622 research outputs found
Historical Statistics of the United States Chapter on Voluntary, Nonprofit, and Religious Entities and Activities: Underlying Concepts, Concerns, and Opportunities
This paper is a draft of the introduction to the chapter on voluntary, nonprofit, and religious entities and activities slated to appear in the Millennial Edition of Historical Statistics of the United States (forthcoming, Cambridge University Press). Conceding the various problematic definitions of the "nonprofit sector," the essay offers a rationale for the broadly inclusive approach to the selection of historical statistics of institutions and activities presented in the chapter. In addition, it reviews the challenges and opportunities for researchers working on the statistical aspects of nonprofit, voluntary, and religious organizations. The essay includes samples of the statistical series that will appear in HSUS.This publication is Hauser Center Working Paper No. 14. The Hauser Center Working Paper Series was launched during the summer of 2000. The Series enables the Hauser Center to share with a broad audience important works-in-progress written by Hauser Center scholars and researchers
The variational slope of quasar light curves is not a distance indicator
When the time difference quotients, or \emph{variational slopes}, of quasar
light curves are plotted against their absolute magnitudes, there is a tight
positive correlation of dex in the variational slope direction or
dex in the absolute magnitude direction. This finding resulted in
suggestions that a variational slope -- luminosity relation could be used as a
distance indicator. However, I show that this relation can be explained almost
entirely from self-correlation with luminosity. After properly accounting for
the self-correlation component, the relation has a true scatter of
dex in luminosity, consistent with established correlations for quasar
variability amplitudes. Given this large scatter, correlation with variational
slope or variability amplitude and luminosity is not by itself a suitable
distance indicator for quasars.Comment: 3 pages, 1 figure. Accepted for publication in MNRA
Giant Cell Tumor of Bone: Documented Progression over 4 Years from Its Origin at the Metaphysis to the Articular Surface.
The exact location of origin for giant cell tumors of bone (GCTB) remains controversial, as lesions are not routinely imaged early but rather late when the tumor is large and clinically symptomatic. At the time of diagnosis, GCTB are classically described as lucent, eccentric lesions with nonsclerotic margins, located within the epiphysis to a greater extent than the metaphysis. Here we present a case of a biopsy proven GCTB initially incidentally seen on MRI as a small strictly metaphyseal lesion, which over the course of several years expanded across a closed physis to involve the epiphysis and abut the articular surface/subchondral bone plate
Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O battery capacity
Among the 'beyond Li-ion' battery chemistries, nonaqueous Li-O batteries
have the highest theoretical specific energy and as a result have attracted
significant research attention over the past decade. A critical scientific
challenge facing nonaqueous Li-O batteries is the electronically insulating
nature of the primary discharge product, lithium peroxide, which passivates the
battery cathode as it is formed, leading to low ultimate cell capacities.
Recently, strategies to enhance solubility to circumvent this issue have been
reported, but rely upon electrolyte formulations that further decrease the
overall electrochemical stability of the system, thereby deleteriously
affecting battery rechargeability. In this study, we report that a significant
enhancement (greater than four-fold) in Li-O cell capacity is possible by
appropriately selecting the salt anion in the electrolyte solution. Using
Li nuclear magnetic resonance and modeling, we confirm that this
improvement is a result of enhanced Li stability in solution, which in turn
induces solubility of the intermediate to LiO formation. Using this
strategy, the challenging task of identifying an electrolyte solvent that
possesses the anti-correlated properties of high intermediate solubility and
solvent stability is alleviated, potentially providing a pathway to develop an
electrolyte that affords both high capacity and rechargeability. We believe the
model and strategy presented here will be generally useful to enhance Coulombic
efficiency in many electrochemical systems (e.g. Li-S batteries) where
improving intermediate stability in solution could induce desired mechanisms of
product formation.Comment: 22 pages, 5 figures and Supporting Informatio
PhoSim-NIRCam: Photon-by-photon image simulations of the James Webb Space Telescope's Near-Infrared Camera
Recent instrumentation projects have allocated resources to develop codes for
simulating astronomical images. Novel physics-based models are essential for
understanding telescope, instrument, and environmental systematics in
observations. A deep understanding of these systematics is especially important
in the context of weak gravitational lensing, galaxy morphology, and other
sensitive measurements. In this work, we present an adaptation of a
physics-based ab initio image simulator: The Photon Simulator (PhoSim). We
modify PhoSim for use with the Near-Infrared Camera (NIRCam) -- the primary
imaging instrument aboard the James Webb Space Telescope (JWST). This photon
Monte Carlo code replicates the observational catalog, telescope and camera
optics, detector physics, and readout modes/electronics. Importantly,
PhoSim-NIRCam simulates both geometric aberration and diffraction across the
field of view. Full field- and wavelength-dependent point spread functions are
presented. Simulated images of an extragalactic field are presented. Extensive
validation is planned during in-orbit commissioning
The Curious Case of PHL 293B : a long-lived transient in a Metal-poor Blue Compact Dwarf Galaxy
