介孔分子筛的制备与苯加氢反应的催化性能

1992年美国Mobil公司的研究人员首次报道合成出具有规则孔结构的M41S系列介孔分子筛材料.由于介孔材料独特的性质,引起了人们极大的兴趣,在其合成与性能等方面进行了大量的研究,合成出了多种系列不同性能的介孔分子筛,并研究了介孔分子筛作为催化剂或催化剂载体在各类催化反应中的催化性能.     

手性聚甲基丙烯酸酯液晶聚合物的合成及相行为的研究

手性聚甲基丙烯酸酯液晶聚合物的合成及相行为的研究向前，张纪宇，张树范（中国科学院化学研究所北京１０００８０）关键词手性液晶聚合物，相行为手性侧链液晶聚合物在侧链中含有不对称碳原子的末端基，使聚合物显示Ｓｔ相．Ｓ？相层中的分子呈倾斜排列而产生自发极化．...     

新型吸附剂——球形碳化树脂的研究Ⅲ.

聚偏二氯乙烯球体经185℃预裂解后,进行960℃高温裂解,得到0.6—0.8mm粒径的球形碳化吸附树脂,碳收率为74％以上。碳化吸附树脂机械强度好,比表面为1,000M~2/g以上,对肌酸酐吸附率可达99％。     

O／W微乳液中聚吡咯超微粒子的制备

选择合适的ＳＤＢＳ／吡咯／Ｈ２Ｏ三组分Ｏ／Ｗ微乳液与吡咯单体共存的两相体系，以单体相为单体源，在Ｏ／Ｗ三组分微乳液中进行了吡咯聚合，所得聚吡咯粒子大小仅为２～３ｎｍ，分布较均匀，且具有较好的导电性能．     

一种转基因猪血中重组人血清白蛋白分离纯化新方法

基因工程技术已经成为研究和生产重组人血清白蛋白(rHSA)替代人血清白蛋白(HSA)的重点技术,而白蛋白的纯化则是该技术的关键。本文主要介绍了从转基因猪血中纯化rHSA的一种新方法,即热乙醇沉淀与多级色谱分离相结合的rHSA纯化方法。热乙醇沉淀法可从猪血浆中获得rHSA粗提取液,此时rHSA的纯度可达69.5%,回收率达51.3%。进一步采用多级色谱分离法,即阴离子交换色谱和反相色谱法进一步纯化,得到rHSA的最终纯度约为100.0%,总回收率为41.1%。该方法为从转基因猪血浆中大规模纯化用于临床和生化研究的高纯度rHSA提供可能,同时也为rHSA替代HSA奠定了基础。     

纳米尺寸团簇NinZrn(n=3～5)的几何结构与成键规律研究

根据化学键理论与拓扑原理，设计了团簇NinZrn(n=3-5)的可能几何构型，并用从头算方法进行构型优化，结果表明，由NiZr组成的团簇原子间的Zr-Zr和Zr-Ni键明显较强，而Ni-Ni的成键较弱，并发与NinZrn(n=3-5)团簇电子性质与有机烯烃分子等瓣相似，原子之间的成键按照强弱相间的规则分布。     

O2在MgO(001)完整和缺陷表面上的吸附

在密度泛函理论的框架下， 采用嵌入点电荷簇模型研究了O2在MgO(001)完整和缺陷表面上的吸附.用电荷自洽的方法确定了点电荷的值.计算结果表明， O2倾向吸附在低配位的角Mg2＋端.并且发现， 当O2为平躺吸附时，键长有较大的拉伸，将有利于O2的解离.同时，分别计算了使用裸簇和嵌入表观±2.0 e点电荷簇模型时的吸附能，并与采用电荷自洽方法的计算值进行了比较.结果表明，电荷自洽方法更能有效反映簇周围的环境，得到的计算结果能够较好地与实验值吻合.最后，分别计算了不同吸附情况下O2的振动频率.     

