1,066 research outputs found
A Farm-Level Evaluation of Conditions Under Which Farmers Will Supply Biomass Feedstocks for Energy Production
This study evaluated the risk management potential of including biomass crops as a diversification strategy for a grain farm in northwest Tennessee. Results indicate that adding biomass crops to the farm enterprise mix could improve mean net revenues and reduced net revenue variability.Resource /Energy Economics and Policy,
ECONOMIC IMPACTS RESULTING FROM CO-FIRING BIOMASS FEEDSTOCKS IN SOUTHEASTERN UNITED STATES COAL-FIRED PLANTS
Economic impacts of using biomass in Southeast United States coal-fired plants are estimated using a county-level biomass database; ORCED, a dynamic electricity distribution model that estimates feedstock value; ORIBAS, a GIS model that estimates feedstock transportation costs; and IMPLAN, an input-output model that determines the impacts of co-firing on economic activity.Resource /Energy Economics and Policy,
Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies
Superluminous supernovae (SLSNe) are very bright explosions that were only
discovered recently and that show a preference for occurring in faint dwarf
galaxies. Understanding why stellar evolution yields different types of stellar
explosions in these environments is fundamental in order to both uncover the
elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In
this paper, we present the first results of our project to study SUperluminous
Supernova Host galaxIES, focusing on the sample for which we have obtained
spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen-poor) often (~50% in
our sample) occur in a class of galaxies that is known as Extreme Emission Line
Galaxies (EELGs). The probability of this happening by chance is negligible and
we therefore conclude that the extreme environmental conditions and the SLSN
phenomenon are related. In contrast, SLSNe-II (hydrogen-rich) occur in more
massive, more metal-rich galaxies with softer radiation fields. Therefore, if
SLSNe-II constitute a uniform class, their progenitor systems are likely
different from those of H-poor SLSNe. Gamma-ray bursts (GRBs) are, on average,
not found in as extreme environments as H-poor SLSNe. We propose that H-poor
SLSNe result from the very first stars exploding in a starburst, even earlier
than GRBs. This might indicate a bottom-light initial mass function in these
systems. SLSNe present a novel method of selecting candidate EELGs independent
of their luminosity.Comment: Published version, matches proofs. Accepted 2015 February 13. 23
pages, 8 figures, 4 tables. Minor changes with respect to previous versio
Microscopic Observation Drug Susceptibility Assay for Rapid Diagnosis of Lymph Node Tuberculosis and Detection of Drug Resistance.
In this study, 132 patients with lymphadenopathy were investigated. Fifty-two (39.4%) were diagnosed with tuberculosis (TB). The microscopic observation drug susceptibility (MODS) assay provided rapid (13 days), accurate diagnosis (sensitivity, 65.4%) and reliable drug susceptibility testing (DST). Despite its lower sensitivity than that of other methods, its faster results and simultaneous DST are advantageous in resource-poor settings, supporting the incorporation of MODS into diagnostic algorithms for extrapulmonary TB
The Magnetic Topology of Coronal Mass Ejection sources
In an attempt to test current initiation models of coronal mass ejections
(CMEs), with an emphasis on the magnetic breakout model, we inspect the
magnetic topology of the sources of 26 CME events in the context of their
chromospheric and coronal response in an interval of approximately nine hours
around the eruption onset. First, we perform current-free (potential)
extrapolations of photospheric magnetograms to retrieve the key topological
ingredients, such as coronal magnetic null points. Then we compare the
reconnection signatures observed in the high cadence and high spatial
resolution of the Transition Region And Coronal Explorer (TRACE) images with
the location of the relevant topological features. The comparison reveals that
only seven events can be interpreted in terms of the breakout model, which
requires a multi-polar topology with pre-eruption reconnection at a coronal
null. We find, however, that a larger number of events (twelve) can not be
interpreted in those terms. No magnetic null is found in six of them. Seven
other cases remain difficult to interpret. We also show that there are no
systematic differences between the CME speed and flare energies of events under
different interpretations.Comment: Accepted for publication in Ap
Phase behavior and material properties of hollow nanoparticles
Effective pair potentials for hollow nanoparticles like the ones made from
carbon (fullerenes) or metal dichalcogenides (inorganic fullerenes) consist of
a hard core repulsion and a deep, but short-ranged, van der Waals attraction.
