We present a comparison of simulated low-frequency electromagnetic fields in the human body, calculated by means of the electro-quasistatic formulation. The geometrical data in these simulations were provided by an anatomically realistic, high-resolution human body model, while the dielectric properties of the various body tissues were modelled by the parametric Cole-Cole equation. The model was examined under two different excitation sources and various spatial resolutions in a frequency range from 10 Hz to 1 MHz. An analysis of the differences in the computed fields resulting from a neglect of the permittivity was carried out. On this basis, an estimation of the impact of the displacement current on the simulated low-frequency electromagnetic fields in the human body is obtained.

Abstract-We present two-dimensional (2-D) spatially and picosecond-resolved measurements of vertical-cavity surface-emitting lasers' emission, unveiling their rich dynamics, manifesting itself in temporal changes of the modal, polarization, spectral, and spatial characteristics. The measurements providing insight into the repetitive part of the dynamics were performed with a newly developed experimental technique. In addition, we present the first 2-D, spatially resolved, single-shot event measurements which provide a full complementary picture of the dynamical behavior. The experimental results are analyzed and discussed with respect to spatio-spectral interaction mechanisms of carriers and photons, explaining the observed behavior.

No abstract

Purpose -Improved numerical calculation techniques for low-frequency current density distributions within high-resolution anatomy models caused by ambient electric or magnetic fields or direct contact to potential drops using the finite integration technique (FIT). Design/methodology/approach -The methodology of calculating low-frequency electromagnetic fields within high-resolution anatomy models using the FIT is extended by a local grid refinement scheme using a non-matching-grid formulation domain. Furthermore, distributed computing techniques are presented. Several numerical examples are analyzed using these techniques. Findings -Numerical simulations of low-frequency current density distributions may now be performed with a higher accuracy due to an increased local grid resolution in the areas of interest in the human body voxel models when using the presented techniques. Originality/value -The local subgridding approach is introduced to reduce the number of unknowns in the very large-scale linear algebraic systems of equations that have to be solved and thus to reduce the required computational time and memory resources. The use of distributed computation techniques such as, e.g. the use of a parallel solver package as PETSc follows the same goals.

PurposeTransient calculation of currents in brain tissue induced during a transcranial magnetic stimulation treatment.Design/methodology/approachBecause of the short pulses used in this technique a time‐harmonic approximation is no longer valid, and transient effects have to be considered. We have performed a Fourier analysis of the induced currents calculated in a high‐resolution model of the brain using the extended scalar potential finite differences (Ex‐SPFD) approach.FindingsThe peak induced currents in the transient development of the pulse are higher by a factor of approximately seven than the time harmonic solutions at the fundamental frequency. Furthermore, an analysis of the impact of the conductivity dispersion revealed an increase in the peak induced currents by 17.3 percent for white matter and by 20.8 percent for gray matter.Originality/valueUsing the numerically efficient Ex‐SPFD approach, along with a high performance cluster, the current densities inside the brain can be calculated incorporating more details than previous calculations of this type.