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61.
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Leonid G. Sokoletsky Olga V. Nikolaeva Leonid P. Bass Victor S. Kuznetsov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(13):1132-5779
Several numerical and analytical solutions of the radiative transfer equation (RTE) were compared for plane albedo in a problem of solar light reflection by sea water. The study incorporated the simplest case—a semi-infinite one-dimensional plane—parallel absorbing and scattering homogeneous layer illuminated by a monodirectional light beam. Inelastic processes (such as Raman scattering and fluorescence), polarization and air-water surface refraction-reflection effects, were not considered. Algorithms were based on the invariant imbedding method and two different variants of the discrete ordinate method (DOM). Calculations were performed using parameters across all possible ranges (single-scattering albedo ω0 and refracted solar zenith angle θ1), but with a special emphasis on natural waters. All computations were made for two scattering phase functions, which included an almost isotropic Rayleigh phase function and strongly anisotropic double-peaked Fournier-Forand-Mobley phase function. Models were validated using quasi-single-scattering (QSSA) and exponential approximations, which represent the extreme cases of ω0→0 and ω0→1, respectively. All methods yielded relative differences within 1.8% for modeled natural waters. An analysis of plane albedo behavior resulted in the development of a new extended QSSA approximation, which when applied in conjunction with the extended Hapke approximation developed earlier, resulted in a maximum relative error of 2.7%. The study results demonstrated that for practical applications, the estimation of inherent optical properties from observed reflectance can best be achieved using an extended Hapke approximation. 相似文献
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Leonid N. Koikov Mingming Han Dawn M. Wellman Jim A. Kelly Irina P. Smoliakova 《合成通讯》2013,43(18):3451-3464
tert-Butyl vinyl ether (1) reacts with p-TolSCl to give 2-tert-butoxy-2-chloroethyl p-tolyl sulfide (2). In the presence of SnCl4, 2 reacts with silyl enol ethers, allyltrimethylsilane, and vinyl ethers to form a C-C bond. In the case of vinyl ethers, the reaction proceeds through the formation of the 5-membered sulfonium salt intermediate which in turn can react with H2O, TMSCN, allyltrimethylsilane, and Grignard reagents. 相似文献
66.
The new ternary carbodiimide LiY(CN2)2 was synthesized by solid state metathesis reaction between YF3 and Li2(CN2) in a silica tube at 550 °C. The X‐ray single‐crystal structure determination yielded an orthorhombic crystal system (Pbcn, Z = 4, a = 982.0(3), b = 698.5(2), c = 613.4(2) pm). The crystal structure can be considered related to the NiAs structure. The carbodiimide ions are arranged in layers following the motif of a hexagonal closest packing of sticks. Lithium and yttrium cations occupy all octahedral voids in an ordered fashion, alternating on top of each other along the hcp stacking direction. 相似文献
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The new carbodiimide compounds Li2RE2Sr(CN2)5 (RE = Sm, Gd, Eu, Tb) were prepared by a straight forward solid state metathesis reaction of REF3, SrF2, and Li2(CN2) at around 600 °C. The crystal structure of Li2Gd2Sr(CN2)5 was solved based on X‐ray single‐crystal diffraction data. Corresponding Li2RE2Sr(CN2)5 compounds were analyzed by isotypic indexing of their powder patterns. The crystal structure of Li2Gd2Sr(CN2)5 can be well related to that of Gd2(CN2)3, because both structures are based on layered structures composed of close packed layers of [N=C=N]2– sticks, alternating with layers of metal ions. The crystal structure of Li2Gd2Sr(CN2)5 can be considered to contain an ABC layer sequence of [N = C=N]2– layers with the interlayer voids being occupied by (three) distinct types of cations. 相似文献
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Nikolay E. Nifant'ev Yury E. Tsvetkov Alexander S. Shashkov Leonid O. Kononov Vladimir M. Menshov Alexander B. Tuzikov 《Journal of carbohydrate chemistry》2013,32(8):939-953
ABSTRACT Synthesis of two isomeric tetrasaccharides, namely Neu5Acα(2→3)Galβ(1→3)[Fucα(1→4)GlcNAcβ (sLea) and Neu5Acα(2→3)Galβ(1→4)[Fucα(1→3)]GlcNAcβ (sLex) as 3-aminopropyl glycosides is described. Preparation of these compounds was performed by sialylation of selectively protected trisaccharides Lea and Lex which contain three unsubstituted OH groups at positions 2, 3 and 4 of Gal residue. Glycosylation of Lex trisaccharide with ethylthio sialoside under promotion by NIS and TfOH in acetonitrile was effective and regio- and stereoselective to give sLex derivative in 81% yield. In contrast, sialylation of the Lca acceptor was accompanied by a variety of undesirable by-processes, namely. N-thioethylation of the GlcNAc residue, β-sialylation, and lactonisation. In order to improve the yield of sLca tetrasaccharide the glycosylation of Lea acceptor by sialyl donors of ethyl and phenyl thioglycoside (promoted by NIS-TfOH or NBS-Bu4NBr), xanthate (promotion by NIS-TfOH mixture or MeOTf) and phosphite (promoted by TMSOTf) types was also studied. Among the reactions investigated the glycosylation by phenyl thioglycoside sialoside promoted by NIS-TfOH gives the best yield (39%) of sLea tetrasaccharide product. 相似文献
70.
Atom-economic Approach to the Synthesis of α-(Hetero)aryl-substituted Furan Derivatives from Biomass
Leonid V. Romashov Kirill S. Kozlov Matvey K. Skorobogatko Alexander Y. Kostyukovich Valentine P. Ananikov 《化学:亚洲杂志》2022,17(1):e202101227
An atom-economic ring construction approach to the synthesis of α-(hetero)arylfurans based on renewable furanic platform chemicals has been developed. Corresponding compounds have been prepared in good to excellent yields via [2+2+2] and [4+2] cycloaddition reactions using metal-catalyzed or photoredox protocols. Easily available HMF-based 2-hydroxymethyl-5-ethynylfuran and 2-hydroxymethyl-5-cyanofuran were used as starting materials. A synthetic route with an improved carbon economy factor has been implemented to achieve sustainability aim. The possible application of arylfurans as molecular conductors has been investigated by DFT calculations, which revealed excellent charge transfer properties. As a future perspective, integration of biomass processing strategy into manufacturing of molecular electronics was pointed out to achieve the aim of sustainability. 相似文献