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131.
Banks CE Kruusma J Hyde ME Salimi A Compton RG 《Analytical and bioanalytical chemistry》2004,379(2):277-282
Bismuth-modified glassy carbon electrodes have been investigated for their suitability in sonoelectroanalysis. The stability of the bismuth film to the application of ultrasound was assessed via voltammetric and atomic force microscopy (AFM) studies which revealed little ablation at powers up to an intensity of 130 W cm–2 delivered from a 25-kHz sonic horn. Furthermore, bismuth-film-modified glassy carbon electrodes were evaluated for the sonoelectroanalytical quantification of zinc and cadmium. Detection limits of 2×10–7 M and 6×10–9 M respectively were found after a 60-s deposition time via an acoustically assisted deposition protocol. 相似文献
132.
Hannan EL 《The Journal of the Operational Research Society》1984,35(2):117-129
The cost allocation process in hospitals typically entails an accounting step-down procedure whereby costs are allocated from non-revenue producing service centres to revenue centres. The resulting revenue centre costs are then compared with the third party (Blue Cross, Medicare, Medicaid) allowable costs. Any costs in excess of the allowable costs are not reimbursable. This procedure has been conceptualized using a Markov chain in a recent journal article. The purpose of this paper is to demonstrate how the Markov model may be used to assess the impact of various changes in the original data without having to recalculate the entire step-down process via a Markov model or any other procedure. The changes include an alternate step-down model, a different cost allocation basis for one or more service centres, and the expansion or contraction of one or more service centres. 相似文献
133.
Some laws in physics describe the change of a flux and are represented by parabolic equations of the form (*) \documentclass{article}\pagestyle{empty}\begin{document}$$\frac{{\partial u}}{{\partial t}}=\frac{\partial}{{\partial x_j }}(\eta \frac{{\partial u}}{{ax_j}}-vju),$$\end{document} j≤m, where η and vj are functions of both space and time. We show under quite general assumptions that the solutions of equation (*) with homogeneous Dirichlet boundary conditions and initial condition u(x, 0) = uo(x) satisfy The decay rate d > 0 only depends on bounds for η, v and G § Rm the spatial domain, while the constant c depends additionally on which norm is considered. For the solutions of equation (*) with homogeneous Neumann boundary conditions and initial condition u0(x) ≥ 0 we derive bounds d1u1 ≤ u(x, t) ≤ d2u2, Where di, i = 1, 2, depend on bounds for η, v and G, and the ui are bounds on the initial condition u0. 相似文献
134.
A study of the reaction of Me3SnCu·.Me2S (1) and [Me3SnCuSPh]Li (2) with α,β - acetylenic N,N-dimethylamides 3 shows (a) that the overall process can be controlled experimentally so as to produce either N,N-dimethyl ()-(4) or ()-3-trimethylstannyl-2-alkenamides (5), (b) that the initially formed intermediate derived from interaction of 2 and 3 is significantly more stable than that obtained by reaction of 2 and α,β-acetylenic esters, and (c) that the intermediate produced by treating 3 with 1 can be trapped with electrophiles other than proton. 相似文献
135.
Fifteen of twenty-four silver(I) carboxylates examined give useful electron impact mass spectra. The compounds vaporize at moderate temperatures, apparently mainly as dimer with traces of higher oligomer in only a few cases. The molecular ion for the dimer is generally weak or absent, with the most abundant silver containing ion being [Ag2(O2CR)]+ in most cases. Metastable defocusing and deuterium labeling experiments on silver acetate have established some of the fragmentation pathways. The reported loss of carbon dioxide from perfluorocarboxylates to give intense peaks for organosilver ions was not observed in this study. Attempts to obtain spectra on the silver salts of organic materials other than carboxylic acids were successful in several cases. Silver trifluoromethanesulfonate, although much less volatile, gives a spectrum and fragmentation very much like the carboxylates, whereas silver trifluoromethanethiolate gives a complex spectrum which suggests tetramer as a major gas phase species. Of three compounds examined which have silver to nitrogen bonding only silver(II) phthalocyanine is sufficiently volatile to give a spectrum without decomposition. The field desorption spectra of the four compounds examined all show the ions AgnXn ? 1 for X=acetate (n=1 ? 6), X=p-chlorobenzoate (n=1 ? 4), X=methanesulfonate (n=1 ? 7) and X=p-toluenesulfonate (n=1 ? 5). 相似文献
136.
The yield of 16OS18O from the 18OH initiated oxidation of CS2 in 16O2 was measured by using a discharge flow reactor coupled to a chemical ionization mass spectrometer. 16OS18O is the dominant SO2 isotopomer produced with a yield of 0.90 ± 0.20 relative to 18OH loss. The errors are estimates for the uncertainty at the 95% confidence level. The implications of these results to the understanding of the CS2 oxidation mechanism are discussed. © 1994 John Wiley & Sons, Inc. 1 This article is a US Government work and, as such, is in the public domain in the United States of America. 相似文献
137.
Mehrzad Mehran William J. Cooper Nahid Golkar Michael G. Nickelsen Eric R. Mittlefehldt Edward Guthrie Walter Jennings 《Journal of separation science》1991,14(11):745-750
The retention behavior of a heterogeneous group of solutes has been examined on seven different stationary phases under isothermal and temperature-programmed conditions. Both ΔHv (enthalpy of solute vaporization from the stationary phase) and ΔSv (entropy of solute vaporization from the stationary phase) values were determined for each solute – stationary phase combination under isothermal conditions. Both program rate and carrier gas velocity were shown to affect solute elution order. Unless these and other experimental factors discussed are controlled, column equivalency studies based on solute elution order have dubious value. 相似文献
138.
The ultrafast N-O bond fragmentation in a series of N-methoxypyridyl radicals, formed by one-electron reduction of the corresponding N-methoxypyridiniums, has been investigated as potentially barrierless electron-transfer-initiated chemical reactions. A model for the reaction involving the electronic and geometric factors that control the shape of the potential energy surface for the reaction is described. On the basis of this model, molecular structural features appropriate for ultrafast reactivity are proposed. Femtosecond kinetic measurements on these reactions are consistent with a kinetic definition of an essentially barrierless reaction, i.e., that the lifetime of the radical is a few vibrational periods of the fragmenting bond, for the p-methoxy-N-methoxypyridyl radical. 相似文献
139.
Jonathan V. Caspar B.Patrick Sullivan Edward M. Kober Thomas J. Meyer 《Chemical physics letters》1982,91(2):91-95
Values of non-radiative decay rate constants (knr) and emission energies (Ecm) have been obtained for Os(Phen3)2+ in a series of solvents and the results are consistent with the energy gap law. For hydroxylic solvents like water or methanol related studies suggest the existence of strong, specific contributions to the vibrational trapping energy of the solvent. 相似文献
140.
George Debney Edward E. Fairchild Jr. Stephen T. C. Siklos 《General Relativity and Gravitation》1978,9(10):879-887
In the Yang-Mills formulation of gravitational dynamics based uponSL(2,C) spin transformations acting on Dirac spinors, the vacuum field equations are R
+C
R
= 0 and and
. HereR
is the Ricci curvature andC
is the Weyl conformal curvature; is a coupling constant. We show the equivalence between solutions of these equations and the vacuum Einstein equationsR
= 0. The proof uses the Newman-Penrose formalism.Supported by a NATO fellowship.Supported by a SRC fellowship. 相似文献