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排序方式: 共有232条查询结果,搜索用时 15 毫秒
61.
62.
Hong B Haddad M Maley F Jensen JH Kohen A 《Journal of the American Chemical Society》2006,128(17):5636-5637
The nature of a H-transfer in the thymidylate synthase catalyzed reaction was investigated by comparison of the wild-type enzyme with the W80M mutant. The nature of the H-transfer was not affected, as indicated by intrinsic isotope effects and their temperature dependence. These findings support a single-step hydride transfer instead of a two-step radical transfer. 相似文献
63.
64.
Two model compounds (3 and 4) having the typical α-tocopherol-type substitution pattern of the aromatic ring, but lacking the annulated pyran ring, have been synthesized. Upon oxidation, the two possible ortho-quinone methides (oQMs) of each are formed in equal ratio. DFT calculations suggest that there is no angular strain in 3 and 4, and each of the oQM pairs is of similar energy. These results prove that the commonly observed regioselectivity in oxidations of vitamin E-type model compounds is not an electronic substitution effect, but a consequence of annulation. 相似文献
65.
Amnon Besser 《Israel Journal of Mathematics》2000,120(1):335-359
We show that the ad hoc regulator of Coleman and de Shalit for elements ofK
2 of curves evaluated on a holomorphic differential is the same as the syntomic regulator of the same elements cup produced
with the same differential. Combined with the results of Coleman and de Shalit this gives a relation between syntomic regulators
and special values ofp-adicL-functions. The main technical innovation is the notion of a local index — a kind of generalized residue. 相似文献
66.
Let X be a compact symplectic manifold, K a compact group acting symplectically on X, and assume there is a moment map. In [3], Kirwan defined a stratification on X, and showed that the associated spectral sequence degenerates. In this note, we ask whether this degeneration comes from
a stable splitting of X into Thom spaces on the strata. One can also ask a related arithmetic question. Is it true that the splitting Kirwan discovered
respects the action of Galois groups?
Received: 20 March 1997 相似文献
67.
68.
From analysis of the high Q modes in a Bragg onion resonator with an omnidirectional reflector cladding, we establish a close analogy between such a resonator and a spherical hollow cavity in perfect metal. We demonstrate that onion resonators are ideal for applications that require a large spontaneous-emission factor beta, such as thresholdless lasers and single-photon devices. 相似文献
69.
Yariv A 《Optics letters》2005,30(17):2191-2193
A methodology for treating the semiconductor laser as a current-controlled oscillator in an optical phase-lock loop is presented. The formalism is applied to phase demodulation of optical beams, reduction of phase noise by self-homodyning, and phase locking of a semiconductor laser array. 相似文献
70.
Amnon Neeman 《K-Theory》2000,20(2):97-174
Let A and B be Abelian categories. Let H: A B be a bounded -functor. We prove that H induces a natural map in higher K-theory. From a more precise analysis of the proof, we deduce that it is possible to define a K-theory of the bounded derived category of A, which contains Quillen's K-theory of A as a retract. 相似文献