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Sample records for low-frequency electromagnetic field

  1. Low-frequency electromagnetic field in a Wigner crystal

    SciTech Connect

    Stupka, Anton

    2013-03-15

    Long-wave low-frequency oscillations are described in a Wigner crystal by generalization of the reverse continuum model for the case of electronic lattice. The internal self-consistent long-wave electromagnetic field is used to describe the collective motions in the system. The eigenvectors and eigenvalues of the obtained system of equations are derived. The velocities of longitudinal and transversal sound waves are found.

  2. Interaction of extremely low-frequency electromagnetic fields with humans

    SciTech Connect

    Tenforde, T.S.

    1990-04-01

    Public concern has grown in recent years concerning the possible health effects of extremely low-frequency (ELF) electromagnetic fields to which we are exposed in all aspects of everyday life. By definition ELF refers to the range of electromagnetic field frequencies below 300 Hz, which includes the power transmission and distribution frequencies used throughout the world. In materials with the electrical and magnetic properties of living tissues, these fields have a long wavelength (5000 m) and skin depth (150 m). As a consequence, in their interactions with humans and other living organisms ELF fields behave as though they are composed of independent electric and magnetic fields components. This paper discusses ELF fields and their interactions with humans and other living organisms as well as their biological effects.

  3. Method for imaging with low frequency electromagnetic fields

    DOEpatents

    Lee, Ki H.; Xie, Gan Q.

    1994-01-01

    A method for imaging with low frequency electromagnetic fields, and for interpreting the electromagnetic data using ray tomography, in order to determine the earth conductivity with high accuracy and resolution. The imaging method includes the steps of placing one or more transmitters, at various positions in a plurality of transmitter holes, and placing a plurality of receivers in a plurality of receiver holes. The transmitters generate electromagnetic signals which diffuse through a medium, such as earth, toward the receivers. The measured diffusion field data H is then transformed into wavefield data U. The traveltimes corresponding to the wavefield data U, are then obtained, by charting the wavefield data U, using a different regularization parameter .alpha. for each transform. The desired property of the medium, such as conductivity, is then derived from the velocity, which in turn is constructed from the wavefield data U using ray tomography.

  4. Method for imaging with low frequency electromagnetic fields

    DOEpatents

    Lee, K.H.; Xie, G.Q.

    1994-12-13

    A method is described for imaging with low frequency electromagnetic fields, and for interpreting the electromagnetic data using ray tomography, in order to determine the earth conductivity with high accuracy and resolution. The imaging method includes the steps of placing one or more transmitters, at various positions in a plurality of transmitter holes, and placing a plurality of receivers in a plurality of receiver holes. The transmitters generate electromagnetic signals which diffuse through a medium, such as earth, toward the receivers. The measured diffusion field data H is then transformed into wavefield data U. The travel times corresponding to the wavefield data U, are then obtained, by charting the wavefield data U, using a different regularization parameter [alpha] for each transform. The desired property of the medium, such as conductivity, is then derived from the velocity, which in turn is constructed from the wavefield data U using ray tomography. 13 figures.

  5. The interference of electronic implants in low frequency electromagnetic fields.

    PubMed

    Silny, J

    2003-04-01

    Electronic implants such as cardiac pacemakers or nerve stimulators can be impaired in different ways by amplitude-modulated and even continuous electric or magnetic fields of strong field intensities. For the implant bearer, possible consequences of a temporary electromagnetic interference may range from a harmless impairment of his well-being to a perilous predicament. Electromagnetic interferences in all types of implants cannot be covered here due to their various locations in the body and their different sensing systems. Therefore, this presentation focuses exemplarily on the most frequently used implant, the cardiac pacemaker. In case of an electromagnetic interference the cardiac pacemaker reacts by switching to inhibition mode or to fast asynchronous pacing. At a higher disturbance voltage on the input of the pacemaker, a regular asynchronous pacing is likely to arise. In particular, the first-named interference could be highly dangerous for the pacemaker patient. The interference threshold of cardiac pacemakers depends in a complex way on a number of different factors such as: electromagnetic immunity and adjustment of the pacemaker, the composition of the applied low-frequency fields (only electric or magnetic fields or combinations of both), their frequencies and modulations, the type of pacemaker system (bipolar, unipolar) and its location in the body, as well as the body size and orientation in the field, and last but not least, certain physiological conditions of the patient (e.g. inhalation, exhalation). In extensive laboratory studies we have investigated the interference mechanisms in more than 100 cardiac pacemakers (older types as well as current models) and the resulting worst-case conditions for pacemaker patients in low-frequency electric and magnetic fields. The verification of these results in different practical everyday-life situations, e.g. in the fields of high-voltage overhead lines or those of electronic article surveillance systems is

  6. Extremely low frequency electromagnetic fields and cancer: the epidemiologic evidence.

    PubMed Central

    Bates, M N

    1991-01-01

    This paper reviews the epidemiologic evidence that low frequency electromagnetic fields generated by alternating current may be a cause of cancer. Studies examining residential exposures of children and adults and studies of electrical and electronics workers are reviewed. Using conventional epidemiologic criteria for inferring causal associations, including strength and consistency of the relationship, biological plausibility, and the possibility of bias as an explanation, it is concluded that the evidence is strongly suggestive that such radiation is carcinogenic. The evidence is strongest for brain and central nervous system cancers in electrical workers and children. Weaker evidence supports an association with leukemia in electrical workers. Some evidence also exists for an association with melanoma in electrical workers. Failure to find consistent evidence of a link between residential exposures and adult cancers may be attributable to exposure misclassification. Studies so far have used imperfect surrogates for any true biologically effective magnetic field exposure. The resulting exposure misclassification has produced relative risk estimates that understate any true risk. PMID:1821368

  7. Enhancement of nitric oxide generation by low frequency electromagnetic field.

    PubMed

    Yoshikawa; Tanigawa; Tanigawa; Imai; Hongo; Kondo

    2000-07-01

    Oxidative stress is implicated in the intracellular signal transduction pathways for nitric oxide synthase (NOS) induction. The electromagnetic field (EMF) is believed to increase the free radical lifespan [S. Roy, Y. Noda, V. Eckert, M.G. Traber, A. Mori, R. Liburdy, L. Packer, The phorbol 12-myristate 13-acetate (PMA)-induced oxidative burst in rat peritoneal neutrophils is increased by a 0.1 mT (60 Hz) magnetic field, FEBS Lett. 376 (1995) 164-6; F.S. Prato, M. Kavaliers, J.J. Carson, Behavioural evidence that magnetic field effects in the land snail, Cepaea nemoralis, might not depend on magnetite or induced electric currents, Bioelectromagnetics 17 (1996) 123-30; A.L. Hulbert, J. Metcalfe, R. Hesketh, Biological response to electromagnetic fields, FASEB 12 (1998) 395-420]. We tested the effects of EMF on endotoxin induced nitric oxide (NO) generation in vivo. Male BALB/C mice were injected with lipopolysaccharide (LPS) intraperitoneously (i.p.), followed by the exposure to EMF (0.1 mT, 60 Hz). Five hours and 30 min after the LPS administration, mice were administered with a NO spin trap, ferrous N-methyl-D-glucaminedithiocarbamate (MGD-Fe). Thirty minutes later, mice were sacrificed, and their livers were removed. The results were compared to three control groups: group A (LPS (-) EMF(-)); group B (LPS(-) EMF(+)); group C (LPS(+) EMF(-)). The ESR spectra of obtained livers were examined at room temperature. Three-line spectra of NO adducts were observed in the livers of all groups. In groups A and B very weak signals were observed, but in groups C and D strong spectra were observed. The signal intensity of the NO adducts in Group D was also significantly stronger than that in Group C. EMF itself did not induce NO generation, however, it enhanced LPS induced NO generation in vivo. PMID:10927193

  8. Static electric and electromagnetic low-frequency fields (biological effects and hygienic assessment)

    SciTech Connect

    Davydov, B.I.; Karpov, V.N.

    1982-11-01

    The literature data are used to analyze the hygienic situation when man is exposed to constant electrical and low frequency electromagnetic radiations. The spectral characteristics and intensities of electrical fields near and on the surface of the earth generated by natural sources of electromagnetic radiations (electrical quasi-static fields, atmospheric electricity, thunderstorm charges, electromagnetic radiation emitted by the Sun and galaxies) are given. They can be employed to determine man's adaptive capabilities to the frequencies described during acute and chronic irradiation. The mechanisms of biological effects of the exposures are discussed. The methods for calculating the safety levels based on the USSR radiation safety standards and the competing frequencies procedure proposed can be applied to the design of electrotechnical devices and evaluation of integral hazard of constant electrical and electromagnetic fields of low frequencies.

  9. Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

    SciTech Connect

    Cadena, M. S. Reyes; Chapul, L. Sanchez; Perez, Javier; Garcia, M. N. Jimenez; Lopez, M. A. Jimenez; Espindola, M. E. Sanchez; Perez, R. Paniagua; Hernandez, N. A.; Paniagua, G.; Uribe, F.; Nava, J. J. Godina; Segura, M. A. Rodriguez

    2008-08-11

    We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-{beta}) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animals subjected to ELF together with the transfer factor.

  10. Impact of Low Frequency Electromagnetic Field Exposure on the Candida Albicans

    NASA Astrophysics Data System (ADS)

    Malíková, Ivona; Janoušek, Ladislav; Fantova, Vladyslava; Jíra, Jaroslav; Kříha, Vítĕzslav

    2015-03-01

    Effect of low frequency electromagnetic field on growth of selected microorganism is studied in the article. The diploid fungus that grows both as yeast and filamentous cell was chosen for this research. The theory of ion parametric resonance was taken as the base for studying the influence of electromagnetic field on biological structures. We tested the hypothesis, whether it is possible to observe the change in growth properties of Candida albicans with an AC electromagnetic field tuned to resonance with calcium ions cyclotron frequency.

  11. Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

    NASA Astrophysics Data System (ADS)

    Cadena, M. S. Reyes; Chapul, L. Sánchez; Pérez, Javiér; García, M. N. Jiménez; López, M. A. Jiménez; Espíndola, M. E. Sánchez; Perez, R. Paniagua; Hernández, N. A.; Paniagua, G.; Uribe, F.; Nava, J. J. Godina; Segura, M. A. Rodríguez

    2008-08-01

    We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-β) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animals subjected to ELF together with the transfer factor.

  12. Characterization of Indoor Extremely Low Frequency and Low Frequency Electromagnetic Fields in the INMA-Granada Cohort

    PubMed Central

    Calvente, Irene; Dávila-Arias, Cristina; Ocón-Hernández, Olga; Pérez-Lobato, Rocío; Ramos, Rosa; Artacho-Cordón, Francisco; Olea, Nicolás; Núñez, María Isabel; Fernández, Mariana F.

    2014-01-01

    Objective To characterize the exposure to electric fields and magnetic fields of non-ionizing radiation in the electromagnetic spectrum (15 Hz to 100 kHz) in the dwellings of children from the Spanish Environment and Childhood-“INMA” population-based birth cohort. Methodology The study sample was drawn from the INMA-Granada cohort. Out of 300 boys participating in the 9–10 year follow-up, 123 families agreed to the exposure assessment at home and completed a specific ad hoc questionnaire gathering information on sources of non-ionizing radiation electric and magnetic fields inside the homes and on patterns of use. Long-term indoor measurements were carried out in the living room and bedroom. Results Survey data showed a low exposure in the children's homes according to reference levels of the International Commission on Non-Ionizing Radiation Protection but with large differences among homes in mean and maximum values. Daytime electrostatic and magnetic fields were below the quantification limit in 78.6% (92 dwellings) and 92.3% (108 dwellings) of houses, with an arithmetic mean value (± standard deviation) of 7.31±9.32 V/m and 162.30±91.16 nT, respectively. Mean magnetic field values were 1.6 lower during the night than the day. Nocturnal electrostatic values were not measured. Exposure levels were influenced by the area of residence (higher values in urban/semi-urban versus rural areas), type of dwelling, age of dwelling, floor of the dwelling, and season. Conclusion Given the greater sensitivity to extremely low-frequency electromagnetic fields of children and following the precautionary principle, preventive measures are warranted to reduce their exposure. PMID:25192253

  13. Extremely low-frequency electromagnetic fields cause DNA strand breaks in normal cells

    PubMed Central

    2014-01-01

    Background Extremely low frequency electromagnetic fields aren’t considered as a real carcinogenic agent despite the fact that some studies have showed impairment of the DNA integrity in different cells lines. The aim of this study was evaluation of the late effects of a 100 Hz and 5.6 mT electromagnetic field, applied continuously or discontinuously, on the DNA integrity of Vero cells assessed by alkaline Comet assay and by cell cycle analysis. Normal Vero cells were exposed to extremely low frequency electromagnetic fields (100 Hz, 5.6 mT) for 45 minutes. The Comet assay and cell cycle analysis were performed 48 hours after the treatment. Results Exposed samples presented an increase of the number of cells with high damaged DNA as compared with non-exposed cells. Quantitative evaluation of the comet assay showed a significantly (<0.001) increase of the tail lengths, of the quantity of DNA in tail and of Olive tail moments, respectively. Cell cycle analysis showed an increase of the frequency of the cells in S phase, proving the occurrence of single strand breaks. The most probable mechanism of induction of the registered effects is the production of different types of reactive oxygen species. Conclusions The analysis of the registered comet indices and of cell cycle showed that extremely low frequency electromagnetic field of 100 Hz and 5.6 mT had a genotoxic impact on Vero cells. PMID:24401758

  14. Resource Letter BELFEF-1: Biological effects of low-frequency electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Hafemeister, David

    1996-08-01

    This Resource Letter provides a guide to the literature on the interaction of extremely low-frequency electromagnetic field (ELF/EMF) interactions with biological matter, and on the possibility that such interactions could have a harmful effect on human health. Journal articles and books are cited for the following topics: ELF/EMF theoretical interactions with biological cells, organs and organisms, magnetic dipole interactions, sensing by animals, biomedical-biophysical experiments, epidemiology, and litigation-mitigation risk issues.

  15. Interaction of extremely-low-frequency electromagnetic fields with living systems

    SciTech Connect

    Tenforde, T.S.

    1991-11-01

    The sources and physical properties of extremely-low-frequency (ELF) electromagnetic fields are described in this paper. Biological effects and mechanisms through which ELF fields interact with humans and other organisms are discussed, including several aspects of this subject that are presently under active laboratory investigation. Studies on the potential health effects of ELF fields present in the home and workplace are also summarized, including a critical evaluation of evidence for a possible linkage between exposure to ELF fields and cancer risk. 53 refs.

  16. Extremely low frequency electromagnetic field measurements at the Hylaty station and methodology of signal analysis

    NASA Astrophysics Data System (ADS)

    Kulak, Andrzej; Kubisz, Jerzy; Klucjasz, Slawomir; Michalec, Adam; Mlynarczyk, Janusz; Nieckarz, Zenon; Ostrowski, Michal; Zieba, Stanislaw

    2014-06-01

    We present the Hylaty geophysical station, a high-sensitivity and low-noise facility for extremely low frequency (ELF, 0.03-300 Hz) electromagnetic field measurements, which enables a variety of geophysical and climatological research related to atmospheric, ionospheric, magnetospheric, and space weather physics. The first systematic observations of ELF electromagnetic fields at the Jagiellonian University were undertaken in 1994. At the beginning the measurements were carried out sporadically, during expeditions to sparsely populated areas of the Bieszczady Mountains in the southeast of Poland. In 2004, an automatic Hylaty ELF station was built there, in a very low electromagnetic noise environment, which enabled continuous recording of the magnetic field components of the ELF electromagnetic field in the frequency range below 60 Hz. In 2013, after 8 years of successful operation, the station was upgraded by extending its frequency range up to 300 Hz. In this paper we show the station's technical setup, and how it has changed over the years. We discuss the design of ELF equipment, including antennas, receivers, the time control circuit, and power supply, as well as antenna and receiver calibration. We also discuss the methodology we developed for observations of the Schumann resonance and wideband observations of ELF field pulses. We provide examples of various kinds of signals recorded at the station.

  17. Treatment of Diabetic Foot Ulcers through Systemic Effects of Extremely Low Frequency Electromagnetic Fields

    NASA Astrophysics Data System (ADS)

    Trejo-Núñez, A. D.; Pérez-Chávez, F.; García-Sánchez, C.; Serrano-Luna, G.; Cañendo-Dorantes, L.

    2008-08-01

    This study was designed to, investigate the healing effects of extremely low frequency electromagnetic fields (ELF-EMF) on diabetic foot ulcers and test two different exposure systems aimed at reducing the ELF-EMF exposure time of patients. In the first system the ELF-EMF were applied to the arm where only 3% of the total blood volume/min circulates at any given time. In the second system the ELF-EMF were applied to the thorax where more than 100% of the total blood volume/minute circulates at any given time. Twenty-six diabetic patients, with superficial neuropathic ulcers unresponsive to medical treatment were included in this preliminary report. In the first group (17 patients), the arm was exposed two hours twice a week to a extremely low frequency electromagnetic field of 0.45-0.9 mTrms, 120 Hz generated inside a solenoid coil of 10.1 cm by 20.5 cm long. In the second group the thorax of 7 patients was exposed 25 minutes twice a week to an electromagnetic field of 0.4-0.85 mTrms, 120 Hz generated in the center of a squared quasi-Helmholtz coil 52 cm by side. One patient was assigned to a placebo configuration of each exposure system with identical appearance as the active equipment but without magnetic field. Patients with deep ulcers, infected ulcers, cancer, or auto-immune disease were excluded. These preliminary results showed that the two exposure systems accelerate the healing process of neuropathic ulcers. Complete healing of the ulcer had a median duration of 90 days in both exposure systems. Therefore thorax exposure where more blood is exposed to ELF-EMF per unit of time was able to reduce 4.8 times the patient treatment time. In those patients assigned to the placebo equipment no healing effects were observed. This study will continue with a parallel, double blind placebo controlled protocol.

  18. Low frequency pulsed electromagnetic field--a viable alternative therapy for arthritis.

    PubMed

    Ganesan, Kalaivani; Gengadharan, Akelayil Chandrapuram; Balachandran, Chidambaram; Manohar, Bhakthavatsalam Murali; Puvanakrishnan, Rengarajulu

    2009-12-01

    Arthritis refers to more than 100 disorders of the musculoskeletal system. The existing pharmacological interventions for arthritis offer only symptomatic relief and they are not definitive and curative. Magnetic healing has been known from antiquity and it is evolved to the present times with the advent of electromagnetism. The original basis for the trial of this form of therapy is the interaction between the biological systems with the natural magnetic fields. Optimization of the physical window comprising the electromagnetic field generator and signal properties (frequency, intensity, duration, waveform) with the biological window, inclusive of the experimental model, age and stimulus has helped in achieving consistent beneficial results. Low frequency pulsed electromagnetic field (PEMF) can provide noninvasive, safe and easy to apply method to treat pain, inflammation and dysfunctions associated with rheumatoid arthritis (RA) and osteoarthritis (OA) and PEMF has a long term record of safety. This review focusses on the therapeutic application of PEMF in the treatment of these forms of arthritis. The analysis of various studies (animal models of arthritis, cell culture systems and clinical trials) reporting the use of PEMF for arthritis cure has conclusively shown that PEMF not only alleviates the pain in the arthritis condition but it also affords chondroprotection, exerts antiinflammatory action and helps in bone remodeling and this could be developed as a viable alternative for arthritis therapy. PMID:20329696

  19. Nanoparticle Interactions with Low-Frequency Electromagnetic Fields for Ablation Therapy

    NASA Astrophysics Data System (ADS)

    Jensen, Scott; Doyle, Timothy

    2009-10-01

    The in vivo ablation of malignant tumors can be significantly enhanced with nanoparticles (NPs) that absorb energy from electromagnetic (EM) waves and subsequently heat targeted regions in the body. Low-frequency EM fields can penetrate much deeper than near-infrared and visible light. Ohmic heating has primarily been the sole mechanism considered for the coupling of the EM fields to the NPs, but few quantitative analyses have been published to predict NP heating rates. To address this issue, this study identified and modeled four excitation mechanisms for the remote heating of NPs by low-frequency EM waves. These mechanisms included (1) ohmic heating of conductive NPs, (2) translational vibrations of charged NPs, (3) rotational vibrations of piezoelectric NPs, and (4) acoustic wave generation by piezoelectric NPs. Preliminary results showed that for a constant NP volume, the heating rate is independent of NP size for ohmic heating. Additionally, ohmic heating produced the lowest heating rates of the four mechanisms. These results point to possible new NP technologies to optimize heating rates and tumor ablation in patients.

  20. Extremely low frequency pulsed electromagnetic fields increase cell proliferation in lymphocytes from young and aged subjects

    SciTech Connect

    Cossarizza, A.; Monti, D.; Bersani, F.; Cantini, M.; Cadossi, R.; Sacchi, A.; Franceschi, C.

    1989-04-28

    The effect of the in vitro exposure to extremely low frequency pulsed electromagnetic fields (PEMFs) on the proliferation of human lymphocytes from 24 young and 24 old subjects was studied. The exposure to PEMFs during a 3-days culture period or during the first 24 hours was able to increase phytohaemagglutinin-induced lymphocyte proliferation in both groups. Such effect was greater in lymphocytes from old people which showed a markedly reduced proliferative capability and, after PEMF exposure, reached values of /sup 3/H-TdR incorporation similar to those of young subjects. The relevance of these data for the understanding and the reversibility of the proliferative defects in cells from aged subjects and for the assessment of risk related to the environmental exposure to PEMFs has to be considered.

  1. The Study of Electromagnetic Field Response Using Very Low Frequency Methods in Geothermal Area, Sabang

    SciTech Connect

    Isa, M.; Lim, H. S.; Jafri, M. Z. Mat

    2011-03-30

    Electromagnetic field measurements have been performed using the method of Very Low Frequency tilt angle pattern in Jaboi, Sabang. A site survey was conducted and carried out to identify the anomalies of location, depth and geometry of hydrothermal based on tilt angle measurement and ellipse. Objective of this study is to see the response of the magnetic and electric field in relation to location, depth and hydrothermal geometry. The devices of T-VLF-R IRIS was used in this study, while the (NWC) station was selected as main station and (JJF4) station was selected as comparison station. The electromagnetic field survey was recorded for a line spanned as long as 900 meters at the interval of 10 meter depth. The results of this study show the greatest anomaly occurred at line interval between 400-600 meters with a depth of 10-140 meters. Anomaly pattern of each depth shows that the propagation pattern of hydrothermal is in the form of vertical pipe flow.

  2. Effects of extremely low frequency electromagnetic fields on intracellular calcium transients in cardiomyocytes.

    PubMed

    Wei, Jinhong; Sun, Junqing; Xu, Hao; Shi, Liang; Sun, Lijun; Zhang, Jianbao

    2015-03-01

    Calcium transients play an essential role in cardiomyocytes and electromagnetic fields (EMF) and affect intracellular calcium levels in many types of cells. Effects of EMF on intracellular calcium transients in cardiomyocytes are not well studied. The aim of this study was to assess whether extremely low frequency electromagnetic fields (ELF-EMF) could affect intracellular calcium transients in cardiomyocytes. Cardiomyocytes isolated from neonatal Sprague-Dawley rats were exposed to rectangular-wave pulsed ELF-EMF at four different frequencies (15 Hz, 50 Hz, 75 Hz and 100 Hz) and at a flux density of 2 mT. Intracellular calcium concentration ([Ca(2+)]i) was measured using Fura-2/AM and spectrofluorometry. Perfusion of cardiomyocytes with a high concentration of caffeine (10 mM) was carried out to verify the function of the cardiac Na(+)/Ca(2+) exchanger (NCX) and the activity of sarco(endo)-plasmic reticulum Ca(2+)-ATPase (SERCA2a). The results showed that ELF-EMF enhanced the activities of NCX and SERCA2a, increased [Ca(2+)]i baseline level and frequency of calcium transients in cardiomyocytes and decreased the amplitude of calcium transients and calcium level in sarcoplasmic reticulum. These results indicated that ELF-EMF can regulate calcium-associated activities in cardiomyocytes. PMID:24499289

  3. A new approach to imaging with low-frequency electromagnetic fields

    SciTech Connect

    Ki Ha Lee; Ganquan Xie )

    1993-06-01

    The authors present a new method for interpreting electromagnetic (EM) data using ray tomography. Direct application of ray tomography to low-frequency EM data is difficult because of the diffusive nature of the field. Diffusive EM fields can, however, be mathematically transformed to wavefields defined in a time-like variable. The transform uniquely relates a field satisfying a diffusion equation in time, or in frequency, to an integral of the corresponding wavefield. If the corresponding wavefields can be computed from low-frequency EM data, one should be able to interpret these data using techniques developed for the wavefields. To test the idea, numerically calculated transient magnetic fields were first transformed to wavefields. The typical window of the time-domain data required for the transform is 1.5 decades. Traveltimes from a source to the receivers were estimated from the reconstructed wavefields. Time-domain data with a Gaussian noise of 3 percent gave a traveltime resolution of better than one percent. For the tomographic inversion, the cross-section between the transmitter and receiver boreholes is divided into a number of rectangular elements, and a continuous slowness is assigned to each of these elements. A functional is formulated by invoking Fermat's principle for the traveltime data. Imposing a stationary condition on the functional gives an iterative procedure for the slowness model. Rays are allowed to bend smoothly within each cell. Incorporating smoothly bending rays is extremely important when the velocity contrast is large. A model with a conductivity contrast of ten (10) has been successfully imaged in 120 iterations with 5 CPU hours on a SUN SPARCstation 2.

  4. Examination of extremely low frequency electromagnetic fields on orthodontic tooth movement in rats

    PubMed Central

    Dogru, Mehmet; Akpolat, Veysi; Dogru, Arzum Guler; Karadede, Beyza; Akkurt, Atilim; Karadede, M. Irfan

    2014-01-01

    The purpose of this study was to evaluate whether 50 Hz extremely low frequency electromagnetic fields (ELF-EMFs) affect the amount of orthodontic tooth movement in rats. The experiments were performed on 18 male Sprague-Dawley rats. The rats were randomly divided into three groups (n = 6): cage-control (Cg-Cnt) group (n = 6); sinusoidal electromagnetic field (SEMF) group (n = 6); and pulsed electromagnetic field (PEMF) group (n = 6). In SEMF and PEMF groups, rats were subjected to 1.5 mT EMF exposure eight hours per day for eight days. In order to obtain tooth movement, holes were drilled on the right and left maxillary central incisors of the rats at a distance 1.5–2 mm away from the gingiva and 20 g of orthodontic forces were applied to the teeth. Generated linear model for repeated measures and Bonferroni tests were used to evaluate the differences between the groups. Interactions among groups by days were found by using Pillai's trace multivariate test. The results showed that significant differences were present among the groups (F = 5.035; p = 0.03) according to the extent of tooth movement. Significant differences between the amount of tooth movements were determined especially after the fifth day and the following days six, seven and eight (p < 0.001). Within the limitations, according to the results of the present study, the application of ELF-EMF accelerated the orthodontic tooth movement in rats. PMID:26019497

  5. The impact of extremely low frequency electromagnetic fields on stream periphyton: An eleven-year study

    USGS Publications Warehouse

    Burton, T.M.; Uzarski, D.G.; Stelzer, R.S.; Eggert, S.L.; Sobczak, W.V.; Mullen, D.M.

    2000-01-01

    Potential effects of extremely low frequency (ELF) electromagnetic fields on periphyton were studied from 1983 to 1993 using a Before, After, Control and Impact design. The study was conducted at two sites on the Ford River, a fourth-order brown water trout stream in Dickinson County, Michigan. The Reference site received 4.9-6.5 times less exposure to ground electric fields and from 300 to 334 times less exposure to magnetic flux from 1989 to 1993 when the antenna was operational at 76 Hz than did the Antenna site. The objective of the study was to determine if ELF electromagnetic fields had caused changes in structure and/or function of algal communities in the Ford River. Significant differences in chlorophyll a standing crop and daily accumulation rate (a surrogate for primary productivity), and organic matter standing crop and daily accumulation rate were observed between the Reference and Antenna site after the antenna became operational. These four related community function variables all increased at the Antenna site with largest and most consistent increases occurring for chlorophyll measures. Compared to pre-operational data, the increase in chlorophyll at the Antenna site also occurred during a period of low amperage testing in 1986-1988, and did not increase further when the antenna became fully operational in 1989, indicating a low threshold for response. There was no significant differences between the Antenna and Reference sites in community structure variables such as diversity, evenness and the relative abundance of dominant diatoms. Thus, 76 Hz ELF electromagnetic radiation apparently did not change the basic makeup of the diatom community but did increase accumulation rates and standing crops of chlorophyll a and organic matter.

