Showing 121 - 130 of 733 Items
Constructing a scientist: Expert authority and public images of Rachel Carson
Date: 2011-06-01
Creator: David K. Hecht
Access: Open access
- This article uses the voluminous public discourse around Rachel Carson and her controversial bestseller Silent Spring to explore Americans' views on science and scientists. Carson provides a particularly interesting case study because of intense and public debates over whether she was a scientist at all, and therefore whether her book should be granted legitimacy as science. Her career defied easy classification, as she acted variously as writer, activist, and environmentalist in addition to scientist. Defending her work as legitimate science, which many though not all commentators did, therefore became an act of defining what both science and scientists could and should be. This article traces the variety of nonscientific images and narratives readers and writers assigned to Carson, such as "reluctant crusader" and "scientist-poet." It argues that nonscientific attributes were central to legitimating her as both admirable person and admirable scientist. It explores how debates over Silent Spring can be usefully read as debates over the desirability of putatively nonscientific attributes in the professional work of a scientist. And it examines the nature of Carson's very democratized image for changing notions of science and scientists in 1960s United States politics and culture. © 2011 by the Regents of the University of California. All rights reserved.
Does political advertising persuade?
Date: 2007-12-01
Creator: Michael M. Franz, Travis N. Ridout
Access: Open access
- Well over $1 billion was spent on televised political advertising in the U.S. in 2004. Given the ubiquity of the 30 second spot, one might presume that ads must affect viewers' vote choices. Somewhat surprisingly, though, scholars have yet to make much progress in confirming this claim. In this paper, we leverage a comprehensive dataset that tracks political ads in the nation's top media markets and a survey of presidential and U.S. Senate voters in 2004. We ask whether exposure to presidential and Senate advertising influences voters' evaluations of candidates and the choices that they make at the ballot box. In the end, we find considerable evidence that advertising persuades-and that its impact varies depending on the characteristics of the viewer. © 2007 Springer Science+Business Media, LLC.
Evaluating measures of campaign advertising exposure on political learning
Date: 2004-09-01
Creator: Travis N. Ridout, Dhavan V. Shah, Kenneth M. Goldstein, Michael M. Franz
Access: Open access
- Scholars employ various methods to measure exposure to televised political advertising but often arrive at conflicting conclusions about its impact on the thoughts and actions of citizens. We attempt to clarify one of these debates while validating a parsimonious measure of political advertising exposure. To do so, we assess the predictive power of six different measurement approaches - from the simple to the complex - on learning about political candidates. Two datasets are used in this inquiry: (1) geo-coded political advertising time-buy data, and (2) a national panel study concerning patterns of media consumption and levels of political knowledge. We conclude that many traditional methods of assessing exposure are flawed. Fortunately, there is a relatively simple measure that predicts knowledge about information featured in ads. This measure involves combining a tally of the volume of advertisements aired in a market with a small number of survey questions about the television viewing habits of geo-coded respondents.
Manipulation of Fgf and Bmp signaling in teleost fishes suggests potential pathways for the evolutionary origin of multicuspid teeth
Date: 2013-03-01
Creator: William R. Jackman, Shelby H. Davies, David B. Lyons, Caitlin K. Stauder, Benjamin R., Denton-Schneider, Andrea Jowdry, Sharon R. Aigler, Scott A. Vogel, David W. Stock
Access: Open access
- Teeth with two or more cusps have arisen independently from an ancestral unicuspid condition in a variety of vertebrate lineages, including sharks, teleost fishes, amphibians, lizards, and mammals. One potential explanation for the repeated origins of multicuspid teeth is the existence of multiple adaptive pathways leading to them, as suggested by their different uses in these lineages. Another is that the addition of cusps required only minor changes in genetic pathways regulating tooth development. Here we provide support for the latter hypothesis by demonstrating that manipulation of the levels of Fibroblast growth factor (Fgf) or Bone morphogenetic protein (Bmp) signaling produces bicuspid teeth in the zebrafish (Danio rerio), a species lacking multicuspid teeth in its ancestry. The generality of these results for teleosts is suggested by the conversion of unicuspid pharyngeal teeth into bicuspid teeth by similar manipulations of the Mexican Tetra (Astyanax mexicanus). That these manipulations also produced supernumerary teeth in both species supports previous suggestions of similarities in the molecular control of tooth and cusp number. We conclude that despite their apparent complexity, the evolutionary origin of multicuspid teeth is positively constrained, likely requiring only slight modifications of a pre-existing mechanism for patterning the number and spacing of individual teeth. © 2013 Wiley Periodicals, Inc.
