5,009 research outputs found
Screening of squirrel monkeys /Saimiri sciureus/ for vestibular function studies
Pathological changes and morphology of squirrel monkeys determined in screening for vestibular function studie
Radiative rates and electron impact excitation rates for transitions in He II
We report calculations of energy levels, radiative rates, collision
strengths, and effective collision strengths for transitions among the lowest
25 levels of the n <= 5 configurations of He~II. The general-purpose
relativistic atomic structure package (GRASP) and Dirac atomic R-matrix code
(DARC) are adopted for the calculations. Radiative rates, oscillator strengths,
and line strengths are reported for all electric dipole (E1), magnetic dipole
(M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among
the 25 levels. Furthermore, collision strengths and effective collision
strengths are listed for all 300 transitions among the above 25 levels over a
wide energy (temperature) range up to 9 Ryd (10**5.4 K). Comparisons are made
with earlier available results and the accuracy of the data is assessed.Comment: 30 pages of text including 12 figures and 5 Tables will appear in
ATOMS 5 (2017
Experimental Observation of Large Chern numbers in Photonic Crystals
Despite great interest in the quantum anomalous Hall phase and its analogs,
all experimental studies in electronic and bosonic systems have been limited to
a Chern number of one. Here, we perform microwave transmission measurements in
the bulk and at the edge of ferrimagnetic photonic crystals. Bandgaps with
large Chern numbers of 2, 3, and 4 are present in the experimental results
which show excellent agreement with theory. We measure the mode profiles and
Fourier transform them to produce dispersion relations of the edge modes, whose
number and direction match our Chern number calculations.Comment: This experimental work was accepted to PRL on Oct. 13, 2015. Our
theoretical work from PRL http://dx.doi.org/10.1103/PhysRevLett.113.11390
Mechanism of resonant x-ray magnetic scattering in NiO
We study the resonant x-ray magnetic scattering (RXMS) around the K edge of
Ni in the antiferromagnet NiO, by treating the 4p states of Ni as a band and
the 3d states as localized states. We propose a mechanism that the 4p states
are coupled to the magnetic order through the intra-atomic Coulomb interaction
between the 4p and the 3d states and through the p-d mixing to the 3d states of
neighboring Ni atoms. These couplings induce the orbital moment in the 4p band,
and thereby give rise to the RXMS intensity at the K edge in the dipolar
process. It is found that the spin-orbit interaction in the 4p band has
negligibly small contribution to the RXMS intensity. The present model
reproduces well the experimental spectra. We also discuss the azimuthal angle
dependence of the intensity.Comment: 10 pages (revtex) and 7 postscript figure
Spin Excitations and Sum Rules in the Heisenberg Antiferromagnet
Various bounds for the energy of collective excitations in the Heisenberg
antiferromagnet are presented and discussed using the formalism of sum rules.
We show that the Feynman approximation significantly overestimates (by about
30\% in the square lattice) the spin velocity due to the non
negligible contribution of multi magnons to the energy weighted sum rule. We
also discuss a different, Goldstone type bound depending explicitly on the
order parameter (staggered magnetization). This bound is shown to be
proportional to the dispersion of classical spin wave theory with a
q-independent normalization factor. Rigorous bounds for the excitation energies
in the anisotropic Heisenberg model are also presented.Comment: 26 pages, Plain TeX including 1 PostScript figure, UTF-307-10/9
Twist Symmetry and Classical Solutions in Open String Field Theory
We construct classical solutions of open string field theory which are not
invariant under ordinary twist operation. From detailed analysis of the moduli
space of the solutions, it turns out that our solutions become nontrivial at
boundaries of the moduli space. The cohomology of the modified BRST operator
and the CSFT potential evaluated by the level truncation method strongly
support the fact that our nontrivial solutions correspond to the closed string
vacuum. We show that the nontrivial solutions are equivalent to the twist even
solution which was found by Takahashi and Tanimoto, and twist invariance of
open string field theory remains after the shift of the classical backgrounds.Comment: 19 pages, 2 figures; v2: errors fixe
Ductility of interstitial-free steel under high strain rate tension: Experiments and macroscopic modeling with a physically-based consideration
AbstractIn this paper, an experimental investigation and a constitutive modeling of the mechanical response of an interstitial-free (IF) steel over a wide range of strain rates (from 0.001/s to 750/s) are presented. Tensile tests at relatively high strain rates, exceeding 100/s, are performed at an initial room temperature, using the so-called one bar technique developed on the basis of the Hopkinson bar method. At a high strain rate, a distinct upper yield limit is observed, and the subsequent flow stress increases remarkably. Furthermore, the ductility is reduced significantly in comparison to the case of low strain rate tension. In order to express such a complicated material response of IF steel, we develop a new constitutive model that takes into account effects of a change in the mobile dislocation density and thermal softening. The model can be easily applicable to large-scale engineering computations, because it is macroscopically formulated. We try to reproduce the tensile response including a diffuse neck formation at high strain rates, using the proposed constitutive model and finite element method. The results indicate that a change in the mobile dislocation density, together with thermal softening, has substantial effects on apparent work hardening behavior at high strain rates, although the change in the mobile dislocation density is transcribed at macroscopic scale in the model. Finally, we discuss characteristics of true stressâtrue strain curves at various strain rates, and their correlation with the plastic instability behavior
Path-Integral Formulation of Casimir Effects in Supersymmetric Quantum Electrodynamics
The Casimir effect is an interesting phenomenon in the sense that it provides
us with one of the primitive means of extracting the energy out of the vacuum.
Since the original work of Casimir a number of works have appeared in extending
the result to the case of more general topological and dynamical configurations
of the boundary condition and to the circumstances at finite temperature and
gravity. In the studies of the Casimir effects it is common to assume the free
electromagnetic field in the bounded region. It may be interesting to extend
our arguments for fields other than the electromagnetic field. The Casimir
effect due to the free fermionic fields has been investigated by several
authors and has been found to result in an attractive force under the suitable
physical boundary conditions.Comment: 12 pages, 6 figures, REVTe
A New Action Principle for Witten's Topological Field Theory
In this letter a new gauge invariant, metric independent action is introduced
from which Witten's Topological Quantum Field Theory may be obtained after
gauge fixing using standard BRST techniques. In our model the BRST algebra of
transformations, under which the effective action is invariant, close off-shell
in distintion with what occurs in the one proposed by Labastida and Pernici.
Our approach provides the geometrical principle for the quantum theory. We also
compare our results with an alternative formulation presented by Baulieu and
Singer.Comment: 8 pages, SB/F-94-22
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