Asymmetric bound states of spiral pairs in excitable media

We present a stable regime of asymmetric bound states for spiral pairs in a generic numerical model of a homogeneous excitable medium. In this regime, one spiral tip (slave) rotates around the other (master). Master-slave dynamics occur for both same-chirality and opposite-chirality spiral pairs in a range of parameters and initial conditions. We study the dependency of master-slave characteristics on the medium's excitation threshold and present a phenomenological model that accounts for the qualitative properties of master-slave dynamics.     

Intermittent self-organization of scroll wave turbulence in three-dimensional excitable media

We study the asymptotic behavior of scroll wave turbulence in large three-dimensional excitable media modeled by FitzHugh-Nagumo equations. The focus is on the type of turbulence caused by negative tension of scroll wave filaments, which is considered to be one of the mechanisms of cardiac fibrillation. We discovered that the initial increase in turbulence complexity can be followed by intermittent self-organization, when complex filament tangles are replaced by a small number of relatively stable triple filament strands. The intermittency is the result of a competition between the destabilizing effect of negative tension and mutual attraction of filaments with similar orientation.     

Predicting filament drift in twisted anisotropy

Excitable media with twisted anisotropy have recently been attracting significant interest because of their applicability to wave propagation in heart tissue. Here we consider the dynamics of an intramural scroll wave whose filament lies initially within an arbitrary layer of mutually parallel cardiac fibers, and drifts parallel to itself from layer to layer. Earlier simulations have demonstrated that such a filament stabilizes in a layer whose fiber direction is the same as its own. In the present paper we analytically derive the trajectory of the filament, and obtain good agreement with earlier numerical data. For sufficiently sparse scrolls, our analysis predicts an equilibrium alignment perpendicular rather than parallel to the fibers.     

Two-dimensional image magnification in an asymmetric-reflection X-ray microscope

The experimental results on the two-dimensional 20× magnification of an x-ray image obtained in an asymmetric-reflection x-ray microscope with the use of a laboratory source of x rays are discussed. The field of view is determined by the linear sizes of the detector and is equal to 0.5 × 0.5 mm in our experiment for an exposure time of 600 s.     

Jumpwise Development of the Processes with the Participation of Colloidal Systems

Concepts of jumpwise evolution with the participation of colloidal systems were formulated using thermodynamics of hierarchic and nonlinear open systems. Using various complex irreversible processes as examples, it was shown that most of these processes obeys the principle of jumpwise development related to the principles of continuity, correspondence, and maximum entropy production. A significant role of colloidal or biocolloidal states of substance was noted in the jumpwise processes beginning with the geological transformation in Earth's core, the evolution of the transition of dead nature to self-organizing and self-reproducing systems and ending with the traditional domains of colloid chemistry. The aforementioned considerations were confirmed by examples from lithology, hydration dispersion of coal-bearing and carbon silicate materials, hydraulic hardening of binder compositions, as well as by the changes in silicon porous structure at various stages of anodization based on the notions of flicker-noise spectroscopy.     

Spectral calibration of filters and detectors of solar telescope at a wavelength of 13.2 nm for the TESIS project

The telescope at a wavelength of 13.2 nm of the TESIS device of the CORONAS-PHOTON satellite is intended for imaging hot plasma (T ～ 10 MK) of the solar corona. In this paper, calibration of optical elements of the telescope is described. The transmittance of multilayer Zr/Si filters and the sensitivity and radiation resistance of the CCD-array-based detector were measured. The transmittance of filters in the operating wavelength range was 40–50% (for filters of various thicknesses); the spectral dependence of the transmittance was close to the calculated one. The transmittance of filters in the visible region was (1–2) × 10^?6. The detector sensitivity was 0.01–0.1 analog-to-digital units per photon (adu/photon), the radiation resistance was better than 10⁹ rad.     

Electrical turbulence as a result of the critical curvature for propagation in cardiac tissue

In cardiac tissue, the propagation of electrical excitation waves is dependent on the active properties of the cell membrane (ionic channels) and the passive electrical properties of cardiac tissue (passive membrane properties, distribution of gap junctions, and cell shapes). Initiation of cardiac arrhythmias is usually associated with heterogeneities in the active and/or passive properties of cardiac tissue. However, as a result of the effect of wave front geometry (curvature) on propagation of cardiac waves, inexcitable anatomical obstacles, like veins and arteries, may cause the formation of self-sustained vortices and uncontrolled high-frequency excitation in normal homogeneous myocardium. (c) 1998 American Institute of Physics.     

On the problem of dispersion work

The approaches to determination of the dispersion work described in the literature are compared. Rigorous consideration of the dependence of surface tension on the particle radius, combined with complete representation of the number of molecules in a particle, makes it possible to conclude that the specific work of dispersion (per unit area of tension surface) is independent of the particle size and equal to the surface tension of the plane surface. This conclusion significantly simplifies the thermodynamic analysis of dispersion processes. The activation energy of droplet dispersion is considered.     

Colloidal and Chemical Processes in Hardening Alkaline Compositions Based on Aluminosilicates and Slags: 1. Control of the Properties of Alkaline Compositions

Chemical interactions in aqueous concentrated compositions based on natural and technogenic aluminosilicates and binders are studied by the rheology and calorimetry methods. It is shown that small amounts of alkali cause the hardening of compositions. Concepts of controlling the properties of hardening compositions by the addition of corresponding alkalis are developed.     

Coordination properties of polymeric azacrown ethers

New polymeric aza-crown ethers (PACE), soluble in water and organic solutions and cross-linked ones, containing different macrocycles in side chains have been synthesised by polymerisation and chemical modification reactions. The coordination próperties of these PACE are studied. It is shown that during coordination of the VO²⁺, Cu²⁺ ions with PACE, cross-linking of macromolecules by metal ions takes place by “sandwich” complex formation. The character of complexes distribution along PACE coils may be equal or nonequal, depending on polymer reactivity. The synthesised PACE are used as high specific polymer reagents for colloid rare metals recovery. It is shown that flocculation of negatively charged inorganic sols with PACE is due to electrostatic adsorption and specific binding. In acid and neutral media, dispersions of gold, silver, copper ferrocyanide and silicon dioxide undergo high flocculation as a result of non-specific electrostatic adsorption. Alkaline media provide conditions for donor-acceptor binding, increasing flocculation selectivity. In the uncharged state (pH 11,2) PACE exhibit high selectivity in binding gold particles. Stability of colloidal dispersions in the presence of monomer aza-crown ether (ACE) indicates an important polymer influence on the fine metal particles flocculation.