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排序方式: 共有282条查询结果,搜索用时 31 毫秒
81.
Alexiane Thevenet Dr. Radu Custelcean Dr. Bruce A. Moyer Dr. Santa Jansone-Popova 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(63):14290-14294
Cooperativity effects among the interconnected anion and cation binding sites can profoundly alter the performance of heteroditopic receptors in selective ion pair recognition, processes that are oftentimes pertinent to biological systems and chemical separations. This work reports the effect of the linker that connects both binding sites on self-assembly of heteroditopic receptors in the presence of divalent first-row transition metal salts in solution and solid phase. Introduction of backbone flexibility in the receptor results in the formation of triple-stranded ion-pair helicates with an extraordinary selectivity towards CuSO4 through an anion-induced fit. 相似文献
82.
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84.
This study focuses on the flow modifications generated by a flat plate stabilizer placed downstream of a half-cylinder compared to the wake formation without the plate. For moderate Reynolds number, a snapshot proper-orthogonal-decomposition method based on particle-image-velocimetry (PIV) is used to analyze the complex dynamics of the flows and to highlight typical swirl formation mechanisms. Using this tool, the near-wake structures, the kinetic aspects, the energy contributions, the degree of organization of the structures and their temporal behaviour are identified. A strong link between the Strouhal number, the mean vorticity and the Total Energy is observed. The interference of the shear layer with the stabilizer has an atypical influence on the wake characteristics. 相似文献
85.
Csaba-Pal Racz Szabolcs Santa Maria Tomoaia-Cotisel Gheorghe Borodi Irina Kacso Adrian Pirnau Ioan Bratu 《Journal of inclusion phenomena and macrocyclic chemistry》2013,76(1-2):193-199
The inclusion of α-lipoic acid (LA) in β-cyclodextrin (β-CD) by increasing the aqueous solubility and photostability can enhance its medicinal use in the oral administration. Different preparation methods were employed to obtain an α-lipoic acid-β-cyclodextrin (LA-β-CD) inclusion complex and to determine the physical–chemical characteristics and the interactions present in this compound. The formation of the solid inclusion compound was confirmed by X-ray powder diffraction, differential scanning calorimetry (DSC) and infrared spectroscopy (FTIR). FTIR and DSC data confirm the new obtained compound. The crystalline structure of this compound belongs to the monoclinic system with four molecules in the unit cell. 1H NMR spectroscopic method was employed to study the inclusion process in aqueous solution. Job plots derived from the 1H NMR spectral data demonstrated an 1:1 stoichiometry of the inclusion complex in liquid state. 2D NMR data suggest the orientation of LA with the carboxyl group near to narrower rim of the β-CD. 相似文献
86.
Dr. Simone Di Motta Dr. Tommaso Avellini Dr. Serena Silvi Prof. Margherita Venturi Dr. Xiang Ma Prof. He Tian Prof. Alberto Credi Prof. Fabrizia Negri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(9):3131-3138
The photophysical properties of a multicomponent [1]rotaxane bearing a β‐cyclodextrin ring covalently connected to an axle comprising an azobenzene photoisomerisable moiety and a naphthalimide‐type fluorescent stopper are investigated by a combined experimental and computational study. The absorption and fluorescence spectra, and particularly the induced circular dichroism (ICD) signal, are determined. The latter shows a sign relation that cannot be rationalised in terms of the simple general rules commonly employed to analyse the ICD spectra of achiral guests encircled by chiral hosts. To assist the interpretation of experimental results, DFT and time‐dependent (TD) DFT calculations are performed to explore the availability of low‐energy conformations and to model their spectroscopic response. Molecular dynamics simulations performed in water show the interconversion of a number of conformers, the contribution of which to the ICD signal is in agreement with the observation. 相似文献
87.
Wang Y Di Motta S Negri F Friedlein R 《Journal of the American Chemical Society》2011,133(26):10054-10057
The electronic structure of highly crystalline picene films with a standing-up orientation grown epitaxially on the Ag(110) surface was investigated. Upon exposure to oxgen gas, O(2) molecules incorporate at the interstitial sites within the a-b plane of the film. Features related to the highest three occupied molecular orbitals shift toward a lower binding energy which results in the inactivation of traps and the reduction of the charge injection barrier by about 1 eV. It is suggested that the highest two picene orbitals are inverted due to the strong interactions between the singly occupied oxygen π orbital and the highest occupied orbital of picene. 相似文献
88.
Enhanced luminescence and degradation resistance in Tb modified Yttrium Borate core-nano silica shell phosphor under UV and VUV excitation 总被引:1,自引:0,他引:1
Santa Chawla RavishankerA.F. Khan Ashish YadavH. Chander V. Shanker 《Applied Surface Science》2011,257(16):7167-7171
Composition variation in optimized solid state reaction conditions has been done to achieve intense green emission in YTbxBO3 phosphor under UV and VUV (147 nm resonant Xe*, 172 nm Xe2* excimer band) excitation. Inert interface layer created by fabricating a shell of silica nanoparticles over individual phosphor grain protected the phosphor surface from deterioration and oxidation of luminescent ion (Tb3+) thus completely arresting phosphor degradation. At optimum Tb content of 20 mol%, integrated photoluminescence intensity of developed YTbxBO3 phosphor is four times higher than commercial green YBT. With short decay time of 4 ms, YTbxBO3 core-nano silica shell green emitting phosphor has great application potential in PDP panel and phosphor coated Xe lamps. 相似文献
89.
Bruno Pereira Motta Anderson Kiyoshi Kaga Juliana Oriel Oliveira Maiara Destro Inacio Cledson Ferreira da Silva Paulo Teixeira de Sousa Junior 《Natural product research》2020,34(16):2389-2393
Abstract Long-term hyperglycemia maintenance is responsible for increased protein glycation and formation of advanced glycation end products (AGEs), both are associated with the onset of diabetes mellitus complications. Efforts have been made to discover new agents having antiglycation potential. The aim of this study was to investigate the effects of the hydroethanolic extract and the ethyl acetate and methanolic fractions of Simaba trichilioides roots on the formation of AGEs. In an in vitro model system of protein glycation, incubations with hydroethanolic extract, ethyl acetate or methanolic fractions of S. trichilioides decreased the fluorescent AGEs, and markers of tyrosine and tryptophan oxidation. Protein crosslinking was reduced in the presence of the ethyl acetate fraction of S. trichilioides. Simaba trichilioides roots seem to be a promising source of compounds having ability to prevent glycoxidation changes, with potential applications in complementary therapies for management of diabetic complications. 相似文献