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211.
Phase boundaries near the bicritical point (Tb = 64.74 ± 0.01 K, Hb = 118.45 ± 0.4 kOe) of the uniaxial antiferromagnet MnF2 were redetermined with higher precision from ultrasonic attenuation measurements. The results are compared with recent theories of Fisher et al. 相似文献
212.
L.C. Dennis K.R. Cordell R.R. Doering R.L. Parks S.T. Thornton J.L.C. Ford J.Gomez Del Campo D. Shapira 《Nuclear Physics A》1981,357(2):521-532
Excitation functions at 7° (lab) have been measured from Ec.m. = 5.1 to 11.4 MeV in approximately 114 keV steps for 15 groups of final states in 17O populated by the 12C(9Be, α) reaction. Statistical tests have been used to locate possible non-statistical structure in the excitation functions. Possible anomalies were found near Ec.m. = 6.3, 7.5, 8.9 and 9.7 MeV. Angular distributions were measured at Ec.m. = 9.20, 9.71 and 10.23 MeV for the three lowest excited states in 17O. The data have been compared with Hauser-Feshbach calculations in addition to the following reaction mechanisms: compound plus a single resonance, compound plus interfering resonances and compound plus direct reactions. 相似文献
213.
Organocuprates and chlorotrimethylsilane are compatible as separate species in THF or ether solution at ?50 to ?78°, and in combination can both accelerate and improve 1,4-addition reactions with conjugated carbonyl compounds. 相似文献
214.
G. Patonay K. Fowler A. Shapira G. Nelson I. M. Warner 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(6):717-723
Pyrene, as a fluorescence probe, has been used to study the cyclodextrin complexation process in the presence of different alcohols. The complex formation as well as the hydrophobicity of the cyclodextrin interior can be significantly influenced by the introduction of alcohols. The alcoholic alkyl group and the primary and secondary hydroxyl groups of the cyclodextrin proved to be the determining factors in the complex formation. 相似文献
215.
Spin-flip Raman scattering, magnetization, and susceptibility data for Zn0.97Mn0.03Se are reported. The exchange energy Noα = 243 ± 10 meV for the conduction electrons is obtained from an analysis of the Raman and magnetization data. At large magnetic fields (H > 60 kOe), the spin-flip energy ΔE saturates at 14 meV. At low fields ΔE does not extrapolate to zero as H → 0, which is characteristic of scattering from donor-bound electrons. The low temperature magnetization curves are fit to a modified Brillouin function. The fit gives as the fraction of active magnetic ions, and an effective temperature Teff = T + To with To = 1.1 K. The magnetic susceptibility follows a Curie-Weiss law between T = 150 and 280 K with a Curie-Weiss temperature θ = ?33 K. 相似文献
216.
217.
218.
Dispersion of inert solutes in spatially periodic,two-dimensional model porous media 总被引:1,自引:0,他引:1
Taylor dispersion of a passive solute within a fluid flowing through a porous medium is characterized by an effective or Darcy scale, transversely isotropic dispersitivity
, which depends upon the geometrical microstructure, mean fluid velocity, and physicochemical properties of the system. The longitudinal,
and lateral,
dispersivity components for two-dimensional, spatially periodic arrays of circular cylinders are here calculated by finite element techniques. The effects of bed voidage, packing arrangement, and microscale Péclet and Reynolds numbers upon these dispersivities are systematically investigated.The longitudinal dispersivity component is found to increase with the microscale Péclet number at a rate less than Pe2. This accords with previous calculations by Eidsath et al. (1983), although the latter calculations were found to yield significantly lower longitudinal dispersivities than those obtained with the present numerical scheme. With increasing Péclet number, a Pe2 dependence is, however, approached asymptotically, particularly for square cylindrical arrays - owing to the creation of a linear streamline zone between cylinders. 相似文献
219.
trapping of reaction intermediates combined with stereochemical studies of the reaction of lithium dimethylcuprate with enones provides evidence for a pathway involving d,π-cuprate-enone and copper(III) β-adducts as important intermediates in cuprate-mediated conjugate addition of carbon. 相似文献
220.