Effects of Spatial Dispersion on Reflection from Mushroom-type Artificial Impedance Surfaces

Several recent works have emphasized the role of spatial dispersion in wire media, and demonstrated that arrays of parallel metallic wires may behave very differently from a uniaxial local material with negative permittivity. Here, we investigate using local and non-local homogenization methods the effect of spatial dispersion on reflection from the mushroom structure introduced by Sievenpiper. The objective of the paper is to clarify the role of spatial dispersion in the mushroom structure and demonstrate that under some conditions it is suppressed. The metamaterial substrate, or metasurface, is modeled as a wire medium covered with an impedance surface. Surprisingly, it is found that in such configuration the effects of spatial dispersion may be nearly suppressed when the slab is electrically thin, and that the wire medium can be modeled very accurately using a local model. This result paves the way for the design of artificial surfaces that exploit the plasmonic-type response of the wire medium slab.Comment: submitted for publication, under revie

Causative Role of Ureaplasma Urealyticum and other Sexually Transmitted Infections in the Urethral Meatus Polyp Development in Women

The objective of this study was the investigation of the influence of ureaplasmal infection on the development of urethral meatus polyps in women. The article presents the results of the examination of women with chronic cystitis and urethritis over a 0.5- to 5-year duration, complicated by the presence of urethral meatus polyps and associated with concomitant Ureaplasma urealyticum and other sexually transmitted infections (STI). This was based on the culture analysis of the cervical and urethral content, and PCR-diagnostics of STI, as well as a complex pathomorphologic study of the resected polyps, including electron microscopy. In this study, 98 women between 45 and 60 years (52.5±4.9 years) were examined, who had undergone radiowave resection of the polyps: 52 women were infected by STI, including Ureaplasma urealyticum, Mycoplasma genitalium, Mycoplasma hominis, Chlamydia trachomatis and Trichomonas vaginalis, while the remaining 46 women had been diagnosed as not having STI. According to the culture results in the women with STI, U. urealyticum was identified as a monoinfection in 69% of cases, while in the remaining 31% of cases it was evident in the form of mixed infections, mainly in association with Mycoplasma hominis (17.5%) and Trichomonas vaginalis (13.5%). Pathomorphological examination of the urethral meatus polyps of the women with U. urealyticum and other STI demonstrated the proliferative character of the remodeling of the surface epithelium with hyperplasia, acanthosis, and keratinization of the stratified squamous epithelium and synchronous changes in the underlying connective tissue - impaired microcirculation and the diffuse inflammatory cell infiltrates with transepithelial leukopedesis. Using electron microscopy in the fibroblasts and plasma cells of the resected polyps the markers of U. urealyticum were detected in patients with negative results of the bacteriological diagnostic methods

Transmission through stacked 2D periodic distributions of square conducting patches

In this paper, we study the transmissivity of electromagnetic waves through stacked two-dimensional printed periodic arrays of square conducting patches. An analytical circuit-like model is used for the analysis. The model accounts for the details of the transmission spectrum provided that the period of the unit cell of each patterned layer is well below the wavelength in the dielectric slabs separating the printed surfaces. In particular, we analyze the low-pass band and rejection band behavior of the multilayer structure, and the results are validated by comparison with a computationally intensive finite element commercial electromagnetic solver. The limiting case of an infinite periodic structure is analytically solved and the corresponding band structure is used to explain the passband/stopband behavior of finite structures. In addition, we study in depth the elementary unit cell consisting of a single dielectric slab coated by two metal patch arrays, and its resonance behavior is explained in terms of Fabry-Pérot resonances when the electrical thickness of the slab is large enough. In such case, the concept of equivalent thickness of the equivalent ideal Fabry-Pérot resonator is introduced. For electrically thinner slabs it is also shown that the analytical model is still valid, and its corresponding first transmission peak is explained in terms of a lumped-circuit LC resonance.Ministerio de Ciencia e Innovación TEC2010-16948, CSD2008-00066Junta de Andalucía P09-TIC-459

Circuit modeling of multiband high-impedance surface absorbers in the microwave regime

