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排序方式: 共有321条查询结果,搜索用时 15 毫秒
81.
Tetsu Tsubogo Yuichiro Kano Koki Ikemoto Yasuhiro Yamashita Shū Kobayashi 《Tetrahedron: Asymmetry》2010,21(9-10):1221-1225
The first catalytic asymmetric 1,4-addition reactions of azlactones with acrylic esters have been developed. A chiral coordinative calcium catalyst was found to be effective for these reactions, and the desired 1,4-adducts were obtained in good yields and enantioselectivities. The product was converted to the corresponding α-alkylated glutamic acid by acid hydrolysis. 相似文献
82.
α-Rhombohedral (α-rh) boron, which is the most stable of boron's polymorphs at low temperatures, has p-type semiconductive properties. There have been some attempts to dope the interstitial sites with alkali atoms to create metallic or n-type semiconductive α-rh boron, but this has yet to be achieved. In a previous work, we proposed the codoping of α-rh boron with Li and P or As, and revealed from first principles calculations that B12PLi and B12AsLi could be synthesized and become narrow-gap semiconductors. The band structure suggested that the mobility of electrons might be greater than that of holes. In this paper, based on these prospective results, we selected a new combination of dopants, Li and O, and theoretically studied such compounds as B12OLi and B12O2Li. The results showed that both of these materials are metallic, while the reaction energies of the Li insertion into B12O and B12O2 are lower (more unstable) than with B12PLi and B12AsLi. It was proved that the differences in the electronic structures are caused by the dangling bonds of the dopant atoms, O, P and As. 相似文献
83.
Murahashi T Otani T Okuno T Kurosawa H 《Angewandte Chemie (International ed. in English)》2000,39(3):537-540
The first dipalladium μ-PPh(3) complex (1) was obtained by the facile loss of two CH(3)CN ligands from [Pd(2)(PPh(3))(2)(CH(3)CN)(4)](PF(6))(2) in CH(2)Cl(2). Coupling of p-tolylacetylene (p-TolC identical withCH) with 1 or its precusor afforded the μ-butenediylidene complex 2, treatment of which with CH(3)CN resulted in PPh(3) migration to give 3. 相似文献
84.
Fohr F Kaltenborn S Hamrle J Schultheiss H Serga AA Schneider HC Hillebrands B Fukuma Y Wang L Otani Y 《Physical review letters》2011,106(22):226601
We determine the dynamic magnetization induced in nonmagnetic metal wedges composed of silver, copper, and platinum by means of Brillouin light scattering microscopy. The magnetization is transferred from a ferromagnetic Ni80Fe20 layer to the metal wedge via the spin pumping effect. The spin pumping efficiency can be controlled by adding an insulating interlayer between the magnetic and nonmagnetic layer. By comparing the experimental results to a dynamical macroscopic spin-transport model we determine the transverse relaxation time of the pumped spin current which is much smaller than the longitudinal relaxation time. 相似文献
85.
Azechi H Sakaiya T Fujioka S Tamari Y Otani K Shigemori K Nakai M Shiraga H Miyanaga N Mima K 《Physical review letters》2007,98(4):045002
The growth rate of the ablative Rayleigh-Taylor instability is approximated by gamma = square root[kg/(1 + kL)] - beta km/rho(a), where k is the perturbation wave number, g the gravity, L the density scale length, m the mass ablation rate, and rho(a) the peak target density. The coefficient beta was evaluated for the first time by measuring all quantities of this formula except for L, which was taken from the simulation. Although the experimental value of beta = 1.2+/-0.7 at short perturbation wavelengths is in reasonably good agreement with the theoretical prediction of beta = 1.7, it is found to be larger than the prediction at long wavelengths. 相似文献
86.
Nakamura S Endo M Yamamoto H Isshiki T Kimura N Aoki H Nojima T Otani S Kunii S 《Physical review letters》2006,97(23):237204
We report unusual evolution of the conduction-electron state in the localized f electron system CexLa1-xB6 from normal electron state to heavy Fermi liquid (FL) state through local FL and non-FL states with increasing Ce concentration and/or with increasing magnetic field. The effective mass of quasiparticle or the coefficient A of T2 term of resistivity is found to increase divergently near the boundary between FL state and non-FL state. The features of the non-FL state are also different from those of the typical non-FL systems previously observed or theoretically predicted. 相似文献
87.
