Volkert Hansen

On the calculation of potential integrals for linear source distributions on triangular domains

Present analytical formulas for the singular field contributions of linear source distributions on triangular domains. The formulas can be used for near-field calculations of electric and magnetic source currents, especially for the calculation of method of moments (MOM) matrix elements due to the solution of surface integral equations. For MOM self-coupling terms involving the scalar Green function of free space, the authors present expressions comprising analytical solutions of both the source integrals and the testing integrals.

Calculation of unbounded field problems in free space by a 3D FEM/BEM-hybrid approach

In recent times electromagnetic scattering calculations are often done by local methods such as Finite Elements or Finite Differences with approximate local absorbing boundary conditions because of their computational efficiency. The exact formulation of the field problem by combining a local with a global method (boundary integral) has the drawback that fully populated matrices have to be handled, making the method often computationally intensive. But there are many cases in which such hybrid-techniques have advantages as compared with pure local methods. We present an FEM/BEM-hybrid approach and show its application to scattering problems with several separated finite inhomogeneous regions and to combined scattering/radiation problems. The calculation of radiation problems (e. g. antennas nearby inhomogeneous bodies) is especially attractive because radiation structures can be modeled by well-established integral equation techniques. Particular attention is paid to the evaluation of the coupling integra...

No effects of GSM-modulated 900 MHz electromagnetic fields on survival rate and spontaneous development of lymphoma in female AKR/J mice.

BackgroundSeveral reports indicated that non-thermal electromagnetic radiation such as from mobile phones and base stations may promote cancer. Therefore, it was investigated experimentally, whether 900 MHz electromagnetic field exposure influences lymphoma development in a mouse strain that is genetically predisposed to this disease. The AKR/J mice genome carries the AK-virus, which leads within one year to spontaneous development of thymic lymphoblastic lymphoma.Methods320 unrestrained female mice were sham-exposed or exposed (each n = 160 animals) to GSM like 900 MHz electromagnetic fields for 24 hours per day, 7 days per week, at an average whole body specific absorption rate (SAR) value of 0.4 W/kg. Animals were visually checked daily and were weighed and palpated weekly. Starting with an age of 6 months, blood samples were taken monthly from the tail. Animals with signs of disease or with an age of about 46 weeks were sacrificed and a gross necropsy was performed.ResultsElectromagnetic field exposure had a significant effect on body weight gain, with higher values in exposed than in sham-exposed animals. However, survival rate and lymphoma incidence did not differ between exposed and sham-exposed mice.ConclusionThese data do not support the hypothesis that exposure to 900 MHz electromagnetic fields is a significant risk factor for developing lymphoma in a genetically predisposed species, even at a relatively high exposure level.

Effects of Radiofrequency Electromagnetic Fields (UMTS) on Reproduction and Development of Mice: A Multi-generation Study

Abstract Sommer, A. M., Grote, K., Reinhardt, T., Streckert, J., Hansen, V. and Lerchl, A. Effects of Radiofrequency Electromagnetic Fields (UMTS) on Reproduction and Development of Mice: A Multi-generation Study. Radiat. Res. 171, 89–95 (2009). Male and female mice (C57BL) were chronically exposed (life-long, 24 h/day) to mobile phone communication electromagnetic fields at approximately 1966 MHz (UMTS). Their development and fertility were monitored over four generations by investigating histological, physiological, reproductive and behavioral functions. The mean whole-body SARs, calculated for adult animals at the time of mating, were 0 (sham), 0.08, 0.4 and 1.3 W/kg. Power densities were kept constant for each group (0, 1.35, 6.8 and 22 W/m2), resulting in varying SARs due to the different numbers of adults and pups over the course of the experiment. The experiment was done in a blind fashion. The results show no harmful effects of exposure on the fertility and development of the animals. The number and the development of pups were not affected by exposure. Some data, albeit without a clear dose–response relationship, indicate effects of exposure on food consumption that is in accordance with some data published previously. In summary, the results of this study do not indicate harmful effects of long-term exposure of mice to UMTS over several generations.

