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31.
Molar extinction coefficients of aqueous solutions of some organic compounds, viz. formamide (CH3NO),N-methylformamide (C2H5NO),NN-dimethylformamide (C3H7NO),NN-dimethylacetamide (C4H9NO), 1,4-dioxane (C4H8O24), succinimide (C4H5NO2) and solutions of acetamide (C2H5NO) and benzoic acid (C7H6O2) in 1,4-dioxane (C4H8O2) have been determined by narrow beam γ-ray transmission method at 81, 356, 511, 662, 1173 and 1332 keV. The experimental
values of mass attenuation coefficients of these compounds have been used to calculate effective atomic numbers and electron
densities. The additivity rule earlier used for aqueous solution has been extended to non-aqueous (1,4-dioxane) solutions. 相似文献
32.
33.
A layer of stratified combination composed of selected radiation shielding materials acquires better shielding property. Albedo
is used in such measurements as an integral measure ofγ-ray scattering. The stratified slabs of alternating heterogeneous layers have been found to have a virtual homogeneous property
with a definite effective atomic number. The angular distribution of back-scattered photons as well as the total number albedo
values for iron, aluminium and concrete in stratified combination for 662 keV and 1250 keV photons are reported. 相似文献
34.
讨论关于在ILC用γγ到Z过程检验非对易时空能标(原文发在hep-ph/0604115). 在通常时空量子场论中, 由杨氏定理可知一个自旋为1的粒子不可能衰变为两个光子. 但在非对易时空中此过程是允许的. 因此这个过程能作为检验非对易时空的工具. ILC的光子对撞模式能实现这个过程. 如果总亮度能达到500fb-1, 我们证明对Gamma (Z to gamma gamma)宽度的测量精度将比现有限制(<5.2×10-5GeV)好3—4个数量级. 对非对易时空能标的检测可高达几个TeV. 相似文献
35.
ZHU Hai-Xia YAN Shi-Lei 《理论物理通讯》2004,42(11)
We study the ferromagnetic properties of spin-1 system, which is considered in the frame of the bond dilution and random positive or negative anisotropy Blume-Capel model in the effective field theory and a cutting approximation. The investigation of phase diagrams displays some rich properties of the trajectory of tricritical point, reentrant henomena at low temperatures. Under certain both bond concentrations and random negative anisotropy, there are new transition lines of double tricritical points. So special emphasis is placed on the influence of the bond dilution and random anisotropy on phase diagrams. The magnetizations of the system are also discussed. Some results have not been evealed in previous reports. 相似文献
36.
《Surface and interface analysis : SIA》2006,38(10):1348-1356
We report changes in electron effective attenuation lengths (EALs) resulting from use of transport mean free paths (TMFPs) obtained from the Dirac–Hartree–Fock (DHF) potential instead of the Thomas–Fermi–Dirac (TFD) potential in an algorithm used in the National Institute of Standards and Technology (NIST) Electron Effective‐Attenuation‐Length Database (SRD 82). TMFPs from the former potential are believed to be more reliable than those obtained from the latter potential. We investigated changes in the EALs for selected photoelectron and Auger‐electron lines in four elemental solids (Si, Cu, Ag, and W), for Si 2p photoelectrons of varying energy in SiO2, and for photoelectrons excited by Al Kα X rays in four candidate gate‐dielectric materials (HfO2, ZrO2, HfSiO4, and ZrSiO4). For each material, we computed the change in the average EAL for a range of overlayer‐film thicknesses from zero to a maximum value corresponding to attenuation of the substrate signal to 10% of its original value. This EAL change was a maximum for electrons emitted normally from the surface and decreased monotonically with increasing emission angle. The maximum EAL change varied between ?4.4% and 2.6% for the three groups of materials. We found that the maximum EAL change correlated mainly with the TMFP change. We found that TMFP changes in other solids could generally lead to maximum EAL changes between ?2.6% and 1.9% for electron energies between 500 and 2000 eV. For lower energies, the maximum EAL changes could be larger for some solids. Our revised EALs for Si 2p photoelectrons in SiO2 excited by Mg and Al Kα X rays agree within 0.5% with values reported by Seah and Spencer from a detailed analysis of SiO2 film‐thickness measurements by XPS and other techniques. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
37.
M~++BrCN─→MCN~++Br气相反应的从头算研究朱荣顺,戴树珊(云南大学化学系,昆明,650091)关键词气相反应,过渡金属阳离子,溴化氰,从头算,相对论赝势对过渡金属离子与一些小分子的气相反应已有大量的实验和理论研究[1~5],MichelS... 相似文献
38.
39.
淫羊藿根与叶活性成分的分析和比较 总被引:8,自引:0,他引:8
采用细胞膜色谱法(CMC)筛选,并结合离体药理实验确定主要活性成分,利用高效液相色谱法分析比较了淫羊藿根与叶中的活性成分及其差异性.色谱条件为Kromasil ODS 柱(150 mm× 4.6 mm.I.D )流动相甲醇-水(70:30,V:V);检测波长270nm。筛选发现淫羊藿根中的两个有效成分YYH-214和YYH-216对血管有较强的舒张作用,表明活性成分在CMC模型体系中的保留特性与药理作用之间存在良好的相关性。在此色谱条件下淫羊藿叶未检测到这两种活性成分. 相似文献
40.
Takao Masuda 《Catalysis Surveys from Asia》2003,7(2-3):133-144
The diffusion mechanisms within zeolite catalysts, such as resistance to diffusion at pore mouths, configurational diffusion, adsorption-controlled diffusion, influence of co-existing molecules and pore blocking, were overviewed. Two kinds of diffusivities, the intracrystalline diffusivity and the effective diffusivity, were discussed separately to clarify the diffusion mechanism. 相似文献