8,103 research outputs found
Power loss and electromagnetic energy density in a dispersive metamaterial medium
The power loss and electromagnetic energy density of a metamaterial
consisting of arrays of wires and split-ring resonators (SRRs) are
investigated. We show that a field energy density formula can be derived
consistently from both the electrodynamic (ED) approach and the equivalent
circuit (EC) approach. The derivations are based on the knowledge of the
dynamical equations of the electric and magnetic dipoles in the medium and the
correct form of the power loss. We discuss the role of power loss in
determining the form of energy density and explain why the power loss should be
identified first in the ED derivation. When the power loss is negligible and
the field is harmonic, our energy density formula reduces to the result of
Landau's classical formula. For the general case with finite power loss, our
investigation resolves the apparent contradiction between the previous results
derived by the EC and ED approaches.Comment: 10 pages, 1 figure, Submitted to Phys. Rev.
Introduction to the Special Issue: Genome-Wide Association Studies
Introduction to the Special Issue: Genome-Wide Association StudiesComment: Published in at http://dx.doi.org/10.1214/09-STS310 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Unusual Glass-Forming Ability of Bulk Amorphous Alloys Based on Ordinary Metal Copper
We report the unusual glass-forming ability (GFA) of a family of Cu-based alloys, Cu46Zr47–xAl7Yx (0<x<=10, in at. %), and investigate the origin of this unique property. By an injection mold casting method, these alloys can be readily solidified into amorphous structures with the smallest dimension ranging from 4 mm up to 1 cm without detectable crystallinity. Such superior GFA is found primarily due to the alloying effect of Y, which lowers the alloy liquidus temperature and brings the composition closer to a quaternary eutectic. Other beneficial factors including appropriate atomic-size mismatch and large negative heat of mixing among constituent elements are also discussed
Isoconfigurational Elastic Constants and Liquid Fragility of a Bulk Metallic Glass Forming Alloy
Samples of Zr46.25Ti8.25Cu7.5Ni10Be27.5 were isothermally annealed and quenched near the glass transition temperature and studied by the pulse-echo overlap technique. The shear modulus G of the samples shows a strong reversible dependence on annealing temperatures and, thus, on the specific configurational potential energy of the equilibrium liquid. The low-T dependence of G of the configurationally frozen glasses shows linear temperature dependence as expected by Debye-GrĂĽneisen theory. The T dependence of G in the liquid state is directly related to the viscosity and fragility of the liquid
Minimum Energy Path to Membrane Pore Formation and Rupture
We combine dynamic self-consistent field theory with the string method to calculate the minimum energy path to membrane pore formation and rupture. In the regime where nucleation can occur on experimentally relevant time scales, the structure of the critical nucleus is between a solvophilic stalk and a locally thinned membrane. Classical nucleation theory fails to capture these molecular details and significantly overestimates the free energy barrier. Our results suggest that thermally nucleated rupture may be an important factor for the low rupture strains observed in lipid membranes
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