24 research outputs found
Bayesian detection of embryonic gene expression onset in C. elegans
To study how a zygote develops into an embryo with different tissues,
large-scale 4D confocal movies of C. elegans embryos have been produced
recently by experimental biologists. However, the lack of principled
statistical methods for the highly noisy data has hindered the comprehensive
analysis of these data sets. We introduced a probabilistic change point model
on the cell lineage tree to estimate the embryonic gene expression onset time.
A Bayesian approach is used to fit the 4D confocal movies data to the model.
Subsequent classification methods are used to decide a model selection
threshold and further refine the expression onset time from the branch level to
the specific cell time level. Extensive simulations have shown the high
accuracy of our method. Its application on real data yields both previously
known results and new findings.Comment: Published at http://dx.doi.org/10.1214/15-AOAS820 in the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
A centi-pc-scale compact radio core in the nearby galaxy M60
M60, an elliptical galaxy located 16.5~Mpc away, has an active nucleus with a
very low luminosity and an extremely low accretion rate. Its central
supermassive black hole has a mass of and a Schwarzschild radii corresponding to . To investigate the nature of its innermost radio
nucleus, data from the Very Long Baseline Array (VLBA) at 4.4 and 7.6~GHz were
reduced. The VLBA images reveal a compact component with total flux densities
of 20~mJy at both frequencies, a size of 0.27~mas (99.7
confidence level), about 0.022~pc () at 7.6~GHz, and a
brightness temperature of ~K. This suggests that the
observed centi-parsec-scale compact core could be attributed to a nonthermal
jet base or an advection-dominated accretion flow (ADAF) with nonthermal
electrons. The extremely compact structure also supports the presence of an
SMBH in the center. Our results indicate that M60 is a promising target for
broad-band VLBI observations at millimeter wavelengths to probe ADAF scenarios
and tightly constrain the potential photon ring (about 28\,as) around its
SMBH.Comment: 15 pages, 5 figures, 3 tables, accepted for publication in
Astrophysical Journa
Topic oriented community detection through social objects and link analysis in social networks
Community detection is an important issue in social network analysis. Most existing methods detect communities through analyzing the linkage of the network. The drawback is that each community identified by those methods can only reflect the strength of connections, but it cannot reflect the semantics such as the interesting topics shared by people. To address this problem, we propose a topic oriented community detection approach which combines both social objects clustering and link analysis. We first use a subspace clustering algorithm to group all the social objects into topics. Then we divide the members that are involved in those social objects into topical clusters, each corresponding to a distinct topic. In order to differentiate the strength of connections, we perform a link analysis on each topical cluster to detect the topical communities. Experiments on real data sets have shown that our approach was able to identify more meaningful communities. The quantitative evaluation indicated that our approach can achieve a better performance when the topics are at least as important as the links to the analysis