Fluid flow and suspended particulates as determinants of polychaete feeding behavior

We examined the interactive effects of fluid flow, bed characteristics and suspended load on the feeding behavior of four species of marine polychaetes. Two species of obligate deposit feeders (Marenzelleria viridis and Ampharete parvidentata) and two species of palp-coiling facultative suspension feeders (Spiochaetopterus oculatus and Spio setosa) were exposed to flow and sediment-bed treatments that served to decouple fluid flow and particle flux. We employed low (no particle transport), medium (transport of flocs only) and high (transport of sand) flow speeds in factorial treatments of natural sediment, winnowed bed (flocs removed), armored bed (no sand transport at high flows), and armored bed plus fines (flocs added). For each species, worms were exposed to an increasing (low, medium and high) and then decreasing (high, medium and low) flow leg for each bed treatment. We recorded visual observations of animal behavior of the four polychaete species. We found little systematic response to flow and bed differences in the two obligate deposit feeders. When fine material was present, one of the two species exhibited higher variability in time spent deposit feeding, possibly responding to small-scale depositional pockets enriched with fine particles and organic matter. For both facultative suspension feeders, there was an increase in time spent suspension feeding with increasing flow and suspended particle concentrations. Percent suspension feeding was also greater on the decreasing flow legs in treatments with fine material available for suspension. Exploratory analyses of the data reveal a direct relationship between time spent suspension feeding and the flux of suspended high quality organic matter. For both species, compositional parameters of particulate nitrogen and enzymatically available amino acid concentrations were the best correlates of suspension feeding behavior

Deposit and suspension feeding in oscillatory flows and sediment fluxes

We present a survey of feeding behavior of benthic organisms in oscillatory flow and sediment fluxes. These results are based on seventeen species from five phyla and several feeding guilds from an intertidal sandflat and the continental shelf of the Mid-Atlantic coast, U.S.A. General responses to oscillatory flows are: (1) nearly immediate change in feeding behavior or position of feeding appendage when flow is initiated, (2) decrease in feeding area for surface deposit feeders, often (3) alteration of feeding mode, and when anatomically permitted (4) rotation of feeding appendages to track flow direction. At high sediment fluxes, responses are functional group and morphology-specific. Organisms with one or two muscular feeding appendages continue to feed (e.g., Spio setosa, Spiochaetopterus oculatus and Emerita talpoida), while those with a crown of tentacles cannot (e.g., Pista palmata, Serpula vermicularis granulosa, and Terebella rubra). A continental shelf brittle star, Amphipholis squamata, ceases suspension feeding in high flows. Organisms with strong tentacles feed at the sediment surface in much restricted feeding area (Marenzelleria jonesi and Saccoglossus kowalevskii). Organisms with long, thin palps coil them helically and capture particles in near-bed flux (Spiochaetopterus oculatus and Spio setosa). Siphonate feeders maintain siphon tips near the sediment surface and continue pumping (Ensis directus, Mercenaria mercenaria and Tagelus plebeius). A sedentary omnivore (Diopatra cuprea) is able to capture food particles in low and moderate flow, but in high flows the tube opening is closed. Motile scavengers may either increase (Pagurus longicarpus) or decrease (Echinarachnius parma and Ilyanassa obsoleta) movement rate. Of all species studied, only the burrowing predatory starfish Astropecten americanus showed no change in behavior with respect to oscillatory flow. In addition, we report detailed quantitative changes in feeding behavior by a facultative suspension-feeding spionid polychaete Spio setosa and an obligate deposit-feeding terebellid polychaete Terebella rubra which indicate hysteresis or time-dependence in the response to flow and sediment flux. We attempt a summary of responses by functional group and morphology and suggest that new descriptive terms combining low-flow feeding behavior and morphology are needed to characterize feeding modes adequately. Our analysis suggests that it is important to consider the possible presence of flow and flux micro-environments, an individual organisms\u27s variability, flow history and the various time scales of behavioral responses and other biological rate processes. There is a current need for dynamic feeding models that incorporate these factors as well as for experimental tests of the derived predictions

Multiwaveband analysis of brightest GRB070125

We present a comprehensive multiwavelength analysis of the bright, long duration gamma-ray burst GRB 070125, comprised of observations in gamma-ray, X-ray, optical, millimeter and centimeter wavebands. Radio light curves show rapid flux variations, which are interpreted as due to interstellar scintillation, and are used to derive an upper limit of 2.4×10^17 cm on the radius of the fireball. Radio light curves and spectra suggest that the afterglow shock wave is moving in a dense medium. Our broadband modeling favors a constant density profile for the circumburst medium over a wind-like profile (R^−2). GRB 070125 is a burst with high radiative efficiency (>60%)

A Resolved Ring of Debris Dust around the Solar Analog HD 107146

We present resolved images of the dust continuum emission from the debris disk around the young (80-200 Myr) solar-type star HD 107146 with CARMA at λ = 1.3 mm and the CSO at λ = 350 μ. Both images show that the dust emission extends over an approximately 10" diameter region. The high-resolution (3") CARMA image further reveals that the dust is distributed in a partial ring with significant decrease in a flux inward of 97 AU. Two prominent emission peaks appear within the ring separated by ~140° in the position angle. The morphology of the dust emission is suggestive of dust captured into a mean motion resonance, which would imply the presence of a planet at an orbital radius of ~45-75 AU

Atmospheric phase correction using CARMA-PACS: high angular resolution observations of the FU Orionis star PP 13S*

We present 0".15 resolution observations of the 227 GHz continuum emission from the circumstellar disk around the FU Orionis star PP 13S*. The data were obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) Paired Antenna Calibration System (C-PACS), which measures and corrects the atmospheric delay fluctuations on the longest baselines of the array in order to improve the sensitivity and angular resolution of the observations. A description of the C-PACS technique and the data reduction procedures are presented. C-PACS was applied to CARMA observations of PP 13S*, which led to a factor of 1.6 increase in the observed peak flux of the source, a 36% reduction in the noise of the image, and a 52% decrease in the measured size of the source major axis. The calibrated complex visibilities were fitted with a theoretical disk model to constrain the disk surface density. The total disk mass from the best-fit model corresponds to 0.06 M_⊙, which is larger than the median mass of a disk around a classical T Tauri star. The disk is optically thick at a wavelength of 1.3 mm for orbital radii less than 48 AU. At larger radii, the inferred surface density of the PP 13S* disk is an order of magnitude lower than that needed to develop a gravitational instability

Pratt & Whitney/Boeing Engine Validation of Noise Reduction Concepts Final Report for NASA Contract NAS3-97144, Phase 2

This report presents results of the work completed in Phase 2 of the Engine Validation of Noise Reduction Concepts (EVNRC) contract. The purpose of the program is to validate, through engine testing, advanced noise reduction concepts aimed at reducing engine noise up to 6 EPNdB and improving nacelle suppression by 50 percent relative to 1992 technology. Phase 1 of the program is completed and is summarized in NASA/CR-2014-218088