Showing 631 - 640 of 2040 Items
Demonstration of loss of heterozygosity by single-nucleotide polymorphism microarray analysis and alterations in strain morphology in Candida albicans strains during infection
Date: 2005-01-01
Creator: Anja Forche
Georgiana May
P. T. Magee
Access: Open access
- Candida albicans is a diploid yeast with a predominantly clonal mode of reproduction, and no complete sexual cycle is known. As a commensal organism, it inhabits a variety of niches in humans. It becomes an opportunistic pathogen in immunocompromised patients and can cause both superficial and disseminated infections. It has been demonstrated that genome rearrangement and genetic variation in isolates of C. albicans are quite common. One possible mechanism for generating genome-level variation among individuals of this primarily clonal fungus is mutation and mitotic recombination leading to loss of heterozygosity (LOH). Taking advantage of a recently published genome-wide single-nucleotide polymorphism (SNP) map (A. Forche, P. T. Magee, B. B. Magee, and G. May, Eukaryot. Cell 3:705-714, 2004), an SNP microarray was developed for 23 SNP loci residing on chromosomes 5, 6, and 7. It was used to examine 21 strains previously shown to have undergone mitotic recombination at the GAL1 locus on chromosome 1 during infection in mice. In addition, karyotypes and morphological properties of these strains were evaluated. Our results show that during in vivo passaging, LOH events occur at observable frequencies, that such mitotic recombination events occur independently in different loci across the genome, and that changes in karyotypes and alterations of phenotypic characteristics can be observed alone, in combination, or together with LOH.
Two databases derived from BGC-Argo float measurements for marine biogeochemical and bio-optical applications
Date: 2017-11-22
Creator: Emanuele Organelli
Marie Barbieux
Hervé Claustre
Catherine Schmechtig
Antoine, Poteau
Annick Bricaud
Emmanuel Boss
Nathan Briggs
Giorgio Dall'Olmo
Fabrizio D'Ortenzio
Edouard Leymarie
Antoine Mangin
Grigor Obolensky
Christophe Penkerc'H
Louis Prieur
Collin Roesler
Romain Serra
Julia Uitz
Xiaogang Xing
Access: Open access
- Since 2012, an array of 105 Biogeochemical-Argo (BGC-Argo) floats has been deployed across the world's oceans to assist in filling observational gaps that are required for characterizing open-ocean environments. Profiles of biogeochemical (chlorophyll and dissolved organic matter) and optical (single-wavelength particulate optical backscattering, downward irradiance at three wavelengths, and photosynthetically available radiation) variables are collected in the upper 1000 m every 1 to 10 days. The database of 9837 vertical profiles collected up to January 2016 is presented and its spatial and temporal coverage is discussed. Each variable is quality controlled with specifically developed procedures and its time series is quality-assessed to identify issues related to biofouling and/or instrument drift. A second database of 5748 profile-derived products within the first optical depth (i.e., the layer of interest for satellite remote sensing) is also presented and its spatiotemporal distribution discussed. This database, devoted to field and remote ocean color applications, includes diffuse attenuation coefficients for downward irradiance at three narrow wavebands and one broad waveband (photosynthetically available radiation), calibrated chlorophyll and fluorescent dissolved organic matter concentrations, and single-wavelength particulate optical backscattering. To demonstrate the applicability of these databases, data within the first optical depth are compared with previously established bio-optical models and used to validate remotely derived bio-optical products. The quality-controlled databases are publicly available from the SEANOE (SEA scieNtific Open data Edition) publisher at https://doi.org/10.17882/49388 and https://doi.org/10.17882/47142 for vertical profiles and products within the first optical depth, respectively.
Are melanized feather barbs stronger?
