2,428 research outputs found
Danish values, the foundation of the Folkeskole
We have imaged with Hubble Space Telescope WFC3/UVIS the central 2′7 × 2′7 region of the giant elliptical galaxy M87, using the ultraviolet filter F275W. In combination with archival ACS/WFC data taken through the F606W and F814W filters, covering the same field, we have constructed integrated-light UV-optical colors and magnitudes for 1460 objects, most of which are believed to be globular clusters (GCs) belonging to M87. The purpose was to ascertain whether the multiple-populations syndrome, ubiquitous among Galactic GCs, also exists among the M87 family of clusters. To achieve this goal, we sought those GCs with exceptionally blue UV-to-optical colors because helium-enriched sub-populations produce a horizontal-branch morphology that is well populated at high effective temperature. For comparison, integrated, synthetic UV-optical and purely optical colors and magnitudes have been constructed for 45 Galactic GCs, starting from individual-star photometry obtained with the same instruments and the same filters. We identify a small group of M87 clusters exhibiting a radial UV-optical color gradient, representing our best candidate GCs hosting multiple populations with extreme helium content. We also find that the central spatial distribution of the bluer GCs is flattened in a direction parallel to the jet, while the distribution of redder GCs is more spherical. We release to the astronomical community our photometric catalog in F275W, F606W, and F814W bands and the high-quality image stacks in the same bands
The effect of 14 weeks of vitamin D3 supplementation on antimicrobial peptides and proteins in athletes
Heavy training is associated with increased respiratory infection risk and antimicrobial proteins are important in defence against oral and respiratory tract infections. We examined the effect of 14 weeks of vitamin D3 supplementation (5000 IU/day) on the resting plasma cathelicidin concentration and the salivary secretion rates of secretory immunoglobulin A (SIgA), cathelicidin, lactoferrin and lysozyme in athletes during a winter training period. Blood and saliva were obtained at the start of the study from 39 healthy men who were randomly allocated to vitamin D3 supplement or placebo. Blood samples were also collected at the end of the study; saliva samples were collected after 7 and 14 weeks. Plasma total 25(OH)D concentration increased by 130% in the vitamin D3 group and decreased by 43% in the placebo group (both P=0.001). The percentage change of plasma cathelicidin concentration in the vitamin D3 group was higher than in the placebo group (P=0.025). Only in the vitamin D3 group, the saliva SIgA and cathelicidin secretion rates increased over time (both P=0.03). A daily 5000 IU vitamin D3 supplement has a beneficial effect in up-regulating the expression of SIgA and cathelicidin in athletes during a winter training period which could improve resistance to respiratory infections
A point process framework for modeling electrical stimulation of the auditory nerve
Model-based studies of auditory nerve responses to electrical stimulation can
provide insight into the functioning of cochlear implants. Ideally, these
studies can identify limitations in sound processing strategies and lead to
improved methods for providing sound information to cochlear implant users. To
accomplish this, models must accurately describe auditory nerve spiking while
avoiding excessive complexity that would preclude large-scale simulations of
populations of auditory nerve fibers and obscure insight into the mechanisms
that influence neural encoding of sound information. In this spirit, we develop
a point process model of the auditory nerve that provides a compact and
accurate description of neural responses to electric stimulation. Inspired by
the framework of generalized linear models, the proposed model consists of a
cascade of linear and nonlinear stages. We show how each of these stages can be
associated with biophysical mechanisms and related to models of neuronal
dynamics. Moreover, we derive a semi-analytical procedure that uniquely
determines each parameter in the model on the basis of fundamental statistics
from recordings of single fiber responses to electric stimulation, including
threshold, relative spread, jitter, and chronaxie. The model also accounts for
refractory and summation effects that influence the responses of auditory nerve
fibers to high pulse rate stimulation. Throughout, we compare model predictions
to published physiological data and explain differences in auditory nerve
responses to high and low pulse rate stimulation. We close by performing an
ideal observer analysis of simulated spike trains in response to sinusoidally
amplitude modulated stimuli and find that carrier pulse rate does not affect
modulation detection thresholds.Comment: 1 title page, 27 manuscript pages, 14 figures, 1 table, 1 appendi
Bostonia: v. 64, no. 1
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
A Glimpse into the Past: The Recent Evolution of Globular Clusters
We present the serendipitous discovery of 195 extragalactic globular clusters
(GCs) in one of the deepest optical images ever obtained, a 126 orbit HST/ACS
imaging study of the nearby Galactic GC NGC 6397. The distant GCs are all found
surrounding a bright elliptical galaxy in the field, and are among the faintest
objects detected in the image, with magnitudes 26 < F814W < 30. We measure the
redshift of the parent elliptical galaxy, using GMOS on Gemini South, to be z =
0.089 (375 Mpc). This galaxy, and its associated clusters, therefore ranks as
one of the most distant such systems discovered to date. The measured light
from these clusters was emitted 1.2 Gyr ago (the lookback time) and therefore
the optical properties hold clues for understanding the evolution of GCs over
the past Gyr. We measure the color function of the bright GCs and find that
both a blue and red population exist, and that the colors of each
sub-population are redder than GCs in local elliptical galaxies of comparable
luminosity. For the blue clusters, the observed color difference from z = 0.089
to today is only slightly larger than predictions from stellar evolution (e.g.,
changes in the luminosity and color of the main-sequence turnoff and the
morphology of the horizontal branch). A larger color difference is found in the
red clusters, possibly suggesting that they are very metal-rich and/or
significantly younger than 12 Gyr.Comment: 5 pages, 2 figures. Accepted for publication in ApJ Letters. Higher
resolution Figure 1 available at
http://www.ucolick.org/~jkalirai/DistantGlobs
Daily emollient during infancy for prevention of eczema: the BEEP randomised controlled trial.
