A likelihood-based method for measuring weak gravitational lensing shear in deep galaxy surveys is described and applied to the Canada-France-Hawaii Telescope (CFHT) Lensing Survey (CFHTLenS). ...CFHTLenS comprises 154 deg2 of multi-colour optical data from the CFHT Legacy Survey, with lensing measurements being made in the i
′ band to a depth i′AB < 24.7, for galaxies with signal-to-noise ratio νSN 10. The method is based on the lensfit algorithm described in earlier papers, but here we describe a full analysis pipeline that takes into account the properties of real surveys. The method creates pixel-based models of the varying point spread function (PSF) in individual image exposures. It fits PSF-convolved two-component (disc plus bulge) models to measure the ellipticity of each galaxy, with Bayesian marginalization over model nuisance parameters of galaxy position, size, brightness and bulge fraction. The method allows optimal joint measurement of multiple, dithered image exposures, taking into account imaging distortion and the alignment of the multiple measurements. We discuss the effects of noise bias on the likelihood distribution of galaxy ellipticity. Two sets of image simulations that mirror the observed properties of CFHTLenS have been created to establish the method's accuracy and to derive an empirical correction for the effects of noise bias.
Little is known about the underlying neurobiology of rhythm and beat perception, despite its universal cultural importance. Here we used functional magnetic resonance imaging to study rhythm ...perception in musicians and nonmusicians. Three conditions varied in the degree to which external reinforcement versus internal generation of the beat was required. The "volume" condition strongly externally marked the beat with volume changes, the "duration" condition marked the beat with weaker accents arising from duration changes, and the "unaccented" condition required the beat to be entirely internally generated. In all conditions, beat rhythms compared with nonbeat control rhythms revealed putamen activity. The presence of a beat was also associated with greater connectivity between the putamen and the supplementary motor area (SMA), the premotor cortex (PMC), and auditory cortex. In contrast, the type of accent within the beat conditions modulated the coupling between premotor and auditory cortex, with greater modulation for musicians than nonmusicians. Importantly, the response of the putamen to beat conditions was not attributable to differences in temporal complexity between the three rhythm conditions. We propose that a cortico-subcortical network including the putamen, SMA, and PMC is engaged for the analysis of temporal sequences and prediction or generation of putative beats, especially under conditions that may require internal generation of the beat. The importance of this system for auditory-motor interaction and development of precisely timed movement is suggested here by its facilitation in musicians.
We present data products from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). CFHTLenS is based on the Wide component of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). It ...encompasses 154 deg2 of deep, optical, high-quality, sub-arcsecond imaging data in the five optical filters u*g
′
r
′
i
′
z
′. The scientific aims of the CFHTLenS team are weak gravitational lensing studies supported by photometric redshift estimates for the galaxies. This paper presents our data processing of the complete CFHTLenS data set. We were able to obtain a data set with very good image quality and high-quality astrometric and photometric calibration. Our external astrometric accuracy is between 60 and 70 mas with respect to Sloan Digital Sky Survey (SDSS) data, and the internal alignment in all filters is around 30 mas. Our average photometric calibration shows a dispersion of the order of 0.01-0.03 mag for g
′
r
′
i
′
z
′ and about 0.04 mag for u* with respect to SDSS sources down to i
SDSS ≤ 21. We demonstrate in accompanying papers that our data meet necessary requirements to fully exploit the survey for weak gravitational lensing analyses in connection with photometric redshift studies. In the spirit of the CFHTLS, all our data products are released to the astronomical community via the Canadian Astronomy Data Centre at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/community/CFHTLens/query.html. We give a description and how-to manuals of the public products which include image pixel data, source catalogues with photometric redshift estimates and all relevant quantities to perform weak lensing studies.
Perception of temporal patterns is critical for speech, movement, and music. In the auditory domain, perception of a regular pulse, or beat, within a sequence of temporal intervals is associated with ...basal ganglia activity. Two alternative accounts of this striatal activity are possible: "searching" for temporal regularity in early stimulus processing stages or "prediction' of the timing of future tones after the beat is found (relying on continuation of an internally generated beat). To resolve between these accounts, we used functional magnetic resonance imaging (fMRI) to investigate different stages of beat perception. Participants heard a series of beat and nonbeat (irregular) monotone sequences. For each sequence, the preceding sequence provided a temporal beat context for the following sequence. Beat sequences were preceded by nonbeat sequences, requiring the beat to be found anew ("beat finding" condition), or by beat sequences with the same beat rate ("beat continuation"), or a different rate ("beat adjustment"). Detection of regularity is highest during beat finding, whereas generation and prediction are highest during beat continuation. We found the greatest striatal activity for beat continuation, less for beat adjustment, and the least for beat finding. Thus, the basal ganglia's response profile suggests a role in beat prediction, not in beat finding.
