635 research outputs found
Moving black holes via singularity excision
We present a singularity excision algorithm appropriate for numerical
simulations of black holes moving throughout the computational domain. The
method is an extension of the excision procedure previously used to obtain
stable simulations of single, non-moving black holes. The excision procedure
also shares elements used in recent work to study the dynamics of a scalarfield
in the background of a single, boosted black hole. The robustness of our
excision method is tested with single black-hole evolutions using a coordinate
system in which the coordinate location of the black hole, and thus the
excision boundary, moves throughout the computational domain.Comment: 9 pages and 11 figure
A FUSE Survey of Interstellar Molecular Hydrogen in the Small and Large Magellanic Clouds
We describe a moderate-resolution FUSE survey of H2 along 70 sight lines to
the Small and Large Magellanic Clouds, using hot stars as background sources.
FUSE spectra of 67% of observed Magellanic Cloud sources (52% of LMC and 92% of
SMC) exhibit absorption lines from the H2 Lyman and Werner bands between 912
and 1120 A. Our survey is sensitive to N(H2) >= 10^14 cm^-2; the highest column
densities are log N(H2) = 19.9 in the LMC and 20.6 in the SMC. We find reduced
H2 abundances in the Magellanic Clouds relative to the Milky Way, with average
molecular fractions = 0.010 (+0.005, -0.002) for the SMC and =
0.012 (+0.006, -0.003) for the LMC, compared with = 0.095 for the
Galactic disk over a similar range of reddening. The dominant uncertainty in
this measurement results from the systematic differences between 21 cm radio
emission and Lya in pencil-beam sight lines as measures of N(HI). These results
imply that the diffuse H2 masses of the LMC and SMC are 8 x 10^6 Msun and 2 x
10^6 Msun, respectively, 2% and 0.5% of the H I masses derived from 21 cm
emission measurements. The LMC and SMC abundance patterns can be reproduced in
ensembles of model clouds with a reduced H2 formation rate coefficient, R ~ 3 x
10^-18 cm^3 s^-1, and incident radiation fields ranging from 10 - 100 times the
Galactic mean value. We find that these high-radiation, low-formation-rate
models can also explain the enhanced N(4)/N(2) and N(5)/N(3) rotational
excitation ratios in the Clouds. We use H2 column densities in low rotational
states (J = 0 and 1) to derive a mean kinetic and/or rotational temperature
= 82 +/- 21 K for clouds with N(H2) >= 10^16 cm^-2, similar to Galactic
gas. We discuss the implications of this work for theories of star formation in
low-metallicity environments. [Abstract abridged]Comment: 30 pages emulateapj, 14 figures (7 color), 7 tables, accepted for
publication in the Astrophysical Journal, figures 11 and 12 compressed at
slight loss of quality, see http://casa.colorado.edu/~tumlinso/h2/ for full
version
The Time-Domain Spectroscopic Survey: Understanding the Optically Variable Sky with SEQUELS in SDSS-III
The Time-Domain Spectroscopic Survey (TDSS) is an SDSS-IV eBOSS subproject
primarily aimed at obtaining identification spectra of ~220,000
optically-variable objects systematically selected from SDSS/Pan-STARRS1
multi-epoch imaging. We present a preview of the science enabled by TDSS, based
on TDSS spectra taken over ~320 deg^2 of sky as part of the SEQUELS survey in
SDSS-III, which is in part a pilot survey for eBOSS in SDSS-IV. Using the
15,746 TDSS-selected single-epoch spectra of photometrically variable objects
in SEQUELS, we determine the demographics of our variability-selected sample,
and investigate the unique spectral characteristics inherent in samples
selected by variability. We show that variability-based selection of quasars
complements color-based selection by selecting additional redder quasars, and
mitigates redshift biases to produce a smooth quasar redshift distribution over
a wide range of redshifts. The resulting quasar sample contains systematically
higher fractions of blazars and broad absorption line quasars than from
color-selected samples. Similarly, we show that M-dwarfs in the TDSS-selected
stellar sample have systematically higher chromospheric active fractions than
the underlying M-dwarf population, based on their H-alpha emission. TDSS also
contains a large number of RR Lyrae and eclipsing binary stars with
main-sequence colors, including a few composite-spectrum binaries. Finally, our
visual inspection of TDSS spectra uncovers a significant number of peculiar
spectra, and we highlight a few cases of these interesting objects. With a
factor of ~15 more spectra, the main TDSS survey in SDSS-IV will leverage the
lessons learned from these early results for a variety of time-domain science
