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排序方式: 共有587条查询结果,搜索用时 15 毫秒
1.
Noriko SUTO Makoto HARADA Jun IZUTSU Toshiyasu NAGAO 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2006,82(5):175-180
In order to accurately estimate the geomagnetic transfer functions in the area of the volcano Mt. Iwate (IWT), we applied the interstation transfer function (ISTF) method to the three-component geomagnetic field data observed at Mt. Iwate station (IWT), using the Kakioka Magnetic Observatory, JMA (KAK) as remote reference station. Instead of the conventional Fourier transform, in which temporary transient noises badly degrade the accuracy of long term properties, continuous wavelet transform has been used. The accuracy of the results was as high as that of robust estimations of transfer functions obtained by the Fourier transform method. This would provide us with possibilities for routinely monitoring the transfer functions, without sophisticated statistical procedures, to detect changes in the underground electrical conductivity structure. 相似文献
2.
A micro-phase sorbent in situ formation from an aqueous solution was proposed for the sensitive spectrophotometric determination of nitrite in environmental waters. Nitrite in a 10 mL sample solution was converted into a cationic azo dye by the reaction with 4-trifluoromethylanilinium ion and N-1-naphthylethylenediammonium ion in an acidic medium. Addition of dodecylbenzenesulfonate ion caused the formation of a suspension of ion associate in the solution. Centrifugation of the solution led to the isolation of a liquid organic phase that extracted the azo dye at the bottom of the centrifuge tube. The volume of the new phase was ca. 5 microL. After the aqueous phase was discarded, the organic phase was dissolved with 1 mL of 2-methoxyethanol to measure the absorbance. Nitrogen as NO2- at concentrations from 1.5 to 30 microg L(-1) was determined with sufficient precision. When 0.2 mL of 2-methoxyethanol was applied to dissolve the organic phase, 0.3-4.8 microg NO2--N L(-1) was determined. The recovery tests for nitrite added to some river water and seawater were satisfactory. This method is very simple and rapid. It takes only 30 min from the dye formation to the measurement of the absorbance. 相似文献
3.
A highly selective and sensitive method of fluorometry is described for determination of the fluoride ion at the parts per billion level via the ion-pair complex formation of the fluoride ion with an expanded prophyrin [2,23-diethyl-8,17-bis(2-ethoxycarbonylethyl)-3,7,12,13,18,22-hexamethylsapphyrin (H3sap)]. The ion-pair complex gives out an enhanced fluorescence intensity at 680 nm on excitation at 450 nm. Since the present method is based on a direct reaction of the fluoride ion with the sappyrin, a 200-fold amount of the aluminum (III) ion [10−4M (M = mol dm−3)] and a 2000-fold amount of the iron(III) ion (10−3M) over the fluoride ion did not interfere with determination of the fluoride ion at concentrations as low as 5 × 10−7M in the presence of 1,2-diaminocyclohexane-N,N,N′,N′-teraacetic acid. The proposed method was applied to determination of the fluoride ion in various water samples (tap water, river water, rain water, underground water, and hot spring water) and satisfactory results were obtained. 相似文献
4.
M Sugiyama T Sakamoto K Tabata K Endo K Ito M Kobayashi H Fukumi 《Chemical & pharmaceutical bulletin》1989,37(8):2122-2131
Thiazolo[3,2-a]thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (6, 11 and 16), and polymethylene condensed thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (19-21), in which the oxygen atom of the oxazolidine moiety in 3 was replaced by a sulfur atom or methylene groups, were synthesized and evaluated for gastric antisecretory activity in pylorus-ligated rats. The structure-activity relationships of these compounds are discussed. 相似文献
5.
Konda-Yamada Y Asano K Satou T Monma S Sakayanagi M Satou N Takeda K Harigaya Y 《Chemical & pharmaceutical bulletin》2005,53(5):529-536
Oxopropyl E-(pyrrolidine-2-ylidene)glycinamide (5c) and allyl E-(pyrrolidine-2-ylidene)glycinate (5d) were effectively synthesized from 2,3,5-tri-O-benzyl-4-O-tert-butyldimethylsilyl(TBDMS)-D-arabinal (7) using intramolecular 1,3-dipolar cyclic reaction of azide and olefin as a key reaction. These results proved this cyclic reaction should be applicable for the synthesis of various (pyrrolidine-2-ylidene)glycinate and glycinamide. In addition, the development of a synthetic route for the precursor of an unsaturated cyclic dehydro amino acid involved in azinomycins (carzinophilin) using relating glycinate, methyl E-(pyrrolidine-2-ylidene)glycinate (5a) was described. 相似文献
6.
