15,244 research outputs found
The envirome and the connectome: exploring the structural noise in the human brain associated with socioeconomic deprivation
Complex cognitive functions are widely recognized to be the result of a number of brain regions working together as large-scale networks. Recently, complex network analysis has been used to characterize various structural properties of the large scale network organization of the brain. For example, the human brain has been found to have a modular architecture i.e. regions within the network form communities (modules) with more connections between regions within the community compared to regions outside it. The aim of this study was to examine the modular and overlapping modular architecture of the brain networks using complex network analysis. We also examined the association between neighborhood level deprivation and brain network structure – modularity and grey nodes. We compared network structure derived from anatomical MRI scans of 42 middle-aged neurologically healthy men from the least (LD) and the most deprived (MD) neighborhoods of Glasgow with their corresponding random networks. Cortical morphological covariance networks were constructed from the cortical thickness derived from the MRI scans of the brain. For a given modularity threshold, networks derived from the MD group showed similar number of modules compared to their corresponding random networks, while networks derived from the LD group had more modules compared to their corresponding random networks. The MD group also had fewer grey nodes – a measure of overlapping modular structure. These results suggest that apparent structural difference in brain networks may be driven by differences in cortical thicknesses between groups. This demonstrates a structural organization that is consistent with a system that is less robust and less efficient in information processing. These findings provide some evidence of the relationship between socioeconomic deprivation and brain network topology
Time transfer using NAVSTAR GPS
A time transfer unit (TTU) developed for the U.S. Naval Observatory (USNO) has consistently demonstrated the transfer of time with accuracies much better than 100 nanoseconds. A new time transfer system (TTS), the TTS 502 was developed. The TTS 502 is a relatively compact microprocessor-based system with a variety of options that meet each individual's requirements, and has the same performance as the USNO system. The time transfer performance of that USNO system and the details of the new system are presented
The effect of electron beam pitch angle and density gradient on solar type III radio bursts
Copyright 2012 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Physics of Plasmas 19, 112903 (2012) and may be found at .supplemental material at http://astro.qmul.ac.uk/~tsiklauri/sp.htmlsupplemental material at http://astro.qmul.ac.uk/~tsiklauri/sp.htm
Infrared images of merging galaxies
Infrared imaging of interacting galaxies is especially interesting because their optical appearance is often so chaotic due to extinction by dust and emission from star formation regions, that it is impossible to locate the nuclei or determine the true stellar distribution. However, at near-infrared wavelengths extinction is considerably reduced, and most of the flux from galaxies originates from red giant stars that comprise the dominant stellar component by mass. Thus near infrared images offer the opportunity to study directly components of galactic structure which are otherwise inaccessible. Such images may ultimately provide the framework in which to understand the activity taking place in many of the mergers with high Infrared Astronomy Satellite (IRAS) luminosities. Infrared images have been useful in identifying double structures in the nuclei of interacting galaxies which have not even been hinted at by optical observations. A striking example of this is given by the K images of Arp 220. Graham et al. (1990) have used high resolution imaging to show that it has a double nucleus coincident with the radio sources in the middle of the dust lane. The results suggest that caution should be applied in the identification of optical bright spots as multiple nuclei in the absence of other evidence. They also illustrate the advantages of using infrared imaging to study the underlying structure in merging galaxies. The authors have begun a program to take near infrared images of galaxies which are believed to be mergers of disk galaxies because they have tidal tails and filaments. In many of these the merger is thought to have induced exceptionally luminous infrared emission (cf. Joseph and Wright 1985, Sanders et al. 1988). Although the optical images of the galaxies show spectacular dust lanes and filaments, the K images all have a very smooth distribution of light with an apparently single nucleus
Close pairs of galaxies with different activity levels
We selected and studied 180 pairs with dV < 800 km/s and Dp < 60 kpc
containing Markarian (MRK) galaxies to investigate the dependence of galaxies'
integral parameters, star-formation (SF) and active galactic nuclei (AGN)
properties on kinematics of pairs, their structure and large-scale
environments. Projected radial separation Dp and perturbation level P are
better measures of interaction strength than dV. The latter correlates with the
density of large-scale environment and with the morphologies of galaxies. Both
galaxies in a pair are of the same nature, the only difference is that MRK
galaxies are usually righter than their neighbors. Specific star formation
rates (SSFR) of galaxies in pairs with smaller Dp or dV is in average 0.5 dex
higher than that of galaxies in pairs with larger Dp or dV. Closeness of a
neighbor with the same and later morphological type increases the SSFR, while
earlier-type neighbors do not increase SSFR. Major interactions/mergers trigger
SF and AGN more effectively than minor ones. The fraction of AGNs is higher in
more perturbed pairs and pairs with smaller Dp. AGNs typically are in stronger
interacting systems than star-forming and passive galaxies. There are
correlations of both SSFRs and spectral properties of nuclei between pair
members.Comment: 4 pages, 3 figures. arXiv admin note: substantial text overlap with
arXiv:1310.024
Close neighbors of Markarian galaxies. II. Statistics and discussions
According to the database from the first paper, we select 180 pairs with dV <
800 km/s and Dp < 60 kpc containing Markarian (MRK) galaxies. We study the
dependence of galaxies integral parameters, star-formation (SF) and active
galactic nuclei (AGN) properties on kinematics of pairs, their structure and
large-scale environments. Following main results were obtained: projected
radial separation Dp between galaxies correlates with the perturbation level P
of the pairs. Both parameters do not correlate with line-of-sight velocity
difference dV of galaxies. Dp and P are better measures of interaction strength
than dV. The latter correlates with the density of large-scale environment and
with the morphologies of galaxies. Both galaxies in a pair are of the same
nature, the only difference is that MRK galaxies are usually brighter than
their neighbors in average by 0.9 mag. Specific star formation rates (SSFR) of
galaxies in pairs with smaller Dp or dV is in average 0.5 dex higher than that
of galaxies in pairs with larger Dp or dV. Closeness of a neighbor with the
same and later morphological type increases the SSFR, while earlier-type
neighbors do not increase SSFR. Major interactions/mergers trigger SF and AGN
more effectively than minor ones. The fraction of AGNs is higher in more
perturbed pairs and pairs with smaller Dp. AGNs typically are in stronger
interacting systems than star-forming and passive galaxies. There are
correlations of both SSFRs and spectral properties of nuclei between pair
members.Comment: 13 pages, 8 figures, 2 table
Smelly maps: the digital life of urban smellscapes
Smell has a huge influence over how we perceive places. Despite its importance, smell has been crucially overlooked by urban planners and scientists alike, not least because it is difficult to record and analyze at scale. One of the authors of this paper has ventured out in the urban world and conducted ``smellwalks'' in a variety of cities: participants were exposed to a range of different smellscapes and asked to record their experiences. As a result, smell-related words have been collected and classified, creating the first dictionary for urban smell. Here we explore the possibility of using social media data to reliably map the smells of entire cities. To this end, for both Barcelona and London, we collect geo-referenced picture tags from Flickr and Instagram, and geo-referenced tweets from Twitter. We match those tags and tweets with the words in the smell dictionary. We find that smell-related words are best classified in ten categories. We also find that specific categories (e.g., industry, transport, cleaning) correlate with governmental air quality indicators, adding validity to our study
Supersonic aircraft Patent
Design of supersonic aircraft with novel fixed, swept wing planfor
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