排序方式: 共有35条查询结果,搜索用时 5 毫秒
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S. L. Ginzburg I. D. Luzyanin I. R. Metskhvarishvili É. G. Tarovik V. P. Khavronin 《Journal of Experimental and Theoretical Physics》2001,92(1):159-168
Linear and nonlinear dynamic response to the penetration of very weak magnetic fields (of the order of 10?2 Oe) into polycrystalline superconductors are studied theoretically and experimentally. The results of experiments are found to be in satisfactory agreement with the conclusions of the low-field electrodynamics. 相似文献
33.
Using recent results for the surface current density on cylindrical surfaces of arbitrary cross-section producing uniform
interior magnetic field and an assumed set of flux-fronts, solutions of Bean’s critical state model for cylindrical samples
with non-elliptic cross-section are presented. Magnetization hysteresis loops for two cross-sections with different aspect ratios are obtained.
A comparison with some exact results shows the limitations of this approach. 相似文献
34.
Kopylovich MN Kukushkin VY Haukka M Luzyanin KV Pombeiro AJ 《Journal of the American Chemical Society》2004,126(46):15040-15041
A novel and efficient method is reported for the preparation of phthalocyanines from phthalonitrile or its derivatives which utilizes low-cost reagents of hydrolytic stability, high simplicity, and easy accessibility, i.e., oximes, and proceeds via an unprecedented double addition of oximes to the nitrile group. 相似文献
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Luzyanin KV Kukushkin VY Kuznetsov ML Ryabov AD Galanski M Haukka M Tretyakov EV Ovcharenko VI Kopylovich MN Pombeiro AJ 《Inorganic chemistry》2006,45(5):2296-2306
The coupling between coordinated propiononitriles in trans-[PtCln(EtCN)2] (n = 2, 4) and the 1,2-hydroxylaminooximes HON(H)CMe2C(R)=NOH (R = Ph 1, Me 2) proceeds smoothly in CHCl(3) at ca. 40-45 degrees C and gives trans-[PtCln{NH=C(Et)ON(H)CMe2C(R)=NOH}2] (n = 2, R = Ph 5, Me 6; n = 4, R = Ph 7, Me 8) in 80-85% isolated yields. The reaction is highly regioselective, and both spectroscopic (IR; FAB+-MS; 1D 1H, 13C{1H}, and 195Pt NMR; and 2D 1H,13C HMQC, 1H,13C HMBC, and 1H,15N HMQC NMR) and X-ray data for 6-8 suggest that the addition proceeds exclusively via the hydroxylamine moiety of the 1,2-hydroxylaminooxime species; the existence of an oxime group remote from the nucleophile was also confirmed. Heating of 6 in air leads to its conversion to the unusual nitrosoalkane complex [PtCl2{HON=C(Me)C(Me)2N=O}] (9), whereas in the case of 5, only the metal-free salt [H3NC(Me)2C(Ph)=NOH]2(NO3)Cl.H2O (10) was isolated. To compare the kinetic aspects and trends in the addition of both types of nucleophiles (oximes and hydroxylamines; for the latter, see our recent work: Inorg. Chem. 2005, 44, 2944) to coordinated nitriles, a kinetic study of the addition of HON=C(CH2Ph)2 to [Ph3PCH2Ph][PtCl5(EtCN)] (11) to give [Ph(3)PCH(2)Ph][PtCl(5){NH=C(Et)ON=C(CH2Ph)2}] (12) was performed. The calculated rate constant k2 of 3.9 x 10(-6) M(-1) s(-1) at -20 degrees C for the addition of the oxime indicates that the hydroxylamine is, by a factor 1.7 x 10(4), more reactive toward the addition to nitriles than the oxime. Results of the synthetic, kinetic, and theoretical (at the B3LYP level of theory) studies have demonstrated that the high regioselectivity of the reactions of the 1,2-hydroxylaminooximes with ligated nitriles is both kinetically and thermodynamically controlled. 相似文献