Observation of Δn=1 dielectronic recombination resonances of boronlike argon

We report here an observation ofn=1 dielectronic recombination resonances of boron-like argon in the energy region 140–195 eV. With the cooler's electron beam as a target, a resolution of approximately 0.6 eV FWHM was obtained in the observed energy range. The energies of the doubly excited states were estimated with a Hartree-Fock calculation, which indicates that the observed resonances are from Ar¹³⁺(1s²2s²2p) to Ar¹²⁺(1s²2s²3l3l) and Ar¹²⁺(1s²2s2p3l3l) transitions.     

Oligodeoxyfluorosides: Strong Sequence Dependence of Fluorescence Emission

We describe the properties of a series of oligomeric polyfluorophores assembled on the DNA backbone. The 11 oligomers (oligodeoxyfluorosides, ODFs), 4-7 monomers in length, were composed of only two fluorescent monomers and a spacer in varied sequences, and were designed to test how fluorescent nucleobases can interact electronically to yield complexity in fluorescence emission. The monomer fluorophores were deoxyribosides of pyrene and perylene, which emit light in violet and blue wavelengths, respectively. The experiments show that simple variation in sequence and spacing can dramatically change fluorescence, yielding emission maxima ranging from 380 to 557 nm and visible colors from violet to orange-red. Fluorescence lifetime data, excitation spectra, and absorption data point to a number of multi-fluorophore electronic interactions, including pyrene-pyrene and perylene-perylene excimers, pyrene-perylene exciplexes, as well as monomer dye emissions, contributing to the final spectral outcomes. Thus, two simple fluorophores can be readily combined to give emissions over much of the visible spectrum, all requiring only a single excitation. The results demonstrate that fluorescent nucleobases in oligomeric form can act cooperatively as electronic units, and that fluorophore sequence in such oligomers is as important as fluorophore composition in determining fluorescence properties.     

稀土—4—（2—吡啶偶氮）间苯二酚螯合物的高效液相色谱分离和测定

本文讨论了反相离子对液相色谱法分离和检测稀土-4-(2-吡啶偶氮)间苯二酚螯合物的各种条件,在12 min内完成了9种稀土螫合物的分离,校正曲线的线性范围是(ppm):La(0.01～3.20),Ce(0.03～2.8),Pr(0.06～3.5),Nd(0.05～3.8),Sm(0.01～3.0),Eu(0.05～3.4),Tb(0.02～3.0),Ho(0.01～3.4),Er(0.06～4.0).变异系数小于1.2％.     

制备方法对WO_3/ZrO_2结构的影响

用XRD、比表面测定、LRS定性和定量的方法对用Zr（OH）4和已晶化的ZrO2作载体制得的两类WO3／ZrO2催化剂进行了表征．揭示了样品比表面、载体物相、活性组分的存在状态与制备方法、WO3含量、焙烧温度之间的关系．结果表明，WO3能单层分散在ZrO2上；单层覆盖在Zr（OH）4上的WO3使载体在焙烧时晶粒生长受阻，形成介稳的四方ZrO2，并阻止载体微粒间的烧结，使从Zr（OH）4出发制得的WO3／ZrO2比表面明显增大，在WO3含量达到单层分散容量时以上作用表现得最充分；WO3与Zr（OH）4（或四方ZrO2）在高温（～800℃）可能发生了某种化学结合，开创出超强酸位．用以上观点可对文献中已报导的主要实验事实作出较满意的解释.     

