铋系超导体反常晶格膨胀X射线衍射研究

本文利用变温X射线衍射方法研究了室温至液氮温度区间铋系超导体晶格热膨胀与畸变特性.在从正常态向超导态转变过程中,铋系2223相和2212相均在高温区和低温区发生反常热膨胀.发生在超导转变前的晶格反常热膨胀与Mossbauer谱和超声内耗测量得到晶格软化温度相对应,这种结构上的反常行为是超导转变的前驱效应.     

Photoluminescence Study of Functionalized Polysiloxane Gel

Photoluminescence of a polysiloxane gel film incorporating a partially conjugated copolymer polyether-polyphenylenevinylene (PEPPV) has been studied and compared with results obtained from bulk and vacuum evaporated films of the same starting material. The evaporation clearly affects the distribution of lengths of the conjugated parts, yet the incorporation in the gel matrix induces only slight changes in the spectroscopic properties of the polymer.     

高功率激光稳定腔选模分析

讨论了在有限菲涅耳数时，稳定凹－凸腔的高功率激光选模特性，研究表明当稳定凹－凸腔工作在临近界稳区时，基模体积显著提高，具有良好的选模效果。     

Single-path interferometer for measuring fluid flows in real time with low-quality optics

An interferometric concept based on a modified version of the Fabry–Perot interferometry is proposed for measuring flow fields in real-time and some results are presented for demonstration. Being based on a single-path configuration of interfering beams, it is very convenient to build a simple compact measurement system. While allowing the deployment of low-quality optics including test-section windows through compensation of system errors, it is also immune to external vibration. In addition, it can easily allow large aperture and long pathlength of probing beams with good precision. These aforementioned features are very appropriate for measuring large flow fields including wind tunnel testing as well as conducting laboratory experiments without elaborate equipment.     

Pteridines. Part CVI. Isolation and characterization of limipterin (1-O-(L-erythro-biopterin-2′-yl)-β-N-acetylglucosamine) and its 5,6,7,8-tetrahydro derivative from green sulfur bacterium Chlorobium limicola f. thiosulfatophilum NCIB 8327

A new pteridine compound was isolated from green sulfur photosynthetic bacteria, Chlorobium limicola f. thiosulfatophilum NCIB 8327. The structure of this pterin derivative was established to be 1-O-(L -erythro-5,6,7,8- tetrahydropterin-2′-yl)-β-N-acetylglucosamine ( 1 ) from ¹H-NMR and CD spectra as well as from various mass spectrometric techniques and chemical-cleavage techniques. Upon acid hydrolysis of 1 , equimolar amounts of biopterin ( 2 ) and N-acetylglucosamine were produced. The structure of the hydrolysis product 2 was confirmed by comparing its NMR, UV, CD, and MS and its chromatographical behavior with those of an authentic specimen. N-Acetylglucosamine was identified by an enzymatic hydrolysis experiment as well as by NMR and thin layer chromatography. Electrospray (ES), fast-atom-bombardment (FAB), and thermospray (TS) mass spectrometry of 1 yielded an MH⁺ at m/z 441. Periodate-oxidation experiments of the intact molecule 1 and of its hydrolysis product 2 are consistent with the proposed structure. Differential I₂ oxidation experiments with the native compound showed that the in vivo oxidation state of this pterin is its tetrahydro form. We propose the trivial name ‘limipterin’ for this new compound.     

Homogeneous enzyme-linked competitive binding assay for riboflavin

A rapid and precise homogeneous enzyme-linked competitive binding assay for riboflavin (vitamin B₂) is described. The method utilizes a malate dehydrogenase/3-carboxymethylriboflavin conjugate in conjunction with soluble riboflavin binding protein. In the absence of the vitamin, the catalytic activity of the enzyme/riboflavin conjugate is inhibited up to 71% by the binding protein. In the presence of riboflavin, activity is regained in an amount dependent on the riboflavin concentration. The detection limits of the dose/response curves are dependent on both the degree of conjugation (average number of 3-carboxymethylriboflavins per enzyme molecule) and the reagent ratio (conjugate/binder) used in the assay tube. Under optimized conditions, a detection limit of 3 ng ml^?1 of riboflavin can be achieved with high selectivity over other vitamins and biomolecules. While malate dehedrogenase activity is inhibited to some degree by components of human urine, use of riboflavin standards prepared in a diluted urine matrix enables the method to be utilized for direct determination of urinary riboflavin.     

Nucleon tunnelling model of mass diffusion in deep inelastic heavy ion collisions

We derive a simple expression for the mass diffusion coefficient in deep inelastic collisions, based on a proximity formulation of nucleon tunnelling. The predicted value of the coefficient is consistent with empirical data. The mass diffusion coefficient has a negligible dependence on excitation energy in the physically interesting domain.     

Mobile Rayleigh Doppler wind lidar based on double-edge technique

<正>We describe a mobile molecular Doppler wind lidar(DWL) based on double-edge technique for wind measurement of altitudes ranging from 10 to 40 km.A triple Fabry-Perot etalon is employed as a frequency discriminator to determine the Doppler shift proportional to the wind velocity.The lidar operates at 355 nm with a 45-cm-aperture telescope and a matching azimuth-over-elevation scanner that provides full hemispherical pointing.To guarantee wind accuracy,a single servo loop is used to monitor the outgoing laser frequency to remove inaccuracies due to the frequency drift of the laser or the etalon.The standard deviation of the outgoing laser frequency drift is 6.18 MHz and the corresponding velocity error is 1.11 m/s.The wind profiles measured by the DWL are in good agreement with the results of the wind profile radar(WPR).Evaluation is achieved by comparing at altitudes from 2 to 8 km.The relative error of horizontal wind speed is from 0.8 to 1.8 m/s in the compared ranges.The wind accuracy is less than 6 m/s at 40 km and 3 m/s at 10 km.