23,425 research outputs found
An assessment of two decades of contaminant monitoring in the Nation’s Coastal Zone.
Executive Summary:
Information found in this report covers the years 1986 through 2005. Mussel Watch began monitoring a suite of trace metals and organic contaminants such as DDT, PCBs and PAHs. Through time additional chemicals were added, and today approximately 140 analytes are monitored. The Mussel Watch Program is the longest running estuarine and coastal pollutant monitoring effort conducted in the United States that is national in scope each year. Hundreds of scientific journal articles and technical reports based on Mussel Watch data have been written; however, this report is the first that presents local, regional and national findings
across all years in a Quick Reference format, suitable for use by policy makers, scientists, resource managers and the general public.
Pollution often starts at the local scale where high concentrations point to a specific source of contamination, yet some contaminants such as PCBs are atmospherically transported across regional and national scales, resulting in contamination far from their origin. Findings presented here showed few national trends for trace metals and decreasing trends for most organic contaminants; however, a wide variety of trends, both increasing and decreasing, emerge at regional and local levels. For most organic contaminants, trends have resulted from state and
federal regulation. The highest concentrations for both metal and organic contaminants are found near urban and industrial areas.
In addition to monitoring throughout the nation’s coastal shores and Great Lakes, Mussel Watch samples are stored in a specimen bank so that trends can be determined retrospectively for new and emerging contaminants of
concern. For example, there is heightened awareness of a group of flame retardants that are finding their way into the marine environment. These compounds, known as polybrominated diphenyl ethers (PBDEs), are now being studied using historic samples from the specimen bank and current samples to determine their spatial distribution. We will continue to use this kind of investigation to assess new contaminant threats.
We hope you find this document to be valuable, and that
you continue to look towards the Mussel Watch Program
for information on the condition of your coastal waters. (PDF contains 118 pages
A flight investigation of simulated data link communications during single-pilot IFR flight
A Flight Data Console (FDC) was developed to allow simulation of a digital communications link to replace the current voice communication system used in air traffic control (ATC). The voice system requires manipulation of radio equipment, read-back of clearances, and mental storage of critical information items, all contributing to high workload, particularly during single-pilot operations. This was an inflight study to determine how a digital communications system might reduce cockpit workload, improve flight proficiency, and be accepted by general aviation pilots. Results show that instrument flight, including approach and landing, can be accomplished quite effectively using a digital data link system for ATC communications. All pilots expressed a need for a back-up voice channel. When included, this channel was used sparingly and principally to confirm any item of information about which there might be uncertainty
Nullspaces and frames
In this paper we give new characterizations of Riesz and conditional Riesz
frames in terms of the properties of the nullspace of their synthesis
operators. On the other hand, we also study the oblique dual frames whose
coefficients in the reconstruction formula minimize different weighted norms.Comment: 16 page
Frequency Dependent Specific Heat from Thermal Effusion in Spherical Geometry
We present a novel method of measuring the frequency dependent specific heat
at the glass transition applied to 5-polyphenyl-4-ether. The method employs
thermal waves effusing radially out from the surface of a spherical thermistor
that acts as both a heat generator and thermometer. It is a merit of the method
compared to planar effusion methods that the influence of the mechanical
boundary conditions are analytically known. This implies that it is the
longitudinal rather than the isobaric specific heat that is measured. As
another merit the thermal conductivity and specific heat can be found
independently. The method has highest sensitivity at a frequency where the
thermal diffusion length is comparable to the radius of the heat generator.