applications.Comment: 17 pages, 14 figures, submitted to Ap
Comparison of patient comprehension of rapid HIV pre-test fundamentals by information delivery format in an emergency department setting
<p>Abstract</p> <p>Background</p> <p>Two trials were conducted to compare emergency department patient comprehension of rapid HIV pre-test information using different methods to deliver this information.</p> <p>Methods</p> <p>Patients were enrolled for these two trials at a US emergency department between February 2005 and January 2006. In Trial One, patients were randomized to a no pre-test information or an in-person discussion arm. In Trial Two, a separate group of patients were randomized to an in-person discussion arm or a Tablet PC-based video arm. The video, "Do you know about rapid HIV testing?", and the in-person discussion contained identical Centers for Disease Control and Prevention-suggested pre-test information components as well as information on rapid HIV testing with OraQuick<sup>®</sup>. Participants were compared by information arm on their comprehension of the pre-test information by their score on a 26-item questionnaire using the Wilcoxon rank-sum test.</p> <p>Results</p> <p>In Trial One, 38 patients completed the no-information arm and 31 completed the in-person discussion arm. Of these 69 patients, 63.8% had twelve years or fewer of formal education and 66.7% had previously been tested for HIV. The mean score on the questionnaire for the in-person discussion arm was higher than for the no information arm (18.7 vs. 13.3, p ≤ 0.0001). In Trial Two, 59 patients completed the in-person discussion and 55 completed the video arms. Of these 114 patients, 50.9% had twelve years or fewer of formal education and 68.4% had previously been tested for HIV. The mean score on the questionnaire for the video arm was similar to the in-person discussion arm (20.0 vs. 19.2; p ≤ 0.33).</p> <p>Conclusion</p> <p>The video "Do you know about rapid HIV testing?" appears to be an acceptable substitute for an in-person pre-test discussion on rapid HIV testing with OraQuick<sup>®</sup>. In terms of adequately informing ED patients about rapid HIV testing, either form of pre-test information is preferable than for patients to receive no pre-test information.</p
Puromycin-sensitive aminopeptidase protects against aggregation-prone proteins via autophagy
A major function of proteasomes and macroautophagy is to eliminate misfolded potentially toxic proteins. Mammalian proteasomes, however, cannot cleave polyglutamine (polyQ) sequences and seem to release polyQ-rich peptides. Puromycin-sensitive aminopeptidase (PSA) is the only cytosolic enzyme able to digest polyQ sequences. We tested whether PSA can protect against accumulation of polyQ fragments. In cultured cells, Drosophila and mouse muscles, PSA inhibition or knockdown increased aggregate content and toxicity of polyQ-expanded huntingtin exon 1. Conversely, PSA overexpression decreased aggregate content and toxicity. PSA inhibition also increased the levels of polyQ-expanded ataxin-3 as well as mutant α-synuclein and superoxide dismutase 1. These protective effects result from an unexpected ability of PSA to enhance macroautophagy. PSA overexpression increased, and PSA knockdown or inhibition reduced microtubule-associated protein 1 light chain 3-II (LC3-II) levels and the amount of protein degradation sensitive to inhibitors of lysosomal function and autophagy. Thus, by promoting autophagic protein clearance, PSA helps protect against accumulation of aggregation-prone proteins and proteotoxicity
PRIMUS: Enhanced Specific Star Formation Rates In Close Galaxy Pairs
Tidal interactions between galaxies can trigger star formation, which
contributes to the global star formation rate density of the universe and could
be a factor in the transformation of blue, star-forming galaxies to red,
quiescent galaxies over cosmic time. We investigate tidally-triggered star
formation in isolated close galaxy pairs drawn from the Prism Multi-Object
Survey (PRIMUS), a low-dispersion prism redshift survey that has measured
~120,000 robust galaxy redshifts over 9.1 deg^2 out to z ~ 1. We select a
sample of galaxies in isolated galaxy pairs at redshifts 0.25 < z < 0.75, with
no other objects within a projected separation of 300 h^-1 kpc and dz/(1+z) =
0.01, and compare them to a control sample of isolated galaxies to test for
systematic differences in their rest-frame FUV-r and NUV-r colors as a proxy
for relative specific SFR. We find that galaxies in r_p < 50 h^-1 kpc pairs
have bluer dust-corrected UV-r colors on average than the control galaxies by
-0.134 +/- 0.045 magnitudes in FUV-r and -0.075 +/- 0.038 magnitudes in NUV-r,
