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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 247 (1975), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 16 (1983), S. 57-61 
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: Application of Twyman–Green interferometry is extended to achieve semi-quantitative assessment of optical qualities of a nonlinear crystal. Interferograms of a proustite crystal are analyzed and effects of crystal imperfections on the conversion efficiency of a parametric upconversion system are evaluated.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 196 (1962), S. 884-885 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Frequency multiplication to sub -millimetre waves by the foregoing scheme is also possible, if the slow electromagnetic waves propagated through the semiconductor plasma are reflected at the moving plasma boundary. Such a reflecting boundary is provided by the depletion (plasma -free) region in a ...
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0197-8462
    Keywords: millimeter-wave radiation ; BHK-21/C13 cells in monolayer culture ; scanning electron microscopy ; transmission electron microscopy ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Both thermal and athermal effects of millimeter-wave radiation on BHK-21/C13 cells were sought using scanning and transmission electron microscopy in conjunction with an in vitro technique that allows direct exposure of monolayer cultures to high average power densities. Culture dishes were irradiated by placing them on the open end of an E- or U-band wave guide. This technique exposes different regions of the cell monolayer lying along the longer axis of the wave guide aperture to varying power densities ranging from zero at each edge to twice the average power density at the center.Cell ultrastructure was unaffected by microwave radiation for 1 hour (41.8 or 74.0 GHz, average power densitites = 320 or 450 mW/cm2, respectively) with or without cooling by rapid recirculation of the culture medium. Temperature in recirculated cultures was held at 37.2 °C, and that in noncooled cultures never exceeded 42 °C during irradiation at either power density. In contrast, cell morphology was affected by microwave exposure whenever irradiation conditions were altered so that the temperature of the monolayer reached or exceeded 44.5 °C. Ultrastructural alterations included breakage of cell processes, progressive detachment of cells from the substrate, increased clumping of heterochromatin in the nuclei, and the appearance of large empty vesicles in the cytoplasm. Such morphological changes resulted from either application of higher average power densities or irradiation at the power densities described above at a higher ambient temperature (〉38.5°C).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0197-8462
    Keywords: millimeter-wave radiation ; BHK-21/C13 cells in monolayer culture ; quantitative autoradiography ; ribonucleic acid (RNA) synthesis ; protein synthesis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A method has been devised whereby both the thermal and possible athermal biological effects resulting from microwave radiation can be assessed. Monolayer cultures of BHK-21/C13 cells were grown on microwave-transparent polystyrene coverslips, placed directly on the open end of a wave guide, and irradiated for 1 hour. In experiments seeking athermal biological effects of millimeter waves, culture medium was continuously recirculated over the cells to prevent temperature increases greater than 0.1 °C. Incorporation of 3H-uridine into RNA and of 3H-methionine into protein was quantified by measurement of optical densities of the autoradiographs in contiguous rectangular regions corresponding to portions of the cell monolayer immediately above the wave guide aperture and lying along its longer axis. Since power density was shown to vary with position along this axis according to a cosine2 relationship, it was possible to assess the extent of microwave effects on macromolecular synthesis at power densities ranging from zero at each edge to twice the average power density at the center of the waveguide.Monolayer cultures maintained at 37.2 °C by recirculation of the medium did not show microwave-induced changes in synthesis of RNA and protein (41.8 or 74.0 GHz at average power densities of 320 or 450 mW/cm2, respectively). Since macromolecular synthesis was examined both during and after irradiation, our results exclude both transient and persistent athermal biological effects of acute exposure to millimeter waves. In contrast, irradiation of cultures incubated in a small volume of nonrecirculated medium resulted in 1) marked heating of the monolayer, 2) a graded decline in macromolecular synthesis with increasing incident power, and 3), in some cases, destruction of the cell monolayer in the region immediately above the center of the waveguide aperture.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0197-8462
    Keywords: protein synthesis ; quantitative autoradiography ; BHK-21/C13 cells ; millimeter-wave radiation ; frequency-specific biological effects ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A method recently developed in this laboratory has been used to directly expose BHK-21/C13 cells to high levels of microwave radiation without significant microwave-induced heating (≤ 0.1 °C). Monolayer cultures were grown on microwave-transparent polystyrene coverslips, placed on the open end of a wave guide, and maintained at 37.2 °C during irradiation at frequencies in both the E- and U-bands (average power densities 292 and 177 mW/cm2, respectively). Effects of microwave radiation were assessed at 0.1 GHz increments in the ranges of 38-48 GHz and 65-75 GHz. Protein synthesis was measured in quadruplicate cultures that were allowed to incorporate labeled methionine during the 15-minute period of microwave irradiation. Autoradiographs of each