Search results for "Effects"

Spectral heterogeneity of oxygen-deficient centers in Ge-doped silica

2004

Abstract We report an experimental investigation of the emission spectra of a 1000 mol ppm sol–gel Ge-doped silica by fine tuning the excitation energy in the ultraviolet (UV) range, around 5 eV , and in the vacuum-UV range, around 7.3 eV , at room temperature and at 10 K . The sample is characterized by a blue (centered at ∼3.2 eV ) and an UV (centered at ∼4.3 eV ) bands. We have found that the ratio between the area of the blue and the UV bands depends on the temperature and on the excitation energy in both the vacuum-UV and the UV range. At both temperatures the spectral features of the blue and the UV bands are weakly affected when the excitation is varied in the vacuum-UV. At variance,…

Unexpected Reaction of the Unsaturated Cluster Host and Catalyst [Pd3(3-CO)(dppm)3]2+ with the Hydroxide Ion: Spectroscopic and Kinetic Evidence of a…

2006

The title cluster, [Pd(3)(mu(3)-CO)(dppm)(3)](2+) (dppm=bis(diphenylphosphino)methane), reacts with one equivalent of hydroxide anions (OH(-)), from tetrabutylammonium hydroxide (Bu(4)NOH), to give the paramagnetic [Pd(3)(mu(3)-CO)(dppm)(3)](+) species. Reaction with another equivalent of OH(-) leads to the zero-valent compound [Pd(3)(mu(3)-CO)(dppm)(3)](0). From electron paramagnetic resonance analysis of the reaction medium using the spin-trap agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the 2-tetrahydrofuryl or methyl radicals, deriving from the tetrahydrofuran (THF) or dimethyl sulfoxide (DMSO) solvent, respectively, were detected. For both [Pd(3)(mu(3)-CO)(dppm)(3)](2+) and [Pd(3)(mu…

OP09.10: Hemodynamic effects of sildenafil administration in an animal model of preeclampsia

2011

Variability of the Si-O-Si angle in amorphous-SiO2 probed by electron paramagnetic resonance and Raman spectroscopy

2009

We report an experimental investigation by electron paramagnetic resonance (EPR) and Raman spectroscopy on a variety of amorphous silicon dioxide materials. Our study by EPR have permitted us to point out that the splitting of the primary hyperfine doublet of the Eγ′ center shows a relevant sample-to-sample variability, changing from ∼41.8 to ∼42.6 mT in the set of materials we considered. The parallel study by Raman spectroscopy has enabled us to state that this variability is attributable to the different Si-O-Si angle characterizing the matrices of the different materials. © 2009 Elsevier B.V. All rights reserved.

Bayesian hierarchical nonlinear modelling of intra-abdominal volume during pneumoperitoneum for laparoscopic surgery

2021

Laparoscopy is an operation carried out in the abdomen or pelvis through small incisions with external visual control by a camera. This technique needs the abdomen to be insufflated with carbon dioxide to obtain a working space for surgical instruments' manipulation. Identifying the critical point at which insufflation should be limited is crucial to maximizing surgical working space and minimizing injurious effects. Bayesian nonlinear growth mixed-effects models are applied to data coming from a repeated measures design. This study allows to assess the relationship between the insufflation pressure and the intra--abdominal volume.

Design of Radiation-Hardened Rare-Earth Doped Amplifiers through a Coupled Experiment/Simulation Approach

2013

International audience; We present an approach coupling a limited experimental number of tests with numerical simulations regarding the design of radiation-hardened (RH) rare earth (RE)-doped fiber amplifiers. Radiation tests are done on RE-doped fiber samples in order to measure and assess the values of the principal input parameters requested by the simulation tool based on particle swarm optimization (PSO) approach. The proposed simulation procedure is validated by comparing the calculation results with the measured degradations of two amplifiers made with standard and RH RE-doped optical fibers, respectively. After validation, the numerical code is used to theoretically investigate the …

Gares exurbanisées et développement urbain : Le cas des gares TGV bourguignonnes

2009

Dès la mise en service de la ligne TGV Sud-Est, au début des années 80, la Bourgogne a bénéficié de la création de deux nouvelles gares TGV, aménagées en périphérie des pôles urbains du Creusot et de Mâcon. Malgré leurs fonctions réduites, ces nouvelles gares périurbaines ont suscité d’ambitieux projets d’aménagement. De nouvelles zones d’activités ont ainsi vu le jour à proximité de ces gares. Ces projets n’ont eu toutefois que des retombées limitées en matière d’implantation d’activités économiques. Since the opening of TGV south-east railway line at the beginning of the 80s Bourgogne has profited by construction of two new stations beyond the edge of Le Creusot and Mâcon. Despite their l…

Untersuchungen von polymeren im massenspektrometer, 4. Abbaureaktionen von polybenzylen

1974

Die Abbaureaktionen von unsubstituierten Poly(1,4-phenylenmethylen)en (A) (Polybenzylen), Poly[(2,5-dimethyl-1,4-phenylen)methylen] [Poly(2,5-dimethylbenzyl)] (B), Poly[(2,3,5,6-tetramethyl-1,4-phenylen)methylen] [Poly(2,3,5,6-tetramethylbenzyl)] (C) und Poly(1,4-phenylenathyliden) [Poly(α-methylbenzyl)] (D) wurden durch direkte Pyrolyse im Massenspektrometer untersucht. Die Massenpyrogramme von unter verschiedenen Reaktionsbedingungen dargestellten Polybenzylen wurden verglichen, mit dem Ziel, direkt Informationen uber Strukturunterschiede wie Kettenverzweigung und unterschiedliche Verknupfung der Benzyleinheiten zu erhalten; hierbei konnten in einem Falle auf hohere Kettenverzweigung deut…

A DFT study of the mechanism and selectivities of the [3 + 2] cycloaddition reaction between 3-(benzylideneamino)oxindole and trans -β-nitrostyrene

2016

The mechanism and regioselectivities and stereoselectivities of the [3 + 2] cycloaddition (32CA) reaction of 3-(benzylideneamino) oxindole (AY) and trans-β-nitrostyrene have been studied using both B3LYP and ωB97XD density functional theory methods together with the standard 6-31G(d) basis set. Four reactive pathways associated with the ortho and meta regioselective channels and endo and exo stereoselective approaches modes have been explored and characterized. While the B3LYP functional fails to predict the experimental regioselectivity, the ωB97XD one succeeds to predict the experimentally observed meta regioselectivity favoring the formation of meta/endo cycloadduct as the major isomer. …

Molecular dynamics simulation in aqueous solution of N -methylazetidinone as a model of β -lactam antibiotics

1999

In this article, we analyze the results of a molecular dynamics simulation in aqueous solution of the N-methylazetidinone molecule, often used to model β-lactam antibiotics. The radial distribution functions (RDFs) corresponding to the most interesting atoms, in terms of reactivity, are presented. We focus our study on the effect of a polar environment on the molecule. The solvent structure around the system is compared to the structure of β-lactam-water complexes, as obtained in a previous study of reaction mechanisms for the neutral and alkaline hydrolyses of N-methylazetidinone. Two types of complexes have been considered which are related to different hydrolysis mechanisms having simila…