具有非广延分布电子的碰撞等离子体磁鞘的结构

很多关于等离子体鞘层的研究工作都是基于电子满足经典的麦克斯韦速度分布函数,而等离子体中的粒子具有长程电磁相互作用,使用Tsallis提出的非广延分布来描述电子更为恰当.本文建立一个具有非广延分布电子的碰撞等离子体磁鞘模型,理论推导出受非广延参数q影响的玻姆判据,离子马赫数的下限数值会随着参数q的增大而减小.经过数值模拟,发现与具有麦克斯韦分布(q=1)电子的碰撞等离子体磁鞘对比,具有超广延分布(q<1)和亚广延分布(q>1)电子的碰撞等离子体磁鞘的结构各有不同,包括空间电势分布、离子电子密度分布、空间电荷密度分布.模拟结果显示非广延分布的参数q对碰撞等离子体磁鞘的结构具有不可忽略的影响.希望这些结论对相关的天体物理、等离子体边界问题的研究有参考价值.     

Analysis of Glasses Coated with Zn–Cr–Sn–O Thin Films by Picosecond Laser-Induced Breakdown Spectroscopy and Transmission Spectroscopy

Journal of Applied Spectroscopy - Glasses coated with different thin fi lm layers exhibit different optical properties. Thus, ZnO thin films with Sn and Cr admixture (ZCTO) were deposited on the...     

Global Existence and Blow-up of Solutions for Parabolic Systems Involving Cross-Diffusions and Nonlinear Boundary Conditions

Abstract In this paper, we investigate the positive solutions of strongly coupled nonlinear parabolic systems with nonlinear boundary conditions： {ut-a（u, v）△u=g（u, v）, vt-b（u, v）△v=h（u, v）, δu/δη=d（u, v）, δu/δη=f（u, v）.Under appropriate hypotheses on the functions a, b, g, h, d and f, we obtain that the solutions may exist globally or blow up in finite time by utilizing upper and lower solution techniques.     

Tracking the Dynamic Folding and Unfolding of RNA G‐Quadruplexes in Live Cells

Because of the absence of methods for tracking RNA G‐quadruplex dynamics, especially the folding and unfolding of this attractive structure in live cells, understanding of the biological roles of RNA G‐quadruplexes is so far limited. Herein, we report a new red‐emitting fluorescent probe, QUMA‐1 , for the selective, continuous, and real‐time visualization of RNA G‐quadruplexes in live cells. The applications of QUMA‐1 in several previously intractable applications, including live‐cell imaging of the dynamic folding, unfolding, and movement of RNA G‐quadruplexes and the visualization of the unwinding of RNA G‐quadruplexes by RNA helicase have been demonstrated. Notably, our real‐time results revealed the complexity of the dynamics of RNA G‐quadruplexes in live cells. We anticipate that the further application of QUMA‐1 in combination with appropriate biological and imaging methods to explore the dynamics of RNA G‐quadruplexes will uncover more information about the biological roles of RNA G‐quadruplexes.     

Trifluoromethanesulfonic Anhydride as a Low‐Cost and Versatile Trifluoromethylation Reagent

A large number of reagents have been developed for the synthesis of trifluoromethylated compounds. However, an ongoing challenge in trifluoromethylation reaction is the use of less expensive and practical trifluoromethyl sources. We report herein the unprecedented direct trifluoromethylation of (hetero)arenes using trifluoromethanesulfonic anhydride as a radical trifluoromethylation reagent by merging photoredox catalysis and pyridine activation. Furthermore, introduction of both the CF₃ and OTf groups of the trifluoromethanesulfonic anhydride into internal alkynes to access tetrasubstituted trifluoromethylated alkenes was achieved. Since trifluoromethanesulfonic anhydride is a low‐cost and abundant chemical, this method provides a cost‐efficient and practical route to trifluoromethylated compounds.     

Benzocyclobutadienes: An Unusual Mode of Access Reveals Unusual Modes of Reactivity

The reaction of an aryne with an alkyne to generate a benzocyclobutadiene (BCB) intermediate is rare. We report here examples of this reaction, revealed by Diels–Alder trapping of the BCB by either pendant or external electron‐deficient alkynes. Mechanistic delineation of the reaction course is supported by DFT calculations. A three‐component process joining the benzyne first with an electron‐rich and then with an electron‐poor alkyne was uncovered. Reactions in which the BCB functions in a rarely observed role as a 4π diene component in Diels–Alder reactions are reported. The results also shed new light on aspects of the hexadehydro‐Diels–Alder reaction used to generate the benzynes.     

Influence of Mobile Phase Composition on the Enantioseparation of Methoxyl Flavanones with Self-prepared CDMPC Column and Chiral Recognition Mechanism

Chiral stationary phases (CSPs) based on the cellulose derivatives have proven to be one type of the most useful CSPs in high-performance liquid chromatography because of their versatility, durability and loadability1, 2. Flavanone was often used as a standard chiral compound for evaluating cellulose derivative for chiral columns1, 3. Krause and Galensa4 reported the enantioseparation of flavanone and its seven derivatives on six kinds of commercial chiral column. 4-Methoxyl flavanone, 5-…     

Determination of Constituents in Hair Dyes by Reversed-phase High-Performance Liquid Chromatography

Therearemanykindsofhairdyeswithdifferentformulae.Thekindwedeterminedcontainsthefollowingfiveconstituentsfl,4-phenylenediamine(P-PDA),4-aminophenol(P-APO),3-aminophenol(m-APO),1,3-benzendiol(m-BDO)and2,6-diaminopyridine(DAP).Withreversed-phasehigh-performanceliquidchromatography(RP-HPLC),someotherkindsofhairdyeshadbeendetermined"',butnotourkind.lnthispaperwedescribeaRP-HPLCmethodsuitabIefortheseparationandquantitativedeterminationofallthosefiveconstituentsinhairdyes.Analyseswereperf…     

A Scheme for Generating Cluster States via Raman Interaction

A scheme for generating cluster states via Raman interaction is proposed. In the scheme, we firstly prepare cluster states of multi-cavities with information encoded in the coherent states and then generate cluster states of multiatoms, which encode the information in the ground states of A-type atoms. The advantages of our scheme are that the atomic spontaneous radiation can be efficiently reduced since the cavity frequency is largely detuned from the atomic transition frequency and the Hadamard gate operation of the coherent states is replaced by measuring the coherent states.     

Transferring a Multi-atom Entangled State via Adiabatic Passage

We present a scheme for transferring atomic entangled states via adiabatic passage. In the scheme, we use photons to achieve efficient quantum transmission among spatially distant atoms. The probability of the successful transferring quantum state approaches 1. Meanwhile, the scheme is robust against the effects of atomic spontaneous emission.