268 research outputs found
An LP-Based Approach for Goal Recognition as Planning
Goal recognition aims to recognize the set of candidate goals that are
compatible with the observed behavior of an agent. In this paper, we develop a
method based on the operator-counting framework that efficiently computes
solutions that satisfy the observations and uses the information generated to
solve goal recognition tasks. Our method reasons explicitly about both partial
and noisy observations: estimating uncertainty for the former, and satisfying
observations given the unreliability of the sensor for the latter. We evaluate
our approach empirically over a large data set, analyzing its components on how
each can impact the quality of the solutions. In general, our approach is
superior to previous methods in terms of agreement ratio, accuracy, and spread.
Finally, our approach paves the way for new research on combinatorial
optimization to solve goal recognition tasks.Comment: 8 pages, 4 tables, 3 figures. Published in AAAI 2021. Updated final
authorship and tex
Pregalactic LiBeB Production by Supernova Cosmic Rays
I calculate the evolution of Be and B abundances produced by cosmic rays
generated by massive stars in the pregalactic phase of the universe. The inputs
for calculation, i.e. the star formation rate and the nuclear abundances of
cosmic rays, which I assume to be the same as those of the ISM, are taken from
the results of a detailed cosmic chemical evolution model with its parameters
best fitted from several items of observational information including an early
reionization of the IGM by . I found that when the Li plateau
abundance observed in metal-poor halo stars originated in the pregalactic
cosmological cosmic ray nucleosynthesis, Be and B simultaneously produced with
Li amount to the lowest levels ever detected in metal-poor halo stars. It
is desirable to observe Be and B abundances in metal-poor halo stars with
[Fe/H] in order to elucidate the possibility of early LiBeB
production by pregalactic supernova cosmic ray nucleosynthesis.Comment: 13 pages, 8 figures, ApJ accepte
An inertial range length scale in structure functions
It is shown using experimental and numerical data that within the traditional
inertial subrange defined by where the third order structure function is linear
that the higher order structure function scaling exponents for longitudinal and
transverse structure functions converge only over larger scales, , where
has scaling intermediate between and as a function of
. Below these scales, scaling exponents cannot be determined for any
of the structure functions without resorting to procedures such as extended
self-similarity (ESS). With ESS, different longitudinal and transverse higher
order exponents are obtained that are consistent with earlier results. The
relationship of these statistics to derivative and pressure statistics, to
turbulent structures and to length scales is discussed.Comment: 25 pages, 9 figure
Saccades and smooth pursuit eye movements in central vertigo
In order to analyze the diagnostic efficiency of saccadic and pursuit eye movements compared to findings from brain magnetic resonance imaging in patients with central vertigo, 108 patients were selected from 580 dizzy patients as cases of suspected central origin; the saccadic and pursuit eye movements were evaluated by electronystagmography and findings were compared to information from magnetic resonance imaging. The study of oculomotor movements in patients suspected of having a central lesion revealed a 83.3% sensitivity and 21.2% specificity. Restricting consideration to severe alterations in eye movements as indicative of a central origin, this test gives a 71.4% sensitivity and 50.0% specificity. In conclusion, the study of alterations in oculomotor movements, in patients with suspected central lesions, proved to be a test with good sensitivity also compared with results of magnetic resonance imaging
Cosmic Ray production of Beryllium and Boron at high redshift
Recently, new observations of Li6 in Pop II stars of the galactic halo have
shown a surprisingly high abundance of this isotope, about a thousand times
higher than its predicted primordial value. In previous papers, a cosmological
model for the cosmic ray-induced production of this isotope in the IGM has been
developed to explain the observed abundance at low metallicity. In this paper,
given this constraint on the Li6, we calculate the non-thermal evolution with
redshift of D, Be, and B in the IGM. In addition to cosmological cosmic ray
interactions in the IGM, we include additional processes driven by SN
explosions: neutrino spallation and a low energy component in the structures
ejected by outflows to the IGM. We take into account CNO CRs impinging on the
intergalactic gas. Although subdominant in the galactic disk, this process is
shown to produce the bulk of Be and B in the IGM, due to the differential metal
enrichment between structures (where CRs originate) and the IGM. We also
consider the resulting extragalactic gamma-ray background which we find to be
well below existing data. The computation is performed in the framework of
hierarchical structure formation considering several star formation histories
including Pop III stars. We find that D production is negligible and that a
potentially detectable Be and B plateau is produced by these processes at the
time of the formation of the Galaxy (z ~ 3).Comment: 9 pages, 7 figure
The Revival of Galactic Cosmic Ray Nucleosynthesis?
