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排序方式: 共有89条查询结果,搜索用时 250 毫秒
61.
V. V. Belaga A. A. Benjaza G. M. Chernov V. V. Rusakova J. A. Salomov 《Radiation measurements》1995,25(1-4)
A search for the coherent dissociation 12C → 3α in emulsion enriched by Pb and the comparative analysis of our data with ones obtained in usual emulsions have been made at 4.5 A GeV/c. Both of experiments cannot be described in the framework of statistical model of the 12C → 3α decay. 相似文献
62.
63.
Spectral luminescence characteristics, viz., quantum yields and luminescence lifetime, of the Yb3+ and Nd3+ ions in aqueous-methanolic solutions of their complexes with chromophoric benzo-15-crown-5 derivatives were determined. The efficient 4f-luminescence (exc = 337 nm) is due to the intramolecular transfer of the excitation energy from the chromophoric moiety of the molecule to the Ln3+ ion. 相似文献
64.
P C Ioannou N V Rusakova D A Andrikopoulou K M Glynou G M Tzompanaki 《The Analyst》1998,123(12):2839-2843
Terbium sensitized fluorescence was used to develop a sensitive and simple spectrofluorimetric method for the determination of the anthranilic acid derivatives furosemide and mefenamic and tolfenamic acids. The method makes use of radiative energy transfer from anthranilates to terbium ions in alkaline methanolic solutions. Optimum conditions for the formation of the anthranilate-Tb3+ complexes were investigated. Under optimized conditions, the detection limits are 6 x 10(-9), 1.4 x 10(-8) and 9.0 x 10(-9) mol l-1 for furosemide, mefenamic acids and tolfenamic acid, respectively. The range of application is 2.5 x 10(-8)-5.0 x 10(-5) mol l-1 for all three drugs. The method was successfully applied to the determination of furosemide and mefenamic and tolfenamic acids in serum after extraction of the samples with ethyl acetate, evaporation of the organic layer under a stream of nitrogen at 40 degrees C and reconstitution of the residue with alkaline methanolic terbium solution prior to instrumental measurement. The mean recoveries from serum samples spiked with furosemide (5.0 x 10(-7), 2.0 x 10(-6) and 8.0 x 10(-6) mol l-1), mefenamic acid (3.0 x 10(-6), 9.0 x 10(-6) and 3.0 x 10(-5) mol l-1) and tolfenamic acid (3.1 x 10(-6), 12.5 x 10(-6) and 2.5 x 10(-5) mol l-1) were 96 +/- 8, 101 +/- 5 and 98 +/- 7%, respectively. The within-run precision (RSD) for the method for two serum samples of each drug varied from 2 to 8% and the day-to-day precision for two concentration levels varied from 2 to 13%. 相似文献
65.
On the HALA effect in the NMR carbon shielding constants of the compounds containing heavy p‐elements
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Yu. Yu. Rusakov Irina L. Rusakova Leonid B. Krivdin 《International journal of quantum chemistry》2016,116(19):1404-1412
The heavy atom (HA) effect on the NMR isotropic carbon shielding constants is computationally investigated in the series of model ethanes, ethylenes, and acetylenes, CβH3? CαH2? XHn, CβH2? CαH? XHn, CβH?Cα? XHn (n = 0, 1, 2, or 3 depending on X), where X covers p‐elements in the 13–17 groups of the 3–6 periods in as many as 60 compounds. Compounds under study provide diverse bonding situations for the α‐ and β‐carbons, which are characterized by the consecutive increase of the s‐character of the Cβ? Cα and Cα? X bonds, being one of the factors influencing spin‐orbit part of the HA on light atom effect (SO‐HALA). The “chalcogen dependence,” “pnictogen dependence,” “tetrel dependence,” and “triel dependence” are established for the 16th, 15th, 14th, and 13th groups, respectively. A well‐known “normal halogen dependence” for the 13C NMR chemical shifts, established much earlier for the compounds containing 17th group elements, also revealed itself in all three series under investigation. The dependence of the spin‐orbit effects size depending on the number of the lone electron pairs (LEPs) on HA X has also been investigated. The comparison of theoretical 13C NMR chemical shifts with experiment is performed for three representative tellurides. The HALA effect in this series has been shown to be strongly dependent on the number of tellurium LEPs. 相似文献
66.
