3,922 research outputs found
Building ontologies from folksonomies and linked data: Data structures and Algorithms
We present the data structures and algorithms used in the approach for building domain ontologies from folksonomies and linked data. In this approach we extracts domain terms from folksonomies and enrich them with semantic information from the Linked Open Data cloud. As a result, we obtain a domain ontology that combines the emergent knowledge of social tagging systems with formal knowledge from Ontologies
Neutral pion decay in dense skyrmion matter
We study the density dependence of the decay using
the Skyrme Lagrangian to describe simultaneously both the matter background and
mesonic fluctuations. Pion properties such as mass and decay constant are
modified by the medium. This leads to large suppression at high density of both
photo-production from the neutral pion and the reverse process. The in-medium
effective charge of are also discussed in the same framework.Comment: 8 pages, 4 figures. Corrections in light of referee comment
Selecting ultra-faint dwarf candidate progenitors in cosmological N-body simulations at high redshifts
The smallest satellites of the Milky Way ceased forming stars during the
epoch of reionization and thus provide archaeological access to galaxy
formation at . Numerical studies of these ultra-faint dwarf galaxies
(UFDs) require expensive cosmological simulations with high mass resolution
that are carried out down to . However, if we are able to statistically
identify UFD host progenitors at high redshifts \emph{with relatively high
probabilities}, we can avoid this high computational cost. To find such
candidates, we analyze the merger trees of Milky Way type halos from the
high-resolution suite of dark matter only simulations.
Satellite UFD hosts at are identified based on four different abundance
matching (AM) techniques. All the halos at high redshifts are traced forward in
time in order to compute the probability of surviving as satellite UFDs today.
Our results show that selecting potential UFD progenitors based solely on their
mass at z=12 (8) results in a 10\% (20\%) chance of obtaining a surviving UFD
at in three of the AM techniques we adopted. We find that the progenitors
of surviving satellite UFDs have lower virial ratios (), and are
preferentially located at large distances from the main MW progenitor, while
they show no correlation with concentration parameter. Halos with favorable
locations and virial ratios are times more likely to survive as
satellite UFD candidates at Comment: 12 pages, 7 figures, accepted for publication at MNRAS after minor
revision
The Caterpillar Project: A Large Suite of Milky Way Sized Halos
We present the largest number of Milky Way sized dark matter halos simulated
at very high mass ( M/particle) and temporal resolution
(5 Myrs/snapshot) done to date, quadrupling what is currently available
in the literature. This initial suite consists of the first 24 halos of the
(www.caterpillarproject.org) whose project goal of 60 -
70 halos will be made public when complete. We resolve 20,000
gravitationally bound subhalos within the virial radius of each host halo. Over
the ranges set by our spatial resolution our convergence is excellent and
improvements were made upon current state-of-the-art halo finders to better
identify substructure at such high resolutions (e.g., on average we recover
4 subhalos in each host halo above 10 M which would have
otherwise not been found using conventional methods). For our relaxed halos,
the inner profiles are reasonably fit by Einasto profiles ( = 0.169
0.023) though this depends on the relaxed nature and assembly history of
a given halo. Averaging over all halos, the substructure mass fraction is
, and mass function slope is d/d though we find scatter in the normalizations for fixed halo
mass due to more concentrated hosts having less subhalos at fixed subhalo mass.
There are no biases stemming from Lagrangian volume selection as all Lagrangian
volume types are included in our sample. Our detailed contamination study of
264 low resolution halos has resulted in obtaining very large and
unprecedented, high-resolution regions around our host halos for our target
resolution (sphere of radius Mpc) allowing for accurate
studies of low mass dwarf galaxies at large galactocentric radii and the very
first stellar systems at high redshift ( 10).Comment: 19 pages; 14 figures; 6 tables; Received September 3, 2015; Accepted
November 15, 2015; Published February 2, 201
Descendants of the first stars: the distinct chemical signature of second generation stars
Extremely metal-poor (EMP) stars in the Milky Way (MW) allow us to infer the
properties of their progenitors by comparing their chemical composition to the
metal yields of the first supernovae. This method is most powerful when applied
to mono-enriched stars, i.e. stars that formed from gas that was enriched by
only one previous supernova. We present a novel diagnostic to identify this
subclass of EMP stars. We model the first generations of star formation
semi-analytically, based on dark matter halo merger trees that yield MW-like
halos at the present day. Radiative and chemical feedback are included
self-consistently and we trace all elements up to zinc. Mono-enriched stars
account for only of second generation stars in our fiducial model
and we provide an analytical formula for this probability. We also present a
novel analytical diagnostic to identify mono-enriched stars, based on the metal
yields of the first supernovae. This new diagnostic allows us to derive our
main results independently from the specific assumptions made regarding Pop III
star formation, and we apply it to a set of observed EMP stars to demonstrate
its strengths and limitations. Our results may provide selection criteria for
current and future surveys and therefore contribute to a deeper understanding
of EMP stars and their progenitors.Comment: 18 pages, 20 figures, published in MNRA
Editorial: Research on emotion and learning: contributions from Latin America
