4,201 research outputs found
Splice variants in apoptotic pathway
Elimination of superfluous or mutated somatic cells is provided by various mechanisms including apoptosis, and deregulation of apoptotic signaling pathways contributes to oncogenesis. 40 years have passed since the term “apoptosis” was introduced by Kerr et al. in 1972; among the programmed cell death, a variety of therapeutic strategies especially targeting apoptotic pathways have been investigated. Alternative precursor messenger RNA splicing, by which the process the exons of pre-mRNA are spliced in different arrangements to produce structurally and functionally distinct mRNA and proteins, is another field in progress, and it has been recognized as one of the most important mechanisms that maintains genomic and functional diversity. A variety of apoptotic genes are regulated through alternative pre-mRNA splicing as well, some of which have important functions as pro-apoptotic and anti-apoptotic factors. In this article we summarized splice variants of some of the apoptotic genes including BCL2L1, BIRC5, CFLAR, and MADD, as well as the regulatory mechanisms of alternative splicing of these genes. If the information of the apoptosis and aberrant splicing in each of malignancies is integrated, it will become possible to target proper variants for apoptosis, and the trans-elements themselves can become specific targets of cancer therapy as well. This article is part of a Special Issue entitled “Apoptosis: Four Decades Later”
Oscillations of rapidly rotating relativistic stars
Non-axisymmetric oscillations of rapidly rotating relativistic stars are
studied using the Cowling approximation. The oscillation spectra have been
estimated by Fourier transforming the evolution equations describing the
perturbations. This is the first study of its kind and provides information on
the effect of fast rotation on the oscillation spectra while it offers the
possibility in studying the complete problem by including spacetime
perturbations. Our study includes both axisymmetric and non-axisymmetric
perturbations and provides limits for the onset of the secular bar mode
rotational instability. We also present approximate formulae for the dependence
of the oscillation spectrum from rotation. The results suggest that it is
possible to extract the relativistic star's parameters from the observed
gravitational wave spectrum.Comment: this article will be published in Physical Review
The chaotic behavior of the black hole system GRS 1915+105
A modified non-linear time series analysis technique, which computes the
correlation dimension , is used to analyze the X-ray light curves of the
black hole system GRS 1915+105 in all twelve temporal classes. For four of
these temporal classes saturates to which indicates that
the underlying dynamical mechanism is a low dimensional chaotic system. Of the
other eight classes, three show stochastic behavior while five show deviation
from randomness. The light curves for four classes which depict chaotic
behavior have the smallest ratio of the expected Poisson noise to the
variability () while those for the three classes which depict
stochastic behavior is the highest (). This suggests that the temporal
behavior of the black hole system is governed by a low dimensional chaotic
system, whose nature is detectable only when the Poisson fluctuations are much
smaller than the variability.Comment: Accepted for publication in Astrophysical Journa
Crustal Oscillations of Slowly Rotating Relativistic Stars
We study low-amplitude crustal oscillations of slowly rotating relativistic
stars consisting of a central fluid core and an outer thin solid crust. We
estimate the effect of rotation on the torsional toroidal modes and on the
interfacial and shear spheroidal modes. The results compared against the
Newtonian ones for wide range of neutron star models and equations of state.Comment: 15 page
Global Twist of Sunspot Magnetic Fields Obtained from High Resolution Vector Magnetograms
The presence of fine structures in the sunspot vector magnetic fields has
been confirmed from Hinode as well as other earlier observations. We studied 43
sunspots based on the data sets taken from ASP/DLSP, Hinode (SOT/SP) and SVM
(USO). In this \emph{Letter}, (i) We introduce the concept of signed shear
angle (SSA) for sunspots and establish its importance for non force-free
fields. (ii) We find that the sign of global (force-free parameter) is
well correlated with the global SSA and the photospheric chirality of sunspots.
