Calculations of electromagnetic fields in longitudinal irregular TEM-cells

TEM-cells can be used as a standardized field generator for field probe calibration purposes or electromagnetic compatibility measurements. Because of its practical use as a measurement environment, the electromagnetic behavior over a broad range of frequencies is essential. However, without the understanding of wave reflection, mode-conversion, and attenuation, using such a measurement environment is impractical. In this contribution, we calculate the electromagnetic fields in a longitudinal irregular coaxial TEM-cell. Using a semi-analytical approach, we can determine these wave characteristics. The method is based on the projection of Maxwell's equations onto eigenfunctions. This work's primary objective is to examine the effect of irregular deformed boundaries on the electromagnetic field and the resonance frequencies.

THE GAIN IN SHIEDLING EFFECTIVENESS ACHIEVED BY SUPERPOSITION OF STAINLES-STEEL PLASMA COATED WOVEN FABRICS

Electromagnetic shielding based on textile fabrics is important in applications for ensuring proper work of electronic equipment and for protection of human’s health. Fibre-based materials include a good capability for a precise design of the physical and electric properties of the EM shields. There are two main methods to impart electroconductive properties to textile fabrics: insertion of conductive yarns into the fabric structure and coating with conductive layers. In our approach, both methods were applied: cotton woven fabrics with conductive yarns of stainless steel and silver, were coated by magnetron sputtering with stainless steel layers. Electromagnetic shielding effectiveness (EMSE) was determined by Transversal-Electric- Magnetic (TEM) cell measurement system, according to standard ASTM ES-07. Moreover, EMSE was determined for the superposition of the manufactured textile shields. The stainless-steel plasma coating improves EMSE with 20 dB in case of the fabrics with stainless steel yarns and with 15-17 dB in case of the fabrics with silver yarns, in the frequency range of 0.1-1000 MHz. By superposition of the plasma coated shields, the gain in EMSE achieved was of 6 dB for the fabrics with stainless steel yarns and of 5-8 dB for the fabrics with silver yarns, on the same frequency range. EMSE has significant higher values in case of the superposed shields with silver yarns and stainless-steel coating for the frequency domain of 100-1000 MHz, due to the higher thickness and the significant contribution of the multiple reflection term.

Inhibitory effect of mitoquinone against the α-synuclein fibrillation and relevant neurotoxicity: possible role in inhibition of Parkinson’s disease

Extensive studies have reported that interaction of α-synuclein amyloid species with neurons is a crucial mechanistic characteristic of Parkinson’s disease (PD) and small molecules can downregulate the neurotoxic effects induced by protein aggregation. However, the exact mechanism(s) of these neuroprotective effects by small molecules remain widely unknown. In the present study, α-synuclein samples in the amyloidogenic condition were aged for 120 h with or without different concentrations of mitoquinone (MitoQ) as a quinone derivative compound and the amyloid characteristics and the relevant neurotoxicity were evaluated by Thioflavin T (ThT)/Nile red fluorescence, Congo red absorption, circular dichroism (CD), transmission electron microscopy (TEM), cell viability, lactate dehydrogenase (LDH), reactive oxygen species (ROS), reactive nitrogen species (RNS), malondialdehyde (MDA), superoxide dismutase (SOD), and caspase-9/-3 activity assays. Results clearly showed the capacity of MitoQ on the inhibition of the formation of α-synuclein fibrillation products through modulation of the aggregation pathway by an effect on the kinetic parameters. Also, it was shown that α-synuclein samples aged for 120 h with MitoQ trigger less neurotoxic effects against SH-SY5Y cells than α-synuclein amyloid alone. Indeed, co-incubation of α-synuclein with MitoQ reduced the membrane leakage, oxidative and nitro-oxidative stress, modifications of macromolecules, and apoptosis.

Modelling the Woven Structures with Inserted Conductive Yarns Coated with Magnetron Plasma and Testing Their Shielding Effectiveness

The paper proposes the analytic modelling of flexible textile shields made of fabrics with inserted conductive yarns and metallic plasma coating in order to calculate their electromagnetic shielding effectiveness (EMSE). This manufacturing process is highly innovative, since copper plasma coating improves EMSE on the fabrics with inserted conductive yarns of stainless steel and silver with 10–15 dB in the frequency range of 0.1–1000 MHz, as shown by the measured EMSE values determined according to the standard ASTM ES-07 via the Transverse Electromagnetic (TEM) cell. On the other hand, modelling of EMSE for such conductive flexible shields gives an insight on estimating EMSE in the design phase of manufacturing the shield, based on its geometric and electrical parameters. An analytic model was proposed based on the sum of EMSE of the fabric with inserted conductive yarns and EMSE of the copper coating. The measurement results show close values to the proposed analytic model, especially in case of fabric with conductive yarns having stainless steel content.

Modeling and Validating Analytic Relations for Electromagnetic Shielding Effectiveness of Fabrics with Conductive Yarns

Electromagnetic (EM) radiation may be harmful for human’s health and for functioning of electronic equipment. The field of Electromagnetic Compatibility approaches various solutions to tackle this problem, while shielding of the radiation is one of the main solutions. Since the development of spinning technology for producing conductive yarns for fabrics, textile electromagnetic shields have become a valuable alternative to metallic shields. Their main advantages are given by the flexibility, the low weight and the good mechanical resistance, as well as by the possibility to precisely design the shield. The scientific literature includes several analytic relations for estimating the electromagnetic shielding effectiveness (EMSE), in case of woven fabrics with conductive yarns, which may be modeled as a grid of electric conductors. This book chapter tackles three different analytic models for estimating EMSE, which are useful to predict this functionality in the design phase of fabrics. The analytic relations are subsequently comparatively validated by EMSE measurements via TEM cell equipment of two woven fabrics with conductive yarns out of stainless steel and silver with a grid of 4 mm. Results of validated analytic relations are used for the approach of designing textile shields with regard to final application requirements.