Because of the roughly linear correlation between Be/H and Fe/H in low
metallicity halo stars, it has been argued that a ``primary'' component in the
nucleosynthesis of Be must be present in addition to the ``secondary''
component from standard Galactic cosmic ray nucleosynthesis. In this paper we
critically re-evaluate the evidence for the primary versus secondary character
of Li, Be, and B evolution, analyzing both in the observations and in Galactic
chemical evolution models. While it appears that [Be/H] versus [Fe/H] has a
logarithmic slope near 1, it is rather the Be-O trend that directly arises from
the physics of spallation production. Using new abundances for oxygen in halo
stars based on UV OH lines, we find that the Be-O slope has a large uncertainty
due to systematic effects, rendering it difficult to distinguish from the data
between the secondary slope of 2 and the primary slope of 1. The possible
difference between the Be-Fe and Be-O slopes is a consequence of the variation
in O/Fe versus Fe: recent data suggests a negative slope rather than zero
(i.e., Fe O) as is often assumed. In addition to a phenomenological
analysis of Be and B evolution, we have also examined the predicted LiBeB, O,
and Fe trends in Galactic chemical evolution models which include outflow.
Based on our results, it is possible that a good fit to the LiBeB evolution
requires only traditional the Galactic cosmic ray spallation, and the (primary)
neutrino-process contribution to B11. We thus suggest that these two processes
might be sufficient to explain Li6, Be, and B evolution in the Galaxy, without
the need for an additional primary source of Be and B.Comment: 25 pages, latex, 8 ps figures, figure 1 correcte
Cosmological Magnetic Fields from Primordial Helicity
Primordial magnetic fields may account for all or part of the fields observed
in galaxies. We consider the evolution of the magnetic fields created by
pseudoscalar effects in the early universe. Such processes can create
force-free fields of maximal helicity; we show that for such a field magnetic
energy inverse cascades to larger scales than it would have solely by flux
freezing and cosmic expansion. For fields generated at the electroweak phase
transition, we find that the predicted wavelength today can in principle be as
large as 10 kpc, and the field strength can be as large as 10^{-10} G.Comment: 13 page
Decay laws for three-dimensional magnetohydrodynamic turbulence
Decay laws for three-dimensional magnetohydrodynamic turbulence are obtained
from high-resolution numerical simulations using up to 512^3 modes...
Salmonella clinical isolates from Brazilian pig herds: genetic relationship and antibiotic resistance profiling.
Abstract In Brazil, since 2011 clinical cases of salmonellosis has been increasing substantially. Nevertheless, few information is available about the antimicrobial profile, distribution, serotypes and genetic relationship among the strains. The objectives of this study were: to identify the Salmonella serotypes, to characterize the in vitro antimicrobial resistance profiles and to determine the genetic relationship of clinical isolates in Brazil. During 2016, clinical isolates of Salmonella (111) from nine States were sent to Embrapa Swine and Poultry for complementary analysis. First, isolates were serotyped by Kauffmann White Scheme. In parallel, the strains were tested against fifteen antimicrobials by disk diffusion method and genotyping was performed by Pulsed Field Gel Electrophoresis (PFGE) using the XbaI restriction enzyme. As expected, the main serovars found were Typhimurium and Choleraesuis. Four strains showed resistance to only one antimicrobial and 76.5% (85/111) were considered multiresistant. The highest level of resistance was found against to tetracycline. More than 80% of the strains were susceptible to fosfomycin, lincomycin/spectinomycin and norfloxacin. It was possible to identify one major Choleraesuis clonal group present in different Brazilian States. Further, several small clonal groups were obtained for Typhimurium. In conclusion, clinical salmonellosis caused by Typhimurium and Choleraesuis is endemic in pig production areas and the majority of the strains are multi-resistantSafePork 2017
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