436 research outputs found
Rheumatoid meningitis sine arthritis.
Rheumatoid meningitis is a rare and very serious extra-articular manifestation of rheumatoid arthritis. We present a case of a 7()year-old female with no history of arthritis who developed stroke-like symptoms, seizures, psychosis and compulsive behavior. Serial brain magnetic resonance images (MRI) over four months demonstrated progressive interhemispheric meningeal thickening. She had mild lymphocytic pleocytosis on the cerebrospinal fluid analysis and serum anti-cyclic citrullinated peptide antibodies resulted positive in high titers. She underwent a brain biopsy showing necrotizing granulomas consistent with rheumatoid meningitis. Her symptoms resolved with treatment with glucocorticoids and cyclophosphamide. She has not been diagnosed with rheumatoid arthritis even after 1 year of follow up. Clinicians should be aware of the possibility of rheumatoid meningitis without rheumatoid arthritis and keep it on the differential for patients with aseptic meningitis and otherwise negative work up
Sequential Bahadur Efficiency
The notion of Bahadur efficiency for test statistics is extended to the sequential case and illustrated in the specific context of testing one-sided hypotheses about a normal mean. An analog of Bahadur\u27s theorem on the asymptotic optimality of the likelihood ratio statistic is seen to hold in the normal case. Some possible definitions of attained level for a sequential experiment are considered
Statistical Inference After Model Selection
Conventional statistical inference requires that a model of how the data were generated be known before the data are analyzed. Yet in criminology, and in the social sciences more broadly, a variety of model selection procedures are routinely undertaken followed by statistical tests and confidence intervals computed for a “final” model. In this paper, we examine such practices and show how they are typically misguided. The parameters being estimated are no longer well defined, and post-model-selection sampling distributions are mixtures with properties that are very different from what is conventionally assumed. Confidence intervals and statistical tests do not perform as they should. We examine in some detail the specific mechanisms responsible. We also offer some suggestions for better practice and show though a criminal justice example using real data how proper statistical inference in principle may be obtained
Properties of Bayes Sequential Tests
Consider the problem of sequentially testing composite, contiguous hypotheses where the risk function is a linear combination of the probability of error in the terminal decision and the expected sample size. Assume that the common boundary of the closures of the null and the alternative hypothesis is compact. Observations are independent and identically distributed. We study properties of Bayes tests. One property is the exponential boundedness of the stopping time. Another property is continuity of the risk functions. The continuity property is used to establish complete class theorems as opposed to the essentially complete class theorems in Brown, Cohen and Strawderman
Bounded Stopping Times for a Class of Sequential Bayes Tests
Consider the problem of sequentially testing a null hypothesis vs an alternative hypothesis when the risk function is a linear combination of probability of error in the terminal decision and expected sample size (i.e., constant cost per observation.) Assume that the parameter space is the union of null and alternative, the parameter space is convex, the intersection of null and alternative is empty, and the common boundary of the closures of null and alternative is nonempty and compact. Assume further that observations are drawn from a p-dimensional exponential family with an open p-dimensional parameter space. Sufficient conditions for Bayes tests to have bounded stopping times are given
Hot Dust Clouds with Pure Graphite Composition around Type-I Active Galactic Nuclei
We fitted the optical to mid-infrared (MIR) spectral energy distributions
(SEDs) of ~15000 type-I, 0.75<z<2, active galactic nuclei (AGNs) in an attempt
to constrain the properties of the physical component responsible for the
rest-frame near-infrared (NIR) emission. We combine optical spectra from the
Sloan Digital Sky Survey (SDSS) and MIR photometry from the preliminary data
release of the Wide Infrared Survey Explorer (WISE). The sample spans a large
range of AGN properties: luminosity, black hole mass, and accretion rate. Our
model has two components: a UV-optical continuum source and very hot,
pure-graphite dust clouds. We present the luminosity of the hot-dust component
and its covering factor, for all sources, and compare it with the intrinsic AGN
properties. We find that the hot-dust component is essential to explain the
(rest) NIR emission in almost all AGNs in our sample, and that it is consistent
with clouds containing pure-graphite grains and located between the dust-free
broad line region (BLR) and the "standard" torus. The covering factor of this
component has a relatively narrow distribution around a peak value of ~0.13,
and it correlates with the AGN bolometric luminosity. We suggest that there is
no significant correlation with either black hole mass or normalized accretion
rate. The fraction of hot-dust-poor AGNs in our sample is ~15-20%, consistent
with previous studies. We do not find a dependence of this fraction on redshift
or source luminosity.Comment: Accepted for publication in ApJ
Simulation of Hyperspectral Images
A software package generates simulated hyperspectral imagery for use in validating algorithms that generate estimates of Earth-surface spectral reflectance from hyperspectral images acquired by airborne and spaceborne instruments. This software is based on a direct simulation Monte Carlo approach for modeling three-dimensional atmospheric radiative transport, as well as reflections from surfaces characterized by spatially inhomogeneous bidirectional reflectance distribution functions. In this approach, "ground truth" is accurately known through input specification of surface and atmospheric properties, and it is practical to consider wide variations of these properties. The software can treat both land and ocean surfaces, as well as the effects of finite clouds with surface shadowing. The spectral/spatial data cubes computed by use of this software can serve both as a substitute for, and a supplement to, field validation data
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