1,255 research outputs found
Threading dislocation densities in semiconductor crystals: a geometric approach
In this letter, we introduce a geometric model to explain the origin of the
observed shallow levels in semiconductors threaded by a dislocation density. We
show that a uniform distribution of screw dislocations acts as an effective
uniform magnetic field which yields bound states for a spin-half quantum
particle, even in the presence of a repulsive Coulomb-like potential. This
introduces energy levels within the band gap, increasing the carrier
concentration in the region threaded by the dislocation density and adding
additional recombination paths other than the near band-edge recombination.Comment: 9 pages, no figur
Derived equivalence classification for cluster-tilted algebras of type
In this paper we give the derived equivalence classification of
cluster-tilted algebras of type An. We show that the bounded derived category
of such an algebra depends only on the number of 3-cycles in the quiver of the
algebra.Comment: 13 pages. New version under a new name. References have been added,
and some proofs have been written out in more detai
Mechanical design of NASA Ames Research Center vertical motion simulator
NASA has designed and is constructing a new flight simulator with large vertical travel. Several aspects of the mechanical design of this Vertical Motion Simulator (VMS) are discussed, including the multiple rack and pinion vertical drive, a pneumatic equilibration system, and the friction-damped rigid link catenaries used as cable supports
On Aharonov-Casher bound states
In this work bound states for the Aharonov-Casher problem are considered.
According to Hagen's work on the exact equivalence between spin-1/2
Aharonov-Bohm and Aharonov-Casher effects, is known that the
term cannot be neglected in the
Hamiltonian if the spin of particle is considered. This term leads to the
existence of a singular potential at the origin. By modeling the problem by
boundary conditions at the origin which arises by the self-adjoint extension of
the Hamiltonian, we derive for the first time an expression for the bound state
energy of the Aharonov-Casher problem. As an application, we consider the
Aharonov-Casher plus a two-dimensional harmonic oscillator. We derive the
expression for the harmonic oscillator energies and compare it with the
expression obtained in the case without singularity. At the end, an approach
for determination of the self-adjoint extension parameter is given. In our
approach, the parameter is obtained essentially in terms of physics of the
problem.Comment: 11 pages, matches published versio
A systematic review of controlled studies: do physicians increase survival with prehospital treatment?
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