Stress-strain state of karst areas

Numerical modeling data on evolution of the stress-strain state of a rock mass containing a karst cavity are reported.     

A Comparative Study of the Reactions of Thermally Activated Tritium with Sugars and Diazines and of Solid-Phase Catalytic Hydrogenation of These Compounds with Tritium

The feasibility of the labeling procedure involving thermal activation (TA) of tritium was examined with the substrates that are commonly labeled by solid-phase catalytic hydrogenation (SCH) with tritium. Comparative characteristics of SCH and TA as procedures for tritium labeling of sugars and diazines were obtained. These two methods ensure comparable rates of tritium incorporation into purine and pyrimidine bases. The SCH allows preparation of tritium-labeled compounds with the maximum possible molar radioactivity. The molar radioactivity of the same compounds labeled using TA did not exceed 37 TBq mol⁻¹, because only a small fraction of the substrate could react with atomic tritium. Longer reaction times and increased amounts of tritium taken into the reaction resulted in stronger degradation of the substrates. On the assumption that the reactive tritium atoms penetrate into the target to a depth of 0.5 nm, the actual specific radioactivity of the labeled compound in the zone accessible for atomic tritium reaches 0.2–2 PBq mol⁻¹. Ways are suggested to increase the molar radioactivity of compounds labeled using thermal activation of tritium.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 284–288.Original Russian Text Copyright © 2005 by Sidorov, Badun, Baitova, Baitov, Platoshina, Myasoedov, Fedoseev.     

Redox equilibrium U(VI) + 2Ce(III) ? U(IV) + 2Ce(IV) in the presence of unsaturated heteropoly anions P2W17O 6110? and SiW11O 398?

The equilibrium of the reaction U(VI) + 2Ce(III) ⇄ U(IV) + 2Ce(IV) in the presence of unsalurated heleropoly compounds K₁₀P₂W₁₇O₆₁ and K₈SiW₁₁O₃₉ in 0.01–1.0 M HClO₄ solutions (ionic strength 1) was studied. The potential of the Ce(IV)/Ce(III) couple in K₈SiW₁₁O₃₉ solutions was measured, from which the overall stability constants β₂^IV of the complexes U^IV(SiW₁₁O₃₉)₂¹²⁻, equal to 10^23.8 and 10^19.8 in 0.1 M HClO₄ + 0.9 M NaClO₄ and in 1.0 M HClO₄, respectively, were calculated. Under the same conditions, for the complex U^IV(P₂W₁₇O₆₁)₂¹⁶⁻ β₂^IV = 10^23.2 and 10^18.5 (the latter value was obtained by extrapolation or data for 0.1 M HClO₄ + 0.9 M NaClO₄ solution). Original Russian Text ? V.P. Shilov. A.B. Yusov, M.N. Sokohva. A.M. Fedoseev, 2008, published in Radiokhimiya, 2008, Vol. 50. No. 3, pp. 203–208.     

Influence of conditions on the potential of the couple of nonoxygenated U5+/U4+ ions bound in complexes with the P2W17O 6110? and SiW11O 398? anions

The formal potential of the couple of nonoxygenated U⁵⁺/U⁴⁺ ions bound in complexes with unsaturated heteropoly anions (HPAs) P₂W₁₇O₆₁¹⁰⁻ (I) and SiW_{11 O39}⁸⁻ (II) in 0–1 M NaNO₃ and 1 M (NaCl + HCl) in the range of pH 0.7–4.7 was measured. In 1 M NaNO₃ solutions at pH 4.7–3.0 for I and 4.3–3.9 for II, the formal potentials are constant: 0.820 and 0.730 V, respectively. They preserve approximately the same value with a decrease in pH to 0.7 in 1 M (NaCl + HCl). The potential noticeably decreases with a decrease in the NaNO₃ or NaCl concentration from 1 M to 0 (pH 4.1–4.7): to 0.09 and 0.05–0.06 V for I and II, respectively. Approximate constancy of the potential of the U⁵⁺/U⁴⁺ couple with a decrease in pH to 1 and lower distinguishes this couple from the M⁴⁺/M³⁺ couples (M = Ce, Am, Bk) whose potential appreciably grows with increasing acidity. This is due to the fact that the U⁵⁺ and M⁴⁺ ions in acid solutions remain in the form of complexes with the ratio M: HPA = 1: 2, whereas the M³⁺ ions pass into the form of 1: 1 complexes. Thus, variation of the formal potentials of all the M ^{n + 1}/M ⁿ⁺ couples in the presence of H⁺ and Na⁺ ions is associated with variation of the stability constants of the complexes M(HPA)₂, which, in turn, is caused by interaction of single-charged ions with HPA. However, the H⁺ and Na⁺ ions interact with HPA by different mechanisms and therefore affect the potential of the U⁵⁺/U⁴⁺ couple differently. Original Russian Text ? V.P. Shilov, A.B. Yusov, A.M. Fedoseev, Ph. Moisy, 2008, published in Radiokhimiya, 2008, Vol. 50, No. 5, pp. 393–396.     