Y. Otani H. Miyajima S. Chikazumi S. Hirosawa M. Sagawa 《Journal of magnetism and magnetic materials》1986,60(2-3):168-170
The hysteresis loop of Nd15Fe77B8 can be decomposed in hysteresis loops of two magnetic phases; one with a comparatively low coercivity and the other with a high coercivity. The volume ratio of these phases depends on the temperature and the angle between the external field and pseudo c-axis. 相似文献
88.
Nobutoshi Kiba Ayumi Koga Masaki Tachibana Kazue Tani Hitoshi Koizumi Tetsuo Koyama Akira Yamamura Kunio Matsumoto Tohru Okuda Koki Yokotsuka 《Analytical sciences》2006,22(1):95-98
A chemiluminometric flow injection analytical system for the quantitation of L-histidine is described. Histidine oxidase (EC 1.4.3.-) from Brevibacillus borstelensis KAIT-B-022 was immobilized on tresylated poly(vinyl alcohol) beads and packed into a stainless-steel column. The hydrogen peroxide produced was detected chemiluminometrically by a flowthrough sensor containing immobilized peroxidase (EC 1.1 1.1.7). The maximum sample throughput was 10 h(-1). The calibration graph was linear from 0.05 to 5 mM; the detection limit (signal to noise ratio = 3) was 0.01 mM. The activity of immobilized histidine oxidase reduced to 65% of the initial value after 350 injections. The system was applied to the determination of L-histidine in fish meat, such as salmon, tunny, bonito, and mackerel. 相似文献
89.
Koki Tsukamoto Hideaki Shimizu Takashi Ishida Yutaka Akiyama Nobuyuki Nukina 《Journal of Molecular Structure》2006,778(1-3):85-95
Polyglutamine (polyQ) diseases, including Huntington’s disease (HD), are caused by expansion of polyQ-encoding repeats within otherwise unrelated gene products. The aggregation mechanism of polyQ diseases, the inhibition mechanism of Congo red, and the alleviation mechanism of trehalose were proposed here based on quantum chemical calculations and molecular dynamics simulations. The calculations and simulations revealed the following. The effective molecular bonding is between glutamine (Gln) and Gln (Gln + Gln), between Gln and Congo red (Gln + Congo red), and between Gln and trehalose (Gln + trehalose). The bonding strength is −13.1 kcal/mol for Gln + Gln, −24.4 kcal/mol for Gln + Congo red, and −12.0 kcal/mol for Gln + trehalose. In the polyQ region, both the number of intermolecular Gln + Gln formations and the total calories generated by the Gln + Gln formation are proportional to the number of repetitions of Gln. We propose an aggregation mechanism whose heat generated by the intermolecular Gln + Gln formation causes the pathogeny of polyQ disease. In our aggregation mechanism, this generated heat collapses the host protein and promotes fibrillogenesis. Without contradiction, our mechanism can explain all the experimental results reported to date. Our mechanism can also explain the inhibition mechanism by Congo red as an inhibitor of polyglutamine-induced protein aggregation and the alleviation mechanism by trehalose as an alleviator of that aggregation. The inhibition mechanism by Congo red is explained by the strong interaction with Gln and by the characteristic structure of Congo red. 相似文献
90.
Nagao Tadaaki Kitamura Kazuo Iizuka Yoshitaka Oshima Chuhei Shigeki Otani 《Surface science》1993,290(3):436-444
The surface phonon dispersion of clean LaB6(100) surface has been measured by means of high resolution electron energy loss spectroscopy. Eight vibrational modes, of which most are located in the energy gaps between the bulk phonon bands, have been detected. The lattice dynamical calculation of a slab-shaped crystal based on a force constant model has reproduced these experimental dispersion curves, which indicates the large increase in the force constant of interoctahedral boron-boron bond at the surface by 25%, and the large decrease in the force constants of intraoctahedral boron-boron bonds at the surface by 25–50%. These changes together with the analysis of the bulk phonon structure of metal hexaborides strongly suggest that the boron octahedra at the surface are expanded by about 0.004 nm parallel to the surface. 相似文献