A convenient one-step preparation of diaminonitrile compounds

A new method for preparation of diaminonitrile compounds is reported.In this method primary aliphatic diamine compounds were condensed with two equivalents of benzaldehyde and sodium cyanide in presence of an aqueous solution of sodium hydrogensulfite under mild conditions.This method provides an efficient,convenient and practical method for the syntheses of diaminonitrile compounds and the products are easily isolated.The prepared new compounds were characterized by elemental analysis,IR,NMR spectroscop...     

An efficient one-step synthesis of 1,4-dihydropyridines via a triphenylphosphine-catalyzed three-component Hantzsch reaction under mild conditions

An efficient one-step synthesis of 1,4-dihydropyridines in good to excellent yields via the triphenylphosphine-catalyzed Hantzsch three-component reaction of an aromatic aldehyde, ethyl acetoacetate and ammonium acetate is described.     

系数函数光滑度互不相同的变系数模型的一步估计法

该文提出了一种一步估计方法用以估计变系数模型中具有互不相同光滑度的未知函数, 所有未知函数和它们的导数的估计量由 一次极小化得到. 给出了估计量的渐近性质, 包括渐近偏差、方差和渐近分布, 一步估计量被证明达到了最优收敛速度.     

In2O3/ZrO2-TiO2空心球复合材料的制备与光解水制氢性能

以聚苯乙烯(PS)胶球为模板, 通过一步法结合煅烧后处理制备了空心球复合材料In₂O₃/ZrO₂-TiO₂. 采用X射线衍射(XRD)、 X射线光电子能谱(XPS)、 扫描电子显微镜(SEM)、 紫外-可见漫反射吸收光谱(UV-Vis DRS)和氮气吸附-脱附等测试手段对复合材料的结构、 组成和形貌进行了表征. 结果表明, In₂O₃/ZrO₂-TiO₂复合材料的晶型结构以锐钛矿型TiO₂为主, 同时存在少量含有Ti—O—Zr键的混合氧化物. 该复合材料经聚苯乙烯模板处理后呈现空心球状结构, 球壁由纳米粒子堆积而成. In₂O₃/ZrO₂-TiO₂空心球复合材料的比表面积较大(66.92 m²/g), 且In₂O₃与ZrO₂-TiO₂复合后光吸收发生了红移. 对该复合材料光解水制氢性能的研究结果表明, 空心球状In₂O₃/ZrO₂-TiO₂具有较好的产氢效果(56.7 μmol/g, 8 h), 明显高于P25、 ZrO₂、 空心球状ZrO₂-TiO₂及粉末状In₂O₃/ZrO₂-TiO₂.     

可溶性侧链含萘聚酰亚胺的合成与性能

以萘甲醛和2,6-二甲基苯胺或苯胺为原料合成了2种含萘的二胺单体, 进一步与二苯醚四酸二酐(ODPA)经高温溶液缩聚, 得到2种侧链含萘的聚酰亚胺, 对聚合物进行了核磁共振谱、 傅里叶变换红外光谱及溶解性、 耐热性、 憎水性、 机械性能等结构与性能的测试. 结果表明, 含醚侧链含萘的聚酰亚胺具有优异的溶解性, 良好的耐热性, 较好的憎水性与机械性能. 另外, 通过静电纺丝的方法制备了侧链含萘的聚酰亚胺纤维, 研究了纤维的形貌与憎水性.     

Qualitative Analysis of One-Step Algebraic Models with Tridiagonal Toeplitz Matrices

One-step algebraic models with symmetric and positive definite (SPD) tridiagonal Toeplitz matrices are introduced and their qualitative properties are studied. Theoretical results are applied to the numerical solution of parabolic differential equations, with illustrations by numerical examples. Possible extensions as well as arising open problems are discussed in concluding remarks.     

Role of final states in photoemission from Al(1 1 1)

Enhancement of surface state peaks in angle resolved ultraviolet photoelectron spectra (ARUPS) from the Al(1 1 1) surface is studied experimentally and theoretically within the one-step model of photoemission. The resonant enhancement of the surface state emission is explained by the crucial role of elastic scattering of the outgoing electron. Dipole transitions to evanescent states in the final bands of the crystal are shown to determine photoemission at the resonant photon energy. The band structure based explanation is confirmed by the measurements of electron reflectivity and of the fine structure of valence band spectra. The surface sensitivity of ARUPS is shown to depend strongly on the complex band structure of the crystal and to be finely tunable by the choice of photoemitted electron energy.     

Conditional Logistic Regression With Longitudinal Follow-up and Individual-Level Random Coefficients: A Stable and Efficient Two-Step Estimation Method

The analysis of data generated by animal habitat selection studies, by family studies of genetic diseases, or by longitudinal follow-up of households often involves fitting a mixed conditional logistic regression model to longitudinal data composed of clusters of matched case-control strata. The estimation of model parameters by maximum likelihood is especially difficult when the number of cases per stratum is greater than one. In this case, the denominator of each cluster contribution to the conditional likelihood involves a complex integral in high dimension, which leads to convergence problems in the numerical maximization. In this article we show how these computational complexities can be bypassed using a global two-step analysis for nonlinear mixed effects models. The first step estimates the cluster-specific parameters and can be achieved with standard statistical methods and software based on maximum likelihood for independent data. The second step uses the EM-algorithm in conjunction with conditional restricted maximum likelihood to estimate the population parameters. We use simulations to demonstrate that the method works well when the analysis is based on a large number of strata per cluster, as in many ecological studies. We apply the proposed two-step approach to evaluate habitat selection by pairs of bison roaming freely in their natural environment. This article has supplementary material online.