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Surface spline interpolation when the domain is all of Rd isknown to converge much faster to the data function f than inthe case when the domain is the unit ball. This difference isunderstood to be due to boundary effects which, as will be shown,also affect the size of the surface spline's coefficients. Wepropose a modified form of surface spline interpolation which,to a great extent, overcomes these boundary effects. This modifiedsurface spline interpolant uses only the values of f at thegiven interpolation points. 相似文献
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A general class of linear two-step schemes for solving stochastic differential equations is presented. Necessary and sufficient conditions on its parameters to obtain mean square order 1.5 are derived. Then the linear stability of the schemes is investigated. In particular, among others, the stability regions of generalizations of the classical two-step schemes Adams-Bashford, Adams-Moulton, and BDF are obtained. 相似文献
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The potential in the vicinity of the stationary points on the surface for the decomposition of ground-state vinoxy and acetyl radicals has been calculated using the RQCISD(T) method extrapolated to the infinite-basis set limit. Rate coefficients for the decomposition pathways of these two radicals were computed using the master equation and variational transition state theory. Agreement between our calculated rate coefficients for H + CH(2)CO <--> CH(3) + CO and experimental data is very good, without the need for empirical adjustments to the ab initio energy barriers. Multireference configuration-interaction calculations indicate two competitive channels for vinoxy decomposition, with the channel leading to H + CH(2)CO being preferred at photodissociation energies. However, at typical combustion conditions, vinoxy decomposes primarily to CO and methyl. In contrast, decomposition of acetyl shows only one decomposition channel, leading to CO and methyl. The implications of a low-lying exit channel for the calculation of theoretical rate coefficients are discussed briefly. 相似文献
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The potential energy surface for the reaction between OH and acetylene has been calculated using the RQCISD(T) method and extrapolated to the complete basis-set limit. Rate coefficients were determined for a wide range of temperatures and pressures, based on this surface and the solution of the one-dimensional and two-dimensional master equations. With a small adjustment to the association energy barrier (1.1 kcal/mol), agreement with experiments is good, considering the discrepancies in such data. The rate coefficient for direct hydrogen abstraction is significantly smaller than that commonly used in combustion models. Also in contrast to previous models, ketene + H is found to be the main product at normal combustion conditions. At low temperatures and high pressures, stabilization of the C2H2OH adduct is the dominant process. Rate coefficient expressions for use in modeling are provided. 相似文献
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Background
Amyotrophic lateral sclerosis (ALS) is an age-dependent neurodegenerative disease that causes motor neuron degeneration, paralysis and death. Mutations in Cu, Zn superoxide dismutase (SOD1) are one cause for the familial form of this disease. Transgenic mice expressing mutant SOD1 develop age-dependent motor neuron degeneration, skeletal muscle weakness, paralysis and death similar to humans. The mechanism whereby mutant SOD1 induces motor neuron degeneration is not understood but widespread mitochondrial vacuolation has been observed during early phases of motor neuron degeneration. How this vacuolation develops is not clear, but could involve autophagic vacuolation, mitochondrial permeability transition (MPT) or uncharacterized mechanisms. To determine which of these possibilities are true, we examined the vacuolar patterns in detail in transgenic mice expressing mutant SOD1G93A. 相似文献19.
van Eis MJ van Der Linde BS de Kanter FJ de Wolf WH Bickelhaupt F 《The Journal of organic chemistry》2000,65(14):4348-4354
In contrast to the terminal phosphinidene complex PhPW(CO)(5) (2), which adds to [5]metacyclophane (1) in a 1,4-fashion, dichlorocarbene preferentially adds in a 1,2-fashion to the formal "anti-Bredt" type double bond of the aromatic ring of 1 to afford the norcaradiene 11b, which immediately rearranges to the bridged cycloheptatriene 12b and further by a [1,5] sigmatropic chlorine migration to the isomeric 13b as the first observable product. More slowly, the latter isomerizes via a dissociative mechanism to give 15b. A computational study supports the notion that the [1,5] chlorine migration in the rearrangement 12b --> 13b, for which an activation barrier of 70.2 kJ mol(-)(1) was calculated, is essentially concerted with minor charge separation. In contrast, the analogous [1,5] chlorine migration in the flat model compound 7,7-dichlorocycloheptatriene (12a) displays features of a dissociative pathway. 相似文献
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