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41.
Shimizu K Freitas AA Farah JP Dias LG 《The journal of physical chemistry. A》2005,109(49):11322-11327
A parametrization of the polarizable continuum model (PCM) is presented having the experimental hydration free energies of 215 neutral molecules as target. The cavitation and dispersion contributions were based on the Tu?on-Silla-Pascual-Ahuir (Tu?on; et al. Chem. Phys. Lett. 1993, 203, 289) and Floris-Tomasi (Floris, F.; Tomasi, J. J. Comput. Chem. 1989, 10, 616) expressions, respectively. Both the polar and nonpolar contributions were evaluated on the same solvent-excluding molecular surface that used unscaled Bondi atomic radii. The parametrization was provided for the HF, Xalpha, LSDA, B3LYP, and mPW1PW91 methods at the 6-31G(d) basis set, and the results are in fair agreement with the experimental data. For the sake of comparison, the PCM(UAHF) and our parametrization (PCM2), both at HF level, have produced DeltaG(PCM(UAHF)) = aDeltaGexp (a = 1.02 +/- 0.02, r = 0.945, sd = 0.987, Ftest = 1778) and DeltaG(PCM2) = aDeltaGexp (a = 0.95 +/- 0.02, r = 0.952, sd = 0.843, Ftest = 2070), respectively. The mean absolute deviations from experimental data were 0.67 and 0.68 kcal/mol for PCM(UAHF) and PCM2, respectively. 相似文献
42.
Summary A simple approach to LF/VLF field calculations for a nonuniform, isotropic ionosphere is developed. The theory introduces
two modifications to the standard wave hop theory: namely the use of local reflection coefficients and the use of an average
reflection height for the path integrals. Sample calculations, including a comparison with measured results, are presented.
Riassunto Si sviluppa un semplice approccio di calcoli di campo LF/VLF per una ionosfera isotropica non uniforme. La teoria introduce due modifiche alla teoria standard del balzo delle onde: cioè l'uso di coefficienti locali di riflessione e l'uso di un'altezza media di riflessione per gli integrali di percorso. Si presentano calcoli campione, compreso un confronto con i valori risultati.
Резюме Развивается простой подход для вычислений LF/VLF поля в неоднородиой изотропниой ионосфере. В этом подходе вводится две модификации в стандартную теорию рассеяния волн. Приводятся простые вычисления, включая сравнение с экспериментальными результатами.相似文献
43.
Summary The purpose of the present investigation is to introduce trivalent molybdenum as a new analytical reducing agent, in hydrochloric as well as sulphuric acid media.The solution is prepared in 9N acid by electrolytic or mercuryreduction of the hexavalent form. It is preferentially stocked and used in high acid concentrations, whereby its stability in air is optimal, falling to half its titer after nearly two months. It has been tested with success as reductant for ceric, dichromate, ferric and vanadate. It has the advantage of being used in ordinary opened burettes. Titrations were followed potentiometrically in general, and alternately visually in decinormal media, whereby molybdenum blue appears at the end-point. The percentage error in fifteen discussed experiments never surpassed ±1%. Some oxidation titrations were also undertaken using iodate and bromate, with the same degree of accuracy, provided they were conducted in 6N acid. In weaker acid concentrations, equilibria were more slowly attained, with a more or less pronounced deviation, due to some oxidisability that necessitates controlled inert atmosphere. 相似文献
44.
Huge amounts of data in hyperspectral images have been caused to represent approaches for the band selection of these images.
In this paper, a new approach based on independent component analysis (ICA) is proposed. The idea of projection pursuit is
used to order the bands on the basis of a non-gaussianity distribution. Applying a negentropy function to weight bands is
a novel idea that leads to the selection of bands with minimum mutual information (MI) and besides maximum entropy, with respected
to the bands selected using other methods. 相似文献
45.
Shan N Ingram JD Easun TL Vickers SJ Adams H Ward MD Thomas JA 《Dalton transactions (Cambridge, England : 2003)》2006,(23):2900-2906
Using a [Ru(II)([9]aneS3)] templating moiety, kinetically-locked, metallomacrocycles incorporating adenine based ligands have been synthesised through self-assembly. The kinetically robust nature of these structures is confirmed by electrochemical studies: each can be reversibly oxidised in a four-member redox series, containing two formally mixed valence states. Unusually, the electrochemically derived comproportionation constants for these mixed valence states are very different, suggesting that intermetallic coupling differs between the two states. Spectroelectochemistry studies confirm that while the [Ru(II)2Ru(III)] state is valence localised, the [Ru(II)Ru(III)2] state is electronically delocalised. Mechanisms by which this switching effect could occur, which involve the unusual connectivities in these mixed valence species, are presented. 相似文献
46.
47.
We study three classes of subgroups of Polish groups: Borel subgroups, Polishable subgroups, and maximal divisible subgroups. The membership of a subgroup in each of these classes allows one to assign to it a rank, that is, a countable ordinal, measuring in a natural way complexity of the subgroup. We prove theorems comparing these three ranks and construct subgroups with prescribed ranks. In particular, answering a question of Mauldin, we establish the existence of Borel subgroups which are -complete, α?3, and -complete, α?2, in each uncountable Polish group. Also, for every α<ω1 we construct an Abelian, locally compact, second countable group which is densely divisible and of Ulm length α+1. All previously known such groups had Ulm length 0 or 1. 相似文献
48.
Ilijas Farah 《Israel Journal of Mathematics》2006,154(1):235-246
We prove two results about the quotient over the asymptotic density zero ideal. First, it is forcing equivalent to
% MathType!End!2!1!, where
% MathType!End!2!1! is the homogeneous probability measure algebra of characterc. Second, if it has analytic Hausdorff gaps, then they look considerably different from proviously known gaps of this form.
Partially supported by NSERC. 相似文献
49.
R. Naz 《Applied mathematics and computation》2010,215(9):3265-3270
When two circular jets impinge upon each other along the axis of a hemi-spherical shell then a free jet on a hemi-spherical shell is formed. The governing equations are Prandtl’s momentum boundary layer equation and the continuity equation. The conserved quantity is required for the free jet on a hemi-spherical shell. The conserved quantity for the free jet on a hemi-spherical shell is established with the help of a conserved vector. The group invariant solution for the third-order partial differential equation for the stream function is constructed. 相似文献
50.
J. M. Martínez J. I. Eguiazábal J. Nazábal 《Journal of Macromolecular Science: Physics》2013,52(4):345-355
The mechanical properties of miscible poly(butylene terephthalate) (PBT)/poly (hydroxy ether of bisphenol A) (phenoxy) blends obtained by melt mixing have been studied by means of the tensile test. The crystallinity of the blends has been studied by means of DSC and density measurements. A synergistic behavior, principally in the break properties, at high PBT contents in the blends is observed. As can be seen from the torque and density data, this synergistic behavior is related with the high level of miscibility which seems to exist at high PBT contents compared with that of the high phenoxy content region. 相似文献