257 research outputs found
Coevolution of Supermassive Black Holes and Circumnuclear Disks
We propose a new evolutionary model of a supermassive black hole (SMBH) and a
circumnuclear disk (CND), taking into account the mass-supply from a host
galaxy and the physical states of CND. In the model, two distinct accretion
modes depending on gravitational stability of the CND play a key role on
accreting gas to a SMBH. (i) If the CMD is gravitationally unstable, energy
feedback from supernovae (SNe) supports a geometrically thick, turbulent gas
disk. The accretion in this mode is dominated by turbulent viscosity, and it is
significantly larger than that in the mode (ii), i.e., the CMD is supported by
gas pressure. Once the gas supply from the host is stopped, the high accretion
phase () changes to the low one (mode
(ii), ), but there is a delay with yr. Through this evolution, the gas-rich CND turns into the gas poor
stellar disk. We found that not all the gas supplied from the host galaxy
accrete onto the SMBH even in the high accretion phase (mode (i)), because the
part of gas is used to form stars. As a result, the final SMBH mass () is not proportional to the total gas mass supplied from the host
galaxy (); decreases with .This would indicate that it is difficult to form a SMBH with observed at high- QSOs. The evolution of the SMBH and CND would
be related to the evolutionary tracks of different type of AGNs.Comment: 11 pages, 11 figures, accepted for publication in Ap
Discovery of Spectral Transitions from Two Ultra-Luminous Compact X-Ray Sources in Ic342
Two {\it ASCA} observations were made of two ultra-luminous compact X-ray
sources (ULXs), Source 1 and Source 2, in the spiral galaxy IC 342. In the 1993
observation, Source 2 showed a 0.5--10 keV luminosity of
ergs s (assuming a distance of 4.0 Mpc), and a hard power-law spectrum
of photon index . As already reported, Source 1 was times
brighter on that occasion, and exhibited a soft spectrum represented by a
multi-color disk model of inner-disk temperature keV. The second
observation made in February 2000 revealed that Source 1 had made a transition
into a hard spectral state, while Source 2 into a soft spectral state. The ULXs
are therefore inferred to exhibit two distinct spectral states, and sometimes
make transitions between them. These results significantly reinforce the
scenario which describes ULXs as mass-accreting black holes.Comment: 11 pages, 3 figures; acceoted for ApJ
Aldose reductase gene is associated with diabetic macroangiopathy in Japanese Type 2 diabetic patients
AIMS: The aldose reductase (AR) gene, a rate-limiting enzyme of the polyol pathway, has been investigated as a candidate gene in determining susceptibility to diabetic microangiopathy. However, the association of the AR gene with diabetic macroangiopathy has not been investigated. Therefore, the present study was conducted to determine whether genetic variations of AR may determine susceptibility to diabetic macroangiopathy. METHODS: There were 378 Type 2 diabetic patients enrolled in this study. A single nucleotide polymorphism in the promoter region (C-106T) was genotyped and the AR protein content of erythrocytes measured by ELISA. RESULTS: There were no significant differences in genotypic or allelic distribution in patients with or without ischaemic heart diseases, but there was a significant increase in the frequency of the CT + TT genotype and T allele in patients with stroke (P = 0.019 and P = 0.012). The erythrocyte AR protein content was increased in patients with the CT and TT genotype compared with those with the CC genotype. After adjustment for age, duration of diabetes, body mass index, systolic blood pressure, HbA(1c), and serum creatinine, triglycerides, and total cholesterol in multivariate logistic-regression models, the association between this AR genotype and stroke remained significant. CONCLUSIONS: Our results suggest that the CT or TT genotype of the AR gene might be a genetic marker of susceptibility to stroke in Type 2 diabetic patients. This observation might contribute to the development of strategies for the prevention of stroke in Type 2 diabetic patients
The Three Spectral Regimes Found in the Stellar Black Hole XTE J1550--564 in its High/Soft State
The present paper describes the analysis of multiple RXTE/PCA data of the
black hole binary with superluminal jet, XTE J1550-564, acquired during its
1999--2000 outburst. The X-ray spectra show features typical of the high/soft
spectral state, and can approximately be described by an optically thick disk
spectrum plus a power-law tail. Three distinct spectral regimes, named standard
regime, anomalous regime, and apparently standard regime, have been found from
the entire set of the observed spectra. When the X-ray luminosity is well below
6E38 erg/s (assuming a distance of 5 kpc), XTE J1550-564 resides in the
standard regime, where the soft spectral component dominates the power-law
component and the observed disk inner radius is kept constant. When the
luminosity exceeds the critical luminosity, the apparently standard regime is
realized, where luminosity of the optically thick disk rises less steeply with
the temperature, and the spectral shape is moderately distorted from that of
the standard accretion disk. In this regime, radial temperature gradient of the
disk has been found to be flatter than that of the standard accretion disk. The
results of the apparently standard regime are suggestive of a slim disk (e.g.,
Abramowicz et al. 1988, Watarai et al. 2000) which is a solution predicted
under high mass accretion rate. In the intermediate anomalous regime, the
spectrum becomes much harder, and the disk inner radius derived using a simple
disk model spectrum apparently varies significantly with time. These properties
can be explained as a result of significant thermal inverse Comptonization of
the disk photons, as was found from GRO J1655-40 in its anomalous regime by
Kubota, Makishima and Ebisawa (2001).Comment: 29 pages, 10 figures; Resubmitted to ApJ by taking referee's comments
into consideratio
Regulation of T helper type 2 cell differentiation by murine Schnurri-2
Schnurri (Shn) is a large zinc finger protein implicated in cell growth, signal transduction, and lymphocyte development. Vertebrates possess at least three Shn orthologues (Shn-1, Shn-2, and Shn-3), which appear to act within the bone morphogenetic protein, transforming growth factor β, and activin signaling pathways. However, the physiological functions of the Shn proteins remain largely unknown. In Shn-2–deficient mice, mature peripheral T cells exhibited normal anti–T cell receptor–induced proliferation, although there was dramatic enhancement in the differentiation into T helper type (Th)2 cells and a marginal effect on Th1 cell differentiation. Shn-2–deficient developing Th2 cells showed constitutive activation of nuclear factor κB (NF-κB) and enhanced GATA3 induction. Shn-2 was able to compete with p50 NF-κB for binding to a consensus NF-κB motif and inhibit NF-κB–driven promoter activity. Thus, Shn-2 plays a crucial role in the control of Th2 cell differentiation by regulating NF-κB function
The Nature of Ultra-Luminous Compact X-Ray Sources in Nearby Spiral Galaxies
Studies were made of ASCA spectra of seven ultra-luminous compact X-ray
sources (ULXs) in nearby spiral galaxies; M33 X-8 (Takano et al. 1994), M81 X-6
(Fabbiano 1988b; Kohmura et al. 1994; Uno 1997), IC 342 Source 1 (Okada et al.
