Geometric sigma model of the Universe

The purpose of this work is to demonstrate how an arbitrarily chosen background of the Universe can be made a solution of a simple geometric sigma model.Geometric sigma models are purely geometric theories in which spacetime coordinates are seen as scalar fields coupled to gravity.Although they look like ordinary sigma models,they have the peculiarity that their complete matter content can be gauged away.The remaining geometric theory possesses a background solution that is predefined in the process of constructing the theory.The fact that background configuration is specified in advance is another peculiarity of geometric sigma models.In this paper,I construct geometric sigma models based on different background geometries of the Universe.Whatever background geometry is chosen,the dynamics of its small perturbations is shown to have a generic classical stability.This way,any freely chosen background metric is made a stable solution of a simple model.Three particular models of the Universe are considered as examples of how this is done in practice.     

Can X(5568) be a tetraquark state?

Very recently, the D0 collaboration has reported the observation of a narrow structure, X(5568), in the decay process X(5568)→ B_s~0π±using the 10.4fb~(-1) data of pp collision at 8~(1/2) = 1.96 TeV. This structure is of great interest since it is the first hadronic state with four different valence quark flavors, b, s, u, d. In this work,we investigate tetraquarks with four different quark flavors. Based on the diquark-antidiquark scheme, we study the spectroscopy of the tetraquarks with one heavy bottom/charm quark and three light quarks. We find that the lowest-lying S-wave state, a tetraquark with the flavor [su][bd] and the spin-parity JP= 0~+, is about 150 MeV higher than the X(5568). Further detailed experimental and theoretical studies of the spectrum, production and decays of tetraquark states with four different flavors are vital to gain a better understanding of the nature and classification of hadron exotic states.     

关于中药质量控制与体内代谢研究的思考

质量控制是保证中药安全、有效的重要基础。体内代谢研究可以为阐明中药的治病机制提供依据。本文以蟾酥为例,讨论了当前中药质量控制及体内代谢研究存在的主要问题和解决办法:认为把中药指纹图谱的全面指认与多指标成分定量相结合是有效控制中药质量的可行途径;液相色谱-质谱联用技术(LC/MS)将在中药化学研究、体内代谢研究等方面发挥重要作用;中药的化学指纹图谱应与药理活性相关联,从而建立合理的中药质量评价体系;结构修饰对基于天然产物的新药发现具有重要意义。     

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Based on the preferred plane theory for regional stability assessment, princIple and methods of artificial neural network (ANN), the model of back propagation (BP) neural network and its algorithm for the preferredfault recognition are discussed in this paper. Practical examples indicate that the new method using BP neural network to determine preferred fault is effective and the prediction result is good.     

Problems in the Study of Electro-Lum inescence Devices Based on Phosphorescent Dyes

本文从光物理和光化学的角度出发对磷光电致发光器件中的一些基本过程和问题, 如发光层材料的选择和激发, 主体化合物分子间的能量迁移, 主客体分子间的能量转移以及磷光的发射等进行了扼要的讨论, 并指出了在设计和制备这类新型的发光器件中应注意的一些问题。