非线性光学格子中的光束演化研究

研究光学格子中(即在光传输的横截面上存在周期格子势的调制)光束的演化，利用变分原理，求出了光束宽度、振幅、频率啁啾参量随传播距离的演化形式.发现光束宽度与调制周期的比值必须小于一定的值才能形成孤子的传输；同时，还得到了光束在不同的条件下存在着不同的传输过程.光学格子中周期格子的作用有类似非线性的良好的特性，周期格子的引入提供了可以更好地控制格子孤子的形成和传输的参考条件.     

Influence of nonlinear dispersion on modulation instability of coherent and partially coherent ultrashort pulses in metamaterials

The combination of dispersive magnetic permeability with nonlinear polarization leads to a series of nonlinear dispersion terms in the propagation equations for ultrashort pulses in metamaterials. Here we present an investigation of modulation instability (MI) of both coherent and partially coherent ultrashort pulses in metamaterials to identify the role of nonlinear dispersion in pulse propagation. The Wigner–Moyal equation for partially coherent ultrashort pulses and the nonlinear dispersion relation for MI in metamaterials are derived. Combining the standard MI theory with the unique properties of the metamaterial, the influence of the controllable first-order nonlinear dispersion, namely self-steepening, and the second-order nonlinear dispersion on both coherent and partially coherent MI, in both negative-index and positive-index regions of the metamaterial for all physically possible cases is analyzed in detail. For the first time to our knowledge, we demonstrate that the role of the second-order nonlinear dispersion in MI is equivalent to that of group-velocity dispersion (GVD) to some extent, and thus due to the role of the second-order nonlinear dispersion, MI may appear in the otherwise impossible cases, such as in the normal GVD regime. PACS 42.25.Kb; 42.65.Sf; 78.20.Ci     

Synthesis of 2,2,6,6-tetrafluoro-4-phenylmethylmorpholin-3-ones: A simple approach from fluorinated triethylene glycol

2,2,6,6-Tetrafluoro-4-phenylmethylmorpholin-3-ones are obtained from a new single step, preparative route by reacting triethylene glycol di(trifluoromethanesulfonate), which contains poly -CF₂O- groups, with benzylamine. Reaction of trifluoromethylsulfonate and trifluoromethoxy derivatives with benzylamine gave either the nucleophilically-substituted product or the product resulting from the basic hydrolysis of the difluoromethoxy group. Replacement of a fluoroether chain by a fluoroalkane gave rise to fluorinated phenylmethylpiperidine and phenylmethylazepine via the combination of trifluoromethanesulfonic fluoroalkyldiyl esters and benzylamine.     

MATLAB语言在X射线衍射谱图处理中的应用

利用MATLAB语言编写了X射线衍射数据处理程序,使之能够导人到Materials Studio软件,进行粉末晶面指标化以及粉末精修等后续处理.处理程序简单易懂,可作为其他测试数据格式转换程序的参考.     

A Small-Molecule Diketopyrrolopyrrole-Based Dye for in vivo NIR-IIa Fluorescence Bioimaging

Organic small-molecule fluorophores with near-infrared IIa (NIR-IIa) emission have great potential in pre-clinical detection and inoperative imaging due to the high-spatial resolution and deep penetration. However, developments of the NIR-IIa fluorophores are still facing considerable challenges. In this work, a series of diketopyrrolopyrrole (DPP)-based fluorophores were designed and synthesized. Subsequently, nanomaterial T25@F127 with significant NIR-IIa emission properties was rationally prepared by encapsulating DPP-based fluorophore T25 , and was selected for fluorescence angiography and cerebral vascular microscopic imaging with nearly 800 μm penetrating depth and excellent signal-background ratio of 4.07 and 2.26 (at 250 and 400 μm), respectively. Furthermore, the nanomaterial T25@cRGD with tumor targeting ability can image tiny metastatic tumor on intestine with a small size of 0.3 mm×1.0 mm and high-spatial resolution (SBR=3.84). This study demonstrates that the nanomaterials which encapsulated T25 behave as excellent NIR-IIa fluorescence imaging agents and have a great potential for in vivo biological application.     

Experimental Verification of Left-Handed Metamaterials Composed of Coplanar Electric and Magnetic Resonators

We verified experimentally left-handed metamaterials （LHM） composed of coplanar electric and magnetic resonators. A typical LHM sample composed of coplanar resonator unit cells was fabricated, investigated and tested. The experimental results show that the tested sample has a left-handed band of width 1.4 GHz in the X band. The experimental results agree quite well with the simulation ones. Moreover, both the simulation and experimental results show that the LHM under study can automatically achieve good impedance-matching in the left-handed band.     

An electromagnetic wave propagation in a non-uniform plasma controlled by EIT

We investigate the conditions in which the propagation of an electromagnetic wave is changed from transparency to cutoff in a non-uniform plasma. The allowed frequency range of the driving wave is obtained for the case that the probe frequency is above the plasma frequency. The effect of the power of the driving field on the range is analyzed. Received 23 May 2001     

Pd-catalyzed direct arylation of 3-fluorofurans utilizing the neighboring effect of fluorine atom: facile synthesis of tetrasubstituted monofluoro furans

Pd-catalyzed direct arylation of 3-fluorofurans with a variety of aryl bromides was facilitated by the neighboring effect of fluorine atom to provide tetrasubstituted monofluoro furans in moderate to good yields.