道路生态研究进展

道路广泛分布在各种景观中 ,其密度和交通量都不断增加 ,随之带来多方面的生态影响 :道路建设导致动植物死亡和生境丧失、物理化学环境变化、路旁植被改变 .对动物种群产生的生态影响包括道路致死、道路回避和巢区转移、移动格局改变、障碍作用导致生境和种群的破碎化 .道路还强烈地改变景观格局和过程 .道路生态影响的定量化测度指数包括道路密度、道路位置和道路影响域 ,道路生态研究在道路规划和野生动物保护中有很广阔的应用前景 ,成为生态学的一个重要领域 .

Considerable effects of diversity indices and spatial scales on conclusions relating to ecological diversity

The relationships between ecological diversity and ecosystem functions such as stability and productivity have long been debated and have no final conclusion until now. It is ignored that the debate should be firstly based on the same diversity index, which should be theoretically complete, and on same observation scale. For the issue on the scale of ecotope observation, ecosystems should be distinguished according to intensity of human disturbance. For the issue on the scale of species observation, either number diversity or biomass diversity should be identified. This paper takes grassland ecosystems located within the Bayin Xile grassland of Xilin Gol League of Inner Mongolia Autonomous Region as an example to analyze effects of different diversity indices and spatial scales on the conclusions of ecological diversity and its relationships with ecosystem functions. The analysis results both on the scale of ecotope observation and on the scale of species observation show that different diversity indices might give different conclusions and spatial resolution has a great effect on the relative conclusions. (c) 2005 Elsevier B.V. All rights reserved.

Synthesis, characterization and catalytic properties of chiral BINOL functionalized mesoporous silicas for enantioselective Morita-Baylis-Hillman reaction

Several Chiral BINOL functionalized mesoporous silicas were prepared by post grafting of organosilane derivatives of (S)-BINOL (1,1'-bi-2-naphthol) on SBA-15 and characterized by C-13 CP/MAS NMR, FT-IR, UV-visible absorption spectra, elemental analysis, powder XRD, nitrogen adsorption-desorption isotherms and TEM techniques. Their catalytic properties were demonstrated in enantioselective Morita-Baylis-Hillman reaction of 3-phenylpropanal and cyclohexenone.

Effect of Zn concentration on the microstructures and mechanical properties of extruded Mg-7Y-4Gd-0.4Zr alloys

Microstructures and mechanical properties of the Mg-7Y-4Gd-xZn-0.4Zr (x = 0.5, 1.5, 3, and 5 wt.%) alloys in the as-cast, as-extruded, and peak-aged conditions have been investigated by using optical microscopy, scanning electron microscope, X-ray diffraction, and transmission electron microscopy. It is found that the peak-aged Mg-7Y-4Gd-1.5Zn-0.4Zr alloys have the highest strength after aging at 220 A degrees C. The highest ultimate tensile strength and yield tensile strength are 418 and 320 MPa, respectively. The addition of 1.5 wt.% Zn to the based alloys results in a greater aging effect and better mechanical properties at both room and elevated temperatures. The improved mechanical properties are mainly ascribed to both a fine beta' phase and a long periodic stacking-ordered structure, which coexist together in the peak-aged alloys.

Structures and elastic properties of OsN2 investigated via first-principles density functional calculations

The structure, elastic, and electronic properties of OsN2 at various space groups: cubic Fm-3m, Pa-3, and orthorhombic Pnnm were studied by first-principles calculations based on density functional theory. Our calculation indicates that the structure in orthorhombic Pnnm phase is energetically more stable compared with cubic systems. It is metallic, mechanically stable and contains diatomic N-N units with the bond distance 1.418 A. These characters are consistent with experimental facts that OsN2 is orthorhombic and metallic. The calculated bulk modulus 394 GPa is also the highest among the considered space groups, slightly larger than previous value 358 GPa. The calculated elastic anisotropic factors and directional bulk modulus showed that OsN2 possess high elastic anisotropy.

