Controlled Measurement Setup for Ultra-Wideband Dielectric Modeling of Muscle Tissue in 20–45 ∘C Temperature Range

In order to design electromagnetic applicators for diagnostic and therapeutic applications, an adequate dielectric tissue model is required. In addition, tissue temperature will heavily influence the dielectric properties and the dielectric model should, thus, be extended to incorporate this temperature dependence. Thus, this work has a dual purpose. Given the influence of temperature, dehydration, and probe-to-tissue contact pressure on dielectric measurements, this work will initially present the first setup to actively control and monitor the temperature of the sample, the dehydration rate of the investigated sample, and the applied probe-to-tissue contact pressure. Secondly, this work measured the dielectric properties of porcine muscle in the 0.5–40 GHz frequency range for temperatures from 20 ∘C to 45 ∘C. Following measurements, a single-pole Cole–Cole model is presented, in which the five Cole–Cole parameters (ϵ∞, σs, Δϵ, τ, and α) are given by a first order polynomial as function of tissue temperature. The dielectric model closely agrees with the limited dielectric models known in literature for muscle tissue at 37 ∘C, which makes it suited for the design of in vivo applicators. Furthermore, the dielectric data at 41–45 ∘C is of great importance for the design of hyperthermia applicators.

Epoxy-Based/BaMnO4 Nanodielectrics: Dielectric Response and Energy Storage Efficiency

Compact capacitive energy storing/harvesting systems could play a key role in the urgent need for more energy-efficient technologies to address both energy and environmental issues. Therein, the purpose of the present work is to develop and investigate epoxy/BaMnO4 nanocomposites at various filler concentrations, which could be applicable as compact materials systems for energy storage and harvesting. Broadband dielectric spectroscopy was used for studying the dielectric properties and the relaxation processes of the examined nanodielectrics. The energy storing/retrieving ability of the nanocomposites was also evaluated via DC charge–discharge experiments. The coefficient of energy efficiency (neff) was found for all prepared nanocomposites to evaluate the energy performance of the systems. Dielectric data divulge the existence of two matrix-related relaxations, i.e., α-mode and β-mode, attributed to the glass-to-rubber transition of the polymer matrix and re-orientation of polar side groups, respectively. Interfacial polarization was also identified in the low-frequency and high-temperature region. The 7 phr BaMnO4 nanocomposite exhibits the best performance in terms of the stored and harvested energies compared to all systems. On the other hand, the 5 phr, 3 phr and 1 phr nanocomposites display optimum energy performance, reaching high values of neff.

Utilization of novel and rapid techniques for characterization of neem Azadirachta indica seed oil and palm oil blends

The authentication of neem oil and its blending with inexpensive vegetable oil, such as, palm oil is a common practice in the neem oil industry. This study was conducted to investigate the neem kernel (Azadirachta indica) oil (NKO) by blending with palm oil and characterize it by studying its effect on the physicochemical properties, dielectric properties and fatty acid profiles of the blend. Blending significantly influenced the color, dielectric, structural and antimicrobial properties of the virgin oil. The NKO was rich in oleic (44.97%), stearic (21.27%), palmitic (16.88%) and linoleic acids (14.08%). The addition of palm oil into NKO significantly influenced the fatty acids profile , which was further confirmed by the FTIR spectra and the dielectric data. Overall, determination of moisture content, palmitic and stearic acid content, color parameter "a" and dielectric measurements were found to be fastest and precise way to detect the NKO and PO blends.

Effect of Open-Ended Coaxial Probe-to-Tissue Contact Pressure on Dielectric Measurements

Open-ended coaxial probes are widely used to gather dielectric properties of biological tissues. Due to the lack of an agreed data acquisition protocol, several environmental conditions can cause inaccuracies when comparing dielectric data. In this work, the effect of a different measurement probe-to-tissue contact pressure was monitored in the frequency range from 0.5 to 20 GHz. Therefore, we constructed a controlled lifting platform with an integrated pressure sensor to exert a constant pressure on the tissue sample during the dielectric measurement. In the pressure range from 7.74 kPa to 77.4 kPa, we observed a linear correlation of − 0.31 ± 0.09 % and − 0.32 ± 0.14 % per kPa for, respectively, the relative real and imaginary complex permittivity. These values are statistically significant compared with the reported measurement uncertainty. Following the literature in different biology-related disciplines regarding pressure-induced variability in measurements, we hypothesize that these changes originate from squeezing out the interstitial and extracellular fluid. This process locally increases the concentration of membranes, cellular organelles, and proteins in the sensed volume. Finally, we suggest moving towards a standardized probe-to-tissue contact pressure, since the literature has already demonstrated that reprobing at the same pressure can produce repeatable data within a 1% uncertainty interval.

Dielectric function modelling and sensitivity forecast for Au–Ag alloy nanostructures

Based on theoretical calculations, FDTD simulations and experimental results, the refractive index sensitivity of Au–Ag alloy nanostructures were investigated, indicating the credibility and feasibility of the modelled dielectric data of alloy.

ENTANGLEMENT-LOOSENING DYNAMICS RESOLVED THROUGH COMPARISON OF DIELECTRIC AND VISCOELASTIC DATA OF TYPE-A POLYMERS: A REVIEW

ABSTRACT For so-called type-A polymer chains having electrical dipoles aligned parallel along their backbone, the large-scale chain motion over the end-to-end distance results in not only viscoelastic but also dielectric relaxation. These two relaxation processes detect the same motion but with different averaging moments, which enables us to experimentally resolve some details of the chain dynamics through comparison of viscoelastic and dielectric data of type-A polymers. For a typical type-A polymer, high-cis polyisoprene (PI), results of such an experimental approach are summarized to discuss characteristic features of an entanglement-loosening process (constraint release and/or dynamic tube dilation process) resolved from the data comparison.