In this work, a multilateral analysis of submicron heterogeneities (SMH) spontaneously formed in aqueous solutions of sugars - glucose, fructose and sucrose - was carried out at 25 degrees C using laser scattering methods. The hydrodynamic diameters of SMH in 0.5 mol% solutions are 100-150 nm and vary slightly over a wide range of concentrations. However, the geometric diameters of SMH turn out to be much larger - 150-250 nm. This observation assumes that SMH are rather loose objects. The absence of depolarization of scattered radiation shows that the shape of MH is close to spherical. A new approach based on the methods of dynamic and multi-angle static light scattering using the Mie theory has been developed, which allows determining the refractive index of SMH. In 0.5 mol% solutions of sugars, the refractive index of SMH differs from the surrounding solution by no more than 0.005 for glucose and fructose and no more than 0.01 for sucrose. This corresponds to a 1.8-fold higher concentration of sugars in SMH compared to the average concentration in solution. Although SMH in sugar solutions are practically invisible due to the very small contrast, their numerical concentration is quite large, similar to 10(11)-10(12) ml(-1), and they occupy a similar to 0.1-1 % volume fraction of the solution. Dispersed and optical characteristics of SMH depend on the type and concentration of sugar.

C помощью оптической микроскопии исследовано влияние воздуха, гелия, аргона, ксенона и гексафторида серы на целостность структуры льда, формирующегося при замораживании воды и ряда криозащитных растворов в температурном диапазоне от 0 до -50°С. Показано, что кристаллизация капли воды объемом ≈ 200 мкл в атмосфере воздуха происходит с нарушением целостности структуры льда. В замороженных образцах наблюдается образование газовых микропузырьков диаметром до 250 мкм. Продувка над поверхностью капли воды аргона, ксенона или гексафторида серы перед замораживанием позволяет снизить максимальный размер микропузырьков до 100 мкм. Продувка гелия над поверхностью воды, растворов DMEM и «ЕвроКоллинз» позволяет полностью устранить или значительно уменьшить образование газовых микропузырьков в процессе кристаллизации. Для формируемого при этом массива льда характерна тенденция к снижению вероятности растрескивания при охлаждении до -50°С, что может способствовать выживаемости биологического материала при консервации. Добавление криопротектора этиленгликоля в концентрации 1-10 об.% в раствор позволяет снизить или полностью предотвратить выделение микропузырьков газа при замораживании. Механизм, с помощью которого реализуется данный феномен, остается неясным. Добавление этиленгликоля в концентрации 10 об.% и более также предотвращает растрескивание льда при охлаждении до -50°С.

The effects of air, helium, argon, xenon, and sulfur hexafluoride on the integrity of the ice structure formed when water and a cryoprotective solutions were frozen in the temperature range from 0 to –50°C was studied using optical microscopy. It was shown that the crystallization of a water drop with a volume of approximately 200 μL in the air atmosphere occurred with a violation of the integrity of the ice structure. Formation of gas microbubbles with a diameter of up to 250 μm was observed in the frozen samples. Purging of argon, xenon, or sulfur hexafluoride over the surface of a water drop before freezing reduced the maximum size of microbubbles to 100 μm. Purging of helium above the surface of water, DMEM (Dulbecco’s Modified Eagle Medium), and EuroCollins solutions made it possible to completely eliminate or significantly reduce the formation of gas microbubbles during crystallization. The ice formed in this case was characterized by a tendency to reduce the probability of cracking when cooled to –50°C, which can contribute to the survival of biological material during preservation. The addition of a cryoprotector, ethylene glycol, at a concentration of 1–10 vol % in the solution made it possible to reduce or completely prevent the release of microbubbles of gas during freezing. The mechanism by which this phenomenon occurred remains unclear. Addition of ethylene glycol at a concentration of 10 vol % or more also prevented ice cracking when it was cooled to –50°C.

It is found experimentally that a mesoscopic droplet phase is formed in low-concentration aqueous solutions of various polar organic compounds, which are considered in the chemical literature as infinitely soluble in water. The content of dissolved organic molecules in droplets is much higher than in the ambient solution. The droplet size increases with temperature. Theory can explain the mesodroplet formation by the phase separation of a binary mixture affected by the dichotomous noise of twinkling hydrogen bonds between molecules of organic compound and water. The Snyder polarity index, which is used by chemists as a miscibility criterion for molecular compounds, depends in the model on the dipole moments of mixed molecules and the energy and number of hydrogen bonds. With this refinement, it can be used as an estimation criterion for the existence and intensity (i.e., the number of droplets per unit volume of organic aqueous solution) of mesodroplet separation.

