2,434 research outputs found
Extended X-ray emission in the IC 2497 - Hanny's Voorwerp system: energy injection in the gas around a fading AGN
We present deep Chandra X-ray observations of the core of IC 2497, the galaxy
associated with Hanny's Voorwerp and hosting a fading AGN. We find extended
soft X-ray emission from hot gas around the low intrinsic luminosity
(unobscured) AGN ( erg s). The
temperature structure in the hot gas suggests the presence of a bubble or
cavity around the fading AGN (\mbox{E_{\rm bub}} \sim 10^{54} - 10^{55}
erg). A possible scenario is that this bubble is inflated by the fading AGN,
which after changing accretion state is now in a kinetic mode. Other
possibilities are that the bubble has been inflated by the past luminous quasar
( erg s), or that the temperature gradient is
an indication of a shock front from a superwind driven by the AGN. We discuss
the possible scenarios and the implications for the AGN-host galaxy
interaction, as well as an analogy between AGN and X-ray binaries lifecycles.
We conclude that the AGN could inject mechanical energy into the host galaxy at
the end of its lifecycle, and thus provide a source for mechanical feedback, in
a similar way as observed for X-ray binaries.Comment: 9 pages, 5 figures, accepted for publication in MNRA
SACY - a Search for Associations Containing Young stars
The scientific goal of the SACY (Search for Associations Containing
Young-stars) was to identify possible associations of stars younger than the
Pleiades Association among optical counterparts of the ROSAT X-ray bright
sources. High-resolution spectra for possible optical counterparts later than
G0 belonging to HIPPARCOS and/or TYCHO-2 catalogs were obtained in order to
assess both the youth and the spatial motion of each target. More than 1000
ROSAT sources were observed, covering a large area in the Southern Hemisphere.
The newly identified young stars present a patchy distribution in UVW and XYZ,
revealing the existence of huge nearby young associations. Here we present the
associations identified in this survey.Comment: 8 pages, 2 figures, to appear in the Proceedings of Open Issues in
Local Formation and Early Stellar Evolution, Ouro Preto, Brazi
The methylation patterns of the IGF2 and IGF2R genes in bovine spermatozoa are not affected by flow-cytometric sex sorting.
The objectives of this study were to investigate the effect of sexing by flow cytometry on the methylation patterns of the IGF2 and IGF2R genes. Frozen-thawed, unsorted, and sex-sorted spermsamples fromfour Nellore bulls were used. Each ejaculate was separated into three fractions: non-sexed (NS), sexed forX-sperm(SX), and sexed for Y-sperm (SY). Sperm were isolated from the extender, cryoprotectant, and other cell types by centrifugation on a 40:70%Percoll gradient, and spermpellets were used for genomic DNA isolation. DNA was used for analyses of the methylation patterns by bisul?te sequencing.Methylation status of the IGF2 and IGF2Rgeneswere evaluated by sequencing 195 and 147 individual clones, respectively. No global differences in DNAmethylation were found between NS, SX, and SY groups for the IGF2 (P¼0.09) or IGF2R genes (P¼0.38). Very speci?c methylation patterns were observed in the 25th and 26th CpG sites in the IGF2R gene. representing higher methylation in NS than in the SX and SY groups compared with the other CpG sites. Further, individual variation in methylation patterns was found among bulls. In conclusion, the sex-sorting procedure by flow cytometry did not affect the overall DNA methylation patterns of the IGF2 and IGF2R genes, although individual variation in their methyla-tion patterns among bulls was observed
Produção de forragem de genótipos de azevém (Lolium multiflorum L.) sob diferentes regimes de adubação nitrogenada.
