1,159 research outputs found
The Effect of Self-gravity of Gas on Gas Fueling in Barred Galaxies with a Supermassive Black Hole
In our previous paper, we have shown that a gas disk in the nuclear region of
a barred galaxy which contains a central supermassive black hole (SMBH) rapidly
evolves into a nuclear gas ring by the effect of an additional inner Lindblad
resonance caused by the SMBH. In this paper, we investigate the fate of the gas
ring, involving self-gravity of gas, using two-dimensional hydrodynamical
simulations. We find that the gas ring becomes gravitationally unstable for a
gas surface density of gas above a critical value, and fragments into several
gas clumps. Some denser clumps increase their mass via the accretion of the
surrounding gas and collisions with other clumps, and finally a very massive
gas clump (10^7 M_sun) is formed. Due to the torque from the most massive
clump, a part of the gas in the ring loses its angular momentum and falls into
the galactic center. As a result, a nuclear gas disk (50 pc) is formed around
the SMBH. The accretion rate for pc attains about 1 M_sun/yr for
3.5*10^7 yr. At the final phase of the bar-driven fueling, self-gravity is
crucial for the angular momentum transfer of the gas. This is a new mechanism
for gas fueling to the vicinity of the SMBH.Comment: 14 pages, 7 figures, AASTeX, submitted to Ap
Antarctic Climate Research Data, Part 3 Radar and Microwave Radiometer Data at Syowa Station, Antarctica in 1989
Shape from shading with interreflections under proximal light source - 3D shape reconstruction of unfolded book surface from a scanner image
We address the problem to recover the 3D shape of an unfolded book surface from the shading information in a scanner image. From a technical point of view, this shape from shading problem in real world environments is characterized by (1) proximal light source, (2) interreflections, (3) moving light source, (4) specular reflection, and (5) nonuniform albedo distribution. Taking all these factors into account, we first formulate the problem based on an iterative nonlinear optimization scheme. Then we introduce piecewise polynomial models of the 3D shape. Image restoration experiments for a real book surface demonstrated that geometric and photometric distortions are almost completely removed by the proposed method</p
Antarctic Climate Research Data, Part 4 37GHz Microwave Radiometer Data in 1987-1989 and Shortwave and Longwave Radiation Data in 1988 at Syowa Station
The Effect of a Central Supermassive black hole on the Gas Fuelling
When a supermassive black hole exists in the centre of a galaxy, an
additional inner Lindblad resonance (ILR) exists inside the usual ILRs. We
study gas dynamics in a weakly barred potential with a central supermassive
black hole by using 2D numerical simulations, and we investigate the effect of
the additional ILR on fuelling gas into nuclear starburst regions or AGNs. Our
numerical results show that strong trailing spiral shocks are formed at the
resonance region, and the gas in the shock region is rapidly fuelled into a
central region and make a nuclear gas ring. As a result, a large amount of gas
is concentrated in the nuclear region beyond the ILR in a dynamical time scale.Comment: 7 pages, 14 Postscript figures, LaTeX 2.09, requires mn.sty, to be
published in MNRA
Cyclic Advantage Hypothesis for the Species Replacement of Pelagic Fishes.(Mathematical Topics in Biology)
Ephrin-A2 regulates position-specific cell affinity and is involved in cartilage morphogenesis in the chick limb bud
AbstractIn the developing limb bud, mesenchymal cells show position-specific affinity, suggesting that the positional identity of the cells is represented as their surface properties. Since the affinity is regulated by glycosylphosphatidylinositol (GPI)-anchored cell surface proteins, and by EphA4 receptor tyrosine kinase, we hypothesized that the GPI-anchored ligand, the ephrin-A family, also contributes to the affinity. Here, we describe the role of ephrin-A2 in the chick limb bud. Ephrin-A2 protein is uniformly distributed in the limb bud during early limb development. As the limb bud grows, expression of ephrin-A2 is strong in its proximal-to-intermediate regions, but weak distally. The position-dependent expression is maintained in vitro, and is regulated by FGF protein, which is produced in the apical ectodermal ridge. To investigate the role of ephrin-A2 in affinity and in cartilage morphogenesis of limb mesenchyme, we ectopically expressed ephrin-A2 in the limb bud using the retrovirus vector, RCAS. Overexpressed ephrin-A2 modulated the affinity of the mesenchymal cells that differentiate into autopod elements. It also caused malformation of the autopod skeleton and interfered with cartilage nodule formation in vitro without inhibiting chondrogenesis. These results suggest that ephrin-A2 regulates the position-specific affinity of limb mesenchyme and is involved in cartilage pattern formation in the limb
L-Arginine treatment may prevent tubulointerstitial nephropathy caused by germanium dioxide
L-Arginine treatment may prevent tubulointerstitial nephropathy caused by germanium dioxide.BackgroundLong-term oral ingestion of germanium dioxide (GeO2) causes progressive renal failure derived from tubulointerstitial nephropathy in humans and animals. The characteristic of GeO2-induced nephropathy is the renal tissue injury persisting for a long time, even after cessation of GeO2 ingestion. However, a treatment that can suppress the long-lasting renal tissue injury has not yet been established.MethodsUsing the methods of immunohistochemistry and reverse transcription-polymerase chain reaction, we examined the expression of ED1-positive cells (macrophages/monocytes), transforming growth factor (TGF)-β1 mRNA and protein and collagen type IV mRNA and protein in the kidneys of rats with GeO2-induced nephropathy. Concomitantly, the effects of L-arginine treatment on their expression was explored in the kidneys of rats with GeO2-induced nephropathy.ResultsChronic administration of GeO2 caused tubulointerstitial nephropathy characterized by leukocyte invasion into the enlarged tubulointerstitial space in rats. The expression of ED1-positive cells, TGF-β1 protein and collagen type IV protein was markedly increased in the tubulointerstitium of the renal cortex from rats with GeO2-induced nephropathy. Similarly, TGF-β1 and collagen type IV mRNA were significantly enhanced in the renal cortex of rats with GeO2-induced nephropathy. A small number of tubulointerstitial cells expressing TGF-β1 protein were also observed in the renal cortex of rats with GeO2-induced nephropathy. However, L-arginine treatment led to a parallel decrease in the expression of ED1-positive cells, TGF-β1 mRNA and collagen type IV mRNA and protein in rats with GeO2-induced nephropathy.ConclusionsIn general, collagen synthesis is driven by TGF-β1 in the fibrotic process associated with a variety of renal disorders. TGF-β1 is secreted by TGF-β1 producing cells such as macrophages, fibroblasts and myofibroblasts. Thus, the present study indicates that the expression of collagen type IV may be mediated by TGF-β1 released from invading macrophages and, to a lesser extent, released from tubulointerstitial cells, presumably fibroblasts and/or myofibroblasts in GeO2-induced nephropathy. L-Arginine treatment inhibits collagen type IV synthesis possibly by suppressing macrophage invasion and the resultant TGF-β1 expression in this nephropathy. L-Arginine treatment may be beneficial in the prevention of tubulointerstitial fibrosis, which is considered to be the terminal stage of GeO2-induced nephropathy
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