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31.
Aleksander S. Golub Aleksander S. Popel Lei Zheng Roland N. Pittman 《Photochemistry and photobiology》1999,69(6):624-632
Analysis of phosphorescence lifetimes using the Stern-Volmer equation is a reliable means of determining quencher concentration for a uniform sample. Methods of analysis for heterogeneous systems are based on the assumption that the excitation is produced by a momentary flash. This condition is an idealization because a real flash has a finite duration and a complex time profile. In the case of a heterogeneous quencher concentration, an excitation flash produces different initial intensities and different times of peak intensity from compartments having different concentrations of quencher. We formulated a model to explore the effects of flash duration on the shape of the emission curve obtained from systems in which the heterogeneity is continuous. We developed mathematical models that can be used to recover fitting parameters of continuous distributions of reciprocal lifetimes approximated as rectangular or Gaussian distributions, or an arbitrary histogram. We also formulated a procedure to convert the distribution of reciprocal lifetimes into a volume distribution of quencher concentration. We found that (1) the Stern-Volmer ratio of phosphorescence intensities cannot be employed for interpretation of pulse phosphorometric data in terms of a volume distribution of quencher; (2) shortening the flash duration decreases the difference of initial intensities between compartments having high and low quencher concentration; (3) the parameters of the volume distribution of quencher concentration can be recovered correctly only after taking account of the difference in initial intensities; and (4) calibration of the initial intensities for a given fitting delay and flash function is necessary. 相似文献
32.
This paper describes a new approach to the problem of computing spherical expansions of zonal functions on Euclidean spheres.
We derive an explicit formula for the coefficients of the expansion expressing them in terms of the Taylor coefficients of
the profile function rather than (as done usually) in terms of its integrals against Gegenbauer polynomials. Our proof of
this result is based on a polynomial identity equivalent to the canonical decomposition of homogeneous polynomials and uses
only basic properties of this decomposition together with simple facts concerning zonal harmonic polynomials. As corollaries,
we obtain direct and apparently new derivations of the so-called plane wave expansion and of the expansion of the Poisson
kernel for the unit ball.
Received: 26 January 2007 相似文献
33.
Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution 下载免费PDF全文
Aleksander Kufelnicki Jolanta Jaciubek‐Rosińska Marta Sobiesiak Agata Paneth Julia Jezierska Elzbieta Budzisz 《无机化学与普通化学杂志》2017,643(16):1067-1074
The study reports the synthesis of complexes Co(HL)Cl2 ( 1 ), Ni(HL)Cl2 ( 2 ), Cu(HL)Cl2 ( 3 ), and Zn(HL)3Cl2 ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the CuII complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the ZnII ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine CoII, NiII, and ZnII complexes in 10/90 (v/v) DMSO/water solution, whereas the CuII complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with CoII, NiII and ZnII, the 2:1 species with CoII and ZnII, and the 3:1 species with ZnII. A distorted tetrahedral arrangement of the CuII complex was suggested on the basis of EPR and Vis/NIR spectra. 相似文献
34.
Alexander S. Antonov Svetlana G. Kachalkina Alexander F. Pozharskii Gennady S. Borodkin Aleksander Filarowski 《Tetrahedron》2017,73(25):3452-3457
A novel approach to pyrrole ring closure in 2-trifluoroacetyl- and 2-ethoxycarbonyl-1,8-bis(dimethylamino)naphthalenes via treatment with 2-lithium-1,8-bis(dimethylamino)naphthalene producing the corresponding benzo[g]indole derivatives, was examined with different alkyl- and aryllithium compounds as well as with LDA. It was found that the highest yields of benzo[g]indoles (up to 70%) are obtained with aryllithium reagents when they contain NMe2 group in ortho-position to the carbanionic centre. In all other cases the formation of acyclic alcohol arising from ordinary intermolecular addition of the carbanion to the CO group strongly prevails. The dramatic facilitation of deprotonation of the N-Me group in substrate followed by pyrrolic cyclization in the case of 2-lithium-N,N-dimethylanilines was explained through a specific structure of the reaction transition state. 相似文献
35.
