A new sample of X-ray selected narrow emission-line galaxies. I. The nature of optically elusive AGN

Using the 3XMM catalogue of serendipitous X-ray sources, and the SDSS-DR9 spectroscopic catalogue, we have obtained a new sample of X-ray selected narrow emission line galaxies. The standard optical diagnostic diagram and selection by hard X-ray luminosity expose a mismatch between the optically-based and X-ray-based classifications. The nature of these misclassified elusive AGN can be understood in terms of their broader X-ray and optical properties and leads to a division of this sub-sample into two groups. A little more than half are likely to be narrow-line Seyfert 1s (NLS1s), so misclassified because of the contribution of the Broad Line Region (BLR) to their optical spectra. The remainder have some of the properties of Seyfert 2 (Sy2) AGN; their optical elusiveness can be explained by optical dilution from the host galaxy plus a star-formation contribution and by their underluminous optical emission due to low accretion rates. Because some of the Sy2 sources have very low accretion rates, are unabsorbed, plus the fact that they lack broad optical emission lines, they are good candidates to be True Sy2 AGN.Comment: 13 pages, 13 figues, accepted for publication in A&

Visual marking and facial affect : can an emotional face be ignored?

Previewing a set of distractors allows them to be ignored in a subsequent visual search task (Watson & Humphreys, 1997). Seven experiments investigated whether this preview benefit can be obtained with emotional faces, and whether negative and positive facial expressions differ in the extent to which they can be ignored. Experiments 1–5 examined the preview benefit with neutral, negative, and positive previewed faces. These results showed that a partial preview benefit occurs with face stimuli, but that the valence of the previewed faces has little impact. Experiments 6 and 7 examined the time course of the preview benefit with valenced faces. These showed that negative faces were more difficult to ignore than positive faces, but only at short preview durations. Furthermore, a full preview benefit was not obtained with face stimuli even when the preview duration was extended up to 3 s. The findings are discussed in terms of the processes underlying the preview benefit, their ecological sensitivity, and the role of emotional valence in attentional capture and guidance

Evaluation of tantalum-alloy-clad uranium mononitride fuel specimens from 7500-hour, 1040 C pumped-lithium-loop test

Simulated nuclear fuel element specimens, consisting of uranium mononitride (UN) fuel cylinders clad with tungsten-lined T-111, were exposed for up to 7500 hr at 1040 C (1900 F) in a pumped-lithium loop. The lithium flow velocity was 1.5 m/sec (5 ft/sec) in the specimen test section. No evidence of any compatibility problems between the specimens and the flowing lithium was found based on appearance, weight change, chemistry, and metallography. Direct exposure of the UN to the lithium through a simulated cladding crack resulted in some erosion of the UN in the area of the defect. The T-111 cladding was ductile after lithium exposure, but it was sensitive to hydrogen embrittlement during post-test handling

When are abrupt onsets found efficiently in complex visual search? : evidence from multi-element asynchronous dynamic search

Previous work has found that search principles derived from simple visual search tasks do not necessarily apply to more complex search tasks. Using a Multielement Asynchronous Dynamic (MAD) visual search task, in which high numbers of stimuli could either be moving, stationary, and/or changing in luminance, Kunar and Watson (M. A Kunar & D. G. Watson, 2011, Visual search in a Multi-element Asynchronous Dynamic (MAD) world, Journal of Experimental Psychology: Human Perception and Performance, Vol 37, pp. 1017-1031) found that, unlike previous work, participants missed a higher number of targets with search for moving items worse than for static items and that there was no benefit for finding targets that showed a luminance onset. In the present research, we investigated why luminance onsets do not capture attention and whether luminance onsets can ever capture attention in MAD search. Experiment 1 investigated whether blinking stimuli, which abruptly offset for 100 ms before reonsetting-conditions known to produce attentional capture in simpler visual search tasks-captured attention in MAD search, and Experiments 2-5 investigated whether giving participants advance knowledge and preexposure to the blinking cues produced efficient search for blinking targets. Experiments 6-9 investigated whether unique luminance onsets, unique motion, or unique stationary items captured attention. The results found that luminance onsets captured attention in MAD search only when they were unique, consistent with a top-down unique feature hypothesis. (PsycINFO Database Record (c) 2013 APA, all rights reserved)

When are abrupt onsets found efficiently in complex visual search? : evidence from multi-element asynchronous dynamic search

Previous work has found that search principles derived from simple visual search tasks do not necessarily apply to more complex search tasks. Using a Multielement Asynchronous Dynamic (MAD) visual search task, in which high numbers of stimuli could either be moving, stationary, and/or changing in luminance, Kunar and Watson (M. A Kunar & D. G. Watson, 2011, Visual search in a Multi-element Asynchronous Dynamic (MAD) world, Journal of Experimental Psychology: Human Perception and Performance, Vol 37, pp. 1017-1031) found that, unlike previous work, participants missed a higher number of targets with search for moving items worse than for static items and that there was no benefit for finding targets that showed a luminance onset. In the present research, we investigated why luminance onsets do not capture attention and whether luminance onsets can ever capture attention in MAD search. Experiment 1 investigated whether blinking stimuli, which abruptly offset for 100 ms before reonsetting-conditions known to produce attentional capture in simpler visual search tasks-captured attention in MAD search, and Experiments 2-5 investigated whether giving participants advance knowledge and preexposure to the blinking cues produced efficient search for blinking targets. Experiments 6-9 investigated whether unique luminance onsets, unique motion, or unique stationary items captured attention. The results found that luminance onsets captured attention in MAD search only when they were unique, consistent with a top-down unique feature hypothesis. (PsycINFO Database Record (c) 2013 APA, all rights reserved)

Visual marking and change blindness : moving occluders and transient masks neutralize shape changes to ignored objects

Visual search efficiency improves by presenting (previewing) one set of distractors before the target and remaining distractor items (D. G. Watson & G. W. Humphreys, 1997). Previous work has shown that this preview benefit is abolished if the old items change their shape when the new items are added (e.g., D. G. Watson & G. W. Humphreys, 2002). Here we present 5 experiments that examined whether such object changes are still effective in recapturing attention if the changes occur while the previewed objects are occluded or masked. Overall, the findings suggest that masking transients are effective in preventing both object changes and the presentation of new objects from capturing attention in time-based visual search conditions. The findings are discussed in relation to theories of change blindness, new object capture, and the ecological properties of time-based visual selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved

Cover pebbling numbers and bounds for certain families of graphs

Given a configuration of pebbles on the vertices of a graph, a pebbling move is defined by removing two pebbles from some vertex and placing one pebble on an adjacent vertex. The cover pebbling number of a graph, gamma(G), is the smallest number of pebbles such that through a sequence of pebbling moves, a pebble can eventually be placed on every vertex simultaneously, no matter how the pebbles are initially distributed. The cover pebbling number for complete multipartite graphs and wheel graphs is determined. We also prove a sharp bound for gamma(G) given the diameter and number of vertices of G.Comment: 10 pages, 1 figure, submitted to Discrete Mathematic

Domination Cover Pebbling: Structural Results

This paper continues the results of "Domination Cover Pebbling: Graph Families." An almost sharp bound for the domination cover pebbling (DCP) number for graphs G with specified diameter has been computed. For graphs of diameter two, a bound for the ratio between the cover pebbling number of G and the DCP number of G has been computed. A variant of domination cover pebbling, called subversion DCP is introducted, and preliminary results are discussed.Comment: 15 page