1,244 research outputs found
Classifying post-traumatic stress disorder using the magnetoencephalographic connectome and machine learning
Given the subjective nature of conventional diagnostic methods for post-traumatic stress disorder (PTSD), an objectively measurable biomarker is highly desirable; especially to clinicians and researchers. Macroscopic neural circuits measured using magnetoencephalography (MEG) has previously been shown to be indicative of the PTSD phenotype and severity. In the present study, we employed a machine learning-based classification framework using MEG neural synchrony to distinguish combat-related PTSD from trauma-exposed controls. Support vector machine (SVM) was used as the core classification algorithm. A recursive random forest feature selection step was directly incorporated in the nested SVM cross validation process (CV-SVM-rRF-FS) for identifying the most important features for PTSD classification. For the five frequency bands tested, the CV-SVM-rRF-FS analysis selected the minimum numbers of edges per frequency that could serve as a PTSD signature and be used as the basis for SVM modelling. Many of the selected edges have been reported previously to be core in PTSD pathophysiology, with frequency-specific patterns also observed. Furthermore, the independent partial least squares discriminant analysis suggested low bias in the machine learning process. The final SVM models built with selected features showed excellent PTSD classification performance (area-under-curve value up to 0.9). Testament to its robustness when distinguishing individuals from a heavily traumatised control group, these developments for a classification model for PTSD also provide a comprehensive machine learning-based computational framework for classifying other mental health challenges using MEG connectome profiles
iCosmo: an Interactive Cosmology Package
Aims: The interactive software package iCosmo, designed to perform
cosmological calculations is described. Methods: iCosmo is a software package
to perform interactive cosmological calculations for the low redshift universe.
Computing distance measures, the matter power spectrum, and the growth factor
is supported for any values of the cosmological parameters. It also computes
derived observed quantities for several cosmological probes such as cosmic
shear, baryon acoustic oscillations and type Ia supernovae. The associated
errors for these observables can be derived for customised surveys, or for
pre-set values corresponding to current or planned instruments. The code also
allows for the calculation of cosmological forecasts with Fisher matrices which
can be manipulated to combine different surveys and cosmological probes. The
code is written in the IDL language and thus benefits from the convenient
interactive features and scientific library available in this language. iCosmo
can also be used as an engine to perform cosmological calculations in batch
mode, and forms a convenient adaptive platform for the development of further
cosmological modules. With its extensive documentation, it may also serve as a
useful resource for teaching and for newcomers in the field of cosmology.
Results: The iCosmo package is described with various examples and command
sequences. The code is freely available with documentation at
http://www.icosmo.org, along with an interactive web interface and is part of
the Initiative for Cosmology, a common archive for cosmological resources.Comment: 6 pages including 2 tables and 4 figures. Accepted and published in
Astronomy and Astrophysics. Public code and further resources available at
http://www.icosmo.or
Impact of Systematics on SZ-Optical Scaling Relations
One of the central goals of multi-wavelength galaxy cluster cosmology is to
unite all cluster observables to form a consistent understanding of cluster
mass. Here, we study the impact of systematic effects from optical cluster
catalogs on stacked SZ signals. We show that the optically predicted
Y-decrement can vary by as much as 50% based on the current 2 sigma systematic
uncertainties in the observed mass-richness relationship. Mis-centering and
impurities will suppress the SZ signal compared to expectations for a clean and
perfectly centered optical sample, but to a lesser degree. We show that the
level of these variations and suppression is dependent on the amount of
