2,117 research outputs found
Optical and X-ray Properties of the Swift BAT-detected AGN
The Swift Gamma-Ray Burst satellite has detected a largely unbiased towards
absorption sample of local () AGN, based solely on their
14--195 keV flux. In the first 9 months of the survey, 153 AGN sources were
detected. The X-ray properties in the 0.3--10 keV band have been compiled and
presented based on analyses with XMM-Newton, Chandra, Suzaku, and the Swift XRT
(Winter et al. 2009). Additionally, we have compiled a sub-sample of sources
with medium resolution optical ground-based spectra from the SDSS or our own
observations at KPNO. In this sample of 60 sources, we have classified the
sources using standard emission line diagnostic plots, obtained masses for the
broad line sources through measurement of the broad H emission line, and
measured the [OIII] 5007\AA luminosity of this sample. Based on continuum fits
to the intrinsic absorption features, we have obtained clues about the stellar
populations of the host galaxies. We now present the highlights of our X-ray
and optical studies of this unique sample of local AGNs, including a comparison
of the 2--10 keV and 14--195 keV X-ray luminosities with the [OIII] 5007\AA
luminosity and the implications of our results towards measurements of
bolometric luminosities.Comment: 4 pages, 2 figures, to appear in proceedings for 'X-ray Astronomy
2009', Bologna 09/2009, AIP Conference Series, Eds. A. Comastri, M. Cappi, L.
Angelin
Chapter 1. The Nitrogen Cycle, Historical Perspective, and Current and Potential Future Concerns
Nitrogen (N) along with carbon and oxygen is the most complex and crucial of the elements essential for life. Supplementing grain and grass forage crops with organic and inorganic N fertilizers has long been recognized as a key to improving crop yields and economic returns. Globally. N fertilizer is largely used for cereal grain production and accounts for an estimated 40(1r of the increase in per capita food production in the past 50 years (Mosier et al.. 200 I). Smil (200 I) estimates that N fertilizer supplies up to 40% of the world\u27s dietary protein and dependence on N from the Haber-Bosch process will increase in the future. Nitrogen compounds also have been recognized for their many potential adverse impacts on the environment and health (Keeney. 2002)
Discovery of a Dwarf Post-Starburst Galaxy Near a High Column Density Ly-alpha Absorber
We report the discovery of a dwarf (M_B = -13.9) post-starburst galaxy
coincident in recession velocity (within uncertainties) with the highest column
density absorber (N_HI = 10^15.85 cm^{-2} at cz = 1586 km/s) in the 3C~273
sightline. This galaxy is by far the closest galaxy to this absorber, projected
just 71 kpc on the sky from the sightline. The mean properties of the stellar
populations in this galaxy are consistent with a massive starburst ~3.5 Gyrs
ago, whose attendant supernovae, we argue, could have driven sufficient gas
from this galaxy to explain the nearby absorber. Beyond the proximity on the
sky and in recession velocity, the further evidence in favor of this conclusion
includes both a match in the metallicities of absorber and galaxy, and the fact
that the absorber has an overabundance of Si/C, suggesting recent type II
supernova enrichment. Thus, this galaxy and its ejecta are the expected
intermediate stage in the fading dwarf evolutionary sequence envisioned by
Babul & Rees to explain the abundance of faint blue galaxies at intermediate
redshifts.Comment: 33 pages, 4 figures, ApJ in pres
Additive utility in prospect theory
Prospect theory is currently the main descriptive theory of decision under uncertainty. It generalizes expected utility by introducing nonlinear decision weighting and loss aversion. A difficulty in the study of multiattribute utility under prospect theory is to determine when an attribute yields a gain or a loss. One possibility, adopted in the theoretical literature on multiattribute utility under prospect theory, is to assume that a decision maker determines whether the complete outcome is a gain or a loss. In this holistic evaluation, decision weighting and loss aversion are general and attribute-independent. Another possibility, more common in the empirical literature, is to assume that a decision maker has a reference point for each attribute. We give preference foundations for this attribute-specific evaluation where decision weighting and loss aversion are depending on the attributes
Nitrogen transformations in flooded rice soils
Transformations of soil and fertilizer N in lowland rice soils are reviewed in relation to improved N management and the N economy of lowland rice soils. Topics discussed include: nitrogen leaching, ammonium fixation and release, ammonia volatilization, N2 fixation, mineralization-immobilization, nitrification-denitrification, dissimilatory nitrate reduction, urea hydrolysis and critical pathways for control of nitrogen loss
Effects of nitrification inhibitors on chemical composition of plants: A review
The potential of nitrification inhibitors to improve N fertilizer efficiency is well recognized. However, their effects on crop quality have received much less attention. Recent literature pertaining to the effects of nitrification inhibitors on chemical composition of plants is reviewed. The topics examined include how the form of inorganic N and retardation of nitrification affects accumulation and content of protein and nitrogenous compounds, cations and anions, and organic acids. There is ample evidence to suggest that nitrification inhibitors hold promise to improve the quality of crops in situations where accumulation of NO− 3 or organic acids such as oxalic acid is a problem. There is need for future research to examine how nitrification retardation affects cation‐anion balance in plants under field conditions because experiments conducted under controlled conditions and in the field have at times given divergent results. Since the use of nitrification inhibitors is increasing, investigations to evaluate their use to improve crop quality In addition to quantity should receive priority
