25,549 research outputs found
Block Spin Ground State and 3-Dimensionality of (K,Tl)FeSe
The magnetic properties and electronic structure of (K,Tl)y Fe1.6 Se2 is
studied using first-principles calculations. The ground state is checkerboard
antiferromagnetically coupled blocks of the minimal Fe4 squares, with a large
block spin moment ~11.2{\mu}B . The magnetic interactions could be modelled
with a simple spin model involving both the inter- and intra-block, as well as
the n.n. and n.n.n. couplings. The calculations also suggest a metallic ground
state except for y = 0.8 where a band gap ~400 - 550 meV opens, showing an
antiferromagnetic insulator ground state for (K,Tl)0.8 Fe1.6 Se2 . The
electronic structure of the metallic (K,Tl)y Fe1.6 Se2 is highly 3-dimensional
with unique Fermi surface structure and topology. These features indicate that
the Fe-vacancy ordering is crucial to the physical properties of (K,Tl)y Fe2-x
Se2 .Comment: Magnetic coupling constants double checked, journal ref. adde
Chung-Li, Taiwan dual mode (Doppler and spaced antenna) VHF radar: Preliminary specifications
A major unresolved question in the field of atmospheric research using VHF radar techniques is the relative merit of the two most widely used systems. These systems are the Doppler method and the spaced antenna method. It has been suggested that one radar of each type be operated side by side for a direct comparison of the two techniques. This duplication of effort is not cost effective. The major components of both systems are identical, and one radar could be operated in both modes by proper design of a suitable antenna system and by proper data analysis. The Chung-Li radar will be able to switch between modes on a time scale of seconds and is the first VHF radar to be able to directly compare the Doppler data with spaced antenna data. The system will have performance comparable with the present SOUSY spaced antenna system and will provide mesospheric data in addition to stratospheric and tropospheric data. The major specifications of the Chung-Li radar are given
Development of affinity-based delivery of NGF from a chondroitin sulfate biomaterial.
Chondroitin sulfate is a major component of the extracellular matrix in both the central and peripheral nervous systems. Chondroitin sulfate is upregulated at injury, thus methods to promote neurite extension through chondroitin sulfate-rich matrices and synthetic scaffolds are needed. We describe the use of both chondroitin sulfate and a novel chondroitin sulfate-binding peptide to control the release of nerve growth factor. Interestingly, the novel chondroitin sulfate-binding peptide enhances the controlled release properties of the chondroitin sulfate gels. While introduction of chondroitin sulfate into a scaffold inhibits primary cortical outgrowth, the combination of chondroitin sulfate, chondroitin sulfate-binding peptide and nerve growth factor promotes primary cortical neurite outgrowth in chondroitin sulfate gels
Avalanche to streamer transition in particle simulations
The avalanche to streamer transition is studied and illustrated in a particle
model. The results are similar to those of fluid models. However, when
super-particles are introduced, numerical artefacts become visible. This
underscores the need of models that are hybrid in space.Comment: 2 pages, 1 figur
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