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252 results on '"mouvement brownien"'

1. Diffusion-weighted Imaging: New Paradigm in Diagnosis of Early Acute Pancreatitis.

Author

Arora, Manali, Lakhera, Devkant, Rawat, Kanica, Thakker, Vishal, Randhawa, Lovepreet Singh, Patel, Amisha, Agarwal, Rachit, and Azad, Rajiv Kumar

Subjects
*MAGNETIC resonance imaging, *DIFFUSION tensor imaging, *DIFFUSION magnetic resonance imaging, *REFERENCE values, *BROWNIAN motion
Abstract

Background: Diffusion-weighted imaging (DWI) has come up as a newer diagnostic modality for the diagnosis of early functional changes in various organs including the pancreas. DWI has shown the ability of early and accurate diagnosis of inflammatory pathologies, before the appearance of morphological changes on imaging. Objectives: The objectives of this study were to study the diagnostic accuracy of DWI in the diagnosis of early acute interstitial pancreatitis. Materials and Methods: The present retrospective observational study was conducted at the department of radiodiagnosis of a tertiary teaching hospital for 1 year. Fifty patients who underwent magnetic resonance imaging of the pancreas with clinical or laboratory diagnosis of early pancreatitis were included in the study. The diagnostic accuracy of DWI was analyzed on the basis of quantitative (apparent diffusion coefficient [ADC] values) evaluation in the diagnosis of early acute pancreatitis. Threshold values for ADC were derived for differentiation of inflamed versus normal pancreas. Sensitivity, specificity, positive predictive value (PPV), and negative predictive values (NPV) were obtained by drawing the receiver operating characteristic (ROC) curve. Results: The mean ADC values in the patient group (0.882 × 10−3 mm2/s ± 0.102) were significantly lower than the control group (1.178 × 10−3 mm2/s ± 0.232) with P < 0.001. The ROC curve deciphered a cutoff value of 0.937 × 10−3 mm2/s with a sensitivity of 84%, specificity of 86%, PPV of 85.71%, and NPV of 84.31% for diagnosis of acute pancreatitis using quantitative ADC values. Conclusion: DWI can thus be a succinct modality for early diagnosis of pancreatitis with excellent diagnostic accuracy and superlative advantage of lack of contrast and radiation in comparison to computed tomography scan. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Processus d’Ornstein-Uhlenbeck

Author

Chafaï, Djalil, Malrieu, Florent, Garnier, Josselin, Editor-in-chief, Perrier, Valérie, Editor-in-chief, Abgrall, Rémi, Series editor, Allaire, Grégoire, Series editor, BenaÏm, Michel, Series editor, Bergounioux, Maïtine, Series editor, Colin, Thierry, Series editor, Costa, Marie-Christine, Series editor, Debussche, Arnaud, Series editor, Gallagher, Isabelle, Series editor, Gaubert, Stéphane, Series editor, Gobet, Emmanuel, Series editor, Herbin, Raphaèle, Series editor, Hoffmann, Marc, Series editor, Le Bris, Claude, Series editor, Méléard, Sylvie, Series editor, Otto, Felix, Series editor, Robert, Philippe, Series editor, Rouchon, Pierre, Series editor, Salvy, Bruno, Series editor, Sartenaer, Annick, Series editor, Sonnendrücker, Eric, Series editor, Trouvé, Alain, Series editor, Villani, Cédric, Series editor, Zuazua, Enrique, Series editor, Chafai, Djalil, and Malrieu, Florent

Published
2016
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3. Modèles de diffusion cinétique

