303 research outputs found
The X-ray Spectrum and Spectral Energy Distribution of FIRST J155633.8+351758: a LoBAL Quasar with a Probable Polar Outflow
We report the results of a new 60 ks Chandra X-ray Observatory Advanced CCD
Imaging Spectrometer S-array (ACIS-S) observation of the reddened,
radio-selected, highly polarized `FeLoBAL' quasar FIRST J1556+3517. We
investigated a number of models of varied sophistication to fit the 531-photon
spectrum. These models ranged from simple power laws to power laws absorbed by
hydrogen gas in differing ionization states and degrees of partial covering.
Preferred fits indicate that the intrinsic X-ray flux is consistent with that
expected for quasars of similarly high luminosity, i.e., an intrinsic,
dereddened and unabsorbed optical to X-ray spectral index of -1.7. We cannot
tightly constrain the intrinsic X-ray power-law slope, but find indications
that it is flat (photon index Gamma = 1.7 or flatter at a >99% confidence for a
neutral hydrogen absorber model). Absorption is present, with a column density
a few times 10^23 cm^-2, with both partially ionized models and partially
covering neutral hydrogen models providing good fits. We present several lines
of argument that suggest the fraction of X-ray emissions associated with the
radio jet is not large.
We combine our Chandra data with observations from the literature to
construct the spectral energy distribution of FIRST J1556+3517 from radio to
X-ray energies. We make corrections for Doppler beaming for the pole-on radio
jet, optical dust reddening, and X-ray absorption, in order to recover a
probable intrinsic spectrum. The quasar FIRST J1556+3517 seems to be an
intrinsically normal radio-quiet quasar with a reddened optical/UV spectrum, a
Doppler-boosted but intrinsically weak radio jet, and an X-ray absorber not
dissimilar from that of other broad absorption line quasars.Comment: to be published in MNRA
Effects of Genetic Captive-Breeding Protocols on Sperm Quality and Fertility in the White-Footed Mouse
P. 540â548Mice (Peromyscus leucopus noveboracensis) from a captive-breeding program were used to test the effects of three genetic breeding protocols (minimizing mean kinship [MK], random breeding, and selection for docility [DOC]) and inbreeding levels on sperm traits and fertility. Earlier, in generation 8, one DOC replicate went extinct because of poor reproductive success. By generation 10, spermatozoa from DOC mice had more acrosome and midpiece abnormalities, which were shown to be strong determinants of fertility, as well as lower sperm production and resistance to osmotic stress. In addition, determinants of fertility, including male and female components, were assessed in a comprehensive manner. Results showed that the probability (P) of siring litters is determined by sperm number, sperm viability, and midpiece and acrosome abnormalities; that the P of siring one versus two litters is determined by tail abnormalities; and that the total number of offspring is influenced by female size and proportion of normal sperm, showing the relative importance of different sperm traits on fertility. On average, males with 20% normal sperm sired one pup per litter, and males with 70% normal sperm sired eight pups per litter. Interestingly, the proportion of normal sperm was affected by docility but not by relatively low inbreeding. However, inbreeding depression in sperm motility was detected. In the MK group, inbreeding depression not only affected sperm motility but also fertility: An increase in the coefficient of inbreeding (f) of 0.03 reduced sperm motility by 30% and translated into an offspring reduction of three pups in second litters. A genetic load of 48 fecundity equivalents was calculated.S
Eight-Dimensional Mid-Infrared/Optical Bayesian Quasar Selection
We explore the multidimensional, multiwavelength selection of quasars from
mid-IR (MIR) plus optical data, specifically from Spitzer-IRAC and the Sloan
Digital Sky Survey (SDSS). We apply modern statistical techniques to combined
Spitzer MIR and SDSS optical data, allowing up to 8-D color selection of
quasars. Using a Bayesian selection method, we catalog 5546 quasar candidates
to an 8.0 um depth of 56 uJy over an area of ~24 sq. deg; ~70% of these
candidates are not identified by applying the same Bayesian algorithm to
4-color SDSS optical data alone. Our selection recovers 97.7% of known type 1
quasars in this area and greatly improves the effectiveness of identifying
3.5<z<5 quasars. Even using only the two shortest wavelength IRAC bandpasses,
it is possible to use our Bayesian techniques to select quasars with 97%
completeness and as little as 10% contamination. This sample has a photometric
redshift accuracy of 93.6% (Delta Z +/-0.3), remaining roughly constant when
the two reddest MIR bands are excluded. While our methods are designed to find
type 1 (unobscured) quasars, as many as 1200 of the objects are type 2
(obscured) quasar candidates. Coupling deep optical imaging data with deep
mid-IR data could enable selection of quasars in significant numbers past the
peak of the quasar luminosity function (QLF) to at least z~4. Such a sample
would constrain the shape of the QLF and enable quasar clustering studies over
the largest range of redshift and luminosity to date, yielding significant
gains in our understanding of quasars and the evolution of galaxies.Comment: 49 pages, 14 figures, 7 tables. AJ, accepte
Evaluating anthropogenic threats to endangered killer whales to inform effective recovery plans
