Synthesis of electroluminescent copoly(aryl ether)s containing alternate 1,4‐distyrylbenzene derivatives and aromatic 1,3,4‐oxadiazole or 3,3″‐terphenyldicarbonitrile segments

New copoly(aryl ether)s ( P1 – P3 ) containing alternate 2,5‐dihexyloxy‐1,4‐di(m‐ethoxystyryl)benzene ( P1 , P2 ) or 2,5‐dihexyloxy‐1,4‐distyrylbenzene ( P3 ) chromophores and aromatic 1,3,4‐oxadiazole ( P1 ) or 3,3″‐terphenyldicarbonitrile ( P2 , P3 ) segments were prepared by Horner reaction ( P1 and P2 ) or nucleophilic displacement reaction ( P3 ). They are basically amorphous materials with 5% weight‐loss temperature above 410 °C. Their absorption, photoluminescence spectra, and quantum yields are dependent on the composition of the isolated fluorophores. The emissions are exclusively dominated by 1,4‐distyrylbenzene segments via excitation energy transfer from electron‐transporting 1,3,4‐oxadiazole ( P1 ) or 3,3″‐terphenyldicarbonitrile ( P2 , P3 ) chromophores. The HOMO and LUMO energy levels have been estimated from their cyclic voltammograms, and the observations confirm that oxidation and reduction start from the emitting 1,4‐distyrylbenzene and electron‐transporting segments, respectively, indicating that both carriers affinity can be enhanced simultaneously. Among the two‐layer PLED devices (ITO/PEDOT/ P1 – P3 /Al), P1 exhibits the best performance with a turn‐on field of 4 × 10⁵ V/cm and a maximum luminance of 225 cd/m². However, P2 emits green–yellow light (555 nm), owing to the excimer emission. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5009–5022, 2005     

A real options approach for entering the Internet securities trading businesses with start‐up time

This paper uses a real options approach to establish a new evaluation model under uncertainty of both the volume of Internet securities transactions and the total transaction volume of a securities firm. The proposed approach can assist securities firms in evaluating the optimal thresholds for entering the Internet securities trading business and withdrawing from the conventional securities trading business. This paper assumes that the annual number of Internet securities transactions and the total annual number of securities transactions both follow a geometric Brownian motion. Besides, this model considers a start‐up time to complete the entry project's procedure. Accordingly, a decision model based on the real options approach is introduced, and the closed form solutions for the optimal threshold values of the entry or withdrawal models are determined. The conclusions provide some valuable references to help strategic managers of securities firms in making decisions on entering the Internet securities trading business or withdrawing from the conventional trading business. Copyright © 2003 John Wiley & Sons, Ltd.     

Enumeration of trees by inversions

Mallows and Riordan “The Inversion Enumerator for Labeled Trees,” Bulletin of the American Mathematics Society, vol. 74 [1968] pp. 92-94) first defined the inversion polynomial, J_n(q) for trees with n vertices and found its generating function. In the present work, we define inversion polynomials for ordered, plane, and cyclic trees, and find their values at q = 0, ± 1. Our techniques involve the use of generating functions (including Lagrange inversion), hypergeometric series, and binomial coefficient identities, induction, and bijections. We also derive asymptotic formulae for those results for which we do not have a closed form. © 1995 John Wiley & Sons, Inc.     

非均匀变厚度梁的动力响应的一般解

在本文中提出一个新方法——阶梯折算法来研究在任意载荷下任意非均匀和任意变厚度伯努利-欧拉梁的动力响应问题.研究了自由振动和强迫振动.新方法需要将区间离散为一定数目的元素,每个元素可看作是均匀和等厚度的.因此均匀、等厚度梁的一般解可在每个元素上应用.然后用初参数表示的整个梁的一般解使之满足相邻二元素间的物理和几何连续条件,这样就可以得到解析形式的自由振动的频率方程和解析形式的强迫振动的最终解,它化为求解二元线性代数方程,与离散元素的数目无关.现在的方法可推广应用至任意非均匀及任意变厚度有粘滞性和其他种类的梁以及其他结构元件问题上去.     

Some Explanations of Dobinski's Formula

The geometric, algebraic, and combinatorial explanations of Dobinski's formula are presented by mixed volumes of compact convex sets, Möbius inversion, difference operator, and species. The employed method may be useful in proving some other combinatorial identities.     

Morphology of microporous poly(vinylidene fluoride) membranes studied by gas permeation and scanning electron microscopy

Microporous poly(vinylidene fluoride) (PVDF) membranes with asymmetric pore structure were prepared by a wet phase inversion process. The polymer was precipitated from a casting solution when immersed in a cold water (gelation) bath. The casting solution was, in most cases, composed of polymer, solvent, and nonsolvent. In this solvent-nonsolvent system, the solvents used were triethylphosphate (TEP) and dimethylsulfoxide (DMSO), and the nonsolvents used were glycerol and ethanol. Mean pore sizes and effective porosity of the microporous membranes were calculated using the gas permeation method. They were studied as a function of evaporation time of wet nascent film, polymer molecular weight, concentration of polymer, and concentration of nonsolvent. The morphology of the membranes was examined by scanning electron microscopy (SEM).     

CH Oxidation of Ingenanes Enables Potent and Selective Protein Kinase C Isoform Activation

Ingenol derivatives with varying degrees of oxidation were prepared by two‐phase terpene synthesis. This strategy has allowed access to analogues that cannot be prepared by semisynthesis from natural ingenol. Complex ingenanes resulting from divergent C? H oxidation of a common intermediate were found to interact with protein kinase C in a manner that correlates well with the oxidation state of the ingenane core. Even though previous work on ingenanes has suggested a strong correlation between potential to activate PKCδ and induction of neutrophil oxidative burst, the current study shows that the potential to activate PKCβII is of key importance while interaction with PKCδ is dispensable. Thus, key modifications of the ingenane core allowed PKC isoform selectivity wherein PKCδ‐driven activation of keratinocytes is strongly reduced or even absent while PKCβII‐driven activation of neutrophils is retained.