4,838 research outputs found
Magnetic-field effects in defect-controlled ferromagnetic Ga_{1-x}Mn_xAs semiconductors
We have studied the magnetic-field and concentration dependences of the
magnetizations of the hole and Mn subsystems in diluted ferromagnetic
semiconductor Ga_{1-x}Mn_xAs. A mean-field approximation to the hole-mediated
interaction is used, in which the hole concentration p(x) is parametrized in
terms of a fitting (of the hole effective mass and hole/local moment coupling)
to experimental data on the Tc critical temperature. The dependence of the
magnetizations with x, for a given temperature, presents a sharply peaked
structure, with maxima increasing with applied magnetic field, which indicates
that application to diluted-magnetic-semiconductor devices would require
quality-control of the Mn-doping composition. We also compare various
experimental data for Tc(x) and p(x) on different Ga_{1-x}Mn_xAs samples and
stress the need of further detailed experimental work to assure that the
experimental measurements are reproducible.Comment: RevTeX 4, 3 two-column pages, 4 colour figures; to appear in J Appl
Phy
Front crawl arm stroke trajectories of physically impaired swimmers: A preliminary study
© 2019 Elsevier Masson SAS. Introduction: This study evaluated three-dimensional kinematic parameters of the front crawl stroke in physically impaired swimmers across a range of functional classification levels. Facts and Results: Eight highly-trained competitive swimmers (5 male and 3 female) from IPC classes S5 to S9 performed 50 m maximal front crawl trials while being video-taped by six cameras (four under- and two above water). The most distal point of the right upper limb was manually digitised at 50 Hz to allow three-dimensional reconstruction of the limb's trajectory through the water. Conclusion: The stroke presented large inter-swimmer variability, reflecting individual characteristics and severity of the impairment. The swimmers who combined shallow and narrow stroke movements produced a shorter trajectory. This study provides swimmers and coaches with an overview of the kinematic characteristics of a range of physically impaired swimmers
Physical properties of a generalized model of multilayer adsorption of dimers
This article investigates the physical and statistical properties of
two-dimensional structures obtained with a dimer packing model, which may be of
great interest in other scientific and technological areas besides theoretical
physics. The study is based on extensive computer simulations in order to
examine the effect of the orientational anisotropy of dimers deposited
following a ballistic deposition process, leading to multilayer networks of
complex morphologies dominated by branched fractal architectures. The geometric
characteristics of the bulk and contours of these systems, and the transport
properties, particularly the electrical conductivity were investigated by
varying the orientational anisotropy of the dimers. The results provide
information about the fundamental mechanisms underlying formation and behavior
of such types of amorphous and disordered matter that are of paramount
importance both to physics as well as to environmental and material sciences
Hybrid confinement of optical and mechanical modes in a bullseye optomechanical resonator
Optomechanical cavities have proven to be an exceptional tool to explore
fundamental and technological aspects of the interaction between mechanical and
optical waves. Such interactions strongly benefit from cavities with large
optomechanical coupling, high mechanical and optical quality factors, and
mechanical frequencies larger than the optical mode linewidth, the so called
resolved sideband limit. Here we demonstrate a novel optomechanical cavity
based on a disk with a radial mechanical bandgap. This design confines light
and mechanical waves through distinct physical mechanisms which allows for
independent control of the mechanical and optical properties. Our device design
is not limited by unique material properties and could be easily adapted to
allow large optomechanical coupling and high mechanical quality factors with
other promising materials. Finally, our demonstration is based on devices
fabricated on a commercial silicon photonics facility, demonstrating that our
approach can be easily scalable.Comment: 16 pages, 11 figure
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