1,832 research outputs found
The subarcsecond mid-infrared view of local active galactic nuclei: II. The mid-infrared--X-ray correlation
We present an updated mid-infrared (MIR) versus X-ray correlation for the
local active galactic nuclei (AGN) population based on the high angular
resolution 12 and 18um continuum fluxes from the AGN subarcsecond MIR atlas and
2-10 keV and 14-195 keV data collected from the literature. We isolate a sample
of 152 objects with reliable AGN nature and multi-epoch X-ray data and minimal
MIR contribution from star formation. Although the sample is not homogeneous or
complete, we show that our results are unlikely to be affected by biases. The
MIR--X-ray correlation is nearly linear and within a factor of two independent
of the AGN type and the wavebands used. The observed scatter is <0.4 dex. A
possible flattening of the correlation slope at the highest luminosities probed
(~ 10^45 erg/s) is indicated but not significant. Unobscured objects have, on
average, an MIR--X-ray ratio that is only <= 0.15 dex higher than that of
obscured objects. Objects with intermediate X-ray column densities (22 < log
N_H < 23) actually show the highest MIR--X-ray ratio on average. Radio-loud
objects show a higher mean MIR--X-ray ratio at low luminosities, while the
ratio is lower than average at high luminosities. This may be explained by
synchrotron emission from the jet contributing to the MIR at low-luminosities
and additional X-ray emission at high luminosities. True Seyfert 2 candidates
and double AGN do not show any deviation from the general behaviour. Finally,
we show that the MIR--X-ray correlation can be used to verify the AGN nature of
uncertain objects. Specifically, we give equations that allow to determine the
intrinsic 2-10 keV luminosities and column densities for objects with complex
X-ray properties to within 0.34 dex. These techniques are applied to the
uncertain objects of the remaining AGN MIR atlas, demonstrating the usefulness
of the MIR--X-ray correlation as an empirical tool.Comment: Accepted for publication in MNRAS, 40 pages, 25 figure
Evolutie van de gehalten aan zware metalen in sedimenten van het Belgisch Continentaal Plat (1979-1995)
Anomalous Periodicity of the Current-Phase Relationship of Grain-Boundary Josephson Junctions in High-Tc Superconductors
The current-phase relation (CPR) for asymmetric 45 degree Josephson junctions
between two d-wave superconductors has been predicted to exhibit an anomalous
periodicity. We have used the single-junction interferometer to investigate the
CPR for this kind of junctions in YBCO thin films. Half-fluxon periodicity has
been experimentally found, providing a novel source of evidence for the d-wave
symmetry of the pairing state of the cuprates.Comment: 4 pages, 5 figure
Grip Force Reveals the Context Sensitivity of Language-Induced Motor Activity during “Action Words
Studies demonstrating the involvement of motor brain structures in language processing typically focus on \ud
time windows beyond the latencies of lexical-semantic access. Consequently, such studies remain inconclusive regarding whether motor brain structures are recruited directly in language processing or through post-linguistic conceptual imagery. In the present study, we introduce a grip-force sensor that allows online measurements of language-induced motor activity during sentence listening. We use this tool to investigate whether language-induced motor activity remains constant or is modulated in negative, as opposed to affirmative, linguistic contexts. Our findings demonstrate that this simple experimental paradigm can be used to study the online crosstalk between language and the motor systems in an ecological and economical manner. Our data further confirm that the motor brain structures that can be called upon during action word processing are not mandatorily involved; the crosstalk is asymmetrically\ud
governed by the linguistic context and not vice versa
Stress-Biased Anisotropic Microcracking in Zirconia Polycrystals
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65263/1/j.1151-2916.1990.tb05152.x.pd
Current sample size conventions: Flaws, harms, and alternatives
<p>Abstract</p> <p>Background</p> <p>The belief remains widespread that medical research studies must have statistical power of at least 80% in order to be scientifically sound, and peer reviewers often question whether power is high enough.</p> <p>Discussion</p> <p>This requirement and the methods for meeting it have severe flaws. Notably, the true nature of how sample size influences a study's projected scientific or practical value precludes any meaningful blanket designation of <80% power as "inadequate". In addition, standard calculations are inherently unreliable, and focusing only on power neglects a completed study's most important results: estimates and confidence intervals. Current conventions harm the research process in many ways: promoting misinterpretation of completed studies, eroding scientific integrity, giving reviewers arbitrary power, inhibiting innovation, perverting ethical standards, wasting effort, and wasting money. Medical research would benefit from alternative approaches, including established <it>value of information </it>methods, simple choices based on cost or feasibility that have recently been justified, sensitivity analyses that examine a meaningful array of possible findings, and following previous analogous studies. To promote more rational approaches, research training should cover the issues presented here, peer reviewers should be extremely careful before raising issues of "inadequate" sample size, and reports of completed studies should not discuss power.</p> <p>Summary</p> <p>Common conventions and expectations concerning sample size are deeply flawed, cause serious harm to the research process, and should be replaced by more rational alternatives.</p
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