(iii) Local patches of opposite signs are present in the umbra of each
sunspot. The amplitude of the spatial variation of local in the umbra
is typically of the order of the global of the sunspot. (iv) We find
that the local is distributed as alternately positive and negative
filaments in the penumbra. The amplitude of azimuthal variation of the local
in the penumbra is approximately an order of magnitude larger than
that in the umbra. The contributions of the local positive and negative
currents and in the penumbra cancel each other giving almost no
contribution for their global values for whole sunspot. (v) Arc-like structures
(partial rings) with a sign opposite to that of the dominant sign of
of the umbral region are seen at the umbral-penumbral boundaries of some
sunspots. (vi) Most of the sunspots studied, belong to the minimum epoch of the
23 solar cycle and do not follow the so-called hemispheric helicity
rule.Comment: 15 pages, 3 figures, 1 table; Accepted for publication in the ApJ
Letter
Nonlinear force-free modelling: influence of inaccuracies in the measured magnetic vector
Context: Solar magnetic fields are regularly extrapolated into the corona
starting from photospheric magnetic measurements that can suffer from
significant uncertainties. Aims: Here we study how inaccuracies introduced into
the maps of the photospheric magnetic vector from the inversion of ideal and
noisy Stokes parameters influence the extrapolation of nonlinear force-free
magnetic fields. Methods: We compute nonlinear force-free magnetic fields based
on simulated vector magnetograms, which have been produced by the inversion of
Stokes profiles, computed froma 3-D radiation MHD simulation snapshot. These
extrapolations are compared with extrapolations starting directly from the
field in the MHD simulations, which is our reference. We investigate how line
formation and instrumental effects such as noise, limited spatial resolution
and the effect of employing a filter instrument influence the resulting
magnetic field structure. The comparison is done qualitatively by visual
inspection of the magnetic field distribution and quantitatively by different
metrics. Results: The reconstructed field is most accurate if ideal Stokes data
are inverted and becomes less accurate if instrumental effects and noise are
included. The results demonstrate that the non-linear force-free field
extrapolation method tested here is relatively insensitive to the effects of
noise in measured polarization spectra at levels consistent with present-day
instruments. Conclusions heading: Our results show that we can reconstruct the
coronal magnetic field as a nonlinear force-free field from realistic
photospheric measurements with an accuracy of a few percent, at least in the
absence of sunspots.Comment: A&A, accepted, 9 Pages, 4 Figure
The underlying physical meaning of the relation
Asteroseismology of stars that exhibit solar-like oscillations are enjoying a
growing interest with the wealth of observational results obtained with the
CoRoT and Kepler missions. In this framework, scaling laws between
asteroseismic quantities and stellar parameters are becoming essential tools to
study a rich variety of stars. However, the physical underlying mechanisms of
those scaling laws are still poorly known. Our objective is to provide a
theoretical basis for the scaling between the frequency of the maximum in the
power spectrum () of solar-like oscillations and the cut-off
frequency (). Using the SoHO GOLF observations together with
theoretical considerations, we first confirm that the maximum of the height in
oscillation power spectrum is determined by the so-called \emph{plateau} of the
damping rates. The physical origin of the plateau can be traced to the
destabilizing effect of the Lagrangian perturbation of entropy in the
upper-most layers which becomes important when the modal period and the local
thermal relaxation time-scale are comparable. Based on this analysis, we then
find a linear relation between and , with a
coefficient that depends on the ratio of the Mach number of the exciting
turbulence to the third power to the mixing-length parameter.Comment: 8 pages, 11 figures. Accepted in A&
Rapid X-Ray Variability of Neutron Stars in Low-Mass Binary Systems
The dramatic discovery with the Rossi X-Ray Timing Explorer satellite of
remarkably coherent 300--1200 Hz oscillations in the X-ray brightness of
some sixteen neutron stars in low-mass binary systems has spurred theoretical
modeling of these oscillations and investigation of their implications for the
neutron stars and accretion flows in these systems. High-frequency oscillations
are observed both during thermonuclear X-ray bursts and during intervals of
accretion-powered emission and appear to be a characteristic feature of
disk-accreting neutron stars with weak magnetic fields. In this review we focus
on the high-frequency quasi-periodic oscillations (QPOs) seen in the
accretion-powered emission. We first summarize the key properties of these
kilohertz QPOs and then describe briefly the models that have been proposed to
explain them. The existing evidence strongly favors beat-frequency models. We
mention several of the difficulties encountered in applying the magnetospheric
beat-frequency model to the kilohertz QPOs. The most fully developed and
successful model is the sonic-point beat-frequency model. We describe the work
on this model in some detail. We then discuss observations that could help to
distinguish between models. We conclude by noting some of the ways in which
study of the kilohertz QPOs may advance our understanding of dense matter and
strong gravitational fields.Comment: 10 pages LaTeX including six figures, uses espcrc2.sty (included),
invited talk at "The Active X-Ray Sky", eds. L. Scarsi, H. Bradt, P. Giommi,
and F. Fior
抗ヒスタミン薬ケトチフェンの連日投与による体内時計位相調節
富山大学・富生命博甲第90号・AHMAD ALSAWAF・2017/03/23Sleep and Biological Rhythms,2016.1,14(1),117-120,doi: 10.1007/s41105-015-0021-yに掲載。富山大学201
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