bluuebunny/crossref_metadata_2025_split huggingface dataset:
Operant control of convective cooling and microwave irradiation by the squirrel monkey
Authors: Bruce‐Wolfe Virginia , Adair Eleanor R. 
Published: February 2006

AbstractAdult male squirrel monkeys (Saimiri sciureus) were individually chair‐restrained in an air‐conditioned Styrofoam box in the far field of a horn antenna. Each monkey first received extensive training to regulate the temperature of the air circulating through the box by selecting between 10 and 50°C air source temperatures. Then, to investigate the ability of the animals to utilize microwaves as a source of thermalizing energy, 2450‐MHz continuous wave microwaves accompanied by thermoneutral (30°C) air were substituted for the 50°C air. Irradiation at each of three power densities was made available, ie, at 20, 25, and 30 mW/cm2 [SAR = 0.15 (W/kg)/(mW/cm2)]. The percentage of time that the monkeys selected microwave irradiation paired with thermoneutral air averaged 90% at 20 and at 25 mW/cm2. The mean percentage declined reliably (p < 0.001) to 81% at 30 mW/cm2, confirming the monkey's ability to utilize microwave irradiation as a source of thermal energy during the course of behavioral thermoregulation. All animals readily made the warm‐air to microwave‐field transition, regulating rectal temperature with precision by sequentially selecting 10°C air, then microwave irradiation accompanied by 30°C air. Although the selection of cooler air resulted in a slight reduction of skin temperatures, normal rectal temperature was maintained. The results indicate that the squirrel monkey can utilize a microwave source in conjunction with convective cooling to regulate body temperature behaviorally.
Effect of 9.6‐GHz pulsed microwaves on the orb web spinning ability of the cross spider (Araneus diadematus)
Authors: Liddle C. G. , Putnam J. P. , Lewter O. L. , Lewis J. Y. , Bell B. , West M. W. , Stead A. 
Published: February 2006

AbstractEight cross spiders (Araneus diadematus) were exposed overnight (16 h) during web‐building activity to pulsed 9.6‐GHz microwaves at average power densities of 10, 1, and 0.1 mW/cm2 (estimated SARs 40, 4, and 0.4 mW/g). Under these conditions, 9.6‐GHz pulsed microwaves did not affect the web‐spinning ability of the cross spider.
Specific absorption rate in electrically coupled biological samples between metal plates
Authors: Joines William T. , Blackman Carl F. , Spiegel Ronald J. 
Published: February 2006

AbstractThe specific absorption rate (SAR) in a biological sample irradiated by electromagnetic fields between the metal plates of a transmission line can be altered significantly by the spacing of the metal plates and the distance between neighboring samples. The SAR in spherical biological samples is calculated for a number of neighboring sample arrangements and metal‐plate spacings by using the method of images and induced dipole coupling. For a decrease in metal‐plate spacing, the derived equations predict an increase in SAR within a sample and a decrease in SAR with a decrease in neighboring‐sample spacing. The calculations are compared with measurements made with the aid of an array of 1‐in radius metal hemispheres on the lower plate of two parallel plates (thus forming an image system). The hemisphere on which measurements are taken is insulated from the metal plate and is connected via a coaxial center conductor to an HP 3582A spectrum analyzer that measures the voltage and hence the electric field intensity at the hemisphere. Measurements made at a frequency where wavelength is large compared with sample size (48 Hz) are in good agreement with calculations.
Off‐center spherical model for dosimetry calculations in chick brain tissue
Authors: Gonzalez Guillermo , Nearing James C. , Spiegel Ronald J. , Joines William T. 
Published: February 2006

AbstractThis 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.
Brain temperature measurements in rats: A comparison of microwave and ambient temperature exposures
Authors: Ward Thomas R. , Svensgaard David J. , Spiegel Ronald J. , Puckett Earl T. , Long Merritt D. , Kinn James B. 
Published: February 2006

