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91.
Experimental evidence for the formation of HXeCCH: the first hydrocarbon with an inserted rare-gas atom 总被引:1,自引:0,他引:1
Feldman VI Sukhov FF Orlov AY Tyulpina IV 《Journal of the American Chemical Society》2003,125(16):4698-4699
Combined FTIR and EPR studies of acetylene irradiated with fast electrons in a solid xenon matrix provide experimental evidence for the formation of HXeCCH, a novel-type organic molecule with an inserted rare-gas atom. The new species resulting from the reaction of H atoms with CCH radicals in xenon was characterized by an intense IR absorption at 1486.0 cm(-1) corresponding to Xe-H stretching. 相似文献
92.
A technique is suggested for evaluating the properties of alkane conformers using the parameters of internal rotation of interdependent C-C bonds. To determine the mean conformational composition of a rotational equilibrium mixture of alkane conformers, one need not exhaust the latter because the contribution of the conformation energy to alkane enthalpy can be expressed in terms of the product of tensors with further convolution over indices. 相似文献
93.
Vladimir V. Kouznetsov Fedor I. Zubkov Eugenia V. Nikitina 《Tetrahedron letters》2004,45(9):1981-1984
An unprecedented intramolecular Friedel-Crafts ipso-alkylation at the ortho-alkyl group of the N-arylamino moiety of 1-allyl-1-N-arylaminocycloalkanes to give alkyl substituted dihydrospiro[(1H) quinoline-2,1′-cycloalkanes] is reported. Unexpected results were explained in the context of intramolecular ipso-substitution of alkyl groups and their 1,2-rearrangement. A plausible mechanism for this type of Friedel-Crafts alkylation by an alkene moiety promoted by a Brönsted acid (H2SO4) is proposed. 相似文献
94.
V. F. Kurshetsov Yu. M. Antipov A. V. Artamonov V. A. Batarin O. V. Eroshin V. Z. Kolganov A. S. Konstantinov A. P. Kozhevnikov A. E. Kushnirenko L. G. Landsberg V. M. Leontiev G. S. Lomkatsi V. V. Molchanov V. A. Mukhin A. F. Nilov D. I. Patalakha S. V. Petrenko V. T. Smolyankin D. V. Vavilov V. A. Victorov 《Physics of Atomic Nuclei》2005,68(3):439-454
A search for narrow Θ+(1540), a candidate for a pentaquark baryon with positive strangeness, has been performed in an exclusive proton-induced reaction $p + C(N) \to \Theta ^ + \bar \kappa ^0 + C(N)$ on carbon nuclei or quasifree nucleons at $E_{beam} = 70GeV(\sqrt s = 11.5GeV)$ studying nK +, pK S 0 , and pK L 0 decay channels of Θ+(1540) in four different final states of the $\Theta ^ + \bar K^0 $ system. In order to assess the quality of the identification of the final states with neutron or K L 0 , we reconstructed Λ(1520) → nK S 0 and ? → K L 0 K S 0 decays in the calibration reactions p + C(N) → Λ (1520)K ++C(N) and p+C(N) → p?+C(N). We found no evidence for a narrow pentaquark peak in any of the studied final states and decay channels. Assuming that the production characteristics of the $\Theta ^ + \bar K^0 $ system are not drastically different from those of the Λ(1520)K + and p? systems, we established upper limits on the cross-section ratios $\sigma (\Theta ^ + \bar K^0 )/\sigma (\Lambda (1520)K^ + ) < 0.02$ and $\sigma (\Theta ^ + \bar K^0 )/\sigma (p\phi ) < 0.15$ at 90% C.L. and a preliminary upper limit for the forward-hemisphere cross section $\sigma (\Theta ^ + \bar K^0 )$ nb/nucleon. 相似文献
95.
96.
Zubkov FI Nikitina EV Turchin KF Aleksandrov GG Safronova AA Borisov RS Varlamov AV 《The Journal of organic chemistry》2004,69(2):432-438
The reactions of 3-acetyl-3-aza-11-oxatricyclo[6.2.1.0(1,6)]undec-9-ene and its 9,10-epoxy derivative with bromine and Ac(2)O/BF(3).OEt(2) under different conditions were studied. Unusual products of Wagner-Meerwein rearrangement bearing the olefin fragment (5-aza-2-oxatricyclo[6.2.1.0(3,9)]undecen-3-enes) were isolated and characterized by X-ray analysis. 相似文献
97.
The oriented diameter of a bridgeless connected undirected (bcu) graph G is the smallest diameter among all the diameters of strongly connected orientations of G. We study algorithmic aspects of determining the oriented diameter of a chordal graph. We (a) construct a linear‐time approximation algorithm that, for a given chordal bcu graph G, finds a strongly connected orientation of G with diameter at most one plus twice the oriented diameter of G; (b) prove that, for every k ≥ 2 and k # 3, to decide whether a chordal (split for k = 2) bcu graph G admits an orientation of diameter k is NP‐complete; (c) show that, unless P = NP, there is neither a polynomial‐time absolute approximation algorithm nor an α‐approximation algorithm that computes the oriented diameter of a bcu chordal graph for α < . © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 255–269, 2004 相似文献
98.
99.
We present a systematic study of asymptotic behaviour of (generalised) ζ-functions and heat kernels used in noncommutative geometry and clarify their connections with Dixmier traces. We strengthen and complete a number of results from the recent literature and answer (in the affirmative) the question raised by M. Benameur and T. Fack (2006) [1]. 相似文献
100.