About
62
Publications
37,864
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
19,148
Citations
Publications
Publications (62)
Dielectric properties of porcine glandular tissues and gonads (in vivo) and
body fluids (in vitro) have been obtained in the frequency range of 50 MHz to
20 GHz. The experimental data were fitted to a two term Cole–Cole expression.
The data presented complement the available dielectric properties of tissues in
the literature and can be used in nume...
The dielectric properties of rat embryos/foetuses have been acquired at several stages of gestation at 37 °C and in the frequency range of 40 MHz-20 GHz. Measurements were carried out on homogenized tissues, as trial experiments did not show any systematic difference between the dielectric data of intact and homogenized tissues at microwave frequen...
The dielectric properties of freshly delivered human placenta, umbilical cord and amniotic fluid have been acquired at 37 °C and in the frequency range of 200 MHz-10 GHz. The experimental data were fitted to a Cole-Cole expression. The results show that dielectric properties of the umbilical cord are significantly higher than placenta due to the pr...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
We have applied the Cole-Cole expression to the dielectric properties of tissues in the frequency range 0.4-10 GHz. The data underpinning the model relate to pig tissue as a function of age. Altogether, we provide the Cole-Cole parameters for 14 tissue types at three developmental stages.
A two-pronged approach, review and measurement, has been adopted to characterize the conductivity of tissues at frequencies below 1 MHz. The review covers data published in the last decade and earlier data not included in recent reviews. The measurements were carried out on pig tissue, in vivo, and pig body fluids in vitro. Conductivity data have b...
In vitro dielectric properties of ageing porcine tissues were measured in the frequency range of 50 MHz-20 GHz, and the total combined uncertainties of the measurements were assessed. The results show statistically significant reduction with age in both permittivity and conductivity of 10 out of 15 measured tissues. At microwave frequencies, the ob...
This study assesses the influence of the head anatomy and tissue properties on the energy absorption and temperature increase of mobile phone users. Anatomically correct head models from different age groups (children and adults) have been used, as well as age dependent dielectric tissue properties and typically used thermal parame- ters. The 10g p...
Whole-body phantoms are required to optimize the design and performance of hand-held, body-mounted, wearable, or portable wireless telecommunication equipment. Where the assessment of electromagnetic exposure is required, the phantom is a hollow shell filled with tissue equivalent material; solid tissue-equivalent material can be used in all other...
We suggest that to best reproduce the interaction between a handheld wireless transceiver and the hand holding it, the dielectric properties of the hand phantom should be similar to those of the palm of the hand. The proposed target permittivity and conductivity values are presented and tabulated at a number of frequencies of interest. We have deve...
The complex permittivity of aqueous solutions at 20 degrees C has been measured at concentrations between 0.001 and 5 mol/L and over a frequency range 0.13-20 GHz. The results were combined with literature values to derive empirical equations to predict the dielectric behavior of sodium chloride solutions between 0 and 5 mol/L and 5 degrees C-35 de...
The dielectric properties of pig cerebrospinal tissues were measured in vivo and in vitro, in the frequency range of 50 MHz-20 GHz. The total combined measurement uncertainty was calculated at each frequency point and is reported over representative frequency regions. Comparisons were made for each tissue between the two sets of data and with the l...
Two formulations for tissue equivalent liquids are presented and characterised in terms of dielectric properties in the frequency range 30-300 MHz. The purpose is to provide viable options for consideration by the standardisation bodies dealing with the assessment of exposure to electromagnetic sources in that frequency range
The advantages and limitations of using partial differential analysis to assess the methodological uncertainty associated with the measurement of the dielectric properties of a material are discussed and an alternative pragmatic approach is proposed. It relies on repeat measurements of the dielectric properties of reference liquids and an analysis...
The dielectric properties of whole brain, skin, and skull were determined experimentally in the frequency range 300 KHz-300 MHz. Tissue samples were excised from 10, 30, and 70 day old Wistar strain rats. The data are presented in graphical format and compared to previously published data in the frequency range 0.1-20 GHz. Good agreement is observe...
Tissue dielectric properties play an important role in determining the specific absorption rate (SAR) of animal models in exposure studies [1-2].
The objective of this study is to assess the effect on SAR of implementing recently reported age-related systematic changes in the dielectric properties of some tissues [3-4] for a heterogeneous rat mode...
