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31.
The paramagnetic BrO2 molecule with lifetime τ > 10 s has been found amoung the products of the O + Br2 reaction in a discharge flow system. Identification was made by the technique of molecular beam focusing in an inhomogeneous magnetic field with mass-spectrometric detection. Its symmetry appeared to be C2, like the stable OClO molecule, as was determined by focusing in an inhomogeneous electric field. Approximate rate constants for the reactions O + BrO2 (k3 = (2.5–6)×10?12 cm3/s) and Br + BrO2 (k7 = 5 × 10?11 cm3/s) were obtained. 相似文献
32.
本文介绍了在日本神奈川县的电话网络结构的演变,详细分析了网络调整的必要性和具体实施方案通过调网前后网络性能的比较,说明了网络调整的重要性,文章学结合北京通信网现状,提出了北京网络结构发展构想。 相似文献
33.
Far-I.R. photoconductivity reveals the existence of at least four different kinds of SA1 acceptors in germanium quenched from T > 800 each acceptor producing two or more hydrogenic excitation line series. One acceptor is correlated with the presence of Ni, another one with strong Cu contamination. The two other acceptors, which we call ‘normal’ and ‘shifted’, occur in samples quenched without intentional doping. The experiments indicate that the SA1 acceptors in germanium are impurity complexes involving fast diffusing elements. We discuss a model according to which the SA1 acceptors would be interstitial-substitutional pairs of transition metals. In particular, we propose to assign the ‘normal’ SA1 acceptors to FeI-CuS pairs. 相似文献
34.
Synthetic routes for the branching pentasaccharides 4 and 5 of glycoproteins are described in a regio- and stereo- controlled way. 相似文献
35.
T. Nakahara T. Wakisaka S. Musha 《Spectrochimica Acta Part B: Atomic Spectroscopy》1981,36(7):661-670
Atomic fluorescence spectrometry with a nondispersive measuring system is combined with a hydride generation technique for the determination of tellurium. Atomic fluorescence measurement is based on the reduction of tellurium by either metallic zinc or sodium borohydride, introduction of the generated tellurium hydride into a premixed argon (entrained air)-hydrogen flame, and excitation with a tellurium electrodeless discharge lamp. The comparison of the zinc and the sodium borohydride reduction methods is discussed in terms of detection limit, precision and interference. The best attainable detection limits for tellurium are 2ng (0.1 ) and 30 ng (1.5 ) with the zinc and the sodium borohydride methods respectively. Analytical working curves obtained from peak-height and peak-area measurements are linear over a range of approximately 4 orders of magnitude. Of the mineral acids examined in the range up to 2.0 m. nitric acid gives a depressing interference in the range greater than 0.5 m in the zinc method, whereas all of the acids greater than 1.0 m give a slight enhancement of the signal in the sodium borohydride method. The presence of several elements including other hydride-forming elements in 1000-fold ratio to tellurium causes a depressing interference, while enhancing interferences from tungsten and vanadium are observed in the zinc and the sodium borohydride methods, respectively. The present system coupled with the zinc method has been applied to the determination of tellurium in several samples of high-purity copper metal after separation of the analyte from copper by passing an ammoniacal solution of the sample through Chelex-100 resin. The results are in good agreement with those obtained by graphite furnace atomic absorption spectrometry. 相似文献
36.
37.
The composition and abundance of phytoplankton in Suruga Bay, Japan, were investigated to evaluate the photosynthetic production structure and population dynamics from surface to oligotrophic layers seasonally for a four-year period. High-performance liquid chromatography analyses separated more than 80 peaks of pigments, and about 50 pigment species were identified. The main chlorophylls (Chls) and carotenoids were mostly found up to 100 m deep, while small amounts of a limited number of species of pigments such as Chl a, Chl c2, and fucoxanthin, which are markers of diatoms, were also detected even in the oligotrophic region, in addition to degradation products of Chl a, such as pheophorbide a and pheophytin a. 相似文献
38.
Deep levels in LPE GaAs were studied in relation to growth conditions. The residual deep levels in LPE layers are hole traps 0.50 and 0.65 eV above the top of the valence band. Their concentrations are of the order of 1013 cm-3 for growth temperatures between 650 and 840°C, and increase with increasing growth temperature. The activation energy of incorporation is about 0.7 eV, which is very close to that of an arsenic vacancy. It is also noted that their concentrations near the grown surface are independent of the growth temperature. This indicates that the hole traps undergo an annealing effect after the growth period. From the experimental results for Fe and oxygen doping, each impurity acts as a deep level only when it makes a complex defect with a gallium vacancy, otherwise they are shallow levels, The distribution coefficients at 750°C are 1 × 10-7 and 1.1 × 10-5 for the deep and Fe and the shallow acceptor, respectively. 相似文献
39.
本文采用文献综述法、总结归纳等方法,借助互联网手段对当前主流的中文学术数据库关于国内外保险体育保险制度进行总结.通过对美国和日本体育保险制度的研究,了解美日体育保险发展现状及未来方向,并结合我国高校体育的快速发展,总结出适合我国高校体育发展的保险制度,并提出加强和借助当前的互联网对校园体育保险的推广,促进我国高校体育安全. 相似文献
40.
我省电子产品生产企业众多,又以中小企业占绝大多数.不少企业对<中华人民共和国计量法>不了解,无计量法制观念.因此要对我省中小企业加强计量监督管理. 相似文献