3,982 research outputs found
Linear Regression of Censored Length-biased Lifetimes
Length-biased lifetimes may be collected in observational studies or sample surveys due to biased sampling scheme. In this article, we use a linear regression model, namely, the accelerated failure time model, for the population lifetime distributions in regression analysis of the length-biased lifetimes. It is discovered that the associated regression parameters are invariant under the length-biased sampling scheme. According to this discovery, we propose the quasi partial score estimating equations to estimate the population regression parameters. The proposed methodologies are evaluated and demonstrated by simulation studies and an application to actual data set
Computation of the order low-energy constants with tensor sources
We present the results of calculations of the and order
low-energy constants for the chiral Lagrangian with tensor sources for both two
and three flavors of pseudoscalar mesons. This is a generalization of our
previous work on similar calculations without tensor sources in terms of the
quark self-energy , based on the first principle derivation of the
low-energy effective Lagrangian and computation of the low-energy constants
with some rough approximations. With the help of partial integration and some
epsilon relations, we find that some order operators with tensor sources
appearing in the literature are related to each other. That leaves 98
independent terms for -flavor, 92 terms for three-flavor, and 65 terms for
two-flavor cases. We also find that the odd-intrinsic-parity chiral Lagrangian
with tensor sources cannot independently exist in any order of low-energy
expansion.Comment: 29 page
Higgsphobic and fermiophobic Z' as a single dark matter candidate
A spin-1 Z' particle as a single dark matter candidate is investigated by
assuming that it does not directly couple to the Higgs boson and standard model
fermions and does not mix with the photon and Z boson. The remaining dominant
vertices are quartic Z'Z'ZZ and Z'Z'W+W-, which can induce effective
Z'Z'q\bar{q} couplings through standard-model gauge-boson loops. We discuss
constraints from the cosmological thermal relic density, and direct and
indirect-detection experiments, and find that a dark Z' can only exist above
the W boson mass threshold, and the effective quartic coupling of Z'Z'VV is
bounded in the region of 10^{-3}~10^{-2}.Comment: 18pages, 14 figure
Attributable Risk Function in the Proportional Hazards Model
As an epidemiological parameter, the population attributable fraction is an important measure to quantify the public health attributable risk of an exposure to morbidity and mortality. In this article, we extend this parameter to the attributable fraction function in survival analysis of time-to-event outcomes, and further establish its estimation and inference procedures based on the widely used proportional hazards models. Numerical examples and simulations studies are presented to validate and demonstrate the proposed methods
- …