Accurate determination of the specific absorption rate (SAR) is an important aspect in understanding the interaction between electromagnetic fields (EMF) and living matter. Influences due to dielectric properties, shape, and size of the exposed tissues have been considered to play an important role in the determination of SAR distributions in anato...
In the last few years, society has witnessed the installation of an ever increasing number of radio base stations as a necessity for handling new capabilities and services to the large number of users. This rapid development of wireless networks, however, has induced a marked mistrustful attitude in people, who fear possible biological effects of e...
Not Available
The effects of added water on the microwave dielectric spectra of pork products has been studied. Results are presented for canned pork, bacon, ham, leg meat and commercial samples of ham and bacon bought from UK retailers. The dielectric spectra were transformed by the method of principal components and the added water content and other compositio...
Accurate determination of the specific absorption rate (SAR) is an important aspect in understanding the interactions of the radio frequency (RF) with biological tissues and living bodies. Studies have confirmed that for animal exposure to a given frequency, the body SAR profiles are affected by the following: dielectric properties, body shape and...
The dielectric properties of ten rat tissues at six different ages were measured at 37 degrees C in the frequency range of 130 MHz to 10 GHz using an open-ended coaxial probe and a computer controlled network analyser. The results show a general decrease of the dielectric properties with age. The trend is more apparent for brain, skull and skin tis...
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,...
A coaxial probe is used in conjunction with a computerised time domain spectrometer (TDS) for dielectric measurements on liquid and solid samples in the frequency range 1 MHz to 10 GHz. In comparison with in-guide methods the technique greatly simplifies the sample handling procedure and enables measurements on tissue to be made in vivo. Measuremen...
It is generally true to say that the dielectric properties are intrinsic parameters that determine the effects of electric fields on matter. This leads to the statement that dielectric properties (relative permittivity ε’ and effective conductivity σ) play a dominant role in the overall consideration of interaction between electromagnetic fields an...
The study of the frequency dependence of the dielectric properties of biological materials has a long history. Systematic studies were carried out in the 1920’s and 1930’s on various aqueous molecular solutions and cell suspensions and on some biological tissues. The interpretation of these data in terms of mechanisms of interaction and molecular a...
In this article, measurements are reported on ice and frozen DNA solutions between 100 Hz–10 MHz. Pure ice is shown to exhibit single relaxation behaviour, which confirms previous work taken over a more restricted frequency range. The frozen DNA solution displays double-dispersion behaviour. One dispersion centred around 3 kHz is due to a defect me...
The European Committee on Electrotechnical Standardisation CENELEC started its work on harmonising European standards for exposure to electromagnetic fields in 1990/1991, based on the initiative of Germany. CENELEC’s members are the national electrotechnical committees of 18 European countries. The harmonisation work was assigned to the Technical C...
Microwave dielectric heating is rapidly becoming an established procedure in synthetic chemistry. This review summarises the basic theory underlying microwave dielectric heating and collates the dielectric data for a wide range of organic solvents which are commmonly used in microwave syntheses. The loss tangents of the solvents, which may be relat...
The dielectric properties of tissues have been extracted from the literature of the past five decades and presented in a graphical format. The purpose is to assess the current state of knowledge, expose the gaps there are and provide a basis for the evaluation and analysis of corresponding data from an on-going measurement programme.
Three experimental techniques based on automatic swept-frequency network and impedance analysers were used to measure the dielectric properties of tissue in the frequency range 10 Hz to 20 GHz. The technique used in conjunction with the impedance analyser is described. Results are given for a number of human and animal tissues, at body temperature,...
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 e...
Knowledge of the dielectric properties of biological materials is of importance in solving electromagnetic interaction problems. There is, as yet, no consensus on such data among scientists dealing with these issues. This project is geared towards producing a database of dielectric data based on measurements using recently developed techniques. Thi...
We have compiled results of scientific investigations about the relationship between external field-strengths and specific absorption rates inside the human body. The data were normalized to SAR-values that form the basis for current safety standards. Results were compared to exposure limits given in these standards. This comparison should serve as...
The dielectric properties of biological materials are a measure of their interaction with electromagnetic fields. When people are exposed to non-ionizing radiation, such interactions take place in the human body at various levels of organization and may initiate biological responses. While these biological effects may or may not be desirable, they...
