755 research outputs found
INCOME TAX EFFECTS ON BEEF COW REPLACEMENT STRATEGY
Livestock Production/Industries,
A Composite Seyfert 2 X-ray Spectrum: Implications for the Origin of the Cosmic X-ray Background
We present a composite 1-10 keV Seyfert 2 X-ray spectrum, derived from ASCA
observations of a distance-limited sample of nearby galaxies. All 29 observed
objects were detected. Above ~3 keV, the composite spectrum is inverted,
confirming that Seyfert 2 galaxies as a class have the spectral properties
necessary to explain the flat shape of the cosmic X-ray background spectrum.
Integrating the composite spectrum over redshift, we find that the total
emission from Seyfert 2 galaxies, combined with the expected contribution from
unabsorbed type 1 objects, provides an excellent match to the spectrum and
intensity of the hard X-ray background. The principal uncertainty in this
procedure is the cosmic evolution of the Seyfert 2 X-ray luminosity function.
Separate composite spectra for objects in our sample with and without polarized
broad optical emission lines are also presented.Comment: 11 pages (AASTeX), including 3 figures. Accepted for publication in
ApJ Letter
Transient and Highly Polarized Double-Peaked H-alpha Emission in the Seyfert 2 Nucleus of NGC 2110
We have discovered an extremely broad, double-peaked H-alpha emission line in
the polarized flux spectrum of NGC 2110, establishing that this well-studied
Seyfert 2 galaxy contains a disk-like hidden broad-line region (BLR). Several
properties of NGC 2110 suggest that it is an obscured twin of Arp 102B, the
prototypical double-peaked emission-line active galactic nucleus (AGN). A
comparison between our data and previous spectra of NGC 2110 indicates that the
double-peaked H-alpha feature is transient. The presence of a disk-like BLR in
NGC 2110 has important implications for AGNs: it expands the range of
properties exhibited by Seyfert 2 galaxies, and the fact that the BLR is
obscured by a torus-like structure provides the first evidence that
double-peaked emitters and classical Seyfert nuclei may have the same basic
parsec-scale geometry.Comment: 5 pages, including 3 postscript figures. Uses emulateapj. Accepted
for publication in ApJ Letter
Sea Ice Prediction Has Easy and Difficult Years
Arctic sea ice follows an annual cycle, reaching its low point in September each year. The extent of sea ice remaining at this low point has been trending downwards for decades as the Arctic warms. Around the long-term downward trend, however, there is significant variation in the minimum extent from one year to the next. Accurate forecasts of yearly conditions would have great value to Arctic residents, shipping companies, and other stakeholders and are the subject of much current research. Since 2008 the Sea Ice Outlook (SIO) (http://www.arcus.org/search-program/seaiceoutlook) organized by the Study of Environmental Arctic Change (SEARCH) (http://www.arcus.org/search-program) has invited predictions of the September Arctic sea ice minimum extent, which are contributed from the Arctic research community. Individual predictions, based on a variety of approaches, are solicited in three cycles each year in early June, July, and August. (SEARCH 2013)
The Frequency of Polarized Broad Emission Lines in Type 2 Seyfert Galaxies
We have discovered polarized broad emission lines in five type 2 Seyfert
galaxies (NGC 424, NGC 591, NGC 2273, NGC 3081, and NGC 4507), establishing
that these objects are type 1 Seyferts obscured by dense circumnuclear
material. The galaxies are part of a distance-limited sample of 31 Seyfert 2s,
for which spectropolarimetric observations are now complete. Combined with
published reports, our results indicate that at least 11 of the galaxies in
this sample, or > 35%, possess hidden broad-line regions. This represents the
first reliable estimate of the frequency of polarized broad emission lines in
type 2 Seyferts, which has important implications for the general applicability
of Seyfert unification models.Comment: 13 pages, including 5 figures. Accepted for publication in ApJ
Letter
Inhibitory Input from the Lateral Hypothalamus to the Ventral Tegmental Area Disinhibits Dopamine Neurons and Promotes Behavioral Activation
