The influence of γ- and UV-radiation dose on the buildup and decay of paramagnetic centers in solid hydrogen cyanide

A decrease in the concentration of paramagnetic centers (PMCs) stabilized at 77 K in crystalline hydrogen cyanide was observed when ionizing radiation doses exceeded 3000 kGy. It was assumed that the decrease is due to a change in the physical properties of the matrix as a result of its deformation, loosening, amorphization, and formation of metastable structures. The decay of the PMCs with an increase in temperature of the irradiated samples depends on the dose and type (UV, γ) of the radiation. The higher the dose of preliminary γ-irradiation, the lower the decay temperature. In UV-irradiated HCN, the paramagnetic centers that occur in the thin photolyzed layer are more stable, since they are localized at defect sites of the crystalline matrix, which hinder the migration of free valence.     

Initiation of Low-Temperature Polymerization with Hexafluoropropylene Ozonide

The feasibility of using hexafluoropropylene ozonides for initiating low-temperature polymerization and copolymerization of tetrafluoroethylene, hexafluoropropylene, and some other monomers was demonstrated.     

Changes in the state of impurities and the corresponding force fields in silicon after high-temperature cyclic annealings

The influence of high-temperature annealings followed by cooling under different conditions on changes in the specific resistance and photoconductivity relaxation time in silicon and on the formation of the acceptor state of gold, when gold diffused from a layer vacuum-deposited on the surface, was studied in experiments including sequences of processes conducted using various temperatures, cooling conditions, and surface states. The experimental data are analyzed based on the concept of changes in the state of impurities present in silicon and in the corresponding dynamic and static force fields.     

Optical absorption by Nd<Superscript>3+</Superscript> and Gd<Superscript>3+</Superscript> ions in epitaxial films grown on Gd<Subscript>3</Subscript>Ga<Subscript>5</Subscript>O<Subscript>12</Subscript> substrates from a lead-containing solution melt

Epitaxial films of composition (Gd,Nd)₃Ga₅O₁₂ or (Gd,Y,Nd)₃Ga₅O₁₂ with a neodymium content varying from 0.3 to 15 at. % are grown by liquid-phase epitaxy from a supercooled PbO-B₂O₃-based solution melt on Gd₃Ga₅O₁₂(111) substrates. The optical absorption spectra of the epitaxial films grown are measured in the wavelength range 0.2–1.0 µm. The results of interpreting the absorption bands observed in the spectra are used to construct the energy level diagrams of Nd³⁺ and Gd³⁺ ions in the matrices of the epitaxial films.     

Calorimetric study of the low-temperature postradiation polymerization of tetrafluoroethylene in the presence of reduced graphite oxide

Low-temperature postradiation polymerization of tetrafluoroethylene in the presence of carbon material obtained by explosive exfoliation of graphite oxide has been studied by the technique of calorimetry. The process results in tetrafluoroethylene grafting onto modified graphite oxide to form a new composite containing ～40–65% polytetrafluoroethylene.     

Post-irradiation grafting of tetrafluoroethylene at low temperatures

Low-temperature postirradiation grafting of tetrafluoroethylene (TFE) to polyolefines and silicone elastomers was the subject of study. After preliminary dissolution of TFE in the polymer at 273°K the system was slowly cooled to 77°K. In this process a certain part of TFE in polyolefines (ethylene-propylene copolymer and polypropylene) is retained by the vitreous polymer matrix. When slowly heated after radiolysis at 77°K this system shows graft polymerization of dissolved TFE after T_g. The graft copolymer is soluble and its IR spectra contain absorption bands characteristic of polytetrafluoroethylene. In polydimethylsiloxane rubber (SKT) the dissolved TFE when frozen to 77°K remains sorbed between the SKT crystallites rather than in a separate phase. When these radiolyzed samples are heated the graft-polymerization occurs primarily over the temperature range between the TFE and SKT melting points. The technique provedes for 100–150% grafting of TFE. This method also permits grafting to silicone rubbers and to several other polymers and elastomers.     

On the rate oscillations in the postradiation polymerization of formaldehyde at 5–50 K

Oscillations in the rate of postradiation polymerization of solid formaldehyde at 5–50 K have been detected. It is supposed that the mechanical factor (brittle failure) is responsible for the oscillations in the rate of formaldehyde postpolymerization at such low temperatures, in contrast to the previously known oscillatory modes of chemical reactions.     

Influence of clay properties on radon emanation

The emanation factor of clay strata was measured in a series of experiments. The clay emanation factor grows with increased dispersion and can reach values of up to 67%. This can be explained, in our view, by the increased number of nanodimensional particles with good emanation characteristics.     

Individually Addressable Patterned Multilayer Microchambers for Site‐Specific Release‐On‐Demand

Patterned arrays of light‐responsive microchambers are suggested as candidates for site‐specific release of chemicals in small and precisely defined quantities on demand. A composite film is made of poly(allylammonium)‐poly(styrene sulfonate) multilayers and gold nanoparticles incorporated between subsequent stacks of polyelectrolytes. The film shaped as microchambers is loaded with colloid particles or oil‐soluble molecules. The microchambers are sealed onto a glass slide precoated with an adhesive poly(diallyldimethylammonium)‐poly(styrene sulfonate) multilayer film. A focused laser beam is used for remote addressing the individual microchambers and site‐specific release of the loaded cargo.     

Effect of the nature of polymer matrix on the process of cholesterol photooxidation in the presence of immobilized tetraphenylporphyrins

It was shown that carrying out the reaction of cholesterol photosensitized oxidation in the presence of porphyrins immobilized on the hydrolyzed copolymer of tetrafluorethylene and H⁺ form of perfluoro-3,6-dioxo-5-methyl-6-sulfonylfluorideoctene-1 leads to the formation of not previously described new products: 6β-phormyl-B-norcholestan-3β,5β-diol, 6β-chlorocholestan-3β,5α-diol, cholestan-3β,5α,6β-triol, and 5α-chlorocholestan-3β,6β-diol.