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1.
Physically meaningful solutions of the field equations for static spherical dust distributions in the Einstein-Cartan theory have been obtained. There is one in which the spin is zero at the center and another with zero spin at the boundary of the sphere. 相似文献
2.
Single-column ion-chromatography (SCIC) was investigated as a routine, rapid, precise and selective analytical method for the determination of chromium(VI) in aqueous extracts of soil and sewage sludge. Chromatographic parameters were optimized for determination of Cr(VI), NO(-)(3) and SO(2-)(4). A low-capacity resin-based column was used for the separation and the anions were determined by conductometric detection. p-Hydroxybenzoic acid (5mM) at pH 8.5 was used as the eluent. The limit of detection, defined as S/N = 3, was 92 mug/l. The resolution between Cr(VI) and SO(2-)(4) was 2.8, the precision ranged from 0.9% for NO(-)(3) to 2.0% for Cr(VI) with a 500-mul injection. The SCIC results for Cr(VI) agreed closely with those obtained by inductively coupled argon-plasma emission and spectrophotometry. 相似文献
3.
Sodium borohydride reduction of 3-methyl-2,3-dioxo-7,8-benzo-3-aza[3.3.3]propellan-6-one (1b) gave 2,4-dioxo-3-methyl-7,8-benzo-3-aza[3.3.3]propellan-6-ol, while lithium aluminum hydride reduction gave 3-methyl-7,8-benzo-3-aza[3.3.3]propellan-6-ol, which on oxidation, gave the corresponding ketone. This ketone formed the corresponding thioketal upon reaction with 1,2-ethanedithiol. Raney nickel desulfurization of the thioketal provided 3-methyl-6,7-benzo-3-aza[3.3.3]propellane. The same compound was also obtained in poor yield by forming the thioketal of Ib followed by lithium aluminum hydride reduction and Raney nickel desulfurization of the product. Desulfurization of the thioketal of Ib gave 2,4-dioxo-6,7-Benzo-3-aza[3.3.3]propellane. 相似文献
4.
The reaction of nucleophilic and non-nucleophilic bases wtih 2-carbamoyl-3-(γ-chloropropyl)-1-indenone ( 5 ) have been investigated. Condensation of γ-chlorobutyrophenone with malono-nitrile afforded α-cyano-β-(3-ehloropropyl)cinnamonitrile which was cyclized in concentrated sulfurie acid to produce 5 . Two other products obtained from the cyclization reaction were 2-carbamoyl-3-(γ-ehloropropylidene)-1-indanone ( 4 ) and α-carbamoyl-β-(3-chloropropyl)cinnam-amide. Treatment of a solution of 4 in ethyl acetate with piperidine resulted in cyclization of the γ-chloropropyl side chain to give 2-carbamoyl-3-cycIopropyl-1-indanone. The same compound was obtained in improved yield by the treatment of 4 or 5 with sodium hydroxide solution. The reaction of dirnethylamine with 5 in benzene gave initial Michael addition of the amine followed by internal alkylation of the carbanion so formed to yield 3a-dimethylamino-2,3,3a,8-tetrahydro-8-oxoeyclopent[a]indene-8a(lH)earboxamide ( 7a ). Similarly addition of ammonia, pyrrolidine, piperidine, benzenethiol, p-toluenethiol, 2-naphthalenethiol and nitromethane to the indenone I gave respective analogs of type 7 . Treatment of 5 with sodium cyanide in aqueous t-butyl alcohol resulted in a similar Michael addition followed by internal alkylation. In addition, cyclization between the nitrile and the carbamoyl functions occurred in the same step to give 2-oxo-4-imino-7,8-benzo-3-aza[3.3.3]-propellan-6-one ( 13a ). Hydrolysis of the iminopyrrolido ring in 13a to the corresponding suecin-irnide gave 2,4-dioxo-7,8-benzo-3-aza[3.3.3]propellan-6-one ( 13b ). Reactión of 13b with methyl iodide, allyl bromide, benzyl bromide, and diethyluminoethyl chloride afforded the corresponding N-alkylated products. A similar sequence starling with δ-ehlorovalerophenone led to 5,6-fused ring systems, including a [4.3.3]propellane. 2,9-Dioxo-4-methyl-7,8-benzo-3-aza[4.3.3]propell-4-ene was obtained by the reaction of 5 with acetone in dilute alkali. 相似文献
5.
