1,371 research outputs found
Antipredator behavior of newts (Cynops pyrrhogaster) against snakes
Newts and salamanders show remarkable diversity in antipredator behavior, developed to enhance their chemical defenses and/or aposematism. The present study reports on the antipredator behavior of newts (Cynops pyrrhogaster) in response to snakes. Newts displayed a significant amount of tail-wagging and tail-undulation in response to a contact stimulus from the snake’s tongue, which is a snake-specific predator stimulus, as compared to a control stimulus (behavioral scores: tongue, 1.05 ± 0.41; control, 0.15 ± 0.15). Newts that were kept in warm temperature conditions, 20°C (at which snakes are active in nature), performed tail displays more frequently than newts kept in low-temperature conditions, 4°C (at which snakes are inactive in nature). Our results suggest that the tail displays of C. pyrrhogaster could function as an antipredator defense; they direct a snake’s attention to its tail to prevent the snake from attacking more vulnerable body parts. We also discussed the reason for inter-populational variation in the tendency of newts to perform tail displays
The “resurrection method” for modification of specific proteins in higher plants
AbstractWe describe a new method designated “the resurrection method” by which a modified protein is expressed in higher plants in place of the original protein. The modified gene constructed by introducing synonymous codon substitutions throughout the original gene to prevent the sequence-specific degradation of its mRNA during RNA silencing is expressed while the expression of the original gene is suppressed. Here, we report the successful alteration of the biochemical properties of green fluorescent protein expressed in transgenic Nicotiana benthamiana, suggesting that this method could be useful for gene control in living plants
Discovery of X-Ray-Emitting O-Ne-Mg-Rich Ejecta in the Galactic Supernova Remnant Puppis A
We report on the discovery of X-ray--emitting O-Ne-Mg-rich ejecta in the
middle-aged Galactic O-rich supernova remnant Puppis A with Chandra and
XMM-Newton. We use line ratios to identify a low-ionization filament running
parallel to the northeastern edge of the remnant that requires supersolar
abundances, particularly for O, Ne, and Mg, which we interpret to be from
O-Ne-Mg-rich ejecta. Abundance ratios of Ne/O, Mg/O, and Fe/O are measured to
be ~2, ~2, and <0.3 times the solar values. Our spatially-resolved spectral
analysis from the northeastern rim to the western rim otherwise reveals
sub-solar abundances consistent with those in the interstellar medium. The
filament is coincident with several optically emitting O-rich knots with high
velocities. If these are physically related, the filament would be a peculiar
fragment of ejecta. On the other hand, the morphology of the filament suggests
that it may trace ejecta heated by a shock reflected strongly off the dense
ambient clouds near the northeastern rim.Comment: Published onlin
A Suzaku Study of Ejecta Structure and Origin of Hard X-ray Emission in the Supernova Remnant G156.2+5.7
We report an X-ray study of the evolved Galactic supernova remnant (SNR)
G156.2+5.7 based on six pointing observations with Suzaku. The remnant's large
extent (100\arcmin in diameter) allows us to investigate its radial structure
in the northwestern and eastern directions from the apparent center. The X-ray
spectra were well fit with a two-component non-equilibrium ionization model
representing the swept-up interstellar medium (ISM) and the metal-rich ejecta.
We found prominent central concentrations of Si, S and Fe from the ejecta
component; the lighter elements of O, Ne and Mg were distributed more
uniformly. The temperature of the ISM component suggests a slow shock (610-960
km s), hence the remnant's age is estimated to be 7,000-15,000 yr,
assuming its distance to be 1.1 kpc. G156.2+5.7 has also been thought to
emit hard, non-thermal X-rays, despite being considerably older than any other
such remnant. In response to a recent discovery of a background cluster of
galaxies (2XMM J045637.2+522411), we carefully excluded its contribution, and
reexamined the origin of the hard X-ray emission. We found that the residual
hard X-ray emission is consistent with the expected level of the cosmic X-ray
background. Thus, no robust evidence for the non-thermal emission was obtained
from G156.2+5.7. These results are consistent with the picture of an evolved
SNR.Comment: 10 pages 8 figures, accepted for PAS
Nearly homogeneous and isotropic turbulence generated by the interaction of supersonic jets
This study reports the development and characterization of a
multiple-supersonic-jet wind tunnel designed to investigate the decay of nearly
homogeneous and isotropic turbulence in a compressible regime. The interaction
of 36 supersonic jets generates turbulence that decays in the streamwise
direction. The velocity field is measured with particle image velocimetry by
seeding tracer particles with ethanol condensation. Various velocity statistics
are evaluated to diagnose decaying turbulence generated by the supersonic jet
interaction. The flow is initially inhomogeneous and anisotropic and possesses
intermittent large-scale velocity fluctuations. The flow evolves into a
statistically homogeneous and isotropic state as the mean velocity profile
becomes uniform. In the nearly homogeneous and isotropic region, the ratio of
root-mean-squared velocity fluctuations in the streamwise and vertical
directions is about 1.08, the longitudinal integral scales are also similar in
these directions, and the large-scale intermittency becomes insignificant. The
turbulent kinetic energy per unit mass decays according to a power law with an
exponent of about 2, larger than those reported for incompressible grid
turbulence. The energy spectra in the inertial subrange agree well with other
turbulent flows when normalized by the dissipation rate and kinematic
viscosity. The non-dimensional dissipation rate is within a range of
0.51--0.87, which is also consistent with incompressible grid turbulence. These
results demonstrate that the multiple-supersonic-jet wind tunnel is helpful in
the investigation of decaying homogeneous isotropic turbulence whose generation
process is strongly influenced by fluid compressibility
X-ray ejecta kinematics of the Galactic core-collapse supernova remnant G292.0+1.8
We report on the results from the analysis of our 114 ks Chandra HETGS
observation of the Galactic core-collapse supernova remnant G292.0+1.8. To
probe the 3D structure of the clumpy X-ray emitting ejecta material in this
remnant, we measured Doppler shifts in emission lines from metal-rich ejecta
knots projected at different radial distances from the expansion center. We
estimate radial velocities of ejecta knots in the range of -2300 <~ v_r <~ 1400
km s^-1. The distribution of ejecta knots in velocity vs. projected-radius
space suggests an expanding ejecta shell with a projected angular thickness of
~90" (corresponding to ~3 pc at d = 6 kpc). Based on this geometrical
distribution of the ejecta knots, we estimate the location of the reverse shock
approximately at the distance of ~4 pc from the center of the supernova
remnant, putting it in close proximity to the outer boundary of the radio
pulsar wind nebula. Based on our observed remnant dynamics and the standard
explosion energy of 10^51 erg, we estimate the total ejecta mass to be <~ 8
M_sun, and we propose an upper limit of <~ 35 M_sun on the progenitor's mass.Comment: 5 figures, accepted by Ap
An Apparent Hard X-ray Decline of CH Cygni
CH Cygni is a symbiotic star consisting of an M giant and an accreting white
dwarf, which is known to be a highly variable X-ray source with a complex,
two-component, spectra. Here we report on two Suzaku observations of CH Cyg,
taken in 2006 January and May, during which the system was seen to be in a soft
X-ray bright, hard X-ray faint state. Based on the extraordinary strength of
the 6.4 keV fluorescent Fe K-alpha line, we show that the hard X-rays observed
with Suzaku are dominated by scattering.Comment: 8 pages, 4 figures, accepted by Publications of the Astronomical
Society of Japa
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