Starting from a rigorous formulation for the admittance of an open ended coaxial probe, this paper identifies the simplifying assumptions that are introduced to obtain more practical solutions. The predictions of the models are compared to each other and to experimental data obtained on an independently calibrated experimental set-up. The advantage...
An accurate technique to measure the complex permittivity of materials based on a rigorous theoretical formulation of the admittance of an open-ended coaxial probe has been achieved. The technique was tested by measurements on standard solutions. The new technique was used to perform a comprehensive study of ionic solutions. The extensive data obta...
An open-ended coaxial line can be used as a sensor in
nondestructive dielectric measurements. The technique is based on the
study of the fringing field of an open-ended coaxial line and its
perturbation by a lossy dielectric. The open end of the coaxial line is
terminated by the sample material and the input reflection coefficient
of the sensor is...
Urea (about 5 mol l-1) causes an approximately five-fold increase of the dielectric increment of bovine serum albumin at 20 degrees C. The increase is reversed by betaine (about 2.5 mol l-1), or prevented if urea and betaine are added together. This result can be seen as an electric counterpart to the protective role of osmolytes which are secreted...
An HP 8720 automatic network analyser has been used with a custom made coaxial probe to measure the complex permittivity of standard limits in the frequency range 130 MHz to 20 GHz. Three equivalent circuit models were used to simulate the admittance of the probe sample interface. The expediency and limitations of these models have been studied. A...
Thermodynamic, luminescent, and dielectric data on diazoluminomelanin (DALM) are presented. DALM was made by codiazotizing 3-amino-L-tyrosine and luminol (5-amino-2, 3-dihydro-1, 4-pthalazinedione). When DALM and luminol mixtures were activated with hydrogen peroxide in aqueous sodium carbonate solution and heated with 2450 MHz radiation, emitted l...
The effects of some 15 organic solutes in aqueous solution, including urea, acetamide, simple amino acids and peptides, upon the dielectric dispersion of water have been studied by measuring the complex permittivity at 70 GHz and 20 °C. The results are expressed by two quantities derived from a simple model according to which water is the only sign...
The dielectric dispersion of urea and acetamide in aqueous solution can be reproduced fairly well by either two Debye relaxations or one Cole–Cole relaxation, with very little room for deciding in favour of one alternative or the other. There appears to be a small additional high-frequency relaxation in urea, revealed only in the measurements at 70...
The relative permittivity and dielectric loss of aqueous solutions of plasmid (pUC8.c1 and pUC8.c2) DNA have been measured at 20 degrees C over the frequency range 100 MHz-10 GHz. The solutions had a concentration of 0.1% DNA, and were studied both in the relaxed and the supercoiled form. The dielectric measurements were made using a variety of tec...
In a recent Nature leading article the possibility of the occurrence of resonance absorption at microwave frequencies in DNA was discussed in terms of the latest available theoretical and experimental evidence, and its implications were assessed. Because of the far-reaching nature of these implications it is important that the existence or otherwis...
The complex permittivity of aqueous glycerol has been measured at several concentrations, at a frequency of 70 GHz and, by time domain spectroscopy, at frequencies from 0.01 to 10 GHz. The results are interpreted in terms of a single concentration-dependent Davidson–Cole dispersion. The distribution parameter β is constant at ca. 0.7 at glycerol mo...
Measurements have been made of the permittivity and conductivity of normal and wounded human skin material over the frequency range 10 MHz-10 GHz. The permittivity of the wounded tissue was found to be about 12% higher than that of the normal tissue. A similar percentage increase was observed for the conductivity. These differences are attributed t...
Values of the relative permittivity and conductivity of the rabbit retina and lens have been measured between 10 MHz and 10 GHz over the temperature range 20 to -20 degrees C. As the temperature was lowered from 20 degrees C the dielectric parameters changed smoothly until -9 degrees C where freezing occurred. At this temperature a sharp transition...
The dielectric constant and conductivity of calf thymus DNA were investigated at frequencies between 0.1 MHz and 70 GHz. This work is to investigate the dielectric properties of DNA in low gigahertz region and also to study whether the dielectric behavior of the water is affected by the presence of highly charged DNA. The results of these measureme...
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...
Values of the complex permittivity of human and rabbit lens material in the frequency range 100--6000 MHz are reported. The data were obtained by using an on-line computer-based time-domain spectrometer. The lenses were divided into an outer (cortical) zone and an inner (nuclear) zone and the dielectric properties of each zone were measured separat...
