504 research outputs found
A catalog of Nearby Poor Clusters of Galaxies
A catalog of 732 optically selected, nearby poor clusters of galaxies
covering the entire sky north of declination is presented. The
poor clusters, called WBL clusters, were identified as concentrations of 3 or
more galaxies with photographic magnitudes brighter than 15.7, possessing a
galaxy surface overdensity of . These criteria are consistent with
those used in the identification of the original Yerkes poor clusters, and this
new catalog substantially increases the sample size of such objects. These poor
clusters cover the entire range of galaxy associations up to and including
Abell clusters, systematically including poor and rich galaxy systems spanning
over three orders of magnitude in the cluster mass function. As a result, this
new catalog contains a greater diversity of richness and structures than other
group catalogs, such as the Hickson or Yerkes catalogs. The information on
individual galaxies includes redshifts and cross-references to other galaxy
catalogs. The entries for the clusters include redshift (where available) and
cross-references to other group and cluster catalogs.Comment: 27 pages, 7 figures, + one 20-page landscape table, accepted for
publication in A
The Superiority of the Minimal Spanning Tree in Percolation Analyses of Cosmological Datasets
In this work we demonstrate the ability of the Minimal Spanning Tree to
duplicate the information contained within a percolation analysis for a point
dataset. We show how to construct the percolation properties from the Minimal
Spanning Tree, finding roughly an order of magnitude improvement in the
computer time required. We apply these statistics to Particle-Mesh simulations
of large-scale structure formation. We consider purely scale-free Gaussian
initial conditions (, with ) in a
critical density universe. We find in general the mass of the percolating
cluster is a much better quantity by which to judge the onset of percolation
than the length of the percolating cluster.Comment: 7 pages, 4 figures included, uses mn.sty & epsf.sty. Accepted by
MNRA
Co-Localization of DNA i-Motif-Forming Sequences and 5-Hydroxymethyl-cytosines in Human Embryonic Stem Cells
G-quadruplexes (G4s) and i-motifs (iMs) are tetraplex DNA structures. Sequences capable of forming G4/iMs are abundant near the transcription start sites (TSS) of several genes. G4/iMs affect gene expression in vitro. Depending on the gene, the presence of G4/iMs can enhance or suppress expression, making it challenging to discern the underlying mechanism by which they operate. Factors affecting G4/iM structures can provide additional insight into their mechanism of regulation. One such factor is epigenetic modification. The 5-hydroxymethylated cytosines (5hmCs) are epigenetic modifications that occur abundantly in human embryonic stem cells (hESC). The 5hmCs, like G4/iMs, are known to participate in gene regulation and are also enriched near the TSS. We investigated genomic co-localization to assess the possibility that these two elements may play an interdependent role in regulating genes in hESC. Our results indicate that amongst 15,760 G4/iM-forming locations, only 15% have 5hmCs associated with them. A detailed analysis of G4/iM-forming locations enriched in 5hmC indicates that most of these locations are in genes that are associated with cell differentiation, proliferation, apoptosis and embryogenesis. The library generated from our analysis is an important resource for investigators exploring the interdependence of these DNA features in regulating expression of selected genes in hESC
Minority status and mental distress: a comparison of group density effects
Background
It has been observed that mental disorders, such as psychosis, are more common for people in some ethnic groups in areas where their ethnic group is less common. We set out to test whether this ethnic density effect reflects minority status in general, by looking at three situations where individual characteristics differ from what is usual in a locality.
Method
Using data from the South East London Community Health study (n = 1698) we investigated associations between minority status (defined by: ethnicity, household status and occupational social class) and risk of psychotic experiences, common mental disorders and parasuicide. We used a multilevel logistic model to examine cross-level interactions between minority status at individual and neighbourhood levels.
Results
Being Black in an area where this was less common (10%) was associated with higher odds of psychotic experiences [odds ratio (OR) 1.34 95% confidence interval (CI) 1.07–1.67], and attempted suicide (OR 1.84 95% CI 1.19–2.85). Living alone where this was less usual (10% less) was associated with increased odds of psychotic experiences (OR 2.18 95% CI 0.91–5.26), while being in a disadvantaged social class where this was less usual (10% less) was associated with increased odds of attempted suicide (OR 1.33 95% CI 1.03–1.71). We found no evidence for an association with common mental disorders.
Conclusions
The relationship between minority status and mental distress was most apparent when defined in terms of broad ethnic group but was also observed for individual household status and occupational social class
A Testable Solution of the Cosmological Constant and Coincidence Problems
We present a new solution to the cosmological constant (CC) and coincidence
problems in which the observed value of the CC, , is linked to other
observable properties of the universe. This is achieved by promoting the CC
from a parameter which must to specified, to a field which can take many
possible values. The observed value of Lambda ~ 1/(9.3 Gyrs)^2\Lambda$-values
and does not rely on anthropic selection effects. Our model includes no
unnatural small parameters and does not require the introduction of new
dynamical scalar fields or modifications to general relativity, and it can be
tested by astronomical observations in the near future.Comment: 31 pages, 4 figures; v2: version accepted by Phys. Rev.
