361 research outputs found
Deciphering cosmological information from redshift surveys of high-z objects - the cosmological light-cone effect and redshift-space distortion -
The three-dimensional distribution of astronomical objects observed in
redshift space significantly differs from the true distribution since the
distance to each object cannot be determined by its redshift only; for the peculiar velocity field contaminates the true recession velocity of
the Hubble flow, while the true distance for objects at sensitively
depends on the (unknown and thus assumed) cosmological parameters. This hampers
the effort to understand the true distribution of large-scale structure of the
universe. In addition, all cosmological observations are carried out on a
light-cone, the null hypersurface of an observer at . This implies that
their intrinsic properties and clustering statistics should change even within
the survey volume. Therefore a proper comparison taking account of the
light-cone effect is important to extract any cosmological information from
redshift catalogues, especially for . We present recent theoretical
development on the two effects -- the cosmological light-cone effect and the
cosmological redshift-space distortion -- which should play key roles in
observational cosmology in the 21st century.Comment: 28pages, 20 figures, minor revision to match the final version to
appear in Progress of Theoretical Physics Supplement, vol. 133 (1999
Iron Emission Lines on the Galactic Ridge Observed with Suzaku
In order to elucidate origin of the Galactic Ridge X-ray Emission, we
analyzed Suzaku data taken at various regions along the Galactic plane and
studied their Fe-K emission line features. Suzaku resolved the Fe line complex
into three narrow lines at ~6.4 keV,~6.7 keV and ~6.97 keV, which are K-lines
from neutral (or low-ionized), He-like, and H-like iron ions, respectively. The
6.7 keV line is clearly seen in all the observed regions and its longitudinal
distribution is consistent with that determined from previous observations. The
6.4 keV emission line was also found in various Galactic plane regions (b~0).
Differences in flux ratios of the 6.4 keV/6.7 keV and 6.97 keV/6.7 keV lines
between the Galactic plane and the Galactic center regions are studied and its
implication is discussed.Comment: Accepted for publication in PASJ Suzaku 3rd special issu
Distribution of Faraday Rotation Measure in Jets from Active Galactic Nuclei II. Prediction from our Sweeping Magnetic Twist Model for the Wiggled Parts of AGN Jets and Tails
Distributions of Faraday rotation measure (FRM) and the projected magnetic
field derived by a 3-dimensional simulation of MHD jets are investigated based
on our "sweeping magnetic twist model". FRM and Stokes parameters were
calculated to be compared with radio observations of large scale wiggled AGN
jets on kpc scales. We propose that the FRM distribution can be used to discuss
the 3-dimensional structure of magnetic field around jets and the validity of
existing theoretical models, together with the projected magnetic field derived
from Stokes parameters. In the previous paper, we investigated the basic
straight part of AGN jets by using the result of a 2-dimensional axisymmetric
simulation. The derived FRM distribution has a general tendency to have a
gradient across the jet axis, which is due to the toroidal component of the
magnetic field generated by the rotation of the accretion disk. In this paper,
we consider the wiggled structure of the AGN jets by using the result of a
3-dimensional simulation. Our numerical results show that the distributions of
FRM and the projected magnetic field have a clear correlation with the large
scale structure of the jet itself, namely, 3-dimensional helix. Distributions,
seeing the jet from a certain direction, show a good matching with those in a
part of 3C449 jet. This suggests that the jet has a helical structure and that
the magnetic field (especially the toroidal component) plays an important role
in the dynamics of the wiggle formation because it is due to a current-driven
helical kink instability in our model.Comment: Accepted for publication in Ap
Intestinal Metaplasia —The Effect of Acid on the Gastric Mucosa and Gastric Carcinogenesis—
This review concerns stem cells and their relation to intestinal metaplasia. When
gastric regions of mice, Mongolian gerbils or several strains of rats were
irradiated with a total dose of 20 Gy of X-rays given in two fractions,
intestinal metaplasia was only induced in rats. In addition, it was greatly
influenced by rat strain and sex. Alkaline phosphatase (ALP) positive
metaplastic foci were increased by administration of ranitidine (H2
receptor antagonist), crude stomach antigens or subtotal resection of the fundus
and decreased by cysteamine (gastric acid secretion stimulator), histamine or
removal of the submandibular glands. Recent studies have shown that
Cdx2 transgenic mice with gastric achlorhydria develop
intestinal metaplasia and that in men and animals, Helicobacter
pylori (H. pyrlori) infection can cause intestinal metaplasias
that are reversible on eradication. Our results combined with findings for
H. pylori infection or eradication and transgenic mice
suggest that an elevation in the pH of the gastric juice due to disappearance of
parietal cells is one of the principal factors for development of reversible
intestinal metaplasia. When different organs were transplanted into the stomach
or duodenum, they were found to transdifferentiate into gastric or duodenal
mucosae, respectively. Organ-specific stem cells in normal non-liver tissues
(heart, kidney, brain and skin) also differentiate into hepatocytes when
transplanted into an injured liver. Therefore, stem cells have a multipotential
