604 research outputs found
Vertical Integration and Trade Protection: The Case of Antidumping Duties
This paper analyzes the interaction of trade policy with the vertical structures of foreign firms exporting goods to the United States, focusing on the case of antidumping duties. I use a model that incorporates both vertical structure and the dynamics of U.S. antidumping duties to show that the policy has a notably different impact on vertically integrated and non-integrated foreign firms. I then successfully test the theoretical predictions using data on 489 antidumping cases. In particular, I find that non-integrated firms are more likely than vertically integrated firms to exit the U.S. market following the imposition of duties, and less likely to pass the duties on to consumers for certain products. My empirical findings also indicate that antidumping duties oscillate between low and high levels -a previously unnoticed, surprising and most-likely unintended consequence of the design of U.S. antidumping policy that is nevertheless predicted by my model.Vertical Intrgration, antidumping duties, trade policy
Superconductor insulator transition in thin films driven by an orbital parallel magnetic field effect
We study theoretically orbital effects of a parallel magnetic field applied
to a disordered superconducting film. We find that the field reduces the phase
stiffness and leads to strong quantum phase fluctuations driving the system
into an insulating behavior. This microscopic model shows that the critical
field decreases with the sheet resistance, in agreement with recent
experimental results. The predictions of this model can be used to discriminate
spin and orbital effects. We find that experiments conducted by A. Johansson
\textit{et al.} are more consistent with the orbital mechanism.Comment: 4 pages, 2 figure
Near-zero-energy end states in topologically trivial spin-orbit coupled superconducting nanowires with a smooth confinement
A one-dimensional spin-orbit coupled nanowire with proximity-induced pairing
from a nearby s-wave superconductor may be in a topological nontrivial state,
in which it has a zero energy Majorana bound state at each end. We find that
the topological trivial phase may have fermionic end states with an
exponentially small energy, if the confinement potential at the wire's ends is
smooth. The possible existence of such near-zero energy levels implies that the
mere observation of a zero-bias peak in the tunneling conductance is not an
exclusive signature of a topological superconducting phase even in the ideal
clean single channel limit.Comment: 4 pages, 4 figure
A scattering matrix formulation of the topological index of interacting fermions in one-dimensional superconductors
We construct a scattering matrix formulation for the topological
classification of one-dimensional superconductors with effective time reversal
symmetry in the presence of interactions. For a closed geometry, Fidkowski and
Kitaev have shown that such systems have a topological
classification. We show that in the weak coupling limit, these systems retain a
unitary scattering matrix at zero temperature, with a topological index given
by the trace of the Andreev reflection matrix, \mbox{tr}\, r_{\rm he}. With
interactions, \mbox{tr}\, r_{\rm he} generically takes on the finite set of
values , , , , and . We show that the two
topologically equivalent phases with \mbox{tr}\, r_{\rm he} = \pm 4 support
emergent many-body end states, which we identify to be a topologically
protected Kondo-like resonance. The path in phase space that connects these
equivalent phases crosses a non-fermi liquid fixed point where a multiple
channel Kondo effect develops. Our results connect the topological index to
transport properties, thereby highlighting the experimental signatures of
interacting topological phases in one dimension.Comment: 4 pages, 1 fi
Shot noise in Weyl semimetals
We study the effect of inelastic processes on the magneto-transport of a
quasi-one dimensional Weyl semi-metal, using a modified Boltzmann-Langevin
approach. The magnetic field drives a crossover to a ballistic regime in which
the propagation along the wire is dominated by the chiral anomaly, and the role
of fluctuations inside the sample is exponentially suppressed. We show that
inelastic collisions modify the parametric dependence of the current
fluctuations on the magnetic field. By measuring shot noise as a function of a
magnetic field, for different applied voltage, one can estimate the
electron-electron inelastic length .Comment: 7 pages, 1 figur
Phonophoresis and topical drug delivery
In this study, investigations into phonophoresis were conducted by employing 3 distinct in vitro models. The aim of the first model was to evaluate the effect of ultrasound on the migration rate of different classes of molecules through agar gel. The derived data suggested that small, relatively hydrophobic molecules are more susceptible to ultrasound-enhanced diffusion through the water-filled channels of the agar gel. The application of heat alone increased drug migration by a similar magnitude as the ultrasound, indicating that ultrasonic heating directly increases the thermodynamic potential for diffusion. In the second experimental system, whole rat skin was pre-sonicated and then examined for changes in its barrier properties. At high intensities (1 to 2W cm-2), ultrasonic waves irreversibly compromised the barrier properties of the skin, following the general patterns described in the literature reports. At low intensities (< 1W cm-2), ultrasound discharged sebum from the sebaceous glands so as to fill much of the hair follicle shafts. This entirely novel phenomenon is probably produced by the mechanical effects of the beam. The deposition of sebaceous lipids within the hair follicle shafts can mean that this absorption pathway is blocked for hydrophilic molecules that penetrate via this route. Consequently, this phenomenon can be utilised as a probe to measure the relative follicular contribution to total penetration for these molecules. In the final phonophoresis model, modified Franz cells were employed in order to assess the ultrasound effect on the concurrent transdermal permeation of various molecules through whole rat skin. For the most lipophilic agent tested, the rate-limiting step of absorption was partitioning from the stratum corneum into the viable epidermis. Sonication did not accelerate this step
A topological classification of interaction-driven spin pumps
When adiabatically varied in time, certain one-dimensional band insulators
allow for the quantized noiseless pumping of spin even in the presence of
strong spin orbit scattering. These spin pumps are closely related to the
quantum spin Hall system, and their properties are protected by a time-reversal
restriction on the pumping cycle. In this paper we study pumps formed of
one-dimensional insulators with a time-reversal restriction on the pumping
cycle and a bulk energy gap which arises due to interactions. We find that the
correlated gapped phase can lead to novel pumping properties. In particular,
systems with different ground states can give rise to different
classes of spin pumps, including a trivial class which does not pump quantized
spin and non-trivial classes allowing for the pumping of quantized spin
on average per cycle, where . We discuss an example
of a spin pump that transfers on average spin without transferring
charge.Comment: 5 pages, 2 figure
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