24,613 research outputs found
Multiple testing via for large-scale imaging data
The multiple testing procedure plays an important role in detecting the
presence of spatial signals for large-scale imaging data. Typically, the
spatial signals are sparse but clustered. This paper provides empirical
evidence that for a range of commonly used control levels, the conventional
procedure can lack the ability to detect statistical
significance, even if the -values under the true null hypotheses are
independent and uniformly distributed; more generally, ignoring the neighboring
information of spatially structured data will tend to diminish the detection
effectiveness of the procedure. This paper first
introduces a scalar quantity to characterize the extent to which the "lack of
identification phenomenon" () of the
procedure occurs. Second, we propose a new multiple comparison procedure,
called , to accommodate the spatial information of
neighboring -values, via a local aggregation of -values. Theoretical
properties of the procedure are investigated under weak
dependence of -values. It is shown that the
procedure alleviates the of the
procedure, thus substantially facilitating the selection of more stringent
control levels. Simulation evaluations indicate that the procedure improves the detection sensitivity of the procedure with little loss in detection specificity. The computational
simplicity and detection effectiveness of the procedure
are illustrated through a real brain fMRI dataset.Comment: Published in at http://dx.doi.org/10.1214/10-AOS848 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Cooperation and Stability through Periodic Impulse
Basic games, where each individual chooses between two strategies, illustrate several issues that immediately emerge from the standard approach that applies strategic reasoning, based on rational decisions, to predict population behavior where no rationality is assumed. These include how mutual cooperation (which corresponds to the best outcome from the population perspective) can evolve when the only individually rational choice is to defect, illustrated by the Prisoner’s Dilemma (PD) game, and how individuals can randomize between two strategies when neither is individually rational, illustrated by the Battle of the Sexes (BS) game that models male-female conflict over parental investment in offspring. We examine these questions from an evolutionary perspective where the evolutionary dynamics includes an impulsive effect that models sudden changes in collective population behavior. For the PD game, we show analytically that cooperation can either coexist with defection or completely take over the population, depending on the strength of the impulse. By extending these results for the PD game, we also show that males and females each evolve to a single strategy in the BS game when the impulsive effect is strong and that weak impulses stabilize the randomized strategies of this game
Detecting fractional Josephson effect through phase slip
Fractional Josephson effect is a unique character of Majorana Fermions in
topological superconductor system. This effect is very difficult to detect
experimentally because of the disturbance of quasiparticle poisoning and
unwanted couplings in the superconductor. Here, we propose a scheme to probe
fractional DC Josephson effect of semiconductor nanowire-based topological
Josephson junction through 4{\pi} phase slip. By exploiting a topological RF
SQUID system we find that the dominant contribution for Josephson coupling
comes from the interaction of Majorana Fermions, resulting the resonant
tunneling with 4{\pi} phase slip. Our calculations with experimentally
reachable parameters show that the time scale for detecting the phase slip is
two orders of magnitude shorter than the poisoning time of nonequilibrium
quasiparticles. Additionally, with a reasonable nanowire length the 4{\pi}
phase slip could overwhelm the topological trivial 2{\pi} phase slip. Our work
is meaningful for exploring the effect of modest quantum fluctuations of the
phase of the superconductor on the topological system, and provide a new method
for quantum information processing.Comment: 5 pages, 3 figure
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