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911.
A new P-chiral phosphine ligand, (R,R)-2,3-bis(tert-butylmethylphosphino)quinoxaline, has been prepared by the reaction of enantiomerically pure tert-butylmethylphosphine-borane with 2,3-dichloroquinoxaline. This ligand, in contrast to most of the previously reported P-chiral ligands, is an air-stable solid and exhibits excellent enantioselectivities in both Rh-catalyzed asymmetric hydrogenations and Rh- or Pd-catalyzed carbon-carbon bond-forming reactions. 相似文献
912.
913.
Toyonobu Yoshida Kunihiko Nakagawa Toshiya Harada Kazuo Akashi 《Plasma Chemistry and Plasma Processing》1981,1(1):113-129
A numerical model has been developed for predicting the two-dimensional flow and temperature fields in a radio-frequency (rf) plasma torch. The method employed here is based on Boulos' model with the exception of the boundary conditions for the electric and magnetic field equations. Calculations have been made for the confirmation of a new sample injection method, which is capable of completely evaporating refractory materials at high feeding rates without interfering with the stability of the plasma. In the newly designed torch, the reagent is radially injected into the hottest part of the plasma through quartz capillary tubes set symmetrically between an inductor coil. Experimental investigations have also been performed for verifying the proper function of the design. These results provide evidence that our radial injection method developed here is more effective in practical processing than the conventional axial injection methods. 相似文献
914.
K. Asahi H. Okuno H. Ueno H. Sato J. Kura T. Kubo T. Nakamura N. Inabe A. Yoshida Y. Ohkubo M. Adachi T. Ichihara M. Ishihara T. Shimoda H. Miyatake N. Takahashi D. Beaumel D. J. Morrissey W. -D. Schmidt-Ott 《Hyperfine Interactions》1992,75(1-4):101-108
Ejectile nuclei in the fragmentation of intermediate-energy heavy-ion projectiles were found to be largely spin polarized.
The observed polarization as a function of the outgoing momentum was nicely explained by a simple kinematical argument based
on the participant-spectator model of projectile fragmentation. The measurements extended to cover several different targets,
incident energies, exit channels, and emission angles revealed that substantial polarization shows up widely in projectile
fragmentation reactions. Furthermore, this polarization exhibits an interesting behavior which may be interpreted as a manifestation
of a gradual change in the deflection angle from positive to negative values as the energy increases and/or the target-Z decreases. The present polarization results also suggests various applications of spin polarized radioactive beams. As the
first example of such an application, we present a recent result on theg-factor measurements on neutron-rich nuclei. 相似文献
915.
Holographic data storage is being widely studied for the purpose of developing next-generation large optical memories. A prospective
use of this type of memory is in building image archives in large-scale data centers. In particular, demand for energy conservation
at data centers, and therefore for holographic data storage, is growing. In holographic data storage, interference between
bits occurs owing to wave aberration in the optical system, shrinkage of the medium, and crosstalk noise from neighboring
holograms during multiplex recording; as a result of the interference, the reproduced image deteriorates and the bit error
rate (BER) increases. In this study, to reduce the BER in both off-axis-type recording and coaxial-type recording, a two-dimensional
finite impulse response (FIR) filter is applied to a reproduced image that has been recorded by angle multiplex recording
and shift multiplex recording. First, for the optimization of the FIR filter coefficients, the linear minimum mean square
error (LMMSE) method is applied; this method optimizes the coefficients by reducing the BER. Furthermore, for evaluating the
optimization performance of the LMMSE method, the optimization performance is compared with that of the real-coded genetic
algorithm (RCGA), which has the capability to search a wide range of coefficients. The optimization by the LMMSE method has
been found to be excellent for off-axis-type recording but not for coaxial-type recording. It is speculated that this is because
of the brightness irregularity in the reproduced image, resulting from crosstalk. On the other hand, a marked reduction in
the BER is observed using the RCGA, despite the brightness irregularity. In this study, the effectiveness of the LMMSE method
for signals recorded by coaxial-type recording, in which large brightness irregularity is expected, is examined using automatic
gain control (AGC). It is found that the application of AGC reduces the BER even in the case of coaxial-type recording. 相似文献
916.
