11,896 research outputs found
Ground Beetles of Islands in the Western Basin of Lake Erie and the Adjacent Mainland (Coleoptera: Carabidae, Including Cicindelini)
We report 241 species representing 63 genera of ground beetles from the islands of the western basin of Lake Erie and selected mainland sites from a 1991-93 survey, plus specimens examined in public and private collections, and previously published sources. Most species are generally distributed; however, a restricted population of Sphaeroderus schaumii schaumii we rediscovered is no doubt imperiled. Comparison of wing morphotype frequencies of the Lake Erie island species with mainland populations from studies in Ohio and Michigan support a hypothesis that vagility is of increased import in the islands. Regression and correlation analysis show a positive relationship between species number and island area, no correlation between species number and distance from the mainland and an improved fit for a multiple regression which includes collecting effort
Enhanced electron correlations, local moments, and Curie temperature in strained MnAs nanocrystals embedded in GaAs
We have studied the electronic structure of hexagonal MnAs, as epitaxial
continuous film on GaAs(001) and as nanocrystals embedded in GaAs, by Mn 2p
core-level photoemission spectroscopy. Configuration-interaction analyses based
on a cluster model show that the ground state of the embedded MnAs nanocrystals
is dominated by a d5 configuration that maximizes the local Mn moment.
Nanoscaling and strain significantly alter the properties of MnAs. Internal
strain in the nanocrystals results in reduced p-d hybridization and enhanced
ionic character of the Mn-As bonding interactions. The spatial confinement and
reduced p-d hybridization in the nanocrystals lead to enhanced d-electron
localization, triggering d-d electron correlations and enhancing local Mn
moments. These changes in the electronic structure of MnAs have an advantageous
effect on the Curie temperature of the nanocrystals, which is measured to be
remarkably higher than that of bulk MnAs.Comment: 4 figures, 2 table
Subsurface processes generated by bore-driven swash on coarse-grained beaches
Peer reviewedPublisher PD
Electronic band structure of cubic CdSe determined by angle-resolved photoemission: Cd 4d and valence-level states
The valence-band structure of epitaxially grown cubic CdSe along the ÎâKâX direction is determined experimentally using angle-resolved photoelectron spectroscopy on the basis of the free-electron final band model. In the upper valence band the three main branches are determined from normal emission spectra over the range from 15 to 90 eV photon energy, and are found to conform with the general shape expected from this class of materials. The Cd 4d level exhibits considerable dispersion, which is reflected in the spectra. The experimental bands are compared with several calculations based on different schemes, and best agreement with respect to dispersion and binding energies is found for a calculation that takes into account electron self-interaction and relaxation
CORE Technology and Exact Hamiltonian Real-Space Renormalization Group Transformations
The COntractor REnormalization group (CORE) method, a new approach to solving
Hamiltonian lattice systems, is presented. The method defines a systematic and
nonperturbative means of implementing Kadanoff-Wilson real-space
renormalization group transformations using cluster expansion and contraction
techniques. We illustrate the approach and demonstrate its effectiveness using
scalar field theory, the Heisenberg antiferromagnetic chain, and the
anisotropic Ising chain. Future applications to the Hubbard and t-J models and
lattice gauge theory are discussed.Comment: 65 pages, 9 Postscript figures, uses epsf.st
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