铁(O)促进的醛与溴代硝基甲烷的Henry型反应高效合成2-硝基-1-醇

以廉价易得、商品化的铁粉为反应促进剂,研究了溴代硝基甲烷与各种醛的Henry型反应,高效地合成了2-硝基-1-醇.该反应在PbCl2和四丁基硫酸氢铵(TBAHS)存在下有效地进行,以中等至良好的产率得到目标产物,并且该反应具有广泛的官能团耐受性.     

Spatial chirp in Ti:sapphire multipass amplifier

The spatial chirp generated in the Ti:sapphire multipass amplifier is numerically investigated based on the onedimensional(1D) and two-dimensional(2D) Frantz–Nodvik equations. The simulation indicates that the spatial chirp is induced by the spatially inhomogeneous gain, and it can be almost eliminated by utilization of proper beam profiles and spot sizes of the signal and pump pulses, for example, the pump pulse has a top-hatted beam profile and the signal pulse has a super-Gaussian beam profile with a relatively larger spot size. In this way, a clear understanding of spatial chirp mechanisms in the Ti:sapphire multipass amplifier is proposed, therefore we can effectively almost eliminate the spatial chirp and improve the beam quality of a high-power Ti:sapphire chirped pulse amplifier system.     

Field-free molecular orientation enhanced by tuning the intensity ratio of a three-color laser field

We theoretically study the field-free molecular orientation induced by a three-color laser field. The three-color laser field with a large asymmetric degree can effectively enhance the molecular orientation. In particular, when the intensity ratio of the three-color laser field is tuned to a proper value of I_3: I_2: I_1= 0.09 : 0.5 : 1, the molecular orientation can be improved by ～ 20% compared with that of the two-color laser field at intensity ratio I_2: I_1= 1 : 1 for the same total laser intensity of 2×10~(13)W/cm~2. Moreover, we investigate the effect of the carrier-envelope phase(CEP) on the molecular orientation and use the asymmetric degree of the laser field to explain the result. We also show the influences of the laser intensity, rotational temperature, and pulse duration on the molecular orientation. These results are meaningful for the theoretical and experimental studies on the molecular orientation.     

First principle study of edge topological defect-modulated electronic and magnetic properties in zigzag graphene nanoribbons

Zigzag graphene nanoribbon(ZGNR) is a promising candidate for next-generation spintronic devices. Development of the field requires potential systems with variable and adjustable electromagnetic properties. Here we show a detailed investigation of ZGNR decorated with edge topological defects(ED-ZGNR) synthesized in laboratory by Ruffieux in 2015[Pascal Ruffieux, Shiyong Wang, Bo Yang, et al. 2015 Nature 531 489]. The pristine ED-ZGNR in the ground state is an antiferromagnetic semiconductor, and the acquired band structure is significantly changed compared with that of perfect ZGNR. After doping heteroatoms on the edge, the breaking of degeneration of band structure makes the doped ribbon a half-semi-metal, and nonzero magnetic moments are induced. Our results indicate the tunable electronic and magnetic properties of ZGNR by deriving unique edge state from topological defect, which opens a new route to practical nano devices based on ZGNR.     

Self-compression of 1.8-μm pulses in gas-filled hollow-core fibers

We numerically study the self-compression of the optical pulses centered at 1.8-μm in a hollow-core fiber(HCF) filled with argon. It is found that the pulse can be self-compressed to 2 optical cycles when the input pulse energy is 0.2-m J and the gas pressure is 500-mbar(1 bar = 10~5 Pa). Inducing a proper positive chirp into the input pulse can lead to a shorter temporal duration after self-compression. These results will benefit the generation of energetic few-cycle mid-infrared pulses.     

基于高斯拟合的光纤型SPR信号的峰值检测算法

光纤型表面等离子共振光谱具有半峰宽较宽,共振峰不尖锐等特征,传统的针对棱镜型SPR光谱的峰值检测算法无法准确定位此类光谱的共振峰值。为了准确计算光纤型SPR光谱的共振波长,提出了一种基于信赖域算法的高斯拟合方法,在拟合的光谱曲线上利用一维搜索的方式确定峰值位置。通过对标准甘油光谱数据的处理,证明高斯拟合法能够适应光纤型SPR光谱的特征,波长计算准确。通过搭建的SPR系统,实验测量了不同浓度下蔗糖溶液的SPR光谱数据,并分别采用加权质心法,追踪质心法和该研究提出的高斯拟合法进行共振波长的计算。结果表明高斯拟合法能够有效提升分辨率,且运算速度较快,有利于工程集成。     

Continuous-wave mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate

This paper reports a continuous-wave (CW) mid-infrared intracavity singly resonant optical parametric oscillator based on periodically poled lithium niobate (PPLN) pumped by a diode-end-pumped CW Nd:YVO$_{4}$ laser. Considering the thermal lens effects, it adopted an optical ballast lens and the near-concentric cavity for better operation. At the PPLN's grating period of 28.5\,$\mu$m and the temperature of 140\du, the maximum idler output power of 155\,mW at 3.86\,$\mu$m has been achieved when the 808\,nm pump power is 8.5\,W, leading to an optical-to-optical conversion efficiency of 1.82{\%}.     

Interaction of Shock Waves in Cement Mortar Plate Investigated by the Digital Speckle Correlation Method

Interaction of shock waves in cement mortar plate is studied by digital speckle correlation method and digital high-speed photography technique. When the plates were destroyed by two detonators exploding at the same time, variation of shock wave field is obtained. Experimental results show that the interaction of shock waves will result in a nonlinear huge increase of local normal strain, leading to large deformation and serious destruction. However, the occurrence of this strongly nonlinear phenomenon sensitively depends on the interval between detonators, and it will only appear when the interval is smaller than the diameter of the region where shock waves exist.     

Gaussian软件在高分子化学教学中的应用

基于计算思维,运用工具化、具象化解决问题的方法,将Gaussian软件用于高分子化学教学.将乙烯自由基聚合中的"回头咬"、乙烯以及氯乙烯自由基聚合中的链增长过程以及自由基聚合中的活性中心自由基的结构等,直观、动态而又准确地呈现了出来,实现了部分自由基聚合过程的可视化、精确化呈现,可帮助学生更容易、更直观、更准确地理解相...     

动态光散射分析不同物化条件下酪蛋白的聚集行为及其胶束尺寸

采用动态光散射技术考察了酪蛋白胶束在各种物化条件(温度、浓度、pH、离子强度、乙醇)下的聚集行为,并测定了胶束尺寸。结果表明:热处理导致酪蛋白胶束发生离解,平均流体力学半径(Rh)值不断减小,且当蛋白浓度较低时热离解过程为可逆,而浓度较高时则为不可逆;酪蛋白胶束的Rh值随蛋白浓度及离子强度的增加均呈现先减小后逐渐增大的趋势,并分别在2g/L和0.1mol/L时达到最小值;而Rh值随pH值的增加则先增大再逐渐减小,并在pH7.0时达到最大值;添加乙醇使酪蛋白胶束不断聚集,Rh值逐渐增加,溶液散射光强(Iθ)呈指数增长。