Date: 2004-01-01
Creator: Michael Butler
Amy S. Johnson
Access: Open access
- Melanin has been associated with increased resistance to abrasion, decreased wear and lowered barb breakage in feathers. But, this association was inferred without considering barb position along the rachis as a potentially confounding variable. We examined the cross-sectional area, breaking force, breaking stress, breaking strain and toughness of melanized and unmelanized barbs along the entire rachis of a primary feather from an osprey (Pandion haliaetus). Although breaking force was higher for melanized barbs, breaking stress (force divided by cross-sectional area) was greater for unmelanized barbs. But when position was considered, all mechanical differences between melanized and unmelanized barbs disappeared. Barb breaking stress, breaking strain and toughness decreased, and breaking stiffness increased, distally along the rachis. These proximal-distal material property changes are small and seem unlikely to affect flight performance of barbs. Our observations of barb bending, breaking and morphology, however, lead us to propose a design principle for barbs. We propose that, by being thicker-walled dorso-ventrally, the barb's flexural stiffness is increased during flight; but, by allowing for twisting when loaded with dangerously high forces, barbs firstly avoid failure by bending and secondly avoid complete failure by buckling rather than rupturing.
Linear relations between N ≥ 4 supergravity and subleading-color SYM amplitudes
Date: 2012-02-27
Creator: Stephen G. Naculich
Horatiu Nastase
Howard J. Schnitzer
Access: Open access
- The IR divergences of supergravity amplitudes are less severe than those of planar SYM amplitudes, and are comparable to those subleading-color SYM amplitudes that are most subleading in the 1/N expansion, namely O(1/ε L) for L-loop amplitudes. We derive linear relations between one- and two-loop four-point amplitudes and one-loop five-point amplitudes of N ≥ 4, 5, and 6 supergravity and the most-subleading-color contributions of the analogous amplitudes of N = 0, 1, and 2 SYM theory, extending earlier results for N = 8 supergravity amplitudes. Our work relies on linear relations between N = 4 supergravity and planar SYM amplitudes that were recently derived using the double-copy property of gravity, and color-kinematic duality of gauge theories. © SISSA 2012.
Interest groups in electoral politics: 2012 in context
Date: 2012-12-01
Creator: Michael M. Franz
Access: Open access
- This paper compares the levels of ad spending from outside groups and traditional party organizations across seven federal election cycles. The data show clearly that outside groups advertised at historic levels in 2012. Such intense efforts send two important signals to students of American campaign finance. The first involves a crisis in the system of limited donations to candidates and party committees moving forward. The second resurrects an old debate in political science about whether parties or candidates should be the center of our electoral process. The paper concludes with a consideration of possible reforms that might help restore parties and candidates to the center of issue debates in competitive federal elections.
Peatlands and their role in the global carbon cycle
Date: 2011-04-20
Creator: Zicheng Yu
D. W. Beilman
S. Frolking
G. M. MacDonald
N. T., Roulet
P. Camill
D. J. Charman
Access: Open access
- Global peatlands store a very large carbon (C) pool located within a few meters of the atmosphere. Thus, peatland-atmosphere C exchange should be a major concern to global change scientists: Will large amounts of respired belowground C be released in a warmer climate, causing the climate to further warm (a positive climate feedback)? Will more C be sequestered due to increased plant growth in a warmer climate? How will land use change, fires, and permafrost thaw affect the magnitude and direction of carbon dioxide (CO ) and methane (CH ) exchange with the atmosphere? These questions remain challenging, but some significant progress has been made recently. 2 4
Lipschitzian multifunctions and a Lipschitzian inverse mapping theorem
Date: 2001-01-01
Creator: A.B. Levy
Access: Open access
One-loop SYM-supergravity relation for five-point amplitudes
Date: 2011-11-21
Creator: Stephen G. Naculich
Howard J. Schnitzer
Access: Open access
- We derive a linear relation between the one-loop five-point amplitude of N = 8 supergravity and the one-loop five-point subleading-color amplitudes of N = 4 supersymmetric Yang-Mills theory. © 2011 SISSA.