42,790 research outputs found
Mediating exchange bias by Verwey transition in CoO/Fe3O4 thin film
We report the tunability of the exchange bias effect by the first-order
metal-insulator transition (known as the Verwey transition) of Fe3O4 in CoO (5
nm)/Fe3O4 (40 nm)/MgO (001) thin film. In the vicinity of the Verwey
transition, the exchange bias field is substantially enhanced because of a
sharp increase in magnetocrystalline anisotropy constant from high-temperature
cubic to lowtemperature monoclinic structure. Moreover, with respect to the
Fe3O4 (40 nm)/MgO (001) thin film, the coercivity field of the CoO (5 nm)/Fe3O4
(40 nm)/MgO (001) bilayer is greatly increased for all the temperature range,
which would be due to the coupling between Co spins and Fe spins across the
interface
Energy dependence of Normal Branch Oscillation in Scorpius X-1
We report the energy dependence of normal branch oscillations (NBOs) in
Scorpius X-1, a low-mass X-ray binary Z-source. Three characteristic quantities
(centroid frequency, quality factor, and fractional root-mean-squared (rms)
amplitude) of a quasi-periodic oscillation signal as functions of photon energy
are investigated. We found that, although it is not yet statistically well
established, there is a signature indicating that the NBO centroid frequency
decreases with increasing photon energy when it is below 6-8 keV, which turns
out to be positively correlated with the photon energy at the higher energy
side. In addition, the rms amplitude increases significantly with the photon
energy below 13 keV and then decreases in the energy band of 13-20 keV. There
is no clear dependence on photon energy for the quality factor. Based on these
results, we suggest that the NBO originates mainly in the transition layer.Comment: 6 pages, 4 figure
Neutrino Flavor Ratio on Earth and at Astrophysical Sources
We present the reconstruction of neutrino flavor ratios at astrophysical
sources. For distinguishing the pion source and the muon-damped source to the
3 level, the neutrino flux ratios,
and
, need to be measured in accuracies better
than 10%.Comment: 3 pages, 8 figures. Talk presented by T.C. Liu in ERICE 2009, Sicily
Risk Spillovers in Oil-Related CDS, Stock and Credit Markets
This paper examines risk transmission and migration among six US measures of credit and market risk during the full period 2004-2011 period and the 2009-2011 recovery subperiod, with a focus on four sectors related to the highly volatile oil price. There are more long-run equilibrium risk relationships and short-run causal relationships among the four oil-related Credit Default Swaps (CDS) indexes, the (expected equity volatility) VIX index and the (swaption expected volatility) SMOVE index for the full period than for the recovery subperiod. The auto sector CDS spread is the most error-correcting in the long run and also leads in the risk discovery process in the short run. On the other hand, the CDS spread of the highly regulated, natural monopoly utility sector does not error correct. The four oil-related CDS spread indexes are responsive to VIX in the short- and long-run, while no index is sensitive to SMOVE which, in turn, unilaterally assembles risk migration from VIX. The 2007-2008 Great Recession seems to have led to “localization†and less migration of credit and market risk in the oil-related sectors.adjustments;MOVE;SMOVE;VIX;risk,;sectoral CDS
Pair Interaction Potentials of Colloids by Extrapolation of Confocal Microscopy Measurements of Collective Structure
A method for measuring the pair interaction potential between colloidal
particles by extrapolation measurement of collective structure to infinite
dilution is presented and explored using simulation and experiment. The method
is particularly well suited to systems in which the colloid is fluorescent and
refractive index matched with the solvent. The method involves characterizing
the potential of mean force between colloidal particles in suspension by
measurement of the radial distribution function using 3D direct visualization.
The potentials of mean force are extrapolated to infinite dilution to yield an
estimate of the pair interaction potential, . We use Monte Carlo (MC)
simulation to test and establish our methodology as well as to explore the
effects of polydispersity on the accuracy. We use poly-12-hydroxystearic
acid-stabilized poly(methyl methacrylate) (PHSA-PMMA) particles dispersed in
the solvent dioctyl phthalate (DOP) to test the method and assess its accuracy
for three different repulsive systems for which the range has been manipulated
by addition of electrolyte.Comment: 35 pages, 14 figure
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