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141.
We show that helical turbulence produced during a first-order phase transition generates circularly polarized cosmological gravitational waves (GWs). The characteristic frequency of these GWs for an extreme case of the phase transition model is around 10(-3)-10(-2) Hz with an energy density parameter as high as 10(-12)-10(-11). The possibility of detection is briefly discussed. 相似文献
142.
We report second-order rate constants of kDO = 120 dm(3) mol(-1) s(-1) and kB = 6.4 x 10(-4) dm(3) mol(-1) s(-1) for exchange for deuterium of the first alpha-methylene proton of the 4-(aminomethyl)pyridine dication in D2O at 25 degree C and I= 1.0 (KCl). These data are consistent with a carbon acid pKa between 17 and 19 for ionization of this simple carbon acid and they show that the effect of an alpha-pyridinium substituent on carbon acidity is similar to that of an alpha-ester substituent. 相似文献
143.
The synthesis of three fluorophore-appended derivatives of dioscin and polyphyllin D is reported herein. Starting from trillin, dansyl derivatives A-C were prepared in overall yields of 7-12% over 7-10 steps. A study of their behavior in a variety of polar solvents suggests that dansyl derivatives A-C are capable of micellar self-assembly and can maintain cytotoxicities (IC50 = 15-18 muM) against the HeLa carcinoma cell line evaluated by standard MTT assay. [structure: see text] 相似文献
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[reaction: see text] A new sequence for the synthesis of various 2,4-disubstituted oxazoles from alpha-amino acids is reported. The method is shown to be general and incorporates the reagent combination, triphenylphosphine/hexachloroethane, for cyclodehydration of intermediate alpha-acylamino aldehydes. Implementation of this reagent system for the conversion of alpha-acylamino ketones to oxazoles is briefly investigated. 相似文献
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