BACKGROUND: Skin barrier dysfunction precedes eczema development. We tested whether daily use of emollient in the first year could prevent eczema in high-risk children. METHODS: We did a multicentre, pragmatic, parallel-group, randomised controlled trial in 12 hospitals and four primary care sites across the UK. Families were approached via antenatal or postnatal services for recruitment of term infants (at least 37 weeks' gestation) at high risk of developing eczema (ie, at least one first-degree relative with parent-reported eczema, allergic rhinitis, or asthma, diagnosed by a doctor). Term newborns with a family history of atopic disease were randomly assigned (1:1) to application of emollient daily (either Diprobase cream or DoubleBase gel) for the first year plus standard skin-care advice (emollient group) or standard skin-care advice only (control group). The randomisation schedule was created using computer-generated code (stratified by recruiting centre and number of first-degree relatives with atopic disease) and participants were assigned to groups using an internet-based randomisation system. The primary outcome was eczema at age 2 years (defined by UK working party criteria) with analysis as randomised regardless of adherence to allocation for participants with outcome data collected, and adjusting for stratification variables. This trial is registered with ISRCTN, ISRCTN21528841. Data collection for long-term follow-up is ongoing, but the trial is closed to recruitment. FINDINGS: 1394 newborns were randomly assigned to study groups between Nov 19, 2014, and Nov 18, 2016; 693 were assigned to the emollient group and 701 to the control group. Adherence in the emollient group was 88% (466 of 532) at 3 months, 82% (427 of 519) at 6 months, and 74% (375 of 506) at 12 months in those with complete questionnaire data. At age 2 years, eczema was present in 139 (23%) of 598 infants with outcome data collected in the emollient group and 150 (25%) of 612 infants in the control group (adjusted relative risk 0·95 [95% CI 0·78 to 1·16], p=0·61; adjusted risk difference -1·2% [-5·9 to 3·6]). Other eczema definitions supported the results of the primary analysis. Mean number of skin infections per child in year 1 was 0·23 (SD 0·68) in the emollient group versus 0·15 (0·46) in the control group; adjusted incidence rate ratio 1·55 (95% CI 1·15 to 2·09). INTERPRETATION: We found no evidence that daily emollient during the first year of life prevents eczema in high-risk children and some evidence to suggest an increased risk of skin infections. Our study shows that families with eczema, asthma, or allergic rhinitis should not use daily emollients to try and prevent eczema in their newborn. FUNDING: National Institute for Health Research Health Technology Assessment
Daily emollient during infancy for prevention of eczema: the BEEP randomised controlled trial.
