Showing 491 - 500 of 733 Items
Mitochondrial genotype influences the response to cold stress in the European green crab, Carcinus maenas
Date: 2019-01-01
Creator: Aidan F. Coyle, Erin R. Voss, Carolyn K. Tepolt, David B. Carlon
Access: Open access
- Hybrid zones provide natural experiments in recombination within and between genomes that may have strong effects on organismal fitness. On the East Coast of North America, two distinct lineages of the European green crab (Carcinus maenas) have been introduced in the last two centuries. These two lineages with putatively different adaptive properties have hybridized along the coast of the eastern Gulf of Maine, producing new nuclear and mitochondrial combinations that show clinal variation correlated with water temperature. To test the hypothesis that mitochondrial or nuclear genes have effects on thermal tolerance, we first measured the response to cold stress in crabs collected throughout the hybrid zone, then sequenced the mitochondrial CO1 gene and two nuclear single nucleotide polymorphisms (SNPs) representative of nuclear genetic lineage. Mitochondrial haplotype had a strong association with the ability of crabs to right themselves at 4.5°C that was sex specific: haplotypes originally from northern Europe gave male crabs an advantage while there was no haplotype effect on righting in female crabs. By contrast, the two nuclear SNPs that were significant outliers in a comparison between northern and southern C. maenas populations had no effect on righting response at low temperature. These results add C. maenas to the shortlist of ectotherms in which mitochondrial variation has been shown to affect thermal tolerance, and suggest that natural selection is shaping the structure of the hybrid zone across the Gulf of Maine. Our limited genomic sampling does not eliminate the strong possibility that mito-nuclear co-adaptation may play a role in the differences in thermal phenotypes documented here. Linkage between mitochondrial genotype and thermal tolerance suggests a role for local adaptation in promoting the spread of invasive populations of C. maenas around the world.
Semileptonic branching fractions of charged and neutral B mesons
Date: 1994-01-01
Creator: M. Athanas, W. Brower, G. Masek, H. P. Paar, J., Gronberg, R. Kutschke, S. Menary, R. J. Morrison, S. Nakanishi, H. N. Nelson, T. K. Nelson, C. Qiao, J. D. Richman, A. Ryd, H. Tajima, D. Sperka, M. S. Witherell, R. Balest, K. Cho, W. T. Ford, D. R. Johnson, K. Lingel, M. Lohner, P. Rankin, J. G. Smith, J. P. Alexander, C. Bebek, K. Berkelman, K. Bloom, T. E. Browder, D. G. Cassel
Access: Open access
- An examination of leptons in (4S) events tagged by reconstructed B meson decays yields semileptonic branching fractions of b-=(10.1±1.8±1. 5)% for charged and b0=(10.9±0.7±1.1)% for neutral B mesons. This is the first measurement for charged B mesons. Assuming equality of the charged and neutral semileptonic widths, the ratio b-b0=0.93±0.18±0.12 is equivalent to the ratio of lifetimes. © 1994 The American Physical Society.
Correcting in situ chlorophyll fluorescence time-series observations for nonphotochemical quenching and tidal variability reveals nonconservative phytoplankton variability in coastal waters
Date: 2019-08-01
Creator: Luke Carberry, Collin Roesler, Susan Drapeau
Access: Open access
- Chlorophyll fluorometry is one of the most commonly implemented approaches for estimating phytoplankton biomass in situ, despite documented sources of natural variability and instrumental uncertainty in the relationship between in vivo fluorescence and chlorophyll concentration. A number of strategies are employed to minimize errors and quantify natural variability in this relationship in the open ocean. However, the assumptions underlying these approaches are unsupported in coastal waters due to the short temporal and small spatial scales of variability, as well as the optical complexity. The largest source of variability in the in situ chlorophyll fluorometric signal is nonphotochemical quenching (NPQ). Typically, unquenched nighttime observations are interpolated over the quenched daytime interval, but this assumes a spatial homogeneity not found in tidally impacted coastal waters. Here, we present a model that provides a tidally resolved correction for NPQ in moored chlorophyll fluorescence measurements. The output of the model is a time series of unquenched chlorophyll fluorescence in tidal endmembers (high and low tide extremes), and thus a time series of phytoplankton biomass growth and loss in these endmember populations. Comparison between modeled and measured unquenched time series yields quantification of nonconservative variations in phytoplankton biomass. Tidally modeled interpolation between these endmember time series yields a highly resolved time series of unquenched daytime chlorophyll fluorescence values at the location of the moored sensor. Such data sets provide a critical opportunity for validating the satellite remotely sensed ocean color chlorophyll concentration data product in coastal waters.
An architecture for emotional decision-making agents
Date: 2002-01-01
Creator: Eric Chown, Randolph M. Jones, Amy E. Henninger
Access: Open access
- Our research focuses on complex agents that are capable of interacting with their environments in ways that are increasingly similar to individual humans. In this article we describe a cognitive architecture for an interactive decision-making agent with emotions. The primary goal of this work is to make the decision-making process of complex agents more realistic with regard to the behavior moderators, including emotional factors that affect humans. Instead of uniform agents that rely entirely on a deterministic body of expertise to make their decisions, the decision making process of our agents will vary according to select emotional factors affecting the agent as well as the agent's parameterized emotional profile. The premise of this model is that emotions serve as a kind of automatic assessment system that can guide or otherwise influence the more deliberative decision making process. The primary components of this emotional system are pleasure/pain and clarity/confusion subsystems that differentiate between positive and negative states. These, in turn, feed into an arousal system that interfaces with the decision-making system. We are testing our model using synthetic special-forces agents in a reconnaissance simulation.
