25,899 research outputs found
A new fractional derivative without singular kernel: Application to the modelling of the steady heat flow
In this article we propose a new fractional derivative without singular
kernel. We consider the potential application for modeling the steady
heat-conduction problem. The analytical solution of the fractional-order heat
flow is also obtained by means of the Laplace transform.Comment: 1 figur
Phase Space Manipulation of Cold Free Radical OH Molecules
We report bunching, slowing, and acceleration of a supersonically cooled beam
of diatomic hydroxyl radicals (OH). \textit{In situ} observation of
laser-induced fluorescence along the beam propagation path allows for detailed
characterization of longitudinal phase-space manipulation of OH molecules
through the Stark effect by precisely sequenced inhomogeneous electric fields.Comment: 5 pages, 4 color figure
Dark matter halo response to the disk growth
We consider the sensitivity of the circular-orbit adiabatic contraction
approximation to the baryon condensation rate and the orbital structure of dark
matter halos in the CDM paradigm. Using one-dimensional hydrodynamic
simulations including the dark matter halo mass accretion history and gas
cooling, we demonstrate that the adiabatic approximation is approximately valid
even though halos and disks may assemble simultaneously. We further demonstrate
the validity of the simple approximation for CDM halos with isotropic
velocity distributions using three-dimensional N-body simulations. This result
is easily understood: an isotropic velocity distribution in a cuspy halo
requires more circular orbits than radial orbits. Conversely, the approximation
is poor in the extreme case of a radial orbit halo. It overestimates the
response a core dark matter halo, where radial orbit fraction is larger.
Because no astronomically relevant models are dominated by low-angular momentum
orbits in the vicinity of the disk and the growth time scale is never shorter
than a dynamical time, we conclude that the adiabatic contraction approximation
is useful in modeling the response of dark matter halos to the growth of a
disk.Comment: 7 pages, 6 figures, accepted for publication in MNRA
A key to room-temperature ferromagnetism in Fe-doped ZnO: Cu
Successful synthesis of room-temperature ferromagnetic semiconductors,
ZnFeO, is reported. The essential ingredient in achieving
room-temperature ferromagnetism in bulk ZnFeO was found to be
additional Cu doping. A transition temperature as high as 550 K was obtained in
ZnFeCuO; the saturation magnetization at room
temperature reached a value of per Fe. Large
magnetoresistance was also observed below K.Comment: 11 pages, 4 figures; to appear in Appl. Phys. Let
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