20,681 research outputs found
Observationally-Motivated Analysis of Simulated Galaxies
The spatial and temporal relationships between stellar age, kinematics, and
chemistry are a fundamental tool for uncovering the physics driving galaxy
formation and evolution. Observationally, these trends are derived using
carefully selected samples isolated via the application of appropriate
magnitude, colour, and gravity selection functions of individual stars;
conversely, the analysis of chemodynamical simulations of galaxies has
traditionally been restricted to the age, metallicity, and kinematics of
`composite' stellar particles comprised of open cluster-mass simple stellar
populations. As we enter the Gaia era, it is crucial that this approach
changes, with simulations confronting data in a manner which better mimics the
methodology employed by observers. Here, we use the \textsc{SynCMD} synthetic
stellar populations tool to analyse the metallicity distribution function of a
Milky Way-like simulated galaxy, employing an apparent magnitude plus gravity
selection function similar to that employed by the RAdial Velocity Experiment
(RAVE); we compare such an observationally-motivated approach with that
traditionally adopted - i.e., spatial cuts alone - in order to illustrate the
point that how one analyses a simulation can be, in some cases, just as
important as the underlying sub-grid physics employed.Comment: Accepted for publication in PoS (Proceedings of Science): Nuclei in
the Cosmos XIII (Debrecen, Jul 2014); 6 pages; 3 figure
The needs of people with dementia living at home from user, caregiver and professional perspectives: a cross-sectional survey
Few reports have been published about differences in perspectives on perceived needs among community-residing people with dementia, their family caregivers, and professionals. The aim of this study was to compare these perspectives
Effective model of the electronic Griffiths phase
We present simple analytical arguments explaining the universal emergence of
electronic Griffiths phases as precursors of disorder-driven metal-insulator
transitions in correlated electronic systems. A simple effective model is
constructed and solved within Dynamical Mean Field Theory. It is shown to
capture all the qualitative and even quantitative aspects of such Griffiths
phases.Comment: 9 pages, 7 figures, one reference corrected; minor corrections
include
Spectroscopic confirmation of the planetary nebula nature of PM1-242, PM1-318 and PM1-333 and morphological analysis of the nebulae
We present intermediate resolution long-slit spectra and narrow-band Halpha,
[NII] and [OIII] images of PM1-242, PM318 and PM1-333, three IRAS sources
classified as possible planetary nebulae. The spectra show that the three
objects are true planetary nebulae and allow us to study their physical
properties; the images provide a detailed view of their morphology. PM1-242 is
a medium-to-high-excitation (e.g., HeII4686/Hbeta ~0.4; [NII]6584/Halpha ~0.3)
planetary nebula with an elliptical shape containing [NII] enhanced
point-symmetric arcs. An electron temperature [Te([SIII])] of ~10250 K and an
electron density [Ne([SII])] of ~2300 cm-3 are derived for PM1-242. Abundance
calculations suggest a large helium abundance (He/H ~0.29) in PM1-242. PM1-318
is a high-excitation (HeII4686/Hbeta ~1) planetary nebula with a ring-like
inner shell containing two enhanced opposite regions, surrounded by a fainter
round attached shell brighter in the light of [OIII]. PM1-333 is an extended
planetary nebula with a high-excitation (HeII4686/Hbeta up to ~0.9) patchy
circular main body containing two low-excitation knotty arcs. A low Ne([SII])
of ~450 cm-3 and Te([OIII]) of ~15000 K are derived for this nebula. Abundance
calculations suggest that PM1-333 is a type I planetary nebula. The lack of a
sharp shell morphology, low electron density, and high-excitation strongly
suggest that PM1-333 is an evolved planetary nebula. PM1-333 also shows two
low-ionization polar structures whose morphology and emission properties are
reminiscent of collimated outflows. We compare PM1-333 with other evolved
planetary nebulae with collimated outflows and find that outflows among evolved
planetary nebulae exhibit a large variety of properties, in accordance with
these observed in younger planetary nebula.Comment: Accepted in The Astronomical Journal, 23 pages, 6 figure
New approaches to crop yield insurance in developing countries:
Natural disasters can be extremely disruptive to farmers and to others whose incomes depend on a successful crop. Society can gain from more efficient sharing of crop and natural disaster risks. However, the costs associated with traditional agricultural risk programs have historically exceeded the gains from improved risk sharing. This paper explores government intervention in agricultural risk markets and discusses new approaches to risk sharing with limited government involvement. In particular, we build the case for introducing negotiable state-contingent contracts settled on area crop yield estimates or locally appropriate weather indices. These instruments could replace traditional crop insurance at a lower cost to government while meeting the risk management needs of a wider clientele.Crop yields., Insurance, Agricultural Crops., Developing countries.,
The reactor antineutrino anomaly and low energy threshold neutrino experiments
Short distance reactor antineutrino experiments measure an antineutrino
spectrum a few percent lower than expected from theoretical predictions. In
this work we study the potential of low energy threshold reactor experiments in
the context of a light sterile neutrino signal. We discuss the perspectives of
the recently detected coherent elastic neutrino-nucleus scattering in future
reactor antineutrino experiments. We find that the expectations to improve the
current constraints on the mixing with sterile neutrinos are promising. We also
analyse the measurements of antineutrino scattering off electrons from short
distance reactor experiments. In this case, the statistics is not competitive
with inverse beta decay experiments, although future experiments might play a
role when compare it with the Gallium anomaly.Comment: 9 pages, 6 figures, 1 table, matches published versio
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