Synthesis of well-defined poly(N-isopropylacrylamide)-b-poly(L-glutamic acid) by a versatile approach and micellization

A novel Fmoc-protected chain transfer agent (CTA) was synthesized and applied in the reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAAm), resulting in well-defined Fmoc-protected PNIPAAm and the amino-end capped PNIPAAm by the subsequent hydrolysis. Poly(N-isopropylacrylamide)-b-poly(l-glutamic acid) (PNIPAAm-b-PLGA) with controlled molecular weight and narrow molecular weight distribution was synthesized successfully via ring-opening polymerization (ROP) of alpha-amino acid N-carboxyanhydrides (NCAs) by using PNIPAAm-NH2 as the macroinitiator. Both pH- and thermo-responsive micellization behaviors of the block copolymer PNIPAAm55-b-PLGA35 in dilute aqueous solution were investigated by means of the pyrene fluorescence, circular dichroism, 1H NMR, transmission electron microscopy and dynamic and static light scattering. Spherical PLGA-core and rod-like PNIPAAm-core micelles are formed in response to pH and temperature. The reversible transition between the PLGA-core and PNIPAAm-core micelles was observed. This work provides a versatile approach for synthesizing well-defined stimuli-responsive polypeptide-based double hydrophilic diblock copolymers (DHBCs), and is of great potential for generating useful stimuli-responsive materials in biomedical applications.     

含刚性链节和脲端基聚醚增韧剂改性环氧树脂的研究———反应活性及力学性能

合成了一系列既含环氧丙烷聚醚（ＰＰＧ）柔性间隔基、又含刚性介晶结构单元的端脲基活性改性剂（ＬＣＥＵＰＰＧ），并对其改性环氧树脂Ｅ ５１／双氰双胺（Ｅ ５１／ｄｉｃｙ）体系的固化反应活性、改性剂含量对增韧体系动态力学性能及冲击性能的影响进行了研究．结果表明：ＬＣＥＵＰＰＧ的加入对固化体系具有明显的增韧作用，冲击强度提高了３～７倍；其对Ｅ ５１／ｄｉｃｙ固化反应具有明显的促进作用，可使固化反应表观活化能（Ｅａ）降低５０～７０ＫＪ／ｍｏｌ、固化温度降低３０～４０℃；体系的玻璃化转变温度（Ｔｇ）略有下降，但模量基本不降低或略有升高；β 转变向低温方向移动．     

Comparative investigation on chemical constituents of flower bud,stem and leaf of Lonicera japonica Thunb. by HPLC-DAD-ESI-MS/MS n and GC-MS

In approaches of HPLC coupled with diode array detector tandem multiple mass spectrometry (HPLC-DAD-ESI-MS/MS ⁿ ) and GC-MS techniques, efficient comparative methods were developed to profile the chemical constituents in flower bud, leaf and stem parts of Lonicera japonica Thunb. (LJT). 22 polar compounds of various chemical structures and 19 volatile or semi-volatile compounds were tentatively identified from aerial parts of the plant. A number of common composition groups in three separate parts of the plant were proposed, including phenolic acids, flavonoids, iridoids, alkanes, olefins and sterols, the leaf showing higher similarity with the flower bud part via their chemical constituents. Considering the fact that the leaf part has a lot of similar components with the flower bud, this study indicates the leaf part of LJT can be expected to be used as an alternative medicinal resource to the flower bud and stem of the plant.     

Normalized Lithium Growth from the Nucleation Stage for Dendrite‐Free Lithium Metal Anodes

Inducing uniform deposition of lithium from the stage of metal crystallization nucleation is of vital importance to achieve dendrite‐free lithium anodes. Herein, using experiments and simulation, homogenization of Li nucleation and normalization of Li growth can be achieved on PNIPAM polymer brushes with lithiophilic functional groups modified Cu substrates. The lithiophilic functional groups of amide O can homogenize ion mass transfer and induce the uniform distribution of Li nucleation sites. What is more, the ultra‐small space between each brush can act as the channels for Li transportation and normalization growth. Owing to the synergistic effect of homogenization and normalization of electrodeposited Li, the obtained planar columnar Li anode exhibits excellent cycle stability at an ultra‐high current density of 20 mA cm^?2.     

