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排序方式: 共有578条查询结果,搜索用时 796 毫秒
91.
Yuriy S. Marfin Olga S. Vodyanova Dmitry A. Merkushev Sergey D. Usoltsev Vladislav O. Kurzin Evgeniy V. Rumyantsev 《Journal of fluorescence》2016,26(6):1975-1985
Four boron-dipyrrine (BODIPY) based dyes with π-extended substituents in 8-position of dipyrrin ligand have been synthesized and characterized. Photophysical properties of the obtained compounds have been investigated in different individual solvents. Deposits of solvent polarity and viscosity were evaluated. BODIPY with 8-biphenyl substituent was found to be the fluorescent molecular rotor in contrast to more extended substituents. The complex nature of solvent-solute interactions leads to the poor applicability of standard multiparameter approaches to BODIPY solvatochromic properties. Fluorescence intensity was found to increase in case of solvent polarity growth, it is not typical for BODIPY. Taking that into account the BODIPY with π-extended substituents could be used for fluorescence viscosity measurements, and as the fluorescent media polarity indicators in analytical chemistry and biochemistry. 相似文献
92.
Presented here is a new approach for analysis of the so-called holey photonic crystals—a class of electro-optical components, in which periodicity of air holes in dielectric media is used for confinement of light. This class includes several kinds of microstructured fibers, semiconductor lasers etc. Accurate evaluation of optical characteristics of those devices is usually a complicated problem due to the large dimensions and the fine structure of their refractive index distribution. Furthermore, usually, only numerical solutions for this class of optical components are available. The overwhelming majority of the physical models, suitable for analysis of holey photonic devices, proceed from the “natural” assumption: the devices are considered as arrays of air holes, surrounded by dielectric material. In this work we propose another model. Namely, we treat them as arrays of dielectric spots (waveguides), embedded in the air (cladding material). This model allows utilization of the extended coupled-mode theory (a relatively new approach designed for analysis of infinite arrays of coupled waveguides and previously considered inapplicable to holey optical components) for calculations of the latter. In this sense, we present a new method for analysis of holey photonic crystals. On the one hand, our method allows analytical evaluation of some optical characteristics of holey optical components (such as the number of photonic bands and bandwidth). On the other hand, accurate numerical computation of the photonic band structure of the holey photonic devices, incorporating a large number of holes, can be done with this technique on a timescale of several minutes. 相似文献
93.
Dana Moravcová Vladislav Kahle Helena Řehulková Jan Chmelík Pavel Řehulka 《Journal of chromatography. A》2009,1216(17):3629-3636
This study records a novel application of methacrylate-based monolithic columns for MALDI-TOF/TOF MS analyses in proteomics for pre-concentration and separation of peptides derived from protein digestion. Reversed-phase monolithic capillary columns (30 mm × 0.32 mm i.d.) were created inside the fused silica capillary via thermal-initiated free-radical polymerization of ethylene glycol dimethacrylate and lauryl methacrylate monomers in the presence of 1-propanol and 1,4-butandiol as a porogen system. The elution of peptides was achieved using a linear gradient of acetonitrile from 0 to 60% in water with 0.1% trifluoroacetic acid formed in a microsyringe. Individual fractions of separated peptides were collected on the MALDI target spots covered with alpha-cyano-4-hydroxycinnamic acid used as a matrix and then they were analyzed using MALDI-TOF/TOF mass spectrometry. The developed method was tested with a mixture of tryptic peptides from bovine serum albumin and its applicability was also tested for tryptic in-gel digests from barley grain extracts of water soluble proteins separated using SDS gel electrophoresis. The number of detected peptides was approximately three to four times higher compared to the analysis without previous separation. These results show an improved quality of sample information with the higher amount of identified peptides which increased protein sequence coverage and improved sensitivity of mass spectrometry measurements. 相似文献
94.
Georg Süss-Fink Farooq-Ahmad Khan Julien Boudon Vladislav Spassov 《Journal of Cluster Science》2009,20(2):341-353
The cationic organometallic aqua complexes formed by hydrolysis of [(C6H6)2RuCl2]2 in water, mainly [(C6H6)Ru(H2O)3]2+, intercalate into white sodium hectorite, replacing the sodium cations between the anionic silicate layers. The yellow hectorite
thus obtained reacts in water with molecular hydrogen (50 bar, 100 °C) to give a dark suspension containing a black hectorite
in which large hexagonally shaped ruthenium nanoparticles (20–50 nm) are intercalated between the anionic silicate layers,
the charges of which being balanced by hydronium cations. If the reduction with molecular hydrogen (50 bar, 100 °C) is carried
out in various alcohols, spherical ruthenium nanoparticles of smaller size (3–38 nm depending on the alcohol) are obtained.
