15,625 research outputs found
Analyzing Disproportionate Reaction via Comparative Multilingual Targeted Sentiment in Twitter
Global events such as terrorist attacks are commented upon in social media, such as Twitter, in different languages and from different parts of the world. Most prior studies have focused on monolingual sentiment analysis, and therefore excluded an extensive proportion of the Twitter userbase. In this paper, we perform a multilingual comparative sentiment analysis study on the terrorist attack in Paris, during November 2015. In particular, we look at targeted sentiment, investigating opinions on specific entities, not simply the general sentiment of each tweet. Given the potentially inflammatory and polarizing effect that these types of tweets may have on attitudes, we examine the sentiments expressed about different targets and explore whether disproportionate reaction was expressed about such targets across different languages. Specifically, we assess whether the sentiment for French speaking Twitter users during the Paris attack differs from English-speaking ones. We identify disproportionately negative attitudes in the English dataset over the French one towards some entities and, via a crowdsourcing experiment, illustrate that this also extends to forming an annotator bias
Searching for Dark Matter Annihilation in the Smith High-Velocity Cloud
Recent observations suggest that some high-velocity clouds may be confined by
massive dark matter halos. In particular, the proximity and proposed dark
matter content of the Smith Cloud make it a tempting target for the indirect
detection of dark matter annihilation. We argue that the Smith Cloud may be a
better target than some Milky Way dwarf spheroidal satellite galaxies and use
gamma-ray observations from the Fermi Large Area Telescope to search for a dark
matter annihilation signal. No significant gamma-ray excess is found coincident
with the Smith Cloud, and we set strong limits on the dark matter annihilation
cross section assuming a spatially-extended dark matter profile consistent with
dynamical modeling of the Smith Cloud. Notably, these limits exclude the
canonical thermal relic cross section () for dark matter masses GeV annihilating via the or channels for certain assumptions of the dark matter
density profile; however, uncertainties in the dark matter content of the Smith
Cloud may significantly weaken these constraints.Comment: 7 pages, 5 figures. Published in Ap
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Lava flow morphology at an erupting andesitic stratovolcano: a satellite perspective on El Reventador, Ecuador
Lava flows pose a significant hazard to infrastructure and property located close to volcanoes, and understanding how flows advance is necessary to manage volcanic hazard during eruptions. Compared to low-silica basaltic flows, flows of andesite composition are infrequently erupted and so relatively few studies of their characteristics and behaviour exist. We use El Reventador, Ecuador as a target to investigate andesitic lava flow properties during a 4.5 year period of extrusive eruption between February 2012 and August 2016. We use satellite radar to map the dimensions of 43 lava flows and look at variations in their emplacement behaviour over time. We find that flows descend the north and south flanks of El Reventador, and were mostly emplaced during durations shorter than the satellite repeat interval of 24 days.Flows ranged in length from 0.3 to 1.7 km, and the length of these flows decreased over the observation period. We measure a decrease in flow volume with time that is correlated with a long-term exponential decrease in eruption rate, and propose that this behaviour is caused by temporary magma storage in the conduit acting as a melt capacitor between the magma reservoir and the surface. We use the dimensions of the flow levees and widths to estimate the flow yield strengths, which were of the order of 10-100 kPa. We observe that some flows were diverted by topographic obstacles, and compare measurements of decreased channel width and increased flow thickness at the obstacles with observations from laboratory experiments. Radar observations, such as those presented here, could be used to map and measure properties of evolving lava flow fields at other remote or difficult to monitor volcanoes
Experimental phase functions of mm-sized cosmic dust grains
We present experimental phase functions of three types of millimeter-sized
dust grains consisting of enstatite, quartz and volcanic material from Mount
Etna, respectively. The three grains present similar sizes but different
absorbing properties. The measurements are performed at 527 nm covering the
scattering angle range from 3 to 170 degrees. The measured phase functions show
two well defined regions i) soft forward peaks and ii) a continuous increase
with the scattering angle at side- and back-scattering regions. This behavior
at side- and back-scattering regions are in agreement with the observed phase
functions for the Fomalhaut and HR 4796A dust rings. Further computations and
measurements (including polarization) for millimeter sized-grains are needed to
draw some conclusions about the fluffy or compact structure of the dust grains
Projective Market Model Approach to AHP Decision-Making
In this paper we describe market in projective geometry language and give
definition of a matrix of market rate, which is related to the matrix rate of
return and the matrix of judgements in the Analytic Hierarchy Process (AHP). We
use these observations to extend the AHP model to projective geometry formalism
and generalise it to intransitive case. We give financial interpretations of
such generalised model and propose its simplification. The unification of the
AHP model and projective aspect of portfolio theory suggests a wide spectrum of
new applications such extended model.Comment: APFA 6 - Applications of Physics in Financial Analysis 6th
International Conference, 4-7 July 2007, Lisbon, Portuga
Second moment constraints and the control problem of Markov jump linear systems
