712 research outputs found
Access to consciousness of briefly presented visual events is modulated by transcranial direct current stimulation of left dorsolateral prefrontal cortex
Adaptive behaviour requires the ability to process goal-relevant events at the expense of irrelevant ones. However, perception of a relevant visual event can transiently preclude access to consciousness of subsequent events â a phenomenon called attentional blink (AB). Here we investigated involvement of the left dorsolateral prefrontal cortex (DLPFC) in conscious access, by using transcranial direct current stimulation (tDCS) to potentiate or reduce neural excitability in the context of an AB task. In a sham-controlled experimental design, we applied between groups anodal or cathodal tDCS over the left DLPFC, and examined whether this stimulation modulated the proportion of stimuli that were consciously reported during the AB period. We found that tDCS over the left DLPFC affected the proportion of consciously perceived target stimuli. Moreover, anodal and cathodal tDCS had opposing effects, and exhibited different temporal patterns. Anodal stimulation attenuated the AB, enhancing conscious report earlier in the AB period. Cathodal stimulation accentuated the AB, reducing conscious report later in the AB period. These findings support the notion that the DLPFC plays a role in facilitating information transition from the unconscious to the conscious stage of processing
DW Cancri in x-rays
We report on the -Newton observation of DW Cnc, a candidate intermediate
polar candidate whose historical optical light curve shows the existence of
periods at , and minutes which were
interpreted as the white dwarf spin, the orbital and the spin-orbit beat
periodicities. By studying the keV light curves, we confirm the
existence of a period at minutes and find in the OM light curve a
signature for a period at minutes which is consistent with both the
orbital and spin-orbit beat. { These findings allow us to unveil without any
doubt, the nature of DW Cnc as an accreting intermediate polar. The EPIC and
RGS source spectra were analyzed and a best fit model, consisting of a
multi-temperature plasma, was found. The maximum temperature found when fitting
the data is keV which can be interpreted as an upper limit
to the temperature of the shock.Comment: 2019. Accepted for publication on MNRAS. 5 figures, 1 table. Updated
as, by mistake, an author affiliation was missing from the lis
A systematic review of genetic polymorphisms associated with binge eating disorder
The genetic polymorphisms involved in the physiopathology of binge eating disorder (BED) are currently unclear. This systematic review aims to highlight and summarize the research on polymorphisms that is conducted in the BED. We looked for observational studies where there was a genetic comparison between adults with BED, in some cases also with obesity or overweight, and healthy controls or obesity/overweight without BED. Our protocol was written using PRISMA. It is registered at PROSPERO (identification: CRD42020198645). To identify potentially relevant documents, the following bibliographic databases were searched without a time limit, but until September 2020: PubMed, PsycINFO, Scopus, and Web of Science. In total, 21 articles were included in the qualitative analysis of the systematic review, as they met the eligibility criteria. Within the selected studies, 41 polymorphisms of 17 genes were assessed. Overall, this systematic review provides a list of potentially useful genetic polymorphisms involved in BED: 5-HTTLPR (5-HTT), Taq1A (ANKK1/DRD2), A118G (OPRM1), C957T (DRD2), rs2283265 (DRD2), Val158Met (COMT), rs6198 (GR), Val103Ile (MC4R), Ile251Leu (MC4R), rs6265 (BNDF), and Leu72Met (GHRL). It is important to emphasize that Taq1A is the polymorphism that showed, in two different research groups, the most significant association with BED. The remaining polymorphisms need further evidence to be confirmed
Correcting the extended-source calibration for the <i>Herschel</i>-SPIRE Fourier-transform spectrometer
