418 research outputs found
Probing Interstellar Dust with Infrared Echoes from the Cas A Supernova
We present the analysis of an IRS 5-38 {\mu}m spectrum and MIPS photometric
measurements of an infrared echo near the Cassiopeia A supernova remnant
observed with the Spitzer Space Telescope. We have modeled the recorded echo
accounting for PAHs, quantum-heated carbon and silicate grains, as well as
thermal carbon and silicate particles. Using the fact that optical light echo
spectroscopy has established that Cas A originated from a type IIb supernova
explosion showing an optical spectrum remarkably similar to the prototypical
type IIb SN 1993J, we use the latter to construct template data input for our
simulations. We are then able to reproduce the recorded infrared echo spectrum
by combining the emission of dust heated by the UV burst produced at the shock
breakout after the core-collapse and dust heated by optical light emitted near
the visual maximum of the supernova light curve, where the UV burst and optical
light curve characteristics are based on SN 1993J. We find a mean density of
\sim680 H cm^{-3} for the echo region, with a size of a few light years across.
We also find evidence of dust processing in the form of a lack of small PAHs
with less than \sim300 carbon atoms, consistent with a scenario of PAHs
destruction by the UV burst via photodissociation at the estimated distance of
the echo region from Cas A. Furthermore, our simulations suggest that the weak
11 {\mu}m features of our recorded infrared echo spectrum are consistent with a
strong dehydrogenated state of the PAHs. This exploratory study highlights the
potential of investigating dust processing in the interstellar medium through
infrared echoes.Comment: 16 pages, 14 figures, accepted for publication in the Astrophysical
Journa
Exploring differences in the role of hospitalization on weight gain based on treatment type from randomized clinical trials for adolescent anorexia nervosa
Background: This study explores the impact of weight gain during medical stabilization hospitalization on weight outcomes between three outpatient treatments for adolescent anorexia nervosa (AN): Adolescent Focused Therapy (AFT), Systemic Family Therapy (SyFT), and Family Based Treatment (FBT). Methods: A secondary analysis of weight gain data (N = 215) of adolescents (12-18 years) meeting DSM-IV criteria for AN (exclusive of amenorrhea criteria) who participated in two randomized clinical trials (RCTs) was conducted. Main outcomes examined were changes in weight restoration (â„95% expected body weight or EBW) and differences in weight change attributable to hospital weight gain. Results: Weight gain resulting from hospitalizations did not substantially change weight recovery rates. Hospital weight gain contributed most to overall treatment weight gain in AFT compared to FBT and SyFT. Conclusion: Brief medical stabilization weight gain does not contribute substantially to weight recovery in adolescents with AN who participated in RCTs
Are the times changing enough? Print media trends across four decades
Media analysis is an established area of sport sociology which has been documented by researchers systematically since the 1980s. Some trends have explored the differences between male and female athletes in the print media with significant evidence demonstrating that female athletes do not gain proportional representation and that many strategies employed by journalists traditionally seek to trivialise, sexualise and emphasise the female identity as âotherâ rather than as athlete. This longitudinal study uniquely documents an analysis of a two week period in the British print media across four decades 1984-2014. This study, grounded in liberal feminism, presents both quantitative and qualitative data and the main quantitative results demonstrate that coverage for female athletes has decreased from 13% to 6.2%. Qualitative themes presented include: relationships, appearance, performance and nationality, the latter emerging as a new theme from the 2014 data set. The results demonstrate that there is little change in amount of representation afforded to female athletes but that there are reporting changes with a greater emphasis on performance and less reliance on appearance. The paper concludes with the position that although sports reporting, in general is on the increase, women athletes are being given less but potentially better coverage
Using Acoustic Sensors to Improve the Efficiency of the Forest Value Chain in Canada: A Case Study with Laminated Veneer Lumber
Engineered wood products for structural use must meet minimum strength and stiffness criteria. This represents a major challenge for the industry as the mechanical properties of the wood resource are inherently variable. We report on a case study that was conducted in a laminated veneer lumber (LVL) mill in order to test the potential of an acoustic sensor to predict structural properties of the wood resource prior to processing. A population of 266 recently harvested aspen logs were segregated into three sub-populations based on measurements of longitudinal acoustic speed in wood using a hand tool equipped with a resonance-based acoustic sensor. Each of the three sub-populations were peeled into veneer sheets and graded for stiffness with an ultrasonic device. The average ultrasonic propagation time (UPT) of each subpopulation was 418, 440 and 453 microseconds for the green, blue, and red populations, respectively. This resulted in contrasting proportions of structural veneer grades, indicating that the efficiency of the forest value chain could be improved using acoustic sensors. A linear regression analysis also showed that the dynamic modulus of elasticity (MOE) of LVL was strongly related to static MOE (R2 = 0.83), which suggests that acoustic tools may be used for quality control during the production process
Occupational airborne exposure in relation to Chronic Obstructive Pulmonary Disease (COPD) and lung function in individuals without childhood wheezing illness: A 50-year cohort study
Background
Evidence from longitudinal population-based studies relating occupational exposure to the full range of different forms of airborne pollutants and lung function and airway obstruction is limited.
