2,590 research outputs found
Sleep architecture in neonatal and infantile onset epilepsies in the first six months of life: A scoping review
AIM: Epilepsy occurs in approximately 80 per 100,000 infants in the first year of life, ranging in severity from self-limited and likely to spontaneously resolve, to severe developmental and epileptic encephalopathies. Sleep plays a key role in early brain development and the reciprocal relationship between sleep and seizures is not yet fully understood, particularly in young children. We conducted a Scoping Review to synthesise current knowledge of sleep architecture in neonates and infants with epilepsy. METHODS: Peer-reviewed publications from 2005 to 2022 describing sleep architecture in infants up to six months of age with unprovoked seizures were included. The analysis set was derived from EMBASE, Web of Science and PubMED using key terms âsleep, epilepsy and infantâ and related descriptors. Inclusion criteria were prospectively described in a Scoping Review protocol. Sleep architecture was assessed as macro- and micro-structural elements. RESULTS: 21 publications were included in the qualitative analysis. In self-limited familial and genetic epilepsy, sleep macrostructure was generally preserved. In DEEs and in epileptic encephalopathies of genetic or structural aetiology, sleep architecture was significantly disrupted. INTERPRETATION: Early identification of infants with epilepsy is important to ensure early and effective treatment. In the DEE spectrum, sleep architecture is significantly impacted, and abnormal sleep architecture may be associated with compromised developmental outcome. Further research is needed to identify the sequence of events in abnormal brain development, epilepsy and sleep disruption and potentially help to predict the course of epilepsy towards a self-limited epilepsy versus a DEE
Multi-wavelength observations of 2HWC J1928+177: dark accelerator or new TeV gamma-ray binary?
2HWC J1928+177 is a Galactic TeV gamma-ray source detected by the High
Altitude Water Cherenkov (HAWC) Observatory up to ~ 56 TeV. The HAWC source,
later confirmed by H.E.S.S., still remains unidentified as a dark accelerator
since there is no apparent supernova remnant or pulsar wind nebula detected in
the lower energy bands. The radio pulsar PSR J1928+1746, coinciding with the
HAWC source position, has no X-ray counterpart. Our SED modeling shows that
inverse Compton scattering in the putative pulsar wind nebula can account for
the TeV emission only if the unseen nebula is extended beyond r ~ 4 [arcmin].
Alternatively, TeV gamma rays may be produced by hadronic interactions between
relativistic protons from an undetected supernova remnant associated with the
radio pulsar and a nearby molecular cloud G52.9+0.1. NuSTAR and Chandra
observations detected a variable X-ray point source within the HAWC error
circle, potentially associated with a bright IR source. The X-ray spectra can
be fitted with an absorbed power-law model with cm and and exhibit
long-term X-ray flux variability over the last decade. If the X-ray source,
possibly associated with the IR source (likely an O star), is the counterpart
of the HAWC source, it may be a new TeV gamma-ray binary powered by collisions
between the pulsar wind and stellar wind. Follow-up X-ray observations are
warranted to search for diffuse X-ray emission and determine the nature of the
HAWC source.Comment: accepted to ApJ, 8 pages, 7 figure
A broadband X-ray study of the Rabbit pulsar wind nebula powered by PSR J1418-6058
We report on broadband X-ray properties of the Rabbit pulsar wind nebula
(PWN) associated with the pulsar PSR J1418-6058 using archival Chandra and
XMM-Newton data, and a new NuSTAR observation. NuSTAR data above 10 keV allowed
us to detect the 110-ms spin period of the pulsar, characterize its hard X-ray
pulse profile, and resolve hard X-ray emission from the PWN after removing
contamination from the pulsar and other overlapping point sources. The extended
PWN was detected up to 20 keV and is well described by a power-law model
with a photon index 2. The PWN shape does not vary significantly
with energy, and its X-ray spectrum shows no clear evidence of softening away
from the pulsar. We modeled the spatial profile of X-ray spectra and broadband
spectral energy distribution in the radio to TeV band to infer the physical
properties of the PWN. We found that a model with low magnetic field strength
( G) and efficient diffusion ( cm s)
fits the PWN data well. The extended hard X-ray and TeV emission, associated
respectively with synchrotron radiation and inverse Compton scattering by
relativistic electrons, suggests that particles are accelerated to very high
energies ( TeV), indicating that the Rabbit PWN is a Galactic
PeVatron candidate.Comment: 21 pages, 10 figures. ApJ accepte
X-ray studies of the pulsar PSR J1420-6048 and its TeV pulsar wind nebula in the Kookaburra region
We present a detailed analysis of broadband X-ray observations of the pulsar
PSR J1420-6048 and its wind nebula (PWN) in the Kookaburra region with Chandra,
XMM-Newton, and NuSTAR. Using the archival XMM-Newton and new NuSTAR data, we
detected 68 ms pulsations of the pulsar and characterized its X-ray pulse
profile which exhibits a sharp spike and a broad bump separated by ~0.5 in
