Search results for "scad"

Dobutamine stress Doppler echocardiography: reproducibility and physiologic left ventricular filling patterns

1997

Qualitatively, dobutamine stress echocardiography has become an established procedure. Quantitative results are in great demand but this is still difficult due to limited endo- and epicardial border definition. Transmitral Doppler variables are strictly quantitative and less subjective. Furthermore, ischemic alterations precede systolic ones (ischemic cascade). There are preliminary reports of the utility of dobutamine stress Doppler echocardiography, but proof of reproducibility and left ventricular filling patterns are still lacking. Fourteen healthy volunteers (10 men, 4 women, median age 25.9 years, range 21-32 years) were investigated according to the usual dobutamine stress echocardio…

IMPLICACIONES DEL USO DE BUSCADORES EN EL COMPORTAMIENTO DE COMPRA ONLINE

2009

RESUMENEl objetivo del presente trabajo es analizar los factores que influyen en el uso de buscadores y su incidencia en el comportamiento de compra en Internet. El análisis de resultados obtenidos a partir de una muestra representativa de 485 compradores por Internet españoles, pone de manifiesto que los consumidores que consideran la comodidad, reducciones de precio y amplitud de surtido como motivaciones relevantes para realizar compras online presentan una mayor predisposición al uso de buscadores en la realización de sus compras virtuales. La experiencia como internauta y como comprador en Internet son factores que influyen negativamente en el uso de buscadores para la realización de c…

Nanocatalysts for High Selectivity Enyne Cyclization: Oxidative Surface Reorganization of Gold Sub-2-nm Nanoparticle Networks

2021

International audience; Ultrasmall gold nanoparticles (NPs) stabilized in networks by polymantane ligands (diamondoids) were successfully used as precatalysts for highly selective heterogeneous gold-catalyzed dimethyl allyl(propargyl)malonate cyclization to 5-membered conjugated diene. Such reaction usually suffers from selectivity issues with homogeneous catalysts. This control over selectivity further opened the way to one-pot cascade reaction, as illustrated by the 1,6-enyne cycloisomerization–Diels–Alder reaction of dimethyl allyl propargyl malonate with maleic anhydride. The ability to assemble nanoparticles with controllable sizes and shapes within networks concerns research in sensor…

X-Ray Diffraction Analysis of Airborne Particulates Collected by a Cascade Impactor Sampler. Phase Distribution Versus Particle Size

1994

Intensity-correlated spiking of infrared and ultraviolet emission from sodium vapors

2021

The directional spiking infrared and ultraviolet emission from sodium vapors excited to the 4D5/2 level by a continuous-wave resonant laser pump, that constitute a novel feature of the cooperative effects, has been analyzed. Cascade mirrorless lasing at 2207 and 2338 nm on population-inverted transitions and ultraviolet radiation at 330 nm that is generated due to four-wave mixing process demonstrate a high degree of intensity correlation.

Theoretical study of cascade laser in erbium-doped chalcogenide glass fibers

2010

International audience; A theoretical investigation of an innovative cascade laser source is performed. The main goal of the work is the design of a continuous-wave (CW) photonic crystal fiber (PCF) laser, based on an erbium-doped chalcogenide glass. Due to the comparable lifetimes of the 4I13/2, 4I11/2 and 4I9/2 erbium energy levels, the simultaneous emissions at the wavelengths close to 2.7 μm and 4.5 μm are obtained with a pump wavelength close to 806 nm (direct pumping into the level 4I9/2). This scheme could be useful to develop high efficiency, high beam-quality and compact Near-IR and Mid-IR oscillators with single-mode output for applications not only in surgery but also in spectros…

Fourth-order cascaded Raman shift in AsSe chalcogenide suspended-core fiber pumped at 2 μm

2011

International audience; Cascaded Raman wavelength shifting up to the fourth order ranging from 2092 to 2450nm is demonstrated using a nanosecond pump at 1995nm in a low-loss As38Se62 suspended-core microstructured fiber. These four Stokes shifts are obtained with a low peak power of 11W, and only 3W are required to obtain three shifts. The Raman gain coefficient for the fiber is estimated to (1.6 +-0.5)x 10e−11 m/W at 1995nm. The positions and the amplitudes of the Raman peaks are well reproduced by the numerical simulations of the nonlinear propagation.

Self-assembled hierarchical nanostructured perovskites enable highly efficient LEDs via an energy cascade

2018

Metal halide perovskites have established themselves as extraordinary optoelectronic materials, exhibiting promise for applications in large area illumination and displays. However, low luminescence, low efficiencies of the light-emitting diodes (LEDs), and complex preparation methods currently limit further progress towards applications. Here, we report on a new and unique mesoscopic film architecture featuring the self-assembly of 3D formamidinium lead bromide (FAPbBr3) nanocrystals of graded size, coupled with microplatelets of octylammonium lead bromide perovskites that enables an energy cascade, yielding very high-performance light-emitting diodes with emission in the green spectral re…

Wideband impedance matrix representation of passive waveguide components based on cascaded planar junctions

2009

[1] A very efficient technique for the full-wave analysis of passive waveguide components, composed of the cascade connection of planar junctions, is presented. This novel technique provides the wideband generalized impedance matrix representation of the whole structure in the form of pole expansions, thus extracting the most expensive computations from the frequency loop. For this purpose, the structure is segmented into planar junctions and uniform waveguide sections, which are characterized in terms of wideband impedance matrices. Then, an efficient iterative algorithm for combining such matrices, and finally providing the wideband generalized impedance matrix of the complete structure, …

Cascade Controller Including Backstepping for Hydraulic-Mechanical Systems

2012

Abstract Development of a cascade controller structure including adaptive backstepping for a nonlinear hydraulic-mechanical system is considered in this paper where a dynamic friction (LuGre) model is included to obtain the necessary accuracy. The paper compares the performance of two variants of an adaptive backstepping tracking controller with earlier results. The new control architecture is analysed and enhanced tracking performance is demonstrated when including the extended friction model. The complexity of the backstepping procedure is significantly reduced due to the cascade structure. Hence, the proposed control structure is better suited to real-time implementation.