corresponding to a ~15-20% increase in SSFR. This indicates an enhancement in
SSFR due to tidal interactions. We also find that this relative enhancement is
greater for a subset of r_p < 30 h^-1 kpc pair galaxies, for which the average
colors offsets are -0.193 +/- 0.065 magnitudes in FUV-r and -0.159 +/- 0.048
magnitudes in NUV-r, corresponding to a ~25-30% increase in SSFR. We test for
evolution in the enhancement of tidally-triggered star formation with redshift
across our sample redshift range and find marginal evidence for a decrease in
SSFR enhancement from 0.25 < z < 0.5 to 0.5 < z < 0.75. This indicates that a
change in enhanced star formation triggered by tidal interactions in low
density environments is not a contributor to the decline in the global star
formation rate density across this redshift range.Comment: Accepted for publication in ApJ, emulateapj format, 12 pages, 9
figures, 2 table
Validation of Aura Microwave Limb Sounder OH measurements with Fourier Transform Ultra-Violet Spectrometer total OH column measurements at Table Mountain, California
The Access Technology Program of the Indiana Clinical Translational Sciences Institute (CTSI): A model to facilitate access to cutting-edge technologies across a state
Introduction:
Access to cutting-edge technologies is essential for investigators to advance translational research. The Indiana Clinical and Translational Sciences Institute (CTSI) spans three major and preeminent universities, four large academic campuses across the state of Indiana, and is mandate to provide best practices to a whole state.
Methods:
To address the need to facilitate the availability of innovative technologies to its investigators, the Indiana CTSI implemented the Access Technology Program (ATP). The activities of the ATP, or any program of the Indiana CTSI, are challenged to connect technologies and investigators on the multiple Indiana CTSI campuses by the geographical distances between campuses (1–4 hr driving time).
Results:
Herein, we describe the initiatives developed by the ATP to increase the availability of state-of-the-art technologies to its investigators on all Indiana CTSI campuses, and the methods developed by the ATP to bridge the distance between campuses, technologies, and investigators for the advancement of clinical translational research.
Conclusions:
The methods and practices described in this publication may inform other approaches to enhance translational research, dissemination, and usage of innovative technologies by translational investigators, especially when distance or multi-campus cultural differences are factors to efficient application
Sustained evaluation of the effectiveness of detector dogs for locating brown tree snakes in cargo outbound from Guam
The Far Ultraviolet Spectroscopic Explorer Survey of OVI Absorption in the Disk of the Milky Way
To probe the distribution and physical characteristics of interstellar gas at
temperatures T ~ 3e5 K in the disk of the Milky Way, we have used the Far
Ultraviolet Spectroscopic Explorer (FUSE) to observe absorption lines of OVI
toward 148 early-type stars situated at distances 1 kpc. After subtracting off
a mild excess of OVI arising from the Local Bubble, combining our new results
with earlier surveys of OVI, and eliminating stars that show conspicuous
localized X-ray emission, we find an average OVI mid-plane density n_0 = 1.3e-8
cm^-3. The density decreases away from the plane of the Galaxy in a way that is
consistent with an exponential scale height of 3.2 kpc at negative latitudes or
4.6 kpc at positive latitudes. Average volume densities of OVI along different
sight lines exhibit a dispersion of about 0.26 dex, irrespective of the
distances to the target stars. This indicates that OVI does not arise in
randomly situated clouds of a fixed size and density, but instead is
distributed in regions that have a very broad range of column densities, with
the more strongly absorbing clouds having a lower space density. Line widths
and centroid velocities are much larger than those expected from differential
Galactic rotation, but they are nevertheless correlated with distance and
N(OVI), which reinforces our picture of a diverse population of hot plasma
regions that are ubiquitous over the entire Galactic disk. The velocity
extremes of the OVI profiles show a loose correlation with those of very strong
lines of less ionized species, supporting a picture of a turbulent, multiphase
medium churned by shock-heated gas from multiple supernova explosions.Comment: Accepted for publication in ApJS. Preprint with full resolution
images and all 148 spectra available at
http://www.astro.princeton.edu/~dvb/o
- …