8,805 research outputs found
Probing O-enrichment in C-rich dust planetary nebulae
The abundance of O in planetary nebulae (PNe) has been historically used as a
metallicity indicator of the interstellar medium (ISM) where they originated;
e.g., it has been widely used to study metallicity gradients in our Galaxy and
beyond. However, clear observational evidence for O self enrichment in
low-metallicity Galactic PNe with C-rich dust has been recently reported. Here
we report asymptotic giant branch (AGB) nucleosynthesis predictions for the
abundances of the CNO elements and helium in the metallicity range Zsun/4 < Z <
2Zsun. Our AGB models, with diffusive overshooting from all the convective
borders, predict that O is overproduced in low-Z low-mass (~1-3 Msun) AGB stars
and nicely reproduce the recent O overabundances observed in C-rich dust PNe.
This confirms that O is not always a good proxy of the original ISM metallicity
and another chemical elements such as Cl or Ar should be used instead. The
production of oxygen by low-mass stars should be thus considered in
galactic-evolution models.Comment: Accepted for publication in MNRAS Letters (5 pages, 1 figure, and 1
table
Disrupting the Narrative on Recruiting Graduate Students of Color in Counselor Education
The voices of students of color are largely absent in the literature on graduate student recruitment in counselor education. The existing literature focuses on university personnel and can portray a deficit perspective of students of color. Using grounded theory and a critical race theory framework, we sought to develop a theory that described the motivations of graduate students of color for pursuing counselor education. We interviewed 19 graduate students of color and used a constant comparative method to understand their motivations for and supports utilized in pursuing counselor training. Grounded in our participantsâ counternarratives, we identified a theory to describe their drive to serve marginalized communities, to attend programs committed to diversity, and the supports they received in applying to graduate school. Based on this theory we provide implications for how counselor education programs can demonstrate a commitment to diversity and support graduate students of color through the application process
Galactic planetary nebulae with precise nebular abundances as a tool to understand the evolution of asymptotic giant branch stars
We present nucleosynthesis predictions (HeCNOCl) from asymptotic giant branch
(AGB) models, with diffusive overshooting from all the convective borders, in
the metallicity range Z/4 < Z < 2Zsun. They are compared to recent precise
nebular abundances in a sample of Galactic planetary nebulae (PNe) that is
divided among double-dust chemistry (DC) and oxygen-dust chemistry (OC)
according to the infrared dust features. Unlike the similar subsample of
Galactic carbon-dust chemistry PNe recently analysed by us, here the individual
abundance errors, the higher metallicity spread, and the uncertain dust
types/subtypes in some PNe do not allow a clear determination of the AGB
progenitor masses (and formation epochs) for both PNe samples; the comparison
is thus more focussed on a object-by-object basis. The lowest metallicity OC
PNe evolve from low-mass (~1 Msun) O-rich AGBs, while the higher metallicity
ones (all with uncertain dust classifications) display a chemical pattern
similar to the DC PNe. In agreement with recent literature, the DC PNe mostly
descend from high-mass (M > 3.5 Msun) solar/supersolar metallicity AGBs that
experience hot bottom burning (HBB), but other formation channels in low-mass
AGBs like extra mixing, stellar rotation, binary interaction, or He
pre-enrichment cannot be disregarded until more accurate C/O ratios would be
obtained. Two objects among the DC PNe show the imprint of advanced CNO
processing and deep second dredge-up, suggesting progenitors masses close to
the limit to evolve as core collapse supernovae (above 6 Msun). Their actual