Syntheses and Characterizations of Two Palladium(II) Complexes of 5‐Mercapto‐1‐methyltetrazole

Reaction of PdCl₂(CH₃CN)₂ with the sodium salt of 5‐mercapto‐1‐methyltetrazole (MetzSNa) in methanol solution affords an interesting dinuclear palladium complex [Pd₂(MetzS)₄ ] ( 1 ). However, treatment of PdCl₂(CH₃CN)₂ with neutral MetzSH ligand in methanol solution produces a mononuclear palladium complex [Pd(MetzSH)₄]Cl₂ ( 2 ). Both complexes were characterized by IR, ¹HNMR, UV‐Vis spectroscopy as well as X‐ray crystallography. Single‐crystal X‐ray diffraction analyses of two complexes lead to the elucidation of the structures and show that 1 possesses an asymmetric structure: one Pd atom is tetracoordinated by three sulfur atoms and one nitrogen atom to form PdS₃N coordination sphere, the other Pd atom is tetracoordinated by three nitrogen atoms and one sulfur atom to form PdSN₃ coordination sphere. The molecules of 1 are associated to 1‐D infinite linear chain by weak intermolecular Pd···S contacts in the crystal lattice. In 2 , the Pd atom lies on an inversion center and has a square‐planar coordination involving the S atoms from four MetzSH ligands. The two chloride ions are not involved in coordination, but are engaged in hydrogen bonding.     

Crystal Structure of Complex Tris（4,4,4—trifluoro—1—pheny1—1,3—butanedione）（1,10—phenanthroline）Europium（Ⅲ）

The complex Eu(btfa)₃ (phen) (btfa=4,4,4‐trifluoro‐1‐phenyl‐1, 3‐butanedione, phen = 1,10‐phenanthroline) has been prepared and characterized by elemental analysis, IR and UV spectroscopies. The crystal and molecular structures of the complex have been determined by X‐ray diffraction analysis. It belongs to the monoclinic crystal system, space group P2₁/c with a = 0.9700(2) nm, b = 3.7450(5) nm, c = 1.0917(3) nm, β = 92.51(2)°, V = 3.962(1) nm⁵, Z = 4, D_c = 1.639 g/cm³, μ = 1.676 mm^?1, F(000) = 1936, R₁, = 0.0388, wR₂ = 0.0775. Structure analysis shows that the europium(III) ion is coordinated to six oxygen atoms of β‐diketonate anions and two nitrogen atoms of phenanthroline molecule. The coordination polyhedron is an approximate square antiprism.     

Inherent speedup limitations in multiple time step/particle mesh Ewald algorithms

Multiple time step (MTS) algorithms present an effective integration approach to reduce the computational cost of dynamics simulations. By using force splitting to allow larger time steps for the more slowly varying force components, computational savings can be realized. The Particle-Mesh-Ewald (PME) method has been independently devised to provide an effective and efficient treatment of the long-range electrostatics interactions. Here we examine the performance of a combined MTS/PME algorithm previously developed for AMBER on a large polymerase beta/DNA complex containing 40,673 atoms. Our goal is to carefully combine the robust features of the Langevin/MTS (LN) methodology implemented in CHARMM-which uses position rather than velocity Verlet with stochasticity to make possible outer time steps of 150 fs-with the PME formulation. The developed MTS/PME integrator removes fast terms from the reciprocal-space Ewald component by using switch functions. We analyze the advantages and limitations of the resulting scheme by comparing performance to the single time step leapfrog Verlet integrator currently used in AMBER by evaluating different time-step protocols using three assessors for accuracy, speedup, and stability, all applied to long (i.e., nanosecond) simulations to ensure proper energy conservation. We also examine the performance of the algorithm on a parallel, distributed shared-memory computer (SGI Origin 2000 with 8 300-MHz R12000 processors). Good energy conservation and stability behavior can be demonstrated, for Newtonian protocols with outer time steps of up to 8 fs and Langevin protocols with outer time steps of up to 16 fs. Still, we emphasize the inherent limitations imposed by the incorporation of MTS methods into the PME formulation that may not be widely appreciated. Namely, the limiting factor on the largest outer time-step size, and hence speedup, is an intramolecular cancellation error inherent to PME. This error stems from the excluded-nonbonded correction term contained in the reciprocal-space component. This cancellation error varies in time and introduces artificial frequencies to the governing dynamics motion. Unfortunately, we find that this numerical PME error cannot be easily eliminated by refining the PME parameters (grid resolution and/or order of interpolating polynomial). We suggest that methods other than PME for fast electrostatics may allow users to reap the full advantages from MTS algorithms.