3,738 research outputs found
Optic neuritis is associated with inner nuclear layer thickening and microcystic macular edema independently of multiple sclerosis
BACKGROUND: Microcystic macular edema (MME) and inner nuclear layer thickening (INL) were described in multiple sclerosis (MS) and neuromyelitis optica (NMO) patients using optical coherence tomography (OCT). The cause of these findings is currently unknown and a relation to inflammatory or degenerative processes in the optic nerve is discussed. OBJECTIVE: The aim of our study was to investigate whether INL thickening and MME are related to optic neuritis (ON) in various neuro-inflammatory disorders causingON: MS, NMO and chronic inflammatory optic neuropathy. METHODS: We retrospectively analyzed data from 216 MS patients, 39 patients with a clinically isolated syndrome, 20 NMO spectrum disorder patients, 9 patients with chronic inflammatory optic neuropathy and 121 healthy subjects. Intra-retinal layer segmentation was performed for the eyes of patients with unilateral ON. Scanning laser ophthalmoscopy (SLO) images were reviewed for characteristic ocular fundus changes. RESULTS: Intra-retinal layer segmentation showed that eyes with a history of ON displayed MME independent INL thickening compared to contralateral eyes without previous ON. MME was detected in 22 eyes from 15 patients (5.3% of all screened patients), including 7 patients with bilateral edema. Of these, 21 had a prior history of ON (95%). The SLO images of all 22 MME-affected eyes showed crescent-shaped texture changes which were visible in the perifoveal region. A second grader who was blinded to the results of the OCT classified all SLO images for the presence of these characteristic fundus changes. All MME eyes were correctly classified (sensitivity = 100%) with high specificity (95.2%). CONCLUSION: This study shows that both MME and INL thickening occur in various neuro-inflammatory disorders associated with ON. We also demonstrate that detection and analysis of MME by OCT is not limited to B-scans, but also possible using SLO images
Quasar Microlensing at High Magnification and the Role of Dark Matter: Enhanced Fluctuations and Suppressed Saddlepoints
Contrary to naive expectation, diluting the stellar component of the lensing
galaxy in a highly magnified system with smoothly distributed ``dark'' matter
increases rather than decreases the microlensing fluctuations caused by the
remaining stars. For a bright pair of images straddling a critical curve, the
saddlepoint (of the arrival time surface) is much more strongly affected than
the associated minimum. With a mass ratio of smooth matter to microlensing
matter of 4:1, a saddlepoint with a macro-magnification of mu = 9.5 will spend
half of its time more than a magnitude fainter than predicted. The anomalous
flux ratio observed for the close pair of images in MG0414+0534 is a factor of
five more likely than computed by Witt, Mao and Schechter if the smooth matter
fraction is as high as 93%. The magnification probability histograms for
macro-images exhibit distinctly different structure that varies with the smooth
matter content, providing a handle on the smooth matter fraction. Enhanced
fluctuations can manifest themselves either in the temporal variations of a
lightcurve or as flux ratio anomalies in a single epoch snapshot of a multiply
imaged system. While the millilensing simulations of Metcalf and Madau also
give larger anomalies for saddlepoints than for minima, the effect appears to
be less dramatic for extended subhalos than for point masses. Morever,
microlensing is distinguishable from millilensing because it will produce
noticeable changes in the magnification on a time scale of a decade or less.Comment: As accepted for publication in ApJ. 17 pages. Substantial revisions
include a discussion of constant M/L models and the calculation of a
"photometric" dark matter fraction for MG0414+053
Diagnostic Performance of a Lower-dose Contrast-Enhanced 4D Dynamic MR Angiography of the Lower Extremities at 3 T Using Multisegmental Time-Resolved Maximum Intensity Projections
Background
For peripheral artery disease (PAD), MR angiography (MRA) is a well-established diagnostic modality providing morphologic and dynamic information comparable to digital subtraction angiography (DSA). However, relatively large amounts of contrast agents are necessary to achieve this.
Purpose
To evaluate the diagnostic accuracy of time-resolved 4D MR-angiography with interleaved stochastic trajectories (TWIST-MRA) by using maximum intensity projections (MIPs) of dynamic images acquired with reduced doses of contrast agent.
Study Type
Retrospective.
Population
Forty adult PAD patients yielding 1088 artery segments.
Field Strength/Sequence
A 3.0 T, time-resolved 4D MR-angiography with TWIST-MRA and MIP of dynamic images.
