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51.
[reaction: see text] The H/D exchange of the lactone-fused cycloheptatriene 1 is over 1000 times faster than that of the epimer 2. Interconversion of 1 and 2 provides an equilibrium mixture of 1:0.7, showing a similar stability of the isomers. Protonation of the common enolate 7 occurs far more readily on the more hindered face. Cycloheptatrienide anion is bent and as stable as a divinylcarbanion. 相似文献
52.
Qingxin Zhang Kimiyoshi Naito Yoshihisa Tanaka Yutaka Kagawa 《Macromolecular rapid communications》2007,28(21):2069-2073
Polyimide/diamond nanocomposites have been synthesized from 4,4′‐diaminodiphenyl ether (ODA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA). All the polyimides show non‐crystalline X‐ray diffraction. The frequent occurrence of particular interatomic distances (R) denoted by the non‐crystalline X‐ray diffraction maxima are determined. An ultramicro‐indentation technique is employed to evaluate the effects of nano‐diamond particles on the indentation behavior of polyimides. Indentation size effect is observed and discussed.
53.
Hideto Minami Atsushi Tanaka Yasuyuki Kagawa Masayoshi Okubo 《Journal of polymer science. Part A, Polymer chemistry》2012,50(13):2578-2584
It is known that it is difficult to polymerize carboxylic acid‐based monomer by atom transfer radical polymerization (ATRP) in polar solvents due to the protonation of ligand caused by acidic dissociation of the monomer. In this study, precipitation reverse ATRP of acrylic acid (AA) was carried out in supercritical carbon dioxide (scCO2), which is a nonpolar solvent to dissolve transition metal complexes, at 30 MPa and 45 °C. The polymerization proceeded smoothly and the conversion reached 86% for 3 h. After vending of scCO2, a dry poly(acrylic acid) (PAA) powder was obtained. Weight‐average molecular weight and polydispersity of the methylated PAA, which were measured by gel‐permeation chromatography after methyl esterification, were 3.5 × 104 and 2.07, respectively, indicating that the precipitation reverse ATRP proceeded with a bad control manner. However, chain extension of the methylated PAA with styrene was possible by ATRP in a bulk system. Moreover, PAA‐b‐polystyrene was successfully prepared in scCO2 directly by two‐step ATRP, although its molecular weight distribution was broad. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
54.
We propose a scalable and practical implementation of spin amplification which does not require individual addressing nor a specially tailored spin network. We have demonstrated a gain of 140 in a solid-state nuclear spin system of which the spin polarization has been increased to 0.12 using dynamic nuclear polarization with photoexcited triplet electron spins. Spin amplification scalable to a higher gain opens the door to the single spin measurement for a readout of quantum computers as well as practical applications of nuclear magnetic resonance spectroscopy to infinitesimal samples which have been concealed by thermal noise. 相似文献
55.
Given the prevalence of the indole nucleus in biologically active compounds, the direct C3-functionalization of 2,3-disubstituted indoles represents an important problem. Described is a general, high-yielding method for the palladium-catalyzed beta-allylation of carba- and heterocycle fused indoles, including complex natural product substrates. 相似文献
56.
Moriguchi Isamu Tsujigo Yoshihiro Teraoka Yasutake Kagawa Shuichi 《Journal of Sol-Gel Science and Technology》2000,19(1-3):227-230
Synthesis of ZrO2 and hetero-layered TiO2/ZrO2 ultrathin films was investigated by two-dimensional sol-gel process assisted by n-octadecylacetoacetate (C18AA). When a hexane solution of tetrabutoxyzirconium (TBZ) and C18AA was spread on the water surface, Zr-based gel films stabilized with C18AA were formed at the air/water interface. After deposition on substrates, the gel films were successfully transformed into ZrO2 ultrathin films by heating at 773 K for 0.5 h, the thickness of which was controllable on the order of sub-nanometer level by the number of gel-layer deposition and the molar ratio of [TBZ]/[C18AA]. Well-organized hetero-multilayers composed of ultrathin TiO2 and ZrO2 layers could be fabricated by the alternate deposition of C18AA-stabilized Ti- and Zr-gel films. 相似文献
57.