AbstractIn an effort to understand microwave heating better, regional brain and core temperatures of rats exposed to microwave radiation (2450 MHz) or elevated air temperatures were measured in two studies. In general, we have found no substantial evidence for temperature differentials, or “hot spots,” in the brain of these animals. In the first study, after a 30‐min exposure, no temperature differences between brain regions either after microwave or ambient air exposure were found. However, a highly significant correlation between brain and core temperatures was found and this correlation was the same for both microwave and ambient air heating. In the second study, time‐temperature profiles were measured in rats exposed to either 30 mW/cm2 or 36.2°C. In this study, the 30‐min exposure period was divided into seven intervals and the change in temperature during each period was analyzed. Only the cortex showed significantly different heating rates between the air heating and microwave heating; however, this difference disappeared after the initial 5 min of exposure.
Effects of in vivo ultrasound hyperthermia on natural killer cell cytotoxicity in the hamster
Authors: Johnston R. L. , Rao G. Rama , Tompkins W. A. F. , Cain C. A. 
Published: February 2006

AbstractThe effects of in vivo ultrasound irradiation of the spleen on immunological functions were assessed with an in vitro natural killer (NK) cell cytotoxic assay. Anesthetized hamsters were exposed to 1 MHz ultrasound at intensity levels currently being used clinically for therapeutic diathermy and hyperthermia (1–5 W/cm2, for 500 sec with constant beam scanning). Hyperthermic levels in the spleen ranged from 38–43°C. Significant depression of natural killer (NK) cell activity was seen 4 h after spleen irradiation as compared to sham irradited and normal animals. A return towards normal levels was observed in experimental groups at 24 h after exposure. Sham and normal animals were not significantly different in NK activity, indicating no significant stress‐related immunosuppressive effects due to handling. Differential leukocyte counts taken for each exposure condition showed significant lymphopenia at 4, 8, and 16 h after exposure, near normal levels at 24 h, and complete recovery by 48 h. The number of circulating mononuclear cells at 4 h showed a dose‐related suppression as the exposure intensities were increased.
Metabolic and vasomotor responses of rhesus monkeys exposed to 225‐MHz radiofrequency energy
Authors: Lotz W. Gregory , Saxton Jack L. 
Published: February 2006

AbstractA previous study showed a substantial increase in the colonic temperature of rhesus monkeys (Macaca mulatta) exposed to radiofrequency (RF) fields at a frequency near whole‐body resonance and specific absorption rates (SAR) of 2–3 W/kg. The present experiments were conducted to determine the metabolic anad vasomotor responses during exposures to similar RF fields. We exposed five adult male rhesus monkeys to 225 MHz radiation (E orientation) in an anechoic chamber. Oxygen consumption and carbon dioxide production were measured before, during, and after RF exposure. Colonic, tail and leg skin temperatures were continuously monitored with RF‐nonperturbing probes. The monkeys were irradiated at two carefully‐controlled ambient temperatures, either cool (20 °C) or thermoneutral (26 °C). Power densities ranged from 0 (sham) to 10.0 mW/cm2 with an average whole‐body SAR of 0.285 (W/kg)/(mW/cm2). We used two experimental protocols, each of which began with a 120‐min pre‐exposure equilibration period. One protocol involved repetitive 10‐min RF exposures at successively higher power densities with a recovery period between exposures. In the second protocol, a 120‐min RF exposure permitted the measurement of steady‐state thermoregulatory responses. Metabolic and vasomotor adjustments in the rhesus monkey exposed to 225 MHz occurred during brief or sustained exposures at SARs at or above 1.4 W/kg. The SAR required to produce a given response varied with ambient temperature. Metabolic and vasomotor responses were coordinated effectively to produce a stable deep body temperature. The results show that the thermoregulatory response of the rhesus monkey to an RF exposure at a resonant frequency limits storage of heat in the body. However, substantial increases in colonic temperature were not prevented by such responses, even in a cool environment.
Behavioral effects of chronic exposure to 0.5 mW/cm2 of 2,450‐MHz microwaves
Authors: Dewitt John R. , D'Andrea John A. , Emmerson Rita Y. , Gandhi Om P. 
Published: February 2006

