631 research outputs found
MILES extended: Stellar population synthesis models from the optical to the infrared
We present the first single-burst stellar population models which covers the
optical and the infrared wavelength range between 3500 and 50000 Angstrom and
which are exclusively based on empirical stellar spectra. To obtain these joint
models, we combined the extended MILES models in the optical with our new
infrared models that are based on the IRTF (Infrared Telescope Facility)
library. The latter are available only for a limited range in terms of both age
and metallicity. Our combined single-burst stellar population models were
calculated for ages larger than 1 Gyr, for metallicities between [Fe/H] = -0.40
and 0.26, for initial mass functions of various types and slopes, and on the
basis of two different sets of isochrones. They are available to the scientific
community on the MILES web page. We checked the internal consistency of our
models and compared their colour predictions to those of other models that are
available in the literature. Optical and near infrared colours that are
measured from our models are found to reproduce the colours well that were
observed for various samples of early-type galaxies. Our models will enable a
detailed analysis of the stellar populations of observed galaxies.Comment: 9 pages, 10 figures, published in A&
Systematic variation of the stellar Initial Mass Function with velocity dispersion in early-type galaxies
An essential component of galaxy formation theory is the stellar initial mass
function (IMF), that describes the parent distribution of stellar mass in star
forming regions. We present observational evidence in a sample of early-type
galaxies (ETGs) of a tight correlation between central velocity dispersion and
the strength of several absorption features sensitive to the presence of
low-mass stars. Our sample comprises ~40,000 ETGs from the SPIDER survey
(z<0.1). The data, extracted from the Sloan Digital Sky Survey, are combined,
rejecting both noisy data, and spectra with contamination from telluric lines,
resulting in a set of 18 stacked spectra at high signal-to-noise ratio (S/N>
400 per A). A combined analysis of IMF-sensitive line strengths and spectral
fitting is performed with the latest state-of the art population synthesis
models (an extended version of the MILES models). A significant trend is found
between IMF slope and velocity dispersion, towards an excess of low-mass stars
in the most massive galaxies. Although we emphasize that accurate values of the
IMF slope will require a detailed analysis of chemical composition (such as
[a/Fe] or even individual element abundance ratios), the observed trends
suggest that low-mass ETGs are better fit by a Kroupa-like IMF, whereas massive
galaxies require bottom-heavy IMFs, exceeding the Salpeter slope at velocity
dispersions above 200km/s.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
Molecular analysis of endocrine disruption in hornyhead turbot at wastewater outfalls in southern california using a second generation multi-species microarray.
Sentinel fish hornyhead turbot (Pleuronichthysverticalis) captured near wastewater outfalls are used for monitoring exposure to industrial and agricultural chemicals of ~ 20 million people living in coastal Southern California. Although analyses of hormones in blood and organ morphology and histology are useful for assessing contaminant exposure, there is a need for quantitative and sensitive molecular measurements, since contaminants of emerging concern are known to produce subtle effects. We developed a second generation multi-species microarray with expanded content and sensitivity to investigate endocrine disruption in turbot captured near wastewater outfalls in San Diego, Orange County and Los Angeles California. Analysis of expression of genes involved in hormone [e.g., estrogen, androgen, thyroid] responses and xenobiotic metabolism in turbot livers was correlated with a series of phenotypic end points. Molecular analyses of turbot livers uncovered altered expression of vitellogenin and zona pellucida protein, indicating exposure to one or more estrogenic chemicals, as well as, alterations in cytochrome P450 (CYP) 1A, CYP3A and glutathione S-transferase-α indicating induction of the detoxification response. Molecular responses indicative of exposure to endocrine disruptors were observed in field-caught hornyhead turbot captured in Southern California demonstrating the utility of molecular methods for monitoring environmental chemicals in wastewater outfalls. Moreover, this approach can be adapted to monitor other sites for contaminants of emerging concern in other fish species for which there are few available gene sequences
Body image, body dissatisfaction and weight status in south asian children: a cross-sectional study
Background
Childhood obesity is a continuing problem in the UK and South Asian children represent a group that are particularly vulnerable to its health consequences. The relationship between body dissatisfaction and obesity is well documented in older children and adults, but is less clear in young children, particularly South Asians. A better understanding of this relationship in young South Asian children will inform the design and delivery of obesity intervention programmes. The aim of this study is to describe body image size perception and dissatisfaction, and their relationship to weight status in primary school aged UK South Asian children.