Matsuda H Morikawa T Ishiwada T Managi H Kagawa M Higashi Y Yoshikawa M 《Chemical & pharmaceutical bulletin》2003,51(4):440-443
The methanolic extract and its fractions from the fresh flowers of Prunus mume SIEB. et ZUCC. were found to show scavenging effects on 1,1-diphenylpicryl-2-hydrazyl (DPPH) radical and superoxide. The fragrance constituents of P. mume were analyzed by GC-MS and a new polyacylated sucrose, prunose III, was isolated from the ethyl acetate-soluble fraction. The structure of prunose III was determined on the basis of chemical and physicochemical evidence as 4,3',4',6'-tetra-O-acetyl-6-O-p-coumaroylsucrose. In addition, the scavenging effects of the principal constituents on DPPH radical and superoxide were examined. 相似文献
58.
Sakai H Fujioka J Fukuda T Okuyama D Hashizume D Kagawa F Nakao H Murakami Y Arima T Baron AQ Taguchi Y Tokura Y 《Physical review letters》2011,107(13):137601
We report a ferroelectric transition driven by the off-centering of magnetic Mn(4+) ions in antiferromagnetic Mott insulators Sr(1-x)Ba(x)MnO(3) with a perovskite structure. As x increases, the perovskite lattice shows the typical soft-mode dynamics, as revealed by the momentum-resolved inelastic x-ray scattering and far-infrared spectroscopy, and the ferroelectricity shows up for x ≥ 0.45. The observed polarization is comparable to that for a prototypical ferroelectric BaTiO(3). We further demonstrate that the magnetic order suppresses the ferroelectric lattice dilation by ~70% and increases the soft-phonon energy by ~50%, indicating the largest magnetoelectric effects yet attained. 相似文献
59.
Takada A Imaichi K Kagawa T Takahashi Y 《The journal of physical chemistry. B》2008,112(32):9660-9662
The effect of adding an inorganic salt, lithium chloride, and water on the viscosity of an ionic liquid, 1-n-butyl-3-methylimidazolium chloride (BmimCl), was investigated by shear stress measurements with a rheometer. The shear rate dependence of the viscosity showed shear thinning behavior, which implies that some structure should exist in the liquid and the structure should change at high shear rates. Addition of LiCl enhances the viscosity of BmimCl. The logarithmic value of zero-shear viscosity, eta(0), of BmimCl increases linearly and largely with increasing added salt content. The increasing rate of the viscosity by addition of LiCl was about 10 times larger than that for an aqueous solution of LiCl. When water is added into BmimCl, viscosity decreased. The increasing rate of the viscosity by addition of LiCl for BmimCl with about 5 wt % of water was almost the same as that for BmimCl without addition of water. 相似文献
60.
H Hirai S Kagawa T Tanaka T Matsuoka T Yagi Y Ohishi S Nakano Y Yamamoto T Irifune 《The Journal of chemical physics》2012,137(7):074505
Low-temperature and high-pressure experiments were performed on the filled ice Ic structure of hydrogen hydrate at previously unexplored conditions of 5-50 GPa and 30-300 K using diamond anvil cells and a helium-refrigeration cryostat. In situ x-ray diffractometry revealed that the cubic filled ice Ic structure transformed to tetragonal at low temperatures and high pressures; the axis ratio of the tetragonal phase changed depending on the pressure and temperature. These results were consistent with theoretical predictions performed via first principle calculations. The tetragonal phase was determined to be stable above 20 GPa at 300 K, above 15 GPa at 200 K, and above 10 GPa at 100 K. Further changes in the lattice parameters were observed from about 45-50 GPa throughout the temperature region examined, which suggests the transformation to another high-pressure phase above 50 GPa. In our previous x-ray study that was performed up to 80 GPa at room temperature, a similar transformation was observed above 50 GPa. In this study, the observed change in the lattice parameters corresponds to the beginning of that transformation. The reasons for the transformation to the tetragonal structure are briefly discussed: the tetragonal structure might be induced due to changes in the vibrational or rotational modes of the hydrogen molecules under low temperature and high pressure. 相似文献