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21.
Synthetic routes to BEDT-TTF derivatives bearing side chain carboxylic ester and amide groups are reported. Methyl ET-ethanoate was prepared in five steps from vinylacetic acid; amide groups were installed early in the synthesis by mixed anhydride methods before the final coupling reaction. 相似文献
22.
James W. Pavlik Theppawut Israsena Na Ayudhaya Chennagiri R. Pandit Supawan Tantayanon 《Journal of heterocyclic chemistry》2004,41(1):61-67
Trifluromethyl substitution on the pyrazole ring was found to enhance photoreactivity via the P4 pathway which involves interchange of the N2‐C3 ring atoms. Thus, 1‐methyl‐3‐(trifluromethyl)pyrazole (1) and 1‐methyl‐5‐(trifluromethyl)pyrazole (3) transposed with a P4/P6 or P4/P6+P7 ratio of 2.1:1. 1‐methyl‐4‐(trifluromethyl)pyrazole (2) transposed regiospecifically by the P4 transposition pathway. Compounds 2 and 3 were also observed to undergo photocleavage to yield enaminonitrile and enaminoisocyanide products. 相似文献
23.
J.J. Pan Xiangdong Qiu Kejian Guan Liang Dong FengQing Zhou Wei Wang Mingjie Zhang James Guo Jun Yang Chunmeng Wu 《光学学报》2003,23(Z1)
A low cost, coolerless 980nm diode pumped, gain flattened L band EDFA with fast transient control, high pump efficiency and gain clamping effect was realized by using FBGs as C band seed generators. 相似文献
24.
Ching Sum Hui Lillian Sze Man Lam Chun Yin Wai Kin Chan Aleksandra B. Djurii 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1708-1715
Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003 相似文献
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Broadband dielectric spectroscopy was used to study the segmental (α) and secondary (β) relaxations in hydrogen‐bonded poly(4‐vinylphenol)/poly(methyl methacrylate) (PVPh/PMMA) blends with PVPh concentrations of 20–80% and at temperatures from ?30 to approximately glass‐transition temperature (Tg) + 80 °C. Miscible blends were obtained by solution casting from methyl ethyl ketone solution, as confirmed by single differential scanning calorimetry Tg and single segmental relaxation process for each blend. The β relaxation of PMMA maintains similar characteristics in blends with PVPh, compared with neat PMMA. Its relaxation time and activation energy are nearly the same in all blends. Furthermore, the dielectric relaxation strength of PMMA β process in the blends is proportional to the concentration of PMMA, suggesting that blending and intermolecular hydrogen bonding do not modify the local intramolecular motion. The α process, however, represents the segmental motions of both components and becomes slower with increasing PVPh concentration because of the higher Tg. This leads to well‐defined α and β relaxations in the blends above the corresponding Tg, which cannot be reliably resolved in neat PMMA without ambiguous curve deconvolution. The PMMA β process still follows an Arrhenius temperature dependence above Tg, but with an activation energy larger than that observed below Tg because of increased relaxation amplitude. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3405–3415, 2004 相似文献
27.
According to a multiphase mixture theory, we have mathematically developed a multiphysical model with chemoelectromechanical coupling considerations, termed the multieffect‐coupling electric‐stimulus (MECe) model, to simulate the responsive behavior of electric‐sensitive hydrogels immersed in a bath solution under an externally applied electric field. For solutions of the MECe model consisting of coupled nonlinear partial differential governing equations, a meshless Hermite–Cloud method with a hierarchical iteration technique has been used for a one‐dimensional steady‐state analysis of a hydrogel strip. The computed results are compared with the experimental data, and there is very good agreement. Simulations within the domains of both hydrogels and surrounding solutions also present distributions of the ionic concentrations and electric potential as well as the hydrogel displacement. The effects of various physical parameters on the response behavior of electric‐stimulus responsive hydrogels are discussed in detail. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1514–1531, 2004 相似文献
28.
In his curriculum vitae, John Hawkes lists his research interestsas geometric measure theory, probability (Lévy processes),and potential theory (probabilistic). In fact, he made significantcontributions to all three areas, and there are strong relationshipsbetween them. He used both geometric measure theory and potentialtheory as tools for his study of the trajectories of particularLévy processes, but in many cases he needed to developthe tool before it was ready to be used. We will summarise hisresearch later, but first we discuss what is known of his lifehistory. 相似文献
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Let f :X→X be a continuous map of a compact metric space to itself. We prove that f is topologically conjugate to an adding machine map if and only if X is an infinite minimal set for f and each point of X is regularly recurrent. Moreover, if X is an infinite minimal set for f and one point of X is regularly recurrent, then f is semiconjugate to an adding machine map. 相似文献