Nuclear magnetic resonance (NMR) in Y-hexaferrite system (Ba1?xSrx)2Zn2Fe12O22 was measured on both monocrystalline and polycrystalline samples at liquid helium temperature. Corresponding ab-initio calculation of the hyperfine parameters was also performed. The signal from 57Fe was detected in the frequency interval 65–76 MHz, while NMR spectrum of 67Zn nuclei occurs between 15 and 30 MHz. Due to the disorder in two tetrahedral sublattices occupied partly by Zn and partly by Fe, the NMR lines are broad and the spectra are poorly resolved. Comparison between the experimentally observed 67Zn spectra and the spectra modelled using the calculated hyperfine parameters was made. It indicates that the spectra of 67Zn can be used to determine the distribution of Zn and Fe between the two tetrahedral sublattices. 相似文献
This article presents results of near-field scanning optical microscope measurement of local luminescence of rhodamine 3B
intercalated in montmorillonite samples. We focus on how local topography affects both the excitation and luminescence signals
and resulting optical artifacts. The Finite Difference in Time Domain method (FDTD) is used to model the electromagnetic field
distribution of the full tip-sample geometry including far-field radiation. Even complex problems like localized luminescence
can be simulated computationally using FDTD and these simulations can be used to separate the luminescence signal from topographic
artifacts. 相似文献
Polymorphous structure, electrical conductivity, absorption coefficient, refractive index, and mechanical characteristics
of crystalline system ZrO2 + x Sm2O3 (x = 4–43 mol %) is investigated. Vickers microhardness is investigated by the well-known quasi-static indentation method. Plastic
microhardness and the effective elastic modulus are studied by the depth-sensing indentation technique. Special attention
is devoted to the ordered defect fluorite structure, pyrochlore phase Sm2Zr2O7, observed for x = 43 mol %. Potential applications of the investigated system are discussed.
Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 4, pp. 402–411.
The text was submitted by the authors in English. 相似文献
Organic dyes are used in many industries, e.g., textile, cosmetics and food. Hence, contamination of organic dyes to water sources is a critical issue. To reduce water pollution by organic dyes, we propose a paper-like adsorbent with a practical and economical production procedure. Subsequently, a flexible adsorbent was produced using a one-step approach by vacuum filtration of graphene oxide (GO) and iron oxide nanoparticles (Fe3O4-NPs) containing dispersion through a membrane and quoted as GO/Fe3O4 paper. For comparison, GO paper was also prepared using the same procedure. Both papers were characterized using UV–VIS absorption spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, electron diffraction X-ray analysis, X-ray photoelectron spectroscopy, and powder X-ray diffraction techniques. At the steady-state conditions, GO/Fe3O4 and GO papers were performed as adsorbent for cationic dyes of methylene blue, neutral red, and anionic dyes of methyl orange and fluorescein. In general, the removal efficiency of GO/Fe3O4 paper was higher than that of GO paper for adsorption of all dyes and this adsorbent revealed satisfactory adsorption properties for cationic dyes when compared to anionic dyes.
The chiral bicyclic imidazol derivatives 7 and 8 were obtained from D-glucose derivative 9 by a sequence of selective protection/deprotection and intramolecular SN2 reactions. Triols 7 and 8 are analogues of 6-epica-stanospermine ( 4 ) and of 3,7a-diepialexine ( 6 ), respectively, and are potential glycosidase inhibitors. However, their anti-HIV activity proved to be only marginal. 相似文献
A new approach to the synthesis of CDE and BCDE molecular fragments of the limonoids havanensin and azadiradione has been achieved from cyclocitral and drimenal in seven steps in overall yields of 20 and 9%, respectively. 相似文献
Several pairs of diastereoisomeric open-chain 1,2:3,4-diepoxides with different substitution patterns were prepared (see 3–9 ). As far as possible, crystal structures were determined to corroborate the relative configurations and to give insight into the solid-state conformations of these compounds. The comparison with our earlier molecular-orbital calculations and with 1H-NMR measurements shows that the solid-state conformations of eight out of the nine open-chain 1,2:3,4-diepoxides, whose crystal structures had been determined, correspond to minima on the calculated energy profiles for these compounds or for closely related derivatives. In solution, highly substituted diepoxides of the erythro-series (e- 6 , e- 7 , e- 9 ) seem to prefer the same conformation as in the crystal. The solution conformations of all other diepoxides differ from the arrangement in the solid state. 相似文献