2,740 research outputs found
Developing a comprehensive framework for multimodal feature extraction
Feature extraction is a critical component of many applied data science
workflows. In recent years, rapid advances in artificial intelligence and
machine learning have led to an explosion of feature extraction tools and
services that allow data scientists to cheaply and effectively annotate their
data along a vast array of dimensions---ranging from detecting faces in images
to analyzing the sentiment expressed in coherent text. Unfortunately, the
proliferation of powerful feature extraction services has been mirrored by a
corresponding expansion in the number of distinct interfaces to feature
extraction services. In a world where nearly every new service has its own API,
documentation, and/or client library, data scientists who need to combine
diverse features obtained from multiple sources are often forced to write and
maintain ever more elaborate feature extraction pipelines. To address this
challenge, we introduce a new open-source framework for comprehensive
multimodal feature extraction. Pliers is an open-source Python package that
supports standardized annotation of diverse data types (video, images, audio,
and text), and is expressly with both ease-of-use and extensibility in mind.
Users can apply a wide range of pre-existing feature extraction tools to their
data in just a few lines of Python code, and can also easily add their own
custom extractors by writing modular classes. A graph-based API enables rapid
development of complex feature extraction pipelines that output results in a
single, standardized format. We describe the package's architecture, detail its
major advantages over previous feature extraction toolboxes, and use a sample
application to a large functional MRI dataset to illustrate how pliers can
significantly reduce the time and effort required to construct sophisticated
feature extraction workflows while increasing code clarity and maintainability
Tools for computing the AGN feedback: radio-loudness distribution and the kinetic luminosity function
We studied the Active Galactic Nuclei (AGN) radio emission from a compilation
of hard X-ray selected samples, all observed in the 1.4 GHz band. A total of
more than 1600 AGN with 2-10 keV de-absorbed luminosities higher than 10^42
erg/s were used. For a sub-sample of about 50 z\lsim 0.1 AGN it was possible to
reach a ~80% fraction of radio detections and therefore, for the first time, it
was possible to almost completely measure the probability distribution function
of the ratio between the radio and the X-ray luminosity Rx=log[L(1.4)/Lx]. The
probability distribution function of Rx was functionally fitted as dependent on
the X-ray luminosity and redshift, P(Rx|Lx,z). It roughly spans over 6 decades
(-7<Rx<-1), and does not show any sign of bi-modality. It resulted that the
probability of finding large values of the Rx ratio increases with decreasing
X-ray luminosities and (possibly) with increasing redshift. No statistical
significant difference was found between the radio properties of the X-ray
absorbed and unabsorbed AGN. The measure of the probability distribution
function of Rx allowed us to compute the kinetic luminosity function and the
kinetic energy density which, at variance with what assumed in many galaxy
evolution models, is observed to decrease of about a factor of five at redshift
below 0.5. About half of the kinetic energy density results to be produced by
the more radio quiet (Rx<-4) AGN. In agreement with previous estimates, the AGN
efficiency in converting the accreted mass energy into kinetic power is, on
average, ~5x10-3.Comment: 13 pages, ApJsty; ApJ in pres
The age-redshift relation for Luminous Red Galaxies in the Sloan Digital Sky Survey
We present a detailed analysis of 17,852 quiescent, Luminous Red Galaxies
(LRGs) selected from Sloan Digital Sky Survey (SDSS) Data Release Seven (DR7)
spanning a redshift range of 0.0 < z < 0.4. These galaxies are co-added into
four equal bins of velocity dispersion and luminosity to produce high
signal-to-noise spectra (>100A^{-1}), thus facilitating accurate measurements
of the standard Lick absorption-line indices. In particular, we have carefully
corrected and calibrated these indices onto the commonly used Lick/IDS system,
thus allowing us to compare these data with other measurements in the
literature, and derive realistic ages, metallicities ([Z/H]) and alpha-element
abundance ratios ([alpha/Fe]) for these galaxies using Simple Stellar
Population (SSP) models. We use these data to study the relationship of these
galaxy parameters with redshift, and find little evidence for evolution in
metallicity or alpha-elements (especially for our intermediate mass samples).
