2,790 research outputs found
NMR measurements on obliquely evaporated Co-Cr films
The distribution of the hyperfine fields or the resonance frequencies in metals and alloys obtained by NMR measurements have been known for a long time. Recently, new experimental data have been published about thin films for studying their chemical inhomogeneities. An example is the study on sputtered and evaporated Co-Cr layers. In this paper we report on the compositional distribution of co-evaporated Co-Cr films by using the Co spin-echo NMR technique. For comparison single source evaporated samples of Co-Cr and pure Co as well as two alloyed ribbons (¿bulk¿ samples) have also been measured. Based on the NMR results the local Cr concentration of the ferromagnetic and less ferromagnetic regions are determined. In comparison the data from the co-evaporated films, even at low substrate temperature, have clearly shown the presence of a process-induced compositional separation. This is in qualitative agreement with the magnetic properties of the samples
X-Ray Study of the Outer Region of Abell 2142 with Suzaku
We observed outer regions of a bright cluster of galaxies A2142 with Suzaku.
Temperature and brightness structures were measured out to the virial radius
() with good sensitivity. We confirmed the temperature drop from 9 keV
around the cluster center to about 3.5 keV at , with the density
profile well approximated by the model with . Within
0.4\r_{200}, the entropy profile agrees with , as predicted by the
accretion shock model. The entropy slope becomes flatter in the outer region
and negative around . These features suggest that the intracluster
medium in the outer region is out of thermal equilibrium. Since the relaxation
timescale of electron-ion Coulomb collision is expected to be longer than the
elapsed time after shock heating at , one plausible reason of the low
entropy is the low electron temperature compared to that of ions. Other
possible explanations would be gas clumpiness, turbulence and bulk motions of
ICM\@. We also searched for a warm-hot intergalactic medium around
and set an upper limit on the oxygen line intensity. Assuming a line-of-sight
depth of 2 Mpc and oxygen abundance of 0.1 solar, the upper limit of an
overdensity is calculated to be 280 or 380, depending on the foreground
assumption.Comment: 14 pages, 8 figure
Molecular transistor coupled to phonons and Luttinger-liquid leads
We study the effects of electron-phonon interactions on the transport
properties of a molecular quantum dot coupled to two Luttinger-liquid leads. In
particular, we investigate the effects on the steady state current and DC noise
characteristics. We consider both equilibrated and unequilibrated on-dot
phonons. The density matrix formalism is applied in the high temperature
approximation and the resulting semi-classical rate equation is numerically
solved for various strengths of electron-electron interactions in the leads and
electron-phonon coupling. The current and the noise are in general smeared out
and suppressed due to intralead electron interaction. On the other hand, the
Fano factor, which measures the noise normalized by the current, is more
enhanced as the intralead interaction becomes stronger. As the electron-phonon
coupling becomes greater than order one, the Fano factor exhibits
super-Poissonian behaviour.Comment: 11 pages, 11 figure
Faraday Rotation with Single Nuclear Spin Qubit in a High-Finesse Optical Cavity
When an off-resonant light field is coupled with atomic spins, its
polarization can rotate depending on the direction of the spins via a Faraday
rotation which has been used for monitoring and controlling the atomic spins.
We observed Faraday rotation by an angle of more than 10 degrees for a single
1/2 nuclear spin of 171Yb atom in a high-finesse optical cavity. By employing
the coupling between the single nuclear spin and a photon, we have also
demonstrated that the spin can be projected or weakly measured through the
projection of the transmitted single ancillary photon.Comment: 6 pages, 6 figure
Nonequilibrium quantum criticality in open electronic systems
A theory is presented of quantum criticality in open (coupled to reservoirs)
itinerant electron magnets, with nonequilibrium drive provided by current flow
across the system. Both departures from equilibrium at conventional
(equilibrium) quantum critical points and the physics of phase transitions
induced by the nonequilibrium drive are treated. Nonequilibrium-induced phase
transitions are found to have the same leading critical behavior as
conventional thermal phase transitions.Comment: 5 pages, 1 figur
Modeling of hyper-adaptability: from motor coordination to rehabilitation
Hyper-adaptability is an ability of humans and animals to adapt to large-scale changes in the nervous system or the musculoskeletal system, such as strokes and spinal cord injuries. Although this adaptation may involve similar neural processes with normal adaptation to usual environmental and body changes in daily lives, it can be fundamentally different because it requires ‘construction’ of the neural structure itself and ‘reconstitution’ of sensorimotor control rules to compensate for the changes in the nervous system. In this survey paper, we aimed to provide an overview on how the brain structure changes after brain injury and recovers through rehabilitation. Next, we demonstrated the recent approaches used to apply computational and neural network modeling to recapitulate motor control and motor learning processes. Finally, we discussed future directions to bridge the gap between conventional physiological and modeling approaches to understand the neural and computational mechanisms of hyper-adaptability and its applications to clinical rehabilitation
Confirming the Detection of an Intergalactic X-ray Absorber Toward PKS 2155-304
We present new observations on PKS 2155-304 with the Chandra Low Energy
Transmission Grating Spectrometer (LETG), using the Advanced CCD Imaging
Spectrometer (ACIS). We confirm the detection of an absorption line plausibly
identified as OVIII Ly-alpha from the warm-hot intergalactic medium associated
with a small group of galaxies along the line of sight, as originally reported
by Fang et al. 2002 (here after FANG02). Combining the previous observations in
FANG02 and five new, long observations on the same target, we increase the
total exposure time by a factor of three, and the total counts per resolution
element by a factor of five. The measured line equivalent width is smaller than
that observed in FANG02, but still consistent at 90% confidence. We also
analyze the XMM-Newton observations on the same target, as well as observations
using the Chandra LETG and the High Resolution Camera (HRC) combination. These
observations have been used to challenge our reported detection. While no line
is seen in either the XMM-Newton and the Chandra LETG+HRC data, we find that
our result is consistent with the upper limits from both data sets. We
attribute the non-detection to (1) higher quality of the Chandra LETG+ACIS
spectrum, and (2) the rather extended wings of the line spread functions of
both the XMM RGS and the Chandra LETG+HRC. We discuss the implication of our
observation on the temperature and density of the absorber. We also confirm the
detection of z ~ 0 OVII absorption and, comparing with previous Chandra
analysis, we obtain much tighter constraints on the line properties.Comment: 10 pages, 8 figures, accepted for publication in Ap
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