Methods
Objective measures of height and weight were undertaken on 574 predominantly South Asian children aged 5-7 (296 boys and 278 girls). BMI z-scores, and weight status (underweight, healthy weight, overweight or obese) were calculated based on the UK 1990 BMI reference charts. Figure rating scales were used to assess perceived body image size (asking children to identify their perceived body size) and dissatisfaction (difference between perceived current and ideal body size). The relationship between these and weight status were examined using multivariate analyses.
Results
Perceived body image size was positively associated with weight status (partial regression coefficient for overweight/obese vs. non-overweight/obese was 0.63 (95% CI 0.26-0.99) and for BMI z-score was 0.21 (95% CI 0.10-0.31), adjusted for sex, age and ethnicity). Body dissatisfaction was also associated with weight status, with overweight and obese children more likely to select thinner ideal body size than healthy weight children (adjusted partial regression coefficient for overweight/obese vs. non-overweight/obese was 1.47 (95% CI 0.99-1.96) and for BMI z-score was 0.54 (95% CI 0.40-0.67)).
Conclusions
Awareness of body image size and increasing body dissatisfaction with higher weight status is established at a young age in this population. This needs to be considered when designing interventions to reduce obesity in young children, in terms of both benefits and harms
An updated MILES stellar library and stellar population models
(Aims) We present a number of improvements to the MILES library and stellar
population models. We correct some small errors in the radial velocities of the
stars, measure the spectral resolution of the library and models more
accurately, and give a better absolute flux calibration of the models.
(Methods) We use cross-correlation techniques to correct the radial velocities
of the offset stars and the penalised pixel-fitting method, together with
different sets of stellar templates, to re-assess the spectral resolution of
the MILES stellar library and models. We have also re-calibrated the zero-point
flux level of the models using a new calibration scheme. (Results) The end
result is an even more homogeneously calibrated stellar library than the
originally released one, with a measured spectral resolution of ~2.5\AA, almost
constant with wavelength, for both the MILES stellar library and models.
Furthermore, the new absolute flux calibration for the spectra excellently
agrees with predictions based on independent photometric libraries.
(Conclusions) This improved version of the MILES library and models (version
9.1) is available at the project's website (http://miles.iac.es).Comment: 7 pages, 8 figures. Accepted for publication in Astronomy &
Astrophysics (Research Note
Understanding Needs, Breaking Down Barriers: Examining Mental Health Challenges and Well-Being of Correctional Staff in Ontario, Canada
Mental health challenges appear to be extremely prolific and challenging for correctional service employees, affecting persons working in community, institutional, and administrative correctional services. Focusing specifically on correctional workers employed by the Ontario Ministry of the Solicitor General, we shed light on their interpretations of the complexities of their occupational work and of how their work affects staff. Using a qualitative thematic approach to data analyses, we show that participants (n = 67) encounter barriers to treatment seeking, which they describe as tremendous, starting with benefits, wages, and shift work. We let the voices of staff elucidate what is needed to create a healthier correctional workforce. Recommendations include more training opportunities and programs; quarterly, semiannual, or annual appointments with a mental health professional who can assess changes in the mental health status of employees; offsite assessments to ensure confidentiality; and team building opportunities to reduce interpersonal conflict at work and increase moral by improving the work environment
Recognizing emotions in bodies: vagus nerve stimulation enhances recognition of anger while impairing sadness
According to the Polyvagal theory, the vagus nerve is the key phylogenetic substrate that supports efficient emotion recognition for promoting safety and survival. Previous studies showed that the vagus nerve affects people's ability to recognize emotions based on eye regions and whole facial images, but not static bodies. The purpose of this study was to verify whether the previously suggested causal link between vagal activity and emotion recognition can be generalized to situations in which emotions must be inferred from images of whole moving bodies. We employed transcutaneous vagus nerve stimulation (tVNS), a noninvasive brain stimulation technique that stimulates the vagus nerve by a mild electrical stimulation to the auricular branch of the vagus, located in the anterior protuberance of the outer ear. In two sessions, participants received active or sham tVNS before and while performing three emotion recognition tasks, aimed at indexing their ability to recognize emotions from static or moving bodily expressions by actors. Active tVNS, compared to sham stimulation, enhanced the recognition of anger but reduced the ability to recognize sadness, regardless of the type of stimulus (static vs. moving). Convergent with the idea of hierarchical involvement of the vagus in establishing safety, as put forward by the Polyvagal theory, we argue that our findings may be explained by vagus-evoked differential adjustment strategies to emotional expressions. Taken together, our findings fit with an evolutionary perspective on the vagus nerve and its involvement in emotion recognition for the benefit of survival.Action Contro