Effects of mobile phone electromagnetic fields at nonthermal SAR values on melatonin and body weight of Djungarian hamsters (Phodopus sungorus)

Abstract:  In three experiments, adult male Djungarian hamsters (Phodopus sungorus) were exposed 24 hr/day for 60 days to radio frequency electromagnetic fields (RF‐EMF) at 383, 900, and 1800 MHz, modulated according to the TETRA (383 MHz) and GSM standards (900 and 1800 MHz), respectively. A radial waveguide system ensured a well defined and uniform exposure at whole‐body averaged specific absorption rates of 80 mW/kg, which is equal to the upper limit of whole‐body exposure of the general population in Germany and other countries. For each experiment, using two identical waveguides, hamsters were exposed (n = 120) and sham‐exposed (n = 120) in a blind fashion. In all experiments, pineal and serum melatonin levels as well as the weights of testes, brain, kidneys, and liver were not affected. At 383 MHz, exposure resulted in a significant transient increase in body weight up to 4%, while at 900 MHz this body weight increase was more pronounced (up to 6%) and not transient. At 1800 MHz, no effect on body weight was seen. The results corroborate earlier findings which have shown no effects of RF‐EMF on melatonin levels in vivo and in vitro. The data are in accordance with the hypothesis that absorbed RF energy may result in metabolic changes which eventually cause body weight increases in exposed animals. The data support the notion that metabolic effects of RF‐EMFs need to be investigated in more detail in future studies.

Electrodynamic analysis of combined microstrip and coplanar/slotine structures with 3-D components based on a surface/volume integral-equation approach

This paper deals with the electrodynamic analysis of structures embedded in multilayered media, which consist of both microstrip/stripline and coplanar/slotline components also comprising three-dimensional components like vertical interconnects, finite dielectric fillings, or coatings. The analysis is based on a surface/volume integral-equation method using a magnetic surface current description for the slot areas, electric surface currents for the planar microstrip/stripline structures, and electric or polarization volume currents for the description of vertical interconnects and finite dielectric regions. The current discretization is performed by rectangular subdomain basis functions with asymmetric segmentations and corresponding volume current functions on arbitrary nonuniform meshes. For the effective and accurate evaluation of the system matrix., we apply a general asymptotic subtraction technique combined with complete analytical solutions of all dominant asymptotic system matrix entries. Furthermore, we use adaptive database techniques employed in the remaining numerical integrations and identify search algorithms for an optimized redundancy reduction. The method was applied to a large class of different structures comprising customary microstrip components, coplanar bandstop filters, and metal-insulation-metal capacitances and a new class of submillimeter-wave receivers. The results are in good agreement with experimental data or with results of finite-difference approaches, where, however, the latter require much more computational and storage effort.

Lymphoma development in mice chronically exposed to UMTS-modulated radiofrequency electromagnetic fields.

Abstract Sommer, A. M., Bitz, A. K., Streckert, J., Hansen, V. W. and Lerchl, A. Lymphoma Development in Mice Chronically Exposed to UMTS-Modulated Radiofrequency Electromagnetic Fields. Radiat. Res. 168, 72–80 (2007). There are public concerns regarding possible carcinogenic or cancer-promoting effects of electromagnetic fields (EMFs) from mobile phones and base stations. The objective of the present study was to investigate whether chronic exposure to EMFs of the UMTS (Universal Mobile Telecommunication System) influences the development of lymphoma in a lymphoma animal model, the AKR/J mouse. Unrestrained mice were chronically sham-exposed (n = 160) or exposed (n = 160) in identical exposure systems (radial waveguides) to a generic UMTS test signal (24 h per day, 7 days per week, 0.4 W/kg SAR). Additionally, 30 animals were kept as cage controls. Animals were checked visually each day and were weighed and palpated weekly to detect swollen lymph nodes. Starting at the age of 6 months, blood samples were taken from the tail every 2 weeks to perform differential leukocyte counts and to measure the hematocrit. Visibly diseased animals or those older than 43 weeks were killed humanely, and tissue slices were examined for metastatic infiltrations and lymphoma type. The study was performed in a blinded way. Cage control animals had a significantly lower growth rate than those kept in the radial waveguides. The number of ill animals, the mean survival time, and the severity code of the disease did not differ between the experimental groups. Therefore, the data show no negative effects from exposure and corroborate earlier findings in AKR/J mice exposed to GSM EMF (Sommer et al., BMC Cancer 4, 77–90, 2004).

