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71.
72.
Bruce D Jacobs Soon-Jae Kwon Leslie D Field Robert K Norris David Randles Karen Wilson Timothy A Wright 《Tetrahedron letters》1985,26(29):3495-3498
The SRN1 reaction between sterically hindered p-nitrobenzylic substrates and tertiary carbanions gives C-alkylated products whose yields depend on the steric bulk of both the benzylic substrate and the carbanion, and on the nature of the groups in the carbanion. 相似文献
73.
1,2-Diaminoethane and 2-aminoethanol-1 were added to the isobutane plasma of a chemical ionization mass spectrometer. The resulting reactant gas mixture did not react with additives containing a single oxygen functional group. Addition reactions were observed with some additives containing multiple oxygen functions. Additives containing nitrogen functions were protonated by the reactant mixture. The relative proportion of protonation to addition depended on the ability of the additive to chelate the reactant ion and on the basicity of the additive. This use of 1,2-diaminoethane and 2-aminoethanol-1 provides a convenient method of varying the reactivity of the plasma in a chemical ionization source. 相似文献
74.
We determine the invariant cross section for pp→ψ(3100)+X near x6=0 at NAL and ISR energies using the assumption that all large p⊥ single leptons originate from the ψ. We adequately reproduce the single lepton data, and by suitable extrapolarion in x6 ensure agreement with the NAL ψ production data (x6?0.3). The magnitude of the resulting ψ production cross section is, however, roughly a factor of 3 larger than that observed by the recent CCRS-ISR experiment. 相似文献
75.
Poly(methyl vinyl ether-alt-ammonium maleamate), when heated at up to 100°C while removing volatiles, is converted to polymer whose infrared, elemental analysis and Tg are consistent with a structure predominantly that of poly(methyl vinyl ether-alt-maleic anhydride). Maleimide comonomer units are a substantially lesser component. Evidence is presented that a part of the reaction sequence may involve hydrolysis of imide or amide. 相似文献
76.
H.J. Behrend Ch. Chen H. Fenner J.H. Field V. Schr?der H. Sindt G. DAgostini W.D. Apel S. Banerjee J. Bodenkamp D. Chrobaczek J. Engler G. Flügge D.C. Fries W. Fues K. Gamerdinger G. Hopp F. Pierre 《Physics letters. [Part B]》1982,114(4):282-286
The e+e?→τ+τ? process has been measured using the CELLO detector at a mean total centre of mass energy of 34.2 GeV using essentially all the decay channels of the τ lepton. The measured cross section yields Rτ=1.03±0.05 (stat)±0.07 (syst). Topological branching fraction are given for τ → 1, 3 or 5 charged tracks. The angular distribution shows a clear 1 + cos2θ dependance with a forward-backward asymmetry of -0.103 ± 0.052 corresponding to an axial-vector coupling aτ of the τ to the weak neutral current given by aτ=?1.12 ± 0.57. 相似文献
77.
A pressure vessel with four radial windows was designed in which to conduct equation-of-state experiments at pressures up to 1 GPa (145,000 psi). To determine the relative safety of the vessel, the stress distribution in the cylindrical sidewalls, particularly the stress concentration near the window openings, was studied. Conventional analysis was used for the initial evaluation but was found to give somewhat higher stress values than were actually present. Better determinations of the stress distribution were obtained by photoelastic analysis of a model of the pressurevessel linear and by proof tests with strain gages of the actual liner and the assembled pressure vessel. Apparently, the tapered sapphire windows, loaded in compression by the internal pressure in the vessel, modify the stress distribution sufficiently to allow operation at higher pressures than otherwise would be attainable. Design features of the pressure vessel are presented, together with a synoptic stress analysis, a photoelastic analysis, and results of the strain-gage studies. 相似文献
78.
The diastereoroeric charge-transfer complexes formed between the two enantiomers of 2,15-dimethoxy[6]helicene and R(?)2-(2,4,5,7-tetranitro- 9-fluorenyloximino)propanoic acid have quite distinct geometries, revealed by NMR. 相似文献
79.
C. Linton M. Dulick R.W. Field P. Carette P.C. Leyland R.F. Barrow 《Journal of Molecular Spectroscopy》1983,102(2):441-497
The electronic spectrum of the CeO molecule is characterized by the existence of many 0-0 bands resulting from transitions between various Ω components of excited states and the 16 lower Ω states which arise from the lowest configuration… (4f)(6s). Classical studies of rotational structure of absorption and emission spectra have been extended, and argon-ion and tunable dye (coumarin 460, rhodamine 6G, rhodamine 101) lasers have been used to excite known transitions in bands which had previously been rotationally analyzed. The resulting fluorescence spectra have been used to establish the relative energies of the lower states. By tuning the lasers to excite analyzed transitions from different known electronic states it has been possible to determine the energies of 16 low-lying states, to assign quantum numbers to 14 with certainty, and to suggest assignments for the other 2. The resulting energy level diagram of lower states is discussed and shown to correlate well with the 4f6s configuration of the Ce2+ ion. From the energies of the low-lying states, those of the higher excited states are calculated and in some cases new values of vibrational and rotational constants are derived. 相似文献
80.
<正>With the evolution of a laser pulse in water,the formation of a nonlinear X wave during femtosecond filamentation is investigated based on numerical simulations.In particular,we analyze the far-field angularly resolved spectra obtained for different temporal portions of the ultrashort pulse during its propagation. Our result shows that the refocusing of ultrashort pulse leads to the formation of dynamic X wave which essentially manifests itself as conical emission. 相似文献