1998), Dwingeloo 1 X-1 (Reynolds et al. 1997), NGC 1313 Source B (Fabbiano &
Trinchieri 1987; Petre et al. 1994), and two sources in NGC 4565 (Mizuno et al.
1999). With the 0.5--10 keV luminosities in the range 10^{39-40} ergs/s, they
are thought to represent a class of enigmatic X-ray sources often found in
spiral galaxies. For some of them, the ASCA data are newly processed, or the
published spectra are reanalyzed. For others, the published results are quoted.
The ASCA spectra of all these seven sources have been described successfully
with so called multi-color disk blackbody (MCD) emission arising from
optically-thick standard accretion disks around black holes. Except the case of
M33 X-8, the spectra do not exhibit hard tails. For the source luminosities not
to exceed the Eddington limits, the black holes are inferred to have rather
high masses, up to ~100 solar masses. However, the observed innermost disk
temperatures of these objects, Tin = 1.1--1.8 keV, are too high to be
compatible with the required high black-hole masses, as long as the standard
accretion disks around Schwarzschild black holes are assumed. Similarly high
disk temperatures are also observed from two Galactic transients with
superluminal motions, GRO 1655-40 and GRS 1915+105. The issue of unusually high
disk temperature may be explained by the black hole rotation, which makes the
disk get closer to the black hole, and hence hotter.Comment: submitted to ApJ, December 199
Racial Disparities at Mixed-Race and Minority Hospitals: Treatment of African American Males With High-Grade Splenic Injuries
INTRODUCTION: Racial and socioeconomic disparities in health access and outcomes for many conditions are well known. However, for time-sensitive high-acuity diseases such as traumatic injuries, disparities in access and outcomes should be significantly diminished. Our primary objective was to characterize racial disparities across majority, mixed-race, and minority hospitals for African American (AA) versus white males with high-grade splenic injuries. METHODS: Data from the National Trauma Data Bank was utilized from 2007 to 2015. A total of 24 855 AA or white males with high-grade splenic injuries were included. Multilevel mixed effects regression analysis was used to evaluate disparities in outcomes and resource allocation. RESULTS: Mortality was significantly higher for AA males at mixed-race (odds ratio [OR] 1.6; 95% CI 1.3-2.1; P < .001) and minority (OR 2.1; 95% CI 1.5-3.0; P < .001) hospitals, but not at majority hospitals. At minority hospitals, AA males were significantly less likely to be admitted to the intensive care unit (OR 0.7; 95% CI 0.49-0.97; P = .04) and experienced a significantly longer time to surgery (IRR 1.5; P = .02). Minority hospitals were significantly more likely to have failures from angiographic embolization requiring operative intervention (OR 2.2; P = .009). At both types of nonmajority hospitals, AA males with penetrating injuries were more likely to be managed with angiography (mixed-race hospitals: OR 1.7; P = .046 vs minority hospitals: OR 1.6; P = .08). DISCUSSION: While multiple studies have shown that minority hospitals have increased mortality compared to majority hospitals, this study found this disparity only existed for AAs
The AKARI/IRC Mid-Infrared All-Sky Survey
Context : AKARI is the first Japanese astronomical satellite dedicated to
infrar ed astronomy. One of the main purposes of AKARI is the all-sky survey
performed with six infrared bands between 9 and 200um during the period from
2006 May 6 to
2007 August 28. In this paper, we present the mid-infrared part (9um and 18um
b ands) of the survey carried out with one of the on-board instruments, the
Infrar ed Camera (IRC). Aims : We present unprecedented observational results
of the 9 and 18um AKARI al l-sky survey and detail the operation and data
processing leading to the point s ource detection and measurements. Methods :
The raw data are processed to produce small images for every scan and point
sources candidates, above the 5-sigma noise level per single scan, are der
ived. The celestial coordinates and fluxes of the events are determined
statisti cally and the reliability of their detections is secured through
multiple detect ions of the same source within milli-seconds, hours, and months
from each other. Results : The sky coverage is more than 90% for both bands. A
total of 877,091 s ources (851,189 for 9um, 195,893 for 18um) are confirmed and
included in the cur rent release of the point source catalogue. The detection
limit for point source s is 50mJy and 90mJy for the 9um and 18um bands,
respectively. The position accu racy is estimated to be better than 2".
Uncertainties in the in-flight absolute flux calibration are estimated to be 3%
for the 9um band and 4% for the 18um ban d. The coordinates and fluxes of
detected sources in this survey are also compar ed with those of the IRAS
survey and found to be statistically consistent.Comment: Accepted for publication in AandA AKARI special issu
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