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排序方式: 共有125条查询结果,搜索用时 0 毫秒
81.
82.
Y. Lemoigne R. Barate P. Bareyre P. Bonamy P. Borgeaud M. David F.X. Gentit G. Laurens B. Pietrzyk G. Villet S. Zaninotti P. Astbury A. Duane G.J. King B.C. Nandi R. Namjoshi D.M. Websdale J. Wiejak T. Marshall 《Physics letters. [Part B]》1982,113(6):509-512
The χ1++(3507) and the χ2++(3553) states have been observed in the Goliath spectrometer at the CERN SPS in 185 GeV/cπ?-Be collisions. Their radiative decays contribute 27.7% (for the χ1++) and 12.8% (for the χ2++) to production. At this energy, their cross sections are 65±19 nb and 96±29 nb, respectively 相似文献
83.
The first total and stereoselective synthesis of (E)-6, 10 dimethyl-9 methylidene undec-5-en-2-one: a constituant of Costus Root oil is reported. It was conducted with an overall yield of 22% from 1-methyl-2-oxo-methylcyclopentane carboxylate (α-methylated Dieckmann-ester) , used as a starting material. 相似文献
84.
Important motional narrowing has been previously experimentally observed by Dion and May in the isotropic Raman Q branch of pure gaseous HD in the fundamental vibrational band. A recent theoretical calculation of the present authors, in good agreement with these experiments, has shown that for pure HD only rotational mechanisms are efficient. In this paper, an infinite order treatment of the vibrational dephasing effects for HD perturbed by rare gases indicates an important role of these last effects in the broadening of the individual lines (particularly in the 0–2 band) leading to a significant decrease of the motional narrowing in the resulting band profile at high density. 相似文献
85.
Jeanine Llinars Jos Elguero Robert Faure Emile-Jean Vincent 《Magnetic resonance in chemistry : MRC》1980,14(1):20-24
13C NMR chemical shifts are reported for several alkyl or aryl amines, acetamides, diacetamides and ammonium and trimethylammonium salts. Substituent effects, determined with respect to chemical shifts of amino derivatives, are rationalized in terms of γ effects, steric interactions and for benzene derivatives, in terms of competition between inductive (σ1) and resonance (σR) effects. These perturbations can be used to assign chemical shifts of complex structures and to study certain chemical processes. 相似文献
86.
Lamsabhi AM Alcamí M Mó O Yáñez M Tortajada J 《The journal of physical chemistry. A》2006,110(5):1943-1950
The deprotonation of Cu2+ complexes with uracil, 2-thiouracil, 4-thiouracil, and 2,4-dithiouracil has been investigated by means of B3LYP/ 6-311+G(2df,2p)//6-31G(d) calculations. The most stable [(uracil-H)Cu]+ and [(thiouracil-H)Cu]+ complexes correspond to bidentate structures in which Cu interacts with the deprotonated ring-nitrogen atom and with the oxygen or the sulfur atom of the adjacent carbonyl or thiocarbonyl group. For 2- and 4-thiouracil derivatives, the structures in which the metal cation interacts with the thiocarbonyl group are clearly favored with respect to those in which Cu interacts with the carbonyl group. This is at variance with what was found to be the most stable structure of the corresponding Cu2+ complexes, where association to the carbonyl oxygen was always preferred over the association to the thiocarbonyl group. The [(uracil-H)Cu]+ and [(thiouracil-H)Cu]+ complexes can be viewed as the result of Cu+ attachment to the uracil-H and thiouracil-H radicals formed by the deprotonation of the corresponding uracil+* and thiouracil+* radical cations. As a matter of fact their relative stability is dictated by the intrinsic stability of the corresponding uracil-H and thiouracil-H radical and by the fact that, in general, the N3-deprotonated site is a better electron donor than the N1. In all complexes, the bonding of Cu both to nitrogen and sulfur and to nitrogen and oxygen has a significantly large covalent character. 相似文献
87.
William Buchmann Alexandre Boutorine Ludovic Halby Jeanine Tortajada Edwin De Pauw 《Journal of mass spectrometry : JMS》2009,44(8):1171-1181
A new method for the determination of the relative affinity of a ligand against various dsDNA sequences is presented by using electrospray ionization time‐of‐flight mass spectrometry (ESI‐QTOF) mass spectrometry. The principle is described here through the complexation of double‐stranded DNA by a polyamide ligand including twelve N‐methylpyrrole rings. However this method could be applied to other ligands especially when dissociation constants (Kd) are in nanomolar range. This method does not require knowing the ligand concentration accurately. It allows determination of the relative affinity of a ligand against various dsDNA sequences for 1 : 1 complex stoichiometries in a quick manner without labeling. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
88.
89.
Françoise Barrière Jean-Claude Barrière Derek H.R. Barton Jeanine Cleophax Alice Gateau-Olesker Stephan D. Géro Fatemeh Tadj 《Tetrahedron letters》1985,26(26):3121-3124
A cyclopentanoid building block has been synthesized in “one pot” cyclization process from epoxides - (which are readily accessible from (R,R)-(+) tartaric acid) with the carbanion derived from phenylthioacetonitrile (PhS-CH2-CN). 相似文献
90.