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By the example of a local inhomogeneity in the form of a horizontal crack, a numerical and experimental confirmation of the existence of resonance effects in an inhomogeneous elastic strip, investigated by I. I. Vorovich, is given. Examples of the use of this phenomenon for detecting delamination in composite plates and determining their size and depth based on the data of ultrasonic monitoring by traveling Lamb waves are given. [ABSTRACT FROM AUTHOR]

The problem of numerical simulation of the steady-state harmonic vibrations of a layered phononic crystal (elastic periodic composite) with a set of strip-like cracks parallel to the layer boundaries is solved, and the accompanying wave phenomena are considered. The transfer matrix method (propagator matrix method) is used to describe the incident wave field. It allows one not only to construct the wave fields but also to calculate the pass bands and band gaps and to find the localization factor. The wave field scattered by multiple defects is represented by means of an integral approach as a superposition of the fields scattered by all cracks. An integral representation in the form of a convolution of the Fourier symbols of Green's matrices for the corresponding layered structures and a Fourier transform of the crack opening displacement vector is constructed for each of the scattered fields. The crack opening displacements are determined by the boundary integral equation method using the Bubnov-Galerkin scheme, where Chebyshev polynomials of the second kind, which take into account the behavior of the solution near the crack edges, are chosen as the projection and basis systems. The system of linear algebraic equations with a diagonal predominance of components arising when the system of integral equations is discretized has a block structure. The characteristics describing qualitatively and quantitatively the wave processes that take place under the diffraction of plane elastic waves by multiple cracks in a phononic crystal are analyzed. The resonant properties of a system of defects and the influence of the relative positions and sizes of defects in a layered phononic crystal on the resonant properties are studied. To obtain clearer results and to explain them, the energy flux vector is calculated and the energy surfaces and streamlines corresponding to them are constructed. [ABSTRACT FROM AUTHOR]

Transport properties of several aromatic polyamides among which there exist fairly subtle structural differences were examined in perva-poration of water-isopropanol solutions. The dependences of the flux density on the membrane area and the oscillatory kinetics of permeability were established, and an unstable steady state arising via predominant permeation of an organic solvent through a highly hydrophilic polymeric membrane was revealed. Conductometric examination of the swelling kinetics showed that chitosan swelling in water gives rise to instabilities in the form of macrofluctuations of local sorbate concentration distribution in the polymer. The wavelet analysis of the time series of the stochastic oscillations was carried out. [ABSTRACT FROM AUTHOR]

Propagation of a time-harmonic plane SH wave and its diffraction in periodic layered elastic composites with both a single infinitesimally thin inhomogeneity and an array of inhomogeneities (cracks, rigid inclusions) are analyzed. The mathematical model is based on an integral approach, a system of boundary integral equations, and a T-matrix; the commonly used spring model is also applied for a damaged composite. The resonances and wave localization in the vicinity of obstacles are focused. [ABSTRACT FROM AUTHOR]

The possibility is studied of applying spring boundary conditions to describe propagation of elastic waves in layered composites with nonperfect contact of components or in the presence of groups of microdefects at the interface. Stiffnesses in spring boundary conditions are determined by crack density, the average size of microdefects, and the elastic properties of the materials surrounding them. In deriving the values of the effective stiffness parameters, the Baik-Thompson and Boström-Wickham approaches are applied, as well as the integral approach. The components of the stiffness matrices are derived from consideration of an incident, at a random angle to the interface, plane wave in the antiplane case, and at a normal angle in the plane case. The efficiency of this model and the possibility of using its results in the three-dimensional case are discussed. [ABSTRACT FROM AUTHOR]

Wave processes that occur in an elastic layer when waves traveling in it are diffracted by a system of horizontal cracks are investigated. Integral representations of wave fields are constructed in terms of the convolution of Green’s matrices and unknown jumps of displacements at the cracks. The displacement jumps are determined from the boundary integral equations, which are obtained from the initial boundary-value problem with the boundary conditions at crack faces being satisfied. The spectrum of the integral operator is studied for different variants of mutual crack arrangement and is compared with the spectrum of the corresponding operators for individual cracks; the relationship between the spectrum and the blocking effects is analyzed. The possibility of obtaining an extended frequency band of waveguide blocking in the case of groups of cracks is demonstrated. [ABSTRACT FROM AUTHOR]

