Thomas Kleine-Ostmann

Spindle disturbances in human-hamster hybrid (AL) cells induced by mobile communication frequency range signals

The production of spindle disturbances in FC2 cells, a human-hamster hybrid (A(L)) cell line, by non-ionizing radiation was studied using an electromagnetic field with a field strength of 90 V/m at a frequency of 835 MHz. Due to the given experimental conditions slide flask cultures were exposed at room temperature in a microTEM (transversal electromagnetic field) cell, which allows optimal experimental conditions for small samples of biological material. Numerical calculations suggest that specific absorption rates of up to 60 mW/kg are reached for maximum field exposure. All exposure field parameters--either measured or calculable--are precisely defined and, for the first time, traceable to the standards of the SI system of physical units. Compared with co-incident negative controls, the results of two independently performed experiments suggest that exposure periods of time from 0.5 to 2 h with an electric field strength of 90 V/m are spindle acting agents as predominately indicated by the appearance of spindle disturbances at the ana- and telophase stages (especially lagging and non-disjunction of single chromosomes) of cell divisions. The spindle disturbances do not change the fraction of mitotic cells with increasing exposure time up to 2 h. Due to the applied experimental conditions an influence of temperature as a confounder parameter for spindle disturbances can be excluded.

Terahertz Electromagnetic Fields (0.106 THz) Do Not Induce Manifest Genomic Damage In Vitro

Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment. Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm2 to 2 mW/cm2, representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction.

A comparison of indoor channel measurements and ray tracing simulations at 300 GHz

This paper presents ultra broadband channel measurements in a typical office room. The measured channel impulse response and transfer function is compared to a ray tracing simulation performed with a 3D model of the scenario. Additionally, we show reflection losses of the building materials in the room which are required as input data for the ray tracing algorithm.

Design and Calibration of a Compact Quasi-Optical System for Material Characterization in Millimeter/Submillimeter Wave Domain

A compact quasi-optical setup based on conventional rectangular horn antennas and two symmetrical parabolic mirrors is designed to provide a plane wave on the material under test. To measure the scattering parameters at millimeter/submillimeter wavelengths, a commercial vector network analyzer and waveguide frequency extension units are used. The calibration of the system is performed with a simple practical deembedding process to determine the S-parameters on the material surface without using high-cost micrometer positioners. A reliable extraction method is presented to derive the material permittivity and calculate the errors and uncertainties as direct functions of the sample and setup geometry and their physical characteristics. Several materials are measured and the complex permittivity is presented together with a detailed uncertainty budget.

Spindle disturbances in human–hamster hybrid (AL) cells induced by the electrical component of the mobile communication frequency range signal

The production of spindle disturbances in a human-hamster hybrid (A(L) ) cell line by an electromagnetic field (EMF) with field strength of 90 V/m at a frequency of 900 MHz was studied in greater detail. The experimental setup presented allows investigating whether either the electrical (E) and/or the magnetic (H) field component of EMF can be associated with the effectiveness of the spindle-disturbing potential. Therefore, both field components of a transversal electromagnetic field (TEM) wave have been separated during exposure of the biological system. This procedure should give more insight on understanding the underlying mechanisms of non-thermal effects of EMF. A statistical comparison of the proportions of the fractions of ana- and telophases with spindle disturbances, obtained for five different exposure conditions with respect to unexposed controls (sham condition), showed that only cells exposed to the H-field component of the EMF were not different from the control. Therefore, the results of the present study indicate that an exposure of cells to EMF at E-field strengths of 45 and 90 V/m, as well as to the separated E component of the EMF, induces significant spindle disturbances in ana- and telophases of the cell cycle.

900 MHz radiation does not induce micronucleus formation in different cell types

The exposure of the population to non-ionising electromagnetic radiation is still increasing, mainly due to mobile communication. Whether low-intensity electromagnetic fields can cause other effects apart from heating has been a subject of debate. One of the effects, which were proposed to be caused by mobile phone radiation, is the occurrence of mitotic disturbances. The aim of this study was to investigate possible consequences of these mitotic disturbances as manifest genomic damage, i.e. micronucleus induction. Cells were irradiated at a frequency of 900 MHz, which is located in one of the main frequency bands applied for mobile communication. Two cell types were used, HaCaT cells as human cells and A(L) cells (human-hamster hybrid cells), in which mitotic disturbances had been reported to occur. After different post-exposure incubation periods, cells were fixed and micronucleus frequencies were evaluated. Both cell types did not show any genomic damage after exposure. To adapt the protocol for the micronucleus test into the direction of the protocol for mitotic disturbances, the post-exposure incubation period was reduced and exposure time was extended to one cell cycle length. This did not result in any increase of the genomic damage. In conclusion, micronucleus induction was not observed as a consequence of exposure to non-ionising radiation, even though this agent was reported to cause mitotic disturbances under similar experimental conditions.

Concept and Perspectives of Future Ultra Broadband THz Communication Systems

Future wireless links for many emerging applications such as peer-to-peer collaboration but also as a wireless extension of existing fiber networks will require increased bandwidth compared to current WLANs/WPANs. The lack of unoccupied bandwidth and the potential to modulate increased carrier frequencies with multi-gigabit data rates will push their operation frequencies above 100 GHz. Based on measurements and ray-tracing simulations we discuss technology and propagation constraints of such systems that will have to rely on directed transmission. We show that dielectric mirrors covering parts of the walls will enhance the signal coverage in a typical indoor scenario.

A reliable simple method to extract the intrinsic material properties in millimeter/sub-millimeter wave domain

A simple method is presented to extract the material characteristics from the scattering parameters in the frequency domain. The method is based on “transmission” measurement data only and can give the complex permittivity and/or the absorption and refraction index via easy arithmetic operations with closed-form formulas. Therefore, a parametric error analysis will be feasible for metrological aspects to show important uncertainty contributions. The actual measurements have been performed with a compact quasi-optical free-space setup in the frequency band from 50 GHz to 500 GHz and the detailed results are presented to show the performance of the method.

Measurement of channel and propagation properties at 300 GHz

The constantly growing need for unoccupied and unregulated bandwidth will lead to the extension of operation frequencies of ultrabroadband communication systems into the lower Terahertz frequency range. Here we present first channel measurements at 300 GHz for two simple indoor scenarios, a point-to-point link on a desktop and a connection from a desktop to an access point within an office room. For the first scenario measurements are taken depending on distance, antenna types and transmitter/receiver placement. For the second scenario, measurements are obtained to identify line-of-sight and non-line-of-sight paths with up to two reflections and obstruction due to objects in the transmission path. From the channel transfer function, temporal channel characteristics are derived to estimate maximum achievable symbol rates.

Waveform metrology for error vector magnitude measurements in a 300 GHz transmission system

The paper presents results of error vector magnitude (EVM) measurements in a 300 GHz transmission system. The EVM was determined using real-time oscilloscope and consecutive mathematical processing in a computer instead of using a commercial vector signal analyser. The uncertainty of EVM measured with the real-time oscilloscope is open to analysis.