372 research outputs found
The Unity of Word: Language in C.S. Lewis\u27 Trilogy
Discusses the theme of language in the Ransom trilogy. Notes Barfieldâs theories of language and Lewisâs apparent agreement with them
The Antioxidant Moiety of MitoQ Imparts Minimal Metabolic Effects in Adipose Tissue of High Fat Fed Mice
Mitochondrial dysfunction is associated with a diverse array of diseases ranging from dystrophy and heart failure to obesity and hepatosteatosis. One of the major biochemical consequences of impaired mitochondrial function is an accumulation of mitochondrial superoxide, or reactive oxygen species (ROS). Excessive ROS can be detrimental to cellular health and is proposed to underpin many mitochondrial diseases. Accordingly, much research has been committed to understanding ways to therapeutically prevent and reduce ROS accumulation. In white adipose tissue (WAT), ROS is associated with obesity and its subsequent complications, and thus reducing mitochondrial ROS may represent a novel strategy for treating obesity related disorders. One therapeutic approach employed to reduce ROS abundance is the mitochondrial-targeted coenzyme Q (MitoQ), which enables mitochondrial specific delivery of a CoQ10 antioxidant via its triphenylphosphonium bromide (TPP+) cation. Indeed, MitoQ has been successfully shown to accumulate at the outer mitochondrial membrane and prevent ROS accumulation in several tissues in vivo; however, the specific effects of MitoQ on adipose tissue metabolism in vivo have not been studied. Here we demonstrate that mice fed high-fat diet with concomitant administration of MitoQ, exhibit minimal metabolic benefit in adipose tissue. We also demonstrate that both MitoQ and its control agent dTPP+ had significant and equivalent effects on whole-body metabolism, suggesting that the dTPP+ cation rather than the antioxidant moiety, was responsible for these changes. These findings have important implications for future studies using MitoQ and other TPP+ compounds
Applying the Risk of Bias Tool in a Systematic Review of Combination Long-Acting Beta-Agonists and Inhaled Corticosteroids for Persistent Asthma
Background: The Risk of Bias (RoB) tool is used to assess internal validity of randomized controlled trials (RCTs). Our objectives were to: 1) evaluate inter-rater agreement of the RoB tool; 2) determine the time to access supplemental study information; 3) compare the RoB tool with the Jadad scale and Schulz allocation concealment (AC); and 4) examine the relationship between RoB and effect estimates. Methods: We conducted a systematic review of long-acting beta agonists (LABA) combined with inhaled corticosteroids (ICS) for adults with persistent asthma. Two reviewers independently assessed 107 trials using RoB, Jadad, and AC. One reviewer searched for study protocols. We assessed inter-rater agreement using weighted Kappa (k) and the correlation between tools using Kendallâs Tau (t). Mean differences in effect sizes for RCTs with different RoB were calculated using inverse variance method and random effects model. Results: Trials had good Jadad scores (median 4, IQR 3-4); however, 85 % had unclear AC and 87 % high RoB. The factor that most influenced RoB was the potential inappropriate influence of study sponsors (95 % industry funded). Agreement on RoB domains was fair (k = 0.40) to almost perfect (k = 0.86), and moderate for overall RoB (k = 0.41). Median time to complete RoB assessments was 21 minutes (IQR 14-27) and 12 minutes (IQR 9-16) to search for protocols. Protocols were identified for 5/42 studies (12%); in 3 cases the assessment of selective outcome reporting changed. There was low correlation between overall RoB vs. Jadad (t =0.04
UVUDF: Ultraviolet Imaging of the Hubble Ultradeep Field with Wide-field Camera 3
We present an overview of a 90-orbit Hubble Space Telescope treasury program
to obtain near ultraviolet imaging of the Hubble Ultra Deep Field using the
Wide Field Camera 3 UVIS detector with the F225W, F275W, and F336W filters.
