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81.
Starting from the vectorial Rayleigh diffraction integral formula and without using the far-field approximation, a solution of the wave equation beyond the paraxial approximation is found, which represents vectorial non-paraxial elliptical Gaussian beams in free space. The far-field expressions for non-paraxial Gaussian beams and elliptical Gaussian beams can be regarded as special cases treated in this paper. Some basic propagation properties of vectorial non-paraxial elliptical Gaussian beams, including the irradiance distribution, phase term, beam widths and divergence angles are studied. Numerical results are given and illustrated. 相似文献
82.
L Jirovetz G Buchbauer W J?ger A Woidich A Nikiforov 《Biomedical chromatography : BMC》1992,6(3):133-134
After inhalation experiments with sandalwood oil and the pure fragrance compounds coumarin and alpha-terpineol, substances were detected and measured in the blood samples of test animals (mice) using gas chromatography/mass spectrometry (GC/MS) (MID) in connection with GC/FTIR (SWC), GC/AES (carbon and oxygen trace) and flame ionization detection/gas chromatography. Using tiglinic acid benzyl ester as the internal standard the following concentrations in serum could be found: alpha-santalol 6.1 ng/mL, beta-santalol 5.3 ng/mL and alpha-santalene 0.5 ng/mL. In separate inhalation experiments with coumarin and with alpha-terpineol the corresponding concentrations were 7.7 ng/mL and 6.9 ng/mL, respectively. 相似文献
83.
Adducts of the conjugate addition of benzylamine to enantiopure amides of aroylacrylic acid possess high enantiomeric and diastereomeric purity. A high degree of stereoselectivity has been achieved by means of crystallization-induced asymmetric transformation. A practical synthesis leading to dipeptides containing homophenylalanine is depicted. 相似文献
84.
Efficient synthesis of ferrocenylenones using a Friedel-Crafts acylation reaction is described. Acryloyl, methacryloyl, crotonoyl, cinnamoyl, and β-methylcrotonoyl chlorides react with ferrocene in the presence of a Lewis acid (EtAlCl2 or EtAlCl2-Me3Al) to give the corresponding ferrocenylenones (acryloyl, methacryloyl, crotonoyl, cinnamoyl, and methylcrotonoylferrocenes) in good isolated yields. Besides ferrocenylenones, chloroactylferrocene is also synthesised by this method. 相似文献
85.
Titanium tetrachloride promoted reaction of silyl ketene acetals with epoxides, followed by acidic work-up, affords butanolides in moderate/good yields. With epihalohydrins the reaction is regioselective and occurs at the less substituted end of the epoxide; the γ-haloalkyl-γ-butanolides thus obtained can be further transformed into various products. 相似文献
86.
The problem of homoaromaticity in mono-, di- and polyfluorinated- homotropylium cations is addressed by the B3LYP/6-311++G** DFT method. The energetic, structural and magnetic criteria are used for this purpose. They convincingly show that the ground state equilibrium species are aromatic, or in other words that the homoaromaticity is preserved by the (poly)fluorination. In contrast, a considerable decrease in the aromatic stabilization is observed in the transition structures (TS). According to the NICS(0) index, they vary form strongly antiaromatic, via weakly and non-aromatic to slightly aromatic transition states. However, the hierarchy of the aromaticity in fluorinated homotropylium ions predicted by NICS(0) is completely unrelated to that obtained by using the energy criterion assuming a kinetic definition of aromaticity. On the other hand the latter is closely related to geometric parameters of the equilibrium and transition structures. 相似文献
87.
88.
Inés CarrancoJosé Luis D?&#x;az Oscar JiménezRodolfo Lavilla 《Tetrahedron letters》2003,44(46):8449-8452
The Lewis acid-catalyzed interaction of dihydropyridines with ethyl glyoxalate and primary aliphatic amines yields, depending on the reaction conditions, bicyclic aminals or rearranged tetrahydropyridines in one-pot multicomponent reactions. 相似文献
89.
Gravimetric measurements of thermodesorption of n-hexane and n-heptane were performed under quasi-equilibrium conditions. Differential thermodesorption profiles for ZSM-5 and ZSM-11 showed two peaks, but for Y zeolites, only one thermodesorption peak was observed. A model function, derived from the Langmiur adsorption model, was fitted to the experimental data, and the model parameters (the adsorption entropy and enthalpy) were estimated. The two-step desorption profiles observed for ZSM-5 and ZSM-11 were attributed to the commensurate freezing effect, i.e. a transition in the adsorbed phase resulting in ordering of the adsorbed molecules in the zeolite channels. The results observed for ZSM-11 indicate that the zigzag channels typical for ZSM-5 micropore system are not necessary for this transition to occur. 相似文献
90.
Ziqing Duan Xiaofeng Wang Danfeng Yang Xiaoming Pan Pingchu Wang 《Solid State Communications》2005,134(8):559-563
0.65Pb(In1/2Nb1/2)O3-0.35PbTiO3 (PINT65/35) (starting composition) single crystals were grown successfully through the solution Bridgman technique using PbO flux and PMNT67/33 seed crystals. Because of the composition variation, the final composition of achievable crystals is in a range of 0.32-0.34 with the corresponding Tc range of 265-269 °C. The (001) plates of as-grown PINT66/34 single crystals show high Curie temperature (Tc=269 °C) and rhombohedral-tetragonal phase transition temperature (Trt=134 °C). Besides, good electrical properties with high dielectric constant (ε>3000), low dielectric loss (tan δ∼1.2%), high piezoelectric constant (d33∼2000 pC/N) and large electromechanical coupling factor (kt≈59%) at room temperature have been obtained on the (001) plates. The sound velocity, acoustic impedance and other piezoelectric parameters were also measured on the (001) plates in this study, which provide us more detailed information about PINT66/34 single crystals. 相似文献