Shogo Ihara Takashi Soma Daigo Yano Shunichi Aikawa Yasuhiko Yoshida 《Journal of heterocyclic chemistry》2011,48(3):577-581
The cycloaddition reaction of cyclic imidates, 2‐benzyl‐5,6‐dihydro‐4H‐1,3‐oxazines 1a , 1b , 1c , 1d , 1e , 1f , with dimethyl acetylenedicarboxylate 2 , trimethyl ethylenetricarboxylate 4 , or dimethyl 2‐(methoxymethylene)malonate 6 afforded new fused heterocyclic compounds, such as methyl (6‐oxo‐3,4‐dihydro‐2H‐pyrrolo[2,1‐b]‐1,3‐oxazin‐7‐ylidene)acetates 3a , 3b , 3c , 3d , 3e , 3f (71–79%), dimethyl 2‐(6‐oxo‐3,4,6,7‐tetrahydro‐2H‐pyrrolo[2,1‐b]‐1,3‐oxazin‐7‐yl)malonates 5b , 5c , 5d , 5e , 5f (43–71%), or methyl 6‐oxo‐3,4‐dihydro‐2H,6H‐pyrido[2,1‐b]‐1,3‐oxazine‐7‐carboxylates 7a , 7b , 7c , 7d , 7e , 7f (32–59%), respectively. In these reactions, 1a , 1b , 1c , 1d , 1e , 1f (cyclic imidates, iminoethers) functioned as their N,C‐tautomers (enaminoethers) 2 to α,β‐unsaturated esters 2 , 4, and 6 to give annulation products 3 , 5 , and 7 following to the elimination of methanol, respectively. J. Heterocyclic Chem., (2011). 相似文献
917.
The iron mixed-valence complex (n-C(3)H(7))(4)N[Fe(II)Fe(III)(dto)(3)] exhibits a novel type of phase transition called charge-transfer phase transition (CTPT), where the thermally induced electron transfer between Fe(II) and Fe(III) occurs reversibly at ~120 K, in addition to the ferromagnetic phase transition at T(C) = 7 K. To investigate the mechanism of the CTPT, we have synthesized a series of magnetically diluted complexes (n-C(3)H(7))(4)N[Fe(II)(1-x)Zn(II)(x)Fe(III)(dto)(3)] (dto = C(2)O(2)S(2); x = 0-1), and carried out magnetic susceptibility and dielectric constant measurements and (57)Fe M?ssbauer spectroscopy. With increasing Zn(II) concentration (x), the CTPT is gradually suppressed and disappears at x ≈ 0.13. On the other hand, the ferromagnetic transition temperature (T(C)) is initially enhanced from 7 K to 12 K between x = 0.00 and 0.05, despite the nonmagnetic nature of Zn(II) ions, and then it decreases monotonically from 12 K to 3 K with increasing Zn(II) concentration. This anomalous dependence of T(C) on Zn(II) concentration is related to a change in the spin configuration of the ferromagnetic state caused by the partial suppression of the CTPT. 相似文献
918.
Lopez-Martens A Døssing T Khoo TL Matsuo M Herskind B Lauritsen T Carpenter MP Janssens RV Hackman G Lee IY Macchiavelli AO Vigezzi E Yoshida K 《Physical review letters》2008,100(10):102501
The E(gamma) - E(gamma) coincidence spectra from the electromagnetic decay of excited superdeformed states in (194)Hg reveal surprisingly narrow ridges, parallel to the diagonal. A total of 100-150 excited bands are found to contribute to these ridges, which account for nearly all the unresolved E2 decay strength. Comparison with theory suggests that these excited bands have many components in their wave functions, yet they display remarkable rotational coherence. This phenomenon can be explained in terms of the combination of shell effects and motional narrowing. 相似文献
919.
Aoto T Ito K Hikosaka Y Shibasaki A Hirayama R Yamamono N Miyoshi E 《The Journal of chemical physics》2006,124(23):234306
The N2(+) states lying in the ionization region of 26-45 eV and the dissociation dynamics are investigated by high-resolution threshold photoelectron spectroscopy and threshold photoelectron-photoion coincidence spectroscopy. The threshold photoelectron spectrum exhibits several broad bands as well as sharp peaks. The band features are assigned to the N2(+) states associated with the removal of an inner-valence electron, by a comparison with a configuration interaction calculation. In contrast, most of the sharp peaks on the threshold photoelectron spectrum are allocated to ionic Rydberg states converging to N2(2+). Dissociation products formed from the inner-valence N2(+) states are determined by threshold photoelectron-photoion coincidence spectroscopy. The dissociation dynamics of the inner-valence ionic states is discussed with reference to the potential energy curves calculated. 相似文献