87 research outputs found
A combined observational and modeling approach to study modern dust transport from the Patagonia desert to East Antarctica
The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. <br><br> This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS, POLDER, OMI), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). <br><br> Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (~54° S) and from the shores of the Colihue Huapi lake in Central Patagonia (~46° S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6–7 and 9–10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant deposition over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and ~800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the presence of dust at ~1500 km SW of South Africa five days after, the limited capabilities of existing satellite platforms to differentiate between aerosol types do not permit a definitive conclusion. In addition, the model simulations show dust lifting to the free troposphere as it travels south but it could not be confirmed by the satellite observations due to cloudiness. <br><br> This work demonstrates that complementary information from existing transport models, satellite and surface data can yield a consistent picture of the dust transport from the Patagonia desert to Antarctica. It also illustrates the limitation of using any of these approaches individually to characterize the transport of dust in a heavily cloudy area
Effects of growth hormone on exercise capacity and cardiopulmonary performance in patients with chronic heart failure.
BACKGROUND: Because GH exerted beneficial effects in various experimental models of heart failure, we investigated the effects of GH on physical exercise capacity and cardiopulmonary performance in patients with dilated cardiomyopathy and chronic heart failure (CHF).
METHODS: Twenty-two patients with CHF (New York Heart Association functional class II-III) underwent spirometry and a symptom-limited, cardiopulmonary exercise testing before and after 3 months of GH (n = 11; seven males; seven idiopathic; 57 +/- 11 yr; 4 IU sc every other day) or placebo (n = 11; eight males; six idiopathic; 54 +/- 10 yr) administration, in a randomized, double-blind trial. Background CHF therapy remained unchanged.
RESULTS: GH, but not placebo, increased IGF-I serum concentration (from 144 +/- 35 to 293 +/- 58 ng/ml; P < 0.005) and improved New York Heart Association functional class (from 2.4 +/- 0.5 to 1.8 +/- 0.4; P < 0.005), exercise duration (from 831 +/- 273 to 925 +/- 266 sec; P < 0.005), peak power output (from 245 +/- 127 to 280 +/- 132 W; P < 0.05), peak minute ventilation (from 52.5 +/- 16.1 to 61.3 +/- 17.3 liters/min; P < 0.05), peak oxygen consumption (from 19.8 +/- 5.6 to 25.1 +/- 5.6 ml/kg.min; P < 0.005), and anaerobic threshold (from 14.9 +/- 4.8 to 20.0 +/- 4.5 ml/kg.min; P < 0.005) without affecting lung function parameters. Furthermore, the slope of the relationship between minute ventilation and pulmonary carbon dioxide production (ventilatory efficiency) decreased from 34.7 +/- 5.1 to 31.7 +/- 5.3 (P < 0.005), whereas the slope of the relation between percent predicted heart rate reserve used and percent observed metabolic reserve used (chronotropic index) rose from 0.57 +/- 0.20 to 0.69 +/- 0.18 (P < 0.005).
CONCLUSION: Given the predictive value of physical exercise capacity and cardiopulmonary performance in CHF progression, these data provide additional insights into the mechanisms by which GH may potentially benefit CHF patients
FORECAST: a flexible software to forward model cosmological hydrodynamical simulations mimicking real observations
We present FORECAST, a new flexible and adaptable software package that
performs forward modeling of the output of any cosmological hydrodynamical
simulations to create a wide range of realistic synthetic astronomical images.
With customizable options for filters, field of view size and survey
parameters, it allows users to tailor the synthetic images to their specific
requirements. FORECAST constructs light-cone exploiting the output snapshots of
a simulation and computes the observed flux of each simulated stellar element,
modeled as a Single Stellar Population, in any chosen set of pass-band filters,
including k-correction, IGM absorption and dust attenuation. As a first
application, we emulated the GOODS-South field as observed for the CANDELS
survey exploiting the IllustrisTNG simulation. We produce images of 200 sq.
