12,877 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
Star Formation in the Field and Clusters of NGC 5253
We investigate the star formation history of both the bright star clusters
and the diffuse `field star' population in the dwarf starburst galaxy NGC 5253
using STIS longslit ultraviolet spectroscopy. Our slit covers a physical area
of 370 x 1.6 pc and includes 8 apparent clusters and several inter-cluster
regions of diffuse light which we take to be the field. The diffuse light
spectrum lacks the strong O-star wind features which are clearly visible in
spectra of the brightest clusters. This discrepancy provides compelling
evidence that the diffuse light is not reflected light from nearby clusters,
but originates in a UV-bright field star population, and it raises the issue of
whether the star formation process may be operating differently in the field
than in clusters. We compare our spectra to STARBURST99 evolutionary synthesis
models which incorporate a new low metallicity atlas of O-star spectra. We
favor a scenario which accounts for the paucity of O-stars in the field without
requiring the field to have a different IMF than the clusters: stellar clusters
form continuously and then dissolve on ~10 Myr timescales and disperse their
remaining stars into the field. We consider the probable contribution of an
O-star deficient field population to the spatially unresolved spectra of high
redshift galaxies. (Abridged)Comment: 26 pages, 10 figures, accepted for publication in Ap
Large scale patterns of genetic variation and differentiation in sugar maple from tropical Central America to temperate North America
© 2015 Vargas-Rodriguez et al. Background: Geological events in the latter Cenozoic have influenced the distribution, abundance and genetic structure of tree populations in temperate and tropical North America. The biogeographical history of temperate vegetation that spans large ranges of latitude is complex, involving multiple latitudinal shifts that might have occurred via different migration routes. We determined the regional structuring of genetic variation of sugar maple (Acer saccharum subsp. saccharum) and its only subspecies in tropical America (Acer saccharum subsp. skutchii) using nuclear and chloroplast data. The studied populations span a geographic range from Maine, USA (46°N), to El Progreso, Guatemala (15°N). We examined genetic subdivisions, explored the locations of ancestral haplotypes, analyzed genetic data to explore the presence of a single or multiple glacial refugia, and tested whether genetic lineages are temporally consistent with a Pleistocene or older divergence. Results: Nuclear and chloroplast data indicated that populations in midwestern USA and western Mexico were highly differentiated from populations in the rest of the sites. The time of the most recent common ancestor of the western Mexico haplotype lineage was dated to the Pliocene (5.9 Ma, 95 % HPD: 4.3-7.3 Ma). Splits during the Pleistocene separated the rest of the phylogroups. The most frequent and widespread haplotype occurred in half of the sites (Guatemala, eastern Mexico, southeastern USA, and Ohio). Our data also suggested that multiple Pleistocene refugia (tropics-southeastern USA, midwestern, and northeastern USA), but not western Mexico (Jalisco), contributed to post-glacial northward expansion of ranges. Current southern Mexican and Guatemalan populations have reduced population sizes, genetic bottlenecks and tend toward homozygosity, as indicated using nuclear and chloroplast markers. Conclusions: The divergence of western Mexican populations from the rest of the sugar maples likely resulted from orographic and volcanic barriers to gene flow. Past connectivity among populations in the southeastern USA and eastern Mexico and Guatemala possible occurred through gene flow during the Pleistocene. The time to the most common ancestor values revealed that populations from the Midwest and Northeast USA represented different haplotype lineages, indicating major divergence of haplotypes lineages before the Last Glacial Maximum and suggesting the existence of multiple glacial refugia
On Signatures of Twisted Magnetic Flux Tube Emergence
Recent studies of NOAA active region 10953, by Okamoto {\it et al.} ({\it
Astrophys. J. Lett.} {\bf 673}, 215, 2008; {\it Astrophys. J.} {\bf 697}, 913,
2009), have interpreted photospheric observations of changing widths of the
polarities and reversal of the horizontal magnetic field component as
signatures of the emergence of a twisted flux tube within the active region and
along its internal polarity inversion line (PIL). A filament is observed along
the PIL and the active region is assumed to have an arcade structure. To
investigate this scenario, MacTaggart and Hood ({\it Astrophys. J. Lett.} {\bf
716}, 219, 2010) constructed a dynamic flux emergence model of a twisted
cylinder emerging into an overlying arcade. The photospheric signatures
observed by Okamoto {\it et al.} (2008, 2009) are present in the model although
their underlying physical mechanisms differ. The model also produces two
additional signatures that can be verified by the observations. The first is an
increase in the unsigned magnetic flux in the photosphere at either side of the
PIL. The second is the behaviour of characteristic photospheric flow profiles
associated with twisted flux tube emergence. We look for these two signatures
in AR 10953 and find negative results for the emergence of a twisted flux tube
along the PIL. Instead, we interpret the photospheric behaviour along the PIL
to be indicative of photospheric magnetic cancellation driven by flows from the
dominant sunspot. Although we argue against flux emergence within this
particular region, the work demonstrates the important relationship between
theory and observations for the successful discovery and interpretation of
signatures of flux emergence.Comment: 14 pages, 8 figures, accepted for publication in Solar Physic
ENERGY ANALYSIS OF LIPID EXTRACTION OF Scenedesmus sp. PRODUCED IN PILOT SCALE
