental Study of the Reactions of Br Atoms with Thiirane and Nitrosyl Chloride
No full textInternational audienceThe kinetics of Br-atom reactions with C2H4S and ClNO were studied as a function of temperature at a total pressure of 2 Torr of helium using a discharge–flow system combined with mass spectrometry: Br + C2H4S → SBr + C2H4 (1) and Br + ClNO →BrCl + NO (2). The rate constant of reaction (1) was determined at T = 340–920 K by absolute measurements under pseudo-first-order conditions, either by monitoring the kinetics of Br-atom or C2H4S consumption in excess of C2H4S or of Br atoms, respectively, and by using a relative rate method: k1 = (6.6 ± 0.7) × 10−11 exp(−(2946 ± 60)/T) cm3molecule−1s−1 (where the uncertainties represent the precision at the 2σ level, the estimated total uncertainty on k1 being 15% at all temperatures). The rate coefficient of reaction (2), determined either from the kinetics of the formation of the reaction product, BrCl, or from the decays of Br-atoms in an excess of ClNO, showed non-Arrhenius behavior, being practically independent of temperature below 400 K and increasing significantly at temperatures above 500 K. The measured rate constant is well reproduced by a sum of two exponential functions: k2 = 1.2 × 10−11 exp(−19/T) + 8.0 × 10−11 exp(−1734/T) cm3 molecule−1 s−1 (with an estimated overall temperature-independent uncertainty of 15%) at T = 225–960 K
Analysis of Early Iron Age / Classical period glass beads from Brili necropolis (Georgia)
No full textInternational audienceWe present the analytical results obtained, using LA-ICP-MS, on a set of 77 glass beads, of various colours, dating to the Pre-classical and Classical period (8th to 4th c. BC) and originating from Brili necropolis (Georgia). This necropolis, located in the North-West of Georgia, in the historical Colchis region, was used continuously between the 15th c. BC and the 4th c. AD and was excavated periodically between 1939 and 1961. Through the comparison with published analytical data of coeval, earlier and later glass samples, the aim of this study is to investigate the provenance of this Brili assemblage in order to highlight the cultural influences and trading network of the Brili community during the Pre-classical and Classical period. The analysed glass beads are classified in three main groups and several sub-groups. The two main groups consist of Egyptian and Syro-Palestinian natron soda lime glasses (34 beads) on the one hand and high lithium, boron and magnesium mineral soda-lime glasses (34 beads) on the other. We also find a group of high magnesium, potassium and phosphorus plant ash soda-lime glass (9 beads) which up to now, was scarcely identified among Early Iron Age glass studies. Among this small group, one of the beads, characterized by lower phosphorus content, belongs probably to the well-established Mesopotamian soda-lime plant ash glass group
Dynamiques de Gouvernance dans l'Écosystème des Start-ups Innovantes
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Deep Trade Agreements and Trade in Value- Added: Does Heterogeneity Matter?
No full textThis paper examines the heterogeneous impact of Global Value Chains (GVC) integration on singing deep trade agreements. Following Fontagné and Santoni (2021), we contribute to the literature in two ways. First, we extend their analysis by examining not only the impact of GVC on signing an agreement, but on the likelihood of signing a deep one. Second, for GVC, we distinguish between backward participation (value added in exports that rely on foreign inputs) and forward linkages (value added that is embodied in exports of other countries). We also distinguish whether GVC occurs in goods or services. To do so, we combine the Eora dataset with the Deep Trade Agreement database (World Bank) using a gravity-type model. Our main findings show that GVC increases the likelihood of signing a deep agreement that focuses on goods and services. More particularly, an increase in GVC by 1% increases the probability of signing a PTA by 2.9 percentage points. More particularly, backward linkages (relative to forward) are more likely to a↵ect the depth of the agreement as they increase the latter by 3.3 percentage points. Our results remain robust after running a set of sensitivity tests. In addition, we show that the impact of GVC is greater on the depth of provisions related to NTMs followed by services. When the development level is considered, GVC flows create a new motive to deepen trade agreements between countries that belong to di↵erent income groups.</div
Analyse MMS d’une séparatrice magnétosphérique comprimée du côté jour en présence d’ions froids et d’un champ guide modéré
No full textInternational audienceThis study reports on a dayside magnetic reconnection event detected by the Magnetospheric Multiscale mission in the presence of a moderate guide field (times the reconnecting magnetic field on the magnetosphere side) and assumed to be present in the whole reconnection region. The spacecraft traversed the compressed magnetospheric separatrix region, observing cold ions with densities up to 10 cm-3 and a large magnetosheath density of up to 150 cm-3. We provide a detailed analysis of current densities, generalized Ohm's law, and energy conversion processes in both the spacecraft and the fluid frames during the separatrix crossing. The normal electric field is directed away from the separatrix due to the cold ion drift on the magnetosphere side and to the magnetosheath ion drift in the presence of a guide field in the exhaust region. In the spacecraft frame, energy transfers from the plasma to the fields due to the convective field associated with the earthward motion of the magnetopause and the ion diamagnetic current associated with the large density gradient. In the fluid frame, energy conversion reverses due to the magnetic field-aligned current density and electric field produced by the divergence of the electron pressure tensor. Additionally, we give insights into the local changes in electromagnetic, bulk flow, and thermal energies. We show that flow and thermal energy variations of the plasma are mostly driven by the compressible term of the electron pressure strain at the separatrix
