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91.
Alexander N Shivanyuk Dmitry M Rudkevich David N Reinhoudt 《Tetrahedron letters》1996,37(52):9341-9344
An assembly of cation receptor 1 and anion receptor 2 via the hydrogen bonding melamine-barbiturate structural motif complexes sodium thiocyanate, sodium iodide, and sodium azide in apolar solvents. 相似文献
92.
Carl W. David 《Journal of computational chemistry》1993,14(6):715-717
A scheme for sprouting peptide side chains using X-PLOR is introduced using an example from the collagen system to show how reasonable starting structures for minimization studies may be created. © 1993 John Wiley & Sons, Inc. 相似文献
93.
94.
David Stanovský 《Czechoslovak Mathematical Journal》2007,57(1):191-200
We investigate the variety of residuated lattices with a commutative and idempotent monoid reduct. 相似文献
95.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
96.
Neutral Community Theory: How Stochasticity and Dispersal-Limitation Can Explain Species Coexistence
Neutral community theory explains biodiversity, i.e. the coexistence of several species, as the result of a stochastic balance
between immigration and extinction on a local level, and between speciation and extinction on a regional level. The most popular
model, presented by Hubbell in 2001, has seen many analytical developments in recent years, which can be used in model analysis,
model testing and model comparison. We review these developments here, and present alternative derivations and shine previously
unnoticed lights on them. 相似文献
97.
Bart M. J. M. Suijkerbuijk Duncan M. Tooke Anthony L. Spek Gerard van Koten Robertus J. M. Klein Gebbink Prof. Dr. 《无机化学与普通化学杂志》2007,633(15):2649-2653
A tin(IV) porphyrin was combined with two axial NCN‐pincer platinum(II) fragments by utilizing the oxophilicity of the apical positions on the tin atom and the acidic nature of the NCN‐pincer platinum derived benzoic acid. The solid‐state structure determined by X‐ray crystallography revealed some close contacts between the pincer complexes and the meso‐p‐tolyl subsitutents of the porphyrin. It was shown by 1H NMR spectroscopy that these close contacts were not present in solution and that this compound can potentially act as a novel building block for supramolecular architectures. 相似文献
98.
Let P(G,λ) be the chromatic polynomial of a graph G with n vertices, independence number α and clique number ω. We show that for every λ≥n, ()α≤≤ ()
n
−ω. We characterize the graphs that yield the lower bound or the upper bound.?These results give new bounds on the mean colour
number μ(G) of G: n− (n−ω)()
n
−ω≤μ(G)≤n−α() α.
Received: December 12, 2000 / Accepted: October 18, 2001?Published online February 14, 2002 相似文献
99.
Jose Manuel Corcuera Joao Guerra David Nualart Wim Schoutens 《Applied Mathematics and Optimization》2006,53(3):279-309
In this paper we consider the optimal investment problem in a market where the stock price process is modeled by a geometric
Levy process (taking into account jumps).
Except for the geometric Brownian model and the geometric Poissonian model, the
resulting models are incomplete and there are many equivalent martingale measures.
However, the model can be completed by the so-called power-jump assets. By doing this we allow investment in these new assets
and we can try to maximize the expected utility of these portfolios. As particular cases we obtain the optimal portfolios
based in stocks
and bonds, showing that the new assets are superfluous for certain martingale measures
that depend on the utility function we use. 相似文献
100.
Many recent algorithmic approaches involve the construction of a differential equation model for computational purposes, typically
by introducing an artificial time variable. The actual computational model involves a discretization of the now time-dependent differential system, usually
employing forward Euler. The resulting dynamics of such an algorithm is then a discrete dynamics, and it is expected to be
“close enough” to the dynamics of the continuous system (which is typically easier to analyze) provided that small – hence
many – time steps, or iterations, are taken. Indeed, recent papers in inverse problems and image processing routinely report
results requiring thousands of iterations to converge. This makes one wonder if and how the computational modeling process
can be improved to better reflect the actual properties sought.
In this article we elaborate on several problem instances that illustrate the above observations. Algorithms may often lend
themselves to a dual interpretation, in terms of a simply discretized differential equation with artificial time and in terms
of a simple optimization algorithm; such a dual interpretation can be advantageous. We show how a broader computational modeling
approach may possibly lead to algorithms with improved efficiency.
AMS subject classification (2000) 65L05, 65M32, 65N21, 65N22, 65D18 相似文献