systematics in the optical cluster catalogs. We also study X-ray
luminosity-dependent sub-sampling of the optical catalog and find that it
creates Malmquist bias increasing the observed Y-decrement of the stacked
signal. We show that the current Planck measurements of the Y-decrement around
SDSS optical clusters and their X-ray counterparts are consistent with
expectations after accounting for the 1 sigma optical systematic uncertainties
using the Johnston mass richness relation.Comment: 6 pages, 4 figures. Revised to match version accepted in the
Astrophysical Journa
The Kinetic Sunyaev-Zel'dovich effect as a probe of the physics of cosmic reionization: the effect of self-regulated reionization
We calculate the angular power spectrum of the Cosmic Microwave Background
(CMB) temperature fluctuations induced by the kinetic Sunyaev-Zel'dovich (kSZ)
effect from the epoch of reionization (EOR). We use detailed N-body+radiative
transfer simulations to follow inhomogeneous reionization of the intergalactic
medium (IGM). For the first time we take into account the "self-regulation" of
reionization: star formation in low-mass dwarf galaxies (10^8 M_\sun \lesssim M
\lesssim 10^9 M_\sun) or minihalos (10^5 M_\sun \lesssim M \lesssim 10^8
M_\sun) is suppressed if these halos form in the regions that were already
ionized or Lyman-Werner dissociated. Some previous work suggested that the
amplitude of the kSZ power spectrum from the EOR can be described by a
two-parameter family: the epoch of half ionization and the duration of
reionization. However, we argue that this picture applies only to simple forms
of the reionization history which are roughly symmetric about the
half-ionization epoch. In self-regulated reionization, the universe begins to
be ionized early, maintains a low level of ionization for an extended period,
and then finishes reionization as soon as high-mass atomically-cooling halos
dominate. While inclusion of self-regulation affects the amplitude of the kSZ
power spectrum only modestly (\sim 10 %), it can change the duration of
reionization by a factor of more than two. We conclude that the simple
two-parameter family does not capture the effect of a physical, yet complex,
reionization history caused by self-regulation. When added to the
post-reionization kSZ contribution, our prediction for the total kSZ power
spectrum is below the current upper bound from the South Pole Telescope.
Therefore, the current upper bound on the kSZ effect from the EOR is consistent
with our understanding of the physics of reionization
Dangerous liaisons: A ‘Big Four’ framework that provides a ‘hint’ to understanding an adversary’s strategy for influence.
Beliefs, attitudes and behaviour can be influenced in myriad ways. History has consistently demonstrated the struggle between protagonist and antagonist to win over ‘the people’, often through the simultaneous promotion and destruction of places, icons, myths, symbols and stories. Neil Verrall, Mark Dunkley and Toby Gane, three army reserve officers, and Richard Byrne, an independent geographer, describe four interconnected ways in which hostile state actors or non-state terrorist groups might attempt to influence their target audiences as part of strategy
Early search for supersymmetric dark matter models at the LHC without missing energy
We investigate early discovery signals for supersymmetry at the Large Hadron
Collider without using information about missing transverse energy. Instead we
use cuts on the number of jets and isolated leptons (electrons and/or muons).
We work with minimal supersymmetric extensions of the standard model, and focus
on phenomenological models that give a relic density of dark matter compatible
with the WMAP measurements. An important model property for early discovery is
the presence of light sleptons, and we find that for an integrated luminosity
of only 200--300 pb at a center-of-mass energy of 10 TeV models with
gluino masses up to GeV can be tested.Comment: 28 pages, 12 figures; published versio
Constraining super-critical string/brane cosmologies with astrophysical data
We discuss fits of unconventional dark energy models to the available data
from high-redshift supernovae, distant galaxies and baryon oscillations. The
models are based either on brane cosmologies or on Liouville strings in which a
relaxation dark energy is provided by a rolling dilaton field (Q-cosmology).