In this paper, we present a simple circuit model to study the absorption of electromagnetic waves by a multilayer structure with a high impedance surface in the microwave regime. The absorber consists of a stack of two-dimensional arrays of sub-wavelength meshes or patches separated by dielectric slabs and backed by a metallic ground plane, with a single resistive sheet placed on the top layer. We observe the appearance of low-frequency resonances of total absorption, which have been identified as the resonances of Fabry-Pérot type associated with the individual reactively loaded dielectric slabs (that are strongly coupled through the subwavelength grids). It is shown that these resonances lie within certain characteristic frequency band defined by the structural parameters of the absorber. The observed resonances are characterized by studying the electromagnetic field behavior using the circuit model and full-wave numerical program. In addition, we show that the patch array absorber provides stable resonances with respect to the angle and the polarization of obliquely incident plane wavesMinisterio de Ciencia e Innovación TEC2010-16948, CSD2008-00066Junta de Andalucía TIC-459

Enhanced transmission with a graphene-dielectric microstructure at low-terahertz frequencies

Here, we report on the transmissivity of electromagnetic waves through a stack of monolayer graphene sheets separated by dielectric slabs at low-terahertz frequencies. It is observed that the multilayer structure possesses band-gap properties and supports a series of bandpass and band-stop regions, similar to the cases of stacked metallic meshes separated by dielectric slabs at microwave/THz frequencies and a metal-dielectric stack at optical frequencies. The transmission resonances in the bandpass region are identified as coupled Fabry-Pérot resonances associated with the individual cavities of dielectric slabs loaded with graphene sheets. It is also noticed that these resonances lie within a certain characteristic frequency band, independent of the number of layers in the graphene-dielectric stack. The study is carried out using a simple analytical transfer-matrix approach or, equivalently, a circuit-theory model, resulting in the exact solution for the multiple dielectric/graphene sheet surface-conductivity model. Also, an independent verification of the observed phenomena is obtained with commercial numerical simulations.Ministerio de Ciencia e Innovación TEC2010-16948Unión Europea FEDER CSD2008-00066Junta de Andalucía TIC-459

Dual capacitive-inductive nature of periodic graphene patches: Transmission characteristics at low-terahertz frequencies

We report on the dual nature (capacitive and inductive) of the surface impedance of periodic graphene patches at low-terahertz frequencies. The transmission spectra of a graphene-dielectric stack shows that patterned graphene exhibits both the low-frequency (capacitive) passband of metal patch arrays and the higher-frequency (inductive) passband of metal aperture arrays in a single tunable configuration. The analysis is carried out using a transfer-matrix approach with two-sided impedance boundary conditions, and the results are verified using full-wave numerical simulations. In addition, the Bloch-wave analysis of the corresponding infinite periodic structure is presented in order to explain the passband and stopband characteristics of the finite graphene-dielectric stack.Ministerio de Ciencia e Innovación TEC2010-16948 y CSD2008- 0006

Circuit modeling of the transmissivity of stacked two-dimensional metallic meshes

This paper presents a simple analytical circuit-like model to study the transmission of electromagnetic waves through stacked twodimensional (2-D) conducting meshes. When possible the application of this methodology is very convenient since it provides a straightforward rationale to understand the physical mechanisms behind measured and computed transmission spectra of complex geometries. Also, the disposal of closed-form expressions for the circuit parameters makes the computation effort required by this approach almost negligible. The model is tested by proper comparison with previously obtained numerical and experimental results. The experimental results are explained in terms of the behavior of a finite number of strongly coupled Fabry-Pérot resonators. The number of transmission peaks within a transmission band is equal to the number of resonators. The approximate resonance frequencies of the first and last transmission peaks are obtained from the analysis of an infinite structure of periodically stacked resonators, along with the analytical expressions for the lower and upper limits of the pass-band based on the circuit model.Ministerio de Ciencia e Innovación TEC2007-65376, CSD2008- 00066Junta de Andalucía TIC-459

Efficiency Assessment of Using Flammable Compounds from Water Treatment and Methanol Production Waste for Plasma Synthesis of Iron-Containing Pigments

This article describes the possibility of applying the low-temperature plasma for obtaining iron-containing pigments from water purification and flammable methanol production waste. In this paper were calculated combustion parameters of water-saltorganic compositions (WSOC) with different consists. Authors determined the modes of energy- efficient processing of the previously mentioned waste in an air plasma. Having considered the obtained results there were carried out experiments with flammable dispersed water-saltorganic compositions on laboratory plasma stand. All the experimental results are confirmed by calculations