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101.
The principle of displacement substoichiometry and the possibilities of its practical use have been outlined. The substoichiometric separation of lead, arsenic, and zinc can be carried out by applying diethyldithiocarbamate complexes and solvent extraction.  相似文献   
102.
A new signal decomposition for repetitive signatures is introduced. This is based on the concept of derived time series, produced by rearranging the original signal by using points one period apart. Time domain averaging is shown to be a special case of such rearrangement, and a second technique of variance analysis is presented. Applications to rotating machinery show that the decomposition can be very sensitive to various generating mechanisms, making them suitable for signature analysis of mechanical systems.  相似文献   
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Synthesis and Investigation of Aminosulphur Trifluorides and of a Hydrolysis Product 1-(Fluorooxothio)-2,5-dihydropyrrole The reaction of previously unknown (trimethylsilyl)amines with sulphur tetrafluoride gives some new aminosulphurtrifluorides. Experiments to cleaver 1-(Trifluorothio)-2,5-dihydropyrrole and 1-(trifluorothio)pyrrolidin into butadiene and ethylene respectively and NSF3 by way of a chelotrope cycloelimination were unsuccessful. 1H-NMR and 19F-NMR spectra revealed the nitrogen in the aminosulphur trifluorides must be regarded sp3 hybridized rather than sp2.  相似文献   
105.
The static vessel pyrolysis of bicyclo[2.2.2]octa-2,5,7-triene (barrelene) has been studied between 483 and 523 K. The products were acetylene and benzene (in equal quantities) with no other detectable C8H8 isomer (down to less than 1% of total). The time dependence fitted first-order kinetics, and the data are consistent with a homogeneous unimolecular reaction close to, if not at, its high-pressure limit at 0.25 torr. The rate constant was fitted to the Arrhenius equation These Arrhenius parameters are shown to imply a concerted single-step process. Alternative mechanisms are discussed and a comparison is made with the retro-Diels—Alder reactions of other bicyclo[2.2.2]octa-olefin systems.  相似文献   
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We analyze the momentum space triple pomeron vertex in perturbative QCD. In addition to the standard form of this vertex which is used in the context of total cross sections at high energies and in the QCD reggeon field theory, there exists an alternative form which has to be used in the study of high-mass diffraction. We review and analyze the relation between these two versions. We discuss some implications for the BK equation. In the second part of our paper we extend this analysis to the pomeron-odderon-odderon vertex.Received: 11 January 2005, Revised: 24 January 2005, Published online: 3 March 2005  相似文献   
110.
Studying the properties and stability of silicon nanoparticles (Si-np) in aqueous environments may lead to novel applications in biological systems. In this work, we use absorption and photoluminescence (PL) spectroscopy to characterize ultrasmall Si-np prepared through anodic etching and ultrasonic fractionation of a crystalline Si wafer. Their behavior is studied over time in 2-propanol and during treatments with water, NaOH, HCl, and H(2)O(2). The observed population is divided into two types of material: bright species consisting of well-etched Si-np, approximately 1 nm in diameter, and dark species derived from partially etched or aggregated Si structures. The dark material is seen by its scattering in the 2-propanol and water solutions and is largely removed via precipitation with the NaOH or HCl treatment. The bright material includes three distinct species with their respective emissions in the UV-B, UV-A, and hard-blue regions of the spectrum. The hard-blue PL is shown to have a simple pH dependence with a pK(a) approximately 3, providing an important insight into its chemical origin and signaling for possible application of Si-np as environmental probes. Our results offer some potential for tailoring the PL properties of ultrasmall Si-np through control of their surface chemistry.  相似文献   
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