Confinement Effects in Droplet Formation on a Solid Particle.

Formation of a droplet around a spherical solid particle in supersaturated vapor is considered. The number and stability of equilibrium solutions in a closed small system are studied in the canonical ensemble in comparison to an open system in the grand canonical ensemble. Depending on the system's parameters, two modes exist in the canonical ensemble: the first one with only one solution and the second one with three solutions; the presence of the third solution is due to confinement.

Regularities of non-stationary diffusion growth of overcritical gas bubbles and kinetics of bubble distribution in presence of capillary and viscous forces.

The regularities of non-stationary diffusion growth of overcritical gas bubbles and kinetics of their distribution in sizes in a supersaturated-by-gas liquid solution on the nucleation stage have been analytically described by taking into account the full-scale influence of viscous and capillary forces on pressure in the overcritical bubbles. The results are general and not limited by values of gas supersaturation and gas solubility in the surrounding liquid solution. It is shown how the nonuniform concentration profile of the dissolved gas in supersaturated solution around the growing bubble changes with time and distance from the center of the overcritical bubble and gradually transforms into a stationary (at low solubility and moderate supersaturation of the dissolved gas) or self-similar profile (at large solubility and supersaturation of the dissolved gas).

Comment on "Size dependence of bubble wetting on surfaces: breakdown of contact angle match between small sized bubbles and droplets" by H. Zhang and X. Zhang, , 2019, , 2823.

The main result of the commented article is based on the use of an erroneous technique in the derivation of the equation for the contact angles of surface bubbles. A correct derivation gives the same Young equation as for sessile droplets, and therefore supplementary contact angles for bubbles and droplets. This cannot explain the presented results of simulations of nanosized droplets and bubbles where there are also several questions.

The effect of a finite number of monomers available for aggregation at nucleation and micellization in a fixed volume.

The expressions for the minimal work of aggregate formation as a function of the aggregation number and monomer concentration for a system with a limited number of monomers and a fixed volume have additional terms in comparison with a bulk metastable phase. The role of these terms has been analyzed in the case of droplet homogeneous nucleation and micellization in a nonionic surfactant solution. The appearance of the potential well and direct and reversal aggregation barriers in such systems and their dependence on the system parameters and monomer concentration have been considered and compared.

Multicomponent condensation on the nucleation stage.

A new analysis of evolution of an ensemble of supercritical (in size) droplets in the atmosphere of several condensing vapors has been presented. The analysis has been performed for the nucleation stage of formation and growth of the supercritical droplets in a closed system with a fixed amount of condensing species. The nucleation stage starts with appearance of supercritical droplets and finishes when nucleation rate of new critical droplets in the closed system ceases due to vapor depletion by the growing supercritical droplets.

Nucleation stage of multicomponent bubbles of gases dissolved in a decompressed liquid.

A new kinetic analysis of degassing and swelling of a decompressed liquid solution with several dissolved gases has been presented. The analysis has been performed for the nucleation stage of formation and growth of supercritical gas bubbles in a closed system under conditions of a limited availability of the dissolved species. The nucleation stage is an important stage of degassing, on which a certain size distribution of gas bubbles is formed, being the starting point for further growth.

Coherent anti-Stokes Raman scattering under frequency comb excitation.

We study the efficiency of coherent anti-Stokes Raman scattering (CARS) under frequency comb excitation. We calculate the power density of the anti-Stokes signal for two major cases: (1) molecular excitation by frequency comb and cw probe and, (2) both excitation and probing by frequency combs. In the first case, average CARS power varies as an inverse third degree of frequency combs free spectral range (FSR); in the second case, it varies as FSR.

Compressed sensing approach for wrist vein biometrics.

The work describes features of the compressed sensing (CS) approach utilized for development of a wearable system for wrist vein recognition with single-pixel detection; we consider this system useful for biometrics authentication purposes. The CS approach implies use of a spatial light modulation (SLM) which, in our case, can be performed differently-with a liquid crystal display or diffusely scattering medium. We show that compressed sensing combined with above-mentioned means of SLM allows us to avoid using an optical system-a limiting factor for wearable devices.

Full-time kinetics of self-assembly and disassembly in micellar solution via the generalized Smoluchowski equation with fusion and fission of surfactant aggregates.

Full-time kinetics of self-assembly and disassembly of spherical micelles with their fusion and fission in non-ionic micellar solutions has been considered in detail on the basis of direct numerical solutions of the generalized Smoluchowski equations describing the evolution of the time-dependent concentrations of molecular aggregates for every aggregation number. The cases of instant increase of the monomer concentration up or dilution of a surfactant solution below the critical micelle concentration at large initial deviations from the final equilibrium state have been studied. Different stages in assembly or disassembly of micelles have been described and compared with the results of the stepwise mechanism of monomer attachment-detachment described by the Becker-Döring kinetic equations.