HOP: A New Group-Finding Algorithm for N-body Simulations
We describe a new method (HOP) for identifying groups of particles in N-body
simulations. Having assigned to every particle an estimate of its local
density, we associate each particle with the densest of the N_hop particles
nearest to it. Repeating this process allows us to trace a path, within the
particle set itself, from each particle in the direction of increasing density.
The path ends when it reaches a particle that is its own densest neighbor; all
particles reaching the same such particle are identified as a group. Combined
with an adaptive smoothing kernel for finding the densities, this method is
spatially adaptive, coordinate-free, and numerically straight-forward. One can
proceed to process the output by truncating groups at a particular density
contour and combining groups that share a (possibly different) density contour.
While the resulting algorithm has several user-chosen parameters, we show that
the results are insensitive to most of these, the exception being the outer
density cutoff of the groups.Comment: LaTeX, 18 pages, 7 Postscript figures included. ApJ, in press. Source
code available from http://www.sns.ias.edu/~eisenste/hop/hop.htm
Primordial Non-Gaussianity and Extreme-Value Statistics of Galaxy Clusters
What is the size of the most massive object one expects to find in a survey
of a given volume? In this paper, we present a solution to this problem using
Extreme-Value Statistics, taking into account primordial non-Gaussianity and
its effects on the abundance and the clustering of rare objects. We calculate
the probability density function (pdf) of extreme-mass clusters in a survey
volume, and show how primordial non-Gaussianity shifts the peak of this pdf. We
also study the sensitivity of the extreme-value pdfs to changes in the mass
functions, survey volume, redshift coverage and the normalization of the matter
power spectrum, {\sigma}_8. For 'local' non-Gaussianity parametrized by f_NL,
our correction for the extreme-value pdf due to the bias is important when f_NL
> O(100), and becomes more significant for wider and deeper surveys. Applying
our formalism to the massive high-redshift cluster XMMUJ0044.0-2-33, we find
that its existence is consistent with f_NL = 0, although the conclusion is
sensitive to the assumed values of the survey area and {\sigma}_8. We also
discuss the convergence of the extreme-value distribution to one of the three
possible asymptotic forms, and argue that the convergence is insensitive to the
presence of non-Gaussianity.Comment: Revised version, 20 pages, 10 figures. Major improvement in the
treatment of non-Gaussian bias. Previous claim of large f_NL associated with
the cluster is no longer supporte
Sputum ACE2, TMPRSS2 and FURIN gene expression in severe neutrophilic asthma
Background Patients with severe asthma may have a greater risk of dying from COVID-19 disease. Angiotensin converting enzyme-2 (ACE2) and the enzyme proteases, transmembrane protease serine 2 (TMPRSS2) and FURIN, are needed for viral attachment and invasion into host cells. Methods We examined microarray mRNA expression of ACE2, TMPRSS2 and FURIN in sputum, bronchial brushing and bronchial biopsies of the European U-BIOPRED cohort. Clinical parameters and molecular phenotypes, including asthma severity, sputum inflammatory cells, lung functions, oral corticosteroid (OCS) use, and transcriptomic-associated clusters, were examined in relation to gene expression levels. Results ACE2 levels were significantly increased in sputum of severe asthma compared to mild-moderate asthma. In multivariate analyses, sputum ACE2 levels were positively associated with OCS use and male gender. Sputum FURIN levels were significantly related to neutrophils (%) and the presence of severe asthma. In bronchial brushing samples, TMPRSS2 levels were positively associated with male gender and body mass index, whereas FURIN levels with male gender and blood neutrophils. In bronchial biopsies, TMPRSS2 levels were positively related to blood neutrophils. The neutrophilic molecular phenotype characterised by high inflammasome activation expressed significantly higher FURIN levels in sputum than the eosinophilic Type 2-high or the pauci-granulocytic oxidative phosphorylation phenotypes. Conclusion Levels of ACE2 and FURIN may differ by clinical or molecular phenotypes of asthma. Sputum FURIN expression levels were strongly associated with neutrophilic inflammation and with inflammasome activation. This might indicate the potential for a greater morbidity and mortality outcome from SARS-CoV-2 infection in neutrophilic severe asthma
Overview of the Kepler Science Processing Pipeline
The Kepler Mission Science Operations Center (SOC) performs several critical
functions including managing the ~156,000 target stars, associated target
tables, science data compression tables and parameters, as well as processing
the raw photometric data downlinked from the spacecraft each month. The raw
data are first calibrated at the pixel level to correct for bias, smear induced
by a shutterless readout, and other detector and electronic effects. A
background sky flux is estimated from ~4500 pixels on each of the 84 CCD
readout channels, and simple aperture photometry is performed on an optimal
aperture for each star. Ancillary engineering data and diagnostic information
extracted from the science data are used to remove systematic errors in the
flux time series that are correlated with these data prior to searching for
signatures of transiting planets with a wavelet-based, adaptive matched filter.
Stars with signatures exceeding 7.1 sigma are subjected to a suite of
statistical tests including an examination of each star's centroid motion to
reject false positives caused by background eclipsing binaries. Physical
parameters for each planetary candidate are fitted to the transit signature,
and signatures of additional transiting planets are sought in the residual
light curve. The pipeline is operational, finding planetary signatures and
providing robust eliminations of false positives.Comment: 8 pages, 3 figure
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