The hot gas content of fossil galaxy clusters

We investigate the properties of the hot gas in four fossil galaxy systems detected at high significance in the Planck Sunyaev-Zeldovich (SZ) survey. XMM-Newton observations reveal overall temperatures of kT ~ 5-6 keV and yield hydrostatic masses M500,HE > 3.5 x 10e14 Msun, confirming their nature as bona fide massive clusters. We measure the thermodynamic properties of the hot gas in X-rays (out to beyond R500 in three cases) and derive their individual pressure profiles out to R ~ 2.5 R500 with the SZ data. We combine the X-ray and SZ data to measure hydrostatic mass profiles and to examine the hot gas content and its radial distribution. The average Navarro-Frenk-White (NFW) concentration parameter, c500 = 3.2 +/- 0.4, is the same as that of relaxed `normal' clusters. The gas mass fraction profiles exhibit striking variation in the inner regions, but converge to approximately the cosmic baryon fraction (corrected for depletion) at R500. Beyond R500 the gas mass fraction profiles again diverge, which we interpret as being due to a difference in gas clumping and/or a breakdown of hydrostatic equilibrium in the external regions. Overall our observations point to considerable radial variation in the hot gas content and in the gas clumping and/or hydrostatic equilibrium properties in these fossil clusters, at odds with the interpretation of their being old, evolved and undisturbed. At least some fossil objects appear to be dynamically young.Comment: 4 pages, 2 figures. Accepted for publication in A&

The role of spatial and non-spatial information in visual selection.

Even though it is undisputed that prior information regarding the location of a target affects visual selection, the issue of whether information regarding nonspatial features, such as color and shape, has similar effects has been a matter of debate since the early 1980s. In the study described in this article, measures derived from signal detection theory were used to show that perceptual sensitivity is affected by a top-down set for spatial information but not by a top-down set for nonspatial information. This indicates that knowing where the target singleton is affects perceptual selectivity but that knowing what it is does not help selectivity. Furthermore, perceptual sensitivity can be enhanced by nonspatial features, but only through a process related to bottom-up priming. These findings have important implications for models of visual selection. © 2007 American Psychological Association

Helmholtz Versus Haute Couture: How Horizontal Stripes and Dark Clothes Make You Look Thinner

In Helmholtz’s illusion, a square with horizontal stripes appears taller than an identical square with vertical stripes. This effect has also been observed in experiments with human stimuli, where a human figure wearing a dress with horizontal stripes appears thinner than a drawing clad in vertical stripes. These findings do not agree with the common belief that clothes with horizontal stripes make someone appear wider, neither do they disentangle whether the horizontal or vertical stripes account for the thinning effect. In the present study, we focused on the effect of horizontal stripes in clothes comparing horizontal stripes against no-stripes (not against vertical; Experiments 1 and 2), using photos of a real-life female model, and controlling for the average luminance of the stripes (Experiment 2). Results showed that horizontal stripes and lower luminance have—independently—a small-to-moderate thinning effect on the perceived size of the body, and the effect is larger when the two variables are combined. In Experiment 3, we further show that the thinning effect due to the luminance of the dress is enhanced when the general background gets darker

Religious beliefs and entrepreneurship among Dutch protestants

Religious beliefs affect the economic behavior of individuals. The aim of this study is to investigate the relation between religious beliefs and entrepreneurship. Empirical evidence that entrepreneurship rates differ among religions suggests that religious beliefs influence the pursuit of entrepreneurship. However, how and which specific religious beliefs play a role in this relationship remains unknown. Therefore, we study the relation between two key religious beliefs and entrepreneurship within one specific branch of Christianity, namely, Protestantism. Using a unique sample of 756 Christian protestant entrepreneurs and employees from the Netherlands, we show that protestant entrepreneurs have a stronger belief than comparable protestant employees that their work is a calling from God and that protestant entrepreneurs are more likely to perceive a duty to add value to society through their occupational work. These results indicate that research on the relation between religion and entrepreneurship is instrumental in explaining the engagement of people in entrepreneurship

Detecting the presence of a singleton involves focal attention

It has been claimed that the detection of a feature singleton can be based on activity in a feature map that allows coarse coding that something unique is present in the visual field. In the present study, participants detected the presence or absence of a color singleton. Even though the letter form of the color singleton was task-irrelevant, we showed that repeating the letter form of the singleton resulted in repetition priming on the next trial. Such repetition priming was not found when a nonsingleton letter was repeated as the singleton. Since the letter form of the color singleton could only be picked up by focal attention, the repetition priming effect indicates that focal attention is allocated to the feature singleton even in the simplest present-absent feature detection tasks. We showed that this effect is equally strong in conditions of low and high perceptual load. These results are inconsistent with theories that it is possible to detect a feature singleton without directing some form of attention to its location. Copyright 2008 Psychonomic Society, Inc