Showing 3381 - 3390 of 5713 Items
Methods for Modernism: American Art, 1876-1925
Date: 2010-01-01
Creator: Diana K. Tuite, Linda J. Docherty
Access: Open access
Projecting global land-use change and its effect on ecosystem service provision and biodiversity with simple models
Date: 2010-12-01
Creator: Erik Nelson, Heather Sander, Peter Hawthorne, Marc Conte, Driss, Ennaanay, Stacie Wolny, Steven Manson, Stephen Polasky
Access: Open access
- Background: As the global human population grows and its consumption patterns change, additional land will be needed for living space and agricultural production. A critical question facing global society is how to meet growing human demands for living space, food, fuel, and other materials while sustaining ecosystem services and biodiversity [1]. Methodology/Principal Findings: We spatially allocate two scenarios of 2000 to 2015 global areal change in urban land and cropland at the grid cell-level and measure the impact of this change on the provision of ecosystem services and biodiversity. The models and techniques used to spatially allocate land-use/land-cover (LULC) change and evaluate its impact on ecosystems are relatively simple and transparent [2]. The difference in the magnitude and pattern of cropland expansion across the two scenarios engenders different tradeoffs among crop production, provision of species habitat, and other important ecosystem services such as biomass carbon storage. For example, in one scenario, 5.2 grams of carbon stored in biomass is released for every additional calorie of crop produced across the globe; under the other scenario this tradeoff rate is 13.7. By comparing scenarios and their impacts we can begin to identify the global pattern of cropland and irrigation development that is significant enough to meet future food needs but has less of an impact on ecosystem service and habitat provision. Conclusions/Significance: Urban area and croplands will expand in the future to meet human needs for living space, livelihoods, and food. In order to jointly provide desired levels of urban land, food production, and ecosystem service and species habitat provision the global society will have to become much more strategic in its allocation of intensively managed land uses. Here we illustrate a method for quickly and transparently evaluating the performance of potential global futures.
The parasexual cycle in Candida albicans provides an alternative pathway to meiosis for the formation of recombinant strains
Date: 2008-05-01
Creator: Anja Forche, Kevin Alby, Dana Schaefer, Alexander D. Johnson, Judith, Berman, Richard J. Bennett
Access: Open access
- Candida albicans has an elaborate, yet efficient, mating system that promotes conjugation between diploid a and α strains. The product of mating is a tetraploid a/α cell that must undergo a reductional division to return to the diploid state. Despite the presence of several "meiosis-specific" genes in the C. albicans genome, a meiotic program has not been observed. Instead, tetraploid products of mating can be induced to undergo efficient, random chromosome loss, often producing strains that are diploid, or close to diploid, in ploidy. Using SNP and comparative genome hybridization arrays we have now analyzed the genotypes of products from the C. albicans parasexual cycle. We show that the parasexual cycle generates progeny strains with shuffled combinations of the eight C. albicans chromosomes. In addition, several isolates had undergone extensive genetic recombination between homologous chromosomes, including multiple gene conversion events. Progeny strains exhibited altered colony morphologies on laboratory media, demonstrating that the parasexual cycle generates phenotypic variants of C. albicans. In several fungi, including Saccharomyces cerevisiae and Schizosaccharomyces pombe, the conserved Spo11 protein is integral to meiotic recombination, where it is required for the formation of DNA double-strand breaks. We show that deletion of SPO11 prevented genetic recombination between homologous chromosomes during the C. albicans parasexual cycle. These findings suggest that at least one meiosis-specific gene has been re-programmed to mediate genetic recombination during the alternative parasexual life cycle of C. albicans. We discuss, in light of the long association of C. albicans with warm-blooded animals, the potential advantages of a parasexual cycle over a conventional sexual cycle. © 2008 Forche et al.
Taming the giant within
Date: 2019-01-01
Creator: Jack R. Bateman, David J. Anderson
Access: Open access
Matrix-model description of N = 2 gauge theories with non-hyperelliptic Seiberg-Witten curves
Date: 2003-12-08
Creator: Stephen G. Naculich, Howard J. Schnitzer, Niclas Wyllard
Access: Open access
- Using matrix-model methods we study three different N=2 models: U(N)×U(N) with matter in the bifundamental representation, U(N) with matter in the symmetric representation, and U(N) with matter in the antisymmetric representation. We find that the (singular) cubic Seiberg-Witten curves (and associated Seiberg-Witten differentials) implied by the matrix models, although of a different form from the ones previously proposed using M-theory, can be transformed into the latter and are thus physically equivalent. We also calculate the one-instanton corrections to the gauge-coupling matrix using the perturbative expansion of the matrix model. For the U(N) theories with symmetric or antisymmetric matter we use the modified matrix-model prescription for the gauge-coupling matrix discussed in our paper: Cubic curves from matrix models and generalized Konishi anomalies (hep-th/0303268). Moreover, in the matrix model for the U(N) theory with antisymmetric matter, one is required to expand around a different vacuum than one would naively have anticipated. With these modifications of the matrix-model prescription, the results of this paper are in complete agreement with those of Seiberg-Witten theory obtained using M-theory methods. © 2003 Elsevier B.V. All rights reserved.
Suspense-optimal college football play-offs
Date: 2014-01-01
Creator: Jarrod Olson, Daniel F. Stone
Access: Open access
- U.S. college football’s traditional bowl system, and lack of a postseason play-off tournament, has been controversial for years. The conventional wisdom is that a play-off would be a more fair way to determine the national champion, and more fun for fans to watch. The colleges finally agreed to begin a play-off in the 2014-2015 season, but with just four teams, and speculation continues that more teams will be added soon. A subtle downside to adding play-off teams is that it reduces the significance of regular season games.We use the framework of Ely, Frankel, and Kamenica (in press) to directly estimate the utility fans would get from this significance, that is, utility from suspense, under a range of play-off scenarios. Our results consistently indicate that play-off expansion causes a loss in regular season suspense utility greater than the gain in the postseason, implying the traditional bowl system (two team play-off) is suspense-optimal. We analyze and discuss implications for TV viewership and other contexts.
Erratum: Sutural loosening and skeletal flexibility during growth: Determination of drop-like shapes in sea urchins (Proceedings of The Royal Society of London B (February 7, 2002) 269 (215-220))
Date: 2002-12-22
Creator: Amy S. Johnson, Olaf Ellers, Jim Lemire, Melissa Minor, Holly A., Leddy
Access: Open access
Prediction of "fear" acquisition in healthy control participants in a de novo fear-conditioning paradigm
Date: 2007-01-01
Creator: Michael W. Otto, Teresa M. Leyro, Kelly Christian, Christen M. Deveney, Hannah, Reese, Mark H. Pollack, Scott P. Orr
Access: Open access
- Studies using fear-conditioning paradigms have found that anxiety patients are more conditionable than individuals without these disorders, but these effects have been demonstrated inconsistently. It is unclear whether these findings have etiological significance or whether enhanced conditionability is linked only to certain anxiety characteristics. To further examine these issues, the authors assessed the predictive significance of relevant subsyndromal characteristics in 72 healthy adults, including measures of worry, avoidance, anxious mood, depressed mood, and fears of anxiety symptoms (anxiety sensitivity), as well as the dimensions of Neuroticism and Extraversion. Of these variables, the authors found that the combination of higher levels of subsyndromal worry and lower levels of behavioral avoidance predicted heightened conditionability, raising questions about the etiological significance of these variables in the acquisition or maintenance of anxiety disorders. In contrast, the authors found that anxiety sensitivity was more linked to individual differences in orienting response than differences in conditioning per se. © 2007 Sage Publications.