原位液相透射电子显微镜及其在 纳米粒子表征方面的应用

近年来,基于透射电子显微技术、微纳加工技术和薄膜制造技术的发展,原位液相透射电子显微技术产生,为构建多种纳米级分辨率尺度下的微实验平台,发展新型纳米表征技术和众多领域的相关研究提供了途径.本文首先介绍了应用于原位液相透射电子显微技术的液体腔设计要求,然后介绍了液体腔的发展和典型的制备工艺,最后综述了近年来液体腔透射电子显微镜在纳米粒子成核和生长方面的应用研究,并探讨了该技术前沿发展面临的机遇和挑战.本文将为提高我国先进纳米表征技术和原子精准构筑技术提供相关讨论和支持.     

Visual exploration of dependency graph in source code via embedding-based similarity

Journal of Visualization -  A large software system contains millions of lines of source code, and the development often involves many developers over a long period. How to understand and...     

基于无人机探测大柴旦地区近地层气溶胶特征

通过改装多旋翼无人机（UAV）和搭载各类载荷以及联合地基观测设备对大柴旦地区大气、环境以及气溶胶参数进行测量。利用获得的数据资料，对该地区近地层气溶胶粒子数浓度（即单位体积空气中气溶胶粒子的数目）、消光系数以及气象要素等特征进行了分析。结果表明，在大柴旦地区，近地层气溶胶粒子数浓度日变化显著，呈现双峰形态，气溶胶粒子数浓度的变化范围为75～220 cm^-3,消光系数的变化范围为0.004～0.038 km^-1;当风速小于6 m/s时，气溶胶粒子数浓度与风速呈负相关关系；当风速大于6 m/s时，二者呈正相关关系；相对湿度对气溶胶粒子的影响较小，这可能是由于该地区以沙尘型气溶胶为主，吸湿性较弱。本研究基于多旋翼无人机探测平台，可以有效地获得近地层精细化大气、环境结构，有助于研究人员了解该地区气溶胶的结构、变化特征以及建立气溶胶模式，同时也为气溶胶及大气环境参数探测方法提供了技术支撑及思路拓展。     

基于离子迁移谱的假币用纸快速检测及溯源

该文采用离子迁移谱（IMS）对20种假币用纸进行分析，通过快速检测假币用纸中的可挥发性组分，构建假币用纸的指纹谱图库。基于主成分分析（PCA）和层次聚类分析（HCA）对迁移时间8 ~ 17.5 ms范围的迁移谱信息进行处理，从而对假币用纸进行分类。PCA可将同种假币用纸聚类，HCA则可进一步将20种假币用纸准确分类，其对6个未知来源的半成品假币的分类正确率达83.33%。结果表明，IMS快速检测分析是比较和分类假币用纸的有效方法。     

Piezoelectric Nanogenerator Based on Electrospun Cellulose Acetate/Nanocellulose Crystal Composite Membranes for Energy Harvesting Application

Nanogenerators, as the typical conversion of mechanical energy to electrical energy devices, have great potential in the application of providing sustainable energy sources for powering miniature devices. In this work, cellulose acetate/cellulose nanocrystal(CA/CNC) composite nanofiber membranes were prepared by electrospinning method and then utilized to manufacture a flexible pressure-driven nanogenerator. The addition of CNC not only increased the content of piezoelectric cellulose I crystallization but also strengthened the mechanical deformation of the nanofiber membranes, which could greatly enhance the piezoelectric performance of CA/CNC composite membranes. The CA/CNC composite nanofiber membrane with 20%(mass fraction) of CNC(CA/CNC-20%) showed optimal piezoelectric conversion performance with the output voltage of 1.2 V under the force of 5 N(frequency of 2 Hz). Furthermore, the output voltage of the CA/CNC-20% nanogenerator device exhibited a linear relationship with applied impact force, indicating the great potential in pressure sensors.     

Acidity Modification of ZSM-5 for Methane Conversion in Co-feeding Method with MTA Reaction

Acidity plays a vital role in methane conversion by co-feeding method, which is one of the best strategies to improve the utilization and gentle the reaction conditions of methane. In this work, Zn, Ni, Mo, La, Ga, Fe and Co-impregnated ZSM-5 zeolites have been prepared with the same substitutions to variate the acidities and tested in co-aromatization of methanol with methane. It is demonstrated that the new medium-strong acid sites formed by metal and strong acid sites are the key role to activate methane in co-reaction. Zn-modified ZSM-5 catalyst is preferred to exhibit the best methane conversion of 12%, whose aromatic selectivity increases from 27.2% to 52.2% compared with that of HZSM-5. Besides, the addition of methane further improves the production of high-valued aromatics compared with methanol to aromatics (MTA) reaction.     

紫色球杆菌视紫红质光谱特性的机器学习研究

近年来，机器学习等人工智能技术被应用于蛋白质工程，其在蛋白质结构、功能预测、催化活性等研究中具有独特优势。在未知蛋白质结构的情况下，将蛋白质序列和功能特性与机器学习相结合，基于序列-活性关系（innovative sequence-activity relationship，ISAR）算法，将蛋白质氨基酸序列数字化，用快速傅里叶变换（fast four transform，FFT）进行预处理，再进行偏最小二乘回归建模，可在数据集较少情况下拟合得到最佳模型。通过机器学习对紫色球杆菌视紫红质（gloeobacter violaceus rhodopsin，GR）的突变体蛋白质氨基酸序列与光谱最大吸收波长进行建模，获得了最佳模型。用最佳索引LEVM760106建模得到的确定系数R² 为0.944，均方误差E为11.64。用小波变换进行的预处理，其R² 虽也约为0.944，但E大于11.64，不及FFT进行的预处理。方法较好地解决了蛋白质序列与功能特性之间的数学建模问题，在蛋白质工程中可为预测更优的突变体提供支持。     

Adsorption kinetics of Eu(III) and Am(III) onto bentonite: analysis and application of the liquid membrane tidal diffusion model

Journal of Radioanalytical and Nuclear Chemistry - A new liquid membrane tidal diffusion model (LMTD) was applied based on three assumptions to analyze the kinetics of Eu(III) adsorption on...     

Syntheses,crystal structures and properties of Cd(II) and Ag(I) complexes based on 2-p-methylphenyl-5-(2-pyridyl)-1,3,4-thiadiazole

Abstract

Complexes of [CdL₂(NO₃)₂]·1.5H₂O and [Ag₂(μ-L)₂(NO₃)₂] were synthesized by the reactions of 2-p-methylphenyl-5-(2-pyridyl)-1,3,4-thiadiazole (L) with Cd(NO₃)₂·4H₂O and AgNO₃, respectively. Their structures were determined by single crystal X-ray diffraction. The photophysical property and thermal stability were characterized by FT???IR, UV???Vis absorption, fluorescence, and thermogravimetric analysis (TGA). Both complexes belong to the triclinic system with space group p???1. The central metal of [CdL₂(NO₃)₂]·1.5H₂O has a distorted octahedral geometry [CdN₄O₂], while two central Ag(I) atoms of [Ag₂(μ-L)₂(NO₃)₂] exhibit distorted tetrahedral geometries [AgN₃O].