Viscoelastic response of contractile filament bundles

The actin cytoskeleton of adherent tissue cells often condenses into filament bundles contracted by myosin motors, so-called stress fibers, which play a crucial role in the mechanical interaction of cells with their environment. Stress fibers are usually attached to their environment at the endpoints, but possibly also along their whole length. We introduce a theoretical model for such contractile filament bundles which combines passive viscoelasticity with active contractility. The model equations are solved analytically for two different types of boundary conditions. A free boundary corresponds to stress fiber contraction dynamics after laser surgery and results in good agreement with experimental data. Imposing cyclic varying boundary forces allows us to calculate the complex modulus of a single stress fiber.Comment: Revtex with 24 pages, 7 Postscript figures included, accepted for publication in Phys. Rev.

Research of Geopolymer Foam Concrete on the Base of the Wastes Produced By Kemerovo Heat and Power Enterprises

The article shows the results of the research on geopolymer foam concrete production on the base of the wastes of Kemerovo heat and power enterprises. Relationships between the compression strength and average density of geopolymer foam concrete and the alkaline activator amount, alkaline concentration, foaming agent amount and duration of the blend mechanical activation were determined. It was found out that being in its optimal composition the material obtained has strength 2.0-3.5 MPa under density from 350 up to 500 kg/m3. Infusion of the developed construction material on the basis of the industrial wastes will allow to change more expensive construction materials on the cement base and provide the utilization of the industrial wastes

СИЛОВЫЕ УСЛОВИЯ ПРЕССОВАНИЯ ЛЕГКОСПЛАВНЫХ БУРИЛЬНЫХ ТРУБ СО СПИРАЛЬНЫМ ОРЕБРЕНИЕМ

Following I.L. Perlin’s technique based on active and reactive forces balance, the formula was suggested to calculate extrusion force for spiral-finned drill pipes. The spiral pipe cross section was regarded as a smooth tube with a screw arrangement of metal fibers and external spiral fins. A component introducing energy spent for the screw motion of metal was added to the formula. It was shown that the extrusion force obtained by the modified formula is 28 % higher than the same for a smooth pipe of equal area. It was discovered that the increase of fin helix angle leads to the increase of force compared to that of longitudinally finned pipes. На основе методики И.Л. Перлина, основанной на балансе активных и реактивных сил, предложено уравнение для расчета усилия прессования бурильных труб со спиральным оребрением. Поперечное сечение спиральной трубы представлено в виде гладкой трубы с винтовым расположением волокон металла и внешних спиральных ребер. В формулу добавлена составляющая, учитывающая энергию, затрачиваемую на винтовое движение металла. Показано, что усилие прессования, полученное по модернизированной формуле, на 28 % больше, чем для равновеликой по площади гладкой трубы. Выявлено, что увеличение угла подъема спирали ребер приводит к росту усилия по сравнению с таковым для продольно-оребренных труб.

Amino-nitrile cleavage in the electrochemical reduction of hydeazones of aromatic aldehydes

1. Factors which determine the possibility of amino-nitrile cleavage of hydrazones on electrochemical reduction (ECR) include the basicity of the anionic product formed in the course of the ECR and the mobility of the aldehyde hydrogen which depends on the character of the electron polarization of the hydrazone fragment and the polarity of the N-N bond. 2. The primary action in amino-nitrile cleavage under conditions of ECR is the deprotonation of the azomethine fragment in the unreduced molecule by electrochemically generated strong base (anion or dianion). © 1988 Plenum Publishing Corporation

Plasma assisted-MBE of GaN and AlN on graphene buffer layers

The possibility of using chemical vapor deposition (CVD) graphene as a 2D buffer layer for epitaxial growth of III-nitrides by plasma assisted-MBE on amorphous substrates (SiO2 prepared by thermal oxidation of Si wafer) was investigated. The comparative study of graphene-coated parts of the wafers and the parts without graphene was carried out by scanning electron microscopy and X-ray diffractometry. It was shown that epitaxial GaN and AlN films with close to 2D surface morphology can be obtained by plasma assisted-MBE on amorphous SiO2 substrates with a multilayer graphene buffer using the HT AlN nucleation layer

On Eigenvalues of the sum of two random projections

We study the behavior of eigenvalues of matrix P_N + Q_N where P_N and Q_N are two N -by-N random orthogonal projections. We relate the joint eigenvalue distribution of this matrix to the Jacobi matrix ensemble and establish the universal behavior of eigenvalues for large N. The limiting local behavior of eigenvalues is governed by the sine kernel in the bulk and by either the Bessel or the Airy kernel at the edge depending on parameters. We also study an exceptional case when the local behavior of eigenvalues of P_N + Q_N is not universal in the usual sense.Comment: 14 page

MELT INCLUSIONS IN OLIVINE AS A SOURCE OF INFORMATION ON THE COMPOSITION AND EVOLUTION OF DEEP MELTS OF AILLIKITES (ULTRAMAFIC LAMPROPHYRES) OF THE ILBOKICHI UPLIFT, THE SW SIBERIAN PLATFORM

Aillikites are kimberlite-like rocks, important for understanding the composition and processes occurring in the mantle. Melt inclusions represent a reliable source of information. The paper provides the first results of studies (Raman, EDS) on primary and secondary melt inclusions in olivine from the Ilbokich uplift aillikites. The composition of primary inclusions is close to that of parent melt of aillikites. It was significantly enriched in CO2, H2O, phosphorus and titanium. Phlogopite, diopside, dolomite, calcite, apatite, Ti-containing phases (brookite, perovskite, Ti-magnetite) and lizardite were identified in these inclusions. The similarity of the composition and ratios of the daughter phases with the aillikite matrix indicates a slight change in the parent melt when it is rising to the surface. As to the secondary inclusions, there are wide variations in compositions and a smaller amount of silicates, as compared to the primary ones. The main daughter phases are carbonates, e.g. dolomite, calcite, magnesite and alkaline carbonates. In addition, phlogopite, clinopyroxene, apatite, halite, pyrrhotite and magnetite, graphite and CO2 were discovered. The variability of the compositions of the secondary inclusions might be due to the silicate-carbonate immiscibility that appeared during the rising of the aillikite melt at pressures <4 GPa

Lyapunov exponents for products of complex Gaussian random matrices

The exact value of the Lyapunov exponents for the random matrix product $P_N = A_N A_{N-1}...A_1$ with each $A_i = \Sigma^{1/2} G_i^{\rm c}$, where $\Sigma$ is a fixed $d \times d$ positive definite matrix and $G_i^{\rm c}$ a $d \times d$ complex Gaussian matrix with entries standard complex normals, are calculated. Also obtained is an exact expression for the sum of the Lyapunov exponents in both the complex and real cases, and the Lyapunov exponents for diffusing complex matrices.Comment: 15 page

Anodic synthesis and molecular structure of dodecaethylhexaamidobisphosphonium diperchlorate

The electrochemical oxidation of hexaethyl triamidophosphite in the absence of nucleophiles specially introduced into the electrolyte was studied by anodic voltamperometry and preparative electrolysis. The reversible one-electron oxidation of the triamidophosphite molecule gives an unstable radical-cation, which reacts with a molecule of the starting compound to give a dimeric radical-cation, whose subsequent oxidation leads to dodecaethylhexaamidobisphosphonium diperchlorate. This product is the first example of an acyclic, doubly charged bisphosphonium cation with a {Mathematical expression}. The crystal structure of this compound was obtained by x-ray diffraction structure analysis. © 1990 Plenum Publishing Corporation