arcmin., in 13 bands (eight Hubble Space Telescope optical and near-infrared
bands from ACS B435 to WFC3 H160, the VLT HAWK-I Ks band, and the four IRAC
filters from Spitzer), with depths consistent with the real data. We analysed
the images with the same processing pipeline adopted for real data in CANDELS
and ASTRODEEP publications, and we compared the results against both the input
data used to create the images, and real data, generally finding good agreement
with both, with some interesting exceptions which we discuss. As part of this
work, we release the FORECAST code and two datasets: the CANDELS dataset
analyzed in this study, and 10 JWST CEERS survey-like images (8 NIRCam and 2
MIRI) in a field of view of 200 sq. arcmin. between z=0-20. FORECAST is a
flexible tool: it creates images that can then be processed and analysed using
standard photometric algorithms, allowing for a consistent comparison among
observations and models, and for a direct estimation of the biases introduced
by such techniques.Comment: 21 pages, 15 figures, 6 tables, submitted to A&
Spitzer UltRa Faint SUrvey Program (SURFS UP). II. IRAC-Detected Lyman-Break Galaxies at 6 < z < 10 Behind Strong-Lensing Clusters
We study the stellar population properties of the IRAC-detected galaxy candidates from the Spitzer UltRa Faint SUrvey Program
(SURFS UP). Using the Lyman Break selection technique, we find a total of 16
new galaxy candidates at with in at
least one of the IRAC m and m bands. According to the best mass
models available for the surveyed galaxy clusters, these IRAC-detected galaxy
candidates are magnified by factors of --. We find that the
IRAC-detected sample is likely not a homogeneous
galaxy population: some are relatively massive (stellar mass as high as ) and evolved (age Myr) galaxies, while
others are less massive () and very
young ( Myr) galaxies with strong nebular emission lines that boost
their rest-frame optical fluxes. We identify two Ly emitters in our
sample from the Keck DEIMOS spectra, one at (in
RXJ1347) and one at (in MACS0454). We show that IRAC
color, when combined with photometric redshift, can be used to
identify galaxies likely with strong nebular emission lines within certain
redshift windows.Comment: ApJ in pres
ALMA Observation of a Galaxy Candidate Discovered with JWST
We report the ALMA observation of a galaxy candidate (GHZ1)
discovered from the GLASS-JWST Early Release Science Program. Our ALMA program
aims to detect the [OIII] emission line at the rest-frame 3393.0062 GHz
(m) and far-IR continuum emission with the spectral window setup
seamlessly covering a 26.125 GHz frequency range (). A total of
7 hours of on-source integration was employed, using four frequency settings to
cover the full range (1.7 hours per setting), with angular resolution.
No line or continuum is clearly detected, with a 5 upper limit of the
line emission of 0.93 mJy beam at 25 km s channel and of
the continuum emission of 30Jy beam. We report marginal spectral
(at 225 km s resolution) and continuum features ( and
peak signal-to-noise ratio, respectively), within from the
JWST position of GHZ1. This spectral feature implies and needs to be
verified with further observations. Assuming that the best photometric redshift
estimate () is correct, the broadband galaxy spectral
energy distribution model for the upper limit of the continuum flux
from GHZ1 suggests that GHZ1 has a small amount of dust () with high temperature (K). The upper limit
of the [OIII] line luminosity and the inferred star formation rate
of GHZ1 is consistent with the properties of the low metallicity dwarf
galaxies. We also report serendipitous clear detections of six continuum
sources at the locations of the JWST galaxy counterparts in the field.Comment: Accepted to ApJ after revising the figures and the analysi
"EDML1": a chronology for the EPICA deep ice core from Dronning Maud Land, Antarctica, over the last 150 000 years.
A chronology called EDML1 has been developed for the EPICA ice core from Dronning Maud Land (EDML). EDML1 is closely interlinked with EDC3, the new chronology for the EPICA ice core from Dome-C (EDC) through a stratigraphic match between EDML and EDC that consists of 322 volcanic match points over the last 128 ka. The EDC3 chronology comprises a glaciological model at EDC, which is constrained and later selectively tuned using primary dating information from EDC as well as from EDML, the latter being transferred using the tight stratigraphic link between the two cores. Finally, EDML1 was built by exporting EDC3 to EDML. For ages younger than 41 ka BP the new synchronized time scale EDML1/EDC3 is based on dated volcanic events and on a match to the Greenlandic ice core chronology GICC05 via <sup>10</sup>Be and methane. The internal consistency between EDML1 and EDC3 is estimated to be typically ~6 years and always less than 450 years over the last 128 ka (always less than 130 years over the last 60 ka), which reflects an unprecedented synchrony of time scales. EDML1 ends at 150 ka BP (2417 m depth) because the match between EDML and EDC becomes ambiguous further down. This hints at a complex ice flow history for the deepest 350 m of the EDML ice core
Early results from GLASS-JWST XVI: Discovering a bluer z~4-7 Universe through UV slopes
We use the GLASS-JWST Early Release Science NIRCam parallel observations to
provide a first view of the UV continuum properties of NIRCam/F444W selected
galaxies at 4<z<7. By combining multiwavelength NIRCam observations, we
constrain the UV continuum slope for a sample of 401 galaxies with stringent
quality controls. We find that >99% of the galaxies are blue star-forming
galaxies with very low levels of dust (Avbeta~0.01+/-0.33). We find no
statistically significant correlation for UV slope with redshift or UV
magnitude. However, we find that in general galaxies at higher redshifts and
fainter UV magnitudes have steeper UV slopes. We find a statistically
significant correlation for UV slope with stellar mass, with galaxies with
higher stellar mass showing shallower UV slopes. Individual fits to some of our
galaxies reach the bluest UV slopes of beta~-3.1 allowed by stellar population
models used in this analysis. Therefore, it is likely that stellar population
models with higher amount of Lyman continuum leakage, AGN effects, and/or
Population III contributions are required to accurately reproduce the rest-UV
and optical properties of some of our bluest galaxies. This dust-free early
view confirms that our current cosmological understanding of gradual mass +
dust buildup of galaxies with cosmic time is largely accurate to describe the
~0.7-1.5 Gyr age window of the Universe. The abundance of a large population of
UV faint dust-poor systems may point to a dominance of low-mass galaxies at z>6
playing a vital role in cosmic reionization.Comment: Accepted in ApJ
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