2,822 research outputs found
Multiple Testing for Neuroimaging via Hidden Markov Random Field
Traditional voxel-level multiple testing procedures in neuroimaging, mostly
-value based, often ignore the spatial correlations among neighboring voxels
and thus suffer from substantial loss of power. We extend the
local-significance-index based procedure originally developed for the hidden
Markov chain models, which aims to minimize the false nondiscovery rate subject
to a constraint on the false discovery rate, to three-dimensional neuroimaging
data using a hidden Markov random field model. A generalized
expectation-maximization algorithm for maximizing the penalized likelihood is
proposed for estimating the model parameters. Extensive simulations show that
the proposed approach is more powerful than conventional false discovery rate
procedures. We apply the method to the comparison between mild cognitive
impairment, a disease status with increased risk of developing Alzheimer's or
another dementia, and normal controls in the FDG-PET imaging study of the
Alzheimer's Disease Neuroimaging Initiative.Comment: A MATLAB package implementing the proposed FDR procedure is available
with this paper at the Biometrics website on Wiley Online Librar
An iterative implicit diagonally-dominant factorization algorithm for solving the Navier-Stokes equations
Presented here is an algorithm for solving the multidimensional unsteady Navier-Stokes equations for compressible flows. It is based on a diagonally-dominant approximate factorization procedure. The factorization error and the timewise linearization error associated with this procedure are reduced by performing Newton-type inner iterations at each time step. The inviscid fluxes are evaluated by the fourth-order central differencing scheme amended with a numerical dissipation directly proportional to the entire dissipative part of the truncation error intrinsic to the third order biased upwind scheme. The important features of the proposed solution are elucidated by the numerical results of the convection of a vortex and the backward-facing step flows
Canine Parvovirus Type 2
Canine parvovirus (CPV) enteritis is characterized by intestinal hemorrhage with severe bloody diarrhea. The causative agent, CPVā2, was first identified in the late 1970s. CPV is a nonenveloped, linear, singleāstranded DNA virus with a genome of approximately 5 kb, and it belongs to the genus Parvovirus, together with feline panleukopenia virus, mink enteritis virus, raccoon parvovirus, and porcine parvovirus. An antigenic variant, CPVā2a, identified within a few years after the emergence of CPVā2, and another variant, CPVā2b, began appearing in the canine population in 1984. In 2000, a novel antigenic variant, CPVā2c, was first detected in Italy. This chapter focuses on the history, viral evolution, epidemiology, pathogenesis, clinical signs, diagnosis, vaccination, and prevention of CPVā2
Electronic Tuning of Mixed QuinoidalāAromatic Conjugated Polyelectrolytes: Direct Ionic Substitution on Polymer MaināChains
The synthesis of conjugated polymers with ionic substituents directly bound to their main chain repeat units is a strategy for generating strongly electron-accepting conjugated polyelectrolytes, as demonstrated through the synthesis of a series of ionic azaquinodimethane (iAQM) compounds. The introduction of cationic substituents onto the quinoidal para-azaquinodimethane (AQM) core gives rise to a strongly electron-accepting building block, which can be employed in the synthesis of ionic small molecules and conjugated polyelectrolytes (CPEs). Electrochemical measurements alongside theoretical calculations indicate notably low-lying LUMO values for the iAQMs. The optical band gaps measured for these compounds are highly tunable based on structure, ranging from 2.30ā
eV in small molecules down to 1.22ā
eV in polymers. The iAQM small molecules and CPEs showcase the band gap reduction effects of combining the donor-acceptor strategy with the bond-length alternation reduction strategy. As a demonstration of their utility, the iAQM CPEs so generated were used as active agents in photothermal therapy
- ā¦