Latin America has increased its share of world scientific publications by nearly twofold during the last two decades (approximately from 2 to 4%). Despite this positive trend, the scholarly impact of scientific research produced in the region - measured in terms of citation rate - remains low. Two interrelated factors that contribute to this situation is that most research groups tend to work in isolation or in local sporadic collaboration, and results are often published in journals that are not indexed in major citation databases (e.g., SCOPUS, or Web of Science). Ultimately, part of Latin American high-quality research seems to remain hidden from the rest of the world. Over the last decades, an important number of Latin American scientists have developed fruitful research agendas on questions on learning and emotion, focusing on basic and/or translational research with humans and other animal models, and implementing diverse methodologies. Notwithstanding the important contributions of these research programs, Latin American research on emotion and learning has followed the overall trend of other research fields throughout the region; namely, remaining partially hidden from the large scientific community of the world. This Research Topic aimed to engage researchers from Latin America to share their empirical and conceptual work on learning and emotion. Ultimately, this effort was expected to strengthen and integrate our regional community of experts, enhance global networking, and establish new challenges and developments for future investigation.Fil: Hurtado Parrado, Camilo. Fundación Universitaria Konrad Lorenz; ColombiaFil: Gantiva, Carlos. Universidad de Los Andes; VenezuelaFil: Gómez A., Alexander. University of North Carolina; Estados UnidosFil: Cuenya, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Médicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Médicas; ArgentinaFil: Ortega, Leonardo. Fundación Universitaria Konrad Lorenz; ColombiaFil: Rico, Javier L.. Fundación Universitaria Konrad Lorenz; Colombi
Survival of the mm-cm size grain population observed in protoplanetary disks
Millimeter interferometry provides evidence for the presence of mm to cm size
"pebbles" in the outer parts of disks around pre-main-sequence stars. The
observations suggest that large grains are produced relatively early in disk
evolution (< 1 Myr) and remain at large radii for longer periods of time (5 to
10 Myr). Simple theoretical estimates of the radial drift time of solid
particles, however, imply that they would drift inward over a time scale of
less than 0.1 Myr. In this paper, we address this conflict between theory and
observation, using more detailed theoretical models, including the effects of
sedimentation, collective drag forces and turbulent viscosity. We find that,
although these effects slow down the radial drift of the dust particles, this
reduction is not sufficient to explain the observationally determined long
survival time of mm/cm-sized grains in protoplanetary disks. However, if for
some reason the gas to dust ratio in the disk is reduced by at least a factor
of 20 from the canonical value of 100 (for instance through photoevaporation of
the gas), then the radial drift time scales become sufficiently large to be in
agreement with observations.Comment: Accepted for publication in Astronomy and Astrophysic
Cardiac electrical defects in progeroid mice and Hutchinson-Gilford progeria syndrome patients with nuclear lamina alterations
Hutchinson–Gilford progeria syndrome (HGPS) is a rare genetic disease caused by defective prelamin A processing, leading to nuclear lamina alterations, severe cardiovascular pathology, and premature death. Prelamin A alterations also occur in physiological aging. It remains unknown how defective prelamin A processing affects the cardiac rhythm. We show age-dependent cardiac repolarization abnormalities in HGPS patients that are also present in the Zmpste24-/- mouse model of HGPS. Challenge of Zmpste24-/- mice with the ß-adrenergic agonist isoproterenol did not trigger ventricular arrhythmia but caused bradycardia-related premature ventricular complexes and slow-rate polymorphic ventricular rhythms during recovery. Patch-clamping in Zmpste24-/- cardiomyocytes revealed prolonged calcium-transient duration and reduced sarcoplasmic reticulum calcium loading and release, consistent with the absence of isoproterenol-induced ventricular arrhythmia. Zmpste24-/- progeroid mice also developed severe fibrosis-unrelated bradycardia and PQ interval and QRS complex prolongation. These conduction defects were accompanied by overt mislocalization of the gap junction protein connexin43 (Cx43). Remarkably, Cx43 mislocalization was also evident in autopsied left ventricle tissue from HGPS patients, suggesting intercellular connectivity alterations at late stages of the disease. The similarities between HGPS patients and progeroid mice reported here strongly suggest that defective cardiac repolarization and cardiomyocyte connectivity are important abnormalities in the HGPS pathogenesis that increase the risk of arrhythmia and premature death.Peer ReviewedPostprint (published version
Synthesis, molecular and electronic structure of an incomplete cuboidal Re3S4 cluster with an anusual quadruplet ground state
A Re(IV) cluster complex [Re3(μ3-S)(μ-S)3(dppe)3Br3]+ with nine cluster skeletal electrons (CSE) and a quadruplet ground state has been prepared by treatment of [Re3S7Br6]Br with 1,2-bis(diphenylphosphino)ethane (dppe) in MeCN
Propuesta de sistema de logística inversa para el sector hospitalario: un enfoque teórico y práctico en Colombia
Presentación de propuesta para la construcción de un sistema de logística inversa basado en el ciclo PHVA (Planear, Hacer, Verificar y Actuar) para la gestión de residuos hospitalarios de las Instituciones Prestadoras de Salud (IPS) de Colombia. Se estudió el caso en una IPS de una universidad en la ciudad de Medellín. La Metodología utilizada fue una investigación descriptiva y estudio de casos basada en la revisión y análisis de los siguientes aspectos: conceptos de logística inversa, el decreto 2676 del 2000 y el Manual de Procedimientos para la Gestión Integral de Residuos Hospitalarios del Ministerio de Protección Social. Como resultado de la investigación, se obtiene una metodología innovadora que permite diseñar sistemas de logística inversa basado en la normativa existente aplicable a cualquier IPS, ofreciendo un enfoque para su planeación, ejecución, control y actuación buscando su eficiencia, productividad y cuidado del ambiente
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