4,077 research outputs found
Uncovering the overlapping community structure of complex networks in nature and society
Many complex systems in nature and society can be described in terms of
networks capturing the intricate web of connections among the units they are
made of. A key question is how to interpret the global organization of such
networks as the coexistence of their structural subunits (communities)
associated with more highly interconnected parts. Identifying these a priori
unknown building blocks (such as functionally related proteins, industrial
sectors and groups of people) is crucial to the understanding of the structural
and functional properties of networks. The existing deterministic methods used
for large networks find separated communities, whereas most of the actual
networks are made of highly overlapping cohesive groups of nodes. Here we
introduce an approach to analysing the main statistical features of the
interwoven sets of overlapping communities that makes a step towards uncovering
the modular structure of complex systems. After defining a set of new
characteristic quantities for the statistics of communities, we apply an
efficient technique for exploring overlapping communities on a large scale. We
find that overlaps are significant, and the distributions we introduce reveal
universal features of networks. Our studies of collaboration, word-association
and protein interaction graphs show that the web of communities has non-trivial
correlations and specific scaling properties.Comment: The free academic research software, CFinder, used for the
publication is available at the website of the publication:
http://angel.elte.hu/clusterin
The inner core hemispheric boundary near 180°W
The inner core (IC) eastâwest hemispheric dichotomy is widely recognized, but the reported position of the hemispheric boundary varies among studies due to uneven sampling coverage and the data analyzed. This study investigates the sharpness of the western hemispheric boundary (WHB) near 180°W by analyzing differential time residuals of PKiKPâPKPdf and PKP(bcâdf) for PKPdf phases that sample 155°Eâ130°W in various azimuthal directions. Using PKiKPâPKPdf observations, the WHB is located at 175°Eâ180°W in the southern hemisphere, based mainly on the lateral isotropyâanisotropy transition. However, based on the lateral isotropic velocity contrast and this isotropyâanisotropy transition between the two hemispheres, its location is 170â160°W in the northern hemisphere. These findings indicate that the WHB is sharp and exhibits a latitudinal dependence with a 10°â20° kink, as well as 1.75% anisotropy in the uppermost IC across the 180â155°W range of the western hemisphere. As suggested by PKP(bcâdf), the WHB could remain at 160°W at depth. The isotropic velocity contrast near the WHB (160°W) between the eastern and western hemispheres is lower than previous estimates using PKPdf phases sampling the bulk part of each hemisphere
Estimated HIV Incidence in the United States, 2006â2009
Background
The estimated number of new HIV infections in the United States reflects the leading edge of the epidemic. Previously, CDC estimated HIV incidence in the United States in 2006 as 56,300 (95% CI: 48,200â64,500). We updated the 2006 estimate and calculated incidence for 2007â2009 using improved methodology.
Methodology
We estimated incidence using incidence surveillance data from 16 states and 2 cities and a modification of our previously described stratified extrapolation method based on a sample survey approach with multiple imputation, stratification, and extrapolation to account for missing data and heterogeneity of HIV testing behavior among population groups.
Principal Findings
Estimated HIV incidence among persons aged 13 years and older was 48,600 (95% CI: 42,400â54,700) in 2006, 56,000 (95% CI: 49,100â62,900) in 2007, 47,800 (95% CI: 41,800â53,800) in 2008 and 48,100 (95% CI: 42,200â54,000) in 2009. From 2006 to 2009 incidence did not change significantly overall or among specific race/ethnicity or risk groups. However, there was a 21% (95% CI:1.9%â39.8%; p = 0.017) increase in incidence for people aged 13â29 years, driven by a 34% (95% CI: 8.4%â60.4%) increase in young men who have sex with men (MSM). There was a 48% increase among young black/African American MSM (12.3%â83.0%; p<0.001). Among people aged 13â29, only MSM experienced significant increases in incidence, and among 13â29 year-old MSM, incidence increased significantly among young, black/African American MSM. In 2009, MSM accounted for 61% of new infections, heterosexual contact 27%, injection drug use (IDU) 9%, and MSM/IDU 3%.
