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排序方式: 共有406条查询结果,搜索用时 15 毫秒
41.
Marandino A De Martino L Mancini E Milella L De Feo V 《Natural product communications》2011,6(11):1735-1738
The essential oils of Hypericum perforatum, H. perfoliatum and H. hircinum, growing in Southern Italy, were analyzed by GC and GC/MS. In the three oils, 111 compounds in all were identified: 53 for the oil of H. hircinum (93.7% of the total oil), 55 for H. perforatum (96.5% of the total oil) and 63 for H. perfoliatum (98.7% of the total oil). The major fraction of the essential oils of H. perforatum and H. hircinum was represented by sesquiterpene hydrocarbons, while the monoterpene alpha-pinene, and the phenol thymol were the most abundant compounds in the essential oil of H. perfoliatum. The oils were evaluated for their potential in vitro phytotoxic activity against germination and early radicle elongation of Raphanus sativus and Lepidium sativum. The germination of this latter was significantly inhibited by the essential oil of H. hircinum, at the highest doses tested, whereas radicle elongation of garden cress was significantly inhibited by the essential oils of H. perfoliatum and H. hircinum. The radicle elongation of radish was inhibited by the essential oil of H. hircinum to a major extent and by H. perforatum and perfoliatum in a minor measure. 相似文献
42.
Abstract
We prove existence and uniqueness of a viscosity solution of the Dirichlet problem related to the prescribed Levi mean curvature
equation, under suitable assumptions on the boundary data and on the Levi curvature of the domain. We also show that such
a solution is Lipschitz continuous by proving that it is the uniform limit of a sequence of classical solutions of elliptic
problems and by building Lipschitz continuous barriers.
Keywords: Levi mean curvature, Quasilinear degenerate elliptic PDE’s, Viscosity solutions, Comparison principle, Global Lipschitz estimates 相似文献
43.
Martino Prizzi 《Journal of Differential Equations》2005,210(2):429-451
We study a non-autonomous parabolic equation with almost-periodic, rapidly oscillating principal part and nonlinear interactions. We associate to the equation a skew-product semiflow and, for a special class of nonlinearities, we define the Conley index of isolated compact invariant sets. As the frequency of the oscillations tends to infinity, we prove that every isolated compact invariant set of the averaged autonomous equation can be continued to an isolated compact invariant set of the skew-product semiflow associated to the non-autonomous equation. Finally, we illustrate some examples in which the Conley index can be explicitly computed and can be exploited to detect the existence of recurrent dynamics in the equation. 相似文献
44.
Summary The dielectric and electronic properties of thianthren (C6H4(S)2H4C6) are determined by means of optical reflectivity, absorption measurements and reflection electron energy loss spectroscopy.
The experimental results are interpreted on the basis of a Complete Neglect of Differential Overlap (CNDO) calculation used
in three different parametrization schemes. Emphasis is laid on the discussion of the problems which generally affect the
analysis of electron energy loss spectra, and a procedure to obtain the complex dielectric function from electron energy loss
measurements performed in the reflection mode is suggested.
Work partially supported by the MURST through the GNSM. 相似文献
45.
Summary The structural and electronic characterization of thieno [3,4-b][1,4]-diazepine and 1,5-benzodiazepine systems was carried
out by semi-empirical quantum-mechanical calculations. A number of electronic properties were computed and examined in order
to study the structure-activity relationship. Theoretical data indicate that the electronic rather than structural properties
appear primarily responsible for the variant degree of anticonvulsant activity exhibited by compounds 1–4. 相似文献
46.
Martino Bardi 《Journal of Differential Equations》1985,58(3):364-380
The method of moving parallel planes, previously used for elliptic and parabolic PDE, is adapted to study solutions of the Cauchy problem for Hamilton-Jacobi equations. This is possible in the framework of the theory of viscosity solutions, using the comparison theorem for such solutions as a kind of maximum principle. One of the main results states that if the initial data are nonnegative and compact supported, the Hamiltonian radial and the level sets expanding, then the level sets become asymptotically spherical as t → ∞, the convergence taking place in the Lipschitz norm. 相似文献
47.
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49.
P. Mison R. Chaabouni Y. Diab R. Martino A. Lopez A. Lattes F. W. Wehrli T. Wirthlin 《Magnetic resonance in chemistry : MRC》1976,8(2):79-89
13C chemical shifts for twenty-nine alkyl and phenyl substituted N-unsubstituted aziridines have been measured. Additivity parameters for methyl, phenyl and aziridyl carbons have been derived with the aim of testing the consistency of the assignments made on the basis of chemical shift considerations and off-resonance decoupling information. The observed chemical shifts are discussed in terms of steric and pseudoconjugation effects. 相似文献
50.
The use of resonantly enhanced stimulated Raman scattering for Q(J) transitions in hydrogen flouride permits a broad coverage of the far infrared spectrum. The tunability was about 5 cm-1 around several transitions (J = 0 to 5). The output power was measured up to 300 kW corresponding to a photon efficiency of 18%. 相似文献