Mays L. Swicord

Microwave dielectric characterization of binary mixtures of water, methanol, and ethanol

The complex dielectric constants of binary mixtures of water–methanol and water–ethanol in the frequency range from 45 MHz to 26.5 GHz, and binary mixtures of methanol–ethanol in the range from 200 MHz to 26.5 GHz have been measured with various volume fractions around room temperature by means of an open‐ended coaxial sensor and a network analyzer. Methanol–ethanol mixtures display a near‐Debye dispersion while water–alcohol mixtures show a Cole–Davidson dispersion. The logarithm of relaxation time log τ  and dielectric decrement Δe for methanol–ethanol mixtures show a good linear relation with the volume fraction of methanol, while log τ and Δe extracted with the Debye function for water–alcohol mixtures display a near‐linear relation with volume fraction of water. Two simple formulas are proposed for identifying the volume fractions of the components in binary mixtures of alcohol–alcohol and water–alcohol from a knowledge of τ and Δe for the pure liquids and the mixtures. The validity of these formulas has been demonstrated with three blind tests. The relation between the mole fraction of water and log τ for water–methanol and water–ethanol mixtures extracted by the use of a Cole–Davidson function clearly shows two linear regions, which implies a change of relaxation mechanism with mole fraction.

QUANTITATIVE EVALUATIONS OF MECHANISMS OF RADIOFREQUENCY INTERACTIONS WITH BIOLOGICAL MOLECULES AND PROCESSES

The complexity of interactions of electromagnetic fields up to 1012 Hz with the ions, atoms, and molecules of biological systems has given rise to a large number of established and proposed biophysical mechanisms applicable over a wide range of time and distance scales, field amplitudes, frequencies, and waveforms. This review focuses on the physical principles that guide quantitative assessment of mechanisms applicable for exposures at or below the level of endogenous electric fields associated with development, wound healing, and excitation of muscles and the nervous system (generally, 1 to 102 V m−1), with emphasis on conditions where temperature increases are insignificant (←1 K). Experiment and theory demonstrate possible demodulation at membrane barriers for frequencies ≤10 MHz, but not at higher frequencies. Although signal levels somewhat below system noise can be detected, signal-to-noise ratios substantially less than 0.1 cannot be overcome by cooperativity, signal averaging, coherent detection, or by nonlinear dynamical systems. Sensory systems and possible effects on biological magnetite suggest paradigms for extreme sensitivity at lower frequencies, but there are no known radiofrequency (RF) analogues. At the molecular level, vibrational modes are so overdamped by water molecules that excitation of molecular modes below the far infrared cannot occur. Two RF mechanisms plausibly may affect biological matter under common exposure conditions. For frequencies below approximately 150 MHz, shifts in the rate of chemical reactions can be mediated by radical pairs and, at all frequencies, dielectric and resistive heating can raise temperature and increase the entropy of the affected biological system.

Microwave effects on plasmid DNA.

The exposure of purified plasmid DNA to microwave radiation at nonthermal levels in the frequency range from 2.00 to 8.75 GHz produces single- and double-strand breaks that are detected by agarose gel electrophoresis. Microwave-induced damage to DNA depends on the presence of small amounts of copper. This effect is dependent upon both the microwave power and the duration of the exposure. Cuprous, but not cupric, ions were able to mimic the effects produced by microwaves on DNA.

DNA Structural Changes Caused by Microwave Radiation

SummaryNon-thermal levels of microwave exposure can produce single- and double-strand breaks in DNA in solution.

Intracellular calcium signaling by Jurkat T-lymphocytes exposed to a 60 Hz magnetic field.

To explore possible biochemical mechanisms whereby electromagnetic fields of around 0.1 mT might affect immune cells or developing cancer cells, we studied intracellular calcium signaling in the model system Jurkat E6-1 human T-leukemia cells during and following exposure to a 60 Hz magnetic field. Cells were labeled with the intracellular calcium-sensitive fluorescent dye Fluo-3, stimulated with a monoclonal antibody against the cell surface structure CD3 (associated with ligand-stimulated T-cell activation), and analyzed on a FACScan flow-cytometer for increases in intensity of emissions in the range of 515-545 nm. Cells were exposed during or before calcium signal-stimulation to 0.15 mTrms 60 Hz magnetic field. The total DC magnetic field of 78.2 microT was aligned 17.5 degrees off the vertical axis. Experiments used both cells cultured at optimal conditions at 37 degrees C and cells grown under suboptimal conditions of 24 degrees C, lowered external calcium, or lowered anti-CD3 concentration. These experiments demonstrate that intracellular signaling in Jurkat E6-1 was not affected by a 60 Hz magnetic field when culture and calcium signal-stimulation were optimal or suboptimal. These results do not exclude field-induced calcium-related effects further down the calcium signaling pathway, such as on calmodulin or other calcium-sensitive enzymes.

