3,126 research outputs found
Arkansas Cotton Variety Test 2002
The primary aim of the Arkansas Cotton Variety Test is to provide unbiased data regarding the agronomic performance of cotton varieties and advanced breeding lines in the major cotton-growing areas of Arkansas. This information helps seed dealers establish marketing strategies and assists producers in choosing varieties to plant. In this way, the annual test facilitates the inclusion of new, improved genetic material into Arkansas cotton production. Variety adaptation is determined by evaluation of the varieties and lines at four University of Arkansas research stations located near Keiser, Clarkedale, Marianna, and Rohwer. Tests are duplicated in irrigated and non-irrigated culture at the Keiser and Marianna locations. In 2002, 37 entries were evaluated in the main test and 25 were evaluated in the first-year test. This report also includes the Mississippi County Cotton Variety Test (a large-plot, on-farm evaluation of 12 Round-up Ready varieties) and 12 other on-farm cotton variety tests conducted by the University of Arkansas Cooperative Extension Service
Stress-Energy Tensor for the Massless Spin 1/2 Field in Static Black Hole Spacetimes
The stress-energy tensor for the massless spin 1/2 field is numerically
computed outside and on the event horizons of both charged and uncharged static
non-rotating black holes, corresponding to the Schwarzschild,
Reissner-Nordstrom and extreme Reissner-Nordstr\"om solutions of Einstein's
equations. The field is assumed to be in a thermal state at the black hole
temperature. Comparison is made between the numerical results and previous
analytic approximations for the stress-energy tensor in these spacetimes. For
the Schwarzschild (charge zero) solution, it is shown that the stress-energy
differs even in sign from the analytic approximation. For the
Reissner-Nordstrom and extreme Reissner-Nordstrom solutions, divergences
predicted by the analytic approximations are shown not to exist.Comment: 5 pages, 4 figures, additional discussio
Counter-Regulation of Interleukin-1α (IL-1α) and IL-1 Receptor Antagonist in Murine Keratinocytes
Interleukin-1α (IL-1α) is a potent proinflammatory cytokine constitutively expressed by keratinocytes, which also synthesize a specific inhibitor of IL-1 activity, intracellular IL-1 receptor antagonist (IL-1ra). Although homeostatic regulation of the IL-1 system in keratinocytes has long been suspected, there is currently little evidence for this. To explore this issue, the PAM212 murine keratinocyte cell line was exposed to increasing concentrations of either IL-1α or IL-1ra and the opposing ligand was assessed by ELISA. Release of IL-1ra was induced following stimulation by murine IL-1α in a concentration-dependent manner and, conversely, IL-1ra stimulation increased IL-1α release. To determine whether a similar homeostatic circuit operates in vivo, epidermis from transgenic mice in which overexpression of IL-1α or IL-1ra was targeted to keratinocytes was analyzed. Epidermal sheets derived from IL-1α transgenic mice released eight times more IL-1ra than those from wild-type mice following ex vivo culture and similarly, IL-1α release was increased 3–4-fold in epidermal sheets derived from IL-1ra transgenic epidermis, Use of specific neutralizing antibodies against type I and type II IL-1 receptors indicated that the counter-regulation mechanism is mediated extracellularly through the type I IL-1 receptor alone. Taken together, these observations provide the first demonstration of mutual counter-regulation of IL-1 receptor ligands in keratinocytes
The metallicity of void dwarf galaxies
The current Lambda CDM cosmological model predicts that galaxy evolution
proceeds more slowly in lower density environments, suggesting that voids are a
prime location to search for relatively pristine galaxies that are
representative of the building blocks of early massive galaxies. To test the
assumption that void galaxies are more pristine, we compare the evolutionary
properties of a sample of dwarf galaxies selected specifically to lie in voids
with a sample of similar isolated dwarf galaxies in average density
environments. We measure gas-phase oxygen abundances and gas fractions for
eight dwarf galaxies (M_r > -16.2), carefully selected to reside within the
lowest density environments of seven voids, and apply the same calibrations to
existing samples of isolated dwarf galaxies. We find no significant difference
between these void dwarf galaxies and the isolated dwarf galaxies, suggesting
that dwarf galaxy chemical evolution proceeds independent of the large-scale
environment. While this sample is too small to draw strong conclusions, it
suggests that external gas accretion is playing a limited role in the chemical
evolution of these systems, and that this evolution is instead dominated mainly
by the internal secular processes that are linking the simultaneous growth and
enrichment of these galaxies.Comment: 6 pages, 3 figures, accepted for publication in ApJ Letter
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Making Change: Diffusion of Technological, Relational, and Cultural Innovation in the Newsroom
Diffusion of innovations theory typically has been applied to the spread of a particular technology or practice rather than the interplay of a cluster of innovations. This case study of a news company undergoing significant change seeks to offer a deeper understanding of multifaceted industry upheaval by considering the diffusion of three interdependent yet distinct changes. Findings suggest technological change faces the fewest hurdles, as journalists recognize the need to adapt their practices to newer capabilities. Changes to audience relationships face greater resistance, while responses to changes to the professional culture of journalism remain the most tepid
