696 research outputs found
Atlantic menhaden, Brevoortia tyrannus, Purse Seine Fishery, 1972-84, with a brief discussion of age and size composition of the Landings
This report summarizes (I) annual purse seine landings of Atlantic menhaden, Brevoortia tyrannus, for 1972-84, (2) estimated numbers of fish caught by fishing area. (3) estimates of nominal fishing effort and catch-per-unit-effort, (4) mean fish length and weight, and (5) major changes in the fishery. During the 1970s stock size and recruitment increased and the age composition broadened. reversing trends witnessed during the fishery's decline in the 1960s. Landings steadily improved and by 1980 the total coast wide landings exceeded 400,000 metric tons.
Nevertheless, the character of the fishery changed considerably. Eleven reduction plants processed fish at seven ports in 1972, but in 1984 only eight plants
operated at live ports. Beginning in the mid-1960s the center of fishing aclivity shifted from the Middle Atlantic area to the Chesapeake Bay area, which has continued to dominate the fishery in landings and effort through the 1970s and 1980s. During this period the average size and age of fish in the catches declined. (PDF file contains 30 pages.
The Feigned Annoyance and Frustration Test to Activate the Sympathoadrenal Medullary System
When perceived as threatening, social interactions have been shown to trigger the sympathoadrenal medullary system as well as the hypothalamic-pituitary-adrenal axis resulting in a physiologic stress response. The allostatic load placed on human health and physiology in the context of acute and chronic stress can have profound health consequences. The purpose of this study was to develop a protocol for a lab-based stress stimulus using social-evaluative threat. While several valid, stress-stimulating protocols exist, we sought to develop one that triggered a physiologic response, did not require significant lab resources, and could be completed in around 10 min. We included 53 participants (29 men and 24 women) and exposed them to a modified version of the Stroop Color-Word Interference Task during which the participants were made to feel they were performing the task poorly while the lead researcher feigned annoyance and frustration. After exposure to this Feigned Annoyance and Frustration (FAF) Test, both the men and women in this study demonstrated a statistically significant and clinically meaningful increase in subjective stress on the visual analog scale. Additionally, the men in this study demonstrated a statistically significant increase in heart rate and salivary α-amylase concentrations after exposure to the test. The women in this study did not demonstrate a statistically significant increase in the physiologic stress biomarkers. This protocol for the FAF Test shows promise to researchers with limited time and resources who are interested in experimentally activating the sympathoadrenal medullary system
Infrared 3-4 Micron Spectroscopic Investigations of a Large Sample of Nearby Ultraluminous Infrared Galaxies
We present infrared L-band (3-4 micron) nuclear spectra of a large sample of
nearby ultraluminous infrared galaxies (ULIRGs).ULIRGs classified optically as
non-Seyferts (LINERs, HII-regions, and unclassified) are our main targets.
