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62.
Pashchenko Larisa L. Druzhinina Anna I. 《Journal of Thermal Analysis and Calorimetry》2018,133(2):1173-1179
Journal of Thermal Analysis and Calorimetry - Enthalpies of vaporization, $$ \Delta _{\text{vap}} H^{\circ }_{298} $$ , were determined for perfluorooctyl-1-bromide (PFOB) at the temperature... 相似文献
63.
Chemistry of Heterocyclic Compounds - In this microreview, we consider the methods used for the synthesis of tetrahydro-4H-thiopyran-4-ones over the last 7 years. 相似文献
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Dr. Oleg G. Salnikov Dr. Dudari B. Burueva Dr. Larisa M. Kovtunova Prof. Valerii I. Bukhtiyarov Dr. Kirill V. Kovtunov Prof. Igor V. Koptyug 《Chemphyschem》2022,23(7):e202200072
In this work the mechanism of methylenecyclobutane hydrogenation over titania-supported Rh, Pt and Pd catalysts was investigated using parahydrogen-induced polarization (PHIP) technique. It was found that methylenecyclobutane hydrogenation leads to formation of a mixture of reaction products including cyclic (1-methylcyclobutene, methylcyclobutane), linear (1-pentene, cis-2-pentene, trans-2-pentene, pentane) and branched (isoprene, 2-methyl-1-butene, 2-methyl-2-butene, isopentane) compounds. Generally, at lower temperatures (150–350 °C) the major reaction product was methylcyclobutane while higher temperature of 450 °C favors the formation of branched products isoprene, 2-methyl-1-butene and 2-methyl-2-butene. PHIP effects were detected for all reaction products except methylenecyclobutane isomers 1-methylcyclobutene and isoprene implying that the corresponding compounds can incorporate two atoms from the same parahydrogen molecule in a pairwise manner in the course of the reaction in particular positions. The mechanisms were proposed for the formation of these products based on PHIP results. 相似文献
66.
Leonid G. Voskressensky Tatiana N. Borisova Innokenti S. Kostenev Larisa N. Kulikova Alexey V. Varlamov 《Tetrahedron letters》2006,47(6):999-1001
Tetrahydropyridopyrimidines (THPPm) 1-3 underwent tandem cleavage-cyclization piperidine ring enlargement under the action of terminal activated alkynes to produce tetrahydropyrimido[4,5-d]azocines 4-7 in good preparative yields. The latter compounds are representatives of a new heterocyclic system. 相似文献
67.
Leonid G. Voskressensky Tatiana N. Borisova Anna V. Listratova Larisa N. Kulikova Alexander A. Titov Alexey V. Varlamov 《Tetrahedron letters》2006,47(27):4585-4589
Tetrahydroisoquinolines 3a-e underwent piperidine ring enlargement under the action of activated alkynes, giving benzoazocines 4, 5 and 7-11 in high yields. 相似文献
68.
Tsarkova L Horvat A Krausch G Zvelindovsky AV Sevink GJ Magerle R 《Langmuir : the ACS journal of surfaces and colloids》2006,22(19):8089-8095
We study the details of the defect dynamics in thin films of a cylinder-forming polystyrene-block-polybutadiene (SB) diblock copolymer melt. The high temporal resolution of in-situ scanning force microscopy (SFM) uncovers elementary dynamic processes of structural rearrangements on time scales not accessible so far. Short-term interfacial undulations and the formation of transient phases (spheres, perforated lamellae, and lamellae) are observed. We demonstrate that the well-known structural defects are annihilated by short-term phase transitions into what may be considered excited states. These temporary phase transitions are reproduced in simulations based on dynamic self-consistent field theory. We discuss the role of the observed structural evolution in the context of the equilibrium phase behavior in SB thin films. 相似文献
69.
Genome sequencing projects resulted in the identification of a large number of new sequence homologs of archaeal rhodopsins in marine bacteria, fungi, and unicellular algae. It is an important task to unambiguously predict the functions of these new rhodopsins, as it is difficult to perform individual experiments on every newly discovered sequence. The transmembrane segments of rhodopsins have similar three-dimensional structures where the seven transmembrane helices form a tightly packed scaffold to accommodate a covalently bound retinal. We use geometric computations to accurately define the retinal-binding pockets in high-resolution structures of rhodopsins and to extract residues forming the wall of the retinal-binding pocket. We then obtain a tree defining the functional relationship of rhodopsins based on the short sequences of residues forming the wall of the retinal-binding pocket concatenated from the primary sequence, and show that these sequence fragments are often sufficient to discriminate phototactic vs transporting function of the bacterial and unicellular algal rhodopsins. We further study the evolutionary history of retinal-binding pockets by estimating the pocket residue substitution rates using a Bayesian Monte Carlo method. Our findings indicate that every functional class of rhodopsins has a specific allowed set of fast-rate amino acid substitutions in the retinal-binding pocket that may contribute to spectral tuning or photocycle modulation. The substitution rates of the amino acid residues in a putative retinal-binding pocket of marine proteorhodopsins together with the clustering of pocket sequences indicate that green-absorbing and blue-absorbing proteorhodopsins have similar function. Our results demonstrate that the evolutionary patterns of the retinal-binding pockets reflect the functional specificity of the rhodopsins. The approach we describe in this paper may be useful for large-scale functional prediction of rhodopsins. 相似文献
70.
The acousto-optical interactions of Bessel and Gaussian light beams with the ultrasonic field in liquids under the condition of Raman-Nath diffraction for the standing-wave mode are experimentally investigated. The main differences of acousto-optical interactions for Bessel and Gaussian light beams are revealed. The various phenomena of refraction and focusing of Bessel beam in liquids owing to sound-field spatial modulation are demonstrated. 相似文献