Understanding cumulative effects of multiple threats is key to guiding effective management to conserve endangered species. The critically endangered, Southern Resident killer whale population of the northeastern Pacific Ocean provides a data-rich case to explore anthropogenic threats on population viability. Primary threats include: limitation of preferred prey, Chinook salmon; anthropogenic noise and disturbance, which reduce foraging efficiency; and high levels of stored contaminants, including PCBs. We constructed a population viability analysis to explore possible demographic trajectories and the relative importance of anthropogenic stressors. The population is fragile, with no growth projected under current conditions, and decline expected if new or increased threats are imposed. Improvements in fecundity and calf survival are needed to reach a conservation objective of 2.3% annual population growth. Prey limitation is the most important factor affecting population growth. However, to meet recovery targets through prey management alone, Chinook abundance would have to be sustained near the highest levels since the 1970s. The most optimistic mitigation of noise and contaminants would make the difference between a declining and increasing population, but would be insufficient to reach recovery targets. Reducing acoustic disturbance by 50% combined with increasing Chinook by 15% would allow the population to reach 2.3% growth
The Massive Hosts of Radio Galaxies Across Cosmic Time
We present the results of a comprehensive Spitzer survey of 69 radio galaxies
across 1<z<5.2. Using IRAC (3.6-8.0um), IRS (16um) and MIPS (24-160um) imaging,
we decompose the rest-frame optical to infrared spectral energy distributions
into stellar, AGN, and dust components and determine the contribution of host
galaxy stellar emission at rest-frame H-band. Stellar masses derived from
rest-frame near-IR data, where AGN and young star contributions are minimized,
are significantly more reliable than those derived from rest-frame optical and
UV data. We find that the fraction of emitted light at rest-frame H-band from
stars is >60% for ~75% the high redshift radio galaxies. As expected from
unified models of AGN, the stellar fraction of the rest-frame H-band luminosity
has no correlation with redshift, radio luminosity, or rest-frame mid-IR (5um)
luminosity. Additionally, while the stellar H-band luminosity does not vary
with stellar fraction, the total H-band luminosity anti-correlates with the
stellar fraction as would be expected if the underlying hosts of these radio
galaxies comprise a homogeneous population. The resultant stellar luminosities
imply stellar masses of 10^{11-11.5}Msun even at the highest redshifts.
Powerful radio galaxies tend to lie in a similar region of mid-IR color-color
space as unobscured AGN, despite the stellar contribution to their mid-IR SEDs
at shorter-wavelengths. The mid-IR luminosities alone classify most HzRGs as
LIRGs or ULIRGs with even higher total-IR luminosities. As expected, these
exceptionally high mid-IR luminosities are consistent with an obscured,
highly-accreting AGN. We find a weak correlation of stellar mass with radio
luminosity.Comment: 63 pages, 14 figures, accepted for publication in ApJ
No effect of ascorbate on cutaneous vasodilation and sweating in older men and those with type 2 diabetes exercising in the heat
Aging and chronic disease such as type 2 diabetes (T2D) are associated with impairments in the body\u27s ability to dissipate heat. To reduce the risk of heatârelated injuries in these heat vulnerable individuals, it is necessary to identify interventions that can attenuate this impairment. We evaluated the hypothesis that intradermal administration of ascorbate improves cutaneous vasodilation and sweating in older adults via nitric oxide synthase (NOS)âdependent mechanisms during exercise in the heat and whether these improvements, if any, are greater in individuals with T2D. Older males with (n = 12, 61 ± 9 years) and without (n = 12, 64 ± 7 years) T2D performed two 30âmin bouts of cycling at a fixed rate of metabolic heat production of 500 W (~70% peak oxygen uptake) in the heat (35°C); each followed by a 20â and 40âmin recovery, respectively. Cutaneous vascular conductance (CVC) and sweat rate were measured at four intradermal microdialysis sites treated with either (1) lactated Ringer (Control), (2) 10 mmol/L ascorbate (an antioxidant), (3) 10 mmol/L LâNAME (nonâselective NOS inhibitor), or (4) a combination of ascorbate + LâNAME. In both groups, ascorbate did not modulate CVC or sweating during exercise relative to Control (all P > 0.05). In comparison to Control, LâNAME alone or combined with ascorbate attenuated CVC during exercise (all P †0.05) but had no influence on sweating (all P > 0.05). We show that in both healthy and T2D older adults, intradermal administration of ascorbate does not improve cutaneous vasodilation and sweating during exercise in the heat. However, NOS plays an important role in mediating cutaneous vasodilation
Gene content evolution in the arthropods
