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Abstract. In this paper we investigate the underlying dynamics associated with a strong, line-shaped submesoscale feature that was observed in radar imagery at the boundary between Gulf Stream (GS) and shelf water near Cape Hatteras during the first Naval Research Laboratory High-Resolution Remote Sensing Experiment (HIRES 1). The lineshaped feature, which appears as a pronounced (---10 dB) increase in radar cross section, extends several kilometers in the east-west direction. In situ current measurements have shown that this feature coincides with the boundary of a sharp current convergence front. These measurements also indicate that the frontal dynamics is associated with the subduction of denser GS water under lighter shelf water. Using the observation that the convergence can be attributed to a hydrodynamic instability at the water interface, we have modeled the resulting subsurface hydrodynamics on the basis of a rigid-lid, twodimensional solution of the Navier Stokes equation. The calculations of subsurface current flow were used as input to a spectral (wave action) model of wave-current interaction to obtain the surface wave field, which in turn was used to provide input for modeling of radar backscatter. The resulting description also includes the effects of surfactant-induced wave damping on electromagnetic backscatter. Our predictions are compared with real aperture radar imagery and in situ measurements from the HIRES 1 experiment. IntroductionThe ability to infer the underlying current and depth structure from microwave frequency radar imagery of the ocean surface is a long-standing problem of considerable interest. Efforts to infer subsurface structure are inherently limited since radar signals at best penetrate the subsurface at the level of tens of centimeters or less. As a consequence, in the absence of ground truth, it is possible to understand subsurface structure in this manner only on the basis of some understanding and modeling of the underlying dynamics. On the other hand, interpretation of features apparent in ocean imagery is possible only if the link between radar modulation and variations in the small-scale surface roughness due to currents, depth, wind, and the associated momentum fluxes is correctly described. Further complicating the problem, especially at low wind speed, is the effect of wave damping from surfactants. A complete analysis of this problem is manifold, involving subsurface and surface hydrodynamics and electromagnetic backscatter. shown that this signature occurs along the boundary of a sharp current convergence front. These measurements also indicate that the frontal dynamics is associated with the subduction of denser Gulf Stream (GS) water under lighter shelf water. The goal of this paper is to marry subsurface current flow, surface wave-current interaction, and radar imaging, on the basis of a full-spectral representation, to obtain an understanding of this high radar backscatter feature, which will be referred to as a current "rip." As shown in Plate 1, the resul...

Protein fluorescence is a powerful tool for studying protein structure and dynamics if we have a means to interpret the spectral data in terms of protein structural properties. Our previous research successfully provided this support through the development of individual software modules implementing the algorithms for fluorescence and structural analyses. Now we have integrated the developed software modules, introduced a new program for the assignment of tryptophan residues to spectral‐structural classes, and created a web‐based toolkit PFAST: protein fluorescence and structural toolkit: http://pfast.phys.uri.edu/. PFAST contains three modules: (1) FCAT is a fluorescence‐correlation analysis tool, which decomposes protein fluorescence spectra to reveal the spectral components of individual tryptophan residues or groups of tryptophan residues located close to each other, and assigns spectral components to one of five previously established spectral‐structural classes. (2) SCAT is a structural‐correlation analysis tool for the calculation of the structural parameters of the environment of tryptophan residues from the atomic structures of the proteins from the Protein Data Bank (PDB), and for the assignment of tryptophan residues to one of five spectral‐structural classes. (3) The last module is a PFAST database that contains protein fluorescence and structural data obtained from results of the FCAT and SCAT analyses. Proteins 2008. © 2008 Wiley‐Liss, Inc.

Silver nanoparticles have been used in various fields, and several synthesis processes have been developed. The stability and dispersion of the synthesized nanoparticles is vital. The present article describes a novel approach for one-step synthesis of silver nanoparticles–embedded chitosan particles. The proposed approach was applied to simultaneously obtain and stabilize silver nanoparticles in a chitosan polymer matrix in-situ. The diameter of the synthesized chitosan composite particles ranged from 1.7 mm to 2.5 mm, and the embedded silver nanoparticles were measured to be 15±3.3 nm. Further, the analyses of ultraviolet-visible spectroscopy, energy dispersive spectroscopy, and X-ray diffraction were employed to characterize the prepared composites. The results show that the silver nanoparticles were distributed over the surface and interior of the chitosan spheres. The fabricated spheres had macroporous property, and could be used for many applications such as fungicidal agents in the future.