Spatially Resolved Spitzer-IRS Spectroscopy of the Central Region of M82
We present high spatial resolution (~ 35 parsec) 5-38 um spectra of the
central region of M82, taken with the Spitzer Infrared Spectrograph. From these
spectra we determined the fluxes and equivalent widths of key diagnostic
features, such as the [NeII]12.8um, [NeIII]15.5um, and H_2 S(1)17.03um lines,
and the broad mid-IR polycyclic aromatic hydrocarbon (PAH) emission features in
six representative regions and analysed the spatial distribution of these lines
and their ratios across the central region. We find a good correlation of the
dust extinction with the CO 1-0 emission. The PAH emission follows closely the
ionization structure along the galactic disk. The observed variations of the
diagnostic PAH ratios across M82 can be explained by extinction effects, within
systematic uncertainties. The 16-18um PAH complex is very prominent, and its
equivalent width is enhanced outwards from the galactic plane. We interpret
this as a consequence of the variation of the UV radiation field. The EWs of
the 11.3um PAH feature and the H_2 S(1) line correlate closely, and we conclude
that shocks in the outflow regions have no measurable influence on the H_2
emission. The [NeIII]/[NeII] ratio is on average low at ~0.18, and shows little
variations across the plane, indicating that the dominant stellar population is
evolved (5 - 6 Myr) and well distributed. There is a slight increase of the
ratio with distance from the galactic plane of M82 which we attribute to a
decrease in gas density. Our observations indicate that the star formation rate
has decreased significantly in the last 5 Myr. The quantities of dust and
molecular gas in the central area of the galaxy argue against starvation and
for negative feedback processes, observable through the strong extra-planar
outflows.Comment: 15 pages, 12 figures, 3 tables, ApJ, emulateap
A Detailed Study of the Radio--FIR Correlation in NGC6946 with Herschel-PACS/SPIRE from KINGFISH
We derive the distribution of the synchrotron spectral index across NGC6946
and investigate the correlation between the radio continuum (synchrotron) and
far-infrared (FIR) emission using the KINGFISH Herschel PACS and SPIRE data.
The radio--FIR correlation is studied as a function of star formation rate,
magnetic field strength, radiation field strength, and the total gas surface
brightness. The synchrotron emission follows both star-forming regions and the
so-called magnetic arms present in the inter-arm regions. The synchrotron
spectral index is steepest along the magnetic arms (), while
it is flat in places of giant H{\sc ii} regions and in the center of the galaxy
(). The map of provides an observational
evidence for aging and energy loss of cosmic ray electrons propagating in the
disk of the galaxy. Variations in the synchrotron--FIR correlation across the
galaxy are shown to be a function of both star formation and magnetic fields.
We find that the synchrotron emission correlates better with cold rather than
with warm dust emission, when the interstellar radiation field is the main
heating source of dust. The synchrotron--FIR correlation suggests a coupling
between the magnetic field and the gas density. NGC6946 shows a power-law
behavior between the total (turbulent) magnetic field strength B and the star
formation rate surface density with an index of
0.14\,(0.16)0.01. This indicates an efficient production of the turbulent
magnetic field with the increasing gas turbulence expected in actively star
forming regions. The scale-by-scale analysis of the synchrotron--FIR
correlation indicates that the ISM affects the propagation of old/diffused
cosmic ray electrons, resulting in a diffusion coefficient of \,cm\,s for 2.2\,GeV CREs.Comment: 23 pages, 13 figures, accepted for publication in Astronomy &
Astrophysics Journa
The dust energy balance in the edge-on spiral galaxy NGC 4565
We combine new dust continuum observations of the edge-on spiral galaxy NGC
4565 in all Herschel/SPIRE (250, 350, 500 micron) wavebands, obtained as part
of the Herschel Reference Survey, and a large set of ancillary data (Spitzer,
SDSS, GALEX) to analyze its dust energy balance. We fit a radiative transfer
model for the stars and dust to the optical maps with the fitting algorithm
FitSKIRT. To account for the observed UV and mid-infrared emission, this
initial model was supplemented with both obscured and unobscured star-forming
regions. Even though these star-forming complexes provide an additional heating
source for the dust, the far-infrared/submillimeter emission long wards of 100
micron is underestimated by a factor of 3-4. This inconsistency in the dust
energy budget of NGC 4565 suggests that a sizable fraction (two-thirds) of the
total dust reservoir (Mdust ~ 2.9e+8 Msun) consists of a clumpy distribution
with no associated young stellar sources. The distribution of those dense dust
clouds would be in such a way that they remain unresolved in current
far-infrared/submillimeter observations and hardly comtribute to the
attenuation at optical wavelengths. More than two-thirds of the dust heating in
NGC 4565 is powered by the old stellar population, with localized embedded
sources supplying the remaining dust heating in NGC 4565. The results from this
detailed dust energy balance study in NGC 4565 is consistent with that of
similar analyses of other edge-on spirals.Comment: 16 pages, 7 figures, accepted for publication in MNRA
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