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991.
The electronic structure and chemical bonding of the title comp-lexes have been studied by an unrestricted INDO program made applicable forthe lanthanoid compounds.The results indicated:(1)In coordinated bonds O-Lnand N-Ln,5d orbitals of Ln have large contribution in all valence orbitalsof Ln and 4f orbitals have very small contribution.(2)The covalent chara-cter and ionic character are almost equal in the chemical bond which iscomparatively weak between phen,C_2H_5OH and Ln are mainly ionic with somecovalent character. 相似文献
992.
Guan Z 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(14):3086-3092
Chain-walking catalysts are demonstrated to control the branching topology of polyethylene by tuning the competition between monomer insertion and chain isomerization (walking). The topology of the polyethylene was controlled from linear with moderate branching to hyperbranched to dendritic. Although overall branching number and distribution of short chain branching are relatively constant, the topology of the polyethylene changes from linear polyethylene with moderate branches at high ethylene pressures to a dendritic polyethylene at low pressures. This provides a straightforward one-pot process for making polymers with a full range of tunable topologies. 相似文献
993.
单级高压微流量电渗泵的研究 总被引:1,自引:0,他引:1
设计了一种高压微流量电渗泵。泵体主要由高压电源、电渗柱、毛细通道、导电空心电极以及气泡去除器、压力传感器等构成。单级电渗泵可以给出0~20MPa范围的输出压力和nL~μL级输出流量。输出压强和输出流量取决于电压、填充柱阻力和流体性质。 相似文献
994.
With chlorosulfonic acid as sulfonating agent, sulfonated poly(phenylene oxide) (SPPO) was prepared by homogeneous method and SPPO membranes were cast from its solutions in dimethylacetamide. The obtained membrane of SPPO was heat-treated and stretched with different forces by thermal mechanical analyzer under its glass transition temperature. In addition, the effects of stretching and heating on ion conductivity of SPPO were investigated by using Solatron phase analyzer. It was shown that the mechanical stretching of SPPO has great effect on electric properties of SPPO under proper heating treatment, and the highest conductivities achieved were increased about 10 times that of the original membranes and reached 0.0983 S cm−1. The X-ray diffraction indicated that the molecular chains of SPPO were arranged more regularly under constraint during the heat treatment, and the scanning electron microscopy demonstrated that the morphologies of the film surfaces possessed more co-continuous regions and the hydrophilic ionic sulfonic acid groups orientated at stretching direction and connected more regularly, which facilitated the exchange and transfer of hydrated proton among these hydrophilic sulfonic acid groups. 相似文献
995.
Guan S Grabley S Groth I Lin W Christner A Guo D Sattler I 《Magnetic resonance in chemistry : MRC》2005,43(12):1028-1031
Three germacrane-type sesquiterpene alcohols were isolated from an endophyte of mangrove plant Kandelia candel. Their structures were characterized as 1(10)E,5E-germacradiene-11-ol (1), 1(10)E,5E-germacradiene-3,11-diol (2), 1(10)E,5E-germacradiene-2,11-diol (3) based on the extensive NMR studies. Among them, 2 and 3 are identified as new compounds. 相似文献
996.
亲水性交联聚合物载体的合成及其固定化青霉素酰化酶 总被引:4,自引:0,他引:4
选用含环氧基团的甲基丙烯酸缩水甘油酯(GMA)和亲水性的N-乙烯吡咯烷酮(NVP)单体,以N,N′-亚甲基双丙烯酰胺(MBAA)为交联剂,甲酰胺作致孔剂,通过反相悬浮聚合技术成功合成了一系列大孔、珠状GMA-NVP-MBAA三元共聚物载体.N-乙烯吡咯烷酮介入共聚物体系,使共聚物载体具有较强的亲水性,有利于青霉素酰化酶的固定化.通过调节交联剂的用量和单体NVP与GMA的比例,可以调节共聚物载体的孔结构与表面性能.用合成的平均孔径为15.7nm、表面环氧基含量1.11mmol·g-1亲水性珠状载体固定青霉素酰化酶,固定化酶水解青霉素G钾盐的活性达491U·g-1;在4℃保存30d,活性保持不变.经4次使用后活性达到稳定(444U·g-1),再经14次使用后,活性没有明显变化. 相似文献
997.
Qing-Guo Zhang Feng Xue Jing Tong Wei Guan Bin Wang 《Journal of solution chemistry》2006,35(3):297-309
In order to test the mole-fraction composition-based models as applied to aqueous solutions of an ionic liquid, the densities
of aqueous 1-methyl-3-butylimidazolium tetrafluoroborate (BMIBF4) were measured using a Westphal balance in the concentration range of about 0.2 to 0.85 mole fraction at temperatures from
283.2 to 323.2 K. Values of the apparent molar volumes of concentrated aqueous BMIBF4 solutions were calculated from these densities and were represented with the Pitzer–Simomson and the Pitzer–Simomson–Clegg
equations. The values of Pitzer–Simomson parameters and Pitzer–Simomson–Clegg parameters were obtained by fitting to experimental
data with small standard deviations. 相似文献
998.
999.
萃取-原子吸收光谱法测定高纯氧化铕、氧化钐中的锌 总被引:2,自引:3,他引:2
在PH3的弱酸性介质中,用吡咯烷二硫代氨基甲酸铵-甲基异丁基酮萃取分离稀土氧化物以消除基体干扰;用火焰原子吸收光谱法测定了氧化铕、氧化钐中的痕量锌,相对标准偏差分别为5.8%,3.6%;试样加标回收率分别为97%-98%,95%-102%。 相似文献
1000.
Poly(phenylene oxide) (PPO) was sulfonated to different ion exchange capacities (IECs) using chlorosulfonic acid as the sulfonating agent. Tough, ductile films were successfully cast from sulfonated PPO (SPPO) solutions in N‐methyl‐2‐pyrrolidone or N,N‐dimethylformamide. The obtained membranes had good thermal stability revealed by thermogravimetric analysis (TGA). Compared with an unsulfonated PPO membrane, the hydrophilicity and water uptake of the SPPO membranes were enhanced, as shown by reduced contact angles with water. The tensile test indicated that the SPPO membranes with IEC ranging from 0.77 to 2.63 meq/g were tough and strong at ambient conditions and still maintained adequate mechanical strength after immersion in water at room temperature for 24 hr. The results of wide‐angle X‐ray diffraction (WAXD) showed amorphous structures for PPO and SPPO while the peak intensity decreased after sulfonation. The proton conductivity of these SPPO membranes was measured as 1.16 × 10?2 S/cm at ambient temperature, which is comparable to that of Nafion 112 at similar conditions and in the range needed for high‐performance fuel cell proton exchange membranes. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献