Studying star formation in spiral arms tells us not only about the evolution of star formation, and molecular clouds, but can also tell us about the nature of spiral structure in galaxies. I will address both these topics using the results of recent simulations and observations. Galactic scale simulations are beginning to examine in detail the evolution of Giant Molecular Clouds (GMC) as they f...

Spiral analysis is a computerized method that measures human motor performance from handwritten Archimedean spirals. It quantifies normal motor activity, and detects early disease as well as dysfunction in patients with movement disorders. The clinical utility of spiral analysis is based on kinematic and dynamic indices derived from the original spiral trace, which must be detected and transfor...

We use hydrodynamical simulations to investigate the response of geometrically thin, self-gravitating, singular isothermal disks of gas to imposed rigidly rotating spiral potentials. By minimizing reflection-induced feedback from boundaries , and by restricting our attention to models where the swing parameter X ∼ 10, we minimize the swing amplification of global normal modes even in models whe...

There is still considerable debate about the optimal diagnostic imaging modality for acute pulmonary embolism. If imaging is deemed necessary from an initial clinical evaluation such as d-dimer testing, options include nuclear medicine scanning, catheter pulmonary angiography, and spiral CT. In many institutions, spiral CT is becoming established as the first-line imaging test in daily clinical...

We have obtained deep near-infrared Ks-band William Herschel Telescope observations of a sample of 15 nearby spiral galaxies having a range of Hubble types and apparent bar strengths. The near-infrared light distributions are converted into gravitational potentials, and the maximum relative gravitational torques due to the bars and the spirals are estimated. We find that spiral strength, Qs, an...

Spiral waves in period-doubled and other complex-oscillatory media possess line defects across which the phase of the oscillation changes by multiples of 2pi. For such systems, the concept of a splay state, introduced for coupled oscillator systems, is generalized to an Archimedean spiral splay field. In this splay field a spiral wave in a two dimensional space is considered to be a special spl...

Spiral structures are one of the most difficult patterns to classify. In this paper, some important characteristics of the two-spiral problem are discussed. The paper discusses the reasons why linear and non-linear approaches have difficulties with classifying such data. The paper focusses on how structural information about spirals can be useful in providing critical information to a neural ne...

Spiral-wave breakup in strongly chaotic media with nonphase-coherent chaotic attractors is investigated. Spiral-wave dynamics is studied for the Rössler reaction diffusion equation as the local attractor changes from a phase-coherent to a funnel form. Stable spiral waves with an Archimedean structure are observed to persist even when the local chaotic attractor has a funnel form. The destructio...

We introduce a new visualization method for temporal data, Spiral Theme Plot, by combining ThemeRiver method, spiral patterns, and scatter plot technique. Similar to ThemeRiver, data in different categories (themes) are visualized in different bands, but also in a spiral pattern. Themes are stacked along a spiral curve, which represent the time axis. Individual data points are plotted within th...

We present optical and IR surface photometry of M51 (NGC 5194) at B V R I J K and CO(2.3μ). These data are used to establish whether K-band (2.2μ) images of spiral galaxies provide reliable maps of stellar surface mass density features such as massive spiral arms or bars. The main distorting agents in the mapping at shorter wavelengths are dust extinction and luminous young stars. From modeling...