Arthropods comprise the largest and most diverse phylum on Earth and play vital roles in nearly every ecosystem. Their diversity stems in part from variations on a conserved body plan, resulting from and recorded in adaptive changes in the genome. Dissection of the genomic record of sequence change enables broad questions regarding genome evolution to be addressed, even across hyper-diverse taxa within arthropods. Using 76 whole genome sequences representing 21 orders spanning more than 500 million years of arthropod evolution, we document changes in gene and protein domain content and provide temporal and phylogenetic context for interpreting these innovations. We identify many novel gene families that arose early in the evolution of arthropods and during the diversification of insects into modern orders. We reveal unexpected variation in patterns of DNA methylation across arthropods and examples of gene family and protein domain evolution coincident with the appearance of notable phenotypic and physiological adaptations such as flight, metamorphosis, sociality, and chemoperception. These analyses demonstrate how large-scale comparative genomics can provide broad new insights into the genotype to phenotype map and generate testable hypotheses about the evolution of animal diversity
High-Redshift Galaxy Outflows and the Formation of Dwarf Galaxies
We examine the effects of galaxy outflows on the formation of dwarf galaxies
in numerical simulations of the high-redshift Universe. Using a Smoothed
Particle Hydrodynamic code, we conduct two detailed simulations of a (5.2
Mpc/h)^3 comoving volume of the Universe. In both simulations we implement
simple, well-motivated models of galaxy identification and star formation,
while our second simulation also includes a simple ``blow-out'' model of galaxy
outflows in which supernova driven winds from newly formed disk galaxies
punch-out and shock the intergalactic medium while leaving the host galaxies
intact. A direct comparison between these simulations suggests that there are
two major mechanisms by which outflows affect dwarf formation. Firstly, the
formation of an outflow slows down the further accretion of gas onto a galaxy,
causing an overall decrease of approximately 50% in the total gas mass accreted
by the objects in our simulations. Additionally, our simulations uncover a
significant population of approximately 10^9 solar mass objects whose formation
is suppressed by the mechanism of ``baryonic stripping,'' in which outflows
from early galaxies strip the gas out of nearby overdense regions that would
have otherwise later formed into dwarf galaxies. This mechanism may be
important in explaining the observed discrepancy between the number of dwarf
galaxies predicted and observed in the local group and provide a natural
explanation for the formation of empty halos which may be required by the
existence of the extremely gas-poor extra-galactic High-Velocity Clouds.Comment: 15 pages, 9 figures, accepted to the Astrophysical Journa
Impacts of urbanisation on the native avifauna of Perth, Western Australia
Urban development either eliminates, or severely fragments, native vegetation, and therefore alters the distribution and abundance of species that depend on it for habitat. We assessed the impact of urban development on bird communities at 121 sites in and around Perth, Western Australia. Based on data from community surveys, at least 83 % of 65 landbirds were found to be dependent, in some way, on the presence of native vegetation. For three groups of species defined by specific patterns of habitat use (bushland birds), there were sufficient data to show that species occurrences declined as the landscape changed from variegated to fragmented to relictual, according to the percentage of vegetation cover remaining. For three other groups (urban birds) species occurrences were either unrelated to the amount of vegetation cover, or increased as vegetation cover declined. In order to maximise the chances of retaining avian diversity when planning for broad-scale changes in land-use (i.e. clearing native vegetation for housing or industrial development), land planners should aim for a mosaic of variegated urban landscapes (\u3e60 % vegetation retention) set amongst the fragmented and relictual urban landscapes (% vegetation retention) that are characteristic of most cities and their suburbs. Management actions for conserving remnant biota within fragmented urban landscapes should concentrate on maintaining the integrity and quality of remnant native vegetation, and aim at building awareness among the general public of the conservation value of remnant native vegetation
Safety and pharmacokinetics of multiple dose myo-inositol in preterm infants
BACKGROUND:
Preterm infants with respiratory distress syndrome (RDS) given inositol had reduced bronchopulmonary dysplasia (BPD), death and severe retinopathy of prematurity (ROP). We assessed the safety and pharmacokinetics of daily inositol to select a dose providing serum levels previously associated with benefit, and to learn if accumulation occurred when administered throughout the normal period of retinal vascularization.
METHODS:
Infants †29âwk GA (n = 122, 14 centers) were randomized and treated with placebo or inositol at 10, 40, or 80âmg/kg/d. Intravenous administration converted to enteral when feedings were established, and continued to the first of 10âwk, 34âwk postmenstrual age (PMA) or discharge. Serum collection employed a sparse sampling population pharmacokinetics design. Inositol urine losses and feeding intakes were measured. Safety was prospectively monitored.
RESULTS:
At 80âmg/kg/d mean serum levels reached 140âmg/l, similar to Hallman's findings. Levels declined after 2âwk, converging in all groups by 6âwk. Analyses showed a mean volume of distribution 0.657 l/kg, clearance 0.058 l/kg/h, and half-life 7.90âh. Adverse events and comorbidities were fewer in the inositol groups, but not significantly so.
CONCLUSION:
Multiple dose inositol at 80âmg/kg/d was not associated with increased adverse events, achieves previously effective serum levels, and is appropriate for investigation in a phase III trial
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