296 research outputs found
Long-term effect of ventilation tubes for persistent otitis media with effusion in children.
Contains fulltext :
164159.pdf (publisher's version ) (Open Access
The Bright End of the z~9 and z~10 UV Luminosity Functions using all five CANDELS Fields
The deep, wide-area (~800-900 arcmin**2) near-infrared/WFC3/IR + Spitzer/IRAC
observations over the CANDELS fields have been a remarkable resource for
constraining the bright end of high redshift UV luminosity functions (LFs).
However, the lack of HST 1.05-micron observations over the CANDELS fields has
made it difficult to identify z~9-10 sources robustly, since such data are
needed to confirm the presence of an abrupt Lyman break at 1.2 microns. We
report here on the successful identification of many such z~9-10 sources from a
new HST program (z9-CANDELS) that targets the highest-probability z~9-10 galaxy
candidates with observations at 1.05 microns, to search for a robust
Lyman-break at 1.2 microns. The potential z~9-10 candidates are preselected
from the full HST, Spitzer/IRAC S-CANDELS observations, and the
deepest-available ground-based optical+near-infrared observations. We
identified 15 credible z~9-10 galaxies over the CANDELS fields. Nine of these
galaxies lie at z~9 and 5 are new identifications. Our targeted follow-up
strategy has proven to be very efficient in making use of scarce HST time to
secure a reliable sample of z~9-10 galaxies. Through extensive simulations, we
replicate the selection process for our sample (both the preselection and
follow-up) and use it to improve current estimates for the volume density of
bright z~9 and z~10 galaxies. The volume densities we find are 5(-2)(+3)x and
8(-3)(+9)x lower, respectively, than found at z~8. When compared with the
best-fit evolution (i.e., dlog_{10} rho(UV)/dz=-0.29+/-0.02) in the UV
luminosities densities from z~8 to z~4 integrated to 0.3L*(z=3) (-20 mag),
these luminosity densities are 2.6(-0.9)(+1.5)x and 2.2(-1.1)(+2.0)x lower,
respectively, than the extrapolated trends. Our new results are broadly
consistent with the "accelerated evolution" scenario at z>8, as seen in many
theoretical models.Comment: 23 pages, 15 figures, 7 tables, updated to match the version in
press, including some minor textual corrections identified at the proof stag
Magnetic properties of a new molecular-based spin-ladder system: (5IAP)2CuBr4*2H2O
We have synthesized and characterized a new spin-1/2 Heisenberg
antiferromagnetic ladder: bis 5-iodo-2-aminopyridinium tetrabromocuprate(II)
dihydrate. X-ray diffraction studies show the structure of the compound to
consist of well isolated stacked ladders and the interaction between the Cu(2+)
atoms to be due to direct Br...Br contacts. Magnetic susceptibility and
magnetization studies show the compound to be in the strong-coupling limit,
with the interaction along the rungs (J' ~ 13 K) much greater than the
interaction along the rails (J ~ 1 K). Magnetic critical fields are observed
near 8.3 T and 10.4 T, respectively, establishing the existence of the energy
gap.Comment: 10 pages, 4 figures, submitted to Phys. Rev. B Figure 4 did not
print. *.eps files replaced with figures.ps fil
Near infrared spectroscopy and star-formation histories of 3<z<4 quiescent galaxies
We present Keck-MOSFIRE H and K spectra for a sample of 24 candidate
quiescent galaxies (QGs) at 3<z<4, identified from UVJ colors and photometric
redshifts in the ZFOURGE and 3DHST surveys. We obtain spectroscopic redshifts
for half of the sample, using absorption or emission lines, and confirm the
high accuracy of the photometric redshifts with a median error of 1.2%. Two
galaxies turn out to be dusty objects at lower redshifts (z<2.5), and are the
only two detected in the sub-mm with ALMA. High equivalent-width [OIII] was
observed in two galaxies, contributing up to 30% of the K-band flux and
mimicking the colors of an old stellar population. This implies a failure rate
of only 20% for the UVJ selection at these redshifts. Balmer absorption was
identified in 4 of the brighest galaxies, confirming the absence of OB stars.
Modeling all QGs with a wide range of star-formation histories, we find sSFR a
factor of 10 below the main sequence (MS) for all but one galaxy, and less than
0.01 Gyr for half of the sample. This is consistent with the H
and [OII] luminosities, and the ALMA non-detections. We then find that these
QGs have quenched on average 300 Myr before observation, between z=3.5 and 5,
and that they formed at z~5.5 with a mean SFR~300 Msun/yr. Considering an
alternative selection of QGs based solely on the sSFR from SED modeling, we
find that galaxies a factor 10 below the MS are 40% more numerous than
UVJ-quiescent galaxies, implying that the UVJ selection is pure but incomplete.
