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201.
The introduction of a double-chopping scheme eliminates the background level in the optical sampling system, where a Si avalanche photodiode acts as a two-photon absorber. We successfully demonstrate background-free optical sampling of 40-GHz and 160-GHz pulse trains. 相似文献
202.
Yasuyuki Kurita Chiyozo Takayama Mitsuru Sasaki 《Journal of computational chemistry》1992,13(5):560-564
Among some 2-substituted 4H-1,3,2-benzodioxaphosphorin 2-sulfides, the 2-OMe derivative has the sulfur atom mainly in the quasiequatorial position. On the other hand, the conformation in which the sulfur is quasiaxial is favored in the 2-NHMe and 2-Et derivatives. We have done ab initio molecular orbital calculations for the model compounds, and such a substituent effect was reproduced. Moreover, the effect was discussed in terms of the intramolecular electrostatic interactions and the degree of charge distribution. 相似文献
203.
204.
Yasumitsu Tamura Takayuki Yakura Jun-ichi Haruta Yasuyuki Kita 《Tetrahedron letters》1985,26(32):3837-3840
A short and efficient synthesis of dihydroxyacetone groups from keto groups involving the oxidation of ethynylcarbinol intermediates with [bis(trifluoroacetoxy) iodo] benzene (PIFA), is described. 相似文献
205.
The reaction conditions of tetrathionate with permanganate were investigated by varying reaction time, temperature and amounts of sulphuric acid and permanganate. Under the optimal conditions for the reaction of tetrathionate with permanganate, both penta- and hexathionate were also oxidised; each one mol of polythionates (S
x
O
6
2–
x=4, 5 and 6) reacts with (x–1.5) mol of permanganate. The proposed method is based on the reaction of tetrathionate with a given excess amount of permanganate in a sulphuric acid medium and on the spectrophotometric measurement of the iodine as triiodide formed by the oxidation of iodide with the excess of permanganate. This method could be successfully applied to the determinations of tetrathionate (4 × 10–7 to 2 × 10–5
M), pentathionate (3 × 10–7 to 1.43 × 10–5
M) and hexathionate (2 × 10–7 to 1.11 × 10–5
M), and gave a higher sensitivity than any previous methods without solvent extraction. 相似文献
206.
207.
1,2-Dicarba-closo-dodecaboranes (o-carboranes) and naphthalenes have potential value as components or building blocks for supramolecular systems. We have efficiently synthesized 1-(1,2-dicarba-closo-dodecaboran-1-yl)naphthalene and 2-(1,2-dicarba-closo-dodecaboran-1-yl)naphthalene derivatives by employing three preparative methods: cyclization of the corresponding acetylenes with decaborane(14), an Ullmann-type coupling reaction of carboranes with aryl halide, and the aromatic nucleophilic substitution (S(N)Ar) reaction of aryl-o-carboranes with nitrophenyl halide. The optimum conditions of each method for synthesis of the title compounds were also investigated. 相似文献
208.
Perez A Vilkas MJ Cabrera CR Ishikawa Y 《The journal of physical chemistry. B》2005,109(49):23571-23578
A density functional theory study of the elementary steps that lead to the removal of CO(ads(Pt)) over alloyed and sequentially deposited Pt/Ru bimetallic nanoclusters is presented. The reaction energies and activation barriers for the H2O(ads(Ru)) dissociation and CO(ads(Pt)) + OH(ads(Ru)) reaction are estimated in solid-gas interface and in a microsolvated environment to determine which surface morphology is more tolerant to COads poisoning. On the basis of the energetics, the sequentially deposited Pt/Ru nanocluster is predicted to be a much more promising anode catalyst than the alloy cluster surface in fuel cell applications. 相似文献
209.
Simultaneous determination of residual antiparasitic lactones in bovine muscle and liver by liquid chromatography with fluorescence detection 总被引:1,自引:0,他引:1
Abamectin, doramectin, eprinomectin, ivermectin, milbemectin, and moxidectin in bovine muscle and liver were extracted with acetonitrile. The extracts were partitioned with n-hexane and then evaporated to dryness. The residue was cleaned up on Bond Elute NH2 cartridge, and the drugs were eluted from the cartridge with methanol-ethyl acetate (3 + 7). The eluate was evaporated to dryness, and residues were derivatized with N,N-dimethylformamide-acetic anhyride-1-methylimidazole. The derivatives were determined by liquid chromatography with fluorescence detection. Recoveries of the 6 drugs were 79.6-63.8% in muscle and 71.6-60.6% in liver at 0.01 ppm levels. The quantitation limits were 5 ppb for each drug. 相似文献
210.
[reaction: see text]. CAN is a good reagent for the transformation of 2-hydroxyethyl ether units to alcohols. Significantly, many functional groups can tolerate the reaction conditions, although they do not survive under many previously reported removal conditions. The reaction mechanism is clarified. 相似文献