Initial State Interactions and J/ψ Production-Rate Suppression in High Energy P-A Collisions

The influence of the initial state intcractions on the J/ψ production-rate supression in p-A collisions is studied. The incident proton energies decrease due to the inelastic interactions with the target nucleus. Considering energy loss of the incident proton,the data are well reproduced by using the final state interaction cross section σ^f_abs=2.1mb.     

Transmission Characteristics with Second Order Approximations of Elliptic-Groove Waveguide

In this paper, the transmission characteristics for the dominant mode H _{e 11} ⁽¹⁾ in the vertical-flat elliptic-groove guide are analysed by using the mode-matching method and Mathieu function. The characteristic equations with the 1st and 2nd order approximations and their solutions for the dominant mode of the elliptic-groove guide are also obtained by a great quantity of theoretical analyses and numerical computations. The cut-off, dispersion and attenuation characteristics are in good agreement with those in the relevant references under limiting conditions and are discussed in detail. The obtained results are of important significance for theoretical researches and actual applications of elliptic-groove guides for millimeter and submillimeter waves.     

Synthesis and optical properties of tetragonal KTa0.6Nb0.4O3 nanoparticles

Tetragonal phase KTa_0.6Nb_0.4O₃ (KTN) nanoparticles have been prepared by hydrothermal method. The obtained particles were characterized by X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy and UV-vis absorption spectrum techniques. A systematic change in crystal structure from cubic to tetragonal is observed with the increase of reaction temperature and KOH concentration. Room temperature UV-vis absorption spectrums of KTN particles show that the band gap changes from 3.24 to 3.34 eV with grain size diminished, which reveals the existence of blue-shift phenomenon of absorption bands.     

Synchronization and Phase Shaping of Single Photons with High-Efficiency Quantum Memory

Time synchronization and phase shaping of single photons both play fundamental roles in quantum information applications that rely on multi-photon quantum interference.Phase shaping typically requires separate modulators with extra insertion losses.Here,we develop an all-optical built-in phase modulator for single photons using a quantum memory.The fast phase modulation of a single photon in both step and linear manner are verified by observing the efficient quantum-memory-assisted Hong-Ou-Mandel interference between two single photons,where the anti-coalescence effect of bosonic photon pairs is demonstrated.The developed phase modulator may push forward the practical quantum information applications.     

脉冲大电流电磁轨道发射装置特性

为获得大电动力、低温升、高结构强度的轨道型电磁发射器,分析了脉冲大电流电磁轨道发射装置的工作性能,对电感梯度、通流能力进行了判定,并分析了重力、电枢电动力与螺栓预紧力共同作用下电磁轨道发射装置的力学特性。结果表明：在导轨长度及截面宽度固定的情况下,截面厚度越小,电感梯度越大;截面厚度越大,温升越低。为了获得大电感梯度、低温升并考虑材料成本,应合理设计各个部件的形状及尺寸。     

Regulating electrodeposition behavior through enhanced mass transfer for stable lithium metal anodes

Electrode process kinetics is a key part that determines the morphology of metal electrodeposition.However,the liquid-phase mass transfer process and its effect on lithium(Li)metal electrodeposition are still poorly understood.Herein,the effect of mass transfer on the electrodeposition behavior of Li metal is explored.Experiments and COMSOL Multiphysics simulations reveal that the enhanced mass transfer,which is induced by ultrasonic wave,can homogenize the ion flow on the surface of electrode to obtain uniform Li nucleation.Meanwhile,the rapid mass transfer of Li⁺provides sufficient cations around the germinated Li to avoid preferential growth of Li in a specific direction.Based on the simultaneous regulation of nucleation and growth behavior,a smooth and compact Li deposits can be achieved,which exhibit a small polarization voltage during repeated Li plating/striping and a considerably enhanced cyclability.This work enriches the fundamental understanding of Li electrodeposition without dendrite structure and affords fresh guidance to develop dendrite-free metal anodes for metal-based batteries.