Current models fail at reproducing our observations and underestimate either
the number density of QGs by more than an order of magnitude or the duration of
their quiescence by a factor two. Overall, these results confirm the existence
of an unexpected population of QGs at z>3, and offer the first insights on
their formation history. [abridged]Comment: 30 pages (+ appendix), 18 figures, accepted for publication in A&
Diurnal Differences in Intracellular Replication Within Splenic Macrophages Correlates With the Outcome of Pneumococcal Infection
Circadian rhythms affect the progression and severity of bacterial infections including those caused by Streptococcus pneumoniae, but the mechanisms responsible for this phenomenon remain largely elusive. Following advances in our understanding of the role of replication of S. pneumoniae within splenic macrophages, we sought to investigate whether events within the spleen correlate with differential outcomes of invasive pneumococcal infection. Utilising murine invasive pneumococcal disease (IPD) models, here we report that infection during the murine active phase (zeitgeber time 15; 15h after start of light cycle, 3h after start of dark cycle) resulted in significantly faster onset of septicaemia compared to rest phase (zeitgeber time 3; 3h after start of light cycle) infection. This correlated with significantly higher pneumococcal burden within the spleen of active phase-infected mice at early time points compared to rest phase-infected mice. Whole-section confocal microscopy analysis of these spleens revealed that the number of pneumococci is significantly higher exclusively within marginal zone metallophilic macrophages (MMMs) known to allow intracellular pneumococcal replication as a prerequisite step to the onset of septicaemia. Pneumococcal clusters within MMMs were more abundant and increased in size over time in active phase-infected mice compared to those in rest phase-infected mice which decreased in size and were present in a lower percentage of MMMs. This phenomenon preceded significantly higher levels of bacteraemia alongside serum IL-6 and TNF-alpha concentrations in active phase-infected mice following re-seeding of pneumococci into the blood. These data greatly advance our fundamental knowledge of pneumococcal infection by linking susceptibility to invasive pneumococcal infection to variation in the propensity of MMMs to allow persistence and replication of phagocytosed bacteria. These findings also outline a somewhat rare scenario whereby the active phase of an organism's circadian cycle plays a seemingly counterproductive role in the control of invasive infection
A low [CII]/[NII] ratio in the center of a massive galaxy at z=3.7: witnessing the transition to quiescence at high-redshift?
Understanding the process of quenching is one of the major open questions in
galaxy evolution, and crucial insights may be obtained by studying quenched
galaxies at high redshifts, at epochs when the Universe and the galaxies were
younger and simpler to model. However, establishing the degree of quiescence in
high redshift galaxies is a challenging task. One notable example is Hyde, a
recently discovered galaxy at z=3.709. As compact (r~0.5 kpc) and massive
(M*~1e11 Msun) as its quenched neighbor Jekyll, it is also extremely obscured
yet only moderately luminous in the sub-millimeter. Panchromatic modeling
suggested it could be the first galaxy found in transition to quenching at z>3,
however the data were also consistent with a broad range of star-formation
activity, including moderate SFR in the lower scatter of the galaxy
main-sequence (MS). Here, we describe ALMA observations of the [CII] 157um and
[NII] 205um far-infrared emission lines. The [CII] emission within the
half-light radius is dominated by ionized gas, while the outskirts are
dominated by PDRs or neutral gas. This suggests that the ionization in the
center is not primarily powered by on-going star formation, and could come
instead from remnant stellar populations formed in an older burst, or from a
moderate AGN. Accounting for this information in the multi-wavelength modeling
provides a tighter constraint on the star formation rate of
SFR= Msun/yr. This rules out fully quenched solutions, and
favors SFRs more than factor of two lower than expected for a galaxy on the MS,
confirming the nature of Hyde as a transition galaxy. Theses results suggest
that quenching happens from inside-out, and starts before the galaxy expels or
consumes all its gas reservoirs. Similar observations of a larger sample would
determine whether this is an isolated case or the norm for quenching at
high-redshift. [abriged]Comment: Accepted for publication in A&A. 14 pages, 9 figure
Novel VIPAS39 mutation in a syndromic patient with arthrogryposis, renal tubular dysfunction and intrahepatic cholestasis
ARC syndrome is a rare autosomal recessive disease, characterized by arthrogryposis, renal tubular dysfunction and cholestasis. Herein a 2.5 month old infant with dysmorphic features, including small anterior fontanel, low set ears, beaked nose and high arched palate is presented who was referred because of icterus. He also suffered from some additional anomalies, including unilateral choanal atresia, club foot, and bilateral developmental dislocation of hip, while further studies showed renal tubular acidosis and hearing impairment in addition to cholestasis. Genetic studies showed a homozygous mutation in the VIPAS39 gene. Making the definite diagnosis of the syndrome is important, while increased risk of mutation in other siblings highlights the importance of prenatal diagnosis
A giant galaxy in the young Universe with a massive ring
In the local (redshift z~0) Universe, collisional ring galaxies make up only
~0.01% of galaxies and are formed by head-on galactic collisions that trigger
radially propagating density waves. These striking systems provide key
snapshots for dissecting galactic disks and are studied extensively in the
local Universe. However, not much is known about distant (z>0.1) collisional
rings. Here we present a detailed study of a ring galaxy at a look-back time of
10.8 Gyr (z=2.19). Compared with our Milky Way, this galaxy has a similar
stellar mass, but has a stellar half-light radius that is 1.5-2.2 times larger
and is forming stars 50 times faster. The large, diffuse stellar light outside
the star-forming ring, combined with a radial velocity on the ring and an
intruder galaxy nearby, provides evidence for this galaxy hosting a collisional
ring. If the ring is secularly evolved, the implied large bar in a giant disk
would be inconsistent with the current understanding of the earliest formation
of barred spirals. Contrary to previous predictions, this work suggests that
massive collisional rings were as rare 11 Gyr ago as they are today. Our
discovery offers a unique pathway for studying density waves in young galaxies,
as well as constraining the cosmic evolution of spiral disks and galaxy groups.Comment: Author's version for the main article (10 pages). The Supplementary
Information (22 pages) and a combined pdf are provided here
http://astronomy.swin.edu.au/~tyuan/paper Published version available online
http://dx.doi.org/10.1038/s41550-020-1102-
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