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Radio noise of man-made origin has been measured and studied since the 50s of the past century. From that time on, especially in the last two decades, the electromagnetic environment has changed due to the wide spread and increasingly complicated electronic and computing equipment in domestic and work premises. Not only the character of man-made noise has changed, but also the density of man-made noise sources has increased. Users of radio receiving and communication equipment experience a limitation of functionality due to a risen noise floor and the appearance of a large numbers of interfering signals today. In order to quantify the observed increase, a series of measurements of man-made noise levels in the well-spread medium-frequency, high-frequency, and lower part of very high-frquency bands of the Amateur Radio Service have been carried out in The Netherlands for a wide group of environments in all parts of the country. The data show that in City and in Residential environments the noise floor is significantly higher than would be expected from the current ITU-R noise floor data. The cumulative effect of the high density of sources is shown in the data. The measurement and analysis results could, with data from other investigations, be used in updating Recommendation ITU-R P.372-13.

Purpose – Electric fields (EFs) are known to influence cell and tissue activity. This influence can be due to thermal or non-thermal effects. While the non-thermal effects are still matter of discussion, thermal effects might be detrimental for cell and tissue viability due to thermal damage, this fact being exploited by applications like hyperthermia and tissue ablation. The paper aims to discuss these issues. Design/methodology/approach – In this work the authors investigate the influence of thermal damage in the consolidation of bone formation during electrostimulation (ES). The authors introduce a mathematical model describing the migration of osteoprogenitor cells, the thermal variation, the thermal damage accumulation and the formation of new bone matrix in an injury (fracture) site. Findings – Numerical results are in agreement with experimental data and show that EFs more intense than 7.5 V/cm are detrimental for the viability of osteoprogenitor cells and the formation of new bone. Originality/value – The model is suitable to conduct dosimetry studies in support of other different ES techniques aimed at improving bone and soft tissues repair.

The potential effects of non-ionizing electromagnetic fields (EMFs), such as those emitted by power-lines (in extremely low frequency range), mobile cellular systems and wireless networking devices (in radio frequency range) on human health have been intensively researched and debated. However, how exposure to these EMFs may lead to biological changes underlying possible health effects is still unclear. To reveal EMF-induced molecular changes, unbiased experiments (without a priori focusing on specific biological processes) with sensitive readouts are required. We present the first proteome-wide semi-quantitative mass spectrometry analysis of human fibroblasts, osteosarcomas and mouse embryonic stem cells exposed to three types of non-ionizing EMFs (ELF 50 Hz, UMTS 2.1 GHz and WiFi 5.8 GHz). We performed controlled in vitro EMF exposures of metabolically labeled mammalian cells followed by reliable statistical analyses of differential protein- and pathway-level regulations using an array of established bioinformatics methods. Our results indicate that less than 1% of the quantitated human or mouse proteome responds to the EMFs by small changes in protein abundance. Further network-based analysis of the differentially regulated proteins did not detect significantly perturbed cellular processes or pathways in human and mouse cells in response to ELF, UMTS or WiFi exposure. In conclusion, our extensive bioinformatics analyses of semi-quantitative mass spectrometry data do not support the notion that the short-time exposures to non-ionizing EMFs have a consistent biologically significant bearing on mammalian cells in culture.

Electrotaxis is the cell migration in the presence of an electric field (EF). This migration is parallel to the EF vector and overrides chemical migration cues. In this paper we introduce a mathematical model for the electrotaxis in osteoblastic cells. The model is evaluated using different EF strengths and different configurations of both electrical and chemical stimuli. Accordingly, we found that the cell migration speed is described as the combination of an electrical and a chemical term. Cell migration is faster when both stimuli orient cell migration towards the same direction. In contrast, a reduced speed is obtained when the EF vector is opposed to the direction of the chemical stimulus. Numerical relations were obtained to quantify the cell migration speed at each configuration. Additional calculations for the cell colonization of a substrate also show mediation of the EF strength. Therefore, the term electro-osteoconduction is introduced to account the electrically induced cell colonization. Since numerical results compare favorably with experimental evidence, the model is suitable to be extended to other types of cells, and to numerically explore the influence of EF during wound healing.

The reception of electromagnetic signals depends on the polarisation matching of the transmitting and receiving antenna. The practical matching differs from the theoretical one because of the noise deterioration of the transmitted and eventually received electromagnetic field. In other applications, the polarisation parameters of the receiving antenna are not known. Both problems are addressed by means of statistical methods, analytical as well as simulation results are obtained. The variation of the noisy matching factor depends mainly on the signal-to-noise ratio. The resulting probability distribution for the polarisation matching factor in case of a stochastic receiver is independent of the phase difference, but strongly affected by the axis ratio of the incident polarised field.

