Pressure and temperature dependence of the gas‐transport properties of dense poly[2,6‐toluene‐2,2‐bis(3,4‐dicarboxylphenyl)hexafluoropropane diimide] membranes

The gas‐transport properties of poly[2,6‐toluene‐2,2‐bis(3,4‐dicarboxylphenyl)hexafluoropropane diimide] (6FDA‐2,6‐DAT) have been investigated. The sorption behavior of dense 6FDA‐2,6‐DAT membranes is well described by the dual‐mode sorption model and has certain relationships with the critical temperatures of the penetrants. The solubility coefficient decreases with an increase in either the pressure or temperature. The temperature dependence of the diffusivity coefficient increases with an increase in the penetrant size, as the order of the activation energy for the diffusion jump is CH₄ > N₂ > O₂ > CO₂. Also, the average diffusion coefficient increases with increasing pressure for all the gases tested. As a combined contribution from sorption and diffusion, permeability decreases with increases in the pressure and the kinetic diameter of the penetrant molecules. Even up to 32.7 atm, no plasticization phenomenon can be observed on flat dense 6FDA‐2,6‐DAT membranes from their permeability–pressure curves. However, just as for other gases, the absolute value of the heat of sorption of CO₂ decreases with increasing pressure at a low‐pressure range, but the trend changes when the feed pressure is greater than 10 atm. This implies that CO₂‐induced plasticization may occur and reduce the positive enthalpy required to create a site into which a penetrant can be sorbed. Therefore, a better diagnosis of the inherent threshold pressure for the plasticization of a glassy polymer membrane may involve examining the absolute value of the heat of sorption as a function of pressure and identifying the turning point at which the gradient of the absolute value of the heat of sorption against pressure turns from a negative value to a positive one. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 354–364, 2004     

Theoretical kinetic study on the decomposition of 1,5‐diaminotetrazole

1,5‐Daminotetrazole (DAT) is of much interest because of the practical significance and the diversity of characteristics. The study on the decomposition pathway and the kinetics of DAT has been performed based on the quantum chemistry theory. The minimum energy path (MEP) calculation has shown that NH₂N₃ and NH₂CN are the initially detected products of DAT. And the structures of reactant, products and transition state were optimized with MP2 methods using 6‐311G** basis sets, and the energies were refined using CCSD(T)/6‐311G** levels of theory. The calculated rate constants were obtained using the conventional transition‐state theory (TST) and the canonical variational transition‐state theory (CVT) methods. The calculation results indicated that the energy barrier of decomposition reaction is 47.98 kcal mol^?1 and the variational effect is small. In addition, the rate constants and the Arrhenius experience formula of DAT decomposition have been obtained between 200 and 2500 K temperature regions. The fitted three‐parameter expressions calculated using the TST and CVT methods are (TST) and (CVT). This work may provide the theoretical support for further experimental synthesis and testing. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and Characterization of a Novel Energetic Complex [Cd(DAT)6](NO3)2 (DAT = 1,5‐diamino‐tetrazole) with High Nitrogen Content

The novel high nitrogen‐containing energetic complex [Cd(DAT)₆](NO₃)₂ was synthesized by reaction of Cd(NO₃)₂·6H₂O with 1,5‐diamino‐tetrazole (DAT). It was characterized by elemental analysis, FT‐IR spectroscopy and single‐crystal X‐ray diffraction analysis. The central Cd²⁺ ion is coordinated by six nitrogen atoms from six DAT ligand molecules to form a hexacoordinate distorted octahedral compound. The [Cd(DAT)₆](NO₃)₂ molecules are linked together through two types of hydrogen bonds thus forming a stable three‐dimensional net structure. The thermal decomposition mechanism of [Cd(DAT)₆](NO₃)₂ was investigated by DSC and TG/DTG analyses and FT‐IR spectroscopy. The kinetic parameters of the exothermic process were studied by using Kissinger’s and Ozawa–Doyle’s methods.     

Experimental Study of Discriminative Adaptive Training and MLLR for Automatic Pronunciation Evaluation

A stronger canonical model was developed to improve the performance of automatic pronunciation evaluations.Three different strategies were investigated with speaker adaptive training to normalize variations among speakers,minimum phone error training to identify easily confused phones and maximum likelihood linear regression(MLLR) adaptation to compensate for accent variations between native and non-native speakers.The three schemes were combined to improve the correlation coefficient between machine scores and human scores from 0.651 to 0.679 on the sentence level and from 0.788 to 0.822 on the speaker level.     

