182,276 research outputs found
Palliative balloon dilation of native coarctation of the aorta in a preterm infant
The role of balloon dilation for native coarctation in neonates is controversial, due to
the relatively high recurrence rate. Balloon dilation may however provide adequate
palliation in preterm infants, by relieving symptoms and allowing somatic growth until
definitive surgical repair can be performed. We report successful balloon angioplasty,
on 2 occasions, in a preterm neonate with coarctation of the aorta and associated left
ventricular cardiomyopathy.peer-reviewe
Dipole-induced vortex ratchets in superconducting films with arrays of micromagnets
We investigate the transport properties of superconducting films with
periodic arrays of in-plane magnetized micromagnets. Two different magnetic
textures are studied: a square array of magnetic bars and a close-packed array
of triangular microrings. As confirmed by MFM imaging, the magnetic state of
both systems can be adjusted to produce arrays of almost point-like magnetic
dipoles. By carrying out transport measurements with ac drive, we observed
experimentally a recently predicted ratchet effect induced by the interaction
between superconducting vortices and the magnetic dipoles. Moreover, we find
that these magnetic textures produce vortex-antivortex patterns, which have a
crucial role on the transport properties of this hybrid system.Comment: 4 pages, 4 figure
Forming the Moon from terrestrial silicate-rich material
Recent high-precision measurements of the isotopic composition of lunar rocks
demonstrate that the bulk silicate Earth and the Moon show an unexpectedly high
degree of similarity. This is inconsistent with one of the primary results of
classic dynamical simulations of the widely accepted giant impact model for the
formation of the Moon, namely that most of the mass of the Moon originates from
the impactor, not Earth.
Resolution of this discrepancy without changing the main premises of the
giant impact model requires total isotopic homogenisation of Earth and impactor
material after the impact for a wide range of elements including O, Si, K, Ti,
Nd and W. Even if this process could explain the O isotope similarity, it is
unlikely to work for the much heavier, refractory elements. Given the
increasing uncertainty surrounding the giant impact model in light of these
geochemical data, alternative hypotheses for lunar formation should be
explored. In this paper, we revisit the hypothesis that the Moon was formed
directly from terrestrial mantle material. We show that the dynamics of this
scenario requires a large amount of energy, almost instantaneously generated
additional energy. The only known source for this additional energy is nuclear
fission. We show that it is feasible to form the Moon through the ejection of
terrestrial silicate material triggered by a nuclear explosion at Earths
core-mantle boundary (CMB), causing a shock wave propagating through the Earth.
Hydrodynamic modelling of this scenario shows that a shock wave created by
rapidly expanding plasma resulting from the explosion disrupts and expels
overlying mantle and crust material.Comment: 26 pages, 5 figures, 1 tabl
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