We report on small-amplitude optical variability and recent dissipation of the unusually persistent broad emission lines in the blue compact dwarf galaxy PHL 293B. The galaxy's unusual spectral features (P Cygni-like profiles with ~800 km s−1 blueshifted absorption lines) have resulted in conflicting interpretations of the nature of this source in the literature. However, analysis of new Gemini spectroscopy reveals the broad emission has begun to fade after being persistent for over a decade prior. Precise difference imaging light curves constructed with the Sloan Digital Sky Survey and the Dark Energy Survey reveal small-amplitude optical variability of ~0.1 mag in the g band offset by 100 ± 21 pc from the brightest pixel of the host. The light curve is well-described by an active galactic nuclei (AGN)-like damped random walk process. However, we conclude that the origin of the optical variability and spectral features of PHL 293B is due to a long-lived stellar transient, likely a Type IIn supernova or nonterminal outburst, mimicking long-term AGN-like variability. This work highlights the challenges of discriminating between scenarios in such extreme environments, relevant to searches for AGNs in dwarf galaxies. This is the second long-lived transient discovered in a blue compact dwarf, after SDSS1133. Our result implies such long-lived stellar transients may be more common in metal-deficient galaxies. Systematic searches for low-level variability in dwarf galaxies will be possible with the upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory
The effect of music on tibial accelerations in recreationally active runners
The purpose of this study was to examine the effects of music on the peak tibial acceleration (PTA) and loading rate (LR) during running, along with other secondary physiological stresses. Thirty college-aged recreationally active subjects completed one continuous 30-minute treadmill bout at a self-selected intensity, with 15 minutes spent listening to music. The music order was counterbalanced. PTA, LR, heart rate (HR), rating of perceived exertion (RPE), and feeling score (FS) were assessed every 3 minutes. Salivary cortisol was assessed before, during, and post-exercise. There was no difference between music and no music conditions for PTA, LR, HR, RPE, or cortisol (p>0.05). FS was significantly greater when listening to music (p<0.005), indicating more enjoyment. In conclusion, listening to music increases feelings of wellbeing but is not enough of a distracting stimulus to alter the biomechanics or physiological stress of running, indicating no heightened risk of injury.Master of Art
Dwarf AGNs from Variability for the Origins of Seeds (DAVOS): Optical Variability of Broad-line Dwarf AGNs from the Zwicky Transient Facility
We study the optical variability of a sample of candidate low-mass (dwarf ang
Seyfert) active galactic nuclei (AGNs) using Zwicky Transient Facility g-band
light curves. Our sample is compiled from broad-line AGNs in dwarf galaxies
reported in the literature with single-epoch virial black hole (BH) masses in
the range --. We measure the
characteristic ``damping'' timescale of the optical variability
, beyond which the power spectral density flattens, of a final
sample of 79 candidate low-mass AGNs with high-quality light curves. Our
results provide further confirmation of the
relation from Burke et al. 2022 within agreement, adding 78 new
low-mass AGNs to the relation. The agreement suggests that the virial BH mass
estimates for these AGNs are generally reasonable. We expect that the optical
light curve of an accreting intermediate-mass black hole (IMBH) to vary with a
rest-frame damping timescale of tens of hours, which could enable
detection and direct mass estimation of accreting IMBHs in wide-field
time-domain imaging surveys with sufficient cadence like with the Vera C. Rubin
Observatory.Comment: 9 pages plus 6 appendix, 7 figure
The curious case of PHL 293B: a long-lived transient in a metal-poor blue compact dwarf galaxy
ArtÃculo escrito por un elevado número de autores, sólo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiereWe report on small-amplitude optical variability and recent dissipation of the unusually persistent broad emission lines in the blue compact dwarf galaxy PHL 293B. The galaxy's unusual spectral features (P Cygni-like profiles with ∼800 km s-1 blueshifted absorption lines) have resulted in conflicting interpretations of the nature of this source in the literature. However, analysis of new Gemini spectroscopy reveals the broad emission has begun to fade after being persistent for over a decade prior. Precise difference imaging light curves constructed with the Sloan Digital Sky Survey and the Dark Energy Survey reveal small-amplitude optical variability of ∼0.1 mag in the g band offset by 100 21 pc from the brightest pixel of the host. The light curve is well-described by an active galactic nuclei (AGN)-like damped random walk process. However, we conclude that the origin of the optical variability and spectral features of PHL 293B is due to a long-lived stellar transient, likely a Type IIn supernova or nonterminal outburst, mimicking long-term AGN-like variability. This work highlights the challenges of discriminating between scenarios in such extreme environments, relevant to searches for AGNs in dwarf galaxies. This is the second long-lived transient discovered in a blue compact dwarf, after SDSS1133. Our result implies such long-lived stellar transients may be more common in metal-deficient galaxies. Systematic searches for low-level variability in dwarf galaxies will be possible with the upcoming Legacy Survey of Space and Time at the Vera C. Rubin ObservatoryThe DES data management system is supported by the National Science Foundation under grant Nos. AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV2016-0588, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007–2013) including ERC grant agreements 240672, 291329, and 30647
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