8,733 research outputs found
Mirror Symmetry of Calabi-Yau Manifolds and Flat Coordinates
We study mirror symmetry of Calabi-Yau manifolds within the framework of the
Gauss-Manin system. Applying the flat coordinates to the Gauss-Manin system for
the periods, we derive differential equations for the mirror map in addition to
the ordinary Picard-Fuchs equations for the periods. These equations are
obtained for a class of one-parameter models and a two-parameter model of
Fermat type Calabi-Yau manifolds.Comment: 27 pages, LaTeX, no figure
Neutron-capture elements in the very metal-poor star HD88609: another st ar with excesses of light neutron-capture elements
We obtained a high resolution, high signal-to-noise UV-blue spectrum of the
extremely metal-poor red giant HD88609 to determine the abundances of heavy
elements. Nineteen neutron-capture elements are detected in the spectrum. Our
analysis revealed that this object has large excesses of light neutron-capture
elements while heavy neutron-capture elements are deficient. The abundance
pattern shows a continuously decreasing trend, as a function of atomic number,
from Sr to Yb, which is quite different from those in stars with excesses of
r-process elements. Such an abundance pattern is very similar to that of
HD122563 that was studied by our previous work. The results indicate that the
abundance pattern found in the two stars could represent the pattern produced
by the nucleosynthesis process that provided light neutron-capture elements in
the very early Galaxy.Comment: 18 pages, 6 figures, accepted for publication in Ap
Expression of blood group antigen (A, B, H, Le<sup>a</sup>, Le<sup>b</sup>) on liver allografts
The Nuclear Activity of the Galaxies in the Hickson Compact Groups
In order to investigate the nuclear activity of galaxies residing in compact
groups of galaxies, we present results of our optical spectroscopic program
made at Okayama Astrophysical Observatory. We have performed optical
spectroscopy of 69 galaxies which belong to 31 Hickson Compact Groups (HCGs) of
Galaxies. Among them, three galaxies have discordant redshifts. Further,
spectral quality is too poor to classify other three galaxies. Therefore, we
describe our results for the remaining 63 galaxies.
Our main results are summarized below. (1) We have found in our sample; 28
AGN, 16 HII nuclei, and 19 normal galaxies which show no emission line. We used
this HCG sample for statistical analyses. (2) Comparing the frequency
distributions of activity types between the HCGs and the field galaxies whose
data are taken from Ho, Filippenko, & Sargent (382 field galaxies), we find
that the frequency of HII nuclei in the HCGs is significantly less than that in
the field. However, this difference may be due to selection bias that our HCG
sample contains more early-type galaxies than the field, because it is known
that HII nuclei are rarer in early-type galaxies than in later ones. (3)
Applying correction this morphological bias to the HCG sample, we find that
there is no statistically significant difference in the frequency of occurrence
of emission-line galaxies between the HCGs and the field. This implies that the
dense galaxy environment in the HCGs does not affect triggering both the AGN
activity and the nuclear starburst. We discuss some implications on the nuclear
activity in the HCG galaxies.Comment: 33 pages (3 aasms4 LaTeX files), 5 figures (5 Postscript files:
excluded Figure 1), Accepted for publication in The Astronomical Journa
Generating Self-Organizing Stomach Tissue from Mouse Embryonic Stem Cells
Advances in developmental research have allowed for the differentiation of pluripotent stem cells into various somatic cells in vitro. Recently, it was revealed that the aggregation of pluripotent stem cells or their derivatives during differentiation in three-dimensional (3D) cultures with collagen gel could mimic the process of spontaneous organogenesis in vitro as mimicking proper development in vivo. These methods are thought to be useful for monitoring the progress of organ formation and disease physiology, as could be done in an experimental animal. Here, we introduce a recently established method for stomach lineage differentiation from pluripotent stem cells with Matrigel-based 3D culture leading to stomach development. This method induces embryonic stem cell (ES cell) aggregates to spontaneously self-organize into stomach tissue; therefore, it has potential for modeling stomach organogenesis and development in vitro. We further discuss the ability of these in vitro stomach tissues to serve as a new model for gastric disease
Self-consistent radiative effect on relativistic electromagnetic particle acceleration
We study the radiation damping effect on the relativistic acceleration of
electron-positron plasmas with two-and-half-dimensional particle-in-cell (PIC)
simulation. Particles are accelerated by Poynting flux via the diamagnetic
relativistic pulse accelerator (DRPA), and decelerated by the self-consistently
solved radiation damping force. With , the
Lorentz factor of the highest energy particles reaches gamma>100, and the
acceleration still continues. The emitted radiation is peaked within few
degrees from the direction of Poynting flux and strongly linearly polarized,
which may be detectable in gamma-ray burst(GRB) observations. We also show that
the DRPA is insensitive to the initial supporting currents.Comment: 6pages, 4figures. Accepted for publication in Il nuovo cimento
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