3,5-二氨基-1,2,4-三唑苦味酸盐的比热容、热力学性质及爆速爆压的估算

目的研究三唑类含能离子化合物3,5-二氨基-1,2,4-三唑苦味酸盐(C8N8H8O7,简称DAT.PA)的比热容,热力学性质及爆速、爆压。方法比热容测定采用Micro-DSCⅢ微热量仪中的连续比热容测定模式;运用Gaussian 03W程序的DFT-RB3LYP/6-31g*方法对DAT·PA在283～353K的温度范围内进行了比热容理论计算;根据热力学基本方程计算以298.15 K为基础DAT.PA的热力学函数;采用氮平衡方程研究化合物的爆速和爆压。结果得到DAT.PA比热容方程为Cp(J/g·K)=-0.233 7+6.005 6×10-3T-5.396 9×10-6T2(283K相似文献   

ADTIQ导致SH-SY5Y细胞凋亡和多巴胺转运体表达降低

新内源性神经毒素1-乙酰基-6,7-二羟基-1,2,3,4-四氢异喹啉(ADTIQ)生成与糖代谢密切相关,可能成为糖尿病并发PD的一个关键因素,但是其神经毒性还不清楚.针对ADTIQ的神经毒性,该研究采用SH-SY5Y细胞为模型,MTT法,Annexin V/PI双染法,Caspase 3/7活性检测细胞存活率和细胞凋亡,Western-blot检测多巴胺转运体(DAT)的表达量.结果表明,随着ADTIQ浓度增大,细胞的存活率逐渐下降,凋亡率增加,同时ADTIQ导致DAT表达降低.研究提示ADTIQ导致多巴胺神经元的凋亡与PD的发生息息相关,糖尿病引起ADTIQ增加,可能成为高糖损伤多巴胺神经元的一个重要原因.     

Steroselective Hydrolysis of DL‐Beta‐Acetylthioisobutyramide Catalyzed by Genetically Engineered E. Coli Immobilized on Celite 580 in a Packed Bed Bioreactor

Pseudomonas putida IFO12996 catalyzes the stereoselective hydrolysis of methyl dl ‐β‐acetylthioisobutyramide (dl ‐ATIA) to form d ‐β‐acetylthioisobutyric acid (DAT), a key intermediate for synthesis of a series of angiotensin converting enzyme inhibitors. The esterase gene of Pseudomonas putida IFO12996 was cloned and expressed in Escherichia coli which was further immobilized and retained on a packed bed bioreactor filled with Celite 580. The packed bed bioreactor was used to conduct the stereoselective hydrolysis of dl ‐ATIA and to give DAT with a yield of 34.5%, enantiometric excess value of 97% and enantioselectivity value > 150. The optimal pH and temperature for the reaction were 9.0 and 57 °C ～ 67 °C, respectively. The kinetic constants (Km and Vmax) of immobilized cells were found to be 372.5 mM and 285.7 μmol min^?1 (g cell)^?1, respectively. The immobilized cells retained over 60% of the initial catalytic activity after 5 batch cycles of production. This paper presents a simple, practical and economical process of immobilization of genetically engineered E. coli on a novel packed bed bioreactor for production of DAT.     

变压器油中多组分故障气体的光纤检测

阐述了变压器油中故障气体光纤检测的意义，分析了气体浓度二次和三次谐波检测与调制点的关系；提出了方波调制ＬＤ的非机械斩波时分－差分检测方法；讨论分析了多组分气体的检测方法及其适用条件     

多巴胺系统相关基因与工作记忆研究进展

COMT、DRD1、DRD2和DAT1等一系列多巴胺系统基因的多态性均被证实与工作记忆表现具有显著的相关关系.对工作记忆和调控多巴胺水平相关基因的一些最新国内外研究成果作一综述,为今后我国工作记忆相关领域的研究提供一些启示与参考.     

聚合物胶乳超细水泥灌缝材料的微观结构

在苯乙烯/丙烯酸脂类聚合物R161乳液改性U型超细水泥的工作性试验研究的基础上,利用X-衍射(XRD)、扫描电镜(SEM)、热差分析(DTA)、热重分析(TG)和压汞测孔等多项现代物相测试分析技术,对R161改性U型超细水泥硬化浆体的微观形貌、水化产物及孔结构进行了研究,分析了聚合物改性超细水泥微观结构与宏观性能之间的相关性。结果表明:改性材料中粗晶粒减少,凝胶增多;聚合物的填充和密封作用使聚合物R161改性超细水泥(RMFC)界面过渡区水化物取向性降低,结构明显细化,总孔隙率减小,孔结构更趋合理,使这种新型裂缝修补材料的微观结构得到了全面改善。