1,523 research outputs found
Influence of external magnetic fields on growth of alloy nanoclusters
Kinetic Monte Carlo simulations are performed to study the influence of
external magnetic fields on the growth of magnetic fcc binary alloy
nanoclusters with perpendicular magnetic anisotropy. The underlying kinetic
model is designed to describe essential structural and magnetic properties of
CoPt_3-type clusters grown on a weakly interacting substrate through molecular
beam epitaxy. The results suggest that perpendicular magnetic anisotropy can be
enhanced when the field is applied during growth. For equilibrium bulk systems
a significant shift of the onset temperature for L1_2 ordering is found, in
agreement with predictions from Landau theory. Stronger field induced effects
can be expected for magnetic fcc-alloys undergoing L1_0 ordering.Comment: 10 pages, 3 figure
Charge-density Waves Survive the Pauli Paramagnetic Limit
Measurements of the resistance of single crystals of (Per)Au(mnt)
have been made at magnetic fields of up to 45 T, exceeding the Pauli
paramagnetic limit of T. The continued presence of
non-linear charge-density wave electrodynamics at T unambiguously
establishes the survival of the charge-density wave state above the Pauli
paramagnetic limit, and the likely emergence of an inhomogeneous phase
analogous to that anticipated to occur in superconductors.Comment: 4 pages, three figure
Psychotherapy in dizziness: a systematic review
About 30-50% of complex dizziness disorders are organically not sufficiently explained or related to a psychiatric disorder. Of patients with such dizziness disorders, 80% are severely impaired by dizziness in their daily and working lives; nevertheless, they are often not diagnosed or treated adequately
Acoustic radiation controls friction: Evidence from a spring-block experiment
Brittle failures of materials and earthquakes generate acoustic/seismic waves
which lead to radiation damping feedbacks that should be introduced in the
dynamical equations of crack motion. We present direct experimental evidence of
the importance of this feedback on the acoustic noise spectrum of
well-controlled spring-block sliding experiments performed on a variety of
smooth surfaces. The full noise spectrum is quantitatively explained by a
simple noisy harmonic oscillator equation with a radiation damping force
proportional to the derivative of the acceleration, added to a standard viscous
term.Comment: 4 pages including 3 figures. Replaced with version accepted in PR
Optimal protocols for Hamiltonian and Schr\"odinger dynamics
For systems in an externally controllable time-dependent potential, the
optimal protocol minimizes the mean work spent in a finite-time transition
between given initial and final values of a control parameter. For an initially
thermalized ensemble, we consider both Hamiltonian evolution for classical
systems and Schr\"odinger evolution for quantum systems. In both cases, we show
that for harmonic potentials, the optimal work is given by the adiabatic work
even in the limit of short transition times. This result is counter-intuitive
because the adiabatic work is substantially smaller than the work for an
instantaneous jump. We also perform numerical calculations of the optimal
protocol for Hamiltonian dynamics in an anharmonic quartic potential. For a
two-level spin system, we give examples where the adiabatic work can be reached
in either a finite or an arbitrarily short transition time depending on the
allowed parameter space.Comment: submitted to J. Stat. Mech.: Theor. Exp
Exactly solvable statistical model for two-way traffic
We generalize a recently introduced traffic model, where the statistical
weights are associated with whole trajectories, to the case of two-way flow. An
interaction between the two lanes is included which describes a slowing down
when two cars meet. This leads to two coupled five-vertex models. It is shown
that this problem can be solved by reducing it to two one-lane problems with
modified parameters. In contrast to stochastic models, jamming appears only for
very strong interaction between the lanes.Comment: 6 pages Latex, submitted to J Phys.
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