Antioxidant activity of a series of hydroxybenzalacetones was determined against peroxynitrite-induced lipid peroxidation in red blood cell membrane and SOS response through DNA damage in bacterial cells. Hydroxybenzalacetone derivatives with hydroxy, methoxy, ethoxy or methyl substitution were analyzed and found to be more effective than the water-soluble vitamin E analogue Trolox. The inhibitory effect against lipid peroxidation correlated well to that against the SOS response, which is dependent on decomposition of peroxynitrite by hydroxybenzalacetones outside of the cell membrane. The antioxidant activity was shown to correlate well with the electric parameter sigma+. Electron-donating substituents with more negative sigma+ values increased the potencies. The result suggests that hydroxybenzalacetones with more electron-donating substituents will protect tissue more effectively against oxidative stress. 相似文献
7.
The tosylation reaction of endocrine-disruptive alkylphenolic compounds in a solid-phase aqueous system was investigated with the aim of developing an environment-friendly and efficient derivatization method for HPLC analyses of environmental samples. The phenols were rapidly and efficiently converted to the tosyl derivatives on a commercially available ODS solid-phase cartridge by passing an aqueous buffer solution through it. The solid-phase aqueous tosylation system has been incorporated into a preconcentration step performed by solid-phase extraction from environmental water. 相似文献
8.
Shinichi Yamabe Noriko Tsuchida Tsutomu Minato Takahisa Machiguchi 《Theoretical chemistry accounts》2005,113(2):95-106
Cheletropic additions forming cyclopropane rings were studied theoretically. Ten addition paths were traced by means of density-functional-theory calculations. Two 1,4-dienes, 1,4-pentadiene, and tricyclo[5.3.1.04,9]undeca-2,5-diene were adopted as substrates. CO, SO2, C2H5PCl2, CCl2 and SiCl2 were employed as cheletropic reagents (Xs). An orbital correlation diagram of the Woodward–Hoffmann (W–H) rule and frontier molecular orbital (FMO) interactions between them were investigated in detail. The FMO interactions, HOMO (1,4-diene)lumo (X) and homo (X)LUMO (diene), work reasonably for the progress of the reactions. Those cause the formation of two C–X bonds and a cyclopropane ring, and alternation of double bonds to single bonds. All the additions are concerted. The easiness of the ring formation depends upon the energy gap between HOMO and lumo and that between homo and LUMO, and the spatial directions of HOMO and LUMO extensions. Symmetry conservation of the W–H rule does not hold necessarily for those addition paths. The symmetry-breaking was discussed in terms of FMO interactions.Acknowledgement This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan and by Nishida Memorial Foundation for Fundamental Chemical Research. 相似文献
9.
Radiation-induced copolymerizations of perfluorovinyl acetic acid and its methyl ester with α-olefin
Mitsuo Kawaguchi Terutaka Watanabe Osamu Matsuda Yoneho Tabata Sueo Machi 《Journal of polymer science. Part A, Polymer chemistry》1981,19(6):1525-1531
Homopolymerizations and copolymerizations of perfluorovinyl acetic acid (FVA) and its methyl ester (MFVA) were carried out by γ radiation at a temperature of 25°C, a dose rate of 1 × 106 rad/hr, and FVA/α-olefin and MFVA/α-olefin ratios of 10/90-90/10 in the monomer mixture. FVA and MFVA gave small quantities of brown and greasy low-molecular-weight homopolymers. The polymerization rates of both FVA and MFVA were extremely small, as shown by the maximum G value of monomer consumption of 12. FVA and MFVA reacted with α-olefin to form waxlike copolymers. The copolymerization rates of both FVA and MFVA with α-olefin were remarkably larger than those of the homopolymerizations, particularly with ethylene. The polymer compositions of FVA/ethylene or MFVA/ethylene was nearly 1/2 over a wide range of the monomer compositions. The Mayo–Lewis method gave negative r1 (FVA) and r1 (MFVA). The polymer composition curves could be well interpreted by introducing the penultimate model. 相似文献
10.
An ammonium-sulfate-precipitable (33–70%) fraction in extracts from eggs of silkworm Bombyx mori contains photoreactivating enzyme that reactivates the transforming activity of UV inactivated Hemophilus influenzae DNA. The action spectrum for in vitro photoreactivation with the enzyme has a broad peak around 365–385 nm, with a shoulder extending to 460 nm. This relatively higher photoreactivation efficiency at wavelengths longer than 450 nm seems to be a unique feature of DNA photoreactivating enzyme of silkworm. Using gel filtration, a mol wt of 42,000 was estimated for the enzyme. Optimum and isoionic pH of the enzyme were 7.2 and 5.4, respectively. These properties of silkworm enzyme are within the range of variations in reported biochemical characteristics of photoreactivating enzymes from different species. 相似文献