Faculty Scholarship
Showing 291 - 300 of 733 Items
On influence, stable behavior, and the most influential individuals in networks: A game-theoretic approach
Date: 2014-01-01
Creator: Mohammad T. Irfan, Luis E. Ortiz
Access: Open access
- We introduce a new approach to the study of influence in strategic settings where the action of an individual depends on that of others in a network-structured way. We propose network influence games as a game-theoretic model of the behavior of a large but finite networked population. In particular, we study an instance we call linear-influence games that allows both positive and negative influence factors, permitting reversals in behavioral choices. We embrace pure-strategy Nash equilibrium, an important solution concept in non-cooperative game theory, to formally define the stable outcomes of a network influence game and to predict potential outcomes without explicitly considering intricate dynamics. We address an important problem in network influence, the identification of the most influential individuals, and approach it algorithmically using pure-strategy Nash-equilibria computation. Computationally, we provide (a) complexity characterizations of various problems on linear-influence games; (b) efficient algorithms for several special cases and heuristics for hard cases; and (c) approximation algorithms, with provable guarantees, for the problem of identifying the most influential individuals. Experimentally, we evaluate our approach using both synthetic network influence games and real-world settings of general interest, each corresponding to a separate branch of the U.S. Government. Mathematically, we connect linear-influence games to important models in game theory: potential and polymatrix games. © 2014 Published by Elsevier B.V.
Exuberant and inhibited toddlers: Stability of temperament and risk for problem behavior
Date: 2008-03-01
Creator: Cynthia A. Stifter, Samuel Putnam, Laudan Jahromi
Access: Open access
- Temperament, effortful control, and problem behaviors at 4.5 years were assessed in 72 children classified as exuberant, inhibited, and low reactive as 2-year-olds. Exuberant toddlers were more positive, socially responsive to novel persons, less shy, and rated as having more problem behaviors, including externalizing and internalizing behaviors, than other children as preschoolers. Two forms of effortful control, the ability to delay a response and the ability to produce a subdominant response, were associated with fewer externalizing behaviors, whereas expressing more negative affect (relative to positive/neutral affect) when disappointed was related to more internalizing behaviors. Interaction effects implicated high levels of unregulated emotion during disappointment as a risk factor for problem behaviors in exuberant children. © 2008 Cambridge University Press.
Sponsorship, Disclosure, and Donors: Limiting the Impact of Outside Group Ads
Date: 2015-03-25
Creator: Travis N. Ridout, Michael M. Franz, Erika Franklin Fowler
Access: Open access
- This research examines how an attack ad’s sponsorship conditions its effectiveness. We use data from a survey experiment that exposed participants to a fictional campaign ad. Treatments varied the ad’s sponsor (candidate vs. group), the group’s donor base (small donor vs. large donors), and the format of the donor disclosure (news reports vs. disclaimers in the ads). We find that ads sponsored by unknown groups are more effective than candidate-sponsored ads, but disclosure of donors reduces the influence of group advertising, leveling the playing field such that candidate- and group-sponsored attacks become equally effective. Increased disclosure does not, however, advantage small-donor groups over large-donor groups.
MAO-A phenotype effects response sensitivity and the parietal old/new effect during recognition memory
Date: 2018-02-13
Creator: Robert S. Ross, Andrew Smolen, Tim Curran, Erika Nyhus
Access: Open access
- A critical problem for developing personalized treatment plans for cognitive disruptions is the lack of understanding how individual differences influence cognition. Recognition memory is one cognitive ability that varies from person to person and that variation may be related to different genetic phenotypes. One gene that may impact recognition memory is the monoamine oxidase A gene (MAO-A), which influences the transcription rate of MAO-A. Examination of how MAO-A phenotypes impact behavioral and event-related potentials (ERPs) correlates of recognition memory may help explain individual differences in recognition memory performance. Therefore, the current study uses electroencephalography (EEG) in combination with genetic phenotyping of the MAO-A gene to determine how well-characterized ERP components of recognition memory, the early frontal old/new effect, left parietal old/new effect, late frontal old/new effect, and the late posterior negativity (LPN) are impacted by MAO-A phenotype during item and source memory. Our results show that individuals with the MAO-A phenotype leading to increased transcription have lower response sensitivity during both item and source memory. Additionally, during item memory the left parietal old/new effect is not present due to increased ERP amplitude for correct rejections. The results suggest that MAO-A phenotype changes EEG correlates of recognition memory and influences how well individuals differentiate between old and new items.
