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Kuehn S.,ETH Zurich | Kelsh M.A.,Amgen Inc. | Kuster N.,ETH Zurich | Sheppard A.R.,Asher Sheppard Consulting | Shum M.,National Collaborating Center for Environmental Health
Bioelectromagnetics | Year: 2013

The US FCC mandates the testing of all mobile phones to demonstrate compliance with the rule requiring that the peak spatial SAR does not exceed the limit of 1.6W/kg averaged over any 1g of tissue. These test data, measured in phantoms with mobile phones operating at maximum antenna input power, permitted us to evaluate the variation in SARs across mobile phone design factors such as shape and antenna design, communication technology, and test date (over a 7-year period). Descriptive statistical summaries calculated for 850MHz and 1900MHz phones and ANOVA were used to evaluate the influence of the foregoing factors on SARs. Service technology accounted for the greatest variability in compliance test SARs that ranged from AMPS (highest) to CDMA, iDEN, TDMA, and GSM (lowest). However, the dominant factor for SARs during use is the time-averaged antenna input power, which may be much less than the maximum power used in testing. This factor is largely defined by the communication system; e.g., the GSM phone average output can be higher than CDMA by a factor of 100. Phone shape, antenna type, and orientation of a phone were found to be significant but only on the order of up to a factor of 2 (3dB). The SAR in the tilt position was significantly smaller than for touch. The side of the head did not affect SAR levels significantly. Among the remaining factors, external antennae produced greater SARs than internal ones, and brick and clamshell phones produced greater SARs than slide phones. Assuming phone design and usage patterns do not change significantly over time, we have developed a normalization procedure and formula that permits reliable prediction of the relative SAR between various communication systems. This approach can be applied to improve exposure assessment in epidemiological research. © 2013 Wiley Periodicals, Inc. Source


Paffi A.,University of Rome La Sapienza | Apollonio F.,University of Rome La Sapienza | Liberti M.,University of Rome La Sapienza | Sheppard A.,Asher Sheppard Consulting | And 2 more authors.
International Journal of Antennas and Propagation | Year: 2015

Biological experiments that expose living cells or tissues to RF energy must have an aqueous medium to provide essential water, ions, nutrients, and growth factors. However, as we show here, the medium inherently functions as a receiving antenna that conveys RF energy to the biological entity in a manner entirely determined by exposure vessel geometry, orientation to the incident RF flux, frequency, and dielectric properties of the medium. We show for two common experimental arrangements that basic antenna theory can predict electromagnetic energy patterns that agree well with those otherwise obtained by computationally intensive methods that require specialized resources. © 2015 Alessandra Paffi et al. Source


Paffi A.,University of Rome La Sapienza | Liberti M.,University of Rome La Sapienza | Apollonio F.,University of Rome La Sapienza | Sheppard A.,Asher Sheppard Consulting | Balzano Q.,University of Maryland University College
Bioelectromagnetics | Year: 2015

We conducted an electromagnetic-thermal analysis of Petri dishes filled with different medium volumes under different radio frequency exposure conditions with the aim of identifying linear and non-linear parameters that might explain contradictory results of many in vitro bioelectromagnetic experiments. We found that power loss density and temperature depend on shape, size, and orientation of the exposed sample with respect to direction of incident energy, showing that the liquid medium acts as a receiving antenna. In addition, we investigated the possibility of convection from thermodynamic principles within the liquid medium. For a 35mm diameter Petri dish, a 2 or 4ml medium volume is too small to support vertical convection. Conversely, horizontal convective motion is possible for H-polarization exposures at 1.8GHz. © 2015 Wiley Periodicals, Inc. Source


Kelsh M.A.,Exponent, Inc. | Shum M.,Exponent, Inc. | Sheppard A.R.,Asher Sheppard Consulting | McNeely M.,Exponent, Inc. | And 6 more authors.
Journal of Exposure Science and Environmental Epidemiology | Year: 2011

Epidemiologic studies of mobile phone users have relied on self reporting or billing records to assess exposure. Herein, we report quantitative measurements of mobile-phone power output as a function of phone technology, environmental terrain, and handset design. Radiofrequency (RF) output data were collected using software-modified phones that recorded power control settings, coupled with a mobile system that recorded and analyzed RF fields measured in a phantom head placed in a vehicle. Data collected from three distinct routes (urban, suburban, and rural) were summarized as averages of peak levels and overall averages of RF power output, and were analyzed using analysis of variance methods. Technology was the strongest predictor of RF power output. The older analog technology produced the highest RF levels, whereas CDMA had the lowest, with GSM and TDMA showing similar intermediate levels. We observed generally higher RF power output in rural areas. There was good correlation between average power control settings in the software-modified phones and power measurements in the phantoms. Our findings suggest that phone technology, and to a lesser extent, degree of urbanization, are the two stronger influences on RF power output. Software-modified phones should be useful for improving epidemiologic exposure assessment. Source


Balzano Q.,University of Maryland University College | Sheppard A.R.,Asher Sheppard Consulting | Bit-Babik G.,Motorola Solutions
IEEE International Symposium on Electromagnetic Compatibility | Year: 2012

Many in vitro experiments have been conducted during the past 50 years to explore the mechanisms of interaction between RF energy and living tissue. There has been practically no consideration given to the thermodynamic events taking place in the cell medium, which absorbs the bulk of the incident energy and evolves towards a temperature equilibrium condition during the exposure. This paper explores the different medium thermodynamic conditions arising during the exposure of cell preparations, depending on their heat exchange environments. The final goal is to determine if the thermodynamic conditions cause convective motion in the medium with possible biological consequences to the exposed cell preparations. © 2012 IEEE. Source

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