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581.
582.
Microbial degradation of a tetramethylarsonium salt during incubation at 25°C was investigated under both aerobic and anaerobic conditions. Two media (1/5 ZoBell 2216E and inorganic salt medium), added with the sediments or suspended substances as the sources of the microorganisms, were used. Degradation of the tetramethylarsonium salt occurred only in the ZoBell medium: under anaerobic conditions, trimethylarsine oxide and dimethylarsinic acid were derived with the sediments, and dimethylarsinic acid with the suspended substances, the salt degrading more rapidly with the former than with the latter. Small amounts of two metabolites, trimethylarsine oxide and inorganic arsenic(V), was also derived in the aerobically incubated ZoBell medium added with the suspended substances. This result means that the tetramethylarsonium salt is degraded to inorganic arsenic, which is the starting material for arsenic circulation in marine ecosystems, via trimethylarsine oxide and dimethylarsinic acid. 相似文献
583.
584.
Ken'Ichi Hanaoka Hideki Yamamoto Keishiro Kawashima Shoji Tagawa Toshikazu Kaise 《应用有机金属化学》1988,2(4):371-376
Arsenic compounds were extracted with chloroform/methanol/water from tissues of marine animals (four carnivores, five herbivores, five plankton feeders). The extracts were purified by cation and anion exchange chromatography. Arsenobetaine [(CH3)3As+CH2COO?], dimethylarsinic acid [(CH3)2AsOOH], trimethylarsine oxide [(CH3)3AsO] and arsenite, arsenate, and methylarsonic acid [(CH3)AsO(OH)2] as a group with the same retention time were identified by high-pressure liquid chromatography. Arsenic was determined in the collected fractions by graphite furnace atomic absorption spectrometry. Arsenobetaine found in all the animals was almost always the most abundant arsenic compound in the extracts. These results show that arsenobetaine is present in marine animals independently of their feeding habits and trophic levels. Arsenobetaine-containing growth media (ZoBell 2216E; solution of inorganic salts) were mixed with coastal marine sediments as the source of microorganisms. Arsenobetaine was converted in both media to trimethylarsine oxide and trimethylarsine oxide was converted to arsenite, arsenate or methylarsonic acid but not to dimethylarsinic acid. The conversion rates in the inorganic medium were faster than in the ZoBell medium. Two dominant bacterial strains isolated from the inorganic medium and identified as members of the Vibro–Aeromonas group were incapable of degrading arsenobetaine. 相似文献
585.
Tomohito Kadota 《Journal of Mathematical Analysis and Applications》2006,323(2):1387-1401
This paper discusses a prey-predator system with strongly coupled nonlinear diffusion terms. We give a sufficient condition for the existence of positive steady state solutions. Our proof is based on the bifurcation theory. Some a priori estimates for steady state solutions will play an important role in the proof. 相似文献
586.
Susumu Chikazawa Toshikazu Satō Yoshihito Miyako Y.G. Yuochunas 《Physics letters. A》1979,72(6):470-472
Anisotropy of the susceptibility, which depends on vanadium concentration, was observed for (Ti1?xVx)2O3(x=0.005, 0.015, 0.02) single crystals. The anisotropy is hard to interpret by localized magnetic states of vanadium ions. 相似文献
587.
Reaction of 1-phenyldiazoethane(1) with tetrachloro-p-benzoquinone(2) gave 1-alkoxy-4-ethenyloxy-tetrachlorobenzene(4). With tetrachloro-o-benzoquinone(5), 1 provided 1-alkoxy-2-ethenyloxy-tetrachlorobenzene(7) and tetrachlorobenzo-1,3-dioxolane(8). The mechanism and the effect of added methanol were discussed. 相似文献
588.
Shinobu Fujihara Yasuhiro Kadota Toshio Kimura 《Journal of Sol-Gel Science and Technology》2002,24(2):147-154
Porous CaF2 anti-reflective coating films were prepared by the sol-gel method. Effects of organic additives on deposition and optical properties of the films were investigated. Amino alcohols (2-aminoethanol, 2-dimethylaminoethanol, and triethanolamine) and alcohols with larger molecular weights (ethyleneglycol, 2-methoxyethanol, cyclohexanol, and 2-(2-n-butoxyethoxy)ethanol) were chosen as the organic additives. Among these additives, cyclohexanol was the most effective to control the surface morphology and the optical properties of the films. By changing the amount of cyclohexanol in the coating solution, it was possible to control the optical thickness of the CaF2 films. Accordingly, the wavelength giving the maximum transmittance could be changed in the UV region. 相似文献
589.
Satoyuki Chikaoka Toshikazu Takata Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1990,28(11):3101-3106
A spiroorthoester, 2-methyl-1,4,6-trioxaspiro[4.6]undecane ( 1 ), was polymerized with aluminium (III) acetylacetonate as a catalyst. The resulting polymer structure was analyzed in detail by FT-IR and 270 MHz 1H NMR, and consisted of poly(orthoester) which was obtained by selective ring-opening of the seven-membered ring. In contrast, 2-methyl-1,4,6-trioxaspiro[4.5]decane ( 2 ) and 2-methyl-1,4,6-trioxaspiro[4.4]nonane ( 3 ) did not afford any polymers. The reactivity difference of these monomers was discussed in terms of their strain energies on the basis of MM2 calculations. 相似文献
590.
Kenichi Takeuchi Toshikazu Kitagawa Akihiko Ueda Yoshihide Senzaki Kunio Okamoto 《Tetrahedron》1985,41(23):5455-5463
7-Cyano-7-methylcycloheptatrienes containing one t-butyl group on the 1-position () or two t-butyl groups on the 1- and 3-, 1- and 4-, or 1- and 5-positions (, , or , respectively) were synthesized and their cyclo- heptatriene (CHT)-norcaradiene (NCD) equilibria measured by variable-temperature 1H NMR for CS2-CD2Cl2 solutions. The 1H NMR chemical shifts of the 7-methyl group indicate that these compounds are composed of essentially one CHT and one NCD tautomer with an endo geometry of the methyl group. The introduction of a t-butyl group at the 1-position of 7-cyano-7-methylcycloheptatriene () markedly shifts the equilibrium to the NCD side and the addition of the second t-butyl group further favors the NCD form, with the NCD populations for , , , and at 25 °C 70.9, 96.5, 92.3, and 99.3%, respectively. An application of molecular mechanics (MMPI) calculations to various t-butylated CHT-NCD systems suggests that the t-butyl groups sterically destabilize the CHT form more than the NCD form, bringing about increased NCD populations. 相似文献