  6. Genetic analysis of circadian responses to low frequency electromagnetic fields in Drosophila melanogaster.

    PubMed

    Fedele, Giorgio; Edwards, Mathew D; Bhutani, Supriya; Hares, John M; Murbach, Manuel; Green, Edward W; Dissel, Stephane; Hastings, Michael H; Rosato, Ezio; Kyriacou, Charalambos P

    2014-12-01

    The blue-light sensitive photoreceptor cryptochrome (CRY) may act as a magneto-receptor through formation of radical pairs involving a triad of tryptophans. Previous genetic analyses of behavioral responses of Drosophila to electromagnetic fields using conditioning, circadian and geotaxis assays have lent some support to the radical pair model (RPM). Here, we describe a new method that generates consistent and reliable circadian responses to electromagnetic fields that differ substantially from those already reported. We used the Schuderer apparatus to isolate Drosophila from local environmental variables, and observe extremely low frequency (3 to 50 Hz) field-induced changes in two locomotor phenotypes, circadian period and activity levels. These field-induced phenotypes are CRY- and blue-light dependent, and are correlated with enhanced CRY stability. Mutational analysis of the terminal tryptophan of the triad hypothesised to be indispensable to the electron transfer required by the RPM reveals that this residue is not necessary for field responses. We observe that deletion of the CRY C-terminus dramatically attenuates the EMF-induced period changes, whereas the N-terminus underlies the hyperactivity. Most strikingly, an isolated CRY C-terminus that does not encode the Tryptophan triad nor the FAD binding domain is nevertheless able to mediate a modest EMF-induced period change. Finally, we observe that hCRY2, but not hCRY1, transformants can detect EMFs, suggesting that hCRY2 is blue light-responsive. In contrast, when we examined circadian molecular cycles in wild-type mouse suprachiasmatic nuclei slices under blue light, there was no field effect. Our results are therefore not consistent with the classical Trp triad-mediated RPM and suggest that CRYs act as blue-light/EMF sensors depending on trans-acting factors that are present in particular cellular environments. PMID:25473952

  7. Genetic Analysis of Circadian Responses to Low Frequency Electromagnetic Fields in Drosophila melanogaster

    PubMed Central

    Fedele, Giorgio; Edwards, Mathew D.; Bhutani, Supriya; Hares, John M.; Murbach, Manuel; Green, Edward W.; Dissel, Stephane; Hastings, Michael H.; Rosato, Ezio; Kyriacou, Charalambos P.

    2014-01-01

    The blue-light sensitive photoreceptor cryptochrome (CRY) may act as a magneto-receptor through formation of radical pairs involving a triad of tryptophans. Previous genetic analyses of behavioral responses of Drosophila to electromagnetic fields using conditioning, circadian and geotaxis assays have lent some support to the radical pair model (RPM). Here, we describe a new method that generates consistent and reliable circadian responses to electromagnetic fields that differ substantially from those already reported. We used the Schuderer apparatus to isolate Drosophila from local environmental variables, and observe extremely low frequency (3 to 50 Hz) field-induced changes in two locomotor phenotypes, circadian period and activity levels. These field-induced phenotypes are CRY- and blue-light dependent, and are correlated with enhanced CRY stability. Mutational analysis of the terminal tryptophan of the triad hypothesised to be indispensable to the electron transfer required by the RPM reveals that this residue is not necessary for field responses. We observe that deletion of the CRY C-terminus dramatically attenuates the EMF-induced period changes, whereas the N-terminus underlies the hyperactivity. Most strikingly, an isolated CRY C-terminus that does not encode the Tryptophan triad nor the FAD binding domain is nevertheless able to mediate a modest EMF-induced period change. Finally, we observe that hCRY2, but not hCRY1, transformants can detect EMFs, suggesting that hCRY2 is blue light-responsive. In contrast, when we examined circadian molecular cycles in wild-type mouse suprachiasmatic nuclei slices under blue light, there was no field effect. Our results are therefore not consistent with the classical Trp triad-mediated RPM and suggest that CRYs act as blue-light/EMF sensors depending on trans-acting factors that are present in particular cellular environments. PMID:25473952

  8. Pro-oxidant effects of extremely low frequency electromagnetic fields in the land snail Helix aspersa.

    PubMed

    Regoli, Francesco; Gorbi, Stefania; Machella, Nicola; Tedesco, Sara; Benedetti, Maura; Bocchetti, Raffaella; Notti, Alessandra; Fattorini, Daniele; Piva, Francesco; Principato, Giovanni

    2005-12-15

    Pro-oxidant effects of extremely low frequency (ELF) 50-Hz magnetic fields were investigated in the land snail Helix aspersa exposed both in short-term laboratory treatments and under field conditions by maintaining the organisms in the proximity of a power line for up to 2 months. Oxidative perturbations were investigated as individual antioxidants (catalase, glutathione reductase, glutathione S-transferases, and total glutathione) and total scavenging capacity toward peroxyl radicals and hydroxyl radicals. Accumulation of lipid peroxidation products, destabilization of lysosomal membranes, and loss of DNA integrity were also evaluated as markers of cell damage. The overall results indicated an oxidative challenge caused by ELF magnetic fields with particularly prompt and sensitive responses for catalase, glutathione reductase, and the overall capability to neutralize peroxyl radicals. Cell injuries occurred to different extents according to duration and intensity of electromagnetic exposure and confirmed complex cause-effect relationships between pro-oxidant factors, efficiency of antioxidant defenses, and the onset of oxidative toxicity. This study highlights the importance of a multimarker approach for detecting a wide panel of biological responses, the necessity of investigating the long-term effects of early oxidative responses, and the role of ELF in enhancing susceptibility to other forms of pathologies or diseases. PMID:16298687

  9. Effects of extremely low frequency electromagnetic fields on human fetal scleral fibroblasts.

    PubMed

    Zhu, Huang; Wang, Jie; Cui, Jiefeng; Fan, Xianqun

    2016-06-01

    This study investigated the effects of extremely low frequency electromagnetic fields (ELF-EMFs) on human fetal scleral fibroblasts (HFSFs). HFSFs were subjected to 50 Hz artificial ELF-EMFs generated by Helmholtz coils with 0.1, 0.2, 0.5, and 1.0 mT field intensities for 6 to 48 h. The viability and factors involved in scleral structuring of HFSFs were determined. The growth rate of HFSFs significantly decreased after only 24 h of exposure to ELF-EMFs (0.2 mT). The messenger RNA (mRNA) expression of collagen type I (COL1A1) decreased and expression of matrix metalloproteinase-2 (MMP-2) increased significantly. There was a decrease in tissue inhibitor of MMP-2 mRNA levels between treated and control cells only at the 1.0 mT intensity level. Transforming growth factor beta-2 mRNA increased in exposed cells, and, simultaneously, fibroblast growth factor-2 mRNA levels decreased. The protein expressions of COL1A1 and MMP-2 were also significantly altered subsequent to exposure (p < 0.05). This study shows that ELF-EMFs had biological effects on HFSFs and could cause abnormality in scleral collagen. PMID:25147305

  10. Effects of extremely low frequency electromagnetic fields (100μT) on behaviors in rats.

    PubMed

    Lai, Jinsheng; Zhang, Yemao; Liu, Xingfa; Zhang, Jiangong; Ruan, Guoran; Chaugai, Sandip; Chen, Chen; Wang, Dao Wen

    2016-01-01

    Recently, extremely low frequency electromagnetic fields (ELF-EMF) have received considerable attentions for their potential pathogenicity. In the present study, we explored the effects of ELF-EMF on behaviors of adult male rats. Sixty adult male rats were randomly divided into two groups, the sham exposure group and the 50Hz/100μT ELF-EMF exposure group. During the 24 weeks exposure, body weight, as well as food and water intake were recorded. Results showed that food and water intake and the body weight of the rats were not affected by the exposure. After 24 weeks exposure, open field test and elevated plus maze were conducted to evaluate the anxiety-like behavior, the tail suspension test and forced swim test were conducted to evaluate depression-like behavior and Morris water maze and fear conditioning tests were used to evaluate the cognitive and memory ability. Exposure to ELF-EMF did not induce any anxiety-like or depression-like behaviors compared with the sham exposure. Moreover, the cognitive and memory ability was not impaired by the ELF-EMF exposure. Furthermore, ELF-EMF exposure did not affect the morphology and histology of the brain. In conclusion, 24 weeks exposure to 50Hz/100μT ELF-EMF had no effect on the behaviors of the adult male rats. PMID:26593281

  11. EMOST: elimination of chronic constipation and diarrhea by low-frequency and intensity electromagnetic fields.

    PubMed

    Bókkon, István; Erdőfi-Szabó, Attila; Till, Attila; Lukács, Tünde; Erdőfi-Nagy, Eva

    2014-01-01

    Previously, we reported about the effectiveness of the EMOST (Electro-Magnetic-Own-Signal-Treatment) treatments in reduction of phantom limb pain as well as improvement of the quality of sleep and mood in subjects under clinical circumstances. We also presented the successful application of EMOST for mental stress management of humans under catastrophic conditions. Our some years experience indicated that the efficiency of EMOST is much greater in children than in adult subjects. In addition, in children much less treatment is needed for recovery compared to adult subjects, as well as the duration of the treatment is shorter. It is possible that this particular success is due to the large plasticity of the central and the autonomic nervous system in young patients. Thus, our research pays special attention regarding the EMOST effectiveness in the field of chronic childhood diseases. Here we report about results of routine alternative treatments carried out at Biolabor Biophysics and Laboratory Services Ltd. by EMOST device regarding to the elimination of chronic constipation and persistent diarrhea in the case of two children. We also briefly present two important possible biological mechanisms such as redox processes and the bidirectional communication between skin cells and the nervous system regarding the efficiency of low-frequency and low-intensity electromagnetic fields (LFI-EMF) treatments. PMID:23781990

  12. Effect of low-frequency electromagnetic field exposure on oocyte differentiation and follicular development

    PubMed Central

    Roshangar, L.; Hamdi, B. A.; Khaki, A. A.; Rad, J Soleimani; Soleimani-Rad, S.

    2014-01-01

    Background: The effect of electromagnetic field (EMF) as an environmental factor on different organs including female reproductive system is of critical concern. The aim of the present study is to evaluate the effect of low-frequency (LF)-EMF on oocyte differentiation and follicular development. Materials and Methods: The experiment was carried out in animal lab of Faculty of Medicine Tabriz University of Medical Sciences. For this purpose, the BALB/c mice were divided into control and experimental group in animal lab. The pregnant mice in the experimental group were exposed to 3 mT EMF field, 4 h/day during the pregnancy period. The LF-EMF was produced by a system using 50 Hz alternative current, in the control group the pregnant mice were kept in a similar condition without exposure to EMF. The neonatal mice from both groups were sacrificed immediately after birth and their ovary was dissected apart and prepared for light and electron microscopy. Result: Microscopy revealed that in the experimental group, in comparison to control group, oocyte nests were mostly broken and irregularly arranged. The primordial follicles were less developed and nuclei of oocytes with an electron microscope appeared heterochromatic, shrunken and had vacuolated cytoplasm. Conclusion: It is concluded that exposure to EMF during the developmental period could affect both oocyte differentiation and folliculogenesis and may result in reduced fertility, by decreasing ovarian reservoir. PMID:24627884

  13. The Energy Metabolism in Caenorhabditis elegans under The Extremely Low-Frequency Electromagnetic Field Exposure

    NASA Astrophysics Data System (ADS)

    Shi, Zhenhua; Yu, Hui; Sun, Yongyan; Yang, Chuanjun; Lian, Huiyong; Cai, Peng

    2015-02-01

    A literal mountain of documentation generated in the past five decades showing unmistakable health hazards associated with extremely low-frequency electromagnetic fields (ELF-EMFs) exposure. However, the relation between energy mechanism and ELF-EMF exposure is poorly understood. In this study, Caenorhabditis elegans was exposed to 50 Hz ELF-EMF at intensities of 0.5, 1, 2, and 3 mT, respectively. Their metabolite variations were analyzed by GC-TOF/MS-based metabolomics. Although minimal metabolic variations and no regular pattern were observed, the contents of energy metabolism-related metabolites such as pyruvic acid, fumaric acid, and L-malic acid were elevated in all the treatments. The expressions of nineteen related genes that encode glycolytic enzymes were analyzed by using quantitative real-time PCR. Only genes encoding GAPDH were significantly upregulated (P < 0.01), and this result was further confirmed by western blot analysis. The enzyme activity of GAPDH was increased (P < 0.01), whereas the total intracellular ATP level was decreased. While no significant difference in lifespan, hatching rate and reproduction, worms exposed to ELF-EMF exhibited less food consumption compared with that of the control (P < 0.01). In conclusion, C. elegans exposed to ELF-EMF have enhanced energy metabolism and restricted dietary, which might contribute to the resistance against exogenous ELF-EMF stress.

  14. Extremely low frequency electromagnetic fields (EMF) and brain cancer in adults and children: review and comment.

    PubMed Central

    Gurney, J. G.; van Wijngaarden, E.

    1999-01-01

    Epidemiologic and experimental research on the potential carcinogenic effects of extremely low frequency electromagnetic fields (EMF) has now been conducted for over two decades. Cancer epidemiology studies in relation to EMF have focused primarily on brain cancer and leukemia, both from residential sources of exposure in children and adults and from occupational exposure in adult men. Because genotoxic effects of EMF have not been shown, most recent laboratory research has attempted to show biological effects that could be related to cancer promotion. In this report, we briefly review residential and occupational EMF studies on brain cancer. We also provide a general review of experimental studies as they relate both to the biological plausibility of an EMF-brain cancer relation and to the insufficiency of such research to help guide exposure assessment in epidemiologic studies. We conclude from our review that no recent research, either epidemiologic or experimental, has emerged to provide reasonable support for a causal role of EMF on brain cancer. PMID:11550314

  15. Characterization of biofilm formation in natural water subjected to low-frequency electromagnetic fields.

    PubMed

    Mercier, Anne; Bertaux, Joanne; Lesobre, Jérôme; Gravouil, Kevin; Verdon, Julien; Imbert, Christine; Valette, Eric; Héchard, Yann

    2016-03-01

    Electromagnetic field (EMF) treatment has proven to be effective against mineral scaling in water systems. Therefore, it should be assessed for the treatment of other deposits such as biofilms. In this study, a commercial device producing low-frequency EMF (1-10 kHz) was applied to a reactor fed with natural water for 45 days. The treatment promoted the concentration of microorganisms in suspension and limited the amount of sessile microorganisms in the biofilm, as determined by the measurement of total DNA, qPCR and microscopy. The structure of the bacterial community was assessed by t-RFLP and pyrosequencing analysis. The results showed that EMF treatment affected both planktonic and sessile community composition. EMFs were responsible for a shift in classes of Proteobacteria during development of the biofilm. It may be speculated that the EMF treatment affected particle solubility and/or microorganism hydration. This study indicated that EMFs modulated biofilm formation in natural water. PMID:26905178

  16. Common behaviors alterations after extremely low-frequency electromagnetic field exposure in rat animal model.

    PubMed

    Mahdavi, Seyed Mohammad; Sahraei, Hedayat; Rezaei-Tavirani, Mostafa; Najafi Abedi, Akram

    2016-01-01

    Naturally, the presence of electromagnetic waves in our living environment affects all components of organisms, particularly humans and animals, as the large part of their body consists of water. In the present study, we tried to investigate the relation between exposure to the extremely low-frequency electromagnetic field (ELF-EMF) and common behaviors such as body weight, food and water intake, anorexia (poor appetite), plasma glucose concentration, movement, rearing and sniffing in rats. For this purpose, rats were exposed to 40  Hz ELF-EMF once a day for 21 days, then at days 1, 3, 7, 14 and 21 after exposure, any changes in the above-mentioned items were assessed in the exposed rats and compared to the non-exposed group as control. Body weight of irradiated rats significantly increased only a week after exposure and decreased after that. No significant change was observed in food and water intake of irradiated rats compared to the control, and the anorexia parameter in the group exposed to ELF-EMF was significantly decreased at one and two weeks after irradiation. A week after exposure, the level of glucose was significantly increased but at other days these changes were not significant. Movements, rearing and sniffing of rats at day 1 after exposure were significantly decreased and other days these changes did not follow any particular pattern. However, the result of this study demonstrated that exposure to ELF-EMF can alter the normal condition of animals and may represent a harmful impact on behavior. PMID:26182237

  17. Comment on ``Constraints on biological effects of weak extremely-low-frequency electromagnetic fields''

    NASA Astrophysics Data System (ADS)

    Kirschvink, Joseph L.

    1992-08-01

    In a recent paper, Adair [Phys. Rev. A 43, 1039 (1991)] concludes that weak extremely-low-frequency (ELF) electromagnetic fields cannot affect biology on the cell level. However, Adair's assertion that few cells of higher organisms contain magnetite (Fe3O4) and his blanket denial of reproducible ELF effects on animals are both wrong. Large numbers of single-domain magnetite particles are present in a variety of animal tissues, including up to a hundred million per gram in human brain tissues, organized in clusters of tens to hundreds of thousand per gram. This is far more than a ``few cells.'' Similarly, a series of reproducible behavioral experiments on honeybees, Apis mellifera, have shown that they are capable of responding to weak ELF magnetic fields that are well within the bounds of Adair's criteria. A biologically plausible model of the interaction of single-domain magnetosomes with a mechanically activated transmembrane ion channel shows that ELF fields on the order of 0.1 to 1 mT are capable of perturbing the open-closed state by an energy of kT. As up to several hundred thousand such structures could fit within a eukaryotic cell, and the noise should go as the square root of the number of independent channels, much smaller ELF sensitivities at the cellular level are possible. Hence, the credibility of weak ELF magnetic effects on living systems must stand or fall mainly on the merits and reproducibility of the biological or epidemiological experiments that suggest them, rather than on dogma about physical implausibility.

  18. Low-Frequency Electromagnetic Backscattering from Tunnels

    SciTech Connect

    Casey, K; Pao, H

    2007-01-16

    Low-frequency electromagnetic scattering from one or more tunnels in a lossy dielectric half-space is considered. The tunnel radii are assumed small compared to the wavelength of the electromagnetic field in the surrounding medium; a tunnel can thus be modeled as a thin scatterer, described by an equivalent impedance per unit length. We examine the normalized backscattering width for cases in which the air-ground interface is either smooth or rough.

  19. Low-frequency pulsed electromagnetic field exposure can alter neuroprocessing in humans

    PubMed Central

    Robertson, John A.; Théberge, Jean; Weller, Julie; Drost, Dick J.; Prato, Frank S.; Thomas, Alex W.

    2010-01-01

    Extremely low-frequency magnetic fields (from DC to 300 Hz) have been shown to affect pain sensitivity in snails, rodents and humans. Here, a functional magnetic resonance imaging study demonstrates how the neuromodulation effect of these magnetic fields influences the processing of acute thermal pain in normal volunteers. Significant interactions were found between pre- and post-exposure activation between the sham and exposed groups for the ipsilateral (right) insula, anterior cingulate and bilateral hippocampus/caudate areas. These results show, for the first time, that the neuromodulation induced by exposure to low-intensity low-frequency magnetic fields can be observed in humans using functional brain imaging and that the detection mechanism for these effects may be different from those used by animals for orientation and navigation. Magnetoreception may be more common than presently thought. PMID:19656823

  20. Mechanisms of interaction and biological effects of extremely-low-frequency electromagnetic fields

    SciTech Connect

    Tenforde, T.S.

    1994-07-01

    Evidence is mounting, that environmental electric and magnetic fields in the extremely-low-frequency (ELF) band below 300 Hz can influence biological functions by mechanisms that are only poorly understood at the present time. The primary objectives of this paper are to review the physical properties of ELF fields, their interactions with living systems at the tissue, cellular, and subcellular levels, and the key role of cell membranes in the transduction of signals from imposed ELF fields. Topics of discussion include signal-to-noise ratios for single cells and cell aggregates, resonance phenomena involving a combination of static and ELF magnetic fields, and the possible influence of ELF fields on molecular signaling pathways that involve membrane receptors and cytoplasmic second messengers. The implications of these findings for promotion of tumor growth by ELF fields are also reviewed.

  1. Cellular and molecular pathways of extremely-low-frequency electromagnetic field interactions with living systems

    NASA Astrophysics Data System (ADS)

    Tenforde, T. S.

    1992-06-01

    There is growing evidence that environmental electric and magnetic fields in the extremely-low-frequency (ELF) band below 300 Hz can influence biological functions by mechanisms that are only poorly understood at the present time. The primary objectives of this paper are to review the physical properties of ELF fields, their interactions with living systems at the tissue, cellular, and subcellular levels, and the key role of cell membranes in the transduction of signals from imposed ELF fields. Topics of discussion include signal-to-noise ratios for single cells and cell aggregates, resonance phenomena involving a combination of static and ELF magnetic fields, and the possible influence of ELF fields on molecular signaling pathways that involve membrane receptors and cytoplasmic second messengers.

  2. Cellular and molecular pathways of extremely-low-frequency electromagnetic field interactions with living systems

    SciTech Connect

    Tenforde, T.S.

    1992-06-01

    There is growing evidence that environmental electric and magnetic fields in the extremely-low-frequency (ELF) band below 300 Hz can influence biological functions by mechanisms that are only poorly understood at the present time. The primary objectives of this paper are to review the physical properties of ELF fields, their interactions with living systems at the tissue, cellular, and subcellular levels, and the key role of cell membranes ;in the transduction of signals from imposed ELF fields. Topics of discussion include signal-to-noise ratios for single cells and cell aggregates, resonance phenomena involving a combination of static and ELF magnetic fields, and the possible influence of ELF fields on molecular signaling pathways that involve membrane receptors and cytoplasmic second messengers.

  3. Bioreactor coupled with electromagnetic field generator: effects of extremely low frequency electromagnetic fields on ethanol production by Saccharomyces cerevisiae.

    PubMed

    Perez, Victor H; Reyes, Alfredo F; Justo, Oselys R; Alvarez, David C; Alegre, Ranulfo M

    2007-01-01

    The effect of extremely low frequency (ELF) magnetic fields on ethanol production by Saccharomyces cerevisiae using sugar cane molasses was studied during batch fermentation. The cellular suspension from the fermentor was externally recycled through a stainless steel tube inserted in two magnetic field generators, and consequently, the ethanol production was intensified. Two magnetic field generators were coupled to the bioreactor, which were operated conveniently in simple or combined ways. Therefore, the recycle velocity and intensity of the magnetic field varied in a range of 0.6-1.4 m s(-1) and 5-20 mT, respectively. However, under the best conditions with the magnetic field treatment (0.9-1.2 m s(-1) and 20 mT plus solenoid), the overall volumetric ethanol productivity was approximately 17% higher than in the control experiment. These results made it possible to verify the effectiveness of the dynamic magnetic treatment since the fermentations with magnetic treatment reached their final stage in less time, i.e., approximately 2 h earlier, when compared with the control experiment. PMID:17663568

  4. Extremely low-frequency electromagnetic fields disrupt magnetic alignment of ruminants

    PubMed Central

    Burda, Hynek; Begall, Sabine; Červený, Jaroslav; Neef, Julia; Němec, Pavel

    2009-01-01

    Resting and grazing cattle and deer tend to align their body axes in the geomagnetic North-South direction. The mechanism(s) that underlie this behavior remain unknown. Here, we show that extremely low-frequency magnetic fields (ELFMFs) generated by high-voltage power lines disrupt alignment of the bodies of these animals with the geomagnetic field. Body orientation of cattle and roe deer was random on pastures under or near power lines. Moreover, cattle exposed to various magnetic fields directly beneath or in the vicinity of power lines trending in various magnetic directions exhibited distinct patterns of alignment. The disturbing effect of the ELFMFs on body alignment diminished with the distance from conductors. These findings constitute evidence for magnetic sensation in large mammals as well as evidence of an overt behavioral reaction to weak ELFMFs in vertebrates. The demonstrated reaction to weak ELFMFs implies effects at the cellular and molecular levels. PMID:19299504

  5. Low-frequency pulsed electromagnetic fields significantly improve time of closure and proliferation of human tendon fibroblasts

    PubMed Central

    2014-01-01

    Background The promotion of the healing process following musculoskeletal injuries comprises growth factor signalling, migration, proliferation and apoptosis of cells. If these processes could be modulated, the healing of tendon tissue may be markedly enhanced. Here, we report the use of the Somagen™ device, which is certified for medical use according to European laws. It generates low-frequency pulsed electromagnetic fields that trigger effects of a nature that are yet to be determined. Methods A 1.5-cm wide, linear scrape was introduced into patellar tendon fibroblast cultures (N = 5 donors). Treatment was carried out every second day. The regimen was applied three times in total with 30 minutes comprising pulsed electromagnetic field packages with two fundamental frequencies (10 minutes of 33 Hz, 20 minutes of 7.8 Hz). Control cells remained untreated. All samples were analyzed for gap closure time, proliferation and apoptosis one week after induction of the scrape wound. Results The mean time for bridging the gap in the nontreated cells was 5.05 ± 0.33 days, and in treated cells, it took 3.35 ± 0.38 days (P <0.001). For cell cultures with scrape wounds, a mean value for BrdU incorporation of OD = 0.70 ± 0.16 was found. Whereas low-frequency pulsed electromagnetic fields treated samples showed OD = 1.58 ± 0.24 (P <0.001). However, the percentage of apoptotic cells did not differ between the two groups. Conclusions Our data demonstrate that low-frequency pulsed electromagnetic fields emitted by the Somagen™ device influences the in vitro wound healing of patellar tendon fibroblasts and, therefore, possibly increases wound healing potential. PMID:24996421

  6. Effects of Extremely Low Frequency Electromagnetic Fields on Vascular Permeability of Circumventricular Organs in the Adult Rat

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Mercado, Y. K.; Cañedo-Dorantes, L.; Bañuelos-Pineda, J.; Serrano-Luna, G.; Feria-Velasco, A.

    2008-08-01

    The present work deals with the effects of extremely low frequency electromagnetic fields (ELF-EMF) on blood vessels permeability to non liposoluble substances of the circumventricular organs (CVO) of adult rats. Male Wistar adult rats were exposed to ELF-EMF and vascular permeability to colloidal carbon was investigated with the use of histological techniques. Results were compared to corresponding data from sham-exposed and control groups of animals. Exposure to ELF-EMF increased the CVO vascular permeability to colloidal carbon intravascularly injected, particularly in the subfornical organ, the median eminence, the pineal gland and the area postrema.

  7. Effects of time-variant extremely low-frequency (ELF) electromagnetic fields (EMF) on cholinesterase activity in Dictyostelium discoideum (Protista).

    PubMed

    Amaroli, Andrea; Trielli, Francesca; Bianco, Bruno; Giordano, Stefano; Moggia, Elsa; Corrado, Maria U Delmonte

    2005-12-15

    Recently, we detected propionylcholinesterase (PrChE) activity in single-cell amoebae of Dictyostelium discoideum using cytochemical, electrophoretic, and spectrophotometric methods. The involvement of this enzyme activity in cell-cell and cell-environment interactions was suggested. In this work, we found that exposure of single-cell amoebae to an extremely low-frequency electromagnetic fields (ELF-EMF) of 300 microT, 50 Hz, from 1 h up to 48 h at 21 +/- 1 degrees C affected PrChE activity. PMID:16425446

  8. Exposure to an extremely low-frequency electromagnetic field only slightly modifies the proteome of Chromobacterium violaceumATCC 12472

    PubMed Central

    Baraúna, Rafael A.; Santos, Agenor V.; Graças, Diego A.; Santos, Daniel M.; Ghilardi, Rubens; Pimenta, Adriano M. C.; Carepo, Marta S. P.; Schneider, Maria P.C.; Silva, Artur

    2015-01-01

    Several studies of the physiological responses of different organisms exposed to extremely low-frequency electromagnetic fields (ELF-EMF) have been described. In this work, we report the minimal effects of in situ exposure to ELF-EMF on the global protein expression of Chromobacterium violaceum using a gel-based proteomic approach. The protein expression profile was only slightly altered, with five differentially expressed proteins detected in the exposed cultures; two of these proteins (DNA-binding stress protein, Dps, and alcohol dehydrogenase) were identified by MS/MS. The enhanced expression of Dps possibly helped to prevent physical damage to DNA. Although small, the changes in protein expression observed here were probably beneficial in helping the bacteria to adapt to the stress generated by the electromagnetic field. PMID:26273227

  9. Exposure to an extremely low-frequency electromagnetic field only slightly modifies the proteome of Chromobacterium violaceumATCC 12472.