phase. A high-resolution Chandra image revealed a complex morphology of the
PWN: a torus-jet structure, a few knots around the torus, one long (~7') and
two short tails extending in the northwest direction, and a bright diffuse
emission region to the south. Spatially integrated Chandra and NuSTAR spectra
of the PWN out to 2.5' are well described by a power law model with a photon
index 2. A spatially resolved spectroscopic study, as well
as NuSTAR radial profiles of the 3--7 keV and 7--20 keV brightness, showed a
hint of spectral softening with increasing distance from the pulsar. A
multi-wavelength spectral energy distribution (SED) of the source was then
obtained by supplementing our X-ray measurements with published radio,
Fermi-LAT, and H.E.S.S. data. The SED and radial variations of the X-ray
spectrum were fit with a leptonic multi-zone emission model. Our detailed study
of the PWN may be suggestive of (1) particle transport dominated by advection,
(2) a low magnetic-field strength (B ~ 5G), and (3) electron
acceleration to ~PeV energies.Comment: 18 pages and 8 figures. Accepted for publication in Ap
High-Energy X-ray Imaging of the Pulsar Wind Nebula MSH~15-52: Constraints on Particle Acceleration and Transport
We present the first images of the pulsar wind nebula (PWN) MSH 15-52 in the
hard X-ray band (>8 keV), as measured with the Nuclear Spectroscopic Telescope
Array (NuSTAR). Overall, the morphology of the PWN as measured by NuSTAR in the
3-7 keV band is similar to that seen in Chandra high-resolution imaging.
However, the spatial extent decreases with energy, which we attribute to
synchrotron energy losses as the particles move away from the shock. The
hard-band maps show a relative deficit of counts in the northern region towards
the RCW 89 thermal remnant, with significant asymmetry. We find that the
integrated PWN spectra measured with NuSTAR and Chandra suggest that there is a
spectral break at 6 keV which may be explained by a break in the
synchrotron-emitting electron distribution at ~200 TeV and/or imperfect cross
calibration. We also measure spatially resolved spectra, showing that the
spectrum of the PWN softens away from the central pulsar B1509-58, and that
there exists a roughly sinusoidal variation of spectral hardness in the
azimuthal direction. We discuss the results using particle flow models. We find
non-monotonic structure in the variation with distance of spectral hardness
within 50" of the pulsar moving in the jet direction, which may imply particle
and magnetic-field compression by magnetic hoop stress as previously suggested
for this source. We also present 2-D maps of spectral parameters and find an
interesting shell-like structure in the NH map. We discuss possible origins of
the shell-like structure and their implications.Comment: 15 pages, 9 figures, accepted for publication in Ap
Hard X-ray observation and multiwavelength study of the PeVatron candidate pulsar wind nebula "Dragonfly"
We studied the PeVatron nature of the pulsar wind nebula G75.2+0.1
("Dragonfly") as part of our NuSTAR observational campaign of energetic PWNe.
The Dragonfly is spatially coincident with LHAASO J2018+3651 whose maximum
photon energy is 0.27 PeV. We detected a compact (radius 1') inner nebula of
the Dragonfly without a spectral break in 3 20 keV using NuSTAR. A joint
analysis of the inner nebula with the archival Chandra and XMM-Newton
observations yields a power-law spectrum with . Synchrotron
burnoff is observed from the shrinkage of the NuSTAR nebula at higher energies,
from which we infer the magnetic field in the inner nebula of 24 G at 3.5
kpc. Our analysis of archival XMM data and 13 years of Fermi-LAT data confirms
the detection of an extended (~10') outer nebula in 2 6 keV
() and non-detection of a GeV nebula, respectively. Using
the VLA, XMM, and HAWC data, we modeled a multi-wavelength spectral energy
distribution of the Dragonfly as a leptonic PeVatron. The maximum injected
particle energy of 1.4 PeV from our model suggests that the Dragonfly is likely
a PeVatron. Our model prediction of the low magnetic field (2.7 G) in the
outer nebula and recent interaction with the host supernova remnant's reverse
shock (4 kyrs ago) align with common features of PeVatron PWNe. The origin of
its highly asymmetric morphology, pulsar proper motion, PWN-SNR interaction,
and source distance will require further investigations in the future including
a multi-wavelength study using radio, X-ray, and gamma-ray observations.Comment: 18 pages, 11 figures, ApJ accepte
NuSTAR observations of X-ray bursts from the magnetar 1E 1048.1-5937
We report the detection of eight bright X-ray bursts from the 6.5-s magnetar
1E 1048.1-5937, during a 2013 July observation campaign with the Nuclear
Spectroscopic Telescope Array (NuSTAR). We study the morphological and spectral
properties of these bursts and their evolution with time. The bursts resulted
in count rate increases by orders of magnitude, sometimes limited by the
detector dead time, and showed blackbody spectra with kT=6-8 keV in the T90
duration of 1-4 s, similar to earlier bursts detected from the source. We find
that the spectra during the tail of the bursts can be modeled with an absorbed
blackbody with temperature decreasing with flux. The bursts flux decays
