No abstract

Lipopolysaccharide (LPS), an endotoxin derived from gram-negative bacteria, promotes the secretion of proinflammatory cytokines and mediates endotoxemia through activation of mitogen activated protein kinases, NF-κB, and interferon regulatory factor-3. Silent information regulator transcript-1 (SIRT1), an NAD-dependent deacetylase, mediates NF-κB deacetylation, and inhibits its function. SIRT1 may affect LPS-mediated signaling pathways and endotoxemia. Here we demonstrate that SIRT1 blocks LPS-induced secretion of interleukin 6 and tumor necrosis factor α in murine macrophages, and protects against lethal endotoxic and septic shock in mice. We also demonstrate that interferon β increases SIRT1 expression by activating the Janus kinase – signal transducer and activator of transcription (JAK-STAT) pathway in mouse bone marrow derived macrophages. In vivo treatment of interferon β protects against lethal endotoxic and septic shock, which is abrogated by infection with dominant negative SIRT1-expressing adenovirus. Our work suggests that both SIRT1 and SIRT1-inducing cytokines are useful targets for treating patients with sepsis.

Powered by a supermassive black hole with an accretion disk, the spectra of active galactic nuclei (AGNs) are characterized by prominent emission lines including Balmer lines. The unification schemes of AGNs require the existence of a thick molecular torus that may hide the broad emission line region from the view of observers near the equatorial direction. In this configuration, one may expect that the far UV radiation from the central engine can be Raman scattered by neutral hydrogen to reappear around Balmer and Paschen emission lines which can be identified with broad wings. We produce Hα, Hβ and Paα wings using a Monte Carlo technique to investigate their properties. The neutral scattering region is assumed to be a cylindrical torus specified by the inner and outer radii and the height. While the covering factor of the scattering region affects the overall strengths of the wings, the wing widths are primarily dependent on the neutral hydrogen column density N HI being roughly proportional to N 1/2 HI . In particular, with N HI = 10 23 cm −2 the Hα wings typically show a width ∼ 2 × 10 4 km s −1 . We also find that Hα and Paα wing profiles are asymmetric with the red part stronger than the blue part and an opposite behavior is seen for Hβ wings.

Symbiotic stars (SySts) are long-period interacting binaries composed of a hot compact star, an evolved giant star, and a tangled network of gas and dust nebulae. They represent unique laboratories for studying a variety of important astrophysical problems, and have also been proposed as possible progenitors of SNIa. Presently, we know 257 SySts in the Milky Way and 69 in external galaxies. However, these numbers are still in striking contrast with the predicted population of SySts in our Galaxy. Because of other astrophysical sources that mimic SySt colors, no photometric diagnostic tool has so far demonstrated the power to unambiguously identify a SySt, thus making the recourse to costly spectroscopic follow-up still inescapable. In this paper we present the concept, commissioning, and science verification phases, as well as the first scientific results, of RAMSES II -a Gemini Observatory Instrument Upgrade Project that has provided each GMOS instrument at both Gemini telescopes with a set of narrow-band filters centered on the Raman OVI 6830Å band. Continuum-subtracted images using these new filters clearly revealed known SySts with a range of Raman OVI line strengths, even in crowded fields. RAMSES II observations also produced the first detection of Raman OVI emission from the SySt LMC 1 and confirmed Hen 3-1768 as a new SySt -the first photometric confirmation of a SySt. Via Raman OVI narrow-band imaging, RAMSES II provides the astronomical community with the first purely photometric tool for hunting SySts in the local Universe.

We present the high resolution spectra of the symbiotic star V1016 Cygni obtained with the Bohyunsan Optical Echelle Spectrograph in 2003 and 2005, from which we find a broad emission feature at 4881Å. We propose that this broad feature is formed from Raman scattering of Ne VIIλ973 by atomic hydrogen. Thus far, the detection of Raman scattered lines by atomic hydrogen is limited to O VIλλ1032, 1038 and He IIλλ940, 972 and 1025. With the adoption of the center wavelength 973.302Å of Ne VIIλ973 and consideration of the air refractive index of n air = 1.000279348, the atomic line center of the Raman scattered Ne VII feature is determined to be 4880.53Å. The total cross section at the line center of Ne VIIλ973 is computed to be 2.62×10−22 cm 2 with the branching ratio of 0.17. We perform Monte Carlo simulations to fit the Raman scattered Ne VIIλ973. Assuming that the Ne VII and He II emission regions share the same kinematics with respect to the neutral scattering region, we find that the Raman scattered He IIλ972 at 4850Å and Ne VIIλ973 at 4881Å are excellently fitted. We also propose that the He II and Ne VII emission regions were stationary with respect to the H I region in 2003 but that they were receding from it with a velocity ∼ 20 km s −1 in 2005.