3D cosmic shear: cosmology from CFHTLenS Kitching, T. D; Heavens, A. F; Alsing, J ...
Monthly notices of the Royal Astronomical Society,
08/2014, Letnik:
442, Številka:
2
Journal Article
Recenzirano
Odprti dostop
This paper presents the first application of 3D cosmic shear to a wide-field weak lensing survey. 3D cosmic shear is a technique that analyses weak lensing in three dimensions using a spherical ...harmonic approach, and does not bin data in the redshift direction. This is applied to CFHTLenS, a 154 square degree imaging survey with a median redshift of 0.7 and an effective number density of 11 galaxies per square arcminute usable for weak lensing. To account for survey masks we apply a 3D pseudo-C
ℓ approach on weak lensing data, and to avoid uncertainties in the highly non-linear regime, we separately analyse radial wavenumbers k ≤ 1.5 and 5.0 h Mpc−1, and angular wavenumbers ℓ ≈ 400–5000. We show how one can recover 2D and tomographic power spectra from the full 3D cosmic shear power spectra and present a measurement of the 2D cosmic shear power spectrum, and measurements of a set of 2-bin and 6-bin cosmic shear tomographic power spectra; in doing so we find that using the 3D power in the calculation of such 2D and tomographic power spectra from data naturally accounts for a minimum scale in the matter power spectrum. We use 3D cosmic shear to constrain cosmologies with parameters ΩM, ΩB, σ8, h , n
s, w
0 and w
a
. For a non-evolving dark energy equation of state, and assuming a flat cosmology, lensing combined with Wilkinson Microwave Anisotropy Probe 7 results in h = 0.78 ± 0.12, ΩM = 0.252 ± 0.079, σ8 = 0.88 ± 0.23 and w = −1.16 ± 0.38 using only scales k ≤ 1.5 h Mpc−1. We also present results of lensing combined with first year Planck results, where we find no tension with the results from this analysis, but we also find no significant improvement over the Planck results alone. We find evidence of a suppression of power compared to Lambda cold dark matter (LCDM) on small scales 1.5 < k ≤ 5.0 h Mpc−1 in the lensing data, which is consistent with predictions of the effect of baryonic feedback on the matter power spectrum.
•We performed meta-analyses on fMRI/PET studies of human intentional decision.•Intentional choices activate a brain network maximal in the medial frontal cortex.•Four types of intentional decision ...paradigms are identified in the literature.•Intentional decisions rely on regions with distinct cognitive and computational roles.
Brain-imaging research on intentional decision-making often employs a “free-choice” paradigm, in which participants choose among options with identical values or outcomes. Although the medial prefrontal cortex has commonly been associated with choices, there is no consensus on the wider network that underlies diverse intentional decisions and behaviours. Our systematic literature search identified 35 fMRI/PET experiments using various free-choice paradigms, with appropriate control conditions using external instructions. An Activation Likelihood Estimate (ALE) meta-analysis showed that, compared with external instructions, intentional decisions consistently activate the medial and dorsolateral prefrontal cortex, the left insula and the inferior parietal lobule. We then categorized the studies into four different types according to their experimental designs: reactive motor intention, perceptual intention, inhibitory intention, and cognitive intention. We conducted conjunction and contrast meta-analyses to identify consistent and selective spatial convergence of brain activation within each specific category of intentional decision. Finally, we used meta-analytic decoding to probe cognitive processes underlying free choices. Our findings suggest that the neurocognitive process underlying intentional decision incorporates anatomically separated components subserving distinct cognitive and computational roles.
