561 research outputs found
Gravitational Wave Signals from Chaotic System: A Point Mass with A Disk
We study gravitational waves from a particle moving around a system of a
point mass with a disk in Newtonian gravitational theory. A particle motion in
this system can be chaotic when the gravitational contribution from a surface
density of a disk is comparable with that from a point mass. In such an orbit,
we sometimes find that there appears a phase of the orbit in which particle
motion becomes to be nearly regular (the so-called ``stagnant motion'') for a
finite time interval between more strongly chaotic phases. To study how these
different chaotic behaviours affect on observation of gravitational waves, we
investigate a correlation of the particle motion and the waves. We find that
such a difference in chaotic motions reflects on the wave forms and energy
spectra. The character of the waves in the stagnant motion is quite different
from that either in a regular motion or in a more strongly chaotic motion. This
suggests that we may make a distinction between different chaotic behaviours of
the orbit via the gravitational waves.Comment: Published in Phys.Rev.D76:024018,200
Possible Charge-Exchange X-Ray Emission in the Cygnus Loop Detected with Suzaku
X-ray spectroscopic measurements of the Cygnus Loop supernova remnant
indicate that metal abundances throughout most of the remnant's rim are
depleted to about 0.2 times the solar value. However, recent X-ray studies have
revealed in some narrow regions along the outermost rim anomalously "enhanced"
abundances (up to about 1 solar). The reason for these anomalous abundances is
not understood. Here, we examine X-ray spectra in annular sectors covering
nearly the entire rim of the Cygnus Loop using Suzaku (21 pointings) and
XMM-Newton (1 pointing). We find that spectra in the "enhanced" abundance
regions commonly show a strong emission feature at about 0.7 keV. This feature
is likely a complex of He-like O K(gamma + delta + epsilon), although other
possibilities cannot be fully excluded. The intensity of this emission relative
to He-like O Kalpha appears to be too high to be explained as thermal emission.
This fact, as well as the spatial concentration of the anomalous abundances in
the outermost rim, leads us to propose an origin from charge-exchange processes
between neutrals and H-like O. We show that the presence of charge-exchange
emission could lead to the inference of apparently "enhanced" metal abundances
using pure thermal emission models. Accounting for charge-exchange emission,
the actual abundances could be uniformly low throughout the rim. The overall
abundance depletion remains an open question.Comment: Published in Ap
Asymptotic power-law tails of massive scalar fields in Reissner-Nordstr\"{o}m background
We investigate dominant late-time tail behaviors of massive scalar fields in
nearly extreme Reissner-Nordstr\"{o}m background. It is shown that the
oscillatory tail of the scalar fields has the decay rate of at
asymptotically late times. The physical mechanism by which the asymptotic
tail yields and the relation between the field mass and the time
scale when the tail begins to dominate, are discussed in terms of resonance
backscattering due to spacetime curvature.Comment: 18 pages, 1 figure, accepted for publication in Physical Review
Subtle changes in chromatin loop contact propensity are associated with differential gene regulation and expression.
While genetic variation at chromatin loops is relevant for human disease, the relationships between contact propensity (the probability that loci at loops physically interact), genetics, and gene regulation are unclear. We quantitatively interrogate these relationships by comparing Hi-C and molecular phenotype data across cell types and haplotypes. While chromatin loops consistently form across different cell types, they have subtle quantitative differences in contact frequency that are associated with larger changes in gene expression and H3K27ac. For the vast majority of loci with quantitative differences in contact frequency across haplotypes, the changes in magnitude are smaller than those across cell types; however, the proportional relationships between contact propensity, gene expression, and H3K27ac are consistent. These findings suggest that subtle changes in contact propensity have a biologically meaningful role in gene regulation and could be a mechanism by which regulatory genetic variants in loop anchors mediate effects on expression
Asymptotic tails of massive scalar fields in Schwarzschild background
We investigate the asymptotic tail behavior of massive scalar fields in
Schwarzschild background. It is shown that the oscillatory tail of the scalar
field has the decay rate of at asymptotically late times, and the
oscillation with the period for the field mass is modulated by the
long-term phase shift. These behaviors are qualitatively similar to those found
in nearly extreme Reissner-Nordstr\"{o}m background, which are discussed in
terms of a resonant backscattering due to the space-time curvature.Comment: 21 pages, 2 figures, accepted for publication in Phys.Rev.