Using the 3.3 micron polycyclic aromatic hydrocarbon (PAH) emission and
absorption features at 3.1 micron due to ice-covered dust and at 3.4 micron
produced by bare carbonaceous dust, we search for signatures of powerful active
galactic nuclei (AGNs) deeply buried along virtually all lines-of-sight. The
3.3 micron PAH emission, the signatures of starbursts, is detected in all but
two non-Seyfert ULIRGs, but the estimated starburst magnitudes can account for
only a small fraction of the infrared luminosities. Three LINER ULIRGs show
spectra typical of almost pure buried AGNs, namely, strong absorption features
with very small equivalent-width PAH emission. Besides these three sources, 14
LINER and 3 HII ULIRGs' nuclei show strong absorption features whose absolute
optical depths suggest an energy source more centrally concentrated than the
surrounding dust, such as a buried AGN. In total, 17 out of 27 (63%) LINER and
3 out of 13 (23%) HII ULIRGs' nuclei show some degree of evidence for powerful
buried AGNs, suggesting that powerful buried AGNs may be more common in LINER
ULIRGs than in HII ULIRGs. The evidence of AGNs is found in non-Seyfert ULIRGs
with both warm and cool far-infrared colors. These spectra are compared with
those of 15 ULIRGs' nuclei with optical Seyfert signatures taken for
comparison.The overall spectral properties suggest that the total amount of
dust around buried AGNs in non-Seyfert ULIRGs is systematically larger than
that around AGNs in Seyfert 2 ULIRGs.Comment: 56 pages, 9 figures, accepted for publication in ApJ (20 January
2006, vol 637 issue
Metal Decorated Multi-Walled Carbon Nanotube/Polyimide Composites with High Dielectric Constants and Low Loss Factors
The measurement of observable electromagnetic phenomena in materials and their derived intrinsic electrical material properties are of prime importance in the discovery and development of material systems for electronic and aerospace applications. Nanocomposite materials comprised of metal decorated multi-walled carbon nanotubes (MWCNTs) were prepared by a facile method and characterized. Metal particles such as silver(Ag), platinum(Pt) and palladium(Pd) with diameters ranging from less than 5 to over 50 nanometers were distributed randomly on the MWCNTs. The present study is focused on silver decorated MWCNTs dispersed in a polyimide matrix. The Ag-containing MWCNTs were melt mixed into Ultem(TradeMark) and the mixture extruded as ribbons. The extruded ribbons exhibited a moderate to high degree of MWCNT alignment as determined by HRSEM. These ribbons were then fabricated into test specimens while maintaining MWCNT alignment and subsequently characterized for electrical and electromagnetic properties at 8-12 GHz. The results of the electromagnetic characterization showed that certain sample configurations exhibited a decoupling of the permittivity (epsilon ) and loss factor (epsilon") indicating that these properties could be tailored within certain limits. The decoupling and independent control of these fundamental electrical material parameters offers a new class of materials with potential applications in electronics, microwave engineering and optics
Antenna with Dielectric Having Geometric Patterns
An antenna includes a ground plane, a dielectric disposed on the ground plane, and an electrically-conductive radiator disposed on the dielectric. The dielectric includes at least one layer of a first dielectric material and a second dielectric material that collectively define a dielectric geometric pattern, which may comprise a fractal geometry. The radiator defines a radiator geometric pattern, and the dielectric geometric pattern is geometrically identical, or substantially geometrically identical, to the radiator geometric pattern
Ice emission and the redshifts of submillimeter sources
Observations at submillimeter wavelengths have revealed a population of
sources thought to be at relatively large redshifts. The position of the 850
m passband on the Rayleigh-Jeans portion of the Planck function leads to a
maximum redshift estimate of 4.5 since sources will not retain their
redshift independent brightness close to the peak of the Planck function and
thus drop out of surveys. Here we review evidence that ice absorption is
present in the spectra of local ultraluminous infrared galaxies which are often
taken as analogs for the 850 m source population. We consider the
implication of this absorption for ice induced spectral structure at far
infrared wavelengths and present marginal astronomical evidence that amorphous
ice may have a feature similar to crystalline ice near 150 m. Recent
corroborative laboratory evidence is supportive of this conclusion. It is
argued that early metal enrichment by pair instability SN may lead to a high
ice content relative to refractory dust at high redshift and a fairly robust
detection of ice emission in a quasar is presented. It is further
shown that ice emission is needed to understand the 450 m sources observed
in the GOODS-N field. We are thus encouraged to apply far infrared ice emission
models to the available observations of HDF 850.1, the brightest submillimeter
source in the {\it Hubble Deep Field}. We suggest that a redshift as large as
13 may need to be considered for this source, nearly a factor of three above
the usual top estimate. Inclusion of the possibility of far infrared ice
emission in the spectral energy distributions of model sources generally
broadens the range of redshifts to be considered for submillimeter sources
compared to models without ice emission.Comment: 37 pages, 8 figures, accepted for publication in the Astrophysical
Journa
Mid-infrared spectral evidence for a luminous dust enshrouded source in Arp220
We have re-analyzed the 6-12 micron ISO spectrum of the ultra-luminous
infrared galaxy Arp220 with the conclusion that it is not consistent with that
of a scaled up version of a typical starburst. Instead, both template fitting
with spectra of the galaxies NGC4418 and M83 and with dust models suggest that
it is best represented by combinations of a typical starburst component,
exhibiting PAH emission features, and a heavily absorbed dust continuum which
contributes ~40% of the 6-12 micron flux and likely dominates the luminosity.
