201 research outputs found
Strain effects on electronic structure of the iron selenide superconductor
The influence of various strains on crystal and electronic structures of
superconducting FeSe has been studied ab initio. We consider changes in the
Fermi surface nesting with a vector Q=(0.5,0.5)*(2\pi /a) as crucial for rising
superconductivity (SC) mediated by spin-fluctuations (SF). Our results indicate
that the c-axis strained FeSe exhibits the most imperfect nesting, which
enhances SF and, hence, also SC. In turn, the ab-plane compressive strain
slightly weakens this} nesting while the tensile strain destroys it completely.
These findings are consistent with reported earlier experimental dependencies
of superconducting transition temperatures on strain in FeSe thin films
Peering into the Campaign Finance Law Crystal Ball: Guiding Principles for the Future of the BCRA and "Issue Advocacy" in Citizens United and Beyond
This is the published version
The Pressure Effects on Electronic Structure of Iron Chalcogenide Superconductors FeSeTe
We study the electronic structure of iron-based superconductors
FeSeTe within the density functional theory. We pay particular
attention to the pressure effects on the Fermi surface (FS) topology, which
seem to be correlated with a critical superconducting temperature TC of iron
chalcogenides and pnictides. A reduction of the FS nesting between hole and
electron cylinders with increasing pressure is observed, which can lead to
higher values of TC . The tellurium substitution into selenium sites yields FS
changes similar to the pressure effect.Comment: 4 pages, 6 figures, 1 tabl
Inferences on Sicilian Mesolithic subsistence patterns from cross-sectional geometry and entheseal changes
Using cross-sectional geometry (CSG), entheseal changes (ECs), and presence of external auditory meatus exostosis (EAE), this study tests the hypothesis—based on isotopic and zooarchaeological evidence—that in the Sicilian Mesolithic terrestrial rather than marine resources were predominantly exploited, in substantial continuity with previous Epigravettian hunters. Results show similarities in the general frequency of ECs—a rough proxy for overall activity—with Late Pleistocene hunters, in contrast with Mesolithic coastal foragers or Neolithic herders/farmers. Yet, CSG suggests that this possible continuity in the type of resources exploited was accompanied by a behavioral change, and in particular the abandonment of the throwing technology, possibly in favor of new tools such as traps and the bow and arrow. In fact, the dramatic decrease in humeral bilateral asymmetry documented at a European level with the Pleistocene-Holocene transition can be found also in the Sicilian Mesolithic. Results for the lower limb appear compatible with a certain degree of terrestrial mobility in a rugged environment. The frequency of EAE suggests that activities related to water were present but not common; however, their prominence is difficult to determine given the small sample size. The pattern of information provided by the proxies for activity used here is complex and partially contrasting, but has the potential to integrate and enrich archeological methods and biochemical approaches. This study corroborates a varied scenario of continuity and discontinuity in subsistence at the Pleistocene-Holocene transition, and highlights the importance of a regional bioarchaeological approach of human biological and behavioral adaptations
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