2,720 research outputs found
Current driven switching of magnetic layers
The switching of magnetic layers is studied under the action of a spin
current in a ferromagnetic metal/non-magnetic metal/ferromagnetic metal spin
valve. We find that the main contribution to the switching comes from the
non-equilibrium exchange interaction between the ferromagnetic layers. This
interaction defines the magnetic configuration of the layers with minimum
energy and establishes the threshold for a critical switching current.
Depending on the direction of the critical current, the interaction changes
sign and a given magnetic configuration becomes unstable. To model the time
dependence of the switching process, we derive a set of coupled Landau-Lifshitz
equations for the ferromagnetic layers. Higher order terms in the
non-equilibrium exchange coupling allow the system to evolve to its
steady-state configuration.Comment: 8 pages, 2 figure. Submitted to Phys. Rev.
Field dependence of magnetization reversal by spin transfer
We analyse the effect of the applied field (Happl) on the current-driven
magnetization reversal in pillar-shaped Co/Cu/Co trilayers, where we observe
two different types of transition between the parallel (P) and antiparallel
(AP) magnetic configurations of the Co layers. If Happl is weaker than a rather
small threshold value, the transitions between P and AP are irreversible and
relatively sharp. For Happl exceding the threshold value, the same transitions
are progressive and reversible. We show that the criteria for the stability of
the P and AP states and the experimentally observed behavior can be precisely
accounted for by introducing the current-induced torque of the spin transfer
models in a Landau-Lifschitz-Gilbert equation. This approach also provides a
good description for the field dependence of the critical currents
Electromagnetic vertex function of the pion at T > 0
The matrix element of the electromagnetic current between pion states is
calculated in quenched lattice QCD at a temperature of . The
nonperturbatively improved Sheikholeslami-Wohlert action is used together with
the corresponding improved vector current. The electromagnetic
vertex function is extracted for pion masses down to and
momentum transfers .Comment: 17 pages, 8 figure
Finite Nuclei in a Relativistic Mean-Field Model with Derivative Couplings
We study finite nuclei, at the mean-field level, using the Zimanyi-Moskowski
model and one of its variations (the ZM3 model). We calculate energy levels and
ground-state properties in nuclei where the mean-field approach is reliable.
The role played by the spin-orbit potential in sorting out mean-field model
descriptions is emphasized.Comment: 17 pages, 9 figures, 30 kbytes. Uses EPSF.TEX. To appear in Zeit. f.
Phys. A (Hadrons and Nuclei
Hadrons in Dense Resonance-Matter: A Chiral SU(3) Approach
A nonlinear chiral SU(3) approach including the spin 3/2 decuplet is
developed to describe dense matter. The coupling constants of the baryon
resonances to the scalar mesons are determined from the decuplet vacuum masses
and SU(3) symmetry relations. Different methods of mass generation show
significant differences in the properties of the spin-3/2 particles and in the
nuclear equation of state.Comment: 28 pages, 9 figure
Hot Nuclear Matter in the Quark Meson Coupling Model with Dilatons
We study hot nuclear matter in an explicit quark model based on a mean field
description of nonoverlapping nucleon bags bound by the self-consistent
exchange of scalar and vector mesons as well as the glueball field. The
glueball exchange as well as a realization of the broken scale invariance of
quantum chromodynamics is achieved through the introduction of a dilaton field.
The calculations also take into account the medium-dependence of the bag
constant. The effective potential with dilatons is applied to nuclear matter.
The nucleon properties at finite temperature as calculated here are found to be
appreciably different from cold nuclear matter. The introduction of the dilaton
potential improves the shape of the saturation curve at T=0 and is found to
affect hot nuclear matter significantly.Comment: LaTeX/TeX 12 pages (zak2), 13 figures in TeX forma
Invited commentary
P>Background: In double-blind, placebo-controlled food challenges (DBPCFCs), the use of challenge materials in which blinding is validated is a prerequisite for obtaining true blinded conditions during the test procedure. Therefore, the aim of this study was to enlarge the available range of validated recipes for DBPCFCs to facilitate oral challenge tests in all age groups, including young children, while maximizing the top dose in an acceptable volume. Methods: Recipes were developed and subsequently validated by a panel recruited by a matching sensory test. The best 30% of candidates were selected to participate in sensory testing using the paired comparison test. Results: For young children, three recipes with cow's milk and one recipe with peanut could be validated which may be utilized in DBPCFCs. For children older than 4 years and adults, one recipe with egg, two with peanut, one with hazelnut, and one with cashew nut were validated for use in DBPCFCs. Conclusions: All recipes contained larger amounts of allergenic foods than previously validated. These recipes increase the range of validated recipes for use in DBPCFCs in adults and children
Evidence on the effectiveness of health literacy interventions in the EU: a systematic review
Microscopic Calculation of Spin Torques in Disordered Ferromagnets
Effects of conduction electrons on magnetization dynamics, represented by
spin torques, are calculated microscopically in the first order in spatial
gradient and time derivative of magnetization. Special attention is paid to the
so-called -term and the Gilbert damping, , in the presence of
electrons' spin-relaxation processes, which are modeled by quenched magnetic
(and spin-orbit) impurities. The obtained results such as
hold for localized as well as itinerant ferromagnetism.Comment: 4 page
Pion structure from improved lattice QCD: form factor and charge radius at low masses
The charge form factor of the pion is calculated in lattice QCD. The
non-perturbatively improved Sheikholeslami-Wohlert action is used together with
the improved vector current. Other choices for the current are
examined. The form factor is extracted for pion masses from 970 MeV down to 360
MeV and for momentum transfers . The mean square
charge radius is extracted, compared to previous determinations and its
extrapolation to lower masses discussed.Comment: 12 pages REVTeX, 15 figures. Designation of currents clarified.
Details concerning extraction of parameters added. Version accepted by Phys.
Rev.
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