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We highlight the self-familar features of the frequency-dependent (absolute) reflection coefficient of a dielectric Cantor prefractal obtained by applying the well-known Cantor-set construction to the optical (rather than physical) layer lengths. The referred properties are first obtained using an exact characteristic matrix representation of the reflection coefficient and then resorting to an (accurate) small-reflection approximatio

Solutions of the boundary-value problem for electromagnetic waves guided by a layer of a homogeneous and isotropic (metal or dielectric) material sandwiched between a structurally chiral material (SCM) and a periodically multilayered isotropic dielectric (PMLID) material were numerically obtained and analyzed. If the sandwiched layer is sufficiently thick, the two bimaterial interfaces decouple from each other, and each interface may guide one or more electromagnetic surface waves (ESWs) by itself. Depending on the constitution of the two materials that partner to form an interface, the ESWs can be classified as surface-plasmon-polariton waves, Tamm waves, Dyakonov–Tamm waves, or Uller–Zenneck waves. When the sandwiched layer is sufficiently thin, the ESWs for single bimaterial interfaces coalesce to form compound guided waves (CGWs). The phase speeds, propagation distances, and spatial profiles of the electromagnetic fields of CGWs are different from those of the ESWs. The energy of a CGW is distributed in both the SCM and the PMLID material, if the sandwiched layer is sufficiently thin. Some CGWs require the sandwiched layer to have a minimum thickness. Indeed, the coupling between the two faces of the sandwiched layer is affected by the ratio of the thickness of the sandwiched layer to the skin depth in that material and the rates at which the fields of the ESWs guided individually by the two interfaces decay away from their respective guiding interfaces

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Low-frequency (LF) electric fields (EFs) are currently used in clinical therapies of several bone diseases to increase bone regenerative processes. To identify possible molecular mechanisms involved in these processes, we evaluated the effects on cell cultures of 1 h exposures to the signal generated by an apparatus of current clinical use (frequency 60 kHz, frequency of the modulating signal 12.5 Hz, 50% duty cycle, peak-to-peak voltage 24.5 V). Two different human cell lines, bone SaOS-2 and liver HepG2, were used. Exposures significantly increased alkaline phosphatase (ALP) enzymatic activity in both cell lines. The increase was about 35% in SaOS-2 cells and about 80% in HepG2 cells and occurred in the first 4 h after exposure and decreased to almost no change by 24 h. Since ALP represents a typical marker of bone regeneration, these results represent a first molecular evidence of biological effects from 60 kHz EF exposures. The finding of similar effects in cells derived from two different tissues more likely indicates the effective operation of the mechanism in living organisms.

Inspired by the apposition compound eyes of many dipterans, we formulated a fractal scheme to design prismatic lenses to improve the performance of silicon solar cells. We simulated the absorption of light, both directly illuminating and diffuse, using the geometrical-optics approximation. We found that properly designed bioinspired compound lenses (BCLs) can significantly improve the light-harvesting capabilities of silicon solar cells. The degree of improvement will depend on the material chosen to make the BCLs as well as the operating conditions.

A traveling wave applicator particularly suitable for heating low loss materials is described. The applicator consists of a dielectric Cantor multilayer inserted in a single-mode rectangular metallic waveguide. Field localization phenomenon occurring in the multilayer allows high field amplitude (several times the amplitude of the incident field) to be obtained in a load placed at the center of the applicator. Design examples and numerical characterization of an applicator in WR-284 waveguide operating at 2.45 GHz are presented for cylindrical and planar loads. Results show that the proposed applicator can significantly enhance the effectiveness of the heating process

The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.