Pseudo-rotations of the closed annulus : variation on a theorem of J. Kwapisz

Consider a homeomorphism h of the closed annulus S^1*[0,1], isotopic to the identity, such that the rotation set of h is reduced to a single irrational number alpha (we say that h is an irrational pseudo-rotation). For every positive integer n, we prove that there exists a simple arc gamma joining one of the boundary component of the annulus to the other one, such that gamma is disjoint from its n first iterates under h. As a corollary, we obtain that the rigid rotation of angle alpha can be approximated by homeomorphisms conjugate to h. The first result stated above is an analog of a theorem of J. Kwapisz dealing with diffeomorphisms of the two-torus; we give some new, purely two-dimensional, proofs, that work both for the annulus and for the torus case

Flowability of plane homeomorphisms

We describe necessary and sufficient conditions for an orientation preserving fixed point free planar homeomorphism that preserves the standard Reeb foliation to embed in a planar flow that leaves the foliation invariant.Comment: 20 pages, 3 figure

The importance of layout and configuration data for flexibility during commissionning and operation of the LHC machine protection systems

Due to the large stored energies in both magnets and particle beams, the Large Hadron Collider (LHC) requires a large inventory of machine protection systems, as e.g. powering interlock systems, based on a series of distributed industrial controllers for the protection of the more than 10'000 normal and superconducting magnets. Such systems are required to be at the same time fast, reliable and secure but also flexible and configurable to allow for automated commissioning, remote monitoring and optimization during later operation. Based on the generic hardware architecture of the LHC machine protection systems presented at EPAC 2002 [2] and ICALEPS 2003, the use of configuration data for protection systems in view of the required reliability and safety is discussed. To achieve the very high level of reliability, it is required to use a coherent description of the layout of the accelerator components and of the associated machine protection architecture and their logical interconnections. Mechanisms to guarantee coherency of data and repositories and secure configuration of safety critical systems are presented. This paper focuses on the first system being commissioned, the complex magnet powering system, to become fully operational before first injection of beam into the LHC

Structure des homeomorphismes de Brouwer

For every Brouwer (ie planar, fixed point free, orientation preserving) homeomorphism h there exists a covering of the plane by translation domains, invariant simply-connected open subsets on which h is conjugate to an affine translation. We introduce a distance d_h on the plane that counts the minimal number of translation domains connecting a pair of points. This allows us to describe a combinatorial conjugacy invariant, and to show the existence of a finite family of generalised Reeb components separating any two points x,y such that d_h(x,y)>1. R\'esum\'e Tout homeomorphisme de Brouwer s'obtient en recollant des domaines de translation (ouverts simplement connexes, invariants, en restriction auxquels la dynamique est conjuguee a une translation). On introduit une distance d_h sur le plan qui compte le nombre minimal de domaines de translation dont la reunion connecte deux points. Ceci nous permet de decrire un invariant combinatoire de conjugaison, qui decrit tres grossierement la maniere dont les domaines de translation se recollent. On montre egalement l'existence de structures dynamiques qui generalisent la presence de composantes de Reeb dans les feuilletages non triviaux du plan.Comment: Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol9/paper39.abs.htm

L-shaped fiber-chip grating couplers with high- directionality and low reflectivity fabricated with deep-UV lithography

International audienc

Low-loss grating-coupled optical interfaces for large-volume fabrication with deep-ultraviolet optical lithography

International audienc

Current Sheets, Magnetic Islands, and Associated Particle Acceleration in the Solar Wind as Observed by Ulysses near the Ecliptic Plane

Recent studies of particle acceleration in the heliosphere have revealed a new mechanism that can locally energize particles up to several MeV nucleon–1. Stream–stream interactions, as well as the heliospheric current sheet (CS)—stream interactions, lead to formation of large magnetic cavities, bordered by strong CSs, which in turn produce secondary CSs and dynamical small-scale magnetic islands (SMIs) of ~0.01 au or less owing to magnetic reconnection. It has been shown that particle acceleration or reacceleration occurs via stochastic magnetic reconnection in dynamical SMIs confined inside magnetic cavities observed at 1 au. The study links the occurrence of CSs and SMIs with characteristics of intermittent turbulence and observations of energetic particles of keV–MeV nucleon–1 energies at ~5.3 au. We analyze selected samples of different plasmas observed by Ulysses during a widely discussed event, which was characterized by a series of high-speed streams of various origins that interacted beyond Earth's orbit in 2005 January. The interactions formed complex conglomerates of merged interplanetary coronal mass ejections, stream/corotating interaction regions, and magnetic cavities. We study properties of turbulence and associated structures of various scales. We confirm the importance of intermittent turbulence and magnetic reconnection in modulating solar energetic particle flux and even local particle acceleration. Coherent structures, including CSs and SMIs, play a significant role in the development of secondary stochastic particle acceleration, which changes the observed energetic particle flux time–intensity profiles and increases the final energy level to which energetic particles can be accelerated in the solar win

A Federated Database for Obesity Research:An IMI-SOPHIA Study

Obesity is considered by many as a lifestyle choice rather than a chronic progressive disease. The Innovative Medicines Initiative (IMI) SOPHIA (Stratification of Obesity Phenotypes to Optimize Future Obesity Therapy) project is part of a momentum shift aiming to provide better tools for the stratification of people with obesity according to disease risk and treatment response. One of the challenges to achieving these goals is that many clinical cohorts are siloed, limiting the potential of combined data for biomarker discovery. In SOPHIA, we have addressed this challenge by setting up a federated database building on open-source DataSHIELD technology. The database currently federates 16 cohorts that are accessible via a central gateway. The database is multi-modal, including research studies, clinical trials, and routine health data, and is accessed using the R statistical programming environment where statistical and machine learning analyses can be performed at a distance without any disclosure of patient-level data. We demonstrate the use of the database by providing a proof-of-concept analysis, performing a federated linear model of BMI and systolic blood pressure, pooling all data from 16 studies virtually without any analyst seeing individual patient-level data. This analysis provided similar point estimates compared to a meta-analysis of the 16 individual studies. Our approach provides a benchmark for reproducible, safe federated analyses across multiple study types provided by multiple stakeholders.</p