11,363 research outputs found
Identifying Emotions in Social Media: Comparison of Word-emotion lexica
In recent years, emotions expressed in social media messages have become a vivid research topic due to their influence on the spread of misinformation and online radicalization over online social networks. Thus, it is important to correctly identify emotions in order to make inferences from social media messages. In this paper, we report on the performance of three publicly available word-emotion lexicons (NRC, DepecheMood, EmoSenticNet) over a set of Facebook and Twitter messages. To this end, we designed and implemented an algorithm that applies natural language processing (NLP) techniques along with a number of heuristics that reflect the way humans naturally assess emotions in written texts. In order to evaluate the appropriateness of the obtained emotion scores, we conducted a questionnaire-based survey with human raters. Our results show that there are noticeable differences between the performance of the lexicons as well as with respect to emotion scores the human raters provided in our surve
Exchange-correlation potential for Current Density Functional Theory of frequency dependent linear response
The dynamical, long-wavelength longitudinal and transverse
exchange-correlation potentials for a homogeneous electron gas are evaluated in
a microscopic model based on an approximate decoupling of the equation of
motion for the current-current response function. The transverse spectrum turns
out to be very similar to the longitudinal one. We obtain evidence for a strong
spectral structure near twice the plasma frequency due to a two-plasmon
threshold for two-pair excitations, which may be observable in inelastic
scattering experiments. Our results give the entire input needed to implement
the Time-Dependent Current Density Functional Theory scheme recently developed
by G. Vignale and W. Kohn [Phys. Rev. Lett. 77, 2037 (1996)] and are fitted to
analytic functions to facilitate such applications.Comment: 6 pages, 3 figure
Thermomechanical properties of amorphous metallic tungsten-oxygen and tungsten-oxide coatings
In this work, we investigate the correlation between morphology, composition,
and the mechanical properties of metallic amorphous tungsten-oxygen and
amorphous tungsten-oxide films deposited by Pulsed Laser Deposition. This
correlation is investigated by the combined use of Brillouin Spectroscopy and
the substrate curvature method. The stiffness of the films is strongly affected
by both the oxygen content and the mass density. The elastic moduli show a
decreasing trend as the mass density decreases and the oxygen-tungsten ratio
increases. A plateaux region is detected in correspondence of the transition
between metallic and oxide films. The compressive residual stresses, moderate
stiffness and high local ductility that characterize compact amorphous
tungsten-oxide films make them promising for applications involving thermal or
mechanical loads. The coefficient of thermal expansion is quite high (i.e. 8.9
10 K), being strictly correlated to the amorphous
structure and stoichiometry of the films. Under thermal treatments they show a
quite low relaxation temperature (i.e. 450 K). They crystallize into the
monoclinic phase of WO starting from 670 K, inducing an increase
by about 70\% of material stiffness.Comment: The research leading to these results has also received funding from
the European Research Council Consolidator Grant ENSURE (ERC-2014-CoG No.
647554). The views and opinions expressed herein do not necessarily reflect
those of the European Commissio
Molecular Basis for poly(A) RNP Architecture and Recognition by the Pan2-Pan3 Deadenylase
The stability of eukaryotic mRNAs is dependent on a ribonucleoprotein (RNP) complex of poly(A)-binding proteins (PABPC1/Pab1) organized on the poly(A) tail. This poly(A) RNP not only protects mRNAs from premature degradation but also stimulates the Pan2-Pan3 deadenylase complex to catalyze the first step of poly(A) tail shortening. We reconstituted this process in vitro using recombinant proteins and show that Pan2-Pan3 associates with and degrades poly(A) RNPs containing two or more Pab1 molecules. The cryo-EM structure of Pan2-Pan3 in complex with a poly(A) RNP composed of 90 adenosines and three Pab1 protomers shows how the oligomerization interfaces of Pab1 are recognized by conserved features of the deadenylase and thread the poly(A) RNA substrate into the nuclease active site. The structure reveals the basis for the periodic repeating architecture at the 3' end of cytoplasmic mRNAs. This illustrates mechanistically how RNA-bound Pab1 oligomers act as rulers for poly(A) tail length over the mRNAs' lifetime.We would like to thank ... the MPIB cryo-EM, and core facilities ..
Tridactyl tracks from the Lavini di Marco dinosaur ichnosite (Hettangian, Southern Alps, NE Italy). Ichnotaxonomical review and palaeobiogeography
The use of aerial- and close-range photogrammetry for the mapping of the Lavini di Marco tracksite (Hettangian, Southern Alps, NE Italy)
(EXCERPT FROM ABSTRACT) Close-range photogrammetry was executed following the procedure proposed by Mallison & Wings (2014). More than seventy 3D models were obtained and interpreted by means of color-coded and contour line images, which allow to improve the ichno- logical knowledge of the tracksite. The 3D models of the best-preserved tracks were used for the osteological reconstruction of the trackmakers’ autopodia, supposing the arthral position of the phalangeal pads. Three indirect methods were used to correlate tracks and their trackmakers: (i) synapomorphy-based approach; (ii) phenetic correlation; (iii) coincidence correlation (see Carrano & Wilson, 2001)
The final map was produced with different level of knowledge due to the distribution of tracks and current state of site preservation. Furthermore, it represents a complete documentation that will be used for future work of enhancement, preservation and valorization of the tracksite.
The ichnotaxonomical review of the quadrupedal trackways led us to emend the diagnosis of Lavinipes cheminii Avanzini et al. (2003) and to assign several other sparse tracks and trackways to L. chemini. The skeletal reconstruction of fore and hind limbs points towards Gongxianosaurus sp. as the most suitable trackmaker of L. cheminii. The herein supposed Laurasian affinity of the Lavini di Marco dinosaur assemblage clashes with the previous hypotheses that always link the Southern Alps sector with the Gondwana mainland
Spatially incoherent modulational instability in a non local medium
We investigate one-dimensional transverse modulational instability in a non
local medium excited with a spatially incoherent source. Employing undoped
nematic liquid crystals in a planar pre-tilted configuration, we investigate
the role of the spectral broadening induced by incoherence in conjunction with
the spatially non local molecular reorientation. The phenomenon is modeled
using the Wigner transform.Comment: 13 pages with 4 figures included. To be published in Laser Physics
Letter
Transverse-momentum distributions in a diquark spectator model
All the leading-twist parton distribution functions are calculated in a
spectator model of the nucleon, using scalar and axial-vector diquarks. Single
gluon rescattering is used to generate T-odd distribution functions. Different
choices for the diquark polarization states are considered, as well as a few
options for the form factor at the nucleon-quark-diquark vertex. The results
are listed in analytic form and interpreted in terms of light-cone wave
functions. The model parameters are fixed by reproducing the phenomenological
parametrization of unpolarized and helicity parton distributions at the lowest
available scale. Predictions for the other parton densities are given and,
whenever possible, compared with available phenomenological parametrizations.Comment: 42 pages, 13 figures in .eps format. RevTeX style. Minor typos
corrected, added one referenc
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