C/O ratio, if confirmed, indicate contamination from the third dredge-up,
rejecting the hypothesis that the chemical composition of such high-metallicity
massive AGBs is modified exclusively by HBB.Comment: Accepted for publication in MNRAS (11 pages, 3 figures, and 2 tables
Prevalence and predictors of inadequate patient medication knowledge
© 2016 John Wiley & Sons, Ltd. Objectives: To assess medication knowledge in adult patients and to explore its determinants. Method: Cross-sectional study. Medication knowledge was the primary outcome and was assessed using a previously validated questionnaire. A multivariate logistic regression analysis was performed to explore the association between medication knowledge and the factors included in the model. Results: Seven thousand two hundred seventy-eight patients participated in the study. 71.9% (n = 5234) (95% CI: 70.9%â73.0%) of the surveyed patients had an inadequate knowledge of the medication they were taking. The dimensions obtaining the highest level of knowledge were the âmedication use processâ and âtherapeutic objective of medicationâ. The items âfrequencyâ (75.4%), âdosageâ (74.5%) and âindicationâ (70.5%) had the highest percentage of knowledge. Conversely, âmedication safetyâ represented the dimension with the lowest scores, ranging from 12.6% in the item âcontraindicationsâ to 15.3% in the item âside effectsâ. The odds ratio (OR) of having an inadequate medication knowledge increased for unskilled workers (OR: 1.33; 85% CI:1.00â1.78; P = 0.050), caregivers (OR:1.46; 95% CI:1.18â1.81; P < 0.001), patients using more than one medication (OR: 1.14; 95% CI: 1.00â1.31; P = 0.050) and patients who did not know the name of the medication they were taking (OR: 2.14, 95% CI: 1.71â2.68 P < 0.001). Conclusion: Nearly three quarters of the analysed patients had inadequate knowledge regarding the medicines they were taking. Unskilled workers and caregivers were at a higher risk of lacking of medication knowledge. Other factors that correlated with inadequate medication knowledge were the use of more than one drug and not knowing the name of the medication dispensed
Continuum-particle hybrid coupling for mass, momentum and energy transfers in unsteady fluid flow
The aim of hybrid methods in simulations is to communicate regions with
disparate time and length scales. Here, a fluid described at the atomistic
level within an inner region P is coupled to an outer region C described by
continuum fluid dynamics. The matching of both descriptions of matter is made
across an overlapping region and, in general, consists of a two-way coupling
scheme (C->P and P->C) which conveys mass, momentum and energy fluxes. The
contribution of the hybrid scheme hereby presented is two-fold: first it treats
unsteady flows and, more importantly, it handles energy exchange between both C
and P regions. The implementation of the C->P coupling is tested here using
steady and unsteady flows with different rates of mass, momentum and energy
exchange. In particular, relaxing flows described by linear hydrodynamics
(transversal and longitudinal waves) are most enlightening as they comprise the
whole set of hydrodynamic modes. Applying the hybrid coupling scheme after the
onset of an initial perturbation, the cell-averaged Fourier components of the
flow variables in the P region (velocity, density, internal energy, temperature
and pressure) evolve in excellent agreement with the hydrodynamic trends. It is
also shown that the scheme preserves the correct rate of entropy production. We
discuss some general requirements on the coarse-grained length and time scales
arising from both the characteristic microscopic and hydrodynamic scales.Comment: LaTex, 12 pages, 9 figure
Resonance expansions in quantum mechanics
The goal of this contribution is to discuss various resonance expansions that
have been proposed in the literature.Comment: 10 pages and 1 figure; presented at the Istanbul workshop on
pseudo-Hermitian Hamiltonian
Handlebar injury in children: Are we ignoring the signs?
