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111.
Traces amounts of arsenic and antimony in water samples were determined by gas chromatography with a photoionization detector after liquidnitrogen cold trapping of their hydrides. The sample solution was treated with sodium hydroborate (NaBH4) under weak-acid conditions for arsenic(III) and antimony(III) determination, and under strong-acid conditions for arsenic(III+V) and antimony(III+V) determination. Large amounts of carbon dioxide (CO2) and water vapor obscured determination of arsine and stibine. Better separation from interference could be achieved by removing CO2 and water vapor in two tubes containing sodium hydroxide pellets and calcium chloride, respectively. The detection limits of this method were 1.8 ng dm?3 for arsenic and 9.4 ng dm?3 for antimony in the case of 100-cm3 sample volumes. Therefore, it is suitable for determination of trace arsenic and antimony in natural waters. 相似文献
112.
Yoshikazu Shizuri Jiro Ohtsuka Seiji Kosemura Yukimasa Terada Shosuke Yamamura 《Tetrahedron letters》1984,25(48):5547-5550
Some macrocyclic diterpenes derived from euphohelioscopin A and euphornin have been stereoselectively converted into the jatropholane- and daphnane-type compounds and the known tricyclic compound which has been treated with phCOCl - pyridine to afford euphohelionone, the new type of diterpene isolated from euphorbia helioscopia L. 相似文献
113.
Steven Altschuler Sigurd B. Angenent Yoshikazu Giga 《Journal of Geometric Analysis》1995,5(3):293-358
In this paper, we study generalized “viscosity” solutions of the mean curvature evolution which were introduced by Chen, Giga,
and Goto and by Evans and Spruck. We devote much of our attention to solutions whose initial value is a compact, smooth, rotationally
symmetric hypersurface given by rotating a graph around an axis. Our main result is the regularity of the solution except
at isolated points in spacetime and estimates on the number of such points. 相似文献
114.
Furusawa M Tanaka T Ito T Nakaya K Iliya I Ohyama M Iinuma M Murata H Inatomi Y Inada A Nakanishi T Matsushita S Kubota Y Sawa R Takahashi Y 《Chemical & pharmaceutical bulletin》2005,53(5):591-593
Fourteen flavonol glycosides including two new compounds were isolated from the leaves of two Diospyros plants (D. cathayensis and D. rhombifolia). The structures of isolated compounds were determined by spectroscopic analysis. The scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical of the isolated compounds was also investigated. 相似文献
115.
116.
D. F. Calhane C. M. Alber J. Ludmila B. G. Šimek V. Kohlschütter H. Schödl P. Jacquet M. Giordani H. Kiyota J. Guzmán A. Ranmcaño C. G. Donova B. Jones M. G. Raeder R. Höiors L. Lucchi A. Bartocci W. Moldenhauer N. Isgarischew A. F. Prede G. Illari G. Damany J. Heyrovský D. Ilkovič G. Semerano I. Slendyk G. Devoto A. Ratti H. Mandai S. Zeltzer G. Kimura M. Tokuoka I. Smolér R. Brdička A. Scheicher 《Analytical and bioanalytical chemistry》1934,96(5-6):193-209
117.
To demonstrate the neighbouring-group participation of the 2-benzyloxy group in the glycosidation of phenols and of strongly acidic alcohols by the diazirine 1 , we examined the glycosidation of 4-nitrophenol, 4-methoxyphenol, (CF3)2CHOH, MeOH, and i-PrOH by the diazirine 11 , derived from the 2-deoxypyranose 6 . Oxidation of the oximes 7 yielded (E)- and (Z)- 8 . In solution, (E)- 8 isomerised to (Z)- 8 . Similarly, the (E)-configurated mesylate 9 , prepared from 8 , underwent acid-catalysed isomerisation to (Z)- 9 . Treatment of (Z)- 9 with NH3, followed by oxidation of the resulting diaziridine 10 with I2, yielded the desired diazirine 11 . Glycosidation by 11 of the above mentioned hydroxy compounds yielded the glycosides 12–21 . In agreement with the postulated neighbouring-group participation, these glycosidation proceeded without, or with a very low diastereoselectivity, favouring the axial anomers. 相似文献
118.
Nobumoto?NagasawaEmail author Shugo?Ikeda Aiko?Shimoda Takeshi?Waki Yoshikazu?Tabata Hiroyuki?Nakamura Hisao?Kobayashi 《Hyperfine Interactions》2016,237(1):39
The 57Fe Mössbauer spectra of the single crystalline and the finely ground Sr1?x La x Fe12?y Co y O19 (x = 0 : y = 0, x = 0.192 : y = 0.152 and x = 0.456 : y = 0.225) samples have been measured to investigate the La-Co substitution effects. All observed spectra at 150 K were well fitted using the five subspectra which correspond to the five crystallographical nonequivalent Fe sites in the M-type hexaferrite, indicating that the valence changes to Fe2+ ions in the Fe3+ ions were not observed in our Sr1?x La x Fe12?y Co y O19 samples. In SrFe12O19, the relative absorption intensities in the five subspectra show the large anisotropies in the recoilless fractions at the five Fe sites whereas these anisotropies were not observed in Sr0.544La0.456Fe11.775Co0.225O19. These results indicate the chemical compositional dependence on the anisotropies of the recoilless fractions at the five Fe sites. The substitution of a Co2+ ion for the Fe3+ ion changes the center shifts of the Fe3+ ions near the Co2+ ion by the perturbation of the Fe-O-Co hybridizations. Therefore, the Co2+ ions occupy the 4f 1 and the 4f 2 sites due to the chemical compositional dependences of the refined magnetic hyperfine field and center shifts of the Fe3+ ions. 相似文献
119.
In this paper, a statistical prediction problem under ordered location and scale parameters are considered. Double-shrinkage predictors are given which use all the available data and improve on single-shrinkage predictors, and hence the best equivariant predictors. 相似文献
120.
C. Akira Horiuchi Yoshikazu Saitoh Takamitsu Utsukihara Shigeo Takahashi Masatoshi Matsushita Liangyou He T. Tomoyoshi Takahashi Chikao Hashimoto Takashi Sugiyama Sukekatsu Nozaki 《应用有机金属化学》2006,20(10):663-668
Reaction of α,β‐unsaturated ketones with cerium(IV) salts or lanthanide triflates in alcohols gave good yields of the corresponding β‐alkoxy compounds. In the case of 2‐cyclopentenone and 2‐cyclohexenone, the 1,1,3‐trialkoxy acetal derivatives were obtained preferentially accompanied by β‐alkoxyketone, except 2‐cycloheptenone. However, in the reaction of 2‐cycloheptenone with alcohol using cerium(IV) sulfate (CS)‐molecular sieve, 1,1,3‐trialkoxy derivatives were obtained. Also, in the cases of 1‐penten‐3‐one, 4‐hexen‐3‐one and 3‐hepten‐2‐one, 1,1,3‐trialkoxy derivatives were obtained preferentially. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献