199 research outputs found
ESA can be a society for all ecologists
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117231/1/fee201412291.pd
Absence of spontaneous disease and comparative prion susceptibility of transgenic mice expressing mutant human prion proteins
Approximately 15 % of human prion disease is associated with autosomal-dominant pathogenic mutations in the prion protein (PrP) gene. Previous attempts to model these diseases in mice have expressed human PrP mutations in murine PrP, but this may have different structural consequences. Here, we describe transgenic mice expressing human PrP with P102L or E200K mutations and methionine (M) at the polymorphic residue 129. Although no spontaneous disease developed in aged animals, these mice were readily susceptible to prion infection from patients with the homotypic pathogenic mutation. However, while variant Creutzfeldt–Jakob disease (CJD) prions transmitted infection efficiently to both lines of mice, markedly different susceptibilities to classical (sporadic and iatrogenic) CJD prions were observed. Prions from E200K and classical CJD M129 homozygous patients, transmitted disease with equivalent efficiencies and short incubation periods in human PrP 200K, 129M transgenic mice. However, mismatch at residue 129 between inoculum and host dramatically increased the incubation period. In human PrP 102L, 129M transgenic mice, short disease incubation periods were only observed with transmissions of prions from P102L patients, whereas classical CJD prions showed prolonged and variable incubation periods irrespective of the codon 129 genotype. Analysis of disease-related PrP (PrPSc) showed marked alteration in the PrPSc glycoform ratio propagated after transmission of classical CJD prions, consistent with the PrP point mutations directly influencing PrPSc assembly. These data indicate that P102L or E200K mutations of human PrP have differing effects on prion propagation that depend upon prion strain type and can be significantly influenced by mismatch at the polymorphic residue 129
The Identification and Synthesis of Lead Apatite Minerals Formed in Lead Water Pipes
Phosphate is added to drinking water in the UK to minimise the release of lead from lead water pipes. The phosphate encourages the formation of insoluble lead apatites on the walls of the pipe. Hydroxylpyromorphite Pb5(PO4)3OH is the lead apatite that is most often used to model lead levels in tap water; however, its presence has not been confirmed. Our aims were to identify the lead pipe apatite and synthesise it. The synthetic mineral would then be used in future solubility studies to produce better predictions of lead levels in tap water. XRD and FTIR were used to characterise the minerals on a range of lead pipes. Pyromorphite and hydroxylpyromorphite were absent and instead a range of mixed calcium lead apatites were present. For every five lead ions in the general formula Pb5(PO4)3X between one and two ions were replaced with calcium and there was evidence of substitution of by either or . Calcium lead apatites with similar unit cell dimensions to those found on lead water pipes were then synthesised. The calcium : lead ratio in these reaction mixtures was in excess of 500 : 1 and the resulting crystals were shown by TEM to be nanosized rods and flakes. The synthetic apatites that most closely resembled the unit cell dimensions of the apatites on lead water pipes were shown to be Pb3.4Ca1.3(PO4)3Cl0.03OH0.97, Pb3.6Ca1.2(PO4)3Cl0.07OH0.93, and Pb3.6Ca1.2(PO4)3Cl0.27OH0.73
Blazar Optical Variability in the Palomar-QUEST Survey
We study the ensemble optical variability of 276 FSRQs and 86 BL Lacs in the
Palomar-QUEST Survey with the goal of searching for common fluctuation
properties, examining the range of behavior across the sample, and
characterizing the appearance of blazars in such a survey so that future work
can more easily identify such objects. The survey, which covers 15,000 square
degrees multiple times over 3.5 years, allows for the first ensemble blazar
study of this scale. Variability amplitude distributions are shown for the FSRQ
and BL Lac samples for numerous time lags, and also studied through structure
function analyses. Individual blazars show a wide range of variability
amplitudes, timescales, and duty cycles. Of the best sampled objects, 35% are
seen to vary by more than 0.4 magnitudes; for these, the fraction of
measurements contributing to the high amplitude variability ranges constantly
from about 5% to 80%. Blazar variability has some similarities to that of type
I quasars but includes larger amplitude fluctuations on all timescales. FSRQ
variability amplitudes are particularly similar to those of QSOs on timescales
of several months, suggesting significant contributions from the accretion disk
to the variable flux at these timescales. Optical variability amplitudes are
correlated with the maximum apparent velocities of the radio jet for the subset
of FSRQs with MOJAVE VLBA measurements, implying that the optically variable
flux's strength is typically related to that of the radio emission. We also
study CRATES radio-selected FSRQ candidates, which show similar variability
characteristics to known FSRQs; this suggests a high purity for the CRATES
sample.Comment: 29 pages, 12 figures. Accepted for publication in Ap
Club, country and clinicians united : ensuring collaborative care in elite sport medical handovers
Medical handovers are fundamental to optimal patient care but can be a source of errors in clinical care with important implications on patient welfare and safety. Care of international athletes presents unique challenges to open and effective communication between medical teams. Handover of complete medical records should occur with athlete consent between medical teams on the transfer of an athlete between clubs. There are currently no specific guidelines or published recommendations advising sports and exercise medicine clinicians about medical handovers. The aim of this editorial is to provide a checklist of recommendations for the handover of elite athlete care between clubs and national medical and sports science teams, with lessons shared from professional football (soccer).http://bjsm.bmj.compm2021Sports Medicin