Diffusion and single molecule dynamics on biomolecular interface binding energy landscape

We propose a new approach to study the diffusion dynamics on biomolecular interface binding energy landscape. The resulting mean first passage time (MFPT) has 'U'curve dependence on the temperature. It is shown that the large specificity ratio of gap to roughness of the underlying binding energy landscape not only guarantees the thermodynamic stability and the specificity [P.A. Rejto, G.M. Verkhivker, in: Proc. Natl. Acad. Sci. 93 (1996) 8945; C.J. Tsai, S. Kumar, B. Ma, R. Nussinov, Protein Sci. 8 (1999) 1181; G.A. Papoian, P.G. Wolynes, Biopolymers 68 (2003) 333; J. Wang, G.M. Verkhivker, Phys. Rev. Lett. 90 (2003) 198101] but also the kinetic accessibility. The complex kinetics and the associated fluctuations reflecting the structures of the binding energy landscape emerge upon temperature changes. The theory suggests a way of connecting the models/simulations with single molecule experiments by analysing the kinetic trajectories.

Syntheses and properties of polyimides derived from diamines containing 2,5-disubstituted pyridine group

A Series of novel homo- and copolyimides containing pyridine units were prepared from the heteroaromatic diamines, 2,5-bis (4-aminophenyl) pyridine and 2-(4aminophenyl)-5-aminopyridine, with pyromelltic dianhydride (PMDA), and 3,3',4,4'-biphenyl tertracarboxylic dianhydride (BPDA) via a conventional two-step thermal imidizaton method. The poly(amic acid) precursors have inherent viscosities of 1.60-9.64 dL/g (c = 0.5 g/dL in DMAC, 30 degrees C) and all of them can be cast and thermally converted into flexible and tough polyimide films. All of the polyimides show excellent thermal stability and mechanical properties. The polyimides have 10% weight loss temperature in the range of 548-598 degrees C in air. The glass transition temperatures of the PMDA-based samples are in the range of 395-438 degrees C, while the BPDA-based polyimides show two glass transition temperatures (T(g)1 and T(g)2), ranging from 268 to 353 degrees C and from 395 to 418 degrees C, respectively. The flexible films possess tensile modulus in the range of 3.42-6.39 GPa, strength in the range of 112-363 MPa and an elongation at break in the range of 1.2-69%. The strong reflection peaks in the wide-angle X-ray diffraction patterns indicate that the polyimides have a high packing density and crystallinity.

Synthesis, crystal structure, spectroscopy and electroluminescence of zinc(II) complexes containing bidentate 2-(2-pyridyl)quinoline derivative ligands

Three bidentate ligands, 4-phenyl-2-(2-pyridyl)-quinoline (ppq), 6-(carbazol-9-yl)-4-phenyl-2-(2-pyridyl)-quinoline (cpq) and 6-diphenylamino-4-phenyl-2-(2-pyridyl)-quinoline (dpq) and their zinc(II) complexes, have been designed and synthesized. The crystal structure of [Zn(ppq)(2)Cl]PF6 shows that the central zinc atom is coordinated with one chloride and four nitrogen atoms from two ligands. The introduction of an electron-donating substituent such as carbazole or an aromatic amine group at the 6-position of the quinoline moiety can generate colored tunable Zn complexes, and the photoluminescence (PL) wavelength was modulated from 418 nm for [Zn(ppq)(2)Cl]PF6 to 591 nm for [Zn(cpq)(2)Cl]PF6 and 638 nm for [Zn(dpq)(2)Cl]PF6 in CH2Cl2 solution. The electroluminescence spectrum of [Zn(dpq)(2)Cl]PF6 exhibits pure red light emission with the Commission Internationale de L'Eclairage (CIE) coordinates (0.63, 0.36) and a maximum at 648 nm.

Destabilization of basic fibroblast growth factor by oligodeoxynucleotides

The effects of oligodeoxynucleotide (ODN) on the conformation of basic fibroblast growth factor (bFGF) were studied by spectral method. The results showed that ODN destabilized the protein.

