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981.
A decrease of the light transmission with increasing excitation intensity is observed in tetraphenylporphyrin/toluene solutions irradiated with 80 ps pulses at λ=532 nm. The experimental data are compared with simulations using a rate equation model. Excited state absorption cross-sections are evaluated. 相似文献
982.
983.
984.
Dennis H. Rouvray 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1993,105(6):962-963
985.
Harish J. Palanthandalam-Madapusi Tobin H. Van Pelt Dennis S. Bernstein 《Journal of Global Optimization》2009,45(4):533-549
We consider minimization of a quadratic objective function subject to a sign-indefinite quadratic equality constraint. We
derive necessary and sufficient conditions for the existence of solutions to the constrained minimization problem. These conditions
involve a generalized eigenvalue of the matrix pencil consisting of a symmetric positive-semidefinite matrix and a symmetric
indefinite matrix. A complete characterization of the solution set to the constrained minimization problem in terms of the
eigenspace of the matrix pencil is provided. 相似文献
986.
S. J. Lugowski Dennis C. Smith Joanna Z. Lugowski Walter Peters John Semple 《Analytical and bioanalytical chemistry》1998,360(3-4):486-488
The role of Si in nature is briefly described, especially the toxic properties of inorganic and organic Si for humans. The use of different forms of silicones in medicine and food industry is noted and potential consequences of their use are discussed. Since Si is an essential trace element there is need for establishment of the “normal” level of Si in blood, other body fluids and tissues and development of speciation of Si forms in biological samples. Numerous difficulties in the determination of Si are described and the need for SRM is stressed. The results of the determination of Si in blood of patients with Si breast implants and controls, Si in milk and blood of nursing mothers – with and without Si breast implants and extractable Si in capsules – are summarized. The obtained data reinforce the need for a reliable SRM. 相似文献
987.
988.
989.
Nelson A. Alves Bernd A. Berg Dennis W. Duke Anders Irb ck Sergiu Sanielevici 《Physics letters. [Part B]》1992,280(3-4):261-266
We apply the spectral density reweighting technique to the analysis of the chiral phase transition in finite-temperature lattice quantum chromodynamics (QCD) with four flavors of dynamical staggered fermions and mqa=0.025. Our simulations were performed using the hybrid Monte Carlo method for LtL3 lattices with Lt=4 and L=6, 8 and 10. We calculate partition function zeros, as well as the maxima of the specific heat and of the susceptibilities for the Polyakov loop and for the chiral condensate. A finite size scaling analysis of these data leads to preliminary results for the critical coupling βc, for the critical exponent ν, for the latent heat, and for the jumps in the Polyakov loop and in the chiral condensate. 相似文献
990.
This paper gives a review of methods where Green's theorem may be employed in solving numerically the Navier–Stokes equations for incompressible fluid motion. They are based on the concept of using the theorem to transform local boundary conditions given on the boundary of a closed region in the solution domain into global, or integral, conditions taken over it. Two formulations of the Navier–Stokes equations are considered: that in terms of the streamfunction and vorticity for two-dimensional motion and that in terms of the primitive variables of the velocity components and the pressure. In the first formulation overspecification of conditions for the streamfunction is utilized to obtain conditions of integral type for the vorticity and in the second formulation integral conditions for the pressure are found. Some illustrations of the principle of the method are given in one space dimension, including some derived from two-dimensional flows using the series truncation method. In particular, an illustration is given of the calculation of surface vorticity for two-dimensional flow normal to a flat plate. An account is also given of the implementation of these methods for general two-dimensional flows in both of the mentioned formulations and a numerical illustration is given. 相似文献