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811.
The conversion of cyclic Baylis–Hillman acetates 1 into the corresponding cyano derivatives 2 was achieved using potassium cyanide in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) in aqueous medium. The obtained Michael acceptors 2 easily add primary amines in absolute ethanol to produce a new family of 1,2,3-trisubstituted cyclpentanes 3 in good yields. 相似文献
812.
N. Azami A. SaÏssy M. P. De Micheli G. Monnom D. B. Ostrowsky P. Mollier 《Fiber and Integrated Optics》2013,32(3):221-229
Wavelength tunability of an Er3+-doped fiber laser is reported by the use of an integrated optics Mach-Zehnder interferometer driven electro-optically. A pump laser threshold of 5 mW and a continuous tunable band from 1530 nm to 1554 nm are achieved with a drive voltage varying between 0 to +7 volts. An evaluation of the design and improvements are given based on the experimental and theoretical analysis. 相似文献
813.
Thøgersen L Olsen J Yeager D Jørgensen P Sałek P Helgaker T 《The Journal of chemical physics》2004,121(1):16-27
The trust-region self-consistent field (TRSCF) method is presented for optimizing the total energy E(SCF) of Hartree-Fock theory and Kohn-Sham density-functional theory. In the TRSCF method, both the Fock/Kohn-Sham matrix diagonalization step to obtain a new density matrix and the step to determine the optimal density matrix in the subspace of the density matrices of the preceding diagonalization steps have been improved. The improvements follow from the recognition that local models to E(SCF) may be introduced by carrying out a Taylor expansion of the energy about the current density matrix. At the point of expansion, the local models have the same gradient as E(SCF) but only an approximate Hessian. The local models are therefore valid only in a restricted region-the trust region-and steps can only be taken with confidence within this region. By restricting the steps of the TRSCF model to be inside the trust region, a monotonic and significant reduction of the total energy is ensured in each iteration of the TRSCF method. Examples are given where the TRSCF method converges monotonically and smoothly, but where the standard DIIS method diverges. 相似文献
814.
Infrared absorption intensities of fundamental bands of chloroacetone CH3COCH2Cl have been measured in carbon disulphide solution, and intensity data have been analysed to determine the energy difference between the rotational isomers by applying the absolute intensity method. The value determined for the energy difference is in good agreement with that obtained by the temperature variation method. Further, in order to determine the dihedral angle of the gauche isomer, normal frequencies and absolute band intensities have been computed for various rotational angles and compared with observed values. As a result, the gauche dihedral angle has been determined as 150° ± 10°, which is in good agreement with that obtained by previous authors. 相似文献
815.
L-半胱氨酸的停流流动注射动力学快速测定法 总被引:1,自引:0,他引:1
利用L-半胱氨酸可还原Fe(3+),使之生成Fe(2+)-邻菲 啉有色络合物的反应,建立了L-半胱氨酸的停流流动注射动力学分光光度测定的新方法。该法简便、灵敏、快速、准确、选择性高,检测限为16mg/L,分析频率达30样/h。取L-半胱氨酸浓度为160mg/L时,测量的相对标准偏差为0.55%(n=6)。实际样品加标回收率达98.7%。 相似文献
816.
Argon matrix infrared spectra of the complexes formed between formohydroxamic acid, HCONHOH (FHA) and nitrogen have been recorded. The experimental results indicate formation of two isomeric complexes in which the nitrogen atom of the N2 molecule is attached to the NH or OH groups of FHA. Theoretical studies of the structure and spectral characteristics of the complexes were carried out on the MP2 level with the 6-311++G(2d,2p) basis set. The calculated vibrational frequencies for the complexes present in the matrices are in good agreement with the experimental data. 相似文献
817.
Rizzo A Cappelli C Jansík B Jonsson D Sałek P Coriani S Wilson DJ Helgaker T Agren H 《The Journal of chemical physics》2005,122(23):234314
A series of electric and magnetic properties of hexafluorobenzene have been calculated, including the electric dipole polarizability, magnetizability, electric quadrupole moment, and nonlinear mixed electric dipole-magnetic dipole-electric quadrupole hyperpolarizabilities needed to obtain estimates of the Kerr, Cotton-Mouton, Buckingham, Jones, and magnetoelectric birefringences in the vapor phase. Time-dependent density-functional theory was employed for the calculation of linear-, quadratic, and cubic response functions. A number of density functionals have been considered, along with Sadlej's triple-zeta basis set and the augmented correlation-consistent polarized valence double zeta and augmented correlation-consistent polarized valence triple zeta basis sets. Comparisons have been made with experiment where possible. The analysis of results allows for an assessment of the capability of time-dependent density-functional theory for high-order electromagnetic properties of an electron-rich system such as hexafluorobenzene. 相似文献
818.
Jean-Michel Gaullier Marc Gèze René Santus Teresa Sa e. Melo Jean-Claude Mazière Marc Bazin Patrice Morlière Louis Dubertret 《Photochemistry and photobiology》1995,62(1):114-122
Abstract— The subcellular localization of protoporphyrin (PP) has been studied by microspectrofluo-rometric techniques in NCTC 2544 keratinocytes incubated with 5-aminolevulinic acid (ALA) for times up to 42 h. Whereas the plasma membrane shows strong staining, fluorescent spots are observed within the cytoplasm especially in the perinuclear region. Although the topographic pattern of the PP distribution does not change much with the incubation time with ALA, the fluorescence spectra suggest that the PP microenvironments are quite different at short and long incubation times. Addition of 18 uJW desferoxamine almost doubles the ALA-induced PP concentration. Colocalization experiments with rhodamine 123, a mitochondrial probe, and lucifer yellow (LY) or neutral red (NR), two lysosome probes, demonstrate that at least some of these spots are of lysosomal origin. Study of the time evolution of the NR fluorescence under irradiation with visible light in the presence and absence of ALA demonstrates that lysosomes are damaged in cells that have synthesized PP. No PP fluorescence can be detected in mitochondria after incubation with ALA. However, photosensitization of mitochondria occurs under irradiation with visible light. Very little formation of lipofuscins by photosensitization with exogenous PP or ALA-induced PP is observed with the NCTC 2544 keratinocytes, as compared to normal human fibroblasts. 相似文献
819.
Rodríguez G Cid MM Saá C Castedo L Domínguez D 《The Journal of organic chemistry》1996,61(8):2780-2782
The alkaloid lennoxamine (1) was synthesized by transannular cyclization of a 10-membered lactam obtained by intramolecular addition of an aryl radical to a (trimethylsilyl)acetylene. The isoindolo[1,2-b][3]benzazepine skeleton present in lennoxamine was also obtained by means of regioselective 7-endo-trig radical cyclization of methylenephthalimidines. 相似文献
820.
[reaction: see text]. A new approach to carbazoles and benzannulated carbazoles by means of intramolecular dehydro Diels-Alder reactions of ynamides is reported. By using this approach, carbazoles and benzo[b]-, tetrahydrobenzo[b]-, naphtho[1,2-b]-, naphtho[2,1-b]-, and dibenzo[a,c]carbazoles have been prepared in moderate-to-good yields. 相似文献