Miniature heaters are immersed in flows of quantum fluid and the efficiency heat transfer is monitored versus velocity, superfluid fraction, time. The $^{4}\mathrm{He}$ helium with a fraction varied from 71% down to 0% an imposed velocity up $3\phantom{\rule{0.28em}{0ex}}\mathrm{m}/\mathrm{s}$, while characteristic sizes range $1.3\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$ few hund...

It was recently conjectured that the ratio of the shear viscosity to entropy density eta/s for any fluid always exceeds [formula: see text]. A theoretical counterexample to this bound can be constructed from a nonrelativistic gas by increasing the number of species in the fluid while keeping the dynamics essentially independent of the species type. The question of whether the underlying structu...

*Correspondence: Yasuhito Narita, Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, A-8042 Graz, Austria e-mail: [email protected] Magnetic reconnection in space plasmas remains a challenge in physics in that the phenomenon is associated with the breakdown of frozen-in magnetic field in a collisionless medium. Such a topology change can also be found in superfluid...