Angular distribution of characteristic photons after radiative electron capture at strong central fields

We investigate the difference in the angular distribution of Ly-alpha(1) and K alpha(1) photons from hydrogenlike and heliumlike ions of uranium after radiative electron capture to the L shell. The strong anisotropy in the former case is changed to a very small one in the latter case. Our calculations support the observation. The effect takes place even in the limiting case of noninteracting electrons, being caused by the Pauli principle.

The effect of the scalar-isovector meson field on hyperon-rich neutron star matter

We investigate the effect of the calar-isovector delta-meson field on the equation of state (EOS) and composition of hyperonic neutron star matter, and the properties of hyperonic neutron stars within the frame work of the relativistic mean field theory. The influence of the delta-field turns out to be quite different and generally weaker for hyperonic neutron star matter as compared to that for npe mu neutron star matter. We find that inclusion of the delta-field enhances the strangeness content slightly and consequently moderately softens the EOS of neutron star matter in its hyperonic phase. As for the composition of hyperonic star matter, the effect of the delta-field is shown to shift the onset of the negatively-charged (positively-charged) hyperons to slightly lower (higher) densities and to enhance (reduce) their abundances. The influence of the delta-field on the maximum mass of hyperonic neutron stars is found to be fairly weak, where as inclusion of the delta-field turns out to enhance sizably both the radii and the moments of inertia of neutron stars with given masses. It is also shown that the effects of the delta-field on the properties of hyperonic neutron stars remain similar in the case of switching off the Sigma hyperons.

次级束流线设备FRS和现有RIBLL2的优化

本文工作分为两个部分：第一部分是设计德国重离子研究中心（GSI）的一段新的次级束流线；第二部分计算了在建的R工已LLZ对裂变反应碎片的传输分离，同时为提高分离本领对RIBLLZ进行了优化计算和设计。FRS是德国重离子研究中心（GSI）的次级束流线。其分支FRS-CAVEB的终端是川JAD工N的实验终端，这条线的束流品质不理想（传输率只有0．1％），因此GSI拟将AI'AD州设备（原在CAVEB）移到CAVEC中，形成FRS一CAVEC束流线，又称FRS-R3Bcave。本文对FRS-CoveC进行了束流光学设计和计算，同时模拟了FRS-CAVEC对弹核碎裂反应的传输分离。新束线按计算结果安装了一个二极磁铁和3个四极磁铁，并通过了实验测试，测试结果表明：（1）系统具有良好的消色散特性，即系统在FRS出口和实验终端处达到了消色差。（2）系统的传输率基本符合理论计算值，相对CAVEB分支传输率提高了一个量级以上。当不放任何阻止物质在束流线上时，Ar主束传输率可以达到100％；当放置3mm厚的Sdntillator探测器在S2，S8，CaveC处时，主束传输率基本和理论计算值相近（640k-计算值，610k-实验值）。对比FRS-C八VEB的实验传输率（0．1％），可知通过改进，FRS-C八VEC的传输率将得到极大的改善。RIBLLZ是连接CSR两环之间的次级束流线。现有的RIBLLZ束流线设计的比较紧凑，立体角接收度大，使得所有粒子都可通过系统，可以作为零度质谱仪，尤其是可以将裂变产生的奇异核素注入到实验环进行质量测量。本文模拟了弹核碎片和裂变反应产生的次级束在现有的RIBLLZ上的传输情况。计算表明，现有的RIBLLZ对通过u裂变产生的大量较重奇异核素，具有很高的传输率。另一方面，现有的RIB七LZ在散焦面只有两个四极磁铁，为达到系统的消色差及较大的分辨率会使得Y方向的束流控制困难。基于此，对现有的R咸喝锻蓄尔＼一些改进计算。还理论计算比较了两个系统对裂变反应的传输分离情况。玺认算试知飞（1）优化后的RIBLLZ系统对束流在Y方向的控制将更灵活。（2）对裂变反应产物的传输，除了作为零度质谱仪外还可以作为单一核素的分离器。（3浑税盯确集磁系统的传输率对降能器厚度敏感度降低，对于u裂变反应产生的132sn的传输率，当降能器厚度从19／cmZ变化到39／clnu时，传输率下降20％，而未优化的RIBLLZ系统的传输率将下降90%。

Double proton transfer and one-electron oxidation behaviors in double H-bonded glycinamide-formamidine complex and comparison with biological base pair