Objective
To relate self-reported COPD and lung function impairment to occupational exposure to different forms of airborne chemical pollutants in individuals who did not have childhood wheeze.
Methods
A prospective cohort study was randomly selected in 1964 at age 10â15 years and followed up in 1989, 1995, 2001 and 2014 (aged 58â64) by spirometry and respiratory questionnaire. Occupational histories were recorded in 2014 and occupational exposures assigned using an airborne chemical job exposure matrix. The risk of COPD and lung function impairment was analyzed in subjects, who did not have childhood wheeze, using logistic and linear regression and linear mixed effects models.
Results
237 subjects without childhood wheeze (mean age 60.6 years, 47% male) were analyzed. There was no association between any respiratory outcomes and exposure to gases, fibers, mists or mineral dusts and no consistent associations with exposure to fumes. Reduced FEV1 was associated with longer duration (years) of exposure to any of the six main pollutant forms - vapors, gases, dusts, fumes, fibers and mists (VGDFFiM) with evidence of a dose-response relationship (p-trend=0.004). Exposure to biological dusts was associated with self-reported COPD and FEV1<Lower Limit of Normal (LLN) (adjusted odds ratio [95%CI] 4.59 [1.15,18.32] and 3.54 [1.21,10.35] respectively), and reduced FEF25â75% (adjusted regression coefficients [95% CIs] â9.11 [â17.38, â0.84] respectively). Exposure to vapors was associated with self-reported COPD and FEV1<LLN (adjOR 6.46 [1.18,35.37] and 4.82 [1.32,17.63]). Longitudinal analysis demonstrated reduced FEV1 and FEF25â75% associated with exposure to biological dusts or vapors.
Conclusions
People with no history of childhood wheezing who have been occupationally exposed to biological dusts or vapors or had longer duration of lifetime exposure to any VGDFFiM are at a higher risk of reduced lung function at age 58â64 years. Occupational exposure to biological dusts or vapors also increased the risk of self-reported COPD
Selection Effects on the Observed Redshift Dependence of GRB Jet Opening Angles
Apparent redshift dependence of the jet opening angles () of
gamma-ray bursts (GRBs) is observed from current GRB sample. We investigate
whether this dependence can be explained with instrumental selection effects
and observational biases by a bootstrapping method. Assuming that (1) the GRB
rate follows the star formation history and the cosmic metallicity history and
(2) the intrinsic distributions of the jet-corrected luminosity () and are a Gaussian or a power-law function, we
generate a mock {\em Swift}/BAT sample by considering various instrumental
selection effects, including the flux threshold and the trigger probability of
BAT, the probabilities of a GRB jet pointing to the instrument solid angle and
the probability of redshift measurement. Our results well reproduce the
observed dependence. We find that in case of
good consistency between the mock and
observed samples can be obtained, indicating that both and
are degenerate for a flux-limited sample. The parameter set
gives the best consistency for the current {\em Swift} GRB sample.
Considering the beaming effect, the derived intrinsic local GRB rate
accordingly is Gpc yr, inferring that of Type Ib/c SNe may be accompanied by a GRB.Comment: 25pages, 7 figures. ApJ in pres
Discovery of a very highly extinguished supernova in a luminous infrared galaxy
We report the discovery of a confirmed supernova (SN) and a
supernova-candidate in near-infrared images from the ALTAIR/NIRI adaptive
optics system on the Gemini-North Telescope and NICMOS on the Hubble Space
Telescope. The Gemini images were obtained as part of a near-infrared K-band
search for highly-obscured SNe in the nuclear regions of luminous infrared
galaxies. SN 2008cs apparent in the Gemini images is the first SN discovered
using laser guide star adaptive optics. It is located at 1500 pc projected
distance from the nucleus of the luminous infrared galaxy IRAS 17138-1017. The
SN luminosity, JHK colors and light curve are consistent with a core-collapse
event suffering from a very high host galaxy extinction of 15.7 +- 0.8
magnitudes in V-band which is to our knowledge the highest yet measured for a
SN. The core-collapse nature of SN 2008cs is confirmed by its radio detection
at 22.4 GHz using our Very Large Array observations 28 days after the SN
discovery, indicating a prominent interaction of the SN ejecta with the
circumstellar medium. An unconfirmed SN apparent in the NICMOS images from 2004
is located in the same galaxy at 660 pc projected distance from the nucleus and
has a lower extinction.Comment: 4 pages, 4 figures, ApJ Letters in press. The SN candidate from 2004
has been assigned the designation SN 2004iq (Kankare et al. 2008, CBET 1569,
1
Hypernovae and Other Black-Hole-Forming Supernovae
During the last few years, a number of exceptional core-collapse supernovae
(SNe) have been discovered. Their kinetic energy of the explosions are larger
by more than an order of magnitude than the typical values for this type of
SNe, so that these SNe have been called `Hypernovae'. We first describe how the
basic properties of hypernovae can be derived from observations and modeling.
