Search results for "dynamics"
showing 10 items of 9782 documents
High-order harmonic generation via bound-bound transitions in an elliptically polarized laser field
2016
We use a simplified five-level system to investigate the high-order harmonic generation (HHG) spectrum emitted by an atom driven by a linearly or elliptically polarized laser field. For this model, the Schrödinger equation is exactly analytically reduced to the system of ordinary differential equations, which is solved numerically. Studying the intensity and polarization of the emitted radiation, we find that under high laser ellipticity the harmonic emission is suppressed. However, the harmonic intensity typically depends nonmonotonously on the laser ellipticity. Such anomalous behavior is very pronounced for the resonant harmonic. We offer an explanation of this behavior based on the incr…
Beating Darwin-Bragg losses in lab-based ultrafast x-ray experiments
2017
The use of low temperature thermal detectors for avoiding Darwin-Bragg losses in lab-based ultrafast experiments has begun. An outline of the background of this new development is offered, showing the relevant history and initiative taken by this work. (C) 2017 Author(s). Funding Agencies|Knut and Alice Wallenberg Foundation; ERC [226136]; Finnish Funding Agency for Technology and Innovation TEKES; Academy of Finland [260880]; NIST Innovations in Measurement Science program; DOE Office of Basic Energy Sciences
Quantum localization and bound state formation in Bose-Einstein condensates
2010
We discuss the possibility of exponential quantum localization in systems of ultracold bosonic atoms with repulsive interactions in open optical lattices without disorder. We show that exponential localization occurs in the maximally excited state of the lowest energy band. We establish the conditions under which the presence of the upper energy bands can be neglected, determine the successive stages and the quantum phase boundaries at which localization occurs, and discuss schemes to detect it experimentally by visibility measurements. The discussed mechanism is a particular type of quantum localization that is intuitively understood in terms of the interplay between nonlinearity and a bou…
First-principles nonequilibrium Green's-function approach to transient photoabsorption: Application to atoms
2015
We put forward a first-principle NonEquilibrium Green's Function (NEGF) approach to calculate the transient photoabsorption spectrum of optically thin samples. The method can deal with pump fields of arbitrary strength, frequency and duration as well as for overlapping and nonoverlapping pump and probe pulses. The electron-electron repulsion is accounted for by the correlation self-energy, and the resulting numerical scheme deals with matrices that scale quadratically with the system size. Two recent experiments, the first on helium and the second on krypton, are addressed. For the first experiment we explain the bending of the Autler-Townes absorption peaks with increasing the pump-probe d…
Can Ventricular Resynchronization Reduce Atrial Fibrillation Recurrences?
2003
In recent years a new pacing therapy has been proposed for patients affected by heart failure (HF) in order to reduce inter- [1,2], intra- [3,4], and atrioventricular [5] (AV) dyssynchrony. Cardiac resynchronization therapy (CRT) has the goal of correcting these hemodynamic disorders, thus improving left ventricular (LV) performance. The benefits of CRT have been evaluated in a series of clinical trials [6-10].
A Mechano-Chemical Coupling for Hydrogen Diffusion in Metals Based on a Thermodynamic Approach
2014
Hydrogen diffusion in metals is still an ongoing topic of research due to its technical relevance (hydrogen embrittlement, hydrogen storage...). In the last decades, significant progress in understanding the time evolution of the hydrogen concentration in solids was completed. This paper presents a modeling of hydrogen diffusion with a general and thermodynamically based diffusion concept coupled with mechanical and chemical aspects. This model was previously used to simulate the oxidation of a metal [1][2]. This concept has been upgraded to offer a thoroughly macroscopic behavior law used to simulate hydrogen diffusion in metal parts under mechanical loadings. The thermodynamic approach of…
Neural Network Approach for Characterizing Structural Transformations by X-Ray Absorption Fine Structure Spectroscopy
2018
AIF acknowledge support by the US Department of Energy, Office of Basic Energy Sciences under Grant No. DE-FG02 03ER15476. AIF acknowledges support by the Laboratory Directed Research and Development Program through LDRD 18-047 of Brookhaven National Laboratory under U.S. Department of Energy Contract No. DE-SC0012704 for initiating his research in machine learning methods. The help of the beamline staff at ELETTRA (project 20160412) synchrotron radiation facility is acknowledged. RMC-EXAFS and MD-EXAFS simulations were performed on the LASC cluster-type computer at Institute of Solid State Physics of the University of Latvia.
Detection of steering direction using EEG recordings based on sample entropy and time-frequency analysis.
2016
Monitoring driver's intentions beforehand is an ambitious aim, which will bring a huge impact on the society by preventing traffic accidents. Hence, in this preliminary study we recorded high resolution electroencephalography (EEG) from 5 subjects while driving a car under real conditions along with an accelerometer which detects the onset of steering. Two sensor-level analyses, sample entropy and time-frequency analysis, have been implemented to observe the dynamics before the onset of steering. Thus, in order to classify the steering direction we applied a machine learning algorithm consisting of: dimensionality reduction and classification using principal-component-analysis (PCA) and sup…
Safety, tolerability, pharmacokinetics, pharmacodynamics, and exploratory efficacy of the novel enzyme replacement therapy avalglucosidase alfa (neoG…
2019
This multicenter/multinational, open-label, ascending-dose study (NCT01898364) evaluated safety, tolerability, pharmacokinetics, pharmacodynamics, and exploratory efficacy of repeat-dose avalglucosidase alfa (neoGAA), a second-generation, recombinant acid α-glucosidase replacement therapy, in late-onset Pompe disease (LOPD). Patients ≥18 years, alglucosidase alfa naïve (Naïve) or previously receiving alglucosidase alfa for ≥9 months (Switch), with baseline FVC ≥50% predicted and independently ambulatory, received every-other-week avalglucosidase alfa 5, 10, or 20 mg/kg over 24 weeks. 9/10 Naïve and 12/14 Switch patients completed the study. Avalglucosidase alfa was well-tolerated; no deaths…
Flots de Smale en dimension 3: présentations finies de voisinages invariants d'ensembles selles
2002
Abstract Given a vector field X on a compact 3-manifold, and a hyperbolic saddle-like set K of that vector field, we consider all the filtering neighbourhood of K: by such, we mean any submanifold which boundary is tranverse to X, the maximal invariant of which is equal to K and which intersection with every orbit of X is connected. Up to topological equivalence, there is only a finite number of such neighbourhoods. We give a finite combinatorial presentation of the global dynamics on any such neighbourhood. A key step is the construction of a unique model of the germ of X along K; this model is, roughly speaking, the simplest three-dimensional manifold and the simplest Smale flow exhibitin…