316 research outputs found
Inter-Seasonal Time Series Imagery Enhances Classification Accuracy of Grazing Resource and Land Degradation Maps in a Savanna Ecosystem
<jats:p>In savannas, mapping grazing resources and indicators of land degradation is important for assessing ecosystem conditions and informing grazing and land management decisions. We investigated the effects of classifiers and used time series imagery—images acquired within and across seasons—on the accuracy of plant species maps. The study site was a grazed savanna in southern Kenya. We used Sentinel-2 multi-spectral imagery due to its high spatial (10–20 m) and temporal (five days) resolution with support vector machine (SVM) and random forest (RF) classifiers. The species mapped were important for grazing livestock and wildlife (three grass species), indicators of land degradation (one tree genus and one invasive shrub), and a fig tree species. The results show that increasing the number of images, including dry season imagery, results in improved classification accuracy regardless of the classifier (average increase in overall accuracy (OA) = 0.1632). SVM consistently outperformed RF, and the most accurate model and was SVM with a radial kernel using imagery from both wet and dry seasons (OA = 0.8217). Maps showed that seasonal grazing areas provide functionally different grazing opportunities and have different vegetation characteristics that are critical to a landscape’s ability to support large populations of both livestock and wildlife. This study highlights the potential of multi-spectral satellite imagery for species-level mapping of savannas.</jats:p>
Effects of supplementation of limit-fed growing diets with either soybean meal or nonenzymatically browned soybean meal on steer performance
Seventy two individually fed Angus × Hereford
steers (642 lb) were used to evaluate the
effects of supplementing limit-fed, growing diets
with either soybean meal (SBM) or nonenzymatically
browned soybean meal (NSBM).
Eight steers were allotted to a control diet
composed of 39.1% high-moisture corn, 42%
cottonseed hulls, 10.4% ground corn, 5% cane
molasses 2.25% urea, and 1.5% vitamins and
minerals (dry basis). The remaining steers were
allotted to diets that derived 100, 80, 60, or
40% of their supplemental protein from SBM or
60, 45, 30, or 15% of their supplemental protein
from NSBN. The balance of supplemental
protein came from urea. All diets were formulated
to contain 13.0% crude protein (dry
basis). Steers were fed once daily for 80 days
at 2.25% of BW. Average daily gain and
efficiency did not differ (P>.05) between
sources (ADG=1.932 + .103 × (% CP from
SBM) + .097 × (% CP from NSBM);
gain:feed=.140 + .0058 × (% CP from SBM) +
.0051 × (% CP from NSBM)). The lack of
response to NBSBM supplementation above
that for SBM suggests that either degradable
intake protein was limiting in the basal diet or a
large proportion of the amino acids in the
NSBM were unavailable due to overprocessing
Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10
Infrared observations from the Spitzer Space Telescope archive are used to
study the dust component of the interstellar medium in the IC~10 irregular
galaxy. Dust distribution in the galaxy is compared to the distributions of
H and [SII] emission, neutral hydrogen and CO clouds, and ionizing
radiation sources. The distribution of polycyclic aromatic hydrocarbons (PAH)
in the galaxy is shown to be highly non-uniform with the mass fraction of these
particles in the total dust mass reaching 4%. PAHs tend to avoid bright HII
regions and correlate well with atomic and molecular gas. This pattern suggests
that PAHs form in the dense interstellar gas. We propose that the significant
decrease of the PAH abundance at low metallicity is observed not only globally
(at the level of entire galaxies), but also locally (at least, at the level of
individual HII regions). We compare the distribution of the PAH mass fraction
to the distribution of high-velocity features, that we have detected earlier in
wings of H and SII lines, over the entire available galaxy area. No
conclusive evidence for shock destruction of PAHs in the IC~10 galaxy could be
found.Comment: Accepted for publication in Astronomy Report
A New Approach to Searching for Dark Matter Signals in Fermi-LAT Gamma Rays
Several cosmic ray experiments have measured excesses in electrons and
positrons, relative to standard backgrounds, for energies from ~ 10 GeV - 1
TeV. These excesses could be due to new astrophysical sources, but an
explanation in which the electrons and positrons are dark matter annihilation
or decay products is also consistent. Fortunately, the Fermi-LAT diffuse gamma
ray measurements can further test these models, since the electrons and
positrons produce gamma rays in their interactions in the interstellar medium.