Although the beneficial and detrimental effects of human cells electic field (EF) exposure are well investigated, the interactions mechanisms between the cell and the EF are still a matter of research. In this work we present a numerical approach to investigate the induced cell-cell EF gradients at different regions of multi-layered spherical cells. Based on a symbolic scattering-matrix approach, the induced EF in a single cell is obtained using the equivalent electrical network for the multilayered sphere. Cell-cell EF interactions are obtained for a group of 60 randomly positioned cells exposed to an EF of 100 V/m. Two cases were analyzed by setting the EF frequency to 50 Hz and 2.45 GHz. Numerical results show cellular electrical responses that are in agreement with experimental observations. Quantitative results show that cell-cell EF interactions might be enough to trigger electrically mediated biological responses in the cells. Therefore, the model can be used to investigate possible interactions mechanism between cells and EFs.

The exposure of biological cells to an incident electric field (EF) affects cellular behaviour. However, the interaction mechanisms are still a matter of discussion. Although most of the evidence comes from experimental trials, numerical simulations are helpful to obviate the lack of reproducible experimental results and to resolve contradictory conclusions. In this work we present a numerical framework for computing the intracellular EF in arbitrary-shaped biological cells with nucleus. As an example, up to four inhomogeneous cells exposed to an incident EF of 1 V/m at 2.45 GHz are studied. The solution is obtained by implementing the electric flux volume integral equation (VIE) and the Method of Moments (MoM) with SchaubertWilton-Glisson (SWG) basis functions. Qualitative results show that the intracellular EF is related to the neighboring cells in terms of number and position. Quantitative analysis shows intracellular variations in the order of 20-30 mV/mm, which might be enough to trigger biological responses in cells. Therefore, this approach may be suitable to further investigate the cell-cell EF interactions, especially in non-canonical shaped cells with non-concentric nucleus.

To evaluate a system or platform on its electromagnetic compatibility generally involves the application of several EMC standards. In order to compare applicable standards, one needs a common denominator as a basis. In this study, EMC norms for electromagnetic radiation are assessed statistically. A framework describing stochastic electromagnetic fields is applied and at the hand of the examples of military (MIL) and international electrotechnical commission (IEC) standards further developed for this purpose. The formalism not only evaluates such requirements but also enables the comparison of different standards in a probabilistic way. First illustrative results are presented. Frequency bands are identified for which IEC complying equipment exceeds the MIL standard with high probability.

A modeling method is proposed to quantify uncertainties affecting electromagnetic interactions. This method considers the uncertainties as random and measures them thanks to probability theory. A practical application is considered through the case of a transmission-line of varying geometry, illuminated by a fixed electromagnetic field. The results of the stochastic numerical model are compared to the measurements performed on the transmission-line setup.

The goal of this research is to detect and identify buried land mines (LM). The technique being investigated is the use of ultra-wideband (100 MHz to 3 GHz) ground penetrating radar (UWB/GPR). The first step is to gain an understanding of the scattered signal received from the use of such a system. A major point of interest is: which electromagnetic scattering features and signal processing techniques can be used in the detection/identification process? Possible candidates of scattering features are late-time resonances and diffusion poles, whereas signal processing techniques are synthetic aperture radar (SAR) imaging, correlation and/or E-pulse receivers. It is important to have good detection and identification algorithms, which work well in the ideal situation, before one can deal with the practical situation, in which there will be uncertainty in various physical parameters such as: the local electrical characteristics of the ground, the local heterogeneity of the ground (rocks, layers, tree and plant roots), surface roughness of the ground and covering foliage, position (depth and orientation) of the LM, and relative position of the radar with respect to the ground and the LM. Thus, in this work, we investigate the post-processing of impulse type radar signals, where the signals are synthesized, for relatively ideal situations, using the finite-difference time-domain (FDTD) technique.

In this paper, we consider the determination of electromagnetic flelds for a (large) number of values of a physical parameter. We restrict ourselves to the case where the linear system originates from one or more integral equations. we apply an iterative procedure based on the minimization of an integrated squared error, and start this procedure from an initial estimate that is a linear combination of the last few "final" raeults. When the coefficients in this extrapolation is determined by minimizing the integrated squared error for the actual value of the parameter, the built-in orthogonality in this type of scheme ensures that only a few iteration steps are required to obtain the solution.

For the detection of a buried object we consider two straight thin-wire antennas above an interface between two homogeneous dielectric half spaces. One antenna is a transmitting wire and the other is a receiving wire. Our aim is to use this simple antenna set up for the detection of buried objects without applying pre and post processing of the received signal. The buried wire can be detected directly from the shape of the current at the receiving antenna. To minimize the effects of repeated reflections at the end faces of the wire antennas, pulse compensation is introduced. Numerical results show that with the aid of pulse compensation a buried wire can easily be detected.

