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51.
A new and facile synthesis of unsymmetrical heterocyclic azines is described. Methyl arylalkylidenehydraz-inecarbodithioates, prepared by the condensation of ketones or aldehydes with methyl hydrazinecarbodithioate, were heated under reflux with various diamines in ethanol. Secondary diamines, such as N,N′-dimethyl-ethylenediamine, N,N′-dimethyl-1,3-diaminopropane or N,N′-dimethyl-o-phenylenediamine, reacted smoothly with loss of hydrogen sulfide to give good yields of unsymmetrical azines. However, primary diamines, such as ethylenediamine or o-phenylenediamine, and primary/secondary diamines, such as N-methylethyl-enediamine and N-methyl-1,3-diaminopropane gave, instead, only the corresponding uncyclized thiosemi-carbazones. A cyclodesulfurization mechanism for azine formation is discussed. 相似文献
52.
The microemulsion of the H2O/Tween 80/benzene derivative (C6H6, CH3C6H5, NO2C6H5 and NH2C6H5) was investigated by the technique of Photon correlation spectroscopy. Autocorrelation data were measured at 90 scattering angle and were analyzed by using a quadratic fit and linear fit. The quadratic fit was found to describe all Properties better than the linear fit, and thus the linear fit was limited to the region of very short sampling time. When the amount of benzene derivative added to the sample solution was lower than Vmax, the Z-average mean radius, <r>z, and the polydispersit Y, μ2/Γ2, increased as the amount of benzene derivative was increased. When the amount of benzene derivative was larger than Vmax, the aqueous and organic phases separated and the <r> z, and μ2/Γ2 of all phases remained constant. Emulsification did not occur in the organic phase of the H2O/Tween 80/aniline system. When we adjusted the Tween 80 concentration, it was found that <r>z and μ2/Γ2 decreased as the Tween 80 concentration increased. 相似文献
53.
Various crown ethers were prepared and applied as phase transfer catalysts for the an ionic copolymerization of bisphenol A and 4,4′‐dichlorodiphenyl sulfone monomers with alkali salts, e.g., NaNH2, NaOH and KOH, as initiators. The catalytic abilities of various crown ethers for the an ionic polymerization of bisphenol A / 4,4′‐dichlorodiphenyl sulfone were found to be in the order: 15‐crown‐5 ? monobenzo‐15‐crown‐5 > 18‐crown‐6 > Dicyclohexano‐18‐crown‐6 > Dibenzo‐18‐crown‐6 > 12‐crown‐4 with sodium amide (NaNH2) as initiator. Sodium amide was shown to be a better initiator than NaOH or KOH with monobenzo‐ 15‐crown‐5 as a catalyst. Effects of solvents and temperature on the crown ether catalytic polymerization were also investigated. Dimethyl sulfoxide (DMSO) exhibited much better for the polymerization than other organic solvents, e.g., toluene, p‐xylene, dimethyl formamide and dioxane. Higher polymerization was found at higher temperatures and about 100% yield of poly(bisphenol A / sulfone) was obtained at 125 °C in 3 hr. The molecular weight of poly(bisphenol A / sulfone) as a function of reaction time was determined with gel permeation chromatography. Concentration effects of crown ether on % yield and molecular weight of poly(bisphenol A / sulfone) were also investigated and discussed. 相似文献
54.
We study efficient two-grid discretization schemes with two-loop continuation algorithms for computing wave functions of two-coupled nonlinear Schrödinger equations defined on the unit square and the unit disk. Both linear and quadratic approximations of the operator equations are exploited to derive the schemes. The centered difference approximations, the six-node triangular elements and the Adini elements are used to discretize the PDEs defined on the unit square. The proposed schemes also can compute stationary solutions of parameter-dependent reaction–diffusion systems. Our numerical results show that it is unnecessary to perform quadratic approximations. 相似文献
55.