âDo i care?â young adults' recalled experiences of early adolescent overweight and obesity: a qualitative study
<p>Objective:Â Individual behaviour change to reduce obesity requires awareness of, and concern about, weight. This paper therefore describes how young adults, known to have been overweight or obese during early adolescence, recalled early adolescent weight-related awareness and concerns. Associations between recalled concerns and weight-, health- and peer-related survey responses collected during adolescence are also examined.</p>
<p>Design:Â Qualitative semi-structured interviews with young adults; data compared with responses to self-report questionnaires obtained in adolescence.</p>
<p>Participants:Â A total of 35 participants, purposively sub-sampled at age 24 from a longitudinal study of a school year cohort, previously surveyed at ages 11, 13 and 15. Physical measures during previous surveys allowed identification of participants with a body mass index (BMI) indicative of overweight or obesity (based on British 1990 growth reference) during early adolescence. Overall, 26 had been obese, of whom 11 had BMI99.6th centile, whereas 9 had been overweight (BMI=95thâ97.9th centile).</p>
<p>Measures:Â Qualitative interview responses describing teenage life, with prompts for school-, social- and health-related concerns. Early adolescent self-report questionnaire data on weight-worries, self-esteem, friends and victimisation (closed questions).</p>
<p>Results:Â Most, but not all recalled having been aware of their overweight. None referred to themselves as having been obese. None recalled weight-related health worries. Recollection of early adolescent obesity varied from major concerns impacting on much of an individual's life to almost no concern, with little relation to actual severity of overweight. Recalled concerns were not clearly patterned by gender, but young adult males recalling concerns had previously reported more worries about weight, lower self-esteem, fewer friends and more victimisation in early adolescence; no such pattern was seen among females.
Conclusion:Â The popular image of the unhappy overweight teenager was not borne out. Many obese adolescents, although well aware of their overweight recalled neither major dissatisfaction nor concern. Weight-reduction behaviours are unlikely in such circumstances.</p>
The Structures of Distant Galaxies V: The Evolution of Galaxy Structure in Stellar Mass at z < 1
Galaxy structure and morphology is nearly always studied using the light
originating from stars, however ideally one is interested in measuring
structure using the stellar mass distribution. Not only does stellar mass trace
out the underlying distribution of matter, it also minimises the effects of
star formation and dust on the appearance and structure of a galaxy. We present
in this paper a study of the stellar mass distributions and structures of
galaxies at z<1 as found within the GOODS fields. We use pixel by pixel
K-corrections to construct stellar mass and mass-to-light ratio maps of 560
galaxies of known morphology at magnitudes z_{850}<24. We measure structural
and size parameters using these stellar mass maps, as well as on ACS BViz band
imaging. This includes investigating the structural CAS-Gini-M_{20} parameters
and half-light radius for each galaxy. We compare structural parameters and
half-light radii in the ACS z_{850}-band and stellar mass maps, finding no
systematic bias introduced by measuring galaxy sizes in z_{850}. We furthermore
investigate relations between structural parameters in the ACS BViz bands and
stellar mass maps, and compare our result to previous morphological studies.
Combinations of various parameters in stellar mass generally reveal clear
separations between early and late type morphologies, but cannot easily
distinguish between star formation and dynamically disturbed systems. We also
show that while ellipticals and early-type spirals have fairly constant CAS
values at z<1 we find a tendency for late-type spiral and peculiar
morphological types to have a higher A(M_{*}) at higher redshift. We argue that
this, and the large fraction of peculiars that appear spiral-like in stellar
mass maps, are possible evidence for either an active bulge formation in some
late-type disks at z<1 or the presence of minor merger events.Comment: 27 pages, MNRAS in pres
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