    PubMed

    Baraúna, Rafael A; Santos, Agenor V; Graças, Diego A; Santos, Daniel M; Ghilardi, Rubens; Pimenta, Adriano M C; Carepo, Marta S P; Schneider, Maria P C; Silva, Artur

    2015-05-01

    Several studies of the physiological responses of different organisms exposed to extremely low-frequency electromagnetic fields (ELF-EMF) have been described. In this work, we report the minimal effects of in situ exposure to ELF-EMF on the global protein expression of Chromobacterium violaceum using a gel-based proteomic approach. The protein expression profile was only slightly altered, with five differentially expressed proteins detected in the exposed cultures; two of these proteins (DNA-binding stress protein, Dps, and alcohol dehydrogenase) were identified by MS/MS. The enhanced expression of Dps possibly helped to prevent physical damage to DNA. Although small, the changes in protein expression observed here were probably beneficial in helping the bacteria to adapt to the stress generated by the electromagnetic field. PMID:26273227

  10. The Effect of Extremely Low Frequency Pulsed Electromagnetic Field on In Vitro Fertilization Success Rate in N MRI Mice

    PubMed Central

    Hafizi, Leili; Sazgarnia, Ameneh; Mousavifar, Nezhat; Karimi, Mohammad; Ghorbani, Saleh; Kazemi, Mohammad Reza; Emami Meibodi, Neda; Hosseini, Golkoo; Mostafavi Toroghi, Hesam

    2014-01-01

    Objective: The effects of exposure to electromagnetic fields (EMF) on reproduction systems have been widely debated. In this study, we aimed to investigate whether low frequency EMF could ameliorate the in vitro fertilization success rate in Naval medical research institute (NMRI) Mice. Materials and Methods: In this randomized comparative animal study, ten NMRI mice were randomly divided into 2 equal groups (control and experimental). 10 IU of human chorionic gonadotropin (hCG) was injected intraperitoneally to both groups in order to stimulate ovulating, and ovums were then aspirated and kept in KSOM (modified version of sequential simplex optimization medium with a higher K+ concentration) culture medium. Metaphase II ovums were separated, and sperms obtained by "swim out" method were added to metaphase II ovums in the culture medium. The experimental group was exposed to 1.3 millitesla pulsed electromagnetic field at 4 kilohertz frequency for 5 hours. To assess the efficacy, we considered the identification of two-pronuclear zygote (2PN) under microscope as fertilizing criterion. Results: Total number of collected ovums in the control and experimental groups was 191 and 173, respectively, from which 58 (30.05%) and 52 (30.36%) ovums were collected from metaphase II, respectively. In vitro fertilization (IVF) success rate was 77% in extremely low frequency- pulsed electromagnetic field (ELFPEMF) for exposed group (experimental), whereas the rate was 68% for control group. Conclusion: Despite increased percentile of IVF success rate in exposed group, there was no statistically significant difference between 2 groups, but this hypothesis has still been stated as a question. Further studies with larger sample sizes and different EMF designs are suggested. PMID:24381855

  11. Effect of low frequency low energy pulsing electromagnetic fields on mice injected with cyclophosphamide

    SciTech Connect

    Cadossi, R.; Zucchini, P.; Emilia, G.; Franceschi, C.; Cossarizza, A.; Santantonio, M.; Mandolini, G.; Torelli, G. )

    1991-03-01

    C3H mice have been used to investigate the effect of a combination of cyclophosphamide (CY) and electromagnetic fields (PEMF). Mice were injected i.p. with a single dose of 200 mg/kg body weight of CY and then exposed to PEMF 24 h per day. In an initial series of experiments immediately after CY injection mice were exposed to PEMF until sacrifice. WBC counts in the peripheral blood demonstrated a quicker decline in WBC at days 1 and 2 in mice exposed to PEMF. Groups of mice were sacrificed at days 1, 4, 6, 8, and 10 after CY injection. In mice exposed to PEMF the spleen weight was less than in controls at days 6, 8, and 10. Autoradiographic studies demonstrated that the labeling index of bone marrow smears did not significantly differ between controls and experimental mice exposed to PEMF, whereas the spleen labeling index proved to be higher among control mice versus mice exposed to PEMF at day 6, and higher among mice exposed to PEMF versus controls at day 8. In a second series of experiments mice were exposed to PEMF only over the 24 h following CY injection. We found that the spleens of mice exposed to PEMF weighed less than those of controls at days 6 and 8. The labeling index of bone marrow did evidence a slight decrease among mice exposed to PEMF at days 8 and 10 after CY injection versus control mice. The spleen labeling index proved to be lower in experimental mice exposed to PEMF than in controls at days 4, 6, and 8. Mice were then injected with CY, half were exposed to PEMF, and 24 h later bone marrow was recovered from both groups of animals. The same number of bone marrow cells was injected via the tail vein into recipient mice irradiated to 8.5 Gy.

  12. Effect of low frequency low energy pulsing electromagnetic field (PEMF) on X-ray-irradiated mice

    SciTech Connect

    Cadossi, R.; Hentz, V.R.; Kipp, J.; Eiverson, R.; Ceccherelli, G.; Zucchini, P.; Emilia, G.; Torelli, G.; Franceschi, C.; Cossarizza, A.

    1989-02-01

    C3H/Km flora-defined mice were used to investigate the effect of exposure to pulsing electromagnetic field (PEMF) after total body x-ray irradiation. Prolonged exposure to PEMF had no effect on normal nonirradiated mice. When mice irradiated with different doses of x-ray (8.5 Gy, 6.8 Gy, and 6.3 Gy) were exposed to PEMF 24 h a day, we observed a more rapid decline in white blood cells (WBC) in the peripheral blood of mice exposed to PEMF at all the x-ray dosages used. No effect of exposure to PEMF was observed on the survival of the mice irradiated with 6.3 Gy and 8.5 Gy; in mice irradiated with 6.8 Gy, 2 out of 12 survived when exposed to PEMF as compared to 10 out of 12 control mice that were irradiated only. At day 4 after irradiation autoradiographic studies performed on bone marrow and spleen of 8.5-Gy-irradiated mice showed no difference between controls and mice exposed to PEMF, whereas on 6.8-Gy mice the bone marrow labeling index was lower in mice exposed to PEMF. In mice irradiated to 6.3 Gy we observed that the recovery of WBC in the peripheral blood was slowed in mice exposed to PEMF and their body weight was significantly lower than in control mice that were irradiated only. The spleen and bone marrow of the mice irradiated to 6.3 Gy and sacrificed at days 4, 14, 20, and 25 after irradiation were analyzed by autoradiography to evaluate the labeling index. Half of the spleens from mice sacrificed at day 25 after irradiation were used to evaluate the RNA content. Autoradiography showed that in the spleen and bone marrow of control mice, there were more cells labeled with (3H)thymidine at days 4 and 14 and less at days 20 and 25 after irradiation in comparison with mice irradiated and exposed to PEMF.

  13. Human osteoarthritic chondrocytes exposed to extremely low-frequency electromagnetic fields (ELF) and therapeutic application of musically modulated electromagnetic fields (TAMMEF) systems: a comparative study.

    PubMed

    Corallo, Claudio; Volpi, Nila; Franci, Daniela; Vannoni, Daniela; Leoncini, Roberto; Landi, Giacomo; Guarna, Massimo; Montella, Antonio; Albanese, Antonietta; Battisti, Emilio; Fioravanti, Antonella; Nuti, Ranuccio; Giordano, Nicola

    2013-06-01

    Osteoarthritis (OA) is the most common joint disease, characterized by matrix degradation and changes in chondrocyte morphology and metabolism. Literature reported that electromagnetic fields (EMFs) can produce benefits in OA patients, even if EMFs mechanism of action is debated. Human osteoarthritic chondrocytes isolated from femoral heads were cultured in vitro in bidimensional (2-D) flasks and in three-dimensional (3-D) alginate beads to mimic closely cartilage environment in vivo. Cells were exposed 30 min/day for 2 weeks to extremely low-frequency electromagnetic field (ELF) with fixed frequency (100 Hz) and to therapeutic application of musically modulated electromagnetic field (TAMMEF) with variable frequencies, intensities, and waveforms. Cell viability was measured at days 7 and 14, while healthy-cell density, heavily vacuolized (hv) cell density, and cluster density were measured by light microscopy only for 3-D cultures after treatments. Cell morphology was observed for 2-D and 3-D cultures by transmission electron microscopy (TEM). Chondrocyte exposure to TAMMEF enhances cell viability at days 7 and 14 compared to ELF. Light microscopy analysis showed that TAMMEF enhances healthy-cell density, reduces hv-cell density and clustering, compared to ELF. Furthermore, TEM analysis showed different morphology for 2-D (fibroblast-like) and 3-D (rounded shape) cultures, confirming light microscopy results. In conclusion, EMFs are effective and safe for OA chondrocytes. TAMMEF can positively interfere with OA chondrocytes representing an innovative non-pharmacological approach to treat OA. PMID:23263545

  14. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Analytical Solutions of Electromagnetic Fields from Current Dipole Moment on Spherical Conductor in a Low-Frequency Approximation

    NASA Astrophysics Data System (ADS)

    Okita, Taishi; Takagi, Toshiyuki

    2010-01-01

    We analytically derive the solutions for electromagnetic fields of electric current dipole moment, which is placed in the exterior of the spherical homogeneous conductor, and is pointed along the radial direction. The dipole moment is driven in the low frequency f = 1 kHz and high frequency f = 1 GHz regimes. The electrical properties of the conductor are appropriately chosen in each frequency. Electromagnetic fields are rigorously formulated at an arbitrary point in a spherical geometry, in which the magnetic vector potential is straightforwardly given by the Biot-Savart formula, and the scalar potential is expanded with the Legendre polynomials, taking into account the appropriate boundary conditions at the spherical surface of the conductor. The induced electric fields are numerically calculated along the several paths in the low and high frequeny excitation. The self-consistent solutions obtained in this work will be of much importance in a wide region of electromagnetic induction problems.

  15. Pseudo-"blindsight" under exposure to extremely low frequency electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Nakagawa, Hidenori; Masamune, Ken; Kotani, Makoto; Ueno, Shoogo

    2014-05-01

    To show distinct evidence of the pseudo-blindsight caused by electromagnetic stimulations in order to reveal a cure for lost visual functions, it is necessary to investigate the differences from the usual optic pathway in terms of the data processing route from the electromagnetically stimulated retina. For elucidating the scheme of phosphenes like blindsight, we designed a new stimulus coil system and measured the hemodynamic responses in the occipital regions during the stimulations, employing a functional brain-imaging technique. Results showed the possibility that the phosphene as a pseudo-blindsight induces activation of a parietal association area by an alternate route without the primary visual cortex and can be expected as therapy for lost visual functions.

  16. The propagation characteristics of electromagnetic waves through plasma in the near-field region of low-frequency loop antenna

    SciTech Connect

    Liu, DongLin Li, XiaoPing; Xie, Kai; Liu, ZhiWei

    2015-10-15

    A high-speed vehicle flying through the atmosphere between 100 and 20 km may suffer from a “communication blackout.” In this paper, a low frequency system with an on-board loop antenna to receive signals is presented as a potential blackout mitigation method. Because the plasma sheath is in the near-field region of the loop antenna, the traditional scattering matrix method that is developed for the far-field region may overestimate the electromagnetic (EM) wave's attenuation. To estimate the EM wave's attenuation in the near-field region, EM interference (EMI) shielding theory is introduced. Experiments are conducted, and the results verify the EMI shielding theory's effectiveness. Simulations are also conducted with different plasma parameters, and the results obtained show that the EM wave's attenuation in the near-field region is far below than that in the far-field region. The EM wave's attenuation increases with the increase in electron density and decreases with the increase in collision frequency. The higher the frequency, the larger is the EM wave's attenuation. During the entire re-entry phase of a RAM-C module, the EM wave's attenuations are below 10 dB for EM waves with a frequency of 1 MHz and below 1 dB for EM waves with a frequency of 100 kHz. Therefore, the low frequency systems (e.g., Loran-C) may provide a way to transmit some key information to high-speed vehicles even during the communication “blackout” period.

  17. The propagation characteristics of electromagnetic waves through plasma in the near-field region of low-frequency loop antenna

    NASA Astrophysics Data System (ADS)

    Liu, DongLin; Li, XiaoPing; Xie, Kai; Liu, ZhiWei

    2015-10-01

    A high-speed vehicle flying through the atmosphere between 100 and 20 km may suffer from a "communication blackout." In this paper, a low frequency system with an on-board loop antenna to receive signals is presented as a potential blackout mitigation method. Because the plasma sheath is in the near-field region of the loop antenna, the traditional scattering matrix method that is developed for the far-field region may overestimate the electromagnetic (EM) wave's attenuation. To estimate the EM wave's attenuation in the near-field region, EM interference (EMI) shielding theory is introduced. Experiments are conducted, and the results verify the EMI shielding theory's effectiveness. Simulations are also conducted with different plasma parameters, and the results obtained show that the EM wave's attenuation in the near-field region is far below than that in the far-field region. The EM wave's attenuation increases with the increase in electron density and decreases with the increase in collision frequency. The higher the frequency, the larger is the EM wave's attenuation. During the entire re-entry phase of a RAM-C module, the EM wave's attenuations are below 10 dB for EM waves with a frequency of 1 MHz and below 1 dB for EM waves with a frequency of 100 kHz. Therefore, the low frequency systems (e.g., Loran-C) may provide a way to transmit some key information to high-speed vehicles even during the communication "blackout" period.

  18. BIOLOGICAL EFFECTS AND DOSIMETRY OF STATIC AND ELF (EXTREMELY LOW FREQUENCY) ELECTROMAGNETIC FIELDS

    EPA Science Inventory

    The book offers a good introduction to the research field for students, as well as a valuable overall review for the experienced investigator. The six chapters on interactions provide concise descriptions of physical processes for natural and man-made environmental exposures and ...

  19. Theoretical discussion of the effect of a low-frequency electromagnetic vibrating field on the as-cast microstructures of DC Al Zn Mg Cu Zr ingots

    NASA Astrophysics Data System (ADS)

    Jie, Dong; Jianzhong, Cui; Wenjiang, Ding

    2006-10-01

    Within the framework of classical solidification theories, the effect of a low-frequency electromagnetic vibrating field on the as-cast microstructures of direct chilling (DC) casting Al-Zn-Mg-Cu-Zr ingots was discussed. In comparison with the conventional DC ingots, the microstructures of the low-frequency electromagnetic vibrating casting (LFEVC) ingots are gradually refined with increasing electromagnetic intensity. The increased number of nuclei is likely to be as a result of electromagnetic undercooling and forced convection. Grains were assumed to grow first into a global morphology and then into a dendritic one after exceeding a critical size. The unstable wavelength of a growing global grain was deduced to evaluate this transition from a global grain to a dendritic grain. Decreasing the electromagnetic frequency and/or increasing of electromagnetic intensity lead to a longer wavelength and therefore are suitable for less dendritic or net-global grains.

  20. Low Frequency Electromagnetic Pulse and Explosions

    SciTech Connect

    Sweeney, J J

    2011-02-01

    This paper reviews and summarizes prior work related to low frequency (< 100 Hz) EMP (ElectroMagnetic Pulse) observed from explosions. It focuses on how EMP signals might, or might not, be useful in monitoring underground nuclear tests, based on the limits of detection, and physical understanding of these signals. In summary: (1) Both chemical and nuclear explosions produce an EMP. (2) The amplitude of the EMP from underground explosions is at least two orders of magnitude lower than from above ground explosions and higher frequency components of the signal are rapidly attenuated due to ground conductivity. (3) In general, in the near field, that is distances (r) of less than 10s of kilometers from the source, the amplitude of the EMP decays approximately as 1/r{sup 3}, which practically limits EMP applications to very close (<{approx}1km) distances. (4) One computational model suggests that the EMP from a decoupled nuclear explosion may be enhanced over the fully coupled case. This has not been validated with laboratory or field data. (5) The magnitude of the EMP from an underground nuclear explosion is about two orders of magnitude larger than that from a chemical explosion, and has a larger component of higher frequencies. In principle these differences might be used to discriminate a nuclear from a chemical explosion using sensors at very close (<{approx}1 km) distances. (6) Arming and firing systems (e.g. detonators, exploding bridge wires) can also produce an EMP from any type of explosion. (7) To develop the understanding needed to apply low frequency EMP to nuclear explosion monitoring, it is recommended to carry out a series of controlled underground chemical explosions with a variety of sizes, emplacements (e.g. fully coupled and decoupled), and arming and firing systems.

  1. Low frequency acoustic and electromagnetic scattering

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.; Maccamy, R. C.

    1986-01-01

    This paper deals with two classes of problems arising from acoustics and electromagnetics scattering in the low frequency stations. The first class of problem is solving Helmholtz equation with Dirichlet boundary conditions on an arbitrary two dimensional body while the second one is an interior-exterior interface problem with Helmholtz equation in the exterior. Low frequency analysis show that there are two intermediate problems which solve the above problems accurate to 0(k/2/ log k) where k is the frequency. These solutions greatly differ from the zero frequency approximations. For the Dirichlet problem numerical examples are shown to verify the theoretical estimates.

  2. Low frequency acoustic and electromagnetic scattering

    NASA Technical Reports Server (NTRS)

    Hariharan, S. I.; Maccamy, R. C.

    1983-01-01

    This paper deals with two classes of problems arising from acoustics and electromagnetics scattering in the low frequency stations. The first class of problem is solving Helmholtz equation with Dirichlet boundary conditions on an arbitrary two dimensional body while the second one is an interior-exterior interface problem with Helmholtz equation in the exterior. Low frequency analysis show that there are two intermediate problems which solve the above problems accurate to 0(k(2) log k) where k is the frequency. These solutions greatly differ from the zero frequency approximations. For the Dirichlet problem numerical examples are shown to verify the theoretical estimates.

  3. Kinetic model of Chlorella vulgaris growth with and without extremely low frequency-electromagnetic fields (EM-ELF).

    PubMed

    Beruto, Dario T; Lagazzo, Alberto; Frumento, Davide; Converti, Attilio

    2014-01-01

    Chlorella vulgaris was grown in two bench-scale photobioreactors with and without the application of a low intensity, low frequency electromagnetic field (EM-ELF) of about 3mT. Cell concentration and tendency of cells to form aggregates inside the reactor were recorded over a 30 days-time period at 0.5L-constant medium volume in the temperature range 289-304K. At 304K, after a cultivation period of 15 days, the rate of cell death became predominant over that of growth. In the temperature range 289-299K, a two step-kinetic model based on the mitotic division and the clusterization processes was developed and critically discussed. The best-fitted curves turned out to have a sigmoid shape, and the competition between mitosis and clusterization was investigated. Without EM-ELF, the temperature dependence of the specific rate constant of the mitotic step yielded an apparent total enthalpy of 15±6kJmol(-1), whose value was not influenced by the EM-ELF application. The electromagnetic field was shown to exert a significant effect on the exothermic clusterization step. The heat exchange due to binding between cells and liquid medium turned out to be -44±5kJmol(-1) in the absence of EM-ELF and -68±8kJmol(-1) when it was active. Optical microscopy observations were in agreement with the model predictions and confirmed that EM-ELF was able to enhance cell clusterization. PMID:24216340

  4. Review of Studies Concerning Electromagnetic Field (EMF) Exposure Assessment in Europe: Low Frequency Fields (50 Hz-100 kHz).

    PubMed

    Gajšek, Peter; Ravazzani, Paolo; Grellier, James; Samaras, Theodoros; Bakos, József; Thuróczy, György

    2016-01-01

    We aimed to review the findings of exposure assessment studies done in European countries on the exposure of the general public to low frequency electric and magnetic fields (EMFs) of various frequencies. The study shows that outdoor average extremely low frequency magnetic fields (ELF-MF) in public areas in urban environments range between 0.05 and 0.2 µT in terms of flux densities, but stronger values (of the order of a few µT) may occur directly beneath high-voltage power lines, at the walls of transformer buildings, and at the boundary fences of substations. In the indoor environment, high values have been measured close to several domestic appliances (up to the mT range), some of which are held close to the body, e.g., hair dryers, electric shavers. Common sources of exposure to intermediate frequencies (IF) include induction cookers, compact fluorescent lamps, inductive charging systems for electric cars and security or anti-theft devices. No systematic measurement surveys or personal exposimetry data for the IF range have been carried out and only a few reports on measurements of EMFs around such devices are mentioned. According to the available European exposure assessment studies, three population exposure categories were classified by the authors regarding the possible future risk analysis. This classification should be considered a crucial advancement for exposure assessment, which is a mandatory step in any future health risk assessment of EMFs exposure. PMID:27598182

  5. Extremely low-frequency electromagnetic field influences the survival and proliferation effect of human adipose derived stem cells

    PubMed Central

    Razavi, Shahnaz; Salimi, Marzieh; Shahbazi-Gahrouei, Daryoush; Karbasi, Saeed; Kermani, Saeed

    2014-01-01

    Background: Extremely low-frequency electromagnetic fields (ELF-EMF) can effect on biological systems and alters some cell functions like proliferation rate. Therefore, we aimed to attempt the evaluation effect of ELF-EMF on the growth of human adipose derived stem cells (hADSCs). Materials and Methods: ELF-EMF was generated by a system including autotransformer, multi-meter, solenoid coils, teslameter and its probe. We assessed the effect of ELF-EMF with intensity of 0.5 and 1 mT and power line frequency 50 Hz on the survival of hADSCs for 20 and 40 min/day for 7 days by MTT assay. One-way analysis of variance was used to assessment the significant differences in groups. Results: ELF-EMF has maximum effect with intensity of 1 mT for 20 min/day on proliferation of hADSCs. The survival and proliferation effect (PE) in all exposure groups were significantly higher than that in sham groups (P < 0.05) except in group of 1 mT and 40 min/day. Conclusion: Our results show that between 0.5 m and 1 mT ELF-EMF could be enhances survival and PE of hADSCs conserving the duration of exposure. PMID:24592372

  6. X-ray-induced apoptosis of BEL-7402 cell line enhanced by extremely low frequency electromagnetic field in vitro.

    PubMed

    Jian, Wen; Wei, Zhao; Zhiqiang, Cheng; Zheng, Fang

    2009-02-01

    This study was designed to test whether extremely low frequency electromagnetic field (ELF-EMF) could enhance the apoptosis-induction effect of X-ray radiotherapy on liver cancer cell line BEL-7402 in vitro. EMF exposure was performed inside an energized solenoid coil. X-ray irradiation was performed using a linear accelerator. Apoptosis rates of BEL-7402 cells were analyzed using Annexin V-Fit Apoptosis Detection kit. Apoptosis rates of EMF group and sham EMF group were compared when combined with X-ray irradiation. Our results suggested that the apoptosis rate of BEL-7402 cells exposed to low doses of X-ray irradiation could be significantly increased by EMF. More EMF exposures obtain significantly higher apoptosis rates than fewer EMF exposures when combined with 2 Gy X-ray irradiation. These findings suggested that ELF-EMF could augment the cell apoptosis effects of low doses of X-ray irradiation on BEL-7402 cells in a synergistic and cumulative way. PMID:19051321

  7. Extremely Low Frequency Electromagnetic Fields Facilitate Vesicle Endocytosis by Increasing Presynaptic Calcium Channel Expression at a Central Synapse.

    PubMed

    Sun, Zhi-Cheng; Ge, Jian-Long; Guo, Bin; Guo, Jun; Hao, Mei; Wu, Yi-Chen; Lin, Yi-An; La, Ting; Yao, Pan-Tong; Mei, Yan-Ai; Feng, Yi; Xue, Lei

    2016-01-01

    Accumulating evidence suggests significant biological effects caused by extremely low frequency electromagnetic fields (ELF-EMF). Although exo-endocytosis plays crucial physical and biological roles in neuronal communication, studies on how ELF-EMF regulates this process are scarce. By directly measuring calcium currents and membrane capacitance at a large mammalian central nervous synapse, the calyx of Held, we report for the first time that ELF-EMF critically affects synaptic transmission and plasticity. Exposure to ELF-EMF for 8 to 10 days dramatically increases the calcium influx upon stimulation and facilitates all forms of vesicle endocytosis, including slow and rapid endocytosis, endocytosis overshoot and bulk endocytosis, but does not affect the RRP size and exocytosis. Exposure to ELF-EMF also potentiates PTP, a form of short-term plasticity, increasing its peak amplitude without impacting its time course. We further investigated the underlying mechanisms and found that calcium channel expression, including the P/Q, N, and R subtypes, at the presynaptic nerve terminal was enhanced, accounting for the increased calcium influx upon stimulation. Thus, we conclude that exposure to ELF-EMF facilitates vesicle endocytosis and synaptic plasticity in a calcium-dependent manner by increasing calcium channel expression at the nerve terminal. PMID:26887777

  8. Bidirectional frequency-dependent effect of extremely low-frequency electromagnetic field on E. coli K-12.

    PubMed

    Martirosyan, Varsik; Baghdasaryan, Naira; Ayrapetyan, Sinerik

    2013-09-01

    In the present work, the frequency-dependent effects of extremely low-frequency electromagnetic field (ELF EMF) on Escherichia coli K-12 growth have been studied. The frequency-dependent effects of ELF EMF have shown that it can either stimulate or inhibit the growth of microbes. However, the mechanism by which the ELF EMF affects the bacterial cells is not clear yet. It was suggested that the aqua medium can serve as a target through which the biological effect of ELF EMF on microbes may be realized. To check this hypothesis, the frequency-dependent effects (2, 4, 6, 8, 10 Hz, B = 0.4 mT, 30 min) of ELF EMF on the bacterial growth were studied in both cases where the microbes were in the culture media during the exposure and where culture media was preliminarily exposed to the ELF EMF before the addition of bacteria. For investigating the cell proliferation, the radioactive [(3)H]-thymidine assay was carried out. It has been shown that EMF at 4 Hz exposure has pronounced stimulation while at 8 Hz it has inhibited cell proliferation. PMID:23046211

  9. Low Frequency Electromagnetic Field Conditioning Protects against I/R Injury and Contractile Dysfunction in the Isolated Rat Heart

    PubMed Central

    Bialy, Dariusz; Wawrzynska, Magdalena; Bil-Lula, Iwona; Krzywonos-Zawadzka, Anna; Wozniak, Mieczyslaw; Cadete, Virgilio J. J.

    2015-01-01

    Low frequency electromagnetic field (LF-EMF) decreases the formation of reactive oxygen species, which are key mediators of ischemia/reperfusion (I/R) injury. Therefore, we hypothesized that the LF-EMF protects contractility of hearts subjected to I/R injury. Isolated rat hearts were subjected to 20 min of global no-flow ischemia, followed by 30 min reperfusion, in the presence or absence of LF-EMF. Coronary flow, heart rate, left ventricular developed pressure (LVDP), and rate pressure product (RPP) were determined for evaluation of heart mechanical function. The activity of cardiac matrix metalloproteinase-2 (MMP-2) and the contents of coronary effluent troponin I (TnI) and interleukin-6 (IL-6) were measured as markers of heart injury. LF-EMF prevented decreased RPP in I/R hearts, while having no effect on coronary flow. In addition, hearts subjected to I/R exhibited significantly increased LVDP when subjected to LF-EMF. Although TnI and IL-6 levels were increased in I/R hearts, their levels returned to baseline aerobic levels in I/R hearts subjected to LF-EMF. The reduced activity of MMP-2 in I/R hearts was reversed in hearts subjected to LF-EMF. The data presented here indicate that acute exposure to LF-EMF protects mechanical function of I/R hearts and reduces I/R injury. PMID:25961016

  10. Extremely Low Frequency Electromagnetic Fields Facilitate Vesicle Endocytosis by Increasing Presynaptic Calcium Channel Expression at a Central Synapse

    PubMed Central

    Sun, Zhi-cheng; Ge, Jian-long; Guo, Bin; Guo, Jun; Hao, Mei; Wu, Yi-chen; Lin, Yi-an; La, Ting; Yao, Pan-tong; Mei, Yan-ai; Feng, Yi; Xue, Lei

    2016-01-01

    Accumulating evidence suggests significant biological effects caused by extremely low frequency electromagnetic fields (ELF-EMF). Although exo-endocytosis plays crucial physical and biological roles in neuronal communication, studies on how ELF-EMF regulates this process are scarce. By directly measuring calcium currents and membrane capacitance at a large mammalian central nervous synapse, the calyx of Held, we report for the first time that ELF-EMF critically affects synaptic transmission and plasticity. Exposure to ELF-EMF for 8 to 10 days dramatically increases the calcium influx upon stimulation and facilitates all forms of vesicle endocytosis, including slow and rapid endocytosis, endocytosis overshoot and bulk endocytosis, but does not affect the RRP size and exocytosis. Exposure to ELF-EMF also potentiates PTP, a form of short-term plasticity, increasing its peak amplitude without impacting its time course. We further investigated the underlying mechanisms and found that calcium channel expression, including the P/Q, N, and R subtypes, at the presynaptic nerve terminal was enhanced, accounting for the increased calcium influx upon stimulation. Thus, we conclude that exposure to ELF-EMF facilitates vesicle endocytosis and synaptic plasticity in a calcium-dependent manner by increasing calcium channel expression at the nerve terminal. PMID:26887777

  11. Extremely low-frequency electromagnetic fields enhance the proliferation and differentiation of neural progenitor cells cultured from ischemic brains.

    PubMed

    Cheng, Yannan; Dai, Yiqin; Zhu, Ximin; Xu, Haochen; Cai, Ping; Xia, Ruohong; Mao, Lizhen; Zhao, Bing-Qiao; Fan, Wenying

    2015-10-21

    In the mammalian brain, neurogenesis persists throughout the embryonic period and adulthood in the subventricular zone of the lateral ventricle and the granular zone (dentate gyrus) of the hippocampus. Newborn neural progenitor cells (NPCs) in the two regions play a critical role in structural and functional plasticity and neural regeneration after brain injury. Previous studies have reported that extremely low-frequency electromagnetic fields (ELF-EMF) could promote osteogenesis, angiogenesis, and cardiac stem cells' differentiation, which indicates that ELF-EMF might be an effective tool for regenerative therapy. The present studies were carried out to examine the effects of ELF-EMF on hippocampal NPCs cultured from embryonic and adult ischemic brains. We found that exposure to ELF-EMF (50 Hz, 0.4 mT) significantly enhanced the proliferation capability both in embryonic NPCs and in ischemic NPCs. Neuronal differentiation was also enhanced after 7 days of cumulative ELF-EMF exposure, whereas glial differentiation was not influenced markedly. The expression of phosphorylated Akt increased during the proliferation process when ischemic NPCs were exposed to ELF-EMF. However, blockage of the Akt pathway abolished the ELF-EMF-induced proliferation of ischemic NPCs. These data show that ELF-EMF promotes neurogenesis of ischemic NPCs and suggest that this effect may occur through the Akt pathway.Video abstract, Supplemental Digital Content 1, http://links.lww.com/WNR/A347. PMID:26339991

  12. Neuroprotective effects of lotus seedpod procyanidins on extremely low frequency electromagnetic field-induced neurotoxicity in primary cultured hippocampal neurons.