Through-focus scanning optical microscopy (TSOM) considering optical aberrations: practical implementation.

Through-focus scanning optical microscopy (TSOM) method based on use of a library, which is composed of simulated defocused images of nanosized silicon lines on the top of a monocrystalline silicon substrate, is demonstrated. The images are simulated using Finite-Differences in Time-Domain (FDTD) method taking into account optical aberrations of the experimental setup, which are measured experimentally. Consideration of the optical aberrations allows us to reduce the discrepancy between experimental and simulated defocused images of the samples under study to the value of ≈2%in contrast to ≈10% when the aberrations are not taken into account.

Relaxation times and modes of disturbed aggregate distribution in micellar solutions with fusion and fission of micelles.

We have performed direct numerical calculations of the kinetics of relaxation in the system of surfactant spherical micelles under joint action of the molecular mechanism with capture and emission of individual surfactant molecules by molecular aggregates and the mechanism of fusion and fission of the aggregates. As a basis, we have taken the difference equations of aggregation and fragmentation in the form of the generalized kinetic Smoluchowski equations for aggregate concentrations. The calculations have been made with using the droplet model of molecular surfactant aggregates and two modified Smoluchowski models for the coefficients of aggregate-monomer and aggregate-aggregate fusions which take into account the effects of the aggregate size and presence of hydrophobic spots on the aggregate surface.

Multi-scale times and modes of fast and slow relaxation in solutions with coexisting spherical and cylindrical micelles according to the difference Becker-Döring kinetic equations.

The eigenvalues and eigenvectors of the matrix of coefficients of the linearized kinetic equations applied to aggregation in surfactant solution determine the full spectrum of characteristic times and specific modes of micellar relaxation. The dependence of these relaxation times and modes on the total surfactant concentration has been analyzed for concentrations in the vicinity and well above the second critical micelle concentration (cmc2) for systems with coexisting spherical and cylindrical micelles. The analysis has been done on the basis of a discrete form of the Becker-Döring kinetic equations employing the Smoluchowsky diffusion model for the attachment rates of surfactant monomers to surfactant aggregates with matching the rates for spherical aggregates and the rates for large cylindrical micelles.

Kinetics of micellisation and relaxation of cylindrical micelles described by the difference Becker-Döring equation.

A numerical description of micellisation and relaxation to an aggregate equilibrium in a nonionic surfactant solution with spherical premicellar aggregates and stable polydisperse cylindrical micelles is presented for a wide interval of total surfactant concentrations and initial conditions. The Smoluchowsky-type model for the attachment-detachment rates of surfactant monomers to and from surfactant aggregates with matching rates for small spherical premicellar aggregates and the rates for larger cylindrical micelles have been used. The full discrete spectrum of characteristic times of micellar relaxation and the first three relaxation modes in their dependence on the equilibrium monomer concentration have been computed using the linearized form of the Becker-Döring difference equations.

[The inborn flat-valgus deformity of the foot in children].

To optimize the diagnosis and treatment for the inborn flat-valgus deformity of the foot (IFVDF), the results of treatment of 78 children, ageing from 1 mo to 12 yrs old, were analyzed. Algorithms of diagnosis and treatment were elaborated. Operative treatment on soft tissues for IFVDF was indicated in the cases of inefficacy or insufficient efficacy of conservative therapy in the age after 1 year old, when a child starts to walk by himself.

Vapor nucleation on a wettable nanoparticle carrying a non-central discrete electric charge.

We have studied thermodynamics of vapor nucleation on a spherical wettable dielectric nanoparticle carrying a discrete electric charge located at a certain distance from the particle center. New general equations for the chemical potential of a condensate molecule in the droplet around the particle, the work of the droplet formation and the droplet shape as functions of the effective radius of condensate film, and the value of an electric charge and its location with respect to the particle center have been derived analytically. These equations take into account both the effects of the non-central electric field and the disjoining pressure in the thin liquid film forming the droplet.

Thermodynamic and kinetic theory of nucleation, deliquescence and efflorescence transitions in the ensemble of droplets on soluble particles.

Thermodynamic and kinetic peculiarities of nucleation, deliquescence and efflorescence transitions in the ensemble of droplets formed on soluble condensation nuclei from a solvent vapor have been considered. The interplay of the effects of solubility and the size of condensation nuclei has been analyzed. Activation barriers for the deliquescence and phase transitions and for the reverse efflorescence transition have been determined as functions of the relative humidity of the vapor-gas atmosphere, initial size, and solubility of condensation nuclei.

