2,013 research outputs found
Recurrent Outbursts and Jet Ejections Expected in Swift J1644+57: Limit-Cycle Activities in a Supermassive Black Hole
The tidal disruption event by a supermassive black hole in Swift J1644+57 can
trigger limit-cycle oscillations between a supercritically accreting X-ray
bright state and a subcritically accreting X-ray dim state. Time evolution of
the debris gas around a black hole with mass M=10^{6} {\MO} is studied by
performing axisymmetric, two-dimensional radiation hydrodynamic simulations. We
assumed the -prescription of viscosity, in which the viscous stress is
proportional to the total pressure. The mass supply rate from the outer
boundary is assumed to be , where
is the Eddington luminosity, and is the light speed. Since
the mass accretion rate decreases inward by outflows driven by radiation
pressure, the state transition from a supercritically accreting slim disk state
to a subcritically accreting Shakura-Sunyaev disk starts from the inner disk
and propagates outward in a timescale of a day. The sudden drop of the X-ray
flux observed in Swift J1644+57 in August 2012 can be explained by this
transition. As long as exceeds the threshold for the
existence of a radiation pressure dominant disk, accumulation of the accreting
gas in the subcritically accreting region triggers the transition from a gas
pressure dominant Shakura-Sunyaev disk to a slim disk. This transition takes
place at days after the X-ray darkening. We expect
that if , X-ray emission with luminosity and jet ejection will revive in Swift J1644+57 in
2013--2014.Comment: 6 pages, 4 figures, accepted for publication in PASJ Letter
Construction of an in vivo System for Functional Analysis of the Genes Involved in Sex Pheromone Production in the Silkmoth, Bombyx mori
Moths produce species-specific sex pheromones to attract conspecific mates. The biochemical processes that comprise sex pheromone biosynthesis are precisely regulated and a number of gene products are involved in this biosynthesis and regulation. In recent years, at least 300 EST clones have been isolated from Bombyx mori pheromone gland (PG) specific cDNA libraries with some of those clones [i.e., B. mori PG-specific desaturase 1 (Bmpgdesat1), PG-specific fatty acyl reductase, PG-specific acyl-CoA-binding protein, B. mori fatty acid transport protein, B. mori lipid storage droplet protein-1] characterized and demonstrated to play a role in sex pheromone production. However, most of the EST clones have yet to be fully characterized and identified. To develop an efficient system for analyzing sex pheromone production-related genes, we investigated the feasibility of a novel gene analysis system using the upstream region of Bmpgdesat1 that should contain a PG-specific gene promoter in conjunction with piggyBac vector-mediated germ line transformation. As a result, we have been able to obtain expression of our reporter gene (enhanced green fluorescent protein) in the PG but not in other tissues of transgenic B. mori. Current results indicate that we have successfully constructed a novel in vivo gene analysis system for sex pheromone production in B. mori
Method for Assessing X-ray-Induced Hydroxyl Radical Scavenging Activity of Biological Compounds/Materials
A method for correctly assessing hydroxyl radical scavenging activity of antioxidative chemicals and/or biological compounds/materials was proposed. This method can simultaneously assess two factors, i.e. hydroxyl radical scavenging and 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide (hydroxyl radical adduct of 5,5-dimethyl-1-pyrroline-N-oxide) reducing ability, as antioxidative properties. In this paper, some biologically common hydrophilic molecules, cell culture media, and rat plasma were tested. X-ray induced hydroxyl radical can be detected using the electron paramagnetic resonance spin trapping technique. Using X-ray irradiation of the reaction mixture as the hydroxyl radical source, the true hydroxyl radical scavenging ability of the subjected antioxidant can be assessed. In addition, the method simultaneously measures the reduction of 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide, to estimate the reducing ability of the antioxidant. Biological materials, such as sugars and proteins, could abolish hydroxyl radical at the biological concentration. Ascorbic acid showed reducing ability at the biological concentration. The simultaneous assessment of hydroxyl radical scavenging and reducing ability of antioxidants can be an informative index for antioxidants
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