This demonstrates that our subsamples are consistent with pure passive evolving
(i.e. no chemical evolution) and represent a homogeneous population over this
redshift range. We also present the age-redshift relation for these LRGs and
clearly see a decrease in their age with redshift (5 Gyrs over the redshift
range studied here) which is fully consistent with the cosmological lookback
times in a concordance Lambda CDM universe. We also see that our most massive
sample of LRGs is the youngest compared to the lower mass galaxies. We provide
these data now to help future cosmological and galaxy evolution studies of
LRGs, and provide in the appendices of this paper the required methodology and
information to calibrate SDSS spectra onto the Lick/IDS system.Comment: 26 pages, with several appendices containing data. Accepted for
publication in MNRA
Structure and stellar content analysis of the open cluster M11 with 2MASS photometry
An overall analysis of the structure and stellar content of M11 is presented,
thanks to the wide-angle 2MASS spatial coverage. We derive photometric and
structural parameters and discuss the spatial dependance of the luminosity and
mass functions. Photometric parameters basically agree with previous ones
mostly based on the optical. We obtained a core radius of 1.23pc and a tidal
radius of 29pc. In particular, the cluster is populous enough so that the tidal
radius could be obtained by fitting the three-parameter King profile to the
radial distribution of stars. We analyzed the spatial distribution of mass
functions, finding that the the slope changes from -0.73 in the core to +2.88
in the outer halo. The spatial distribution of mass function slopes derived
from 2MASS agrees with that derived from optical CCD data, which further
confirms the reliability of 2MASS data for future analyses of this kind at
comparable observational limits. We detect mass segregation up to distances
from the center of ~20arcmin. We emphasize that the mass function slope in the
core is flatter than anywhere else as a consequence of mass segregation. The
derived total cluster mass is ~11000 solar masses.Comment: 9 pages, 11 figures. Accepted for publication in A&
Velocity Dispersion of Dissolving OB Associations Affected by External Pressure of Formation Environment
This paper presents a possible way to understand dissolution of OB
associations (or groups). Assuming rapid escape of parental cloud gas from
associations, we show that the shadow of the formation environment for
associations can be partially imprinted on the velocity dispersion at their
dissolution. This conclusion is not surprising as long as associations are
formed in a multiphase interstellar medium, because the external pressure
should suppress expansion caused by the internal motion of the parental clouds.
Our model predicts a few km s as the internal velocity dispersion.
Observationally, the internal velocity dispersion is km s which
is smaller than our prediction. This suggests that the dissipation of internal
energy happens before the formation of OB associations.Comment: 6 pages. AJ accepte
The trochlear isometric point is different in patients with recurrent patellar instability compared to controls: a radiographical study
Purpose: The purpose of the study was to investigate the theoretical isometric point based of the curve of the femoral groove and relating it to the origin of the MPFL femoral tunnel on lateral radiograph by comparing a patellar instability cohort with a control cohort. Methods: From a Patellar Instability database the radiographs of 40 consecutive patients were analysed to define Schöttleâs point, and the arc of the circle of the trochlear groove. A comparison population of 20 radiographs from comparable patients with tibiofemoral joint disorders was used as a control. The distance from Schöttleâs point to the most anterior part of the groove (extension) was also compared to the distance to the distal end of the roof of the notch (flexion). Results: The trochlea was circular in the controls but not the Patellofemoral Instability cohort where trochlear dysplasia is usually present. The difference between the extension and flexion length was a mean of ââ2.0â±â0.5 mm in the controls and +â6.0â±â0.5 mm in the patellofemoral cohort. In neither cohort did the centre of the circle correspond to Schöttleâs point. The extension distance correlated with the boss height. Conclusions: The dysplastic