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891.
XIA Dao-cheng LI Wan-cheng WANG Xu YU Shu-kun FAN Cui-xiang MA Chun-yu CHENG Chuan-hui FAN Zhao-qi DU Guo-tong CONG Fang-di DU Xi-guang 《高等学校化学研究》2008,24(4):407-410
A novel solvothermal synthesis method for the direct growth of B-form crystals of copper phthalocyanine(CuPc) is presented in this article. With quinoline as solvent, crystals were grown after cooling the reaction mixture of 1,3-diiminoisoindoline and copper oxide, heated for 9 h at 270 ℃, to room temperature in an autoclave. These high quality crystals were suitable for characterization measurements. The single-crystal diffraction data show a monoclinic system unit cell: a=1.4668(3) nm, b=0.48109(10) nm, c=1.9515(7) nm, a=90°, B=121.04(2)°, r=90°, where the corresponding cell volume is 1.17991 nm^3. Needle-like single crystals of CuPc up to 10.5 mm in length were obtained. The influences of different temperatures, reaction time and solvent volume on the crystal yields were also discussed. Optimum reaction conditions were 10 mL of quinoline, at 270 ℃ for 8 h. 相似文献
892.
溶剂浮选-紫外分光光度法测定厚朴中总厚朴酚 总被引:2,自引:0,他引:2
建立了一种测定厚朴中总厚朴酚的新方法,即采用溶剂浮选法分离富集厚朴中的总厚朴酚,用紫外分光光度法测定其含量。考察了浮选溶剂、试液pH、氮气流速、浮选时间及电解质NaCl等因素对浮选效果的影响,优选出最佳浮选条件。采用所述方法对不同产地厚朴样品中总厚朴酚含量进行测定,样品加标回收率为94.9%-100.8%,RSD为2.8-4.1%。 相似文献
893.
《International Journal of Solids and Structures》2014,51(19-20):3422-3430
One of the most fruitful and elegant approach (known as Kolosov–Muskhelishvili formulas) for plane isotropic elastic problems is to use two complex-valued holomorphic potentials. In this paper, the algebra of real quaternions is used in order to propose in three dimensions, an extension of the classical Muskhelishvili formulas. The starting point is the classical harmonic potential representation due to Papkovich and Neuber. Alike the classical complex formulation, two monogenic functions very similar to holomorphic functions in 2D and conserving many of interesting properties, are used in this contribution. The completeness of the potential formulation is demonstrated rigorously. Moreover, body forces, residual stress and thermal strain are taken into account as a left side term. The obtained monogenic representation is compact and a straightforward calculation shows that classical complex representation for plane problems is embedded in the presented extended formulas. Finally the classical uniqueness problem of the Papkovich–Neuber solutions is overcome for polynomial solutions by fixing explicitly linear dependencies. 相似文献
894.
An analytical method has been developed to quantitatively determine the residual lactide monomer in polylactide (PLA) using an internal standard method of gas chromatography (GC). The experimental results showed that diphenyl ether (DPE) was an appropriate internal standard for quantitative analysis of residual lactide in PLA. PLA and DPE were dissolved in dichloromethane and precipitated in hexane. At the same time, the residual lactide in PLA and DPE as an internal standard were extracted to hexane from the polymer solution. The resulting solution could be directly injected into a GC system. Therefore, the residual lactide was determined quantitatively using an internal standard method of GC. This method is practical for measuring the residual lactide content in PLA. When the lactide content is 5.0%, the relative standard deviation (RSD) of the measurements is 1.7%, while RSD is 6.9% at the low level of 0.4%, which indicates that the method is sufficiently precise. 相似文献
895.
《Arabian Journal of Chemistry》2014,7(3):335-339
Sulfonic acid functionlized silica (SiO2-Pr-SO3H) was found to be an efficient and recyclable solid acid catalyst in the synthesis of 1,8-dioxo-decahydroacridine derivatives under solvent free conditions. Short reaction time, excellent yields and simple work-up are the advantages of this procedure. 相似文献
896.
A metal-free and solvent free click-chemistry procedure has been revealed for the synthesis of 4-trifluoroacetyl-1,2,3-triazoles from corresponding azides and alkyne with high yield and selectivity. The pure products could be easily obtained via crystallization of the reaction mixture (standing for 1 day). Among the 4-trifluoroacetyl-1,2,3-triazoles, 3ba showed the best anticancer activity against HepG2 cell with IC50 of 0.0267?μmol/ml. This method has the advantages of less pollution, low cost, simple treatment and more efficiency. 相似文献
897.
CHARACTERIZATION FOR BINOMIAL SEQUENCES AMONG RENEWAL SEQUENCES 总被引:2,自引:1,他引:1
成世学 《高校应用数学学报(A辑)》1992,(1)
In this paper a binomial sequence is defined as a special sequence whose renewal lifes are identically distributed with a common geometric distribution. Therefore, it can be regarded as the discrete version of a Poisson process. Mainly, we discuss the characterization problem associated with binomial sequences. First, we sketch the properties of some important quantities of a renewal sequence. The emphasis of discussion is laid on the current life, the residual life and the total life. Then, we describe three main approaches to identify a geometric distribution. Finally, based on these concepts and techniques, we give a series of characterization theorems for a binomial sequence. These results are quite similar to those obtained for a Poisson process. 相似文献
898.
Frieder Birnstock Hans -Jörg Hofmann Hans -Joachim Köhler 《Theoretical chemistry accounts》1976,42(4):311-323
Based on Sinanolu's solvent theory in connection with a method for the calculation of the molecular volume given by Beveridge a modified continuum model is suggested. The model is tested by the determination of the conformational structure of the title compounds. The predictions obtained by this model are in good agreement with the experimentally determined data. 相似文献
899.
900.
用Laplace变换方法求出了Bloch方程在各种不同物理条件下的解析解,这些解析解物理图象清楚,便于分析,克服了数值解中的困难.解析解和相应的结论已用于水峰抑制和特形脉冲的设计.对于水峰抑制,本文指出抑制效果是有极限的,并给出了抑制效果的极限以及最佳抑制时间的近似计算公式.在特形脉冲的模拟过程中,我们发现只有同时考虑全部四类解析解,才能得到正确的模拟结果,另外,模拟还表明,要在保持激励频谱形状不变的条件下,得到不同倾倒角的脉冲必须改变激励脉冲的形状,相应实验的结果与我们给出的上述结论完全吻合。 相似文献