This survey is designed to: (i) Investigate the episode of peak star formation
activity in galaxies at 1<z<2.5; (ii) Probe the evolution of massive galaxies
by resolving sub-galactic units (clumps); (iii) Examine the escape fraction of
ionizing radiation from galaxies at z~2-3; (iv) Greatly improve the reliability
of photometric redshift estimates; and (v) Measure the star formation rate
efficiency of neutral atomic-dominated hydrogen gas at z~1-3. In this overview
paper, we describe the survey details and data reduction challenges, including
both the necessity of specialized calibrations and the effects of charge
transfer inefficiency. We provide a stark demonstration of the effects of
charge transfer inefficiency on resultant data products, which when
uncorrected, result in uncertain photometry, elongation of morphology in the
readout direction, and loss of faint sources far from the readout. We agree
with the STScI recommendation that future UVIS observations that require very
sensitive measurements use the instrument's capability to add background light
through a "post-flash". Preliminary results on number counts of UV-selected
galaxies and morphology of galaxies at z~1 are presented. We find that the
number density of UV dropouts at redshifts 1.7, 2.1, and 2.7 is largely
consistent with the number predicted by published luminosity functions. We also
confirm that the image mosaics have sufficient sensitivity and resolution to
support the analysis of the evolution of star-forming clumps, reaching 28-29th
magnitude depth at 5 sigma in a 0.2 arcsecond radius aperture depending on
filter and observing epoch.Comment: Accepted A
A Detailed Observational Analysis of V1324 Sco, the Most Gamma-Ray Luminous Classical Nova to Date
It has recently been discovered that some, if not all, classical novae emit
GeV gamma rays during outburst, but the mechanisms involved in the production
of the gamma rays are still not well understood. We present here a
comprehensive multi-wavelength dataset---from radio to X-rays---for the most
gamma-ray luminous classical nova to-date, V1324 Sco. Using this dataset, we
show that V1324 Sco is a canonical dusty Fe-II type nova, with a maximum ejecta
velocity of 2600 km s and an ejecta mass of few
M. There is also evidence for complex shock interactions, including a
double-peaked radio light curve which shows high brightness temperatures at
early times. To explore why V1324~Sco was so gamma-ray luminous, we present a
model of the nova ejecta featuring strong internal shocks, and find that higher
gamma-ray luminosities result from higher ejecta velocities and/or mass-loss
rates. Comparison of V1324~Sco with other gamma-ray detected novae does not
show clear signatures of either, and we conclude that a larger sample of
similarly well-observed novae is needed to understand the origin and variation
of gamma rays in novae.Comment: 26 pages, 13 figure
CMB observations from the CBI and VSA: A comparison of coincident maps and parameter estimation methods
We present coincident observations of the Cosmic Microwave Background (CMB)
from the Very Small Array (VSA) and Cosmic Background Imager (CBI) telescopes.
The consistency of the full datasets is tested in the map plane and the Fourier
plane, prior to the usual compression of CMB data into flat bandpowers. Of the
three mosaics observed by each group, two are found to be in excellent
agreement. In the third mosaic, there is a 2 sigma discrepancy between the
correlation of the data and the level expected from Monte Carlo simulations.
This is shown to be consistent with increased phase calibration errors on VSA
data during summer observations. We also consider the parameter estimation
method of each group. The key difference is the use of the variance window
function in place of the bandpower window function, an approximation used by
the VSA group. A re-evaluation of the VSA parameter estimates, using bandpower
windows, shows that the two methods yield consistent results.Comment: 10 pages, 6 figures. Final version. Accepted for publication in MNRA
Formation and Evolution of the Disk System of the Milky Way: [alpha/Fe] Ratios and Kinematics of the SEGUE G-Dwarf Sample
We employ measurements of the [alpha/Fe] ratio derived from low-resolution
(R~2000) spectra of 17,277 G-type dwarfs from the SEGUE survey to separate them
into likely thin- and thick-disk subsamples. Both subsamples exhibit strong
gradients of orbital rotational velocity with metallicity, of opposite signs,
-20 to -30 km/s/dex for the thin-disk and +40 to +50 km/s/dex for the
thick-disk population. The rotational velocity is uncorrelated with
Galactocentric distance for the thin-disk subsample, and exhibits a small trend
for the thick-disk subsample. The rotational velocity decreases with distance
from the plane for both disk components, with similar slopes (-9.0 {\pm} 1.0
km/s/kpc). Thick-disk stars exhibit a strong trend of orbital eccentricity with
metallicity (about -0.2/dex), while the eccentricity does not change with
metallicity for the thin-disk subsample. The eccentricity is almost independent
of Galactocentric radius for the thin-disk population, while a marginal
gradient of the eccentricity with radius exists for the thick-disk population.
Both subsamples possess similar positive gradients of eccentricity with
distance from the Galactic plane. The shapes of the eccentricity distributions
for the thin- and thick-disk populations are independent of distance from the
plane, and include no significant numbers of stars with eccentricity above 0.6.
Among several contemporary models of disk evolution we consider, radial
migration appears to have played an important role in the evolution of the
thin-disk population, but possibly less so for the thick disk, relative to the
gas-rich merger or disk heating scenarios. We emphasize that more physically
realistic models and simulations need to be constructed in order to carry out
the detailed quantitative comparisons that our new data enable.Comment: Accepted for publication in ApJ, 18 pages, 12 figures, 2 tables,
emulateapj forma
The Case for the Dual Halo of the Milky Way
Carollo et al. have recently resolved the stellar population of the Milky Way
halo into at least two distinct components, an inner halo and an outer halo.