AbstractThe diagnosis of blunt intestinal injury in children is difficult and often delayed. We describe two cases of delayed diagnosis of intestinal injury following handlebar injury with abdominal wall tattooing. We review the literature to try and determine the usefulness of handlebar tattooing characteristics as a clinical sign for underlying small bowel injury in order to reduce delayed treatment. We propose a management algorithm for patients with handlebar tattooing
Mechanism of Action of Secreted Newt Anterior Gradient Protein
Anterior gradient (AG) proteins have a thioredoxin fold and are targeted to the secretory pathway where they may act in the ER, as well as after secretion into the extracellular space. A newt member of the family (nAG) was previously identified as interacting with the GPI-anchored salamander-specific three-finger protein called Prod1. Expression of nAG has been implicated in the nerve dependence of limb regeneration in salamanders, and nAG acted as a growth factor for cultured newt limb blastemal (progenitor) cells, but the mechanism of action was not understood. Here we show that addition of a peptide antibody to Prod1 specifically inhibit the proliferation of blastema cells, suggesting that Prod1 acts as a cell surface receptor for secreted nAG, leading to S phase entry. Mutation of the single cysteine residue in the canonical active site of nAG to alanine or serine leads to protein degradation, but addition of residues at the C terminus stabilises the secreted protein. The mutation of the cysteine residue led to no detectable activity on S phase entry in cultured newt limb blastemal cells. In addition, our phylogenetic analyses have identified a new Caudata AG protein called AG4. A comparison of the AG proteins in a cell culture assay indicates that nAG secretion is significantly higher than AGR2 or AG4, suggesting that this property may vary in different members of the family
The Nature of LINERs
We present -band (m) spectroscopy of a sample of nine
galaxies showing some degree of LINER activity (classical LINERs, weak-[O {\sc
i}] LINERs and transition objects), together with -band spectroscopy for
some of them. A careful subtraction of the stellar continuum allows us to
obtain reliable [Fe {\sc ii}]m/Pa line ratios. We conclude
that different types of LINERs (i.e., photoionized by a stellar continuum or by
an AGN) cannot be easily distinguished based solely on the [Fe {\sc ii}]m/Pa line ratio.
The emission line properties of many LINERs can be explained in terms of an
aging starburst. The optical line ratios of these LINERs are reproduced by a
model with a metal-rich H {\sc ii} region component photoionized with a single
stellar temperature K, plus a supernova remnant (SNR) component.
The [Fe {\sc ii}] line is predominantly excited by shocks produced by SNRs in
starbursts and starburst-dominated LINERs, while Pa tracks H {\sc ii}
regions ionized by massive young stars. The contribution from SNRs to the
overall emission line spectrum is constrained by the [Fe {\sc ii}]m/Pa line ratio. Although our models for aging starbursts are
constrained only by these infrared lines, they consistently explain the optical
spectra of the galaxies also.
The LINER-starburst connection is tested by predicting the time dependence of
the ratio of the ionizing luminosity () to the supernova rate
(SNr), /(SNr). We predict the relative number of starbursts to
starburst-dominated LINERs (aging starbursts) and show that it is in
approximate agreement with survey findings for nearby galaxies.Comment: Accepted in ApJ (19 pages, 8 figures, uses emulateapj.sty
Multiwavelength study of the starburst galaxy NGC7714. I: Ultraviolet-Optical spectroscopy
We have studied the physical conditions in the central 300 pc of the
proto-typical starburst galaxy NGC 7714. Our analysis is based on ultraviolet
spectroscopy with the HST+GHRS and ground-based optical observations.The data
are interpreted using evolutionary models optimized for young starburst
regions. The massive stellar population is derived in a self-consistent way
using the continuum and stellar absorption lines in the ultraviolet and the
nebular emission line optical spectrum.
The central starburst has an age of about 4.5 Myr, with little evidence for
an age spread. Wolf-Rayet features at the ultraviolet indicates a stellar
population of 2000 Wolf-Rayet stars. The overall properties of the newly
formed stars are quite similar to those derived, e.g., in 30 Doradus. A
standard Salpeter IMF is consistent with all observational constraints. We find
evidence for spatial structure within the central 300 pc sampled. Therefore it
is unlikely that the nucleus of NGC 7714 hosts a single star cluster exceeding
the properties of other known clusters. Contrary to previous suggestions, we
find no evidence for a nuclear supernova rate that would significantly exceed
the total disk-integrated rate. About one supernova event per century is
predicted.Comment: 19 pages, 9 figures in a tar file. Accepted for publication in ApJ,
1999, March, issue 51
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