Unusual Reactivities of ortho-Hydroxy-β-nitrostyrene

Nitrostyrene derivatives are widely used in organic syntheses as a substrate for Michael addition, photoisomerization and cycloaddition. In contrast, ortho-hydroxy derivatives exhibit unusual behaviors in these reactions. Conjugate addition proceeded upon treatment of the ortho-hydroxy-β-nitrostyrene with an amine; however, subsequent C–C bond cleavage readily occurred to afford the corresponding imine. Moreover, conversion of the trans-isomer to a cis-isomer did not occur efficiently, even when UV light was irradiated. We studied these unusual behaviors of β-nitrostyrene, focusing on the role of the ortho-hydroxy group.     

Approach for the Direct Synthesis of β-Dichlorosubstituted Acetanilides Using Iodine Trichloride (ICl3) as the Oxidant and Catalyst

A reliable method for direct synthesis of β‐dichlorosubstituted acetanilides is reported. The key transformation involves the oxidative and catalytic cleavage of a carbon‐carbon bond in the presence of iodine trichloride (ICl₃). In this protocol ICl₃ is used not only as the catalyst but also as the oxidant which widely broadens the scope of its application in organic synthetic chemistry.     

Open Chain Chiral Macrolide Building Blocks by Opening of Deoxygenated 1,6-Anhydrosugars with 1,3-Propanedithiol

Chiral building blocks for macrolides and related natural products are obtained from 1,6-anhydrosugars by conversion of the bicyclic acetals 2 or 12 into the open chain chiral 1,3-dithianes 6 and 13. Branched precursors can be obtained by opening of the ?erný epoxide 1 with the 1,3-dithiane anion to yield 7, followed by ring opening with 1,3-propanedithiol to the bis-1,3-dithiane 8.     

用于全光缓存的光阈值门理论和实验研究

提出了一种基于光阈值门的全光缓存方案,采用两个非对称的SOA环形腔激光器耦合构成光阈值门,其输出光可以在两种波长上切换,可控制波长转换器实现光包路由,从而将需缓存的数据包路由到缓存端口,避免了复杂的包头处理.建立了光阈值门的理论模型,对10 Gbit/s的光阈值门的动态特性进行了数值模拟和实验研究,实验结果和理论计算结果相符合,实验也表明光阈值门两种输出状态的消光比可达30dB.     

Influence of nonlinear absorption effects on optical bistability in semiconductor ring resonators

We present a theoretical investigation of optical bistability in a nonlinear semiconductor ring resonator, by taking into account the two-photon absorption and the free-carrier absorption. By solving the intensity equation within the ring resonator, a parametric formulation is obtained for describing the bistability relation between the input and the output intensities. Numerical results show that the nonlinear absorption effects can affect the critical points and domain of the optical bistability.     

Crack growth on the basal plane in single crystal zinc: experiments and computations

Crack propagation on the basal planes in zinc was examined by means of in situ fracture testing of pre-cracked single crystals, with specific attention paid to the fracture mechanism. During quasistatic loading, crack propagation occurred in short bursts of dynamic crack extension followed by periods of arrests, the latter accompanied by plastic deformation and blunting of the crack-tip. In situ observations confirmed nucleation and propagation of microcracks on parallel basal planes and plastic deformation and failure of the linking ligaments. Pre-existing twins in the crack path serve as potent crack arrestors. The crystallographic orientation of the crack growth direction on the basal plane was found to influence both the fracture load as well as the deformation at the crack-tip, producing fracture surfaces of noticeably different appearances. Finite element analysis incorporating crystal plasticity was used to identify dominant slip systems and the stress distribution around the crack-tip in plane stress and plane strain. The computational results are helpful in rationalizing the experimental observations including the mechanism of crack propagation, the orientation dependence of crack-tip plasticity and the fracture surface morphology.     

Effects of band mixing on the radiative properties of a quantum well

The effect of band mixing and non-parabolicity on quantum well gain and spontaneous emission is studied using k.p theory. Spectra of gain and spontaneous emission are strongly modified but the relation of maximum gain versus nominal current density is not strongly affected.     

硬X射线焦斑环孔编码成像的理论与实验研究

针对几十~百keV能量的低强度X射线焦斑源测量,建立了高探测效率环孔编码成像技术。研究给出了环孔成像效率和信噪比与环孔结构参数的关系,采用微联结的环孔结构设计并模拟了联结区尺寸对成像质量的影响,解决了环孔结构同轴成像技术难题。所建立环孔成像系统应用于Unique-II X射线焦斑源成像实验。结果表明,X射线焦斑的空间分布近似为‘马鞍’形状,而且中间部分的强度低于两侧的强度,与针孔成像结果相似,但环孔的探测效率明显高于针孔的效率。最后,分析了维纳滤波与R-L两种复原图像方法的效果。     

All-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity

A novel scheme for all-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity is proposed and investigated numerically. The results show, for a 2.5 GHz driving pulse train, it can be generated 5-25 GHz repetition rate pulse trains with low clock amplitude jitter, polarization independence and high peak power. Furthermore, the extraction of the clock signal from a pseudorandom bit sequence signal can be realized based on the proposed scheme.     

微型圆光栅刻划偏心量的控制

对微型圆光栅刻划偏心误差问题进行了讨论。提出了微型圆光栅刻划时偏心调试误差的公差范围。