70,475 research outputs found
The Search for AGN in Distant Galaxy Clusters
We are undertaking the first systematic study of the prevalence of AGN
activity in a large sample of high redshift galaxy clusters. Local clusters
contain mainly red elliptical galaxies, and have little or no luminous AGN
activity. However, recent studies of some moderate to high redshift clusters
have revealed significant numbers of luminous AGN within the cluster. This
effect may parallel the Butcher-Oemler effect - the increase in the fraction of
blue galaxies in distant clusters compared to local clusters. Our aim is to
verify and quantify recent evidence that AGN activity in dense environments
increases with redshift, and to evaluate the significance of this effect. As
cluster AGN are far less prevalent than field sources, a large sample of over
120 cluster fields at z > 0.1 has been selected from the Chandra archives and
is being analysed for excess point sources. The size of the excess, the radial
distribution and flux of the sources and the dependence of these on cluster
redshift and luminosity will reveal important information about the triggering
and fueling of AGN.Comment: 2 pages, to appear in proceedings of 'Multi-wavelength AGN surveys',
Cozumel, 200
On the maximum entropy principle and the minimization of the Fisher information in Tsallis statistics
We give a new proof of the theorems on the maximum entropy principle in
Tsallis statistics. That is, we show that the -canonical distribution
attains the maximum value of the Tsallis entropy, subject to the constraint on
the -expectation value and the -Gaussian distribution attains the maximum
value of the Tsallis entropy, subject to the constraint on the -variance, as
applications of the nonnegativity of the Tsallis relative entropy, without
using the Lagrange multipliers method. In addition, we define a -Fisher
information and then prove a -Cram\'er-Rao inequality that the -Gaussian
distribution with special -variances attains the minimum value of the
-Fisher information
Evolution of Resource Competition between Mutually Dependent Digital Organisms
We study the emergence and dynamics of competing strains of digital organisms in a world with two depletable resources. Consumption of one resource produces the other resource as a by-product, and vice versa. As a consequence, two types of mutually dependent organisms emerge that each prey on the waste product of the other. In the absence of mutations, that is, in a purely ecological setting, the abundances of the two types of organisms display a wide range of different types of oscillations, from regular
oscillations with large amplitude to irregular oscillations with amplitudes ranging from small to large. In this regime,
time-averaged abundance levels seem to be controlled by the
relative fitness of the organisms in the absence of resources. Under mutational pressure, on the other hand, populations evolve that seem to avoid the oscillations of intermediate to large amplitudes. In this case, the relative fitness of the organisms in the presence of resources plays an important role in the time-averaged abundance levels as well
Fluid power transmission Patent
Fluid power transmission and gas bearing syste
Pneumatic power is transmitted through air bearing
A more efficient method for supplying high pressure air to an air bearing and pneumatic equipment mounted on it has been developed. The system uses a conventional air bearing and an air-supported sphere with a central passage. High pressure air is channeled through it into the pneumatic equipment on the sphere
Child Poverty in Rural America
This report explores the well-being of the 14 million children who live in rural America. Rural families represent a significant share of our total population and they are disproportionately poor, less educated, and underemployed. Yet poor children and the unique challenges they face are often overlooked by policymakers. Poor children living in rural America face significant educational, social, and economic challenges just as their urban counterparts do, but many of these problems are exacerbated by the isolation and limited access to support services common in rural areas
Specialization of neural mechanisms underlying face recognition in human infants
Newborn infants respond preferentially to simple face-like patterns, raising the possibility that the face-specific region, identified in the adult cortex are functioning from birth. We sought to evaluate this hypothesis by characterizing the specificity Of infants' electrocortical responses to faces in two ways: (1) comparing responses to faces of humans with those to faces of nonhuman primates; and 2) comparing responses to upright and inverted faces. Adults' face-responsive N170 event-related potential (ERP) component showed specificity to upright human faces that was not observable at any point in the ERPs Of infants. A putative "infant N170" did show sensitivity to the species of the face, but the orientation of the face did not influence processing until a later stage. These findings suggest a process of gradual specialization of cortical face processing systems during postnatal development
Specificity of aequorin luminescence to calcium
The presence of Pb(++), Co(++), Cu(++), and Cd(++), each of which possesses a certain luminescence-triggering activity of aequorin, potentially interferes with the specificity of the aequorin luminescence response to Ca(++). Interference by the above cations can be eliminated, without influencing the sensitivity of the luminescence of aequorin to Ca(++), by adding 1 mM of sodium diethyldithiocarbamate
A new puzzle for random interaction
We continue a series of numerical experiments on many-body systems with
random two-body interactions, by examining correlations in ratios in excitation
energies of yrast = 0, 2, 4, 6, 8 states. Previous studies, limited only to
= 0,2,4 states, had shown strong correlations in boson systems but not
fermion systems. By including states and considering different
scatter plots, strong and realistic correlations appear in both boson and
fermion systems. Such correlations are a challenge to explanations of random
interactions.Comment: 4 pages, 4 figure
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