1,325 research outputs found
Response-related potentials during semantic priming: the effect of a speeded button response task on ERPs
This study examines the influence of a button response task on the event-related potential (ERP) in a semantic priming experiment. Of particular interest is the N400 component. In many semantic priming studies, subjects are asked to respond to a stimulus as fast and accurately as possible by pressing a button. Response time (RT) is recorded in parallel with an electroencephalogram (EEG) for ERP analysis. In this case, the response occurs in the time window used for ERP analysis and response-related components may overlap with stimulus-locked ones such as the N400. This has led to a recommendation against such a design, although the issue has not been explored in depth. Since studies keep being published that disregard this issue, a more detailed examination of influence of response-related potentials on the ERP is needed. Two experiments were performed in which subjects pressed one of two buttons with their dominant hand in response to word-pairs with varying association strength (AS), indicating a personal judgement of association between the two words. In the first experiment, subjects were instructed to respond as fast and accurately as possible. In the second experiment, subjects delayed their button response to enforce a one second interval between the onset of the target word and the button response. Results show that in the first experiment a P3 component and motor-related potentials (MRPs) overlap with the N400 component, which can cause a misinterpretation of the latter. In order to study the N400 component, the button response should be delayed to avoid contamination of the ERP with response-related components
Optical variability of the accretion disk around the intermediate mass black hole ESO 243-49 HLX-1 during the 2012 outburst
We present dedicated quasi-simultaneous X-ray (Swift) and optical (Very Large
Telescope (VLT), V- and R-band) observations of the intermediate mass black
hole candidate ESO 243-49 HLX-1 before and during the 2012 outburst. We show
that the V-band magnitudes vary with time, thus proving that a portion of the
observed emission originates in the accretion disk. Using the first quiescent
optical observations of HLX-1, we show that the stellar population surrounding
HLX-1 is fainter than V~25.1 and R~24.2. We show that the optical emission may
increase before the X-ray emission consistent with the scenario proposed by
Lasota et al. (2011) in which the regular outbursts could be related to the
passage at periastron of a star circling the intermediate mass black hole in an
eccentric orbit, which triggers mass transfer into a quasi-permanent accretion
disk around the black hole. Further, if there is indeed a delay in the X-ray
emission we estimate the mass-transfer delivery radius to be ~1e11 cm.Comment: 9 pages, 2 figures, accepted for publication in ApJ
Jet trails and Mach cones: The interaction of microquasars with the ISM
A sub-set of microquasars exhibit high peculiar velocity with respect to the
local standard of rest due to the kicks they receive when being born in
supernovae. The interaction between the radio plasma released by microquasar
jets from such high-velocity binaries with the ISM must lead to the production
of trails and bow shocks similar to what is observed in narrow-angle tailed
radio galaxies and pulsar wind nebulae. We present a set of numerical
simulations of this interaction that illuminate the long term dynamical
evolution and the observational properties of these microquasar bow shock
nebulae and trails. We find that this interaction always produces a structure
that consists of a bow shock, a trailing neck, and an expanding bubble. Using
our simulations to model emission, we predict that the shock surrounding the
bubble and the neck should be visible in H{\alpha} emission, the interior of
the bubble should be visible in synchrotron radio emission, and only the bow
shock is likely to be detectable in X-ray emission. We construct an analytic
model for the evolution of the neck and bubble shape and compare this model
with observations of X-ray binary SAX J1712.6-3739.Comment: 33 pages, 13 figures, 1 table; Accepted to Ap
Variational Neural Annealing
Many important challenges in science and technology can be cast as
optimization problems. When viewed in a statistical physics framework, these
can be tackled by simulated annealing, where a gradual cooling procedure helps
search for groundstate solutions of a target Hamiltonian. While powerful,
simulated annealing is known to have prohibitively slow sampling dynamics when
the optimization landscape is rough or glassy. Here we show that by
generalizing the target distribution with a parameterized model, an analogous
annealing framework based on the variational principle can be used to search
for groundstate solutions. Modern autoregressive models such as recurrent
neural networks provide ideal parameterizations since they can be exactly
sampled without slow dynamics even when the model encodes a rough landscape. We
implement this procedure in the classical and quantum settings on several
prototypical spin glass Hamiltonians, and find that it significantly
outperforms traditional simulated annealing in the asymptotic limit,
illustrating the potential power of this yet unexplored route to optimization.Comment: 19 pages, 9 figures, 1 tabl
Developmental changes in mu suppression to observed and executed actions in autism spectrum disorders