Conclusions/Significance
Overall, HIV incidence in the United States was relatively stable 2006â2009; however, among young MSM, particularly black/African American MSM, incidence increased. HIV continues to be a major public health burden, disproportionately affecting several populations in the United States, especially MSM and racial and ethnic minorities. Expanded, improved, and targeted prevention is necessary to reduce HIV incidence
Source Characteristics of the 2016 Meinong (ML 6.6) Taiwan Earthquake Revealed from Dense Seismic Arrays: Double Sources and Pulse-like Velocity Ground Motion
The 5 February 2016, Meinong, Taiwan, earthquake brought extensive damage to nearby cities with significant pulseâlike velocity ground motions. In addition to the spatial slip distribution determination using filtered strongâmotion data, we show that, with the advantage of the densely distributed seismic network as a seismic array, we can project the earthquake sources (asperities) directly using nearly unfiltered data, which is crucial to the understanding of the generation of the pulseâlike velocity ground motions. We recognize that the moderate but damaging ML 6.6 Meinong earthquake was a composite of an Mw 5.5 foreshock and an Mw 6.18 mainshock with a 1.8â5.0 s time delay. The foreshock occurred at the hypocenter reported by the official agency, followed by the mainshock with a centroid located at 12.3 km to the northânorthwest of the hypocenter and at a depth of 15 km. This foreshockâmainshock composition is not distinguishable in the finiteâfault inversion because it filtered the seismic data to low frequencies. Our results show that the pulseâlike velocity ground motions are mainly attributed to the source of mainshock with its directivity and site effects, resulting in the disastrous damages in the city of Tainan. Although finiteâfault inversion using filtered seismic data for spatial slip distribution on the fault has been a classic procedure in understanding earthquake rupture processes, using a dense seismic network as a seismic array for unfiltered records helps us delineate the earthquake sources directly and provide more delicate information for future understanding of earthquake source complexity
Lifshitz/Schr\"odinger D-p-branes and dynamical exponents
We extend our earlier study of special double limits of `boosted'
black hole solutions to include all black D-branes of type II strings. We
find that Lifshitz solutions can be obtained in generality, with varied
dynamical exponents, by employing these limits. We then study such double
limits for `boosted' D-brane bubble solutions and find that the resulting
non-relativistic solutions instead describe Schr\"odinger like spacetimes,
having varied dynamical exponents. We get a simple map between these Lifshitz &
Schr\"odinger solutions and a relationship between two types of dynamical
exponents. We also discuss about the singularities of the Lifshitz solutions
and an intriguing thermodynamic duality.Comment: 20 pages; 3 figures; v3: similar to JHE
Set optimization - a rather short introduction
Recent developments in set optimization are surveyed and extended including
various set relations as well as fundamental constructions of a convex analysis
for set- and vector-valued functions, and duality for set optimization
problems. Extensive sections with bibliographical comments summarize the state
of the art. Applications to vector optimization and financial risk measures are
discussed along with algorithmic approaches to set optimization problems
Improved annotation of 3' untranslated regions and complex loci by combination of strand-specific direct RNA sequencing, RNA-seq and ESTs
The reference annotations made for a genome sequence provide the framework
for all subsequent analyses of the genome. Correct annotation is particularly
important when interpreting the results of RNA-seq experiments where short
sequence reads are mapped against the genome and assigned to genes according to
the annotation. Inconsistencies in annotations between the reference and the
experimental system can lead to incorrect interpretation of the effect on RNA
expression of an experimental treatment or mutation in the system under study.
Until recently, the genome-wide annotation of 3-prime untranslated regions
received less attention than coding regions and the delineation of intron/exon
boundaries. In this paper, data produced for samples in Human, Chicken and A.
thaliana by the novel single-molecule, strand-specific, Direct RNA Sequencing
technology from Helicos Biosciences which locates 3-prime polyadenylation sites
to within +/- 2 nt, were combined with archival EST and RNA-Seq data. Nine
examples are illustrated where this combination of data allowed: (1) gene and
3-prime UTR re-annotation (including extension of one 3-prime UTR by 5.9 kb);
(2) disentangling of gene expression in complex regions; (3) clearer
interpretation of small RNA expression and (4) identification of novel genes.
While the specific examples displayed here may become obsolete as genome
sequences and their annotations are refined, the principles laid out in this
paper will be of general use both to those annotating genomes and those seeking
to interpret existing publically available annotations in the context of their
own experimental dataComment: 44 pages, 9 figure
White matter changes in microstructure associated with a maladaptive response to stress in rats
In today's society, every individual is subjected to stressful stimuli with different intensities and duration. This exposure can be a key trigger in several mental illnesses greatly affecting one's quality of life. Yet not all subjects respond equally to the same stimulus and some are able to better adapt to them delaying the onset of its negative consequences. The neural specificities of this adaptation can be essential to understand the true dynamics of stress as well as to design new approaches to reduce its consequences. In the current work, we employed ex vivo high field diffusion magnetic resonance imaging (MRI) to uncover the differences in white matter properties in the entire brain between Fisher 344 (F344) and Sprague-Dawley (SD) rats, known to present different responses to stress, and to examine the effects of a 2-week repeated inescapable stress paradigm. We applied a tract-based spatial statistics (TBSS) analysis approach to a total of 25 animals. After exposure to stress, SD rats were found to have lower values of corticosterone when compared with F344 rats. Overall, stress was found to lead to an overall increase in fractional anisotropy (FA), on top of a reduction in mean and radial diffusivity (MD and RD) in several white matter bundles of the brain. No effect of strain on the white matter diffusion properties was observed. The strain-by-stress interaction revealed an effect on SD rats in MD, RD and axial diffusivity (AD), with lower diffusion metric levels on stressed animals. These effects were localized on the left side of the brain on the external capsule, corpus callosum, deep cerebral white matter, anterior commissure, endopiriform nucleus, dorsal hippocampus and amygdala fibers. The results possibly reveal an adaptation of the SD strain to the stressful stimuli through synaptic and structural plasticity processes, possibly reflecting learning processes.We thank Neurospin (high ïŹeld MRI center CEA Saclay) for providing its support for MRI acquisition. JB was supported by grants from Fondation pour la Recherche MĂ©dicale (FRM) and Groupe Pasteur MutualitĂ© (GPM). This work was supported by a grant from ANR (SIGMA). This work was performed on a platform of France Life Imaging (FLI) network partly funded by the grant ANR-11-INBS-0006. This work and RM were supported by a fellowship of the project FCT-ANR/NEU-OSD/0258/2012 founded by FCT/MEC (www.fct.pt) and by Fundo Europeu de Desenvolvimento Regional (FEDER). AC was supported by a grant from the Fondation NRJ.info:eu-repo/semantics/publishedVersio
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