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291.
Rhodium-catalyzed asymmetric 1,6-addition of aryltitanates to enynones giving axially chiral allenes
[reaction: see text] The addition of aryltitanate reagents ArTi(OPr-i)4Li to 3-alkynyl-2-en-1-ones in the presence of chlorotrimethylsilane and a rhodium-(R)-segphos as a catalyst proceeded in a 1,6-fashion to give a high yield of axially chiral allenylalkenyl silyl enol ethers with up to 93% ee. 相似文献
292.
Freytag N Tokunaga Y Horvatić M Berthier C Shayegan M Lévy LP 《Physical review letters》2001,87(13):136801
The average electron spin polarization Rho of a two-dimensional electron gas confined in GaAs/GaAlAs multiple quantum wells was measured by NMR near the fractional quantum Hall state with filling factor nu = 2/3. Above this filling factor (2/3< or = nu < 0.85), a strong depolarization is observed corresponding to two spin flips per additional flux quantum. The most remarkable behavior of the polarization is observed at nu = 2/3, where a quantum phase transition from a partially polarized (Rho approximately 3/4) to a fully polarized (Rho = 1) state can be driven by increasing the ratio between the Zeeman and the Coulomb energy above a critical value eta(c) = Delta(Z)/Delta(C) = 0.0185. 相似文献
293.
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296.
Enrique Artal Bartolo José Ignacio Cogolludo Hiro-o Tokunaga 《Geometriae Dedicata》2006,121(1):129-142
Globally irreducible nodes (i.e. nodes whose branches belong to the same irreducible component) have mild effects on the most
common topological invariants of an algebraic curve. In other words, adding a globally irreducible node (simple nodal degeneration)
to a curve should not change them a lot. In this paper we study the effect of nodal degeneration of curves on fundamental
groups and show examples where simple nodal degenerations produce non-isomorphic fundamental groups and this can be detected
in an algebraic way by means of Galois covers.
相似文献
297.
Alan Tokunaga Prasad Varanasi 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(12):1057-1059
The intensity of the RQ0 branch of the v9 fundamental of ethane has been measured to be 0.74±0.09cm-2atm-1 at 300°K. Rotational structure of the laboratory spectrum is discussed by means of a comparison with a computed spectrum. 相似文献
298.
The v1 internal breathing mode of PO4 tetrahedrons in KH2PO4 is observed with the (yx) Raman spectra. It has been found that its intensity depends upon the direction of the scattering wave vector by means of the observations with the z-Δx(yx)y and x-Δz(yx)y scattering geometries. While this mode is very weak in intensity in the x(yx)y spectrum, it becomes very strong as the scattering geometry approaches the z(yx)y one. 相似文献
299.
We have obtained the first experimental evidence for the Pockels effect of water, which is induced by a high electric field in the electric double layer (EDL) on the water-transparent electrode interface. The electric-field induced energy shift of the visible interference fringes of a 300 nm indium-tin-oxide (ITO) electrode layer is observed, indicating a negative refractive index change at the interface. Numerical calculation reproduces well the experimental observation, showing that the signal mainly originates from water in the EDL. The Pockels constants of water are estimated to be r33 = 5.1 × 100 pm/V and r13 = 1.7 × 100 pm/V. The large anisotropy of the Pockels effect of water is deduced from the incidence angle dependence of the p-polarization signal. At the same time, the ITO shows a blue shift of the band gap in the UV due to the band population effect in the space charge layer. The plasma frequency in the near IR is also expected to increase due to the band population effect, since the ITO has a high doped carrier population close to metal. A negative refractive index change in the ITO space charge layer is induced from both effects, but its effect on the signal is estimated to be much smaller than that of the negative refractive index change of water in the EDL. 相似文献
300.
Takayuki Arai Junichi Hidaka Hiroki Tokunaga Koh Matsumoto 《Journal of Crystal Growth》1997,170(1-4):88-91
A novel horizontal metal organic vapor phase epitaxy (MOVPE) system, which is capable of handling six 3 inch wafers or eighteen 2 inch wafers mounted on a 10 inch diameter susceptor, has been developed for the growth of III–V compound semiconductors. The characteristic features in this system are “triple flow channel” gas injection and “face-down” wafer setting configuration. The inlet for the source gas flow is divided into three zones (upper, middle and lower flows for hydrides, organometals and hydrogen, respectively) to control the concentration boundary layer and the growth area. The wafers are placed inversely to prevent thermal convection and particles on the growing surface. The independent controlled three-part heating system is also adopted to achieve a uniform temperature distribution over an 8 inch growing surface. The thickness and the doping of GaAs, Al0.3Ga0.7As, In0.48Ga0.52P and In0.2Ga0.8As grown by this system are uniform within ± 2% over all 3 inch wafers. 相似文献