共查询到20条相似文献,搜索用时 156 毫秒
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基于金属有机和元素有机化合物参与的新合成方法学 的研究 总被引:1,自引:0,他引:1
包括下列研究工作:碱催化形成碳-碳双键的合成方法学;双烯化反应的合成方法学;立体选择性地控制合成烯炔和丙烯类化合物的合成方法等;连串反应的合成方法学。 相似文献
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第二代氨合成催化体系——钌系氨合成催化剂及其工业应用* 总被引:12,自引:0,他引:12
本文综述了第二代氨合成催化体系——钌系氨合成催化剂的研制、开发及工业应用情况。介绍了钌系氨合成催化剂的载体、促进剂、钌活性前身物对氨合成催化活性的影响。比较了钌系氨合成催化剂与铁系氨合成催化剂的反应机理与性能特点。新型氨合成催化工艺流程的成功开发为钌系氨合成催化剂的工业应用提供了有力的保障。 相似文献
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DNA芯片的制备方法主要有离片合成法和在片合成法.离片合成是用点样法将DNA探针固定在基片上;在片合成是在基片表面直接原位合成寡核苷酸探针阵列.目前国外已有多种DNA芯片原位合成方法的报道,但其中仅Fordor等提出的光脱保护DNA固相原位合成技术已商品化,该方法制备成本高, 相似文献
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黄烷酮是含有二氢色原酮骨架结构的黄酮类化合物。本文梳理了合成黄烷酮的文献,总结了其合成方法,按原料结构特征分类论述其合成方法:即从黄烷酮衍生物经官能团变换合成黄烷酮;查耳酮经氧-Michael加成合成黄烷酮;非查耳酮结构构建合成黄烷酮。重点论述了第二类合成方法。参考文献82篇。 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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氢气在炭狭缝微孔内吸附的预测 总被引:1,自引:0,他引:1
通过边界的平均场近似,推导二平板狭缝孔格子理论Ono-Kondo吸附等温方程.利用格子气模型特性和微观物理学理论,计算氢分子在石墨平面的最大吸附容量.比较由氢分子在石墨平面二典型聚集状态标定的Ono-Kondo方程,并用预测精度较高的方程计算了与文献相同条件下的吸附等温线.在比较了计算结果、试验结果和GCMC分子模拟结果后,对Ono-Kondo吸附等温方程的特点、理论基础作了分析,指出了方程的适用范围. 相似文献
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利用元胞动力学方法在二维情况下对浓度、取向序参量的含时Ginzberg-Landau方程进行数值求解,研究了液晶聚合物/柔性链聚合物共混体系的相分离动力学,考察了浓度、取向有序过程的耦合对相分离形态的影响.结果表明,此耦合作用对相分离的时间进程以及相分离图样的空间排布都有影响.液晶聚合物的取向有序相当于增加了两组分间的不相容性而促进两相分离;两个序参量在热力学方面的耦合使液晶聚合物趋向于沿着界面方向取向,而动力学方面的耦合使液晶聚合物分子沿着其取向方向扩散,相分离图样的空间排布由这两种效应共同决定通过极化率张量的定义用数值方法模拟得到了相分离体系的小角光散射图样,结果表明,散射强度分布具有方位角依赖性,它是由浓度、取向序参量的空间变化共同决定的. 相似文献
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Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene (LDPE), ethylene copolymer and organoclay. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer. 相似文献
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Yakov I. Estrin 《Central European Journal of Chemistry》2004,2(1):52-81
Bimodal molecular mass distribution (MWD) of polymers, obtained upon polymerization of hydrocarbon monomers in the nonpolar
media under the action of dilithium initiators, is the consequence of separation of the reaction mixture into two phases.
Bifunctional /living/ oligomers produce the insoluble sediment due to tetrameric association of the lithium active sites (the
swollen gel-fraction). Part of the active site remains in the solution (the solfraction). Difference in the concentrations
of the active sites into the phases leads to difference between the propagation rates of the /living/ chains and, as a result,
to Bimodal MWD. The mathematical model of polymerization in the two-phase system is proposed. Satisfactory agreement between
the calculations and the experiments is shown for butadiene polymerization in heptane under the action of 1,4-dilithiumpentane.