ability, transdifferentiating into different organs when transplanted into
different environments. Finally, intestinal metaplasia has been found to
possibly increase sensitivity to the induction of tumors by colon carcinogens of
the 1,2-dimethylhydrazine (DMH), azoxymethane (AOM) or
2-amino-1-methyl-6-phenylimidazo[4.5-b]pyridine (PhIP) type. This carcinogenic
process, however, may be relatively minor compared with the main gastric
carcinogenesis process induced by N-methy1-N’-nitro-N-nitrosoguanidine (MMNG) or
N-methylnitrosourea (MNU), which is not affected by the presence of intestinal
metaplasia. The protocol used in these experiments may provide a new approach to
help distinguish between developmental events associated with intestinal
metaplasia and gastric tumors
Binary Quantum Turbulence Arising from Countersuperflow Instability in Two-Component Bose-Einstein Condensates
We theoretically study the development of quantum turbulence from two
counter-propagating superfluids of miscible Bose-Einstein condensates by
numerically solving the coupled Gross-Pitaevskii equations. When the relative
velocity exceeds a critical value, the counter-superflow becomes unstable and
quantized vortices are nucleated, which leads to isotropic quantum turbulence
consisting of two superflows. It is shown that the binary turbulence can be
realized experimentally in a trapped system.Comment: 5 pages, 3 figure
Roles of type II H+-PPases and PPsPase1/PECP2 in early developmental stages and PPi homeostasis of Arabidopsis thaliana
The regulation of intracellular pyrophosphate (PPi) level is crucial for proper morphogenesis across all taxonomic kingdoms. PPi is released as a byproduct from ~200 metabolic reactions, then hydrolyzed by either membrane-bound (H+-PPase) or soluble pyrophosphatases (PPases). In Arabidopsis, the loss of the vacuolar H+-PPase/FUGU5, a key enzyme in PPi homeostasis, results in delayed growth and a number of developmental defects, pointing to the importance of PPi homeostasis in plant morphogenesis. The Arabidopsis genome encodes several PPases in addition to FUGU5, such as PPsPase1/PECP2, VHP2;1 and VHP2;2, although their significance regarding PPi homeostasis remains elusive. Here, to assess their contribution, phenotypic analyses of cotyledon aspect ratio, palisade tissue cellular phenotypes, adaxial side pavement cell complexity, stomatal distribution, and etiolated seedling length were performed, provided that they were altered due to excess PPi in a fugu5 mutant background. Overall, our analyses revealed that the above five traits were unaffected in ppspase1/pecp2, vhp2;1 and vhp2;2 loss-of-function mutants, as well as in fugu5 mutant lines constitutively overexpressing PPsPase1/PECP2. Furthermore, metabolomics revealed that ppspase1/pecp2, vhp2;1 and vhp2;2 etiolated seedlings exhibited metabolic profiles comparable to the wild type. Together, these results indicate that the contribution of PPsPase1/PECP2, VHP2;1 and VHP2;2 to PPi levels is negligible in comparison to FUGU5 in the early stages of seedling development
Distribution of Faraday Rotation Measure in Jets from Active Galactic Nuclei I. Prediction from our Sweeping Magnetic Twist Model
Using the numerical data of MHD simulation for AGN jets based on our
``sweeping magnetic twist model'', we calculated the Faraday rotation measure
(FRM) and the Stokes parameters to compare with observations. We propose that
the FRM distribution can be used to discuss the 3-dimensional structure of
magnetic field around jets, together with the projected magnetic field derived
from the Stokes parameters. In the present paper, we supposed the basic
straight part of AGN jet, and used the data of axisymmetric simulation. The FRM
distribution we derived has a general tendency to have gradient across the jet
axis, which is due to the toroidal component of the helical magnetic field
generated by the rotation of the accretion disk. This kind of gradient in the
FRM distribution is actually observed in some AGN jets (e.g. Asada et al.
2002), which suggests helical magnetic field around the jets and thus supports
our MHD model. Following this success, we are now extending our numerical
observation to the wiggled part of the jets using the data of 3-dimensional
simulation based on our model in the following paper.Comment: Accepted for publication in Ap
Boundary States for Supertubes in Flat Spacetime and Godel Universe
We construct boundary states for supertubes in the flat spacetime. The T-dual
objects of supertubes are moving spiral D1-branes (D-helices). Since we can
obtain these D-helices from the usual D1-branes via null deformation, we can
construct the boundary states for these moving D-helices in the covariant
formalism. Using these boundary states, we calculate the vacuum amplitude
between two supertubes in the closed string channel and read the open string
spectrum via the open closed duality. We find there are critical values of the
energy for on-shell open strings on the supertubes due to the non-trivial
stringy correction. We also consider supertubes in the type IIA Godel universe
in order to use them as probes of closed timelike curves. This universe is the
T-dual of the maximally supersymmetric type IIB PP-wave background. Since the
null deformations of D-branes are also allowed in this PP-wave, we can
construct the boundary states for supertubes in the type IIA Godel universe in
the same way. We obtain the open string spectrum on the supertube from the
vacuum amplitude between supertubes. As a consequence, we find that the
tachyonic instability of open strings on the supertube, which is the signal of
closed time like curves, disappears due to the stringy correction.Comment: 26 pages, 3 figures, v2: explanations added, references added, v3:
explanations adde
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