Evolution of the Primary Pulse in 1D Granular Crystals Subject to On-Site Perturbations: Analytical Study

Propagation of primary pulse through an un-compressed granular chain subject to external on-site perturbation is studied. Analytical procedure predicting the evolution of the primary pulse is devised for the general form of the on-site perturbation applied on the chain. The validity of the analytical model is confirmed with several specific granular setups such as, chains mounted on the nonlinear elastic foundation, chains perturbed by the dissipative forces as well as randomly perturbed chains. Additional interesting finding made in the present study corresponds to the chains subject to a special type of perturbations including the terms leading to dissipation and those acting as an energy source. It is shown in the study that application of such perturbation may lead to formation of stable stationary shocks acting as attractors for the initially unperturbed, propagating Nesterenko solitary waves. Interestingly enough the developed analytical procedure provides an extremely close estimations for the amplitudes of these stationary shocks as well as predicts zones of their stability. In conclusion we would like to stress that the developed analytical model have demonstrated spectacular correspondence to the results of direct numerical simulations for all the setups considered in the study

Sequential phosphorylation of SLP-76 at tyrosine 173 is required for activation of T and mast cells.

Cooperatively assembled signalling complexes, nucleated by adaptor proteins, integrate information from surface receptors to determine cellular outcomes. In T and mast cells, antigen receptor signalling is nucleated by three adaptors: SLP-76, Gads and LAT. Three well-characterized SLP-76 tyrosine phosphorylation sites recruit key components, including a Tec-family tyrosine kinase, Itk. We identified a fourth, evolutionarily conserved SLP-76 phosphorylation site, Y173, which was phosphorylated upon T-cell receptor stimulation in primary murine and Jurkat T cells. Y173 was required for antigen receptor-induced phosphorylation of phospholipase C-γ1 (PLC-γ1) in both T and mast cells, and for consequent downstream events, including activation of the IL-2 promoter in T cells, and degranulation and IL-6 production in mast cells. In intact cells, Y173 phosphorylation depended on three, ZAP-70-targeted tyrosines at the N-terminus of SLP-76 that recruit and activate Itk, a kinase that selectively phosphorylated Y173 in vitro. These data suggest a sequential mechanism whereby ZAP-70-dependent priming of SLP-76 at three N-terminal sites triggers reciprocal regulatory interactions between Itk and SLP-76, which are ultimately required to couple active Itk to its substrate, PLC-γ1

Periodic Travelling Waves in Dimer Granular Chains

We study bifurcations of periodic travelling waves in granular dimer chains from the anti-continuum limit, when the mass ratio between the light and heavy beads is zero. We show that every limiting periodic wave is uniquely continued with respect to the mass ratio parameter and the periodic waves with the wavelength larger than a certain critical value are spectrally stable. Numerical computations are developed to study how this solution family is continued to the limit of equal mass ratio between the beads, where periodic travelling waves of granular monomer chains exist

ИССЛЕДОВАНИЕ ОСТЕОПЛАСТИЧЕСКИХ СВОЙСТВ РЕЗОРБИРУЕМОГО ПОЛИ-3-ГИДРОКСИБУТИРАТА IN VIVO НА МОДЕЛЯХ СЕГМЕНТАРНОЙ ОСТЕОТОМИИ

A family of materials  based  on biodegradable polymer-3-hydroxybutyric acid (polyhydroxybutyrate, PHB) has been  developed for the purposes of reparative osteogenesis. Osteoplastic properties of bulk implants  PHB and PHB composition with hydroxyapatite (HA) have been  investigated in comparison with branded drugs Bio-Oss ® in vivo via the model of segmental osteotomy. It is indicated that  reconstructive bone  formation is more  active when implants  with PHB as a main component are used.Для целей  репаративного остеогенеза разработано семейство материалов на основе биоразрушаемого полимера-3-гидроксимасляной кислоты (полигидроксибутирата, ПГБ). Остеопластические свойства  объемных имплантатов из ПГБ и композиции ПГБ с гидроксилапатитом (ГАП) исследованы in vivo на модели сегментарной остеотомии в сравнении с фирменным препаратом Bio-Oss®.  Показано, что реконструктивный остеогенез происходит более активно  при использовании имплантатов, содержащих в качестве основного компонента ПГБ.

Electrophoretic applications of sol-gel matrices

Abstract Biological application of sol-gel matrices has been extensively used through doping process. However the bioactivity of these materials is impaired mainly by uneven distribution of the biological molecules into the sol-gel matrix. The main objective of the present study was to apply electrophoretic field in order to concentrate biomolecules alongside sol-gel surface in order to increase the interaction capability with external molecules. Two potential applications of an electrophoretic field on sol-gel matrices were demonstrated. Silica gels in solid and liquid states were used as an electrophoretic matrix. In the first application, cylindrical rods made of solid silica gel and filled with tracking dye at one end, were subjected to applied electrical field. A well-defined movement of the tracking dye was attained from one edge to the other under applied electrophoretic current through the sol-gel rod pores. In the second application, accumulation of small biomolecules at one pole was obtained in a liquid pre-gelation sol-gel matrix during its polymerization. In order to optimize biologically active compounds movement in electrical field applied to sol-gel matrixes, parameters of both sol-gel and electrophoretic processes were studied. Under optimal conditions, it was feasible to increase the concentration of small biomolecules at sol-gel surface and consequently to enhance their availability towards external reactants.

Performance comparison between a nonlinear energy sink and a linear tuned vibration absorber for broadband control

The performance of a linear tuned vibration absorber (LTVA) and a nonlinear energy sink (NES) for the vibration mitigation of an uncertain linear primary system is investigated. An analytic tuning rule for the LTVA when the primary system contains uncertainty is derived. The behavior of the linear system coupled to the NES is analyzed theoretically. A tuning methodology for the NES in the deterministic as well as for the uncertain case is presented. © The Society for Experimental Mechanics, Inc. 2016

Vibro-Impact NES: A Correlation Between Experimental Investigation and Analytical Description

International audienceIn this work the dynamics of a Vibro-Impact Nonlinear Energy Sink (VI-NES) is experimentally investigated via a harmonically forced single-degree-of- freedom linear oscillator (LO) to which a VI-NES is attached. Depending on external force amplitude and frequency, either a Strongly Modulated Response (SMR) or a constant amplitude response (CAR) is observed. In both cases an irreversible transfer of energy occurs from the LO towards the VI-NES: process known as passive Targeted Energy Transfer(TET). Furthermore, the problem is analytically studied by using the multiple scales method. For the fast and the slow time scales the Slow Invariant Manifold (SIM) is obtained. The 0-order SIM shows the existence of a stable and an unstable branch of solution, and of an energy threshold (a saddle-node bifurcation) for the solutions to appear. Subsequently the 1-order SIM is calculated to find the fixed points of the problem. When a stable fixed point exists, the system is naturally drawn to it and a CAR is reached. Otherwise a SMR state is established and no stable point is attained. Finally a good agreement between experimental and analytical results is shown