This result has been criticized by Schoenrich et al., who claim that the
retrograde signature associated with the outer halo is due to the adoption of
faulty distances. We refute this claim, and demonstrate that the Schoenrich et
al. photometric distances are themselves flawed because they adopted an
incorrect main-sequence absolute magnitude relationship from the work of
Ivezi\'c et al. When compared to the recommended relation from Ivezi\'c et al.,
which is tied to a Milky Way globular cluster distance scale and accounts for
age and metallicity effects, the relation adopted by Schoenrich et al. yields
up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use
of the correct relationship yields agreement between the distances assigned by
Carollo et al. and Ivezi\'{c} et al. for low-metallicity dwarfs to within
6-10%. Schoenrich et al. also point out that intermediate-gravity stars (3.5 <=
log g <= 4.0) with colors redder than the TO region are likely misclassified,
with which we concur. We implement a new procedure to reassign luminosity
classifications for the TO stars that require it. New derivations of the
rotational behavior demonstrate that the retrograde signature and high velocity
dispersion of the outer-halo population remains. We summarize additional lines
of evidence for a dual halo, including a test of the retrograde signature based
on proper motions alone, and conclude that the preponderance of evidence
strongly rejects the single-halo interpretation.Comment: 46 pages, 2 tables, 15 figures, Accepted for publication in the
Astrophysical Journa
The Milky Way Tomography With SDSS. III. Stellar Kinematics
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r 20 degrees). We find that in the region defined by 1 kpc < Z < 5 kpc and 3 kpc < R < 13 kpc, the rotational velocity for disk stars smoothly decreases, and all three components of the velocity dispersion increase, with distance from the Galactic plane. In contrast, the velocity ellipsoid for halo stars is aligned with a spherical coordinate system and appears to be spatially invariant within the probed volume. The velocity distribution of nearby (Z < 1 kpc) K/M stars is complex, and cannot be described by a standard Schwarzschild ellipsoid. For stars in a distance-limited subsample of stars (< 100 pc), we detect a multi-modal velocity distribution consistent with that seen by HIPPARCOS. This strong non-Gaussianity significantly affects the measurements of the velocity-ellipsoid tilt and vertex deviation when using the Schwarzschild approximation. We develop and test a simple descriptive model for the overall kinematic behavior that captures these features over most of the probed volume, and can be used to search for substructure in kinematic and metallicity space. We use this model to predict further improvements in kinematic mapping of the Galaxy expected from Gaia and the Large Synoptic Survey Telescope.NSF AST-615991, AST-0707901, AST-0551161, AST-02-38683, AST-06-07634, AST-0807444, PHY05-51164NASA NAG5-13057, NAG5-13147, NNXO-8AH83GPhysics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA) PHY 08-22648U.S. National Science FoundationMarie Curie Research Training Network ELSA (European Leadership in Space Astrometry) MRTN-CT-2006-033481Fermi Research Alliance, LLC, United States Department of Energy DE-AC02-07CH11359Alfred P. Sloan FoundationParticipating InstitutionsJapanese MonbukagakushoMax Planck SocietyHigher Education Funding Council for EnglandMcDonald Observator
The Atacama Cosmology Telescope: Two-Season ACTPol Lensing Power Spectrum
We report a measurement of the power spectrum of cosmic microwave background
(CMB) lensing from two seasons of Atacama Cosmology Telescope Polarimeter
(ACTPol) CMB data. The CMB lensing power spectrum is extracted from both
temperature and polarization data using quadratic estimators. We obtain results
that are consistent with the expectation from the best-fit Planck LCDM model
over a range of multipoles L=80-2100, with an amplitude of lensing A_lens =
1.06 +/- 0.15 (stat.) +/- 0.06 (sys.) relative to Planck. Our measurement of
the CMB lensing power spectrum gives sigma_8 Omega_m^0.25 = 0.643 +/- 0.054;
including baryon acoustic oscillation scale data, we constrain the amplitude of
density fluctuations to be sigma_8 = 0.831 +/- 0.053. We also update
constraints on the neutrino mass sum. We verify our lensing measurement with a
number of null tests and systematic checks, finding no evidence of significant
systematic errors. This measurement relies on a small fraction of the ACTPol
data already taken; more precise lensing results can therefore be expected from
the full ACTPol dataset.Comment: 17 pages, 11 figures, to be submitted to Physical Review
- âŠ