Copper(I)-catalyzed synthesis of 3,3-disubstituted isoindolin-1-ones from enamides via cascade radical addition and cyclization

Copper(I) catalyzed radical benzylation and cyclization reaction of tertiary enamides was investigated and 3,3-disubstituted N-Alkyl isoindolin-1-ones were obtained in moderate to good yields. In this reaction, two new C–C bonds were formed in one step with high atom economy. Possible reaction pathway for the formation of the products was also discussed in this paper.     

Rotational viscosity of a liquid crystal mixture: a fully atomistic molecular dynamics study

Fully atomistic molecular dynamics (MD) simulations at 293, 303 and 313~K have been performed for the four-component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions (TCFs) were calculated from MD trajectories. The rotational viscosity coefficients (RVCs) of the mixture were calculated using the Nemtsov--Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detail. Reasonable agreement between the simulated and experimental values was found.     

Observation of coexistence of 1D and 2D nanostructures in cobalt dipyrromethene trimer complexes adsorbed on a graphite surface

We report the direct observation of 1D and 2D nanostructures of cobalt dipyrromethene trimer complexes adsorbed on a highly oriented pyrolytic graphite surface using scanning tunneling microscopy (STM). STM images showed two types of ordered structures coexisting on the surface: long 1D molecular chains isolated on the terraces, and 2D hexagonal patterns confined by a 1D chain and/or a graphite step edge. These 1D and 2D structures are attributed to ‘edge-on’ and ‘face-on’ complex alignments on the surface, respectively. In both configurations, substrate-mediated molecule-molecule interactions may play a significant role in stabilizing the nanostructures.     

Tomographic probability representation for quantum fermion fields

Tomographic probability representation is introduced for fermion fields. The states of the fermions are mapped onto the probability distribution of discrete random variables (spin projections). The operators acting on the fermion states are described by fermionic tomographic symbols. The product of the operators acting on the fermion states is mapped onto the star-product of the fermionic symbols. The kernel of the star-product is obtained. The antisymmetry of the fermion states is formulated as a specific symmetry property of the tomographic joint probability distribution associated with the states.     

New type of exactly solvable potential

It is shown that, starting from an exactly solvable potential and making use of the theory of a system of coupled differential equations, it is possible to construct a new type of second-generation potential which is also exactly solvable.     

Double-slit diffraction of terahertz wave generated by tilted-pulse-front pumping

We propose a spatial diffraction diagnostic method via inserting a millimeter-gap double slit into the collimated terahertz beam to monitor the minute variation of the terahertz beam in strong-field terahertz sources, which is difficult to be resolved in conventional terahertz imaging systems. To verify the method, we intentionally fabricate tiny variations of the terahertz beam through tuning the iris for the infrared pumping beam before the tilted-pulse-front pumping setups.The phenomena can be well explained by the theory based on the tilted-pulse-front technique and terahertz diffraction.     

基于MCPT解法器库的专用辐射探测模拟软件研发与应用北大核心CSCD

甲状腺内^(131)I放射性活度与辐射探测结果的比例关系与甲状腺几何尺寸、探测距离等因素相关,是估算甲状腺内^(131)I含量与其可能造成的辐照损伤的关键参数。基于MCPT辐射输运数值模拟算法器库开发了用于开展NaI探测器伽马辐射测量模拟的应用程序,进而建立了多组具有不同容积的甲状腺型容器和不同探测距离的物理模型,最终通过蒙特卡罗数值计算得到了不同测量状态下探测器的探测效率。在甲状腺型容器与探测器距离较远时,数值模拟给出的结果与理论计算结果一致,证明此应用程序可用于定量分析NaI的探测效率。数值模拟结果表明,小距离模型的结果受甲状腺样容器的大小和距离的显著影响,模拟给出的探测效率表为开展深入细致的实验研究奠定了基础。     

Optimal time decay of the quantum Landau equation in the whole space

We are concerned with the Cauchy problem of the quantum Landau equation in the whole space. The existence of local in time nearby quantum Maxwellian solutions is proved by the iteration method and generalized maximum principle. Based on Kawashima?s compensating function and nonlinear energy estimates, the global existence and the optimal time decay rate of those solutions are obtained under some conditions on initial data.     

An efficient rough feature selection algorithm with a multi-granulation view

Feature selection is a challenging problem in many areas such as pattern recognition, machine learning and data mining. Rough set theory, as a valid soft computing tool to analyze various types of data, has been widely applied to select helpful features (also called attribute reduction). In rough set theory, many feature selection algorithms have been developed in the literatures, however, they are very time-consuming when data sets are in a large scale. To overcome this limitation, we propose in this paper an efficient rough feature selection algorithm for large-scale data sets, which is stimulated from multi-granulation. A sub-table of a data set can be considered as a small granularity. Given a large-scale data set, the algorithm first selects different small granularities and then estimate on each small granularity the reduct of the original data set. Fusing all of the estimates on small granularities together, the algorithm can get an approximate reduct. Because of that the total time spent on computing reducts for sub-tables is much less than that for the original large-scale one, the algorithm yields in a much less amount of time a feature subset (the approximate reduct). According to several decision performance measures, experimental results show that the proposed algorithm is feasible and efficient for large-scale data sets.