Although the dark matter gamma ray signal consistent with the local electron
and positron measurements should be quite large, as we review, there are
substantial uncertainties in the modeling of diffuse backgrounds and,
additionally, experimental uncertainties that make it difficult to claim a dark
matter discovery. In this paper, we introduce an alternative method for
understanding the diffuse gamma ray spectrum in which we take the intensity
ratio in each energy bin of two different regions of the sky, thereby canceling
common systematic uncertainties. For many spectra, this ratio fits well to a
power law with a single break in energy. The two measured exponent indices are
a robust discriminant between candidate models, and we demonstrate that dark
matter annihilation scenarios can predict index values that require "extreme"
parameters for background-only explanations.Comment: v1: 11 pages, 7 figures, 1 table, revtex4; v2: 13 pages, 8 figures, 1
table, revtex4, Figure 4 added, minor additions made to text, references
added, conclusions unchanged, published versio
A Region of Violent Star Formation in the Irr Galaxy IC 10: Structure and Kinematics of Ionized and Neutral Gas
We have used observations of the galaxy IC 10 at the 6-m telescope of the
Special Astrophysical Observatory with the SCORPIO focal reducer in the
Fabry-Perot interferometer mode and with the MPFS spectrograph to study the
structure and kinematics of ionized gas in the central region of current
intense star formation. Archive VLA 21-cm observations are used to analyze the
structure and kinematics of neutral gas in this region. High-velocity wings of
the H-alpha and [SII] emission lines were revealed in the inner cavity of the
nebula HL 111 and in other parts of the complex of violent star formation. We
have discovered local expanding neutral-gas shells around the nebulae HL 111
and HL 106.Comment: 22 pages, 10 figures; accepted in Astronomy Report
Gas Emission Spectrum in the Irr Galaxy IC 10
Spectroscopic long-slit observations of the dwarf Irr galaxy IC 10 were
conducted at the 6-m Special Astrophysical Observatory telescope with the
SCORPIO focal reducer. The ionized-gas emission spectra in the regions of
intense current star formation were obtained for a large number of regions in
IC 10. The relative abundances of oxygen, N+, and S+ in about twenty HII
regions and in the synchrotron superbubble were estimated. We found that the
galaxy-averaged oxygen abundance is 12 + log(O/H) = 8.17 +- 0.35 and the
metallicity is Z = 0.18 +- 0.14 Z_sun. Our abundances estimated from the strong
emission lines are found to be more reliable than those obtained by comparing
diagnostic diagrams with photoionization models.Comment: Abridged; accepted in Astronomy Letter
VERITAS: the Very Energetic Radiation Imaging Telescope Array System
The Very Energetic Radiation Imaging Telescope Array System (VERITAS)
represents an important step forward in the study of extreme astrophysical
processes in the universe. It combines the power of the atmospheric Cherenkov
imaging technique using a large optical reflector with the power of
stereoscopic observatories using arrays of separated telescopes looking at the
same shower. The seven identical telescopes in VERITAS, each of aperture 10 m,
will be deployed in a filled hexagonal pattern of side 80 m; each telescope
will have a camera consisting of 499 pixels with a field of view of 3.5 deg
VERITAS will substantially increase the catalog of very high energy (E >
100GeV) gamma-ray sources and greatly improve measurements of established
sources.Comment: 44 pages, 16 figure
Low-mass pre--main-sequence stars in the Magellanic Clouds
[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar
stars form in very large numbers. Most attractive places for catching low-mass
star formation in the act are young stellar clusters and associations, still
(half-)embedded in star-forming regions. The low-mass stars in such regions are
still in their pre--main-sequence (PMS) evolutionary phase. The peculiar nature
of these objects and the contamination of their samples by the evolved
populations of the Galactic disk impose demanding observational techniques for
the detection of complete numbers of PMS stars in the Milky Way. The Magellanic
Clouds, the companion galaxies to our own, demonstrate an exceptional star
formation activity. The low extinction and stellar field contamination in
star-forming regions of these galaxies imply a more efficient detection of
low-mass PMS stars than in the Milky Way, but their distance from us make the
application of special detection techniques unfeasible. Nonetheless, imaging
with the Hubble Space Telescope yield the discovery of solar and sub-solar PMS
stars in the Magellanic Clouds from photometry alone. Unprecedented numbers of
such objects are identified as the low-mass stellar content of their
star-forming regions, changing completely our picture of young stellar systems
outside the Milky Way, and extending the extragalactic stellar IMF below the
persisting threshold of a few solar masses. This review presents the recent
developments in the investigation of PMS stars in the Magellanic Clouds, with
special focus on the limitations by single-epoch photometry that can only be
circumvented by the detailed study of the observable behavior of these stars in
the color-magnitude diagram. The achieved characterization of the low-mass PMS
stars in the Magellanic Clouds allowed thus a more comprehensive understanding
of the star formation process in our neighboring galaxies.Comment: Review paper, 26 pages (in LaTeX style for Springer journals), 4
figures. Accepted for publication in Space Science Review
Molecular mechanisms linking high body mass index to breast cancer etiology in post-menopausal breast tumor and tumor-adjacent tissues
Purpose: In post-menopausal women, high body mass index (BMI) is an established breast cancer risk factor and is associated with worse breast cancer prognosis. We assessed the associations between BMI and gene expression of both breast tumor and adjacent tissue in estrogen receptor-positive (ER+) and estrogen receptor-negative (ER−) diseases to help elucidate the mechanisms linking obesity with breast cancer biology in 519 post-menopausal women from the Nurses’ Health Study (NHS) and NHSII. Methods: Differential gene expression was analyzed separately in ER+ and ER− disease both comparing overweight (BMI ≥ 25 to < 30) or obese (BMI ≥ 30) women to women with normal BMI (BMI< 25), and per 5 kg/m 2 increase in BMI. Analyses controlled for age and year of diagnosis, physical activity, alcohol consumption, and hormone therapy use. Gene set enrichment analyses were performed and validated among a subset of post-menopausal cases in The Cancer Genome Atlas (for tumor) and Polish Breast Cancer Study (for tumor-adjacent). Results: No gene was differentially expressed by BMI (FDR < 0.05). BMI was significantly associated with increased cellular proliferation pathways, particularly in ER+ tumors, and increased inflammation pathways in ER− tumor and ER− tumor-adjacent tissues (FDR < 0.05). High BMI was associated with upregulation of genes involved in epithelial-mesenchymal transition in ER+ tumor-adjacent tissues. Conclusions: This study provides insights into molecular mechanisms of BMI influencing post-menopausal breast cancer biology. Tumor and tumor-adjacent tissues provide independent information about potential mechanisms
- …