177 research outputs found
Expanded Search for z~10 Galaxies from HUDF09, ERS, and CANDELS Data: Evidence for Accelerated Evolution at z>8?
We search for z~10 galaxies over ~160 arcmin^2 of WFC3/IR data in the Chandra
Deep Field South, using the public HUDF09, ERS, and CANDELS surveys, that reach
to 5sigma depths ranging from 26.9 to 29.4 in H_160 AB mag. z>~9.5 galaxy
candidates are identified via J_125-H_160>1.2 colors and non-detections in any
band blueward of J_125. Spitzer IRAC photometry is key for separating the
genuine high-z candidates from intermediate redshift (z~2-4) galaxies with
evolved or heavily dust obscured stellar populations. After removing 16 sources
of intermediate brightness (H_160~24-26 mag) with strong IRAC detections, we
only find one plausible z~10 galaxy candidate in the whole data set, previously
reported in Bouwens et al. (2011). The newer data cover a 3x larger area and
provide much stronger constraints on the evolution of the UV luminosity
function (LF). If the evolution of the z~4-8 LFs is extrapolated to z~10, six
z~10 galaxies are expected in our data. The detection of only one source
suggests that the UV LF evolves at an accelerated rate before z~8. The
luminosity density is found to increase by more than an order of magnitude in
only 170 Myr from z~10 to z~8. This increase is >=4x larger than expected from
the lower redshift extrapolation of the UV LF. We are thus likely witnessing
the first rapid build-up of galaxies in the heart of cosmic reionization.
Future deep HST WFC3/IR data, reaching to well beyond 29 mag, can enable a more
robust quantification of the accelerated evolution around z~10.Comment: 13 pages, 11 figures, ApJ resubmitted after referee repor
Implementation of Vascularized Composite Allografts in the United States: Recommendations From the ASTS VCA Ad Hoc Committee and the Executive Committee
Like all other areas of transplantation, vascularized composite allografts (VCA) has the capacity to transform the lives of patients, for the better or for the worse. It is this duality that mandates VCA be performed in centers prepared for the intricacies accompanying other transplant procedures. Similarly, the complexities of VCA require that the procedures be driven by surgeons and physicians with experience in the multidisciplinary management of immunocompromised postsurgical patients. Furthermore, the grafts should be considered as organs rather than tissues from a regulatory and a biological standpoint. The ASTS supports the field of VCA and has demonstrated its support and leadership by actively formulating a strategy for its systematic development. The goal of this document is to provide a framework for the prospective, thoughtful realization of VCA in the United States from the American Society of Transplant Surgeons (ASTS) perspective.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79113/1/j.1600-6143.2010.03374.x.pd
UV Luminosity Functions from 132 z~7 and z~8 Lyman-Break Galaxies in the ultra-deep HUDF09 and wide-area ERS WFC3/IR Observations
We identify 73 z~7 and 59 z~8 candidate galaxies in the reionization epoch,
and use this large 26-29.4 AB mag sample of galaxies to derive very deep
luminosity functions to <-18 AB mag and the star formation rate density at z~7
and z~8. The galaxy sample is derived using a sophisticated Lyman-Break
technique on the full two-year WFC3/IR and ACS data available over the HUDF09
(~29.4 AB mag, 5 sigma), two nearby HUDF09 fields (~29 AB mag, 14 arcmin) and
the wider area ERS (~27.5 AB mag) ~40 arcmin**2). The application of strict
optical non-detection criteria ensures the contamination fraction is kept low
(just ~7% in the HUDF). This very low value includes a full assessment of the
contamination from lower redshift sources, photometric scatter, AGN, spurious
sources, low mass stars, and transients (e.g., SNe). From careful modelling of
the selection volumes for each of our search fields we derive luminosity
functions for galaxies at z~7 and z~8 to <-18 AB mag. The faint-end slopes
alpha at z~7 and z~8 are uncertain but very steep at alpha = -2.01+/-0.21 and
alpha=-1.91+/-0.32, respectively. Such steep slopes contrast to the local
alpha<~-1.4 and may even be steeper than that at z~4 where alpha=-1.73+/-0.05.
With such steep slopes (alpha<~-1.7) lower luminosity galaxies dominate the
galaxy luminosity density during the epoch of reionization. The star formation
rate densities derived from these new z~7 and z~8 luminosity functions are
consistent with the trends found at later times (lower redshifts). We find
reasonable consistency, with the SFR densities implied from reported stellar
mass densities, being only ~40% higher at z<7. This suggests that (1) the
stellar mass densities inferred from the Spitzer IRAC photometry are reasonably
accurate and (2) that the IMF at very high redshift may not be very different
from that at later times.Comment: 38 pages, 21 figures, 20 tables, ApJ, accepted for publicatio
An investigation of dietary intake, nutrition knowledge and hydration status of Gaelic Football players.
Resistance to Mucosal Lysozyme Compensates for the Fitness Deficit of Peptidoglycan Modifications by Streptococcus pneumoniae
The abundance of lysozyme on mucosal surfaces suggests that successful colonizers must be able to evade its antimicrobial effects. Lysozyme has a muramidase activity that hydrolyzes bacterial peptidoglycan and a non-muramidase activity attributable to its function as a cationic antimicrobial peptide. Two enzymes (PgdA, a N-acetylglucosamine deacetylase, and Adr, an O-acetyl transferase) that modify different sites on the peptidoglycan of Streptococcus pneumoniae have been implicated in its resistance to lysozyme in vitro. Here we show that the antimicrobial effect of human lysozyme is due to its muramidase activity and that both peptidoglycan modifications are required for full resistance by pneumococci. To examine the contribution of lysozyme and peptidoglycan modifications during colonization of the upper respiratory tract, competition experiments were performed with wild-type and pgdAadr mutant pneumococci in lysozyme M-sufficient (LysM+/+) and -deficient (LysM−/−) mice. The wild-type strain out-competed the double mutant in LysM+/+, but not LysM−/− mice, indicating the importance of resistance to the muramidase activity of lysozyme during mucosal colonization. In contrast, strains containing single mutations in either pgdA or adr prevailed over the wild-type strain in both LysM+/+ and LysM−/− mice. Our findings demonstrate that individual peptidoglycan modifications diminish fitness during colonization. The competitive advantage of wild-type pneumococci in LysM+/+ but not LysM−/− mice suggests that the combination of peptidoglycan modifications reduces overall fitness, but that this is outweighed by the benefits of resistance to the peptidoglycan degrading activity of lysozyme
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