A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation
Date: 2014-09-01
Creator: Julie Loisel, Zicheng Yu, David W. Beilman, Philip Camill, Jukka, Alm, Matthew J. Amesbury, David Anderson, Sofia Andersson, Christopher Bochicchio, Keith Barber, Lisa R. Belyea, Joan Bunbury, Frank M. Chambers, Daniel J. Charman, François De Vleeschouwer, Barbara Fiałkiewicz-Kozieł
Access: Open access
- Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45°N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan Plateau. For all northern peatlands, carbon content in organic matter was estimated at 42 ± 3% (standard deviation) for Sphagnum peat, 51 ± 2% for non-Sphagnum peat, and at 49 ± 2% overall. Dry bulk density averaged 0.12 ± 0.07 g/cm3, organic matter bulk density averaged 0.11 ± 0.05 g/cm3, and total carbon content in peat averaged 47 ± 6%. In general, large differences were found between Sphagnum and non-Sphagnum peat types in terms of peat properties. Time-weighted peat carbon accumulation rates averaged 23 ± 2 (standard error of mean) g C/m2/yr during the Holocene on the basis of 151 peat cores from 127 sites, with the highest rates of carbon accumulation (25–28 g C/m2/yr) recorded during the early Holocene when the climate was warmer than the present. Furthermore, we estimate the northern peatland carbon and nitrogen pools at 436 and 10 gigatons, respectively. The database is publicly available at https://peatlands.lehigh.edu.
A new data set for estimating organic carbon storage to 3 m depth in soils of the northern circumpolar permafrost region
Date: 2013-12-23
Creator: G. Hugelius, J. G. Bockheim, P. Camill, B. Elberling, G., Grosse, J. W. Harden, K. Johnson, T. Jorgenson, C. D. Koven, P. Kuhry, G. Michaelson, U. Mishra, J. Palmtag, J. O'Donnell, L. Schirrmeister, E. A.G. Schuur
Access: Open access
- High-latitude terrestrial ecosystems are key components in the global carbon cycle. The Northern Circumpolar Soil Carbon Database (NCSCD) was developed to quantify stocks of soil organic carbon (SOC) in the northern circumpolar permafrost region (a total area of 18.7 × 106 km2). The NCSCD is a geographical information system (GIS) data set that has been constructed using harmonized regional soil classification maps together with pedon data from the northern permafrost region. Previously, the NCSCD has been used to calculate SOC storage to the reference depths 0–30 cm and 0–100 cm (based on 1778 pedons). It has been shown that soils of the northern circumpolar permafrost region also contain significant quantities of SOC in the 100–300 cm depth range, but there has been no circumpolar compilation of pedon data to quantify this deeper SOC pool and there are no spatially distributed estimates of SOC storage below 100 cm depth in this region. Here we describe the synthesis of an updated pedon data set for SOC storage (kg C m−2) in deep soils of the northern circumpolar permafrost regions, with separate data sets for the 100–200 cm (524 pedons) and 200–300 cm (356 pedons) depth ranges. These pedons have been grouped into the North American and Eurasian sectors and the mean SOC storage for different soil taxa (subdivided into Gelisols including the sub-orders Histels, Turbels, Orthels, permafrost-free Histosols, and permafrost-free mineral soil orders) has been added to the updated NCSCDv2. The updated version of the data set is freely available online in different file formats and spatial resolutions that enable spatially explicit applications in GIS mapping and terrestrial ecosystem models. While this newly compiled data set adds to our knowledge of SOC in the 100–300 cm depth range, it also reveals that large uncertainties remain. Identified data gaps include spatial coverage of deep (> 100 cm) pedons in many regions as well as the spatial extent of areas with thin soils overlying bedrock and the quantity and distribution of massive ground ice.©Author(s) 2013.
Scattering equations and BCJ relations for gauge and gravitational amplitudes with massive scalar particles
Date: 2014-09-01
Creator: Stephen G. Naculich
Access: Open access
- Abstract: We generalize the scattering equations to include both massless and massive particles. We construct an expression for the tree-level n-point amplitude with n − 2 gluons or gravitons and a pair of massive scalars in arbitrary spacetime dimension as a sum over the (n − 3)! solutions of the scattering equations, à la Cachazo, He, and Yuan. We derive the BCJ relations obeyed by these massive amplitudes.
