348 research outputs found

    Domain Wall Resistance in Perpendicular (Ga,Mn)As: dependence on pinning

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    We have investigated the domain wall resistance for two types of domain walls in a (Ga,Mn)As Hall bar with perpendicular magnetization. A sizeable positive intrinsic DWR is inferred for domain walls that are pinned at an etching step, which is quite consistent with earlier observations. However, much lower intrinsic domain wall resistance is obtained when domain walls are formed by pinning lines in unetched material. This indicates that the spin transport across a domain wall is strongly influenced by the nature of the pinning.Comment: 9 pages, 3 figure

    Automatic segmentation, detection and quantification of coronary artery stenoses on CTA

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    Accurate detection and quantification of coronary artery stenoses is an essential requirement for treatment planning of patients with suspected coronary artery disease. We present a method to automatically detect and quantify coronary artery stenoses in computed tomography coronary angiography. First, centerlines are extracted using a two-point minimum cost path approach and a subsequent refinement step. The resulting centerlines are used as an initialization for lumen segmentation, performed using graph cuts. Then, the expected diameter of the healthy lumen is estimated by applying robust kernel regression to the coronary artery lumen diameter profile. Finally, stenoses are detected and quantified by computing the difference between estimated and expected diameter profiles. We evaluated our method using the data provided in the Coronary Artery Stenoses Detection and Quantification Evaluation Framework. Using 30 testing datasets, the method achieved a detection sensitivity of 29 % and a positive predi

    Phylogenetic and non-phylogenetic structure in trophic links between gall-forming herbivores and their parasitoid natural enemies.

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    Revealing processes that structure species interactions is central to understanding community assembly and dynamics. Species interact via their phenotypes, but identifying and quantifying the traits that structure species-specific interactions (links) can be challenging. Where these traits show phylogenetic signal, however, link properties are predictable using models that incorporate phylogenies in place of trait data. We analysed variation in link richness, frequency, and identity in a multi-site dataset of interactions between host oak cynipid galls and parasitoid natural enemies, using a Bayesian mixed modelling framework allowing concurrent fitting of terms for phylogenies of both trophic levels. In both link incidence (presence/absence) and link frequency datasets, we identified strong signatures of cophylogeny (related parasitoids attack related host galls) and patterns independent of either phylogeny. Our results are robust to simulations of substantially reduced sample completeness, and are consistent with the structuring of trophic interactions by a combination of phylogenetically conserved and convergently evolving traits at both trophic levels. We discuss our results in light of phenotypic traits thought to structure gall-parasitoid interactions and wider applications of this approach, including inference of underlying community assembly processes and prediction of economically important trophic interactions

    Phylogenetic and non-phylogenetic structure in trophic links between gall-forming herbivores and their parasitoid natural enemies.

    Get PDF
    Revealing processes that structure species interactions is central to understanding community assembly and dynamics. Species interact via their phenotypes, but identifying and quantifying the traits that structure species-specific interactions (links) can be challenging. Where these traits show phylogenetic signal, however, link properties are predictable using models that incorporate phylogenies in place of trait data. We analysed variation in link richness, frequency, and identity in a multi-site dataset of interactions between host oak cynipid galls and parasitoid natural enemies, using a Bayesian mixed modelling framework allowing concurrent fitting of terms for phylogenies of both trophic levels. In both link incidence (presence/absence) and link frequency datasets, we identified strong signatures of cophylogeny (related parasitoids attack related host galls) and patterns independent of either phylogeny. Our results are robust to simulations of substantially reduced sample completeness, and are consistent with the structuring of trophic interactions by a combination of phylogenetically conserved and convergently evolving traits at both trophic levels. We discuss our results in light of phenotypic traits thought to structure gall-parasitoid interactions and wider applications of this approach, including inference of underlying community assembly processes and prediction of economically important trophic interactions

    A rapid and cheap protocol for preparation of PCR templates in peanut

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    This paper describes a simple, low cost and reliable DNA template preparation protocol for polymerase chain reaction (PCR) using immature leaves from peanut seeds or leaves from field-grown plants. The technique may find wide utility in studies involving PCR-based molecular markers, rapid screening for transformants and gene cloning

    Structure and composition of tritrophic communities associated with Fagaceae-feeding cynipid gallwasps in Sichuan, China

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    We provide the first description and analysis of species-rich communities of Fagaceae host plants, cynipid gall inducers and Hymenopteran parasitoids from two sites in western Sichuan, China. We use quantified interaction data to test the hypothesis that metabolically intimate cynipid-Fagaceae interactions are more specialised, resulting in more modular networks and stronger signatures of turnover than nestedness for beta diversity, than associations between parasitoids and Fagaceae. Rearing of nearly 27,000 cynipid gall specimens from 22 host plant species in Castanea, Castanopsis, Lithocarpus and Quercus (sections Cerris, Cyclobalanopsis, Ilex and Quercus) yielded 168 morphologically distinct cynipid gall morphotypes, and 3800 parasitoids in 67 morphospecies. The Sichuan parasitoid assemblage is similar in composition to cynipid-centred communities in the Western Palearctic and Nearctic. All of our predictions were confirmed. We discuss our findings in light of the processes thought to structure tritrophic interactions centred on gall inducing insect herbivores

    Superconductivity in carbon nanotube ropes

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    We investigate the conditions in which superconductivity may develop in ropes of carbon nanotubes. It is shown that the interaction among a large number of metallic nanotubes favors the appearance of a metallic phase in the ropes, intermediate between respective phases with spin-density-wave and superconducting correlations. These arise in samples with about 100 metallic nanotubes or more, where the long-range Coulomb interaction is very effectively reduced and it may be overcome by the attractive interaction from the exchange of optical phonons within each nanotube. We estimate that the probability for the tunneling of Cooper pairs between neighboring nanotubes is much higher than that for single electrons in a disordered rope. The effect of pair hopping is therefore what establishes the intertube coherence, and the tunneling amplitude of the Cooper pairs dictates the scale of the transition to the superconducting state.Comment: 12 page

    Discovery of large genomic inversions using long range information

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    Background: Although many algorithms are now available that aim to characterize different classes of structural variation, discovery of balanced rearrangements such as inversions remains an open problem. This is mainly due to the fact that breakpoints of such events typically lie within segmental duplications or common repeats, which reduces the mappability of short reads. The algorithms developed within the 1000 Genomes Project to identify inversions are limited to relatively short inversions, and there are currently no available algorithms to discover large inversions using high throughput sequencing technologies. Results: Here we propose a novel algorithm, Valor, to discover large inversions using new sequencing methods that provide long range information such as 10X Genomics linked-read sequencing, pooled clone sequencing, or other similar technologies that we commonly refer to as long range sequencing. We demonstrate the utility of Valor using both pooled clone sequencing and 10X Genomics linked-read sequencing generated from the genome of an individual from the HapMap project (NA12878). We also provide a comprehensive comparison of Valor against several state-of-the-art structural variation discovery algorithms that use whole genome shotgun sequencing data. Conclusions: In this paper, we show that Valor is able to accurately discover all previously identified and experimentally validated large inversions in the same genome with a low false discovery rate. Using Valor, we also predicted a novel inversion, which we validated using fluorescent in situ hybridization. Valor is available at https://github.com/BilkentCompGen/Valor. © 2017 The Author(s)
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