2,110 research outputs found
Sorption of Binary Mixtures of Aromatic Nitrogen Heterocyclic Compounds on Subsurface Materials
Single and binary solute sorption of pyridine, quinoline, and acridine has been investigated on two low organic carbon subsurface materials with similar properties but different equilibrium pH when saturated with water. Single solute sorption for all compounds is higher in the acidic soil as compared to the basic soil, reflecting stronger sorption of the protonated organic cations. The protonated species exhibit high selectivity for the exchange complex at low aqueous concentration with selectivity increasing with ring number. Binary sorption experiments with quinoline/pyridine and quinoline/acridine demonstrate that competitive sorption occurs between compounds in the acidic subsoil where the protonated compound species predominate in solution. In contrast, competition is minimal in the basic subsoil when the compounds are neutral. The competition between compounds is consistent with their measured single solute sorption and suggests mass action on a common set of high-affinity surface sites. A simplified model based on ideal adsorbed solution theory (IAS) is used to provide simulations of binary solute sorption that are in good qualitative agreement with experimental results. It is suggested that competition between ionized solutes may significantly influence transport of organic mixtures when the groundwater pH is near the pKa of the compounds
GMASS Ultradeep Spectroscopy of Galaxies at redshift z~2. I. The stellar metallicity
Context: Galaxy metallicities have been measured to redshift z~2 by gas-phase
oxygen abundances of the interstellar medium using the R23 and N2 methods.
Galaxy stellar metallicities provide crucial data for chemical evolution models
but have not been assessed reliably much outside the local Universe. Aims: We
determine the iron-abundance, stellar metallicity of star-forming galaxies
(SFGs) at redshift z~2, observed as part of the Galaxy Mass Assembly ultra-deep
Spectroscopic Survey (GMASS). Methods: We compute the equivalent width of a
rest-frame mid-ultraviolet, photospheric absorption-line index, the 1978 index
found to vary monotonically with stellar metallicity by Rix and collaborators.
We normalise and combine 75 SFG spectra from the GMASS survey to produce a
spectrum corresponding to a total integration time 1652.5 hours (and a
signal-to-noise ratio ~100 for our 1.5 angstrom binning) of FORS2 spectroscopic
observations at the Very Large Telescope. Results: We measure an
iron-abundance, stellar metallicity of log (Z/Zsolar) = -0.574+/-0.159 for our
spectrum representative of a galaxy of stellar mass 9.4 x 10^9 Msolar assuming
a Chabrier IMF. We find that the R04 model SFG spectrum for log (Z/Zsolar) =
-0.699 solar metallicity provides the best description of our GMASS coadded
spectrum. For similar galaxy stellar mass, our stellar metallicity is ~0.25 dex
lower than the oxygen-abundance, gas-phase metallicity quantified by Erb and
collaborators for UV-selected star-forming galaxies at z=2. Conclusions: We
conclude that we are witnessing the establishment of a light-element
overabundance in galaxies as they are being formed at redshift z~2. Our
measurements are reminiscent of the alpha-element enhancement seen in
low-redshift, galactic bulges and early-type galaxies. (Abridged)Comment: Accepted for publication in Astronomy and Astrophysics on 18 December
2007, 9 pages, 8 figures, aa.bst and aa.cls A&A style file
A Randomized Study Comparing Digital Imaging to Traditional Glass Slide Microscopy for Breast Biopsy and Cancer Diagnosis.
BACKGROUND: Digital whole slide imaging may be useful for obtaining second opinions and is used in many countries. However, the U.S. Food and Drug Administration requires verification studies.
METHODS: Pathologists were randomized to interpret one of four sets of breast biopsy cases during two phases, separated by ≥9 months, using glass slides or digital format (sixty cases per set, one slide per case,
RESULTS: Sixty-five percent of responding pathologists were eligible, and 252 consented to randomization; 208 completed Phase I (115 glass, 93 digital); and 172 completed Phase II (86 glass, 86 digital). Accuracy was slightly higher using glass compared to digital format and varied by category: invasive carcinoma, 96% versus 93% (
CONCLUSIONS: In this large randomized study, digital format interpretations were similar to glass slide interpretations of benign and invasive cancer cases. However, cases in the middle of the spectrum, where more inherent variability exists, may be more problematic in digital format. Future studies evaluating the effect these findings exert on clinical practice and patient outcomes are required
Galaxy Counts at 24 Microns in the SWIRE Fields
This paper presents galaxy source counts at 24 microns in the six Spitzer
Wide-field InfraRed Extragalactic (SWIRE) fields. The source counts are
compared to counts in other fields, and to model predictions that have been
updated since the launch of Spitzer. This analysis confirms a very steep rise
in the Euclidean-normalized differential number counts between 2 mJy and 0.3
mJy. Variations in the counts between fields show the effects of sample
variance in the flux range 0.5-10 mJy, up to 100% larger than Poisson errors.
