Generation of a Polarization Sensitive Photocurrent in a CuSe/Se Nanocomposite Thin Film

JETP Letters - CuSe-based structures are widely used in various fields of photonics and optoelectronics. It has been shown for the first time that a photocurrent depending on the direction of the...     

On numerical study of periodic solutions of a delay equation in biological models

Some results are presented of the numerical study of periodic solutions of a nonlinear equation with a delayed argument in connection with themathematical models having real biological prototypes. The problem is formulated as a boundary value problem for a delay equation with the conditions of periodicity and transversality. A spline-collocation finite-difference scheme of the boundary value problem using a Hermitian interpolation cubic spline of the class C ¹ with fourth order error is proposed. For the numerical study of the system of nonlinear equations of the finitedifference scheme, the parameter continuation method is used, which allows us to identify possible nonuniqueness of the solution of the boundary value problem and, hence, the nonuniqueness of periodic solutions regardless of their stability. By examples it is shown that the periodic oscillations occur for the parameter values specific to the real molecular-genetic systems of higher species, for which the principle of delay is quite easy to implement.     

Diadamantylation of dihydric phenols and their derivatives

Dihydric phenols and their monomethyl ethers were converted into diadamantyl derivatives by the reaction with 1-adamantanol in trifluoroacetic acid.     

Effects of molecular weight on macropore sizes and characterization of porous hydroxyapatite ceramics fabricated using polyethylene glycol: mechanisms to generate macropores and tune their sizes

Hydroxyapatite (HAp) is a raw material used to fabricate scaffolds. Scaffolds are required to be porous to facilitate nutrient flow and vascularization. This study aims to produce porous HAp ceramics with macropores (>200 μm) and bioactivity and tune their macropore size. Polyethylene glycol (PEG) with molecular weights of 400, 3,400, and 8,300 was used to generate macropores. The macropore size increased as the molecular weight of PEG increased. In this method, emulsions were formed by hydrophobic PEG binding HAp nanoparticles during chemical syntheses. Water foams, as a core of the emulsion, were transformed into steam, and the steam expanded under heat treatment. Macropores were generated by the evaporation of the steam and consolidation of HAp nanoparticles. The difference in the molecular weight of PEG did not affect cell adhesion to the porous HAp ceramics. Cells adhered well to and spread widely on the HAp ceramics regardless of macropore size.     

Critical conditions for spontaneous relaxation in self-organizing dissipative film systems

It is established that the necessary conditions for spontaneous relaxation of elastic strain energy in a copper-As₆₀Se₄₀ self-organizing dissipative heterostructure is that the elastic deformation energy and the temperature must reach their threshold values. It is shown that in the temperature range 270–340 K the spontaneous relaxation of elastic deformation energy is accompanied by structural-chemical ordering and anomalous diffusion of copper into the glassy chalcogenide semiconductor layer. The maximum concentration of copper dissolved in the films is 40 at. %. Conductivity inversion from p to n type is observed in doped layers obtained by this method. Zh. Tekh. Fiz. 69, 128–129 (August 1999)     

Spontaneous explosive crystallization and phase transformations in a selenium/copper bilayer nanofilm

Spontaneous explosive crystallization in a selenium/copper bilayer nanofilm has been experimentally studied. It has been shown that the formation of a microcrack network in the selenium film is a decisive factor for spontaneous explosive crystallization. The microcrack network is an efficient channel for the relaxation of the collected energy of elastic stresses in the selenium film. The relaxation of this energy accelerates crystallization and transfers it to the explosive regime. It has been found that crystalline phases appearing in the products of the reaction after spontaneous explosive crystallization depend on the ratio of the thicknesses of the copper and selenium films.