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61.
Peng Xi Yuqing Duan Pengfei Fei Lei Xia Ran Liu Bowen Cheng 《European Polymer Journal》2012,48(7):1295-1303
Based on the phase change theory, a novel tetrahydroxy compound (THCD) was designed and prepared. Depending on the spatial structure of the tetrahydroxy compound, a form-stable thermoplastic polyurethane solid–solid phase change material (TPUPCM) was synthesized via employing PEG as soft segments, while multi-benzene ring structure made by 4,4′-diphenylmethane diisocyanate and tetrahydroxy compound as hard segments. The composition and structure of THCD and TPUPCM, the TPUPCM’s the weight average molecular weight and number average molecular weight, dissolving and melting abilities, phase change behaviors, thermal performances and crystalline morphology were investigated by Fourier transform infrared spectrometer, 1H nuclear magnetic resonance spectrometer, multiangle laser light scattering apparatus, differential scanning calorimentry, dynamic mechanical thermal analysis, thermogravimetry analysis system, wide-angle X-ray diffraction, polarizing optical microscopy. The results show that the solid–solid phase change material owns excellent phase change properties and a broad processing temperature range. The heating cycle phase change enthalpy is 137.4 J/g, and the cooling cycle phase change enthalpy is 127.6 J/g. The started decomposition temperature and the maximum decomposition temperature are at 323.5 and 396.2 °C, respectively. Furthermore, the solid–solid phase change material is dissolvable, meltable and can be processed directly, and has great potential applications in thermal energy storage. 相似文献
62.
63.
9-Methylfluorene was tested as an indicator in the titration of commonly used organometallic reagents. This indicator is readily prepared in three steps from fluorenone. In THF solution the deprotonated indicator is red and exhibits a sharp endpoint. The highly basic reagents sec-butyllithium and tert-butyllithium can be titrated in ether solution, where the color of the deprotonated indicator is yellow. 相似文献
64.
It is shown that the ‘metastable’ mass spectra of a series of monosubstituted benzenes are consistent with reaction over the lowest available energy surfaces. The non-occurrence of some qualitatively possible decomposition pathways may therefore be used to place lower limits on the heats of formation of gaseous cations. Conversely, where characterized reactions are preempted by new reactions upon introduction of additional substituents, upper limits may be placed upon the heats of formation of the ionic products of the new reactions. The concepts are employed to deduce that C3H6 elimination from n-butylbenzence subsequent to ionization leads to ionized toluene rather than ionized methyleneclohexadience. 相似文献
65.
66.
67.
Lewis Bowen 《Geometriae Dedicata》2003,98(1):211-226
We prove the following conjecture of G. Fejes Toth, G. Kuperberg, and W.Kuperberg: every body K in either n-dimensional Euclidean or n-dimensional hyperbolic space admits a completely saturated packing and a completely reduced covering. Also we prove the following counterintuitive result: for every >0, there is a body K in hyperbolic n-space which admits a completely saturated packing with density less than but which also admits a tiling. 相似文献
68.
69.
Lesley A. Chesson Luciano O. Valenzuela Gabriel J. Bowen Thure E. Cerling James R. Ehleringer 《Rapid communications in mass spectrometry : RCM》2011,25(24):3713-3722
Published datasets of proteinaceous animal tissues suggest that co‐variation between amino acid hydrogen (δ2H) and oxygen (δ18O) isotope ratios is a common feature in systems where isotopic variation is driven by geographic or temporal variation in the δ2H and δ18O values of environmental water. This has led to the development of models relating tissue δ2H and δ18O values to those of water, with potential application in a number of fields. However, the strength and ubiquity of the influence of environmental water on protein isotope ratios across taxonomic groups, and thus the relevance of predictive models, is an open question. Here we report strong co‐variation of δ2H and δ18O values across a suite of terrestrial and aquatic animal meats purchased in American food markets, including beef, poultry (chicken and turkey), chicken eggs, pork, lamb, freshwater fish, and marine fish. Significant isotope co‐variation was not found for small collections of marine bivalves and crustaceans. These results imply that isotopic signals from environmental water were propagated similarly through most of the diverse natural and human‐managed foodwebs represented by our samples. Freshwater fish had the largest variation in δ2H and δ18O values, with ranges of 121 ‰ and 19.2 ‰, respectively, reflecting the large isotopic variation in environmental freshwaters. In contrast marine animals had the smallest variation for both δ2H (7 ‰ range, crustaceans) and δ18O (3.0 ‰ range, bivalves) values. Known‐origin beef samples demonstrated direct relationships between the variance of environmental water isotope ratios and that of collected meats. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
70.
Yuanlin Ren Bowen Cheng Jinshu Zhang Weimin Kang Zhenhuan Li Xupin Zhuang 《Frontiers of Chemistry in China》2009,4(2):136-141
The thermal decomposition kinetics of the N,N′-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxan-2-yl) ethylenediamine (DPTDEDA) in air were studied by TGDTG techniques. The
kinetic parameters of the decomposition process for the title compound in the two main thermal decomposition steps were calculated
through the Friedman and Flynn-Wall-Ozawsa (FWO) methods and the thermal decomposition mechanism of DPTDEDA was also studied
with the Coats-Redfern and Achar methods. The results show that the activation energies for the two main thermal decomposition
steps are 128.03 and 92.59 kJ·mol−1 with the Friedman method, and 138.75 and 106.78 kJ·mol−1 with the FWO method, respectively. Although there are two main thermal decomposition steps for DPTDEDA in air, the thermal
decomposition mechanism of DPTDEDA in the two steps are the same, i.e. f(α) = 3/2(1 − α)4/3[(1 − α)−1/3 − 1]−1.
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Translated from Acta Chimica Sinica, 2008, 66(9) (in Chinese) 相似文献