Nonetheless, a "shoulder" in the normalized counts persists at around 3 mJy.
The peak of the normalized counts at 0.3 mJy is higher and narrower than most
models predict. In the ELAIS N1 field, the 24 micron data are combined with
Spitzer-IRAC data and five-band optical imaging, and these bandmerged data are
fit with photometric redshift templates. Above 1 mJy the counts are dominated
by galaxies at z less than 0.3. By 300 microJy, about 25% are between z ~
0.3-0.8, and a significant fraction are at z ~ 1.3-2. At low redshifts the
counts are dominated by spirals, and starbursts rise in number density to
outnumber the spirals' contribution to the counts below 1 mJy.Comment: 10 pages, 8 figures, accepted 3 November 2007 for publication in The
Astronomical Journal, formatted with emulateapj styl
GMASS ultradeep spectroscopy of galaxies at z~2 - VII. Sample selection and spectroscopy
The populations of both quiescent and actively star-forming galaxies at 1<z<2
are still under-represented in our spectroscopic census of galaxies throughout
the history of the Universe. In the light of galaxy formation models, however,
the evolution of galaxies at these redshifts is of pivotal importance and
merits further investigation. We therefore designed a spectroscopic observing
campaign of a sample of both massive, quiescent and star-forming galaxies at
z>1.4, called Galaxy Mass Assembly ultra-deep Spectroscopic Survey (GMASS). To
determine redshifts and physical properties, such as metallicity, dust content,
dynamical masses, and star formation history, we performed ultra-deep
spectroscopy with the red-sensitive optical spectrograph FORS2 at the VLT. Our
sample consists of objects, within the CDFS/GOODS area, detected at 4.5 micron,
to be sensitive to stellar mass rather than star formation intensity. The
spectroscopic targets were selected with a photometric redshift constraint
(z>1.4) and magnitude constraints (B(AB)<26, I(AB)<26.5), which should ensure
that these are faint, distant, and fairly massive galaxies. We present the
sample selection, survey design, observations, data reduction, and
spectroscopic redshifts. Up to 30 hours of spectroscopy of 174 spectroscopic
targets and 70 additional objects enabled us to determine 210 redshifts, of
which 145 are at z>1.4. From the redshifts and photometry, we deduce that the
BzK selection criteria are efficient (82%) and suffer low contamination (11%).
Several papers based on the GMASS survey show its value for studies of galaxy
formation and evolution. We publicly release the redshifts and reduced spectra.
In combination with existing and on-going additional observations in
CDFS/GOODS, this data set provides a legacy for future studies of distant
galaxies.Comment: Accepted by A&A in August 2012, 45 pages, public release of reduced
spectra currently on www.mpe.mpg.de/~kurk/gmas
Disclosing Harmful Mammography Errors to Patients
To assess radiologists’ attitudes about disclosing errors to patients by using a survey with a vignette involving an error interpreting a patient's mammogram, leading to a delayed cancer diagnosis
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric Characterization
A key legacy of the recently launched TESS mission will be to provide the
astronomical community with many of the best transiting exoplanet targets for
atmospheric characterization. However, time is of the essence to take full
advantage of this opportunity. JWST, although delayed, will still complete its
nominal five year mission on a timeline that motivates rapid identification,
confirmation, and mass measurement of the top atmospheric characterization
targets from TESS. Beyond JWST, future dedicated missions for atmospheric
studies such as ARIEL require the discovery and confirmation of several hundred
additional sub-Jovian size planets (R_p < 10 R_Earth) orbiting bright stars,
beyond those known today, to ensure a successful statistical census of
exoplanet atmospheres. Ground-based ELTs will also contribute to surveying the
atmospheres of the transiting planets discovered by TESS. Here we present a set
of two straightforward analytic metrics, quantifying the expected
signal-to-noise in transmission and thermal emission spectroscopy for a given
planet, that will allow the top atmospheric characterization targets to be
readily identified among the TESS planet candidates. Targets that meet our
proposed threshold values for these metrics would be encouraged for rapid
follow-up and confirmation via radial velocity mass measurements. Based on the
catalog of simulated TESS detections by Sullivan et al. (2015), we determine
appropriate cutoff values of the metrics, such that the TESS mission will
ultimately yield a sample of high-quality atmospheric
characterization targets across a range of planet size bins, extending down to
Earth-size, potentially habitable worlds.Comment: accepted to PAS
Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector
A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13 TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV
Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector
The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30
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