In alcohols other than methanol, the reduction also works without H2 under reflux conditions, the alcohol itself being the reducing agent; the ruthenium nanoparticles obtained in this case are
spherical and small (2–9 nm) but tend to aggregate to form clusters of nanoparticles. Whereas the ruthenium nanoparticles
prepared by reduction of the yellow hectorite in refluxing alcohols without hydrogen pressure are almost inactive, the nanoparticles
formed by hydrogen reduction catalyze the hydrogenation of benzene to give cyclohexane under mild conditions (50 °C) with
turnover frequencies up to 6500 catalytic cycles per hour, the best solvent being ethanol.
Dedicated to Professor C. N. R. Rao, pioneer of nanocluster chemistry, on the occasion of his 75th birthday. 相似文献
95.
Gordeeva LG Glaznev IS Savchenko EV Malakhov VV Aristov YI 《Journal of colloid and interface science》2006,301(2):685-691
The effect of a "guest-host" interaction on the phase composition and sorption properties of the composite sorbents "salt in a porous host matrix" has been studied. The matrix was a mesoporous silica of KSK type, while the confined salts were CaCl(2), CuSO(4), MgSO(4), and Na(2)SO(4). Both structure and properties of the composites were studied by X-ray diffraction, titration in the pH range of 2-9, differential dissolution, and TG techniques. Chemical interaction between the silica surface and the salt during preparation results in the formation of the salt surface complexes and stabilization of the dispersed salt in two phases, namely, a crystalline phase and an X-ray amorphous phase. The water sorption properties of the composites depend on the phase composition and can be intently modified by using variation of the preparation conditions. 相似文献
96.
Leonid N. Bochkarev Vladislav I. Scherbakov Irina P. Malysheva Galina V. Basova Natalia E. Stolyarova Irina K. Grigorieva Andrey L. Bochkarev Georgii K. Fukin Yurii A. Kurskii Gleb A. Abakumov 《Journal of organometallic chemistry》2006,691(5):983-986
The novel silicon-, germanium- and tin-containing imido alkyl complexes of tungsten of the type (ArN)2W(CH2EMe3)2 (; E = Si (1), Ge (2), Sn (3)) have been prepared by the reactions of (ArN)2WCl2(dme) (dme = 1,2-dimethoxyethane) with heteroelement-containing alkyllithium or Grignard reagents Me3ECH2Li (E = Si, Ge), Me3ECH2MgCl (E = Ge, Sn). The title compounds were isolated in high yields as crystalline solids and characterized by elemental analysis, IR, 1H, 13C, 29Si and 119Sn NMR spectroscopy and X-ray diffraction studies. The geometry of the W atoms in the compounds can be described as a distorted tetrahedron. 相似文献
97.
Sosnovskikh VY Korotaev VY Chizhov DL Kutyashev IB Yachevskii DS Kazheva ON Dyachenko OA Charushin VN 《The Journal of organic chemistry》2006,71(12):4538-4543
Polyhaloalkyl-substituted chromones, gamma-pyrones, and beta-furanones react with salicylaldehydes in the presence of piperidine to give a wide variety of fused 2H-chromenes in good yields. This novel annulation reaction presumably proceeds by a tandem intermolecular oxa-Michael addition and subsequent intramolecular Mannich condensation. 相似文献
98.
Dolník V 《Electrophoresis》2006,27(1):126-141
This review article with 304 references describes recent developments in CE of proteins, and covers the two years since the previous review (Hutterer, K., Dolník, V., Electrophoresis 2003, 24, 3998-4012) through Spring 2005. It covers topics related to CE of proteins, including modeling of the electrophoretic migration of proteins, sample pretreatment, wall coatings, improving separation, various forms of detection, special electrophoretic techniques such as affinity CE, CIEF, and applications of CE to the analysis of proteins in real-world samples including human body fluids, food and agricultural samples, protein pharmaceuticals, and recombinant protein preparations. 相似文献
99.
Thalictrum is an important plant genus that is widely used in traditional medicine. In this review considerable attention has been given to triterpenoid saponins in connection with their specific distribution in the Thalictrum genus and with their biological activity. All other non-alkaloid compounds isolated from the Thalictrum genus are also reviewed; these metabolites are discussed in relation to their structural features and to their role in the plants. 相似文献
100.
Petrov GI Shcheslavskiy VI Yakovlev VV Golovan LA Krutkova EY Fedotov AB Zheltikov AM Timoshenko VY Kashkarov PK Stepovich EM 《Optics letters》2006,31(21):3152-3154
Anisotropic photonic crystal structures consisting of birefringent porous silicon layers with alternating porosity were fabricated. The in-plane birefringence formed as a result of anisotropic etching in Si(110) results in unique multilayered structures with two distinct photonic bandgaps for orthogonal light polarizations. Nonlinear optical studies based on the third-harmonic generation from these structures demonstrate variation in the symmetry of the nonlinear optical response. 相似文献