The behaviors of double proton transfer (DPT) occurring in a representative glycinamide-formamidine complex have been investigated employing the B3LYP/6-311++G** level of theory. Computational results suggest that the participation of a formamidine molecule favors the proceeding of the proton transfer (PT) for glycinamide compared with that without mediator-assisted case. The DPT process proceeds with a concerted mechanism rather than a stepwise one since no zwitterionic complexes have been located during the DPT process. The barrier heights are 14.4 and 3.9 kcal/mol for the forward and reverse directions, respectively. However, both of them have been reduced by 3.1 and 2.9 kcal/mol to 11.3 and 1.0 kcal/mol with further inclusion of zero-point vibrational energy (ZPVE) corrections, where the lower reverse barrier height implies that the reverse reaction should proceed easily at any temperature of biological importance. Additionally, the one-electron oxidation process for the double H-bonded glycinamide-formamidine complex has also been investigated. The oxidated product is characterized by a distonic radical cation due to the fact that one-electron oxidation takes place on glycinamide fragment and a proton has been transferred from glycinamide to formamidine fragment spontaneously. As a result, the vertical and adiabatic ionization potentials for the neutral double H-bonded complex have been determined to be about 8.46 and 7.73 eV, respectively, where both of them have been reduced by about 0.79 and 0.87 eV relative to those of isolated glycinamide due to the formation of the intermolecular H-bond with formamidine. Finally, the differences between model system and adenine-thymine base pair have been discussed briefly.

四氯乙烯和对二氯苯对草鱼的联合毒性

采用水生污染暴露试验和水生毒理联合效应相加指数法,研究了四氯乙烯(PCE)和对二氯苯(P-DCB)对草鱼(Ctenopharyngodon idellus)的单一毒性与联合毒性.结果表明,PCE和P-DCB的单一毒性均为高毒,且P-DCB的毒性大于PCE.PCE和P-DCB对草鱼的联合染毒在浓度1:1时,暴露时间为24,48,72,96h的相加指数(AI)分别为0.26,0.37,0.78,0.98,联合毒性为相加作用.PCE与P-DCB对草鱼的联合染毒在毒性1:1时,暴露时间为24,48,72,96h的AI分别为-0.15,0.24,0.83,1.30,联合毒性主要是相加作用,但是随着染毒时间的延长,联合毒性由相加作用向协同作用转变.

Coating Didodecyldimethylammonium Bromide onto Au Nanoparticles Increases the Stability of Its Complex with DNA

The stability of the complex of cationic lipid with nucleic acid, especially when facing serum, is crucial for the efficiency of gene delivery. Here, we demonstrated that the stability of the complex of didodecyldimethylammonium bromide (DDAB, a cationic lipid) with DNA in the presence of serum dramatically increased after coating DDAB onto the surface of the gold nanoparticles. The stability of the complex was demonstrated with dye intercalation assay, and agarose gel electrophoresis.

Large-area silver-coated silicon nanowire arrays for molecular sensing using surface-enhanced Raman spectroscopy

A new and facile method to prepare large-area silver-coated silicon nanowire arrays for surface-enhanced Raman spectroscopy (SERS)-based sensing is introduced. High-quality silicon nanowire arrays are prepared by a chemical etching method and used as a template for the generation of SERS-active silver-coated silicon nanowire arrays. The morphologies of the silicon nanowire arrays and the type of silver-plating solution are two key factors determining the magnitude of SERS signal enhancement and the sensitivity of detection; they are investigated in detail for the purpose of optimization.

Environmentally friendly synthesis of highly monodisperse biocompatible gold nanoparticles with urchin-like shape

We report a facile and environmentally friendly strategy for high-yield synthesis of highly monodisperse gold nanoparticles with urchin-like shape. A simple protein, gelatin, was first used for the control over shape and orientation of the gold nanoparticles. These nanoparticles, ready to use for biological systems, are promising in the optical imaging-based disease diagnostics and therapy because of their tunable surface plasmon resonance (SPR) and excellent surface-enhanced Raman scattering (SERS) activity.

Hydrogen-Bonding Recognition-Induced Color Change of Gold Nanoparticles for Visual Detection of Melamine in Raw Milk and Infant Formula

The color change induced by triple hydrogen-bonding recognition between melamine and a cyanuric acid derivative grafted on the surface of gold nanoparticles can be used for reliable detection of melamine. Since such a color change can be readily seen by the naked eye, the method enables on-site and real-time detection of melamine in raw milk and infant formula even at a concentration as low as 2.5 ppb without the aid of any advanced instruments.

Monitoring catalytic degradation of dye molecules on silver-coated ZnO nanowire arrays by surface-enhanced Raman spectroscopy

Catalytic degradation of organic dye molecules has attracted extensive attention due to their high toxicity to water resources. In this paper, we propose a novel method for the fabrication of uniform silver-coated ZnO nanowire arrays. The degradation of typical dye molecule rhodamine 6G (R6G), as an example, is investigated in the presence of the as-prepared silver-coated ZnO nanowire arrays. The experimental results show that such composite nanostructures exhibit high catalytic activity, and the reaction follows pseudo-first-order kinetics. Furthermore, these nanowire arrays are desirable SERS substrates for monitoring the catalytic degradation of dye molecules. Compared with traditional UV-visible spectroscopy, SERS technology can reflect more truly the catalytic degradation process occurring on the surface of the catalysts.

Design of polymeric stabilizers for size-controlled synthesis of monodisperse gold nanoparticles in water

A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (similar to 2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.