he production of biodiesel from lipids extracted from microalgae biomass is a promising approach to biofuels. However, this approach is still not commercialized because of the high costs of processes associated with, for example, time consumption and / or biomass drying with intense energy usage. However, it was not possible to show extraction methods among the lipids existing in the literature, which could be applied specifically to the extraction of lipids from the microalgae Scenedesmus sp. from the large-scale wet biomass, which is the current challenge faced by the Center for Research and Development of Sustainable Energy Auto (NPDEAS). Therefore, in this study, the possibility of avoiding the drying process, and extracting lipids directly from humid biomass, using the saponification method, was tested and compared with conventional Bligh and Dyer extraction (B & D). This study introduced the cultivation of microalgae Scenedesmus sp. compact tubular photobioreactors 12 m3 in area 10 m2 (8 x 5 x 2 m). The classical method of lipid extraction from microalgae - B & D - brings many pigments and polar lipids that exist in the biomass and the conversion rate was only 65-66%, whereas the recovery of fatty material in the wet biomass by the saponification method showed high conversion rate (90-95%). Therefore, the saponification process showed a high recovery of fatty acids that can be easily converted into biodiesel by esterification, and it was shown that the stage of drying the biomass can be removed without losing the fatty acids. In relation to the energy usage in the process, it was shown that drying the biomass for extraction of fatty acids uses more energy than that produced in the final product, biodiesel, showing that the removal of fatty acids of the wet biomass is of strategic importance to the viability of microalgae biodiesel
On the energy of homogeneous cosmologies
An energy for the homogeneous cosmological models is presented. More
specifically, using an appropriate natural prescription, we find the energy
within any region with any gravitational source for a large class of gravity
theories--namely those with a tetrad description--for all 9 Bianchi types. Our
energy is given by the value of the Hamiltonian with homogeneous boundary
conditions; this value vanishes for all regions in all Bianchi class A models,
and it does not vanish for any class B model. This is so not only for
Einstein's general relativity but, moreover, for the whole 3-parameter class of
tetrad-teleparallel theories. For the physically favored one parameter
subclass, which includes the teleparallel equivalent of Einstein's theory as an
important special case, the energy for all class B models is, contrary to
expectation, negative.Comment: 11 pages, reformated with minor change
A unified approach on Springer fibers in the hook, two-row and two-column cases
We consider the Springer fiber over a nilpotent endomorphism. Fix a Jordan
basis and consider the standard torus relative to this. We deal with the
problem to describe the flags fixed by the torus which belong to a given
component of the Springer fiber. We solve the problem in the hook, two-row and
two-column cases. We provide two main characterizations which are common to the
three cases, and which involve dominance relations between Young diagrams and
combinatorial algorithms. Then, for these three cases, we deduce topological
properties of the components and their intersections.Comment: 42 page
Multiplicity of Galactic Cepheids from long-baseline interferometry I. CHARA/MIRC detection of the companion of V1334 Cygni
We aim at determining the masses of Cepheids in binary systems, as well as
their geometric distances and the flux contribution of the companions. The
combination of interferometry with spectroscopy will offer a unique and
independent estimate of the Cepheid masses. Using long-baseline interferometry
at visible and infrared wavelengths, it is possible to spatially resolve binary
systems containing a Cepheid down to milliarcsecond separations. Based on the
resulting visual orbit and radial velocities, we can then derive the
fundamental parameters of these systems, particularly the masses of the
components and the geometric distance. We therefore performed interferometric
observations of the first-overtone mode Cepheid V1334 Cyg with the CHARA/MIRC
combiner. We report the first detection of a Cepheid companion using
long-baseline interferometry. We detect the signature of a companion orbiting
V1334 Cyg at two epochs. We measure a flux ratio between the companion and the
Cepheid f = 3.10+/-0.08%, giving an apparent magnitude mH = 8.47+/-0.15mag. The
combination of interferometric and spectroscopic data have enabled the unique
determination of the orbital elements: P = 1938.6+/-1.2 days, Tp = 2 443
616.1+/-7.3, a = 8.54+/-0.51mas, i = 124.7+/-1.8{\deg}, e = 0.190+/-0.013,
{\omega} = 228.7+/-1.6{\deg}, and {\Omega} = 206.3+/-9.4{\deg}. We derive a
minimal distance d ~ 691 pc, a minimum mass for both stars of 3.6 Msol, with a
spectral type earlier than B5.5V for the companion star. Our measured flux
ratio suggests that radial velocity detection of the companion using
spectroscopy is within reach, and would provide an orbital parallax and
model-free masses.Comment: Published in A&
Physicochemical properties of expanded extrudates from colored sorghum genotypes.
The diversity of sorghum grainsis relatedto their intrinsic properties, which include starch type,non-starch components and phenolic compounds. The latter are genotype dependent and affect the pericarp characteristics such as color and presence of a pigmented testa. This diversity can be valuable for developing new food products by thermoplastic extrusion intended for human consumption. Flours from sorghum grains from the genotypes of varied pericarp color: white (CMSXS180; 9010032), red (BRS 310; BRS 308) and light brown (BRS 305; 9929034) were processed in a co-rotating twin-screw extruder. Changes promoted by extrusion cooking were evaluated via specific mechanical energy (SME), die pressure, apparent density, sectional expansion index (SEI), water absorption index (WAI) and water solubility index (WSI). Pericarp color affected diepressure, apparent density and WSI values of extrudates. Light brown genotypes, rich in tannin and fiber content, generated the lowest die pressure and SEI values. Red genotypes presented the lowest SME and the highest WAI values. White genotypes presented intermediate SME and the highest die pressure values. These results reflect differences in starch conversion induced by the pericarp type. These results further suggest the potential use of pigmented sorghum extrudates for human consumption
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