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  • Articles  (603)
  • Chemistry and Pharmacology  (603)
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  • Articles  (603)
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  • Chemistry and Pharmacology  (603)
  • 11
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    Stereochemistry of Neptunium in Oxygen-Containing Compounds (2018)
    Springer
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    Publication Date: 2018-03-09
    Description: Coordination of Np(III–VII) atoms in the crystal structures of all the oxygen-containing compounds characterized with the R -factor lower than 0.1 was analyzed with the aid of Voronoi–Dirichlet polyhedra (VDPs). Nine types of NpO n coordination polyhedra (6 ≤ n ≤ 12) are realized. The most characteristic of them are trigonal dodecahedra [Np(IV)], penta- and hexagonal bipyramids [Np(V) and Np(VI)], and octahedra [Np(VII)] based on square NpO 4 – cores. For Np atoms of a fixed oxidation state, the volume of their VDPs in the NpO n complexes is virtually independent of the coordination number n . The VDP parameters can be used for determining the valence state of the Np atoms, finding compounds with the maximal nonlinearity of the NpO 2 + and NpO 2 2+ dioxocations, and revealing errors in the crystal structure data. Anion–anion interactions involving NpO 4 – and OH – ions are an important structure-forming factor in Np(VII) compounds. In sublattices consisting of Np atoms only (Np sublattices), the rule of 14 neighbors is fulfilled. Compounds in which binding Np···Np 5f interactions in crystal structures are possible were revealed by analysis of the VDPs of the atoms in the Np sublattices. In such compounds, the metal atoms form bent Np=O–Np bridging fragments and the Np V O 7 bipyramids are combined in dimers sharing a common axial edge, with the Np atoms of the dimers being also bound via two carboxylate bridges.
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    Electronic ISSN: 1608-3288
    Topics: Chemistry and Pharmacology
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  • 12
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    Estimation of U, 226 Ra, and 210 Po Concentrations in Cauvery River Basin, South Interior Karnataka Region, India (2018)
    Springer
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    Publication Date: 2018-03-09
    Description: The radioactivity concentration of 210 Po, 226 Ra, and U in Cauvery river basin was analyzed using radiochemical analysis, emanometry, and LED fluorimetry, respectively. Due to transfer with water in cracks and pores, leaching, and heavy usage of phosphate fertilizers, 210 Po, 226 Ra, and U radionuclides get into the environmental samples studied. The 210 Po concentration ranges from 0.7 ± 0.11 to 5.0 ± 0.7 and from 0.83 ± 0.12 to 5.2 ± 0.8 mBq L –1 ; the 226 Ra concentration, from 11.7 ± 1.8 to 62 ± 9 and from 10.5 ± 1.6 to 68 ± 10 mBq L –1 ; and the U concentration, from 0.08 ± 0.01 to 4.4 ± 0.7 and from 2.0 ± 0.3 to 7.4 ± 1.1 ppb in river and borewell water samples, respectively.
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    Topics: Chemistry and Pharmacology
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  • 13
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    Deposition of 63 Ni onto a Semiconductor Structure of Power Cells (2018)
    Springer
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    Publication Date: 2018-03-09
    Description: A procedure was developed for electrochemical deposition of 63 Ni onto the surface of a siliconbased semiconductor converter. A special electrochemical cell allowing the electrolysis to be performed in an inert atmosphere was developed. The principal possibility of preparing Ni metal films of preset thickness on the surface of a semiconductor converter was demonstrated.
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    Topics: Chemistry and Pharmacology
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  • 14
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    Synthesis of 99m Tc-Radiolabeled Uridine as a Potential Tumor Imaging Agent (2018)
    Springer
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    Publication Date: 2018-03-09
    Description: Uridine, a pyrimidine nucleoside essential for the synthesis of RNA and biomembranes, was radiolabeled with 99 m Tc to obtain a potential tumor imaging agent. The maximal radiochemical yield of about 96.5%, as determined by paper chromatography and instant thin-layer chromatography, was reached under the following optimum conditions: 1 mg of uridine, 20 μg of SnCl 2 ·2H 2 O as reducing agent, 20 mg of mannitol as a stabilizer, and pH 8. 99 m Tc-uridine is stable in vitro at room temperature for up to 6 h post labeling. The biodistrbution study in tumor-bearing mice shows high target-to-nontarget ratio. These results match with the high docking score of the complex on uridine phosphorylase enzyme. 99 m Tc-uridine shows promise as a tumor imaging agent.
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    Topics: Chemistry and Pharmacology
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  • 15
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    Nuclear Chemical Effects in the Paragenetic Mineral Association Based on Polycrase (2018)
    Springer
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    Publication Date: 2018-03-09
    Description: A natural polymineral compound in which the major uranium-containing mineral is polycrase (Ti- Ta-niobate) described by the formula АВ 2 О 6 was chosen as a model for studying the behavior of recoil atoms produced by α-decay of actinides. Polycrase, despite its metamict structure, is characterized by the following features distinguishing it from Ti-Ta-niobates of the formula А 2 В 2 О 7 (pyrochlore and betafite): (1) 1/3 of uranium atoms preserve the initial valence state, U(IV); (2) the U(IV) fraction is characterized by the isotope activity ratio AR( 234 U/ 238 U) close to that at secular equilibrium; (3) the uranium atoms that underwent oxidation “memorize” their radiogenic origin; as a result, the AR( 234 U/ 238 U) ratio in the U(VI) fraction is 0.90, and in the most altered part of the mineral it decreases to 0.77; (4) the parent uranium is relatively stable in the metamict structure of polycrase: The half-leaching time for 238 U atoms is 2 times longer than that in betafite, zircon, or sphene.
