A three-dimensional analytical solution of the microheater temperature before bubble nucleation

A three-dimensional analytical solution of the microheater temperature based on heat diffusion equation is developed and compared with experimental results. Dimensionless parameters are introduced to analyze the temperature rise time and the distribution under steady state. To study the microheater temperatures before bubble nucleation, a set of working fluids and microheaters are considered. It is shown that the dimensionless time xi(-)(0) required for the temperature rise from room to 95% of the steady state temperature is about 75, not dependent on working fluids and microheaters. Heat transfer to the surrounding liquid is mainly caused by conduction, not by convection and radiation mechanisms. The microheater length affects the surface temperature uniformity, while its width influences the steady temperatures significantly, yielding the transition from heterogeneous to homogeneous nucleation mechanism from square microheaters to narrow line microheaters. 

A new quaternary ammonium heteropolyoxotungstate catalyst for propylene epoxidation to propylene oxide

A new quaternary ammonium heteropolyoxotungstant (cat.C) is prepared and characterized. And the cat.C also is an reaction-controlled phase-transfer catalyst. The catalytic system of O-2/EAHQ (2-ethylanthrahydroquinone)/cat.c is used for the epoxidation of propylene. Under the optimal conditions, the yield of propylene oxide based on EAHQ is 84.1%, the selectivity for propylene oxide based on propylene is 99.8% and the conversion of propylene based on EAHQ is 84.3%. The cat.c precipitates after the epoxidation reaction for easy separation. The cat. C is stable enough to be recycled three times without any loss in selectivity.

土壤中难降解有机污染物锁定机理研究进展

有机污染物进入土壤后,随着与土壤接触时间的延长,被锁定在土壤中,生物可利用性下降.锁定可能导致过高估计难降解有机污染物的暴露风险,影响修复技术的实施.锁定发生的内在机制主要源于粘土矿物、有机质及非水相液体的不可逆吸附和微孔束缚,而影响土壤难降解有机污染物锁定的关键因素包括土壤物理化学性质和环境条件(湿度、温度、pH等).基于此,进一步阐明了目前土壤中难降解有机污染物锁定机理研究需要解决的问题,并对未来的发展趋势进行了展望.

改进的以SMT为基础的实时系统限界模型检测

基于SAT的限界模型检测在处理实时系统时具有很高的复杂度.SMT求解器在计算可满足性的同时,还能处理算术和其他可判定性理论.在对实时系统进行检测时,用SMT求解器代替SAT求解器,系统里的时钟就可以用整型或实型变量表示,时钟约束则可以直接表示成线性算术表达式,从而使整个检测过程更加高效.带时间参数的计算树逻辑(timed computation tree logic,简称TCTL)被用来描述实时系统里的性质.同时,还对检测方法作了相应的改进.

NMR investigation of phenolphthalein polyether ether ketone .1. The chain structure and assignments of H-1, C-13 NMR lines of PEK-C

Amorphous samples of polyether ketone with cardo(PEK-C) have been studied in the solution state by C-13, H-1 high-resolution NMR, The H-1 and C-13 1D NMR spectra were assigned using two dimensional chemical shift correlated spectroscopy, 2D homonuclear correlated(COSY) and heteronuclear correlated (HETCOR) spectroscopy present important information. In this work, the structural units of PEK-C was determined by NMR. For some peaks, these assignments are confirmed by two dimensional long-range heteronuclear correlation experiments, A little modification is made on the original C-13 peak assignments for the main chain, The symmetry and the isotacticity of the chain structure for PEK-C are obvious on NMR data.

酞侧基聚芳醚酮的核磁共振研究（Ⅰ）──链结构及NMR谱的归属

用１Ｄ　ＮＭＲ方法研究酞侧基聚芳醚酮（ＰＥＫ－Ｃ）链结构，用二维同核化学位移相关与二维异核化学位移相关实验方法对１Ｄ　ＮＭＲ谱峰进行归属，探讨了二维异核远程相关实验在缩聚高分子研究中的应用，为ＰＥＫ－Ｃ修饰机理以及共混相容机理的研究提供重要信息。溶液ＮＭＲ谱图数据表明，ＰＥＫ－Ｃ具有较规整的链结构。

A novel hydroperoxyl substituted cembranolide diterpene from marine soft coral Lobophytum crassum

A new cembranolide diterpene with a hydroperoxyl substitution was isolated from the marine soft coral Lobophytum crassum. The structure was elucidated on the basis of chemical and spectral methods.

青藏高原不同海拔矮蒿草抗氧化系统的比较

对生长在青藏高原不同海拔自然生境下的多年生典型抗寒植物－矮蒿草（Kobresia humilis）的抗氧化系统进行了比较研究。结果表明，矮蒿草的叶组织中，非酶抗氧化系统物质脯氨酸（Pro）和抗坏血酸（AsA），随着海拔升高具有明显的增加趋势。在抗氧化酶系统中，过氧化物酶（POD）和过氧化氢酶（CAT）活性均随海拔的升高，而明显增强。但叶中的超氧化物歧化酶（SOD），随着海拔的升高，其活性有下降趋势，三者变化趋势并不一致。高海拔矮蒿草的植株与低海拔的植株相比，叶细胞内的膜脂过氧化加剧，丙二醛（MDA）含量明显增。细胞可溶性蛋白也随海拔升高显著增加。根中的抗氧化系统变化与叶中的有所不同。根中AsA含量随海拔而显著升高，且较叶中的增加明显，但Pro含量则有所减少。根中的CAT和POD活性变化与叶中的变化趋势基本一致，且随海拔高度的增加，根中的CAT活性较叶中的变化更为明显。而根中的SOD活性变化不如叶中明显，MDA含量随海拔增高，其变化趋势比叶中的小。可见，青藏高原典型抗寒植物矮蒿草体内的两类抗氧化系统，在不同海拔条件下可能存在互补协同的调节作用，这可能是矮蒿草适应或抵抗高原极端高寒低温和强UV－B辐射等环境胁迫的重要生理机制之一。