368 research outputs found
The Spitzer South Pole Telescope Deep Field Survey: Linking galaxies and halos at z=1.5
We present an analysis of the clustering of high-redshift galaxies in the
recently completed 94 deg Spitzer-SPT Deep Field survey. Applying flux and
color cuts to the mid-infrared photometry efficiently selects galaxies at
in the stellar mass range , making this
sample the largest used so far to study such a distant population. We measure
the angular correlation function in different flux-limited samples at scales
(corresponding to physical distances Mpc) and
thereby map the one- and two-halo contributions to the clustering. We fit halo
occupation distributions and determine how the central galaxy's stellar mass
and satellite occupation depend on the halo mass. We measure a prominent peak
in the stellar-to-halo mass ratio at a halo mass of , 4.5 times higher than the value. This supports
the idea of an evolving mass threshold above which star formation is quenched.
We estimate the large-scale bias in the range and the satellite
fraction to be , showing a clear evolution compared to
. We also find that, above a given stellar mass limit, the fraction of
galaxies that are in similar mass pairs is higher at than at . In
addition, we measure that this fraction mildly increases with the stellar mass
limit at , which is the opposite of the behavior seen at low-redshift.Comment: 32 pages, 22 figures. Published in MNRA
Incorporation of Eye-Tracking and Gaze Feedback to Characterize and Improve Radiologist Search Patterns of Chest X-rays: A Randomized Controlled Clinical Trial
Diagnostic errors in radiology often occur due to incomplete visual
assessments by radiologists, despite their knowledge of predicting disease
classes. This insufficiency is possibly linked to the absence of required
training in search patterns. Additionally, radiologists lack consistent
feedback on their visual search patterns, relying on ad-hoc strategies and peer
input to minimize errors and enhance efficiency, leading to suboptimal patterns
and potential false negatives. This study aimed to use eye-tracking technology
to analyze radiologist search patterns, quantify performance using established
metrics, and assess the impact of an automated feedback-driven educational
framework on detection accuracy. Ten residents participated in a controlled
trial focused on detecting suspicious pulmonary nodules. They were divided into
an intervention group (received automated feedback) and a control group.
Results showed that the intervention group exhibited a 38.89% absolute
improvement in detecting suspicious-for-cancer nodules, surpassing the control
group's improvement (5.56%, p-value=0.006). Improvement was more rapid over the
four training sessions (p-value=0.0001). However, other metrics such as speed,
search pattern heterogeneity, distractions, and coverage did not show
significant changes. In conclusion, implementing an automated feedback-driven
educational framework improved radiologist accuracy in detecting suspicious
nodules. The study underscores the potential of such systems in enhancing
diagnostic performance and reducing errors. Further research and broader
implementation are needed to consolidate these promising results and develop
effective training strategies for radiologists, ultimately benefiting patient
outcomes.Comment: Submitted for Review in the Journal of the American College of
Radiology (JACR
The Spitzer-South Pole Telescope Deep Field: Survey Design and IRAC Catalogs
The Spitzer-South Pole Telescope Deep Field (SSDF) is a wide-area survey
using Spitzer's Infrared Array Camera (IRAC) to cover 94 square degrees of
extragalactic sky, making it the largest IRAC survey completed to date outside
the Milky Way midplane. The SSDF is centered at 23:30,-55:00, in a region that
combines observations spanning a broad wavelength range from numerous
facilities. These include millimeter imaging from the South Pole Telescope,
far-infrared observations from Herschel/SPIRE, X-ray observations from the XMM
XXL survey, near-infrared observations from the VISTA Hemisphere Survey, and
radio-wavelength imaging from the Australia Telescope Compact Array, in a
panchromatic project designed to address major outstanding questions
surrounding galaxy clusters and the baryon budget. Here we describe the
Spitzer/IRAC observations of the SSDF, including the survey design,
observations, processing, source extraction, and publicly available data
products. In particular, we present two band-merged catalogs, one for each of
the two warm IRAC selection bands. They contain roughly 5.5 and 3.7 million
distinct sources, the vast majority of which are galaxies, down to the SSDF
5-sigma sensitivity limits of 19.0 and 18.2 Vega mag (7.0 and 9.4 microJy) at
3.6 and 4.5 microns, respectively.Comment: Accepted by ApJS; this version updated to conform to refereed articl
Combining alkali metals and zinc to harness heterometallic cooperativity in cyclic ester ring-opening polymerisation
Heterometallic cooperativity is an emerging strategy to elevate polymerisation catalyst performance. Here, we report the first heterotrimetallic Na/Zn(2) and K/Zn(2) complexes supported by a ProPhenol ligand, which deliver âbest of bothâ in cyclic ester ring-opening polymerisation, combining the outstanding activity (Na/K) and good control (Zn(2)) of homometallic analogues. Detailed NMR studies and density-functional theory calculations suggest that the Na/Zn(2) and K/Zn(2) complexes retain their heterometallic structures in the solution-state. To the best of our knowledge, the K/Zn(2) analogue is the most active heterometallic catalyst reported for rac-lactide polymerisation (k(obs) = 1.7 Ă 10(â2) s(â1)), giving activities five times faster than the Na/Zn(2) complex. These versatile catalysts also display outstanding performance in Δ-caprolatone and ÎŽ-valerolactone ring-opening polymerisation. These studies provide underpinning methodologies for future heterometallic polymerisation catalyst design, both in cyclic ester polymerisation and other ring-opening (co)polymerisation reactions
