Crossing in the magnetic force-gap hysteresis curve of magnetic levitation systems with a high-Tc superconductor

For the magnetic levitation system consisting of a high-T_c superconductor and permanent magnet, the relation curve of magnetic force with gap between these two components is known as a hysteresis loop, that is, the approaching and departing portions envelop a complete one, and generally these two portions do not cross each other. However, in some special cases this crossing arises, and makes the complete loop broken. In this paper, by the numerical simulation of the magnetic force-gap curve in large numbers of physical and geometrical parameters, two typical crossings were found. To investigate the crossing and explore its physical causes, for one of the crossings, the current density in the superconductor was further calculated and its magnitude and vector distribution at the gaps nearby where the crossing arises were obtained. Based on these calculation results and an adequate discussion, the conclusion was induced that the crossing in the magnetic force-gap hysteresis curve results from applied magnetic field’s incomplete and insufficient penetrating in superconductor.     

Different charging behaviors between electrons and holes in Si nanocrystals embedded in SiN_x matrix by the influence of near-interface oxide traps

Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method,followed by thermal annealing to form the Si nanocrystals(Si-NCs)embedded in Si Nx floating gate MOS structures.The capacitance–voltage(C–V),current–voltage(I–V),and admittance–voltage(G–V)measurements are used to investigate the charging characteristics.It is found that the maximum flat band voltage shift(△VFB)due to full charged holes(～6.2 V)is much larger than that due to full charged electrons(～1 V).The charging displacement current peaks of electrons and holes can be also observed by the I–V measurements,respectively.From the G–V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the Si O2/Si-substrate interface.Combining the results of C–V and G–V measurements,we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism.The evolution of G–V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs.     

交错跃迁Hofstadter梯子的量子流相

为玻色Hofstadter梯子模型引入交错跃迁,来扩展模型支持的量子流相.基于精确对角化和密度矩阵重整化群计算发现,无相互作用时,系统中包含横流相、涡旋相和纵流相;横流相来自均匀跃迁时Hofstadter梯子模型的Meissner相,纵流相是交错跃迁时才可见的流相.强相互作用极限下系统的超流区也包含横流相、纵流相和涡旋相,但存在更多的相变级数;超流区的横流相、纵流相之间存在相变但Mott区的不存在,把Mott区的"横、纵流相"称为Mott-均匀相,在Mott区只存在均匀相和涡旋相.跃迁的交错会压缩涡旋相存在的区域,使Mott区最终只剩下均匀相;跃迁的交错不仅能驱动Mott-超流相变,还使磁通的改变也能够驱动系统的Mott-超流相变.对这一系统的研究丰富了磁通系统中的量子流相,同时为研究拓扑流特性提供了模型支持.     

微乳电动色谱法的研究进展

微乳电动色谱(MEEKC)是一种以微乳为背景电解质,以电压为驱动力的分离技术。本文对MEEKC中的各调节参数进行了概述,重点归纳了MEEKC法在正辛醇-水分配系数测定、中药和手性化合物分离方面的应用,以及在操作技术上的新进展,如多路进样技术以及在线联用质谱检测技术等,并通过对相关文献的分析,对一直存有争议的MEEKC与胶束电动色谱(MEKC)的联系与区别进行了讨论,最后提出了MEEKC法未来的发展空间。     

Faraday-Michelson system for quantum cryptography

Quantum key distribution provides unconditional security for communication. Unfortunately, current experimental schemes are not suitable for long-distance fiber transmission because of phase drift or Rayleigh backscattering. In this Letter we present a unidirectional intrinsically stable scheme that is based on Michelson-Faraday interferometers, in which ordinary mirrors are replaced with 90 degree Faraday mirrors. With the scheme, a demonstration setup was built and excellent stability of interference fringe visibility was achieved over a fiber length of 175 km. Through a 125 km long commercial communication fiber cable between Beijing and Tianjin, the key exchange was performed with a quantum bit-error rate of less than 6%, which is to our knowledge the longest reported quantum key distribution experiment under field conditions.     

The Tri(imidazole)-Derivative Moiety: A New Category of Electron Acceptors for the Design of Crystalline Hybrid Photochromic Materials

The intermarriage of neutral and tripodal imidazole ligand, tris(4-(1H-imidazol-1-yl)phenyl)amine (TIPA), with zinc phosphite yields two hybrid phosphites, [Zn₂(HPO₃)₂(TIPA)]⋅2 H₂O ( 1 ) and [Zn₃(HPO₃)₃(TIPA)]⋅6 H₂O ( 2 ). Compound 1 has a hybrid sheet with neutral zinc-phosphite chains as supramolecular building blocks (SBBs), whereas 2 exhibits a 3D hybrid architecture with other neutral zincophosphite chains as supramolecular building blocks. The structural discrepancy between 1 and 2 is mainly due to the distinct linkage modes between organic TIPA ligands and inorganic zincophosphite chains. Interestingly, compounds 1 and 2 feature fast photochromism in response to UV light irradiation under ambient conditions. The discrepancy of photochromic performance between 1 and 2 is mainly due to the different geometrical configuration of the TIPA ligand. Different to majority of reported hybrid photochromic compounds driven by photochromic active units, the photochromism in 1 and 2 is derived from the electron transfer (ET) between phosphite and non-photochromic triimidazole-derivative ligand TIPA. Compared with the widely explored nonphotochromic polypyridine-derivative as electron acceptors (EAs), our work provides a new EA model for the design of hybrid photochromic materials based on the ligand-to-ligand ET mechanism. A multiple anti-counterfeiting application based on 1 and 2 was investigated.     

Effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency

The effects of clouds, sea surface temperature, and its diurnal variation on precipitation efficiency are investigated using grid-scale data from nine equilibrium sensitivity cloud-resolving model experiments driven without large-scale vertical velocity. The precipitation efficiencies are respectively defined in surface rainfall, cloud, and rain microphysical budgets. We mathematically and physically demonstrate the relationship between these precipitation efficiencies. The 2℃ increases in spatiotemporal invariant sea surface temperature (SST) from 27℃ to 29℃ and from 29℃ to 31℃, and the inclusion of diurnal SST difference 1℃ and the 1℃ increase in diurnal SST difference generate opposite changes in the precipitation efficiency by changing ice cloud-radiation interactions. The radiative and microphysical processes of ice clouds have opposite effects on the precipitation efficiency because of the rainfall increase associated with the reduction in the saturation mixing ratio caused by the exclusion of radiative effects and the decrease in rainfall related to the reduction in net condensation caused by the exclusion of deposition processes. The radiative effects of water clouds on the precipitation efficiency are statistically insensitive to the radiative effects of ice clouds.     

Extensible router for a quantum key distribution network

Building a quantum key distribution network is crucial for practical quantum cryptography. We present a scheme to build a star topology quantum key distribution network based on wavelength division multiplexing which, with current technology, can connect at least a hundred users. With the scheme, a 4-user demonstration network was built up and key exchanges were performed.     

魔芋总生物碱量的测定

用酸性染料比色法测定魔芋总生物碱量,以盐酸金刚烷胺计,在2—10μg/mL范围内线性关系良好。设计正交试验选择总生物碱的最佳提取条件为：料液比1：12,乙醇浓度85%,索氏提取4h。