2,483 research outputs found
Sulu Speaks: George Takei on "Star Trek"
This record contains recordings of an interview with George Takei. The recordings are being made available in both .mp3 and .aiff formats
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Experimental Study of Dislocation Damping Using a Rock Analogue
In order to explore the effects of dislocations on seismic velocity and attenuation, we conducted a series of forced oscillation and ultrasonic tests on rock analogue samples (polycrystalline borneol) that were pre-deformed under various differential stress ∆σ. Additionally, creep experiments were conducted to determine the steady-state flow law for borneol. The dominant deformation mechanism of polycrystalline borneol changes from diffusion to dislocation creep at about ∆σ = 2 MPa. At high stresses, power law creep with a stress exponent of ∼4 was measured. Microstructure of the deformed samples showed wavy grain boundaries due to dislocation-induced migration, and the occasional existence of microcracks. A borneol sample deformed in the dislocation creep regime showed a significant reduction in Young’s modulus E and a slight increase in attenuation Q^−1 at frequencies lower than 100 Hz, whereas E at ultrasonic frequency (10^6 Hz) did not reduce. Therefore, a major part of the dislocation creep-induced anelastic relaxation is a peak with a characteristic frequency between 100 and 10^6 Hz, which is much higher than the range of grain boundary-induced anelasticity of this material. Further experiments under higher confining pressure are needed to assess the relative contribution from dislocations and microcracks to this peak.JSPS KAKENHI Grant Number JP15K1356
Orientational Defects in Ice Ih: An Interpretation of Electrical Conductivity Measurements
We present a first-principles study of the structure and energetics of
Bjerrum defects in ice Ih and compare the results to experimental electrical
conductivity data. While the DFT result for the activation energy is in good
agreement with experiment, we find that its two components have quite different
values. Aside from providing new insight into the fundamental parameters of the
microscopic electrical theory of ice, our results suggest the activity of traps
in doped ice in the temperature regime typically assumed to be controlled by
the free migration of L defects.Comment: 4 pages, 4 Figures, 1 Tabl
Hole burning in a nanomechanical resonator coupled to a Cooper pair box
We propose a scheme to create holes in the statistical distribution of
excitations of a nanomechanical resonator. It employs a controllable coupling
between this system and a Cooper pair box. The success probability and the
fidelity are calculated and compared with those obtained in the atom-field
system via distinct schemes. As an application we show how to use the
hole-burning scheme to prepare (low excited) Fock states.Comment: 7 pages, 10 figure
Thermodynamics of the Coma Cluster Outskirts
We present results from a large mosaic of Suzaku observations of the Coma
Cluster, the nearest and X-ray brightest hot, dynamically active, non-cool core
system, focusing on the thermodynamic properties of the ICM on large scales.
For azimuths not aligned with an infalling subcluster towards the southwest,
our measured temperature and X-ray brightness profiles exhibit broadly
consistent radial trends, with the temperature decreasing from about 8.5 keV at
the cluster center to about 2 keV at a radius of 2 Mpc, which is the edge of
our detection limit. The SW merger significantly boosts the surface brightness,
allowing us to detect X-ray emission out to ~2.2 Mpc along this direction.
Apart from the southwestern infalling subcluster, the surface brightness
profiles show multiple edges around radii of 30-40 arcmin. The azimuthally
averaged temperature profile, as well as the deprojected density and pressure
profiles, all show a sharp drop consistent with an outward propagating shock
front located at 40 arcmin, corresponding to the outermost edge of the giant
radio halo observed at 352 MHz with the WSRT. The shock front may be powering
this radio emission. A clear entropy excess inside of r_500 reflects the
violent merging events linked with these morphological features. Beyond r_500,
the entropy profiles of the Coma Cluster along the relatively relaxed
directions are consistent with the power-law behavior expected from simple
models of gravitational large-scale structure formation. The pressure is also
in agreement at these radii with the expected values measured from SZ data from
the Planck satellite. However, due to the large uncertainties associated with
the Coma Cluster measurements, we cannot yet exclude an entropy flattening in
this system consistent with that seen in more relaxed cool core clusters.Comment: submitted to ApJ; revised after first referee repor
Large-scale Motions in the Perseus Galaxy Cluster
By combining large-scale mosaics of ROSAT PSPC, XMM-Newton, and Suzaku X-ray
observations, we present evidence for large-scale motions in the intracluster
medium of the nearby, X-ray bright Perseus Cluster. These motions are suggested
by several alternating and interleaved X-ray bright, low-temperature,
low-entropy arcs located along the east-west axis, at radii ranging from ~10
kpc to over a Mpc. Thermodynamic features qualitatively similar to these have
previously been observed in the centers of cool core clusters, and were
successfully modeled as a consequence of the gas sloshing/swirling motions
induced by minor mergers. Our observations indicate that such sloshing/swirling
can extend out to larger radii than previously thought, on scales approaching
the virial radius.Comment: 6 pages, 6 figures, accepted for publication in Ap
The Expression of Wnt4 Is Regulated by Estrogen via an Estrogen Receptor Alpha-dependent Pathway in Rat Pituitary Growth Hormone-producing Cells
Wnt signaling is important in many aspects of cell biology and development. In the mouse female reproductive tract, Wnt4, Wnt5a, and Wnt7a show differential expression during the estrus cycle, suggesting that they participate in female reproductive physiology. Although the pituitary is a major gland regulating reproduction, the molecular mechanism of Wnt signaling here is unclear. We elucidated the subcellular distribution of Wnt4 in the pituitary of estrogen-treated ovariectomized female rats. Expression of Wnt4 mRNA increased dramatically, particularly in proestrus compared with estrus and metestrus. Wnt4 protein was observed in the cytoplasm of almost all growth hormone (GH)-producing cells and in only a few thyroid-stimulating hormone β (TSHβ)-producing cells. In rat GH-producing pituitary tumor (MtT/S) cells, estrogen-induced expression of Wnt4 mRNA was completely inhibited by estrogen receptor antagonist ICI 182,780 in vitro. Thus, rat pituitary GH cells synthesize Wnt4 and this is induced by estrogen mediated via an estrogen receptor alpha-dependent pathway
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