8,787 research outputs found
Ocean services user needs assessment. Volume 1: Survey results, conclusions and recommendations
An interpretation of environmental information needs of marine users, derived from a direct contact survey of eight important sectors of the marine user community is presented. Findings of the survey and results and recommendations are reported. The findings consist of specific and quantized measurement and derived product needs for each sector and comparisons of these needs with current and planned NOAA data and services. The following supportive and reference material are examined: direct contact interviews with industry members, analyses of current NOAA data gathering and derived product capabilities, evaluations of new and emerging domestic and foreign satellite data gathering capabilities, and a special commercial fishing survey conducted by the Jet Propulsion Laboratory (JPL)
Flight tests of a direct lift control system during approach and landing
Flight tests of modified aileron direct lift control system during approach and landing of F8-C aircraf
Clues to the Origin of the Mass-Metallicity Relation: Dependence on Star Formation Rate and Galaxy Size
We use a sample of 43,690 galaxies selected from the Sloan Digital Sky Survey
Data Release 4 to study the systematic effects of specific star formation rate
(SSFR) and galaxy size (as measured by the half light radius, r_h) on the
mass-metallicity relation. We find that galaxies with high SSFR or large r_h
for their stellar mass have systematically lower gas phase-metallicities (by up
to 0.2 dex) than galaxies with low SSFR or small r_h. We discuss possible
origins for these dependencies, including galactic winds/outflows, abundance
gradients, environment and star formation rate efficiencies.Comment: Accepted by ApJ Letter
Induced superfluidity of imbalanced Fermi gases near unitarity
The induced intraspecies interactions among the majority species, mediated by
the minority species, is computed for a population-imbalanced two-component
Fermi gas. Although the Feshbach-resonance mediated interspecies interaction is
dominant for equal populations, leading to singlet s-wave pairing, we find that
in the strongly imbalanced regime the induced intraspecies interaction leads to
p-wave pairing and superfluidity of the majority species. Thus, we predict that
the observed spin-polaron Fermi liquid state in this regime is unstable to
p-wave superfluidity, in accordance with the results of Kohn and Luttinger,
below a temperature that, near unitarity, we find to be within current
experimental capabilities. Possible experimental signatures of the p-wave state
using radio-frequency spectroscopy as well as density-density correlations
after free expansion are presented.Comment: 15 pages, 13 figures, submitted to Phys. Rev.
A definitive merger-AGN connection at z~0 with CFIS: mergers have an excess of AGN and AGN hosts are more frequently disturbed
The question of whether galaxy mergers are linked to the triggering of active
galactic nuclei (AGN) continues to be a topic of considerable debate. The issue
can be broken down into two distinct questions: 1) Can galaxy mergers trigger
AGN? 2) Are galaxy mergers the dominant AGN triggering mechanism? A complete
picture of the AGN-merger connection requires that both of these questions are
addressed with the same dataset. In previous work, we have shown that galaxy
mergers selected from the Sloan Digital Sky Survey (SDSS) show an excess of
both optically-selected, and mid-IR colour-selected AGN, demonstrating that the
answer to the first of the above questions is affirmative. Here, we use the
same optical and mid-IR AGN selection to address the second question, by
quantifying the frequency of morphological disturbances in low surface
brightness r-band images from the Canada France Imaging Survey (CFIS). Only ~30
per cent of optical AGN host galaxies are morphologically disturbed, indicating
that recent interactions are not the dominant trigger. However, almost 60 per
cent of mid-IR AGN hosts show signs of visual disturbance, indicating that
interactions play a more significant role in nuclear feeding. Both mid-IR and
optically selected AGN have interacting fractions that are a factor of two
greater than a mass and redshift matched non-AGN control sample, an excess that
increases with both AGN luminosity and host galaxy stellar mass.Comment: Accepted for publication in MNRA
Fixed base simulator study of an externally blown flap STOL transport airplane during approach and landing
A fixed-base simulator study was conducted to determine the flight characteristics of a representative STOL transport having a high wing and equipped with an external-flow jet flap in combination with four high-bypass-ratio fan-jet engines during the approach and landing. Real-time digital simulation techniques were used. The computer was programed with equations of motion for six degrees of freedom and the aerodynamic inputs were based on measured wind-tunnel data. A visual display of a STOL airport was provided for simulation of the flare and touchdown characteristics. The primary piloting task was an instrument approach to a breakout at a 200-ft ceiling with a visual landing