Dynamic Changes of Sp6 Transgene Expression in Dental Epithelial Cells during Long-term Culture
To investigate the function of specificity protein 6 (SP6) transcription factor by gain-of-function procedure, we established cytomegalovirus (CMV) promoter-driven Sp6 stable transformants, C9 cells, using dental epithelial-derived cells. Initially, C9 cells produced a significant amount of SP6 protein. However, SP6 expression was reduced in these cells upon long-term culture. We could detect Sp6 transcripts in C9 cells by RT-PCR throughout the passages, although the CMV promoter is known to be epigenetically silenced. We recently found that SP6 was a short-lived protein that was degraded by a ubiquitin-independent proteasome pathway, although it is yet unclear how Sp6 expression was regulated during culture. Thus, we studied the possibility of epigenetic regulation of Sp6 expression. Comparative analysis of endogenous and exogenous Sp6 mRNA expressions demonstrated the specific down-regulation of exogenous Sp6 mRNA levels during culture passages. A DNA methyltransferase inhibitor, 5-Aza-2'-deoxycytidine (5AC), and a histone deacetylase inhibitor, valproic acid (VPA), enhanced or induced SP6 protein expression up to passage 28 without enhancing the mRNA level. The dramatic up-regulation of exogenous Sp6 mRNA was uniquely observed only at passage 50 by 5AC or VPA treatment. These findings indicate that multiple epigenetic regulatory mechanisms operate to fine-tune Sp6 expression during long-term culture
Possible Linkage of SP6 Transcriptional Activity with Amelogenesis by Protein Stabilization
Ameloblasts produce enamel matrix proteins such as amelogenin, ameloblastin, and amelotin during tooth development. The molecular mechanisms of ameloblast differentiation (amelogenesis) are currently not well understood. SP6 is a transcription factor of the Sp/KLF family that was recently found to regulate cell proliferation in a cell-type-specific manner. Sp6-deficient mice demonstrate characteristic tooth anomalies such as delayed eruption of the incisors and supernumerary teeth with disorganized amelogenesis. However, it remains unclear how Sp6 controls amelogenesis. In this study, we used SP6 high producer cells to identify SP6 target genes. Based on the observations that long-term culture of SP6 high producer cells reduced SP6 protein expression but not Sp6 mRNA expression, we found that SP6 is short lived and specifically degraded through a proteasome pathway. We established an in vitro inducible SP6 expression system coupled with siRNA knockdown and found a possible linkage between SP6 and amelogenesis through the regulation of amelotin and Rock1 gene expression by microarray analysis. Our findings suggest that the regulation of SP6 protein stability is one of the crucial steps in amelogenesis
Possible Linkage of SP6 Transcriptional Activity with Amelogenesis by Protein Stabilization
Ameloblasts produce enamel matrix proteins such as amelogenin, ameloblastin, and amelotin during tooth development. The molecular mechanisms of ameloblast differentiation (amelogenesis) are currently not well understood. SP6 is a transcription factor of the Sp/KLF family that was recently found to regulate cell proliferation in a cell-type-specific manner. Sp6-deficient mice demonstrate characteristic tooth anomalies such as delayed eruption of the incisors and supernumerary teeth with disorganized amelogenesis.However, it remains unclear how Sp6 controls amelogenesis. In this study, we used SP6 high producer cells to identify SP6 target genes. Based on the observations that long-term culture of SP6 high producer cells reduced SP6 protein expression but not Sp6 mRNA expression, we found that SP6 is short lived and specifically degraded through a proteasome pathway. We established an in vitro inducible SP6 expression system coupled with siRNA knockdown and found a possible linkage between SP6 and amelogenesis through the regulation of amelotin and Rock1 gene expression by microarray analysis. Our findings suggest that the regulation of SP6 protein stability is one of the crucial steps in amelogenesis
Dynamic Changes of Sp6 Transgene Expression in Dental Epithelial Cells during Long-term Culture
To investigate the function of specificity protein 6 (SP6) transcription factor by gain-of-function procedure, we established cytomegalovirus (CMV) promoter-driven Sp6 stable transformants, C9 cells, using dental epithelialderived cells. Initially, C9 cells produced a significant amount of SP6 protein. However, SP6 expression was reduced in these cells upon long-term culture. We could detect Sp6 transcripts in C9 cells by RT-PCR throughout the passages, although the CMV promoter is known to be epigenetically silenced. We recently found that SP6 was a short-lived protein that was degraded by a ubiquitin-independent proteasome pathway, although it is yet unclear how Sp6 expression was regulated during culture. Thus, we studied the possibility of epigenetic regulation of Sp6 expression. Comparative analysis of endogenous and exogenous Sp6 mRNA expressions demonstrated the specific down-regulation of exogenous Sp6 mRNA levels during culture passages. A DNA methyltransferase inhibitor, 5-Aza-2'-deoxycytidine (5AC), and a histone deacetylase inhibitor, valproic acid (VPA), enhanced or induced SP6 protein expression up to passage 28 without enhancing the mRNA level. The dramatic up-regulation of exogenous Sp6 mRNA was uniquely observed only at passage 50 by 5AC or VPA treatment. These findings indicate that multiple epigenetic regulatory mechanisms operate to fine-tune Sp6 expression during long-term culture
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