We present new constraints on the relationship between galaxies and their host dark matter haloes, measured from the location of the peak of the stellar-to-halo mass ratio (SHMR), up to the most ...massive galaxy clusters at redshift z ∼ 0.8 and over a volume of nearly 0.1 Gpc3. We use a unique combination of deep observations in the CFHTLenS/VIPERS field from the near-UV to the near-IR, supplemented by ∼60 000 secure spectroscopic redshifts, analysing galaxy clustering, galaxy–galaxy lensing and the stellar mass function. We interpret our measurements within the halo occupation distribution (HOD) framework, separating the contributions from central and satellite galaxies. We find that the SHMR for the central galaxies peaks at
$M_{\rm h, peak} = 1.9^{+0.2}_{-0.1}\times 10^{12}{\,{\rm M}_{{\odot }}}$
with an amplitude of 0.025, which decreases to ∼0.001 for massive haloes (
${{{M}_{\rm h}}}> 10^{14} {\,{\rm M}_{{\odot }}}$
). Compared to central galaxies only, the total SHMR (including satellites) is boosted by a factor of 10 in the high-mass regime (cluster-size haloes), a result consistent with cluster analyses from the literature based on fully independent methods. After properly accounting for differences in modelling, we have compared our results with a large number of results from the literature up to z = 1: we find good general agreement, independently of the method used, within the typical stellar-mass systematic errors at low to intermediate mass (
${{{M}_{\rm \star }}}<10^{11} {\,{\rm M}_{{\odot }}}$
) and the statistical errors above. We have also compared our SHMR results to semi-analytic simulations and found that the SHMR is tilted compared to our measurements in such a way that they over- (under-) predict star formation efficiency in central (satellite) galaxies.
Fossil Evidence on Origin of the Mammalian Brain Rowe, Timothy B.; Macrini, Thomas E.; Luo, Zhe-Xi
Science (American Association for the Advancement of Science),
05/2011, Letnik:
332, Številka:
6032
Journal Article
Recenzirano
Many hypotheses have been postulated regarding the early evolution of the mammalian brain. Here, x-ray tomography of the Early Jurassic mammaliaforms Morganucodon and Hadrocodium sheds light on this ...history. We found that relative brain size expanded to mammalian levels, with enlarged olfactory bulbs, neocortex, olfactory (pyriform) cortex, and cerebellum, in two evolutionary pulses. The initial pulse was probably driven by increased resolution in olfaction and improvements in tactile sensitivity (from body hair) and neuromuscular coordination. A second pulse of olfactory enhancement then enlarged the brain to mammalian levels. The origin of crown Mammalia saw a third pulse of olfactory enhancement, with ossified ethmoid turbinals supporting an expansive olfactory epithelium in the nasal cavity, allowing full expression of a huge odorant receptor genome.
In this paper we develop a simple model of the inhaled flow rate of aerosol particles of respiratory origin i.e. that have been exhaled by other people. A connection is made between the exposure dose ...and the probability of developing an airborne disease. This allows a simple assessment of the outdoor versus indoor risk of contamination to be made in a variety of meteorological situations. It is shown quantitatively that for most cases, the outdoor risk is orders of magnitude less than the indoor risk and that it can become comparable only for extremely specific meteorological and topographical situations. It sheds light on various observations of COVID-19 spreading in mountain valleys with temperature inversions while at the same time other areas are much less impacted.
•Risk of COVID-19 airborne transmission.•Quantitative assessment of outdoor versus indoor airborne risk of transmission.•Meteorological and topographical influence on COVID-19 airborne transmission.
We address the problem of separating stars from galaxies in future large photometric surveys. We focus our analysis on simulations of the Dark Energy Survey (DES). In the first part of the paper, we ...derive the science requirements on star/galaxy separation, for measurement of the cosmological parameters with the gravitational weak lensing and large-scale structure probes. These requirements are dictated by the need to control both the statistical and systematic errors on the cosmological parameters, and by point spread function calibration. We formulate the requirements in terms of the completeness and purity provided by a given star/galaxy classifier. In order to achieve these requirements at faint magnitudes, we propose a new method for star/galaxy separation in the second part of the paper. We first use principal component analysis to outline the correlations between the objects parameters and extract from it the most relevant information. We then use the reduced set of parameters as input to an Artificial Neural Network. This multiparameter approach improves upon purely morphometric classifiers (such as the classifier implemented in SExtractor), especially at faint magnitudes: it increases the purity by up to 20 per cent for stars and by up to 12 per cent for galaxies, at i-magnitude fainter than 23.
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