Syntheses and properties of novel polyimides derived from 2-(4-aminophenyl)-5-aminopyrimidine

2-(4-Aminophenyl)-5-aminopyrimidine (4) is synthesized via a condensation reaction of vinamidium salts and amidine chloride salts, followed by hydrazine palladium catalyzed reduction. A series of novel homo- and copolyimides containing pyrimidine unit are prepared from the diamine and 1,4-phenylenediamine (PDA) with pyromellitic dianhydride (PMDA) or 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidization method. The poly(amic acid) precursors had inherent viscosities of 0.97-4.38 dL/g (c = 0.5 g/dL, in DMAc, 30 degrees C) and all of them could be cast and thermally converted into flexible and tough polyimide films. All of the polyimides showed excellent thermal stability and mechanical properties. The glass transition temperatures of the resulting polyimides are in the range of 307-434 degrees C and the 10% weight loss temperature is in the range of 556-609 degrees C under air. The polyimide films possess strength at break in the range of 185-271 MPa, elongations at break in the range of 6.8-51%, and tensile modulus in the range of 3.5-6.46 GPa. The polymer films are insoluble in common organic solvents, exhibiting high chemical resistance.

Hydrogen peroxide biosensor based on sol-gel-derived glasses doped with Eastman AQ polymer

A hydrogen peroxide biosensor based on sol-gel-derived glasses doped with poly(ester sulfonic acid) Eastman AQ 55D was constructed. Thionine (TH), as a mediator, was incorporated in this matrix by electrostatic force between TH+ and the negatively charged sulfonic acid group in Eastman AQ polymer. Performance and characteristics of the sensor were evaluated with respect to response time, sensitivity and storage stability. The enzyme electrode has a sensitivity of 11.36 muA mM(-1) with a detection limit of 5.0 x 10(-7) M H2O2, and the sensor achieved 95% of the steady state current within 20 s. (C) 2001 Elsevier Science B.V. All rights reserved.

In situ FTIR spectroelectrochemistry of a microarray electrode

A thin-layer microdisk array electrode (TLMDAE) was designed for in situ reflectance FTIR spectroelectrochemical studies. A theoretical estimation, cyclic voltammetry, chronoamperometry and in situ IR measurements demonstrate that this novel design of array electrode results in advantages such as reduced ohmic potential drop, small cell constant and facility for diffusional exchange between thin layer and bulk solution. It has been suggested that the enhanced edge diffusion on the TLMDAE leads to a reduced accumulation of species in the thin layer. (C) 1997 Elsevier Science S.A.

On highly discriminating molecular topological index

A highly discriminating molecular topological index, EAID, is proposed based on the extended adjacency matrix. A systematic search for degeneracy was performed for 3 807 434 alkane trees, 202 558 complex cyclic or polycyclic graphs, and 430 472 structures containing heteroatoms. No counterexamples (two or more nonisomorphic structures with the same EAID number) were found. This is a hitherto unheard of power of discrimination. Thus EAID might be possibly used as supplementary reference for CAS Registry Numbers for structure documentation.

硝酸铕和铽与穴醚固体配合物的发光

应用荧光光谱研究了稀土硝酸铕和硝酸铽的穴醚配合物，结果指出配合物的发光强度强于稀土硝酸盐，说明有机大环配体穴醚能有效地吸收和传递能量给稀土离子．

H-1 and C-13 NMR studies of TTHA complexes with diamagnetic rare earth ions

TTHA complexes with diamagnetic rare earth ions (La3+, Y3+ and LU(3+)) were studied by H-1 and C-13 NMR spectroscopy. A symmetric structural model was suggested for La(TTHA) complex and an asymmetric model for Y(TTHA) and Lu(TTHA) complexes. The complex formation was dependent on the pH value of the solution. The interactions of La(TTHA) with the additional metal ions (La3+, Y3+ and Ca2+) were relatively weak, but relatively strong for that of Lu(TTHA) with the additional Lu3+.

