Taxanes from the leaves of <Emphasis Type="Italic">Taxus cuspidata</Emphasis>

A new taxane, 13-oxobaccatin III (2), and five known taxanes, 10-deacetyl-13-oxobaccatin III (1), baccatin III (3), 7-epi-10-deacetyltaxol (4), 19-debenzoyl-19-acetyltaxinine M (5), and 5a-decinnamoyltaxagifine (6), were isolated from the leaves of the Japanese yew, Taxus cuspidate. Their structures were established on the basis of the analysis of their spectral data.     

Completely positive tensors in the complex field

In this paper, we introduce the complex completely positive tensor, which has a symmetric complex decomposition with all real and imaginary parts of the decomposition vectors being non-negative. Some properties of the complex completely positive tensor are given. A semidefinite algorithm is also proposed for checking whether a complex tensor is complex completely positive or not. If a tensor is not complex completely positive, a certificate for it can be obtained; if it is complex completely positive, a complex completely positive decomposition can be obtained.     

Global Hopf bifurcation of differential equations with threshold type state-dependent delay

We develop global Hopf bifurcation theory of differential equations with state-dependent delay using the S¹$S^1$-equivariant degree and investigate a two-degree-of-freedom mechanical model of turning processes. For the model of turning processes we show that the extreme points of each vibration component of the non-constant periodic solutions can be embedded into a manifold with explicit algebraic expression. This observation enables us to establish analytical upper and lower bounds of the amplitudes of the periodic solutions in terms of the system parameters and to exclude certain periods. Using the achieved global bifurcation theory we reveal that if the relative frequency between the natural frequency and the turning frequency varies in a certain interval, then generically every bifurcated continuum of periodic solutions must terminate at a bifurcation point. This termination means that the underlying system with parameters in the stability region near the vertical asymptotes of the stability lobes is less subject to chatter. In the process, several sufficient conditions for the non-existence of non-constant periodic solutions are also obtained.     

A novel approach to prepare silver chloride nanoparticles grown on the surface of PAN nanofibre via electrospinning combined with gas–solid reaction

Well-defined silver chloride nanoparticles grown on the surface of PAN nanofibre were synthesized by electrospinning technology combined with gas–solid reaction. This method can avoid the possibility of the waste of raw material as well as enhance the usage rate of AgNO₃. The PAN nanofibre can be recycled easily. X-ray powder diffraction (XRD) shows the presence of crystal AgCl, X-ray photoelectron spectroscopy (XPS) confirm that there are chemical bonds and interaction between the surface modified PAN nanofibre and Ag ions. This will be propitious to prevent nanoparticles from aggregation. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) gave the direct evidence that AgCl nanoparticles have been dispersed on the surface of PAN nanofibre homogeneously.     

我国人口就业增长与经济发展状况的关系分析

Today the one of the main social problem is employment. It is very important that how to treat with the relations among growth rates of economy, reformation strength and good employment and find the key point of macro control. In this paper the relationship among the employment of each industries, population, GDP and total investment in fixed assets is studied by mathematical modeling and applied mathematical statistics analysis. It is drawn that the outline of growth rates of employed persons in recent years. By these analyses our point view is to develop the tertiary industry so as to enhance the growth rates of employed persons when the economic increasing keeps appropriate rate.     

Synthesis of Biaryls via Pd-Catalyzed Decarboxylative Coupling of Substituted Benzoic Acids with Phenylboronic Acids

A Pd-catalyzed decarboxylative coupling of substituted benzoic acids with phenylboronic acid has been developed. Under the optimized conditions, a variety of substituted benzoic acids were found to undergo decarboxylative coupling with various phenylboronic acids to give the desired unsymmetrical biaryls in good yields.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

邻基参与与水解反应

描述了邻基参与的各种水解反应。     

关于体上矩阵方程Am×nXn×s＝Bm×s的解

根据体上矩阵研究的新近进展，本文给出了任意体上的矩阵力方程A_m×nX_n×s＝B_m×s(1)的解判别定理及其通解的显式表示，并给出了（１）的一种有实用价值的简便解法。     

Roth定理及一类方程的求解在环上的推广

设Ｒ是一个含幺环且它的中心包含一个域，本文将Ｒｏｔｈ的等价与相似定理推广到了Ｒ上，研究了含幺正则环上的一类方程ａｘｂ＋ｃｙｄ＝ｅ有解的充要条件及其通解表达式．