We describe an update to the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) Fourier-transform spectrometer (FTS) calibration for extended sources, which incorporates a correction for the frequency-dependent far-field feedhorn efficiency, ηff. This significant correction affects all FTS extended-source calibrated spectra in sparse or mapping mode, regardless of the spectral resolution. Line fluxes and continuum levels are underestimated by factors of 1.3â2 in thespectrometer long wavelength band (447â1018 GHz; 671â294 ÎŒm) and 1.4â1.5 in the spectrometer short wavelength band (944â1568 GHz; 318â191 ÎŒm). The correction was implemented in the FTS pipeline version 14.1 and has also been described in the SPIRE Handbook since 2017 February. Studies based on extended-source calibrated spectra produced prior to this pipeline version should be critically reconsidered using the current products available in the Herschel Science Archive. Once the extended-source calibrated spectra are corrected for ηff, the synthetic photometry and the broad-band intensities from SPIRE photometer maps agree within 2â4âperâcent â similar levels to the comparison of point-source calibrated spectra and photometry from point-source calibrated maps. The two calibration schemes for the FTS are now self-consistent: the conversion between the corrected extended-source and point-source calibrated spectra can be achieved with the beam solid angle and a gain correction that accounts for the diffraction loss
HerMES: Current Cosmic Infrared Background Estimates Can be Explained by Known Galaxies and their Faint Companions at z < 4
We report contributions to cosmic infrared background (CIB) intensities
originating from known galaxies and their faint companions at submillimeter
wavelengths. Using the publicly-available UltraVISTA catalog, and maps at 250,
350, and 500 {\mu}m from the \emph{Herschel} Multi-tiered Extragalactic Survey
(HerMES), we perform a novel measurement that exploits the fact that
uncatalogued sources may bias stacked flux densities --- particularly if the
resolution of the image is poor --- and intentionally smooth the images before
stacking and summing intensities. By smoothing the maps we are capturing the
contribution of faint (undetected in K_S ~ 23.4) sources that are physically
associated, or correlated, with the detected sources. We find that the
cumulative CIB increases with increased smoothing, reaching 9.82 +- 0.78, 5.77
+- 0.43, and 2.32 +- 0.19 at 250, 350, and 500 {\mu}m
at 300 arcsec FWHM. This corresponds to a fraction of the fiducial CIB of 0.94
+- 0.23, 1.07 +- 0.31, and 0.97 +- 0.26 at 250, 350, and 500 {\mu}m, where the
uncertainties are dominated by those of the absolute CIB. We then propose, with
a simple model combining parametric descriptions for stacked flux densities and
stellar mass functions, that emission from galaxies with log(M/Msun) > 8.5 can
account for the most of the measured total intensities, and argue against
contributions from extended, diffuse emission. Finally, we discuss prospects
for future survey instruments to improve the estimates of the absolute CIB
levels, and observe any potentially remaining emission at z > 4.Comment: Accepted to ApJL. 6 Pages, 3 figure
Poly-essential and general Hyperelastic World (brane) models
This article provides a unified treatment of an extensive category of
non-linear classical field models whereby the universe is represented (perhaps
as a brane in a higher dimensional background) in terms of a structure of a
mathematically convenient type describable as hyperelastic, for which a
complete set of equations of motion is provided just by the energy-momentum
conservation law. Particular cases include those of a perfect fluid in
quintessential backgrounds of various kinds, as well as models of the elastic
solid kind that has been proposed to account for cosmic acceleration. It is
shown how an appropriately generalised Hadamard operator can be used to
construct a symplectic structure that controles the evolution of small
perturbations, and that provides a characteristic equation governing the
propagation of weak discontinuities of diverse (extrinsic and extrinsic) kinds.
