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排序方式: 共有168条查询结果,搜索用时 15 毫秒
111.
Haruka Shimizu 《Tetrahedron letters》2006,47(33):5927-5931
A novel repetitive two-step method for oligoarene synthesis, based on Negishi cross-coupling of zinciophenoxides or zinciopyridinoxides with aryl triflates and subsequent triflation of the hydroxy group, was developed. Reaction conditions were optimized for the preparation of the arylzinc compounds and the palladium-catalyzed cross-coupling step. 相似文献
112.
Hiromitsu Imai Kensuke Inaba Haruka Tanji-Suzuki Makoto Yamashita Tetsuya Mukai 《Applied physics. B, Lasers and optics》2014,116(4):821-829
A Bose–Einstein condensate was achieved in a stable magnetic trap on a persistent-supercurrent atom chip with a superconducting closed-loop circuit. We determined precisely the shape of the magnetic trapping potential by systematically controlling the persistent supercurrent. The condensation was verified by time-of-flight imaging and by atom number decay measurements. The measured decay rates agreed quantitatively with numerical simulations on the three-body loss process assuming all of the atoms to be a condensate. We also discuss the feasibility of creating a quasi-one-dimensional Bose gas on our atom chip. 相似文献
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115.
The reaction of the Si8O208? silicate anion with X(CH3)2SiCl (X?H or CH3) has been studied to develop a cost‐effective procedure for synthesizing Si8O20[Si(CH3)2X]8 in high yield. Use of hexane as solvent and adjustment of the reaction temperature to ca 20 °C were found to be effective in promoting the reaction, by which Si8O20[Si(CH3)2X]8 could be produced in good yield employing 24 mol of X(CH3)2SiCl per mole of Si8O208?. It was also demonstrated that the yield of Si8O20[Si(CH3)2X]8 depends on the amount of solvent, suggesting that the amount is an important factor when scaling up the reaction to produce a large quantity of Si8O20[Si(CH3)2X]8. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
116.
A radio-frequency (RF) ion trap has been constructed for high resolution laser spectroscopy of metallic ions. Ions in externally
generated laser plasma have been directly introduced into the RF ion trap. An Nd:YAG laser is used to vaporize and ionize
sample metals placed behind a ring electrode. Both hyperbolic and cylindrical electrodes are successfully used for confinement
of the ions. Trapped ions are detected either with a quadrupole mass spectrometer or with a photomultiplier for the measurement
of laser-induced fluorescence. Metallic ions such as Ca+, Ba+, La+, Nd+, Tm+, Lu+, and Ta+ have been confined for the time range of several to 20 minutes in the presence of He buffer gas, and a doubly charged ion
Ba2+ for several seconds. Some ions like Nd+, Lu+, Hf+, and Ta+ are found to be highly reactive with background gaseous molecules. 相似文献
117.
118.
M. Yoshioka A. Noda M. Daigo Y. Hemmi R. Kikuchi M. Minowa K. Miyake T. Nakamura M. Ono Y. Suzuki S. Kato K. Ukai K. Toshioka K. Sugano T. Shimomura T. Shinohara M. Chiba Y. Hoshi 《Nuclear Physics B》1980,168(2):222-242
The differential cross sections of the reaction γp→π0p have been measured at photon energies between 390 MeV and 975 MeV with an energy step of 20 or 25 MeV. The angular region covers 11 angles between 15° and 130° in the c.m.s. A combination of a magnetic spectrometer and photon detector was used for the measurement in the angular region from 50° to 130°. At forward angles of 15°, 35° and 50°, π0 mesons were detected using a π0 detector consisting of a pair of photon detectors. The data obtained with two different detection systems overlap at the angle of 50° and coincide with each other within the experimental error. The results are compared with those of phenomenological partial-wave analyses. 相似文献
119.
M Abe H Furunaga D Ma L Gagliardi GJ Bodwell 《The Journal of organic chemistry》2012,77(17):7612-7619
Stretch effects induced by two types of molecular strain were examined by quantum chemical calculations at the B3LYP/6-31G(d), B3LYP/cc-PVDZ, CCSD/6-31G(d), and CASPT2/ANO-RCC-VTZP level of theory, to design persistent multiradicals such as localized diradicals and oxyallyls. The cooperative molecular strain (Type-1) induced by the spiro[5.5]undecane and bicyclo[2.1.0]cyclopentane structures was found to significantly destabilize in energy the ring-closed compounds of the diradicals, leading to small energy differences between the diradicals and the σ-bonded compounds. Another stretch effect (Type-2) induced by macrocyclic systems was also found to energetically destabilize the corresponding ring-closed structures of the 1,3-diradicals. The computational studies predict that the two types of stretch effects are quite effective in lowering the energy barriers of the bond-breaking reaction of the ring-closed compounds and in generating long-lived localized diradicals and oxyallyl derivatives. 相似文献
120.
Kishikawa Y Shinohara H Maeda K Nakamura Y Wiegand S Kita R 《Physical chemistry chemical physics : PCCP》2012,14(29):10147-10153
We studied the thermal diffusion behavior for binary aqueous solutions of glucose, maltotriose, maltohexaose, pullulan, and dextran by means of thermal diffusion forced Rayleigh scattering (TDFRS). The investigated saccharides with molar masses between 0.180 and 440 kg mol(-1) were studied in the temperature range between 15 and 55 °C. The thermal diffusion coefficient D(T) and the Soret coefficient S(T) of all solutions increase with increasing temperature. For maltohexaose and the polymers the thermal diffusion coefficient changes sign from negative to positive with increasing temperature, whereas glucose and maltotriose show only positive values in the entire investigated temperature range. While we were able to find a master curve to describe the temperature dependence of D(T), we were not able to find a similar expression for S(T). This comprehensive study allows for the first time the determination of the interaction parameters for the polymer and the solvent within the theoretical framework suggested by Würger [Phys. Rev. Lett., 2009, 102, 078302]. 相似文献