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排序方式: 共有197条查询结果,搜索用时 31 毫秒
101.
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103.
Supramolecular composites composed of fullerene C60 and carbon nanodiamond (ND) were constructed through spontaneous complexation of C60 aggregates onto the surface of ND aggregates in N‐methylpyrrolidone (NMP). The resulting C60‐ND composite was assembled onto a nanostructured SnO2 electrode by an electrophoretic deposition method. Formation of the C60‐ND composite was confirmed by dynamic light scattering (DLS) and field‐emission scanning electron microscopy (FESEM). The C60‐ND composite on the SnO2 electrode showed high incident photon‐to‐current efficiencies (IPCEs) in the visible region as compared with the single component system of C60 or ND. The improved photocurrent generation of the C60‐ND composite may result from the photoinduced charge separation at the interface between C60 and ND. These results obtained here will provide valuable information on the design of optoelectronic devices based on all‐nanocarbon materials. 相似文献
104.
Satoshi Kakihara Atsumi Ohara Takashi Tsuchiya 《Computational Optimization and Applications》2014,57(3):623-665
In this paper, we study iteration complexities of Mizuno-Todd-Ye predictor-corrector (MTY-PC) algorithms in SDP and symmetric cone programs by way of curvature integrals. The curvature integral is defined along the central path, reflecting the geometric structure of the central path. Integrating curvature along the central path, we obtain a precise estimate of the number of iterations to solve the problem. It has been shown for LP that the number of iterations is asymptotically precisely estimated with the integral divided by $\sqrt{\beta}$ , where β is the opening parameter of the neighborhood of the central path in MTY-PC algorithms. Furthermore, this estimate agrees quite well with the observed number of iterations of the algorithm even when β is close to one and when applied to solve large LP instances from NETLIB. The purpose of this paper is to develop direct extensions of these two results to SDP and symmetric cone programs. More specifically, we give concrete formulas for curvature integrals in SDP and symmetric cone programs and give asymptotic estimates for iteration complexities. Through numerical experiments with large SDP instances from SDPLIB, we demonstrate that the number of iterations is explained quite well with the integral even for a large step size which is enough to solve practical large problems. 相似文献
105.
Ohara K Jacquinet JC Jouanneau D Helbert W Smietana M Vasseur JJ 《Journal of the American Society for Mass Spectrometry》2009,20(1):131-137
A better understanding of the biological roles of carbohydrates requires the use of tools able to provide efficient and rapid structural information. Unfortunately, highly acidic oligomers-such as polysulfated oligosaccharides-are very challenging to characterize because of their high polarity, structural diversity, and sulfate lability. These features pose special problems for matrix-assisted laser desorption/ionization mass spectrometric (MALDI-MS) analysis because polysulfated carbohydrates exhibit poor ionization efficiency and usually do not produce any signal. The present report demonstrates how MALDI-MS can be used to derive structural and compositional information from pure and mixed fractions of polysulfated oligosaccharides. Indeed, pyrenemethylguanidine (pmg, a derivatizing agent and ionization efficiency enhancer) was used for the analysis of di- to decasaccharides, carrying from two to nine sulfate groups. The method is applied to various highly sulfated chondroitin and carrageenan oligosaccharides as well as to the analysis of mixtures of compounds. In the mass spectra, the observation of a unique pmg-complexed ladder of peaks in both ionization modes allows an easy and rapid determination of both the number of sulfate groups carried by the analyte and its molecular weight. Moreover, we have developed a software tool for the rapid and automatic structural elucidation of carrageenans based on the mass spectra obtained. 相似文献
106.
Satoshi Iwatsuki Yuki Kanamitsu Hidetaka Ohara Eisuke Watanabe Koji Ishihara 《Journal of Physical Organic Chemistry》2012,25(9):760-768
The pKas of 3‐pyridylboronic acid and its derivatives were determined spectrophotometrically. Most of them had two pKas assignable to the boron center and pyridine moiety. The pKa assignment performed by 11B nuclear magnetic resonance spectroscopy revealed that both boron centers in 3‐pyridylboronic acid [3‐PyB(OH)2] and the N‐methylated derivative [3‐(N‐Me)Py+B(OH)2] have strong acidities (pKa = 4.4 for both). It was found that introduction of a substituent to pyridine‐C atom in 3‐pyridylboronic acid drastically increased the acidity of the pyridinium moiety, but decreased the acidity of the boron center, whereas the introduction to pyridine‐N atom had no influence on the acidity of the boron center. Kinetic studies on the complexation reactions of 3‐pyridinium boronic acid [3‐HPy+B(OH)2] with 4‐isopropyltropolone (Hipt) carried out in strongly acidic aqueous solution indicated that the positive charge on the boronic acid influenced little on its reactivity; 3‐HPy+B(OH)2 reacts with Hipt and protonated H2ipt+, and its reactivity was in line with those of a series of boronic acids. Kinetics in weakly acidic aqueous solution revealed that 3‐HPy+B(OH)2 reacts with Hipt faster than its conjugate boronate [3‐HPy+B(OH)3–], which is consistent with our recent results. The reactivity of 3‐(N‐Me)Py+B(OH)2 towards Hipt was also examined kinetically; the reactivities of 3‐(N‐Me)Py+B(OH)2 and 3‐(N‐Me)Py+B(OH)3– are almost the same as those of their original 3‐HPy+B(OH)2 and 3‐HPy+B(OH)3–, respectively. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
107.
