75 research outputs found
Energy landscape of relaxed amorphous silicon
We analyze the structure of the energy landscape of a well-relaxed 1000-atom
model of amorphous silicon using the activation-relaxation technique (ART
nouveau). Generating more than 40,000 events starting from a single minimum, we
find that activated mechanisms are local in nature, that they are distributed
uniformly throughout the model and that the activation energy is limited by the
cost of breaking one bond, independently of the complexity of the mechanism.
The overall shape of the activation-energy-barrier distribution is also
insensitive to the exact details of the configuration, indicating that
well-relaxed configurations see essentially the same environment. These results
underscore the localized nature of relaxation in this material.Comment: 8 pages, 12 figure
The genomic basis of the plant island syndrome in Darwin’s giant daisies
The repeated, rapid and often pronounced patterns of evolutionary divergence observed in insular plants, or the ‘plant island syndrome’, include changes in leaf phenotypes, growth, as well as the acquisition of a perennial lifestyle. Here, we sequence and describe the genome of the critically endangered, Galápagos-endemic species Scalesia atractyloides Arnot., obtaining a chromosome-resolved, 3.2-Gbp assembly containing 43,093 candidate gene models. Using a combination of fossil transposable elements, k-mer spectra analyses and orthologue assignment, we identify the two ancestral genomes, and date their divergence and the polyploidization event, concluding that the ancestor of all extant Scalesia species was an allotetraploid. There are a comparable number of genes and transposable elements across the two subgenomes, and while their synteny has been mostly conserved, we find multiple inversions that may have facilitated adaptation. We identify clear signatures of selection across genes associated with vascular development, growth, adaptation to salinity and flowering time, thus finding compelling evidence for a genomic basis of the island syndrome in one of Darwin’s giant daisies
Combustible et conditions stationnelles dans un paysage forestier isolé et non géré du centre de l’Oregon
First measurement of the 2H(6He,7Li)n angular distribution and proton spectroscopic factor in 7Li
Induction of hepatoma in rainbow trout Salmo gaivdneri Richardson by the egg bath technique
XMDS 2.0
We outline a new version of the XMDS code-generator for computational simulations, with many new features and applications to quantum-atom optics
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