    PubMed

    Yin, Chunchun; Luo, Xiaoping; Duan, Yuqing; Duan, Wenyi; Zhang, Haihui; He, Yuanqing; Sun, Guibo; Sun, Xiaobo

    2016-08-01

    The present study investigated the protective effects of lotus seedpod procyanidins (LSPCs) on extremely low frequency electromagnetic field (ELF-EMF)-induced neurotoxicity in primary cultured rat hippocampal neurons and the underlying molecular mechanism. The results of MTT, morphological observation, superoxide dismutase (SOD) and malondialdehyde (MDA) assays showed that compared with control, incubating neurons under ELF-EMF exposure significantly decreased cell viability and increased the number of apoptotic cells, whereas LSPCs evidently protected the hippocampal neurons against ELF-EMF-induced cell damage. Moreover, a certain concentration of LSPCs inhibited the elevation of intracellular reactive oxygen species (ROS) and Ca(2+) level, as well as prevented the disruption of mitochondrial membrane potential induced by ELF-EMF exposure. In addition, supplementation with LSPCs could alleviate DNA damage, block cell cycle arrest at S phase, and inhibit apoptosis and necrosis of hippocampal neurons under ELF-EMF exposure. Further study demonstrated that LSPCs up-regulated the activations of Bcl-2, Bcl-xl proteins and suppressed the expressions of Bad, Bax proteins caused by ELF-EMF exposure. In conclusion, these findings revealed that LSPCs protected against ELF-EMF-induced neurotoxicity through inhibiting oxidative stress and mitochondrial apoptotic pathway. PMID:27470406

  13. Chemoprotective action of lotus seedpod procyanidins on oxidative stress in mice induced by extremely low-frequency electromagnetic field exposure.

    PubMed

    Luo, Xiaoping; Chen, Meng; Duan, Yuqing; Duan, Wenyi; Zhang, Haihui; He, Yuanqing; Yin, Chunchun; Sun, Guibo; Sun, Xiaobo

    2016-08-01

    With the increasing use of electromagnetic technology, the effects of extremely low-frequency electromagnetic fields (ELF-EMF) on biological systems, central neurotransmitter systems, and human health have attracted extensive attention worldwide. In this study, lotus seedpod procyanidins (LSPCs) were evaluated for their protective effects on ELF-EMF induced oxidative stress injury in mice. Sixty male ICR mice were used for the experiment. The mice were randomly divided into five equal groups. The control group did not receive LSPCs or ELF-EMF but orally received normal saline. The ELF-EMF group received ELF-EMF exposure plus normal saline orally. The other three groups received ELF-EMF exposure plus LSPCs orally (60, 90, or 120mg kg(-1).bw, respectively). Each group exposed to ELF-EMF at 8 mT, 4h day(-1) for 28 consecutive days after administration daily of LSPCs or normal saline to mice for 15 consecutive days with the exception of the control group. Thereafter, blood and cerebral cortex of the mice were analyzed for antioxidant indices, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione-S-transferase (GST) and malondialdehyde (MDA). LSPCs administration at different doses significantly inhibited oxidative stress damage of mice induced by ELF-EMF. LSPCs treatment augmented SOD, CAT, GSH-Px, GR and GST activity. Furthermore, administration significantly lowered MDA level in LSPCs treatment groups LSPCs. All results indicated LSPCs can effectively prevent oxidative stress injury induced by ELF-EMF exposure, which may be related to its ability of scavenging free radicals and stimulating antioxidant enzyme activity. PMID:27470407

  14. Protective effect of procyanidins extracted from the lotus seedpod on immune function injury induced by extremely low frequency electromagnetic field.

    PubMed

    Zhang, Haihui; Cheng, Yanxiang; Luo, Xiaoping; Duan, Yuqing

    2016-08-01

    This study aimed to evaluate the protective effect of Lotus seedpod procyanidins (LSPCs) from extremely low frequency electromagnetic field (ELF-EMF) exposure (50Hz, 8mT, 28 days) and their protective mechanism against radiation damage. The results showed that LSPCs increased the organ index of mice and made the damaged blood-producing function and cytokine(INF-γ, TNF-α, IL-2, IL-6 and IL-10 in spleen) levels by ELF-EMF-irradiation recovered to normal appearance. And experimental results proved that dosing LSPCs inhibit more stagnation of splenocytes in G0/G1 phase caused by ELF-EMF, thus the spleen cells from G0/G1 phase to S phase shift, restore normal cell metabolism, promote the splenocytes proliferation, reduced the apoptosis of spleen cells, effective protect the damage induced by the ELF-EMF radiation. In addition, LSPCs prevented the decline of DNA content caused by ELF-EMF. Western blot determinated the levels of apoptosis genes including Bcl-2, Bax, Bcl-cl, Caspase-3 and Caspase-9. The results revealed that a significant suppression in Bcl-2 expression and increase in Bax, Caspase-3 and Caspase-9 expression in splenic cells in ELF-EMF group. However, LSPCs restored these changes. Taking these results together, it may be summarized that LSPCs could protect hematopoietic tissues and the immune system from ELF-EMF. And it may be hypothesized that ELF-EMF-induced apoptosis in splenocytes might occur via triggers the trans-activation of Bax and activates caspases-3 and -9, which then cleaves the death substrates, leading to apoptosis in splenocytes of mice treated with ELF-EMF. PMID:27470374

  15. Meta-analysis of extremely low frequency electromagnetic fields and cancer risk: a pooled analysis of epidemiologic studies.

    PubMed

    Zhang, Yemao; Lai, Jinsheng; Ruan, Guoran; Chen, Chen; Wang, Dao Wen

    2016-03-01

    Studies have suggested that extremely low frequency electromagnetic fields (ELF-EMF) may affect physiological functions in animal models. However, epidemiologic studies investigating the association of ELF-EMF with the susceptibility to cancer yield contradictory results. In this comprehensive analysis, we conducted a search for case-control surveys regarding the associations of ELF-EMF and cancer susceptibility in electronic databases. A total of 42 studies involving 13,259 cases and 100,882 controls were retrieved. Overall, increased susceptibility to cancer was identified in the ELF-EMF exposed population (OR=1.08, 95% CI: 1.01, 1.15, P=0.02). In the stratified analyses, increased risk was found in North America (OR=1.10; 95% CI: 1.02, 1.20, P=0.02), especially the United States (OR=1.10; 95% CI: 1.01, 1.20, P=0.03). However, studies from Europe contradict these results. Moreover, a higher risk was found to be statistically significantly associated with the residential exposed population (OR=1.18; 95% CI: 1.02, 1.37, P=0.03). Furthermore, an increased cancer risk was found in interview-based surveys (OR=1.16; 95% CI: 1.00, 1.35, P=0.04). In device measurement-based studies, a slight increased risk was found only in premenopausal breast cancer (OR=1.23; 95% CI: 1.01, 1.49, P=0.04). Our meta-analysis suggests that ELF-EMFs are associated with cancer risk, mainly in the United States and in residential exposed populations. Methodological challenges might explain the differences among studies. PMID:26703095

  16. Extremely low frequency pulsed electromagnetic field designed for antinociception does not affect microvascular responsiveness to the vasodilator acetylcholine.

    PubMed

    McKay, Julia C; Corbacio, Michael; Tyml, Karel; Prato, Frank S; Thomas, Alex W

    2010-01-01

    A 225 microT, extremely low frequency, pulsed electromagnetic field (PEMF) that was designed for the induction of antinociception, was tested for its effectiveness to influence blood flow within the skeletal microvasculature of a male Sprague-Dawley rat model (n = 103). Acetylcholine (0.1, 1.0, or 10 mM) was used to perturb normal blood flow and to delineate differential effects of the PEMF, based on degree of vessel dilation. After both 30 and 60 min of PEMF exposure, we report no effects on peak perfusion response to acetylcholine (with only 0.2% of the group difference attributed to exposure). Spectral analysis of blood flow data was generated to obtain information related to myogenic activity (0.15-0.40 Hz), respiratory rate (0.4-2.0 Hz), and heart rate (2.0-7.0 Hz), including the peak frequency within each of the three frequency regions identified above, peak power, full width at half maximum (FWHM), and mean within band. No significant effects due to exposure were observed on myogenic activity of examined blood vessels, or on heart rate parameters. Anesthesia-induced respiratory depression was, however, significantly reduced following PEMF exposure compared to shams (although exposure only accounted for 9.4% of the group difference). This set of data suggest that there are no significant acute physiological effects of 225 microT PEMF after 30 and 60 min of exposure on peak blood flow, heart rate, and myogenic activity, but perhaps a small attenuation effect on anesthetic-induced respiratory depression. PMID:19644977

  17. Extremely low frequency electromagnetic field sensitizes cisplatin-resistant human ovarian adenocarcinoma cells via P53 activation.

    PubMed

    Baharara, Javad; Hosseini, Nasrin; Farzin, Tayebe Ramezani

    2016-08-01

    In the following study, extremely low frequency electromagnetic fields (EL-EMF) radiation was used to restore sensitivity in the cisplatin-resistant A2780 ovarian cancer cells. For this purpose A2780 cells were treated with different doses of cisplatin and EL-EMF (50 Hz, 200 gauss, and 2 h) alone. Cytotoxicity was the measurement using MTT assay. After calculating IC50 for cisplatin (90 µg/ml) a lower concentration from IC50 (30 and 60 µg/ml) was used to be combined with EL-EMF. We compare the effects of each cisplatin, EL-EMF and combination groups using acridine orange-propidium iodide (AO/PI) and DAPI staining, caspase 3/9 activation assay and Annexin/PI assay. We also assessed changes in P53 and Matrix metalloproteinases 2 (MMPs) gene expression with semi-quantitative RT-PCR. Results indicated an EL-EMF-dependent proliferative decrease which was found <10 %, and occurred independently of cisplatin. The decreased proliferation rate for 30 and 60 µg/ml cisplatin was about 20 and 40 %, respectively, while for synergistic groups 30 and 60 µg/ml cisplatin with 2 h EL-EMF exposer, showed 47 and 71 % decrease in viability in rats. DAPI staining indicated that chromatin break down significantly increased in synergistic groups. Acridine orange staining also confirmed MTT assay results. Caspase activity significantly increased in the combined groups. Semi-quantitative RT-PCR showed that in synergistic groups of cisplatin and EL-EMF, expression of P53 was increased but the expression level of MPP-2 gene decreased. Results from this study showed that changes generated by the non-invasive EL-EMF can make resistant cells sensitive to cisplatin. PMID:26370097

  18. Physics-based modeling of power system components for the evaluation of low-frequency radiated electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Barzegaranbaboli, Mohammadreza

    The low-frequency electromagnetic compatibility (EMC) is an increasingly important aspect in the design of practical systems to ensure the functional safety and reliability of complex products. The opportunities for using numerical techniques to predict and analyze system's EMC are therefore of considerable interest in many industries. As the first phase of study, a proper model, including all the details of the component, was required. Therefore, the advances in EMC modeling were studied with classifying analytical and numerical models. The selected model was finite element (FE) modeling, coupled with the distributed network method, to generate the model of the converter's components and obtain the frequency behavioral model of the converter. The method has the ability to reveal the behavior of parasitic elements and higher resonances, which have critical impacts in studying EMI problems. For the EMC and signature studies of the machine drives, the equivalent source modeling was studied. Considering the details of the multi-machine environment, including actual models, some innovation in equivalent source modeling was performed to decrease the simulation time dramatically. Several models were designed in this study and the voltage current cube model and wire model have the best result. The GA-based PSO method is used as the optimization process. Superposition and suppression of the fields in coupling the components were also studied and verified. The simulation time of the equivalent model is 80-100 times lower than the detailed model. All tests were verified experimentally. As the application of EMC and signature study, the fault diagnosis and condition monitoring of an induction motor drive was developed using radiated fields. In addition to experimental tests, the 3DFE analysis was coupled with circuit-based software to implement the incipient fault cases. The identification was implemented using ANN for seventy various faulty cases. The simulation results were

  19. Extremely Low Frequency Electromagnetic Investigation on Mars

    NASA Astrophysics Data System (ADS)

    Kozakiewicz, Joanna; Kulak, Andrzej; Kubisz, Jerzy; Zietara, Krzysztof

    2016-07-01

    Natural electromagnetic (EM) signals of extremely low frequencies (ELF, 3 Hz-3 kHz) can be used to study many of the electromagnetic processes and properties occurring in the Martian environment. Sources of these signals, related to electrical activity in the atmosphere, are very significant since they can influence radio wave propagation on the planet, the atmospheric composition, and the ionospheric structure. In addition, such EM signals can be employed in many purposes such as: surveying the subsurface of Mars or studying the impact of the space weather on the Martian ionosphere. As ELF waves propagate on very long distances, it is possible to explore properties of the entire planet using single-station recordings. In this study, we propose an experiment that allows measuring ELF signals from the Martian surface. Such measurements can be used for detection of electric discharges in the atmosphere and water reservoirs in the planetary subsurface.

  20. The effect of low-frequency electromagnetic field on human bone marrow stem/progenitor cell differentiation

    PubMed Central

    Ross, Christina L.; Siriwardane, Mevan; Almeida-Porada, Graça; Porada, Christopher D.; Brink, Peter; Christ, George J.; Harrison, Benjamin S.

    2015-01-01

    Human bone marrow stromal cells (hBMSCs, also known as bone marrow-derived mesenchymal stem cells) are a population of progenitor cells that contain a subset of skeletal stem cells (hSSCs), able to recreate cartilage, bone, stroma that supports hematopoiesis and marrow adipocytes. As such, they have become an important resource in developing strategies for regenerative medicine and tissue engineering due to their self-renewal and differentiation capabilities. The differentiation of SSCs/BMSCs is dependent on exposure to biophysical and biochemical stimuli that favor early and rapid activation of the in vivo tissue repair process. Exposure to exogenous stimuli such as an electromagnetic field (EMF) can promote differentiation of SSCs/BMSCs via ion dynamics and small signaling molecules. The plasma membrane is often considered to be the main target for EMF signals and most results point to an effect on the rate of ion or ligand binding due to a receptor site acting as a modulator of signaling cascades. Ion fluxes are closely involved in differentiation control as stem cells move and grow in specific directions to form tissues and organs. EMF affects numerous biological functions such as gene expression, cell fate, and cell differentiation, but will only induce these effects within a certain range of low frequencies as well as low amplitudes. EMF has been reported to be effective in the enhancement of osteogenesis and chondrogenesis of hSSCs/BMSCs with no documented negative effects. Studies show specific EMF frequencies enhance hSSC/BMSC adherence, proliferation, differentiation, and viability, all of which play a key role in the use of hSSCs/BMSCs for tissue engineering. While many EMF studies report significant enhancement of the differentiation process, results differ depending on the experimental and environmental conditions. Here we review how specific EMF parameters (frequency, intensity, and time of exposure) significantly regulate hSSC/BMSC differentiation in

  1. The synergic effect of glycyrrhizic acid and low frequency electromagnetic field on angiogenesis in chick chorioallantoic membrane

    PubMed Central

    Majidian Eydgahi, Shokat; Baharara, Javad; Zafar Balanezhad, Saeideh; Asadi Samani, Majid

    2015-01-01

    Objective: Much attention is paid to angiogenesis due to its mutual role in health and disease. Therefore, the effect of various chemical and physical agents on inhibition of this process has been recently studied. This study was conducted to investigate the synergic effect of glycyrrhizic acid and electromagnetic field on angiogenesis. Materials and Methods: In this experimental study, 44 Ross fertilized chicken eggs were randomly divided into four groups, one control and three experimental. Control group was kept with dimethyl sulfoxide on the eighth day, experimental group 1 treated with 200 gauss, 50 Hz electromagnetic field on the 10th day, experimental group 2 treated with 1 mg/ml glycyrrhizic acid on the eighth day, and experimental group 3 simultaneously treated with glycyrrhizic acid on the eighth day and electromagnetic field on the 10th day. On the 12th day, the images of chorioallantoic membrane samples were prepared using photostreomicroscope and the number and length of vessels were measured. Results: The mean number of vessels in the experimental groups 1 and 3 (29.31±3.60 and 27.43±4.61, respectively) was not significantly different from that in the control group (29.11±4.76) (p>0.05). The length of vessels in the experimental groups 1 and 3 (52.35±3.25 mm and 54.94±4.70 mm, respectively) decreased significantly (p<0.05) compared with the control group (61.79±6.46 mm). In experimental group 2, both length and number of vessels (54.53±5.85 mm and 23.96±3.94) decreased significantly compared with the control group (p<0.05). Conclusion: Electromagnetic field and glycyrrhizic acid separately led to inhibition of angiogenesis. However, use of electromagnetic field accompanied with glycyrrhizic acid not only did not increase but also decreased the inhibitory effect. PMID:26101751

  2. Computer simulation of low-frequency electromagnetic data acquisition

    SciTech Connect

    SanFilipo, W.A.; Hohmann, G.W.

    1982-02-01

    Computer simulation of low frequency electromagnetic (LFEM) digital data acquisition in the presence of natural field noise demonstrates several important limitations and considerations. Without the use of a remote reference noise removal scheme it is difficult to obtain an adequate ratio of signal to noise below 0.1 Hz for frequency domain processing and below 0.3 Hz base frequency for time domain processing for a typical source-receiver configuration. A digital high-pass filter substantially facilitates rejection of natural field noise above these frequencies but, at lower frequencies where much longer stacking times are required, it becomes ineffective. Use of a remote reference to subtract natural field noise extends these low-frequency limits a decade, but this technique is limited by the resolution and dynamic range of the instrumentation. Gathering data in short segments so that natural field drift can be offset for each segment allows a higher gain setting to minimize dynamic range problems.

  3. Intrauterine effects of electromagnetic fields--(low frequency, mid-frequency RF, and microwave): review of epidemiologic studies.

    PubMed

    Robert, E

    1999-04-01

    Electromagnetic radiations are named according to frequency or to wavelength (which is inversely proportional to frequency) and create electromagnetic fields (EMFs). Frequencies widely vary according to sources: high-voltage power lines, electrically heated beds, MRI, VDTs, microwave ovens, satellite, and radio/TV transmissions or cellular phone transmitters/receivers. Public concern has increased about the potential health effects of EMFs. There are arguments in favour of EMFs being biologically active, but no mechanism has been identified that explains the link between EMFs and bioeffects. Human data reviewed concern the potential reproductive effects (mainly spontaneous abortions, low birthweight and congenital malformations) of exposure to sources of EMFs: maternal residence, electrically heated beds, occupational exposure (mainly video display terminals), and medical exposures. The available epidemiologic studies all have limitations that prevent to draw clearcut conclusions on the effects of EMFs on human reproduction. EMFs are ubiquitous and unavoidable exposures. The matter of possible effects cannot be considered closed, but until our understanding of the biologic important parameters of EMFs exposures is stronger,design of new studies will be difficult and small epidemiologic studies are unlikely to provide definitive answers and should not be given high priority. No conclusion can be drawn for radiofrequencies and microwaves because of lack of data. There is no convincing evidence today that EMFs of the sort pregnant women or potential fathers meet in occupational or daily life exposures does any harm to the human reproductive process. PMID:10331531

  4. Low frequency electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Spaniol, Craig

    1989-01-01

    Following preliminary investigations of the low frequency electric and magnetic fields that may exists in the Earth-ionospheric cavity, measurements were taken with state-of-the art spectrum analyzers. As a follow up to this activity, an investigation was initiated to determine sources and values for possible low frequency signal that would appear in the cavity. The lowest cavity resonance is estimated at about 8 Hz, but lower frequencies may be an important component of our electromagnetic environment. The potential field frequencies produced by the electron were investigated by a classical model that included possible cross coupling of the electric and gravitation fields. During this work, an interesting relationship was found that related the high frequency charge field with the extremely low frequency of the gravitation field. The results of numerical calculations were surprisingly accurate and this area of investigation is continuing. The work toward continued development of a standardized monitoring facility is continuing with the potential of installing the prototype at West Virginia State College early in 1990. This installation would be capable of real time monitoring of ELF signals in the Earth-ionoshpere cavity and would provide some directional information. A high gain, low noise, 1/f frequency corrected preamplifier was designed and tested for the ferrite core magnetic sensor. The potential application of a super conducting sensor for the ELF magnetic field detection is under investigation. It is hoped that a fully operational monitoring network could pinpoint the location of ELF signal sources and provide new information on where these signals originate and what causes them, assuming that they are natural in origin.

  5. Prenatal exposure to a low-frequency electromagnetic field demasculinizes adult scent marking behavior and increases accessory sex organ weights in rats

    SciTech Connect

    McGivern, R.F.; Sokol, R.Z.; Adey, W.R.

    1990-01-01

    Pregnant Sprague-Dawley dams were exposed to a low-level, low-frequency pulsed electromagnetic (EM) field (15 Hz, 0.3 msec duration, peak intensity 8 gauss) for 15 min twice a day from day 15 through day 20 of gestation, a period in development that is critical for sexual differentiation of the male rat brain. No differences in litter size, number of stillborns, or body weight were observed in offspring from field-exposed dams. At 120 days of age, field-exposed male offspring exhibited significantly less scent marking behavior than controls. Accessory sex organ weights, including epididymis, seminal vesicles, and prostate, were significantly higher in field-exposed subjects at this age. However, circulating levels of testosterone, luteinizing hormone, and follicle-stimulating hormone, as well as epididymal sperm counts, were normal. These data indicate that brief, intermittent exposure to low-frequency EM fields during the critical prenatal period for neurobehavioral sex differentiation can demasculinize male scent marking behavior and increase accessory sex organ weights in adulthood.

  6. Low Frequency Electromagnetic Background Radiation From Electron Acceleration Above Thunderclouds

    NASA Astrophysics Data System (ADS)

    Fullekrug, Martin; Mezentsev, Andrew; Soula, Serge; van der Velde, Oscar; Farges, Thomas

    2013-04-01

    It was recently proposed that the acceleration of electrons during the growth and branching of streamers above thunderclouds initiated by intense lightning discharges could result in detectable low frequency electromagnetic radiation from several tens of kHz up to several hundreds of kHz (Qin et al., GRL, 2012). The intensity of the predicted radiation scales with the streamer density which is particularly large during spectacular sprite occurrences such as jellyfish sprites and/or dancing sprites. Dancing sprites are up to one second long sequences of consecutive sprites or sprite groups which are typically separated by some hundreds of milliseconds and which tend to follow the spatial development of large scale intracloud lightning discharges. A particularly spectacular series of 10 dancing sprite events over a Mediterranean mesoscale convective system was recorded with a low light video camera in south-eastern France during the early morning hours of August 31, 2012. Each dancing sprite event was composed of ~3-4 consecutive sprites or groups of sprites. All of these sprite occurrences were associated with a sudden enhancement ~2 uV/m/Hz-1/2 of the low frequency electromagnetic background radiation as measured with a radio receiver in south-west England. It is estimated that ~1000 streamers at a height of ~40 km are necessary to epxlain the observed electric field strengths. These sudden enhancements are superimposed on a more continuous low frequency electromagnetic background radiation which accompanies each dancing sprite event. It is speculated that this low frequency 'radio glow' results from filamentary streamers near the cloud top as a result of the large scale electrostatic charging of the thundercloud and that it may be used as an indicator for sprite occurrences in future studies.

  7. Low frequency and low intensity pulsed electromagnetic field exerts its antiinflammatory effect through restoration of plasma membrane calcium ATPase activity.

    PubMed

    Selvam, Ramasamy; Ganesan, Kalaivani; Narayana Raju, K V S; Gangadharan, Akkalayi Chandrapuram; Manohar, Bhakthavatchalam Murali; Puvanakrishnan, Rengarajulu

    2007-06-01

    Rheumatoid arthritis (RA) is a chronic inflammatory disorder affecting 1% of the population worldwide. Pulsed electromagnetic field (PEMF) has a number of well-documented physiological effects on cells and tissues including antiinflammatory effect. This study aims to explore the antiinflammatory effect of PEMF and its possible mechanism of action in amelioration of adjuvant induced arthritis (AIA). Arthritis was induced by a single intradermal injection of heat killed Mycobacterium tuberculosis at a concentration of 500 microg in 0.1 ml of paraffin oil into the right hind paw of rats. The arthritic animals showed a biphasic response regarding changes in the paw edema volume. During the chronic phase of the disease, arthritic animals showed an elevated level of lipid peroxides and depletion of antioxidant enzymes with significant radiological and histological changes. Besides, plasma membrane Ca(2+) ATPase (PMCA) activity was inhibited while intracellular Ca(2+) level as well as prostaglandin E(2) levels was noticed to be elevated in blood lymphocytes of arthritic rats. Exposure of arthritic rats to PEMF at 5 Hzx4 microT x 90 min, produced significant antiexudative effect resulting in the restoration of the altered parameters. The antiinflammatory effect could be partially mediated through the stabilizing action of PEMF on membranes as reflected by the restoration of PMCA and intracellular Ca(2+) levels in blood lymphocytes subsequently inhibiting PGE(2) biosynthesis. The results of this study indicated that PEMF could be developed as a potential therapy for RA in human beings. PMID:17537462

  8. A new theoretical model for transmembrane potential and ion currents induced in a spherical cell under low frequency electromagnetic field.

    PubMed

    Zheng, Yu; Gao, Yang; Chen, Ruijuan; Wang, Huiquan; Dong, Lei; Dou, Junrong

    2016-10-01

    Time-varying electromagnetic fields (EMF) can induce some physiological effects in neuronal tissues, which have been explored in many applications such as transcranial magnetic stimulation. Although transmembrane potentials and induced currents have already been the subjects of many theoretical studies, most previous works about this topic are mainly completed by utilizing Maxwell's equations, often by solving a Laplace equation. In previous studies, cells were often considered to be three-compartment models with different electroconductivities in different regions (three compartments are often intracellular regions, membrane, and extracellular regions). However, models like that did not take dynamic ion channels into consideration. Therefore, one cannot obtain concrete ionic current changes such as potassium current change or sodium current change by these models. The aim of the present work is to present a new and more detailed model for calculating transmembrane potentials and ionic currents induced by time-varying EMF. Equations used in the present paper originate from Nernst-Plank equations, which are ionic current-related equations. The main work is to calculate ionic current changes induced by EMF exposure, and then transmembrane potential changes are calculated with Hodgkin-Huxley model. Bioelectromagnetics. 37:481-492, 2016. © 2016 Wiley Periodicals, Inc. PMID:27438778

  9. Ultra low frequency electromagnetic fire alarm system for underground mines

    SciTech Connect

    Not Available

    1991-01-01

    During an underground mine fire, air can be rapidly depleted of oxygen and contaminated with smoke and toxic fire gases. Any delay in warning miners could have disastrous consequences. Unfortunately, present mine fire alarm systems, such as stench, audible or visual alarms, telephones, and messengers, are often slow, unreliable, and limited in mine area coverage. Recent research by the U.S. Bureau of Mines has demonstrated that ultra-low-frequency electromagnetic signaling can be used for an underground mine fire alarm. In field tests of prototype equipment at five mines, electromagnetic signals from 630 to 2,000 Hz were transmitted through mine rock for distances as great as 1,645 m to an intrinsically safe receiver. The prototype system uses off-the-shelf components and state-of-the-art technology to ensure high reliability and low cost. When utilized, this technology would enable simultaneous and instantaneous warning of all underground personnel, regardless of their location or work activity, thereby increasing the likelihood of their successfully escaping a mine disaster. This paper presents the theoretical basis for through-the-rock ultra-low-frequency electromagnetic transmission, design of the prototype transmitter and receiver, and the results of in-mine tests of the prototype system.

  10. Low-Frequency Electromagnetic Exploration for Groundwater on Mars

    NASA Technical Reports Server (NTRS)

    Grimm, Robert E.

    2002-01-01

    Water with even a small amount of dissolved solids has an electrical conductivity orders of magnitude higher than dry rock and is therefore a near-ideal exploration target on Mars for low frequency, diffusive electromagnetic methods. Models of the temperature- and frequency-dependent electrical properties of rock-ice-water mixtures are used to predict the electromagnetic response of the Martian subsurface. Detection of ice is difficult unless it is massively segregated. In contrast, liquid water profoundly affects soundings, and even a small amount of adsorbed water in the cryosphere can be detected. Subcryospheric water is readily distinguishable at frequencies as low as 100 Hz for fresh water to 10 mHz for brines. These responses can be measured using either natural or artificial sources. Ultra low frequency signals from solar wind and diurnal-heating perturbations of the ionosphere are likely, and disturbances of regional crustal magnetic fields may also be observable. Spherics, or extremely to very low frequency signals from lightning discharge, would provide optimal soundings; however, lightning may be the least likely of the possible natural sources. Among the active techniques, only the time-domain electromagnetic (TDEM) method can accommodate a closely spaced transmitter and receiver and sound to depths of hundreds of meters or more. A ground- or aircraft-based TDEM system of several kilograms can detect water to a depth of several hundred meters, and a system of tens of kilograms featuring a large, fixed, rover- or ballistically deployed loop can detect water to several kilometers depth.

