6,845 research outputs found
Simulations of Electron Capture and Low-Mass Iron Core Supernovae
The evolutionary pathways of core-collapse supernova progenitors at the
low-mass end of the spectrum are beset with major uncertainties. In recent
years, a variety of evolutionary channels has been discovered in addition to
the classical electron capture supernova channel of super-AGB stars. The few
available progenitor models at the low-mass end have been studied with great
success in supernova simulations as the peculiar density structure makes for
robust neutrino-driven explosions in this mass range. Detailed nucleosynthesis
calculations have been conducted both for models of electron capture supernovae
and low-mass iron core supernovae and revealed an interesting production of the
lighter trans-iron elements (such as Zn, Sr, Y, Zr) as well as rare isotopes
like Ca-48 and Fe-60. We stress the need to explore the low-mass end of the
supernova spectrum further and link various observables to understand the
diversity of explosions in this regime.Comment: 7 page, 3 figures, proceedings of the conference "The AGB-Supernova
Mass Transition", to appear in Memorie della Societ\`a Astronomica Italian
The Consequences of Child Market Work on the Growth of Human Capital
Child labor is a phenomenon that has attracted a great amount of attention and research. theoretical propositions suggest that child labor is inefficient if it adversely affects future potential earning ability. this paper contributes to the literature on the effects of child market work on human capital by focusing on the long-term growth in human capital, which is widely known to significantly affect earning ability. the paper also uses better measures of human capital by focusing on the output of the human capital production function: numeracy skills, cognitive skills, and pulmonary function. using a rich longitudinal dataset on Indonesia, we find strong negative effects of child labor on the growth of both numeracy and cognitive skills in the next seven years. in addition, we find a strong and negative effect on pulmonary function as measured through lung capacity. comparing the effects by gender and type of work, we find that female child workers suffer from more adverse effects on their mathematical skills growth, while male child workers experience a much smaller growth in their pulmonary function. we also find that child workers who work for a wage outside the family bear worse effects compared to child workers who work in the family business.
keywords: child labor, human capital, skills, health, Indonesia
jel classifications: i12, i21, j13, j22, o1
Postfledging Survival, Movements, and Dispersal of Ring Ouzels (Turdus torquatus)
We thank Invercauld Estate for cooperation with access to Glen Clunie. S. Redpath, J. Wilson, and S. Roos provided valuable comments on the manuscript. This study was funded by the Royal Society for the Protection of Birds, Scottish Natural Heritage, and the Cairngorms National Park Authority. J.L.L. was supported by the Natural Environment Research Council.Peer reviewedPublisher PD
Measurement of Photon Statistics with Live Photoreceptor Cells
We analyzed the electrophysiological response of an isolated rod
photoreceptor of Xenopus laevis under stimulation by coherent and
pseudo-thermal light sources. Using the suction electrode technique for single
cell recordings and a fiber optics setup for light delivery allowed
measurements of the major statistical characteristics of the rod response. The
results indicate differences in average responses of rod cells to coherent and
pseudo-thermal light of the same intensity and also differences in
signal-to-noise ratios and second order intensity correlation functions. These
findings should be relevant for interdisciplinary studies seeking applications
of quantum optics in biology.Comment: 6 pages, 7 figure
Fast Algorithm for Partial Covers in Words
A factor of a word is a cover of if every position in lies
within some occurrence of in . A word covered by thus
generalizes the idea of a repetition, that is, a word composed of exact
concatenations of . In this article we introduce a new notion of
-partial cover, which can be viewed as a relaxed variant of cover, that
is, a factor covering at least positions in . We develop a data
structure of size (where ) that can be constructed in time which we apply to compute all shortest -partial covers for a
given . We also employ it for an -time algorithm computing
a shortest -partial cover for each
The Cop Number of the One-Cop-Moves Game on Planar Graphs
Cops and robbers is a vertex-pursuit game played on graphs. In the classical
cops-and-robbers game, a set of cops and a robber occupy the vertices of the
graph and move alternately along the graph's edges with perfect information
about each other's positions. If a cop eventually occupies the same vertex as