monolayer culture were scanned along the region corresponding to the longer axis of the wave guide aperture using a microdensitometer to quantify incorporation. Since microwave power incident on the cells was previously shown to vary along this axis according to a cosine2 relationship from zero at each edge of the wave guide to twice the average power density at the center of the wave guide, this technique should reveal biological effects that might only be manifested in narrow amplitude domains or “power windows.” Observations of protein synthesis in monolayer cultures irradiated at 202 closely spaced frequencies in the E- and U-bands failed to reveal changes associated with microwave exposure. Thus no evidence was obtained in support of the existence of frequency-specific athermal biological effects of microwaves. In addition, no support was found for the existence of amplitude-specific “power windows”.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 3 (1982), S. 81-90 
    ISSN: 0197-8462
    Keywords: dosimetry ; far-fields/near-fields ; inhomogeneous dielectric properties ; SAR distribution ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The advances made in quantifying electromagnetic absorption and its distribution for various exposure profiles are described. The conditions that have been studied extensively are: free-space irradiation and its variations, such as the presence of ground and reflecting surfaces and other humans in close proximity. Using an inhomogeneous block model of man, work has recently been extended to leakage-type near-fields such as those from RF heat sealers and other electronic equipment. Projections are made for the extension of this work to evaluate coupled near-fields, design of multielement near-field applicators to obtain physician-prescribed uniform or nonuniform rates of regional heating, and for the inverse scattering problem necessary for electromagnetic biomedical imaging. Accurate information about the dielectric properties of various tissues becomes increasingly important for proper inhomogeneous modeling of man.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 285-298 
    ISSN: 0197-8462
    Keywords: absorption ; millimeter wave ; biological media ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A solid-state computer-controlled system has been used to make swept-frequency measurements of absorption of biological specimens from 26.5 to 90.0 GHz. A wide range of samples was used, including solutions of DNA and RNA, and suspensions of BHK-21/C13 cells, Candida albicans, C krusei, and Escherichia coli. Sharp spectra reported by other workers were not observed. The strong absorbance of water (10-30 dB/mm) caused the absorbance of all aqueous preparations that we examined to have a water-like dependence on frequency. Reduction of incident power (to below 1.0 μW), elimination of modulation, and control of temperature to assure cell viability were not found to significantly alter the water-dominated absorbance. Frozen samples of BHK-21/C13 cells tested at dry ice and liquid nitrogen temperatures were found to have average insertion loss reduced to 0.2 dB/cm but still showed no reproducible peaks that could be attributed to absorption spectra. It is concluded that the spectral resonances reported by others are likely to be in error.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 363-377 
    ISSN: 0197-8462
    Keywords: near field ; plane-wave exposure ; electromagnetic energy absorption ; homogeneous tissue slab ; fast Fourier transform ; 2450 MHz ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The exposure of humans to electromagnetic near fields has not been sufficiently emphasized by researchers. We have used the plane-wave-spectrum approach to evaluate the electromagnetic field and determine the energy deposited in a lossy, homogeneous, semi-infinite slab placed in the near field of a source leaking radiation. Values of the fields and absorbed energy in the target are obtained by vector summation of the contributions of all the plane waves into which the prescribed field is decomposed. Use of a fast Fourier transform algorithm contributes to the high efficiency of the computations. The numerical results show that, for field distributions that are nearly constant over a physical extent of at least a free-space wavelength, the energy coupled into the target is approximately equal to that resulting from plane-wave exposure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 379-388 
    ISSN: 0197-8462
    Keywords: near fields ; plane-wave spectrum (PWS) ; energy deposition ; layering resonance ; multilayered slab model ; plane wave ; fast Fourier transform ; 2,450 MHz ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The electromagnetic energy deposited in a semi-infinite slab model consisting of skin, fat, and muscle layers is calculated for both plane-wave and near-field exposures. The plane-wave spectrum (PWS) approach is used to calculate the energy deposited in the model by fields present due to leakage from equipment using electromagnetic energy. This analysis applies to near-field exposures where coupling of the target to the leakage source can be neglected. Calculations were made for 2,450 MHz, at which frequency the layered slab adequately models flat regions of the human body. Resonant absorption due to layering is examined as a function of the skin and fat thicknesses for plane-wave exposure and as a function of the physical extent of the near-field distribution. Calculations show that for fields that are nearly constant over at least a free-space wavelength, the energy deposition (for the skin, fat, and muscle combination that gives resonant absorption) is equal to or less than that resulting from plane-wave exposure, but is appreciably greater than that obtained for a homogeneous muscle slab model.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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