Of particular significance relative to previous studies of Arp220 is the fact
that the emission feature at 7.7 micron comprises both PAH emission and a
broader component resulting from ice and silicate absorption against a heavily
absorbed continuum. Extinction to the PAH emitting source, however, appears to
be relatively low. We tentatively associate the PAH emitting and heavily
dust/ice absorbed components with the diffuse emission region and the two
compact nuclei respectively identified by Soifer et al. (2002) in their higher
spatial resolution 10 micron study. Both the similarity of the absorbed
continuum with that of the embedded Galactic protostars and results of the dust
models imply that the embedded source(s) in Arp220 could be powered by, albeit
extremely dense, starburst activity. Due to the high extinction, it is not
possible with the available data to exclude that AGN(s) also contribute some or
all of the observed luminosity. In this case, however, the upper limit measured
for its hard X-ray emission would require Arp220 to be the most highly obscured
AGN known.Comment: 11 pages, 9 figures. Accepted for publication in A&A. Also available
at http://www.astro.rug.nl/~spoon/publications.htm
Consumer\u27s Guide to Regulatory Impact Analysis: Ten Tips for Being an Informed Policymaker
Regulatory impact analyses (RIAs) weigh the benefits of regulations against the burdens they impose and are invaluable tools for informing decision makers.We offer 10 tips for nonspecialist policymakers and interested stakeholders who will be reading RIAs as consumers. Core problem: Determine whether the RIA identifies the core problem (compelling public need) the regulation is intended to address. Alternatives: Look for an objective, policy-neutral evaluation of the relative merits of reasonable alternatives. Baseline: Check whether the RIA presents a reasonable “counterfactual” against which benefits and costs are measured. Increments: Evaluate whether totals and averages obscure relevant distinctions and trade-offs. Uncertainty: Recognize that all estimates involve uncertainty, and ask what effect key assumptions, data, and models have on those estimates. Transparency: Look for transparency and objectivity of analytical inputs. Benefits: Examine how projected benefits relate to stated objectives. Costs: Understand what costs are included. Distribution: Consider how benefits and costs are distributed. Symmetrical treatment: Ensure that benefits and costs are presented symmetrically
Consumer\u27s Guide to Regulatory Impact Analysis: Ten Tips for Being an Informed Policymaker
Regulatory impact analyses (RIAs) weigh the benefits of regulations against the burdens they impose and are invaluable tools for informing decision makers.We offer 10 tips for nonspecialist policymakers and interested stakeholders who will be reading RIAs as consumers. Core problem: Determine whether the RIA identifies the core problem (compelling public need) the regulation is intended to address. Alternatives: Look for an objective, policy-neutral evaluation of the relative merits of reasonable alternatives. Baseline: Check whether the RIA presents a reasonable “counterfactual” against which benefits and costs are measured. Increments: Evaluate whether totals and averages obscure relevant distinctions and trade-offs. Uncertainty: Recognize that all estimates involve uncertainty, and ask what effect key assumptions, data, and models have on those estimates. Transparency: Look for transparency and objectivity of analytical inputs. Benefits: Examine how projected benefits relate to stated objectives. Costs: Understand what costs are included. Distribution: Consider how benefits and costs are distributed. Symmetrical treatment: Ensure that benefits and costs are presented symmetrically
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