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141.
Mohammad Mehdi Khodaei Davood Kordestani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2403-2405
Abstract Direct conversion of acylals to the corresponding bisulfites can be easily performed in the presence of bismuth (III) nitrate pentahydrate in ethanol at room temperature in good yields. 相似文献
142.
David J. Lunn Emre H. Discekici Javier Read de Alaniz Will R. Gutekunst Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):2903-2914
The development of “controlled” and “living” polymerization processes with high end-group fidelity has enabled an unprecedented range of polymeric materials with specific chain-end functionality to be prepared. This highlight provides an overview of available strategies and evaluation of recent approaches for the chain-end functionalization of polymers prepared through controlled chain-growth polymerizations. As a tribute to Professor Robert B. Grubbs on the occasion of his 75th birthday, we also take this opportunity to highlight methods for the chain-end modification of polymers prepared by ring-opening metathesis polymerization within the broader context of functional group tolerant, living polymerizations. Finally, we focus attention toward new directions in polymer chain-end modifications, describing existing gaps in current strategies, and detailing recently reported protocols that show significant improvements over traditional methods. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2903–2914 相似文献
143.
《Journal of Macromolecular Science: Physics》2012,51(8):689-721
AbstractIsotactic polybutene-1 exhibits excellent physical, mechanical and chemical properties dependent on its most important polymorphic crystal forms, called forms I, II and III. The most stable form, form I, is generated via a slow, solid-state transformation of the tetragonal, kinetically favored form II. The slow transformation rate of form II to I, accompanied by sample shrinkage, attains its maximum at ca 25?°C and takes 7–10?days, which is a technical problem for iPB-1 practical applications. We describe here the results reported in the literature by the authors and others of the effect of various physical factors that affect the transformation rate, with the goal of determining means of accelerating it; it is noted explanations of the effects are limited and in many cases, not given. 相似文献
144.
《Journal of mass spectrometry : JMS》2018,53(4):353-360
An ion‐mobility mass spectrometry study showed that the preferred O‐protonated form of p‐aminobenzoic in the gas phase can be converted to the thermodynamically less favored N‐protomer by in‐source collision‐induced ion activation during the ion transfer process from the atmospheric region to the first vacuum region if the humidity is high in the ion source. Upon the addition of water vapor to the nitrogen gas used to promote the solid analyte to the gas phase under helium‐plasma ionization conditions, the intensity of the ion‐mobility arrival‐time peak for the N‐protomer increased dramatically. Evidently, the ion‐activation process in the first vacuum region is able to provide the energy required to surmount the barrier to isomerize the O‐protomer to the more energetic N‐protomer. The transfer of the proton attached to the carbonyl oxygen atom of the O‐protomer to the amino group takes place by a water‐bridge mechanism. Apparently, the postionization transformations that take place during the transmission of ions from the atmospheric‐pressure ion source to the detector, via different physical compartments of low to high vacuum, play an eminent role in determining the population ratios eventually manifested at the detector. 相似文献
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146.
In this paper, we mainly study three types of gauge transformation operators for the q-mKP hierarchy. The successive applications of these gauge transformation operators are derived. And the corresponding communities between them are also investigated. 相似文献
147.
In this paper, we investigate a generalized nonautonomous nonlinear equation which describes the ultrashort optical pulse propagating in a nonlinear inhomogeneous fiber. By virtue of the generalized Darboux transformation, the first- and second-order rogue-wave solutions for the generalized nonautonomous nonlinear equation are obtained, under some variable–coefficient constraints. Properties of the first- and second-order rogue waves are graphically presented and analyzed: When the coefficients are all chosen as the constants, we can observe the some functions, the shapes of wave crests and troughs for the first- and second-order rogue waves change. Oscillating behaviors of the first- and second-order rogue waves are observed when the coefficients are the trigonometric functions. 相似文献
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The thermal behavior of zinc carbodiimide Zn(NCN) was examined in the temperature range between 200 and 1100 °C in Ar atmosphere. The material starts to partially decompose at about 800 °C. Heat treatment at temperatures beyond 800 °C results in the formation of the byproducts nitrogen-containing bamboo-like multiwall carbon-nanotubes of 20–50 nm in diameter due to a partial decomposition of Zn(NCN) into dicyan (CN)2, zinc and nitrogen gas followed by the polymerization of the former product to paracyanogen (CN)n. At 1100 °C, the yield of the residual carbodiimide depends on the dwelling time and the initial amount of powder used for pyrolysis. One hour dwelling at 1100 °C yields ∼50% of the Zn(NCN) separated as pure material. Temperature-induced change in the band structure, namely indirect-to-direct band gap transition, is registered when compared the Zn(NCN) at room temperature with the residual material annealed at 1100 °C. The transition from indirect (Eg = 4.32 eV) to direct band gap (Eg = 4.93 eV) is due to the thermal annealing process which results in healing of crystal defects. 相似文献