AbstractAdult male, Long‐Evans rats were exposed 7 h a day for 90 days to continuous wave (CW) 2,450‐MHz microwaves at an average power density of 0.5 mW/cm2. Exposures were in a monopole‐above‐ground radiation chamber with rats in Plexiglas cages. The resulting specific absorption rate (SAR) was 0.14 W/kg (±0.01 SEM). Additional rats served as sham‐exposed and home‐caged controls. All were evaluated daily for body mass and food and water intakes. Once each 30 days, throughout baseline and exposure phases of the experiment, rats in the sham‐ and microwave‐exposed groups were tested for their sensitivity to footshock. After 90‐days of exposure, the rats were evaluated an open field, an active avoidance task and an operant task for food reinforcement. Performance of sham‐and microwave‐irradiated rats was reliably different on only one measure, the lever‐pressing task. The general conclusion reached was that exposure to CW 2,450‐MHz microwave radiation at 0.5 mW/cm2 was below the threshold for behavioral effects over a wide range of variables, but did have an effect on a time‐related operant task, although the direction of the effect was unpredictable.
Some behavioral effects of short‐term exposure of rats to 2.45 GHz microwave radiation
Authors: Mitchell Clifford L. , McRee Donald I. , Peterson N. John , Tilson Hugh A. 
Published: February 2006

AbstractRats were tested for neurobehavioral alterations immediately after exposure to 2.45‐GHz (CW) microwave radiation at 10 mW/cm2 for 7 h. Behavioral tests used were locomotor activity, startle to an acoustic stimulus and acquisition and retention of a shock‐motivated passive avoidance task. Both horizontal and vertical components of locomotor activity were assessed in 5‐min epochs for a period of 30 min using photoelectric detectors. Microwave‐exposed animals exhibited less activity than sham‐exposed animals. This was most evident during the last 10–15 min of the 30‐min test session. Twenty identical acoustical stimuli (8 KHz, 110 dB) were delivered to each rat at 40‐s intervals. The microwave‐exposed animals were less responsive to the stimuli than sham‐exposed animals. Microwave exposure had no effect on the retention of a passive avoidance procedure when tested at 1 week after training. Both the locomotor activity and acoustic startle data demonstrate that, under the conditions of this experiment, microwave exposure may alter responsiveness of rats to novel environmental conditions or stimuli.
Electromagnetic pulse propagation in dispersive planar dielectrics
Authors: Moten Krishnan , Durney Carl H. , Stockham Thomas G. 
Published: February 2006

AbstractThe responses of a plane‐wave pulse train irradiating a lossy dispersive dielectric half‐space are investigated. The incident pulse train is expressed as a Fourier series with summing done by the inverse fast Fourier transform. The Fourier series technique is adopted to avoid the many difficulties often encountered in finding the inverse Fourier transform when transform analyses are used. Calculations are made for propagation in pure water, and typical waveforms inside the dielectric half‐space are presented. Higher harmonics are strongly attenuated, resulting in a single continuous sinusoidal waveform at the frequency of the fundamental depth in the material. The time‐averaged specific absorption rate (SAR) for pulse‐train propagation is shown to be the sum of the time‐averaged SARs of the individual harmonic components of the pulse train. For the same average power, calculated SARs reveal that pulse trains generally penetrate deeper than carrier‐frequency continuous waves but not deeper than continuous waves at frequencies approaching the fundamental of the pulse train. The effects of rise time on the propagating pulse train in the dielectrics are shown and explained. Since most practical pulsed systems are very limited in bandwidth, no pronounced differences between their response and continuous wave (CW) response would be expected. Typical results for pulse‐train propagation in arrays of dispersive planar dielectric slabs are presented. Expressing the pulse train as a Fourier series provides a practical way of interpreting the dispersion characteristics from the spectral point of view.
Specific absorption rate (SAR) in models of the human head exposed to hand‐held UHF portable radios
Authors: Cleveland Robert F. , Athey T. Whit 
Published: February 2006

