111 research outputs found
Dysthyroid optic neuropathy: update on pathogenesis, diagnosis, and management
INTRODUCTION:
Dysthyroid optic neuropathy (DON) is a severe manifestation of thyroid eye disease (TED) that can result in permanent vision loss. Management is complex, multidisciplinary, and involves medical and/or surgical therapies. This review describes current concepts in the epidemiology, pathophysiology, diagnosis, and treatment of DON.
AREAS COVERED:
An extensive review of the literature was performed to detail current concepts on the diagnosis and management of DON. This includes utilization of various medical and surgical modalities for disease management.
EXPERT COMMENTARY:
DON can result in permanent blindness and often requires the use of corticosteroids and surgical decompression. We favor the use of intravenous corticosteroids and a transcaruncular approach when surgical decompression is indicated. The use of orbital radiation for DON is often reserved for patients that are poor surgical candidates and/or patients with refractory disease
Rotating "Black Holes" with Holes in the Horizon
Kerr-Schild solutions of the Einstein-Maxwell field equations, containing
semi-infinite axial singular lines, are investigated.
It is shown that axial singularities break up the black hole, forming holes
in the horizon. As a result, a tube-like region appears which allows matter to
escape from the interior without crossing the horizon. It is argued that axial
singularities of this kind, leading to very narrow beams, can be created in
black holes by external electromagnetic or gravitational excitations and may be
at the origin of astrophysically observable effects such as jet formation.Comment: Revtex, 6 pages, 3 figures. Corrected version. To appear in Phys Rev
D, Rapid Communication
Effects of neutrino-driven kicks on the supernova explosion mechanism
We show that neutrino-driven pulsar kicks can increase the energy of the
supernova shock. The observed large velocities of pulsars are believed to
originate in the supernova explosion, either from asymmetries in the ejecta or
from an anisotropic emission of neutrinos (or other light particles) from the
cooling neutron star. In this paper we assume the velocities are caused by
anisotropic neutrino emission and study the effects of these neutrino-driven
kicks on the supernova explosion. We find that if the collapsed star is
marginally unable to produce an explosion, the neutrino-driven mechanisms can
drive the convection to make a successful explosion. The resultant explosion is
asymmetric, with the strongest ejecta motion roughly in the direction of the
neutron star kick. This is in sharp contrast with the ejecta-driven mechanisms,
which predict the motion of the ejecta in the opposite direction. This
difference can be used to distinguish between the two mechanisms based on the
observations of the supernova remnants.Comment: 22 pages including 8 figures, submitted to ApJ, version with high
resolution figures can be found at http://qso.lanl.gov/~cl
Opportunities and barriers for adoption of a decision-support tool for Alzheimer's Disease
Clinical decision-support tools (DSTs) represent a valuable resource in healthcare. However, lack of Human
Factors considerations and early design research has often limited their successful adoption. To complement
previous technically focused work, we studied adoption opportunities of a future DST built on a predictive
model of Alzheimer’s Disease (AD) progression. Our aim is two-fold: exploring adoption opportunities for
DSTs in AD clinical care, and testing a novel combination of methods to support this process. We focused
on understanding current clinical needs and practices, and the potential for such a tool to be integrated
into the setting, prior to its development. Our user-centred approach was based on field observations and
semi-structured interviews, analysed through workflow analysis, user profiles, and a design-reality gap model.
The first two are common practice, whilst the latter provided added value in highlighting specific adoption
needs. We identified the likely early adopters of the tool as being both psychiatrists and neurologists based in
research-oriented clinical settings. We defined ten key requirements for the translation and adoption of DSTs
for AD around IT, user, and contextual factors. Future works can use and build on these requirements to stand
a greater chance to get adopted in the clinical setting
Obscured AGN: the hidden side of the X-ray Universe
Most Active Galactic Nuclei (AGN) are `obscured', i.e. the nucleus is hiding
behind a screen of absorbing material. The advantage of having the nucleus
obscured is to make easier the observations of those emission components which
originate in circumnuclear matter outside the absorbing regions, because in
this case they are not outshined by the nuclear emission. This is particularly
important in X-rays, where spatial resolution is (with the notable exception of
Chandra) poorer than in the optical, and the study of circumnuclear regions is
often based on spectral analysis only.