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  • 16
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    How can the cost of spent fuel reprocessing be reduced and reliable isolation of all the wastes be ensured? (2018)
    Springer
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    Publication Date: 2018-03-06
    Description: The facilities operating in the world are today incapable of reprocessing the whole amount of the already accumulated and annually unloaded NPP spent fuel. Therefore, the spent nuclear fuel (SNF) reprocessing is not considered today as the only alternative of the nuclear fuel cycle. The paper attempts to analyze measures aimed at reducing expenditures for NPP fuel reprocessing. In the author’s opinion, the existing approach to the SNF reprocessing technology should be revised taking into account prospects for using REMIX fuel, with possible expansion of the range of fission products suitable for further use.
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    Topics: Chemistry and Pharmacology
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  • 17
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    Coextraction and successive selective stripping of cerium(IV) and thorium from monazite leach solutions with tributyl phosphate (TBP) (2018)
    Springer
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    Publication Date: 2018-03-06
    Description: Solvent extraction of Ce(IV) and Th(IV) from 8 M HNO 3 with TBP in kerosene was studied. The dependence of the extraction on the TBP concentration, kind of diluent, O/A phase ratio, and contact time was examined. The extraction efficiency reaches 99.3 and 97.7% for Ce and Th, respectively, at 5% TBP in kerosene, 1/1 O/A phase ratio, and 5 min contact time. Successive selective stripping of Ce(III) and Th(IV) from the loaded organic phase was reached at 1.1 M H 2 O 2 concentration, 10 min contact time, 3/1 O/A phase ratio, and room temperature (25 ± 2°C). After stripping of cerium, the remaining organic was contacted with H 2 O for thorium stripping at 5 min contact time, 2/1 O/A phase ratio, and room temperature (25 ± 2°C).
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  • 18
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    Beyond-design-basis regimes of uranium stripping and of carbonate regeneration of the solvent (2018)
    Springer
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    Publication Date: 2018-03-06
    Description: Beyond-design-basis regimes of centrifugal contactors for U stripping and of mixer–settlers for carbonate regeneration of the solvent, 30% TBP in Isopar M, were studied from the viewpoint of the influence of incomplete uranium stripping on the phase stability of the extraction system in the step of the carbonate scrubbing of the solvent. Dynamic relationship between these two operations was determined. A mathematical model of uranium stripping at stepwise–20% deviation from the nominal value was developed and verified; it was shown that the beyond-design-basis regime develops in such apparatuses within 4 h at the total trial time longer than 8 h. The mathematical relationships obtained were used in the development of software for calculating transient processes that occur when the stream parameters in the course of carbonate regeneration of the solvent change. The beyond-design-basis regime of the solvent regeneration was found to have two regions: region of stoichiometric excess of carbonate ions over uranyl ions with the risk of precipitation and region of excess of uranyl ions over carbonate ions with acidification of the unit and uranium breakthrough with the recycled solvent. The conditions of the tests performed correspond to the second region.
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  • 19
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    Thermal stability of irradiated solutions of 2,2′-bipyridine-6,6′-dicarboxylic acid bis( N -ethyl-4-hexylanilide) in fluorinated sulfones (2018)
    Springer
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    Publication Date: 2018-03-06
    Description: The effect exerted by irradiation with accelerated electrons on the thermolysis kinetics in two-phase systems consisting of 14 M aqueous HNO 3 and FS-13 diluent or 0.1 M solution of 2,2′-bipyridine-6,6′-dicarboxylic acid bis( N -ethyl-4-hexylanilide) in FS-13 was determined. Samples were irradiated at an electron accelerator at a dose rate of 10 kGy h –1 to integral doses of 0.1, 0.5, and 1 MGy. The mixtures were heated in an autoclave at 170 and 200°С. A study of the heat and gas evolution processes occurring in the course of thermolysis of extraction mixtures irradiated to doses of 1 MGy showed that conditions for the development of autocatalytic oxidation are not created even in the systems kept for 2 weeks in contact with 14 M HNO 3 .
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  • 20
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    Radiochemical and biological characterization of 99m Tc-oxiracetam as a model for brain imaging (2018)
    Springer
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    Publication Date: 2018-03-06
    Description: 99 m Tc-oxiracetam was prepared. It can be used as a radiotracer for brain imaging. Under the optimum conditions (0.5 mg of oxiracetam, 50 μg of SnCl 2 ·2H 2 O, pH 7, room temperature, 30 min), the radio-chemical yield determined by chromatographic methods reached 96%. Biodistribution studies with mice showed that the brain uptake of the complex was 5.1% injected dose per gram (% ID/g) at 5 min post injection. In this parameter, the complex surpasses the commercially available 99 m Tc-ECD (4.7% ID/g) and 99 m Tc-HMPAO (2.25% ID/g).
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