Perspectives for research on development of nitrification inhibitors
A brief review of the present status and scope of research on nitrification inhibitors pertaining to agricultural production and environmental pollution is presented. An approach is advanced for identification and evaluation of nitrification inhibitors from indigenous resources. Concurrently, research to identify functional groups retarding nitrification would be conducted. These approaches will aid in developing inexpensive and effective materials for nitrification inhibition. Future research needs relating to nitrification inhibitors are also examined
Parkinson's disease brain mitochondria have impaired respirasome assembly, age-related increases in distribution of oxidative damage to mtDNA and no differences in heteroplasmic mtDNA mutation abundance
Abstract Background Sporadic Parkinson's disease (sPD) is a nervous system-wide disease that presents with a bradykinetic movement disorder and is frequently complicated by depression and cognitive impairment. sPD likely has multiple interacting causes that include increased oxidative stress damage to mitochondrial components and reduced mitochondrial bioenergetic capacity. We analyzed mitochondria from postmortem sPD and CTL brains for evidence of oxidative damage to mitochondrial DNA (mtDNA), heteroplasmic mtDNA point mutations and levels of electron transport chain proteins. We sought to determine if sPD brains possess any mtDNA genotype-respiratory phenotype relationships. Results Treatment of sPD brain mtDNA with the mitochondrial base-excision repair enzyme 8-oxyguanosine glycosylase-1 (hOGG1) inhibited, in an age-dependent manner, qPCR amplification of overlapping ~2 kbase products; amplification of CTL brain mtDNA showed moderate sensitivity to hOGG1 not dependent on donor age. hOGG1 mRNA expression was not different between sPD and CTL brains. Heteroplasmy analysis of brain mtDNA using Surveyor nuclease® showed asymmetric distributions and levels of heteroplasmic mutations across mtDNA but no patterns that statistically distinguished sPD from CTL. sPD brain mitochondria displayed reductions of nine respirasome proteins (respiratory complexes I-V). Reduced levels of sPD brain mitochondrial complex II, III and V, but not complex I or IV proteins, correlated closely with rates of NADH-driven electron flow. mtDNA levels and PGC-1α expression did not differ between sPD and CTL brains. Conclusion PD brain mitochondria have reduced mitochondrial respiratory protein levels in complexes I-V, implying a generalized defect in respirasome assembly. These deficiencies do not appear to arise from altered point mutational burden in mtDNA or reduction of nuclear signaling for mitochondrial biogenesis, implying downstream etiologies. The origin of age-related increases in distribution of oxidative mtDNA damage in sPD but not CTL brains is not clear, tracks with but does not determine the sPD phenotype, and may indicate a unique consequence of aging present in sPD that could contribute to mtDNA deletion generation in addition to mtDNA replication, transcription and sequencing errors. sPD frontal cortex experiences a generalized bioenergetic deficiency above and beyond aging that could contribute to mood disorders and cognitive impairments.</p
Optimal percolation in correlated multilayer networks with overlap
Multilayer networks have been found to be prone to abrupt cascading failures
under random and targeted attacks, but most of the targeting algorithms
proposed so far have been mainly tested on uncorrelated systems. Here we show
that the size of the critical percolation set of a multilayer network is
substantially affected by the presence of inter-layer degree correlations and
edge overlap. We provide extensive numerical evidence which confirms that the
state-of-the-art optimal percolation strategies consistently fail to identify
minimal percolation sets in synthetic and real-world correlated multilayer
networks, thus overestimating their robustness. We propose two new targeting
algorithms, based on the local estimation of path disruptions away from a given
node, and a family of Pareto-efficient strategies that take into account both
intra-layer and inter-layer heuristics, and can be easily extended to multiplex
networks with an arbitrary number of layers. We show that these strategies
consistently outperform existing attacking algorithms, on both synthetic and
real-world multiplex networks, and provide some interesting insights about the
interplay of correlations and overlap in determining the hyperfragility of
real-world multilayer networks. Overall, the results presented in the paper
suggest that we are still far from having fully identified the salient
ingredients determining the robustness of multiplex networks to targeted
attacks.Comment: 14 pages, 9 figures, 1 tabl
Relationships among pro-inflammatory and degradation-related biomarkers released by articular cartilage from osteoarthritic knees
"Orthpaedic Surgery, School of Medicine."Introduction: Osteoarthritis (OA) is a multifactorial disease often progressing from an initial insult or injury to whole-joint inflammation and degeneration causing pain and dysfunction ; Previous studies have indicated moderate to weak linear correlations between inflammatory and degradation related biomarker production levels by OA cartilage during culture ; This study was designed to characterize non-linear relationships among pro-inflammatory and degradation- related biomarkers produced by articular cartilage recovered from patients with knee OA."This study was funded by the Thompson Laboratory for Regenerative Orthopaedics."Neurological Surgery, University of Missouri School of Medicin
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