A dual-wave atmosphere transparency radiometer of the millimeter wave range

The MIAP-2 radiometric complex intended for measuring the atmospheric absorption in the millimeter wavelength range (2 and 3 mm) is described. The complex is based on two solid-state modulation radiometers with wave ranges of 84–99 GHz and 132–148 GHz, which are equipped with horn-lens antennas. The device determines an optical depth in the millimeter wave range using the atmospheric-dip method and the absolute signal calibration method in the fully automated mode under the remote control via the Internet. A set of observations was performed in the stationary mode and in mountain expedition conditions. The reliability of the device was evaluated from 2-year operation results.     

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.     

Extraction of rare-earth elements from nitric acid solutions with polyalkylphosphonitrilic acid

The distribution of microamounts of La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between aqueous HNO₃ solutions and solutions of polyalkylphosphonitrilic acid in a fluorinated alcohol was studied. The stoichiometry of the extractable REE complexes was determined. An increase in the concentration of fluorinated alcohol in the organic phase leads to a decrease in the REE distribution ratios, which is due to solvation of the extractant with the alcohol molecules.     

Oxidation of uranium(IV) with oxygen in NaHCO<Subscript>3</Subscript> solution

The kinetics of U(IV) oxidation with atmospheric oxygen in NaHCO₃ solutions was studied by spectrophotometry. In 1 M NaHCO₃ at [U(IV)]₀ = 20 mM, an induction period is observed, which virtually disappears with decreasing [U(IV)]₀ to 1.0 mM. The induction period is caused by the fact that initially U(IV) exists in a weakly active polymeric form. Addition of U(VI) to the initial solution accelerates the oxidation. In a 1 M NaHCO₃ solution containing 0.1–1.0 mM U(IV), the U(IV) loss follows the first-order rate law with respect to U(IV) and O₂. The pseudo-first-order rate constants, bimolecular rate constants, and activation energy of the U(IV) oxidation were calculated. In dilute NaHCO₃ solutions (0.5–0.01 M), the hydrolysis and polymerization of U(IV) become more pronounced. The autocatalysis mechanism presumably involves formation of a complex [U(IV) · U(VI)] with which O₂ reacts faster than with U(IV). Oxidation of U(IV) occurs by the two-electron charge-transfer mechanism.     

The treatment of acute endotoxicosis in diabetic patients with surgical diseases requiring emergency intervention

During the 1990s the number of dental establishments in New York State continued to increase at a slow rate, while the resident population per establishment remained stable. The number of dental facilities with fewer than five employees continued to decrease; employee salaries increased, but did not keep pace with the rate of inflation. Statewide averages, however, mask marked variations between counties. Bureau of the Census data provide important means for monitoring developments for the general profession and for individual practitioners.     

Analysis of the dynamics of mechanical systems using symmetry groups

A technique of analysis of dynamics of mechanisms with symmetry elements is given. One of possible schemes of such analysis is considered by example of the tooth wheel mechanism.     

Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: II. Effect of H2O2

Oxidation of various Cr(III) hydroxides and mixed Cr(III)-Ni(II) and Cr(III)-Fe(III) hydroxides with hydrogen peroxide was studied. The initial reaction rate increases as the Cr(III) content in the suspension and H₂O₂ concentration are increased and nonmonotonicaly decreases with increasing NaOH concentration within the 0.2-2.0 M range. The activation energy in 0.5 M NaOH is equal to 82 kJ mol^{- 1} (30-90°C). The oxidant consumption substantially exceeds the stoichiometry.     

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.     

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.