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931.
932.
Liquid-liquid phase transfer conditions have been found to provide highly selective monoalkylation of tert-butyl 3,4-dihydroxy-4-phenylpiperidine-1-carboxylate, a transformation for which many other common alkylation protocols proved inadequate. The high preference for 3-O-alkylation in the phase transfer alkylation is emphasised by the absence of diether formation even in the presence of a large excess of reagents. 相似文献
933.
Samarium(II) diiodide mediated intramolecular cyclisation of mixed enone-enoate substrates in THF/MeOH is described. Spirocyclic ethers are obtained, and the stereodefined preparation of 1-oxaspiro[4.4]nonan-7-one products is included. 相似文献
934.
Mark Krusemeyer 《代数通讯》2013,41(7):657-663
935.
936.
In previous studies, the moment‐of‐fluid interface reconstruction method showed dramatic accuracy improvements in static and pure advection tests over existing methods, but this did not translate into an equivalent improvement in volume‐tracked multimaterial incompressible flow simulation using low‐order finite elements. In this work, the combined effects of the spatial discretization and interface reconstruction in flow simulation are examined. The mixed finite element pairs, Q1Q0 (with pressure stabilization) and Q2P ? 1 are compared. Material order‐dependent and material order‐independent first and second‐order accurate interface reconstruction methods are used. The Q2P ? 1 elements show significant improvements in computed flow solution accuracy for single material flows but show reduced convergence using element‐average piecewise constant density and viscosity in volume‐tracked simulations. In general, a refined Q1Q0 grid, with better material interface resolution, provided an accuracy similar to the Q2P ? 1 element grid with a comparable number of degrees of freedom. Moment‐of‐fluid shows more benefit from the higher‐order accurate flow simulation than the LVIRA, Youngs', and power diagram interface reconstruction methods, especially on unstructured grids, but does not recover the dramatic accuracy improvements it has shown in advection tests. Published 2012. This article is a US Government work and is in the public domain in the USA. 相似文献
937.
Shae Anne Vaughn Mark D. Smith Hans-Conrad zur Loye 《Journal of chemical crystallography》2012,42(1):7-11
Abstract
Complex (1), which is comprised of a typical Keggin type anion, four protonated 3-amino-1,2,4-triazole (AmTAZ) ligands, one nitrate anion and an area of disordered unidentifiable species was synthesized via hydrothermal methods followed by slow evaporation. The structure is held together through a web of hydrogen bonding and crystallizes in the monoclinic space group P21/c with unit cell dimensions of a = 13.789(3) b = 15.551(3) c = 24.401(7) ?, β = 93.898(8)°, V = 5220(2) ?3 Z = 4, D = 2.896 Mg/m3. 相似文献938.
The recent interest in human dynamics has led researchers to investigate the processes that explain human behaviour within different contexts. Here we are concerned in modelling the human response to a deadline, and in particular we look at the process of conference registration with an early bird deadline. We provide empirical evidence from a six-year conference registration data set that the bi-logistic growth function, with the interpretation as registration with an early bird deadline, can be viewed as a social mechanism. 相似文献
939.
Mark J. Logan 《代数通讯》2013,41(8):3739-3742
This note points out a factor of the Poincaré polynomial of the λ-isotypic component of the exterior algebra λL, where L is a complex semisimple Lie algebra and λ is a dominant weight. Although these polynomials have been studied with regard to their factorizations, this particular factor seems to have gone unstated. 相似文献
940.