Formulation of an equation of diffusion for heterogeneous rods

International audienceA new formulation for predicting the energy flow in heterogeneous rods id developed on the basis of an equation of diffusion. It succeeds in surpassing traditional studies for homogeneous ones, for which vibratory responses are often easily known by simple displacement formulation. However, one stays difficult to describe the mechanical behavior for heterogeneous structures: in this case, the energy flow is governed by structural damping, as for homogeneous medium, but by discontinuities too. The study presented here proposes to identify for heterogeneous structures a factor of diffusion involving proportionality between transmitted power and energy gradient. An equation of diffusion is then formulated considering an energetic balance. The formulation is semi-local, that is spatial average is locally made to take into account several heterogeneities in studied element. An analytical formulation is first developed for rod with area discontinuities. The proposed theoretical factor of diffusion is in good agreements with the numerical predictions

Takotsubo Cardiomyopathy in a Squash Player

Takotsubo cardiomyopathy is usually described following acute emotional stress. We report here the case of a 48-year-old woman admitted for acute coronary syndrome after an intensive squash match. Diagnosis of Takotsubo cardiomyopathy due to acute physical stress was suspected in presence of normal coronary arteries and transitory left ventricular dysfunction with typical apical ballooning. Cardiac magnetic resonance imaging confirmed regional wall-motion abnormalities and was helpful in excluding myocardial infarction diagnosis. During squash the body is subject to sudden and vigorous demands inducing a prolonged and severe workload on the myocardium

A remarkably unsymmetric hexairon core embraced by two high-symmetry tripodal oligo-α-pyridylamido ligands

Oligo-α-pyridylamides offer an appealing route to polyiron complexes with short Fe-Fe separations and large room temperature magnetic moments. A derivative of tris(2‐aminoethyl)amine (H6tren) containing three oligo-α-pyridylamine branches and thirteen nitrogen donors (H6L) reacts with [Fe2(Mes)4] to yield an organic nanocage built up by two tripodal ligands with interdigitated branches (HMes = mesitylene). The nanocage has crystallographic D3 symmetry but hosts a remarkably unsymmetric hexairon-oxo core, with a central Fe5(μ5-O) square pyramid, two oxygen donors bridging basal sites, and an additional Fe center residing in one of the two tren-like pockets. Bond Valence Sum (BVS) analysis, Density Functional Theory (DFT) calculations, and electrochemical data were then used to establish the protonation state of oxygen atoms and the formal oxidation states of the metals. To this purpose, a specialized set of BVS parameters was devised for Fe2+-N3- bonds with nitrogen donors of oligo-α-pyridylamides. This allowed us to formulate the compound as [Fe6O2(OH)(H3L)L], with nominally four FeII and two FeIII ions. Mössbauer spectra indicate that the compound contains two unique FeII sites, identified as a pair of closely spaced hydroxo-bridged metal ions in the central Fe5(μ5-O) pyramid, and a substantially valence-delocalized FeII2FeIII2 unit. Broken-symmetry DFT calculations predict strong ferromagnetic coupling between the two iron(II) ions, leading to a local S = 4 state that persists to room temperature and explaining the large magnetic moment measured at 300 K. The compound behaves as a single-molecule magnet, with magnetization dynamics detectable in zero static field and dominated by an Orbach-like mechanism with Ueff/kB = 49(2) K and τ0 = 4(2)·10−10 s

A Combine On-Line Acoustic Flowmeter and Fluorocarbon Coolant Mixture Analyzer for The ATLAS Silicon Tracker

An upgrade to the ATLAS silicon tracker cooling control system may require a change from C3F8 (octafluoro-propane) to a blend containing 10-30% of C2F6 (hexafluoro-ethane) to reduce the evaporation temperature and better protect the silicon from cumulative radiation damage with increasing LHC luminosity. Central to this upgrade is a new acoustic instrument for the real-time measurement of the C3F8/C2F6 mixture ratio and flow. The instrument and its Supervisory, Control and Data Acquisition (SCADA) software are described in this paper. The instrument has demonstrated a resolution of 3.10-3 for C3F8/C2F6 mixtures with ~20%C2F6, and flow resolution of 2% of full scale for mass flows up to 30gs-1. In mixtures of widely-differing molecular weight (mw), higher mixture precision is possible: a sensitivity of < 5.10-4 to leaks of C3F8 into the ATLAS pixel detector nitrogen envelope (mw difference 160) has been seen. The instrument has many potential applications, including the analysis of mixtures of hydrocarbons, vapours for semi-conductor manufacture and anaesthesia

