Demonstration of the effect of stirring on nucleation from experiments on the International Space Station using the ISS-EML facility.

The effect of fluid flow on crystal nucleation in supercooled liquids is not well understood. The variable density and temperature gradients in the liquid make it difficult to study this under terrestrial gravity conditions. Nucleation experiments were therefore made in a microgravity environment using the Electromagnetic Levitation Facility on the International Space Station on a bulk glass-forming Zr57Cu15.4Ni12.6Al10Nb5 (Vit106), as well as Cu50Zr50 and the quasicrystal-forming Ti39.5Zr39.5Ni21 liquids. The maximum supercooling temperatures for each alloy were measured as a function of controlled stirring by applying various combinations of radio-frequency positioner and heater voltages to the water-cooled copper coils. The flow patterns were simulated from the known parameters for the coil and the levitated samples. The maximum nucleation temperatures increased systematically with increased fluid flow in the liquids for Vit106, but stayed nearly unchanged for the other two. These results are consistent with the predictions from the Coupled-Flux model for nucleation.

Discontinuities in slow finger movements in patients with Parkinson's disease.

Slow finger movements in healthy humans are characterized by discontinuous rhythmic changes in a low frequency band about 8 Hz. These pulsatile changes in velocity are thought to present the central output of an oscillatory cerebello-thalamo-cortical network in the same frequency. Hypothesizing that patients with Parkinson's disease (PD) in the dopaminergic OFF- and ON-condition show changes in the characteristics of discontinuities compared to healthy humans, we used a 3D-ultrasound device to measure slow finger movements of 16 patients with PD and 12 age-matched controls. We provide evidence that slow finger movements of patients with PD are characterized by discontinuities in acceleration, which are significantly slower in the OFF- but not in the ON-condition compared to healthy controls. Correlation analysis between clinical motor improvement after dopaminergic medication and changes of peak frequencies and peak power of discontinuities was not significant. We conclude that the oscillatory brain network of slow finger movements is affected in PD, presenting in a lower frequency in the OFF-condition. We suggest that one factor of the modulation of this network is a dopaminergic stimulation.