Institution
University of Maryland, Baltimore County
Education•Baltimore, Maryland, United States•
About: University of Maryland, Baltimore County is a education organization based out in Baltimore, Maryland, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 8749 authors who have published 20843 publications receiving 795706 citations. The organization is also known as: UMBC.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this paper, the first 9 months of data of the Swift BAT survey of AGN in the 14-195 keV band were analyzed and a power law was fit to the logN - log S distribution, and the slope was found to be 1.42+/-0.26.
Abstract: We present the results1 of the analysis of the first 9 months of data of the Swift BAT survey of AGN in the 14-195 keV band. Using archival X-ray data or follow-up Swift XRT observations, we have identified 129 (103 AGN) of 130 objects detected at [b] > 15deg and with significance > 4.8-delta. One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects. We fit a power law to the logN - log S distribution, and find the slope to be 1.42+/-0.14. Characterizing the differential luminosity function data as a broken power law, we find a break luminosity logL*(ergs/s)= 43.85+/-0.26. We obtain a mean photon index 1.98 in the 14-195 keV band, with an rms spread of 0.27. Integration of our luminosity function gives a local volume density of AGN above 10(exp 41) erg/s of 2.4x10(exp -3) Mpc(sup -3), which is about 10% of the total luminous local galaxy density above M* = -19.75. We have obtained X-ray spectra from the literature and from Swift XRT follow-up observations. These show that the distribution of log nH is essentially flat from nH = 10(exp 20)/sq cm to 10(exp 24)/sq cm, with 50% of the objects having column densities of less than 10(exp 22)/sq cm. BAT Seyfert galaxies have a median redshift of 0.03, a maximum log luminosity of 45.1, and approximately half have log nH > 22.
334 citations
••
Oak Ridge National Laboratory1, Goddard Space Flight Center2, Massachusetts Institute of Technology3, University of Maryland, College Park4, École Centrale Paris5, Versailles Saint-Quentin-en-Yvelines University6, University of Maryland, Baltimore County7, University of Michigan8, University of Paris9, Ames Research Center10, Cornell University11, Spanish National Research Council12, California Institute of Technology13, Utrecht University14, Rensselaer Polytechnic Institute15, Universities Space Research Association16, The Catholic University of America17, Luleå University of Technology18, National Autonomous University of Mexico19, Carnegie Institution for Science20, University of California, Davis21
TL;DR: Chlorinated hydrocarbons identified in the Sheepbed mudstone by SAM are the reaction products of Martian chlorine and organic carbon derived from Martian sources or exogenous sources such as meteorites, comets, or interplanetary dust particles.
Abstract: The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150–300 parts per billion by weight (ppbw)) and C2 to C4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles.
334 citations
••
TL;DR: In this paper, the authors address the recent trajectory of local e-government in the United States and compare it with the predictions of early eGovernment writings, using empirical data from two nationwide surveys of eGovernment among American local governments.
Abstract: In this article, the authors address the recent trajectory of local e-government in the United States and compare it with the predictions of early e-government writings, using empirical data from two nationwide surveys of e-government among American local governments. The authors find that local e-government has not produced the results that those writings predicted. Instead, its development has largely been incremental, and local e-government is mainly about delivering information and services online, followed by a few transactions and limited interactivity. Local e-government is also mainly one way, from government to citizens, and there is little or no evidence that it is transformative in any way. This disparity between early predictions and actual results is partly attributable to the incremental nature of American public administration. Other reasons include a lack of attention by early writers to the history of information technology in government and the influence of technological determinism on those writings.
332 citations
••
TL;DR: In this article, a global shallow-water model based on the flux-form semi-lagrangian scheme is described, which is a multidimensional semi-Lagrangian extension of the higher order Godunov-type finite-volume schemes (e.g., the piece-wise parabolic method).
Abstract: A global shallow-water model based on the flux-form semi-lagrangian scheme is described. the mass-conserving flux-form semi-Lagrangian scheme is a multidimensional semi-Lagrangian extension of the higher order Godunov-type finite-volume schemes (e.g., the piece-wise parabolic method). Unlike the piece-wise parabolic methodology, neither directional splitting nor a Riemann solver is involved. A reverse engineering procedure is introduced to achieve the goal of consistent transport of the absolute vorticity and the mass, and hence, the potential vorticity. Gravity waves are treated explicitly, in a manner that is consistent with the forward-in-time flux-form semi-Lagrangian transport scheme. Due to the finite-volume nature of the flux-form semi-lagrangian scheme and the application of the monotonicity constraint, which can be regarded as a subgrid-scale flux parametrization, essentially noise-free solutions are obtained without additional diffusion. Two selected shallow-water test cases proposed by Williamson et al. (1992) and a stratospheric vortex erosion simulation are presented. Discussions on the accuracy and computational efficiency are given based on the comparisons with a Eulerian spectral model and two advective-form semi-implicit semi-Lagrangian models.
331 citations
••
TL;DR: A study of the messages from an on-line medical support group shows that empathy is an essential ingredient in participants’ discussions and better tools are needed to empower patients to help themselves by finding information and contacting other patients in bulletin board communities.
331 citations
Authors
Showing all 8862 results
Name | H-index | Papers | Citations |
---|---|---|---|
Robert C. Gallo | 145 | 825 | 68212 |
Paul T. Costa | 133 | 406 | 88454 |
Igor V. Moskalenko | 132 | 542 | 58182 |
James Chiang | 129 | 308 | 60268 |
Alex K.-Y. Jen | 128 | 921 | 61811 |
Alan R. Shuldiner | 120 | 557 | 71737 |
Richard N. Zare | 120 | 1201 | 67880 |
Vince D. Calhoun | 117 | 1234 | 62205 |
Rita R. Colwell | 115 | 781 | 55229 |
Kendall N. Houk | 112 | 997 | 54877 |
Elliot K. Fishman | 112 | 1335 | 49298 |
Yoram J. Kaufman | 111 | 263 | 59238 |
Paulo Artaxo | 107 | 454 | 44346 |
Braxton D. Mitchell | 102 | 558 | 49599 |
Sushil Jajodia | 101 | 664 | 35556 |