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.     

Interaction of U(VI), Np(VI), Pu(VI), and Np(V) with benzenetricarboxylic acids: Complexation in aqueous solutions, synthesis, and crystal structure of uranyl complexes [UO2(H2O)2{C6H3(COO)2(COOH)}]2·2H2O and [(UO2)3(H2O)4{C6H3(COO)3}2]

The complexation of U(VI), Np(VI), and Pu(VI) and of Np(V) with 1,2,3- and 1,2,4-benzenetricarboxylic acids (BTC) in aqueous solutions was studied in wide ranges of pH and actinyl ion concentrations. The compositions of the forming hexavalent actinide complexes were determined. Their apparent stability constants β₁′ depend on pH of the solution: in the pH range 2–4, logβ₁′ from 2 to 4 for the complexes of U(VI), Np(VI), and Pu(VI) with 1,2,3-BTC and from 1.5 to 3.5 for the complexes with 1,2,4-BTC. For Np(V), the β₁′ values are close with both acids, and at equal pH values the Np(V) complexes are less stable than the An(VI) complexes (An = U, Np, Pu). With an increase in pH from ～3 to 6.2–6.9, logβ₁′ of the Np(V) complexes increases approximately from 0.5 to 3. Solid U(VI) complexes with 1,2,3- and 1,2,4-benzenetricarboxylic acids were synthesized by the hydrothermal method, their crystal structure was determined, and the IR spectra were examined.     

Reduction of Np(VI) and Pu(VI) with anions of some substituted carboxylic acids

The reaction of Np(VI) with organic acid anions in solutions containing lithium salts of tartaric, malic, α-aminoglutaric, and trihydroxyglutaric acids was studied. Changes in the solution spectra show that Np(VI) forms complexes with organic acid anions, which is followed by the reduction of Np(VI) to Np(V). Similar processes occur in solutions containing Pu(VI) and sodium phenylglycolate or ammonium salicylate. In weakly acidic solutions, the loss of the Np(VI) and Pu(VI) concentrations is a linear function of time. The possible mechanism of the redox reactions was suggested.     

Synthesis and crystal structure of americium(V) dichromate, Cs3AmO2(Cr2O7)2·H2O

A new Am(V) chromate complex with outer-sphere cesium cation, Cs₃AmO₂(Cr₂O₇)₂·H₂O, was prepared from aqueous solution. Its composition and structure were determined by single crystal X-ray diffraction. The Am(V) atom has coordination surrounding in the form of a distorted pentagonal bipyramid with the O atoms of the AmO ₂ ⁺ group in apical positions. The equator of the bipyramid is formed by the O atoms of four dichromate groups and of the water molecule. The mean bond lengths (Å) are as follows: Am=O 1.802(5), Am-O(Cr₂O₇) 2.443(6), and Am-O_w 2.519(6). The Am(V) pentagonal bipyramids are combined via bidentate bridging Cr₂O ₇ ^2? anions into infinite chains [AmO₂(Cr₂O₇)₂H₂O] _n ^3? arranged in layers parallel to the series of diagonal planes (111). A system of hydrogen bonds links the chains in a layer and the layers with each other. The Cs cations are arranged between the layers, forming cationic interlayers.     

Construction of the welded body of vehicles from aluminium alloys

The theory of thermal processes, developed by N.N. Rykalin, is used for calculating the cooling rate, the temperature in heating and the width of quenched grooves in surface quenching with the electric arc. The results confirm that high-quality surface quenching of the components can be carried out without additional cooling of the surface with water.     

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.