6,704 research outputs found
Density functional calculations of the electronic structure and magnetic properties of the hydrocarbon K3picene superconductor near the metal-insulator transition
We have investigated the electronic structures and magnetic properties of of
K3picene, which is a first hydrocarbon superconductor with high transition
temperature T_c=18K. We have shown that the metal-insulator transition (MIT) is
driven in K3picene by 5% volume enhancement with a formation of local magnetic
moment. Active bands for superconductivity near the Fermi level E_F are found
to have hybridized character of LUMO and LUMO+1 picene molecular orbitals.
Fermi surfaces of K3picene manifest neither prominent nesting feature nor
marked two-dimensional behavior. By estimating the ratio of the Coulomb
interaction U and the band width W of the active bands near E_F, U/W, we have
demonstrated that K3picene is located in the vicinity of the Mott transition.Comment: 5 pages, 5 figure
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An ontology for cell types.
We describe an ontology for cell types that covers the prokaryotic, fungal, animal and plant worlds. It includes over 680 cell types. These cell types are classified under several generic categories and are organized as a directed acyclic graph. The ontology is available in the formats adopted by the Open Biological Ontologies umbrella and is designed to be used in the context of model organism genome and other biological databases. The ontology is freely available at http://obo.sourceforge.net/ and can be viewed using standard ontology visualization tools such as OBO-Edit and COBrA.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Quasi-dark Mode in a Metamaterial for Analogous Electromagnetically-induced Transparency
We study a planar metamaterial supporting electromagnetically-induced
transparency (EIT)-like effect by exploiting the coupling between bright and
quasi-dark eigenmodes. The specific design of such a metamaterial consists of a
cut-wire (CW) and a single-gap split-ring resonator (SRR). From the numerical
and the analytical results we demonstrate that the response of SRR, which is
weakly excited by external electric field, is mitigated to be a quasi-dark
eigenmode in the presence of strongly radiative CW. This result suggests more
relaxed conditions for the realization of devices utilizing the EIT-like
effects in metamaterial, and thereby widens the possibilities for many
different structural implementations.Comment: 11 pages, 4 figure
Two-Temperature Intracluster Medium in Merging Clusters of Galaxies
We investigate the evolution of intracluster medium during a cluster merger,
explicitly considering the relaxation process between the ions and electrons by
N-body and hydrodynamical simulations. When two subclusters collide each other,
a bow shock is formed between the centers of two substructures and propagate in
both directions along the collision axis. The shock primarily heats the ions
because the kinetic energy of an ion entering the shock is larger than that of
an electron by the ratio of masses. In the post-shock region the energy is
transported from the ions to electrons via Coulomb coupling. However, since the
energy exchange timescale depends both on the gas density and temperature,
distribution of electron temperature becomes more complex than that of the
plasma mean temperature, especially in the expanding phase. After the collision
of two subclusters, gas outflow occurs not only along the collision axis but
also in its perpendicular direction. The gas which is originally located in the
central part of the subclusters moves both in the parallel and perpendicular
directions. Since the equilibrium timescale of the gas along these directions
is relatively short, temperature difference between ions and electrons is
larger in the directions tilted by the angles of with respect to
the collision axis. The electron temperature could be significantly lower that
the plasma mean temperature by at most. The significance of our
results in the interpretation of X-ray observations is briefly discussed.Comment: 20 pages, 11 figures, Accepted for publication in Ap
What Drives Management Accounting Innovations? A Survey of Activity-Based Costing Journal Publications
The purpose of this study is to examine the driving forces behind the diffusion of an important management accounting innovation, activity-based costing (ABC). Driving forces are analyzed within five main aspects (volume, journal field, journal type, author type, and content type) through a survey of English-language journal publications relating to ABC and its recent iteration, Time-Driven Activity-Based Costing (TDABC), between 1988 and 2019. Employing linear regression and Mann-Kendall statistical analyses, our results find some diffusion patterns. First, ABC/TDABC initially appears in business management then spread to non-business management fields, in particular to the bio/medical field. Second, driving forces behind ABC/TDABC diffusion have changed. At the beginning of the spread of ABC (1988-2003), it shows a push by academics and consultants. However from 2004 to 2019, there is a clear pull by practitioners, in particular medical doctors in the bio/medical field who see a need for this innovative tool. Third, academics and consultants attempt to spread ABC/TDABC to generate more research activities and business, whilst practitioners’ quests for ABC/TDABC are driven by their intrinsic needs and external demands. The longitudinal picture of ABC diffusion may shed light on how to enable such a management accounting innovation to achieve its long term success
The Origin of the Silicate Emission Features in the Seyfert 2 Galaxy, NGC 2110
The unified model of active galactic nuclei (AGN) predicts silicate emission
features at 10 and 18 microns in type 1 AGN, and such features have now been
observed in objects ranging from distant QSOs to nearby LINERs. More
surprising, however, is the detection of silicate emission in a few type 2 AGN.
By combining Gemini and Spitzer mid-infrared imaging and spectroscopy of NGC
2110, the closest known Seyfert 2 galaxy with silicate emission features, we
can constrain the location of the silicate emitting region to within 32 pc of
the nucleus. This is the strongest constraint yet on the size of the silicate
emitting region in a Seyfert galaxy of any type. While this result is
consistent with a narrow line region origin for the emission, comparison with
clumpy torus models demonstrates that emission from an edge-on torus can also
explain the silicate emission features and 2-20 micron spectral energy
distribution of this object. In many of the best-fitting models the torus has
only a small number of clouds along the line of sight, and does not extend far
above the equatorial plane. Extended silicate-emitting regions may well be
present in AGN, but this work establishes that emission from the torus itself
is also a viable option for the origin of silicate emission features in active
galaxies of both type 1 and type 2.Comment: ApJL, accepte
On the Age and Binarity of Fomalhaut
The nearby (d = 7.7 pc) A3V star Fomalhaut is orbited by a resolved dusty
debris disk and a controversial candidate extrasolar planet. The commonly cited
age for the system (200+-100 Myr) from Barrado y Navascues et al. (1997) relied
on a combination of isochronal age plus youth indicators for the K4V common
proper motion system TW PsA. TW PsA is 1.96 deg away from Fomalhaut, and was
first proposed as a companion by Luyten (1938), but the physicality of the
binarity is worth testing with modern data. I demonstrate that TW PsA is
unequivocally a physical stellar companion to Fomalhaut, with true separation
0.280+0.019-0.012 pc (57.4+3.9-2.5 kAU) and sharing velocities within 0.1+-0.5
km/s -- consistent with being a bound system. Hence, TW PsA should be
considered "Fomalhaut B". Combining modern HR diagram constraints with four
sets of evolutionary tracks, and assuming the star was born with protosolar
composition, I estimate a new isochronal age for Fomalhaut of 450+-40 Myr and
mass of 1.92+-0.02 Msun. Various stellar youth diagnostics are re-examined for
TW PsA. The star's rotation, X-ray emission, and Li abundances are consistent
with approximate ages of 410, 380, and 360 Myr, respectively, yielding a
weighted mean age of 400+-70 Myr. Combining the independent ages, I estimate a
mean age for the Fomalhaut-TW PsA binary of 440+-40 Myr. The older age implies
that substellar companions of a given mass are approximately one magnitude
fainter at IR wavelengths than previously assumed.Comment: ApJ Letters, in press, 5 pages in emulateapj, 1 figure. Minor edits.
Difference in velocity between Fomalhaut and TW PsA corrected to be 0.1+-0.5
km/
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