This limits in practise the frequency range to 2-3 decades. An account of the
3omega-technique used including higher order terms in the temperature
dependency of the thermistor and in the power generated is furthermore given.Comment: 17 pages, 15 figures, Substantially revised versio
A flight investigation of simulated data-link communications during single-pilot IFR flight. Volume 1: Experimental design and initial test
A Flight Data Console simulation of a digital communication link to replace the current voice communication system used in air traffic control (ATC) was developed. The study determined how a digital communications system reduces cockpit workload, improve, flight proficiency, and is acceptable to general aviation pilots. It is shown that instrument flight, including approach and landing, can be accomplished by using a digital data link system for ATC communication
Progress report on solar age calibration
We report on an ongoing investigation into a seismic calibration of solar
models designed for estimating the main-sequence age and a measure of the
chemical abundances of the Sun. Only modes of low degree are employed, so that
with appropriate modification the procedure could be applied to other stars. We
have found that, as has been anticipated, a separation of the contributions to
the seismic frequencies arising from the relatively smooth, glitch-free,
background structure of the star and from glitches produced by helium
ionization and the abrupt gradient change at the base of the convection zone
renders the procedure more robust than earlier calibrations that fitted only
raw frequencies to glitch-free asymptotics. As in the past, we use asymptotic
analysis to design seismic signatures that are, to the best of our ability,
contaminated as little as possible by those uncertain properties of the star
that are not directly associated with age and chemical composition. The
calibration itself, however, employs only numerically computed
eigenfrequencies. It is based on a linear perturbation from a reference model.
Two reference models have been used, one somewhat younger, the other somewhat
older than the Sun. The two calibrations, which use BiSON data, are
more-or-less consistent, and yield a main-sequence age Gy, coupled with a formal initial heavy-element abundance .
The error analysis has not yet been completed, so the estimated precision must
be taken with a pinch of salt.Comment: 8 pages, 3 figures, in L. Deng, K.L. Chan, C. Chiosi, eds, The Art of
Modelling Stars in the 21st Century, Proc. IAU Symp. No. 252, invited
contributed pape
Low-Energy Effective Theory, Unitarity, and Non-Decoupling Behavior in a Model with Heavy Higgs-Triplet Fields
We discuss the properties of a model incorporating both a scalar electroweak
Higgs doublet and an electroweak Higgs triplet. We construct the low-energy
effective theory for the light Higgs-doublet in the limit of small (but
nonzero) deviations in the rho parameter from one, a limit in which the triplet
states become heavy. For small deviations in the rho parameter from one,
perturbative unitarity of WW scattering breaks down at a scale inversely
proportional to the renormalized vacuum expectation value of the triplet field
(or, equivalently, inversely proportional to the square-root of the deviation
of the rho parameter from one). This result imposes an upper limit on the
mass-scale of the heavy triplet bosons in a perturbative theory; we show that
this upper bound is consistent with dimensional analysis in the low-energy
effective theory. Recent articles have shown that the triplet bosons do not
decouple, in the sense that deviations in the rho parameter from one do not
necessarily vanish at one-loop in the limit of large triplet mass. We clarify
that, despite the non-decoupling behavior of the Higgs-triplet, this model does
not violate the decoupling theorem since it incorporates a large dimensionful
coupling. Nonetheless, we show that if the triplet-Higgs boson masses are of
order the GUT scale, perturbative consistency of the theory requires the
(properly renormalized) Higgs-triplet vacuum expectation value to be so small
as to be irrelevant for electroweak phenomenology.Comment: Revtex, 11 pages, 7 eps figures included; references updated and
three footnotes adde
The Temperature Evolution of the Out-of-Plane Correlation Lengths of Charge-Stripe Ordered La(1.725)Sr(0.275)NiO(4)
The temperature dependence of the magnetic order of stripe-ordered
La(1.725)Sr(0.275)NiO(4) is investigated by neutron diffraction. Upon cooling,
the widths if the magnetic Bragg peaks are observed to broaden. The degree of
broadening is found to be very different for l = odd-integer and l =
even-integer magnetic peaks. We argue that the observed behaviour is a result
of competition between magnetic and charge order.Comment: 3 figure
Casimir energy density in closed hyperbolic universes
The original Casimir effect results from the difference in the vacuum
energies of the electromagnetic field, between that in a region of space with
boundary conditions and that in the same region without boundary conditions. In
this paper we develop the theory of a similar situation, involving a scalar
field in spacetimes with compact spatial sections of negative spatial
curvature.Comment: 10 pages. Contribution to the "Fifth Alexander Friedmann
International Seminar on Gravitation and Cosmology," Joao Pessoa, Brazil,
2002. Revised version, with altered Abstract and one new referenc
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