500 research outputs found
Constraining inputs to realistic kilonova simulations through comparison to observed -process abundances
Kilonovae, one source of electromagnetic emission associated with neutron
star mergers, are powered by the decay of radioactive isotopes in the
neutron-rich merger ejecta. Models for kilonova emission consistent with the
electromagnetic counterpart to GW170817 predict characteristic abundance
patterns, determined by the relative balance of different types of material in
the outflow. Assuming the observed source is prototypical, this inferred
abundance pattern in turn must match -process abundances deduced by other
means, such as what is observed in the solar system. We report on analysis
comparing the input mass-weighted elemental compositions adopted in our
radiative transfer simulations to the mass fractions of elements in the Sun, as
a practical prototype for the potentially universal abundance signature from
neutron-star mergers. We characterize the extent to which our parameter
inference results depend on our assumed composition for the dynamical and wind
ejecta and examine how the new results compare to previous work. We find that a
dynamical ejecta composition calculated using the FRDM2012 nuclear mass and
FRLDM fission models with extremely neutron-rich ejecta ()
along with moderately neutron-rich () wind ejecta composition
yields a wind-to-dynamical mass ratio of = 0.47 which
best matches the observed AT2017gfo kilonova light curves while also producing
the best-matching abundance of neutron-capture elements in the solar system.Comment: 16 pages, 9 figures, submitted to PR
The r-Process Pattern of a Bright, Highly r-Process-Enhanced, Metal-Poor Halo Star at [Fe/H] ~ -2
A high-resolution spectroscopic analysis is presented for a new highly
r-process-enhanced ([Eu/Fe] = 1.27, [Ba/Eu] = -0.65), very metal-poor ([Fe/H] =
-2.09), retrograde halo star, RAVE J153830.9-180424, discovered as part of the
R-Process Alliance survey. At V = 10.86, this is the brightest and most
metal-rich r-II star known in the Milky Way halo. Its brightness enables
high-S/N detections of a wide variety of chemical species that are mostly
created by the r-process, including some infrequently detected lines from
elements like Ru, Pd, Ag, Tm, Yb, Lu, Hf, and Th, with upper limits on Pb and
U. This is the most complete r-process census in a very metal-poor r-II star.
J1538-1804 shows no signs of s-process contamination, based on its low [Ba/Eu]
and [Pb/Fe]. As with many other r-process-enhanced stars, J1538-1804's
r-process pattern matches that of the Sun for elements between the first,
second, and third peaks, and does not exhibit an actinide boost.
Cosmo-chronometric age-dating reveals the r-process material to be quite old.
This robust main r-process pattern is a necessary constraint for r-process
formation scenarios (of particular interest in light of the recent neutron star
merger, GW 170817), and has important consequences for the origins of r-II
stars. Additional r-I and r-II stars will be reported by the R-Process Alliance
in the near future.Comment: Accepted for publication in ApJ letter
Decreased demand for olfactory periglomerular cells impacts on neural precursor cell viability in the rostral migratory stream
The subventricular zone (SVZ) provides a constant supply of new neurons to the
olfactory bulb (OB). Different studies have investigated the role of olfactory
sensory input to neural precursor cell (NPC) turnover in the SVZ but it was
not addressed if a reduced demand specifically for periglomerular neurons
impacts on NPC-traits in the rostral migratory stream (RMS). We here report
that membrane type-1 matrix metalloproteinase (MT1-MMP) deficient mice have
reduced complexity of the nasal turbinates, decreased sensory innervation of
the OB, reduced numbers of olfactory glomeruli and reduced OB-size without
alterations in SVZ neurogenesis. Large parts of the RMS were fully preserved
in MT1-MMP-deficient mice, but we detected an increase in cell death-levels
and a decrease in SVZ-derived neuroblasts in the distal RMS, as compared to
controls. BrdU-tracking experiments showed that homing of NPCs specifically to
the glomerular layer was reduced in MT1-MMP-deficient mice in contrast to
controls while numbers of tracked cells remained equal in other OB-layers
throughout all experimental groups. Altogether, our data show the demand for
olfactory interneurons in the glomerular layer modulates cell turnover in the
RMS, but has no impact on subventricular neurogenesis
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Parent-child interactions and adolescent anxiety: a systematic review
Parental behaviours have been implicated in the development and maintenance of anxiety in children and young people; however the degree to which findings apply to adolescents specifically remains unclear. We conducted a systematic review of studies examining the evidence for an association between parental behaviours and adolescent anxiety. Twenty two studies were identified. The results of this systematic review provide fairly consistent preliminary evidence for an association between anxiety and perceived parental control and anxious rearing in adolescence. The findings relating to an association between adolescent anxiety and perceived parental rejection and lack of warmth are somewhat less consistent. Methodological shortcomings in the studies mean that these results should be interpreted with caution. Future research should be conducted using observational and experimental design with adolescents from referred, clinical populations to help identify the critical parental processes and clarify the direction of effects
Autonomy support, basic need satisfaction and the optimal functioning of adult male and female sport participants: A test of basic needs theory
Grounded in Basic Needs Theory (BNT; Ryan and Deci, American Psychologist, 55, 68–78, 2000a), the present study aimed to: (a) test a theoretically-based model of coach autonomy support, motivational processes and well-/ill being among a sample of adult sport participants, (b) discern which basic psychological need(s) mediate the link between autonomy support and well-/ill-being, and (c) explore gender invariance in the hypothesized model. Five hundred and thirty nine participants (Male = 271;Female = 268; Mage = 22.75) completed a multi-section questionnaire tapping the targeted variables. Structural Equation Modeling (SEM) analysis revealed that coach autonomy support predicted participants’ basic need satisfaction for autonomy, competence and relatedness. In turn, basic need satisfaction predicted greater subjective vitality when engaged in sport. Participants with low levels of autonomy were more susceptible to feeling emotionally and physically exhausted from their sport investment. Autonomy and competence partially mediated the path from autonomy support to subjective vitality. Lastly, the results supported partial invariance of the model with respect to gender
Self-Reported Adolescent Health Status of Extremely Low Birth Weight Children Born 1992-1995
To compare the self-reported health of extremely low birth weight (ELBW
- …