Synthesis and herbicidal activity of O,O-dialkyl phenoxyacetoxyalkylphosphonates containing fluorine

A series of substituted phenoxyacetoxyalkylphosphonates bearing fluorine were designed and synthesized. All the new compounds were identified by elemental analysis, IR, ¹H NMR and MS and were tested for herbicidal activity in greenhouse at a rate of 1.5 kg/ha. The results of preliminary bioassay showed that fluorine moiety introduced to the core structure could help to improve the herbicidal activity, and compounds with a 3-trifluoromethyl in benzene ring exhibited higher inhibitory activity.     

用定义求解高等数学中的有关问题

应用导数的定义，为分段函数的分界点提供了一种行之有效的求导方法，利用微分的定义判断函数在分界点及其他特殊点的可微性，运用定和分的定义求一类特殊类型的极限．     

"全反射"与课堂教学素质化

素质教育的主阵地是课堂教学.如何切实做到物理教学素质化呢?下面结合“全反射”的教学,谈几点看法和做法.1 课堂教学目标构建的多元性 课堂教学强调目标构建的多元性,以完成教学多方位的艰巨任务,这是素质教育的重要教学特征之一.因而在制定具体的物理教学目标时,既要有知识、技能方面的要求,     

Effect of track stiffness on vibration levels in railway tunnels

The paper discusses the difficulties in comparing and drawing conclusions from vibration measurements made in different railway tunnels. A number of new measurements are presented, which have been made and analyzed on a consistent basis. The track stiffness has been determined for each of the measurements. Graphs are presented which indicate the level of rail and tunnel floor vibration likely to occur for different track stiffnesses. The variance in the measurement results also indicates the potential error in using the data to predict vibration levels in new situations.     

New Synthetic Method for Industrial Manufacture of Glutaric Dialdehyde

A new synthetic method for the manufacture of glutaric dialdehyde is investigated. Glutaric dialdehyde was prepared by the addition-hydrolysis reaction of benzimidazolium salt with saturated dihalide as the di-Grignard reagent. The yield of glutaric dialdehyde by this method can reach 73%. Both infrared spectra and melting point of the compound were consistent with those reported earlier. Translated from Journal of Northwest University (Natural Science Edition), 2005, 35(2) (in Chinese)     

Multiple recurrence and nilsequences

Aiming at a simultaneous extension of Khintchine(X,X,m,T)(X,\mathcal{X},\mu,T) and a set A ? XA\in\mathcal{X} of positive measure, the set of integers n such that A T^2nA T^knA)(A)^k+1-\mu(A{\cap} T^{n}A{\cap} T^{2n}A{\cap} \ldots{\cap} T^{kn}A)>\mu(A)^{k+1}-\epsilon is syndetic. The size of this set, surprisingly enough, depends on the length (k+1) of the arithmetic progression under consideration. In an ergodic system, for k=2 and k=3, this set is syndetic, while for kòf(x)f(Tⁿx)f(T²ⁿx)? f(T^knx)  dm(x)\int{f(x)f(T^{n}x)f(T^{2n}x){\ldots} f(T^{kn}x) \,d\mu(x)} , where k and n are positive integers and f is a bounded measurable function. We also derive combinatorial consequences of these results, for example showing that for a set of integers E with upper Banach density d^*(E)>0 and for all {n ? \mathbbZ\colon d^*(E?(E+n)?(E+2n)?(E+3n)) > d^*(E)⁴-e}\big\{n\in\mathbb{Z}{\colon} d^*\big(E\cap(E+n)\cap(E+2n)\cap(E+3n)\big) > d^*(E)^4-\epsilon\big\}     

Analysis of Radiation Phenomena in a Wedge Ended Dielectric Slab Waveguide

Radiation phenomena observed in a wedge shape ended dielectric slab waveguide are analyzed using mode matching technique. The case of transverse electric polarization (TE) being parallel to dielectric slab waveguide is assumed. In order to describe the fields in the wedge region, a stack of dielectric plates is assumed and in each layer the fields are expanded in terms of the mixed spectrum of guided and radiated modes. A similar expansion is used in the constant thickness slab waveguide while in free space medium a continuous-radiation mode expansion is used. Then a mode matching approach is applied, incorporating the orthogonality properties of mixed spectrum modes, in order to compute the wave fields inside the dielectric slab waveguide and wedge medium. Mode matching is achieved by discretizing the continuous radiation mode spectrum leading into a numerically stable solution provided a sufficient large number of points are used to convert integrals into finite summations. Numerical computations are carried out for various wedge geometries and shapes including linear and exponential profiles.     

On the use of enzyme adsorption and specific hydrolysis rate to characterize thermal-chemical pretreatment

Applied Biochemistry and Biotechnology - The pseudo enzyme adsorption isotherm of the pretreated substrate is used to estimate the pretreatment’s effectiveness in generating accessible...