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81.
82.
Y. Hashimoto L. Matsuoka D. NagamotoS. Hasegawa 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
We developed an ion trap — laser cooling system for observing the laser induced fluorescence (LIF) of a single ion, in the view of utilizing it for the trace isotope analysis of Ca. We observed stepwise LIF signals, which correspond to the numbers of trapped 40Ca+ ions (40Ca/Ca = 96.9%). The detection efficiency was evaluated and the observation of single ions demonstrated the experimental feasibility of trace isotope analysis. Furthermore, as the next step towards trace isotope analysis, we report observation of the even calcium isotopes, 44Ca (44Ca/Ca = 2.09%) and 48Ca (48Ca/Ca = 0.187%), without the use of a selective loading method. 相似文献
83.
Chelation of cadmium ions by phytochelatin synthase: role of the cysteine-rich C-terminal. 总被引:1,自引:0,他引:1
Mun'delanji Vestergaard Sachiko Matsumoto Shingo Nishikori Kentaro Shiraki Kazumasa Hirata Masahiro Takagi 《Analytical sciences》2008,24(2):277-281
The interactions between Cd(2+) and the C-terminal region of phytochelatin (PC) synthase using recombinant wild-type and mutant PC synthase were studied. We show that site-directed mutagenesis of Cys residues at C(358)C(359)XXXC(363)XXC(366) motif decreases the number of Cd(2+) and other heavy metal ions interacting with the enzyme, and that the motif binds the metals discriminatingly. The optimum binding ratio of PC synthase to Cd(2+) was also determined. The findings indicate that Cys exists as a free SH residue and that it is involved in the regulation of PC enzyme activity by transferring the metals into closer proximity with the catalytic domain. These results are important in understanding heavy metal detoxification mechanisms in higher plants, a step towards phytoremediated-applications. 相似文献
84.
Asit K. Chandra Shingo Urata Tadafumi Uchimaru Masaaki Sugie Akira Sekiya 《国际化学动力学杂志》2002,34(8):500-507
Kinetics and mechanism of the hydrogen abstraction reaction between trifluoromethyl formate, CF3OCHO, and OH radical have been investigated by using ab initio molecular orbital theory up to G2(MP2) level. The hydrogen abstraction rate constant has been calculated for the first time over a temperature range of 250–450 K by using standard transition state theory including the tunneling correction. Arrhenius parameters of the reaction have been estimated from the temperature dependence of the calculated rate constant. The calculated value for the rate constant (2.0 × 10?14 cm3 molecule?1 s?1) at 298 K is found to be in very good agreement with the recent experimental results. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 500–507, 2002 相似文献
85.
86.
Hiroaki Aizawa Ken Hatano Hitoshi Saeki Nobuaki Honsho Tetsuo Koyama Koji Matsuoka Daiyo Terunuma 《Tetrahedron letters》2010,51(12):1545-6442
A new compound having a 2,3,4,5-tetraphenylsilole derivative on the center silicon of Dumbbell(1)6Gb3; Silole-Dumbbell(1)6Gb3 (1) was previously reported. It was found that 1 exhibited strongly increased fluorescence both in water and in a 96% acetone/water mixed solvent. The physical behavior of 1 in water and in the 96% acetone/water mixed solvent was investigated, and analyses including fluorescence quantum yields, dynamic-light-scattering (DLS), atomic-force-microscopy (AFM), and fluorescence microscopy were carried out. It was clarified that 1 dynamically formed different types of aggregates in water and in higher acetone concentrations to yield high aggregation-induced emission (AIE) effects due to the formation of micelle-like particles in water and inversion-type micelles in the acetone/water mixed solvent, respectively. 相似文献
87.
Dollar F Matsuoka T Petrov GM Thomas AG Bulanov SS Chvykov V Davis J Kalinchenko G McGuffey C Willingale L Yanovsky V Maksimchuk A Krushelnick K 《Physical review letters》2011,107(6):065003
By using temporal pulse shaping of high-contrast, short pulse laser interactions with solid density targets at intensities of 2 × 10(21) W cm(-2) at a 45° incident angle, we show that it is possible to reproducibly generate quasimonoenergetic proton and ion energy spectra. The presence of a short pulse prepulse 33 ps prior to the main pulse produced proton spectra with an energy spread between 25% and 60% (ΔE/E) with energy of several MeV, with light ions becoming quasimonoenergetic for 50 nm targets. When the prepulse was removed, the energy spectra was broad. Numerical simulations suggest that expansion of the rear-side contaminant layer allowed for density conditions that prevented the protons from being screened from the sheath field, thus providing a low energy cutoff in the observed spectra normal to the target surface. 相似文献
88.
Shimizu M Sakakura M Kanehira S Nishi M Shimotsuma Y Hirao K Miura K 《Optics letters》2011,36(11):2161-2163
We report on the formation mechanism of element distribution in glass under high-repetition-rate femtosecond laser irradiation. We simultaneously focused two beams of femtosecond laser pulses inside a glass and confirmed the formation of characteristically shaped element distributions. The results of the numerical simulation in which we considered concentration- and temperature-gradient-driven diffusions were in excellent qualitative agreement with the experimental results, indicating that the main driving force is the sharp temperature gradient. Since the composition of a glass affects its refractive index, absorption, and luminescence property, the results in this study provide a framework to fabricate a functional optical device such as optical circuits with a high-repetition-rate femtosecond laser. 相似文献
89.
The development of axially chiral dicarboxylic acid catalyzed desymmetrizing asymmetric semipinacol rearrangement of symmetrically substituted six-membered cyclic β-hydroxy-α-diazo esters is reported as a means to give chiral cycloheptanones with good enantioselectivities. 相似文献
90.