Showing 201 - 210 of 722 Items
Level-rank duality of untwisted and twisted D-branes
Date: 2006-05-15
Creator: Stephen G. Naculich
Howard J. Schnitzer
Access: Open access
- Level-rank duality of untwisted and twisted D-branes of WZW models is explored. We derive the relation between D0-brane charges of level-rank dual untwisted D-branes of over(su, ̂) ( N )K and over(sp, ̂) ( n )k, and of level-rank dual twisted D-branes of over(su, ̂) ( 2 n + 1 )2 k + 1. The analysis of level-rank duality of twisted D-branes of over(su, ̂) ( 2 n + 1 )2 k + 1 is facilitated by their close relation to untwisted D-branes of over(sp, ̂) ( n )k. We also demonstrate level-rank duality of the spectrum of an open string stretched between untwisted or twisted D-branes in each of these cases. © 2006 Elsevier B.V. All rights reserved.
Evolution of pathogenicity and sexual reproduction in eight Candida genomes
Date: 2009-06-04
Creator: Geraldine Butler
Matthew D. Rasmussen
Michael F. Lin
Manuel A.S. Santos
Sharadha, Sakthikumar
Carol A. Munro
Esther Rheinbay
Manfred Grabherr
Anja Forche
Jennifer L. Reedy
Ino Agrafioti
Martha B. Arnaud
Steven Bates
Alistair J.P. Brown
Sascha Brunke
Maria C. Costanzo
David A. Fitzpatrick
Piet W.J. De Groot
David Harris
Lois L. Hoyer
Bernhard Hube
Frans M. Klis
Chinnappa Kodira
Nicola Lennard
Mary E. Logue
Ronny Martin
Aaron M. Neiman
Elissavet Nikolaou
Michael A. Quail
Janet Quinn
Maria C. Santos
Access: Open access
- Candida species are the most common cause of opportunistic fungal infection worldwide. Here we report the genome sequences of six Candida species and compare these and related pathogens and non-pathogens. There are significant expansions of cell wall, secreted and transporter gene families in pathogenic species, suggesting adaptations associated with virulence. Large genomic tracts are homozygous in three diploid species, possibly resulting from recent recombination events. Surprisingly, key components of the mating and meiosis pathways are missing from several species. These include major differences at the mating-type loci (MTL); Lodderomyces elongisporus lacks MTL, and components of the a1/α2 cell identity determinant were lost in other species, raising questions about how mating and cell types are controlled. Analysis of the CUG leucine-to-serine genetic-code change reveals that 99% of ancestral CUG codons were erased and new ones arose elsewhere. Lastly, we revise the Candida albicans gene catalogue, identifying many new genes. © 2009 Macmillan Publishers Limited. All rights reserved.
Evolution of the interaction between Hox genes and a downstream target
Date: 1998-05-07
Creator: Michael F. Palopoli
Nipam H. Patel
Access: Open access
- Segmental identifies along the insect body depend on the activities of Hox genes [1,2]. In Drosophila melanogaster, one well-studied Hox regulatory target is Distal-less (DII), which Is required for the development of distel limb structures [3]. In abdominal segments, DII transcription is prevented when Hox proteins of the Bithorax Complex (BX-C) bind to cis-regulatory elements upstream of the DII transcription start site [4,5]. Previous evolutionary comparisons of gene expression patterns suggest that this direct repression is conserved between Diptera and Lepidoptera, but is absent in the Crustacea [6,7]. We examined gene expression patterns in three orders of hexapods, all of which develop abdominal appendages, in order to determine when the strong repressive interaction between BX-C proteins and DII appeared during evolution. In each of the species examined, DII expression was initiated in abdominal cells despite the presence of high levels of BX-C proteins. It appears that the strong repressive effects of BX-C proteins on DII expression arose relatively late in insect evolution. We suggest that the regulatory interaction between the BX-C genes and DII has evolved within the hexapods in a complex, segment-specific manner.
CHY representations for gauge theory and gravity amplitudes with up to three massive particles
Date: 2015-05-28
Creator: Stephen G. Naculich
Access: Open access
- We show that a wide class of tree-level scattering amplitudes involving scalars, gauge bosons, and gravitons, up to three of which may be massive, can be expressed in terms of a Cachazo-He-Yuan representation as a sum over solutions of the scattering equations. These amplitudes, when expressed in terms of the appropriate kinematic invariants, are independent of the masses and therefore identical to the corresponding massless amplitudes.
An isochromosome confers drug resistance in vivo by amplification of two genes, ERG11 and TAC1
Date: 2008-05-01
Creator: Anna Selmecki
Maryam Gerami-Nejad
Carsten Paulson
Anja Forche
Judith, Berman
Access: Open access
- Acquired azole resistance is a serious clinical problem that is often associated with the appearance of aneuploidy and, in particular, with the formation of an isochromosome [i(5L)] in the fungal opportunist Candida albicans. Here we exploited a series of isolates from an individual patient during the rapid acquisition of fluconazole resistance (FluR). Comparative genome hybridization arrays revealed that the presence of two extra copies of Chr5L, on the isochromosome, conferred increased FluR and that partial truncation of Chr5L reduced FluR. In vitro analysis of the strains by telomere-mediated truncations and by gene deletion assessed the contribution of all Chr5L genes and of four specific genes. Importantly, ERG11 (encoding the drug target) and a hyperactive allele of TAC1 (encoding a transcriptional regulator of drug efflux pumps) made independent, additive contributions to FluR in a gene copy number-dependent manner that was not different from the contributions of the entire Chr5L arm. Thus, the major mechanism by which i(5L) formation causes increased azole resistance is by amplifying two genes: ERG11 and TAC1. © 2008 The Authors.
