Young Measures as Measurable Functions and Their Applications to Variational Problems

In this paper, we give a systematic exposition of our approach to the Young measure theory. This approach is based on characterzation of these objects as measurable functions into a compact metric space with a metric of integral form. We explain advantages of this approach in the study of the behavior of integral functionals on weakly convergent sequences. Bibliography: 38 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 310, 2004, pp. 191–212.     

Changes in electrical and optical properties of polyimide films under the action of accelerated electrons

Changes in the structure and optical and electrical properties of Apical brand polyimide films under the action in air of accelerated electrons with an energy of 0.5 MeV and absorbed dose varied in the range 1–300 MGy were studied.     

The effect of composition and structure on dielectric characteristics of films based on poly(vinyl alcohol) cyano ether

The composition, bulk structure, and supramolecular structure of poly(vinyl alcohol) cyano ether are studied by the methods of IR and high-resolution NMR spectroscopy and by atomic force microscopy. According to the data on the parameter of blockiness (η = 1.03), this copolymer is characterized by a random structure; the content of residual acetate groups is below the detection level of the applied methods. When the films are formed by screen printing, owing to the high orientation of polymer in the direction perpendicular to the direction of the supporting plane, the dielectric permeability of the films is higher than that of the films prepared by film casting. Films with a thickness of 20–40 μm are prepared, and their dielectric permeability approaches 23.     

Bulk strain energy density in randomly reinforced polymer composites with antifriction dispersed additives

Bulk strain energy density was numerically simulated for epoxy-phenol-based composites randomly reinforced with short polyimide fibers, with antifriction dispersed polytetrafluoroethylene (PTFE) additives. A mathematical model was constructed using the notion of a stress concentration operator (fourth-rank tensor) that relates volume averaged, or external, stresses within a heterogeneous material with their local values within an individual heterogeneity. The simulation was based on a generalized singular approximation of random field theory used to solve a stochastic differential equation of equilibrium of an elastic medium. This approximation yields an explicit expression for stress concentration in a composite material. The explicit expression allows one to analyze the distribution of bulk strain energy density depending on the composition, structure, volume and mass fraction of heterogeneities, and on the type and value of applied load. We studied how the considered energy characteristic depends on the type of external mechanical loading and concentration of isotropic components in the model composites. It is shown that with the increasing concentration of polyimide fibers at a fixed concentration of PTFE inclusions, the bulk strain energy density values of all components decrease and approach each other independently of the type of external loading. The form of these dependences is nonlinear. A change in the mass fraction of dispersed PTFE inclusions in the model composites exerts little effect on local energy values of all components under any of the considered applied external loads.     

Advantages of STED-Inspired 3D Direct Laser Writing for Fabrication of Hybrid Nanostructures

We present a new method of additive laser technology referred to as STED nanolithography technique. This technique provides a means for fabrication of 3D dielectric and plasmonic composite nanostructures. The new technology is of the utmost interest for the electronics manufacturing industry, in particular, for formation of specific hybrid (metal–dye) nanostructures, which can be utilized as luminescent markers in biology, medicine, criminalistics, and the trade industry. In the present study, we demonstrate the advantages of STED-inspired nanolithography for fabrication of metallic and hybrid nanostructures. The 3D-scanning setup implemented offers the possibility to form both periodic and aperiodic nanostructured arrays. We show the possibility to decrease substantially the lateral size of the lines formed with the use of STED nanolithography as compared to the direct laser writing (DLW) method. The STED nanolithography technique proposed provides a means for synthesizing metallic nanoparticles in the specified points of the volume of the studied object in vivo. In addition, we demonstrate the synthesis of metallic lines by means of STED nanolithography. Moreover, nanometer spatial precision of positioning of the synthesized nanoobjects is achieved. Therefore, it is possible to obtain significant local enhancement of the emission of luminescent markers (surface enhanced luminescence) at any desired point or area of the sample due to plasmonic enhancement of the electromagnetic fields near the surface of metallic nanostructures.     

Photodielectric Processes in ZnS : Cu Polycrystalline Layers

The frequency dependences of dielectric parameters of zinc sulfide electroluminescent polycrystalline structures doped with copper are studied in the dark and under light excitation in the visible wavelength range. A positive photodielectric effect most pronounced in the low-frequency range was revealed. The experimental results are explained within framework of formation of a space charge in the bulk of a semiconductor. The analysis of data indicates they can be correlated with luminance characteristics of an electroluminescent layer.     

Toward Artificial Mussel-Glue Proteins: Differentiating Sequence Modules for Adhesion and Switchable Cohesion

Artificial mussel-glue proteins with pH-triggered cohesion control were synthesized by extending the tyrosinase activated polymerization of peptides to sequences with specific modules for cohesion control. The high propensity of these sequence sections to adopt β-sheets is suppressed by switch defects. This allows enzymatic activation and polymerization to proceed undisturbed. The β-sheet formation is regained after polymerization by changing the pH from 5.5 to 6.8, thereby triggering O→N acyl transfer rearrangements that activate the cohesion mechanism. The resulting artificial mussel glue proteins exhibit rapid adsorption on alumina surfaces. The coatings resist harsh hypersaline conditions, and reach remarkable adhesive energies of 2.64 mJ m⁻² on silica at pH 6.8. In in situ switch experiments, the minor pH change increases the adhesive properties of a coating by 300 % and nanoindentation confirms the cohesion mechanism to improve bulk stiffness by around 200 %.     

Chemical Concept of Geodynamic Shocks in Coal Strata

A chemical concept of geodynamic shocks in coal strata, accompanied by ejection of coal dust and gas, is suggested.     

Ferroelectric photonic crystals based on nanostructured lead zirconate titanate

The first results obtained in the synthesis of one-dimensional ferroelectric photonic crystals based on nanostructured lead zirconate titanate and porous silicon are reported. The samples synthesized are studied using linear reflection and second optical harmonic spectroscopy.