921 research outputs found
Incorporating social practices in BDI agent systems
When agents interact with humans, either through embodied agents or because
they are embedded in a robot, it would be easy if they could use fixed
interaction protocols as they do with other agents. However, people do not keep
fixed protocols in their day-to-day interactions and the environments are often
dynamic, making it impossible to use fixed protocols. Deliberating about
interactions from fundamentals is not very scalable either, because in that
case all possible reactions of a user have to be considered in the plans. In
this paper we argue that social practices can be used as an inspiration for
designing flexible and scalable interaction mechanisms that are also robust.
However, using social practices requires extending the traditional BDI
deliberation cycle to monitor landmark states and perform expected actions by
leveraging existing plans. We define and implement this mechanism in Jason
using a periodically run meta-deliberation plan, supported by a
metainterpreter, and illustrate its use in a realistic scenario.Comment: An extended abstract of this paper has been accepted for the
Eighteenth International Conference on Autonomous Agents and Multiagent
Systems (AAMAS), 201
The winds of young Solar-type stars in Coma Berenices and Hercules-Lyra
We present wind models of 10 young Solar-type stars in the Hercules-Lyra association and the Coma Berenices cluster aged around ∼0.26 and ∼0.58 Gyr, respectively. Combined with five previously modelled stars in the Hyades cluster, aged ∼0.63 Gyr, we obtain a large atlas of 15 observationally based wind models. We find varied geometries, multi-armed structures in the equatorial plane, and a greater spread in quantities such as the angular momentum loss. In our models, we infer variation of a factor of ∼6 in wind angular momentum loss J˙ and a factor of ∼2 in wind mass-loss M˙ based on magnetic field geometry differences when adjusting for the unsigned surface magnetic flux. We observe a large variation factor of ∼4 in wind pressure for an Earth-like planet; we attribute this to variations in the ‘magnetic inclination’ of the magnetic dipole axis with respect to the stellar axis of rotation. Within our models, we observe a tight correlation between unsigned open magnetic flux and angular momentum loss. To account for possible underreporting of the observed magnetic field strength we investigate a second series of wind models where the magnetic field has been scaled by a factor of 5. This gives M˙∝B0.4 and J˙∝B1.0 as a result of pure magnetic scaling
Field linkage and magnetic helicity density
The helicity of a magnetic field is a fundamental property that is conserved
in ideal MHD. It can be explored in the stellar context by mapping large-scale
magnetic fields across stellar surfaces using Zeeman-Doppler imaging. A recent
study of 51 stars in the mass range 0.1-1.34 M showed that the
photospheric magnetic helicity density follows a single power law when plotted
against the toroidal field energy, but splits into two branches when plotted
against the poloidal field energy. These two branches divide stars above and
below 0.5 M. We present here a novel method of visualising the
helicity density in terms of the linkage of the toroidal and poloidal fields
that are mapped across the stellar surface. This approach allows us to classify
the field linkages that provide the helicity density for stars of different
masses and rotation rates. We find that stars on the lower-mass branch tend to
have toroidal fields that are non-axisymmetric and so link through regions of
positive and negative poloidal field. A lower-mass star may have the same
helicity density as a higher-mass star, despite having a stronger poloidal
field. Lower-mass stars are therefore less efficient at generating large-scale
helicity.Comment: 8 pages, 7 figures, 1 tabl
Filling a blank on the map: 60 years of fisheries in Equatorial Guinea
Despite a scarcity of pertinent information, it has been possible to reconstruct time series of marine fisheries catches for Equatorial Guinea from 1950 to 2010 using per capita fish consumption and population numbers for small-scale fisheries, catch rates and number of vessels for industrial fisheries and discard rates to estimate the discarded bycatch. Small-scale fisheries, industrial large-scale fisheries, domestic and legal and illegal foreign fisheries and their discards are all included. Total catches were estimated at 2.7 million tonnes over the time period considered, of which 653 000 t were caught domestically compared to 187 000 t reported by FAO. This shows that fisheries have more importance for Equatorial Guinea's food security than the official data suggest. In contrast to what is suggested by official figures, fisheries were shown to be strongly impacted by civil and political unrest; notably, they declined overall because of civil and political conflicts, socio-demographic dynamics, and a growing role of the newly discovered oil resources, which directly and indirectly threaten the food security of the people of Equatorial Guinea
Low birth weight and markers of inflammation and endothelial activation in adulthood: The ARIC study
To investigate the hypothesis that intrauterine growth restriction might produce a longstanding pro-inflammatory tendency, we investigated the association of low birth weight with blood levels of markers of inflammation and endothelial activation in middle-aged adults
Ages for exoplanet host stars
Age is an important characteristic of a planetary system, but also one that
is difficult to determine. Assuming that the host star and the planets are
formed at the same time, the challenge is to determine the stellar age.