Author

Chafaï, Djalil, Malrieu, Florent, Garnier, Josselin, Editor-in-chief, Perrier, Valérie, Editor-in-chief, Abgrall, Rémi, Series editor, Allaire, Grégoire, Series editor, BenaÏm, Michel, Series editor, Bergounioux, Maïtine, Series editor, Colin, Thierry, Series editor, Costa, Marie-Christine, Series editor, Debussche, Arnaud, Series editor, Gallagher, Isabelle, Series editor, Gaubert, Stéphane, Series editor, Gobet, Emmanuel, Series editor, Herbin, Raphaèle, Series editor, Hoffmann, Marc, Series editor, Le Bris, Claude, Series editor, Méléard, Sylvie, Series editor, Otto, Felix, Series editor, Robert, Philippe, Series editor, Rouchon, Pierre, Series editor, Salvy, Bruno, Series editor, Sartenaer, Annick, Series editor, Sonnendrücker, Eric, Series editor, Trouvé, Alain, Series editor, Villani, Cédric, Series editor, Zuazua, Enrique, Series editor, Chafai, Djalil, and Malrieu, Florent

Published
2016
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4. Problème de Dirichlet

Author

Chafaï, Djalil, Malrieu, Florent, Garnier, Josselin, Editor-in-chief, Perrier, Valérie, Editor-in-chief, Abgrall, Rémi, Series editor, Allaire, Grégoire, Series editor, BenaÏm, Michel, Series editor, Bergounioux, Maïtine, Series editor, Colin, Thierry, Series editor, Costa, Marie-Christine, Series editor, Debussche, Arnaud, Series editor, Gallagher, Isabelle, Series editor, Gaubert, Stéphane, Series editor, Gobet, Emmanuel, Series editor, Herbin, Raphaèle, Series editor, Hoffmann, Marc, Series editor, Le Bris, Claude, Series editor, Méléard, Sylvie, Series editor, Otto, Felix, Series editor, Robert, Philippe, Series editor, Rouchon, Pierre, Series editor, Salvy, Bruno, Series editor, Sartenaer, Annick, Series editor, Sonnendrücker, Eric, Series editor, Trouvé, Alain, Series editor, Villani, Cédric, Series editor, Zuazua, Enrique, Series editor, Chafai, Djalil, and Malrieu, Florent

Published
2016
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5. TEXTES & DOCUMENTS: LOUIS BACHELIER’S 1938 MONOGRAPH ON THE CALCULUS OF SPECULATION: MATHEMATICAL FINANCE AND RANDOMNESS OF ASSET PRICES IN BACHELIER’S LATER WORK.

Author

BEN-EL-MECHAIEKH, HICHEM and DIMAND, ROBERT W.

Subjects
SPECULATION, FINANCE, ASSETS (Accounting), STOCHASTIC processes, MATHEMATICS
Abstract

Copyright of Revue d'Histoire des Mathématiques is the property of Societe Mathematique de France and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2018

6. The Langevin equation.

Author

Pomeau, Yves and Piasecki, Jarosław

Subjects
*LANGEVIN equations, *THERMODYNAMICS, *BROWNIAN motion, *VISCOSITY, *SCHRODINGER equation
Abstract

The existence of atoms has been long predicted by philosophers and scientists. The development of thermodynamics and of the statistical interpretation of its concepts at the end of the nineteenth century and in the early years of the twentieth century made it possible to bridge the gap of scales between the macroscopic world and the world of atoms. Einstein and Smoluchowski showed in 1905 and 1906 that the Brownian motion of particles of measurable size is a manifestation of the motion of atoms in fluids. Their derivation was completely different from each other. Langevin showed in 1908 how to put in a coherent framework the subtle effect of the randomness of the atomic world, responsible for the fluctuating force driving the motion of the Brownian particle and the viscosity of the “macroscopic” flow taking place around the same Brownian particle. Whereas viscous forces were already well understood at this time, the “Langevin” force appears there for the first time: it represents the fluctuating part of the interaction between the Brownian particle and the surrounding fluid. We discuss the derivation by Einstein and Smoluchowski as well as a previous paper by Sutherland on the diffusion coefficient of large spheres. Next we present Langevin's short note and explain the fundamental splitting into a random force and a macroscopic viscous force. This brings us to discuss various points, like the kind of constraints on Langevin-like equations. We insist in particular on the one arising from the time-reversal symmetry of the equilibrium fluctuations. Moreover, we discuss another constraint, raised first by Lorentz, which implies that, if the Brownian particle is not very heavy, the viscous force cannot be taken as the standard Stokes drag on an object moving at uniform speed. Lastly, we examine the so-called Langevin–Heisenberg and/or Langevin–Schrödinger equation used in quantum mechanics. [ABSTRACT FROM AUTHOR]

