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排序方式: 共有791条查询结果,搜索用时 15 毫秒
761.
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Ma YuGang Fang DeQing Sun XiaoYan Zhou Pei Cai XiangZhou Chen JinGen Guo Wei Tian WenDong Wang HongWei Zhang GuoQiang Cao XiGuang Fu Yao Hu ZhengGuo Wang JianSong Wang Meng Togano Y. Aoi N. Baba H. Honda T. Okada K. Hara Y. Ieki K. Ishibashi Y. Itou Y. Iwasa N. Kanno S. Kawabata T. Kimura H. Kondo Y. Kurita K. Kurokawa M. Moriguchi T. Murakami H. Oishi H. Ota S. Ozawa A. Sakurai H. Shimoura S. Shioda R. Takeshita E. Takeuchi S. Yamada K. Yamada Y. Yasuda Y. Yoneda K. Motobayashi T. 《中国科学:物理学 力学 天文学(英文版)》2011,54(1):18-23
Two-proton relative momentum distributions from the break-up channels 23Al→p+p+21Na and 22Mg→p+p+20Ne at an energy of 60–70 A MeV have been measured together with two-proton opening angles at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility. The results demonstrate the existence of diproton emission component from single-step 2He for highly excited 23Al and 22Mg. 相似文献
764.
Guizhong Qi Yuu Nitto Akira Saiki Taketoshi Tomohiro Yuushou Nakayama Hajime Yasuda 《Tetrahedron》2003,59(52):10409-10418
Yb[C(SiMe3)3]2 initiates the living polymerization of methyl methacrylate (MMA) at −78°C to give the polymer with Mn of 51.0×104 (Mw/Mn=1.1) and high isotacticity (97%) in a quantitative yield. Mixing of the acetone solution of resulting polymer (Mn=16.3×104) with the acetone solution of syndiotactic poly(MMA) (Mn=15.7×104) prepared by the (C5Me5)2SmMe(THF) initiator produces desired stereocomplex in high yield bearing very high Tm whose tensile modulus is higher than the respective isotactic and syndiotactic poly(MMA)s. Yb[C(SiMe3)3]2 also generated isotactic (98%) poly[2-(dimethylamino)ethyl methacrylate] (DMEMA), and (C5Me5)2SmMe(THF) affords the syndiotactic (97%) polymer in high yields. The combination of isotactic poly(MMA)-block-poly(DMEMA) (97/3) and syndiotactic poly(MMA)-block-poly(DMEMA) (97/3) provides the amphiphathic stereocomplex. In sharp contrast to the catalysis of Yb[C(SiMe3)3]2 in toluene, the addition of THF or HMPA resulted in the formation of syndio-rich poly(MMA). 相似文献
765.
Amides, 2 and 3 related to the potent antifungal triazole-amide 3-acylamino-2-aryl-1-triazolyl-butanol(1) were synthesized starting from the triazole-alcohol 6. The antifungal activity of 2 and 3 against a mouse systemic Candida albicans infection was found to be less potent than that of 1. 相似文献
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767.
Fragmentation cross sections are essential input parameters for propagation calculations which describe the effect of shielding against cosmic ray heavy nuclei by the walls of spacecraft or planetary habitat. Cross sections for the breakup of different elements are needed for different types of target material and for a wide range of energy.
For this purpose, we have extended our studies of projectile fragmentation. By using stacks containing CR-39 track detectors and targets ranging from CH2 to Pb we have measured total and elemental fragmentation cross sections for fragments with charges ZF>5, for silicon projectiles with energies of 490 AMeV. These new data sets allow us to improve our knowledge about the target and energy dependence of fragmentation cross sections. 相似文献
768.
Keiji Ogata Yuushou Nakayama Hajime Yasuda 《Journal of polymer science. Part A, Polymer chemistry》2002,40(16):2759-2771
1‐(2‐N,N‐Dimethylaminoethyl)‐2,3,4,5‐tetramethylcyclopentadienyl‐chromium dichloride ( 1 ), (2‐N,N‐dimethylaminoethyl)cyclopentadienylchromium dichloride ( 6 ), and (2‐N,N‐dimethylaminoethyl)indenylchromium dichloride ( 7 ) in the presence of modified methylaluminoxane exhibit high catalytic activities for the polymerization of ethylene with random copolymerizations of ethylene with propylene, ethylene with 1‐hexene, and propylene with 1‐hexene. These initiators conduct polymerizations to give high molecular weight polymers with low polydispersities. However, the stereoregularities are very poor in these reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2759–2771, 2002 相似文献
769.
Hayashi Y Katsumoto Y Omori S Kishii N Yasuda A 《The journal of physical chemistry. B》2007,111(5):1076-1080
Dielectric spectroscopy measurements for aqueous urea solutions were performed at 298 K through a concentration range from 0.5 to 9.0 M with frequencies between 200 MHz and 40 GHz. Observed dielectric spectra were well represented by the superposition of two Debye type relaxation processes attributable to the bulk-water clusters and the urea-water coclusters. Our quantitative analysis of the spectra shows that the number of hydration water molecules is approximately two per urea molecule for the lower concentration region below 5.0 M, while the previous molecular dynamics studies predicted approximately six water molecules. It was also indicated by those studies, however, that there are two types of hydration water molecule in urea solution, which are strongly and weakly associated to the urea molecule, respectively. Only the strongly associated water was distinguishable in our analysis, while the weakly associated water exhibited the same dynamic feature as bulk water. This implies that urea retains the weakly associated water in the tetrahedral structure and, thus, is not a strong structure breaker of water. We also verified the model of liquid water where water consists of two states: the icelike-ordered and dense-disordered phases. Our dielectric data did not agree with the theoretical prediction based on the two-phase model. The present work supports the argument that urea molecules can easily replace near-neighbor water in the hydrogen-bonding network and do not require the presence of the disordered phase of water to dissolve into water. 相似文献
770.
Y. Tanaka N. Kimura K. Hono K. Yasuda T. Sakurai 《Journal of magnetism and magnetic materials》1997,170(3):291
We have investigated the magnetic properties of Fe38.5Pt, Fe39.5Pt and Fe50.0Pt (at%) alloys after various heat treatment conditions using a vibrating sample magnetometer, and correlated these properties with the microstructures of the alloys by transmission electron microscopy. The Fe50Pt alloy shows poor magnetic hardness regardless of the heat treatment conditions. The magnetic hardness of the Fe39.5Pt alloy shows a maximum value after annealing for 10 h at 873 K, while it monotonically decreases after annealing at 1073 K. The alloy with the highest coercivity was composed of a single phase γ1 with an average domain size of approximately 10 nm. The electron diffraction results indicate that the alloy is frustrated with accumulated stress, induced by a cubic → tetragonal transformation which occurs without twinning. On the other hand, when stress is relieved by twin formation after prolonged aging, the coercivity decreases. By annealing at 1073 K, the well known polytwin structure evolves. However, only poor hard magnetic properties are observed when this polytwin structure appears. Hence, the highest coercivity is attributed to the formation of nanoscale L10 ordered antiphase domains which is expected to be a highly anisotropic single domain magnetic particle. 相似文献