BACKGROUND: Skin barrier dysfunction precedes eczema development. We tested whether daily use of emollient in the first year could prevent eczema in high-risk children. METHODS: We did a multicentre, pragmatic, parallel-group, randomised controlled trial in 12 hospitals and four primary care sites across the UK. Families were approached via antenatal or postnatal services for recruitment of term infants (at least 37 weeks' gestation) at high risk of developing eczema (ie, at least one first-degree relative with parent-reported eczema, allergic rhinitis, or asthma, diagnosed by a doctor). Term newborns with a family history of atopic disease were randomly assigned (1:1) to application of emollient daily (either Diprobase cream or DoubleBase gel) for the first year plus standard skin-care advice (emollient group) or standard skin-care advice only (control group). The randomisation schedule was created using computer-generated code (stratified by recruiting centre and number of first-degree relatives with atopic disease) and participants were assigned to groups using an internet-based randomisation system. The primary outcome was eczema at age 2 years (defined by UK working party criteria) with analysis as randomised regardless of adherence to allocation for participants with outcome data collected, and adjusting for stratification variables. This trial is registered with ISRCTN, ISRCTN21528841. Data collection for long-term follow-up is ongoing, but the trial is closed to recruitment. FINDINGS: 1394 newborns were randomly assigned to study groups between Nov 19, 2014, and Nov 18, 2016; 693 were assigned to the emollient group and 701 to the control group. Adherence in the emollient group was 88% (466 of 532) at 3 months, 82% (427 of 519) at 6 months, and 74% (375 of 506) at 12 months in those with complete questionnaire data. At age 2 years, eczema was present in 139 (23%) of 598 infants with outcome data collected in the emollient group and 150 (25%) of 612 infants in the control group (adjusted relative risk 0·95 [95% CI 0·78 to 1·16], p=0·61; adjusted risk difference -1·2% [-5·9 to 3·6]). Other eczema definitions supported the results of the primary analysis. Mean number of skin infections per child in year 1 was 0·23 (SD 0·68) in the emollient group versus 0·15 (0·46) in the control group; adjusted incidence rate ratio 1·55 (95% CI 1·15 to 2·09). INTERPRETATION: We found no evidence that daily emollient during the first year of life prevents eczema in high-risk children and some evidence to suggest an increased risk of skin infections. Our study shows that families with eczema, asthma, or allergic rhinitis should not use daily emollients to try and prevent eczema in their newborn. FUNDING: National Institute for Health Research Health Technology Assessment
Stellar Proper Motions in the Galactic Bulge from deep HST ACS/WFC Photometry
We present stellar proper motions in the Galactic bulge from the Sagittarius
Window Eclipsing Extrasolar Search (SWEEPS) project using ACS/WFC on HST.
Proper motions are extracted for more than 180,000 objects, with >81,000
measured to accuracy better than 0.3 mas/yr in both coordinates. We report
several results based on these measurements: 1. Kinematic separation of bulge
from disk allows a sample of >15,000 bulge objects to be extracted based on
>6-sigma detections of proper motion, with <0.2% contamination from the disk.
This includes the first detection of a candidate bulge Blue Straggler
population. 2. Armed with a photometric distance modulus on a star by star
basis, and using the large number of stars with high-quality proper motion
measurements to overcome intrinsic scatter, we dissect the kinematic properties
of the bulge as a function of distance along the line of sight. This allows us
to extract the stellar circular speed curve from proper motions alone, which we
compare with the circular speed curve obtained from radial velocities. 3. We
trace the variation of the {l,b} velocity ellipse as a function of depth. 4.
Finally, we use the density-weighted {l,b} proper motion ellipse produced from
the tracer stars to assess the kinematic membership of the sixteen transiting
planet candidates discovered in the Sagittarius Window; the kinematic
distribution of the planet candidates is consistent with that of the disk and
bulge stellar populations.Comment: 71 pages, 30 figures, ApJ Accepte
A Survey of UV Bright Sources Behind the Halo of M31
We have performed a wide-area ultraviolet (UV) imaging survey using the
GALaxy Evolution eXplorer (GALEX) to search for bright, point-like UV sources
behind M31's extended halo. Our survey consisted of 46 pointings covering an
effective area of ~50 deg^2, in both the far-UV and near-UV channels. We
combined these data with optical R-band observations acquired with the WIYN
Mosaic-1 imager on the Kitt Peak National Observatory 0.9m WIYN telescope. An
analysis of the brightness and colors of sources matched between our
photometric catalogs yielded ~100 UV-bright quasar candidates. We have obtained
discovery spectra for 76 of these targets with the Kast spectrometer on the
Lick 3m telescope and confirm 30 active galactic nuclei and quasars, 29
galaxies at z > 0.02 including several early-type systems, 16 Galactic stars
(hot main-sequence stars), and one featureless source previously identified as
a BL Lac object. Future UV spectroscopy of the brightest targets with the
Cosmic Origins Spectrograph on the Hubble Space Telescope will enable a
systematic search for diffuse gas in the extended halo of M31.Comment: 10 pages, 10 figures. Accepted to MNRA
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