Published
2017
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23. De champs vers chemins, histoire d’un aller et retour

Author

Lupu, Titus and Lupu, Titus

Subjects
random walk, invariance conforme, [MATH.MATH-PR] Mathematics [math]/Probability [math.PR], conformal invariance, marche aléatoire, Gaussian free field GFF, SLE, Brownian motion, champ libre gaussien CLG, mouvement brownien
Abstract

The Gaussian free field (GFF) is one of the most fundamental objects of Statistical Physics and Quantum Field Theory. There is a strong connection between this GFF and the random walks (in discrete) and the Brownian motion (in continuum). These are the so called ”isomorphism theorems”, which originate from Euclidean Quantum Field Theory. This manuscript presents an overview of the results obtained by myself and my coauthors on this topic. An important aspect of my work was to relate in dimension 2 the isomorphism theorems to the theory of Schramm-Loewner Evolutions (SLE) and to describe the intrinsic geometry of the 2D continuum GFF in terms of clusters of Brownian trajectories. A method commonly used throughout this manuscript is that of metric graphs, which I introduced earlier during my PhD. Other aspects of the isomorphism theorems covered by this manuscript include their relation to the 2D Gaussian multiplicative chaos, their relation to the topological expansion, and the inversion of the isomorphism theorems and how it involves self-repelling processes., Le champ libre gaussien (CLG) est un des objets le plus fondamentaux de la Physique Statistique et de la Théorie Quantique des Champs. Il y a une forte relation entre ce CLG et les marches aléatoires (dans le discret) et le mouvement brownien (dans le continu). Ce sont les théorèmes dit ”d’isomorphisme”, qui proviennent de la Théorie Quantique des Champs Euclidienne. Ce manuscrit présente un panorama des résultats obtenus par moi-même et mes coauteurs sur ce sujet. Un aspect important de mon travail a été de relier en dimension 2 les théorèmes d’isomorphisme à la théorie des Évolutions de Schramm-Loewner (SLE) et de décrire la géométrie intrinsèque du CLG sur espace continu 2D en termes d’amas de trajectoires browniennes. Une méthode beaucoup utilisée dans ce manuscrit est celle des graphes métriques, que j’ai introduite pendant mon Doctorat. Les autres aspects des théorèmes d’isomorphisme traités dans ce manuscrit incluent leurs relations avec le chaos multiplicatif gaussien en dimension 2, leurs relations avec l’expansion topologique, ainsi que l’inversion des théorèmes d’isomorphisme et comment cela fait intervenir des processus auto-répulsifs.

Published
2022

43. Mouvement brownian en confinement

Author

Lavaud, Maxime, Laboratoire Ondes et Matière d'Aquitaine (LOMA), Université de Bordeaux (UB)-Centre National de la Recherche Scientifique (CNRS), Université de Bordeaux, Thomas Salez, and STAR, ABES

Subjects
[PHYS.PHYS]Physics [physics]/Physics [physics], Interfaces, Colloïdes, [PHYS.PHYS] Physics [physics]/Physics [physics], Colloids, Brownian motion, Mouvement brownien, Statistical inference, Confinement, Inférence statistique
Abstract