Cotranslational Protein Folding and Terminus Hydrophobicity
Peptides fold on a time scale that is much smaller than the time required for synthesis, whence all proteins potentially fold cotranslationally to some degree (followed by additional folding events after release from the ribosome). In this paper, in three different ways, we find that cotranslational folding success is associated with higher hydrophobicity at the N-terminus than at the C-terminus. First, we fold simple HP models on a square lattice and observe that HP sequences that fold better cotranslationally than from a fully extended state exhibit
a positive difference (N−C) in terminus hydrophobicity. Second, we examine real proteins using a previously established measure of potential cotranslationality known as ALR (Average Logarithmic Ratio of the extent of previous contacts) and again find a correlation with the difference in terminus hydrophobicity. Finally, we use the cotranslational protein structure prediction program SAINT and again find that such an approach to
folding is more successful for proteins with higher N-terminus than C-terminus hydrophobicity. All results indicate that cotranslational folding is promoted in part by a hydrophobic start and a less hydrophobic finish to the sequence
The Millennium Galaxy Catalogue: The connection between close pairs and asymmetry; implications for the galaxy merger rate
We compare the use of galaxy asymmetry and pair proximity for measuring
galaxy merger fractions and rates for a volume limited sample of 3184 galaxies
with -21 < M(B) -5 log h < -18 mag. and 0.010 < z < 0.123 drawn from the
Millennium Galaxy Catalogue. Our findings are that:
(i) Galaxies in close pairs are generally more asymmetric than isolated
galaxies and the degree of asymmetry increases for closer pairs. At least 35%
of close pairs (with projected separation of less than 20 h^{-1} kpc and
velocity difference of less than 500 km s^{-1}) show significant asymmetry and
are therefore likely to be physically bound.
(ii) Among asymmetric galaxies, we find that at least 80% are either
interacting systems or merger remnants. However, a significant fraction of
galaxies initially identified as asymmetric are contaminated by nearby stars or
are fragmented by the source extraction algorithm. Merger rates calculated via
asymmetry indices need careful attention in order to remove the above sources
of contamination, but are very reliable once this is carried out.
(iii) Close pairs and asymmetries represent two complementary methods of
measuring the merger rate. Galaxies in close pairs identify future mergers,
occurring within the dynamical friction timescale, while asymmetries are
sensitive to the immediate pre-merger phase and identify remnants.
(iv) The merger fraction derived via the close pair fraction and asymmetries
is about 2% for a merger rate of (5.2 +- 1.0) 10^{-4} h^3 Mpc^{-3} Gyr^{-1}.
These results are marginally consistent with theoretical simulations (depending
on the merger time-scale), but imply a flat evolution of the merger rate with
redshift up to z ~1.Comment: 10 pages, 10 figures, emulateapj format. ApJ, accepte
Spatially explicit model of wintering common loons: conservation implications
Common loons Gavia immer are a conservation concern in New England due to a variety of anthropogenic factors, yet little is known about biotic and abiotic environmental factors determining their wintering distribution and abundance in nearshore and offshore waters. The primary objective of this study was to develop a spatially explicit abundance model of wintering common loons in the maritime waters of southern New England (USA) that could inform decisions about offshore development. Aerial line-transect surveys were conducted throughout a 3800 km2 study area off the coast of Rhode Island during the winters of 2010–2011 and 2011–2012. A density surface model (DSM) approach was used to account for imperfect detection and incorporate spatially explicit environmental covariates. Common loon densities were greatest in watersdeep, with high chl a surface concentrations (\u3e2 mg m−3). The DSM predicted 5047 (95% CI = 3993−6379) common loons in the study area during winter, which suggests this region provides key habitat for this species in eastern North America. This study highlights important areas for common loons in the region, suggests key biotic (primary productivity as measured by long-term chl a surface concentrations) and abiotic covariates (water depth) driving the spatial distribution and abundance of common loons in southern New England, and identifies sites that should be considered for protection from offshore development, including offshore wind facilities
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