A three‐dimensional coordination polymer based on the Zn4(μ3‐OH)2 unit: poly[[(μ4‐benzene‐1,4‐dicarboxylato)bis(μ3‐benzene‐1,4‐dicarboxylato)bis(μ3‐hydroxido)bis(1,10‐phenanthroline‐5,6‐dione)tetrazinc] dihydrate]

The title compound, {[Zn₄(C₈H₄O₄)₃(OH)₂(C₁₂H₆N₂O₂)₂]·2H₂O}_n, has been prepared hydrothermally by the reaction of Zn(NO₃)₂·6H₂O with benzene‐1,4‐dicarboxylic acid (H₂bdc) and 1,10‐phenanthroline‐5,6‐dione (pdon) in H₂O. In the crystal structure, a tetranuclear Zn₄(OH)₂ fragment is located on a crystallographic inversion centre which relates two subunits, each containing a [ZnN₂O₄] octahedron and a [ZnO₄] tetrahedron bridged by a μ₃‐OH group. The pdon ligand chelates to zinc through its two N atoms to form part of the [ZnN₂O₄] octahedron. The two crystallographically independent bdc²⁻ ligands are fully deprotonated and adopt μ₃‐κO:κO′:κO′′ and μ₄‐κO:κO′:κO′′:κO′′′ coordination modes, bridging three or four Zn^II cations, respectively, from two Zn₄(OH)₂ units. The Zn₄(OH)₂ fragment connects six neighbouring tetranuclear units through four μ₃‐bdc²⁻ and two μ₄‐bdc²⁻ ligands, forming a three‐dimensional framework with uninodal 6‐connected α‐Po topology, in which the tetranuclear Zn₄(OH)₂ units are considered as 6‐connected nodes and the bdc²⁻ ligands act as linkers. The uncoordinated water molecules are located on opposite sides of the Zn₄(OH)₂ unit and are connected to it through hydrogen‐bonding interactions involving hydroxide and carboxylate groups. The structure is further stabilized by extensive π–π interactions between the pdon and μ₄‐bdc²⁻ ligands.     

液相色谱-串联质谱法测定尿液中的泛酸

该文建立了检测尿液中泛酸含量的液相色谱-串联质谱(HPLC-MS/MS)方法,尿液经过离心、稀释后,采用ACPUITY UPLC SS T3(2.1 mm×100 mm,1.8μm)色谱柱进行分离,电喷雾正离子模式电离,多反应监测模式进行检测,方法的线性关系良好(r=0.999 3),方法检出限为0.46 ng/m L,回收率为87.9%~95.3%,相对标准偏差(RSD)为2.5%~13.0%。该方法具有灵敏度高、分析时间短等特点,可用于尿液中泛酸含量的分析。     

有限元分析中硬化弹塑性本构方程积分算法

基于增量段上的应变关于塑性拉氏乘子的变化率为常矢量的假定,导出一种精确有效的、对有限元分析中线性混合硬化弹塑性本构方程的积分算法。以精确算例和等误差分布图的形式检验了本文方法以及其他两种常用方法的精度。     

Nanospherical Surface‐Supported Seeded Growth of Au Nanowires: Investigation on a New Growth Mechanism and High‐Performance Hydrogen Peroxide Sensors

In this paper, a novel strategy with a new growth mechanism for fast and large‐scale growth of Au long nanowires on high‐curvature SiO₂ nanospherical surfaces has been developed. The synthesis includes three steps, i.e., amino modification of SiO₂ nanospheres, Au seed loading on aminated SiO₂ nanospheres and subsequently, Au seed‐mediated nanowire growth on SiO₂ nanospheres. The prepared Au nanowires (Au NWs) (exhibit long length, high aspect ratio, and good flexibility, and can naturally form the dense nanowire film, which is promising as a stable conductive electrode. In addition, the effect of synthetic conditions such as reactant feeding order, Au seeds and SiO₂@Au seeds on the morphology of Au nanostructures (nanowires, nanoteeth, and nanoflowers) has been investigated. It is found that Au seeds and high‐curvature SiO₂ nanospherical surfaces are necessary conditions for the successful preparation of Au NWs and nanowire films. The different growth mechanisms for Au NWs and nanoteeth have been proposed and discussed. Moreover, the novel nonenzymatic H₂O₂ sensor based on Au NWs exhibits much enhanced performance such as higher sensitivity, stability, and selectivity, wider linear range and lower detection limit, compared with that of Au nanoparticles‐based H₂O₂ sensor.     

Identification and cloning of molecular markers for UV-B tolerant gene in wild sugarcane (Saccharum spontaneum L.)