These hypernovae seem to come from rather massive stars, thus forming black
holes. On the other hand, there are some examples of massive SNe with only a
small kinetic energy. We suggest that stars with non-rotating black holes are
likely to collapse "quietly" ejecting a small amount of heavy elements (Faint
supernovae). In contrast, stars with rotating black holes are likely to give
rise to very energetic supernovae (Hypernovae). We present distinct
nucleosynthesis features of these two types of "black-hole-forming" supernovae.
Hypernova nucleosynthesis is characterized by larger abundance ratios
(Zn,Co,V,Ti)/Fe and smaller (Mn,Cr)/Fe. Nucleosynthesis in Faint supernovae is
characterized by a large amount of fall-back. We show that the abundance
pattern of the most Fe deficient star, HE0107-5240, and other extremely
metal-poor carbon-rich stars are in good accord with those of
black-hole-forming supernovae, but not pair-instability supernovae. This
suggests that black-hole-forming supernovae made important contributions to the
early Galactic (and cosmic) chemical evolution.Comment: 49 pages, to be published in "Stellar Collapse" (Astrophysics and
Space Science; Kluwer) ed. C. L. Fryer (2003
Intrinsic and dust-induced polarization in gamma-ray burst afterglows: the case of GRB 021004
Polarization measurements for the optical counterpart to GRB 021004 are
presented and discussed. Our observations were performed with the TNG and the
VLT-UT3 (Melipal) during the first and fourth night after the gamma-ray burst
discovery. We find robust evidence of temporal evolution of the polarization,
which is therefore, at least partially, intrinsic to the optical transient. We
do not find convincing evidence of wavelength dependence for the intrinsic
polarization of the transient, in agreement with current polarization models
for optical afterglows. We discuss the role of dust, both in our galaxy and in
the host, in modifying the transmitted polarization vector, showing how a
sizable fraction of the observed polarized flux is due to Galactic selective
extinction, while it is not possible to single out any clear contribution from
dust in the host galaxy. We discuss how our data compare to those obtained by
different groups showing that a two-component model is required to describe the
complete dataset. This is not surprising given the complex lightcurve of GRB
021004.Comment: 9 pages, 6 postscript figures, A&A in pres
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Postpartum womenâs use of medicines and breastfeeding practices: a systematic review
The objectives of this article are to systematically review i) the extent of medicine use in postpartum women, and ii) the impact of maternal medicine use (excluding contraceptives and galactogogues) on breastfeeding outcomes (initiation and/or duration). PubMed, Medline (Ovid), Scopus (Elsevier), Cinahl (EBSCO), PsycINFO (Ovid), Embase (Ovid) and Web of Science (ISI) databases were searched to find original studies on medicine use in women after the birth. Additional studies were identified by searching Google Scholar, Wiley Online Library, Springer Link, selected journals and from the reference list of retrieved articles. Observational studies with information about postpartum womenâs use of any type of medicine either for chronic or acute illnesses with or without breastfeeding information were included. The majority of relevant studies suggest that more than 50 % of postpartum women (breastfeeding or not) required at least one medicine. Due to the lack of uniform medication use reporting system and differences in study designs, settings and samples, the proportion of medicine use by postpartum women varies widely, from 34 to 100 %. Regarding the impact of postpartum womenâs medicine use on breastfeeding, a few studies suggest that womenâs use of certain medicines (e.g. antiepileptics, propylthiouracil, antibiotics) during lactation can reduce initiation and/ or duration of breastfeeding. These studies are limited by small sample size, and with one exception, all were conducted in Canada more than a decade ago. Large scale studies are required to establish the relationship between maternal medicine use and breastfeeding, considering type of illness, period of use and total duration of medicine use
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