  11. Neuritin reverses deficits in murine novel object associative recognition memory caused by exposure to extremely low-frequency (50 Hz) electromagnetic fields

    PubMed Central

    Zhao, Qian-Ru; Lu, Jun-Mei; Yao, Jin-Jing; Zhang, Zheng-Yu; Ling, Chen; Mei, Yan-Ai

    2015-01-01

    Animal studies have shown that electromagnetic field exposure may interfere with the activity of brain cells, thereby generating behavioral and cognitive disturbances. However, the underlying mechanisms and possible preventions are still unknown. In this study, we used a mouse model to examine the effects of exposure to extremely low-frequency (50 Hz) electromagnetic fields (ELF MFs) on a recognition memory task and morphological changes of hippocampal neurons. The data showed that ELF MFs exposure (1 mT, 12 h/day) induced a time-dependent deficit in novel object associative recognition memory and also decreased hippocampal dendritic spine density. This effect was observed without corresponding changes in spontaneous locomotor activity and was transient, which has only been seen after exposing mice to ELF MFs for 7-10 days. The over-expression of hippocampal neuritin, an activity-dependent neurotrophic factor, using an adeno-associated virus (AAV) vector significantly increased the neuritin level and dendritic spine density. This increase was paralleled with ELF MFs exposure-induced deficits in recognition memory and reductions of dendritic spine density. Collectively, our study provides evidence for the association between ELF MFs exposure, impairment of recognition memory, and resulting changes in hippocampal dendritic spine density. Neuritin prevented this ELF MFs-exposure-induced effect by increasing the hippocampal spine density. PMID:26138388

  12. EMOST: Report about the application of low-frequency and intensity electromagnetic fields in disaster situation and commando training.

    PubMed

    Bókkon, István; Erdöfi-Szabó, Attila; Till, Attila; Balázs, Róbert; Sárosi, Zoltán; Szabó, Zoltán László; Kolonics, Gábor; Popper, George

    2012-12-01

    Recently, we published our results (Bókkon et al., 2011. Electromagn Biol Med.) regarding the effectiveness of the EMOST (Electro-Magnetic-Own-Signal-Treatment) method for the reduction of phantom limb pain under clinical circumstances. However, EMOST treatments not only significantly reduced phantom pain, but that most of the patients also reported about additional benefits such as improvement of their sleep and mood quality after treatments. Here we report some unusual applications of EMOST method under special situations. That is, we report about our effective EMOST treatments of humans under catastrophic conditions and commando training course. This article points out that it is reasonable to apply biophysical electromagnetic management under unique circumstances. We also report some preliminary experiments on 12 members of our BioLabor regarding the effectiveness of single EMOST treatment on some serum parameters and electrocardiogram. PMID:22676138

  13. Effects of electromagnetic field stimulation on cellular signal transduction mechanisms: Analyses of the effects of low frequency electromagnetic fields on calcium spiking in ROS 17/2.8 cells. Final report

    SciTech Connect

    Sisken, B.F.; Sisken, J.E.

    1997-12-01

    The general goals of this work were to determine whether resting levels of cellular second messengers, especially calcium, are affected by low-level electromagnetic fields and the mechanisms that could lead to such changes. The work performed was directed at (1) verifying the report of McLeod et al (1990) that low frequency sinusoidal EMF can alter basal calcium fluctuations in cultured ROS 17/2.8 osteoblast-like cells and (2) reproducing the findings of Luben et al (1982) that pulsed electromagnetic fields can affect PTH-stimulated adenylate cyclase activity in osteoblasts. Initially a system was constructed so that cells could be exposed to sinusoidal electric fields using platinum electrodes. In this system, the electrodes were separated from the cells and culture medium by agar barriers. A series of experiments indicated that this system was subject to a significant, though little-known artifact in which a not well understood interaction between the electrodes and sodium ions in the medium or in plain salt solutions led to frequency and amplitude dependent emission of photons that are recorded by the detection system. They therefore designed and constructed an air gap reactor system that utilizes a ferromagnetic core to direct the magnetic flux generated by a sinusoidal coil. Studies on the effects of a 15 Hz pulsed electromagnetic field (PEMF) on cyclic AMP metabolism were performed on ROS 17/2.8 and MC3T3 cells.

  14. No effects of power line frequency extremely low frequency electromagnetic field exposure on selected neurobehavior tests of workers inspecting transformers and distribution line stations versus controls.

    PubMed

    Li, Li; Xiong, De-fu; Liu, Jia-wen; Li, Zi-xin; Zeng, Guang-cheng; Li, Hua-liang

    2014-03-01

    We aimed to evaluate the interference of 50 Hz extremely low frequency electromagnetic field (ELF-EMF) occupational exposure on the neurobehavior tests of workers performing tour-inspection close to transformers and distribution power lines. Occupational short-term "spot" measurements were carried out. 310 inspection workers and 300 logistics staff were selected as exposure and control. The neurobehavior tests were performed through computer-based neurobehavior evaluation system, including mental arithmetic, curve coincide, simple visual reaction time, visual retention, auditory digit span and pursuit aiming. In 500 kV areas electric field intensity at 71.98% of total measured 590 spots were above 5 kV/m (national occupational standard), while in 220 kV areas electric field intensity at 15.69% of total 701 spots were above 5 kV/m. Magnetic field flux density at all the spots was below 1,000 μT (ICNIRP occupational standard). The neurobehavior score changes showed no statistical significance. Results of neurobehavior tests among different age, seniority groups showed no significant changes. Neurobehavior changes caused by daily repeated ELF-EMF exposure were not observed in the current study. PMID:24379132

  15. Field models and numerical dosimetry inside an extremely-low-frequency electromagnetic bioreactor: the theoretical link between the electromagnetically induced mechanical forces and the biological mechanisms of the cell tensegrity.

    PubMed

    Mognaschi, Maria Evelina; Di Barba, Paolo; Magenes, Giovanni; Lenzi, Andrea; Naro, Fabio; Fassina, Lorenzo

    2014-01-01

    We have implemented field models and performed a detailed numerical dosimetry inside our extremely-low-frequency electromagnetic bioreactor which has been successfully used in in vitro Biotechnology and Tissue Engineering researches. The numerical dosimetry permitted to map the magnetic induction field (maximum module equal to about 3.3 mT) and to discuss its biological effects in terms of induced electric currents and induced mechanical forces (compression and traction). So, in the frame of the tensegrity-mechanotransduction theory of Ingber, the study of these electromagnetically induced mechanical forces could be, in our opinion, a powerful tool to understand some effects of the electromagnetic stimulation whose mechanisms remain still elusive. PMID:25202652

  16. Low-frequency electromagnetic technique for nondestructive evaluation

    NASA Astrophysics Data System (ADS)

    Dalichaouch, Yacine; Singsaas, Alan L.; Putris, Firas; Perry, Alexander R.; Czipott, Peter V.

    2000-05-01

    We have developed a low frequency electromagnetic technique using sensitive room temperature magnetoresistive (MR) sensors for a variety of nondestructive evaluation (NDE) applications. These applications include the NDE of medical implants and aircraft structures, the detection of cracks and corrosion in metals, the detection of ferromagnetic foreign objects in the eye and the brain, and the noninvasive determination of iron content in the liver. Our technique consists of applying a low frequency ac magnetic field to the sample and detecting the sample response. The low excitation frequency enables us to probe deep into metal structures; the sensitivity of the MR sensor allows us to detect weak responses from the sample without applying too large an excitation field, particularly in the case of human tissue. The MR sensors are small and relatively inexpensive compared to other sensitive magnetic field sensors such as fluxgates and superconducting quantum interference devices or SQUIDs; hence the resulting NDE instrument will be compact and cost-efficient, enabling its commercialization for practical applications. In this paper, we focus primarily on NDE of orthopedic implants.

  17. Minimization of nanosatellite low frequency magnetic fields.

    PubMed

    Belyayev, S M; Dudkin, F L

    2016-03-01

    Small weight and dimensions of the micro- and nanosatellites constrain researchers to place electromagnetic sensors on short booms or on the satellite body. Therefore the electromagnetic cleanliness of such satellites becomes a central question. This paper describes the theoretical base and practical techniques for determining the parameters of DC and very low frequency magnetic interference sources. One of such sources is satellite magnetization, the reduction of which improves the accuracy and stability of the attitude control system. We present design solutions for magnetically clean spacecraft, testing equipment, and technology for magnetic moment measurements, which are more convenient, efficient, and accurate than the conventional ones. PMID:27036801

  18. Minimization of nanosatellite low frequency magnetic fields

    NASA Astrophysics Data System (ADS)

    Belyayev, S. M.; Dudkin, F. L.

    2016-03-01

    Small weight and dimensions of the micro- and nanosatellites constrain researchers to place electromagnetic sensors on short booms or on the satellite body. Therefore the electromagnetic cleanliness of such satellites becomes a central question. This paper describes the theoretical base and practical techniques for determining the parameters of DC and very low frequency magnetic interference sources. One of such sources is satellite magnetization, the reduction of which improves the accuracy and stability of the attitude control system. We present design solutions for magnetically clean spacecraft, testing equipment, and technology for magnetic moment measurements, which are more convenient, efficient, and accurate than the conventional ones.

  19. Effects of whole body exposure to extremely low frequency electromagnetic fields (ELF-EMF) on serum and liver lipid levels, in the rat

    PubMed Central

    Torres-Duran, Patricia V; Ferreira-Hermosillo, Aldo; Juarez-Oropeza, Marco A; Elias-Viñas, David; Verdugo-Diaz, Leticia

    2007-01-01

    Backgound The effects of extremely low-frequency electromagnetic fields (ELF-EMF) on the blood serum and liver lipid concentrations of male Wistar rats were assessed. Methods Animals were exposed to a single stimulation (2 h) of ELF-EMF (60 Hz, 2.4 mT) or sham-stimulated and thereafter sacrificed at different times (24, 48 or 96 h after beginning the exposure). Results Blood lipids showed, at 48 h stimulated animals, a significant increase of cholesterol associated to high density lipoproteins (HDL-C) than those observed at any other studied time. Free fatty acid serum presented at 24 h significant increases in comparison with control group. The other serum lipids, triacylglycerols and total cholesterol did not show differences between groups, at any time evaluated. No statistical differences were shown on total lipids of the liver but total cholesterol was elevated at 24 h with a significant decrease at 96 h (p = 0.026). The ELF-EMF stimulation increased the liver content of lipoperoxides at 24 h. Conclusion Single exposures to ELF-EMF increases the serum values of HDL-C, the liver content of lipoperoxides and decreases total cholesterol of the liver. The mechanisms for the effects of ELF-EMF on lipid metabolism are not well understand yet, but could be associated to the nitric oxide synthase EMF-stimulation. PMID:18021407

  20. Low-Frequency Electromagnetic Backscatter from Buried Tunnels

    SciTech Connect

    Casey, K; Pao, H

    2006-06-21

    This progress report is submitted under a contract between the Special Project Office of DARPA and Lawrence Livermore National Laboratory. The Project Manager at DARPA is Dr. Michael Zatman. Our purpose under this contract is to investigate interactions between electromagnetic waves and a class of buried targets located in multilayered media with rough interfaces. In this report, we investigate three preliminary problems. In each case our specific goal is to understand various aspects of the electromagnetic wave interaction mechanisms with targets in layered media. The first problem, discussed in Section 2, is that of low-frequency electromagnetic backscattering from a tunnel that is cut into a lossy dielectric half-space. In this problem, the interface between the upper (free space) region and the lower (ground) region is smooth. The tunnel is assumed to be a cylindrical free-space region of infinite extent in its axial direction and with a diameter that is small in comparison to the free-space wavelength. Because its diameter is small, the tunnel can be modeled as a buried ''wire'' described by an equivalent impedance per unit length. In Section 3 we extend the analysis to include a statistically rough interface between the air and ground regions. The interface is modeled as a random-phase screen. Such a screen reduces the coherent power in a plane wave that is transmitted through it, scattering some of the total power into an incoherent field. Our analysis of this second problem quantifies the reduction in the coherent power backscattered from the buried tunnel that is caused by the roughness of the air-ground interface. The problem of low-frequency electromagnetic backscattering from two buried tunnels, parallel to each other but at different locations in the ground, is considered in Section 4. In this analysis, we wish to determine the conditions under which the presence of more than one tunnel can be detected via backscattering. Section 5 concludes the report

  1. A short-term extremely low frequency electromagnetic field exposure increases circulating leukocyte numbers and affects HPA-axis signaling in mice.

    PubMed

    de Kleijn, Stan; Ferwerda, Gerben; Wiese, Michelle; Trentelman, Jos; Cuppen, Jan; Kozicz, Tamas; de Jager, Linda; Hermans, Peter W M; Verburg-van Kemenade, B M Lidy

    2016-10-01

    There is still uncertainty whether extremely low frequency electromagnetic fields (ELF-EMF) can induce health effects like immunomodulation. Despite evidence obtained in vitro, an unambiguous association has not yet been established in vivo. Here, mice were exposed to ELF-EMF for 1, 4, and 24 h/day in a short-term (1 week) and long-term (15 weeks) set-up to investigate whole body effects on the level of stress regulation and immune response. ELF-EMF signal contained multiple frequencies (20-5000 Hz) and a magnetic flux density of 10 μT. After exposure, blood was analyzed for leukocyte numbers (short-term and long-term) and adrenocorticotropic hormone concentration (short-term only). Furthermore, in the short-term experiment, stress-related parameters, corticotropin-releasing hormone, proopiomelanocortin (POMC) and CYP11A1 gene-expression, respectively, were determined in the hypothalamic paraventricular nucleus, pituitary, and adrenal glands. In the short-term but not long-term experiment, leukocyte counts were significantly higher in the 24 h-exposed group compared with controls, mainly represented by increased neutrophils and CD4 ± lymphocytes. POMC expression and plasma adrenocorticotropic hormone were significantly lower compared with unexposed control mice. In conclusion, short-term ELF-EMF exposure may affect hypothalamic-pituitary-adrenal axis activation in mice. Changes in stress hormone release may explain changes in circulating leukocyte numbers and composition. Bioelectromagnetics. 37:433-443, 2016. © 2016 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc. PMID:27553635

  2. Extremely Low-Frequency Electromagnetic Fields Promote In Vitro Neuronal Differentiation and Neurite Outgrowth of Embryonic Neural Stem Cells via Up-Regulating TRPC1

    PubMed Central

    Ma, Qinlong; Chen, Chunhai; Deng, Ping; Zhu, Gang; Lin, Min; Zhang, Lei; Xu, Shangcheng; He, Mindi; Lu, Yonghui; Duan, Weixia; Pi, Huifeng; Cao, Zhengwang; Pei, Liping; Li, Min; Liu, Chuan; Zhang, Yanwen; Zhong, Min; Zhou, Zhou; Yu, Zhengping

    2016-01-01

    Exposure to extremely low-frequency electromagnetic fields (ELF-EMFs) can enhance hippocampal neurogenesis in adult mice. However, little is focused on the effects of ELF-EMFs on embryonic neurogenesis. Here, we studied the potential effects of ELF-EMFs on embryonic neural stem cells (eNSCs). We exposed eNSCs to ELF-EMF (50 Hz, 1 mT) for 1, 2, and 3 days with 4 hours per day. We found that eNSC proliferation and maintenance were significantly enhanced after ELF-EMF exposure in proliferation medium. ELF-EMF exposure increased the ratio of differentiated neurons and promoted the neurite outgrowth of eNSC-derived neurons without influencing astrocyes differentiation and the cell apoptosis. In addition, the expression of the proneural genes, NeuroD and Ngn1, which are crucial for neuronal differentiation and neurite outgrowth, was increased after ELF-EMF exposure. Moreover, the expression of transient receptor potential canonical 1 (TRPC1) was significantly up-regulated accompanied by increased the peak amplitude of intracellular calcium level induced by ELF-EMF. Furthermore, silencing TRPC1 expression eliminated the up-regulation of the proneural genes and the promotion of neuronal differentiation and neurite outgrowth induced by ELF-EMF. These results suggest that ELF-EMF exposure promotes the neuronal differentiation and neurite outgrowth of eNSCs via up-regulation the expression of TRPC1 and proneural genes (NeuroD and Ngn1). These findings also provide new insights in understanding the effects of ELF-EMF exposure on embryonic brain development. PMID:26950212

  3. Effects of combined delivery of extremely low frequency electromagnetic field and magnetic Fe3O4 nanoparticles on hepatic cell lines.

    PubMed

    Ju, Huixiang; Cui, Yubao; Chen, Zhiqiang; Fu, Qinping; Sun, Mingzhong; Zhou, Ying

    2016-01-01

    Magnetic Fe3O4 nanoparticles (MNPs) have shown promise as drug carriers for treating lung and liver tumors in vivo. However, little is known about the combined delivery of these MNPs with a second approach, extremely low frequency electro-magnetic field (ELFF) exposure, which has been shown to have value for in vitro treatment of tumor cells. Here, ELFF and MNPs were combined to treat healthy (HL-7702) and cancerous (Bel-7402, HepG2) hepatic cells lines to explore the potential therapeutic effects, bio-mechanisms, and potential toxicity of a combined drug-free treatment in vitro. Flow cytometry for anti-AFP (alpha fetal protein) antibody, which coated the MNPs, indicated that the combined treatment induced Bel-7402 and HepG2 hepatoma cells lines into early apoptosis, without significant effects on healthy hepatic cells. This effect appeared to be mediated through cellular membrane ion metabolism. The presence of AFP-loaded MNPs strengthened the effects of ELFF on tumor cells, inducing a higher frequency of early apoptosis, while having minimal toxic effects on healthy HL-7702 cells. Western blotting revealed that the apoptosis-triggering BCL proteins were up regulated in hepatoma cells compared to healthy cells. Flow cytometry and patch-clamp studies revealed that this resulted from a higher MNP uptake ratio and greater cellular membrane ion exchange current in tumor cells compared to HL-7702 cells. Further, patch-clamp results showed that combining MNPs with ELFF treatment induces cells into early apoptosis through an ion metabolism disturbance in cells, similar to ELFF treatment. In brief, the combination of ELFF and MNPs had beneficial effects on tumor cells without significant toxicity on healthy cells, and these effects were associated with cellular MNP uptake. PMID:27186307

  4. Short-term effects of extremely low-frequency pulsed electromagnetic field and pulsed low-level laser therapy on rabbit model of corneal alkali burn.

    PubMed

    Rezaei Kanavi, Mozhgan; Tabeie, Faraj; Sahebjam, Farzin; Poursani, Nima; Jahanbakhsh, Nazanin; Paymanpour, Pouya; AfsarAski, Sasha

    2016-04-01

    This study was conducted to investigate the effect of combining extremely low frequency-pulsed electromagnetic field (ELF-PEMF) and low-level laser therapy (LLLT) on alkali-burned rabbit corneas. Fifty alkali-burned corneas of 50 rabbits were categorized into five groups: ELF-PEMF therapy with 2 mT intensity (ELF 2) for 2 h daily; LLLT for 30 min twice daily; combined ELF-PEMF and LLLT (ELF + LLLT); medical therapy (MT); and control (i.e., no treatment). Clinical examination and digital photography of the corneas were performed on days 0, 2, 7, and 14. After euthanizing the rabbits, the affected eyes were evaluated by histopathology. The clinical and histopathologic results were compared between the groups. On days 7 and 14, no significant difference in the corneal defect area was evident between the ELF, LLLT, ELF + LLLT, and MT groups. Excluding the controls, none of the study groups demonstrated a significant corneal neovascularization in both routine histopathology and immunohistochemistry for CD31. Keratocyte loss was significantly higher in the MT group than in the ELF, LLLT, and ELF + LLLT groups. Moderate to severe stromal inflammation in the LLLT group was comparable with that in the MT group and was significantly lower than that in the other groups. In conclusion, combining LLLT and ELF was not superior to ELF alone or LLLT alone in healing corneal alkali burns. However, given the lower intensity of corneal inflammation and the lower rate of keratocytes loss with LLLT, this treatment may be superior to other proposed treatment modalities for healing alkali-burned corneas. PMID:26795389

  5. Effects of combined delivery of extremely low frequency electromagnetic field and magnetic Fe3O4 nanoparticles on hepatic cell lines

    PubMed Central

    Ju, Huixiang; Cui, Yubao; Chen, Zhiqiang; Fu, Qinping; Sun, Mingzhong; Zhou, Ying

    2016-01-01

    Magnetic Fe3O4 nanoparticles (MNPs) have shown promise as drug carriers for treating lung and liver tumors in vivo. However, little is known about the combined delivery of these MNPs with a second approach, extremely low frequency electro-magnetic field (ELFF) exposure, which has been shown to have value for in vitro treatment of tumor cells. Here, ELFF and MNPs were combined to treat healthy (HL-7702) and cancerous (Bel-7402, HepG2) hepatic cells lines to explore the potential therapeutic effects, bio-mechanisms, and potential toxicity of a combined drug-free treatment in vitro. Flow cytometry for anti-AFP (alpha fetal protein) antibody, which coated the MNPs, indicated that the combined treatment induced Bel-7402 and HepG2 hepatoma cells lines into early apoptosis, without significant effects on healthy hepatic cells. This effect appeared to be mediated through cellular membrane ion metabolism. The presence of AFP-loaded MNPs strengthened the effects of ELFF on tumor cells, inducing a higher frequency of early apoptosis, while having minimal toxic effects on healthy HL-7702 cells. Western blotting revealed that the apoptosis-triggering BCL proteins were up regulated in hepatoma cells compared to healthy cells. Flow cytometry and patch-clamp studies revealed that this resulted from a higher MNP uptake ratio and greater cellular membrane ion exchange current in tumor cells compared to HL-7702 cells. Further, patch-clamp results showed that combining MNPs with ELFF treatment induces cells into early apoptosis through an ion metabolism disturbance in cells, similar to ELFF treatment. In brief, the combination of ELFF and MNPs had beneficial effects on tumor cells without significant toxicity on healthy cells, and these effects were associated with cellular MNP uptake. PMID:27186307

  6. Elf (extremely low frequency) communications system ecological monitoring program. The effects of exposing the slime mold Physarum polycephalum to electromagnetic fields

    SciTech Connect

    Goodman, E.M.; Marron, M.T.; Greenebaum, B.

    1982-11-01

    Laboratory exposure of the slime mold Physarum polycephalum to weak electromagnetic fields results in a lengthened mitotic cycle and depressed oxygen consumption. This research program has been designed to ascertain if the same physiological effects are obtained when Physarum polycephalum is exposed to electromagnetic fields in the vicinity of the Wisconsin Test Facility at Clam Lake, Wisconsin.

  7. Extremely Low-Frequency Electromagnetic Fields Affect the miRNA-Mediated Regulation of Signaling Pathways in the GC-2 Cell Line

    PubMed Central

    Liu, Kai-jun; Ao, Lin; Cao, Jia; Zhong, Julia Li; Liu, Jin-yi

    2015-01-01

    Extremely low-frequency electromagnetic fields (ELF-EMFs) can affect male reproductive function, but the underlying mechanism of this effect remains unknown. miRNA-mediated regulation has been implicated as an important epigenetic mechanism for regulatory pathways. Herein, we profiled miRNA expression in response to ELF-EMFs in vitro. Mouse spermatocyte-derived GC–2 cells were intermittently exposed to a 50 Hz ELF-EMF for 72 h (5 min on/10 min off) at magnetic field intensities of 1 mT, 2 mT and 3 mT. Cell viability was assessed using the CCK–8 assay. Apoptosis and the cell cycle were analyzed with flow cytometry. miRNA expression was profiled using Affymetrix Mouse Genechip miRNA 3.0 arrays. Our data showed that the growth, apoptosis or cell cycle arrest of GC–2 cells exposed to the 50 Hz ELF-EMF did not significantly change. However, we identified a total of 55 miRNAs whose expression significantly changed compared with the sham group, including 19 differentially expressed miRNAs (7 miRNAs were upregulated, and 12 were downregulated) in the 1 mT exposure group and 36 (9 miRNAs were upregulated, and 27 were downregulated) in the 3 mT exposure group. The changes in the expression of 15 selected miRNAs measured by real-time PCR were consistent with the microarray results. A network analysis was used to predict core miRNAs and target genes, including miR-30e-5p, miR-210-5p, miR-196b-5p, miR-504-3p, miR-669c-5p and miR-455-3p. We found that these miRNAs were differentially expressed in response to different magnetic field intensities of ELF-EMFs. GO term and KEGG pathway annotation based on the miRNA expression profiling results showed that miRNAs may regulate circadian rhythms, cytokine-cytokine receptor interactions and the p53 signaling pathway. These results suggested that miRNAs could serve as potential biomarkers, and the miRNA-mediated regulation of signaling pathways might play significant roles in the biological effects of ELF-EMFs. PMID:26439850

  8. Low-frequency electromagnetic exploration for groundwater on Mars

    NASA Astrophysics Data System (ADS)

    Grimm, Robert E.

    2002-02-01

    Water with even a small amount of dissolved solidshas an electrical conductivity orders of magnitude higher than dry rock andis therefore a near-ideal exploration target on Mars for low-frequency, diffusiveelectromagnetic methods. Models of the temperature- and frequency-dependentelectrical properties of rock-ice-water mixtures are used to predict the electromagneticresponse of the Martian subsurface. Detection of ice is difficult unless itis massively segregated. In contrast, liquid water profoundly affects soundings,and even a small amount of adsorbed water in the cryosphere can be detected.Subcryospheric water is readily distinguishable at frequencies as low as 100Hz for fresh water to 10 mHz for brines. These responses can be measured usingeither natural or artificial sources. ULF signals from solar wind and diurnal-heatingperturbations of the ionosphere are likely, and disturbances of regional crustalmagnetic fields may also be observable. Spherics, or ELF-VLF signals fromlightning discharge, would provide optimal soundings; however, lightning maybe the least likely of the possible natural sources. Among the active techniques,only the time-domain electromagnetic (TDEM) method can accommodate a closelyspaced transmitter and receiver and sound to depths of hundreds of metersor more. A ground- or aircraft-based TDEM system of several kilograms candetect water to a depth of several hundred meters, and a system of tens ofkilograms featuring a large, fixed, rover- or ballistically deployed loopcan detect water to several kilometers depth.

  9. Low-frequency computational electromagnetics for antenna analysis

    SciTech Connect

    Miller, E.K. ); Burke, G.J. )

    1991-01-01

    An overview of low-frequency, computational methods for modeling the electromagnetic characteristics of antennas is presented here. The article presents a brief analytical background, and summarizes the essential ingredients of the method of moments, for numerically solving low-frequency antenna problems. Some extensions to the basic models of perfectly conducting objects in free space are also summarized, followed by a consideration of some of the same computational issues that affect model accuracy, efficiency and utility. A variety of representative computations are then presented to illustrate various modeling aspects and capabilities that are currently available. A fairly extensive bibliography is included to suggest further reference material to the reader. 90 refs., 27 figs.

  10. Subsurface Ice Detection via Low Frequency Surface Electromagnetic Method

    NASA Astrophysics Data System (ADS)

    Stillman, D. E.; Grimm, R. E.; Mcginnis, R. N.

    2014-12-01

    The geophysical detection of ice in the Cryosphere is typically conducted by measuring the absence of water. These interpretations can become non-unique in dry soils or in clay- and silt-rich soils that contain significant quantities of unfrozen water. Extensive laboratory measurements of electrical properties were made on permafrost samples as a function of frequency, temperature, and water content. These laboratory measurements show that the amount of ice can be uniquely obtained by measuring a frequency dependence of the electrical properties over a large frequency range (20 kHz - 10 Hz). In addition, the electrical properties of permafrost are temperature dependent, which can allow for an estimate of subsurface temperature. In order to test this approach in the field, we performed field surveys at four locations in Alaska. We used three low frequency electromagnetic methods: Spectral Induced Polarization (SIP: 20 kHz - 10 Hz), Capacively Coupled Resistivity (CCR: OhmMapper - 16.5 kHz), and DC Resistivity (Syscal ~ 8 Hz). At the Cold Regions Research and Engineering Laboratory permafrost tunnel near Fox, AK, we used SIP to measure the average ice concentration of 80 v% and determined the temperature to be -3±1°C by matching survey results to lab data. SIP data acquisition is very slow; therefore, at three sites near Tok, AK, we used CCR to perform reconnaissance of the area. Then SIP and DC resistivity were performed at anomalous areas. The three survey types give very similar absolute resistivity values. We found that while SIP gives the most quantitative results, the frequency dependence from the CCR and DC resistivity surveys is all that are needed to determine ice content in permafrost.

  11. Low-Frequency Electromagnetic Thermal Fluctuations in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Gaelzer, R.; Yoon, P. H.; Ziebell, L. F.; Pavan, J.

    2012-12-01

    It is well known that the solar wind proton temperature anisotropy is constrained in the temperature ratio vs. beta parameter space by the mirror/proton-cyclotron and parallel/oblique firehose instability threshold conditions (Hellinger et al., 2006). However, the actual solar wind is found in the parameter regime stable to these instabilities (Bale et al., 2009). Since no waves can be generated in the purely collisionless and stable plasma, the source of the low-frequency electromagnetic fluctuations in the solar wind must be owing to spontaneous thermal effects. The problem of the spontaneously emitted electromagnetic waves from magnetized plasmas is generally poorly understood (Araneda et al., 2011). In the present paper, we formulate the theory of spontaneous thermal emission of electromagnetic radiation in the vicinity of the low-frequency modes of Alfvén, ion-cyclotron, and whistler modes. We carry out a statistical analysis by varying the temperature anisotropy and parallel beta and compare the theoretical fluctuation intensity against the observation such as that reported by Bale et al. (2009). Hellinger et al., GRL, 33, L09101 (2006). Bale et al., PRL, 103, 211101 (2009). Araneda et al., Space Sci. Rev., DOI:10.1007/s11214-011-9773-0 (2011).