Micellization and relaxation in solution with spherical micelles via the discrete Becker-Döring equations at different total surfactant concentrations.

A numerical description of micellization and relaxation to an aggregate equilibrium in surfactant solution with nonionic spherical micelles has been developed on the basis of a discrete form of the Becker-Döring kinetic equations. Two different models for the monomer-aggregate attachment-detachment rates have been used, and it has been shown that the results are qualitatively the same. The full discrete spectrum of characteristic times of micellar relaxation and first relaxation modes in their dependence on equilibrium monomer concentration have been found with using the linearized form of the Becker-Döring kinetic equations.

Excess equimolar radius of liquid drops.

The curvature dependence of the surface tension is related to the excess equimolar radius of liquid drops, i.e., the deviation of the equimolar radius from the radius defined by the macroscopic capillarity approximation.

Aggregation work at polydisperse micellization: ideal solution and "dressed micelle" models comparing to molecular dynamics simulations.

General thermodynamic relations for the work of polydisperse micelle formation in the model of ideal solution of molecular aggregates in nonionic surfactant solution and the model of "dressed micelles" in ionic solution have been considered. In particular, the dependence of the aggregation work on the total concentration of nonionic surfactant has been analyzed. The analogous dependence for the work of formation of ionic aggregates has been examined with regard to existence of two variables of a state of an ionic aggregate, the aggregation numbers of surface active ions and counterions.

Nucleation stage with nonsteady growth of supercritical gas bubbles in a strongly supersaturated liquid solution and the effect of excluded volume.

An approach to the kinetics of barrier formation of supercritical gas bubbles in a strongly supersaturated liquid solution is presented. A common assumption of uniform reduction of a dissolved gas supersaturation in a liquid solution via stationary diffusion to nucleating gas bubbles is shown to be not applicable to the case of high gas supersaturations. The approach recognizes that the diffusion growth of supercritical bubbles at high gas supersaturation is essentially nonstationary.

Grand potential in thermodynamics of solid bodies and surfaces.

Using the chemical potential of a solid in a dissolved state or the corresponding component of the chemical potential tensor at equilibrium with the solution, a new concept of grand thermodynamic potential for solids has been suggested. This allows generalizing the definition of Gibbs' quantity sigma (surface work often called the solid-fluid interfacial free energy) at a planar surface as an excess grand thermodynamic potential per unit surface area that (1) does not depend on the dividing surface location and (2) is common for fluids and solids.

Nonlinear kinetics of fast relaxation in solutions with short and lengthy micelles.

An analytical treatment of the nonlinear kinetic equations for fast relaxation of coexisting short and lengthy micelles in surfactant solutions is presented. The kinetic equations can be written as a hierarchical set of differential equations for the moments of the aggregation number distribution function of micelles. It is shown that the moment equations can be successively integrated.

Thermodynamics of droplet formation around a soluble condensation nucleus in the atmosphere of a solvent vapor.

An expression for the work of formation of a spherical droplet condensing on a soluble condensation nucleus out of a solvent vapor is derived. The dependence of the formation work on the solvent vapor chemical potential and the droplet and the nucleus residue sizes is analyzed. The balance of the solute matter between the liquid film and the nucleus residue and the effect of overlapping the surface layers of the thin film have been taken into account.

Generalization of the Gibbs-Kelvin-Kohler and Ostwald-Freundlich equations for a liquid film on a soluble nanoparticle.

A derivation of chemical equilibrium equations for a spherical thin film of solution around a soluble solid nanoparticle is presented. The equations obtained generalize the Gibbs-Kelvin-Kohler and Ostwald-Freundlich equations for a soluble particle immersed in the bulk phase. The generalized equations describe the dependence of the chemical potentials of a condensate and dissolved nanoparticle matter in the thin solution film, the condensate saturated pressure, and the solubility of the nanoparticle matter on the film thickness, and the nanoparticle size with account of the disjoining pressure of the liquid film.

Kinetics of stimulated polariton scattering in planar microcavities: evidence for a dynamically self-organized optical parametric oscillator.

Strong temporal hysteresis effects in the population kinetics of pumped and scattered lower polaritons (LPs) have been observed in a planar semiconductor microcavity under a nanosecond-long pulsed resonant excitation (by frequency and angle) near the inflection point of the LPs' dispersion. The hysteresis loops have a complicated shape due to the interplay of two instabilities. The self-instability (bistability) of the nonlinear pumped LP is accompanied by a strong parametric instability which causes an explosive growth of the scattered LPs' population over a wide range of wave vectors.