Institution
Universities Space Research Association
Nonprofit•Columbia, Maryland, United States•
About: Universities Space Research Association is a nonprofit organization based out in Columbia, Maryland, United States. It is known for research contribution in the topics: Gamma-ray burst & Galaxy. The organization has 1921 authors who have published 5412 publications receiving 255681 citations. The organization is also known as: USRA.
Topics: Gamma-ray burst, Galaxy, Pulsar, Neutron star, Aerosol
Papers published on a yearly basis
Papers
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TL;DR: The Dense Media Radiative Transfer (DMRT) model as discussed by the authors is a physically based numerical model designed to compute the thermal microwave emission of a given snowpack, and it has been used to simulate the thermal emission of the deep firn on ice sheets, shallow snowpacks overlying soil in Arctic and Alpine regions, and overlying ice on the large ice-sheet margins and glaciers.
Abstract: . DMRT-ML is a physically based numerical model designed to compute the thermal microwave emission of a given snowpack. Its main application is the simulation of brightness temperatures at frequencies in the range 1–200 GHz similar to those acquired routinely by space-based microwave radiometers. The model is based on the Dense Media Radiative Transfer (DMRT) theory for the computation of the snow scattering and extinction coefficients and on the Discrete Ordinate Method (DISORT) to numerically solve the radiative transfer equation. The snowpack is modeled as a stack of multiple horizontal snow layers and an optional underlying interface representing the soil or the bottom ice. The model handles both dry and wet snow conditions. Such a general design allows the model to account for a wide range of snow conditions. Hitherto, the model has been used to simulate the thermal emission of the deep firn on ice sheets, shallow snowpacks overlying soil in Arctic and Alpine regions, and overlying ice on the large ice-sheet margins and glaciers. DMRT-ML has thus been validated in three very different conditions: Antarctica, Barnes Ice Cap (Canada) and Canadian tundra. It has been recently used in conjunction with inverse methods to retrieve snow grain size from remote sensing data. The model is written in Fortran90 and available to the snow remote sensing community as an open-source software. A convenient user interface is provided in Python.
139 citations
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TL;DR: Children from a region at high risk for eBL were infected very early in life with EBV, resulting in higher viral loads throughout infancy, and residence in Kisumu and younger age at first EBV infection were significant predictors for having a higher EBV viral load throughout the period of observation.
Abstract: Background. Infection with Epstein–Barr virus (EBV) early in life and repeated malaria exposure have been proposed as risk factors for endemic Burkitt lymphoma (eBL). Methods. Infants were enrolled from 2 rural sites in Kenya: the Kisumu District, where malaria transmission is holoendemic and risk for eBL is high, and the Nandi District, where malaria transmission is limited and the risk for eBL is low. Blood samples were taken from infants through 2 years of age to measure EBV viral load, EBV antibodies, and malaria parasitemia. Results. We observed a significantly younger age at time of primary EBV infection in children from Kisumu compared with children from Nandi (mean age, 7.28 months [60.33 SEM] in Kisumu vs 8.39 months [60.26 SEM] in Nandi), with 35.3% of children in Kisumu infected before 6 months of age. To analyze how different predictors affected EBV viral load over time, we performed multilevel mixed modeling. This modeling revealed that residence in Kisumu and younger age at first EBV infection were significant predictors for having a higher EBV viral load throughout the period of observation. Conclusions. Children from a region at high risk for eBL were infected very early in life with EBV, resulting in higher viral loads throughout infancy.
139 citations
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TL;DR: In this article, the washout effect of summertime rain on surface air pollutants (O3, CO, NO2, SO2, and PM10) has been investigated over South Korea during 2002-2012 using routinely available air-monitored and meteorological data.
139 citations
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TL;DR: The early history of the terrestrial planets was punctuated by a period of heavy bombardment Frequent large impacts condensed in a short, 002-05-Ga-long time period resulted in heavily cratered planetary surfaces In volatile-bearing planetary crusts, each large impacts created a volume of hot rock and melt that drove vast subsurface hydrothermal systems as discussed by the authors.
