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971.
Uesaka A Ueda M Makino A Imai T Sugiyama J Kimura S 《Langmuir : the ACS journal of surfaces and colloids》2012,28(14):6006-6012
A pH-responsive rolled-sheet morphology was prepared from a triskelion A(2)B-type amphiphilic polypeptide having a histidine residue as a pH-responsive unit. The dimensions of the rolled sheet were 85 nm diameter and 210 nm length with a sheet turn number of 2.0 at pH 7.4. Upon decreasing the pH from 7.4 to 5.0, the layer spacing of the rolled sheets was widened from ca. 9 to ca. 19 nm due to electrostatic repulsion caused by histidine protonation. This morphology change occurred reversibly with a pH change between 7.4 and 5.0. The molecular packing in the rolled sheets was shown to be loosened at pH 5.0 on the basis of electron diffraction measurements. The tightness of the rolled sheets was thus controlled reversibly by a pH change due to a single protonation in the amphiphilic polypeptide. 相似文献
972.
Hirokazu Masai Toshiro Tanimoto Takumi Fujiwara Syuji Matsumoto Yoshihiro Takahashi Yomei Tokuda Toshinobu Yoko 《Journal of Non》2012,358(2):265-269
The authors investigate the structural change of a ZnO–P2O5 sintered matrix for the preparation of SnO-doped zinc phosphate (SZP) glass using a platinum crucible. Heat treatment of zinc oxide and ammonium phosphate at 800 °C causes the formation of a Zn2P2O7-like species, which is effective in preventing damage to the platinum crucible. Although the thermal property of the glass was affected by added Al2O3, Al2O3 hardly affects the quantum efficiency of the SZP glass phosphor. This process is important for the fabrication of contamination-free phosphate glass using ammonium phosphate as a starting material. 相似文献
973.
Carefully designed indentation creep experiments and detailed finite-element computations were carried out in order to establish a robust and systematic method to extract creep properties accurately during indentation creep tests. Samples made from an Al–5.3?mol%?Mg solid-solution alloy were tested at temperatures ranging from 573 to 773?K. Finite-element simulations confirmed that, for a power-law creep material, the indentation creep strain field is indeed self-similar in a constant-load indentation creep test, except during short transient periods at the initial loading stage and when there is a deformation mechanism change. Self-similar indentation creep leads to a constitutive equation from which the power-law creep exponent n, the activation energy Q c for creep, the back or internal stress and so on can be evaluated robustly. The creep stress exponent n was found to change distinctively from 4.8 to 3.2 below a critical stress level, while this critical stress decreases rapidly with increasing temperature. The activation energy for creep in the stress range of n = 3.2 was evaluated to be 123?kJ?mol?1, close to the activation energy for mutual diffusion of this alloy, 130?kJ?mol?1. Experimental results suggest that, within the n = 3.2 regime, the creep is rate controlled by viscous glide of dislocations which drag solute atmosphere and the back or internal stress is proportional to the average applied stress. These results are in good agreement with those obtained from conventional uniaxial creep tests in the dislocation creep regime. It is thus confirmed that indentation creep tests of Al–5.3?mol%?Mg solid-solution alloy at temperatures ranging from 573 to 773?K can be effectively used to extract material parameters equivalent to those obtained from conventional uniaxial creep tests in the dislocation creep regime. 相似文献
974.
The paper proposes a novel joint estimation of the frequency offset, frequency-independent I/Q imbalance, and frequency-dependent I/Q imbalance, using periodic pilots in orthogonal frequency division multiplexing (OFDM) based wireless local area networks (LANs). Although a low-complexity frequency offset estimation in the presence of I/Q imbalance can be obtained via a periodic pilot, the corresponding closed-form solution encounters a sign ambiguity. A method based on a power comparison between the signal and image interference is then proposed to detect the sign. Meanwhile, since one periodic pilot only is unable to estimate I/Q imbalance in the absence of a frequency offset, we also propose an estimation method based on two different periodic pilots available in the preamble. The validity and superiority of the proposed method are demonstrated by computer simulations. 相似文献
975.