  12. Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Analysis and interpretation

    NASA Technical Reports Server (NTRS)

    Neubauer, Fritz M.; Glassmeier, Karl-Heinz; Coates, A. J.; Johnstone, A. D.

    1993-01-01

    The propagation and polarization characteristic of low-frequency electromagnetic wave fields near comet P/Grigg-Skjellerup (P/GS) are analyzed using magnetic field and plasma observations obtained by the Giotto magnetometer experiment and the Johnstone plasma analyzer during the encounter at the comet on July 10, 1992. The results have been physically interpreted.

  13. Diatom response to extremely low-frequency magnetic fields

    SciTech Connect

    Parkinson, W.C.; Sulik, G.L. )

    1992-06-01

    Reports that extremely low-frequency magnetic fields can interfere with normal biological cell function continue to stimulate experimental activity as well as investigations into the possible mechanism of the interaction. The cyclotron resonance' model of Liboff has been tested by Smith et al. using as the biological test system the diatom Amphora coffeiformis. They report enhanced motility of the diatom in response to a low-frequency electromagnetic field tuned to the cyclotron resonance condition for calcium ions. We report here an attempt to reproduce their results. Following their protocol diatoms were seeded onto agar plates containing varying amounts of calcium and exposed to colinear DC and AC magnetic fields tuned to the cyclotron resonant condition for frequencies of 16, 30, and 60 Hz. The fractional motility was compared with that of control plates seeded at the same time from the same culture. We find no evidence of a cyclotron resonance effect.

  14. Interference of the mechanisms of influence that weak extremely low-frequency electromagnetic fields have on the human body and animals

    NASA Astrophysics Data System (ADS)

    Martynyuk, V. S.; Tseyslyer, Yu. V.; Temuryants, N. A.

    2012-12-01

    This review is devoted to the problem of interference between the mechanisms of biological action of natural and artificial electromagnetic fields (EMFs) for different levels of the organization of life. We discuss the problem of specific and nonspecific responses of the human body and animals to the action of EMFs on cellular and organismal levels.

  15. MEASUREMENT OF SMALL MECHANICAL VIBRATIONS OF BRAIN TISSUE EXPOSED TO EXTREMELY-LOW-FREQUENCY ELECTRIC FIELDS

    EPA Science Inventory

    Electromagnetic fields can interact with biological tissue both electrically and mechanically. This study investigated the mechanical interaction between brain tissue and an extremely-low-frequency (ELF) electric field by measuring the resultant vibrational amplitude. The exposur...

  16. Characterization of microstructure with low frequency electromagnetic techniques

    SciTech Connect

    Cherry, Matthew R.; Sathish, Shamachary; Pilchak, Adam L.; Blodgett, Mark P.; Cherry, Aaron J.

    2014-02-18

    A new computational method for characterizing the relationship between surface crystallography and electrical conductivity in anisotropic materials with low frequency electromagnetic techniques is presented. The method is discussed from the standpoint of characterizing the orientation of a single grain, as well as characterizing statistical information about grain ensembles in the microstructure. Large-area electron backscatter diffraction (EBSD) data was obtained and used in conjunction with a synthetic aperture approach to simulate the eddy current response of beta annealed Ti-6Al-4V. Experimental eddy current results are compared to the computed eddy current approximations based on electron backscatter diffraction (EBSD) data, demonstrating good agreement. The detectability of notches in the presence of noise from microstructure is analyzed with the described simulation method and advantages and limitations of this method are discussed relative to other NDE techniques for such analysis.

  17. Effects of weak, low-frequency pulsed electromagnetic fields (BEMER type) on gene expression of human mesenchymal stem cells and chondrocytes: an in vitro study.

    PubMed

    Walther, Markus; Mayer, Florian; Kafka, Wolf; Schütze, Norbert

    2007-01-01

    In vitro effects of electromagnetic fields appear to be related to the type of electromagnetic field applied. Previously, we showed that human osteoblasts display effects of BEMER type electromagnetic field (BTEMF) on gene regulation. Here, we analyze effects of BTEMF on gene expression in human mesenchymal stem cells and chondrocytes. Primary mesenchymal stem cells from bone marrow and the chondrocyte cell line C28I2 were stimulated 5 times at 12-h intervals for 8 min each with BTEMF. RNA from treated and control cells was analyzed for gene expression using the affymetrix chip HG-U133A. A limited number of regulated gene products from both cell types mainly affect cell metabolism and cell matrix structure. There was no increased expression of cancer-related genes. RT-PCR analysis of selected transcripts partly confirmed array data. Results indicate that BTEMF in human mesenchymal stem cells and chondrocytes provide the first indications to understanding therapeutic effects achieved with BTEMF stimulation. PMID:17886005

  18. A physical model for low-frequency electromagnetic induction in the near field based on direct interaction between transmitter and receiver electrons

    PubMed Central

    Smith, Ray T.; Jjunju, Fred P. M.; Young, Iain S.; Taylor, Stephen

    2016-01-01

    A physical model of electromagnetic induction is developed which relates directly the forces between electrons in the transmitter and receiver windings of concentric coaxial finite coils in the near-field region. By applying the principle of superposition, the contributions from accelerating electrons in successive current loops are summed, allowing the peak-induced voltage in the receiver to be accurately predicted. Results show good agreement between theory and experiment for various receivers of different radii up to five times that of the transmitter. The limitations of the linear theory of electromagnetic induction are discussed in terms of the non-uniform current distribution caused by the skin effect. In particular, the explanation in terms of electromagnetic energy and Poynting’s theorem is contrasted with a more direct explanation based on variable filament induction across the conductor cross section. As the direct physical model developed herein deals only with forces between discrete current elements, it can be readily adapted to suit different coil geometries and is widely applicable in various fields of research such as near-field communications, antenna design, wireless power transfer, sensor applications and beyond. PMID:27493580

  19. The Design and Implementation of Instruments for Low-Frequency Electromagnetic Sounding of the Martian Subsurface

    NASA Technical Reports Server (NTRS)

    Delory, G. T.; Grimm, R. E.

    2003-01-01

    Low-frequency electromagnetic soundings of the subsurface can identify liquid water at depths ranging from hundreds of meters to approx. 10 km in an environment such as Mars. Among the tools necessary to perform these soundings are low-frequency electric and magnetic field sensors capable of being deployed from a lander or rover such that horizontal and vertical components of the fields can be measured free of structural or electrical interference. Under a NASA Planetary Instrument Definition and Development Program (PIDDP), we are currently engaged in the prototype stages of low frequency sensor implementations that will enable this technique to be performed autonomously within the constraints of a lander platform. Once developed, this technique will represent both a complementary and alternative method to orbital radar sounding investigations, as the latter may not be able to identify subsurface water without significant ambiguities. Low frequency EM methods can play a crucial role as a ground truth measurement, performing deep soundings at sites identified as high priority areas by orbital radars. Alternatively, the penetration depth and conductivity discrimination of low-frequency methods may enable detection of subsurface water in areas that render radar methods ineffective. In either case, the sensitivity and depth of penetration inherent in low frequency EM exploration makes this tool a compelling candidate method to identify subsurface liquid water from a landed platform on Mars or other targets of interest.

  20. Resonant interactions between cometary ions and low frequency electromagnetic waves

    NASA Technical Reports Server (NTRS)

    Thorne, Richard M.; Tsurutani, Bruce T.

    1987-01-01

    The conditions for resonant wave amplification in a plasma with a ring-beam distribution which is intended to model pick-up ions in a cometary environment are investigated. The inclination between the interplanetary field and the solar wind is found to play a crucial role in governing both the resonant frequency and the growth rate of any unstable mode. It is suggested that the low-frequency MHD mode should experience the most rapid amplification for intermediate inclination. In the frame of the solar wind, such waves should propagate along the field in the direction upstream toward the sun with a phase speed lower than the beaming velocity of the pick-up ions. This mechanism may account for the presence of the interior MHD waves noted by satellites over a region surrounding comets Giacobini-Zinner and Halley.

  1. Low-Frequency Electromagnetic Sounding for Planetary Volatiles (Invited)

    NASA Astrophysics Data System (ADS)

    Grimm, R. E.

    2013-12-01

    EM sounding is divided by loss tangent << 1 (surface-penetrating radars) and >> 1 (inductive methods). The former have high resolution and responses dominated by dielectric permittivity. They have been useful for sounding the polar caps of Mars and are very promising to image the shells of icy satellites as well as the uppermost crusts of silicate bodies. The latter have poorer resolution but greater penetration depth, responses dominated by electrical conductivity, and are the subject of this talk. Low-frequency inductive methods are further divided by comparing the source-receiver separation to the skin depth. Large separations are parametric in frequency so that the variation of EM response with frequency is translated to change in conductivity with depth. Parametric soundings can exploit natural sources from the solar wind, magnetosphere, ionosphere, or atmosphere. Small source-sensor separations are geometric with transmitter-receiver positions: both conductivity and permittivity can be recovered as a function of frequency (a dielectric spectrum), but at greater resource requirements. Subsurface liquid water is an optimal low-frequency EM target because even small quantities of dissolved ions make it a powerful electrical conductor compared to dry, resistive, silicate crusts. Water at kms or even tens of kms can be detected using the magnetotelluric, geomagnetic-depth sounding, or wave-tilt methods: these are all natural-source soundings using different combinations of field components and receiver geometries. If natural sources are weak or absent, a transmitter can be used to obtain high SNR; the time-domain EM (TDEM) method has been used extensively for terrestrial groundwater exploration. Using a ballistically deployed 200-m diameter transmitter loop, TDEM can detect groundwater at depths of several km. If landed in a region of strong local crustal magnetism, the characteristic Larmor frequency of liquid water can be detected with a TDEM-like setup using

  2. Modeling of the propagation of low-frequency electromagnetic radiation in the Earth’s magnetosphere

    SciTech Connect

    Lebedev, N. V. Rudenko, V. V.

    2015-06-15

    A numerical algorithm for solving the set of differential equations describing the propagation of low-frequency electromagnetic radiation in the magnetospheric plasma, including in the presence of geomagnetic waveguides in the form of large-scale plasma density inhomogeneities stretched along the Earth’s magnetic field, has been developed. Calculations of three-dimensional ray trajectories in the magnetosphere and geomagnetic waveguide with allowance for radiation polarization have revealed characteristic tendencies in the behavior of electromagnetic parameters along the ray trajectory. The results of calculations can be used for magnetospheric plasma diagnostics.

  3. Field Testing, Installation, and Calibration of a new Data Acquisition System for the USGS-Stanford-Berkley Ultra-Low Frequency Electromagnetic (ULFEM) Array

    NASA Astrophysics Data System (ADS)

    Creasy, N.; Gardner, J.; Spritzer, J. M.; Keneally, I.; Glen, J. M.; McPhee, D.; Klemperer, S. L.

    2013-12-01

    Since 2006, Stanford University, USGS, and UC Berkeley collaboratively maintain five permanent stations, to measure electric and magnetic data from 0.01 to 40Hz. Each station consists of three orthogonal coil magnetometers and two orthogonal 100m electrodes. The acquisition of ULFEM data helps study possible correlations between electromagnetic fields and seismic events related to the San Andreas Fault system. The current data acquisition system uses a Quanterra Q330 analog-to-digital converter. In 2010, we began development of a new 24-bit digitizing system known as the ULFEM 2010 digitizer in order to replace the Q330. The design of the new recorder was to be more economical and better tailored to the ULFEM network by providing power, calibration, and improved protection from lightning. However, the prototype had many problems, including a daily phase shift, amplifying error, and a time delay of 15 seconds (Bowden, et al., AGU, 2010). Currently, comparative testing of an improved prototype, ULFEM 2013, and the Q330 is taking place at the Jasper Ridge ULFEM station. The ULFEM 2013 contains eight channels that record input from three coil magnetometers, four electrodes, and temperature. Testing is ongoing and involves comparing the coil magnetometer and electrode signals processed by the Q330 and ULFEM 2013 digitizer. Data from the two systems will be compared in the time and frequency domains, and analyses will include calculating error and cross correlations. The ULFEM 2013 digitizer provides power to the magnetometer sensors as well as a calibration coil system (CCS). Every 24 hours, the CCS sends a calibration signal to calibration induction coils fitted to each of the three orthogonal magnetometers with the aim of testing the sensors' sensitivity and accuracy. The CCS produces a frequency sweep of 0.08, 0.51, 5, and 10Hz, creating a field nearly ten times greater than the Earth's field. The CCS consists of open source hardware and an amplifying frequency

  4. Generation of electromagnetic waves in the very low frequency band by velocity gradient

    SciTech Connect

    Ganguli, G. Tejero, E.; Crabtree, C.; Amatucci, W.; Rudakov, L.

    2014-01-15

    It is shown that a magnetized plasma layer with a velocity gradient in the flow perpendicular to the ambient magnetic field is unstable to waves in the Very Low Frequency band that spans the ion and electron gyrofrequencies. The waves are formally electromagnetic. However, depending on wave vector k{sup ¯}=kc/ω{sub pe} (normalized by the electron skin depth) and the obliqueness, k{sub ⊥}/k{sub ||}, where k{sub ⊥,||} are wave vectors perpendicular and parallel to the magnetic field, the waves are closer to electrostatic in nature when k{sup ¯}≫1 and k{sub ⊥}≫k{sub ||} and electromagnetic otherwise. Inhomogeneous transverse flows are generated in plasma that contains a static electric field perpendicular to the magnetic field, a configuration that may naturally arise in the boundary layer between plasmas of different characteristics.

  5. Low-frequency fluctuations in plasma magnetic fields

    SciTech Connect

    Cable, S.; Tajima, T.

    1992-02-01

    It is shown that even a non-magnetized plasma with temperature T sustains zero-frequency magnetic fluctuations in thermal equilibrium. Fluctuations in electric and magnetic fields, as well as in densities, are computed. Four cases are studied: a cold, gaseous, isotropic, non-magnetized plasma; a cold, gaseous plasma in a uniform magnetic field; a warm, gaseous plasma described by kinetic theory; and a degenerate electron plasma. For the simple gaseous plasma, the fluctuation strength of the magnetic field as a function of frequency and wavenumber is calculated with the aid of the fluctuation-dissipation theorem. This calculation is done for both collisional and collisionless plasmas. The magnetic field fluctuation spectrum of each plasma has a large zero-frequency peak. The peak is a Dirac {delta}-function in the collisionless plasma; it is broadened into a Lorentzian curve in the collisional plasma. The plasma causes a low frequency cutoff in the typical black-body radiation spectrum, and the energy under the discovered peak approximates the energy lost in this cutoff. When the imposed magnetic field is weak, the magnetic field were vector fluctuation spectra of the two lowest modes are independent of the strength of the imposed field. Further, these modes contain finite energy even when the imposed field is zero. It is the energy of these modes which forms the non-magnetized zero-frequency peak of the isotropic plasma. In deriving these results, a simple relationship between the dispersion relation and the fluctuation power spectrum of electromagnetic waves if found. The warm plasma is shown, by kinetic theory, to exhibit a zero-frequency peak in its magnetic field fluctuation spectrum as well. For the degenerate plasma, we find that electric field fluctuations and number density fluctuations vanish at zero frequency; however, the magnetic field power spectrum diverges at zero frequency.

  6. Low-frequency electrical dosimetry: research agenda of the IEEE International Committee on Electromagnetic Safety.

    PubMed

    Reilly, J Patrick; Hirata, Akimasa

    2016-06-21

    This article treats unsettled issues in the use of numerical models of electrical dosimetry as applied to international limits on human exposure to low-frequency (typically  <  100 kHz) electromagnetic fields and contact current. The perspective in this publication is that of Subcommittee 6 of IEEE-ICES (International Committee on Electromagnetic Safety) Technical Committee 95. The paper discusses 25 issues needing attention, fitting into three general categories: induction models; electrostimulation models; and human exposure limits. Of these, 9 were voted as 'high priority' by members of Subcommittee 6. The list is presented as a research agenda for refinements in numerical modeling with applications to human exposure limits. It is likely that such issues are also important in medical and electrical product safety design applications. PMID:27223463

  7. Low-frequency electrical dosimetry: research agenda of the IEEE International Committee on Electromagnetic Safety

    NASA Astrophysics Data System (ADS)

    Reilly, J. Patrick; Hirata, Akimasa

    2016-06-01

    This article treats unsettled issues in the use of numerical models of electrical dosimetry as applied to international limits on human exposure to low-frequency (typically  <  100 kHz) electromagnetic fields and contact current. The perspective in this publication is that of Subcommittee 6 of IEEE-ICES (International Committee on Electromagnetic Safety) Technical Committee 95. The paper discusses 25 issues needing attention, fitting into three general categories: induction models; electrostimulation models; and human exposure limits. Of these, 9 were voted as ‘high priority’ by members of Subcommittee 6. The list is presented as a research agenda for refinements in numerical modeling with applications to human exposure limits. It is likely that such issues are also important in medical and electrical product safety design applications.

  8. A hybrid electromagnetic energy harvesting device for low frequency vibration

    NASA Astrophysics Data System (ADS)

    Jung, Hyung-Jo; Kim, In-Ho; Min, Dong Yi; Sim, Sung-Han; Koo, Jeong-Hoi

    2013-04-01

    An electromagnetic energy harvesting device, which converts a translational base motion into a rotational motion by using a rigid bar having a moving mass pivoted on a hinged point with a power spring, has been recently developed for use of civil engineering structures having low natural frequencies. The device utilizes the relative motion between moving permanent magnets and a fixed solenoid coil in order to harvest electrical power. In this study, the performance of the device is enhanced by introducing a rotational-type generator at a hinged point. In addition, a mechanical stopper, which makes use of an auxiliary energy harvesting part to further improve the efficiency, is incorporated into the device. The effectiveness of the proposed hybrid energy harvesting device based on electromagnetic mechanism is verified through a series of laboratory tests.

  9. A mathematical model of extremely low frequency ocean induced electromagnetic noise

    NASA Astrophysics Data System (ADS)

    Dautta, Manik; Faruque, Rumana Binte; Islam, Rakibul

    2016-07-01

    Magnetic Anomaly Detection (MAD) system uses the principle that ferromagnetic objects disturb the magnetic lines of force of the earth. These lines of force are able to pass through both water and air in similar manners. A MAD system, usually mounted on an aerial vehicle, is thus often employed to confirm the detection and accomplish localization of large ferromagnetic objects submerged in a sea-water environment. However, the total magnetic signal encountered by a MAD system includes contributions from a myriad of low to Extremely Low Frequency (ELF) sources. The goal of the MAD system is to detect small anomaly signals in the midst of these low-frequency interfering signals. Both the Range of Detection (Rd) and the Probability of Detection (Pd) are limited by the ratio of anomaly signal strength to the interfering magnetic noise. In this paper, we report a generic mathematical model to estimate the signal-to-noise ratio or SNR. Since time-variant electro-magnetic signals are affected by conduction losses due to sea-water conductivity and the presence of air-water interface, we employ the general formulation of dipole induced electromagnetic field propagation in stratified media [1]. As a first step we employ a volumetric distribution of isolated elementary magnetic dipoles, each having its own dipole strength and orientation, to estimate the magnetic noise observed by a MAD system. Numerical results are presented for a few realizations out of an ensemble of possible realizations of elementary dipole source distributions.

  10. ELF (extremely-low-frequency) field interactions at the animal, tissue and cellular levels

    SciTech Connect

    Tenforde, T.S.

    1990-10-01

    A description is given of the fundamental physical properties of extremely-low-frequency (ELF) electromagnetic fields, and the mechanisms through which these fields interact with the human body at a macroscopic level. Biological responses to ELF fields at the tissue, cellular and molecular levels are summarized, including new evidence that ELF field exposure produces alterations in gene expression and the cytoplasmic concentrations of specific proteins.

  11. An investigation of the usefulness of extremely low-frequency electromagnetic measurements for treaty verification

    SciTech Connect

    Sweeney, J.J.

    1989-01-01

    From FY 1986 through FY 1988, we monitored extremely low-frequency (ELF) electromagnetic (EM) fields to determine whether these signals could be detected from underground nuclear explosions. Signals clearly related to underground tests were detected only when the ELF field sensors were located within 10 km of surface ground zero. Theoretical analysis, based on the results of these measurements, shows that the ELF impulse signals from underground nuclear tests are of longer duration than those from lightning sources and are, therefore, less efficient in exciting resonances in the earth-ionosphere cavity, even though the source strength for each may be the same. Thus, ELF signals from underground nuclear tests with yields of <150 kT are generally lower than the background signals caused by worldwide lightning activity. Our conclusion is that ELF monitoring probably will not be useful for detecting underground nuclear tests at distances >10 km from the tests. 16 refs., 24 figs., 3 tabs.

  12. Appraisal of current density in Very Low Frequency electromagnetic measurements using preconditioned conjugate gradient approach

    NASA Astrophysics Data System (ADS)

    Singh, A.; Sharma, S. P.

    2015-12-01

    We describe the implementation of a new fast imaging technique to invert very low frequency (VLF) data measured on profiles into corresponding apparent current density systems over the 2D earth. First, a formulation has been derived to compute the vertical component of the magnetic field for a given 2D current density distribution in the Earth's subsurface. Since the vertical component of the magnetic field is proportional to the real anomaly of VLF electromagnetic measurement, the derived formulation has been used for imaging subsurface structures. The 2D inversion code incorporating the preconditioned conjugate gradient approach was developed for imaging of the subsurface conductors using the real VLF anomaly in terms of apparent current density distribution in the subsurface. The preconditioner determined by the distances between the cells and the observation points greatly improved the quality of the very low frequency imaging. Finally, we tested our method using synthetic and real data and all tests returned favorable results. The presented formulation were also compared with other imaging techniques in terms of apparent current density and resistivity distribution using a standard numerical forward modeling and inversion technique. The presented imaging technique shows improvement with respect to the filtering approaches in depicting subsurface conductors. Further, results obtained using the presented approach is closer to the results of rigorous resistivity inversion.

  13. A multiphysics and multiscale model for low frequency electromagnetic direct-chill casting

    NASA Astrophysics Data System (ADS)

    Košnik, N.; Guštin, A. Z.; Mavrič, B.; Šarler, B.

    2016-03-01

    Simulation and control of macrosegregation, deformation and grain size in low frequency electromagnetic (EM) direct-chill casting (LFEMC) is important for downstream processing. Respectively, a multiphysics and multiscale model is developed for solution of Lorentz force, temperature, velocity, concentration, deformation and grain structure of LFEMC processed aluminum alloys, with focus on axisymmetric billets. The mixture equations with lever rule, linearized phase diagram, and stationary thermoelastic solid phase are assumed, together with EM induction equation for the field imposed by the coil. Explicit diffuse approximate meshless solution procedure [1] is used for solving the EM field, and the explicit local radial basis function collocation method [2] is used for solving the coupled transport phenomena and thermomechanics fields. Pressure-velocity coupling is performed by the fractional step method [3]. The point automata method with modified KGT model is used to estimate the grain structure [4] in a post-processing mode. Thermal, mechanical, EM and grain structure outcomes of the model are demonstrated. A systematic study of the complicated influences of the process parameters can be investigated by the model, including intensity and frequency of the electromagnetic field. The meshless solution framework, with the implemented simplest physical models, will be further extended by including more sophisticated microsegregation and grain structure models, as well as a more realistic solid and solid-liquid phase rheology.

  14. Low-frequency electromagnetic waves driven by gyrotropic gyrating ion beams

    NASA Technical Reports Server (NTRS)

    Sharma, O. P.; Patel, V. L.

    1986-01-01

    The origin of left- and right-hand-polarized low-frequency waves in space plasmas is analyzed. It has been shown that a gyrotropic gyrating ion beam, a ring in velocity space, can excite electromagnetic modes in the plasma near the beam gyrofrequency. It excites left-hand-polarized shear Alfven waves and their harmonics via the coupling of Alfven modes with the beam modes. It can also excite right-hand-polarized fast-mode magnetosonic waves and their harmonics as well. The excitation is possible for beam ions heavier than the plasma ions. The growth rate varies as one-third power of the beam density and decreases with the angle of wave propagation with respect to the ambient magnetic field. The nonlocality has a stabilizing effect on the instability. The predicted values of the wave frequencies compare reasonably well with those observed in satellite data.

  15. Extremely low frequency band station for natural electromagnetic noise measurement

    NASA Astrophysics Data System (ADS)

    Fornieles-Callejón, J.; Salinas, A.; Toledo-Redondo, S.; Portí, J.; Méndez, A.; Navarro, E. A.; Morente-Molinera, J. A.; Soto-Aranaz, C.; Ortega-Cayuela, J. S.

    2015-03-01

    A new permanent ELF measurement station has been deployed in Sierra Nevada, Spain. It is composed of two magnetometers, oriented NS and EW, respectively. At 10 Hz, their sensitivity is 19 μV/pT and the signal-to-noise ratio (SNR) is 28 dB for a time-varying signal of 1 pT, the expected field amplitude in Sierra Nevada. The station operates for frequencies below 24 Hz. The magnetometers, together with their corresponding electronics, have been specifically designed to achieve such an SNR for small signals. They are based on high-resolution search coils with ferromagnetic core and 106 turns, operating in limited geometry configuration. Different system noise sources are considered, and a study of the SNR is also included. Finally, some initial Schumann resonance measurements are presented in order to validate the performance of the measurement station, including 1 h length spectra, daily variations of resonance amplitudes and frequencies for the different seasons, and a 3 day spectrogram.

  16. Low frequency electrostatic and electromagnetic modes in nonuniform cold quantum plasmas

    SciTech Connect

    Saleem, H.; Ahmad, Ali; Khan, S. A.

    2008-01-15

    The low frequency electrostatic and electromagnetic linear modes in a nonuniform cold quantum electron-ion plasma are studied. The effect of stationary dust on an electrostatic mode is also investigated. The quantum corrections in the linear dispersion relations of a cold dense plasma are presented with possible applications.

  17. BIOLOGICAL INFLUENCES OF LOW-FREQUENCY SINUSOIDAL ELECTROMAGNETIC SIGNALS ALONE AND SUPERIMPOSED ON RF CARRIER WAVES

    EPA Science Inventory

    The report describes in a historical context the experiments that have been performed to examine the biological responses caused by exposure to low frequency electromagnetic radiation directly or as modulation of RF carrier waves. A detailed review is provided of the independentl...

  18. Fetal exposure to low frequency electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Cech, R.; Leitgeb, N.; Pediaditis, M.

    2007-02-01

    To investigate the interaction of low frequency electric and magnetic fields with pregnant women and in particular with the fetus, an anatomical voxel model of an 89 kg woman at week 30 of pregnancy was developed. Intracorporal electric current density distributions due to exposure to homogeneous 50 Hz electric and magnetic fields were calculated and results were compared with basic restrictions recommended by ICNIRP guidelines. It could be shown that the basic restriction is met within the central nervous system (CNS) of the mother at exposure to reference level of either electric or magnetic fields. However, within the fetus the basic restriction is considerably exceeded. Revision of reference levels might be necessary.

  19. Low frequency electromagnetic oscillations in dense degenerate electron-positron pair plasma, with and without ions

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Ayub, M. K.; Ahmad, Ali

    2012-10-01

    Quantum plasma oscillations are studied in a strongly magnetized, ultra-dense plasma with degenerate electrons and positrons. The dispersive role of electron and positron quantum effects on low frequency (in comparison to electron cyclotron frequency) shear electromagnetic wave is investigated by employing hydrodynamic formulation. In the presence of ions, the density balance changes, and the electromagnetic wave (with frequency lower than the ion cyclotron frequency) is shown to couple with electrostatic ion mode under certain conditions. For such low frequency waves, it is also seen that the contribution of electron and positron degeneracy pressure is dominant as compared to their diffraction effects. The results are analyzed numerically for illustrative purpose pointing out their relevance to the dense laboratory (e.g., super-intense laser-dense matter interactions) and astrophysical plasmas.

  20. Low frequency electromagnetic oscillations in dense degenerate electron-positron pair plasma, with and without ions

    SciTech Connect

    Khan, S. A.; Ayub, M. K.; Ahmad, Ali

    2012-10-15

    Quantum plasma oscillations are studied in a strongly magnetized, ultra-dense plasma with degenerate electrons and positrons. The dispersive role of electron and positron quantum effects on low frequency (in comparison to electron cyclotron frequency) shear electromagnetic wave is investigated by employing hydrodynamic formulation. In the presence of ions, the density balance changes, and the electromagnetic wave (with frequency lower than the ion cyclotron frequency) is shown to couple with electrostatic ion mode under certain conditions. For such low frequency waves, it is also seen that the contribution of electron and positron degeneracy pressure is dominant as compared to their diffraction effects. The results are analyzed numerically for illustrative purpose pointing out their relevance to the dense laboratory (e.g., super-intense laser-dense matter interactions) and astrophysical plasmas.

  1. An evaluation of parallelization strategies for low-frequency electromagnetic induction simulators using staggered grid discretizations

    NASA Astrophysics Data System (ADS)

    Weiss, C. J.; Schultz, A.