Abstract: The early history of the terrestrial planets was punctuated by a period of heavy bombardment Frequent large impacts condensed in a short, 002–05-Ga-long time period resulted in heavily cratered planetary surfaces In volatile-bearing planetary crusts, each of these large impacts created a volume of hot rock and melt that drove vast subsurface hydrothermal systems In Mars' basaltic crust, these systems produced a variety of alteration phases, the nature of which we explored with thermochemical modeling Using the computer code CHILLER, we found a variety of oxides, hydroxides, and hydrous and water-free silicates resulting from the hydrothermal alteration The main hydrous silicates are serpentine, chlorite, nontronite, and other clay minerals Some of the resulting assemblages contain up to 15 wt% bound water Our results constrain the temperature and water rock ratio at the time of alteration and compare well to the mineral assemblages found on Mars by OMEGA (Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite) and CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) and, therefore, provide an interpretative framework for analyzing Martian mineralogy from orbital data Our results also provide a geological template needed to select landing locations for future missions that search for water and energy sources associated with potential habitats on early Mars
138 citations
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University of Copenhagen1, European Southern Observatory2, National Fund for Scientific Research3, Subaru4, University of Leicester5, Liverpool John Moores University6, INAF7, Spanish National Research Council8, Tokyo Institute of Technology9, University of Hertfordshire10, Universities Space Research Association11, Goddard Space Flight Center12, University of Amsterdam13
TL;DR: In this paper, the optical afterglow spectrum of GRB 050401 (at z = 2.8992 ± 0.0004) shows the presence of a damped Lyα absorber (DLA), with log N = 22.6 ± 1.3.
Abstract: The optical afterglow spectrum of GRB 050401 (at z = 2.8992 ± 0.0004) shows the presence of a damped Lyα absorber (DLA), with log N = 22.6 ± 0.3. This is the highest column density ever observed in a DLA and is about 5 times larger than the strongest DLA detected so far in any QSO spectrum. From the optical spectrum, we also find a very large Zn column density, implying an abundance of [Zn/H] = -1.0 ± 0.4. These large columns are supported by the early X-ray spectrum from Swift XRT, which shows a column density (in excess of Galactic) of log NH = 22.21 assuming solar abundances (at z = 2.9). The comparison of this X-ray column density, which is dominated by absorption due to α-chain elements, and the H I column density derived from the Lyα absorption line allows us to derive a metallicity for the absorbing matter of [α/H] = -0.4 ± 0.3. The optical spectrum is reddened and can be well reproduced with a power law with SMC extinction, where AV = 0.62 ± 0.06. But the total optical extinction can also be constrained independent of the shape of the extinction curve: from the optical to X-ray spectral energy distribution, we find 0.5 AV 4.5. However, even this upper limit, independent of the shape of the extinction curve, is still well below the dust column that is inferred from the X-ray column density, i.e., AV = 9.1. This discrepancy might be explained by a small dust content with high metallicity (low dust-to-metals ratio). Gray extinction cannot explain the discrepancy, since we are comparing the metallicity to a measurement of the total extinction (without reference to the reddening). Little dust with high metallicity may be produced by sublimation of dust grains or may naturally exist in systems younger than a few hundred megayears.
138 citations
Authors
Showing all 1930 results
Name | H-index | Papers | Citations |
---|---|---|---|
Alexander S. Szalay | 166 | 936 | 145745 |
Naomi J. Halas | 140 | 435 | 82040 |
Krzysztof M. Gorski | 132 | 380 | 105912 |
William T. Reach | 131 | 535 | 90496 |
David C. Koo | 119 | 568 | 49040 |
Ranga B. Myneni | 114 | 393 | 53054 |
Chryssa Kouveliotou | 109 | 671 | 47748 |
Darren L. DePoy | 99 | 554 | 38932 |
Mario Hamuy | 95 | 389 | 30391 |
A. A. Moiseev | 95 | 263 | 36948 |
Holland C. Ford | 93 | 347 | 29661 |
Alistair R. Walker | 93 | 580 | 35142 |
Jonathan F. Ormes | 89 | 306 | 27022 |
Andreas Quirrenbach | 89 | 678 | 33504 |
Tyson Littenberg | 89 | 297 | 61373 |