We have examined the neutron-deuteron low-energy effective-range parameters, differential cross sections and spin polarization observables of the elastic nucleon-deuteron scattering up to the incident nucleon energy E N = 65 MeV, using the quark-model nucleon–nucleon interaction fss2. These observables are consistently described without introducing three nucleon forces except for the nucleon analyzing power A y (θ) and the deuteron vector analyzing power iT 11(θ) in the low-energy region E N ≤ 25 MeV. The long-standing A y puzzle is slightly improved, but still remains. We have incorporated the screened Coulomb force to the proton-deuteron scattering, modifying the Vincent–Phatak approach for the sharp cutoff Coulomb force. The Coulomb effect on the elastic scattering observables is discussed. 相似文献
976.
Shoichi Kondo Masayuki Ishikawa Masakazu Fujiwara Isamu Ono Shigeru Mita 《Molecular Crystals and Liquid Crystals》2013,570(1):777-784
Abstract The orientational order parameters of six solutes with different shapes and sizes dissolved in two nematic solvents have been measured as a function of temperature. The parameter, Sxx-Syy is correlated with the molecular geometrical structure, while Szz is affected by not only the geometry but also the anisotropy in the polarizability. The molecular dynamics simulations are carried out using a realistic atom-atom potential for evaluating the ordering properties in the nematic phase. The results provide reasonable values of Szz corresponding to experimental ones for solutes and solvents, and also a prediction of uniaxiality for the nematic phase. 相似文献
977.
Horike S Umeyama D Inukai M Itakura T Kitagawa S 《Journal of the American Chemical Society》2012,134(18):7612-7615
An ionic coordination network consisting of protonated imidazole and anionic one-dimensional chains of Zn(2+) phosphate was synthesized. The compound possesses highly mobile ions in the crystal lattice and behaves as an ionic plastic crystal. The dynamic behavior provides a proton conductivity of 2.6 × 10(-4) S cm(-1) at 130 °C without humidity. 相似文献
978.
Hiroyoshi Takamura Takashi Abe Naoki Nishiuma Rie Fujiwara Takahiko Tsukeshiba Isao Kadota 《Tetrahedron》2012,68(10):2245-2260
A convergent synthesis of the right-hand fragment of ciguatoxin CTX3C was investigated. The first and second generation stereocontrolled syntheses of the LM ring fragment were achieved via spiroacetalization as a key step, respectively. The polyether framework of the HIJKLM ring fragment was constructed in a convergent manner by using intramolecular allylation, ring-closing metathesis, and stereoselective hydrogenation to form the 36-methyl substituent as the key transformations. 相似文献
979.
Misae Kanai Tomoya Hirano Isao Azumaya Iwao Okamoto Hiroyuki Kagechika Aya Tanatani 《Tetrahedron》2012,68(13):2778-2783
The conformation of N-phenylbenzohydroxamic acid has been reported to change depending on the solvent properties. Here, we newly synthesized N-phenylbenzohydroxamic acid derivative, which contains two pyrene moieties separated from the phenyl rings by ethylene linkers. It showed solvent-dependent conformational change, and its fluorescence was also solvent-dependent, that is, only monomer fluorescence of pyrene was observed in DMSO or DMF, whereas the excimer fluorescence was observed in CH2Cl2 or CHCl3. Thus, the structural characteristics could be converted to fluorescence change as output, which would be a good candidate as a fluorescent sensor. 相似文献
980.
Tomoya HiranoHaruko Kubo Takuya ShiraishiKenichi Hiromoto Takashi FujiwaraHiroyuki Kagechika 《Tetrahedron letters》2012,53(44):5916-5919
A series of coumarins with two aryl moieties was constructed from 3-azide-6-bromocoumarin scaffold by means of two sequential reactions, Huisgen 1,3-cycloaddition and Suzuki-Miyaura coupling reactions. Evaluation of their fluorescence properties indicated that the mode of fluorescent change by substituted group on each aryl group would be different. So this structure could be promising candidates as multi-analyte type fluorescent sensors, whose mode of spectroscopic changes, such as fluorescence intensity, and absorption or fluorescence maximum wavelength, are different for each analyte. 相似文献