9,050 research outputs found
Spin projection and spin current density within relativistic electronic transport calculations
A spin projection scheme is presented which allows the decomposition of the
electric conductivity into two different spin channels within fully
relativistic transport calculations that account for the impact
of spin-orbit coupling. This is demonstrated by calculations of the
spin-resolved conductivity of FeCr and CoPt disordered
alloys on the basis of the corresponding Kubo-Greenwood equation implemented
using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA)
band structure method. In addition, results for the residual resistivity of
diluted Ni-based alloys are presented that are compared to theoretical and
experimental ones that rely on Mott's two-current model for spin-polarized
systems. The application of the scheme to deal with the spin-orbit induced spin
Hall effect is discussed in addition
Benefits of host genetic diversity for resistance to infection depend on parasite diversity
Host populations with high genetic diversity are predicted to have lower levels of infection prevalence. This theory assumes that host genetic diversity results in variation in susceptibility and that parasites exhibit variation in infectivity. Empirical studies on the effects of host heterogeneity typically neglect the role of parasite diversity. We conducted three laboratory experiments designed to test if genetic variation in Daphnia magna populations and genetic variation in its parasites together influence the course of parasite spread after introduction. We found that a natural D. magna population exhibited variation in susceptibility to infection by three parasite species and had strong host clone–parasite species interactions. There was no effect of host heterogeneity in experimental host populations (polycultures and monocultures) separately exposed to single strains of three parasite species. When we manipulated the genetic diversity of a single parasite species and exposed them to host monocultures and polycultures, we found that parasite prevalence increased with the number of parasite strains. Host monocultures exposed to several parasite strains had higher mean parasite prevalence and higher variance than polycultures. These results indicate that effect of host genetic diversity on the spread of infection depends on the level of genetic diversity in the parasite population
Coherent description of the intrinsic and extrinsic anomalous Hall effect in disordered alloys on an level
A coherent description of the anomalous Hall effect (AHE) is presented that
is applicable to pure as well as disordered alloy systems by treating all
sources of the AHE on equal footing. This is achieved by an implementation of
the Kubo-St\v{r}eda equation using the fully relativistic
Korringa-Kohn-Rostoker (KKR) Green's function method in combination with the
Coherent Potential Approximation (CPA) alloy theory. Applications to the pure
elemental ferromagnets bcc-Fe and fcc-Ni led to results in full accordance with
previous work. For the alloy systems fcc-FePd and
fcc-NiPd very satisfying agreement with experiment could be
achieved for the anomalous Hall conductivity (AHC) over the whole range of
concentration. To interpret these results an extension of the definition for
the intrinsic AHC is suggested. Plotting the corresponding extrinsic AHC versus
the longitudinal conductivity a linear relation is found in the dilute regimes,
that allows a detailed discussion of the role of the skew and side-jump
scattering processes.Comment: * shortened manuscript * slight rewordings * changed line style in
Fig 1 * corrected misprinted S (skewness) factor * merged Fig. 3 with Fig. 1
* new citation introduce
Ab-initio calculation of the Gilbert damping parameter via linear response formalism
A Kubo-Greenwood-like equation for the Gilbert damping parameter is
presented that is based on the linear response formalism. Its implementation
using the fully relativistic Korringa-Kohn-Rostoker (KKR) band structure method
in combination with Coherent Potential Approximation (CPA) alloy theory allows
it to be applied to a wide range of situations. This is demonstrated with
results obtained for the bcc alloy system FeCo as well as for a
series of alloys of permalloy with 5d transition metals.
To account for the thermal displacements of atoms as a scattering mechanism,
an alloy-analogy model is introduced. The corresponding calculations for Ni
correctly describe the rapid change of when small amounts of
substitutional Cu are introduced
Stability of negative ionization fronts: regularization by electric screening?
We recently have proposed that a reduced interfacial model for streamer
propagation is able to explain spontaneous branching. Such models require
regularization. In the present paper we investigate how transversal Fourier
modes of a planar ionization front are regularized by the electric screening
length. For a fixed value of the electric field ahead of the front we calculate
the dispersion relation numerically. These results guide the derivation of
analytical asymptotes for arbitrary fields: for small wave-vector k, the growth
rate s(k) grows linearly with k, for large k, it saturates at some positive
plateau value. We give a physical interpretation of these results.Comment: 11 pages, 2 figure
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