Search results for "medium"
showing 10 items of 3746 documents
Bond stretching and redox behavior in coinage metal complexes of the dichalcogenide dianions [(SPh2P)2CEEC(PPh2S)2]2- (E=S, Se): diradical character …
2011
The metathetical reactions of a) [Li(tmeda)](2)[(S)C(PPh(2)S)(2)] (Li(2)·3c) with CuCl(2) and b) [Li(tmeda)](2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)] (Li(2)·4c) with two equivalents of CuCl both afford the binuclear Cu(I) complex {Cu(2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)]} (5c). The elongated (C)S-S(C) bond (ca. 2.54 and 2.72 A) of the dianionic ligand observed in the solid-state structure of 5c indicate the presence of diradical character as supported by theoretical analyses. The treatment of [Li(tmeda)](2)[(SPh(2)P)(2)CSeSeC(PPh(2)S)(2)] (Li(2)·4b) and Li(2)·4c with AgOSO(2)CF(3) produce the analogous Ag(I) derivatives, {Ag(2)[(SPh(2)P)(2)CEEC(PPh(2)S)(2)]} (6b, E=Se; 6c, E=S), respectively. The disele…
Perron's method for the porous medium equation
2016
O. Perron introduced his celebrated method for the Dirichlet problem for harmonic functions in 1923. The method produces two solution candidates for given boundary values, an upper solution and a lower solution. A central issue is then to determine when the two solutions are actually the same function. The classical result in this direction is Wiener’s resolutivity theorem: the upper and lower solutions coincide for all continuous boundary values. We discuss the resolutivity theorem and the related notions for the porous medium equation ut −∆u = 0
Damping effect on the ITER vacuum vessel displacements during slow downward locked and rotating asymmetric vertical displacement events
2018
Abstract In this paper, we present the electromechanical coupled analysis of the ITER vacuum vessel in case of slow downward locked and rotating Asymmetric VDEs. The numerical model for simulating the AVDE includes the asymmetric distribution of the halo currents obtained by a suitable 3D kink perturbation of a slow VDE downward computed by the 2D code DINA. In the case of a rotational AVDE, the rotation frequency of the kink asymmetry has been chosen to be ω = 2π × 5 rad/s. The model includes the mesh of the main passive components facing the plasma. The whole torus (360 degrees) has been discretized. It is shown that the very high complexity of the numerical model can be suitably treated.…
A distributed model for continuous-wave erbium-doped fiber laser
2011
Abstract A distributed model of a continuous-wave erbium-doped fiber laser is discussed. The model is based on two contra-propagated traveling laser waves, and includes inhomogeneous pumping, excited state absorption at the pump and the laser wavelengths, amplified spontaneous emission and radial distribution of populations of erbium levels. It is shown that excited state absorption is a main limiting factor to the laser's efficiency. Moreover, consideration of radial distributions of erbium levels' populations in the model reduces laser efficiency and decreases optimal reflection of the laser output coupler. The modeling results are in excellent agreement with the experimental study on the…
High-efficiency Q-switched erbium fiber laser using a Bragg grating-based modulator
2002
Abstract In this work we analyze the behavior of an erbium-doped fiber laser which is based on a simple scheme. Excitation of the active medium is performed in the 980 nm pump band with a CW semiconductor laser source. Two fiber Bragg gratings acting as mirrors of the Fabry–Perot laser cavity were used. One of these gratings was mounted over a piezoelectric (PZT) element. By applying voltage pulses to the piezoelectric, the laser cavity was temporally modulated and Q-switched laser pulses up to 530 mW peak powers at 3 kHz were obtained. Typical laser emission of 2–3 μs temporal widths and 0.1 nm of optical bandwidth have been achieved when the system was operated at 18.5 kHz repetition rate…
Stochastic multiscale model for carbonate rocks.
2007
A multiscale model for the diagenesis of carbonate rocks is proposed. It captures important pore scale characteristics of carbonate rocks: wide range of length scales in the pore diameters; large variability in the permeability; and strong dependence of the geometrical and transport parameters on the resolution. A pore scale microstructure of an oolithic dolostone with generic diagenetic features is successfully generated. The continuum representation of a reconstructed cubic sample of sidelength $2\phantom{\rule{0.3em}{0ex}}\mathrm{mm}$ contains roughly $42\ifmmode\times\else\texttimes\fi{}{10}^{6}$ crystallites and pore diameters varying over many decades. Petrophysical parameters are com…
Evidence of superatom electronic shells in ligand-stabilized aluminum clusters
2011
Ligand-stabilized aluminum clusters are investigated by density functional theory calculations. Analysis of Kohn-Sham molecular orbitals and projected density of states uncovers an electronic shell structure that adheres to the superatom complex model for ligand-stabilized aluminum clusters. In this current study, we explain how the superatom complex electron-counting rule is influenced by the electron-withdrawing ligand and a dopant atom in the metallic core. The results may guide the prediction of new stable ligand-stabilized (superatom) complexes, regardless of core and electron-withdrawing ligand composition.
Effects of Silver Doping on the Geometric and Electronic Structure and Optical Absorption Spectra of the Au_{25-n}Ag_{n}(SH)_{18}^{-} (n = 1, 2, 4, 6…
2012
The effect of silver doping of the Au25(SH)18– nanoparticle is studied by investigating Au25–nAgn(SH)18– (n = 1, 2, 4, 6, 8, 10, 12) systems using DFT. For n = 1, doping of the icosahedral shell of the metal core is energetically more favorable than doping of the metal–thiolate units or the center of the core. For n ≥ 2, only doping of the core surface is considered, and arrangements where the silver dopants are in close proximity tend to be slightly less favorable. However, energy differences are small, and all conformations are accessible under experimental conditions. Boltzmann-averaged excitation spectra for these systems show similar features to the undoped Au25(SH)18–. The main differ…
Loading, release and stability of epirubicin-loaded drug-eluting beads.
2015
Purpose The aim of this study was to determine the loading efficiency, physico-chemical stability and release of epirubicin-loaded DC Bead™ (Biocompatibles UK Ltd, a BTG International group company) (bead size 70–150 µm (=DC Bead M1™) and 100–300 µm) after loading with epirubicin solution (2 mg/ml) or reconstituted powder formulation (25 mg/ml) and controlled storage. Methods DC Bead™ were loaded with 76 mg epirubicin solution (Epimedac™, Medac GmbH) or 75 mg epirubicin powder formulation (Farmorubicin™, Pharmacia Pfizer GmbH) per 2 ml of beads. Drug loading efficiency and stability were determined by measuring the epirubicin concentration in the excess solution after predetermined interval…
Analysis of the Effects of Modifying Agents on Six Different Phenotypes in Preneoplastic Foci in the Liver in Medium-Term Bioassay Model in Rats
1988
Recently a great deal of interest has been expressed in characterizing the altered enzyme phenotype of putative preneoplastic rat liver lesions. In particular, attention has been given to the changes in drug metabolizing potential, conferring physiological advantage to initiated cells, and their usefulness as marker lesions for the analysis of the development of neoplasia1–2.