低温冷冻靶温度动态特性的数值模拟研究

惯性约束聚变点火成功的关键之一在于靶丸内形成均匀的氘氚冰层,靶丸周围的温度场对冰层质量有很大影响.首先通过实验靶系统实验验证了数值计算模型的可靠性,在此模型的基础上,对低温冷冻靶装置的热物理问题特别是温度动态特性问题展开了数值模拟,重点考察冷环温度波动时,温度传递衰减过程的规律以及各影响因素对于温度传递衰减过程的影响.结果显示:冷环温度一定时,填充气体压力降低、填充气体中氦气比例增大,靶丸表面温度均匀性提高;当冷环温度波动时,温度波动的周期减小、振幅减小、填充气体压力升高、填充气体中氦气比例降低有利于控制靶丸表面温度波动;冷环温度波动的周期适中、振幅减小、填充气体压力降低、填充气体中氦气比例提高有利于改善靶丸表面温度均匀性.研究结果对实验中冷冻靶合理配置各参数实现温度控制具有重要参考价值.     

Topological confinement effect of edge potentials in zigzag-edge graphene nanoribbons under a staggered bulk potential

We have investigated topological confinement effects of edge potentials on gapless edge states in zigzag-edge graphene nanoribbons (ZGNRs) under a staggered bulk potential. A variety of gapless edge states were predicted with the concept of topological confinement effect alone, which was confirmed by using tight-binding model calculations. Half-metallicity of ZGNR, which has been semiclassically described, was revealed to fundamentally result from a topological confinement effect. Edge potentials were found to allow an infinitesimal staggered bulk potential to result in gapless edge states, regardless of the ribbon width. A uniform or staggered potential applied to the boundary region narrower than a critical width was found to play a role of the edge potentials, and the critical width was estimated.     

Incorporating Copper Nanoclusters into Metal‐Organic Frameworks: Confinement‐Assisted Emission Enhancement and Application for Trinitrotoluene Detection

Herein, a strategy for improving both the stability and the emission intensity of Cu nanoclusters based on their entrapment into metal‐organic frameworks (MOFs) is demonstrated. The latter effect reaches 20 times and is ascribed to a confinement‐assisted emission enhancement similar to the aggregation induced emission of fluorescent species in solution, evidenced by the prolonged emission lifetime. Cu nanoclusters are distributed homogeneously over the entire MOFs structure, as confirmed by combination of structural and elemental mapping studies. Toward potential applications of Cu nanocluster/MOF composites as chemical sensors, the authors demonstrate the selective quenching of their emission by 2,4,6‐trinitrotoluene attributed to specific electron‐withdrawing interactions with glutathione ligands on Cu clusters.     

ECR离子源外电子注入技术研究

使用电子枪对ECR（Electron Cyclotron Resonance）等离子体注入外电子束是继铝衬弧腔、偏压盘之后,对等离子体电子的额外补充的又一种手段,通过向弧腔中注入一定能量与流强的电子束,以期提高引出束流的流强与电荷态。但由于该方法可控参数繁多,经验积累与报道资料都很少,且设计与操作远不如偏压盘等手段简便,故一直未能得到深入研究。通过以三维仿真软件CST粒子工作室对注入到弧腔电子束的运动轨迹的模拟结果为依据、以18 GHz ECR蒸发冷却源为平台,进行了ECR等离子体注入电子束的实验,结果表明:在一定实验条件下,当注入电子束能量超过1 800 eV时,会产生一种引出的离子束流的激增现象。在这个现象中,脉冲与直流的流强均比未注入电子时要高,束流电荷态向高价方向移动,且可通过控制实验条件来控制这种现象。最后对于这种电子并未通过共振面,却能起到提高电荷态与流强的作用进行了分析与讨论,并认为该现象在改善直流束与脉冲束性能的方面都有着积极的意义。The injection of the electron beam into the ECR (Electron Cyclotron Resonance)plasma by electron gun is a new method for the additional supplementary of the plasma electron, following the aluminum chamber wall and the bias plate, we are expecting for the higher current and charge state of the ion beam with it. However, because of the controllable parameter's variety, the lack of the accumulation of experience and data, and the shortage of convenience in designing and experimental practicing compared by biased disk and other means,it has always not been intensively studied. In this article, we take the 18 GHz ECR Ion Source using evaporative cooling technique as experimental platform, do the experiment of injecting electron into ECR plasma base on the simulation result of the electron beam's path in ECR's chamber by the 3D simulation software CST the particle studio. It shows that a pulsing leap of the current of the extracting ion beam appears when the injecting electron's energy is above 1 800 eV. In the mean time, the top of the pulse and the average current of the ion beam rises, the ionization state moves to a higher level. This phenomenon can be turned on and off by controlling the experimental condition. At the last part of the article, we discuss this improvement of the current and charge state of the ion beam despite of the position's missing between the injection of electron beam and the resonance surface, and hold the opinion that this phenomenon is positive to both pulsed and direct beam.     

A novel symmetric sulfur-containing biscembranoid from the Formosan soft coral Sinularia flexibilis

A structurally unique symmetric sulfur-containing biscembranoid, namely, thioflexibilolide A (1), was isolated from the soft coral Sinularia flexibilis. The structure was determined by extensive spectroscopic analyses. Compound 1 has been found to possess significant anti-inflammatory and neuroprotective activities.     