AbstractSpecific absorption rate (SAR) was measured in models of the human head exposed to hand‐held portable radios (“transceivers”) transmitting at frequencies in the 800‐MHz band. An isotropic implantable electric‐field probe was used to measure internal fields induced in the head models, and SARs were determined by calculation. As well as determining representative values and distributions for SARs under various conditions, it was shown that antenna type and orientation with respect to the head are important factors affecting energy absorption.
Chronic exposure of primates to 60‐Hz electric and magnetic fields: II. Neurochemical effects
Authors: Seegal Richard F. , Wolpaw Jonathan R. , Dowman Robert 
Published: February 2006

AbstractWe exposed Macaca nemestrina (pig‐tailed macaques) to electric (E) and magnetic (B) fields ranging in intensity from 3 kV/m and 0.1 G to 30 kV/m and 0.9 G for three 21‐day (d) periods. Experimental animals were exposed to sham E and B fields for two 21‐d periods, one prior to and one following actual exposure to E and B fields, resulting in a total of five 21‐d periods. Control animals were exposed to sham E and B fields for the entire 105‐d interval. At the end of each 21‐d period cerebrospinal fluid (CSF) was obtained by lumbar puncture and analyzed for concentrations of homovanillic acid (HVA) and 5‐hydroxyindoleacetic acid (5‐HIAA), metabolites of dopamine and serotonin neurotransmitters, respectively, by high‐performance liquid chromatography with electrochemical detection (HPLC‐ECD). Results are based on an examination of six experimental and four control animals.Exposure to E and B fields at all strengths was associated with a significant decline in CSF concentrations of both HVA and 5‐HIAA when statistical comparisons were made against values obtained at the end of the preexposure interval. However, HVA returned to preexposure levels during the postexposure period, while 5‐HIAA did not. No significant change in the concentrations of HVA or 5‐HIAA was noted in the control animals.These results strongly suggest that exposure of the nonhuman primate to E and B fields can significantly affect specific biochemical estimates of nervous system function. These effects may involve alterations either in neuronal activity or in the activity of enzymes that catabolize the neurotransmitters.
Sensitive model with which to detect athermal effects of non‐ionizing electromagnetic radiation
Authors: Saffer Jeffrey D. , Profenno Louis A. 
Published: February 2006

AbstractTo clarify the potential of non‐ionizing electromagnetic radiation to cause biological effects by athermal mechanisms, and to initiate elucidation of those mechanisms, a model system amenable to scrutiny at the molecular level has been designed and characterized. Assessment of β‐galactosidase activity in E. coli JM101 containing the plasmid pUC8 provides a sensitive assay with many important advantages. The ability to examine at the molecular level each of the processes involved in producing β‐galactosidase should permit elucidation of the molecular mechanism(s) that give rises to an observed effect.
Studies on the alignment of fibroblasts in uniform applied electrical fields
Authors: Ross Stephen M. , Ferrier Jack M. , Aubin Jane E. 
Published: February 2006

AbstractUniform electrical fields have been applied to human gingival fibroblasts by means of uniform ionic currents passed through a thin chamber. Cells were observed to align in fields between 0.1 and 1.5 V/mm but did not display directed motion toward the anode or the cathode of the chamber. Statistical analysis of directional data was used to distinguish threshold levels of orientation at low field intensities, to quantify the dependence of alignment on time and field intensity, and to analyze differences between alignment of cells treated with the Ca2+ transport modifiers A23187, verapamil, and lanthanum. Alignment occurred at a steady rate and was dependent in a saturating fashion on field strength. The Ca2+ ionophore A23187 had a significant inhibitory effect on cell alignment in applied electrical fields; however, the Ca2+ channel blockers lanthanum and verapamil did not have a significant effect on alignment.
Effect of negative air ions on morphine‐induced changes in the latency of the tail‐flick reflex
Authors: Beardwood C. J. , Jordi P. M. 
Published: February 2006