Asteroseismology provides precise age determination, but in many cases the
required detailed pulsation observations are not available. Here we concentrate
on other techniques, which may have broader applicability but also serious
limitations. Further development of this area requires improvements in our
understanding of the evolution of stars and their age-dependent
characteristics, combined with observations that allow reliable calibration of
the various techniques.Comment: To appear in "Handbook of Exoplanets", eds. Deeg, H.J. & Belmonte,
J.A, Springer (2018
Dietary Phosphorus, Blood Pressure, and Incidence of Hypertension in the Atherosclerosis Risk in Communities Study and the Multi-Ethnic Study of Atherosclerosis
Greater phosphorus intake has been associated with lower levels of blood pressure in cross-sectional studies. This association, however, has not been assessed prospectively. We studied 13444 participants from the Atherosclerosis Risk in Communities cohort and the Multi-Ethnic Study of Atherosclerosis, with diet assessed at baseline using validated food frequency questionnaires. Blood pressure and use of antihypertensive medication were determined at baseline and during follow-up visits. Compared to individuals in the lowest quintile of phosphorus intake at baseline, those in the highest quintile had lower baseline systolic and diastolic blood pressure after adjustment for dietary and non-dietary confounders (−2.0 mmHg, 95% confidence interval −3.6, −0.5; p for trend=0.01; and −0.6, 95% confidence interval −1.6, +0.3, p for trend=0.20, respectively). During an average 6.2 years of follow-up, 3345 cases of hypertension were identified. Phosphorus intake was associated with the risk of hypertension (hazard ratio 0.80, 95% confidence interval 0.80-1.00, comparing extreme quintiles; p for trend=0.02) after adjustment for non-dietary factors, but not after additional adjustment for dietary variables (hazard ratio 1.01, 95% confidence interval 0.82-1.23, p for trend=0.88). Phosphorus from dairy products but not from other sources was associated with lower baseline blood pressure and reduced risk of incident hypertension. Hazard ratios (95% confidence interval) comparing extreme quintiles were 0.86 (0.76-0.97), p for trend=0.01, for phosphorus from dairy foods and 1.04 (0.93-1.17), p for trend=0.48, for phosphorus from other foods. These findings could indicate an effect of phosphorus in conjunction with other dairy constituents or of dairy itself without involvement of phosphorus
Systematically missing confounders in individual participant data meta-analysis of observational cohort studies.
One difficulty in performing meta-analyses of observational cohort studies is that the availability of confounders may vary between cohorts, so that some cohorts provide fully adjusted analyses while others only provide partially adjusted analyses. Commonly, analyses of the association between an exposure and disease either are restricted to cohorts with full confounder information, or use all cohorts but do not fully adjust for confounding. We propose using a bivariate random-effects meta-analysis model to use information from all available cohorts while still adjusting for all the potential confounders. Our method uses both the fully adjusted and the partially adjusted estimated effects in the cohorts with full confounder information, together with an estimate of their within-cohort correlation. The method is applied to estimate the association between fibrinogen level and coronary heart disease incidence using data from 154,012 participants in 31 cohort
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