Design of an apparatus for polarization measurement in soft X-ray region

A novel apparatus for polarization measurement in the soft X-ray region has been designed, constructed, and installed in the evaluation beamline for soft X-ray optical elements (BL-11) at the SR Center of Ritsumeikan University, Shiga, Japan. It allows us to perform conventional reflection and transmission measurements including rocking curve measurement as well as polarimetric and ellipsometric measurements based on the rotating-analyzer method by using six independently movable motorized stages. As a preliminary test of the apparatus, the reflection profile of a Mo/SiO₂ multilayer mirror prepared by an ion beam sputtering technique, which is designed as a reflection polarizer for use of 13.9 nm, has been measured by the apparatus. The result is compared with that by an existing reflectometer, and the azimuth angle dependence of the reflection intensity has been demonstrated. Consequently, it is shown that the apparatus has the capability to perform the rotating-analyzer ellipsometry.     

高双折射的混合格子太赫兹光子晶体光纤的设计与研究

提出了一种新型高双折射的混合格子太赫兹光子晶体光纤,通过对芯区亚波长尺寸的空气孔进行多种格子组合排列,增加结构的非对称性实现高的模式双折射. 全文仿真建模采用专业的有限元计算软件COMSOL Multiphysics 4.0,结果表明:混合格子太赫兹光子晶体光纤在很宽的频率范围内都具有较高的双折射(达到10^-2)和低的限制损耗,且通过改变光纤的某些参数可以灵活地控制其双折射或限制损耗特性. 相比于同类光通信波段光纤,由于太赫兹波波长较大,能够降低芯区微结构加工的难度,具有可行性. 关键词： 双折射 混合格子 太赫兹光子晶体光纤 限制损耗     

Multiscale dynamics of the cell envelope of Shewanella putrefaciens as a response to pH change

The bacterial surface properties of gram-negative Shewanella putrefaciens were characterized by microbial adhesion to hydrocarbons (MATH), adhesion to polystyrene dishes, and electrophoresis at different values of pH and ionic strength. The bacterial adhesion to these two apolar substrates shows significant variations according to pH and ionic strength. Such behavior could be partly explained by electrostatic repulsions between bacteria and the solid or liquid interface. However, a similar trend was also observed at rather high ionic strength where electrostatic interactions are supposed to be screened. The nanomechanical properties at pH 4 and 10 and at high ionic strength were investigated by using atomic force microscopy (AFM). The indentation curves revealed the presence of a polymeric external layer that swells and softens up with increasing pH. This suggests a concomitant increase of the water permeability and so did of the hydrophilicity of the bacterial surface. Such evolution of the bacterial envelope in response to changes in pH brings new insight to the pH dependence in the bacterial adhesion tests. It especially demonstrates the necessity to consider the hydrophobic/hydrophilic surface properties of bacteria as not univocal for the various experimental conditions investigated.     

On the analysis of ionic surface conduction to unravel charging processes at macroscopic soft and hard solid–liquid interfaces

The electrohydrodynamics of soft interfaces and the processes underlying interfacial charge formation by, for example, unsymmetrical ion adsorption are important aspects of current research on the electrosurface phenomena. In particular, the recent progress in both fields greatly benefits from the now-possible accurate evaluation and quantitative interpretation of (ionic) excess conductivities at solid surfaces and in 3D polyelectrolytic architectures. Achievements in the proper formulation of the conceptual and theoretical framework and in the improvement of measurement capabilities have been tightly connected to the work of Johannes (Hans) Lyklema (1930–2017). Considering his valuable contributions, we herein summarize the theoretical basis of surface conductivity analyses, review the experimental options for the quantification of the surface conductivity at macroscopic planar solid–liquid interfaces, and discuss exemplary surface conductivity case studies for soft and hard interfaces permeable or not to ions and fluid flow.Dedication: Johannes Lyklema (November 23, 1930–October 31, 2017) was a key scientist in colloid and interface science. He completed his doctorate at the University of Utrecht in 1957 under the supervision of Professor J. Th. G. Overbeek with a thesis entitled ‘Adsorption of counterions.’ In 1963, he was appointed a Professor of Physical and Colloid Chemistry at Wageningen Agricultural College (later named Wageningen University), a position he kept until his retirement in 1995. Under his directorate, the Laboratory of Physical and Colloid Chemistry at the Wageningen University became a world-leading research center known for its key research in the fields of interfaces, macromolecules, and electrochemistry. Johannes Lyklema published almost 400 articles and wrote the five-volume text book ‘Fundamentals of Interface and Colloid Science’; he gave lectures in five languages and in five continents, received honorary doctorates in Belgium, Sweden, and Spain, and has been awarded with the Order of the Dutch Lion, to quote only a few of the distinctions and awards he received during his career. In his research, Johannes Lyklema paid particular attention to the analysis and interpretation of the electrosurface phenomena. He was the founder and chairman of the International Advisory Board of the conference series Electrokinetic Phenomena (ELKIN) and section editor on electrokinetics in this journal (Current Opinion in Colloid and Interface Science). We will remember Johannes Lyklema as an eminent scientist as well as a warm-hearted and outstanding person.     

Responsive hydrogel colloids: Structure,interactions, phase behavior,and equilibrium and nonequilibrium transitions of microgel dispersions

Soft and responsive colloids based on polymer hydrogels have moved into the focus of the colloid community. This review gives a brief overview of the recent literature on the structure and phase behavior of neutral and ionic poly(N-isopropylacrylamide) microgel dispersions from dilute to over-packed conditions, focusing in particular on the ability of these particles to adapt their size and shape in response to external stimuli. The review is hierarchical; it first covers the aspects of an individual microgel particle viz., the internal structure of inhomogeneous and homogeneously cross-linked particles, followed by studies of ensembles of particles covering in particular structural ordering, phase behavior, and liquid–solid and solid–solid transitions. Insights on the ability of the microgel particles to deform, compress, and interpenetrate beyond the close-packed volume fractions are discussed. Building complex architectures using microgel particles for fundamental studies as well as future applications is reviewed towards the end of the article.