Observation of level splitting within the natural width by saturation spectroscopy

A saturation-spectroscopy experiment is performed in a three-level system in Xe I, and shows that a narrow dip occurs in the power-broadened Lorentzian response. It is due to the Zeeman splitting of common level by the earth magnetic field. Other splittings, typically larger than 0.2 the natural width, can be observed using this saturation effect. Interpretation is made on the basis of simple realistic assumptions. Associé à l'Université Paris-Sud     

H^—5的正四面体中心和正方形中心构型能量的理论计算

文中用ＭＡＣＱＭ（ｍｏｄｉｆｉｅｄａｒａｎｇｅｍｅｎｔｃｈａｎｎｅｌｑｕａｎｔｕｍｍｅｃｈａｎｉｃｓ）方法计算了负离子团簇Ｈ－５的正四面体中心和正方形中心构型的能量随中心原子核到顶角原子核间距离Ｒ变化的曲线。计算得知，两种构型均在Ｒ＝１．５５ａ０时有能量极小值Ｅ正四面体中心＝－２．７８９９ａ．ｕ．，Ｅ正方形中心＝－２．７５３９ａ．ｕ．。说明Ｈ－５的这两种结构都可能存在，但正四面体中心结构较为稳定。     

电磁散射问题的两种反演方法研究

提出了电磁散射问题的两种反演方法:确定性梯度搜索方法和MonteCarlo随机搜索方法.给出了两种方法的基本原理,并对反演性能包括对散射体的定位能力、反演精度、反演时间进行了系统的分析与比较.数值计算结果表明,确定性方法定位精确,而随机性方法对散射体电磁参数的反演精度高且速度快,利用两者优点可以增强反演效果.     

The Haldane–Shastry spin chain and the topological basis realization

In this paper, based on the topological basis states, we investigate the Hamiltonian family {H₂,H₃,H₄}$\{H_2,H_3,H_4\}$ of a closed four-qubit Haldane–Shastry spin chain. Not only the two-qubit interaction form, but also the three-qubit interaction form and the four-qubit interaction form are presented in terms of spin operators. Meanwhile, we explore some particular properties of the topological basis states in these systems. With Yangian algebra, the symmetry of the systems and the transitions between the eigenstates have been investigated. We find a really useful effect of Y(sl(2))$Y\left(sl\left(2\right)\right)$ operators {J_±,J₃}$\{J_{\pm },J_3\}$, which is that they can describe the transitions between the spin single state and the spin triple states. Furthermore, we construct a new Hamiltonian, whose energy degeneracies can be changed by adjusting the strengths of the two-qubit interactions, three-qubit interactions, four-qubit interactions, and the external magnetic field.     

The Barrier to Proton Transfer in the Dimer of Formic Acid: A Pure Rotational Study

The rotational spectra of three C‐deuterated isotopologues of the dimer of formic acid have been measured, thanks to the small dipole moment induced by asymmetric H→D substitution(s). For the DCOOH–HCOOH species, the concerted double proton transfer of the two hydroxy hydrogen atoms takes place between two equivalent minima and generates a tunneling splitting of 331.2(6) MHz. This splitting can be reproduced by a 3D model with a barrier of 2559 cm^?1 (30.6 kJ mol^?1) as obtained from theoretical calculations.     

6,8-di-C-glycosyl flavones with β-furanoarabinose from Scutellaria baicalensis and their anti-inflammatory activities

Two flavone di-C-glycosides, a pair of isomers, were isolated from Scutellaria baicalensis. The structures of compounds 1 and 2 were elucidated by means of physical data, including 1D and 2D NMR and HR-ESI-MS. Supporting theoretical calculations of the compound conformational landscape has also been conducted for geometry optimization. This is the first report of the natural occurrence of β-furanoarabinoside. In addition, the effects of compounds 1 and 2 on NO, pro-inflammatory cytokines, PGE2 and COX-2 levels were measured in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. The pair of isomers exhibited significant inhibitory effects on inflammation.     

Small-scale seismic inversion using surface waves extracted from noise cross correlation

Green's functions can be retrieved between receivers from the correlation of ambient seismic noise or with an appropriate set of randomly distributed sources. This principle is demonstrated in small-scale geophysics using noise sources generated by human steps during a 10-min walk in the alignment of a 14-m-long accelerometer line array. The time-domain correlation of the records yields two surface wave modes extracted from the Green's function between each pair of accelerometers. A frequency-wave-number Fourier analysis yields each mode contribution and their dispersion curve. These dispersion curves are then inverted to provide the one-dimensional shear velocity of the near surface.     

Generation of finite subgroups of the mapping class group of genus 2 surface by Dehn twists

In this note we give presentations, up to conjugacy, of all finite subgroups of the mapping class group of a closed surface of genus 2, using the Humphries generators. An application to homology representations is given.