Poly(vinyl alcohol)/heteropolyacid nanocomposites as new materials for radiochromic dosimetry in radiation processing

Radiochromic films composed of polymer matrices and organic dyes are widely used for routine dosimetry purposes in operation of various radiation facilities—gamma and X-ray-irradiation, electron accelerators, and so on. However, the sensitivity of these films rapidly decreases at doses exceeding 30–50 kGy due to a saturation of their optical response, making them unsuitable for accurate dosimetry in radiation processing of polymers and composites where doses up to 200 kGy are typically employed. To overcome this limitation, the use of inorganic substances as the coloring agents of polymer-based radiochromic films was proposed in this paper, specifically, heteropolyacidacid H₃PW₁₂O₄₀ (tungstophosphoric acid) in the matrix of poly(vinyl alcohol) (PVA). Nanocomposite PVA/H₃PW₁₂O₄₀ films were prepared by solution casting and their optical responses toward ⁶⁰Co gamma radiation and beams of 6 MeV electrons for a dose range of 10–200 kGy were investigated. It was established that upon exposure to gamma rays and electron beams, the films turn blue and a broad absorption band at 750 nm appears in their spectra. Importantly, the radiation-induced optical absorption increases in a linear fashion up to the dose of 150 kGy and only slightly deviates from linearity at 200 kGy. Moreover, it was found that the PVA/H₃PW₁₂O₄₀ films have a long shelf life, are dose-rate independent within a wide range, and color-stable after irradiation. All these features make the nanocomposite PVA/H₃PW₁₂O₄₀ films promising for use as routine dosimeters and dose labels in a much wider range of high doses as compared to radiochromic films based on organic dyes.     

Determination of the degree of palladium reduction in supported catalysts based on anion exchangers

A procedure is suggested for determining the degree of palladium reduction in fibrous anion exchangers from data on the quantitative recovery of Pd(II) from samples with a hydrochloric acid solution of thiourea before and after the reduction stage.     

On the Maxwell problem

We study the large-time behavior of global smooth solutions to the Cauchy problem for hyperbolic regularization of conservation laws. An attracting manifold of special smooth global solutions is determined by the Chapman–Enskog projection onto the phase space of consolidated variables. For small initial data we construct the Chapman–Enskog projection and describe its properties in the case of the Cauchy problem for moment approximations of kinetic equations. The existence conditions for the Chapman–Enskog projection are expressed in terms of the solvability of the Riccati matrix equations with parameter. Bibliography: 21 titles. Translated from Problems in Mathematical Analysis 39 February, 2009, pp. 27–63.     

Well-posedness of mathematical models of continuum mechanics and thermodynamics

Mathematical models of nonequilibrium thermodynamics related to the concepts of stability and well-posedness are considered.Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 3, Partial Differential Equations, 2003.     

Synthesis,Structure, and Thermal Stability of a Sulfonic Cation Exchanger Grafted to Carbonized Fiber

A new kind of sulfonic cation exchanger based on carbonized fiber modified with poly(styrene-divinylbenzene) was prepared by radiation grafting. The structural features and thermal stability of the cation exchangers prepared were studied.