Candidate Clusters of Galaxies at z > 1.3 Identified in the Spitzer South Pole Telescope Deep Field Survey
We present 279 galaxy cluster candidates at z > 1.3 selected from the 94 deg^2 Spitzer South Pole Telescope Deep Field (SSDF) survey. We use a simple algorithm to select candidate high-redshift clusters of galaxies based on Spitzer/IRAC mid-infrared data combined with shallow all-sky optical data. We identify distant cluster candidates adopting an overdensity threshold that results in a high purity (80%) cluster sample based on tests in the Spitzer Deep, Wide-Field Survey of the Boötes field. Our simple algorithm detects all three 1.4 < z †1.75 X-ray detected clusters in the Boötes field. The uniqueness of the SSDF survey resides not just in its area, one of the largest contiguous extragalactic fields observed with Spitzer, but also in its deep, multi-wavelength coverage by the South Pole Telescope (SPT), Herschel/SPIRE, and XMM-Newton. This rich data set will allow direct or stacked measurements of Sunyaev-Zel'dovich effect decrements or X-ray masses for many of the SSDF clusters presented here, and enable a systematic study of the most distant clusters on an unprecedented scale. We measure the angular correlation function of our sample and find that these candidates show strong clustering. Employing the COSMOS/UltraVista photometric catalog in order to infer the redshift distribution of our cluster selection, we find that these clusters have a comoving number density N_c = (0.7^(+6.3)_(0.6)) x 10^(-7) h^3 Mpc^(-3) and a spatial clustering correlation scale length r_ 0 = (32 ± 7) h^(â1) Mpc. Assuming our sample is comprised of dark matter halos above a characteristic minimum mass, M _(min), we derive that at z = 1.5 these clusters reside in halos larger than M_(min) = 1.5^(+0.9)_(0.7) x 10^(14) h^(-1) M_â. We find that the mean mass of our cluster sample is equal to M_(mean) = 1.9^(+1.0)_(0.8) x 10^(14) h^(-1) M_â ; thus, our sample contains the progenitors of present-day massive galaxy clusters
Cosmic Chronometers: Constraining the Equation of State of Dark Energy. I: H(z) Measurements
We present new determinations of the cosmic expansion history from
red-envelope galaxies. We have obtained for this purpose high-quality spectra
with the Keck-LRIS spectrograph of red-envelope galaxies in 24 galaxy clusters
in the redshift range 0.2 < z < 1.0. We complement these Keck spectra with
high-quality, publicly available archival spectra from the SPICES and VVDS
surveys. We improve over our previous expansion history measurements in Simon
et al. (2005) by providing two new determinations of the expansion history:
H(z) = 97 +- 62 km/sec/Mpc at z = 0.5 and H(z) = 90 +- 40 km/sec/Mpc at z =
0.8. We discuss the uncertainty in the expansion history determination that
arises from uncertainties in the synthetic stellar-population models. We then
use these new measurements in concert with cosmic-microwave-background (CMB)
measurements to constrain cosmological parameters, with a special emphasis on
dark-energy parameters and constraints to the curvature. In particular, we
demonstrate the usefulness of direct H(z) measurements by constraining the
dark- energy equation of state parameterized by w0 and wa and allowing for
arbitrary curvature. Further, we also constrain, using only CMB and H(z) data,
the number of relativistic degrees of freedom to be 4 +- 0.5 and their total
mass to be < 0.2 eV, both at 1-sigma.Comment: Submitted to JCA
A Measurement of the Correlation of Galaxy Surveys with CMB Lensing Convergence Maps from the South Pole Telescope
We compare cosmic microwave background lensing convergence maps derived from South Pole Telescope (SPT) data with galaxy survey data from the Blanco Cosmology Survey, WISE, and a new large Spitzer/IRAC field designed to overlap with the SPT survey. Using optical and infrared catalogs covering between 17 and 68 deg^2 of sky, we detect a correlation between the SPT convergence maps and each of the galaxy density maps at >4Ï, with zero correlation robustly ruled out in all cases. The amplitude and shape of the cross-power spectra are in good agreement with theoretical expectations and the measured galaxy bias is consistent with previous work. The detections reported here utilize a small fraction of the full 2500 deg^2 SPT survey data and serve as both a proof of principle of the technique and an illustration of the potential of this emerging cosmological probe
Improved constraints on the expansion rate of the Universe up to z~1.1 from the spectroscopic evolution of cosmic chronometers
We present new improved constraints on the Hubble parameter H(z) in the
redshift range 0.15 < z < 1.1, obtained from the differential spectroscopic
evolution of early-type galaxies as a function of redshift. We extract a large
sample of early-type galaxies (\sim11000) from several spectroscopic surveys,
spanning almost 8 billion years of cosmic lookback time (0.15 < z < 1.42). We
select the most massive, red elliptical galaxies, passively evolving and
without signature of ongoing star formation. Those galaxies can be used as
standard cosmic chronometers, as firstly proposed by Jimenez & Loeb (2002),
whose differential age evolution as a function of cosmic time directly probes
H(z). We analyze the 4000 {\AA} break (D4000) as a function of redshift, use
stellar population synthesis models to theoretically calibrate the dependence
of the differential age evolution on the differential D4000, and estimate the
Hubble parameter taking into account both statistical and systematical errors.
