Showing 61 - 70 of 733 Items
More pendants for Polya: Two loops in the SU(2) sector
Date: 2005-07-01
Creator: Marta Gómez-Reino, Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- We extend the methods of Spradlin and Volovich to compute the partition function for a conformally-invariant gauge theory on ℝ × S 3 in which the dilatation operator is represented by a spin-chain hamiltonian acting on pairs of states, not necessarily nearest neighbors. A specific application of this is the two-loop dilatation operator of the planar SU(2) subsector of the N ≤ 4 SU(N) super Yang-Mills theory in the large-N limit. We compute the partition function and Hagedorn temperature for this sector to second order in the gauge coupling. The Hagedorn temperature is to be interpreted as giving the exponentially-rising portion of the density of states of the SU(2) sector, which may be a signal of stringy behavior in the dual theory. © SISSA 2005.
Environmental issues in Russia
Date: 2008-12-01
Creator: Laura A. Henry, Vladimir Douhovnikoff
Access: Open access
- This review examines the literature available on the state of the environment and environmental protection in the Russian Federation. As the largest country on Earth, rich in natural resources and biodiversity, Russia's problems and policies have global consequences. Environmental quality and management are influenced by the legacy of Soviet economic planning and authoritarian governance, as well as by Russia's post-Soviet economic recession and current strategies of economic development. Russia achieved a reduction in some pollutants owing to the collapse of industrial production in the 1990s, but many environmental indicators suggest growing degradation. Russia has signed on to a number of international environmental agreements, but its record on implementation is mixed, and it discourages environmental activism. Scholarship on the Russian environment is a limited, but growing, field, constrained by challenges of data availability, yet it offers great potential for testing scientific and social scientific hypotheses. ©2008 by Annual Reviews.
Partisan selective engagement: Evidence from Facebook
Date: 2020-09-01
Creator: Marcel Garz, Jil Sörensen, Daniel F. Stone
Access: Open access
- This study investigates the effects of variation in “congeniality” of news on Facebook user engagement (likes, shares, and comments). We compile an original data set of Facebook posts by 84 German news outlets on politicians that were investigated for criminal offenses from January 2012 to June 2017. We also construct an index of each outlet's media slant by comparing the language of the outlet with that of the main political parties, which allows us to measure the congeniality of the posts. We find that user engagement with congenial posts is higher than with uncongenial ones, especially in terms of likes. The within-outlet, within-topic design allows us to infer that the greater engagement with congenial news is likely driven by psychological and social factors, rather than a desire for accurate or otherwise instrumental information.
Aneuploid chromosomes are highly unstable during DNA transformation of candida albicans∇
Date: 2009-10-01
Creator: Kelly Bouchonville, Anja Forche, Karen E.S. Tang, Anna Selmecki, Judith, Berman
Access: Open access
- Candida albicans strains tolerate aneuploidy, historically detected as karyotype alterations by pulsed-fleld gel electrophoresis and more recently revealed by array comparative genome hybridization, which provides a comprehensive and detailed description of gene copy number. Here, we first retrospectively analyzed 411 expression array experiments to predict the frequency of aneuploidy in different strains. As expected, significant levels of aneuploidy were seen in strains exposed to stress conditions, including UV light and/or sorbose treatment, as well as in strains that are resistant to antifungal drugs. More surprisingly, strains that underwent transformation with DNA displayed the highest frequency of chromosome copy number changes, with strains that were initially aneuploid exhibiting ∼3-fold more copy number changes than strains that were initially diploid. We then prospectively analyzed the effect of lithium acetate (LiOAc) transformation protocols on the stability of trisomie chromosomes. Consistent with the retrospective analysis, the proportion of karyotype changes was highly elevated in strains carrying aneuploid chromosomes. We then tested the hypothesis that stresses conferred by heat and/or LiOAc exposure promote chromosome number changes during DNA transformation procedures. Indeed, a short pulse of very high temperature caused frequent gains and losses of multiple chromosomes or chromosome segments. Furthermore, milder heat exposure over longer periods caused increased levels of loss of heterozygosity. Nonetheless, aneuploid chromosomes were also unstable when strains were transformed by electroporation, which does not include a heat shock step. Thus, aneuploid strains are particularly prone to undergo changes in chromosome number during the stresses of DNA transformation protocols. Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Intron Size Correlates Positively with Recombination Rate in Caenorhabditis elegans
Date: 2004-03-01
Creator: Anuphap Prachumwat, Laura DeVincentis, Michael F. Palopoli
Access: Open access
- A negative correlation between intron size and recombination rate has been reported for the Drosophila melanogaster and human genomes. Population-genetic models suggest that this pattern could be caused by an interaction between recombination rate and the efficacy of natural selection. To test this idea, we examined variation in intron size and recombination rate across the genome of the nematode Caenorhabditis elegans. Interestingly, we found that intron size correlated positively with recombination rate in this species.