This paper addresses the optimal solution for the regulator control problem of Markov jump linear systems subject to second moment constraints. We can characterize and obtain the solution explicitly using linear matrix inequalities techniques. The constraints are imposed on the second moment of both the system state and control vector, and the optimal solution is obtained in a computable form. To illustrate the usefulness of the approach, specially that for systems subject to abrupt variations and physical limitations, we present an application for one joint of the European Robotic Arm
Separador de fragmentos (F.R.S.) como herramienta para el análisis de reacciones nucleares a FAIR (FAcility for Antiproton and Ion Research in Europe)
Cada día la ciencia ha tenido que recurrir a la construcción de grandes instalaciones e instrumentos para realizar experimentos que permitan obtener información para que posteriormente sea analizada. En la física nuclear la creación de nuevas instalaciones ha venido creciendo a enormes pasos ya que para estudiar esta área de la física ha sido necesario construir aceleradores, espectrómetros magnéticos y detectores con el objetivo de obtener información experimental de sucesos a escala microscópica. En el presente artículo se hace una revisión acerca del proceso del diseño y construcción del espectrómetro de alta resolución magnética SUPER-FRS (Super-Fragment Separator) es resultado de una gran colaboración llamada FAIR en (Darmstadt) Alemania en las instalaciones del GSI con el fin de conocer la motivación científica que llevó a construirlo, su diseño técnico y trabajos que se han de realizar en él.Everyday science has had to resort to the construction of large facilities and instruments to carry out experiments that allow obtaining information so that it can be analyzed later. In nuclear physics, the creation of new facilities has been growing enormously since to study this area of physics it has been necessary to build accelerators, magnetic spectrometers and detectors in order to obtain experimental information of events on a microscopic scale. This article reviews the design and construction process of the SUPER-FRS (Super-Fragment Separator) magnetic high resolution spectrometer resulting from a great collaboration called FAIR in (Darmstadt) Germany in the GSI facilities with the In order to know the scientific motivation that led to build it, its technical design and work that has been done on it
Trypanosoma cruzi IIc: phylogenetic and phylogeographic insights from sequence and microsatellite analysis and potential impact on emergent Chagas disease.
Trypanosoma cruzi, the etiological agent of Chagas disease, is highly genetically diverse. Numerous lines of evidence point to the existence of six stable genetic lineages or DTUs: TcI, TcIIa, TcIIb, TcIIc, TcIId, and TcIIe. Molecular dating suggests that T. cruzi is likely to have been an endemic infection of neotropical mammalian fauna for many millions of years. Here we have applied a panel of 49 polymorphic microsatellite markers developed from the online T. cruzi genome to document genetic diversity among 53 isolates belonging to TcIIc, a lineage so far recorded almost exclusively in silvatic transmission cycles but increasingly a potential source of human infection. These data are complemented by parallel analysis of sequence variation in a fragment of the glucose-6-phosphate isomerase gene. New isolates confirm that TcIIc is associated with terrestrial transmission cycles and armadillo reservoir hosts, and demonstrate that TcIIc is far more widespread than previously thought, with a distribution at least from Western Venezuela to the Argentine Chaco. We show that TcIIc is truly a discrete T. cruzi lineage, that it could have an ancient origin and that diversity occurs within the terrestrial niche independently of the host species. We also show that spatial structure among TcIIc isolates from its principal host, the armadillo Dasypus novemcinctus, is greater than that among TcI from Didelphis spp. opossums and link this observation to differences in ecology of their respective niches. Homozygosity in TcIIc populations and some linkage indices indicate the possibility of recombination but cannot yet be effectively discriminated from a high genome-wide frequency of gene conversion. Finally, we suggest that the derived TcIIc population genetic data have a vital role in determining the origin of the epidemiologically important hybrid lineages TcIId and TcIIe
Efficient plot-based floristic assessment of tropical forests
The tropical flora remains chronically understudied and the lack of floristic understanding hampers ecological research and its application for large-scale conservation planning. Given scarce resources and the scale of the challenge there is a need to maximize the efficiency of both sampling strategies and sampling units, yet there is little information on the relative efficiency of different approaches to floristic assessment in tropical forests. This paper is the first attempt to address this gap. We repeatedly sampled forests in two regions of Amazonia using the two most widely used plot-based protocols of floristic sampling, and compared their performance in terms of the quantity of floristic knowledge and ecological insight gained scaled to the field effort required. Specifically, the methods are assessed first in terms of the number of person-days required to complete each sample (‘effort’), secondly by the total gain in the quantity of floristic information that each unit of effort provides (‘crude inventory efficiency’), and thirdly in terms of the floristic information gained as a proportion of the target species pool (‘proportional inventory efficiency’). Finally, we compare the methods in terms of their efficiency in identifying different ecological patterns within the data (‘ecological efficiency’) while controlling for effort. There are large and consistent differences in the performance of the two methods. The disparity is maintained even after accounting for regional and site-level variation in forest species richness, tree density and the number of field assistants. We interpret our results in the context of selecting the appropriate method for particular research purposes
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