The effect of positive thermodiffusion of colloidal particles under convection of magnetic fluids in connected vertical channels of 3.2 × 3.2 mm
2
square cross-section and height 50 mm heated from ...below is analyzed. Below the critical Rayleigh number, particle thermophoresis in vertical generates unstable density stratification in fluid at rest. This leads to rapid bursts (~1 min) of concentration convection arising periodically (~4 h). Under developed convection, above the critical Rayleigh number particle thermophoresis in horizontal direction generates concentration inhomogeneities in the neighborhood of the channel walls and provokes convective flow instability that leads to the periodic change (~1 h) in the direction of convective stream. The reasons of the oscillatory instability of mechanical equilibrium observed experimentally at positive sign of the Soret coefficient are discussed.
The reasons for the experimentally observable periodic transitions between two possible magnetic fluid flow directions in vertical connected channels heated from below are analyzed. It is shown that ...the key role is played by thermal diffusion of colloid particles due to the horizontal temperature gradients in the cross-sections of the narrow channels. On one hand, convection favors fluid mixing and, on the other hand, it itself generates concentration inhomogeneities. The gravitational sedimentation of the particles is excluded from the list of possible reasons of these oscillations.
We have described an express technique for processing the results of experiments with a DAKON-M convection sensor on board the Service Module of the International Space Station (
ISS
) in 2011. The ...technique uses a certain rule to compare the sensor measurements with the calculated data on the quasistatic component of microacceleration at the point of installation. The sensor experiments have been conducted during shuttle docking and undocking, when low-frequency microaccelerations on the
ISS
were significant. The microaccelerations have been calculated using measurement data of the MAMS low-frequency accelerometer installed in the Lab module and the telemetry data on the
ISS
rotational motion. This has made it possible to convert the MAMS measurement data to the DAKON-M convection sensor installation point. A comparison of sensor readings with calculated microaccelerations has revealed fairly good agreement between them.
Increased maternal serum bile acid concentrations in intrahepatic cholestasis of pregnancy (ICP) are associated with fetal cardiac arrhythmias. Ursodeoxycholic acid (UDCA) has been shown to ...demonstrate anti-arrhythmic properties via preventing ICP-associated cardiac conduction slowing and development of reentrant arrhythmias, although the cellular mechanism is still being elucidated.
High-resolution fluorescent optical mapping of electrical activity and electrocardiogram measurements were used to characterize effects of UDCA on one-day-old neonatal and adult female Langendorff-perfused rat hearts. ICP was modelled by perfusion of taurocholic acid (TC, 400μM). Whole-cell calcium currents were recorded from neonatal rat and human fetal cardiomyocytes.
TC significantly prolonged the PR interval by 11.0±3.5% (P<0.05) and slowed ventricular conduction velocity (CV) by 38.9±5.1% (P<0.05) exclusively in neonatal and not in maternal hearts. A similar CV decline was observed with the selective T-type calcium current (ICa,T) blocker mibefradil 1μM (23.0±6.2%, P<0.05), but not with the L-type calcium current (ICa,L) blocker nifedipine 1μM (6.9±6.6%, NS). The sodium channel blocker lidocaine (30μM) reduced CV by 60.4±4.5% (P<0.05). UDCA co-treatment was protective against CV slowing induced by TC and mibefradil, but not against lidocaine. UDCA prevented the TC-induced reduction in the ICa,T density in both isolated human fetal (-10.2±1.5 versus -5.5±0.9 pA/pF, P<0.05) and neonatal rat ventricular myocytes (-22.3±1.1 versus -9.6±0.8 pA/pF, P<0.0001), whereas UDCA had limited efficacy on the ICa,L.
Our findings demonstrate that ICa,T plays a significant role in ICP-associated fetal cardiac conduction slowing and arrhythmogenesis, and is an important component of the fetus-specific anti-arrhythmic activity of UDCA.
The efficiency of injection from a linear accelerator into the damping ring of the BINP injection complex has been experimentally studied. The estimations of the injection efficiency are in good ...agreement with the experimental results. Our method of increasing the capture efficiency can enhance the productivity of the injection complex by a factor of 1.5–2.
The results of comparative experiments on the convection of magnetic fluids and molecular binary fluid mixtures in connected vertical channels heated from below are discussed. In both media, near the ...equilibrium stability threshold, flows in the form of specific swing oscillations are observed. The results of the experiment form a basis for a three-component model for magnetic fluid convection which takes into account the thermodiffusion separation of the dispersion medium components and the weak sedimentation of magnetic particles. The results of numerical simulation and experiment are compared.
The convective flows of a binary mixture in connected channels heated from below are studied experimentally. In contrast to homogeneous fluids, in magnetic colloids “hard” convection excitation, ...specific transient flows, and oscillatory convection regimes can be observed. The temperature fields and concentration inhomogeneities are measured.
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