trochlea is not circular and the centre of the best matched circle was different to the control trochleae which were circular. The circle centres did not correlate with Schöttleâs point for either cohort, and was more proximal in the Patellofemoral Instability cohort. Clinical relevance: For the MPFL to have equal tension throughout flexion within the groove, the length should not change. In normal knees the MPFL does not behave isometrically. The change in length, as measured from Schöttleâs point to the trochlea, was greater for patellofemoral instability patients explaining why an isolated MPFL reconstruction in the presence of severe trochlear dysplasia risks poor outcomes
Cognitive appraisal of environmental stimuli induces emotion-like states in fish
The occurrence of emotions in non-human animals has been the focus of debate over the years. Recently, an interest in expanding this debate to non-tetrapod vertebrates and to invertebrates has emerged. Within vertebrates, the study of emotion in teleosts is particularly interesting since they represent a divergent evolutionary radiation from that of tetrapods, and thus they provide an insight into the evolution of the biological mechanisms of emotion. We report that Sea Bream exposed to stimuli that vary according to valence (positive, negative) and salience (predictable, unpredictable) exhibit different behavioural, physiological and neuromolecular states. Since according to the dimensional theory of emotion valence and salience define a two-dimensional affective space, our data can be interpreted as evidence for the occurrence of distinctive affective states in fish corresponding to each the four quadrants of the core affective space. Moreover, the fact that the same stimuli presented in a predictable vs. unpredictable way elicited different behavioural, physiological and neuromolecular states, suggests that stimulus appraisal by the individual, rather than an intrinsic characteristic of the stimulus, has triggered the observed responses. Therefore, our data supports the occurrence of emotion-like states in fish that are regulated by the individual's perception of environmental stimuli.European Commission [265957 Copewell]; Fundacao para a Ciencia e Tecnologia [SFRH/BD/80029/2011, SFRH/BPD/72952/2010]info:eu-repo/semantics/publishedVersio
The Relation Between Galaxy Morphology and Environment in the Local Universe: An RC3-SDSS Picture
We present an analysis of the z ~ 0 morphology-environment relation for 911
bright (M_B < -19) galaxies, matching classical RC3 morphologies to the
SDSS-based group catalog of Yang et al. We study how the relative fractions of
spirals, lenticulars, and ellipticals depend on halo mass over a range of
10^11.7-10^14.8 h^-1 Msol. We pay particular attention to how morphology
relates to central (most massive) vs satellite galaxy status. The fraction of
galaxies which are elliptical is a strong function of stellar mass; it is also
a strong function of halo mass, but only for central galaxies. We interpret
this in a scenario where elliptical galaxies are formed, probably via mergers,
as central galaxies within their halos; satellite ellipticals are previously
central galaxies accreted onto larger halos. The overall fraction of S0
galaxies increases strongly with halo mass, from ~10% to ~70%. We find striking
differences between the central and satellites: 20+/-2% of central M_* >
10^10.5 Msol galaxies are S0 regardless of halo mass, but satellite S0 galaxies
are only found in massive (> 10^13 h^-1 Msol) halos, where they are 69+/-4% of
the M_* > 10^10.5 Msol satellite population. This suggests two channels for S0
formation: one for central galaxies, and another which transforms lower mass
(M_* <~ 10^11 Msol) accreted spirals into satellite S0 galaxies in massive
halos. Analysis of finer morphological structure (bars and rings in disk
galaxies) shows some trends with stellar mass, but none with halo mass; this is
consistent with other recent studies which indicate that bars are not strongly
influenced by galaxy environment. Radio sources in high-mass central galaxies
are common, similarly so for elliptical and S0 galaxies, with a frequency that
increases with halo mass. Emission-line AGN (mostly LINERs) are more common in
S0s, but show no strong environmental trends (abridged).Comment: Accepted for publication in the Astrophysical Journal (ApJ
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