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161.
K. Asayama Y. Kitaoka G. -Q. Zheng K. Ishida Y. Tokunaga H. Mukuda T. Ohno 《Applied magnetic resonance》2000,19(3-4):305-319
This paper introduces nuclear magnetic resonance works in the strongly correlated super-conductors: heavy-Fermion, high-T C superconductors and Sr2RuO4. The analyses strongly support the spin-fluctuation-mediated superconductivity model in a high-T C superconductor. 相似文献
162.
Kazuki Fukushima Yoshiharu Kimura 《Journal of polymer science. Part A, Polymer chemistry》2008,46(11):3714-3722
Simultaneous solid‐state polycondensation (SSP) of the powdery prepolymers of poly(L ‐lactic acid) (PLLA) and poly(D ‐lactic acid) (PDLA) can produce entire stereocomplexed poly(lactic acid)s (sc‐PLA) with high molecular weight and can be an alternative synthetic route to sc‐PLA. Ordinary melt polycondensations of L ‐ and D ‐lactic acids gave the PLLA and PDLA prepolymers having medium molecular weight which were pulverized for blending in 1:1 ratio. The resultant powder blends were then subjected to SSP at 130–160 °C for 30 h under a reduced pressure of 0.5 Torr. Some of the products thus obtained attained a molecular weight (Mw) as high as 200 kDa, consisting of stereoblock copolymer of PLLA and PDLA. A small amount of the stereocomplex should be formed in the boundaries of the partially melted PLLA and PDLA where the hetero‐chain connection is induced to generate the blocky components. The resultant SSP products showed predominant stereocomplexation after their melt‐processing in the presence of the stereoblock components in spite of containing a small amount of racemic sequences in the homo‐chiral PLLA and PDLA chains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3714–3722, 2008 相似文献
163.
Nonlinear resonances and self-excited oscillations of a rotor caused by radial clearance and collision 总被引:1,自引:0,他引:1
This paper investigates oscillations in a flexible rotor system with radial clearance between an outer ring of the bearing
and a casing by experiments and numerical simulations. The mathematical model considers the collisions of the bearing with
the casing. The following phenomena are found: (1) Nonlinear resonances of subharmonic, super-subharmonic and combination
oscillation occur. (2) Self-excited oscillation of a forward whirling mode occurs in a wide range above the major critical
speed. (3) Entrainment phenomena from self-excited oscillation to nonlinear forced oscillation occur at these nonlinear resonance
ranges. Moreover, this study analyzes periodic solutions of the mathematical model by the Harmonic Balance Method (HBM). As
the results, the nonlinear resonances of subharmonic oscillation and its entrainment phenomenon can be explained theoretically
by investigating the stability of the periodic solutions. The influence of the static force and the bearing damping on these
oscillation are also clarified. 相似文献
164.
We designed bisnitroxide compounds where the radical sites are located close to each other in a molecule. Two new pincer-type bisnitroxide compounds have been synthesized, involving xanthene-4,5-diyl as a spacer and tert-butyl phenyl nitroxides as arms. From the X-ray crystal structure analysis, the shortest intramolecular interatomic N?O and O?O distances respectively are 5.074(6) and 5.258(6) Å for the m,m′-derivative and 3.624(3) and 3.771(3) Å for the p,p′-derivative. The N?O distance in the latter satisfies the empirical criterion for possible dimerization/degradation reaction accompanied by dia-/paramagnetic transition. However, the magnetic study clarified paramagnetic behavior in all the temperature range. According to a singlet-triplet model, antiferromagnetic couplings were characterized with 2J/kB = ?7.71(2) and ?8.83(4) K for the m,m′ and p,p′-derivatives, respectively. The present result suggests that a more flexible spacer is required for realization of possible dia-/paramagnetic transition. 相似文献
165.
Kazuki Kawabe 《Catalysis Surveys from Asia》2010,14(3-4):111-115
A new process for the production of mono-ethylene glycol (MEG; HOCH2CH2OH) was developed by Mitsubishi Chemical Corporation (MCC) to meet its growing demand in the world. While the MEG selectivity of conventional non-catalyzed process is around 89% under typical conditions, that of the new process exceeds 99%. The key of the high selectivity is the two-step synthesis via ethylene carbonate. The first step reaction is catalyzed by phosphonium salts and generates ethylene carbonate as an intermediate. This is followed by hydrolysis of ethylene carbonate in the second step. Several commercial plants of the new process have already been operated world-wide. 相似文献
166.
Aliakbar Dehno Khalaji Gholamhossein Grivani Samaneh Jalali Akerdi Kazuma Gotoh Hiroyuki Ishida Hossein Mighani 《Structural chemistry》2010,21(5):995-1003
Two thiosemicarbazones, (E)-2-(2,4-dimethoxybenzylidene)thiosemicarbazone (24-MBTSC (1)) and (E)-2-(2,5-dimethoxybenzylidene)thiosemicarbazone (25-MBTSC (2)), derived from 2,4-dimethoxybenzaldehyde and 2,5-dimethoxybenzaldehyde, respectively, with thiosemicarbazide have been synthesized and their structures were characterized by elemental analyses, FT-IR, 1H NMR spectroscopy, and X-ray single-crystal diffraction analysis. Molecular orbital calculations have been carried out for 1 and 2 by using an ab initio method (HF) and also density functional method (B3LYP) at 6-31G basis set. Compound 1 crystallizes in the monoclinic system, space group P21/c, with a = 8.1342(5) Å, b = 18.1406(10) Å, c = 8.2847(6) Å, β = 109.7258(17)°, V = 1150.75(12) Å3, and Z = 4, whereas compound 2 crystallizes in the orthorhombic system, space group Pbca, with a = 11.0868(6) Å, b = 13.1332(6) Å, c = 15.9006(8) Å, V = 2315.2(2) Å3, and Z = 8. The compounds 1 and 2 displays a trans-configuration about the C=N double bond. 相似文献
167.
Kazuki Itoh 《Geometriae Dedicata》2014,168(1):177-196
We prove an analogue of the Cheeger–Gromoll splitting theorem for sub-Riemannian manifolds with the measure contraction property instead of the nonnegativity of the Ricci curvature. If such a sub-Riemannian manifold contains a straight line, then the manifold splits diffeomorphically, where the splitting is not necessarily isometric. We prove that such a sub-Riemannian manifold containing a straight line cannot split isometrically under some typical condition in sub-Riemannian geometry. Heisenberg groups are such examples. 相似文献
168.
169.
170.
Akira Hasegawa Takao Nagahama Hitoshi Ohki Kenji Hotta Hideharu Ishida Makoto Kiso 《Journal of carbohydrate chemistry》2013,32(3):493-498
Development of an efficient α-glycoside synthesis of sialic acids is critically significant for the syntheses of sialoglycoconjugates, especially gangliosides which carry important biological functions1 in biological systems. Previously, we demonstrated2 a new α-glycosylation of sialic acids by use of dimethyl(methylthio)sulfonium triflate (DMTST)3 as the glycosyl promoter, the suitably protected glycosyl acceptors and the methyl 2-thioglycoside 1 of N-acetylneuraminic acid (Neu5Ac) as the donor in acetonitrile under kinetically controlled conditions, and accomplished4 the syntheses of a variety of gangliosides and their analogs. 相似文献