A novel hyperbranched polyester acrylate used for microfabrications

A novel hyperbranched polyester acrylate (HPEA) was synthesized based upon ethylenediamine tetraacetic acid as a “core” molecule, 5‐hydroxyisophthalic acid as an AB₂ monomer, and 2‐hydroxyethyl acrylate as an endcapping reagent. The obtained oligomer has an unsaturation concentration of 4.10 mmol_C?C g^?1 measured by nuclear magnetic resonance and a wide molecular weight distribution of 1.64 measured by gel permeation chromatography. The two‐photon absorption (TPA) photopolymerization of HPEA under the exposure of a Ti : sapphire femtosecond laser with a wavelength of 800 nm was investigated through laser exposure dose‐dependant spatial resolutions of its resins. The TPA photopolymerization thresholds at the range 1.6–4.3 × 10⁷ mJ cm^?2, and exposure dose windows at the range 3.4–4.3 for three formulations were determined. A spatial resolution of 0.85 μm was obtained through the TPA photopolymerization of the formulation containing 1 wt% photoinitiator and 0.3 wt% photoinhibitor. A diffraction grating and real three‐dimensional coupled gear wheel created by TPA photopolymerization were described to demonstrate the unique capability of HPEA in microfabrications. Copyright © 2004 John Wiley & Sons, Ltd.     

Effect of initiators on grafting in the initial stage of the emulsion polymerization of methyl methacrylate using poly(vinyl alcohol) as a protective colloid

 To make clear the reason of unsuitability of poly(vinyl alcohol) (PVA) protective colloid for the emulsion polymerization of conjugated monomers, a model experiment of emulsion polymerization of methyl methacrylate (MMA) was carried out with ammonium persulfate (APS) or azobis(isobutyronitrile) (AIBN) initiators, where a small amount of MMA (1/100th of the concentration compared with ordinary emulsion polymerization) was employed. This corresponds to the initial stage of the emulsion polymerization. Grafting of MMA onto PVA took place remarkably irrespective of the kind of the initiators. Formation of homo-poly(MMA) was observed to a small extent. The formation of new emulsion particles smaller than 100 nm continued to increase to almost the end of the polymerization. PVA molecules in the grafted polymer are supposed to act as stabilizers of newly formed particles. From kinetic treatment using the experimental data, the important issues were derived as follows. Firstly, the sulfate anion radical from APS is much more reactive than the isobutyronitrile radical from AIBN in terms of hydrogen abstraction from PVA. Secondly, high grafting ability of the latter initiator system, notwithstanding the much lower reactivity in the hydrogen abstraction compared with the APS system, is attributed to the relative reactivity of the primary radicals, i.e., hydrogen abstraction reaction from PVA to initiation reaction with MMA. The much slower rate of addition of the isobutyronitrile radical to the monomer compared with that of hydrogen abstraction from PVA facilitates the grafting, although the rate constant of hydrogen abstraction is far smaller than that with the sulfate anion radical by 10⁻⁴ times. Received: 26 April 2001 Accepted: 6 September 2001     

二维卷积在动力学分析中的应用

本文用计算机模拟和二维卷积研究了稀土与间乙酰基偶氮氯膦的显色反应，选择不同的模型参数可描述这类反应的细节，二维卷积则增强对叠合二维谱的分辨。     

云南两高辐合背景下低涡强降水过程对比分析

基于气象观测和欧洲中期天气预报中心第五代大气再分析资料（ERA5）,选取2018—2020年发生在云南的3次两高压辐合区（以下简称两高辐合）背景下低涡连续性强降水过程进行对比分析,探究其环流形势、动热力因子及水汽辐合的相似性和差异性.结果显示：(1)夏半年西太平洋副热带高压（以下简称西太副高）西伸时,云南常受两高辐合影响,当辐合区中有低涡生成,易发生连续性强降水,且强降水落区并不完全分布在整个狭长的两高辐合区内.(2)两高辐合区低涡降水具有相似的雨带分布和移动特征,但雨带的集中程度、分布范围、小时雨强和总雨量存在差异.强降水开始时,落区偏东,随着西太副高西伸及东北引导气流的引导,低涡向南向西移动,强降水落区也随之向南向西移动.低涡在某一地区徘徊导致降水集中在该区域,且西太副高西伸较强时,两高辐合形势更强,低涡降水大雨及以上量级雨带也更窄.(3)低涡造成的降水主要分布在低涡中心及低涡切变附近,且降水发生在低层暖湿的环境中,低层及中高层有冷空气侵入时,小时雨强的极端性更强,降水落区也相对偏北.两高辐合区低涡降水落区与水汽辐合区对应较好,水汽辐合强度较弱时,对应的总降水量较小.     

Randomized algorithms for the separation of point sets and for solving quadratic programs

A randomized algorithm for finding a hyperplane separating two finite point sets in the Euclidean space ^d and a randomized algorithm for solving linearly constrained general convex quadratic problems are proposed. The expected running time of the separating algorithm isO(dd! (m + n)), wherem andn are cardinalities of sets to be separated. The expected running time of the algorithm for solving quadratic problems isO(dd! s) wheres is the number of inequality constraints. These algorithms are based on the ideas of Seidel's linear programming algorithm [6]. They are closely related to algorithms of [8], [2], and [9] and belong to an abstract class of algorithms investigated in [1]. The algorithm for solving quadratic problems has some features of the one proposed in [7].This research was done when the author was supported by the Alexander von Humboldt Foundation, Germany.On leave from the Institute of Mathematics and Mechanics, Ural Department of the Russian Academy of Sciences, 620219 Ekaterinburg, S. Kovalevskaya str. 16, Russia.     

统一认识和准确把握我国的基本国情

在世纪之交、继往开来的重要时刻,党的十五大重新强调我国正处于并将长时期处于社会主义初级阶段,内涵深刻,意义深远。统一认识和准确把握我国的基本国情,搞清楚什么是初级阶段的社会主义,在初级阶段怎样建设社会主义等问题,对坚持走有中国特色社会主义发展道路,实现跨世纪宏伟大业,到下个世纪中叶基本实现社会主义现代化,具有重大的理论意义和现实意义。     

拟塑性流体理论中一类奇异非线性边界值问题

研究了起源于拟塑性流体理论中的一类奇异非线性两点边界值问题正确的存在性和唯一性。     

一维双向耦合映象网络及其应用

全局耦合映象具有硬件集成化实现不便的缺点,为此本文研究了各混沌神经元之间局部耦全的一维双向耦合混沌神经网络,发现它同样具有全局耦合映象的分类功能,对一维双向耦合网络的动态特性进行了分析,提出了利用网络的时空特性对信息进行存储的思想,并提出了将其应用到保密通信的初步设想。     

Structural and expressional analysis of a cDNA that expresses predominantly in rice stamens

The development of stamen is an important stage during the sexual reproduction in higher plants. Studying the genes that predominantly or even specifically expressed in stamens will aid in undestanding the molecular mechanism of stamen development. The structure of a rice CHS-like gene (D5) which predominantly expressed in anthers has been analysised, showing high structural similarity with two other anther-specific genes (A1 and BA42) fromBrassica napus. Northern analysis also reveals that the three genes share a similar expression pattern and that the expression of D5 may relate to the early development of pollens. It is concluded that D5, A1 and BA42 represent a group of diverged CHS-like genes which are related to stamen development.