Problems in the hygienic rationalization of the therapeutic and prophylactic nutrition of industrial workers

Based on generalization and analysis of instructions and guidelines for therapeutical and prophylactic diets of workers, ways of its optimization were proposed, by using bifide-containing acid dairy products as a preventive agent against possible occupational diseases caused by occupational factors.     

Consumption of basic foods, state of health and physical work capacity of middle school students

Actual nutrition, health state and physical working capacity were studied in schoolchildren of three age groups after intake of the polyvitamin "Undevitum" during a month. The results of the investigation conducted have shown that prophylactic measures produced a positive effect on the schoolchildren aged from 11 to 13 and from 14 to 17 years who received 1 degree of "Undevitum" daily. No positive effect was recorded in schoolchildren aged 7-10 years who received 1 degree of "undevitum"/day, every other day.     

Correspondence of the scheme and method of calculating the stability factor

The use of the main methods of calculating K_c in practice guarantees an accuracy of the calculation within

Investigation of fibres based on rigid-chain polyamides by the wide-line nmr and ultrasonic acoustics

Conclusions -- A dependence of the second moment of the NMR line on the angle between the fibre axis and the magnetic field has been given; the structural coefficient C ₀, C ₂, and C ₄ have been calculated for fibres based on poly-p-phenyleneterephthalamide and poly-p-benzamide at temperatures of –196 and +20°C and for Kevlar-49, from –196 to +400°C.-- The intramolecular structural coefficients C ₀ ^im, C ₂ ^im, and C ₄ ^im have been calculated theoretically, and the orientation parameters and and the acoustic orientation factor f have been obtained, values for which indicate a high degree of orientation of the macromolecules in fibres.-- The smaller values of the second moment of the NMR line for PABI as compared with fibres based on PPTA in the temperature region 250–380°C indicate a more mobile structure for the PABI.-- In the range from –196 to +20°C thermal action leads to a more important change in the coefficient C ₀ for Kevlar-29 and Kevlar-49 as compared with PABI; this is apparently connected with thermal expansion in planes having a predominant concentration of van der Waals bonds for Kevlar-29 and Kevlar-49.Translated from Khimicheskie Volokna, No. 4, pp. 23–26, July–August, 1990.     

Preparation of Ti<Subscript>3</Subscript>SiC<Subscript>2</Subscript> through reduction of titanium dioxide with silicon carbide

This paper describes the reduction of titanium dioxide with a mixture of silicon carbide and silicon powders at a temperature of 1550°C under vacuum. It has been shown that the use of the combined reductant enables the preparation of the ternary phase Ti₃SiC₂ through concurrent carboand silicothermic processes. The optimal compositions for Ti₃SiC₂ formation are TiO₂ + (1.5–x)SiC + 2xSi with x = 0.4–0.5. The Ti₃SiC₂ yield then reaches 96 wt %.     

Influence of the mechanical activation of REE oxides on the electrical conductivity of borate melts

The influence of the mechanical activation of oxides M₂O₃ (La₂O₃, Ce₂O₃, Nd₂O₃, Sm₂O₃, Eu₂O₃, Gd₂O₃, Tb₂O₃, Dy₂O₃, Ho₂O₃, Er₂O₃, Yb₂O₃, and Lu₂O₃) on electrical conductivity (æ) of the B₂O₃-M₂O₃ molten systems is investigated. It is assumed that the majority carriers in these melts can be protons which enter the melts due to the hydration of B₂O₃. The variation in the magnitude of for various M₂O₃ contents is explained by the corresponding variation in the structure of structural units as a result of the dissociation of the boron-oxygen groups, which include the OH groups. The activation energy of electrical conductivity in the B₂O₃-M₂O₃ melts increases due to the decay of superstructural units [B₃O_4.5] and B₃O₃O_3/2OH as the temperature increases. The dependence of is found. In the B₂O₃-La₂O₃ → B₂O₃-Lu₂O₃ melts series, this energy follows the intraseries periodicity, which depends on the stabilization energy of fundamental terms of the ions of rare-earth elements (REE).     

Effect of Retardation of the Transfer of Sr‐89 to the Body of Rats Drinking Water Filtered Through Coarsely Divided Naturally Occurring Mineral Flint

Data of experimental studies of the influence of flint water on the processes of accumulation and elimination of Sr89 from the body of white rats and results of theoretical investigations aimed at substantiating an increase in the bond energy of flint water molecules with strontium ions are presented.     

Electron reflection spectra of Ce3+ in BeF2 and B2O3 melts

The electron spectra of the melts of BeF₂-CeF₃ and B₂O₃-Ce₂O₃ systems have been obtained via electron reflection spectroscopy in the near UV range. Coordination numbers of cerium(III) ions have been determined in these systems from spectral data. It has been found that the nephelauxetic shift of interconfigurational 4f → 5d electron transitions in cerium ions depends on the degree of covalence of the bonds and the valence of ligands in complex groups, CeF₆ and CeO₆. It has been shown that the character of spectrograms of the B₂O₃-Ce₂O₃ melts depends on the preliminary preparation of the components of the mixture. This is related to the structural heterogeneity of oxide complex groups of cerium(III) ions in borate melts.     

Synthesis, structure, and properties of mixed niobium(IV,V) oxides

This review paper summarizes data on mixed oxides containing niobium in an intermediate valence state, between 4+ and 5+. The major preparation procedures are considered, and the effects of different process parameters—composition of the starting reagents, temperature, pressure, duration, and environment—are analyzed from the viewpoint of the preparation of bulk, single-phase materials with niobium in a controlled formal oxidation state. The optimal synthesis conditions are established for reduced niobates with different structures. The oxidation behavior of the niobates(IV,V) is examined as a function of the structure type. The structural and electrical properties of the reduced niobates are shown to correlate with the carrier concentration (formal oxidation state of niobium). The major factors determining the carrier concentration in the niobates are identified. The results are used to establish the conditions under which a semiconductor—metal transition is possible in reduced niobates