Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance. 相似文献
A practical synthesis of 1,2,3,4,5,6-hexahydro-1,5-imino-10-hydroxy-9-methoxy-3,8,11-trimethyl-3- benzazocin-4-one (3) as an ABC ring model compound of ecteinascidin 743 and safracins from 3-hydroxy-4-methoxy-5-methylbenzaldehyde (7) is described. The overall yield in 15 steps is 27%. 相似文献
Armed crown ethers (1-4) bonding through an amine, amide, ether, or ester linkage to naphthyl group were found to display unique photophysical properties in the presence of guest salts. Complexation of PET fluoroionophores (1a and 1b) with Zn(2+) increased the fluorescence intensities of the host by a factor of 2.4 and 2.7, respectively. (1)H and (13)C NMR analyses of this complexation behavior of 1a revealed that Zn(2+) strongly coordinates with the armed crown nitrogen to cause a dramatic decrease in an intramolecular charge-transfer character. The armed crowns (2 and 3), bonding through an ether or ester linkage to a naphthalene, gave fluorescence quenching with guest thiocyanates. While the amide derivative (4) exhibited high Ba(2+) fluorescence selectivity and in the presence of this cation the host fluorescence intensity was by a factor of 3.69. 相似文献
A series of 9,10-dihydro-9,10-(1,2-tropylio)anthracene tetrafluoroborates has been prepared. The intramolecular charge-transfer interactions in were confirmed by their UV spectra and pKR+ values. As a model compound 1,2,3,4-tetrahydro-1,4-(1,2-tropylio)naphthalene tetrafluoroborate ()_was also examined. 相似文献
Kinetic theory of early stages of coherent clustering and continuous ordering in ordered phase is developed using the concept of concentration waves on the assumption of mean field energy. Linear differential equations of atom diffusion in ordered phase are solved by diagonalizing the coefficient matrix of the equations. It is shown that at the early stages of the reaction the concentration (fluctuation) waves evolve exponentially with respect to time on the sublattices of the ordered phase.The theory is applied to the Fe-10.9 at. %Si alloy which exhibits a sequence of transitions on aging at 775K. It is proved that the first transition from the disordered to the B2 phase occurs purely due to the kinetic reason that the amplification factors of the fluctuation waves have a positive maximum value only at the superlattice point of the B2 structure in the first Brillouin zone of the disordered phase. The second transition, which is from the metastable B2 phase to the stable phase, i.e. the spinodally decomposed D03 phase, is also explained consistently by the present theory that the amplifications calculated in the B2 phase exhibit two positive maxima in the first Brillouin zone. The maximum at point represents the amplification factor of the D03 ordering-wave in the B2 phase, while the other close to the Brillouin zone center represents the amplification factor of the fluctuation wave of the spinodal decomposition. 相似文献
A Ni(0)/ZnCl(2) system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(0) species on enones across the alkyne part followed by ZnCl(2)-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting sigma-alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyclopentane derivatives. On the other hand, a sigma-alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the cleavage of one C-C bond. 相似文献
The irradiation of N-(4-substituted benzoyl)-α-dehydroarylalanine alkyl esters (1) in methanol containing triethylamine (TEA) was found to quantitatively give cis- and trans-4,5-dihydrooxazole derivatives (2), which were described as being formed via electron transfer from TEA to the excited-state (E)-1 followed by kinetically-controlled cyclization of the (E)-1-derived anion radical. A product composition analysis showed that the cis-2/trans-2 composition ratio is greatly varied depending on the stereoelectronic properties of the substituents, the polarity of protic solvents and the concentration of TEA. 相似文献
Two new iridoid glycosides, 7 beta,8 beta-epoxy-8 alpha-dihydrogeniposide (1) and 8-epiapodantheroside (2), were isolated, together with six known (3-8) and three artifact (9-11) iridoids, from the leaves of Gardenia jasminoides cv. fortuneana Hara. Their structures were established based on chemical and spectral data. 相似文献