The specific features of dependences of the magnetic anisotropy constants on the thickness of yttrium iron garnet films prepared by pulsed laser deposition were studied. Films with thicknesses of 96–333 nm were produced by pulsed laser evaporation of the target material and deposition onto gadolinium-gallium-garnet substrates with the (111) orientation. The results of an investigation into static magnetic properties showed that the saturation magnetization decreases as the films get thinner. The high-frequency properties were studied by ferromagnetic resonance (FMR). The uniaxial and cubic anisotropy fields and the relaxation parameter were determined by analyzing the angular dependences of the resonance field and the FMR line width. It was found that as the thickness decreases, the strength of the uniaxial anisotropy field increases monotonically, while the cubic anisotropy field decreases and reverses its sign.

A mesoscale droplet phase, which is spontaneously formed in aqueous solutions of some polar organic compounds, has been experimentally investigated by methods of dynamic light scattering and laser phase microscopy. It is shown that tetrahydrofuran and tert-butanol aqueous solutions demonstrate a strong peak of light scattering intensity in the range of molecular concentrations of about 0.02 to 0.08, which corresponds to inhomogeneities with a characteristic size of about 100 nm. These liquid droplets are enriched with molecules of dissolved substance. A similar light scattering peak for aqueous solutions of glycerol and ethylene glycol is less pronounced. A theoretical model of the phase separation of binary solutions with twinkling (i.e., existing for a finite time) intermolecular hydrogen bonds is developed. The model predicts the existence of an additional low-concentration light scattering peak near the spinodal of the solution free of hydrogen bonds. A characterization of solutions according to the numerical values of twinkling hydrogen bond parameters is outlined.

A droplet formation in aqueous solutions of tetrahydrofuran (THF) has been experimentally detected at the submicrometer scale using two independent laser diagnostic techniques (dynamic light scattering and laser phase microscopy) and described in terms of THF-water intermolecular hydrogen bonding. It is shown that the nanodroplets have a mean size of 300 nm, their refractive index is higher than that of the ambient liquid, and they are highly enriched with THF molecules. The maximum of light scattering intensity falls within the THF concentration range 2-8 mol. %, which corresponds to the volume number density of the nanodroplets ∼1010-1011 cm-3. A theoretical explanation of forming the nanodroplets with a high content of THF, which is based on a model of dichotomous noise being applied to the so-termed "twinkling" hydrogen bonds and involves spinodal decomposition in the unstable region enclosed within the dichotomous binodal, is proposed. The parameters of hydrogen bonds in the molecular system "water-THF" were found, and the phase diagram of the solution with allowance for cross-linking hydrogen bonds was constructed.

This work is devoted to the problem of extracting the contribution of the anisotropy of relaxation to the angular dependence of the FMR linewidth and to the opportunity of determining the values of the parameters of relaxation. The results of the FMR study of films based on the yttrium iron garnet prepared by the method of liquid-phase epitaxy are given. The orientational dependence of the linewidth has been calculated using the traditional method of measuring an FMR spectrum and a method based on scanning at an angle to the resonance field for obtaining the minimum linewidth. A model for calculating the linewidth has been proposed that takes into account the anisotropy of the relaxation term in the equation of motion of the magnetic moment. The model leads to a dependence that agrees well with the experimental data, which makes it possible to state that the anisotropy of relaxation most likely takes place in the samples under consideration at the temperatures employed.

Three independent experimental laser techniques (dynamic light scattering, nanoparticle tracking analysis, and laser phase microscopy) have been used to find and quantitatively characterize a lowconcentration domain of existence for the droplet-stratified phase in an aqueous solution of tetrahydrofurane (THF) molecules acting as hydrogen bond acceptors. The concentration and temperature dependences of the light scattering intensity and droplet sizes in the solution have been measured. It is shown that the nanodroplets found have a higher light refractive index than that of water and that they are highly enriched with THF molecules. An estimation of the volume number density of 300-nm droplets, based on the data obtained, yields a value on the order of 10(8) cm(-3). The droplet lifetime is limited by the effect of the buoyancy force and amounts to several days. A crossover is found in the temperature dependence of scattering intensity in the droplet phase, which indicates possible interaction of two order parameters: the THF concentration and the number of hydrogen bonds of THF and H2O molecules. A model stochastic theory is proposed to describe the stratification of solutions with cross hydrogen bonds, which predicts stratification in the low-concentration range adjacent to the spinodal decay region.

