16,755 research outputs found
Detection of amblyopia utilizing generated retinal reflexes
Investigation confirmed that GRR images can be consistently obtained and that these images contain information required to detect the optical inequality of one eye compared to the fellow eye. Digital analyses, electro-optical analyses, and trained observers were used to evaluate the GRR images. Two and three dimensional plots were made from the digital analyses results. These plotted data greatly enhanced the GRR image content, and it was possible for nontrained observers to correctly identify normal vs abnormal ocular status by viewing the plots. Based upon the criteria of detecting equality or inequality of ocular status of a person's eyes, the trained observer correctly identified the ocular status of 90% of the 232 persons who participated in this program
Magneto-optics in pure and defective Ga_{1-x}Mn_xAs from first-principles
The magneto-optical properties of GaMnAs including their most
common defects were investigated with precise first--principles
density-functional FLAPW calculations in order to: {\em i}) elucidate the
origin of the features in the Kerr spectra in terms of the underlying
electronic structure; {\em ii}) perform an accurate comparison with
experiments; and {\em iii}) understand the role of the Mn concentration and
occupied sites in shaping the spectra. In the substitutional case, our results
show that most of the features have an interband origin and are only slightly
affected by Drude--like contributions, even at low photon energies. While not
strongly affected by the Mn concentration for the intermediately diluted range
( 10%), the Kerr factor shows a marked minimum (up to 1.5) occurring
at a photon energy of 0.5 eV. For interstitial Mn, the calculated
results bear a striking resemblance to the experimental spectra, pointing to
the comparison between simulated and experimental Kerr angles as a valid tool
to distinguish different defects in the diluted magnetic semiconductors
framework.Comment: 10 pages including 2 figures, submitted to Phys. Rev.
IRIS Observations of the Mg II h & k Lines During a Solar Flare
The bulk of the radiative output of a solar flare is emitted from the
chromosphere, which produces enhancements in the optical and UV continuum, and
in many lines, both optically thick and thin. We have, until very recently,
lacked observations of two of the strongest of these lines: the Mg II h & k
resonance lines. We present a detailed study of the response of these lines to
a solar flare. The spatial and temporal behaviour of the integrated
intensities, k/h line ratios, line of sight velocities, line widths and line
asymmetries were investigated during an M class flare (SOL2014-02-13T01:40).
Very intense, spatially localised energy input at the outer edge of the ribbon
is observed, resulting in redshifts equivalent to velocities of ~15-26km/s,
line broadenings, and a blue asymmetry in the most intense sources. The
characteristic central reversal feature that is ubiquitous in quiet Sun
observations is absent in flaring profiles, indicating that the source function
increases with height during the flare. Despite the absence of the central
reversal feature, the k/h line ratio indicates that the lines remain optically
thick during the flare. Subordinate lines in the Mg II passband are observed to
be in emission in flaring sources, brightening and cooling with similar
timescales to the resonance lines. This work represents a first analysis of
potential diagnostic information of the flaring atmosphere using these lines,
and provides observations to which synthetic spectra from advanced radiative
transfer codes can be compared.Comment: 12 pages, 14 figures, Accepted for publication in Astronomy and
Astrophysic
Pion-Nucleus Scattering at Medium Energies with Densities from Chiral Effective Field Theories
Recently developed chiral effective field theory models provide excellent
descriptions of the bulk characteristics of finite nuclei, but have not been
tested with other observables. In this work, densities from both relativistic
point-coupling models and mean-field meson models are used in the analysis of
meson-nucleus scattering at medium energies. Elastic scattering observables for
790
MeV/ on Pb are calculated in a relativistic impulse
approximation, using the Kemmer-Duffin-Petiau formalism to calculate the
nucleus optical potential.Comment: 9 page
Highly active iridium(I) complexes for the selective hydrogenation of carbon-carbon multiple bonds
New iridium(I) complexes, bearing a bulky NHC/phosphine ligand combination, have been established as extremely efficient hydrogenation catalysts that can be used at low catalyst loadings, and are compatible with functional groups which are often sensitive to more routinely employed hydrogenation methods
Astrophysical limitations to the identification of dark matter: indirect neutrino signals vis-a-vis direct detection recoil rates
A convincing identification of dark matter (DM) particles can probably be
achieved only through a combined analysis of different detections strategies,
which provides an effective way of removing degeneracies in the parameter space
of DM models. In practice, however, this program is made complicated by the
fact that different strategies depend on different physical quantities, or on
the same quantities but in a different way, making the treatment of systematic
errors rather tricky. We discuss here the uncertainties on the recoil rate in
direct detection experiments and on the muon rate induced by neutrinos from
dark matter annihilations in the Sun, and we show that, contrarily to the local
DM density or overall cross section scale, irreducible astrophysical
uncertainties affect the two rates in a different fashion, therefore limiting
our ability to reconstruct the parameters of the dark matter particle. By
varying within their respective errors astrophysical parameters such as the
escape velocity and the velocity dispersion of dark matter particles, we show
that the uncertainty on the relative strength of the neutrino and
direct-detection signal is as large as a factor of two for typical values of
the parameters, but can be even larger in some circumstances.Comment: 12 pages, 3 figures. Improved presentation and Fig.3; clarifications,
references and an appendix added; conclusions unchanged. Matches version
published in PR
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