There has been debate over whether disruptions in the mirror neuron system (MNS) play a key role in the core social deficits observed in autism spectrum disorders (ASD). EEG mu suppression during the observation of biological actions is believed to reflect MNS functioning, but understanding of the developmental progression of the MNS and EEG mu rhythm in both typical and atypical development is lacking. To provide a more thorough and direct exploration of the development of mu suppression in individuals with ASD, a sample of 66 individuals with ASD and 51 typically developing individuals of 6-17 years old were pooled from four previously published studies employing similar EEG methodology. We found a significant correlation between age and mu suppression in response to the observation of actions, both for individuals with ASD and typical individuals. This relationship was not seen during the execution of actions. Additionally, the strength of the correlation during the observation of actions did not significantly differ between groups. The results provide evidence against the argument that mirror neuron dysfunction improves with age in individuals with ASD and suggest, instead, that a diagnosis-independent developmental change may be at the root of the correlation of age and mu suppression
Herschel/PACS observations of the host galaxy of GRB 031203
We present Herschel/PACS observations of the nearby (z = 0.1055) dwarf galaxy that has hosted the long gamma-ray burst (LGRB) 031203. Using the PACS data, we have been able to place constraints on the dust temperature, dust mass, total infrared (IR) luminosity and IR-derived star formation rate (SFR) for this object. We find that the GRB host galaxy (GRBH) 031203 has a total IR luminosity of 3 × 1010 L⊙ placing it in the regime of the IR-luminous galaxy population. Its dust temperature and specific SFR are comparable to that of many high-redshift (z = 0.3–2.5) IR-detected GRB hosts (Tdust > 40 K; sSFR > 10 Gyr−1); however, its dust-to-stellar mass ratio is lower than what is commonly seen in IR-luminous galaxies. Our results suggest that GRBH 031203 is undergoing a strong starburst episode and its dust properties are different to those of local dwarf galaxies within the same metallicity and stellar mass range. Furthermore, our measurements place it in a distinct class to the well-studied nearby host of GRB 980425 (z = 0.0085), confirming the notion that GRB host galaxies can span a large range in properties even at similar cosmological epochs, making LGRBs an ideal tool in selecting samples of star-forming galaxies up to high redshift
Temporal artery temperature measurements versus bladder temperature in critically ill patients, a prospective observational study
PurposeAccurate measurement of body temperature is important for the timely detection of fever or hypothermia in critically ill patients. In this prospective study, we evaluated whether the agreement between temperature measurements obtained with TAT (test method) and bladder catheter-derived temperature measurements (BT; reference method) is sufficient for clinical practice in critically ill patients.MethodsPatients acutely admitted to the Intensive Care Unit were included. After BT was recorded TAT measurements were performed by two independent researchers (TAT1; TAT2). The agreement between TAT and BT was assessed using Bland-Altman plots. Clinical acceptable limits of agreement (LOA) were defined a priori (ResultsIn total, 90 critically ill patients (64 males; mean age 62 years) were included. The observed mean difference (TAT-BT; ±SD, 95% LOA) between TAT and BT was 0.12°C (-1.08°C to +1.32°C) for TAT1 and 0.14°C (-1.05°C to +1.33°C) for TAT2. 36% (TAT1) and 42% (TAT2) of all paired measurements failed to meet the acceptable LOA of 0.5°C. Subgroup analysis showed that when patients were receiving intravenous norepinephrine, the measurements of the test method deviated more from the reference method (p = NS).ConclusionThe TAT is not sufficient for clinical practice in critically ill adults
Polarized kilonovae from black hole-neutron star mergers
We predict linear polarization for a radioactively powered kilonova following the merger of a black hole and a neutron star. Specifically, we perform 3D Monte Carlo radiative transfer simulations for two different models, both featuring a lanthanide-rich dynamical ejecta component from numerical-relativity simulations while only one including an additional lanthanide-free disc-wind component. We calculate polarization spectra for nine different orientations at 1.5, 2.5, and 3.5 d after the merger and in the 0.1-2 μ wavelength range. We find that both models are polarized at a detectable level 1.5 d after the merger while show negligible levels thereafter. The polarization spectra of the two models are significantly different. The model lacking a disc wind shows no polarization in the optical, while a signal increasing at longer wavelengths and reaching ∼ 1-6 per cent at 2 μ depending on the orientation. The model with a disc-wind component, instead, features a characteristic 'double-peak' polarization spectrum with one peak in the optical and the other in the infrared. Polarimetric observations of future events will shed light on the debated neutron richness of the disc-wind component. The detection of optical polarization would unambiguously reveal the presence of a lanthanide-free disc-wind component, while polarization increasing from zero in the optical to a peak in the infrared would suggest a lanthanide-rich composition for the whole ejecta. Future polarimetric campaigns should prioritize observations in the first ∼48 h and in the 0.5-2 μ range, where polarization is strongest, but also explore shorter wavelengths/later times where no signal is expected from the kilonova and the interstellar polarization can be safely estimated
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