In this paper we study ergodic properties of some classes of anomalous diffusion processes. Using the recently developed measure of dependence called the Correlation Cascade, we derive a generalization of the classical Khinchin theorem. This result allows us to determine ergodic properties of Lévy-driven stochastic processes. Moreover, we analyze the asymptotic behavior of two different fractional Ornstein–Uhlenbeck processes, both originating from subdiffusive dynamics. We show that only one of them is ergodic. 相似文献
36.
Nevenka Rajic Djordje Stojakovic Aleksander Recnik 《Journal of Physics and Chemistry of Solids》2011,72(6):800-803
Nanoparticles of NiO, ZnO and Cu2O crystallize when the Ni-, Zn- and Cu-exchanged natural clinoptilolite, respectively, are dehydrated by heating in air at 550 °C. The dehydration of Mn-exchanged clinoptilolite does not lead to the crystallization of manganese oxide but affects the crystallinity of the host clinoptilolite lattice, which becomes amorphous. The NiO, ZnO and Cu2O nanoparticles are found to be randomly dispersed in the clinoptilolite matrix. The particle size varies from 2 to 5 nm and exceeds the aperture of the clinoptilolite channel (approximately 0.4 nm), suggesting that the crystallization of the oxide phases takes place on the surfaces of clinoptilolite microcrystals. 相似文献
37.
Dmitry A. Sibgatulin Dmitry M. Volochnyuk Aleksander N. Kostyuk Sergey P. Ivonin Andriy V. Lapandin 《Monatshefte für Chemie / Chemical Monthly》2009,13(4):639-643
Abstract
The reaction of push–pull enamines with 1,2-biselectrophilic phenylglyoxal was investigated. Phenylglyoxal was found to react depending on the structure of the push–pull enamine, affording either a hydroxyalkylation product at the methyl group or the cyclic product via participation of the methyl group and the β-carbon of the enamine. 相似文献38.
Ewa Katzenellenbogen Nina A. Kocharova Georgy V. Zatonsky Maria Bogulska Danuta Witkowska Aleksander S. Shashkov 《Journal of carbohydrate chemistry》2013,32(5):545-558
ABSTRACT Lipopolysaccharide (LPS) of Hafnia alvei 23 has an acid-labile O-specific polysaccharide (OPS) with a pentasaccharide-phosphate repeating unit containing D-Glc1P, D-GlcNAc, L-Fuc, 6-deoxy-D-talose (D-6dTal), 4-acetamido-4,6-dideoxy-D-glucose (D-Qui4NAc), and an O-acetyl group. A partially degraded OPS was obtained by hydrolysis of LPS with 0.25 M sodium acetate in aqueous 0.5% acetic acid. Fractionation of LPS on Sephadex G-200 in DOC buffer allowed isolation of long-chain LPS species which, together with OPS, were studied by methylation analysis, chemical degradations (O-deacetylation, dephosphorylation with 48% hydrofluoric acid, Smith degradation), and 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, NOESY, and H-detected 1H,13C heteronuclear single-quantum coherence (HSQC) experiments. The following structure of the repeating unit of OPS was established: 相似文献
39.
Aleksander A. Kubicki Piotr Bojarski Marek Grinberg Micha? Sadownik Benedykt Kukliński 《Optics Communications》2006,263(2):275-280
Apparatus to study time-evolution of emission spectra over very wide time and spectral range is described. Excitation part of the equipment consists of solid state Nd:YAG laser and optical parametric generator. The heart of the detection system consists of spectrograph and streak camera. The significance of optics and electronics built in the system for proper, fast and convenient measurements is underlined. The results of donor-acceptor energy transfer in a rigid polyvinyl alcohol matrix serve here as an example of application our equipment to study complex systems. 相似文献
40.