90,737 research outputs found
Phase controlled superconducting proximity effect probed by tunneling spectroscopy
Using a dual-mode STM-AFM microscope operating below 50mK we measured the
Local Density of States (LDoS) along small normal wires connected at both ends
to superconductors with different phases. We observe that a uniform minigap can
develop in the whole normal wire and in the superconductors near the
interfaces. The minigap depends periodically on the phase difference. The
quasiclassical theory of superconductivity applied to a simplified 1D model
geometry accounts well for the data.Comment: Accepted for publication in Physical Review Letter
Determination of population structure and stock composition of chum salmon (Oncorhynchus keta) in Russia determined with microsatellites
Variation at 14 microsatellite loci was examined in 34 chum
salmon (Oncorhynchus keta) populations from Russia and evaluated for its use in the determination of population
structure and stock composition in simulated mixed-stock fishery samples. The genetic differentiation index (Fst) over all populations and loci was 0.017, and individual locus values ranged from 0.003 to 0.054. Regional population structure was observed, and populations from Primorye, Sakhalin Island, and northeast Russia were the most distinct. Microsatellite variation provided evidence of a more fine-scale population structure than those that had previously been demonstrated with other genetic-based markers. Analysis of simulated mixed-stock samples indicated that accurate and precise regional estimates of stock composition were produced when the microsatellites
were used to estimate stock compositions. Microsatellites can be used to determine stock composition in geographically separate Russian coastal chum salmon fisheries and provide a greater resolution of stock
composition and population structure than that previously provided with other techniques
A model for atomic and molecular interstellar gas: The Meudon PDR code
We present the revised ``Meudon'' model of Photon Dominated Region (PDR
code), presently available on the web under the Gnu Public Licence at:
http://aristote.obspm.fr/MIS. General organisation of the code is described
down to a level that should allow most observers to use it as an interpretation
tool with minimal help from our part. Two grids of models, one for low
excitation diffuse clouds and one for dense highly illuminated clouds, are
discussed, and some new results on PDR modelisation highlighted.Comment: accepted in ApJ sup
Optical Morphology Evolution of Infrared Luminous Galaxies in GOODS-N
We combine optical morphologies and photometry from HST, redshifts from Keck,
and mid-infrared luminosities from Spitzer for an optically selected sample
of~800 galaxies in GOODS-N to track morphology evolution of infrared luminous
galaxies (LIRGs) since redshift z=1. We find a 50% decline in the number of
LIRGs from z~1 to lower redshift, in agreement with previous studies. In
addition, there is evidence for a morphological evolution of the populations of
LIRGs. Above z=0.5, roughly half of all LIRGs are spiral, the
peculiar/irregular to spiral ratio is ~0.7, and both classes span a similar
range of L_{IR} and M_B. At low-z, spirals account for one-third of LIRGs, the
peculiar to spiral fraction rises to 1.3, and for a given M_B spirals tend to
have lower IR luminosity than peculiars. Only a few percent of LIRGs at any
redshift are red early-type galaxies. For blue galaxies (U-B < 0.2), M_B is
well correlated with log(L_{IR}) with an RMS scatter (about a bivariate linear
fit) of ~0.25 dex in IR luminosity. Among blue galaxies that are brighter than
M_B = -21, 75% are LIRGs, regardless of redshift. These results can be
explained by a scenario in which at high-z, most large spirals experience an
elevated star formation rate as LIRGs. Gas consumption results in a decline of
LIRGs, especially in spirals, to lower redshifts.Comment: 6 pages, 2 figures, accepted ApJ
Galois coverings of weakly shod algebras
We investigate the Galois coverings of weakly shod algebras. For a weakly
shod algebra not quasi-tilted of canonical type, we establish a correspondence
between its Galois coverings and the Galois coverings of its connecting
component. As a consequence, we show that a weakly shod algebra is simply
connected if and only if its first Hochschild cohomology group vanishes.Comment: Some references were added. The proof of Lemma 6.5 was modifie
Micromechanics of sea urchin spines
The endoskeletal structure of the Sea Urchin, Centrostephanus rodgersii, has numerous long spines whose known functions include locomotion, sensing, and protection against predators. These spines have a remarkable internal microstructure and are made of single-crystal calcite. A finite-element model of the spine's unique porous structure, based on micro-computed tomography (microCT) and incorporating anisotropic material properties, was developed to study its response to mechanical loading. Simulations show that high stress concentrations occur at certain points in the spine's architecture; brittle cracking would likely initiate in these regions. These analyses demonstrate that the organization of single-crystal calcite in the unique, intricate morphology of the sea urchin spine results in a strong, stiff and lightweight structure that enhances its strength despite the brittleness of its constituent material
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