pH/enzyme/light triple-responsive vesicles from lysine-based amphiphilic diblock copolymers

We report the synthesis of pH- and enzyme-responsive amphiphilic diblock copolymers through reversible addition-fragmentation chain transfer polymerization of a lysine-derived methacrylate monomer comprising p-nitrobenzyl carbamate (pNBC) functionality using a poly(ethylene glycol)-modified macro-chain transfer agent. Depending on the hydrophobic block length, the diblock copolymers self-assemble to form spherical micelles, wormlike micelles, and bilayered vesicles in the aqueous solution. The responsive behaviors of the polymeric vesicles to pH, enzyme, and light are investigated in detail. As the pH lowers to pH 5.0, the polymeric vesicles undergo a morphological transition from vesicles to spherical micelles. In the presence of nitroreductase and a cofactor NADH, the decomposition of pNBC releases the ε-NH₂ of the lysine moiety and hence induces the generation of the vesicles with crosslinked membranes at pH 7.4. Moreover, owing to the degradation of pNBC moiety under UV irradiation, the polymeric vesicles also demonstrate a photo-responsive feature. As the irradiation time prolongs, it is observed a light-triggered morphological transition from vesicles to wormlike micelles with network-like structures.     

DPIS-RFQ系统的高频参数测试及功率锻炼

中国科学院近代物理研究所于2007年开始进行等离子体直接注入项目的预研。详细介绍了RFQ系统的高频参数测试的方法及结果,并针对高脉冲功率的测试提出通过标定定向耦合器来测试脉冲功率的方法。介绍了系统锻炼的情况,包括针对功率源末级和腔内电极的打火问题提出了理论的分析和改善的方法。高频参数的测试和载束实验证实整套系统满足加速器的设计要求。     

200 kV/200 kA脉冲源的研制

研制了一台200 kV/200 kA脉冲源,脉冲源由初级储能单元、水介质整形与传输单元、气体开关和负载组成。通过优化设计由2 到1 的水介质变阻抗线、高压气体主开关和陡化开关,使得脉冲功率源在匹配负载下产生输出电压200 kV、电流200 kA、前沿40 ns、脉宽40 ns的高压脉冲。在此脉冲源平台上已开展了低阻抗1 二极管发射特性研究,并且将在高压气体开关、同步触发、二极管等离子体发射诊断等方面发挥作用。     

FLTD系统放电开关自击穿性能优化

针对快前沿直线脉冲变压器驱动源(FLTD)系统中放电开关自击穿性能劣化的问题,模拟计算了带电线缆、FLTD模块结构对开关间隙电场分布的影响规律,研究分析开关自击穿性能下降的主要原因,开展了电晕针均压和电阻均压两种方式下开关自击穿性能对比实验,获得了不同电晕针长度、不同阻值开关自击穿电压的变化规律：两种均压方式下开关自击穿电压分别提高3.2%和4.3%。FLTD系统中放电开关有均压措施的情况下,系统自击穿电压提高8.9%,自放电概率降低60%,系统短路输出电流的稳定性明显提高,电流幅值提高8.1%,标准偏差减小30.8%。     

Trifluoromethylation of Carbonyl and Unactivated Olefin Derivatives by C(sp3)−C Bond Cleavage

Herein, we report a Cu-mediated trifluoromethylation of carbonyl-type compounds and unactivated olefins enabled by visible-light irradiation via σ C(sp³)−C bond-functionalization. The reaction is distinguished by its modularity, mild conditions and wide scope—even in the context of late-stage functionalization—thus offering a complementary approach en route to valuable C(sp³)−CF₃ architectures from easily accessible precursors.     

Neutron diffraction study of unusual phase separation in the antiperovskite nitride Mn3ZnN

The antiperovskite Mn(3)ZnN is studied by neutron diffraction at temperatures between 50 and 295 K. Mn(3)ZnN crystallizes to form a cubic structure at room temperature (C1 phase). Upon cooling, another cubic structure (C2 phase) appears at around 177 K. Interestingly, the C2 phase disappears below 140 K. The maximum mass concentration of the C2 phase is approximately 85% (at 160 K). The coexistence of C1 and C2 phase in the temperature interval of 140-177 K implies that phase separation occurs. Although the C1 and C2 phases share their composition and lattice symmetry, the C2 phase has a slightly larger lattice parameter (Δa ≈ 0.53%) and a different magnetic structure. The C2 phase is further investigated by neutron diffraction under high-pressure conditions (up to 270 MPa). The results show that the unusual appearance and disappearance of the C2 phase is accompanied by magnetic ordering. Mn(3)ZnN is thus a valuable subject for study of the magneto-lattice effect and phase separation behavior because this is rarely observed in nonoxide materials.     

Silanol as a removable directing group for the Pd(II)-catalyzed direct olefination of arenes

Need some direction? Silanol was developed as a directing group for the Pd(II)-catalyzed oxidative Heck-type reaction of arenes. A one-pot C-H activation/desilylation process of benzyldiisopropylsilanol was also demonstrated, providing a powerful approach for the synthesis of ortho-alkenyl-substituted alkylarenes. Considering the easily attachable and readily removable properties of the silanol group, this reaction will find broad synthetic applications.     

Quantum molecular dynamic simulations of warm dense carbon monoxide

Using quantum molecular dynamic simulations, we have studied the thermophysical properties of warm dense carbon monoxide under extreme conditions. The principal Hugoniot pressure up to 286 GPa, which is derived from the equation of state, is calculated and compared with available experimental and theoretical data. The chemical decomposition of carbon monoxide has been predicted at 8 GPa by means of pair correlation function and the charge density distribution. Based on Kubo-Greenwood formula, the dc electrical conductivity and the optical reflectivity are determined, and the nonmetal-metal transition for shock compressed carbon monoxide is observed around 40 GPa.     

Formation of iron(III) meso-chloro-isoporphyrin as a reactive chlorinating agent from oxoiron(IV) porphyrin π-cation radical

Iron(III) isoporphyrin, a tautomer of porphyrin with a saturated meso carbon, is one of the isoelectronic forms of oxoiron(IV) porphyrin π-cation radical, which is known as an important reactive intermediate of various heme enzymes. The isoporphyrin has been believed to be incapable of catalyzing oxygenation and oxidation reactions. Here, we report that an oxoiron(IV) porphyrin π-cation radical can be converted to iron(III) meso-chloro-isoporphyrin in the presence of trifluoroacetic acid and chloride ion. More importantly, this study shows the first evidence that iron(III) meso-chloro-isoporphyrin is an excellent reactive agent for chlorinating aromatic compounds and olefins. The results of this study suggest that the mechanism involves electrophilic chlorination of substrate with iron(III) meso-chloro-isoporphyrin.     

A selective one-step synthesis of tris N-alkylated cyclens

A general one-step synthesis for tris N-alkylated cyclens with good yield and unprecedented selectivity is presented. Tris and 1,4-bis N-alkylated cyclens, as the only two major products are isolated. Furthermore, according to the single crystal X-ray structures of tris and 1,4-bis N-alkylated cyclen 1 and 1a, one nitrogen atom on the cyclen ring can be protonated under this reaction condition, which prevents its further alkylation, and gives rise to the regioselectivity ultimately.