Anodic synthesis of Np(VII) compounds from acetate solutions

A procedure was suggested for the synthesis of Np(VII) compounds by electrochemical oxidation in acetate solutions. The conditions for preparing compounds of type MNpO₄·nH₂O, where M is a single-charged cation of alkali metals, ammonium, silver, guanidinium, or tetraalkylammonium, and of Np(VII) compounds with double-charged cations of alkaline-earth metals, Cu, Cd, and Zn were studied in detail. The compounds were characterized by chemical analysis and by IR and electronic spectroscopy.     

Synthesis and properties of complexes of hexavalent actinides with dimethyl sulfoxide [AnO<Subscript>2</Subscript>(DMSO)<Subscript>5</Subscript>](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript> (An = U,Np, Pu)

The complexes [NpO₂(DMSO)₅](ClO₄)₂ (1) and [PuO₂(DMSO)₅](ClO₄)₂ (2), isostructural to the known uranyl complex, were synthesized in the form of single crystals. Their crystallographic characteristics were determined by single crystal X-ray diffraction. The IR and electronic absorption spectra of the crystalline U(VI), Np(VI), and Pu(VI) complexes were measured and analyzed.     

Speciation, stability, and reactions of Np(III–VII) in aqueous solutions

Published data on the structure of Np ions in acid and alkali solutions, on hydrolysis of Np ions and their complexation with anions and cations, on their redox reactions with water and with each other (disproportionation, reproportionation), and on the effect of anions on this process are analyzed. Possible directions of research in chemistry of Np ions are outlined.     

A Method for Determination of Alcohol Content in Dielectric Liquids by a Longitudinal-Slot Waveguide

A new method is proposed to determine the content of alcohol in dielectric liquids. The method is based on measuring the attenuation of a wave propagating in a rectangular waveguide with a longitudinal slot in its narrow wall, immersed in a liquid under test. The propagation constant of the H ₁₀ mode in such a waveguide is calculated numerically for various parameters of the medium and the waveguide. It is shown that the attenuation of the wave depends on the parameters of the dielectric medium outside the waveguide. Experiment is carried out on two different types of waveguide at frequencies from 29 to 37 GHz with a solution of ethyl alcohol in water as the external medium. The results of the measurements show that the method can be used for the on-line measurement of alcohol concentration during fermentation.     

Solid-phase synthesis of deuterium- and tritium-labeled dopamine using carbon nanomaterials

Various procedures for preparing dopamine labeled with deuterium (²H) and tritium (³H) were considered. The labeled dopamine into which the hydrogen isotopes were introduced by solid-phase halogenation contained, on the average, 2.8 ²H (³H) atoms. The labeled dopamine prepared by solid-phase isotope exchange using nanodiamonds as support contained, on the average, 4.8 ²H (³H) atoms. The process was accompanied by the substrate deamination; as a result, the yield of the labeled analog was low (7–10%). Mass spectrometric analysis shows that the phenolic fragments formed by the dopamine deamination undergo dimerization.     

Role of peroxynitrite in oxidation of f-element ions in HNO3 solutions

Published data on the kinetics of Ce(III) oxidation with ozone in HNO₃ solutions are analyzed. The formation of peroxynitrite in the course of ozonation of nitric acid solutions, hypothesized previously in the literature, is confirmed. Peroxynitrite is capable to oxidize Ce(III), but with time it decomposes to HNO₂ and H₂O₂, which reduce Ce(IV). Similar phenomenon is observed in ozonation of nitric acid solutions of berkelium.