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61.
Expectation values of the total spinS of nucleons in nuclei are very quenched. This quenching is shown to be hardly explained by the mixture of-hole states. The quenching thus provides the best evidence for the role of non-central parts of the nucleon-nucleon interaction, especially the tensor interaction. 相似文献
62.
63.
Effect of molecular orientation distribution and crystallinity on the measurement of the crystal lattice modulus of nylon 6 by x-ray diffraction 总被引:1,自引:0,他引:1
The crystal lattice modulus of nylon 6 (-type) was measured by x-ray diffraction using nylon 6 films drawn up to five times. The measured crystal lattice modulus was 173–175 GPa for all specimens whose crystallinity and the Young's modulus were beyond 46% and 3.75 GPa, respectively. These results indicate that a state of homogenous stress can be achieved. In contrast, the values were scattered for the speciments whose crystallinity and Young's modulus are less than the above values. To study the origin, a numerical calculation of the crystal lattice modulus, as measured by x-ray diffraction, was carried out by considering effects on the orientation factors of molecular chains and crystallinity. In this calculation, a previously introduced model was employed, in which oriented crystalline layers are surrounded by oriented amorphous phases so that the strains of the two phases at the boundary are identical. The theoretical results calculated by the introduced model indicated that the crystal lattice modulus by x-ray diffraction is almost equal to the intrinsic crystal modulus if the morphology of the test specimen can be represented as a series model. In contrast, if a parallel model is more appropriate, the difference between the measured modulus and the intrinsic value can be pronounced. Such morphological dependence was found to be less pronounced with increasing high degree of molecular orientation and crystallinity. 相似文献
64.
Production of micron-sized monodispersed composite polymer particles by seeded polymerization utilizing the dynamic swelling method 总被引:1,自引:0,他引:1
In order to develop the seeded polymerization technique utilizing the dynamic swelling method (DSM) proposed by authors for
the production of micron-sized mono-dispersed “composite” polymer particles consisting of two kinds of polymers, the seeded
polymerization for the dispersion of ethyl methacry-late (EMA)-swollen PS particles prepared utilizing DSM was carried out.
Monodispersed PS/poly(ethyl methacrylate) (PEMA) composite particles having 7 μm in diameter were produced by the addition
of NaCl to lower the solubility of EMA in medium and by the addition of CuCl2 as a water-soluble inhibitor to depress the by-production of submicron-sized PEMA particles.
Received: 16 July 1996 Accepted: 10 October 1996 相似文献
65.
66.
Mikio Hori Tadashi Kataoka Hiroshi Shimizu Eiji Imai Yukiharu Matsumoto Iwao Miura 《Tetrahedron letters》1981,22(13):1259-1262
The novel ring transformation reactions were found in the reactions of 1,3,7,9-tetra-alkyl-8,9-dihydroxanthines and acetylenic compounds. The reaction of the dihydroxanthine with DMAD gave a propellane type compound and with methyl propiolate afforded the similar type compound and a pyrimido[4,5-b]diazepine derivative. The mechanism of these reactions was also discussed. 相似文献
67.
K Otsubo S Morita M Uchida K Yamasaki T Kanbe T Shimizu 《Chemical & pharmaceutical bulletin》1991,39(11):2906-2909
The enantiomers of 2-(4-chlorobenzoylamino)-3-[2(1H)-quinolinon-4-yl] propionic acid [(+/-)-1, rebamipide, OPC-12759], a new antiulcer agent that enhances mucosal resistance, were synthesized from optically active alpha-amino acid derivatives of 2(1H)-quinolinone. The key intermediates, alpha-amino acid derivatives, were prepared by asymmetric synthesis and optical resolution. The (+)-1 was about 1.7 times as potent as the (-)-isomer in antiulcer activity against ethanol-induced gastric ulcers. 相似文献
68.
[reaction: see text] A bridged N,N-di(aryl)-1,2,4,5-benzenediimide was synthesized in which restricted rotation led to two diasteriomeric conformations at room temperature. The more stable syn-macrocycle is achiral, whereas the strained anti-macrocycle possesses planar chirality similar to that of trans-cyclooctene. The structure was characterized by X-ray crystallography, and the enantiomers were resolved by chiral chromatography. 相似文献
69.
Kyoichiro Shibatani Yuzuru Fujiwara Kiyoshi Fujii 《Journal of polymer science. Part A, Polymer chemistry》1970,8(7):1693-1703
High-resolution proton magnetic resonance and infrared spectra of poly(vinyl formal) were studied in comparison with those of the model formals obtained from stereoisomers of pentane-2,4-diol and heptane-2,4,6-triol in order to learn spectral changes due to differences of the steric structures of the polymer. In the NMR spectrum of transformal obtained from dl diol or dl,dl (syndiotactic) triol, all proton signals were well interpreted by assuming a rapid chair-chair inversion of the formal ring. On the other hand, no such inversion was observed spectroscopically in cis-formal obtained from the meso diol or meso,meso (isotactic) triol, and the cis-formal ring was supposed to take a diequatorial form preferentially. Consequently, dioxymethylene protons gave a single peak (equivalent) in trans-formal and an AB quartet (nonequivalent) in cis-formal. In the spectra of poly(vinyl formal), the dioxymethylene signal was an overlap of the singlet and quartet in dimethylsulfoxide solution. Observations of the spectra of various poly(vinyl formals) obtained from poly(vinyl alcohols) of different tacticities and study of temperature dependence of the signal have shown that the singlet and quartet are attributed to trans- and cis- formals, respectively, in the polymer spectrum also. In the infrared spectra of poly(vinyl formals), the 800 and 785 cm-1 bands were found to be related to cis- and trans-formal rings respectively. A linear relationship was confirmed between D785/D800 and trans/cis ratios determined from the peak intensities of the dioxymethylene proton signals. 相似文献
70.
Large-scale separation of metallic and semiconducting single-walled carbon nanotubes 总被引:6,自引:0,他引:6
Maeda Y Kimura S Kanda M Hirashima Y Hasegawa T Wakahara T Lian Y Nakahodo T Tsuchiya T Akasaka T Lu J Zhang X Gao Z Yu Y Nagase S Kazaoui S Minami N Shimizu T Tokumoto H Saito R 《Journal of the American Chemical Society》2005,127(29):10287-10290
In the applications of single-walled carbon nanotubes (SWNTs), it is extremely important to separate semiconducting and metallic SWNTs. Although several methods have been reported for the separation, only low yields have been achieved at great expense. We show a separation method involving a dispersion-centrifugation process in a tetrahydrofuran solution of amine, which makes metallic SWNTs highly concentrated to 87% in a simple way. 相似文献