Large-scale synthesis and microstructure of SnO2 nanowires coated with quantum-sized ZnO nanocrystals on a mesh substrate

Large-quantity single-crystal SnO(2) nanowires coated with quantum-sized ZnO nanocrystals (nc-ZnO/SnO(2) nanowires) were directly synthesized by thermal evaporation of SnO powder and a mixture of basic ZnCO(3) and graphite powders. A common stainless steel mesh was used to collect the products. The microstructure and possible growth mechanism of the nc-ZnO/SnO(2) nanowires were investigated. Results showed that tetragonal structured SnO(2) nanowires were obtained, whose surfaces were coated with single-layer ZnO nanocrystals with an average diameter of less than 5 nm. The nanowires had cross-rectangle section with width-to-thickness aspect ratio ranging from 2:1 to 5:1. The lengths of the nanowires were several tens of micrometers. ZnO nanocrystals were single crystalline wurtzite structures, which coated the whole nanowires and distributed uniformly. The possible growth mechanism of the composite nanowires may be enucleated that Zn atoms in the source vapor will replace the Sn atoms on the surface of the formed SnO(2) nanowires due to the higher reducibility of Zn than Sn. Two strong Raman scattering peaks at 626 and 656 cm(-1) appeared in the micro-Raman spectrum of nc-ZnO/SnO(2) nanowires. The origins of the peaks were discussed. Most importantly, the method can be extended to other composite oxide nanowires that are synthesized by oxidizing two kinds of metals, such as high reducibility elements Mg, Al, Zn, and Ti, and low reducibility elements In, Ge, Ga, etc.     

Chromatographic evaluation of perphenylcarbamoylated β-cyclodextrin bonded stationary phase for micro-high performance liquid chromatography and pressurized capillary electrochromatography

Application of mono (6^A-N-ethylenediamine-6^A-deoxy) perphenylcarbamoylated β-cyclodextrin (β-CD) bonded stationary phase (CSP) in micro-high performance liquid chromatography (micro-HPLC) and pressurized capillary electrochromatography (p-CEC) was firstly presented. A series of racemic α-amidophosphonates were resolved in reversed- and normal-phase modes on this CSP. The investigated chromatographic parameters include retention factor (k′), separation factor (α) and resolution (Rs) of solutes. In addition, the structural variation of the solutes and the experimental factors affecting chiral separations have been examined, including the percentage of alcohol modifier, the linear velocity (u) of the mobile phase, electrical field strength, etc. Baseline separation was achieved for most of the entities. Hydrophobic interaction, steric effect and π-π interaction contribute to the possible mechanism. Comparative results indicate that higher Rs value up to 3.1 was found in micro-HPLC, higher efficiency up to 29,970 in p-CEC.     

Dynamics of an enzymatic substitution reaction in haloalkane dehalogenase

Reactive flux molecular dynamics simulations have been carried out using a combined QM/MM potential to study the dynamics of the nucleophilic substitution reaction of dichloroethane by a carboxylate group in haloalkane dehalogenase and in water. We found that protein dynamics accelerates the reaction rate by a factor of 2 over the uncatalyzed reaction. Compared to the thermodynamic effect in barrier reduction, protein dynamic contribution is relatively small. However, analyses of the friction kernel reveal that the origins of the reaction dynamics in water and in the enzyme are different. In aqueous solution, there is significant electrostatic solvation effect, which is reflected by the slow reorganization relaxation of the solvent. On the other hand, there is no strong electrostatic coupling in the enzyme and the major effect on reaction coordinate motion is intramolecular energy relaxation.     

人尿中异黄酮的高效液相色谱分析

建立了测定人尿中异黄酮组分(大豆苷原、黄豆黄素、雌马酚、染料木黄酮)含量的反相高效液相色谱法。在尿样中加入黄酮作为内标,异黄酮经酶解后在pH=7.0中性条件下用乙酸乙酯(1∶1)提取,然后用0.02%TFA-M eOH-ACN三元梯度洗脱的方法分离异黄酮。在该条件下,大豆苷原、黄豆黄素、雌马酚、染料木黄酮的检出限分别为12.9 nmol/L、13.9 nmol/L、71.6 nmol/L和11.8 nmol/L;回收率均在89%以上。本方法具有测试步骤简单、准确度高、重现性好等优点,适合大批量样品测定。     

硝酸钆低水合物的制备及表征

本文用两种方法制得硝酸钆的低水合物Gd(NO_3)_3·5H_2O、Gd(NO_3)_3·3.5H_2O,其中Gd(NO_3)_3·3.5H_2O是文献中尚未报道的 ,给出了它们的M.P.和X-衍射特征值。