Highly efficient C-H insertion reactions of hydrogen peroxide catalyzed by homogeneous and heterogeneous methyltrioxorhenium systems in ionic liquids

A convenient and efficient C-H insertion reaction of environment friendly H₂O₂ into representative hydrocarbon derivatives by homogeneous methyltrioxorhenium (MTO), heterogeneous poly(4-vinylpyridine)/methyltrioxorhenium (PVP/MTO) and microencapsulated polystyrene/methyltrioxorhenium (PS/MTO) systems in ionic liquids, is described. In some cases a higher activity was observed if compared with the same reaction in molecular solvents. The heterogeneous catalysts are stable systems under the reaction conditions and can be recycled for more transformations.     

Palladium-catalyzed carbene insertion into benzyl bromides

Palladium can catalyze the insertion of ethyl diazoacetate into benzyl bromides. The key step in the catalytic cycle is the migratory insertion of a carbene, derived from ethyl diazoacetate, into a Pd-C bond.     

低插损平坦谱响应阵列波导光栅解复用器优化设计

通过在输入波导与输入平板波导之间加入一种模式转换结构,获得了一个具有平坦光谱响应,低插损,光谱响应对称的阵列波导光栅型波分复用器,该模式转换结构由一个与输入波导的输出端连接的第一锥形波导,一个与此锥形波导输出端连接的细直波导,一个与细直波导输出端连接的第二个锥形波导以及一个连接输入平板波导和第二个锥形波导的梯形波导组成,通过优化设计梯形波导和第二个锥形波导的形状可以获得较宽的1dB通带带宽和较低的插损,同时光谱响应具有非常好的平坦性,而且通过对第一个锥形波导和细直波导的优化设计,在不引入明显的额外插损的条件下,能大大减小由于输入波导的弯曲引入的光谱响应的不平坦.     

光纤双向应变-位移点式传感器

选择不同间距的基片自由端和不同长度的自由悬垂光纤研制了利用光纤弯曲损耗的光纤双向应变-位移传感器.该传感器可分别用于测量应变和位移.实验表明:悬臂梁上的应变标准误差约为～26 με.微位移架上的位移标准误差约～0.06 mm.基本满足建筑结构对测量精度的要求.     

Millimeter and submillimeter wave measurements of complex optical and dielectric parameters of materials

These two promising millimeter wave materials were found to exhibit one order of magnitude higher absorption coefficient than the common low-loss ceramics such as alumina, fused silica and beryllia. A modular, polarizing, dispersive Fourier transform spectrometer capable of operating over the range 5 mm to 0.004 mm was used to provide a continuous spectrum of the refractive index and absorption coefficient to an accuracy of five decimal places and less than 1 percent, respectively.Partially supported by the U.S. Army Research Office under Contract Number DAAG-29-81-K-0009 and the Office of Fusion Energy, U.S. Department of Energy, under Contract W-7405-eng-26 with Union Carbide Corporation.Supported by the National Science Foundation.     

Spectral‐Luminescence Characteristics of Polyphenyls and Polyacenes in the Gas Phase in Electron‐Beam Excitation

The spectra of electronenergy loss, excitation functions, and fluorescence spectra in excitation of the vapor of polyphenyls and polyacenes by electron beams of different energies are determined. The influence of successive complication of the molecules under study on these spectralluminescence characteristics is tracked. Unlike the optical absorption spectra, in the spectra of electronenergy loss of all the substances studied one observes a band which is related to the singlettriplet transition S ₀–T ₁. The transitions up to S ₀–S ₅ are recorded in excitation of the molecules by highenergy electrons, including the region of vacuum ultraviolet. From the functions of fluorescence excitation the authors have determined the excitation thresholds that correlate with the energies of the S ₁ levels, except for pyrene in which the S ₀–S ₁ transition is forbidden and does not show up not only in photon excitation but also in electronbeam excitation, although the intercombination forbiddenness in the latter case is removed and the S ₀–T ₁ band is observed.     

Processing,structure, microstructure,and transport properties of the oxygen-conducting ceramics (La,Sr)(Ga,M)O<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> (M=Mg,Fe, Ni)

The structure, microstructure, and dielectric and transport properties of (La,Sr)(Ga,M)O_y (M=Mg, Fe, and Ni) ceramic solid solutions have been studied by X-ray diffraction, thermogravimetry, and dilatometry in various gas atmospheres. Enhancement of conductivity and an increase of the thermal expansion coefficient have been confirmed to correlate with an increasing concentration of oxygen vacancies at high temperatures in the samples studied. Transformation from pure ionic to mixed conductivity has been revealed in the samples with increasing iron or nickel content.Presented at the OSSEP Workshop Ionic and Mixed Conductors: Methods and Processes, Aveiro, Portugal, 10–12 April 2003