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671.
MA Hongjun PEI Chunchuan & ZENG QinPurple Mountain Observatory Chinese Academy of Sciences Nanjing China 《中国科学G辑(英文版)》2005,(2)
W51GMC, an HII region complex in the Sagittarius spiral arm about 7—8 kpc from the Sun[1], is one of the most active star-forming regions. It was first reported by Westerhout[2] as an intense radio continuum source in the area. Among 5000 galactic GMCs, the W51GMC, which many astronomers have extensively studied at multi- wavelengths, is the top 5%—10% by mass and the top 1% by size[3]. However, owing to its large distance, limitation of the spatial resolution and mapping area of obser… 相似文献
672.
喻洪俊 《数学物理学报(B辑英文版)》2006,26(3):491-501
Global classical solutions near Maxwellians are constructed for the Bolt.zma.nn equation in a periodic box with angular soft cutoff, that is, -3<γ< 0. The construction of global solution is based on an energy method used in [9]. 相似文献
673.
The cluster [Cu4(S5)2(C5H5N)4]·S8 with cage structure has been obtained by reaction of copper powder with sulfur and K2S
x
in pyridine, and its structure was determined by X-ray crystallography. The crystal data for the title compound: triclinic, P
(No. 2),Z = 2,a = 11.818(4) Å,b = 13.155(3) Å,c = 14.177(4) Å, = 93.79(2)°, = 96.68(2)°, = 115.76(2)°,V = 1954.52(1) Å3. The structure was refined toR = 0.038R
w
= 0.053) for 6444 data withI > 3.0(I).Dedicated to Professor Jiaxi Lu on the occasion of his 80th birthday. 相似文献
674.
Wen Y Yi W Meng L Feng M Jiang G Yuan W Zhang Y Gao H Jiang L Song Y 《The journal of physical chemistry. B》2005,109(30):14465-14468
Azobenzene-containing compounds were covalently attached onto Si(111) surfaces via Si-O linkages using a two-step procedure. The modified Si(111) surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy measurements. The monolayer surface showed preferably chemical stability. Switchable photoisomerizability of azobenzene molecules on these modified surfaces was observed in response to alternating UV and visible light exposure. The measured conductivity showed distinct difference with trans and cis forms of azobenzene compounds on as-modified Si(111) surfaces. 相似文献
675.
研究了在H2 SO4 介质中 ,氯离子存在下 ,用甲苯萃取二甲基吲哚羰花青 (DIC)染料与Cr(Ⅵ )配合物的显色反应。基于此 ,建立了一种光度法测定微量Cr(Ⅵ )的新方法。结果表明在 0 .0 5~ 0 .3mol L的H2 SO4 介质中 ,甲苯对配合物的萃取率最高。最大吸收波长为 5 60nm ,摩尔吸光系数为 2 .5×1 0 5L·mol-1·cm-1,检出限为 4× 1 0 -9g mL ,有色溶液的吸光度与Cr(Ⅵ )量在 0 .0 1~ 2 .1mg L范围内符合比尔定律 ,加标回收率为 96.4 %~ 1 0 4 .8% (n =6) ,n(Cr(Ⅵ ) ) :n(Cl-)∶n(DIC) =1∶1∶1。本法满意地测定了非晶态FeNiCr合金中的铬 相似文献
676.
677.
678.
679.
Guocheng Yang Hongwei Guo Mingkui Wang Minghua Huang Hongjun Chen Baifeng Liu Shaojun Dong 《Journal of Electroanalytical Chemistry》2007,600(2):318-324
Based on the electrostatic attraction Keggin-type polyoxometalate H4SiW12O40 (SiW12) and small molecule 4-aminobenzo-15-crown-5 ether (4-AB15C5) were alternately deposited on poly (allylamine hydrochloride) (PAH)-derived indium tin oxide (ITO) substrate through a layer-by-layer (LBL) self-assembly, forming a supramolecular multilayer film (film-A). SiW12 was also deposited on a glassy carbon electrode (GCE) derived by 4-AB15C5 via covalent bonding in 0.1 M NaCl aqueous solution and formed a composite monolayer film (film-B). UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared (FTIR) spectroscopy measurements demonstrated that the interactions between SiW12 and 4-AB15C5 in both two film electrodes were the same and caused by the bridging action of oxonium ions. But, the nanostructure in the two film electrodes was different. 4-AB15C5 in film-A was oriented horizontally to ITO substrate, however, that in film-B was oriented vertically to GCE. Namely film-A corresponded to a layer structure, and film-B corresponded to an intercalation structure. 相似文献
680.
Padwa A Brodney MA Lynch SM Rashatasakhon P Wang Q Zhang H 《The Journal of organic chemistry》2004,69(11):3735-3745
The intramolecular Diels-Alder reaction between an amidofuran moiety tethered onto an indole component was examined as a strategy for the synthesis of Aspidosperma alkaloids. Furanyl carbamate 23 was acylated using the mixed anhydride 26 to provide amidofuran 22 in 68% yield. Further N-acylation of this indole furnished 27 in 88% yield. Cyclization precursors were prepared by removing the carbamate moiety followed by N-alkylation with the appropriate alkyl halides. Large substituent groups on the amido nitrogen atom causes the reactive s-trans conformation of the amidofuran to be more highly populated, thereby facilitating the Diels-Alder cycloaddition. The reaction requires the presence of an electron-withdrawing substituent on the indole nitrogen in order for the cycloaddition to proceed. Treatment of N-allyl-bromoenamide 48 with n-Bu(3)SnH/AIBN preferentially led to the 6-endo trig cyclization product 50, with the best yield (91%) being obtained under high dilution conditions. The initially generated cyclohexenyl radical derived from 48 produces the pentacyclic heterocycle 50 by either a direct 6-endo trig cyclization or, alternatively, by a vinyl radical rearrangement pathway. 相似文献