单丝及多丝Z箍缩的X射线背光成像

基于X箍缩软X射线辐射点源对单丝及多丝Z箍缩发展过程进行了背光成像研究,实验平台为清华大学电机系研制的脉冲功率装置PPG-Ⅰ（500 kV/400 kA/100 ns）。成像光路安排为：作为X射线源的X箍缩和作为目标物的单丝或多丝（双丝）Z箍缩分别安装在装置的输出主电极阴阳极之间或回流导电杆处,成像胶片采用高分辨力、高灵敏度的X射线胶片。利用自行设计的电流传感器和罗氏线圈对目标物实际流过的电流进行监测。为了测定目标物金属细丝的质量消融率,设计了m级厚度的阶梯光楔。通过大量成像实验,获取了Z箍缩等离子体融合、先驱等离子体形成及不稳定性发展等过程的相关物理图像以及质量消融率、丝芯膨胀率等重要定量参数。     

民族地区高校社会主义核心价值观教育现状与对策

在社会主义核心价值观的教育中,民族地区高校除了应对与内地高校面临的共同挑战外,还必须正视民族地区经济社会发展的差距、多民族宗教信仰影响等因素给教育活动带来的特殊性和复杂性。在阐述民族地区高校社会主义核心价值观教育现状的基础上,提出民族地区高校社会主义核心价值观教育,要因地制宜,体现其地域特色、校情特色、实践特色、民族特色等对策。     

Native agarose gel electrophoresis and electroelution: A fast and cost‐effective method to separate the small and large hepatitis B capsids

Hepatitis B core antigen (HBcAg) expressed in Escherichia coli is able to self‐assemble into large and small capsids comprising 240 (triangulation number T = 4) and 180 (triangulation number T = 3) subunits, respectively. Conventionally, sucrose density gradient ultracentrifugation and SEC have been used to separate these capsids. However, good separation of the large and small particles with these methods is never achieved. In the present study, we employed a simple, fast, and cost‐effective method to separate the T = 3 and T = 4 HBcAg capsids by using native agarose gel electrophoresis followed by an electroelution method (NAGE‐EE). This is a direct, fast, and economic method for isolating the large and small HBcAg particles homogenously based on the hydrodynamic radius of the spherical particles. Dynamic light scattering analysis demonstrated that the T = 3 and T = 4 HBcAg capsids prepared using the NAGE‐EE method are monodisperse with polydispersity values of ～15% and ～13%, respectively. ELISA proved that the antigenicity of the capsids was not affected in the purification process. Overall, NAGE‐EE produced T = 3 and T = 4 capsids with a purity above 90%, and the recovery was 34% and 50%, respectively (total recovery of HBcAg is ～84%), and the operation time is 15 and 4 times lesser than that of the sucrose density gradient ultracentrifugation and SEC, respectively.     

Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing

The transverse and longitudinal mechanical properties of aramid fibers like Kevlar? 29 (K29) fibers are strongly linked to their highly oriented structure. Mechanical characterization at the single fiber scale is challenging especially when the diameter is as small as 15 µm. Longitudinal tensile tests on single K29 fibers and single fiber transverse compression test (SFTCT) have been developed. Our approach consists of coupling morphological observations and mechanical experiments with SFTCT analysis by comparing analytical solutions and finite element modeling. New insights on the analysis of the transverse direction response are highlighted. Systematic loading/unloading compression tests enable to experimentally determine a transverse elastic limit. Taking account of the strong anisotropy of the fiber, the transverse mechanical response sheds light on a skin/core architecture. More importantly, results suggest that the skin of the fiber, typically representing a shell of one micrometer in thickness, has a transverse apparent modulus of 0.2 GPa. That is around more than fifteen times lower than the transverse modulus of 3.0 GPa in the core. By comparison, the measured longitudinal modulus is about 84 GPa. The stress distribution in the fiber is explored and the critical areas for damage initiation are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 374–384     

Redox‐responsive core cross‐linked micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) by Diels‐Alder reaction for doxorubicin release

Redox‐responsive core cross‐linked (CCL) micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) (PEO‐b‐PFMA) block copolymers were prepared by the Diels‐Alder click‐type reaction. First, the PEO‐b‐PFMA amphiphilic block copolymer was synthesized by the reversible addition‐fragmentation chain transfer polymerization. The hydrophobic blocks of PFMA were employed to encapsulate the doxorubicin (DOX) drug, and they were cross‐linked using dithiobismaleimidoethane at 60 °C without any catalyst. Under physiological circumstance, the CCL micelles demonstrated the enhanced structural stability of the micelles, whereas dissociation of the micelles took place rapidly through the breaking of disulfide bonds in the cross‐linking linkages under reduction environment. The core‐cross‐linked micelles showed fine spherical distribution with hydrodynamic diameter of 68 ± 2.9  nm. The in vitro drug release profiles presented a slight release of DOX at pH 7.4, while a significant release of DOX was observed at pH 5.0 in the presence of 1,4‐dithiothreitol. MTT assays demonstrated that the block copolymer did not have any practically cytotoxicity against the normal HEK293 cell line while DOX‐loaded CCL micelles exhibited a high antitumor activity towards HepG2 cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3741–3750     

Topological textures and their bifurcation processes in 2D ferromagnetic thin films

In this paper, by the use of the topological current theory, the topological structures and the dynamic processes in thin-film ferromagnetic systems are investigated directly from the viewpoint of topology. It is found that the topological charge of a thin-film ferromagnetic system can be changed by annihilation or creation processes of opposite polarized vortex–antivortex pairs taking place at space–time singularities of the normalized magnetization vector field of the system, the variation of the topological charge is integer and can further be expressed in terms of the Hopf indices and Brouwer degrees of the magnetization vector field around the singularities. Moreover, the change of the topological charge of the system is crucial to vortex core reversal processes in ferromagnetic thin films. With the help of the topological current theory and implicit function theorem, the processes of vortex merging, splitting as well as vortex core reversal are discussed in detail.     

现代远程教育条件下的核心课程体系构建与整合研究

以培养学生的职业技能为核心,提出了构建远程教育核心课程体系的指导原则、基本思路和流程,以远程教育网络技术专业(网页设计方向)为例对远程核心课程体系进行构建与整合.     

Preparation and Characterisation of a Bis-μ-Hydroxo-NiIII2 Complex

Hydroxide-bridged high-valent oxidants have been implicated as the active oxidants in methane monooxygenases and other oxidases that employ bimetallic clusters in their active site. To understand the properties of such species, bis-μ-hydroxo-Ni^II₂ complex ( 1 ) supported by a new dicarboxamidate ligand (N,N′-bis(2,6-dimethyl-phenyl)-2,2-dimethylmalonamide) was prepared. Complex 1 contained a diamond core made up of two Ni^II ions and two bridging hydroxide ligands. Titration of the 1 e⁻ oxidant (NH₄)₂[Ce^IV(NO₃)₆] with 1 at −45 °C showed the formation of the high-valent species 2 and 3 , containing Ni^IINi^III and Ni^III₂ diamond cores, respectively, maintaining the bis-μ-hydroxide core. Both complexes were characterised using electron paramagnetic resonance, X-ray absorption, and electronic absorption spectroscopies. Density functional theory computations supported the spectroscopic assignments. Oxidation reactivity studies showed that bis-μ-hydroxide-Ni^III₂ 3 was capable of oxidizing substrates at −45 °C at rates greater than that of the most reactive bis-μ-oxo-Ni^III complexes reported to date.