513 research outputs found
A Super Bubble Candidate in the Galactic Center and a Local Enhancement G359.77-0.09
A 20' \times 16' elliptical ring-like structure has been found near the
Galactic center in the narrow energy band corresponding to the K line
from He-like sulfur. In the ring, two diffuse sources are found, a supernova
remnant candidate G359.79-0.26 and an unidentified source G359.77-0.09. The
X-ray spectrum of G359.77-0.09 is similar to that of G359.79-0.26, which can be
explained by an absorbed thin thermal plasma model with temperatures of 0.7 and
1.0 keV. The absorption column densities of these two sources are large (N_H =
6.9 \times 10^{22} and 4.5 \times 10^{22} cm^{-2}) and are consistent with that
of the Galactic center distance. The X-ray spectrum extracted from the
ring-like structure is also represented by an absorbed thin thermal plasma
model (kT_e \sim 0.9 keV). The thermal energy of the plasma filling the
ring-like structure is estimated to be 1.0 \times 10^{51} erg. We therefore
propose that the two sources comprise a single ring-like object, which is
possibly a super bubble with a size of 49 pc \times 40 pc in the Galactic
center region.Comment: 9 pages, 7 figures, accepted for publication in PAS
Global Radiation-Magnetohydrodynamic Simulations of Black Hole Accretion Flow and Outflow: Unified Model of Three States
Black-hole accretion systems are known to possess several distinct modes (or
spectral states), such as low/hard state, high/soft state, and so on. Since the
dynamics of the corresponding flows is distinct, theoretical models were
separately discussed for each state. We here propose a unified model based on
our new, global, two-dimensional radiation-magnetohydrodynamic simulations. By
controlling a density normalization we could for the first time reproduce three
distinct modes of accretion flow and outflow with one numerical code. When the
density is large (model A), a geometrically thick, very luminous disk forms, in
which photon trapping takes place. When the density is moderate (model B), the
accreting gas can effectively cool by emitting radiation, thus generating a
thin disk, i.e., the soft-state disk. When the density is too low for radiative
cooling to be important (model C), a disk becomes hot, thick, and faint; i.e.,
the hard-state disk. The magnetic energy is amplified within the disk up to
about twice, 30%, and 20% of the gas energy in models A, B, and C,
respectively. Notably, the disk outflows with helical magnetic fields, which
are driven either by radiation pressure force or magnetic pressure force, are
ubiquitous in any accretion modes. Finally, our simulations are consistent with
the phenomenological alpha-viscosity prescription, that is, the disk viscosity
is proportional to the pressure.Comment: 5 pages, 2 figures, accepted for publication in PASJ Letter
Isoxaben analogs inhibit chitin synthesis in the cultured integument of the rice stem borer Chilo suppressalis
Benzoylphenylureas (BPUs) were discovered as novel type insecticides about a half century ago; many analogs have been launched as insecticides and acaricides. BPUs are known to inhibit chitin synthesis in insects and other arthropods, but they have no effect against microorganisms such as fungi. We designed new chitin synthesis inhibitors based on the hypothesis that biomolecules that play important roles in cellulose and chitin biosynthesis are similar. In the full automatic modeling system (FAMS), the cellulose synthase was selected as a template three-dimensional structure. Thus, we focused on the structure of cellulose synthase inhibitor, isoxaben, to develop new chemistry. The 1, 1-diethylethyl [-C(CH₃)(CH₂CH₃)₂] group of isoxaben was changed to a 4-substituted phenyl group bearing Cl, Et, or Ph. These compounds significantly inhibited chitin synthesis in the cultured integument of the rice stem borer Chilo suppressalis. The activity of the 4-ethylphenyl analog was enhanced 30-fold by adding piperonyl butoxide to the culture medium
Abelian dominance and the dual Meissner effect in local unitary gauges in SU(2) gluodynamics
Performing highly precise Monte-Carlo simulations of SU(2) gluodynamics, we
observe for the first time Abelian dominance in the confining part of the
static potential in local unitary gauges such as the F12 gauge. We also study
the flux-tube profile between the quark and antiquark in these local unitary
gauges and find a clear signal of the dual Meissner effect. The Abelian
electric field is found to be squeezed into a flux tube by the monopole
supercurrent. This feature is the same as that observed in the non-local
maximally Abelian gauge. These results suggest that the Abelian confinement
scenario is gauge independent. Observing the important role of space-like
monopoles in the Polyakov gauge also indicates that the monopoles defined on
the lattice do not necessarily correspond to those proposed by 't Hooft in the
context of Abelian projection.Comment: 4 pages, 7 figure
Production Method of High Purity Copper for Semiconductor Use and Evaluation of the Quality (Report I)(Materials, Metallurgy & Weldability)
A Genome-wide Approach to Identify the Genes Involved in Biofilm Formation in E. coli
Biofilm forming cells are distinctive from the well-investigated planktonic cells and exhibit a different type of gene expression. Several new Escherichia coli genes related to biofilm formation have recently been identified through genomic approaches such as DNA microarray analysis. However, many others involved in this process might have escaped detection due to poor expression, regulatory mechanism, or genetic backgrounds. Here, we screened a collection of single-gene deletion mutants of E. coli named ‘Keio collection’ to identify genes required for biofilm formation. Of the 3985 mutants of non-essential genes in the collection thus examined, 110 showed a reduction in biofilm formation nine of which have not been well characterized yet. Systematic and quantitative analysis revealed the involvement of genes of various functions and reinforced the importance in biofilm formation of the genes for cell surface structures and cell membrane. Characterization of the nine mutants of function-unknown genes indicated that some of them, such as yfgA that genetically interacts with a periplasmic chaperone gene surA together with yciB and yciM, might be required for the integrity of outer membrane
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