Assessment
DSA was available in 14 patients (256 artery segments) and used as reference standard. Three-segmental MIP reconstructions of TWIST-images after administration of 3 mL of gadolinium-based contrast agent (Gadoteridol/Prohance®, 0.5 M) per anatomical level (pelvis, thighs, and lower legs) yielded 256 artery segments for correlation between MRA and DSA. Three independent observers rated image quality (scale: 1 [nondiagnostic] to 4 [excellent]) and the degree of venous overlay (scale: 0 [none] to 2 [significant]) for all segments. Diagnostic accuracy for the detection of >50% stenosis and artery occlusion was calculated for all observers.
Statistical Tests
Binary classification test (sensitivity, specificity, positive/negative predictive values, diagnostic accuracy). Intraclass correlation coefficients (ICCs), logistic regression analysis with comparison of areas under the receiver-operating-characteristics (ROC) curves (AUCs) with the DeLong method. Bland–Altman-comparison.
Results
High diagnostic performance was achieved for the detection of >50% stenosis (sensitivity 92.9% [84.3–99.9% (95%-CI)] and specificity 98.5% [95.7–99.8% (95%-CI)]) and artery occlusion (sensitivity 93.1% [77.2–99.2% (95%-CI)] and specificity 99.1% [96.9–99.9% (95%-CI)]). Inter-reader agreement was excellent with ICC values ranging from 0.95 to 1.0 for >50% artery stenosis and occlusion. Image quality was good to excellent for both readers (3.41 ± 0.72, 3.33 ± 0.65, and 3.38 ± 0.61 [mean ± SD]) with good correlation between observer ratings (ICC 0.71–0.81). No significant venous overlay was observed (0.06 ± 0.24, 0.23 ± 0.43 and 0.11 ± 0.45 [mean ± SD]).
Data Conclusion
MIPs of dynamic TWIST-MRA offer a promising diagnostic alternative necessitating only reduced amounts (50%) of gadolinium-based contrast agents for the entire runoff vasculature.
Evidence Level
3
Technical Efficacy
Stage
The Mid-Infrared Instrument for the James Webb Space Telescope, VIII: The MIRI Focal Plane System
We describe the layout and unique features of the focal plane system for
MIRI. We begin with the detector array and its readout integrated circuit
(combining the amplifier unit cells and the multiplexer), the electronics, and
the steps by which the data collection is controlled and the output signals are
digitized and delivered to the JWST spacecraft electronics system. We then
discuss the operation of this MIRI data system, including detector readout
patterns, operation of subarrays, and data formats. Finally, we summarize the
performance of the system, including remaining anomalies that need to be
corrected in the data pipeline
Type II Quasars from the Sloan Digital Sky Survey: V. Imaging host galaxies with the Hubble Space Telescope
Type II quasars are luminous Active Galactic Nuclei whose centers are
obscured by large amounts of gas and dust. In this paper we present 3-band HST
images of nine type II quasars with redshifts 0.2 < z < 0.4 selected from the
Sloan Digital Sky Survey based on their emission line properties. The intrinsic
luminosities of these AGN are estimated to be -24 > M_B > -26, but optical
obscuration allows their host galaxies to be studied unencumbered by bright
nuclei. Each object has been imaged in three continuum filters (`UV', `blue'
and `yellow') placed between the strong emission lines. The spectacular, high
quality images reveal a wealth of details about the structure of the host
galaxies and their environments. Six of the nine galaxies in the sample are
ellipticals with de Vaucouleurs light profiles, one object has a well-defined
disk component and the remaining two have marginal disks. Stellar populations
of type II quasar hosts are more luminous (by a median of 0.3-0.7 mag,
depending on the wavelength) and bluer (by about 0.4 mag) than are M* galaxies
at the same redshift. When smooth fits to stellar light are subtracted from the
images, we find both positive and negative residuals that become more prominent
toward shorter wavelengths. We argue that the negative residuals are due to
kpc-scale dust obscuration, while most positive residuals are due to the light
from the nucleus scattered off interstellar material in the host galaxy.
Scattered light makes a significant contribution to the broad band continuum
emission and can be the dominant component of the extended emission in the UV
in extreme cases.Comment: 51 pages, including 12 grey scale figures, 4 color figures, 5 tables.
In press in AJ. Version with higher-resolution images available at
http://www.astro.princeton.edu/~nadia/qso2.html. (Minor changes in response
to the referee report
Testing Scalar-Tensor Gravity Using Space Gravitational-Wave Interferometers
We calculate the bounds which could be placed on scalar-tensor theories of
gravity of the Jordan, Fierz, Brans and Dicke type by measurements of
gravitational waveforms from neutron stars (NS) spiralling into massive black
holes (MBH) using LISA, the proposed space laser interferometric observatory.