Projections from the lateral hypothalamus (LH) to the ventral tegmental area (VTA), containing both GABAergic and glutamatergic components, encode conditioned responses and control compulsive reward-seeking behavior. GABAergic neurons in the LH have been shown to mediate appetitive and feeding-related behaviors. Here we show that the GABAergic component of the LH-VTA pathway supports positive reinforcement and place preference, while the glutamatergic component mediates place avoidance. In addition, our results indicate that photoactivation of these projections modulates other behaviors, such as social interaction and perseverant investigation of a novel object. We provide evidence that photostimulation of the GABAergic LH-VTA component, but not the glutamatergic component, increases dopamine (DA) release in the nucleus accumbens (NAc) via inhibition of local VTA GABAergic neurons. Our study clarifies how GABAergic LH inputs to the VTA can contribute to generalized behavioral activation across multiple contexts, consistent with a role in increasing motivational salience.National Institute of Mental Health (U.S.) (Grant R01-MH102441-01
Using self-management to control seizures
The aim of this study was to develop, deliver and evaluate the impact of an education intervention regarding lifestyle self-management in the control of seizures, health related quality of life (HRQoL), satisfaction with life and resilience for adults with epilepsy
Decoding Neural Circuits that Control Compulsive Sucrose Seeking
SummaryThe lateral hypothalamic (LH) projection to the ventral tegmental area (VTA) has been linked to reward processing, but the computations within the LH-VTA loop that give rise to specific aspects of behavior have been difficult to isolate. We show that LH-VTA neurons encode the learned action of seeking a reward, independent of reward availability. In contrast, LH neurons downstream of VTA encode reward-predictive cues and unexpected reward omission. We show that inhibiting the LH-VTA pathway reduces âcompulsiveâ sucrose seeking but not food consumption in hungry mice. We reveal that the LH sends excitatory and inhibitory input onto VTA dopamine (DA) and GABA neurons, and that the GABAergic projection drives feeding-related behavior. Our study overlays information about the type, function, and connectivity of LH neurons and identifies a neural circuit that selectively controls compulsive sugar consumption, without preventing feeding necessary for survival, providing a potential target for therapeutic interventions for compulsive-overeating disorder
Design and conduct of 'Xtreme Alps' : a double-blind, randomised controlled study of the effects of dietary nitrate supplementation on acclimatisation to high altitude
The study of healthy human volunteers ascending to high altitude provides a robust model of the complex physiological interplay that emulates human adaptation to hypoxaemia in clinical conditions. Nitric oxide (NO) metabolism may play an important role in both adaptation to high altitude and response to hypoxaemia during critical illness at sea level. Circulating nitrate and nitrite concentrations can be augmented by dietary supplementation and this is associated with improved exercise performance and mitochondrial efficiency. We hypothesised that the administration of a dietary substance (beetroot juice) rich in nitrate would improve oxygen efficiency during exercise at high altitude by enhancing tissue microcirculatory blood flow and oxygenation. Furthermore, nitrate supplementation would lead to measurable increases in NO bioactivity throughout the body.
This methodological manuscript describes the design and conduct of the âXtreme Alpsâ expedition, a double-blind randomised controlled trial investigating the effects of dietary nitrate supplementation on acclimatisation to hypobaric hypoxia at high altitude in healthy human volunteers. The primary outcome measure was the change in oxygen efficiency during exercise at high altitude between participants allocated to receive nitrate supplementation and those receiving a placebo. A number of secondary measures were recorded, including exercise capacity, peripheral and microcirculatory blood flow and tissue oxygenation.
Results from this study will further elucidate the role of NO in adaption to hypoxaemia and guide clinical trials in critically ill patients. Improved understanding of hypoxaemia in critical illness may provide new therapeutic avenues for interventions that will improve survival in critically ill patients
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