常压敞开式离子化质谱技术研究进展

近年来,无需复杂样品前处理、且在开放环境下实现离子化的常压敞开式离子化质谱技术( Ambientionization mass spectrometry,AI - MS)的研制与应用成为质谱学领域的前沿及备受关注的研究方向.该文综述了AI离子源的基本原理、特征与应用进展,并结合笔者研制的空气动力辅助离子化(Air flow assisted ionization,AFAI)技术,介绍了气流辅助常压敞开式离子化技术的基本特点及其应用.展望了常压敞开式离子化技术的发展趋势.     

Ionization of methane clusters in helium nanodroplets

The electron ionization of helium droplets doped with methane clusters is investigated for the first time using high-resolution mass spectrometry. The dominant ion products ejected into the gas phase are the unprotonated (CH(4))(n)(+) cluster ions along with the protonated ions, CH(5)(+)(CH(4))(n-1). The mass spectra show clear evidence for magic numbers, which are broadly consistent with icosahedral shell closings. However, unusual features were observed, including different magic numbers for CH(5)(+)(CH(4))(n-1) (n=55, 148) when compared to (CH(4))(n)(+) (n=54, 147). Possible interpretations for some of these differences are proposed. Products of the type [C(2)H(x)(CH(4))(n)](+), which result from ion-molecule chemistry, are also observed and these too show clear magic number features. Finally, we report the first observation of (CH(4))(n)(2+) dications from methane clusters. The threshold for dication survival occurs at n≥70 and is in good agreement with a liquid droplet model for fission of multiply charged ions. Furthermore, we present evidence showing that these dications are formed by an unusual two-step mechanism which is initiated by charge transfer to generate a monocation and is then followed by Penning ionization to generate a dication.     

Recent progress of inverted organic-inorganic halide perovskite solar cells

In recent years, inverted perovskite solar cells(IPSCs) have attracted significant attention due to their low-temperature and cost-effective fabrication processes, hysteresis-free properties, excellent stability,and wide application. The efficiency gap between IPSCs and regular structures has shrunk to less than 1%. Over the past few years, IPSC research has mainly focused on optimizing power conversion efficiency to accelerate the development of IPSCs. This review provides an overview of recent...     

Piezomagnetic vibration energy harvester with an amplifier

We study the effect of an amplification mechanism in a nonlinear vibration energy harvesting system where a ferromagnetic beam resonator is attached to the vibration source through an additional linear spring with a damper.The beam moves in the nonlinear double-well potential caused by interaction with two magnets.The piezoelectric patches with electrodes attached to the electrical circuit support mechanical energy transduction into electrical power.The results show that the additional spring ca...     

Magnetic and quadrupole moments of the Zc(4020)+,Zc(4050)+,and Zc(4600)+ states in the diquark-antidiquark picture

The magnetic and quadrupole moments of the Z_c(4020)⁺,Z_c(4050)⁺,and Z_c(4600)⁺ states are calculated within the QCD light-cone sum rules.The compact diquark-antidiquark interpolating currents and the distribution amplitudes of the on-shell photon are used to extract the magnetic and quadrupole moments of these states.The magnetic moments are acquired as μ_Zc=0.50_-0.22^+0.22μ_N,μ     

Experimental study of the elastic scattering of ~(10)Be on ~(208)Pb at the energy of around three times the Coulomb barrier

Elastic scattering of 10Be on a 208Pb target was measured at ELab=127 MeV,which corresponds to three times the Coulomb barrier.The secondary 10Be beam was produced at the Radioactive Ion Beam Line in Lanzhou of the Heavy-Ion Research Facility in Lanzhou.The angular distribution of elastic scattering in the 10 Be+208Pb system shows a typical Fresnel diffraction peak.Optical model analysis of the angular distribution was performed using the Woods-Saxon,double-folding and global potentials.With the global potential,different density distributions were used.The results indicate that different density distributions for the projectile induce distinct effects in the angular distribution.     

关于确定“规定非比例伸长应力”的探索

关于确定“规定非比例伸长应力”的探索黄帆，刘承安（北京联合大学自动化工程学院北京１０００８３）（北京科技大学北京１０００８３）１引言高精度电子万能试验机采用两点法求弹性模量Ｅ，出现与传统值差别较大的问题［’］，已为用户所公认．但是，求得合适的Ｅ以后，...     

大型汽轮发电机的若干力学问题

本文对大型火力发电设备中的汽轮发电机设计与制造及运行中的若干力学问题作一简要的评述.列举了下述题目:(1)转子及轴系的振动问题;(2)定子铁芯及其支撑力学;(3)定子绕组端部振动问题;(4)发电机转子护环的强度;(5)发电机整机静动态力学特性与响应;(6)大件运输中的力学问题.     

“伯努利升力原理”批判

我的瑞典朋友马丁·宋贝先生于1953-1983年长期担任瑞典航空研究院(FFA)低速气动力部主任.他是一名至今还开飞机上天的有54年历史的老飞行员.这两年他常和我讨论飞机升力产生原理的传统说法,他认为许多人误用了伯努利定理来解释升力.他说:长达半个世纪,遍布全世界的飞行员教材中的错误概念,已经酿成了飞行事故,他有责任为此进行斗争.退体后的这几年,他东奔西跑到处说服人们接受他的意见,先是在 FFA内有了市场,接着欧洲民航年会(ECAC)采纳了他的批评,现在他又在争取国际民航组织(ICAO)和美国联邦航空局(FAA)纠正错误.不久前他寄给我一篇用英文写成的“檄文”,希望我帮助征求中国同行的意见.我将它翻译整理并加了标题“伯努利升力原理批判”介绍给大家.我觉得这篇文章涉及到科学原理的准确表述和科学普及的通谷解释的关系问题.飞机为什么能飞?或升力怎么产生的?这既是航空空气动力学要研究的课题,也是科普教育要回答的问题.文章所批判的说法在我国的科普读物、中学教材、飞行员课程、航空概论中也都采用,因为其通俗易懂,当然在真正的高等空气动力学教程中又是另外的讲法.关键是通俗解释不应当引入错误的概念,更不应当因错误概念导致危险的...     

Electrochemical synthesis of magnetic iron oxide nanoparticles with controlled size

We present a novel and facile method enabling synthesis of iron oxide nanoparticles, which are composed mainly of maghemite according to X-ray diffraction (XRD) and Mössbauer spectroscopy studies. The proposed process is realized by anodic iron polarization in deaerated LiCl solutions containing both water and ethanol. Water seems to play an important role in the synthesis. Morphology of the product was studied by means of transmission electron microscopy and XRD. In the solution containing almost 100% of water a black suspension of round shaped maghemite nanoparticles of 20–40 nm size is obtained. Regulating water concentration allows to control nanoparticle size, which is reduced to 4–6 nm for 5% of water with a possibility to reach intermediate sizes. For 3% or lower water concentration nanoparticles are of a needle-like shape and form a reddish suspension. In this case phase determination is problematic due to a small particle size with the thickness of roughly 3 nm. However, XRD studies indicate the presence of ferrihydrite. Coercivities of the materials are similar to those reported for nanoparticle magnetite powders, whereas the saturation magnetization values are considerably smaller.