The semianalytic methods developed for solving the problems of elastodynamic diffraction by a horizontal strip-like crack are used to analyze the transmission and reflection of Rayleigh waves in a half-plane and normal modes in a layer with the aim to determine the parameters of blocking and study the blocking mechanism. The resonance blocking is shown to be accompanied by energy localization near the crack. For the case of a crack in a half-plane, a possibility of nonresonance blocking is revealed. The transmission and reflection coefficients are analyzed as functions of frequency, crack size, and crack depth. Numerical examples of energy streamline and power distribution structures are given for the resonance and nonresonance blocking, as well as examples of the behavior of stress intensity factors at the crack tips. [ABSTRACT FROM AUTHOR]

Scanning electron microscope (SEM) investigation of the highly conducting organic composites of general formulae (BEDT-TTF) x/(AuI) and (BEDT-TTF) x/(AuI3), where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, obtained by direct charge-transfer (CT) reaction in the solid state is performed. The granular structure of the composites with domination of three types of the grains: (BEDT-TTF)2I3, (BEDT-TTF)2AuI2 and Au, is suggested. The changes in the composite structure caused by their composition and/or thermal treatment are connected with the d.c. electrical conductivity of the samples. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that stimulation of intestinal mucosal afferent nerves produces an increase in superior mesenteric artery (SMA) but a decrease in mesenteric adipose tissue (MAT) blood flow. In anesthetized rats, blood flow in the SMA (pulsed Doppler flowmetry) and MAT (hydrogen gas clearance) was measured simultaneously before and after administration of 0.9% saline, 640 microM capsaicin, or 5% dextrose into the intestinal lumen. The changes in the SMA were 3.8 +/- 3.0, 15.9 +/- 4.0, and 18.8 +/- 7.6%; and those in the MAT, 4.7 +/- 4.0, -11.5 +/- 3.4, and -0.07 +/- 3.4% of baseline, respectively. The data indicate that exposure of the intestinal lumen to an afferent nerve stimulant or nutrient induced a dichotomous pattern of blood flow changes, an increase in the SMA and a reduction in MAT. The capsaicin-sensitive afferent nerves may be instrumental in mediating these energy responses. [ABSTRACT FROM AUTHOR]

The possibility was demonstrated for surface and bulk modification of chitosan films with dodecyl sulfate anions and oligoethylene oxide substituents which are added to chitosan macromolecules with ionic and covalent bonds, respectively, including forming cross-linked structures. Modification allows increasing the working range on the pH scale without altering the physicomechanical indexes of chitosan films and varying the hydrophilic properties and water absorption within wide limits, which should be reflected in the transport properties of the films and allows expanding the area of their practical application. [ABSTRACT FROM AUTHOR]

Lipid composition of human low-density lipoprotein (LDL) and its physicochemical characteristics are relevant for proper functioning of lipid transport in the blood circulation. To explore dynamical and structural features of LDL particles with either a normal or a triglyceride-rich lipid composition we combined coherent and incoherent neutron scattering methods. The investigations were carried out under high hydrostatic pressure (HHP), which is a versatile tool to study the physicochemical behavior of biomolecules in solution at a molecular level. Within both neutron techniques we applied HHP to probe the shape and degree of freedom of the possible motions (within the time windows of 15 and 100 ps) and consequently the flexibility of LDL particles. We found that HHP does not change the types of motion in LDL, but influences the portion of motions participating. Contrary to our assumption that lipoprotein particles, like membranes, are highly sensitive to pressure we determined that LDL copes surprisingly well with high pressure conditions, although the lipid composition, particularly the triglyceride content of the particles, impacts the molecular dynamics and shape arrangement of LDL under pressure. [ABSTRACT FROM AUTHOR]