激光诱导熔石英表面损伤修复中的气泡形成和控制研究

基于熔石英材料在CO_2激光作用下的温度分布和结构参数变化的计算结果,对熔石英损伤修复中的气泡形成和控制进行了研究.针对损伤尺寸介于150—250μm之间的损伤点,提出了一种能够有效控制气泡形成的长时间低温预热修复方法.基于低温下熔石英材料结构弛豫时间常数较长的特点,该方法在不引起熔石英材料结构发生显著变化的同时,能够解吸附表面和裂纹处所附着的气体和杂质,可有效降低裂纹闭合过程中气泡形成的概率.实验结果表明,长时间低温预热修复方法的成功修复概率可达到98%.     

色散缓变光纤中宽带调制不稳定性谱的产生

本文报道色散缓变光纤中调制不稳定性效应研究.从非线性Schrodinger方程出发,获得了增益谱与纵向色散变化参量和光纤传输距离的一般关系.研究发现,色散缓变光纤中调制不稳定性的增益谱较常规光纤中的宽得多.调节光纤色散纵向变化参量,可以得到较宽的增益谱.该文的研究结果为光纤中利用调制不稳定性产生超短孤子脉冲提供了理论根据.     

Entropy squeezing of an atom with a k-photon in the Jaynes--Cummings model

The entropy squeezing of an atom with a k-photon in the Jaynes-Cummings model is investigated. For comparison, we also study the corresponding variance squeezing and atomic inversion. Analytical results show that entropy squeezing is preferable to variance squeezing for zero atomic inversion. Moreover, for initial conditions of the system the relation between squeezing and photon transition number is also discussed. This provides a theoretical approach to finding out the optimal entropy squeezing.     

新型宽谱电磁脉冲试验系统

 研制了一套新型宽谱电磁脉冲试验系统,该系统采用全电感隔离型重复频率Marx发生器产生高压冲击脉冲,经双极脉冲形成线馈入宽带天线进行宽谱辐射。介绍了发生器工作原理和双极脉冲形成原理。实验结果表明：发生器输出脉冲电压500 kV,脉冲前沿20 ns,重复频率20 Hz,宽谱辐射因子195 kV,辐射中心频率200 MHz,频谱宽度37%。该试验系统结构紧凑、操作灵活,并具有方位辐射方向360°旋转和运程控制等功能。     

Synthesis and structure of bis(dibenzoylmethane)copper(II)

Bis(dibenzoylmethane)copper Cu(dbm)₂ has been synthesized and its structure determined by x-ray diffraction. It crystallizes in the monoclinic system, space group C2/c, with a = 25.936(3), b = 5.9806(8), c = 16.4908(16) Å, = 114.998(8)°, Z = 4, and V = 2318.3(4) ų. The Cu atom is located at a symmetry center and surrounded by four O atoms from two dbm molecules to form a plane square coordination environment. On the a–c plane the molecules are orderly arranged to result in a layered structure, and parallel to crystallographic b-axis they form a molecular column due to the effect of aromatic stacking.     

TEMPO/CuI synergetic catalyzed oxidative cross-coupling of indoles with benzylamines: Synthesis of bis(indolyl)phenylmethanes

TEMPO/CuI was found to be an effective catalyst for the cross-coupling of indoles with benzylic amines affording the corresponding bis(indolyl)phenylmethanes under air atmosphere at room temperature in good to excellent yields. The efficiency, easy workup, simplicity, and chemoselectivity of this protocol provide a green and low-cost procedure for the synthesis of these compounds.     

Crystal structures and spectroscopic properties of copper(II) and zinc(II) complexes with the macrocycle 1,4,7-tris(2-pyridylmethyl)-1,4,7-triazacyclononane

Two novel transition-metal copper and zinc complexes [(CuL)₂]·(ClO₄) (1) and [(ZnL)]·(ClO₄)₂ (2) (L = 1,4,7-tris(2-pyridylmethyl)-1,4,7-triazacyclononane) have been synthesized and structurally determined. The two complexes are both crystallized in monoclinic space group P2(1)/c with a = 14.318(4), b = 17.214(5), c = 22.403(7) Å, = 93.096(6)°, V = 5522(3) ų, and Z = 4 for 1 and a = 9.371(2), b = 17.615(4), c = 17.579(4) Å, =104.070(4)°, V = 2814.6(11) ų, and Z = 4 for 2. The center metal ions are coordinated to six nitrogen atoms, three of which are from triazacyclononane and other three from the pendant-arms 2-pyridylmethyl, forming a slightly distorted octahedral geometry. Two complexes have been characterized by element analysis, infrared spectroscopy, and the UV–Vis and ESR spectra for 1 have also been determined.     

Isolation, structure determination, and synthesis of galaxamide, a rare cytotoxic cyclic pentapeptide from a marine algae Galaxaura filamentosa

Galaxamide (1), a rare cyclic pentapeptide, was isolated from the marine algae Galaxaura filamentosa. A preliminary bioassay of Galaxamide showed remarkable in vitro antiproliferative activities against GRC-1 and HepG2 cell lines. The first total synthesis of the cyclic peptide was achieved for further biological evaluation.     

Single-molecule study of lateral mobility of epidermal growth factor receptor 2/HER2 on activation

The transmembrane protein HER2, a member of the epidermal growth factor receptor family of tyrosine kinase, plays important roles in many fundamental cellular processes as well as the pathogenesis of many cancers. In this work, we have applied the single-molecule fluorescence microscopic method to study lateral mobility change of HER2 on activation by imaging and tracking individual GFP-tagged HER2 molecules on the membrane of living cells. The single HER2 molecules displayed different diffusion rates and modes. It was interesting to find that the mobility of HER2 increased upon stimulation by heregulin beta1, the specific ligand of HER3. The faster diffusion was related to the tyrosine phosphorylation of HER2 or EGFR. The results provided new information for the understanding of HER2 activation and molecular mechanism of signal transduction through HER2/HER3 heterodimerization.     

Synthesis, Structure and Growth Mechanism of ZnS Nanowires with High Aspect Ratio

ZnS nanowires were successfully synthesized through the direct reaction of Zn and S vapor via carbon-assisted chemical evaporation deposition method with Au catalyst. The investigations indicated that the size of ZnS nanowires with a diameter of approximately 40 nm was uniform along the axis of the wire and the surfaces were slick. The ZnS nanowire with a hexagonal wurtzite structure was a typical single crystalline structure. HRTEM and SEAD results demonstrated that the nanowire grew along [100] direction, which was different from the common direction reported in literatures. The growth of nanowires was controlled by vapor-liquid-solid (VLS) mechanism.