1,169 research outputs found
Complex Radio Spectral Energy Distributions in Luminous and Ultraluminous Infrared Galaxies
We use the Expanded Very Large Array to image radio continuum emission from
local luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) in 1 GHz
windows centered at 4.7, 7.2, 29, and 36 GHz. This allows us to probe the
integrated radio spectral energy distribution (SED) of the most energetic
galaxies in the local universe. The 4-8 GHz flux densities agree well with
previous measurements. They yield spectral indices \alpha \approx -0.67 (where
F_\nu \propto \nu^\alpha) with \pm 0.15 (1\sigma) scatter, typical of
nonthermal (synchrotron) emission from star-forming galaxies. The contrast of
our 4-8 GHz data with literature 1.5 and 8.4 GHz flux densities gives further
evidence for curvature of the radio SED of U/LIRGs. The SED appears flatter
near \sim 1 GHz than near \sim 6 GHz, suggesting significant optical depth
effects at the lower frequencies. The high frequency (28-37 GHz) flux densities
are low compared to extrapolations from the 4-8 GHz data. We confirm and extend
to higher frequency a previously observed deficit of high frequency radio
emission for luminous starburst galaxies.Comment: 7 pages, 3 figures, 1 table, accepted for publication in the EVLA
Special Issue of ApJ Letter
Inhibition of NAPDH Oxidase 2 (NOX2) Prevents Oxidative Stress and Mitochondrial Abnormalities Caused by Saturated Fat in Cardiomyocytes
Obesity and high saturated fat intake increase the risk of heart failure and arrhythmias. The molecular mechanisms are poorly understood. We hypothesized that physiologic levels of saturated fat could increase mitochondrial reactive oxygen species (ROS) in cardiomyocytes, leading to abnormalities of calcium homeostasis and mitochondrial function. We investigated the effect of saturated fat on mitochondrial function and calcium homeostasis in isolated ventricular myocytes. The saturated fatty acid palmitate causes a decrease in mitochondrial respiration in cardiomyocytes. Palmitate, but not the monounsaturated fatty acid oleate, causes an increase in both total cellular ROS and mitochondrial ROS. Palmitate depolarizes the mitochondrial inner membrane and causes mitochondrial calcium overload by increasing sarcoplasmic reticulum calcium leak. Inhibitors of PKC or NOX2 prevent mitochondrial dysfunction and the increase in ROS, demonstrating that PKC-NOX2 activation is also required for amplification of palmitate induced-ROS. Cardiomyocytes from mice with genetic deletion of NOX2 do not have palmitate-induced ROS or mitochondrial dysfunction. We conclude that palmitate induces mitochondrial ROS that is amplified by NOX2, causing greater mitochondrial ROS generation and partial depolarization of the mitochondrial inner membrane. The abnormal sarcoplasmic reticulum calcium leak caused by palmitate could promote arrhythmia and heart failure. NOX2 inhibition is a potential therapy for heart disease caused by diabetes or obesity
Discovery and Prevalence of Divergent RNA Viruses in European Field Voles and Rabbits
The advent of unbiased metagenomic virus discovery has revolutionized studies of virus biodiversity and evolution. Despite this, our knowledge of the virosphere, including in mammalian species, remains limited. We used unbiased metagenomic sequencing to identify RNA viruses in European field voles and rabbits. Accordingly, we identified a number of novel RNA viruses including astrovirus, rotavirus A, picorna-like virus and a morbilli-like paramyxovirus. In addition, we identified a sobemovirus and a novel luteovirus that likely originated from the rabbit diet. These newly discovered viruses were often divergent from those previously described. The novel astrovirus was most closely related to a virus sampled from the rodent-eating European roller bird (Coracias garrulous). PCR screening revealed that the novel morbilli-like paramyxovirus in the UK field vole had a prevalence of approximately 4%, and shared common ancestry with other rodent morbilli-like viruses sampled globally. Two novel rotavirus A sequences were detected in a UK field vole and a French rabbit, the latter with a prevalence of 5%. Finally, a highly divergent picorna-like virus found in the gut of the French rabbit virus was only ~35% similar to an arilivirus at the amino acid level, suggesting the presence of a novel viral genus within the Picornaviridae
Key Science Goals for the Next Generation Very Large Array (ngVLA): Report from the ngVLA Science Advisory Council
This document describes some of the fundamental astrophysical problems that
require observing capabilities at millimeter- and centimeter wavelengths well
beyond those of existing, or already planned, telescopes. The results
summarized in this report follow a solicitation from the National Radio
Astronomy Observatory to develop key science cases for a future U. S.-led radio
telescope, the "next generation Very Large Array" (ngVLA). The ngVLA will have
roughly 10 times the collecting area of the Jansky VLA, operate at frequencies
from 1 GHz to 116 GHz with up to 20 GHz of bandwidth, possess a compact core
for high surface-brightness sensitivity, and extended baselines of at least
hundreds of kilometers and ultimately across the continent to provide
high-resolution imaging. The ngVLA builds on the scientific and technical
legacy of the Jansky VLA and ALMA, and will be designed to provide the next
leap forward in our understanding of planets, galaxies, and black holes.Comment: ngVLA memo 1
First Views of a Nearby LIRG: Star Formation and Molecular Gas in IRAS 04296+2923
We present a first look at the local LIRG, IRAS04296+2923. This barred
spiral, overlooked because of its location in the Galactic plane, is among the
half dozen closest LIRGs. More IR-luminous than either M82 or the Antennae, it
may be the best local example of a nuclear starburst caused by bar-mediated
secular evolution. We present Palomar J and Pa beta images, VLA maps from
20-1.3cm, a Keck LWS image at 11.7mic and OVRO CO(1-0) and ^13CO(1-0), and 2.7
mm continuum images. The J-band image shows a symmetric barred spiral. Two
bright, compact mid-IR/radio sources in the nucleus comprise a starburst that
is equivalent to 10^5 O7 stars, probably a pair of young super star clusters
separated by 30pc. The nuclear starburst is forming stars at the rate of
~12Msun/yr, half of the total star formation rate for the galaxy of ~25Msun/yr.
IRAS04296 is bright in CO, and among the most gas-rich galaxies in the local
universe. The CO luminosity of the inner half kpc is equivalent to that of the
entire Milky Way. While the most intense CO emission extends over a 15"(2 kpc)
region, the nuclear starburst is confined to ~1-2"(150-250 pc) of the dynamical
center. From ^13CO, we find that the CO conversion factor in the nucleus is
higher than the Galactic value by a factor 3-4, typical of gas-rich spiral
nuclei. The nuclear star formation efficiency is M_gas/SFR^nuc = 2.7x10^-8
yr^-1, corresponding to gas consumption timescale, tau_SF^nuc~4x10^7 yrs. The
star formation efficiency is ten times lower in the disk, tau_SF^disk~3.3x10^8
yrs. The low absolute star formation efficiency in the disk implies that the
molecular gas is not completely consumed before it drifts into the nucleus, and
is capable of fueling a sustained nuclear starburst. IRAS04296 is beginning a
100Myr period as a LIRG, during which it will turn much of its 6x10^9Msun of
molecular gas into a nuclear cluster of stars. (abridged)Comment: Accepted, Astronomical Journa
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