It is pointed out that the problem of two-dimensional scattering of a transverse electric (TE) polarized wave by a dielectric object can be formulated in terms of a hypersingular integral equation, in which a grad-div operator acts on a vector potential. The vector potential is a spatial convolution of the free-space Green's function and the contrast source over the domain of interest. A weak form of the integral equation for the unknown electric flux density is obtained by testing it with roof-top functions. As the next step, the vector potential is expanded in a sequence of the roof-top functions and the grad-div operator is integrated analytically over the dielectric object domain only. Numerical results are presented for a lossy dielectric coaxially layered cylinder. The method considered shows excellent numerical performance. >

In this study we evaluated for a realistic head model the 3D temperature rise induced by a mobile phone. This was done numerically with the consecutive use of an FDTD model to predict the absorbed electromagnetic power distribution, and a thermal model describing bioheat transfer both by conduction and by blood flow. We calculated a maximum rise in brain temperature of 0.11 degrees C for an antenna with an average emitted power of 0.25 W, the maximum value in common mobile phones, and indefinite exposure. Maximum temperature rise is at the skin. The power distributions were characterized by a maximum averaged SAR over an arbitrarily shaped 10 g volume of approximately 1.6 W kg(-1). Although these power distributions are not in compliance with all proposed safety standards, temperature rises are far too small to have lasting effects. We verified our simulations by measuring the skin temperature rise experimentally. Our simulation method can be instrumental in further development of safety standards.

At TNO-FEL, one of the research programs is to explore the use of ultra-wideband (UWB) electromagnetic fields in a bi-static ground-penetrating radar (GPR) system for the detection, location and identification of buried items of unexploded ordnance (e.g. land mines). In the present paper we describe the current status of the development of this system. The UWB ground-penetrating radar system is designed to operate in the frequency band from 200 MHz to 3 GHz and uses impulse radiating antennas (IRAs) as transponders to radiate and receive very short electromagnetic pulses from a short distance above the soil. The receiving IRA is similar to the transmitting IRA and is connected to a receiving unit which comprises of an attenuator, time gate switch, trigger delay generator and a sampling oscilloscope (see figure 1). A personal computer is used to control the equipment, In order to perform controlled radar experiments, a full-size experimenting and testing facility has been erected on the premises of TNO-FEL.

The effect of electromagnetic fields on human beings is a growing concern. Especially the possible health hazards of using mobile communication devices such as hand-held telephones is an increasing topic of attention. One of the ways to examine these effects is to compute the electromagnetic field distribution in the human body that is exposed. Mutual coupling between the antenna wire structure and the human body has to be taken into account in most cases. We present the results of a pilot study in which we solve the mutual coupling between two wires of arbitrary length and finite conductivity. The coupling problem is solved in terms of an integral equation in the temporal Laplace domain. This integral equation in its strong form is weakened such that the spatial derivatives are integrated analytically. The integral equation is solved numerically by using the conjugate-gradient FFT method. Further, an appropriate weakened form of the Green's function is presented. It is noted that both the wires are non-perfectly conducting. The complete system of two wires is excited by applying a /spl delta/-gap voltage excitation on one of them. Numerical computations have been carried out for different test geometries.

A number of electromagnetic field problems can be formulated in terms of a hypersingular integral equation, in which a grad-div operator acts on a vector potential. A weak form of this integral equation is obtained by testing it with subdomain basis functions. As the next step, the vector potential is expanded in a sequence of subdomain basis functions and the grad-div operator is integrated analytically. It is shown that a well-behaved operator is obtained which can properly be solved numerically by a conjugate gradient FFT (fast Fourier transform) iterative method. For the problem of electromagnetic scattering by a plate, the present method shows excellent numerical performance. The numerical difficulties encountered in the previous CGFFT methods have been eliminated. >

Peter and Zwamborn comment on the paper by Tran and McCowen (IEEE Trans. Antenn. Propag., vol.41, p.185-90, 1993) which presents pulse-basis expansion functions and Dirac /spl delta/ testing functions within a conjugate gradient FFT (CGFFT) formulation. In the conclusions, Tran and McCowen state: "Although these spurious effects do not appear in the CGFFT formulation using the rooftop basis function proposed by Zwamborn and van den Berg (1991), there are more computational costs associated with their method than with ours." Peter and Zwamborn disagree with this statement. A reply is given by Tran and McCowen. >

The electromagnetic heat dissipation in a radially layered biological tissue inside a circular cylinder has been investigated theoretically. The theory is based on a three- dimensional model and the electromagnetic field is assumed to be generated by a prescribed electric field along a ring-shaped aperture. The method of computation employs the spatial Fourier transform of all field quantities with respect to the axial coordinate, after which the field equations are solved in the spectral domain. Subsequently, an inverse Fourier transform is carred out to compute the quantities that are of interest to the clinical deep-body hyperthermia system at hand. For a number of representative configurations numerical results at 70 MHz are given.