2,013 research outputs found
Vortex Lines or Vortex-Line Chains at the Lower Critical Field in Anisotropic Superconductors?
The vortex state at the lower critical field, H_{c1}, in clean anisotropic
superconductors placed in an external field tilted with respect to the axis of
anisotropy (c-axis) is considered assuming two possible arrangements: dilute
vortex-lines or dilute vortex-line chains. By minimizing the Gibbs free
energies in the London limit for each possibility we obtain the corresponding
lower critical fields as a function of the tilt angle. The equilibrium
configuration at H_{c1} for a given tilt angle is identified with that for
which H_{c1} is the smallest. We report results for parameter values typical of
strong and moderate anisotropy. We find that for strong anisotropy vortex-line
chains are favored for small tilt angles (< 7.9^o) and that at 7.9^o there is
coexistence between this configuration and a vortex-line one. For moderate
anisotropy we find that there is little difference between the vortex-line and
the vortex-chain lower critical fields.Comment: 5 pages, 4 figures, accepted to appear on Physica
SAFT-Îł force field for the simulation of molecular fluids: 8. hetero-group coarse-grained models of perfluoroalkylalkanes assessed with new vapour-liquid interfacial tension data
The air-liquid interfacial behaviour of linear perfluoroalkylalkanes (PFAAs) is reported through a combined experimental and computer simulation study. The surface tensions of seven liquid PFAAs (perfluorobutylethane, F4H2; perfluorobutylpentane, F4H5; perfluorobutylhexane, F4H6, perfluorobutyloctane, F4H8; perfluorohexylethane, F6H2; perfluorohexylhexane, F6H6; and perfluorohexyloctane, F6H8) are experimentally determined over a wide temperature range (276 to 350 K). The corresponding surface thermodynamic properties and the critical temperatures of the studied compounds are estimated from the temperature dependence of the surface tension. Experimental density and vapour pressure data are employed to parameterize a generic heteronuclear coarse-grained intermolecular potential of the SAFT- Îł family for PFAAs. The resulting force field is used in direct molecular dynamics simulations to predict with quantitative agreement the experimental tensions and to explore the conformations of the molecules in the interfacial region revealing a preferential alignment of the PFAA molecules towards the interface and an enrichment of the perfluoro-groups at the outer interface region
Supporting the Voice of People with Disabilities in Kenya, Uganda and Jordan
Research methods need to be adapted to the cultural
context and traditions with which participants are
familiar. Limited work has been attempted to explore
ways to engage people with disabilities in low resource
settings. In this paper we present methods used in two
research projects that engage and actively support the
voice of people with disabilities living in low resource
settings. We discuss which methods have worked well
and which not, with recommendations based on our
experience and the research results
Individuality over function: the role of technology in disability identity
When designing or investigating technology use among
people with disabilities, researchers often overstate the
importance of functional aspects at the expenses of
identity. We present three case studies that showcase
how people with disabilities use, or aspire to use,
technology to advertise, reframe or hide their
identities
Super collimation of the radiation by a point source in a uniaxial wire medium
We investigate the radiation properties of a short horizontal dipole embedded
in a uniaxial wire medium. It is shown that the uniaxial wire medium enables a
super-collimation of the dipole radiation such that the radiation pattern has a
singularity and the radiated fields are non-diffractive in the broadside
direction. We derive a closed analytical formula for the power radiated by the
dipole. Our theory demonstrates that as a consequence of the ultrahigh density
of photonic states of the nanowire array, the power radiated by the dipole is
strongly enhanced as compared to that emitted in the dielectric host material
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