Изучена комплексная диэлектрическая проницаемость водных растворов LiI в широком интервале концентраций при температурах 288–323 К в области дисперсии диэлектрической проницаемости воды на семи частотах в интервале 7.5–25 ГГц. В растворах наблюдается одна область релаксации, описываемая уравнениями Дебая или Коула–Коула. Изучены температурные и концентрационные зависимости времени диэлектрической релаксации ( ) и статической диэлектрической проницаемости ( s). Время и энтальпия активации процесса диэлектрической релаксации уменьшаются при переходе от воды к растворам, что соответствует нарушению исходной структуры воды и повышенной подвижности молекул воды в гидратных оболочках ионов. В начальной области концентраций наблюдается линейная зависимость активности воды от 1/ s. Отрицательная температурная зависимость s. исчезает при переходе к концентрированным растворам. При высоких концентрациях статическая диэлектрическая константа растет с увеличением температуры. Новые закономерности изменений s и при повышенных температурах 313–323 К определяются образованием ионных пар и других ионно-водных группировок с высоким дипольным моментом.

The complex permittivity of aqueous LiI solutions is studied over a wide range of concentrations at temperatures of 288–323 K in the water permittivity dispersion region at seven frequencies in the range of 7.5–25 GHz. One relaxation region describable by the Debye or Cole-Cole equation is observed in these solutions. Dielectric relaxation time τ and static permittivity ɛ s are studied as dependent on temperature and concentration. The time and enthalpy of activation of dielectric relaxation decrease in going from water to solutions, which corresponds to the distortion of the initial water structure and the increasing mobility of water molecules in hydration shells of ions. In the initial concentration range, the water activity is a linear function of 1/ɛ s . The negative temperature dependence of ɛ s disappears in going to concentrated solutions. At high concentrations, the static dielectric constant increases in response to increasing temperature. The new trends in ɛ s and τ at elevated temperatures of 313–323 K are due to the formation of ion pairs and other ion-water groups having high dipole moments.

Recently the materials possessing structure of molecular and supramolecular matrix are more and more actively studied. They are relative to many polymeric materials of a technological origin, such as rubber, and living biological tissues. Processes of mechanical deformation of these continuous media have peculiarities connected, first, with accounting for internal friction and dissipation of energy, and secondly, with nonlinearity of their elastic and viscous properties, that is with violation of Hook and Newtons laws. Traditional approaches to mechanics of viscoelastic bodies sometimes are excessively difficult, and more evident and available representations are necessary. The invaluable role in studying of the operating processes mechanisms of elastic deformation and motility of biological materials is played by the mathematical modeling. New effect obtained by means of computer experiment of nonmonotonic relaxation of deformation in heterogeneous media is considered in the present work. Rheological properties of described media are governed by the differential equations of the first order on time (the evolution equations), as well as a huge variety of other physical processes. The physical phenomena in nonlinear systems with dissipation have a big community, including such it would seem far areas, as dynamics of magnetization in ferrite. Therefore the problem of studying new effects of viscous friction in the conditions of nonlinearity and heterogeneity, is very actual as in respect of fundamental research nonlinear and non-uniform environments, and in many areas of materials science, design of new materials, engineering of biological substitutes of living tissues and development of the micromagnetic devices using essentially new opportunities.

The high-frequency dielectric permittivity and losses of CsI solutions were studied at 288–323 K in the range of water dielectric permittivity dispersion (7–25 GHz). The low-frequency electrical conductivity of these solutions was measured, and ionic losses at high frequencies were calculated. The Debye or Cole-Cole relaxation model was used for describing the spectra. The low-frequency limits of these relaxation region were calculated, which are the static dielectric constants ɛS and well as dielectric relaxation times (τ) and activation enthalpies (ΔH ɛ ++ ). The ɛS values decrease in going from water to a solution. In concentrated solutions, the slope of the plot of ɛS versus temperature become zero. The decrease in τ and gDH ɛ ++ is evidence of the structure-breaking effect of ions on water. At elevated temperatures (313 K), the decrease in τ is minimal. At 323 K, τ slightly increases in going from water to a solution.