Development of a custom on-line ultrasonic vapour analyzer/flowmeter for the ATLAS inner detector, with application to gaseous tracking and Cherenkov detectors

Precision sound velocity measurements can simultaneously determine binary gas composition and flow. We have developed an analyzer with custom electronics, currently in use in the ATLAS inner detector, with numerous potential applications. The instrument has demonstrated ~0.3% mixture precision for C3F8/C2F6 mixtures and < 10-4 resolution for N2/C3F8 mixtures. Moderate and high flow versions of the instrument have demonstrated flow resolutions of +/- 2% F.S. for flows up to 250 l.min-1, and +/- 1.9% F.S. for linear flow velocities up to 15 ms-1; the latter flow approaching that expected in the vapour return of the thermosiphon fluorocarbon coolant recirculator being built for the ATLAS silicon tracker.Comment: Paper submitted to TWEPP2012; Topical Workshop on Electronics for Particle Physics, Oxford, UK, September 17-21, 2012. KEYWORDS: Sonar; Saturated fluorocarbons; Flowmetry; Sound velocity, Gas mixture analysis. 8 pages, 7 figure

Memory Self-Efficacy in its Social Cognitive Context

This chapter takes a primarily cognitive construct - memory self-efficacy (MSE) - and returns it to its roots - social cognition (Bandura, 1986). This is a natural and obvious move. MSE has evolved since the mid-1980s (Berry, West, & Powlishta, 1986; Hertzog, Dixon, Schulenberg, & Hultsch, 1987) to its present identity and status in the cognitive aging and adult developmental research literature. If it is to avoid becoming a hypothesis in search of data (Light, 1991) or worse, an epiphenomenon to more robust explanations of cognitive aging (e.g., speed) (Salthouse, 1993), its potential and limits must be scrutinized and subjected to rigorous new research agendas. Arguably, MSE has arrived at its present destination via metamemory (Dixon, Hertzog, & Hultsch, 1986; Hertzog, Dixon, & Hultsch, 1990a; Hertzog et al., 1987; Hultsch, Hertzog, Dixon, & Davidson, 1988), thereby acquiring a more cognitive emphasis than its clinical and social underpinnings suggest. This chapter presents MSE research from my lab that has been conducted from the orienting framework of self-efficacy theory and methodology (Bandura, 1977, 1986, 1997; Bandura, Adams, Hardy, & Howells, 1980; Bandura, Reese, & Adams, 1982). The value of this framework lies in its rich theoretical foundation, its unique measurement approach, and its ties to social cognition. The goal of the chapter is to evaluate the present status of MSE research and to suggest new research directions

Implementation of ultrasonic sensing for high resolution measurement of binary gas mixture fractions

We describe an ultrasonic instrument for continuous real-time analysis of the fractional mixture of a binary gas system. The instrument is particularly well suited to measurement of leaks of a high molecular weight gas into a system that is nominally composed of a single gas. Sensitivity &#60; 5 × 10−5 is demonstrated to leaks of octaflouropropane (C3F8) coolant into nitrogen during a long duration (18 month) continuous study. The sensitivity of the described measurement system is shown to depend on the difference in molecular masses of the two gases in the mixture. The impact of temperature and pressure variances on the accuracy of the measurement is analysed. Practical considerations for the implementation and deployment of long term, in situ ultrasonic leak detection systems are also described. Although development of the described systems was motivated by the requirements of an evaporative fluorocarbon cooling system, the instrument is applicable to the detection of leaks of many other gases and to processes requiring continuous knowledge of particular binary gas mixture fractions

Simulation of Astrocytic Calcium Dynamics in Lattice Light Sheet Microscopy Images

International audienceAstrocytes regulate neuronal information processing through a variety of spatio-temporal calcium signals. Advances in calcium imaging started to reveal astrocytic activities, but the complexity of the recorded data strongly call for computational analysis tools. Their development is hindered by the lack of reliable annotations that are essential for their evaluation and for the design of learning-based methods. To overcome the labeling problem, we present a framework to simulate realistic astrocytic calcium signals in 3D+time lattice light sheet microscopy (LLSM) images by closely modeling calcium kinetics in real astrocytes

Emerging topics in FXTAS

This paper summarizes key emerging issues in fragile X-associated tremor/ataxia syndrome (FXTAS) as presented at the First International Conference on the FMR1 Premutation: Basic Mechanisms & Clinical Involvement in 2013