James K. E. Tunaley

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Sporulation in Bacillus subtilis begins with an asymmetric cell division producing two genetically identical cells with different fates. SpoIIE is a membrane protein that localizes to the polar cell division sites where it causes FtsZ to relocate from mid-cell to form polar Z-rings. Following polar septation, SpoIIE establishes compartment-specific gene(More)
SpoIIE is a dual function protein that plays important roles during sporulation in Bacillus subtilis. It binds to the tubulin-like protein FtsZ causing the cell division septum to relocate from mid-cell to the cell pole, and it dephosphorylates SpoIIAA phosphate leading to establishment of differential gene expression in the two compartments following the(More)
The performance of a space-based Automatic Identification System (AIS) receiver, can be estimated in terms of the probability of detection of an uncorrupted ship’s AIS message. Signal collisions arising from other ships outside its selforganizing cell often limit performance. A probabilistic approach based on Poisson statistics is adopted to predict this.(More)
 Abstract---As a part of Maritime Domain Awareness, there is a requirement to detect ships in satellite-borne Synthetic Aperture Radar (SAR) images, which provide wide area ocean surveillance. When ship detection is implemented using a Constant False Alarm Rate (CFAR), statistical theory can be employed to ensure that proper parameters are used to find the(More)
 Abstract—Approximation is found for the K-distribution probability density function. This avoids detailed calculation of modified Bessel functions of the second kind. The K-distribution is often used to model sea clutter in radar images and a simplified algorithm is important for the automatic detection of ships in radar images. The approximation is(More)
The narrow-V ship wake in a radar image is typically a bright V-shaped or wedge-like return with an angle of a few degrees. It is often seen in images from satellite-borne Synthetic Aperture Radar (SAR), especially when the ship is traveling in a direction close to the SAR track and when the wind is light. Though explanation for the narrow-V wake exists(More)
--The observations of ship wakes in RADARSAT-2 Synthetic Aperture Radar fine beam mode images are described. Wakes were observed in about 50 percent of cases where ship detection was accompanied by an Automatic Identification of Ships (AIS) report. These were mostly turbulent wakes. The goal of the research was to understand the physical mechanisms and the(More)
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