Pattern formation by kicked solitons in the two-dimensionnal Ginzburg-Landau medium with a transverse grating

We consider the kick-induced mobility of two-dimensional (2D) fundamental dissipative solitons in models of lasing media based on the 2D complex Ginzburg-Landau (CGL) equation including a spatially periodic potential (transverse grating). The depinning threshold is identified by means of systematic simulations, and described by means of an analytical approximation, depending on the orientation of the kick. Various pattern-formation scenarios are found above the threshold. Most typically, the soliton, hopping between potential cells, leaves arrayed patterns of different sizes in its wake. In the laser cavity, this effect may be used as a mechanism for selective pattern formation controlled by the tilt of the seed beam. Freely moving solitons feature two distinct values of the established velocity. Elastic and inelastic collisions between free solitons and pinned arrayed patterns are studied too.Comment: 15 pages, 20 figures (with 41 sub-figures

Building patterns by traveling vortices and dipoles in periodic dissipative media

We analyze pattern-formation scenarios in the two-dimensional (2D) complex Ginzburg-Landau (CGL) equation with the cubic-quintic (CQ) nonlinearity and a cellular potential. The equation models laser cavities with built-in gratings, which are used to stabilize 2D patterns. The pattern-building process is initiated by kicking a localized compound mode, in the form of a dipole, quadrupole, or vortex which is composed of four local peaks. The hopping motion of the kicked mode through the cellular structure leads to the generation of various extended patterns pinned by the structure. In the ring-shaped system, the persisting freely moving dipole hits the stationary pattern from the opposite side, giving rise to several dynamical regimes, with the pinned multi-soliton chain playing the role of the Newton's cradle (NC)

Spatio-temporal coherent control of thermal excitations in solids

X-ray reflectivity (XRR) measurements of femtosecond laser-induced transient gratings are applied to demonstrate the spatio-temporal coherent control of thermally induced surface deformations on ultrafast timescales. Using gracing incidence X-ray diffraction we unambiguously measure the amplitude of transient surface deformations with sub-\AA{} resolution. Understanding the dynamics of femtosecond TG excitations in terms of superposition of acoustic and thermal gratings makes it possible to develop new ways of coherent control in X-ray diffraction experiments. Being the dominant source of TG signal, the long-living thermal grating with spatial period $\Lambda$ can be canceled by a second, time-delayed TG excitation shifted by $\Lambda/2$. The ultimate speed limits of such an ultrafast X-ray shutter are inferred from the detailed analysis of thermal and acoustic dynamics in TG experiments

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

A study of light dynamics and measurements of the nonlinear optical characteristics of carbon disulphide

Nous présentons une étude de la dynamique de la lumière et des mesures des caractéristiques non-linéaires optiques dans le disulfure de carbone.Dans la première partie, nous calculons dans le cadre d’un modèle classique des expressions des susceptibilités non-linéaires jusqu’au cinquième ordre, en tenant compte des corrections de champ local. Nous formulons différentes hypothèses que nous confirmons ou infirmons par la mesure des indices d’absorption et de réfraction non-linéaires. Celles-ci sont obtenues en combinant deux méthodes de caractérisation des non-linéarités au sein d’un système 4fd’imagerie. L’analyse des données expérimentales utilise une méthode nouvellement développée, qui consiste à inverser numériquement, par la méthode de Newton, les solutions analytiques des équations différentielles qui décrivent l’évolution du faisceau.Dans la deuxième partie, nous observons la filamentation d’un faisceau laser à la longueur d’onde de 532 nm et en régime picoseconde. Puis nous procédons à la mesure de l’indice de réfraction non-linéaire effectif du troisième ordre n2,eff en fonction de l’intensité incidente. Par un ajustement de la courbe de saturation de l’effet Kerr,nous développons un nouveau modèle. La résolution numérique de celui-ci reproduit la filamentation observée.La dernière partie est consacrée à l’étude de la dynamique des solitons dissipatifs au sein de milieux à gains et pertes non-linéaires. La résolution numérique de l’équation complexe de Ginzburg-Landau cubique-quintique est réalisée suivant différentes configurations :soliton fondamental, dipôle, quadrupôle,vortex carré et rhombique.We present a study of light dynamics and measurements of the nonlinear optical characteristics of carbon disulphide. In the first part, we calculate using the classical model, the nonlinear susceptibilities up to the fifth order taking into account local field corrections. We express different assumptions that we confirm or refute by measuring the nonlinear absorption coefficient and the nonlinear refractive index. The measurements are performed by means of two nonlinear characterization methods combined with an imaging 4f system. We analyse the experimental data using a newly developed method which numerically inverts the analytical solutions of the differential equations which describe the evolution of the beam, using Newton’s method. In the second part, we observe light filamentation at wavelength 532 nm, in the picoseconds regime. Then we measure the effective third order nonlinear refractive index n2,eff versus the incident intensity. By fitting the curve of the Kerr effect saturation, we develop a new model. Numerically solving this model, allows us to reproducethe experimentally observed filamentation. The last part is dedicated to the study of dissipative solitons dynamics. The complex Ginzburg-Landau equation with cubic-quintic nonlineraties is numerically solved in various configurations : soliton fundamental dipole, quadrupole, vortex and square rhombic