In this manuscript, I present the work done during my PhD on confined Brownian motion. Brownian motion is the erratic movement of microscopic particles when immersed into a fluid. Thanks to Einstein and his successors, it is generally possible to describe Brownian motion using simple equations. However, in the last two decades a scientific revolution has taken place with the advent of miniaturization and in particular microfluidics, enabling the creation of complex networks of pipes at the micrometer scale. Microfluidics makes it possible to sort out particles, such as drops, cells or bubbles, but also to distribute drugs in cells and observe their effect on thousands of them. Regarding Brownian motion, it has been observed that once confined near a wall, a particle moves much slower due to non-slip boundary conditions at the wall. The mobility is thus modified by confinement-induced effects.My thesis work consists in experimentally measuring, analyzing and modeling the movement of micrometric colloids diffusing near a wall. To track the motion of confined Brownian microparticles, I use Lorenz-Mie holography. The Lorenz-Mie framework allows me to record the thermally-induced three-dimensional trajectories of individual microparticles, within salty aqueous solutions, in the vicinity of a rigid wall, and in the presence of surface charge with a nanometric resolution. From the recorded trajectory, I construct the time-dependent position and displacement probability density functions, and analyze the non-Gaussian character of the latter which is a direct signature of the hindered mobility near the wall. Based on these distributions, I implement a novel, robust and self-calibrated multifitting method, allowing thermal-noise-limited inference of diffusion coefficients spatially-resolved at the nanoscale, equilibrium potentials, and forces at the femtonewton resolution. Moreover, I use this novel tool to deduce non-conservative forces and study long-time higher-order statistical properties. Our objective for the future is to use this novel tool to have a new approach in various problems relevant to nanophysics and microbiology., Dans ce manuscrit, je présente le travail effectué pendant mon doctorat sur le mouvement brownien confiné. Le mouvement brownien est le mouvement erratique de particules microscopiques lorsqu'elles sont immergées dans un fluide. Grâce à Einstein et ses successeurs, il est généralement possible de décrire le mouvement brownien à l'aide d'équations simples. Cependant, au cours des deux dernières décennies, une révolution scientifique a eu lieu avec l'avènement de la miniaturisation et en particulier de la microfluidique, permettant la création de réseaux complexes de tuyaux à l'échelle micrométrique. La microfluidique permet de trier des particules, comme des gouttes, des cellules ou des bulles, mais aussi de distribuer des médicaments dans des cellules et d'observer leur effet sur des milliers d'entre elles. En ce qui concerne le mouvement brownien, il a été observé qu'une fois confinée près d'une paroi, une particule se déplace beaucoup plus lentement en raison des conditions de non-glissement à la paroi. La mobilité est donc modifiée par les effets induits par le confinement.Mon travail de thèse consiste à mesurer, analyser et modéliser expérimentalement le mouvement de colloïdes micrométriques diffusant près d'une paroi. Pour suivre le mouvement de microparticules browniennes confinées, j'utilise l'holographie de Lorenz-Mie. Le cadre de Lorenz-Mie me permet d'enregistrer les trajectoires tridimensionnelles thermiquement induites de microparticules individuelles, dans des solutions aqueuses salées, à proximité d'une paroi rigide, et en présence d'une charge de surface avec une résolution nanométrique. A partir de la trajectoire enregistrée, je construis les fonctions de densité de probabilité de position et de déplacement en fonction du temps, et j'analyse le caractère non-gaussien de ces dernières qui est une signature directe de la mobilité modifiée près de la paroi. Sur la base de ces distributions, je mets en œuvre une nouvelle méthode d'ajustement multiple, robuste et auto-calibrée, permettant l'inférence limitée par le bruit thermique des coefficients de diffusion résolus spatialement à l'échelle nanométrique, des potentiels d'équilibre et des forces résolus au femtonewton. De plus, j'utilise ce nouvel outil pour déduire les forces non-conservatives et étudier les propriétés statistiques d'ordre supérieur à long terme. Notre objectif pour l'avenir est d'utiliser ce nouvel outil pour avoir une nouvelle approche dans divers problèmes liés à la nanophysique et à la microbiologie.

Published
2021

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