92,901 research outputs found
Searching for radiative pumping lines of OH masers: II. The 53.3um absorption line towards 1612MHz OH maser sources
This paper analyzes the 53.3um line in the ISO LWS spectra towards a similar
sample of OH/IR sources. We find 137 LWS spectra covering 53.3um and associated
with 47 galactic OH/IR sources. Ten of these galactic OH/IR sources are found
to show and another 5 ones tentatively show the 53.3um absorption while another
7 sources highly probably do not show this line. The source class is found to
be correlated with the type of spectral profile: red supergiants (RSGs) and AGB
stars tend to show strong blue-shifted filling emission in their 53.3um
absorption line profiles while HII regions tend to show a weak red-shifted
filling emission in the line profile. GC sources and megamasers do not show
filling emission feature. It is argued that the filling emission might be the
manifestation of an unresolved half emission half absorption profile of the
53.3um doublet. The 53.3 to 34.6um equivalent width (EW) ratio is close to
unity for RSGs but much larger than unity for GC sources and megamasers while H
II regions only show the 53.3um line. The pump rate defined as maser to IR
photon flux ratio is approximately 5% for RSGs. The pump rates of GC sources
are three order of magnitude smaller. Both the large 53.3 to 34.6um EW ratio
and the small pump rate of the GC OH masers reflect that the two detected
`pumping lines' in these sources are actually of interstellar origin. The pump
rate of Arp 220 is 32%--much larger than that of RSGs, which indicates that the
contribution of other pumping mechanisms to this megamaser is important.Comment: 34 pages, 12 figures, 4 table
Coauthor prediction for junior researchers
Research collaboration can bring in different perspectives and generate more productive results. However, finding an appropriate collaborator can be difficult due to the lacking of sufficient information. Link prediction is a related technique for collaborator discovery; but its focus has been mostly on the core authors who have relatively more publications. We argue that junior researchers actually need more help in finding collaborators. Thus, in this paper, we focus on coauthor prediction for junior researchers. Most of the previous works on coauthor prediction considered global network feature and local network feature separately, or tried to combine local network feature and content feature. But we found a significant improvement by simply combing local network feature and global network feature. We further developed a regularization based approach to incorporate multiple features simultaneously. Experimental results demonstrated that this approach outperformed the simple linear combination of multiple features. We further showed that content features, which were proved to be useful in link prediction, can be easily integrated into our regularization approach. © 2013 Springer-Verlag
Effects of spin current on ferromagnets
When a spin-polarized current flows through a ferromagnet, the local
magnetization receives a spin torque. Two consequences of this spin torque are
studied. First, the uniformly magnetized ferromagnet becomes unstable if a
sufficiently large current is applied. The characteristics of the instability
include spin wave generation and magnetization chaos. Second, the spin torque
has profound effects on the structure and dynamics of the magnetic domain wall.
A detail analysis on the domain wall mass, kinetic energy and wall depinning
threshold is given
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Duality walls, duality trees and fractional branes
We compute the NSVZ beta functions for N = 1 four-dimensional quiver theories arising from D-brane probes on singularities, complete with anomalous dimensions, for a large set of phases in the corresponding duality tree. While these beta functions are zero for D-brane probes, they are non-zero in the presence of fractional branes. As a result there is a non-trivial RG behavior. We apply this running of gauge couplings to some toric singularities such as the cones over Hirzebruch and del Pezzo surfaces. We observe the emergence in string theory, of ``Duality Walls,'' a finite energy scale at which the number of degrees of freedom becomes infinite, and beyond which Seiberg duality does not proceed. We also identify certain quiver symmetries as T-duality-like actions in the dual holographic theory
Energy-Conserving Lattice Boltzmann Thermal Model in Two Dimensions
A discrete velocity model is presented for lattice Boltzmann thermal fluid dynamics.
This model is implemented and tested in two dimensions with a finite difference scheme. Comparison with analytical solutions shows an excellent agreement even for wide temperature differences. An alternative approximate approach is then presented for traditional lattice transport schemes
Local electronic structure near oxygen dopants in BSCCO-2212: a window on the high-Tc pair mechanism?
The cuprate material BSCCO-2212 is believed to be doped by a combination of
cation switching and excess oxygen. The interstitial oxygen dopants are of
particular interest because scanning tunnelling microscopy (STM) experiments
have shown that they are positively correlated with the local value of the
superconducting gap, and calculations suggest that the fundamental attraction
between electrons is modulated locally. In this work, we use density functional
theory to try to ascertain which locations in the crystal are energetically
most favorable for the O dopant atoms, and how the surrounding cage of atoms
deforms. Our results provide support for the identification of STM resonances
at -1eV with dopant interstitial O atoms, and show how the local electronic
structure is modified nearby.Comment: 5 pages, 3 figure
Quantum Entanglement of Electromagnetic Fields in Non-inertial Reference Frames
Recently relativistic quantum information has received considerable attention
due to its theoretical importance and practical application. Especially,
quantum entanglement in non-inertial reference frames has been studied for
scalar and Dirac fields. As a further step along this line, we here shall
investigate quantum entanglement of electromagnetic fields in non-inertial
reference frames. In particular, the entanglement of photon helicity entangled
state is extensively analyzed. Interestingly, the resultant logarithmic
negativity and mutual information remain the same as those for inertial
reference frames, which is completely different from that previously obtained
for the particle number entangled state.Comment: more explanatory material added in the introduction, version to
appear in Journal of Physics
Current-driven vortex domain wall dynamics by micromagnetic simulations
Current-driven vortex wall dynamics is studied by means of a two-dimensional
analytical model and micromagnetic simulation. By constructing a trial function
for the vortex wall in the magnetic wire, we analytically solve for domain wall
velocity and deformation in the presence of the current-induced spin torque. A
critical current for the domain wall transformation from the vortex wall to the
transverse wall is calculated. A comparison between the field- and
current-driven wall dynamics is carried out. Micromagnetic simulations are
performed to verify our analytical results.Comment: 7 pages, 4 figure
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