Optical proxy for phytoplankton biomass in the absence of photophysiology: Rethinking the absorption line height
Date: 2013-01-01
Creator: Collin S. Roesler, Andrew H. Barnard
Access: Open access
- The pigment absorption peak in the red waveband observed in phytoplankton and particulate absorption spectra is primarily associated with chlorophyll-a and exhibits much lower pigment packaging compared to the blue peak. The minor contributions to the signature by accessory pigments can be largely removed by computing the line height absorption at 676 nm above a linear background between approximately 650 nm and 715 nm. The line height determination is also effective in removing the contributions to total or particulate absorption by colored dissolved organic matter and non-algal particles, and is relatively independent of the effects of biofouling. The line height absorption is shown to be significantly related to the extracted chlorophyll concentration over a large range of natural optical regimes and diverse phytoplankton cultures. Unlike the in situ fluorometric method for estimating chlorophyll, the absorption line height is not sensitive to incident irradiance, in particular non-photochemical quenching. The combination of the two methods provides a combination of robust phytoplankton biomass estimates, pigment based taxonomic information and a means to estimate the photosynthetic parameter, , the irradiance at which photosynthesis transitions from light limitation to light saturation. © 2013 The Authors. E K
Campaign advertising and democratic citizenship
Date: 2004-01-01
Creator: Paul Freedman, Michael Franz, Kenneth Goldstein
Access: Open access
- Concern about the state of American democracy is a staple of political science and popular commentary. Critics warn that levels of citizen participation and political knowledge are disturbingly low and that seemingly ubiquitous political advertising is contributing to the problem. We argue that political advertising is rife with both informational and emotional content and actually contributes to a more informed, more engaged, and more participatory citizenry. With detailed advertising data from the 2000 election, we show that exposure to campaign advertising produces citizens who are more interested in the election, have more to say about the candidates, are more familiar with who is running, and ultimately are more likely to vote. Importantly, these effects are concentrated among those citizens who need it most: those with the lowest pre-existing levels of political information.
Pleiotropic functions of embryonic sonic hedgehog expression link jaw and taste bud amplification with eye loss during cavefish evolution
Date: 2009-06-01
Creator: Yoshiyuki Yamamoto, Mardi S. Byerly, William R. Jackman, William R. Jeffery
Access: Open access
- This study addresses the role of sonic hedgehog (shh) in increasing oral-pharyngeal constructive traits (jaws and taste buds) at the expense of eyes in the blind cavefish Astyanax mexicanus. In cavefish embryos, eye primordia degenerate under the influence of hyperactive Shh signaling. In concert, cavefish show amplified jaw size and taste bud numbers as part of a change in feeding behavior. To determine whether pleiotropic effects of hyperactive Shh signaling link these regressive and constructive traits, shh expression was compared during late development of the surface-dwelling (surface fish) and cave-dwelling (cavefish) forms of Astyanax. After an initial expansion along the midline of early embryos, shh was elevated in the oral-pharyngeal region in cavefish and later was confined to taste buds. The results of shh inhibition and overexpression experiments indicate that Shh signaling has an important role in oral and taste bud development. Conditional overexpression of an injected shh transgene at specific times in development showed that taste bud amplification and eye degeneration are sensitive to shh overexpression during the same early developmental period, although taste buds are not formed until much later. Genetic crosses between cavefish and surface fish revealed an inverse relationship between eye size and jaw size/taste bud number, supporting a link between oral-pharyngeal constructive traits and eye degeneration. The results suggest that hyperactive Shh signaling increases oral and taste bud amplification in cavefish at the expense of eyes. Therefore, selection for constructive oral-pharyngeal traits may be responsible for eye loss during cavefish evolution via pleiotropic function of the Shh signaling pathway. © 2009 Elsevier Inc. All rights reserved.