Previously we have selected wild sugarcane (Saccharum spontaneum L.) sterile lines that are tolerant or susceptible to UV-B radiation based on response index (RI) in a field screening test. The RI was established according to plant height, tiller number, leaf index, total biomass and brix under enhanced ultraviolet-B (UV-B, 280-310 nm) radiation. In this experiment, molecular markers linked to the UV-B tolerant and susceptible genes were identified and cloned. RAPD (Randomly amplified polymorphic DNAs) assay using 100 arbitrary primers followed by clustering analysis separated the tolerant and susceptible lines into two groups at the genetic distance of 0.380. The UV-B tolerant and susceptible gene pools were constructed and compared using the Bulked Segregate Analysis (BSA) approach. Of the 100 arbitrary RAPD primers, primer OPR16 produced polymorphic DNA banding patterns from both gene pools. The OPR16-1200 bp DNA fragment was only amplified from the tolerant lines and the OPR16-800 bp from the susceptible ones. These two PCR fragments were cloned onto T-vector. DNA sequence alignment analysis determined that 42% homology existed between the reverse and forward sequences of the OPR16-1200 bp clone, and 36% homology between the forward sequences of the OPR16-800 bp and OPR16-1200 bp clones. The two DNA clones were determined to be linked to the UV-B tolerant and susceptible genes, and they can be used to develop molecular markers for the associated traits.     

Ionic liquid-based microwave-assisted extraction of essential oil and biphenyl cyclooctene lignans from Schisandra chinensis Baill fruits

Ionic liquid-based microwave-assisted extraction (ILMAE) has been successfully applied in extracting essential oil and four kinds of biphenyl cyclooctene lignans from Schisandra chinensis Baill. 0.25 M 1-lauryl-3-methylimidazolium bromide ionic liquid is selected as solvent. The optimum parameters of dealing with 25.0 g sample are 385 W irradiation power, 40 min microwave extraction time and 1:12 solid-liquid ratio. The yields of essential oil and lignans are 12.12±0.37 ml/kg and 250.2±38.2 mg/kg under the optimum conditions. The composition of the essential oil extracted by hydro-distillation, steam-distillation and ILMAE is analyzed by GC-MS. With ILMAE method, the energy consumption time has not only been shortened to 40 min (hydro-distillation 3.0 h for extracting essential oil and reflux extraction 4.0 h for extracting lignans, respectively), but also the extraction efficiency has been improved (extraction of lignans and distillation of essential oil at the same time) and reduces the environmental pollution. S. chinensis materials treated by different methods are observed by scanning electronic microscopy. Micrographs provide more evidence to prove that ILMAE is a better and faster method. The experimental results also indicate that ILMAE is a simple and efficient technique for sample preparation.     

Geometric realization of Adams maps

Let G/P be a homogenous space with G a compact connected Lie group and P a connected subgroup of G of equal rank. As the rational cohomology ring of G/P is concentrated in even dimensions, for an integer k we can define the Adams map of type k to be l _k : H*(G/P, ℚ) → H*(G/P, ℚ), l _k (u) = k ⁱ u, u ∈ H ²ⁱ (G/P, ℚ). We show that if k is prime to the order of the Weyl group of G, then l _k can be induced by a self map of G/P. We also obtain results which imply the condition that k is prime to the order of the Weyl group of G is necessary.     

Monodisperse polystyrene microspheres prepared by dispersion polymerization with microwave irradiation

Monodisperse polystyrene microspheres with diameters of 200–500 nm were prepared by dispersion polymerization with microwave irradiation with poly(N‐vinylpyrrolidone) as a steric stabilizer and 2,2′‐azobisisobutyronitrile as a radical initiator in an ethanol/water medium. The morphology, size, and size distribution of the polystyrene microspheres were characterized with transmission electron microscopy and photon correlation spectroscopy, and the formed films of the polystyrene dispersions were characterized with atomic force microscopy. The effects of the monomer concentration, stabilizer concentration, and initiator concentration on the size and size distribution of the polystyrene microspheres were investigated. The polystyrene microspheres prepared by dispersion polymerization with microwave irradiation were smaller, more uniform, and steadier than those obtained with conventional heating. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2368‐2376, 2005     

VALUE-AT-RISK的核估计理论

如何根据历史数据估计Value-at-Risk（VaR）;是风险分析与管理中一个重要的基本问题.木文基于非参数核估计方法,通过拟合实际数据过程的分布,构造了VaR的估计.在合适的相依数据条件下,证明了该估计量的渐近正态性,并给出了渐近方差的估计.由此表明:本文所构造的估计量不仅比参数模型具有更广泛的适应性,而且如同参数模型具有n~（-1/2）的收敛速度.本文假设的数据过程避免使用混合性,可很好地适用于金融管理中广泛应用的ARMA与GARCH模型族及非线性模型.     

22Na(p,γ)23Mg反应的实验研究

讨论了目前有关²²Na(p,γ)²³Mg反应的实验研究工作,结合兰州放射性束流线上的放射性束流²³Al的β⁺延发质子衰变实验的测量结果,给出了²³Al延发衰变的质子能谱,并比较了近期实验给出的相关能级的自旋、宇称值,正是由于这种自旋、宇称和能级部分宽度的不确定性,导致了反应率计算的不确定性.计算了同位旋相似态的共振强度.对于测量到的新的延发衰变能级E_d=8.916MeV,由于没有相应的能级宽度值,实验仅给出其相对共振强度值.