We describe simulations of the response of a gaseous disc to an active spiral potential. The potential is derived from an N-body calculation and leads to a multi-armed timeevolving pattern. The gas forms long spiral arms typical of grand design galaxies, although the spiral pattern is asymmetric. The primary difference from a grand-design spiral galaxy, which has a consistent 2/4-armed pattern,...

The detailed processes involved in spiral wave breakup, believed to be one major mechanism by which tachycardia evolves into fibrillation, are still poorly understood. This has rendered difficult the proper design of an efficient and practical control stimulus protocol to eliminate such events. In order to gain new insights into the underlying electrophysiological and dynamical mechanisms of br...

Spiral-driven instabilities may drive gas inflow to enhance central star formation in disk galaxies. We investigate this hypothesis using the Sloan Digital Sky Survey (SDSS) a sample of 2779 nearby unbarred star-forming main sequence spiral The strength arms is quantified by their average Fourier amplitude relative axisymmetric disk. properties 1–3 kpc region were derived from SDSS spectra. sho...

– The spiral-wave breakup to turbulence in an excitable medium, starting from the spiral-wave center via Doppler instability, is controlled by modulating a local region around the spiral-wave center. The modulation signal is extracted from the controlled region with a certain time delay. By injecting a feedback signal with very low intensity into a very small space area, we can successfully sta...

This Thesis describes ultralow temperature studies of helium quantum crystals. Owing to the surrounding superfluid, small latent heat of crystallization and correspondingly short relaxation times, which are unreachable in ordinary crystals, helium crystals offer a unique and clean modeling system to study surface phenomena in a solid. The measurements of the crystal shape and growth rates are e...

Single point incremental sheet metal forming is a sheet metal forming process that forms products without the complex dies and tools with low cost. In this study, the incremental sheet metal forming process has been experimentally investigated on the explosively-welded Al/Cu bimetal sheets. Also, the effects of process parameters, such as arrangement of layer`s bimetal, tool diameter and tool p...

Figure 3: Spiral-In and Spiral-Out raw images in a human brain (24cm x 24cm, a-c) and cylindrical phantom placed perpendicular to B0 (6cm x 6cm, d-f). The various TEs are a) Spiral-Out 18ms, b) Spiral-In 30ms, c) Spiral-In 42ms, d) Spiral-Out 7.4ms, e) SpiralIn 30ms and f) Spiral-In 52.6ms. Figure 1: R2* map of cylindrical phantom filled with tubes containing materials with varying R2* (arrow i...