380 research outputs found
Quantum Turbulent Structure in Light
The infinite superpositions of random plane waves are known to be threaded
with vortex line singularities which form complicated tangles and obey strict
topological rules. We observe that within these structures a timelike axis
appears to emerge with which we can define vortex velocities in a useful way:
with both numerical simulations and optical experiments, we show that the
statistics of these velocities match those of turbulent quantum fluids such as
superfluid helium and atomic Bose-Einstein condensates. These statistics are
shown to be independent of system scale. These results raise deep questions
about the general nature of quantum chaos and the role of nonlinearity in the
structure of turbulence.Comment: 4 pages, 2 figure
ICP curve morphology and intracranial flow-volume changes: a simultaneous ICP and cine phase contrast MRI study in humans
Background: The intracranial pressure (ICP) curve with its different peaks has been extensively studied, but the exact physiological mechanisms behind its morphology are still not fully understood. Both intracranial volume change (ΔICV) and transmission of the arterial blood pressure have been proposed to shape the ICP curve. This study tested the hypothesis that the ICP curve correlates to intracranial volume changes. Methods: Cine phase contrast magnetic resonance imaging (MRI) examinations were performed in neuro-intensive care patients with simultaneous ICP monitoring. The MRI was set to examine cerebral arterial inflow and venous cerebral outflow as well as flow of cerebrospinal fluid over the foramen magnum. The difference in total flow into and out from the cranial cavity (Flowtot) over time provides the ΔICV. The ICP curve was compared to the Flowtot and the ΔICV. Correlations were calculated through linear and logarithmic regression. Student’s t test was used to test the null hypothesis between paired samples. Results: Excluding the initial ICP wave, P1, the mean R2 for the correlation between the ΔICV and the ICP was 0.75 for the exponential expression, which had a higher correlation than the linear (p = 0.005). The first ICP peaks correlated to the initial peaks of Flowtot with a mean R2 = 0.88. Conclusion: The first part, or the P1, of the ICP curve seems to be created by the first rapid net inflow seen in Flowtot while the rest of the ICP curve seem to correlate to the ΔICV
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