27,821 research outputs found
Ground-state configurations in ferromagnetic nanotori
Magnetization ground states are studied in toroidal nanomagnets. The
energetics associated to the ferromagnetic, vortex and onion-like
configurations are explicitly computed. The analysis reveals that the vortex
appears to be the most prominent of such states, minimizing total energy in
every torus with internal radius (for Permalloy). For
the vortex remains the most favorable pattern whenever
( is the torus external radius and is
the exchange length), being substituted by the ferromagnetic state whenever
.Comment: 16 pages, 9 figures, 3 apendices, Revtex forma
Minimilho: mais uma opção para o produtor brasileiro e para a indĂşstria de conservas alimentĂcias.
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Effect of stent position on flow characteristics in a cerebral aneurysm
The position of an intracranial stent in relation to the ostium of a cerebral aneurysm can
significantly affect the blood flow characteristics through the ostium and inside the aneurysm.
An idealised cerebral artery and aneurysm were simulated with a pulsatile flow. Simulation
results show that the effect on mass inflow between two stent positions is about 20%
whereas the difference in the porosity effect of the pattern at these two positions is around
3%. The remainder may be attributed to differences in flow velocity profile across the stent
into the aneurysm. The implications for clinical practice are an important consideration as the
surgeon may place the stent in any position between the two investigated and hence this will
lead to markedly different stent performance. Therefore, computational tools that take into
account the variability of stent placement will be valuable for assisting surgical planning
Universal theory of nonlinear Luttinger liquids
One-dimensional quantum fluids are conventionally described by using an
effective hydrodynamic approach known as Luttinger liquid theory. As the
principal simplification, a generic spectrum of the constituent particles is
replaced by a linear one, which leads to a linear hydrodynamic theory. We show
that to describe the measurable dynamic response functions one needs to take
into account the nonlinearity of the generic spectrum and thus of the resulting
quantum hydrodynamic theory. This nonlinearity leads, for example, to a
qualitative change in the behavior of the spectral function. The universal
theory developed in this article is applicable to a wide class of
one-dimensional fermionic, bosonic, and spin systems.Comment: final published version with supporting online materia
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