N-乙基吡啶四(α-噻吩甲酰三氟丙酮)合铕的合成和晶体结构

合成了标题络合物的晶体,在四圆衍射仪上测得其晶体结构。晶体Eu(TTA)_4Epy属三斜晶系,P(?)空间群,中心离子Eu(Ⅲ)和4个TTA~-通过8个氧原子螯合配位,Epy为外界阳离子。晶胞参数如下:a=12.437(5),b=17.816(3),c=10,706(3)(?),α=90.92(2)°,β=102.01(3)°,γ=87.10(2)°,Z=2。此外,还对该化合物的热稳定性、红外及紫外可见光谱以及荧光性质进行了研究。

高聚物玻璃化转变温度和分子参数的关系 Ⅰ.高聚物链柔性与T_g的关系

本文采用晶格模型,以动力学链段长度作为统计单元大小,推导了高聚物玻璃化温度T_8和链静态刚性因子σ~2(T_8),链动态刚性因子β(T_8)以及聚合度DP等分子参数之间的关系。具体讨论了链柔性对T_8的影响。理论预测和几十种聚合物的实验数据能较好吻合,分析结果表明T_8值基本上取决于高聚物链σ(T_8)大小。

环辛二烯基稀土配合物的合成与表征

迄今,有关环辛二烯基作为配体的金属有机化合物报道得很少,只报道过它的碱金属、碱土金属及为数不多的过渡金属化合物,而从未报道过环辛二烯基稀土化合物。本文通过元素分析、红外光谱、核磁共振、质谱、热失重及气相色谱分析,确认合成了下述环辛二烯基稀

钙钛石型催化剂La_(1-x)Sr_xFeO_(3-λ)的高分辨电子显微镜研究

钙钛石型复合氧化物的缺陷性质与其催化性能密切相关。在以前的报告中,作者用XRD、TG、Mssbauer谱等技术,研究了La_(1-x)Sr_xFeO_(3-λ)体系催化剂的晶体结构和缺陷性质以及它们与该体系催化剂在氨氧化反应中催化性能之间的关系,提出了在氧缺陷浓度较大的钙钛石中可能产生氧空位有序排列的结构.本文通过对上述体

钐与磷酸二甲酯配合物的合成和结构

合成了钐与磷酸二甲酯的配合物,该配合物的组成为Sm〔(CH_3O)_2PO_2〕_3,测定了该配合物的红外和拉曼光谱。x射线单晶衍射法测定配合物的晶体属单斜晶系,P2_(1/c)空间群,α=10.434(4)A,b=16.541(3)A,c=10.804(4)A,β=111.75(3)°,V=1731.7(9)A~3,Z=4。钐与6个氧原子配位,每2个相邻的钐原子通过双“O—P—O”桥相连接,形成奇特的“双桥24元环”的环套环网状结构。钐氧配位多面体为稍微扭曲的正八面体。

Phycobilisomes linker family in cyanobacterial genomes: divergence and evolution

Cyanobacteria are the oldest life form making important contributions to global CO2 fixation on the Earth. Phycobilisomes (PBSs) are the major light harvesting systems of most cyanobacteria species. Recent availability of the whole genome database of cyanobacteria provides us a global and further view on the complex structural PBSs. A PBSs linker family is crucial in structure and function of major light-harvesting PBSs complexes. Linker polypeptides are considered to have the same ancestor with other phycobiliproteins (PBPs), and might have been diverged and evolved under particularly selective forces together. In this paper, a total of 192 putative linkers including 167 putative PBSs-associated linker genes and 25 Ferredoxin-NADP oxidoreductase (FNR) genes were detected through whole genome analysis of all 25 cyanobacterial genomes (20 finished and 5 in draft state). We compared the PBSs linker family of cyanobacteria in terms of gene structure, chromosome location, conservation domain, and polymorphic variants, and discussed the features and functions of the PBSs linker family. Most of PBSs-associated linkers in PBSs linker family are assembled into gene clusters with PBPs. A phylogenetic analysis based on protein data demonstrates a possibility of six classes of the linker family in cyanobacteria. Emergence, divergence, and disappearance of PBSs linkers among cyanobacterial species were due to speciation, gene duplication, gene transfer, or gene loss, and acclimation to various environmental selective pressures especially light.

Depth inversion in coastal water based on SAR image of waves

Wave-number spectrum technique is proposed to retrieve coastal water depths by means of Synthetic Aperture Radar (SAR) image of waves. Based on the general dispersion relation of ocean waves, the wavelength changes of a surface wave over varying water depths can be derived from SAR. Approaching the analysis of SAR images of waves and using the general dispersion relation of ocean waves, this indirect technique of remote sensing bathymetry has been applied to a coastal region of Xiapu in Fujian Province, China. Results show that this technique is suitable for the coastal waters especially for the near-shore regions with variable water depths.

