Propriété macroscopique

Une propriété macroscopique est une caractéristique d'un corps qui peut être observée en l'observant globalement. C'est une propriété à grande échelle, par opposition aux « propriétés microscopiques » qui caractérisent les plus petits constituants du corps. C'est le cas d'une particule, tant qu'on peut la voir. En biologie c'est en général à notre échelle, mais cette traduction ne convient pas vraiment à la chimie ou à la physique moléculaire. Dans ces disciplines, les propriétés macroscopiques de la matière sont des propriétés qui caractérisent le comportement collectif d'un ensemble de sous-structures assemblées en grand nombre. Et à l'inverse, on parle de propriétés microscopiques lorsque l'on considère les propriétés individuelles de chacune de ces sous-structures. Par exemple, pour un matériau cristallin, une quantité telle que la conductivité électrique est une propriété macroscopique. Celle-ci est dépendante de propriétés microscopiques, telles que la structure cristalline

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Coevolution of Synchronization and Cooperation in Costly Networked Interactions

Alberto Antonioni, Alessio Vincenzo Cardillo

Despite the large number of studies on synchronization, the hypothesis that interactions bear a cost for involved individuals has seldom been considered. The introduction of costly interactions leads, instead, to the formulation of a dichotomous scenario in which an individual may decide to cooperate and pay the cost in order to get synchronized with the rest of the population. Alternatively, the same individual can decide to free ride, without incurring any cost, waiting for others to get synchronized to his or her state. Thus, the emergence of synchronization may be seen as the byproduct of an evolutionary game in which individuals decide their behavior according to the benefit-to-cost ratio they accrued in the past. We study the onset of cooperation and synchronization in networked populations of Kuramoto oscillators and report how topology is essential in order for cooperation to thrive. We also display how different classes of topology foster synchronization differently both at microscopic and macroscopic levels.

American Physical Society2017

Chargement

The effect of high relative humidity on a network of water-sensitive particles (couscous) as revealed by in situ X-ray tomography

Edward Ando, Gioacchino Viggiani

Water significantly influences the mechanical behaviour of all granular materials but none as much as hygroscopic amorphous particles. With sufficiently high water content, particles can swell, agglomerate and their mechanical properties can be reduced, having direct effects on the macroscopic response of the material. In the food and pharmaceutical industry this can cause loss of product functionality. Despite their relevance, very little is known about the microscopic processes that induce these phenomena. Previous studies focused on single particle behaviour, the strength of agglomerated particles and the material flowability, leaving unexplored the link connecting the particle behaviour and the bulk response. This experimental study aims to investigate this aspect with quantitative measurements at both particle and macroscopic scales. A sample of fine couscous is exposed to a high relative humidity (RH) air flow, while being subjected to oedometric conditions, in order to reproduce the storage-silo conditions. In the meantime, X-ray tomographies are acquired continuously and the resulting images are analysed. The designed spatial resolution allows each particle of the sample to be identified and tracked, allowing volumetric evolution to be compared to the properties of the whole sample. The analysis reveals a dilation-compaction macroscopic behaviour, a result of the competition between the particle swelling and the higher deformability as the water content increases. The number, orientations and inter-particle contacts are computed. Their area is related to the applied boundary conditions, and is found to be consistent with the particle swelling and dependent on the applied stress direction.

ROYAL SOC CHEMISTRY2022

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Inhomogeneity of charge-density-wave order and quenched disorder in a high-T-c superconductor

Davide Innocenti, Janusz Andrzej Karpinski

It has recently been established that the high-transition-temperature (high-T-c) superconducting state coexists with short-range charge-density-wave order(1-11) and quenched disorder(12,13) arising from dopants and strain(14-17). This complex, multiscale phase separation(18-21) invites the development of theories of high-temperature superconductivity that include complexity(22-25). The nature of the spatial interplay between charge and dopant order that provides a basis for nanoscale phase separation remains a key open question, because experiments have yet to probe the unknown spatial distribution at both the nanoscale and mesoscale (between atomic and macroscopic scale). Here we report micro X-ray diffraction imaging of the spatial distribution of both short-range charge-density-wave 'puddles' (domains with only a few wavelengths) and quenched disorder in HgBa2CuO4+y, the single-layer cuprate with the highest T-c, 95 kelvin (refs 26-28). We found that the charge-density-wave puddles, like the steam bubbles in boiling water, have a fat-tailed size distribution that is typical of self-organization near a critical point(19). However, the quenched disorder, which arises from oxygen interstitials, has a distribution that is contrary to the usually assumed random, uncorrelated distribution(12,13). The interstitial-oxygen-rich domains are spatially anticorrelated with the charge-density-wave domains, because higher doping does not favour the stripy charge-density-wave puddles, leading to a complex emergent geometry of the spatial landscape for superconductivity.

Nature Publishing Group2015

Chargement

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L'électron, un des composants de l'atome avec les neutrons et les protons, est une particule élémentaire qui possède une charge élémentaire de signe négatif. Il est fondamental en chimie, car il part

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vignette|Tunnel du LHC avec le tube contenant les électroaimants supraconducteurs. Le Grand collisionneur de hadrons (en anglais : Large Hadron Collider — LHC), est un accélérateur de particules mis

CH-242(b): Statistical thermodynamics

This course enables the acquisition of basic concepts in statistical thermodynamics including the Boltzmann distribution law, partition functions, ensembles, calculations of thermodynamic properties, Bose-Einstein and Fermi-Dirac statistics, metals, and applications.

ME-271: Fluid flow

Dans ce cours introductif à la physique des fluides, l'étudiant commence par apprendre, au moyen de bilans de masse et de contraintes, à décrire et à prédire les écoulements types. Ces méthodes sont appliquées à des écoulements complexes, tels que les écoulements atmosphériques et tourbillonnaires.

ChE-204: Introduction to transport phenomena

This course aims at understanding the basic equations behind macroscopic and microscopic transport phenomena (mass, heat and momentum).