Dmitry Deryabin Kseniya Inchagova Elena Rusakova Galimzhan Duskaev 《Molecules (Basel, Switzerland)》2021,26(1)
Coumarins are class of natural aromatic compounds based on benzopyrones (2H-1-benzopyran-2-ones). They are identified as secondary metabolites in about 150 different plant species. The ability of coumarins to inhibit cell-to-cell communication in bacterial communities (quorum sensing; QS) has been previously described. Coumarin and its derivatives in plant extracts are often found together with other small molecules that show anti-QS properties too. The aim of this study was to find the most effective combinations of coumarins and small plant-derived molecules identified in various plants extracts that inhibit QS in Chromobacterium violaceum ATCC 31532 violacein production bioassay. The coumarin and its derivatives: 7-hydroxycoumarin, 7.8-dihydroxy-4-methylcoumarin, were included in the study. Combinations of coumarins with gamma-octalactone, 4-hexyl-1.3-benzenediol, 3.4.5-trimethoxyphenol and vanillin, previously identified in oak bark (Quercus cortex), and eucalyptus leaves (Eucalyptus viminalis) extracts, were analyzed in a bioassay. When testing two-component compositions, it was shown that 7.8-dihydroxy-4-methylcoumarin, 4-hexyl-1.3-benzendiol, and gamma-octalactone showed a supra-additive anti-QS effect. Combinations of all three molecules resulted in a three- to five-fold reduction in the concentration of each compound needed to achieve EC50 (half maximal effective concentration) against QS in C. violaceum ATCC 31532. 相似文献
67.
Mariia Nesterkina Serhii Smola Nataliya Rusakova Iryna Kravchenko 《Molecules (Basel, Switzerland)》2022,27(1)
Hydrazones based on mono- and bicyclic terpenoids (verbenone, menthone and carvone) have been investigated in vitro as potential biomembrane penetration enhancers. In this regard, liposomes composed of lecithin or cardiolipin as phospholipid phase components with incorporated fluorescence probes have been prepared using the thin-film ultrasonic dispersion method. The mean particle size of the obtained liposomes, established using laser diffraction, was found to be 583 ± 0.95 nm, allowing us to categorize them as multilamellar vesicles (MLVs) according to their morphology. Pursuant to fluorescence analysis, we may assume a reduction in microviscosity and, consequently, a decrease in the packing density of lecithin and cardiolipin lipids to be the major mechanism of action for terpenoid hydrazones 1–15. In order to determine the molecular organization of the lipid matrix, lipids were isolated from rat strata cornea (SCs) and their interaction with tested compounds was studied by means of Fourier transform infrared spectroscopy. FT-IR examination suggested that these hydrazones fluidized the SC lipids via the disruption of the hydrogen-bonded network formed by polar groups of SC constituents. The relationship between the structure of terpenoid hydrazones and their ability to enhance biomembrane penetration is discussed. 相似文献
68.
T. V. Kudayarova E. A. Danilova M. K. Islyaikin N. N. Semenishin N. V. Rusakova 《Russian Journal of General Chemistry》2014,84(9):1706-1710
Luminescence properties of thiadiazole-containing compounds of cyclic and acyclic structure have been investigated. All compounds are characterized by fluorescence in the region 500–600 nm. The highest quantum yield of luminescence in the studied series is exhibited by acyclic product of the ABA type (where A is thiadiazole cycle, B is isoindole cycle) with N-pentylthiadiazoline fragments. 相似文献
69.
Irina L. Rusakova Yury Yu. Rusakov Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2014,52(9):500-510
One‐bond spin–spin coupling constants involving selenium of seven different types, 1 J(Se,X), X = 1H, 13C, 15 N, 19 F, 29Si, 31P, and 77Se, were calculated in the series of 14 representative compounds at the SOPPA(CCSD) level taking into account relativistic corrections evaluated both at the RPA and DFT levels of theory in comparison with experiment. Relativistic corrections were found to play a major role in the calculation of 1 J(Se,X) reaching as much as almost 170% of the total value of 1 J(Se,Se) and up to 60–70% for the rest of 1 J(Se,X). Scalar relativistic effects (Darwin and mass‐velocity corrections) by far dominate over spin–orbit coupling in the total relativistic effects for all 1 J(Se,X). Taking into account relativistic corrections at both random phase approximation and density functional theory levels essentially improves the agreement of theoretical results with experiment. The most ‘relativistic’ 1 J(Se,Se) demonstrates a marked Karplus‐type dihedral angle dependence with respect to the mutual orientation of the selenium lone pairs providing a powerful tool for stereochemical analysis of selenoorganic compounds. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
70.
R. R. Kattabekov K. Z. Mamatkulov S. S. Alikulov D. A. Artemenkov R. N. Bekmirzaev V. Bradnova P. I. Zarubin I. G. Zarubina N. V. Kondratieva N. K. Kornegrutsa D. O. Krivenkov A. I. Malakhov K. Olimov N. G. Peresadko N. G. Polukhina P. A. Rukoyatkin V. V. Rusakova R. Stanoeva S. P. Kharlamov 《Physics of Atomic Nuclei》2013,76(10):1219-1223
The dissociation of relativistic 12N nuclei having a momentum of 2 GeV/c per nucleon and undergoing the most peripheral interactions in a track emulsion is studied. The picture of charged topology of product ensembles of relativistic fragments and special features of their angular distributions are presented. 相似文献