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991.
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We present a direct and rather elementary method for defining and analyzing one-dimensional Schrödinger operators H = −d2/dx2 + μ with measures as potentials. The basic idea is to let the (suitably interpreted) equation −f′′ + μ f = zf take center stage.We show that the basic results from direct and inverse spectral theory then carry over to Schrödinger operators with measures. 相似文献
995.
We examine domino tilings of rectangular boards, which are in natural bijection with perfect matchings of grid graphs. This
leads to the study of their associated perfect matching polytopes, and we present some of their properties, in particular,
when these polytopes are Gorenstein. We also introduce the notion of domino stackings and present some results and several
open questions. Our techniques use results from graph theory, polyhedral geometry, and enumerative combinatorics. 相似文献
996.
Brajendra K. Singh Christian V. Stevens Davy R.J. Acke Erik V. Van der Eycken 《Tetrahedron letters》2009,50(1):15-4274
A continuous flow procedure has been elaborated for the copper(II)-mediated N- and O-arylation of a range of compounds with arylboronic acids using a commercial microreactor setup. The compounds could be continuously generated in good yields paving the way for efficient scalability. 相似文献
997.
Christian Corda 《General Relativity and Gravitation》2008,40(10):2201-2212
An oscillating Universe which arises from the linearized R 2 theory of gravity is discussed, showing that some observative evidences like the cosmological redshift and the Hubble law are in agreement with the model. In this context Dark Energy is seen like a pure curvature effect arising by the Ricci scalar. 相似文献
998.
Christian Okonek 《Mathematische Zeitschrift》1986,191(2):207-223
Ohne Zusammenfassung 相似文献
999.
Christian J.L. Hermes Robson O. Piucco Jader R. Barbosa Cláudio Melo 《Experimental Thermal and Fluid Science》2009,33(2):371-379
The present study advances a theoretical and experimental investigation of the frost growth and densification on flat surfaces. This study focuses on the most important factors affecting the frost formation process, i.e. the surrounding air temperature, humidity and velocity, and the surface temperature. The processes of frost growth and densification were investigated experimentally in order to provide a physical basis for the development of a theoretical model to predict the variation of the frost layer thickness and mass with time. The mathematical model was based on mass and energy balances within the frost layer, assuming the frost as a porous medium and accounting for the supersaturation of the moist air on the frost surface. The governing equations for mass and heat diffusion were integrated analytically, giving rise to a semi-algebraic formulation which requires numerical integration of only one time dependent ordinary differential equation. When compared with experimental data, the model predictions of the frost thickness as a function of time agreed to within ±10% error bands. The experimentally-validated model was then used to predict the frost layer growth and densification with respect to the operation conditions such as plate surface temperature, air stream temperature, humidity and velocity. 相似文献
1000.
Brad M. Rosen Gerard Lligadas Christian Hahn Virgil Percec 《Journal of polymer science. Part A, Polymer chemistry》2009,47(15):3940-3948
The development of a novel nucleophilic thio‐bromo “Click” reaction, specifically base‐mediated thioetherification of thioglycerol with α‐bromoesters was reported in an earlier article. The combination of this thio‐bromo click reaction with subsequent acylation with 2‐bromopropionyl bromide provides an iterative two‐step divergent growth approach to the synthesis of a new class of poly(thioglycerol‐2‐ propionate) (PTP) dendrimers. In this article, the addition of a third step, the single‐electron transfer living radical polymerization (SET‐LRP) of methyl acrylate (MA), was shown to provides access to a three‐step “branch” and “grow” divergent approach to dendritic macromolecules wherein poly(methyl acrylate) (PMA) connects the branching subunits. This facile methodology can provide a diversity of dendritic macromolecular topologies and will ultimately provide the means to the development of self‐organizable dendritic macromolecules. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3940–3948, 2009 相似文献