Let X
1, X
2, ..., X
n be independent observations from an (unknown) absolutely continuous univariate distribution with density f and let % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% GabmOzayaajaGaaiikaiaadIhacaGGPaGaeyypa0Jaaiikaiaad6ga% caWGObGaaiykamaaCaaaleqabaGaeyOeI0IaaGymaaaakmaaqadaba% Gaam4saiaacUfadaWcgaqaaiaacIcacaWG4bGaeyOeI0Iaamiwamaa% BaaaleaacaWGPbaabeaakiaacMcaaeaacaWGObGaaiyxaaaaaSqaai% aadMgacqGH9aqpcaaIXaaabaGaamOBaaqdcqGHris5aaaa!5356!\[\hat f(x) = (nh)^{ - 1} \sum\nolimits_{i = 1}^n {K[{{(x - X_i )} \mathord{\left/ {\vphantom {{(x - X_i )} {h]}}} \right. \kern-\nulldelimiterspace} {h]}}} \] be a kernel estimator of f(x) at the point x, \s-<x<, with h=h
n
(h
n
O and nh
n
, as n) the bandwidth and K a kernel function of order r. Optimal rates of convergence to zero for the bias and mean square error of such estimators have been studied and established by several authors under varying conditions on K and f. These conditions, however, have invariably included the assumption of existence of the r-th order derivative for f at the point x. It is shown in this paper that these rates of convergence remain valid without any differentiability assumptions on f at x. Instead some simple regularity conditions are imposed on the density f at the point of interest. Our methods are based on certain results in the theory of semi-groups of linear operators and the notions and relations of calculus of finite differences.This research was supported in part by grants from the Natural Sciences and Engineering Research Council of Canada and the University of Alberta Central Research Fund. 相似文献
6.
7.
Localized state conduction through a variable-range hopping mechanism in the low-temperature region (~180–270 K) and thermally activated phonon-assisted tunneling in the higher-temperature region (~270–320 K) has been observed in a polycrystalline Sb35Se65 sample. 相似文献
8.
A. L. Mehra 《General Relativity and Gravitation》1980,12(3):187-193
In the present paper the field equations of general relativity have been solved to obtain the different solutions for the static charged gas sphere. These solutions are free from singularities and satisfy the necessary physical conditions. 相似文献
9.
Max Planck introduced the concept of zero-point energy in spring 1911. In the early struggles to establish the concept of the energy-quantum, it provided a helpful heuristic principle, to guide as well as supplement the efforts of some leading physicists in understanding the laws that applied in the atomic domain. The history and growth of this concept, and its application in the general development of quantum theory during the past many decades are studied under three principal headings: (1) The Birth of the Concept of zero-Point Energy; (2) Does Zero-Point Energy Really Exist? and (3) The Ground State of Quantum Systems. 相似文献
10.
Jagdish Mehra 《Foundations of Physics》1987,17(12):1141-1188
This article (Part II) deals with the creation of the theory of wave mechanics by Erwin Schrödinger in Zurich during the early months of 1926; he laid the foundations of this theory in his first two communications toAnnalen der Physik. The background of Schrödinger's work on, and his actual creation of, wave mechanics are analyzed.This article (in three parts) is an expanded version of the Schrödinger Centenary Lecture delivered by the author at CERN (Organisation Européenne pour la Recherche Nucléaire), 1211 Geneva 23, Switzerland, on July 30, 1987. 相似文献