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11.
A convenient, 40% overall yield synthesis of 2,3,17β-triacetoxy-1,3,5(10)-estratriene is described, which involves epoxidation of 19-nortestosterone and subsequent acetylation, lead tetra-acetate acetoxylation of the so-formed 17β-acetoxy-4β,5-epoxy-5β-estran-3-one, and aromatization of ring A, by means of acidic alumina, of the resulting 2α and 2β epimers of 2,17β-diacetoxy-4β,5-epoxy-5β-estran-3-one. 相似文献
12.
Exact solutions for nonlinear Schr?dinger equation in phase space: applications to Bose-Einstein condensate 下载免费PDF全文
The stationary-state nonlinear Schr?dinger equation, which models the dilute-gas Bose-Einstein condensate, is introduced within the framework of the quantum phase-space representation established by Torres-Vega and Frederick. The exact solutions of equation are obtained in the phase space, by means of the wave-mechanics method. The eigenfunctions in position and momentum spaces are obtained through the ‘Fourier-like' projection transformation from the phase space eigenfunctions. The eigenfunction with a hypersecant part is discussed as an example. 相似文献
13.
B离子掺杂TiO2催化剂(TiO2-xBx)光催化活性的研究 总被引:3,自引:0,他引:3
采用溶胶-凝胶法制备出纳米TiO2和TiO2-xBx催化剂. 光催化实验证明, TiO2-xBx催化剂的紫外、可见光催化活性均高于TiO2. XRD, XPS和Raman结果表明, B离子是以取代式掺杂占据了TiO2的O2-的晶格位置. UV-Vis和PL谱的结果表明, B离子的2p轨道与O的2p轨道形成混合价带, 产生可见光响应, B离子的掺入有效地阻止了光生载流子的复合, 促进了其分离, 是TiO2-xBx催化剂紫外、可见光催化活性提高的主要原因. 相似文献
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Monodisperse emulsion copolymer was synthesized by semi-continuous core-shell emulsion polymerization of styrene, butyl acrylate and γ-methacryloxypropyl trimethoxy silane(KH570). The emulsion particles size and its polydispersion were measured by dynamic light scattering(DLS). The properties of emulsion copolymer were characterized by differential scanning calorimetry(DSC), thermogravimetric analysis(TGA) and measurement of contact angle. The particle morphology was observed under a transmission electron microscope(TEM) and atomic force microscopy(AFM). The results indicate that emulsion nanoparticles containing silicon possess core-shell structures and narrow polydispersity(PDI≤0.08). The thermal stability and hydrophobicity of emulsion copolymer were improved with KH570 introduced into the system. 相似文献
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A type of system, in which the specific volume can be divided into several parts according to its Hamiltonian, has been obtained in a grand ensemble. The main character of such a system is that its Hamiltonian is absolutely separable. We also discuss the partial specific volume contributed by thermoelectrons in metals under a free-interaction approximation, and the corresponding Wu-Jing parameter is obtained as a simple example. 相似文献
18.
The effect of divalent cation substitution on the structure and magnetic properties of La1.2Sr1.8-xCaxMn2O7 (x = 0-0.900) is investigated in this paper. Partly replacing divalent cation Sr2+ by Ca2+ ions results in the weakening and then disappearance of long-range ferromagnetic ordering, and the formation of spin canting and low-temperature spin-glass. Based on structural analysis by Rietveld profile fitting, we suggest that this variation of magnetic property be related to a Jahn-Teller-type attice distortion of MnO6 octahedra due to the introduction of the smaller sized Ca2+ ions. 相似文献
19.
In this paper, new explicit and exact travelling wave solutions for a compound KdV-Burgers equation are obtained by using the hyperbola function method and the Wu elimination method, which include new solitary wave solutions and periodic solutions. Particularly important cases of the equation, such as the compound KdV, mKdV-Burgers and mKdV equations can be solved by this method. The method can also solve other nonlinear partial differential equations. 相似文献
20.
Polarised IR and Raman spectra for KH2PO3 single crystal samples were measured at room temperature. Additionally, the IR spectra for the Xb(Z) sample were also measured at low temperatures (300–14 K). The spectra are discussed on the basis of oriented gas model and group theory. The stretching νOH vibrations of the hydrogen bonds with the OO distances of 2.547 and 2.529 Å give characteristic broad ABC-type bands in the IR (polarised parallel to the X and to the b(Z) directions) and Raman (xx, xz and yx) spectra. The Davydov-type (correlation field or factor group) splitting is not observed for the νOH modes. The presence of two independent hydrogen bonds in the crystal is manifested by splitting of the C band into two (C′, C″) components and by the different frequencies of the out-of-plane bending γOH vibrations. The in-plane bending modes δOH are strongly mixed/coupled with the stretching vibrations of the PO3 groups.
The C bands (C′ and C″) change into quite sharp bands on lowering of the temperature. Various simplified models for internal vibrations of the phosphite anions are applied for finding a correlation between the crystal structure and polarised vibrational spectra. The stretching vibrations of the νPH groups manifest their unequivalence in two symmetry-independent hydrogenphosphite anions. 相似文献