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141.
Riccardo Salvati Manni 《Proceedings of the American Mathematical Society》2007,135(5):1241-1247
In this paper we consider varieties defined by Riemann-Mumford's relations. An irreducible component of these varieties is related to Siegel modular varieties. We prove that in most cases Riemann-Mumford varieties are not irreducible.
142.
Plasma treatments in Radio Frequency Glow Discharges fed with NH3−H2 mixtures have been performed for modifying polyethylene surfaces. Treatment kinetics and the role of species present in the
glow have been investigated. Actinometric Optical Emission Spectroscopy has been utilized as a plasma diagnostic technique.
Electron Spectroscopy for Chemical Analysis has been utilized for studying surface composition of treated substrates, which
have been examined both astreated and after derivatization of amine-functionalities with 4-trifluoromethylbenzaldehyde vapors.
It has been found that experimental plasma parameters and plasma density of active species can be controlled to achieve selective
grafting of-NH2 among all other nitrogen-containing groups. 相似文献
143.
Semiempirical molecular orbital calculations for the porphyrins tetrakis(4-N-methyl pyridyl)porphine (H2TMpyP-4) and tetrakis(2-N-methyl pyridyl)porphine using the MNDO and AM -1 Hamiltonians suggest that twisting one or more of the pyridinium rings results, at considerable energy expense, in highly nonplanar macrocycle configurations as the exocyclic ring(s) approach coplanarity. The results imply that the mechanism of intercalation of H2TMpyP-4 into DNA cannot require twisting the exocyclic rings anywhere close to coplanarity with the central porphine core, but involves, instead, the inherent flexibility of DNA itself. © 1993 John Wiley & Sons, Inc. 相似文献
144.
Riccardo Zecchina 《Pramana》2005,64(6):1161-1173
The combinatorial problem of satisfying a given set of constraints that depend on N discrete variables is a fundamental one in optimization and coding theory. Even for instances of randomly generated problems, the question “does there exist an assignment to the variables that satisfies all constraints?” may become extraordinarily difficult to solve in some range of parameters where a glass phase sets in. We shall provide a brief review of the recent advances in the statistical mechanics approach to these satisfiability problems and show how the analytic results have helped to design a new class of message-passing algorithms — the survey propagation (SP) algorithms — that can efficiently solve some combinatorial problems considered intractable. As an application, we discuss how the packing properties of clusters of solutions in randomly generated satisfiability problems can be exploited in the design of simple lossy data compression algorithms. 相似文献
145.
Daniele Simoni Giuseppe GianniniPier Giovanni Baraldi Romeo RomagnoliMarinella Roberti Riccardo RondaninRiccardo Baruchello Giuseppina GrisoliaMarcello Rossi Danilo MirizziFrancesco Paolo Invidiata Stefania GrimaudoManlio Tolomeo 《Tetrahedron letters》2003,44(14):3005-3008
A double Suzuki cross-coupling protocol has been devised as a practical route to a variety of terphenyls. Good chemoselectivity was observed. Unsymmetrically substituted triphenylenes were also easily prepared. 相似文献
146.
The equilibrium and transport properties of interacting ad-particles on bivariate heterogeneous chains are studied by combining analytical and simulation approaches. Heterogeneity is introduced in the way of patches of shallow and deep adsorbing sites distributed in a deterministic alternating way. Adsorption isotherms and mean-square fluctuations of the surface coverage, as well as the jump and collective diffusion coefficients, are calculated for different values of lateral interactions between ad-particles and substrate heterogeneity. In addition, different elementary jump mechanisms are introduced and their influence in the coverage dependence of the collective diffusion coefficient is investigated. 相似文献
147.
148.
Luigi Fortuna Mattia Frasca Salvatore Graziani Salvatore Reddiconto 《Nonlinear dynamics》2006,44(1-4):55-61
In this paper, the possibility of observing strange attractors in an electronic circuit including a nonlinear ferroelectric
component has been investigated. The ferroelectric constitutes the medium interposed between the two plates of a capacitor.
A circuit including the nonlinearity of the ferroelectric has been designed, while the parameters have been found by performing
numerical integration with respect to different values of them. The circuit has been realized on a discrete components board.
Experimental results, showing that for a suitable range of parameters a chaotic attractor emerges, are reported. 相似文献
149.
150.
Comparison of the Adomian decomposition method and regular perturbation techniques applied to the solution of nonlinear vector random differential equations shows that the decomposition method is superior and generally applicable. Even for the cases where perturbation is applicable, the comparison shows that the decomposition method is easier to compute and supplies quantitatively reliable results. 相似文献