SR-Like RNA-binding protein Slr1 affects Candida albicans filamentation and virulence
Date: 2013-04-01
Creator: Chaiyaboot Ariyachet, Norma V. Solis, Yaoping Liu, Nemani V. Prasadarao, Scott G., Filler, Anne E. McBride
Access: Open access
- Candida albicans causes both mucosal and disseminated infections, and its capacity to grow as both yeast and hyphae is a key virulence factor. Hyphal formation is a type of polarized growth, and members of the SR (serine-arginine) family of RNA-binding proteins influence polarized growth of both Saccharomyces cerevisiae and Aspergillus nidulans. Therefore, we investigated whether SR-like proteins affect filamentous growth and virulence of C. albicans. BLAST searches with S. cerevisiae SR-like protein Npl3 (ScNpl3) identified two C. albicans proteins: CaNpl3, an apparent ScNpl3 ortholog, and Slr1, another SR-like RNAbinding protein with no close S. cerevisiae ortholog. Whereas ScNpl3 was critical for growth, deletion of NPL3 in C. albicans resulted in few phenotypic changes. In contrast, the slr1δ/δ mutant had a reduced growth rate in vitro, decreased filamentation, and impaired capacity to damage epithelial and endothelial cells in vitro. Mice infected intravenously with the slr1δ/δ mutant strain had significantly prolonged survival compared to that of mice infected with the wild-type or slr1δ/δ mutant complemented with SLR1 (slr1δ/δ+SLR1) strain, without a concomitant decrease in kidney fungal burden. Histopathology, however, revealed differential localization of slr1δ/δ hyphal and yeast morphologies within the kidney. Mice infected with slr1δ/δ cells also had an increased brain fungal burden, which correlated with increased invasion of brain, but not umbilical vein, endothelial cells in vitro. The enhanced brain endothelial cell invasion was likely due to the increased surface exposure of the Als3 adhesin on slr1δ/δ cells. Our results indicate that Slr1 is an SR-like protein that influences C. albicans growth, filamentation, host cell interactions, and virulence. © 2013, American Society for Microbiology.
The interest group response to campaign finance reform
Date: 2008-04-03
Creator: Michael M. Franz
Access: Open access
- Has the most recent campaign finance reform failed relative to interest groups? More broadly, what's next in the realm of interest group electioneering? This paper explores the role of interest groups in two areas: as contributors to candidates and parties and as candidate and issue advocates. Overall, the numbers reported here show that direct interest group influence with candidates and parties likely declined in the wake of reform. On the other hand, recent uncertainty in the regulatory environment should foster the expansion of interest group advocacy efforts (and has already done so in this year's presidential primary elections). On this score, the attempts of reformers to reduce interest group electioneering have likely failed. Instead of concluding that such a development is bad for American elections, however, this paper argues that such discontent is misplaced. Copyright ©2008 The Berkeley Electronic Press. All rights reserved.
Implementing the optimal provision of ecosystem services
Date: 2014-04-29
Creator: Stephen Polasky, David J. Lewis, Andrew J. Plantinga, Erik Nelson
Access: Open access
- Many ecosystem services are public goods whose provision depends on the spatial pattern of land use. The pattern of land use is often determined by the decisions of multiple private landowners. Increasing the provision of ecosystem services, though beneficial for society as a whole, may be costly to private landowners. A regulator interested in providing incentives to landowners for increased provision of ecosystem services often lacks complete information on landowners' costs. The combination of spatially dependent benefits and asymmetric cost information means that the optimal provision of ecosystem services cannot be achieved using standard regulatory or payment for ecosystem services approaches. Here we show that an auction that sets payments between landowners and the regulator for the increased value of ecosystem services with conservation provides incentives for landowners to truthfully reveal cost information, and allows the regulator to implement the optimal provision of ecosystem services, even in the case with spatially dependent benefits and asymmetric information.
Rachel Carson and the rhetoric of revolution
Date: 2019-07-01
Creator: David K. Hecht
Access: Open access
- Rachel Carson's Silent Spring is justly remembered as a landmark in the history of modern environmentalism. It is, however, a more complicated text than cultural memory tends to acknowledge. Blending conservative and traditional elements with more progressive and pioneering ones, Silent Spring is marked by a complexity that extends to its reception and legacy. This article argues that-in a seeming paradox-it was the more conservative elements of Silent Spring that allowed it to be considered a revolutionary book. Carson carefully constructed her argument in ways that facilitated its initial acceptance. But those same decisions made it easier for supporters to de-emphasize its more radical implications, even as they granted it revolutionary status.
Local adaptation of a parasite to solar radiation impacts disease transmission potential, spore yield, and host fecundity*
Date: 2020-08-24
Creator: Mary Alta Rogalski, Meghan A. Duffy
Access: Open access
Lankapura: The Legacy of the Ramayana in Sri Lanka
Date: 2019-01-01
Creator: Justin W. Henry, Sree Padma
Access: Open access
- The five articles which make up this special issue of South Asia explore the role of the Ramayana in Sri Lankan art, literature, religious ritual and political discourse in shaping Sinhala Buddhist and Tamil Saiva perceptions of the island’s distant past. Contributors work to answer the question as to when and how Sri Lanka came to be equated with the mythic ‘Lankapura’ of Valmiki’s epic, exploring both positive and negative portrayals of Ravana (ruler of Lanka antagonist of the Ramayana) in Sinhala and Tamil literature from the late medieval period to the present day. Authors work to account for the politicisation and historicisation of the Ramayana in twenty-first century Sri Lanka (including similarities to and differences from the contemporary Indian situation), along with the appropriation of Ravana as a Sinhala Buddhist cultural hero, and the incorporation of Vibhishana as a ‘guardian deity’ in the Sinhala Buddhist pantheon.