排序方式: 共有35条查询结果,搜索用时 31 毫秒
31.
Stanislas Mayer Axelle Arrault GRald Guillaumet Jean‐Yves Mrour 《Journal of heterocyclic chemistry》2001,38(1):221-225
Ethyl 3,4‐dihydro‐2H‐1,4‐benzoxazine‐3‐carboxylate derivatives 2 were obtained and isolated in low yields from the condensation of 2‐aminophenol and ethyl 2,3‐dibromopropanoate. They can be obtained by hydrogenation of ethyl 2H‐1,4‐benzoxazine‐3‐carboxylate in satisfactory yield. Using 2‐iminophenol did not direct the condensation with ethyl 2,3‐dibromopropanoate towards 2 but was fruitfull for the preparation of ethyl 2‐(4‐benzyl‐3,4‐dihydro‐2H‐1,4‐benzoxazin‐3‐yl)acetate from ethyl bromocrotonate. 相似文献
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Although deterministic chaos has been predicted to occur in the triply resonant optical parametric oscillator (TROPO) 15 years ago, experimental evidence of chaotic behavior in this system has been lacking so far, in marked contrast with most nonlinear systems, where chaos has been actively tracked and found. This situation is probably linked to the high sensitivity of the TROPO to perturbations, which adversely affects stationary operation at high power. We report the experimental observation in this system of a burst of irregular behavior of duration 80 micros. Although the system is highly nonstationary over this time interval, a topological analysis allows us to extract a clear-cut signature of deterministic chaos from a time series segment of only nine base cycles (3 micros). This result suggests that nonstationarity is not necessarily an obstacle to the characterization of chaos. 相似文献
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Two-frequency operation of a composite Er,Yb:glass-LiTaO3 monolithic microlaser is demonstrated at 1.53 microm. The thermo-optic effect of the intracavity birefringent crystal makes it possible to control the wavelengths of the two orthogonal linearly polarized eigenstates. It provides a tunable beat note from 0 to 60 GHz. Direct evaluation of the Lamb-type coupling constant C between the two eigenstates is obtained from a single intensity noise spectrum measurement, yielding values from 0.33 to 0.86, depending on transverse and axial distributions of the eigenstates. Applications to radar and telecommunication systems are discussed. 相似文献
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Sandrine Duluard Joseph Grondin Jean‐Luc Bruneel Isabelle Pianet Axelle Grlard Guy Campet Marie‐Hlne Delville Jean‐Claude Lassgues 《Journal of Raman spectroscopy : JRS》2008,39(5):627-632
The Raman spectra of (1 − x)(BMITFSI), xLiTFSI ionic liquids, where 1‐butyl‐3‐methylimidazolium cation (BMI+) and bis(trifluoromethane‐sulfonyl)imide anion (TFSI−) are analyzed for LiTFSI mole fractions x < 0.4. As expected from previous studies on similar TFSI‐based systems, most lithium ions are shown to be coordinated within [Li(TFSI)2]− anionic clusters. The variation of the self‐diffusion coefficients of the 1H, 19F, and 7Li nuclei, measured by pulsed‐gradient spin‐echo NMR (PGSE‐NMR) as a function of x, can be rationalized in terms of the weighted contribution of BMI+ cations, TFSI− ‘free’ anions, and [Li(TFSI)2]− anionic clusters. This implies a negative transference number for lithium. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献