Evaluating the Return in Ecosystem Services from Investment in Public Land Acquisitions
Date: 2013-06-11
Creator: Kent Kovacs, Stephen Polasky, Erik Nelson, Bonnie L. Keeler, Derric, Pennington, Andrew J. Plantinga, Steven J. Taff
Access: Open access
- We evaluate the return on investment (ROI) from public land conservation in the state of Minnesota, USA. We use a spatially-explicit modeling tool, the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST), to estimate how changes in land use and land cover (LULC), including public land acquisitions for conservation, influence the joint provision and value of multiple ecosystem services. We calculate the ROI of a public conservation acquisition as the ratio of the present value of ecosystem services generated by the conservation to the cost of the conservation. For the land scenarios analyzed, carbon sequestration services generated the greatest benefits followed by water quality improvements and recreation opportunities. We found ROI values ranged from 0.21 to 5.28 depending on assumptions about future land use change, service values, and discount rate. Our study suggests conservation is a good investment as long as investments are targeted to areas with low land costs and high service values. © 2013 Kovacs et al.
Vulnerability of high-latitude soil organic carbon in North America to disturbance
Date: 2011-12-01
Creator: Guido Grosse, Jennifer Harden, Merritt Turetsky, A. David McGuire, Philip, Camill, Charles Tarnocai, Steve Frolking, Edward A.G. Schuur, Torre Jorgenson, Sergei Marchenko, Vladimir Romanovsky, Kimberly P. Wickland, Nancy French, Mark Waldrop, Laura Bourgeau-Chavez, Robert G. Striegl
Access: Open access
- This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools into (1) near-surface soils where SOC is affected by seasonal freeze-thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not affected by short-term changes. We address key factors (permafrost, vegetation, hydrology, paleoenvironmental history) and processes (C input, storage, decomposition, and output) responsible for the formation of the large high-latitude SOC pool in North America and highlight how climate-related disturbances could alter this pool's character and size. Press disturbances of relatively slow but persistent nature such as top-down thawing of permafrost, and changes in hydrology, microbiological communities, pedological processes, and vegetation types, as well as pulse disturbances of relatively rapid and local nature such as wildfires and thermokarst, could substantially impact SOC stocks. Ongoing climate warming in the North American high-latitude region could result in crossing environmental thresholds, thereby accelerating press disturbances and increasingly triggering pulse disturbances and eventually affecting the C source/sink net character of northern high-latitude soils. Finally, we assess postdisturbance feedbacks, models, and predictions for the northern high-latitude SOC pool, and discuss data and research gaps to be addressed by future research. Copyright 2011 by the American Geophysical Union.
Drag, drafting, and mechanical interactions in canopies of the red alga Chondrus crispus
Date: 2001-01-01
Creator: A. S. Johnson
Access: Open access
- Dense algal canopies, which are common in the lower intertidal and shallow subtidal along rocky coastlines, can alter flow-induced forces in their vicinity. Alteration of flow-induced forces on algal thalli may ameliorate risk of dislodgement and will affect important physiological processes, such as rates of photosynthesis. This study found that the force experienced by a thallus of the red alga Chondrus crispus (Stackhouse) at a given flow speed within a flow tank depended upon (1) the density of the canopy surrounding the thallus, (2) the position of the thallus within the canopy, and (3) the length of the stipe of the thallus relative to the height of the canopy. At all flow speeds, a solitary thallus experienced higher forces than a thallus with neighbors. A greater than 65% reduction in force occurred when the thallus drafted in the region of slower velocities that occurs in the wake region of even a single upstream neighbor, similar to the way racing bicyclists draft one behind the other. Mechanical interactions between thalli were important to forces experienced within canopies. A thallus on the upstream edge of a canopy experienced 6% less force than it did when solitary, because the canopy physically supported it. A thallus in the middle of a canopy experienced up to 83% less force than a solitary thallus, and forces decreased with increasing canopy density. Thus, a bushy morphology that increases drag on a solitary thallus may function to decrease forces experienced by that thallus when it is surrounded by a canopy, because that morphology increases physical support provided by neighbors.