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231.
Yamamoto Y Saigoku T Nishiyama H Ohgai T Itoh K 《Organic & biomolecular chemistry》2005,3(9):1768-1775
In the presence of catalytic amounts of Cp*RuCl(cod), the partially intramolecular cyclotrimerizations of various C-alkynylglycosides and C-diynylglycosides proceeded at ambient temperature to afford C-arylglycosides. 相似文献
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Masahiro HonmaMasahisa Nakada 《Tetrahedron letters》2003,44(50):9007-9011
Catalytic asymmetric synthesis of some new chiral building blocks useful for natural product synthesis is described. The intramolecular cyclopropanation (IMCP) reaction of α-diazo-β-keto sulfones affording bicyclo[4.1.0]heptanes such as 9a-d is found to proceed with high enantioselectivity (93-98% ee). The yield is moderate due to the competing intramolecular C-H insertion reaction. As intramolecular C-H insertion reaction is not observed in the reaction of the substrates possessing a quaternary carbon at the allylic position, the reactions of 19a and 19b proceed with high enantioselectivity (95% ee) and yield. It was also found that the substrates possessing an ether group, such as 19a and 19b, could be used in this enantioselective IMCP reaction. 相似文献
234.
With respect to the quasi-one dimensionality of single crystals of Nb3Se4, the electrical resistivity from 1.3 to 320 K and the critical magnetic field for superconductivity are measured. The resistivity along the Nb-chain direction is represented as a sum of a temperature independent and an intrinsic temperature dependent term. The temperature dependence of the intrinsic resistivity subjects to T3 form between 10 and 80 K above which it tends to a T linear form. The critical magnetic field is proportional to the temperature difference from the transition temperature. Its dependence is well fitted by the elliptical fluxoid model of Ginzburg-Landau theory. The ratio of the parallel and the perpendicular to the c-axis is 5.7. 相似文献
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K. Doroba D. Drijard H. G. Fischer H. Frehse W. Geist R. Gokieli P. Hanke M. Heiden W. Herr W. Hofmann P. G. Innocenti E. E. Kluge J. W. Lamsa T. Lohse W. T. Meyer G. Mornacchi T. Nakada M. Pamter A. Putzer K. Rauschnabel R. Sosnowski J. Spengler O. Ullaland D. Wegener 《Zeitschrift fur Physik C Particles and Fields》1984,24(1):31-37
Events with a single highp T charged particle were recorded with the Split-Field-Magnet Detector in proton-proton collisions at the CERN-ISR. In the jet opposite to the trigger region the densities of photons and reconstructed neutral pions were measured with a liquid argon shower counter. Scaled momentum distributions of these particles are given and compared with those of charged pions. The spectra of charged and neutral pions coincide. The production cross-section of neutrals in the away jet shows no dependence on the flavour of the trigger particle. 相似文献
237.
Takenaka K Nakada K Osuka A Horii S Ikuta H Hirabayashi I Sugai S Mizutani U 《Physical review letters》2000,85(25):5428-5431
The optical spectra of PrBa2Cu4O8 show large in-plane anisotropy. For the a polarization (E perpendicular chain), the spectrum is characterized by a gap of 1.4 eV, indicating the charge-transfer insulating nature of the CuO2 planes. For the metallic chain direction (E // b), the spectrum deviates from a simple Drude response; reflectivity R(b)(omega) shows a sharp edge at approximately 1 eV but it also shows a dip at approximately 15 meV, which splits the conductivity spectrum into two parts--a zero-energy mode with small weight and a pronounced 40 meV mode. These features are discussed in terms of a Tomonaga-Luttinger liquid in a doped 1D Mott insulator and compared with 1D Bechgaard salts. 相似文献
238.
An automated testing and taping process on a LSI production system is modelled as a variant of M/G/1 finite capacity queue with multiple transactions, where each package receives either a normal service or normal service plus postservice. The system has N spaces for waiting. We successfully define states of system to regard as those of a Markov renewal process even though some time points are not regeneration points. Using the model, we derive properties of stochastic behaviour of the system, in particular, throughput, process of overflows, busy period, and idle period as cost-effective tools for system evaluation. 相似文献
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