AbstractAdult male Long‐Evans rats were exposed to negatively charged air ions at high concentrations (7 × 105/cm3) for six days. Sham‐exposed rats were treated identically except that the source of ions was not activated. At the end of the exposure, the latency of the tail‐flick reflex was measured in each rat before and 30 and 60 min after an injection of morphine sulphate. The tail‐flick reflex was initiated by thermal stimulation. Two heat settings were employed, the lower considered to impart a submaximal and the higher a maximal thermal stimulus. Three morphine doses were tested: 0.5, 1.0, and 1.5 mg/kg. Statistically significant differences between ion‐exposed and sham‐exposed rats were observed in tail‐flick latencies 30 min after the administration of the two lower doses, but not after the highest dose of morphine sulphate. These differences were found at both intensities of thermal stimulation. Tail‐flick latencies measured in each group prior to morphine injection were not affected by negative‐ion exposure. The data indicate that exposure of rats to negative air ions tends to inhibit the action of morphine on the latency of the tail‐flick reflex at morphine doses below 1.0 mg/kg.
Brown‐colored deposits on hair of female rats chronically exposed to 60‐Hz electric fields
Authors: Leung F. C. , Rommereim D. N. , Miller R. A. , Anderson L. E. 
Published: February 2006

AbstractAn increased incidence and severity of a brownish coloration of hair has been observed around the nose and on the ears of female rats that were chronically exposed to 60‐Hz electric fields. Microscopic examination of the colored areas revealed a red‐brown globular deposit on hair shafts in affected areas without signs of physical injury.
Comparison of indices of ambient exposure to 60‐hertz electric and magnetic fields
Authors: Armstrong Ben G. , Deadman Jan Erik , Thériault Gilles 
Published: February 2006

AbstractOccupational, environmental, or domestic exposure of human beings to extremely low‐frequency (50‐ or 60‐Hz) electric and magnetic fields varies continuously over time. In epidemiological studies of possible health effects, exposures over long durations must be aggregated in terms of simple summary indices. However, there are many different, biologically plausible, ways of aggregating the data. While awake, each of 20 electric utility personnel and 16 office workers had provided minute‐by‐minute measures of incident electric (V/m) and magnetic (μ T) fields over a 7‐day period via personal dosimeters. Once the measures were aggregated as means, medians, peaks, and other indices, intercorrelations between all index pairs were calculated; correlation matrices are presented for the utility and office workers both by group and when pooled. Product‐moment coefficients (r) greater that .80 were found between the time‐weighted arithmetic mean (TWA) and indices that explicitly emphasize short but highly intense exposures, such as peak values and time above thresholds. Medians and geometric means were less highly correlated with the TWA. Use of only a few indices, perhaps the TWA alone, may sacrifice but little statistical power in most epidemiological studies of utility workers exposed to ELF fields. However, correlations between electric‐field strength and magnetic‐field density were generally quite weak, as were correlations of either with high‐frequency transients; these findings underscore the need to measure each of these variables in epidemiological studies. Indices of exposure incurred outside the workplace were less strongly correlated, which may indicate the need to use several indices in general‐population studies.
Search for ion‐cyclotron resonance in an Na+‐transport system
Authors: Liboff Abraham R. , Parkinson W. C. 
Published: February 2006

AbstractColonic tissue from the turtle (Pseudemys scripta) was exposed in a Ussing chamber to simultaneously applied static and time‐varying magnetic fields. Transepithelial differences of potential were monitored as frequency of the AC field was varied continuously or in discrete steps from 3 to 770 Hz. Density of the DC field was varied from 10 to 220 μT and that of the AC field from 1 to 20 μT. Short‐circuit currents through tissue were monitored for changes that might have been observed under ion‐cyclotron resonance (ICR) conditions for each of several ions: H+, Li+, Na+, K+, Ca2+, and Cl−. No discernible changes of transepithelial current were observed. The negative findings are discussed in relation to positive and negative findings that have appeared in the literature.