749 research outputs found
Universal Adversarial Perturbations for CNN Classifiers in EEG-Based BCIs
Multiple convolutional neural network (CNN) classifiers have been proposed
for electroencephalogram (EEG) based brain-computer interfaces (BCIs). However,
CNN models have been found vulnerable to universal adversarial perturbations
(UAPs), which are small and example-independent, yet powerful enough to degrade
the performance of a CNN model, when added to a benign example. This paper
proposes a novel total loss minimization (TLM) approach to generate UAPs for
EEG-based BCIs. Experimental results demonstrated the effectiveness of TLM on
three popular CNN classifiers for both target and non-target attacks. We also
verified the transferability of UAPs in EEG-based BCI systems. To our
knowledge, this is the first study on UAPs of CNN classifiers in EEG-based
BCIs. UAPs are easy to construct, and can attack BCIs in real-time, exposing a
potentially critical security concern of BCIs
The Origin of [OII] in Post-Starburst and Red-Sequence Galaxies in High-Redshift Clusters
We present the first results from a near-IR spectroscopic campaign of the
Cl1604 supercluster at z~0.9 and the cluster RX J1821.6+6827 at z~0.82 to
investigate the nature of [OII] 3727A emission in cluster galaxies at high
redshift. Of the 401 members in the two systems, 131 galaxies have detectable
[OII] emission with no other signs of current star-formation, as well as strong
absorption features indicative of a well-established older stellar population.
The combination of these features suggests that the primary source of [OII]
emission in these galaxies is not the result of star-formation, but rather due
to the presence of a LINER or Seyfert component. Using the NIRSPEC spectrograph
on the Keck II 10-m telescope, 19 such galaxies were targeted, as well as six
additional [OII]-emitting cluster members that exhibited other signs of ongoing
star-formation. Nearly half (~47%) of the 19 [OII]-emitting, absorption-line
dominated galaxies exhibit [OII] to Ha equivalent width ratios higher than
unity, the typical value for star-forming galaxies. A majority (~68%) of these
19 galaxies are classified as LINER/Seyfert based on the emission-line ratio of
[NII] and Ha, increasing to ~85% for red [OII]-emitting, absorption-line
dominated galaxies. The LINER/Seyfert galaxies exhibit L([OII])/L(Ha) ratios
significantly higher than that observed in populations of star-forming
galaxies, suggesting that [OII] is a poor indicator of star-formation in a
large fraction of high-redshift cluster members. We estimate that at least ~20%
of galaxies in high-redshift clusters contain a LINER/Seyfert component that
can be revealed with line ratios. We also investigate the effect this
population has on the star formation rate of cluster galaxies and the
post-starburst fraction, concluding that LINER/Seyferts must be accounted for
if these quantities are to be meaningful.Comment: 33 pages, 17 figures, to appear in Ap
The Dynamical Status of the Cluster of Galaxies 1E0657-56
We present the results of a new spectroscopic and photometric survey of the
hot X-ray cluster 1E0657-56, at z=0.296. We determine the presence of a low
velocity dispersion subcluster, which is offset from the main cluster position
by 0.7 Mpc and about 600 km/s. We determine the virial masses and total
luminosities of the cluster and its subcluster, and solve for the two-body
dynamical model. With additional constraints from the results of the analysis
of the cluster X-ray emission by Markevitch et al. (2001), we find that the
subcluster passed through the cluster centre about 0.15 Gyr ago. Taken at face
value the mass of the subcluster is typical of a loose group. It is however
difficult to establish the pre-merger mass of the colliding system. We provide
tentative evidence that the subcluster is in fact the remnant core of a
moderately massive cluster, stripped by the collision with 1E0657-56. The main
cluster dynamics does not seem to have suffered from this collision. On the
contrary, the cluster X-ray properties seem to have been significantly
affected. We also discuss the effect of the subcluster collision in relation to
starburst events and the cluster radio halo.Comment: Accepted for publication on A&
A semi-parametric approach to estimate risk functions associated with multi-dimensional exposure profiles: application to smoking and lung cancer
A common characteristic of environmental epidemiology is the multi-dimensional aspect of exposure patterns, frequently reduced to a cumulative exposure for simplicity of analysis. By adopting a flexible Bayesian clustering approach, we explore the risk function linking exposure history to disease. This approach is applied here to study the relationship between different smoking characteristics and lung cancer in the framework of a population based case control study
A Bayesian Semiparametric Approach for Incorporating Longitudinal Information on Exposure History for Inference in CaseâControl Studies
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92073/1/j.1541-0420.2011.01686.x.pd
An assessment of aerosolâcloud interactions in marine stratus clouds based on surface remote sensing
An assessment of aerosol-cloud interactions (ACI) from ground-based remote sensing under coastal stratiform clouds is presented. The assessment utilizes a long-term, high temporal resolution data set from the Atmospheric Radiation Measurement (ARM) Program deployment at Pt. Reyes, California, United States, in 2005 to provide statistically robust measures of ACI and to characterize the variability of the measures based on variability in environmental conditions and observational approaches. The average ACIN (= dlnNd/dlna, the change in cloud drop number concentration with aerosol concentration) is 0.48, within a physically plausible range of 0â1.0. Values vary between 0.18 and 0.69 with dependence on (1) the assumption of constant cloud liquid water path (LWP), (2) the relative value of cloud LWP, (3) methods for retrieving Nd, (4) aerosol size distribution, (5) updraft velocity, and (6) the scale and resolution of observations. The sensitivity of the local, diurnally averaged radiative forcing to this variability in ACIN values, assuming an aerosol perturbation of 500 c-3 relative to a background concentration of 100 cm-3, ranges betwee-4 and -9 W -2. Further characterization of ACI and its variability is required to reduce uncertainties in global radiative forcing estimates
B-mode polarization forecasts for GreenPol
We present tensor-to-scalar ratio forecasts for GreenPol, a hypothetical
ground-based B-mode experiment aiming to survey the cleanest regions of the
Northern Galactic hemisphere at five frequencies between 10 and 44 GHz. Its
primary science goal would be to measure large-scale CMB polarization
fluctuations at multipoles , and thereby constrain the
primordial tensor-to-scalar ratio. The observations for the suggested
experiment would take place at the Summit Station (72deg N, 38deg W) on
Greenland, at an altitude of 3216 meters above sea level. In this paper we
simulate various experimental setups, and derive limits on the tensor-to-scalar
ratio after CMB component separation using a Bayesian component separation
implementation called Commander. When combining the proposed experiment with
Planck HFI observations for constraining polarized thermal dust emission, we
find a projected limit of r<0.02 at 95 % confidence for the baseline
configuration. This limit is very robust with respect to a range of important
experimental parameters, including sky coverage, detector weighting, foreground
priors etc. Overall, GreenPol would have the possibility to provide deep CMB
polarization measurements of the Northern Galactic hemisphere at low
frequencies.Comment: 10 pages, 8 figures. To be submitted to A&
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