Polymers in linear shear flow: a numerical study

We study the dynamics of a single polymer subject to thermal fluctuations in a linear shear flow. The polymer is modeled as a finitely extendable nonlinear elastic FENE dumbbell. Both orientation and elongation dynamics are investigated numerically as a function of the shear strength, by means of a new efficient integration algorithm. The results are in agreement with recent experiments.Comment: 7 pages, see also the preceding paper (http://arxiv.org/nlin.CD/0503028

Study of dose-dependent actoprotective effect of ATACL on physical performancend psychoemotional status of animals under exhausting exercise

The aim of the study was to investigate the dose-dependent actoprotective effect of ATACL on physical performance and psychoemotional status of animals under conditions of exhausting exercis

Dynamics of threads and polymers in turbulence: power-law distributions and synchronization

We study the behavior of threads and polymers in a turbulent flow. These objects have finite spatial extension, so the flow along them differs slightly. The corresponding drag forces produce a finite average stretching and the thread is stretched most of the time. Nevertheless, the probability of shrinking fluctuations is significant and is known to decay only as a power-law. We show that the exponent of the power law is a universal number independent of the statistics of the flow. For polymers the coil-stretch transition exists: the flow must have a sufficiently large Lyapunov exponent to overcome the elastic resistance and stretch the polymer from the coiled state it takes otherwise. The probability of shrinking from the stretched state above the transition again obeys a power law but with a non-universal exponent. We show that well above the transition the exponent becomes universal and derive the corresponding expression. Furthermore, we demonstrate synchronization: the end-to-end distances of threads or polymers above the transition are synchronized by the flow and become identical. Thus, the transition from Newtonian to non-Newtonian behavior in dilute polymer solutions can be seen as an ordering transition.Comment: 13 pages, version accepted to Journal of Statistical Mechanic

RNA sequencing of single cells obtained from immunolabeled tumor sections: the first experience

We performed laser microdissection-assisted RNA sequencing of single cells of breast tumo

Elastic turbulence in curvilinear flows of polymer solutions

Following our first report (A. Groisman and V. Steinberg, \sl Nature $\bf 405$, 53 (2000)) we present an extended account of experimental observations of elasticity induced turbulence in three different systems: a swirling flow between two plates, a Couette-Taylor (CT) flow between two cylinders, and a flow in a curvilinear channel (Dean flow). All three set-ups had high ratio of width of the region available for flow to radius of curvature of the streamlines. The experiments were carried out with dilute solutions of high molecular weight polyacrylamide in concentrated sugar syrups. High polymer relaxation time and solution viscosity ensured prevalence of non-linear elastic effects over inertial non-linearity, and development of purely elastic instabilities at low Reynolds number (Re) in all three flows. Above the elastic instability threshold, flows in all three systems exhibit features of developed turbulence. Those include: (i)randomly fluctuating fluid motion excited in a broad range of spatial and temporal scales; (ii) significant increase in the rates of momentum and mass transfer (compared to those expected for a steady flow with a smooth velocity profile). Phenomenology, driving mechanisms, and parameter dependence of the elastic turbulence are compared with those of the conventional high Re hydrodynamic turbulence in Newtonian fluids.Comment: 23 pages, 26 figure

Influence of ATACL compounds on some biochemical indicators in conditions of exhausting exercise in animals

Objective: to study the effect of the ATACL (4-hydroxy-3,5-di-tert-butylcinnamicacid) compound on some biochemical parameters under conditions of exhausting exercise in animals. Materials and methods: the study was conducted to study the effect of a cinnamic acid derivative on certain biochemical parameters under conditions of exhausting exercise in animals. The experiment was performed on 40 outbred male mice weighing 22-24 grams. Animals were subject to daily exhausting exercise for 5 days in the treadmill running test. The test compound ATACL was administered intragastrically at a dose of 100 mg/kg for 30 minutes before the exercise. At the end of the experiment, the animals were decapitated and blood was taken to assess lactic, pyruvic acid, the lactate/pyruvate coefficient and myoglobin as the marker of muscle damage. Results: It was found that upon exercise, 4-hydroxy-3,5-di-tert-butylcinnamic acid neutralizes the acidic pH. 10.7 times (p<0.05) increase in the concentration of pyruvate in the blood was observed compared to the negative control group, and a decrease in the lactate / pyruvate coefficient by 28.6 times (p<0.05). At the same time, the level of myoglobin in the group receiving ATACL was 2.1 times lower compared to the negative control group (p<0.05). No significant differences were observed in terms of lactate, pyruvate, and myoglobin concentration in the group treated with ATACL, in comparison with the group of animals treated with Metaprot. Conclusions: the data obtained allow us to recommend this compound as a corrector of biochemical shifts that are possible during physical exertion

Fundamental scaling laws of on-off intermittency in a stochastically driven dissipative pattern forming system

Noise driven electroconvection in sandwich cells of nematic liquid crystals exhibits on-off intermittent behaviour at the onset of the instability. We study laser scattering of convection rolls to characterize the wavelengths and the trajectories of the stochastic amplitudes of the intermittent structures. The pattern wavelengths and the statistics of these trajectories are in quantitative agreement with simulations of the linearized electrohydrodynamic equations. The fundamental $\tau^{-3/2}$ distribution law for the durations $\tau$ of laminar phases as well as the power law of the amplitude distribution of intermittent bursts are confirmed in the experiments. Power spectral densities of the experimental and numerically simulated trajectories are discussed.Comment: 20 pages and 17 figure