Microwave-field-driven acoustic modes in DNA.

The direct coupling of a microwave field to selected DNA molecules is demonstrated using standard dielectrometry. The absorption is resonant with a typical lifetime of 300 ps. Such a long lifetime is unexpected for DNA in aqueous solution at room temperature. Resonant absorption at fundamental and harmonic frequencies for both supercoiled circular and linear DNA agrees with an acoustic mode model. Our associated acoustic velocities for linear DNA are very close to the acoustic velocity of the longitudinal acoustic mode independently observed on DNA fibers using Brillouin spectroscopy. The difference in acoustic velocities for supercoiled circular and linear DNA is discussed in terms of solvent shielding of the nonbonded potentials in DNA.

Enhancement of anchorage-independent growth in JB6 cells exposed to 60 hertz magnetic fields

Abstract Extremely low frequency electromagnetic fields (EMFs) are implicated in the genesis of childhood leukemias and lymphomas after residential exposure, and of tumors in adults after occupational exposure. Experiments in vitro have demonstrated biochemical changes with cultured cells including modulation of signal transduction pathways. We examined the ability of 60 Hz sinusoidal EMFs to alter the growth of a promotion-sensitive mouse epidermal cell line (JB6) under anchorage-independent conditions. Cells (10 4 per dish) were suspended in 0,3% agar in 60 mm dishes and exposed to a 1.1 × 10 −3 T field generated by a Helmholtz coil held in an incubator at 37°C, 5% 002 and 90%–97% relative humidity. Growth of colonies more than 60 nm in diameter was scored after 10–14 days. Exposure to the EMF significantly increased the colony-forming efficiency, by 40%–70% compared with control cells ( > 95% confidence level), suggesting interaction with a growth control/signal transduction pathway.

Radiofrequency Dosimetry for the Ferris-Wheel Mouse Exposure System

Abstract Faraone, A., Luengas, W., Chebrolu, S., Ballen, M., Bit-Babik, G., Gessner, A. V., Kanda, M. Y., Babij, T., Swicord, M. L. and Chou, C-K. Radiofrequency Dosimetry for the Ferris-Wheel Mouse Exposure System. Radiat. Res. 165, 105–112 (2006). Numerical and experimental methods were employed to assess the individual and collective dosimetry of mice used in a bioassay on the exposure to pulsed radiofrequency energy at 900 MHz in the Ferris-wheel exposure system (Utteridge et al., Radiat. Res. 158, 357–364, 2002). Twin-well calorimetry was employed to measure the whole-body specific absorption rate (SAR) of mice for three body masses (23 g, 32 g and 36 g) to determine the lifetime exposure history of the mice used in the bioassay. Calorimetric measurements showed about 95% exposure efficiency and lifetime average whole-body SARs of 0.21, 0.86, 1.7 and 3.4 W kg−1 for the four exposure groups. A larger statistical variation in SAR was observed in the smallest mice because they had the largest variation in posture inside the plastic restrainers. Infrared thermography provided SAR distributions over the sagittal plane of mouse cadavers. Thermograms typically showed SAR peaks in the abdomen, neck and head. The peak local SAR at these locations, determined by thermometric measurements, showed peak-to-average SAR ratios below 6:1, with typical values around 3:1. Results indicate that the Ferris wheel fulfills the requirement of providing a robust exposure setup, allowing uniform collective lifetime exposure of mice.

Comparison of the Effect of ELF on c-myc Oncogene Expression in Normal and Transformed Human Cells

EWA CZERSKA? JON CASAMENT0,O JOHN NINGF MAYS SWICORDF HEBA AL-BARAZI? CHRISTOPHER DAVIS! AND EDWARD ELSONC aCenter for Devices and Radiological Health Food and Drug Administration Rockville, Maryland 20857 bDepartment of Electrical Engineering Universiv of Maryland College Park Maryland 20742 CDepartment of Microwave Research Walter Reed A m y Institute of Research Washington, District of Columbia 20307

Food and drug administration low‐level extremely‐low‐frequency magnetic field exposure facility

We describe the design, construction details, and performance characteristics of an exposure system designed to provide very well controlled extremely-low-frequency magnetic field exposures of in vitro samples. This system uses Helmholtz coils placed inside temperature-controlled mu-metal chambers to provide simultaneous ac and dc field exposures at any relative angle with minimal residual background field. The system has both exposed and sham-exposed chambers and is operated under computer control in such a way as to ensure blind exposure of samples.