the robber, then the cops win; the robber wins if she can indefinitely evade
capture. Aigner and Frommer established that in every connected planar graph,
three cops are sufficient to capture a single robber. In this paper, we
consider a recently studied variant of the cops-and-robbers game, alternately
called the one-active-cop game, one-cop-moves game or the lazy-cops-and-robbers
game, where at most one cop can move during any round. We show that Aigner and
Frommer's result does not generalise to this game variant by constructing a
connected planar graph on which a robber can indefinitely evade three cops in
the one-cop-moves game. This answers a question recently raised by Sullivan,
Townsend and Werzanski.Comment: 32 page
Nursing sensitive outcomes: identifying a definition, exploration of conceptual challenges and an overview of the literature
Introduction/background: A literature review on nursing sensitive outcomes has been conducted as part of a larger research project. The literature was reviewed to: - identify a definition of nursing sensitive outcomes - determine the conceptual models used to describe nursing sensitive outcomes - identify significant contributions made by researchers on the development and use of nursing sensitive outcomes in clinical practice.The overall aim of the research project is to develop a set of indicators that provides a balanced view of nursing care and its contribution to patient outcomes. It is anticipated that this research will broaden the debate on nursing sensitive outcomes so that the contribution that nursing care makes to patient outcomes is able to be identified and measured
Multi-D Simulations of Ultra-Stripped Supernovae to Shock Breakout
The recent discoveries of many double neutron star systems and their
detection as LIGO-Virgo merger events call for a detailed understanding of
their origin. Explosions of ultra-stripped stars in binary systems have been
shown to play a key role in this context and have also generated interest as a
potential explanation for rapidly evolving hydrogen-free transients. Here we
present the first attempt to model such explosions based on binary evolution
calculations that follow the mass transfer to the companion to obtain a
consistent core-envelope structure as needed for reliable predictions of the
supernova transient. We simulate the explosion in 2D and 3D, and confirm the
modest explosion energies ~10^50erg and small kick velocities reported earlier
in 2D models based on bare carbon-oxygen cores. The spin-up of the neutron star
by asymmetric accretion is small in 3D with no indication of spin-kick
alignment. Simulations up to shock breakout show the mixing of sizeable amounts
of iron group material into the helium envelope. In view of recent ideas for a
mixing-length treatment (MLT) of Rayleigh-Taylor instabilities in supernovae,
we perform a detailed analysis of the mixing, which reveals evidence for
buoyancy-drag balance, but otherwise does not support the MLT approximation.
The mixing may have implications for the spectroscopic signatures of
ultra-stripped supernovae that need to be investigated in the future. Our
stellar evolution calculation also predicts presupernova mass loss due to an
off-centre silicon deflagration flash, which suggests that supernovae from
extremely stripped cores may show signs of interactions with circumstellar
material.Comment: 15 pages, 15 figures, submitted to MNRA
Multi-dimensional modelling of X-ray spectra for AGN accretion-disk outflows III: application to a hydrodynamical simulation
We perform multi-dimensional radiative transfer simulations to compute
spectra for a hydrodynamical simulation of a line-driven accretion disk wind
from an active galactic nucleus. The synthetic spectra confirm expectations
from parameterized models that a disk wind can imprint a wide variety of
spectroscopic signatures including narrow absorption lines, broad emission
lines and a Compton hump. The formation of these features is complex with
contributions originating from many of the different structures present in the
hydrodynamical simulation. In particular, spectral features are shaped both by
gas in a successfully launched outflow and in complex flows where material is
lifted out of the disk plane but ultimately falls back. We also confirm that
the strong Fe Kalpha line can develop a weak, red-skewed line wing as a result
of Compton scattering in the outflow. In addition, we demonstrate that X-ray
radiation scattered and reprocessed in the flow has a pivotal part in both the
spectrum formation and determining the ionization conditions in the wind. We
find that scattered radiation is rather effective in ionizing gas which is
shielded from direct irradiation from the central source. This effect likely
makes the successful launching of a massive disk wind somewhat more challenging
and should be considered in future wind simulations.Comment: 14 pages, 8 figures. Accepted for publication by MNRA
- …