Aggarwal VK Charmant JP Fuentes D Harvey JN Hynd G Ohara D Picoul W Robiette R Smith C Vasse JL Winn CL 《Journal of the American Chemical Society》2006,128(6):2105-2114
The reactions of a range of amide-stabilized sulfur ylides derived from readily available camphor-derived sulfonium salts for the synthesis of glycidic amides have been studied. Primary, secondary, and tertiary amides were tested, and it was found that the highest enantioselectivities were observed with tertiary amides, which provided glycidic amides in good to excellent yields, exclusive trans selectivity, and excellent enantioselectivities. The reaction was general for aromatic aldehydes, but aliphatic aldehydes gave more variable enantioselectivities. The epoxy amides could be converted cleanly into epoxy ketones by treatment with organolithium reagents. We were also able to effect selective ring opening of the epoxy amides with a variety of nucleophiles, followed by hydrolysis of the amide to yield the corresponding carboxylic acid. This methodology was applied to the total synthesis of the target compound SK&F 104353. A combination of crossover experiments and theoretical calculations has revealed that the rate- and selectivity-determining step is ring closure, not betaine formation as was the case for phenyl-stabilized ylides. 相似文献
108.
A highly sensitive adsorptive stripping voltammetric protocol for measuring trace beryllium, in which the preconcentration is achieved by adsorption of the beryllium-arsenazo-I complex at a preplated mercury-coated carbon-fiber electrode, is described. Optimal conditions were found to be a 0.05 M ammonium buffer (pH 9.7) containing 5 μM arsenazo-I, an accumulation potential of 0.0 V (versus Ag/AgCl) and a square-wave voltammetric scan. The new procedure obviates the need for renewable mercury-drop electrodes used in early stripping protocols for beryllium. A linear response is observed over the 10-60 μg l−1 concentration range (90 s accumulation), along with a detection limit of 0.25 μg l−1 beryllium (10 min accumulation). A 15-s electrochemical cleaning enables the same mercury film to be used for a prolonged operation. High stability is thus indicated from the reproducible response of a 100 μg l−1 beryllium solution (n = 60; RSD = 3.3%) over a 2.5-h operation. Applicability to a seawater sample is illustrated. The attractive behavior of the new sensor holds great promise for on-site environmental and industrial monitoring of beryllium. Preliminary data in this direction using mercury-coated screen-printed electrodes are encouraging. 相似文献
109.
Onitsuka K Ohara N Takei F Takahashi S 《Dalton transactions (Cambridge, England : 2003)》2006,(30):3693-3698
Novel trinuclear ruthenium complexes have been prepared by using tri(4-ethynylphenyl)amine as a bridging ligand. Cyclic voltammetry of the trinuclear ruthenium complexes revealed stepwise quasi-reversible redox behavior of three ruthenium-acetylide species and the central triphenylamine unit, whereas the mononuclear analog showed two sequential quasi-reversible redox waves. The spectroelectrochemical UV-VIS spectral studies suggested that the 1e- oxidized triruthenium species was stable and showed a characteristic absorption at lambda(max) = 505 nm. Chemical oxidation of the triruthenium complex with ferrocenium hexafluorophosphate led to the isolation of the 1e- oxidized complex, the near-IR spectrum of which revealed an intervalence charge transfer band due to the electronic coupling among three ruthenium species. The 1e(-) oxidized triruthenium complexes can be classified as class II mixed-valence compounds. 相似文献
110.
Hiroki Ohara Satoshi Sasaki Yukiko Konoike Takeshi Toyoda Kouji Yamawaki Masahiko Tanaka 《Physica B: Condensed Matter》2004,350(4):353-365
Synchrotron X-ray diffraction study for single crystals of Eu3S4 has revealed that a Th3P4-type
structure transforms to a charge-ordered
one at Tc=188.5 K. The crystal structures of Eu3S4 at T=300, 180 and 160 K were determined in the least-squares refinements with the Mo K intensity data. The valence-difference contrast method was applied at the LII absorption edge of Eu, utilizing a large difference in anomalous scattering factors between Eu2+ and Eu3+. The cation distribution of Eu2+ and Eu3+ was determined by crystal-structure analyses based on the intensity data collected at two wavelengths of λ=1.6312 and 1.6298 Å.The least-squares structural refinements suggest that the most plausible atomic arrangement is [Eu3+]4a[Eu2+Eu3+]8dS4. The charge-ordering scheme is that a half of Eu3+ ions occupy the whole 4a sites in the
crystal structure, while the remaining half of Eu3+ ions mix with Eu2+ in the 8d sites. The scheme is also supported by the energy dependence of Bragg intensities for 400 and 004 reflections. 相似文献