123,583 research outputs found
A concave pairwise fusion approach to subgroup analysis
An important step in developing individualized treatment strategies is to
correctly identify subgroups of a heterogeneous population, so that specific
treatment can be given to each subgroup. In this paper, we consider the
situation with samples drawn from a population consisting of subgroups with
different means, along with certain covariates. We propose a penalized approach
for subgroup analysis based on a regression model, in which heterogeneity is
driven by unobserved latent factors and thus can be represented by using
subject-specific intercepts. We apply concave penalty functions to pairwise
differences of the intercepts. This procedure automatically divides the
observations into subgroups. We develop an alternating direction method of
multipliers algorithm with concave penalties to implement the proposed approach
and demonstrate its convergence. We also establish the theoretical properties
of our proposed estimator and determine the order requirement of the minimal
difference of signals between groups in order to recover them. These results
provide a sound basis for making statistical inference in subgroup analysis.
Our proposed method is further illustrated by simulation studies and analysis
of the Cleveland heart disease dataset
Hamilton-Souplet-Zhang's gradient estimates for two types of nonlinear parabolic equations under the Ricci flow
In this paper, we consider gradient estimates for two type of nonlinear
parabolic equations under the Ricci flow: one is the equation with two real constants, the other is with two real constants. By a suitable
scaling for the above two equations, we obtain Hamilton-Souplet-Zhang type
gradient estimates.Comment: All comments are welcom
Constraints on absolute neutrino Majorana mass from current data
We present new constraints on the neutrino Majorana masses from the current
data of neutrinoless double beta decay and neutrino flavour mixing. With the
latest results of progresses from various isotopes, including
the recent calculations of the nuclear matrix elements, we find that the
strongest constraint of the effective Majorana neutrino mass is from the
data of the EXO-200 and KamLAND-Zen collaborations. Further
more, by combining the experimental data with the neutrino
mixing parameters from new analyses, we get the mass upper limits of neutrino
mass eigenstates and flavour eigenstates and suggest several relations among
these neutrino masses.Comment: 6 latex pages, 2 figures. Final version for publication in "The
Universe
- …