A parametric model was developed to describe the variation of dielectric properties of tissues as a function of frequency. The experimental spectrum from 10 Hz to 100 GHz was modelled with four dispersion regions. The development of the model was based on recently acquired data, complemented by data surveyed from the literature. The purpose is to enable the prediction of dielectric data that are in line with those contained in the vast body of literature on the subject. The analysis was carried out on a Microsoft Excel spreadsheet. Parameters are given for 17 tissue types.

https://iopscience.iop.org/article/10.1088/0031-9155/41/11/003/pdf

The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues

Dielectric Relaxation and Solvation Dynamics of Water in Complex Chemical and Biological Systems

The following topics are discussed: a summary of dielectric theory; amino acids, peptides, proteins and DNA; bound water in biological systems; biological electrolytes; membranes and cells; tissues.

/pdf/the-passive-electrical-properties-of-biological-systems-2tkz7wn98j.pdf

The passive electrical properties of biological systems: their significance in physiology, biophysics and biotechnology

Dielectric relaxation and NMR spectrum of water in biological systems such as proteins, DNA, and reverse micelles can often be described by two widely different time constants, one of which is in the picosecond while the other is in the nanosecond regime. Although it is widely believed that the bimodal relaxation arises from water at the hydration shell, a quantitative understanding of this important phenomenon is lacking. In this article we present a theory of dielectric relaxation of biological water. The time dependent relaxation of biological water is described in terms of a dynamic equilibrium between the free and bound water molecules. It is assumed that only the free water molecules undergo orientational motion; the bound water contribution enters only through the rotation of the biomolecule, which is also considered. The dielectric relaxation is then determined by the equilibrium constant between the two species and the rate of conversion from bound to free state and vice versa. However, the diele...

/pdf/dielectric-relaxation-of-biological-water-2zevupbr37.pdf

Dielectric Relaxation of Biological Water

This review covers approximately 15 years of development in the techniques used to measure dielectric properties of materials over the frequency range 1 MHz to 1500 GHz. An introductory section summarizes the broad development trends and is followed by short sections which deal with developments at a more detailed level. The approaches described include time- and frequency-domain methods; reflection, transmission, and resonant methods, guided and free-space methods; discrete-frequency and broad-band methods, especially Fourier Transform Spectroscopy. Measurements on magnetic materials are also briefly discussed.

The measurement of the properties of materials

Dielectric behavior of DNA solution at radio and microwave frequencies (at 20 degrees C)

Values of the relative permittivity, dielectric loss and conductivity are given for various rabbit ocular tissues at frequencies in the range 10 MHz-10 GHz. The tissues measured were cornea, retina, choroid, iris, and the cortical and nuclear zones of the lens. The dielectric parameters were determined using the technique of multiple response time domain spectroscopy. For all tissues the water relaxation could be characterised by a Debye dispersion with a relaxation time longer than that of pure water, indicating that its dielectric behaviour was affected by the presence of the biological macromolecules.

Dielectric properties of ocular tissues at 37 degrees C

The single reflection TDS technique is compared with the total reflection technique on the basis of measurements performed on ethanediol and formamide over the frequency range of 108-1010 Hz. While confirming that single reflection TDS does indeed offer superior precision for measurements on high permittivity materials, such as water and formamide, at gigahertz frequencies, the results also illustrated the extent of the problem caused by timing errors. They showed that if the extra performance offered by single reflection TDS is to be realised then the effect of the timing errors must be corrected for by using suitable measurements from an independent technique. The main conclusion from this work, however, is that the two TDS techniques complement each other rather well. Total reflection TDS can be used for the measurements on the lower permittivity materials over the whole range 106-1010 Hz, as well as the measurements on the higher permittivity materials up to about 109 Hz. Single reflection TDS can then be used to extend these latter measurements up to at least 1010 Hz.

https://iopscience.iop.org/article/10.1088/0022-3735/17/6/018/pdf

C Gabriel

Papers

Dielectric behavior of DNA solution at radio and microwave frequencies (at 20 degrees C)

Dielectric properties of ocular tissues at 37 degrees C

Comparison of the single reflection and total reflection TDS techniques