Such observations may yield significantly more stringent bounds on the
Brans-Dicke coupling parameter \omega than are achievable from solar system or
binary pulsar measurements. For NS-MBH inspirals, dipole gravitational
radiation modifies the inspiral and generates an additional contribution to the
phase evolution of the emitted gravitational waveform. Bounds on \omega can
therefore be found by using the technique of matched filtering. We compute the
Fisher information matrix for a waveform accurate to second post-Newtonian
order, including the effect of dipole radiation, filtered using a currently
modeled noise curve for LISA, and determine the bounds on \omega for several
different NS-MBH canonical systems. For example, observations of a 1.4 solar
mass NS inspiralling to a 1000 solar mass MBH with a signal-to-noise ratio of
10 could yield a bound of \omega > 240,000, substantially greater than the
current experimental bound of \omega > 3000.Comment: 18 pages, 4 figures, 1 table; to be submitted to Phys. Rev.
Model-Based Security Testing
Security testing aims at validating software system requirements related to
security properties like confidentiality, integrity, authentication,
authorization, availability, and non-repudiation. Although security testing
techniques are available for many years, there has been little approaches that
allow for specification of test cases at a higher level of abstraction, for
enabling guidance on test identification and specification as well as for
automated test generation.
Model-based security testing (MBST) is a relatively new field and especially
dedicated to the systematic and efficient specification and documentation of
security test objectives, security test cases and test suites, as well as to
their automated or semi-automated generation. In particular, the combination of
security modelling and test generation approaches is still a challenge in
research and of high interest for industrial applications. MBST includes e.g.
security functional testing, model-based fuzzing, risk- and threat-oriented
testing, and the usage of security test patterns. This paper provides a survey
on MBST techniques and the related models as well as samples of new methods and
tools that are under development in the European ITEA2-project DIAMONDS.Comment: In Proceedings MBT 2012, arXiv:1202.582
Midwives\u27 knowledge, attitudes and learning needs regarding antenatal vaccination
Objective: To determine the knowledge, attitudes and learning needs of midwives regarding antenatal vaccination.
Design & Setting: A cross-sectional, paper-based survey of midwives employed at the only public tertiary maternity hospital in the Australian state of XX between November 2015 and July 2016.
Participants: 252 midwives providing care in antepartum, intrapartum, and/or postpartum settings.
Measurements: Self-reported responses to a 41-item survey.
Findings: The vast majority of midwives supported influenza and pertussis vaccination for pregnant women, with 90.0% and 71.7% reporting they would recommend pertussis and influenza vaccine, respectively, to a pregnant friend or family member, and almost all stating that midwives should administer vaccines to pregnant patients (94.8%). Seven out of ten midwives (68.1%) responded correctly to all knowledge items regarding vaccines recommended during pregnancy; 52.8% demonstrated correct knowledge regarding vaccine administration despite only 36.6% having attended an education session on antenatal vaccination in the previous two years. Nearly all midwives (97.3%) expressed a need for more education on vaccine administration. The most commonly reported barrier to administering influenza (61.3%) and pertussis (59.0%) vaccination was having staff available with the certification required to administer vaccines.
Key Conclusions: Midwives view antenatal vaccination as their responsibility and are interested and receptive to education.
Implications for Practice: There is an unmet need and demand among midwives for professional development that would enable them to recommend and administer vaccines to pregnant women in accordance with national immunisation guidelines and integrate vaccination into routine antenatal care
L\'evy-Schr\"odinger wave packets
We analyze the time--dependent solutions of the pseudo--differential
L\'evy--Schr\"odinger wave equation in the free case, and we compare them with
the associated L\'evy processes. We list the principal laws used to describe
the time evolutions of both the L\'evy process densities, and the
L\'evy--Schr\"odinger wave packets. To have self--adjoint generators and
unitary evolutions we will consider only absolutely continuous, infinitely
divisible L\'evy noises with laws symmetric under change of sign of the
independent variable. We then show several examples of the characteristic
behavior of the L\'evy--Schr\"odinger wave packets, and in particular of the
bi-modality arising in their evolutions: a feature at variance with the typical
diffusive uni--modality of both the L\'evy process densities, and the usual
Schr\"odinger wave functions.Comment: 41 pages, 13 figures; paper substantially shortened, while keeping
intact examples and results; changed format from "report" to "article";
eliminated Appendices B, C, F (old names); shifted Chapters 4 and 5 (old
numbers) from text to Appendices C, D (new names); introduced connection
between Relativistic q.m. laws and Generalized Hyperbolic law
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