Such cosmologies feature the possibility of effective four-dimensional
negative-energy dust and/or exotic scaling of dark matter. We find evidence for
a negative-energy dust at the current era, as well as for exotic-scaling
(a^{-delta}) contributions to the energy density, with delta ~= 4, which could
be due to dark matter coupling with the dilaton in Q-cosmology models. We
conclude that Q-cosmology fits the data equally well with the LambdaCDM model
for a range of parameters that are in general expected from theoretical
considerations.Comment: 4 pages, 2 figures, Contributed to 11th International Conference on
Topics in Astroparticle and Underground Physics (TAUP 2009) 1-5 Jul 2009,
Rome, Italy; J. Phys. Conf. Series to appea
The DeepMIP contribution to PMIP4: methodologies for selection, compilation and analysis of latest Paleocene and early Eocene climate proxy data, incorporating version 0.1 of the DeepMIP database
The early Eocene (56 to 48 million years ago) is inferred to have been the most recent time that Earth’s atmospheric
CO2 concentrations exceeded 1000 ppm. Global mean temperatures were also substantially warmer than present day. As such,
study of early Eocene climate provides insight into how a super-warm Earth system behaves and offers an opportunity to
evaluate climate models under conditions of high greenhouse gas forcing. The Deep Time Model Intercomparison Project
(DeepMIP) is a systematic model-model and model-data intercomparison of three early Paleogene time slices: latest Paleocene,
Paleocene-Eocene thermal maximum and early Eocene climatic optimum. A previous article outlined the model experimental
design for climate model simulations. In this article, we outline the methodologies to be used for the compilation and analysis of climate proxy data, primarily proxies for temperature and CO2. This paper establishes the protocols for a concerted and
coordinated effort to compile the climate proxy records across a wide geographic range. The resulting climate “atlas” will be
used to constrain and evaluate climate models for the three selected time intervals, and provide insights into the mechanisms
that control these warm climate states. We provide version 0.1 of this database, in anticipation that this will be expanded in
subsequent publication
Evading the pulsar constraints on the cosmic string tension in supergravity inflation
The cosmic string is a useful probe of the early Universe and may give us a
clue to physics at high energy scales where any artificial particle
accelerators cannot reach. Although one of the most promising tools is the
cosmic microwave background, the constraint from gravitational waves is
becoming so stringent that one may not hope to detect its signatures in the
cosmic microwave background. In this paper, we construct a scenario that
contains cosmic strings observable in the cosmic microwave background while
evading the constraint imposed by the recent pulsar timing data. We argue that
cosmic strings with relatively large tension are allowed by delaying the onset
of the scaling regime. We also show that this scenario is naturally realized in
the context of chaotic inflation in supergravity, where the phase transition is
governed by the Hubble induced mass.Comment: 24pages, 3 figures, published in JCA
Power-law Template for Infrared Point-source Clustering
We perform a combined fit to angular power spectra of unresolved infrared (IR) point sources from the Planck
satellite (at 217, 353, 545, and 857 GHz, over angular scales 100 ≾ ℓ ≾ 2200), the Balloon-borne Large-Aperture
Submillimeter Telescope (BLAST; 250, 350, and 500μm; 1000 ≾ ℓ ≾ 9000), and from correlating BLAST and Atacama Cosmology Telescope (ACT; 148 and 218 GHz) maps. We find that the clustered power over the range of angular scales and frequencies considered is well fitted by a simple power law of the form C^(clust)_ℓ ∝ ℓ^(-n) with n = 1.25 ± 0.06. While the IR sources are understood to lie at a range of redshifts, with a variety of dust properties, we find that the frequency dependence of the clustering power can be described by the square of a modified blackbody, ν^(β)B(ν, T_(eff)), with a single emissivity index β = 2.20 ± 0.07 and effective temperature T_(eff) = 9.7 K. Our predictions for the clustering amplitude are consistent with existing ACT and South Pole Telescope results at around 150 and 220 GHz, as is our prediction for the effective dust spectral index, which we find to be α_(150–220) = 3.68±0.07 between 150 and 220 GHz. Our constraints on the clustering shape and frequency dependence can be used to model the IR clustering as a contaminant in cosmic microwave background anisotropy measurements. The combined Planck and BLAST data also rule out a linear bias clustering model
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