Synthesis and characterization of polypropylene/montmorillonite nanocomposites via an in-situ polymerization approach

Polypropylene/montmorillonite (PP/MMT) nanocomposites were prepared by in-situ polymerization using a MMT/MgCl2/TiCl4-EB Ziegler-Natta catalyst activated by trietbylaluminum (TEA). The enlarged layer spacing of MMT was confirmed by X-ray wide angle diffraction (WAXD), demonstrating that MMT were intercalated by the catalyst components. X-ray photoelectron spectrometry (XPS) analysis proved that TiCl4 was mainly supported on MgCl2 instead of on the surface of MMT The exfoliated structure of MMT layers in the PP matrix of PP/MMT composites was demonstrated by WAXD patterns and transmission electron microscopy (TEM) observation. The higher glass transition temperature and higher storage modulus of the PP/MMT composites in comparison with pure PP were revealed by dynamic mechanical analysis (DMA).

二价茂稀土配合物催化左旋丙交酯的开环聚合

合成了一种新型丙交酯开环聚合的催化剂——二价茂稀土配合物,研究了它对左旋丙交酯（L-LA）的聚合反应.结果表明,单体的转化率和聚合物的分子量随反应时间的延长而增加;单体/催化剂的摩尔比增加,聚合物的分子量也增加;在极性四氢呋喃中聚合反应比在甲苯溶剂中慢.聚合产物不论分子量的大小,都具有不同程度的结晶度,其DSC图都有熔融峰,且都保持很高的旋光性.

Synthesis and crystal structure of a polymeric erbium(III)-sodium(I) coordination complex of picolinic acid N-oxide

A new Er(III)-Na(I) coordination polymer of stoichiometry [NaEr2L5(H2O)(6)(NO3)](NO3). 3.5H(2)O (HL = picolinic acid N-oxide) has been synthesized and characterized by single-crystal X-ray analysis. Crystals are triclinic, P (1) over bar with a = 9.823(2), b = 12.453(2), c = 20.643(4) Angstrom; alpha = 98.49(3), beta = 101.40(3), gamma = 108.69(3)degrees; V = 2284(1) Angstrom(3); Z = 2. Of the two independent eight-coordinate erbium(III) ions in this complex, one is surrounded by four bidentate chelating L ligands, and the other by one bidentate chelating L ligand, four aqua ligands and two anti-carboxylate oxygen atoms from two neighboring [ErL4] units. The sodium(I) ion is in a distorted octahedral environment, being coordinated by a unidentate nitrate anion, three aqua ligands and two anti-carboxylate oxygen atoms from two adjacent [ErL4] units. The complex is built from zigzag chains of syn-anti carboxylate-bridged erbium(III) moieties directed in the a direction, which are cross-linked pairwise by aqua-bridged dimeric sodium(I) units. The resulting composite polymeric chains are further connected by hydrogen bonds to form a three-dimensional network.

Studies on the elimination of NO over the La-Ba-Cu mixed oxide catalysts with perovskite structure

The mixed oxides, including YBa2Cu3O7, LaBa2Cu3O7, LaBaCu2O5, La2BaCu3O7, La4BaCu5O12 with perovskite structure, were prepared. The catalysts were characterized by means of chemical analysis, XRD, TPD and TPR method. It was found that they were the active catalysts for the NO decomposition and NO reduction by CO. The existance of Cu3+ is an important factor to give the catalysts a high activity for the NO reduction by CO.

La-Ba-Cu复合氧化物在催化消除NO反应中催化性能的研究

合成了具有钙钛石结构的复合氧化物ＹＢａ２Ｃｕ３Ｏ７、ＬａＢａ２Ｃｕ３Ｏ７、ＬａＢａＣｕ２Ｏ５、Ｌａ２ＢａＣｕ３Ｏ７和Ｌａ４ＢａＣｕ５Ｏ１２．考察了它们对ＮＯ分解和ＮＯ＋ＣＯ反应的催化性能．结合化学分析、ＸＲＤ、ＴＰＤ和ＴＰＲ对催化剂的表征结果，探讨了该系列复合氧化物对ＮＯ分解和ＮＯ＋ＣＯ反应的催化机理.