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A Large, Uniform Sample of X-Ray-emitting Active Galactic Nuclei from the ROSAT All Sky and Sloan Digital Sky Surveys: The Data Release 5 Sample
We describe further results of a program aimed at yielding ~104 fully characterized optical identifications of ROSAT X-ray sources. Our program employs X-ray data from the ROSAT All Sky Survey (RASS) and both optical imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS). RASS/SDSS data from 5740 deg² of sky spectroscopically covered in SDSS Data Release 5 provide an expanded catalog of 7000 confirmed quasars and other active galactic nuclei (AGNs) that are probable RASS identifications. Again, in our expanded catalog the identifications as X-ray sources are statistically secure, with only a few percent of the SDSS AGNs likely to be randomly superposed on unrelated RASS X-ray sources. Most identifications continue to be quasars and Seyfert 1 galaxies with 15 < m < 21 and 0.01 < z < 4, but the total sample size has grown to include very substantial numbers of even quite rare AGNs, e.g., it now includes several hundreds of candidate X-ray-emitting BL Lac objects and narrow-line Seyfert 1 galaxies. In addition to exploring rare subpopulations, such a large total sample may be useful when considering correlations between the X-ray and the optical and may also serve as a resource list from which to select the "best" object (e.g., X-ray-brightest AGN of a certain subclass at a preferred redshift or luminosity) for follow-up X-ray spectral or alternate detailed studies
The Ultraviolet-to-Mid-Infrared Spectral Energy Distribution of Weak Emission Line Quasars
We present Spitzer Space Telescope photometry of 18 Sloan Digital Sky Survey
(SDSS) quasars at 2.7 <= z <= 5.9 which have weak or undetectable
high-ionization emission lines in their rest-frame ultraviolet (UV) spectra
(hereafter weak-lined quasars, or WLQs). The Spitzer data are combined with
SDSS spectra and ground-based, near-infrared (IR) photometry of these sources
to produce a large inventory of spectral energy distributions (SEDs) of WLQs
across the rest-frame ~0.1-5 mum spectral band. The SEDs of our sources are
inconsistent with those of BL Lacertae objects which are dominated by
synchrotron emission due to a jet aligned close to our line-of-sight, but are
consistent with the SED of ordinary quasars with similar luminosities and
redshifts that exhibit a near-to-mid-IR 'bump', characteristic of hot dust
emission. This indicates that broad emission lines in WLQs are intrinsically
weak, rather than suffering continuum dilution from a jet, and that such
sources cannot be selected efficiently from traditional photometric surveys.Comment: 10 pages (emulateapj), 4 figures. Accepted for publication in Ap
Highly Variable Objects in the Palomar-QUEST Survey: A Blazar Search using Optical Variability
We identify 3,113 highly variable objects in 7,200 square degrees of the
Palomar-QUEST Survey, which each varied by more than 0.4 magnitudes
simultaneously in two broadband optical filters on timescales from hours to
roughly 3.5 years. The primary goal of the selection is to find blazars by
their well-known violent optical variability. Because most known blazars have
been found in radio and/or X-ray wavelengths, a sample discovered through
optical variability may have very different selection effects, elucidating the
range of behavior possible in these systems. A set of blazars selected in this
unusual manner will improve our understanding of the physics behind this
extremely variable and diverse class of AGN. The object positions, variability
statistics, and color information are available using the Palomar-QUEST CasJobs
server. The time domain is just beginning to be explored over large sky areas;
we do not know exactly what a violently variable sample will hold. About 20% of
the sample has been classified in the literature; over 70% of those objects are
known or likely AGN. The remainder largely consists of a variety of variable
stars, including a number of RR Lyrae and cataclysmic variables.Comment: 22 pages (preprint format), 2 figures. Accepted for publication in
ApJ. References update
A Large, Uniform Sample of X-ray Emitting AGN from the ROSAT All-Sky and Sloan Digital Sky Surveys: the Data Release 5 Sample
We describe further results of a program aimed to yield ~10^4 fully
characterized optical identifications of ROSAT X-ray sources. Our program
employs X-ray data from the ROSAT All-Sky Survey (RASS), and both optical
imaging and spectroscopic data from the Sloan Digital Sky Survey (SDSS).
RASS/SDSS data from 5740 deg^2 of sky spectroscopically covered in SDSS Data
Release 5 (DR5) provide an expanded catalog of 7000 confirmed quasars and other
AGN that are probable RASS identifications. Again in our expanded catalog, the
identifications as X-ray sources are statistically secure, with only a few
percent of the SDSS AGN likely to be randomly superposed on unrelated RASS
X-ray sources. Most identifications continue to be quasars and Seyfert 1s with
15<m<21 and 0.01<z<4; but the total sample size has grown to include very
substantial numbers of even quite rare AGN, e.g., now including several
hundreds of candidate X-ray emitting BL Lacs and narrow-line Seyfert 1
galaxies. In addition to exploring rare subpopulations, such a large total
sample may be useful when considering correlations between the X-ray and the
optical, and may also serve as a resource list from which to select the "best"
object (e.g., X-ray brightest AGN of a certain subclass, at a preferred
redshift or luminosity) for follow-on X-ray spectral or alternate detailed
studies.Comment: Accepted for publication in AJ; 32 pages, including 11 figures, and 6
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