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A new method has been developed for the generation and subsequent reaction of ynolates in a micro flow reactor system. This new procedure allowed for ynolates to be prepared at 0 °C or ambient temperature within 1 min via a reductive lithiation reaction, whereas the corresponding batch processes generally require low temperature control and extended reaction times of up to 1 h. The resulting ynolates were applied to the olefination of carbonyl compounds, with the reactions reaching completion in a much shorter reaction time in the continuous flow reactor than the batch reactor. These results highlight the practical utility of the ynolate reaction, and represent the first reported example of the use of lithium naphthalenide in a flow microreactor, which would contribute to progress of the flash chemistry. 相似文献
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T. Makino M. Inada K. Yoshida I. Umezu A. Sugimura 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1391-1393
We studied the structural and optical properties of silicon (Si) nanoparticles (np-Si) prepared by pulsed laser ablation (PLA) in hydrogen (H2) background gas. The mean diameter of the np-Si was estimated to be approximately 5 nm. The infrared absorption corresponding to Si-Hn (n=1,2,3) bonds was observed at around 2100 cm-1, and a Raman scattering peak corresponding to crystalline Si was observed at around 520 cm-1. These results indicate that nanoparticles are not an alloy of Si and hydrogen but Si nanocrystal covered by hydrogen or hydrogenated silicon. This means that surface passivated Si nanoparticles can be prepared by PLA in H2 gas. The band-gap energy of np-Si prepared in H2 gas (1.9 eV) was larger than that of np-Si prepared in He gas (1.6 eV) even though they are almost the same diameter. After decreasing the hydrogen content in np-Si by thermal annealing, the band-gap energy decreased, and reached the same energy level as np-Si prepared in He gas. Thus, the optical properties of np-Si were affected by the hydrogenation of the surface of np-Si. PACS 81.15.Fg; 61.46.+W; 78.67.Bf 相似文献
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We investigate the problem (P λ) ?Δu = λb(x)|u| q?2 u + a(x)|u| p?2 u in Ω, ?u/?n = 0 on ?Ω, where Ω is a bounded smooth domain in R N (N ≥ 2), 1 < q < 2 < p, λ ∈ R, and a, b ∈ \({C^\alpha }\left( {\overline \Omega } \right)\) with 0 < α < 1. Under certain indefinite type conditions on a and b, we prove the existence of two nontrivial nonnegative solutions for small |λ|. We then characterize the asymptotic profiles of these solutions as λ → 0, which in some cases implies the positivity and ordering of these solutions. In addition, this asymptotic analysis suggests the existence of a loop type component in the non-negative solutions set. We prove the existence of such a component in certain cases, via a bifurcation and a topological analysis of a regularized version of (P λ). 相似文献
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Kenichiro Umezu 《Applicable analysis》2013,92(11):1313-1325
A Robin type boundary condition with a sign-changing coefficient is treated. First, the associated linear elliptic eigenvalue problem is studied, where the existence of a principal eigenvalue is discussed by the use of a variational approach. Second, the associated semilinear elliptic boundary value problem of logistic type is studied and the one parameter-dependent structure of positive solutions is investigated, where results obtained are due to the construction of suitable super- and subsolutions by using the principal positive eigenfunctions of the linear eigenvalue problem. 相似文献
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Kenichiro Umezu 《Journal of Differential Equations》2012,252(2):1146-1168
In this paper, we consider a semilinear elliptic boundary value problem in a smooth bounded domain, having the so-called logistic nonlinearity that originates from population dynamics, with a nonlinear boundary condition. Although the logistic nonlinearity has an absorption effect in the problem, the nonlinear boundary condition is induced by the homogeneous incoming flux on the boundary. The objective of our study is to analyze the existence of a bifurcation component of positive solutions from trivial solutions and its asymptotic behavior and stability. We perform this analysis using the method developed by Lyapunov and Schmidt, based on a scaling argument. 相似文献
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When an equimolar solution of various azoxybenzenes and SbCl5 in carbon tetrachloride were mixed, a 1:1 complex immediately deposited as orange crystals in high yield. The thermal reaction of these complexes in inert solvents gives o-hydroxy-azobenzene selectively. On the contrary, other Lewis acids such as TiCl4, AlCl3, FeCl3 and ZnBr2 failed to give an isolatable complex with azoxybenzene, and their direct thermal reaction with azoxybenzene resulted in deoxygenation to yield azobenzene as a main product. 相似文献
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Masatoshi Tamaru Kazuto Umezu Chika Maejima Hiroyuki Kageyama Yoshikazu Kimura 《合成通讯》2013,43(19):2749-2756
A new and efficient synthesis of the title compound is reported. The method includes a regioselective ortho-lithiation step in none polar solvents at an ambient temperature and the overall yield for 5 steps is more than 70% from a commercially available 3-hydroxyacetophenone. 相似文献
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Syun-ichi Kiyooka Satoshi Matsumoto Satoshi Umezu Ryoji Fujiyama Daisuke Kaneno 《Tetrahedron letters》2010,51(13):1651-1653
The Mukaiyama aldol reaction of 2-aryl-1-cyclohexene-1-carboxaldehydes with phenyl trimethylsilyl ketene acetal unexpectedly resulted in the formation of 9-substituted-1,2,3,4-tetrahydrofluorene derivatives via a novel intramolecular titanium-promoted deoxygenative cyclization. By successive treatment of the corresponding allyl alcohols with n-butyllithium and titanium tetrachloride, the cyclization products were obtained in good yields. 相似文献