Dynamique spatiale de la lumière et saturation de l’effet Kerr

We present a study of light dynamics and measurements of the nonlinear optical characteristics of carbon disulphide. In the first part, we calculate using the classical model, the nonlinear susceptibilities up to the fifth order taking into account local field corrections. We express different assumptions that we confirm or refute by measuring the nonlinear absorption coefficient and the nonlinear refractive index. The measurements are performed by means of two nonlinear characterization methods combined with an imaging 4f system. We analyse the experimental data using a newly developed method which numerically inverts the analytical solutions of the differential equations which describe the evolution of the beam, using Newton’s method. In the second part, we observe light filamentation at wavelength 532 nm, in the picoseconds regime. Then we measure the effective third order nonlinear refractive index n2,eff versus the incident intensity. By fitting the curve of the Kerr effect saturation, we develop a new model. Numerically solving this model, allows us to reproducethe experimentally observed filamentation. The last part is dedicated to the study of dissipative solitons dynamics. The complex Ginzburg-Landau equation with cubic-quintic nonlineraties is numerically solved in various configurations : soliton fundamental dipole, quadrupole, vortex and square rhombic.Nous présentons une étude de la dynamique de la lumière et des mesures des caractéristiques non-linéaires optiques dans le disulfure de carbone.Dans la première partie, nous calculons dans le cadre d’un modèle classique des expressions des susceptibilités non-linéaires jusqu’au cinquième ordre, en tenant compte des corrections de champ local. Nous formulons différentes hypothèses que nous confirmons ou infirmons par la mesure des indices d’absorption et de réfraction non-linéaires. Celles-ci sont obtenues en combinant deux méthodes de caractérisation des non-linéarités au sein d’un système 4fd’imagerie. L’analyse des données expérimentales utilise une méthode nouvellement développée, qui consiste à inverser numériquement, par la méthode de Newton, les solutions analytiques des équations différentielles qui décrivent l’évolution du faisceau.Dans la deuxième partie, nous observons la filamentation d’un faisceau laser à la longueur d’onde de 532 nm et en régime picoseconde. Puis nous procédons à la mesure de l’indice de réfraction non-linéaire effectif du troisième ordre n2,eff en fonction de l’intensité incidente. Par un ajustement de la courbe de saturation de l’effet Kerr,nous développons un nouveau modèle. La résolution numérique de celui-ci reproduit la filamentation observée.La dernière partie est consacrée à l’étude de la dynamique des solitons dissipatifs au sein de milieux à gains et pertes non-linéaires. La résolution numérique de l’équation complexe de Ginzburg-Landau cubique-quintique est réalisée suivant différentes configurations :soliton fondamental, dipôle, quadrupôle,vortex carré et rhombique

Emerging Economies:Changing Business Practices

This book highlights the current business practices in the emerging markets of China, Ghana, India, Kenya, Nigeria and UAE, and explains how forces of global competition have set the culture of competitiveness and an era of consumerism. The region-specific issues, tested theories and empirical evidence make the book an asset to both researchers and managers

Magnetization switching in bistable nanomagnets by picosecond pulses of surface acoustic waves

International audienceWe perform a theoretical investigation of the magnetization switching in polycrystalline Ni nanoparticles induced by ultrashort pulses of surface acoustic waves via magnetoelastic interactions. In our numerical simulations, a Ni nanoparticle is modeled as an ellipsoidal disk deposited on a dielectric substrate. The in-plane external magnetic field breaks the symmetry and allows us to adjust the height of the energy barrier between two metastable magnetization states of the free-energy density and dramatically lower the amplitude of elastic strain pulses required for magnetization switching. The switching threshold is shown to depend on the duration of an acoustic pulse, the magnetic shape anisotropy of an elliptical nanoparticle, the amplitude of the external magnetic field, and the magnetostriction coefficient. We introduce the magnetoelastic switching diagram, allowing for the simultaneous visualization of the switching threshold and its characteristic timescale as a function of various physical parameters

Additional file 1 of Handling missing rows in multi-omics data integration: multiple imputation in multiple factor analysis framework

Supplementary figures. Figures S1–S3. (PDF 225 kb