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  • 1985-1989  (4)
  • Occupational Health and Environmental Toxicology  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Interaction of ethanol and microwaves on the blood-brain barrier of rats (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 7 (1986), S. 405-414 
    Details
    ISSN: 0197-8462
    Keywords: temperature ; hyperthermia ; Evans-blue ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The combined effects of ethanol and microwaves on the permeation of Evans blue dye through the mammalian blood-brain barrier was studied in male Wistar rats. Anesthetized rats were infused through a cannula in the left femoral vein with 0.1, 0.3, 0.5 or 0.7 grams of absolute ethanol per kilogram of body mass. A control group was given 0.7 g/kg of isotonic saline. The left hemisphere of the brain was irradiated by 3.15-GHz microwave energy at 3.0 W/cm2 rms for 15 min. The rat's rectal temperature was maintained at 37.0°C. Immediately after irradiation, 2% Evans blue dye in saline (2.0 ml/kg body mass) was injected through the cannula. The results show that as the quantity of alcohol was increased, the degree of staining was decreased or eliminated. The temperature of the irradiated area of the brain increased for the first 4 to 5 minutes of irradiation and then stabilized for the remainder of the irradiation period. The steady-state temperature was highest in animals receiving saline or the smallest dose of alcohol. As the quantity of alcohol was increased, the steady-state temperature was reduced. These results indicate that ethanol inhibits microwave-induced permeation of the blood-brain barrier through reduced heating of the brain.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250070408
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave-induced thermoelastic pressure wave propagation in the cat brain (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 9 (1988), S. 141-147 
    Details
    ISSN: 0197-8462
    Keywords: microwave pulses ; acoustic pressure ; speed of propagation ; attenuation coefficient ; frequency spectrum ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This paper presents direct measurements of acoustic pressure wave propagation in cat brains irradiated with pulsed 2.45-GHz microwaves. Short rectangular microwave pulses (2 μs, 15 kW peak power) were applied singly through a direct-contact applicator located at the occipital pole of a cat's head. Acoustic pressure waves were detected by using a small hydrophone transducer, which was inserted stereotaxically into the brain of an anesthetized animal through a matrix of holes drilled on the skull. The measurements clearly indicate that pulsed microwaves induce acoustic pressure waves which propagate with an acoustic wave velocity of 1523 m/s.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250090205
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Off-center spherical model for dosimetry calculations in chick brain tissue (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 7 (1986), S. 209-221 
    Details
    ISSN: 0197-8462
    Keywords: brain tissue ; radiofrequency ; radiation ; dosimetry ; calcium ions ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This paper presents calculations for the electric field and absorbed power density distribution in chick brain tissue inside a test tube, using an off-center spherical model. It is shown that the off-center spherical model overcomes many of the limitations of the concentric spherical model, and permits a more realistic modeling of the brain tissue as it sits in the bottom of the test tube surrounded by buffer solution. The effect of the unequal amount of buffer solution above the upper and below the lower surfaces of the brain is analyzed. The field distribution is obtained in terms of a rapidly converging series of zonal harmonics. A method that permits the expansion of spherical harmonics about an off-center origin in terms of spherical harmonics at the origin is developed to calculate in closed form the electric field distribution. Numerical results are presented for the absorbed power density distribution at a carrier frequency of 147 MHz. It is shown that the absorbed power density increases toward the bottom of the brain surface. Scaling relations are developed by keeping the electric field intensity in the brain tissue the same at two different frequencies. Scaling relations inside, as well as outside, the brain surface are given. The scaling relation distribution is calculated as a function of position, and compared to the scaling relations obtained in the concentric spherical model. It is shown that the off-center spherical model yields scaling ratios in the brain tissue that lie between the extreme values predicted by the concentric and isolated spherical models.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250070210
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Microwave-induced changes in nerve cells: Effects of modulation and temperature (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 6 (1985), S. 257-270 
    Details
    ISSN: 0197-8462
    Keywords: microwaves ; noise modulation ; temperature ; snail neurons ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Helix aspersa neurons were irradiated with continuous-wave (CW) and noise-amplitudemodulated microwaves (carrier frequency 2450 MHz, 20% AM, 2 Hz-20 kHz) in a specially designed waveguide exposure system. Continuous-wave microwave irradiations were conducted at 8°, 21°, and 28°C, while noise-modulated irradiation was performed at 21°C. The results showed that exposure of snail neurons to CW microwaves for 60 min at 12.9 W/kg inhibited spontaneous activity and reduced input resistance at 8° and 21°C but not at 28°C. The relative decrease in resistance at 21°C was half that at 8°C. Exposure of neurons to noise-modulated microwaves at 6.8 and 14.4 W/kg predominately caused excitatory responses characterized by augmented membrane resistance and the appearance of greater activity. The effect differed qualitatively from the inhibition observed with continuous, unmodulated microwave irradiation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250060306
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    Paper (German National Licenses)
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