Selection of Candida albicans trisomy during oropharyngeal infection results in a commensal-like phenotype
Date: 2019-05-01
Creator: Anja Forche, Norma V. Solis, Marc Swidergall, Robert Thomas, Alison, Guyer, Annette Beach, Gareth A. Cromie, Giang T. Le, Emily Lowell, Norman Pavelka, Judith Berman, Aimeé M. Dudley, Anna Selmecki, Scott G. Filler
Access: Open access
- When the fungus Candida albicans proliferates in the oropharyngeal cavity during experimental oropharyngeal candidiasis (OPC), it undergoes large-scale genome changes at a much higher frequency than when it grows in vitro. Previously, we identified a specific whole chromosome amplification, trisomy of Chr6 (Chr6x3), that was highly overrepresented among strains recovered from the tongues of mice with OPC. To determine the functional significance of this trisomy, we assessed the virulence of two Chr6 trisomic strains and a Chr5 trisomic strain in the mouse model of OPC. We also analyzed the expression of virulence-associated traits in vitro. All three trisomic strains exhibited characteristics of a commensal during OPC in mice. They achieved the same oral fungal burden as the diploid progenitor strain but caused significantly less weight loss and elicited a significantly lower inflammatory host response. In vitro, all three trisomic strains had reduced capacity to adhere to and invade oral epithelial cells and increased susceptibility to neutrophil killing. Whole genome sequencing of pre- and post-infection isolates found that the trisomies were usually maintained. Most post-infection isolates also contained de novo point mutations, but these were not conserved. While in vitro growth assays did not reveal phenotypes specific to de novo point mutations, they did reveal novel phenotypes specific to each lineage. These data reveal that during OPC, clones that are trisomic for Chr5 or Chr6 are selected and they facilitate a commensal-like phenotype.
Flow around phoronids: Consequnces of a neighbor to suspension feeders
Date: 1990-01-01
Creator: Amy S. Johnson
Access: Open access
- This article is in Free Access Publication and may be downloaded using the “Download Full Text PDF” link at right. © 1990, by the Association for the Sciences of Limnology and Oceanography, Inc.
Genotypic evolution of azole resistance mechanisms in sequential Candida albicans isolates
Date: 2007-10-01
Creator: Alix Coste, Anna Selmecki, Anja Forche, Dorothée Diogo, Marie Elisabeth, Bougnoux, Christophe D'Enfert, Judith Berman, Dominique Sanglard
Access: Open access
- TAC1 (for transcriptional activator of CDR genes) is critical for the upregulation of the ABC transporters CDR1 and CDR2, which mediate azole resistance in Candida albicans. While a wild-type TAC1 allele drives high expression of CDR1/2 in response to inducers, we showed previously that TAC1 can be hyperactive by a gain-of-function (GOF) point mutation responsible for constitutive high expression of CDR1/2. High azole resistance levels are achieved when C. albicans carries hyperactive alleles only as a consequence of loss of heterozygosity (LOH) at the TAC1 locus on chromosome 5 (Chr 5), which is linked to the mating-type-like (MTL) locus. Both are located on the Chr 5 left arm along with ERG11 (target of azoles). In this work, five groups of related isolates containing azole-susceptible and -resistant strains were analyzed for the TAC1 and ERG11 alleles and for Chr 5 alterations. While recovered ERG11 alleles contained known mutations, 17 new TAC1 alleles were isolated, including 7 hyperactive alleles with five separate new GOF mutations. Single-nucleotide- polymorphism analysis of Chr 5 revealed that azole-resistant strains acquired TAC1 hyperactive alleles and, in most cases, ERG11 mutant alleles by LOH events not systematically including the MTL locus. TAC1 LOH resulted from mitotic recombination of the left arm of Chr 5, gene conversion within the TAC1 locus, or the loss and reduplication of the entire Chr 5. In one case, two independent TAC1 hyperactive alleles were acquired. Comparative genome hybridization and karyotype analysis revealed the presence of isochromosome 5L [i(5L)] in two azole-resistant strains. i(5L) leads to increased copy numbers of azole resistance genes present on the left arm of Chr 5, among them TAC1 and ERG11. Our work shows that azole resistance was due not only to the presence of specific mutations in azole resistance genes (at least ERG11 and TAC1) but also to their increase in copy number by LOH and to the addition of extra Chr 5 copies. With the combination of these different modifications, sophisticated genotypes were obtained. The development of azole resistance in C. albicans is therefore a powerful instrument for generating genetic diversity. Copyright © 2007, American Society for Microbiology. All Rights Reserved.