The biomechanical modeling of a papillary muscle preparation as an adequate object for studying the properties of the myocardial tissue under uniaxial stretching has been performed. The steady-state and relaxation tests of the papillary muscle of laboratory animals (rabbit and rat) have been conducted in normal conditions and after the maceration of intracellular structures with high ionic strength solution. It has been shown that the main contribution to the viscoelastic properties in the initial range of physiological deformations is made by the connective tissue skeleton, whereas under large physiological deformations, by intracellular structures.

The complex dielectric permittivity of aqueous KI solutions was studied for molalities of 0.50–4.01 m and temperatures of 288–323 K in the region of water dielectric permittivity dispersion. The values of high-frequency of dielectric permittivity (ε) and dielectric losses (ε″) were obtained at seven frequencies ranging between 7.5 and 25 GHz. The low-frequency electrical conductivity of the aforementioned solutions was measured for calculating ionic losses. A single relaxation process is observed in these solutions, fitted by the Debye or Cole-Cole equation with small distribution parameters. The static dielectric constant and dielectric relaxation time were studied as functions of temperature and concentration; the activation enthalpy of dielectric relaxation was calculated. The temperature dependence of the static dielectric constant was found to disappear in highly concentrated solutions. The structure-breaking effect on water caused by K + and I − ions was affirmed, this effect disappearing in going to elevated temperatures.

Peculiarities of viscoelastic behavior of rabbit papillary muscle in passive state are studied by transversal versus longitudinal deformation curves, stress-strain and hysteresis curves, and stress relaxation curves under ramp stretching. The papillary muscle was chosen because of mostly longitudinal orientation of fibers and its elongated shape, which both make it as an appropriate model for uniaxial tests. The problem of evaluation of connective tissue protein structures and intracellular matrix contribution into the properties under consideration is solved by using the maceration method to remove intracellular structures. The different contribution of intracellular and extracellular protein features into total properties of a papillary muscle leads to nonlinearity of myocardial viscoelastic properties, such as the increase of differential elastic module and relaxation time with deformation.

The review of our approach to the specific rheological properties modeling of myocardium has been given. We are working on the level of ‘fascicule’ as a tissue element, which consists of several cardiomyocytes surrounded by a connective tissue shell. Actually, these properties are characteristic of large majority of living soft tissues. In order to describe essentially nonlinear static ‘force-deformation’ curves and quasi-static hysteresis loops together with non-exponential stress relaxation and creep time courses we suggest a set of 2D graphs with different topology composed of classical linear Hook’s springs and Newtonian damps. Each spring and dashpot represents a group of 3D tissue structural elements. The stress response functions of these models are found for the uniaxial step-wise, or pulse (column-like) external stretching. The inverse response functions of the longitudinal displacement for the external stress loading of the pulse shape time dependencies were also found. The values of elastic modules and viscous coefficients are estimated by comparison theoretical curves of relaxation, creep and recovery with the experimental data. The latter are obtained on rather different objects, passive muscle preparations (the stress relaxation response) and endothelium cells (the creep response). It has been stated that the proposed 2D models appear to be quite general to describe nonlinear relaxation and creep properties, which are lacking in the traditionally used uniaxial 1D models.

Identified rheological 2D models of myocardium proposed earlier by us to analyze static ‘forcedeformation’ curves and quasi-static hysteresis loops are used to describe stress relaxation and creep in a wide range of living soft tissues, beginning with myocite level and up to the muscle fibers. The viscous properties are determined with the help of the dampers connected in series or in parallel to certain elastic primary elements of the models. The stress response functions of the models are found for the external longitudinal step-wise or pulse (column-like) stretching. The inverse response functions of the longitudinal displacement for the external stress loading of the pulse shape time dependencies are also found. The values of both elastic modules, as in the static case, and also viscous coefficients are estimated by comparing theoretical curves of relaxation, creep and recovery with the experimental data. The latter are obtained on rather different objects, passive muscles preparations (the stress relaxation response) and endothelium cells (the creep response). It is stated that 2D models proposed appear to be too general to describe nonlinear relaxation and creep properties, which are lacking the traditionally used 1D ones without essential modification of those models.