Abelian symmetries in multi-Higgs-doublet models
N-Higgs doublet models (NHDM) are a popular framework to construct
electroweak symmetry breaking mechanisms beyond the Standard model. Usually,
one builds an NHDM scalar sector which is invariant under a certain symmetry
group. Although several such groups have been used, no general analysis of
symmetries possible in the NHDM scalar sector exists. Here, we make the first
step towards this goal by classifying the elementary building blocks, namely
the abelian symmetry groups, with a special emphasis on finite groups. We
describe a strategy that identifies all abelian groups which are realizable as
symmetry groups of the NHDM Higgs potential. We consider both the groups of
Higgs-family transformations only and the groups which also contain generalized
CP transformations. We illustrate this strategy with the examples of 3HDM and
4HDM and prove several statements for arbitrary N.Comment: 33 pages, 2 figures; v2: conjecture 3 is proved and becomes theorem
3, more explanations of the main strategy are added, matches the published
versio
The MAGIC Experiment and Its First Results
With its diameter of 17m, the MAGIC telescope is the largest Cherenkov
detector for gamma ray astrophysics. It is sensitive to photons above an energy
of 30 GeV. MAGIC started operations in October 2003 and is currently taking
data. This report summarizes its main characteristics, its rst results and its
potential for physics.Comment: 6 pages, 3 figures, to be published in the Proceedings of the 6th
International Symposium ''Frontiers of Fundamental and Computational
Physics'' (FFP6), Udine (Italy), Sep. 26-29, 200
Desempenho de consórcios forrageiros de estação fria com espécies leguminosas em diferentes anos de cultivo.
A fixação biológica de nitrogênio e os benefícios que podem acarretar desta capacidade atestam a importância do uso de Leguminosas forrageiras na produção animal a pasto. O objetivo foi avaliar a produção de consórcios forrageiros com leguminosas de estação fria no 1° a 3° anos de cultivo. Os tratamentos constituíram os consórcios de aveia preta + azevém com cornichão e trevos. As unidades amostrais foram piquetes de 450 m² pastejados por vacas em lactação. Foram avaliadas a produção de matéria seca total e de lâminas foliares dos consórcios e das leguminosas, acumuladas durante o período experimental. Não foi verificada diferença significativa na produção de matéria seca total e de lâminas foliares dos consórcios, mas é evidente a contribuição do trevo branco na produção de lâminas foliares dos consórcios, especialmente após sua perenização. Foi verificada diferença significativa na produção de matéria seca total e de lâminas foliares das leguminosas nos anos de cultivo, com superioridade para as áreas de 3° ano, o que evidencia a importância do manejo objetivo ao estabelecimento e à perenização destas forrageiras para desempenhos superiores. A produção de matéria seca total e de lâminas foliares das leguminosas é superior no 3° ano de cultivo em relação ao 1° ano e pastagens compostas por trevo branco se destacam pela maior produção de lâminas foliares
Salmeterol for the prevention of high-altitude pulmonary edema.
BACKGROUND: Pulmonary edema results from a persistent imbalance between forces that drive water into the air space and the physiologic mechanisms that remove it. Among the latter, the absorption of liquid driven by active alveolar transepithelial sodium transport has an important role; a defect of this mechanism may predispose patients to pulmonary edema. Beta-adrenergic agonists up-regulate the clearance of alveolar fluid and attenuate pulmonary edema in animal models.
METHODS: In a double-blind, randomized, placebo-controlled study, we assessed the effects of prophylactic inhalation of the beta-adrenergic agonist salmeterol on the incidence of pulmonary edema during exposure to high altitudes (4559 m, reached in less than 22 hours) in 37 subjects who were susceptible to high-altitude pulmonary edema. We also measured the nasal transepithelial potential difference, a marker of the transepithelial sodium and water transport in the distal airways, in 33 mountaineers who were prone to high-altitude pulmonary edema and 33 mountaineers who were resistant to this condition.
RESULTS: Prophylactic inhalation of salmeterol decreased the incidence of high-altitude pulmonary edema in susceptible subjects by more than 50 percent, from 74 percent with placebo to 33 percent (P=0.02). The nasal potential-difference value under low-altitude conditions was more than 30 percent lower in the subjects who were susceptible to high-altitude pulmonary edema than in those who were not susceptible (P<0.001).
CONCLUSIONS: Prophylactic inhalation of a beta-adrenergic agonist reduces the risk of high-altitude pulmonary edema. Sodium-dependent absorption of liquid from the airways may be defective in patients who are susceptible to high-altitude pulmonary edema. These findings support the concept that sodium-driven clearance of alveolar fluid may have a pathogenic role in pulmonary edema in humans and therefore represent an appropriate target for therapy
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