Simulations Euler-Euler pour décrire le transport colloïdal en vue de la remédiation des eaux souterraines
No full textInternational audienceNon-aqueous liquids (NAPLs) are water-immiscible pollutants that can disperse and release significant amounts of toxic compounds into underground water resources. Numerous methods have been developed to remove these pollutants from aquifers, but NAPL droplets remain trapped by capillary forces in the porous matrix even after depollution. The aim of our research is to explore the potential of colloids (e.g. nanoparticles, bacteria) to remobilize immiscible pollutant droplets. Our final objective is to develop a multiphase model that includes colloidal interactions with the solid phase, the aqueous phase, and the NAPL. Euler-Lagrange models allow us an accurate description of colloidal particle interactions (e.g. transport and retention) but remains very time-and resource-intensive. In this work, we are developing Euler-Euler approaches based on OpenFOAM's multiphaseEuler module to represent particles as a dispersed phase in water. The use of this model in the context of the remediation of polluted porous media is currently under development. Our model includes new viscosity models and plastic behavior, as well as the poromechanic properties. We present preliminary results such as: i) comparisons with Euler-Lagrange simulations for very diluted suspension, and ii) response to fluid stresses and its compressibility.Les liquides non aqueux (NAPLs) sont des polluants non miscibles à l'eau qui peuvent se disperser et libérer des quantités importantes de composés toxiques dans les ressources en eau souterraines. De nombreuses méthodes ont été développées pour éliminer ces polluants des aquifères, mais les gouttelettes de NAPL restent piégées par les forces capillaires dans la matrice poreuse, même après la dépollution. Le but de notre recherche est d'explorer le potentiel des colloïdes (par exemple, les nanoparticules, les bactéries) pour remobiliser les gouttelettes de polluants non miscibles. Notre objectif final est de développer un modèle multiphasique qui inclut les interactions des colloïdes avec la phase solide, la phase aqueuse et le NAPL. Les modèles d'Euler-Lagrange nous permettent d'obtenir une description précise des interactions entre les particules colloïdales (par exemple, le transport et la rétention), mais ils nécessitent beaucoup de temps et de ressources numériques. Dans ce travail, nous développons des approches Euler-Euler basées sur le module multiphaseEuler d'OpenFOAM pour représenter les particules comme une phase dispersée dans l'eau. L'utilisation de ce modèle dans le contexte de la remédiation des milieux poreux pollués est actuellement en cours de développement. Notre modèle inclut de nouveaux modèles de viscosité et un comportement plastique, ainsi que les propriétés poromécaniques. Nous présentons des résultats préliminaires tels que : i) des comparaisons avec des simulations d'Euler-Lagrange pour une suspension très diluée, et ii) la réponse aux contraintes du fluide et sa compressibilité
Influence de la dynamique des paramètres de contrôle et phénomène de basculement dans un modèle simple d’instrument à anche
No full textInternational audienceLes instruments de musique à anche simple comme les clarinettes sont des systèmes dynamiques non linéaires liant des paramètres de contrôle, utilisés par le musicien pour contrôler l’instrument, à des variables de sortie caractérisant le son musical perçu par l’auditeur. Les études théoriques précédentes sur la production sonore ont été réalisées en considérant les paramètres de contrôle constants dans le temps. Ces études ont montré que la propriété de multistabilité - c.-à-d la coexistence de plusieurs solutions stables pour un jeu donné de paramètres - est souvent observée dans les modèles. Cependant, pendant les transitoires, le musicien fait varier les paramètres de contrôle dans le temps. Par exemple, pendant l'attaque d'une note, il augmente la pression dans sa bouche (le paramètre de contrôle principal) pour atteindre la note désirée. Il a également été montré, principalement en science du climat, qu’un système dynamique multistable dont les paramètres de contrôle évoluent dans le temps peut subir un basculement (ou tipping) qui désigne une transition brusque entre deux solutions stables, provoquée uniquement par la variation d’un paramètre. Les concepts traditionnels de diagramme de bifurcation et de bassins d’attraction sont essentiels pour l’étude de ce phénomène mais ne permettent pas de l’expliquer pleinement. Ce travail étudie théoriquement le basculement pendant le transitoire d’attaque d'un modèle simplifié de clarinette représentant une note spécifique et possédant une bistabilité entre sa solution d’équilibre (le silence) et sa solution périodique (la note). L’étude détermine, en fonction des conditions initiales et du taux de variation de la pression buccale, si un son est produit lors du transitoire d’attaque. Elle contribue également à mieux comprendre l'impact de la dynamique des paramètres de contrôle sur le comportement transitoire des instruments à anche. Une présentation complémentaire réalisée par les auteurs examine cet impact sur le comportement en régime établi de ces instruments
A Mechanized Formalization of an FRP Language with Effects
No full textInternational audienceFunctional Reactive Programming (FRP) is a functional programming paradigm designed for systems interacting with their environment. The Yampa library, a Haskell implementation, allows users to construct signal functions that synchronously process input streams to produce output streams. While this library facilitates concise and robust coding, managing I/O is cumbersome. To address this issue, the Wormholes library extends Yampa with constructs to bind I/O to resource names, accessible in an imperative style. Few FRP languages are formalized, and Wormholes added challenging features. This article presents a mechanized formalization of a slightly modified version of Wormholes, improving the result and correcting some issues