followed a power-law of index 0.8-0.9. In the burst tail spectra, we detect a
~13 keV emission feature, similar to those reported in previous bursts from
this source as well as from other magnetars observed with the Rossi X-ray
Timing Explorer (RXTE). We explore possible origins of the spectral feature
such as proton cyclotron emission, which implies a magnetic field strength of
B~2X10^15 G in the emission region. However, the consistency of the energy of
the feature in different objects requires further explanation.Comment: 10 pages, 6 figures, accepted for publication in Ap
NuSTAR study of Hard X-Ray Morphology and Spectroscopy of PWN G21.5-0.9
We present NuSTAR high energy X-ray observations of the pulsar wind nebula
(PWN)/supernova remnant G21.5-0.9. We detect integrated emission from the
nebula up to ~40 keV, and resolve individual spatial features over a broad
X-ray band for the first time. The morphology seen by NuSTAR agrees well with
that seen by XMM-Newton and Chandra below 10 keV. At high energies NuSTAR
clearly detects non-thermal emission up to ~20 keV that extends along the
eastern and northern rim of the supernova shell. The broadband images clearly
demonstrate that X-ray emission from the North Spur and Eastern Limb results
predominantly from non-thermal processes. We detect a break in the spatially
integrated X-ray spectrum at ~9 keV that cannot be reproduced by current SED
models, implying either a more complex electron injection spectrum or an
additional process such as diffusion compared to what has been considered in
previous work. We use spatially resolved maps to derive an energy-dependent
cooling length scale, with . We find
this to be inconsistent with the model for the morphological evolution with
energy described by Kennel & Coroniti (1984). This value, along with the
observed steepening in power-law index between radio and X-ray, can be
quantitatively explained as an energy-loss spectral break in the simple scaling
model of Reynolds (2009), assuming particle advection dominates over diffusion.
This interpretation requires a substantial departure from spherical
magnetohydrodynamic (MHD), magnetic-flux-conserving outflow, most plausibly in
the form of turbulent magnetic-field amplification.Comment: 13 pages, 8 figures, 1 table, Accepted for publication in the
Astrophysical Journa
The Nuclear Spectroscopic Telescope Array (NuSTAR)
The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer
mission that will carry the first focusing hard X-ray (5 -- 80 keV) telescope
to orbit. NuSTAR will offer a factor 50 -- 100 sensitivity improvement compared
to previous collimated or coded mask imagers that have operated in this energy
band. In addition, NuSTAR provides sub-arcminute imaging with good spectral
resolution over a 12-arcminute field of view. After launch, NuSTAR will carry
out a two-year primary science mission that focuses on four key programs:
studying the evolution of massive black holes through surveys carried out in
fields with excellent multiwavelength coverage, understanding the population of
compact objects and the nature of the massive black hole in the center of the
Milky Way, constraining explosion dynamics and nucleosynthesis in supernovae,
and probing the nature of particle acceleration in relativistic jets in active
galactic nuclei. A number of additional observations will be included in the
primary mission, and a guest observer program will be proposed for an extended
mission to expand the range of scientific targets. The payload consists of two
co-aligned depth-graded multilayer coated grazing incidence optics focused onto
solid state CdZnTe pixel detectors. To be launched in early 2012 on a Pegasus
rocket into a low-inclination Earth orbit. Data will be publicly available at
GSFC's High Energy Astrophysics Science Archive Research Center (HEASARC)
following validation at the science operations center located at Caltech.Comment: 9 pages, 5 figures, to appear in Proceedings of the SPIE, Space
Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ra
Combining Deep Facial and Ambient Features for First Impression Estimation
14th European Conference on Computer Vision (ECCV) -- OCT 08-16, 2016 -- Amsterdam, NETHERLANDSFirst impressions influence the behavior of people towards a newly encountered person or a human-like agent. Apart from the physical characteristics of the encountered face, the emotional expressions displayed on it, as well as ambient information affect these impressions. In this work, we propose an approach to predict the first impressions people will have for a given video depicting a face within a context. We employ pre-trained Deep Convolutional Neural Networks to extract facial expressions, as well as ambient information. After video modeling, visual features that represent facial expression and scene are combined and fed to a Kernel Extreme Learning Machine regressor. The proposed system is evaluated on the ChaLearn Challenge Dataset on First Impression Recognition, where the classification target is the Big Five personality trait labels for each video. Our system achieved an accuracy of 90.94% on the sequestered test set, 0.36% points below the top system in the competition
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