Showing 4101 - 4110 of 5831 Items
Discrimination of phytoplankton functional groups using an ocean reflectance inversion model
Date: 2014-08-01
Creator: P. Jeremy Werdell, Collin S. Roesler, Joaquim I. Goes
Access: Open access
- Ocean reflectance inversion models (ORMs) provide a mechanism for inverting the color of the water observed by a satellite into marine inherent optical properties (IOPs), which can then be used to study phytoplankton community structure. Most ORMs effectively separate the total signal of the collective phytoplankton community from other water column constituents; however, few have been shown to effectively identify individual contributions by multiple phytoplankton groups over a large range of environmental conditions. We evaluated the ability of an ORM to discriminate between Noctiluca miliaris and diatoms under conditions typical of the northern Arabian Sea. We: (1) synthesized profiles of IOPs that represent bio-optical conditions for the Arabian Sea; (2) generated remote-sensing reflectances from these profiles using Hydrolight; and (3) applied the ORM to the synthesized reflectances to estimate the relative concentrations of diatoms and N. miliaris. By comparing the estimates from the inversion model with those from synthesized vertical profiles, we identified those conditions under which the ORM performs both well and poorly. Even under perfectly controlled conditions, the absolute accuracy of ORM retrievals degraded when further deconstructing the derived total phytoplankton signal into subcomponents. Although the absolute magnitudes maintained biases, the ORM successfully detected whether or not Noctiluca miliaris appeared in the simulated water column. This quantitatively calls for caution when interpreting the absolute magnitudes of the retrievals, but qualitatively suggests that the ORM provides a robust mechanism for identifying the presence or absence of species.
Donald Lent: Paintings, Drawings, Etchings
Date: 1967-01-01
Access: Open access
- Catalog of an exhibition held at the Bowdoin College Museum of Art. "Design and composition by the Anthoensen Press."
Political advertising and persuasion in the 2004 and 2008 presidential elections
Date: 2010-03-01
Creator: Michael M. Franz, Travis N. Ridout
Access: Open access
- The 2008 presidential election was historic in many respects. The campaign included the first African American major-party candidate, and neither candidate was an incumbent president or vice president. In addition, one candidate took public funding and the other candidate did not. This latter disparity resulted in an imbalance of resources across the two campaigns, especially in the purchase of political advertising. But did that imbalance matter for who won? Did advertising move voters, and if so, by how much? This article examines patterns of presidential ad buys in 2008 and compares them with presidential ad buys in 2004. It also examines the impact of advertising on county-level vote returns in both years. The results demonstrate some important differences in advertising patterns across years, especially in terms of ad sponsorship and market-level advertising advantages. We also find significant and strong advertising persuasion effects in 2008. © The Author(s) 2010.