    2011-12-01

    The high computational cost of the forward solution for modeling low-frequency electromagnetic induction phenomena is one of the primary impediments against broad-scale adoption by the geoscience community of exploration techniques, such as magnetotellurics and geomagnetic depth sounding, that rely on fast and cheap forward solutions to make tractable the inverse problem. As geophysical observables, electromagnetic fields are direct indicators of Earth's electrical conductivity - a physical property independent of (but in some cases correlative with) seismic wavespeed. Electrical conductivity is known to be a function of Earth's physiochemical state and temperature, and to be especially sensitive to the presence of fluids, melts and volatiles. Hence, electromagnetic methods offer a critical and independent constraint on our understanding of Earth's interior processes. Existing methods for parallelization of time-harmonic electromagnetic simulators, as applied to geophysics, have relied heavily on a combination of strategies: coarse-grained decompositions of the model domain; and/or, a high-order functional decomposition across spectral components, which in turn can be domain-decomposed themselves. Hence, in terms of scaling, both approaches are ultimately limited by the growing communication cost as the granularity of the forward problem increases. In this presentation we examine alternate parallelization strategies based on OpenMP shared-memory parallelization and CUDA-based GPU parallelization. As a test case, we use two different numerical simulation packages, each based on a staggered Cartesian grid: FDM3D (Weiss, 2006) which solves the curl-curl equation directly in terms of the scattered electric field (available under the LGPL at www.openem.org); and APHID, the A-Phi Decomposition based on mixed vector and scalar potentials, in which the curl-curl operator is replaced operationally by the vector Laplacian. We describe progress made in modifying the code to

  2. Quantification of Low Frequency Magnetic Fields Generated by Household Appliances

    NASA Astrophysics Data System (ADS)

    Tanaka, Kenji; Mizuno, Yukio; Naito, Katsuhiko

    Resultant low frequency magnetic field generated was measured as a function of distance from them over broadband range (40-800Hz) and harmonic range (100-800Hz) on eleven kinds and more than two hundred recent household appliances in total. The relationship between magnetic filed measured and the power consumption of household appliances was also examined. As a result, it is verified that magnetic field from appliances is drastically reduced as the distance goes. And, any clear dependence of what on the power consumption of appliances is not recognized. Furthermore, from harmonic component analysis by using FFT for current flowing in appliances, it is assumed that relatively large amount of harmonic components with odd numbers is contained in the magnetic field.

  3. A theoretical study of hot plasma spheroids in the presence of low-frequency electromagnetic waves

    NASA Astrophysics Data System (ADS)

    Ahmadizadeh, Y.; Jazi, B.; Barjesteh, S.

    2016-07-01

    While taking into account thermal motion of electrons, scattering of electromagnetic waves with low frequency from hot plasma spheroids is investigated. In this theoretical research, ions are heavy to respond to electromagnetic fluctuations. The solution of scalar wave equation in spheroidal coordinates for electric potential inside the plasma spheroids are obtained. The variations of resonance frequencies vs. Debye length are studied and consistency between the obtained results in this paper and the results for the well-known plasma objects such as plasma column and spherical plasma have been proved.

  4. Low frequency electromagnetic signals in the atmosphere caused by geodynamics and solar activity

    NASA Astrophysics Data System (ADS)

    Novik, Oleg; Ruzhin, Yuri; Ershov, Sergey; Volgin, Max; Smirnov, Fedor

    Due to the composed structure of the medium and large portions of energy transferred, a seismic excitation in the oceanic or continental lithosphere disturbs all types of geophysical fields. To investigate the problem of electromagnetic (EM) forcing on the atmosphere from the seismically activated lithosphere, we have formulated two mathematical models of interaction of fields of different physical nature resulting in arising of the low-frequency (from 0.1 to 10 Hz by amplitude of a few hundreds of pT) EM signals in the atmosphere. First we have considered the EM field generation in the moving oceanic lithosphere and then in the moving continental one. For both cases, the main physical principles and geological data were applied for formulation of the model and characteristics of the computed signals of different nature agree with measurements of other authors. On the basis of the 2D model of the seismo-hydro-EM-temperature interaction in a lithosphere-Ocean-atmosphere domain, a block-scheme of a multisensory vertically distributed (from a seafloor up to the ionosphere) tsunami precursors’ detection system is described. On the basis of the 3D model of the seismo-EM interaction in a lithosphere-atmosphere domain, we explain effect of location of the future seismic epicenter area (obtained by Prof. Kopytenko, Yu. A. from Inst. IZMIRAN of Russian Acad. Sci. and co-authors) as the result of the magnetic field measurements in the atmosphere near the earth’s surface. We believe that the biosphere effects of forcing on the atmosphere may not be ignored. We formulate the result of our measurements with the system of micro-voltmeters: low-frequency EM disturbances of the atmosphere caused by solar activity (namely, geomagnetic storms with the geomagnetic index values K = 5 and K = 6), are decreasing temporarily the coherence of oscillations of the electric potentials of different points on the surface of a head, i.e. the coherence of the human brain EM processes. We are

  5. A Review of Low Frequency Electromagnetic Wave Phenomena Related to Tropospheric-Ionospheric Coupling Mechanisms

    NASA Technical Reports Server (NTRS)

    Simoes, Fernando; Pfaff, Robert; Berthelier, Jean-Jacques; Klenzing, Jeffrey

    2012-01-01

    Investigation of coupling mechanisms between the troposphere and the ionosphere requires a multidisciplinary approach involving several branches of atmospheric sciences, from meteorology, atmospheric chemistry, and fulminology to aeronomy, plasma physics, and space weather. In this work, we review low frequency electromagnetic wave propagation in the Earth-ionosphere cavity from a troposphere-ionosphere coupling perspective. We discuss electromagnetic wave generation, propagation, and resonance phenomena, considering atmospheric, ionospheric and magnetospheric sources, from lightning and transient luminous events at low altitude to Alfven waves and particle precipitation related to solar and magnetospheric processes. We review in situ ionospheric processes as well as surface and space weather phenomena that drive troposphere-ionosphere dynamics. Effects of aerosols, water vapor distribution, thermodynamic parameters, and cloud charge separation and electrification processes on atmospheric electricity and electromagnetic waves are reviewed. We also briefly revisit ionospheric irregularities such as spread-F and explosive spread-F, sporadic-E, traveling ionospheric disturbances, Trimpi effect, and hiss and plasma turbulence. Regarding the role of the lower boundary of the cavity, we review transient surface phenomena, including seismic activity, earthquakes, volcanic processes and dust electrification. The role of surface and atmospheric gravity waves in ionospheric dynamics is also briefly addressed. We summarize analytical and numerical tools and techniques to model low frequency electromagnetic wave propagation and solving inverse problems and summarize in a final section a few challenging subjects that are important for a better understanding of tropospheric-ionospheric coupling mechanisms.

  6. WFC3 Low-Frequency Flat Field Corrections

    NASA Astrophysics Data System (ADS)

    Mack, Jennifer

    2010-07-01

    Multiple dithered observations of the globular cluster Omega Centauri (NGC 5139) have been used to measure inflight corrections to the WFC3 UVIS and IR ground flat fields for a subset of key filters. To obtain an adequate characterization of the flat field over the detector field of view (FOV), 9 pointings were obtained for each filter using a 3x3 box dither pattern with steps of approximately 25% of the FOV. By measuring relative changes in the brightness of a star over different portions of the detector, low-frequency spatial variations in the detector response (L-flats) have been used to correct the flat fields obtained during ground testing. The broad wavelength range covered by these observations allow an interpolation of the L-flat correction for the remaining wide, medium and narrow-band filters, assuming a simple linear dependence with pivot wavelength. Initial results indicate that the required L-flat corrections are ±1.5% (standard deviation) in the IR and ±1.0% in the UVIS, and that the photometric response for a given star after applying the L-flat correction is now stable to better than 1% for any position in the field of view. Followup observations of the same field at multiple orientations will be used to verify the accuracy of the L-flat solutions and to quantify any temporal changes in the detector response while in orbit.

  7. Low-frequency losses at high fields in multifilamentary superconductors

    SciTech Connect

    Zaleski, A.J.; Orlando, T.P.; Zieba, A.; Schwartz, B.B.; Foner, S.

    1984-12-01

    Low-frequency (approx.1 Hz) ac loss measurements were made at applied fields up to 20 T with field modulation amplitudes of up to 1 T. Results for the alternative in situ and powder metallurgy (P/M) processed Nb/sub 3/Sn and Nb--Al wires are presented for single-strand and multistrand geometries. Loss measurements for commercial continuous-fiber Nb/sub 3/Sn wires manufactured by Holec and Supercon also are presented and show that the effective fiber size determined by these ac-loss measurements corresponds to that measured optically. The effective fiber size for alternative processed wires was intermediate between the wire size and the fiber size, and the losses (and effective fiber size) were reduced by twisting. Multistrand geometries showed further reductions in losses. The smallest effective fiber size at high field was measured for P/M processed Nb--Al. The losses were fully hysteretic and the ac losses were used to determine the critical-current density at low fields where it was difficult to measure directly.

  8. The oblique behavior of low-frequency electromagnetic waves excited by newborn cometary ions

    NASA Technical Reports Server (NTRS)

    Brinca, Armando L.; Tsurutani, Bruce T.

    1989-01-01

    The free energy in oxygen or hydrogen ions freshly created in the solar wind stimulates low-frequency electromagnetic waves whose growth does not always maximize at parallel propagation. Exploration of the wave vector plane discloses the frequent occurrence of islets of oblique growth unconnected to the unstable parallel modes. Contour plots of the growth rate, real frequency, polarization, and magnetic compression characterize the oblique wave behavior for large values of the initial pitch angle of the cometary particles. Although wave-particle (Landau and cyclotron) resonances feed most of the surveyed oblique instabilities, some are seemingly fluidlike. The results, obtained from the numerical solution of the kinetic dispersion and wave equations, imply that newborn ions can easily excite significant oblique hydromagnetic wave activity. Cometary environments provide the adopted plasma model, but the study is helpful in the interpretation of other low-frequency wave observations in space.

  9. Office worker exposure to extremely low frequency magnetic fields

    SciTech Connect

    Hiebert, D.G.

    1994-05-01

    A study of office worker exposure to extremely low frequency magnetic fields (ELF MF) was conducted at Los Alamos National Laboratory. The main purpose of this study was to quantitatively assess ELF MF exposures. A secondary objective was to determine whether or not exposures to ELF MF can be reduced by implementing administrative controls and educating workers on the sources of such fields. EMDEX dosimeters were used to determine full shift personal exposures for 12 volunteers from two personnel sections and one training section. In addition, using the EMDEX meter in survey mode, office area evaluations were conducted. Administrative controls and training were implemented in an attempt to reduce exposures. Post control monitoring was conducted to determine if a reduction in ELF MF occurred among the workers. On average, baseline office worker exposures to ELF MF were 2.3 mG, ranging from 0.6 to 9.7 mG. The post control exposures averaged 1.1 mG with a range from 0.5 to 2.2 mG. A reduction of 53% overall was seen after implementation of administrative controls and training. The office area survey indicated that many sources of ELF MF influence exposure and that magnetic field strengths vary not only from one type of equipment to another, but also vary between two similar pieces of equipment.

  10. Extremely low frequency fields and cancer: laboratory studies

    SciTech Connect

    Anderson, Larry E.)

    1998-10-01

    There is now convincing evidence from a large number of laboratories, that exposure to extremely low frequency (ELF) magnetic and electric fields produces biological responses in animals. However, no animal studies clearly demonstrate deleterious effects of ELF fields, although several are suggestive of potential health impacts. A major current emphasis in laboratory research is to determine whether or not the reported epidemiological studies that suggest an association between EMF exposure and risk of cancer are supported in studies using animal models. Several approaches are outlined in the experimental approach to this question. With specific reference to the radiofrequencies (RF) associated with wireless technology, even less research has been carried out than with ELF. Particularly, in regard to research on carcinogenesis and RF exposure in animals, little is known This section addresses laboratory studies in animals exposed to extremely low-power-frequency EMF, the relevance of which, to RF, is unknown. However, the approaches used with ELF may be useful in guiding laboratory research on the issue of RF exposure and cancer. From the perspective of laboratory animal studies, this paper will discuss studies investigating the potential relationship between ELF magnetic and/or electric field exposure and the risk of cancer.

  11. Oil and gas reservoir exploration based on hyperspectral remote sensing and super-low-frequency electromagnetic detection

    NASA Astrophysics Data System (ADS)

    Qin, Qiming; Zhang, Zili; Chen, Li; Wang, Nan; Zhang, Chengye

    2016-01-01

    This paper proposes a method that combined hyperspectral remote sensing with super-low-frequency (SLF) electromagnetic detection to extract oil and gas reservoir characteristics from surface to underground, for the purpose of determining oil and gas exploration target regions. The study area in Xinjiang Karamay oil-gas field, China, was investigated. First, a Hyperion dataset was used to extract altered minerals (montmorillonite, chlorite, and siderite), which were comparatively verified by field survey and spectral measurement. Second, the SLF electromagnetic datasets were then acquired where the altered minerals were distributed. An inverse distance weighting method was utilized to acquire two-dimensional profiles of the electrical feature distribution of different formations on the subsurface. Finally, existing geological data, field work, and the results derived from Hyperion images and SLF electromagnetic datasets were comprehensively analyzed to confirm the oil and gas exploration target region. The results of both hyperspectral remote sensing and SLF electromagnetic detection had a good consistency with the geological materials in this study. This paper demonstrates that the combination of hyperspectral remote sensing and SLF electromagnetic detection is suitable for the early exploration of oil and gas reservoirs, which is characterized by low exploration costs, large exploration areas, and a high working efficiency.

  12. Prediction of the shielding effectiveness at low frequency in near magnetic field

    NASA Astrophysics Data System (ADS)

    Frikha, Amin; Bensetti, Mohamed; Duval, Fabrice; Lafon, Frédéric; Pichon, Lionel

    2014-04-01

    Equipment used in hybrid or electric vehicles (HEVs) must meet certain requirements. Beyond issues of electro-magnetic compatibility (EMC), it's necessary to assess the risks related to the exposure of the passengers to electromagnetic field inside an HEV. At low frequencies, using the electromagnetic shielding as protection is inefficient. The compliance can be achieved done by defining the harness's architecture or by the use of permeable materials. In this paper, we will focus on the prediction of the shielding effectiveness of materials subjected to a near magnetic field source at low frequency (9 kHz-10 MHz).We will focus our study on two cases. In the first case, we will work on the numerical modeling of an enclosure with and without opening. The result from the model is compared to the measurement's results obtained with a test bench developed in our laboratory. In the second case, the impact of the slot in the enclosure will be studied. An analytical method based on magnetic moments approximation is developed to predict the shielding effectiveness for infinite plane with slot. The results obtained with the latter are compared with the numerical results.

  13. Extremely Low Frequency Magnetic Field Modulates the Level of Neurotransmitters

    PubMed Central

    Chung, Yoon Hee; Lee, Young Joo; Lee, Ho Sung; Chung, Su Jin; Lim, Cheol Hee; Oh, Keon Woong; Sohn, Uy Dong

    2015-01-01

    This study was aimed to observe that extremely low frequency magnetic field (ELF-MF) may be relevant to changes of major neurotransmitters in rat brain. After the exposure to ELF-MF (60 Hz, 2.0 mT) for 2 or 5 days, we measured the levels of biogenic amines and their metabolites, amino acid neurotransmitters and nitric oxide (NO) in the cortex, striatum, thalamus, cerebellum and hippocampus. The exposure of ELF-MF for 2 or 5 days produced significant differences in norepinephrine and vanillyl mandelic acid in the striatum, thalamus, cerebellum and hippocampus. Significant increases in the levels of serotonin and 5-hydroxyindoleacetic acid were also observed in the striatum, thalamus or hippocampus. ELF-MF significantly increased the concentration of dopamine in the thalamus. ELF-MF tended to increase the levels of amino acid neurotransmitters such as glutamine, glycine and γ -aminobutyric acid in the striatum and thalamus, whereas it decreased the levels in the cortex, cerebellum and hippocampus. ELF-MF significantly increased NO concentration in the striatum, thalamus and hippocampus. The present study has demonstrated that exposure to ELF-MFs may evoke the changes in the levels of biogenic amines, amino acid and NO in the brain although the extent and property vary with the brain areas. However, the mechanisms remain further to be characterized. PMID:25605992

  14. Worldwide extremely low frequency magnetic field sensor network for sprite studies

    NASA Astrophysics Data System (ADS)

    Whitley, Toby; Füllekrug, Martin; Rycroft, Michael; Bennett, Alec; Wyatt, Frank; Elliott, Don; Heinson, Graham; Hitchman, Adrian; Lewis, Andrew; Sefako, Ramotholo; Fourie, Pieter; Dyers, Jaci; Thomson, Alan; Flower, Simon

    2011-08-01

    The first measurements from a new globally distributed extremely low frequency magnetic field sensor network are presented. The recorded data demonstrate that the system observed lightning with continuing currents on a global scale with a timing accuracy of ˜30 μs. The network consists of four state of the art instruments at sites in Scotland, the United States, South Africa and Australia. Each instrument records the two horizontal magnetic field components (Bx and By) with a sampling frequency of 4 kHz. The first results show the typical electromagnetic signature of a transient airglow increase (sprite) above a thunderstorm in southern Europe which is simultaneously imaged with a video camera. A similar electromagnetic signature is recorded from a lightning discharge in central Africa, and it is also attributed to a sprite occurrence. Studies using this global network should advance lightning and sprite research considerably.

  15. Extremely Low Frequency Magnetic Fields Induce Spermatogenic Germ Cell Apoptosis: Possible Mechanism

    PubMed Central

    Lee, Sang-Kon; Park, Sungman; Gimm, Yoon-Myoung; Kim, Yoon-Won

    2014-01-01

    The energy generated by an extremely low frequency electromagnetic field (ELF-EMF) is too weak to directly induce genotoxicity. However, it is reported that an extremely low frequency magnetic field (ELF-MF) is related to DNA strand breakage and apoptosis. The testes that conduct spermatogenesis through a dynamic cellular process involving meiosis and mitosis seem vulnerable to external stress such as heat, MF exposure, and chemical or physical agents. Nevertheless the results regarding adverse effects of ELF-EMF on human or animal reproductive functions are inconclusive. According to the guideline of the International Commission on Non-Ionizing Radiation Protection (ICNIRP; 2010) for limiting exposure to time-varying MF (1 Hz to 100 kHz), overall conclusion of epidemiologic studies has not consistently shown an association between human adverse reproductive outcomes and maternal or paternal exposure to low frequency fields. In animal studies there is no compelling evidence of causal relationship between prenatal development and ELF-MF exposure. However there is increasing evidence that EL-EMF exposure is involved with germ cell apoptosis in testes. Biophysical mechanism by which ELF-MF induces germ cell apoptosis has not been established. This review proposes the possible mechanism of germ cell apoptosis in testes induced by ELF-MF. PMID:25025060

  16. Study of electromagnetic vibration energy harvesting with free/impact motion for low frequency operation

    NASA Astrophysics Data System (ADS)

    Haroun, Ahmed; Yamada, Ichiro; Warisawa, Shin`ichi

    2015-08-01

    This paper presents study of an electromagnetic vibration energy harvesting configuration that can work effectively at low frequencies. Unlike the conventional form of vibration energy harvesters in which the mass is directly connected to a vibrating frame with spring suspension, in the proposed configuration a permanent magnet mass is allowed to move freely within a certain distance inside a frame-carrying coil and make impacts with spring end stops. The free motion distance allows matching lower vibration frequencies with an increase in the relative amplitude at resonance. Hence, significant power could be generated at low frequencies. A nonlinear mathematical model including impact and electromagnetic induction is derived. Study of the dynamic behaviour and investigation of the system performance is carried out with the aid of case study simulation. The proposed harvester shows a unique dynamic behaviour in which different ways of response of the internal relative oscillation appear over the range of input frequencies. A mathematical condition for the response type at which the higher relative amplitude appears is derived, followed by an investigation of the system resonant frequency and relative amplitude. The resonant frequency shows a dependency on the free motion distance as well as the utilized mass and spring stiffness. Simulation and experimental comparisons are carried out between the proposed harvester and similar conventional one tuned at the same input frequency. The power generated by the proposed harvesting configuration can reach more than 12 times at 11 Hz in the simulation case and about 10 times at 10 Hz in the experimental case. Simulation comparison also shows that this power magnification increases by matching lower frequencies which emphasize the advantages of the proposed configuration for low frequency operation.

  17. Stanford - USGS Ultra-Low Frequency Electromagnetic Network: Hardware Developments in Magnetometer Calibration and Data Recording

    NASA Astrophysics Data System (ADS)

    Bowden, D. C.; Engelland-Gay, H.; Enright, A.; Gardner, J.; Klemperer, S. L.; McPhee, D. K.; Glen, J. M.

    2010-12-01

    Since 2006 a collaborative effort between Stanford University, the USGS, and UC Berkeley has maintained five ultra-low frequency electromagnetic (UFLEM) stations along the San Andreas Fault system. The standard site is equipped with three orthogonal coil magnetometers and two sets of orthogonal 100m electrode pairs, provides data in the 0.01- 20 Hz bandwidth, and operates alongside a broadband seismometer. We intend to use these data to characterize the generation of subsurface EM signals, and determine whether there exists a correlation to seismic activity or tectonic processes of the region. Our EM data is archived with the collocated seismic data at UC Berkeley’s Northern California Earthquake Data Center (NCEDC) and is available to the public at http://ulfem-data.stanford.edu/. Two new hardware developments in 2010 will provide more reliable calibration of our magnetic recorders, and will improve station reliability while reducing station cost. We have developed a method for calibration of buried magnetic sensor coils. As our strategy for detecting possible EM anomalies related to earthquake processes relies on comparing measured EM signals across multiple sites, it is necessary to confirm that each magnetic sensor at each site responds similarly and accurately. A portable coil placed on the ground surface, in turn above each buried magnetic sensor, generates a time-varying magnetic field of known magnitude at several different known frequencies in the bandwidth of interest. In this way, the health of each sensor can be tested and factory produced response curve verified. Signal generation and power supply for the coil is designed to be cheap (< $100), easily portable, and exactly reproducible between trials to within 95%, but does require an operator visit to each site for the measurements. In the future we intend to modify the portable system to create a winding that can be permanently installed around every magnetic sensor to provide regular calibration by

  18. Stanford - USGS Ultra-Low Frequency Electromagnetic Network: Status Report and Data Availability Via the Web

    NASA Astrophysics Data System (ADS)

    Neumann, D. A.; McPherson, S.; Kappler, K.; Klemperer, S.; Glen, J. M.; McPhee, D. K.

    2008-12-01

    As part of the PBO (Plate Boundary Observatory) mission we have installed three ultra-low frequency electromagnetic (ULF-EM) recording sites in northern California. We hope to use this data to better understand physical processes associated with earthquakes and to find evidence for the generation of subsurface electromagnetic fields, including the presence or absence of pre-seismic transients. Our ULF-EM sites complement two existing sites maintained by UC Berkeley at Parkfield and Hollister in central California and a growing California network of magnetometers managed by Quakefinder, Inc. (www.quakefinder.com). We installed our first station in 2005 close to the Stanford University campus. In 2006, we completed two additional installations in the North Bay and East Bay. Each site has three orthogonal magnetometers and duplicate sets of orthogonal horizontal electrode pairs, recording signals from 0.001 to 20 Hz, collocated with an existing broadband seismometer. All data are archived at UC Berkeley's Northern California Earthquake Data Center (NCEDC). We have created a website, http://ulfem-data.stanford.edu/, that collects and stores ULF-EM data from our stations. Users can request data plots on the website and view them immediately or after a few minutes, depending on whether or not the information is more than a year old. Currently we can display time-series data on demand from all our stations, with data available 30 minutes after acquisition. In the near-future we will be able to provide spectrograms on demand, and ultimately a range of user-selected transfer functions computed for chosen time periods. 2009 efforts will focus on expanding our network of ULF-EM stations, by installing the first of several new stations, and upgrading primary remote reference stations. Each site will include state-of-the-art magnetic and electric sensors sensitive from 0.001-100 Hz, and data will be fed to the NCEDC. The first phase of this work, which has already begun

  19. Anomaly Identification from Super-Low Frequency Electromagnetic Data for the Coalbed Methane Detection

    NASA Astrophysics Data System (ADS)

    Zhao, S. S.; Wang, N.; Hui, J.; Ye, X.; Qin, Q.

    2016-06-01

    Natural source Super Low Frequency(SLF) electromagnetic prospecting methods have become an increasingly promising way in the resource detection. The capacity estimation of the reservoirs is of great importance to evaluate their exploitation potency. In this paper, we built a signal-estimate model for SLF electromagnetic signal and processed the monitored data with adaptive filter. The non-normal distribution test showed that the distribution of the signal was obviously different from Gaussian probability distribution, and Class B instantaneous amplitude probability model can well describe the statistical properties of SLF electromagnetic data. The Class B model parameter estimation is very complicated because its kernel function is confluent hypergeometric function. The parameters of the model were estimated based on property spectral function using Least Square Gradient Method(LSGM). The simulation of this estimation method was carried out, and the results of simulation demonstrated that the LGSM estimation method can reflect important information of the Class B signal model, of which the Gaussian component was considered to be the systematic noise and random noise, and the Intermediate Event Component was considered to be the background ground and human activity noise. Then the observation data was processed using adaptive noise cancellation filter. With the noise components subtracted out adaptively, the remaining part is the signal of interest, i.e., the anomaly information. It was considered to be relevant to the reservoir position of the coalbed methane stratum.

  20. Characterizing potential earthquake signals on the Stanford-USGS ultra-low frequency electromagnetic (ULFEM) array

    NASA Astrophysics Data System (ADS)

    Christman, L.; Connor, D.; McPhee, D. K.; Glen, J. M.; Klemperer, S. L.

    2012-12-01

    Anomalous ultra-low frequency (0.01-10 Hz) electromagnetic signals have been reported prior to and during M ≥ 6.0 earthquakes in a variety of places around the world, most notably prior to the 1989 Ms 7.1 Loma Prieta earthquake in California. Stanford University, in conjunction with the USGS and UC Berkeley, has maintained five ULFEM recording stations along the San Andreas Fault. We are searching our ULFEM data for anomalous signals before earthquakes. Previous reports of possible ULFEM precursors, or their absence following exhaustive searches of available data, define a crude distance-magnitude relationship with larger-closer earthquakes capable of producing detectable precursors. No earthquakes exceeding this distance-magnitude relationship have yet occurred within 500 km of our network; therefore our study is as yet mostly an attempt to develop appropriate methodologies. We examined 40 Hz EM data around the arrival time of the largest/closest earthquakes to our array, focusing on co-shaking signals and pulsations as have been described preceding the 10/31/2007 Alum Rock M 5.4 earthquake. For the three stations in the Bay Area, our search included data from when the BART electric train was operating and also dormant. We observed co-shaking signals at stations between 10-40 km from the epicenters of earthquakes with varying magnitudes (M 2.6-M 6.0). A search of data in the week prior to the Alum Rock earthquake on our closest station (41 km from the epicenter) has thus far identified pulsations of similar duration and polarity as those identified by other workers on a station 2 km from the epicenter (~9 km from the hypocenter). The amplitudes of the majority of the pulsations identified in this study are within several standard deviations of background noise levels and are otherwise not distinguishable from other signals of similar frequency in the time series. To establish and maintain the integrity of the data recorded from the stations in our array, a

  1. Low frequency electromagnetic waves as a supplemental energy source to sustain microbial growth?

    NASA Astrophysics Data System (ADS)

    Gusev, Victor A.; Schulze-Makuch, Dirk

    2005-03-01

    Microbial populations in tetra-distilled water collapsed when cultured in a permalloy chamber shielding the populations from the sun's and earth's electromagnetic field, but thrived when cultured in an ordinary thermostat open to the electromagnetic field. Theoretically, protons in liquid water can be excited at their natural resonance frequencies through Langmuir oscillations and obtain enough kinetic energy to charge the transmembrane potential of a cell. Microbes may be capable of converting this energy into chemical energy to supplement their energy needs.

  2. Influence of multiple ion species on low-frequency electromagnetic wave instabilities. [in solar wind

    NASA Technical Reports Server (NTRS)

    Brinca, Armando L.; Tsurutani, Bruce T.

    1989-01-01

    The effect of multiple (singly ionized) coexisting newborn ion species on the stability of low-frequency electromagnetic waves was investigated using a plasma model in which solar wind magnetoplasma is made up of isotropic Maxwellian electron and proton populations with a common number density of 4.95/cu cm and temperatures equal to 17.2 eV and 6.9 eV, respectively. It is shown that the effect of multiple ions on wave growth, for given background magnetoplasma conditions and relative densities, depends not only on their mass but also on the physical nature of the wave modes. If the ion masses are disparate, each one of the coexisting ion beams tends to stimulate instabilities without undue influence from the other species. If the masses of newborn ions are similar, they can strongly catalyze wave growth of fluidlike nonresonant modes, but bring about weak growth enhancements in cyclotron resonant instabilities.

  3. Electromagnetic sounding of the Kola Peninsula with a powerful extremely low frequency source

    NASA Astrophysics Data System (ADS)

    Velikhov, E. P.; Grigoriev, V. F.; Zhdanov, M. S.; Korotayev, S. M.; Kruglyakov, M. S.; Orekhova, D. A.; Popova, I. V.; Tereschenko, E. D.; Schors, Y. G.

    2011-05-01

    Experiment on electromagnetic sounding of the Kola Peninsula using unique mobile measuring complex of the low-frequency sounding was conducted, allowing to investigate a geoelectric section with a depth of several kilometers on distances up to 100 km from the stationary transmitting aerial. Excess on the order of amplitudes of the vertical component above the horizontal at all frequencies of sounding was registered in a number of points of measurements. This feature managed to be explained quantitatively by circulation of current on regional faults with the closure of current through the sea—before unknown galvanic coastal effect. Interpretation of the results of modeling and neural network solving of inverse problem essentially specifies the fault tectonics of the central part of the Kola Peninsula. Anomaly remote from the observation profile was found out—local pinch of a crustal conductive layer consisting of graphitized rocks and associated with the zone of overthrust.

