纳米颗粒的短脉冲激光烧蚀制备及其非线性光学应用

本文主要介绍了纳米颗粒的短脉冲激光制备及其在非线性光学领域的应用。短脉冲激光制备纳米颗粒具有纯度高、操作简单和适用性广等优点,所制备的非线性纳米颗粒尺寸分布均匀,粒度小且可调控,在非线性光学材料中有着独特的地位。为了更深入地对此进行研究,本文介绍了纳米颗粒的光学非线性和激光的特点和原理。在此基础上,通过阐述短脉冲激光与物质相互作用的机理,说明了激光制备纳米颗粒所具有的优点,详细分析了制备条件对合成纳米颗粒的影响,并结合激光制备不同的纳米颗粒,介绍当前激光制备各类纳米颗粒的研究现状。激光制备纳米颗粒是一种操作简便、适用性广,且对环境友好的方法。

     

Dynamics of alternative modes of RNA replication for positive-sense RNA viruses

We propose and study nonlinear mathematical models describing the intracellular time dynamics of viral RNA accumulation for positive-sense single-stranded RNA viruses. Our models consider different replication modes ranging between two extremes represented by the geometric replication (GR) and the linear stamping machine replication (SMR). We first analyse a model that quantitatively reproduced experimental data for the accumulation dynamics of both polarities of turnip mosaic potyvirus RNAs. We identify a non-degenerate transcritical bifurcation governing the extinction of both strands depending on three key parameters: the mode of replication (α), the replication rate (r) and the degradation rate (δ) of viral strands. Our results indicate that the bifurcation associated with α generically takes place when the replication mode is closer to the SMR, thus suggesting that GR may provide viral strands with an increased robustness against degradation. This transcritical bifurcation, which is responsible for the switching from an active to an absorbing regime, suggests a smooth (i.e. second-order), absorbing-state phase transition. Finally, we also analyse a simplified model that only incorporates asymmetry in replication tied to differential replication modes.     

具有核-壳结构的金纳米包覆磁性纳米复合颗粒的研究进展

具有核-壳结构的金纳米包覆的磁性纳米粒子,既具有磁性纳米粒子的特点又增加了金纳米的表面化学性质,近年来受到研究人员的广泛关注。简要综述了近年来国内外制备2类核-壳结构的金包铁磁性纳米复合材料的研究进展及相关应用,并对其应用前景进行了展望。     

Light bullets in coupled nonlinear Schrödinger equations with spatially modulated coefficients and Bessel trapping potential

We discuss three-dimensional (3D) light bullets (LBs) in a system of coupled nonlinear Schrödinger equations with spatially modulated diffraction and nonlinearity coefficients, under the action of a Bessel trapping potential. Exact spatiotemporal vector solitary waves, or LBs, are obtained using the method of separation of variables and the Hirota’s bilinear method. An inverse solution procedure is introduced, in which the desired localized solutions of equations are proposed first and then the corresponding diffraction and nonlinearity coefficients determined. New 3D wave packets are built with the help of spherical harmonics in the form of multipole, necklace, and toroidal solitary pulses. Numerical solution of the full system of equations indicates that an initial wave in the form of such 3D wave packets is longlived but slowly changing along the propagation direction.     

花状纳米金和球形纳米金的催化活性对比研究

以花状纳米金(AuNFs)或球形纳米金(AuNPs)为催化剂,硼氢化钠为供氢体,在不同温度下以对硝基苯酚为模板发生还原反应。结果表明,该催化反应温度与时间呈负相关。50℃时,AuNFs所需反应时间为7min,37℃时所需时间为15 min,20℃时所需时间为45 min。该反应为准一级动力学反应。AuNFs的Ea值37.97 kJ/mol,比AuNPs的Ea值51.51 kJ/mol小,说明花状纳米金比球形纳米金具有更高的催化活性。