This study adopts the Tersoff-Brenner interaction potential function in a series of molecular dynamic (MD) simulations which investigate the mechanical properties under tensile loading of (10,0) zigzag, (8,3) chiral and (6,6) armchair single-walled carbon nanotubes (SWCNTs) of similar radii. The Young's modulus values of the (10,0), (8,3) and (6,6) nanotubes are determined to be approximately 0.92, 0.95, and 1.03 TPa, respectively. Of these nanotubes, the results reveal that the (6,6) nanotube possesses the best tensile strength and toughness properties under tension. Although it is noted that under small tensions, the mechanical properties such as Young's modulus are essentially insensitive to helicity, under larger plastic deformations, they may be influenced by helicity effects. Finally, the simulations demonstrate that the values of the majority of the considered mechanical properties decrease with increasing temperature and increasing vacancy percentage. 相似文献
56.
ZrNx films were sputtered in an Ar + N2 atmosphere, with different substrate biases (0 to −200 V) at various nitrogen flow ratios (%N2 = 0.5-24%). The surface morphology, resistivity, crystllinity, and bonding configuration of ZrNx films, before and after vacuum annealing, were investigated. As compared with ZrNx films grown without substrate bias, before and after annealing, the resistivity of 1% and 2% N2 films decreases with increasing substrate biases. Simultaneously, if the applied bias is too high, the crystallinity of ZrNx film will decrease. The surfaces of 1% and 2% N2 flow films deposited without bias have small nodules, whereas the surface morphology of films deposited at −100 V of substrate bias exhibits large nodules and rugged surface. Once a −200 V of substrate bias is applied to the substrate, the surface morphology of ZrNx films, grown at 1% and 2% nitrogen flow ratios, is smooth. Furthermore, there are two deconvoluted peaks in XPS spectra (i.e., Zr-O and Zr-N) of ZrNx films deposited at −200 V of substrate bias before and after annealing. On the other hand, the surface morphology changes dramatically from rugged surfaces for film deposited at lower nitrogen flow ratio (%N2 < 1%) to smoother and denser surfaces for film grown at higher nitrogen flow ratio (%N2 ≥ 1%). The Zr-N bonding in 2% N2 films still exist after annealing at 700 °C, while the Zr-N bonding in 0.5% and 16% N2 flow film vanish at the same temperature. The connection between the resistivity, crystallinity, surface morphology, and bonding configuration of ZrNx films and how they are influenced by the substrate bias and nitrogen flow ratio are discussed in this paper. 相似文献
57.
Hsiao‐Fan Tseng Ming‐Hsiang Cheng Kai‐Sheng Jeng Jia‐Wei Li Jiun‐Tai Chen 《Macromolecular rapid communications》2016,37(22):1825-1831
Anisotropic polymer particles such as Janus particles have attracted significant attention in recent years because of their unique properties and unusual self‐assembly behavior. Most anisotropic polymer particles synthesized so far, however, only have different chemical regions compartmentalized on the particles. It remains a great challenge to fabricate anisotropic polymer particles with different shapes within a single particle. A novel approach is developed to prepare anisotropic polymer particles that contain two hemispheres with different curvatures by annealing polystyrene microspheres on poly(vinyl alcohol) films. During the annealing process, the polymer microspheres gradually sink into the polymer films and transform to asymmetric polymer particles, driven by the surface and interfacial tensions of the polymers. Selective removal techniques are also used to confirm the morphologies of the asymmetric particles.
58.
We describe a two-parameter continuation algorithm for computing Bloch waves of Bose-Einstein condensates (BEC) in optical lattices which is governed by the Gross-Pitaevskii equation (GPE). The Fourier collocation method and fourth-order Adini’s elements with penalty are used to discretize the GPE. We propose two different approaches so that the two-parameter continuation algorithm can be modified to compute closed tubes at the four corners of the Bloch band. We also study linear stability analysis for the GPE. We show that all the discrete steady-state solutions are numerically neutrally stable. Numerical results show that the four edges of the Bloch waves are surrounded by closed loops if the coefficient of the cubic nonlinear term is greater than that of the periodic potential. Moreover, closed tubes at the four corners of the Bloch band are obtained. The numerical results display superfluidity of BEC. 相似文献
59.
In this paper, for two nonempty subsets X and Y of a linear space E, we define the class KKM(X,Y) and investigate the fixed point problem for T∈KKM(X,X) with X an almost convex subset of a locally convex space. Our fixed point theorem contains Lassonde fixed point theorem for Kakutani factorizable multifunctions as special case. 相似文献