On the effective medium model for particles with a complex structure

We consider a generalization of the effective medium approximation to the case of matrices containing macroscopically inhomogeneous particles with an arbitrary structure (cermet topology). The form of the result is determined to a considerable extent by the heuristic choice of effective cells used to estimate the field and induction values averaged over the volume. The simplest choice of a particle in an unperturbed field as a cell leads to the Maxwell–Garnett approximation, while the self-consistent effective medium approximation corresponds to the replacement of the unperturbed field by the mean field. As an example, we describe particles with a shell, as well as statistically anisotropic media with a single preferred direction.     

Multivariate processing of atomic-force microscopy images for detection of the response of plasticized polymeric membranes

The possibility of using the atomic-force microscopy as a method for detection of the analytical signal from plasticized polymeric sensor membranes was analyzed. The surfaces of cadmium-selective membranes based on two polymeric matrices were examined. The digital images were processed with multivariate image analysis techniques. A correlation was found between the surface profile of an ion-selective membrane and the concentration of the ion in solution.     

Diamond direct and inverse opal matrices produced by chemical vapor deposition

Diamond structures with inverse and direct three-dimensional opal lattices with period of 250–530 nm were grown by microwave plasma deposition in methane-hydrogen mixtures using porous SiO₂ opal matrix and its Si replica as templates, respectively. The Si templates can be filled with diamond to the depth as large as 80 layers of the spheres.     

Positioning of HPPE production on post-Soviet space by technology development and output

The comparative analysis of the molecular mass distribution, temperatures and heat effect of phase transitions, degree of crystallinity of defect materials and matrix polyethylene film were carried out. Possible reasons of deterioration of the quality of polyethylene on stages of its synthesis, transportation, storage, and processing were determined.     

Hysteresis phenomena in the light self-diffraction in a dense resonant medium

On the basis of the modified Bloch equations a theory is developed of the light self-diffraction in a thin film of a dense resonant medium with allowance for the dipole-dipole interactions of atoms. It is shown that for certain values of intensity of an external field, there occurs in the film the light-induced first-kind phase transition which causes the emergence of regions (domains) with the high excitation of atoms. The switching effects of the system dense resonant medium + periodically-modulated field under consideration result in a hysteresis behaviour in the dependence of the diffraction efficiency on the adiabatically changing intensity of the external field. The predicted hysteresis offers additional potentialities in the investigation of the dynamics of the first-kind phase transition in dense media and outlook for usage of the film as a switching logical element.     

Almost convex sets

The concept of a wedgoid, a generalized wedge, is introduced and studied. Almost all convex sets are characterized by the fact that balls can be separated from such a set by means of wedgoids.     

Potentiometric and theoretical studies of the carbonate sensors based on 3-bromo-4-hexyl-5-nitrotrifluoroacetophenone

Novel carbonate ionophore, trifluoroacetophenone derivative (TFA) substituted by two acceptor substituents in the phenyl ring (3-bromo-4-hexyl-5-nitrotrifluoroacetophenone), was synthesized. Solvent polymeric membrane sensors based on this ionophore exhibited heightened selectivity to carbonate ions in the presence of the most important interfering anions. A wide range of potentiometric properties were studied and compared with those of sensors based on mono-substituted ionophores. Special attention was paid to pH dependence of sensor responses and to elaboration of appropriate conditions for carbonate analysis. A segmented-sandwich membrane method was applied for determination of the stoichiometry of ionophore-carbonate complexes, which was determined to be 1:3, and apparent complex formation constants which were 14.4 and 13.6 for DOS- and NPOE-plasticized membranes, respectively. Theoretical studies on TFA derivatives by semi-empirical (AM1 and PM3) and ab initio(6-31+G*) methods were performed, considering different types of possible ionophore-ion interactions. The formation of hydrogen bonds between carbonate and hydrated TFA was proved to be much more favourable in terms of energy compared to tetrahedral nucleophilic adducts that earlier were postulated to being formed in the membrane phase. The final conclusion on the mechanism of carbonate sensing by TFA-based solvent polymeric membrane sensors was made on the basis of computational data and detailed analysis of the literature.     

Radiation Recoil Problem for Classical Charged Dust Grains

We consider several classical problems (Coulomb scattering, motion in a constant external electromagnetic field, Brownian motion) for the Sommerfeld model of an extended charged particle (dust grain). We find essential differences from the classical result in both quantitative aspects (a change of the angle in Coulomb scattering, decrease of the diffusion coefficient for a Brownian particle, deceleration of outspiraling of the dust grain in a cyclotron) and in qualitative aspects (occurrence of the tunneling effect through a potential barrier). These differences do not disappear as the size of the particle tends to zero. The equation of motion of an extended object therefore does not have a smooth limit transition to the Newton equation for a point.