A Study of cryostructuring of polymer systems. 41. Complex and composite poly(vinyl alcohol) cryogels containing soluble and insoluble forms of chitosan,respectively

Complex macroporous poly(vinyl alcohol) (PVA) cryogels have been obtained by cryogenic treatment (freezing at–20°C for 12 h followed by defrosting at a rate of 0.03°C/min) of PVA–chitosan hydrochloride mixed solutions. The subsequent alkaline treatment of the cryogels has resulted in the transformation of the water-soluble salt form of chitosan into its insoluble basic form, which coagulates inside the bulk of the continuous phase of PVA cryogel into small particles with sizes of 2–5 µm. In the resulting composite cryogels, these particles play the role of an “active” filler, which increases the rigidity and heat endurance of the gel material. It has been shown that the sorption capacity of such chitosan particles entrapped into the bulk of composite cryogels with respect of bivalent copper ions is noticeably higher than the sorption capacity of ground chitosan particles incorporated as a discrete filler into the continuous phase PVA cryogels. The study of the properties of PVA–chitosan hydrochloride mixed solutions revealed that these polymers are, to a large extent, compatible with one another in a common solvent at a low ionic strength. Therefore, liquidliquid phase separation of these systems due to the thermodynamic incompatibility of macromolecules of different natures is observed only upon increasing the ionic strength by adding a low-molecular-mass salt (NaCl, 0.15 mol/L) to the solution.     

Optimal Motion Law of a Resonant Nuclear Absorber for the Formation of Short Pulses of Mössbauer Radiation

Radiophysics and Quantum Electronics - In this paper, the method of transforming the Mössbauer gamma radiation into a train of ultrashort pulses in a resonant nuclear absorber, which...     

Production of High-Transverse-Momentum Deuterons and Tritons at an Angle of 40 $${{}^{\circ}}$$ in Proton–Nucleus Interactions at a Beam Energy of 50 GeV

Physics of Atomic Nuclei - Data on the production of positively charged particles emitted at an angle of 40 $${}^{\circ}$$ (in the laboratory frame) with transverse momenta of up to 2.7 GeV $$/c$$...     

Superscaling predictions for neutrino-induced charged-current charged pion production at MiniBooNE

Superscaling approximation (SuSA) predictions to neutrino-induced charged-current charged pion production in the Δ-resonance region are explored under MiniBooNE experimental conditions. The results obtained within SuSA for the flux-averaged double-differential cross sections of the π⁺${\pi }^{+}$ production for the _νμ+_CH2${\nu }_{\mu }+{\mathrm{CH}}_2$ reaction as a function of the muon kinetic energy and of the scattering angle, the cross sections averaged over the angle, the total cross section for the π⁺${\pi }^{+}$ production, as well as CC1π⁺$\mathrm{CC}1{\pi }^{+}$ to CCQE cross section ratio are compared with the corresponding MiniBooNE experimental data. The SuSA predictions are in good agreement with data on neutrino flux average cross sections, but a somewhat different dependence on the neutrino energy is predicted than the one resulting from the experimental analysis.     

Microscopic analysis of the elastic scattering of 11Li neutron-rich nuclei on protons

Amicroscopic optical potential is used to calculate cross sections for elastic ¹¹Li +p scattering at the energies of 62, 68.4, and 75 MeV per nucleon, and the results are compared with available experimental data. The potential used does not involve free parameters, but the depths of its real and imaginary parts are renormalized. The known trend in the energy dependence of the volume integrals of the optical potential is taken into account in analyzing experimental data. The role of spin-orbit interaction is studied, and the total reaction cross sections that are proposed to be measured in future experiments are calculated.     

Synthesis of bimetallic powders of alloys of platinum with tin

Technique of obtaining nanosized bimetallic powders of alloys of platinum metals with tin by reduction of complexes of metals with tin halide ligands using zinc from aqueous HCl solutions was developed. These powders were studied by X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy.     

Electroconduction of rubidium pyrophosphate modified by divalent cations

Solid solutions based on rubidium pyrophosphate are synthesized in the Rb_{4 -2x}M_xP₂O₇ systems (M = Ca, Sr, Ba, Pb). The temperature and concentration dependences of their rubidium-cation conductivity are investigated. The X-ray data for the low and high-temperature forms of Rb₄P₂O₇ and also for solid solutions based on it are reported. The effect exerted by modifying cation M²⁺ on electrical properties of synthesized solid solutions is considered     

On a class of modular lattices

Translated from Algebra i Logika, Vol. 30, No. 1, pp. 3–14, January-February, 1991.     

Deflection of IR-radiation in n-InSb in the presence of temperature-electrical instability in a magnetic field

The formation of an S-shaped volt-ampere characteristic (VAC) during the heating of a specimen of n-type indium antimonide by a dc electric current in the presence of an external magnetic field is considered. In the calculation of the VAC the temperature dependences of the band gap width, the carrier density, the mobility, and the heat conductivity are taken into account. The angle of deflection of IR-radiation in indium antimonide is calculated using the density distribution over the cross section of the specimen derived from the integration of heat conductivity equation. The experimental and theoretical dependences of the deflection angle on the current are in agreement in order of magnitude and indicate that it is possible to use the temperature instability for the construction of laser radiation deflectors in the IR range.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 35–40, November, 1984.The authors are grateful to V. L. Bonch-Bruevich and I. P. Zvyagin for useful discussion and valuable critical remarks.     

Fabrication of polymer scaffolds for tissue engineering using surface selective laser sintering

A new approach to the fabrication of individual implants and scaffolds for tissue engineering—surface selective laser sintering (SSLS)—is proposed and realized. In contrast to the conventional selective laser sintering, the SSLS method makes it possible to sinter polymer microparticles and melt the near-surface layer rather than the microparticle as a whole. The effect of the laser radiation parameters and the structure and composition of the raw products on the structure and properties of the biomaterials sintered by the laser radiation is analyzed. This approach makes possible both the application of thermally unstable polymers (e.g., polylactides or polylactoglycolides) and the fabrication of scaffolds with incorporated bioactive proteins. The results obtained yield a regular physical basis for a new technology of the fabrication of various polymer scaffolds that represent important materials and elements of modern tissue engineering. The flexibility of the SSLS method is especially important at the stage of investigation of the cell and tissue responses needed for the optimization of the material for a specific application in tissue engineering.