The aim of this study was to analyse the evolution of critical velocity and critical stroke rate during 12 weeks of training in age group swimmers. Fourteen age group male swimmers took part in this investigation. The evaluation took place in two different trials. The first one was conducted at the beginning of the season and the second one after 12 weeks of training. For each subject the criti...

We report an experiment that uses a superfluid helium quantum interference device to probe the initial onset of the motion of a single vortex line driven by axial flow in a macroscopic channel. When the superfluid velocity reaches a temperature independent critical value !vc#1 mm/s" periodic 2! phase slippage occurs with a frequency of the order of a few Hz. As the axial flow velocity increases...

Observations show significant Hα-emissions in the Galactic halo near the edges of cold gas clouds of the Magellanic Stream. The source for the ionization of the cold gas is still a widely open question. In our paper we discuss the critical velocity effect as a possible explanation for the observed Hα-emission. The critical velocity effect can yield a fast ionization of cold gas if this neutral ...

We study the instability of a moving spinor Bose-Einstein condensate when the speed of flow reaches the critical velocity. This we identify on the basis of Landau’s criterion, i.e. the velocity above which some elementary excitation energy becomes negative. We show that the first-to-become unstable excitations are spin-carrying quasiparticles. We also discuss the temperature dependence of the c...

This study was designed to calculate the critical velocity (vcrit) and anaerobic distance capacity (ADC) of prepubescent children for running events. Thirty-four prepubertal children underwent a graded field test to exhaustion in order to determine peak oxygen uptake (peak VO2) and maximal aerobic velocity (MAV). Then, in random order, they performed five runs to exhaustion (tlim) at relative v...

In recent work we have shown that a black hole stacked on a brane escapes once it acquires a recoil velocity. This result was obtained in the probe-brane approximation, i.e., when the tension of the brane is negligibly small. Therefore, it is not clear whether the effect of the brane tension may prevent the black hole from escaping for small recoil velocities. The question is whether a critical...

In ventilated tunnel fires, smoke and hot combustion products may form a layer near the ceiling and flow in the direction opposite to the ventilation stream. The existence of this reverse stratified flow has an important bearing on fire fighting and evacuation of underground mine roadways, tunnels and building corridors. In the present study, conducted by the National Institute for Occupational...

We investigate theoretically and numerically a model of a supersolid in a dipole-blockaded Bose-Einstein condensate. The dependence of the superfluid fraction with an imposed thermal bath and a uniform boost velocity on the condensate is considered. Specifically, we observe a critical velocity for the nucleation of vortices in our system that is strongly linked to a steplike decrease in the sup...

Swimming critical velocity is defined as the maximum velocity that could be maintained during a long period of time without exhaustion, being accepted as a valid parameter to assess aerobic capacity. Our purpose was to observe the patterns of the stroking parameters during a typical aerobic capacity training set conducted at critical velocity. Thirtysix juvenile swimmers performed front crawl 2...