153 research outputs found
Monte-Carlo Modeling of Non-Gravitational Heating Processes in Galaxy Clusters
We consider non-gravitational heating effects on galaxy clusters on the basis
of the Monte-Carlo modeling of merging trees of dark matter halos combined with
the thermal evolution of gas inside each halo. Under the assumption of
hydrostatic equilibrium and the isothermal gas profiles, our model takes
account of the metallicity evolution, metallicity-dependent cooling of gas,
supernova energy feedback, and heating due to jets of radio galaxies in a
consistent manner. The observed properties of galaxy clusters can be explained
in models with higher non-gravitational heating efficiency than that in the
conventional model. Possibilities include jet heating by the Fanaroff-Riley
Type II radio galaxies, and the enhanced star formation efficiency and/or
supernova energy feedback, especially at high redshifts.Comment: 29 pages, 12 figures. To appear in PASJ, February 25, 200
Reliability of merger tree realizations of dark halos in the Monte-Carlo modeling of galaxy formation
We examine the reliability of the merger trees generated for the Monte-Carlo
modeling of galaxy formation. In particular we focus on the cold gas fraction
predicted from the merger trees with different assumptions on the progenitor
distribution function, the timestep, and the mass resolution. We show that the
cold gas fraction is sensitive to the accuracy of the merger trees at
small-mass scales of progenitors at high redshifts. One can reproduce the
Press-Schechter prediction to a reasonable degree by adopting a fairly large
number of redshift bins, N_{step} ~ 1000 in generating merger trees, which is a
factor of ten larger than the canonical value used in previous literature.Comment: 9 pages, 10 figures. To appear in PASJ, October 25, 200
Systematic bias in the estimate of cluster mass and the fluctuation amplitude from cluster abundance statistics
We revisit the estimate of the mass fluctuation amplitude, sigma_8, from the
observational X-ray cluster abundance. In particular, we examine the effect of
the systematic difference between the cluster virial mass estimated from the
X-ray spectroscopy, M_{vir, spec}, and the true virial mass of the
corresponding halo, M_{vir}. Mazzotta et al. (2004) recently pointed out the
possibility that alpha_M = M_{vir, spec}/M_{vir} is systematically lower than
unity. We perform the statistical analysis combining the latest X-ray cluster
sample and the improved theoretical models and find that sigma_8 \sim 0.76 +/-
0.01 + 0.50 (1-alpha_M) for 0.5 \le alpha_M \le 1, where the quoted errors are
statistical only. Thus if alpha_M \sim 0.7, the value of sigma_8 from cluster
abundance alone is now in better agreement with other cosmological data
including the cosmic microwave background, the galaxy power spectrum and the
weak lensing data. The current study also illustrates the importance of
possible systematic effects in mapping real clusters to underlying dark halos
which changes the interpretation of cluster abundance statistics.Comment: 13 pages, 4 figures. To appear in PASJ, April 25, 200
Crystalline lens changes in porcine eyes with implanted phakic IOL (ICL) with a central hole
BACKGROUND: We calculated the smallest diameter of a hole in the center of the optic at which the optical character of a phakic IOL (ICL) may be maintained. The changes induced in the aqueous humor dynamics and the pathology of cataract development with such a hole were investigated. METHODS: A simulation was performed using ZEMAX software to calculate the hole diameter that makes possible the maintenance of a stable optical character of a phakic IOL. After a hole of calculated diameter was trepanned in the center of the optic of the ICL, the latter was implanted into one eye of a 5-month-old minipig, and an unperforated ICL into the other. The postoperative course was observed for 3 months. Then, Evans blue was injected into the vitreous body under general anesthesia to stain the anterior capsule of the crystalline lens. Within 30 min, the eye was enucleated and the tissues removed were fixed. RESULTS: The MTF of the perforated ICL (hole diameter, 1.0 mm) in the center of the optic resembled that of the unperforated ICL. In all cases with non-perforated ICLs, subcapsular turbidity developed, but no staining caused by EB was observed in the anterior capsule. On the other hand, the anterior capsules of the eyes fitted with ICLs with a 1.0-mm hole were stained, but exhibited no turbidity. CONCLUSION: An ICL with a central hole of diameter 1.0 mm in the optic is similar to an unperforated ICL. The size of the hole influenced the aqueous humor dynamics and increased the aqueous humor perfusion volume over the entire anterior surface of the crystalline lens. The possibility of preventing cataracts was therefore suggested
Structural basis of L-glucose oxidation by scyllo-inositol dehydrogenase: Implications for a novel enzyme subfamily classification
For about 70 years, L-glucose had been considered non-metabolizable by either mammalian or bacterial cells. Recently, however, an L-glucose catabolic pathway has been discovered in Paracoccus laeviglucosivorans, and the genes responsible cloned. Scyllo-inositol dehydrogenase is involved in the first step in the pathway that oxidizes L-glucose to produce L-glucono-1,5-lactone with concomitant reduction of NAD+ dependent manner. Here, we report the crystal structure of the ternary complex of scyllo-inositol dehydrogenase with NAD+ and L-glucono-1,5-lactone at 1.8 Å resolution. The enzyme adopts a homo-tetrameric structure, similar to those of the inositol dehydrogenase family, and the electron densities of the bound sugar was clearly observed, allowing identification of the residues responsible for interaction with the substrate in the catalytic site. In addition to the conserved catalytic residues (Lys106, Asp191, and His195), another residue, His318, located in the loop region of the adjacent subunit, is involved in substrate recognition. Site-directed mutagenesis confirmed the role of these residues in catalytic activity. We also report the complex structures of the enzyme with myo-inositol and scyllo-inosose. The Arg178 residue located in the flexible loop at the entrance of the catalytic site is also involved in substrate recognition, and plays an important role in accepting both L-glucose and inositols as substrates. On the basis of these structural features, which have not been identified in the known inositol dehydrogenases, and a phylogenetic analysis of IDH family enzymes, we suggest a novel subfamily of the GFO/IDH/MocA family. Since many enzymes in this family have not biochemically characterized, our results could promote to find their activities with various substrates
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