Next-to-soft corrections to high energy scattering in QCD and gravity
Date: 2017-01-01
Creator: A. Luna, S. Melville, S. G. Naculich, C. D. White
Access: Open access
- We examine the Regge (high energy) limit of 4-point scattering in both QCD and gravity, using recently developed techniques to systematically compute all corrections up to next-to-leading power in the exchanged momentum i.e. beyond the eikonal approximation. We consider the situation of two scalar particles of arbitrary mass, thus generalising previous calculations in the literature. In QCD, our calculation describes power-suppressed corrections to the Reggeisation of the gluon. In gravity, we confirm a previous conjecture that next-to-soft corrections correspond to two independent deflection angles for the incoming particles. Our calculations in QCD and gravity are consistent with the well-known double copy relating amplitudes in the two theories.
Molecular basis of the copulatory plug polymorphism in Caenorhabditis elegans
Date: 2008-08-21
Creator: Michael F. Palopoli, Matthew V. Rockman, Aye TinMaung, Camden Ramsay, Stephen, Curwen, Andrea Aduna, Jason Laurita, Leonid Kruglyak
Access: Open access
- Heritable variation is the raw material for evolutionary change, and understanding its genetic basis is one of the central problems in modern biology. We investigated the genetic basis of a classic phenotypic dimorphism in the nematode Caenorhabditis elegans. Males from many natural isolates deposit a copulatory plug after mating, whereas males from other natural isolates-including the standard wild-type strain (N2 Bristol) that is used in most research laboratories-do not deposit plugs. The copulatory plug is a gelatinous mass that covers the hermaphrodite vulva, and its deposition decreases the mating success of subsequent males. We show that the plugging polymorphism results from the insertion of a retrotransposon into an exon of a novel mucin-like gene, plg-1, whose product is a major structural component of the copulatory plug. The gene is expressed in a subset of secretory cells of the male somatic gonad, and its loss has no evident effects beyond the loss of male mate-guarding. Although C. elegans descends from an obligate-outcrossing, male?female ancestor, it occurs primarily as self-fertilizing hermaphrodites. The reduced selection on male-male competition associated with the origin of hermaphroditism may have permitted the global spread of a loss-of-function mutation with restricted pleiotropy. ©2008 Macmillan Publishers Limited. All rights reserved.
Metric properties of diestel-leader groups
Date: 2013-06-01
Creator: Melanie Stein, Jennifer Taback
Access: Open access
Matrix model approach to the N = 2 U (N) gauge theory with matter in the fundamental representation
Date: 2003-01-01
Creator: Stephen G. Naculich, Howard J. Schnitzer, Niclas Wyllard
Access: Open access
- We use matrix model technology to study the N = 2 U (N) gauge theory with Nf massive hypennultiplets in the fundamental representation. We perform a completely perturbative calculation of the periods ai and the prepotential F(a) up to the first instanton level, finding agreement with previous results in the literature. We also derive the Seiberg-Witten curve and differential from the large-M solution of the matrix model. We show that the two cases Nf < N and N ≤ Nf < 2N can be treated simultaneously. © SISSA/ISAS 2003.
Elliptic models, type IIB orientifolds, and the AdS/CFT correspondence
Date: 2000-12-18
Creator: Isabel P. Ennes, Carlos Lozano, Stephen G. Naculich, Howard J. Schnitzer
Access: Open access
- We analyze the large N supergravity descriptions of the class of type IIB models T-dual to elliptic type IIA brane configurations containing two orientifold 6-planes and up to two NS 5-branes. The T-dual IIB configurations contain N D3-branes in the background of an orientifold 7-plane and, in some models, a Z2 orbifold and/or D7-branes, which give rise to four-dimensional N=2 (or N=4) gauge theories with at most two factors. We identify the chiral primary states of the supergravity theories, and match them to gauge invariant operators of the corresponding superconformal theories using Maldacena's duality. © 2000 Elsevier Science B.V.