We provide 8 new measurements of H(z) (see Tab. 4), and determine its change in
H(z) to a precision of 5-12% mapping homogeneously the redshift range up to z
\sim 1.1; for the first time, we place a constraint on H(z) at z \neq 0 with a
precision comparable with the one achieved for the Hubble constant (about 5-6%
at z \sim 0.2), and covered a redshift range (0.5 < z < 0.8) which is crucial
to distinguish many different quintessence cosmologies. These measurements have
been tested to best match a \Lambda CDM model, clearly providing a
statistically robust indication that the Universe is undergoing an accelerated
expansion. This method shows the potentiality to open a new avenue in constrain
a variety of alternative cosmologies, especially when future surveys (e.g.
Euclid) will open the possibility to extend it up to z \sim 2.Comment: 34 pages, 15 figures, 6 tables, published in JCAP. It is a companion
to Moresco et al. (2012b, http://arxiv.org/abs/1201.6658) and Jimenez et al.
(2012, http://arxiv.org/abs/1201.3608). The H(z) data can be downloaded at
http://www.physics-astronomy.unibo.it/en/research/areas/astrophysics/cosmology-with-cosmic-chronometer
Community of Practice of Promotoras de Salud to address health inequities during and beyond the COVID-19 pandemic
Using principles of Community-Based Participatory Research, we describe a community of practice for community health workers and promotoras (CHW/Ps) to address COVID-19 inequities in the Latinx community. We offer a concrete example of how programs can engage CHW/Ps as full partners in the research process, and how programs can support CHW/Psâ capacity and workforce development during implementation. We conducted four focus groups with CHW/Ps (nâ=â31) to understand needs and invited 15 participants to the community of practice to work on issues identified by the group. We examined impact according to number of community members reached, types of outreach activities, surveys, and online views of educational materials. Process evaluation involved two focus groups with seven organizations and a Ripple Effects Mapping session with the CHW/Ps. Our community of practice has built CHW/Psâ capacity via 31 workshop and co-created culturally and linguistically relevant COVID-19 materials that have reached over 40,000 community members and over 3 million people online. The community of practice proved effective in supporting CHW/Ps to address COVID-19 inequities in the Latinx community. Our evaluations demonstrated benefits for community-academic partnerships, for CHW/Ps, and for the community. This model represents an innovative workforce training model to address health inequities and can be applied to other health topics
Improving the practicality of using non-aversive handling methods to reduce background stress and anxiety in laboratory mice
Handling can stimulate stress and anxiety in laboratory animals that negatively impacts welfare
and introduces a confounding factor in many areas of research. Picking up mice by the tail is a major
source of handling stress that results in strong aversion to the handler, while mice familiarised with
being picked up in a tunnel or cupped on the open hand show low stress and anxiety, and actively seek
interaction with their handlers. Here we investigate the duration and frequency of handling required for
effective familiarisation with these non-aversive handling methods, and test whether this is sufficient
to prevent aversion and anxiety when animals then experience immobilisation and a mild procedure
(subcutaneous injection). Very brief handling (2 s) was sufficient to familiarise mice with tunnel
handling, even when experienced only during cage cleaning. Brief but more frequent handling was
needed for familiarisation with cup handling, while pick up by tail induced strong aversion even when
handling was brief and infrequent. Experience of repeated immobilisation and subcutaneous injection
did not reverse the positive effects of tunnel handling. Our findings demonstrate that replacing tail with
tunnel handling during routine cage cleaning and procedures provides a major refinement with little if
any cost for familiarisation
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