中国鲳属鱼灯形态和生化特征及系统发育研究

鲳属鱼类是鲈形目中具有很高经济价值的名贵鱼类，广泛分布于我国沿海。我国是鲳鱼产量最高的国家之一，仅1995年产量就达20.9万吨(中国渔业统计年鉴,1995),约占世界鲳鱼达的60%以上.近二、三十年来，由于受传统业资源的过度开发、近海资源不足以及海洋环境污染因素影响，我国四大渔业中的大、小黄鱼及带鱼资源相继衰竭，使年产约２０万吨的鲳属鱼类在我国海洋渔业中占据越来越理要的地位，引起了国内外鱼类学家的广泛注意。然而，鲳属鱼类的分布和命名问题，长期以来，国内外专家学者众说纷绘纭、菲衷一是。本文总结的近二百年来有问中国鲳属鱼类分类研究的国内外文献资料，根据中国科学院海洋研究所历年（1951－1998）采集并收藏的以及新补充采集的鲳鱼标本，对我国沿海鲳属鱼类的外部形态（包括体形、体色、鳍、鳞片）、消化器官（包括牙齿、食道侧囊、胃、幽门盲囊、肠、肝）、呼吸器官、感觉器官、骨骼系统（包括脑颅、咽颅、脊椎骨、附肢骨骼）等生化特征作了系统地比较研究，并用支序分类学原理和方法分析了中国鲳属种间的系统发育关第，得到如下结果：1. 中国沿海鲳属鱼分共有5种:银鲳Pampus argenteus (Euphrasen,1788)、翎鲳P. punctatissimus (Temminck et Schlegel, 1845)、灰鲳 P.cinereus (Bloch, 1793) 、中国鲳P. chinensis (Euphrasen, 1788)和珍鲳P. minor Liu et Li, 1998, sp. nov,. 其中银鲳、灰鲳和中国鲳曾多次出现在我国近海地区性鱼类志和地方鱼类志中，本文对它们进物了准确的鉴定和描述，对翎属P. punctatissimus 进行了重新描述，在我国为新记录；论证了珍鲳P. minor为区别于鲳属其它独立有效的一新种。2. 形态学化较研究表明，5种鲳属鱼类在体形、体色、鳍棘、鳍条、牙齿、幽门盲囊、鳃耙、头后部侧线管、 头骨、脊椎骨、耳石等特征方面存在明显的种间差异，可作为鲳属鱼类分类的有效鉴别特征。3.中国沿海的中国鲳P. chinensis (Euphrasen,1788)与印渡洋的瑷鲳 P. ctous (Cuvier et Valenciennes, 1833)形态差异很小，认为P. atous (Cuivier et Valenciennes, 1833) 与P.chinensis (Euphrasen, 1788)可能为同一种，P. atous 应为P. chinesnsis 的同物异名。4.鲳属鱼类的肌浆蛋白酶（Pm）、酯酶（EST）和超氧化物歧化酶（SOD）具有明显的种的特异性，乳酸脱氢酶（LDH）则无种间差异。青岛、上海、厦门和珠海4个取样地点的银鲳的Pm和EST酶谱完全相同，同样，上述4个取地点的瓴鲳Pmt EST 酶谱也完全相同，从生化学的角度证明我国各海区的银鲳的翎鲳各为同一个种。5.银鲳和翎鲳为广盐广域种，我国黄渤海、东海、台湾海峡和地海均有分布，而且种群数量最大；灰鲳和中国鲳分布于我国东海南部、台湾海峡中部以南和南海，为亚暖水种，种数量次之：珍鲳仅分布于台湾海峡南部的大陆沿岸及南海，为暖水种，其种群数量较小，在当在形成一定的渔汛。6.系统发育关系分析表明，中国鲳属鱼类构成一个单群，此属的共同离征有：1）成鱼无腹鳍；2）背鳍鳍条多于31枚；3）臀鳍鳍条多于30 枚；4）背鳍和臀鳍前部鳍条延长；5）下颌牙齿为三峰型； 6）食道侧囊1个；7）食道侧囊内乳突有放射状脚根；8）脊椎骨数目少、眼眶窝大、后颞窝骨显、耳石厚等近祖特征，但它们仍然具有鳃耙数目多、下颌牙禽少等近祖特征，也是较早期分化种；中国鲳具有个体大、背鳍和臀鲳不具鳍棘、背鳍和臀鳍鳍条数目较多、鳃耙数少且短、翼蝶骨较发达等特征，是毗较特化种； 翎鲳和灰鲳具有鳍第鳍棘和脊椎骨数目较多、鳃耙数较少等区同祖征和具有显著延长的背鳍和臀鳍前部鳍条等共同离征，是一对姐妹种。