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101.
2,2,3,3-Tetrafluorooxetane reacted easily with organolithium reagents to give 1,1,3-trisubstituted 2,2-difluoropropan-1-ols in good to excellent yields. On the other hand, the reaction with Grignard reagent led to 3-bromo-1,1-disubstituted 2,2-difluoropropan-1-ols in good yields. On treating with lithium enolates, generated from enol silyl ethers and MeLi/LiBr, the corresponding 1-bromo-2,2-difluoro-3,5-dicarbonyl compounds were obtained in fair to good yields. 3-Iodo-2,2-difluoropropanoate, prepared readily from 2,2,3,3-tetrafluorooxetane and NaI, reacted successfully with various silyl enol ethers in the presence of a radical initiator to provide the corresponding coupling products in good yields. 相似文献
102.
The shuffle product plays an important role in the study of multiple zeta values (MZVs). This is expressed in terms of multiple integrals, and also as a product in a certain non-commutative polynomial algebra over the rationals in two indeterminates. In this paper, we give a new interpretation of the shuffle product. In fact, we prove that the procedure of shuffle products essentially coincides with that of partial fraction decompositions of MZVs of root systems. As an application, we give a proof of extended double shuffle relations without using Drinfel??d integral expressions for MZVs. Furthermore, our argument enables us to give some functional relations which include double shuffle relations. 相似文献
103.
The size of structural vacancies and structural vacancy density of 1/1-Al–Re–Si approximant crystals with different Re compositions were evaluated by positron annihilation lifetime and Doppler broadening measurements. Incident positrons were found to be trapped at the monovacancy-size open space surrounded by Al atoms. From a previous analysis using the maximum entropy method and Rietveld method, such an open space is shown to correspond to the centre of Al icosahedral clusters, which locates at the vertex and body centre. The structural vacancy density of non-metallic Al73Re17Si10 was larger than that of metallic Al73Re15Si12. The observed difference in the structural vacancy density reflects that in bonding nature and may explain that in the physical properties of the two samples. 相似文献
104.
Inagaki S Tokuzawa T Itoh K Ida K Itoh SI Tamura N Sakakibara S Kasuya N Fujisawa A Kubo S Shimozuma T Ido T Nishimura S Arakawa H Kobayashi T Tanaka K Nagayama Y Kawahata K Sudo S Yamada H Komori A;LHD Experiment Group 《Physical review letters》2011,107(11):115001
This Letter presents the discovery of macroscale electron temperature fluctuations with a long radial correlation length comparable to the plasma minor radius in a toroidal plasma. Their spatiotemporal structure is characterized by a low frequency of ~1-3 kHz, ballistic radial propagation, a poloidal or toroidal mode number of m/n=1/1 (or 2/1), and an amplitude of ~2% at maximum. Nonlinear coupling between the long-range fluctuations and the microscopic fluctuations is identified. A change of the amplitude of the long-range fluctuation is transmitted across the plasma radius at the velocity which is of the order of the drift velocity. 相似文献
105.
Masaru Kojima Yutaka NakamuraKazuki Komori Shoji AkaiKen-ichi Sato Seiji Takeuchi 《Tetrahedron》2011,67(43):8276-8292
The first and simultaneous total syntheses of cucurbitosides A, B, G, and I, seguinosides C and D, and two unnatural analogs were achieved using the technique of fluorous mixture synthesis. The eight precursors of cucurbitoside-like phenolic glycosides were prepared by glycosylation of a mixture of two glucopyranosyl acceptors bearing different fluorous benzyl groups with a mixture of four apiofuranosyl donors bearing benzoyl, 3-methylbutyryl, 4-benzyloxybenzoyl, and 4-nitrobenzoyl groups, followed by a single run of HPLC with serially connected Fluophase® RP and Inertsil® ODS-3 columns. Finally, the individual pure disaccharide precursors were detagged to yield the eight cucurbitoside-like phenolic glycosides. 相似文献
106.
Numerical schemes for initial value problems of stochastic differential equations (SDEs) are considered so as to derive the
order conditions of ROW-type schemes in the weak sense. Rooted tree analysis, the well-known useful technique for the counterpart
of the ordinary differential equation case, is extended to be applicable to the SDE case. In our analysis, the roots are bi-colored
corresponding to the ordinary and stochastic differential terms, whereas the vertices have four kinds of label corresponding
to the terms derived from the ROW-schemes. The analysis brings a transparent way for the weak order conditions of the scheme.
An example is given for illustration. 相似文献
107.
Yasuyuki Shibata Katsuaki Tsuzuku Sumiko Komori Chieko Umedzu Hiroe Imai Masatoshi Morita 《应用有机金属化学》2005,19(2):276-281
A simple, rapid and robust analytical method for determining diphenylarsinic acid in human and environmental samples was developed based on a combination of hydrophilic polymer‐based gel‐permeation high‐performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP‐MS). Hair and nail samples were digested with alkali, and liberated diphenylarsinic acid (derivative) was extracted with diethyl ether, redissolved in water and injected for HPLC–ICP‐MS analysis. Human urine, groundwater and water extracts from soils were injected for HPLC–ICP‐MS directly after filtration. Using the method, diphenylarsinic acid in a solution was quantified in 7 min duration for an analysis with a detection limit of sub‐nanograms per milliliter. The method has been applied to groundwater arsenic pollution recently uncovered in Japan. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
108.
Noriaki Tsurumachi Chang-Sik Son Tae Geun Kim Kazunori Hikosaka Kazuhiro Komori Mutsuo Ogura 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):300
We investigated the temperature dependence of the time-resolved photoluminescence (PL) spectra of high-density InGaAs/AlGaAs quantum wire (QWR) distributed-feedback laser structure on a submicron grating. A red-shift of peak in the time-resolved PL after photo-excitation was observed due to the relaxation of the photo-generated excitons from the entire QWR to localized centers at 10 K. On the other hand, at 60 K, no red-shift in the time-resolved PL spectra was observed since the localization centers are thermally activated and the excitons are delocalized. 相似文献
109.
Reduction currents for H2O2 at a heme peptide (HP)-modified electrodes are suppressed by inhibitors, such as imidazole derivatives. Although this inhibition effect allows determinations of the total inhibition ability of imidazole derivatives, it has no selectivity. In this study the selectivity control of HP-modified electrodes for imidazole derivatives was performed utilizing the thermoresponsive phase transition of poly(N-isopropylacrylamide), which was chemically immobilized on HP-modified electrodes. The inhibition ratios for imidazole derivatives appeared to be small at temperatures below the lower critical solution temperature (LCST), and to be large above the LCST. This change was ascribed to a steric hindrance caused by a phase transition of the polymer. On the other hand, the inhibition ratio for histamine, which has a larger molecular size relative to imidazole, was not significantly changed by the phase transition. Thus, the selectivity of the HP-modified electrode was found to be controllable using an immobilized phase-transition polymer. 相似文献
110.