The special case of a poly-essential model - the k-essential analogue of an
ordinary polytropic fluid - is examined and shown to be well behaved (like the
fluid) only if the pressure to density ratio is positive.Comment: 16 pages Latex, Contrib. to 10th Peyresq Pysics Meeting, June 2005:
Micro and Macro Structures of Spacetim
Serendipitous detection of an overdensity of Herschel-SPIRE 250 micron sources south of MRC1138-26
We report the serendipitous detection of a significant overdensity of
Herschel-SPIRE 250 micron sources in the vicinity of MRC1138-26. We use an
adaptive kernel density estimate to quantify the significance, including a
comparison with other fields. The overdensity has a size of ~3.5-4' and stands
out at ~5sigma with respect to the background estimate. No features with
similar significance were found in four extragalactic control fields:
GOODS-North, Lockman, COSMOS and UDS. The chance of having a similar
overdensity in a field with the same number but randomly distributed sources is
less than 2%. The clump is also visible as a low surface brightness feature in
the Planck 857 GHz map. We detect 76 sources at 250 micron (with a
signal-to-noise ratio greater than 3), in a region of 4' radius; 43 of those
are above a flux density limit of 20 mJy. This is a factor of 3.6 in excess
over the average in the four control fields, considering only the sources above
20 mJy. We also find an excess in the number counts of sources with 250 micron
flux densities between 30 and 40 mJy, compared to deep extragalactic
blank-field number counts. Assuming a fixed dust temperature (30 K) and
emissivity (beta=1.5) a crude, blackbody-derived redshift distribution, zBB, of
the detected sources is significantly different from the distributions in the
control fields and exhibits a significant peak at zBB ~ 1.5, although the
actual peak redshift is highly degenerate with the temperature. We tentatively
suggest, based on zBB and the similar S250/S350 colours of the sources within
the peak, that a significant fraction of the sources in the clump may be at a
similar redshift. Since the overdensity lies ~7' south of the z=2.16 Spiderweb
protocluster MRC1138-26, an intriguing possibility (that is presently
unverifiable given the data in hand) is that it lies within the same
large-scale structure.(abridged)Comment: 10 pages, 8 figures, accepted for publication in MNRA
EXIT-chart aided hybrid multiuser detector design for frequency-domain-spread chip-interleaved MC-CDMA
With the advent of EXtrinsic Information Transfer (EXIT) charts, we are capable of analyzing, predicting and visually comparing the convergence behaviours of different turbo Multi-User Detectector (MUD)s. The different MUDs have diverse EXIT characteristics and hence their superposition allows us to create a combined EXIT curve, which closely matches that of the channel decoder. Hence a near-capacity operation is facilitated by combining the benifits of different MUDs and therefore to create a superior MUD. Thus in this contribution, we propose a novel hybrid MUD combining scheme, which combines the advantages of a high performance and low complexity in form of an advanced hybrid MUD solution. The transmitted bits are unknown at the receiver, hence it is not feasible to directly evaluate the mutual information gain of the iterative MUD in consecutive iterations, hence we propose a realistic algorithm for estimating this mutual information gain, which is then used for activating the most appropriate constituent MUD as and when it is necessary. The constituent MUDs are the Matched Filter (MF) based Soft Interference Cancellation (SoIC) and the optimum Bayesian MUDs, which are invoked in the scenario of Frequency-Domain-Spread Chip-Interleaved (FDSCI) Multiple Carrier Code Division Multiple Access (MC-CDMA). The resultant hybrid MUD is capable of outperforming both the MF-SoIC and Bayesian turbo MUDs in the terms of the attainable complexity and Bit-Error-Rate (BER) performance
Flux calibration of the Herschel-SPIRE photometer
We describe the procedure used to flux calibrate the three-band submillimetre photometer in the Spectral and Photometric Imaging Receiver instrument on the Herschel Space Observatory. This includes the equations describing the calibration scheme, a justification for using Neptune as the primary calibration source, a description of the observations and data processing procedures used to derive flux calibration parameters (for converting from voltage to flux density) for every bolometer in each array, an analysis of the error budget in the flux calibration for the individual bolometers and tests of the flux calibration on observations of primary and secondary calibrators. The procedure for deriving the flux calibration parameters is divided into two parts. In the first part, we use observations of astronomical sources in conjunction with the operation of the photometer internal calibration source to derive the unscaled derivatives of the flux calibration curves. To scale the calibration curves in Jy beam^(â1) V^(â1), we then use observations of Neptune in which the beam of each bolometer is mapped using a very fine scan pattern. The total instrumental uncertainties in the flux calibration for most individual bolometers is âŒ0.5â perâcent, although a few bolometers have uncertainties of âŒ1â5â perâcent because of issues with the Neptune observations. Based on application of the flux calibration parameters to Neptune observations performed using typical scan map observing modes, we determined that measurements from each array as a whole have instrumental uncertainties of 1.5â perâcent. This is considerably less than the absolute calibration uncertainty associated with the model of Neptune, which is estimated at 4 âperâcent
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