We investigate them for single- and multi-walled nanoparticles and show that in
both cases, in the limit of large radii the interaction range scales inversely
with the radius, , while the well depth scales linearly with . We predict
the values of the radius and the wall thickness at which the gas-liquid
coexistence disappears from the phase diagram. We also discuss unusual material
properties of the solid, which include a large heat of sublimation and a small
surface energy.Comment: Revtex, 13 pages with 8 Postscript files included, submitted to Phys.
Rev.
Variable Ly alpha sheds light on the environment surrounding GRB 090426
Long duration gamma-ray bursts are commonly associated with the deaths of
massive stars. Spectroscopic studies using the afterglow as a light source
provide a unique opportunity to unveil the medium surrounding it, probing the
densest region of their galaxies. This material is usually in a low ionisation
state and at large distances from the burst site, hence representing the normal
interstellar medium in the galaxy. Here we present the case of GRB 090426 at
z=2.609, whose optical spectrum indicates an almost fully ionised medium
together with a low column density of neutral hydrogen. For the first time, we
also observe variations in the Ly alpha absorption line. Photoionisation
modeling shows that we are probing material from the vicinity of the burst (~80
pc). The host galaxy is a complex of two luminous interacting galaxies, which
might suggest that this burst could have occurred in an isolated star-forming
region outside its host galaxy created in the interaction of the two galaxies.Comment: 11 pages, 9 figures, submitted to MNRA
Emission heights of coronal bright points on Fe XII radiance map
We study the emission heights of the coronal bright points (BPs) above the
photosphere in the bipolar magnetic loops that are apparently associated with
them. As BPs are seen in projection against the disk their true emission
heights are unknown. The correlation of the BP locations on the Fe XII radiance
map from EIT with the magnetic field features (in particular neutral lines) was
investigated in detail. The coronal magnetic field was determined by an
extrapolation of the photospheric field to different altitudes above the disk.
It was found that most BPs sit on or near a photospheric neutral line, but that
the emission occurs at a height of about 5 Mm. Some BPs, while being seen in
projection, still seem to coincide with neutral lines, although their emission
takes place at heights of more than 10 Mm. Such coincidences almost disappear
for emissions above 20 Mm. We also projected the upper segments of the 3-D
magnetic field lines above different heights, respectively, on to the x-y
plane. The shape of each BP was compared with the respective field-line segment
nearby. This comparison suggests that most coronal BPs are actually located on
the top of their associated magnetic loops. Finally, we calculated for each
selected BP region the correlation coefficient between the Fe XII intensity
enhancement and the horizontal component of the extrapolated magnetic field
vector at the same x-y position in planes of different heights, respectively.
We found that for almost all the BP regions we studied the correlation
coefficient, with increasing height, increases to a maximal value and then
decreases again. The height corresponding to this maximum was defined as the
correlation height, which for most bright points was found to range below 20
Mm.Comment: 7 pages, 4 figures, 1 tabl
Electronic interactions in fullerene spheres
The electron-phonon and Coulomb interactions inC, and larger fullerene
spheres are analyzed. The coupling between electrons and intramolecular
vibrations give corrections meV to the electronic energies for
C, and scales as in larger molecules. The energies associated
with electrostatic interactions are of order eV, in C and
scale as . Charged fullerenes show enhanced electron-phonon coupling,
meV, which scales as . Finally, it is argued that non only
C, but also C are highly polarizable molecules. The
polarizabilities scale as and , respectively. The role of this large
polarizability in mediating intermolecular interactions is also discussed.Comment: 12 pages. No figure
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