The properties of circumnuclear matter, in the light of recent high spectral
and/or angular resolution and XMM--Newton observations, will be
reviewed in Sec.2. In Sec.3 we will discuss obscured AGN in the framework of
the Unification Model. Recent discoveries of X-ray obscured Seyfert 1, and of
X-ray loud but optically normal galaxies, are calling for a revision of the
Unification Model.
Obscured AGN have also a cosmological relevance. Not only are they a
fundamental ingredient of synthesis models of the Cosmic X-ray Background
(XRB), but provide a link between the XRB and the Cosmic Infrared Background,
as briefly discussed in Sec.4.Comment: 12 pages; to appear in Philosophical Transactions of the Royal
Society (Series A: Mathematical, Physical, and Engineering Sciences
A method of estimation of the dynamical age of FR II-type radio sources from multifrequency data
We propose a new approach in determining ages of FR II type radio sources. We
apply the assumed dynamical model of Kaiser et al. (1997) to a number of FR II
type radio galaxies observed at different radio frequencies, and fit - for each
frequency separately - the model free parameters to the observed sources'
quantities. Such a procedure, using enlarged in fact a number of observables,
enables us to determine relatively precise ages and other crucial
characteristics of the analyzed sources. The resulting age estimates agree very
well with those obtained by means of `classical' spectral ageing method for
objects not older than 10 Myr, for which good-quality spectral data are
available. The presented method is however also applicable in the case of the
sources older than this, and/or the ones for which the only available
low-resolution radio data do not allow for detailed spectral ageing studies.
Our analysis indicates that the main factor precluding precise age
determination for FR II type radio galaxies regards the poorly known shape of
the initial electron energy distribution injected by the jet terminal shocks to
the expanding lobes/cocoons. We briefly consider this issue, and conclude that
the broad-band single power-law form assumed here may be accurate enough for
the presented estimates, although most likely it does not strictly correspond
to some well-defined realistic particle acceleration process. Instead, it
should be considered as a simplest model approximation of the initial electron
continuum, averaged over a very broad energy range and over the age of the
source, with the effective spectral index which may be different for different
sources.Comment: 15 pages, 9 figures included. Accepted for publication in A&
A blind test of photometric redshift prediction
Results of a blind test of photometric redshift predictions against
spectroscopic galaxy redshifts obtained in the Hubble Deep Field with the Keck
Telescope are presented. The best photometric redshift schemes predict
spectroscopic redshifts with a redshift accuracy of |Delta-z|<0.1 for more than
68 percent of sources and with |Delta-z|<0.3 for 100 percent, when
single-feature spectroscopic redshifts are removed from consideration. This
test shows that photometric redshift schemes work well at least when the
photometric data are of high quality and when the sources are at moderate
redshifts.Comment: 14 pp., accepted for publication in A
Warped discs and the directional stability of jets in Active Galactic Nuclei
Warped accretion discs in Active Galactic Nuclei (AGN) exert a torque on the
black hole that tends to align the rotation axis with the angular momentum of
the outer disc. We compute the magnitude of this torque by solving numerically
for the steady state shape of the warped disc, and verify that the analytic
solution of Scheuer and Feiler (1996) provides an excellent approximation. We
generalise these results for discs with strong warps and arbitrary surface
density profiles, and calculate the timescale on which the black hole becomes
aligned with the angular momentum in the outer disc. For massive holes and
accretion rates of the order of the Eddington limit the alignment timescale is
always short (less than a Myr), so that jets accelerated from the inner disc
region provide a prompt tracer of the angular momentum of gas at large radii in
the disc. Longer timescales are predicted for low luminosity systems, depending
on the degree of anisotropy in the disc's hydrodynamic response to shear and
warp, and for the final decay of modest warps at large radii in the disc that
are potentially observable via VLBI. We discuss the implications of this for
the inferred accretion history of those Active Galactic Nuclei whose jet
directions appear to be stable over long timescales. The large energy
deposition rate at modest disc radii during rapid realignment episodes should
make such objects transiently bright at optical and infrared wavelengths.Comment: MNRAS, in press. Revised to match accepted version, with one new
figure showing alignment timescale as a function of black hole mas
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