Activity pulses induce spontaneous flow reversals in viscoelastic environments

Complex interactions between cellular systems and their surrounding extracellular matrices are emerging as important mechanical regulators of cell functions, such as proliferation, motility and cell death, and such cellular systems are often characterized by pulsating actomyosin activities. Here, using an active gel model, we numerically explore spontaneous flow generation by activity pulses in the presence of a viscoelastic medium. The results show that cross-talk between the activity-induced deformations of the viscoelastic surroundings and the time-dependent response of the active medium to these deformations can lead to the reversal of spontaneously generated active flows. We explain the mechanism behind this phenomenon based on the interaction between the active flow and the viscoelastic medium. We show the importance of relaxation time scales of both the polymers and the active particles and provide a phase space over which such spontaneous flow reversals can be observed. Our results suggest new experiments investigating the role of controlled pulses of activity in living systems ensnared in complex mircoenvironments.     

General Aspects of the Combustion Synthesis of a Cobalt Alloy with Dispersion and Precipitation Modification

Inorganic Materials - We have studied the potentialities of dispersion and precipitation modification of a cobalt alloy in combustion mode under the effect of centrifugal forces. The starting...     

Integral characteristics of branched tractional power-supply systems

A fast method is proposed for calculating the characteristics of tractional power-supply systems. The method is suitable for the power-supply systems of electrified railroad networks with a complex branched equivalent circuit (10³–10⁶ branches).     

On the optimization of process heating applied to the assembly of wheel sets of railroad vehicles

A systematic computational investigation of a diesel locomotive??s wheel elements during thermal assembly by process heating using induction heating units was performed on the basis of experimental data. The search algorithm for the optimal heating of the parts representing rotating bodies as applied to the interference assembling of the railroad wheels was described.     

Developing Methods for Wet Chemical Etching of a Separation Mesa Structure during Creation of Multijunction Solar Cells

Technical Physics Letters - The postgrowth processing of mesa structures for multijunction solar cells based on GaInP/GaInAs/Ge heterostructure has been studied. Methods of wet chemical and...     

Ultracold neutron cooling upon reflection from a moving wall

The process of neutron cooling upon adiabatic increase in the storage volume has been studied on an ultracold neutron beam of the ILL reactor. The cooling of neutrons in the course of magnetic trap filling allows the number of stored neutrons to be significantly increased and, hence, the statistical accuracy of determination of their lifetimes to be improved.     

Effect of postgrowth techniques on the characteristics of triple-junction InGaP/Ga(In)As/Ge solar cells

The photoelectric characteristics of triple-junction InGaP/Ga(In)As/Ge solar cells are studied in relation to the method used to form the photocell chip. It is shown that the application of a postgrowth technique developed in the study for separating a nanoheterostructure into chips in a single process makes it possible to improve the quality of passivation of the chip edges, which diminishes the surface leakage currents and makes larger the yield of devices with improved characteristics.     

Effect of doping on the mechanical properties of nonlinear GaSe crystals

The effect of doping with sulfur, indium, tellurium, aluminum, erbium, and silver on the mechanical properties of nonlinear GaSe crystals grown by a modified Bridgman method with the rotation of a thermal field is studied. GaSe:S crystals have the best optical properties and GaSe:Al crystals have the highest microhardness. Under identical experimental conditions, we revealed an additive influence of double doping on the properties of GaSe: the crystals doped with sulfur and aluminum demonstrate the maximum efficiency of laser radiation frequency conversion and the maximum hardness. The increased hardness is supported by the appearing ability of the crystals to undergo cracking under the action of high-intensity radiation, which is characteristic of glass.