Regulation of MWD up to the complete elimination of bimodality is possible via the programmed dosage of monomer and solvent
into the reactor. 相似文献
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The applicability of the method of Giese to the measurement of the influence of monomer reactivity is examined. The reaction of alkyl mercuric salts with sodium borohydride permits the production of alkyl (cyclohexyl and butyl) radicals. Since hydrogen radicals are present in high concentration, the addition of alkenes to the reaction mixture leads to radicals from the alkenes. Further addition of alkene (polymerization) can be nearly completely excluded in this way. The composition of the reaction products is determined by gas chromatography. The addition rate of the alkenes relative to styrene allows correlation with the e value of the Q-e scheme of Alfrey and Price. The method answers the question of how far addition of the monomer complex occurs in one step or as separate addition of both monomers during copolymerization in the presence of charge-transfer (CT) complexes of the monomers. The investigations are performed by using the styrene/acrylonitrile/ZnCl2system, and it is demonstrated that the reactivity of the complexed 相似文献
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The micellar properties of aqueous binary mixed solutions of sodium glycocholate, NaGC, and octa-oxyethylene glycol mono-n-decyl ether, C10E8, have been studied on the basis of surface tensions, the mean aggregation number and the polarity of the interior of the micelles. The mean aggregation number, measured by steady state quenching method, decreased with the increase of the mole fraction of NaGC in the mixed system. The polarity of the interior, estimated by the ratio of first and third vibronic peak in a monomeric pyrene fluorescence emission spectrum, suggested that the hydrophobicity of intramicelles increased with the increase of the mole fraction of NaGC in the mixed system. These are considered to be caused by the differences in the chemical structure and the hydrophobic nature between NaGC and C10E8. The mean aggregation number and the polarity of the interior for each micelle near the CMC in lower total concentration of surfactants showed the tendency approaching those of pure micelle of the nonionic surfactant. This suggests that the ratio of NaGC in the initial micelles in the range of lower total concentration near the CMC is lower than that of the corresponding prepared mole fraction in the mixed system. This lower value was confirmed also from theoretical calculation of the ratio of NaGC at the CMC in the mixed micelle by regular solution treatment of Rubingh in the solution. 相似文献
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When drugs are poorly soluble then, instead of the potentiometric determination of dissociation constants, pH-spectrophotometric
titration can be used along with nonlinear regression of the absorbance response surface data. Generally, regression models
are extremely useful for extracting the essential features from a multiwavelength set of data. Regression diagnostics represent
procedures for examining the regression triplet (data, model, method) in order to check (a) the data quality for a proposed model; (b) the model quality for a given set of data; and (c) that
all of the assumptions used for least squares hold. In the interactive, PC-assisted diagnosis of data, models and estimation
methods, the examination of data quality involves the detection of influential points, outliers and high leverages, that cause many problems when regression fitting the absorbance response hyperplane. All graphically
oriented techniques are suitable for the rapid estimation of influential points. The reliability of the dissociation constants
for the acid drug silybin may be proven with goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration
data. The uncertainty in the measurement of the pK
a of a weak acid obtained by the least squares nonlinear regression analysis of absorption spectra is calculated. The procedure
takes into account the drift in pH measurement, the drift in spectral measurement, and all of the drifts in analytical operations,
as well as the relative importance of each source of uncertainty. The most important source of uncertainty in the experimental
set-up for the example is the uncertainty in the pH measurement. The influences of various sources of uncertainty on the accuracy
and precision are discussed using the example of the mixed dissociation constants of silybin, obtained using the SQUAD(84)
and SPECFIT/32 regression programs. 相似文献
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S. Havriliak Jr 《Colloid and polymer science》1990,268(5):426-439
The dielectric relaxation data of Ishida et al. on a number of acrylic polymers are represented in terms of the relaxation function proposed by Havriliak and Negami using the multi-response techniques developed by Havriliak and Watts. Two of the parameters of this function are interpreted in terms of a temperature dependent distribution of relaxation times. In this method of interpretation the breadth of the distribution function is temperature-dependent while the skewness is not. The temperature dependence of the breadth of the distribution function is similar for most of these acrylic polymers.The parameters of the relaxation function are also interpreted in terms of Mansfield's model which represents intra- and inter-molecular interactions in terms of springs and dash pots. Briefly, increasing the side chain length for the methacrylate series increases the inter-molecular relaxation time which may be due to an increase in the entropy of activation for the orientation process. The difference between the one acrylate in this study and the four methacrylates of the series is a reduction in the intra-molecular relaxation time, apparently due to the lack of the alpha methyl group. 相似文献
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We have theoretically resolved phonon excitations in quasi-two-dimensional organic crystals of polyacenic semiconductor material which may be obtained by the pyrolytic treatment of phenol-formaldehyde resin. A model for studying the dynamical properties using three polyacene chains is proposed with the aim to present the vibrational properties of this structure. It employs the formalism of solid states in two dimensions which admit phonons. A simulation process of the two-dimensional lattice structure shows that elastic waves may explain the existence of vibrational modes in the frequency range 100-400 cm-1. The presence of acoustic and optical like phonons is discussed in terms of the elastic force constants. A hyperfine resonance structure is obtained. It allows the analysis of the dynamical evolution in thin films of polyacene. It is found that the behavior of the phonon density of states exhibits resonance between modes in the structure. 相似文献