11,022 research outputs found
Coke Oven Emissions: A Case Study of Technology-Based Regulation
After examining and analyzing the experience with coke ovens, the authors conclude that attempts to force technology beyond its demonstrated competence can be both expensive and ineffective in controlling hazards. They also suggest implications for pending proposals to further control air pollution
Determining Energy Balance in the Flaring Chromosphere from Oxygen V Line Ratios
The impulsive phase of solar flares is a time of rapid energy deposition and
heating in the lower solar atmosphere, leading to changes in the temperature
and density structure of the region. We use an O V density diagnostic formed of
the 192 to 248 line ratio, provided by Hinode EIS, to determine the density of
flare footpoint plasma, at O V formation temperatures of 250,000 K, giving a
constraint on the properties of the heated transition region. Hinode EIS
rasters from 2 small flare events in December 2007 were used. Raster images
were co-aligned to identify and establish the footpoint pixels,
multiple-component Gaussian line fitting of the spectra was carried out to
isolate the diagnostic pair, and the density was calculated for several
footpoint areas. The assumptions of equilibrium ionization and optically thin
radiation for the O V lines were found to be acceptable. Properties of the
electron distribution, for one event, were deduced from earlier RHESSI hard
X-ray observations and used to calculate the plasma heating rate, delivered by
an electron beam adopting collisional thick-target assumptions, for 2 model
atmospheres. Electron number densities of at least log n = 12.3 cm-3 were
measured during the flare impulsive phase, far higher than previously expected.
For one footpoint, the radiative loss rate for this plasma was found to exceed
that which can be delivered by an electron beam implied by the RHESSI data.
However, when assuming a completely ionised target atmosphere the heating rate
exceeded the losses. A chromospheric thickness of 70-700 km was found to be
required to balance a conductive input to the O V-emitting region with
radiative losses. The analysis shows that for heating by collisional electrons,
it is difficult, or impossible to raise the temperature of the chromosphere to
explain the observed densities without assuming a completely ionised
atmosphere.Comment: Accepted to A&A 14th September 201
Impulsive Heating of Solar Flare Ribbons Above 10 MK
The chromospheric response to the input of flare energy is marked by extended
extreme ultraviolet (EUV) ribbons and hard X-ray (HXR) footpoints. These are
usually explained as the result of heating and bremsstrahlung emission from
accelerated electrons colliding in the dense chromospheric plasma. We present
evidence of impulsive heating of flare ribbons above 10 MK in a two-ribbon
flare. We analyse the impulsive phase of SOL2013-11-09T06:38, a C2.6 class
event using data from Atmospheric Imaging Assembly (AIA) on board of Solar
Dynamics Observatory (SDO) and the Reuven Ramaty High Energy Solar
Spectroscopic Imager (RHESSI) to derive the temperature, emission measure and
differential emission measure of the flaring regions and investigate the
evolution of the plasma in the flaring ribbons. The ribbons were visible at all
SDO/AIA EUV/UV wavelengths, in particular, at 94 and 131 \AA\ filters,
sensitive to temperatures of 8 MK and 12 MK. Time evolution of the emission
measure of the plasma above 10 MK at the ribbons has a peak near the HXR peak
time. The presence of hot plasma in the lower atmosphere is further confirmed
by RHESSI imaging spectroscopy analysis, which shows resolved sources at 11-13
MK associated with at least one ribbon. We found that collisional beam heating
can only marginally explain the necessary power to heat the 10 MK plasma at the
ribbons.Comment: 21 pages, 15 figure
Managerial Overconfidence and Corporate Policies
Miscalibration is a standard measure of overconfidence in both psychology and economics. Although it is often used in lab experiments, there is scarcity of evidence about its effects in practice. We test whether top corporate executives are miscalibrated, and whether their miscalibration impacts investment behavior. Over six years, we collect a unique panel of nearly 7,000 observations of probability distributions provided by top financial executives regarding the stock market. Financial executives are miscalibrated: realized market returns are within the executives' 80% confidence intervals only 38% of the time. We show that companies with overconfident CFOs use lower discount rates to value cash flows, and that they invest more, use more debt, are less likely to pay dividends, are more likely to repurchase shares, and they use proportionally more long-term, as opposed to short-term, debt. The pervasive effect of this miscalibration suggests that the effect of overconfidence should be explicitly modeled when analyzing corporate decision-making.
Error correction and diversity analysis of population mixtures determined by NGS
The impetus for this work was the need to analyse nucleotide diversity in a viral mix taken from honeybees. The paper has two findings. First, a method for correction of next generation sequencing error in the distribution of nucleotides at a site is developed. Second, a package of methods for assessment of nucleotide diversity is assembled. The error correction method is statistically based and works at the level of the nucleotide distribution rather than the level of individual nucleotides. The method relies on an error model and a sample of known viral genotypes that is used for model calibration. A compendium of existing and new diversity analysis tools is also presented, allowing hypotheses about diversity and mean diversity to be tested and associated confidence intervals to be calculated. The methods are illustrated using honeybee viral samples. Software in both Excel and Matlab and a guide are available at http://www2.warwick.ac.uk/fac/sci/systemsbiology/research/software/,the Warwick University Systems Biology Centre software download site.Publisher PDFPeer reviewe
Prosomal-width-to-weight relationships in American horseshoe crabs (Limulus polyphemus): examining conversion factors used to estimate landings
Horseshoe crabs (Limulus polyphemus) are valued by many
stakeholders, including the commercial fishing industry, biomedical companies, and environmental interest groups. We designed a study to test the accuracy of the conversion factors that were used by NOAA Fisheries and state agencies to estimate horseshoe crab landings before mandatory
reporting that began in 1998. Our results indicate that the NOAA Fisheries conversion factor consistently overestimates the weight of male horseshoe crabs, particularly those from New England populations. Because of the inaccuracy of this and other conversion factors, states are now mandated to report the number (not biomass) and sex of landed horseshoe
crabs. However, accurate estimates of biomass are still necessary for use in prediction models that are being developed to better manage the horseshoe crab fishery. We recommend that managers use the conversion factors presented in this study to convert current landing data from numbers to biomass of harvested horseshoe crabs
for future assessments
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