Clarifying (Opportunity) Costs
Date: 2015-05-01
Creator: Daniel F. Stone
Access: Open access
- Opportunity cost is widely considered to be a fundamental concept in economics. But the definition of the term continues to be both unclear and controversial. I describe how the term is widely used in two distinct ways, both in academic and non-academic contexts. I propose a practical way for educators to clarify the concept and related terminology.
Investigating the Role of Interpretation Bias in Mindfulness-Based Treatment of Adults With Generalized Anxiety Disorder
Date: 2020-02-11
Creator: Elizabeth A. Hoge
Hannah E. Reese
Isabelle A. Oliva
Caroline D. Gabriel
Brittany M., Guidos
Eric Bui
Naomi M. Simon
Mary Ann Dutton
Access: Open access
- Although mindfulness-based interventions (MBIs) have garnered empirical support for a wide range of psychological conditions, the psychological processes that mediate the relationship between MBIs and subsequent symptomatic improvement are less well-understood. In the present study we sought to examine, for the first time, the relationship between mindfulness, negative interpretation bias as measured by the homophone task, and anxiety among adults with Generalized Anxiety Disorder (GAD). Forty-two individuals with GAD completed measures of mindfulness, interpretation bias, and anxiety before and after treatment with Mindfulness-based Stress Reduction (MBSR). Contrary to prior research, we did not find evidence of an indirect relationship between baseline levels of mindfulness and anxiety via negative interpretation bias. MBSR did result in significant reductions in negative interpretation bias from baseline to post-treatment; however, we did not find evidence of an indirect relationship between changes in mindfulness and changes in anxiety via changes in interpretation bias. Taken together, these results provide minimal support for the hypothesized relationship between mindfulness, negative interpretation bias, and anxiety among adults with GAD. Limitations and specific suggestions for further inquiry are discussed.
Haplotype mapping of a diploid non-meiotic organism using existing and induced aneuploidies
Date: 2008-01-01
Creator: Melanie Legrand
Anja Forche
Anna Selmecki
Christine Chan
David T., Kirkpatrick
Judith Berman
Access: Open access
- Haplotype maps (HapMaps) reveal underlying sequence variation and facilitate the study of recombination and genetic diversity. In general, HapMaps are produced by analysis of Single-Nucleotide Polymorphism (SNP) segregation in large numbers of meiotic progeny. Candida albicans, the most common human fungal pathogen, is an obligate diploid that does not appear to undergo meiosis. Thus, standard methods for haplotype mapping cannot be used. We exploited naturally occurring aneuploid strains to determine the haplotypes of the eight chromosome pairs in the C. albicans laboratory strain SC5314 and in a clinical isolate. Comparison of the maps revealed that the clinical strain had undergone a significant amount of genome rearrangement, consisting primarily of crossover or gene conversion recombination events. SNP map haplotyping revealed that insertion and activation of the UAU1 cassette in essential and non-essential genes can result in whole chromosome aneuploidy. UAU1 is often used to construct homozygous deletions of targeted genes in C. albicans; the exact mechanism (trisomy followed by chromosome loss versus gene conversion) has not been determined. UAU1 insertion into the essential ORC1 gene resulted in a large proportion of trisomic strains, while gene conversion events predominated when UAU1 was inserted into the non-essential LRO1 gene. Therefore, induced aneuploidies can be used to generate HapMaps, which are essential for analyzing genome alterations and mitotic recombination events in this clonal organism. © 2008 Legrand et al.
Expert assessment of vulnerability of permafrost carbon to climate change
Date: 2013-07-01
Creator: E. A.G. Schuur
B. W. Abbott
W. B. Bowden
V. Brovkin
P., Camill
J. G. Canadell
J. P. Chanton
F. S. Chapin
T. R. Christensen
P. Ciais
B. T. Crosby
C. I. Czimczik
G. Grosse
J. Harden
D. J. Hayes
G. Hugelius
Access: Open access
- Approximately 1700 Pg of soil carbon (C) are stored in the northern circumpolar permafrost zone, more than twice as much C than in the atmosphere. The overall amount, rate, and form of C released to the atmosphere in a warmer world will influence the strength of the permafrost C feedback to climate change. We used a survey to quantify variability in the perception of the vulnerability of permafrost C to climate change. Experts were asked to provide quantitative estimates of permafrost change in response to four scenarios of warming. For the highest warming scenario (RCP 8.5), experts hypothesized that C release from permafrost zone soils could be 19-45 Pg C by 2040, 162-288 Pg C by 2100, and 381-616 Pg C by 2300 in CO equivalent using 100-year CH global warming potential (GWP). These values become 50 % larger using 20-year CH GWP, with a third to a half of expected climate forcing coming from CH even though CH was only 2.3 % of the expected C release. Experts projected that two-thirds of this release could be avoided under the lowest warming scenario (RCP 2.6). These results highlight the potential risk from permafrost thaw and serve to frame a hypothesis about the magnitude of this feedback to climate change. However, the level of emissions proposed here are unlikely to overshadow the impact of fossil fuel burning, which will continue to be the main source of C emissions and climate forcing. © 2013 The Author(s). 2 4 4 4 4