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971.
972.
Gianluca Ambrosi Mauro Formica Vieri Fusi Luca Giorgi Mauro Micheloni 《Coordination chemistry reviews》2008,252(10-11):1121
The coordination properties of a selected series of acyclic and macrocyclic ligands containing one or more phenolic groups are explored. The formation of polynuclear metal complexes was only considered highlighting the key role played by the phenoxide oxygen atom in binding two metal centres in a bridge disposition. This arrangement allows two metal ions to stay close each other and consequently these dinuclear centres are able to mimic many biological sites, especially those where the two metals can cooperate to form an active centre. Catalytic properties of these polynuclear complexes, when studied, have been reported. Also some of the numerous heterodinuclear metal complexes that have been synthesized are here reviewed, included several crystal structures. 相似文献
973.
Luca Vincenzo Ballestra Graziella Pacelli Francesco Zirilli 《Nonlinear Analysis: Hybrid Systems》2008,2(2):568-589
We consider the problem of pricing European interest rate derivatives based on the LIBOR Market Model (LMM) with one driving factor. We derive a closed-form approximation of the transition probability density functions associated to the stochastic dynamical systems that describe the behaviour of the forward LIBOR interest rates in the LMM. These approximate formulae are based on a truncated power series expansion of the solutions of the Fokker–Planck equations associated to the LMM. The approximate probability density functions obtained are used to price European interest rate derivatives using the method of discounted expectations. The resulting integrals are low dimensional when the most commonly traded European interest rate derivatives are considered, and they can be computed efficiently using elementary numerical quadrature schemes (i.e. Simpson’s rule). The algorithm obtained is very well suited for parallel computing and is tested on the problem of pricing several derivatives including an European swaption and an interest rate spread option. In both cases, the method proposed in this paper appears to be accurate (i.e. relative error of order 10−2, 10−3, or even 10−4) and approximately between 278 and 63 000 times faster than previous methods based on the Monte Carlo simulation of the LMM stochastic dynamical systems.
The website http://www.econ.univpm.it/pacelli/ballestra/finance/w2 contains material that helps the understanding of this paper and makes available to the interested users the computer programs that implement the numerical method proposed. 相似文献
974.
Luca Paglieri Giorgina Corongiu Darío A. Estrin 《International journal of quantum chemistry》1995,56(5):615-625
The effects of the solvent on the tautomeric equilibria of cytosine and uracil are studied using Onsager's reaction field model in the framework of density functional theory. In this model, the solute molecule is placed in a spherical cavity of radius ao immersed in a continuous medium with a dielectric constant e, treating the solute-solvent electrostatic interactions at the dipole level. The cavity radius is evaluated by determining the molecular volume with a quantum mechanical approach. The solvent effect brings significant changes in the geometrical parameters of some cytosine tautomers, but only very small changes to those of the uracil tautomers. Our results are in good agreement with available experimental results and confirm that the polarization of the solute by the continuum has important effects on the absolute and relative solvation energies. Frequency shifts and intensity variations in the infrared spectra due to the presence of the solvent are also presented. © 1995 John Wiley & Sons, Inc. 相似文献
975.
Let b?2 be an integer. We prove that real numbers whose b-ary expansion satisfies some given, simple, combinatorial condition are transcendental. This implies that the b-ary expansion of any algebraic irrational number cannot be generated by a finite automaton. To cite this article: B. Adamczewski et al., C. R. Acad. Sci. Paris, Ser. I 339 (2004). 相似文献
976.
In this note, we show that the set of n such that the arithmeticmean of the first n primes is an integer is of asymptotic densityzero. We use the same method to show that the set of n suchthat the sum of the first n primes is a square is also of asymptoticdensity zero. We also prove that both the arithmetic mean ofthe first n primes as well as the square root of the sum ofthe first n primes are well distributed modulo 1. 相似文献
977.
978.
Luca Lussardi 《Mathematical Methods in the Applied Sciences》2008,31(18):2133-2146
We approximate, in the sense of Γ‐convergence, free discontinuity functionals with linear growth by a sequence of non‐local integral functionals depending on the average of the gradient on small balls. The result extends to a higher dimension what is already proved in (Ann. Mat. Pura Appl. 2007; 186 (4): 722–744), where there is the proof of the general one‐dimensional case, and in (ESAIM Control Optim. Calc. Var. 2007; 13 (1):135–162), where the n‐dimensional case with ?=Id is treated. Moreover, we investigate whether it is possible to approximate a given free discontinuity functional by means of non‐local energies. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
979.
980.
Luca F. Pavarino 《Numerische Mathematik》1993,66(1):493-515
Summary In this paper, we study some additive Schwarz methods (ASM) for thep-version finite element method. We consider linear, scalar, self adjoint, second order elliptic problems and quadrilateral elements in the finite element discretization. We prove a constant bound independent of the degreep and the number of subdomainsN, for the condition number of the ASM iteration operator. This optimal result is obtained first in dimension two. It is then generalized to dimensionn and to a variant of the method on the interface. Numerical experiments confirming these results are reported. As is the case for other additive Schwarz methods, our algorithms are highly parallel and scalable.This work was supported in part by the Applied Math. Sci. Program of the U.S. Department of Energy under contract DE-FG02-88ER25053 and, in part, by the National Science Foundation under Grant NSF-CCR-9204255 相似文献