Effects of universal mobile telecommunications system (UMTS) electromagnetic fields on the blood-brain barrier in vitro

Abstract Franke, H., Streckert, J., Bitz, A., Goeke, J., Hansen, V., Ringelstein, E. B., Nattkämper, H., Galla, H-J. and Stögbauer, F. Effects of Universal Mobile Telecommunications System (UMTS) Electromagnetic Fields on the Blood-Brain Barrier In Vitro. Radiat. Res. 164, 258–269 (2005). The extensive use of mobile phone communication has raised public concerns about adverse health effects of radiofrequency (RF) electromagnetic fields (EMFs) in recent years. A central issue in this discussion is the question whether EMFs enhance the permeability of the blood-brain barrier (BBB). Here we report an investigation on the influence of a generic UMTS (Universal Mobile Telecommunications System) signal on barrier tightness, transport processes and the morphology of porcine brain microvascular endothelial cell cultures (PBEC) serving as an in vitro model of the BBB. An exposure device with integrated online monitoring system was developed for simultaneous exposure and measuring of transendothelial electrical resistance (TEER) to determine the tightness of the BBB. PBEC were exposed continuously for up to 84 h at an average electric-field strength of 3.4–34 V/m (maximum 1.8 W/kg) ensuring athermal conditions. We did not find any evidence of RF-field-induced disturbance of the function of the BBB. After and during exposure, the tightness of the BBB quantified by 14C-sucrose and serum albumin permeation as well as by TEER remained unchanged compared to sham-exposed cultures. Permeation of transporter substrates at the BBB as well as the localization and integrity of the tight-junction proteins occludin and ZO1 were not affected either.

Hybrid/sup 2/: combining the three-dimensional hybrid finite element-boundary integral technique for planar multilayered media with the uniform geometrical theory of diffraction

The fully three-dimensional (3-D) hybrid finite element (FE)-boundary integral (BI) technique is extended by further hybridization with the uniform geometrical theory of diffraction (UTD) resulting in a so-called hybrid/sup 2/ FE-BI-UTD approach. The formulation is capable of modeling arbitrarily shaped strongly inhomogeneous objects together with electrically large obstacles of relatively simple shape within the common environment of a planar-multilayered medium. The arbitrarily shaped inhomogeneous objects are discretized by finite elements, whereas, the electrically-large obstacles are described by the UTD and both of these models are included into an integral equation derived from the equivalence principle for planar-multilayered media. Thus, full-electromagnetic coupling is realized between all parts of the formulation. The integral equation is implemented using mixed potentials with appropriate Greens functions derived from Sommerfeld integral representations for planar-multilayered media. The UTD contributions are accounted for by corresponding modifications of the Greens functions and the FE technique is coupled to the integral equation via introduction of equivalent surface current densities in the bounding surfaces of the discretized objects. After presenting the formulation of this novel fully 3-D hybrid/sup 2/ technique, the implemented computer code is validated against conventional hybrid FE-BI computations and a wireless base station antenna is analyzed in several situations of complex real world, microcell environments.

Indication of cocarcinogenic potential of chronic UMTS-modulated radiofrequency exposure in an ethylnitrosourea mouse model

Purpose: To evaluate putative effects on tumour susceptibility in mice exposed to a UMTS (universal mobile telecommunications system) test signal for up to 24 months, commencing with embryo-fetal exposure. Material and methods: Animals were exposed to UMTS fields with intensities of 0, 4.8, and 48 W/m2, the low-dose group (4.8 W/m2) was subjected to additional prenatal ethylnitrosourea treatment (40 mg ENU/kg body weight). Results: The high-level UMTS exposure (48 W/m2), the sham exposure, and the cage control groups showed comparable tumour incidences in the protocol organs. In contrast, the ENU-treated group UMTS-exposed at 4.8 W/m2 displayed an enhanced lung tumour rate and an increased incidence of lung carcinomas as compared to the controls treated with ENU only. Furthermore, tumour multiplicity of the lung carcinomas was increased and the number of metastasising lung tumours was doubled in the ENU/UMTS group as compared to the ENU control group. Conclusion: This pilot study indicates a cocarcinogenic effect of lifelong UMTS exposure (4.8 W/m2) in female B6C3F1 descendants subjected to pretreatment with ethylnitrosourea.