  4. S ystematic Characterization Of Low Frequency Electric And Magnetic Field Data Applicable To Solar O rbiter

    NASA Astrophysics Data System (ADS)

    Bergman, J. E. S.; Carozzi, T. D.

    2007-01-01

    We present a systematic and physically motivated characterization of incoherent or coherent electric and magnetic fields, as measured for instance by the low frequency receiver on-board the Solar Orbiter spacecraft. The characterization utilizes the 36 auto/cross correla- tions of the 3 + 3 complex Cartesian components of the electric and magnetic fields; hence, they are second order in the field strengths and so have physical dimension energy density. Although such 6 × 6 correlation matrices have been successfully employed on previous space missions, they are not physical quantities; because they are not manifestly space-time tensors. In this paper we propose a systematic representation of the 36 degrees-of- freedom of partially coherent electromagnetic fields as a set of manifestly covariant space-time tensors, which we call the Canonical Electromagnetic Observables (CEO). As an example, we apply this formalism to analyze real data from a chorus emission in the mid-latitude magnetosphere, as registered by the STAFF-SA instrument on board the Cluster-II spacecraft. We find that the CEO analysis increases the amount of information that can be extracted from the STAFF-SA dataset; for instance, the reactive energy flux density, which is one of the CEO parameters, identifies the source region of electromagnetic emissions more directly than the active energy (Poynting) flux density alone.

  5. Dielectric behavior of some ferrofluids in low-frequency fields.

    PubMed

    Malaescu, I; Marin, C N

    2002-07-01

    The dielectric behavior of a ferrofluid with magnetite particles dispersed in kerosene was analyzed taking into account the Schwarz model, concerning the low-frequency dielectric behavior in systems consisting of colloidal particles suspended in electrolytes. For this reason, the complex dielectric permittivity and dielectric loss factor, in the frequency range of 10 Hz-500 kHz, at different temperatures between 20 degrees C and 100 degrees C were measured. Based on these experimental results, the experimental dependencies on both temperature of the relaxation time and activation energy of the relaxation process were analyzed. The obtained results show that the Schwarz model can be applied, in order to explain the low-frequency dielectric behavior of a ferrofluid with magnetite particles in kerosene, if the change of counterion concentration at the surface of colloidal particles is taken into account. Consequently, it is shown that the dielectric spectroscopy can be used in order to analyze the presence of particle agglomerations within ferrofluids. PMID:16290703

  6. Low frequency electromagnetic signals from underground explosions: On-site inspections research progress report

    SciTech Connect

    Sweeney, J.J.

    1995-07-21

    We are investigating the characteristics of extremely low frequency (ELF) electromagnetic pulse (EMW) phenomena from underground nuclear and chemical explosions and from surface chemical explosions as they may be applied in an On-Site Inspection (OSI) context under a Comprehensive Test-Ban Treaty (CTBT). The principal application of these phenomena is for discrimination among underground chemical explosions, underground nuclear explosions, and earthquakes. Underground chemical and nuclear explosions both generate low-frequency EMP signals (about 1 Hz) that are observable within several kilometers of ground zero. During this fiscal year we have been gathering data from explosions of opportunity to see if ELF EMP signals are observable from large ripple-fired blasts and from smaller dedicated explosions such as those occurring at the NTS. In addition, we are continuing to review data from the Henderson Mine deployment that took place during FY94 and data from previous underground nuclear tests including Hunter`s Trophy and past underground nuclear tests have been analyzed and we here make estimates of the properties of the EMP ftom underground nuclear ard chemical explosions, including detectability, dependence on yield, and dependence on distance from the source. Data from the Henderson Mine provide information about detection of EMP from typical moderate size underground chemical explosions in hard rock and problems related to detection of EMP in a mine environment located at high elevations. Data from the Carlin Mine site provide information about EMP from surface ripple-fired chemical explosions and detection in an open-pit mine environment. Data from the Kuchen experiment at NTS provide additional data about small underground chemical explosions in a setting similar to that for underground nuclear tests at the NTS.

  7. Electromagnetic Fields

    MedlinePlus

    ... cancer. Some people worry that wireless and cellular phones cause cancer. They give off radio-frequency energy (RF), a form of electromagnetic radiation. Scientists need to do more research on this ...

  8. Low frequency electromagnetic waves as a supplemental energy source to sustain microbial growth?

    PubMed

    Gusev, Victor A; Schulze-Makuch, Dirk

    2005-03-01

    Microbial populations in tetra-distilled water collapsed when cultured in a permalloy chamber shielding the populations from the sun's and earth's electromagnetic field, but thrived when cultured in an ordinary thermostat open to the electromagnetic field. Theoretically, protons in liquid water can be excited at their natural resonance frequencies through Langmuir oscillations and obtain enough kinetic energy to charge the transmembrane potential of a cell. Microbes may be capable of converting this energy into chemical energy to supplement their energy needs. PMID:15700175

  9. Assessing the value of multi-receiver low-frequency electromagnetic-induction (EMI) measurement for assessing variation in soil moisture content in field experiments with winter wheat (Triticum aestivum)

    NASA Astrophysics Data System (ADS)

    Shanahan, Peter; Binley, Andrew; Dodd, Ian; Whalley, Richard; Watts, Chris; Ashton, Rhys; Ober, Eric

    2014-05-01

    In large plant breeding field trials with multiple genotypes, measuring soil water status (an indicator of crop water uptake) by conventional techniques (e.g. core extraction and penetration resistance) is limited by the cost and effort needed to achieve sufficient replication to apply robust statistical analysis. Geophysical methods may provide a more cost-effective means of more assessing valuable information about soil water status for such studies. We present here results from a field experiment using geophysical techniques for remote mapping of soil water content on sandy loam and silt loam soils in spring/summer 2013 in the UK. The aim of the study was to assess electromagnetic-induction (EMI) conductivity measurements for sensitivity to variations in shallow soil electrical properties and the spatial and temporal mapping of soil water. The CMD Mini-Explorer (GF Instruments) operates with three receiver coils at fixed distances from a transmitter coil (0.32 m, 0.71 m, 1.2 m). Measurement of magnetic field quadrature in horizontal coplanar (HC) and vertical coplanar (VC) of the three receiver coils provides six depths of investigation for the given coil spacing cumulative sensitivities. At the two field sites the instrument was applied to measuring apparent electrical conductivity (ECa) below 7.0 x 1.8 m plots consisting of 23 rain fed winter wheat cultivars and bare soil fallow control plots. These plots were sown in March 2013 and organised into a randomised block design. Electrical resistivity tomography (ERT) surveys along 15 m transects were also conducted at the two sites in order to compare EMI measured ECa. Our results show that progressive soil drying at both sites due to crop uptake significantly decreased (p<0.05) soil ECa. The difference in soil ECa as a result of water uptake between cultivars was found to be significant (p<0.05) from one of the coil configurations (coil spacing 1.8m in HC mode), and only at the silty loam site (no significant

  10. Low-frequency electromagnetic measurements as a zero-time discriminant of nuclear and chemical explosions -- OSI research final report

    SciTech Connect

    Sweeney, J. J.

    1996-12-01

    This is the final report on a series of investigations of low frequency (1-40 Hz) electromagnetic signals produced by above ground and underground chemical explosions and their use for confidence building under the Comprehensive Test-Ban Treaty. I conclude that low frequency electromagnetic measurements can be a very powerful tool for zero-time discrimination of chemical and nuclear explosions for yields of 1 Kt or greater, provided that sensors can be placed within 1-2 km of the suspected detonation point in a tamper-proof, low noise environment. The report includes descriptions and analyses of low frequency electromagnetic measurements associated with chemical explosions carried out in a variety of settings (shallow borehole, open pit mining, underground mining). I examine cavity pressure data from the Non-Proliferation Experiment (underground chemical explosion) and present the hypothesis that electromagnetic signals produced by underground chemical explosions could be produced during rock fracturing. I also review low frequency electromagnetic data from underground nuclear explosions acquired by Lawrence Livermore National Laboratory during the late 1980s.

  11. Final report on passive and active low-frequency electromagnetic spectroscopy for airborne detection of underground facilities

    SciTech Connect

    SanFilipo, Bill

    2000-04-01

    The objective of this program is to perform research to advance the science in the application of both passive and active electromagnetic measurement techniques for the detection and spatial delineation of underground facilities. Passive techniques exploit the electromagnetic fields generated by electrical apparatus within the structure, including generators, motors, power distribution circuitry, as well as communications hardware and similar electronics equipment. Frequencies monitored are generally in the audio range (60-20,000 Hz), anticipating strong sources associated with normal AC power (i.e., 50 or 60 Hz and associated harmonics), and low frequency power from broad-band sources such as switching circuits. Measurements are made using receiver induction coils wired to electronics that digitize and record the voltage induced by the time varying magnetic fields. Active techniques employ electromagnetic field transmitters in the form of AC current carrying loops also in the audio frequency range, and receiving coils that measure the resultant time varying magnetic fields. These fields are perturbed from those expected in free space by any conductive material in the vicinity of the coils, including the ground, so that the total measured field is comprised of the primary free-space component and the secondary scattered component. The latter can be further delineated into an average background field (uniform conductive half-space earth) and anomalous field associated with heterogeneous zones in the earth, including both highly conductive objects such as metallic structures as well as highly resistive structures such as empty voids corresponding to rooms or tunnels. Work performed during Phase I included the development of the prototype GEM-2H instrumentation, collection of data at several test sites in the passive mode and a single site in the active mode, development of processing and interpretation software. The technical objectives of Phase II were to: (1

  12. ELF electric and magnetic fields: Pacific Northwest Laboratory studies. [Extremely Low Frequency (ELF)

    SciTech Connect

    Anderson, L.E.

    1992-06-01

    Studies have been conducted at Battelle, Pacific Northwest Laboratory, to examine extremely-low-frequency (ELF) electromagnetic fields for possible biological effects in animals. Three areas of investigation are reported here: (1) studies on the nervous system, including behavior and neuroendocrine function, (2) experiments on cancer development in animals, and (3) measurements of currents and electric fields induced in animal models by exposure to external magnetic fields. In behavioral experiments, rats have been shown to be responsive to ELF electric field exposure. Furthermore, experimental data indicate that short-term memory may be affected in albino rats exposed to combined ELF and static magnetic fields. Neuroendocrine studies have been conducted to demonstrate an apparent stress-related response in rats exposed to 60-Hz electric fields. Nighttime pineal melatonin levels have been shown to be significantly depressed in animals exposed to either electric or magnetic fields. A number of animal tumor models are currently under investigation to examine possible relationships between ELF exposure and carcinogenesis. Finally, theoretical and experimental measurements have been performed which form the basis for animals and human exposure comparisons.

  13. Correlated low-frequency electric and magnetic noise along the auroral field lines

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Huff, R. L.; Menietti, J. D.; Burch, J. L.; Winningham, J. D.; Shawhan, S. D.

    1984-01-01

    Dynamics Explorer 1 measurements of intense low-frequency electric and magnetic noise observed at low altitudes over the auroral zone are described. The intensity of both the electric and magnetic fields decreases rapidly with increasing frequency. Most of the energy is at frequencies below the O(+) cyclotron frequency, and some evidence is found for a cutoff or change in spectral slope near that frequency. The magnetic to electric field ratio decreases rapidly with increasing radial distance and also decreases with increasing frequency. The polarization of the electric field in a plane perpendicular to the earth's magnetic field is essentially random. The transverse electric and magnetic fields are closely correlated, with the average Poynting flux directed toward the earth. The total electromagnetic power flow associated with the noise is substantial. Two general models are discussed to interpret these observations, one based on static electric and magnetic fields imbedded in the ionosphere and the other based on Alfven waves propagating along the auroral field lines.

  14. Obliquely propagating low frequency electromagnetic shock waves in two dimensional quantum magnetoplasmas

    SciTech Connect

    Masood, W.

    2009-04-15

    Linear and nonlinear propagation characteristics of low frequency magnetoacoustic waves in quantum magnetoplasmas are studied employing the quantum magnetohydrodynamic model. In this regard, a quantum Kadomtsev-Petviashvili-Burgers (KPB) equation is derived using the small amplitude expansion method. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. Furthermore, the solution of KPB equation is presented using the tangent hyperbolic (tanh) method. The variation in the fast and slow magnetoacoustic shock profiles with the quantum Bohm potential via increasing number density, obliqueness angle {theta}, magnetic field, and the resistivity are also investigated. It is observed that the aforementioned plasma parameters significantly modify the propagation characteristics of nonlinear magnetoacoustic shock waves in quantum magnetoplasmas. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.

  15. Documentation for a web site to serve ULF-EM (Ultra-Low Frequency Electromagnetic) data to the public

    USGS Publications Warehouse

    Neumann, Danny A.; McPherson, Selwyn; Klemperer, Simon L.; Glen, Jonathan M.G.; McPhee, Darcy K.; Kappler, Karl

    2011-01-01

    The Stanford Ultra-Low Frequency Electromagnetic (ULF-EM) Monitoring Project is recording naturally varying electromagnetic signals adjacent to active earthquake faults, in an attempt to establish whether there is any variation in these signals associated with earthquakes. Our project is collaborative between Stanford University, the U.S. Geological Survey (USGS), and UC Berkeley. Lead scientists are Simon Klemperer (Stanford University), Jonathan Glen (USGS) and Darcy Karakelian McPhee (USGS). Our initial sites are in the San Francisco Bay Area, monitoring different strands of the San Andreas fault system, at Stanford University's Jasper Ridge Biological Preserve (JRSC), Marin Headlands of the Golden Gate National Recreation Area (MHDL), and the UC Berkeley's Russell Reservation Field Station adjacent to Briones Regional Park (BRIB). In addition, we maintain in conjunction with the Berkeley Seismological Laboratory (BSL) two remote reference stations at the Bear Valley Ranch in Parkfield, Calif., (PKD) and the San Andreas Geophysical Observatory at Hollister, Calif., (SAO). Metadata about our site can be found at http://ulfem-data.stanford.edu/info.html. Site descriptions can be found at the BSL at http://seismo.berkeley.edu/, and seismic data can be obtained from the Northern California Earthquake Data Center at http://www.ncedc.org/. The site http://ulfem-data.stanford.edu/ allows access to data from the Stanford-USGS sites JRSC, MHDL and BRIB, as well as UC Berkeley sites PKD and SAO.

  16. Extremely Low Frequency (ELF) communications program: Non-ionizing electromagnetic radiation literature evaluation and assessment, 1986-1987 literature review

    NASA Astrophysics Data System (ADS)

    1987-11-01

    This report deals with the evaluation and assessment of literature concerned with the bioeffects of Extremely Low Frequency Electromagnetic Radiation. The report covers the period from November 1986 to October 1987. The objective of this program is to conduct a thorough and comprehensive review and evaluation, of the published professional literature containing scientific information pertaining to biological effects, including but not limited to human health effects of nonionizing electromagnetic radiation, germane to the Extremely Low Frequency (ELF) Communication Program of the United States Navy. The published professional literature reviewed, evaluated and assessed includes books, research reports, and articles and papers in peer-reviewed journals that discuss and/or describe biological and health effects of nonionizing electromagnetic radiation in the frequency range of 1-300 Hz. In some instances documents discussing effects of frequencies above 300 Hz were also reviewed. The review and evaluation included both domestic and international literature published in English or other foreign languages.

  17. Extremely low-frequency magnetic fields of transformers and possible biological and health effects.

    PubMed

    Sirav, Bahriye; Sezgin, Gaye; Seyhan, Nesrin

    2014-12-01

    Physiological processes in organisms can be influenced by extremely low-frequency (ELF) electromagnetic energy. Biological effect studies have great importance; as well as measurement studies since they provide information on the real exposure situations. In this study, the leakage magnetic fields around a transformer were measured in an apartment building in Küçükçekmece, Istanbul, and the measurement results were evaluated with respect to the international exposure standards. The transformer station was on the bottom floor of a three-floor building. It was found that people living and working in the building were exposed to ELF magnetic fields higher than the threshold magnetic field value of the International Agency for Research on Cancer (IARC). Many people living in this building reported health complaints such as immunological problems of their children. There were child-workers working in the textile factories located in the building. Safe distances or areas for these people should be recommended. Protective measures could be implemented to minimize these exposures. Further residential exposure studies are needed to demonstrate the exposure levels of ELF magnetic fields. Precautions should, therefore, be taken either to reduce leakage or minimize the exposed fields. Shielding techniques should be used to minimize the leakage magnetic fields in such cases. PMID:24131394

  18. Low frequency radio observations of coronal magnetic field

    NASA Astrophysics Data System (ADS)

    Ramesh, R.; Kathiravan, C.

    2012-07-01

    Magnetic fields play an important role in the dynamics as well as the formation of the structures in the solar corona. Despite its fundamental importance, only a few direct measurements of the coronal magnetic field are available. The existing direct estimates using optical/infrared and radio emissions are limited to the inner corona, i.e., r < 1.2 R , where R is the radius of the Sun. In the outer corona beyond r > 3 R , Faraday rotation observations are used to derive the magnetic field. But due to lack of observational techniques, measurements in the range 1.2 R < r > 3 R (middle corona) are not available until now. As the photosphere, chromosphere, and corona are coupled by the solar magnetic field, the magnetic field strength at these distances is generally obtained by mathematical extrapolation of the observed line-of-sight component of the photospheric magnetic field assuming a potential or force-free model. The Indian Institute of Astrophysics has recently commissioned a radio polarimeter (based on inteferometer techniques) for dedicated obervations of the polarized radio emission from the solar corona. The frequency range of observation is 120-30 MHz which corresponds to a radial distance range of about 1.2-1.8 R. Estimates of weak magnetic fields in the 'undisturbed' Sun (non-flaring sunspot active regions, coronal streamers, etc.) obtained from observations with the above instrument will be presented.

  19. Lay understanding of low-frequency electric and magnetic fields.

    PubMed

    Morgan, M G; Florig, H K; Nair, I; Cortés, C; Marsh, K; Pavlosky, K

    1990-01-01

    People do not start with a blank slate when they hear risk-communication messages. All such messages are processed through existing knowledge structures and understanding. Hence, to design effective and reliable risk-communication materials one must understand the state of people's knowledge--correct and incorrect--about an issue. We developed a simple "mental model" of what people minimally need to know to make informed decisions about field-related issues. Then we performed studies to explore how and to what extent respondents of various groups understood physical properties of 60-Hz electric and magnetic fields. Actual knowledge of respondents was then compared with the predicates of the model. Electrical engineering juniors and semi-technical employees of utilities displayed a good command of most of the concepts in the simple model, but little awareness of the limits to their knowledge. Lay respondents correctly knew only a few of the simplest elements of the model, but they displayed a much greater awareness of the limits to their knowledge. Both lay and semi-technical respondents were found to share several misconceptions. On average, they correctly rank-ordered some common field-exposure conditions by field strength, but they could not differentiate between electric and magnetic fields and could not differentiate among field strengths associated with different appliances. Most respondents dramatically underestimated the range of actual field strengths. Many respondents understood that field strength decreases with distance from a source, but they underestimated the rate of decrease. In contrast to X-rays and microwaves, which respondents appeared to think about in rather similar terms, 60-Hz fields were not thought of as being highly similar to any other agent, although the closest parallels were found with ultrasound. Changes in mood, thought, and behavior, and the existence of an "electrical aura," were all seen as plausible results of exposure to a 60-Hz

  20. Measurement of low frequency magnetic fields from digital cellular telephones

    SciTech Connect

    Linde, T.; Mild, K.H.

    1997-05-01

    All previous discussions about possible health effects in connection with the use of digital cellular telephones have been focused on the microwaves. However, the pulsed transmitting mode causes pulsed currents in the phone and the battery pack, which give rise to concomitant magnetic fields. Digital cellular telephones using the GSM (Global System for Mobile Communication) transmit information in bursts of microwaves. This pulsed transmitting mode causes the battery current and currents in the electronics of the apparatus to be pulsed. These pulsed currents produce corresponding pulsed magnetic fields near the phones. A study to determine the magnitude of these fields involved two models of digital telephones. The highest value of the magnetic flux density was 1.8 {micro}T (rms).

  1. Hydraulic continuity and biological effects of low strength very low frequency electromagnetic waves: Case of microbial biofilm growth in water treatment.

    PubMed

    Gérard, Merlin; Noamen, Omri; Evelyne, Gonze; Eric, Valette; Gilles, Cauffet; Marc, Henry

    2015-10-15

    This study aims to elucidate the interactions between water, subjected to electromagnetic waves of very low frequency (VLF) (kHz) with low strength electromagnetic fields (3.5 mT inside the coils), and the development of microbial biofilms in this exposed water. Experimental results demonstrate that in water exposed to VLF electromagnetic waves, the biomass of biofilm is limited if hydraulic continuity is achieved between the electromagnetic generator and the biofilm media. The measured amount of the biofilm's biomass is approximately a factor two lower for exposed biofilm than the non-exposed biofilm. Measurements of electromagnetic fields in the air and simulations exhibit very low intensities of fields (<10 nT and 2 V/m) in the biofilm-exposed region at a distance of 1 m from the electromagnetic generator. Exposure to electric and magnetic fields of the quoted intensities cannot explain thermal and ionizing effects on the biofilm. A variable electrical potential with a magnitude close to 20 mV was detected in the tank in hydraulic continuity with the electromagnetic generator. The application of quantum field theory may help to explain the observed effects in this case. PMID:26150067

  2. Alternative low frequency magnetic field theranostics: recent advances, safety and hazards

    NASA Astrophysics Data System (ADS)

    Golovin, Y.; Klyachko, N.; Majouga, A.; Golovin, D.; Gribanovsky, S.

    2015-11-01

    The paper presents a brief review and comparative analysis of low frequency (nonheating) and radio-frequency electromagnetic nanomedicine technologies. The former are shown to have a considerable advantage over the latter ones: a higher flexibility and penetrating ability, easier to dose and control, easier to localize, as well as safer and less costly. This makes their employment promising for building a new technological platform for low frequency magnetic theranostics with a wider range of options, i.e. possessing a wider multimodality than traditional radio-frequency methods.

  3. Ionization with low-frequency fields in the tunneling regime

    PubMed Central

    Dura, J.; Camus, N.; Thai, A.; Britz, A.; Hemmer, M.; Baudisch, M.; Senftleben, A.; Schröter, C. D.; Ullrich, J.; Moshammer, R.; Biegert, J.

    2013-01-01

    Strong-field ionisation surprises with richness beyond current understanding despite decade long investigations. Ionisation with mid-IR light has promptly revealed unexpected kinetic energy structures that seem related to unanticipated quantum trajectories of the electrons. We measure first 3D momentum distributions in the deep tunneling regime (γ = 0.3) and observe surprising new electron dynamics of near-zero momentum electrons and extremely low momentum structures, below the eV, despite very high quiver energies of 95 eV. Such level of high-precision measurements at only 1 meV above the threshold, despite 5 orders higher ponderomotive energies, has now become possible with a specifically developed ultrafast mid-IR light source in combination with a reaction microscope, thereby permitting a new level of investigations into mid-IR recollision physics. PMID:24043222

  4. Safety of high speed guided ground transportation systems: Potential health effects of low frequency electromagnetic fields due to maglev and other electric rail systems. Final report, October 1991-July 1993

    SciTech Connect

    Creasey, W.A.; Goldberg, R.B.

    1993-08-01

    Table of Contents: Executive Summary; Clinical and Epidemiologic Studies of Railroad Workers and Others Exposed to EMF Associated with Railroad Operation; Dosimetry: Characterization of EMF Exposure of Railroad Workers, Utility Workers, and the General Public; Epidemiologic Studies of Workers and the General Public Exposed to Power Frequency (50 and 60 HZ) Electric and Magnetic Fields; Clinical and Epidemiologic Studies of Human Exposure to Static Magnetic Fields (MRI and Research Facilities); Animal Health Effects and Behavioral Studies; Animal and Cellular Studies on Window' EMF Effects; EMF Guidelines; and Conclusions.

  5. Survey of low-frequency electromagnetic waves stimulated by two coexisting newborn ion species

    NASA Technical Reports Server (NTRS)

    Brinca, Armando L.; Tsurutani, Bruce T.

    1988-01-01

    Parallel electromagnetic instabilities generated by coexisting newborn hydrogen and oxygen ions are studied for different orientations of the interplanetary magnetic field with respect to the solar wind velocity. The wave growth dependence on the densities and temperatures of the newborn species is investigated. The results indicate that in most domains of the Brillouin plane each ion beam can excite resonant instabilities without undue influence from the other newborn ion species. Although comparable resonant instabilities are more efficiently generated by the lighter newborn ions in ion-rich environments, the growth stimulated by the heavier species can withstand large beam density decreases.

  6. High Accuracy Tiny Crack Detection in Metal by Low Frequency Electromagnetic Technique

    NASA Astrophysics Data System (ADS)

    Lou, Weimin; Shen, Changyu; Shentu, Fengying; Li, Guanghai; Chang, Yu; Lu, Xinyuan

    2016-01-01

    A low frequency testing technology based on eddy current technique is proposed for detecting defects in some special equipment surface. A two-dimension model is built to simulate the distribution of low frequency (10 Hz) magnetic flux density nearby the surface of a metal plate. The influence of lift-off effect, coil diameter, crack shape on the measurement are discussed. And the crack measurement sensitivity of 0.6 pm was obtained.

  7. Cellular processes involved in human epidermal cells exposed to extremely low frequency electric fields.

    PubMed

    Collard, J-F; Hinsenkamp, M

    2015-05-01

    We observed on different tissues and organisms a biological response after exposure to pulsed low frequency and low amplitude electric or electromagnetic fields but the precise mechanism of cell response remains unknown. The aim of this publication is to understand, using bioinformatics, the biological relevance of processes involved in the modification of gene expression. The list of genes analyzed was obtained after microarray protocol realized on cultures of human epidermal explants growing on deepidermized human skin exposed to a pulsed low frequency electric field. The directed acyclic graph on a WebGestalt Gene Ontology module shows six categories under the biological process root: "biological regulation", "cellular process", "cell proliferation", "death", "metabolic process" and "response to stimulus". Enriched derived categories are coherent with the type of in vitro culture, the stimulation protocol or with the previous results showing a decrease of cell proliferation and an increase of differentiation. The Kegg module on WebGestalt has highlighted "cell cycle" and "p53 signaling pathway" as significantly involved. The Kegg website brings out interactions between FoxO, MAPK, JNK, p53, p38, PI3K/Akt, Wnt, mTor or NF-KappaB. Some genes expressed by the stimulation are known to have an exclusive function on these pathways. Analyses performed with Pathway Studio linked cell proliferation, cell differentiation, apoptosis, cell cycle, mitosis, cell death etc. with our microarrays results. Medline citation generated by the software and the fold change variation confirms a diminution of the proliferation, activation of the differentiation and a less well-defined role of apoptosis or wound healing. Wnt and DKK functional classes, DKK1, MACF1, ATF3, MME, TXNRD1, and BMP-2 genes proposed in previous publications after a manual analysis are also highlighted with other genes after Pathway Studio automatic procedure. Finally, an analysis conducted on a list of genes

  8. Very-low-frequency and low-frequency electric and magnetic fields associated with electric shuttle bus wireless charging.

    PubMed

    Tell, R A; Kavet, Robert; Bailey, J R; Halliwell, John

    2014-01-01

    Tests conducted to date at the University of Tennessee at Chattanooga (UTC) indicate that wireless charging of the Chattanooga Area Regional Transportation Authority's (CARTA) downtown shuttle bus, currently operating with off-board battery charging technology, offers significant improvements in performance and cost. The system operates at a frequency of 20 kHz and a peak power of 60 kW. Because the system's wireless charging is expected to occur during a nominal 3-min charging period with passengers on-board, the magnetic and electric fields associated with charging were characterised at UTC's Advanced Vehicle Test Facility and compared with established human exposure limits. The two most prominent exposure limits are those published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Institute for Electrical and Electronic Engineers (IEEE). Both organisations include limits for groups who are trained (workers in specific industries) to be aware of electromagnetic environments and their potential hazards, as well as a lower set of limits for the general public, who are assumed to lack such awareness. None of the magnetic or electric fields measured either within or outside the bus during charging exceeded either the ICNIRP or the IEEE exposure limits for the general public. PMID:24043876

  9. Extension to 3-D of the low-frequency electromagnetic plasma simulation models, LDRD Final Report 95-ERD-036

    SciTech Connect

    Hewett, D.W.; DiPeso, G.; Gibbons, M; Lambert, M.; Tung, L.S.

    1997-02-03

    Low-frequency electromagnetic simulation models have a wide range of industrial applications. We have built several models, differentiated by slightly different physics approximations or computational solution methods, that have proven quite useful in a variety of applications. Our models been used to investigate beam plasma interactions in ICF targets, antenna plasma coupling in plasma processing, and magnetic implosion drive in Z-pinch pulsed power generators. The common feature of these models is that they retain inductive effects but implicitly ignore computationally intensive, fully electromagnetic effects. However, the preponderance of our work has been limited to only two dimensions. We have made significant progress modeling low-frequency electromagnetic physics with a new model in 2-D that is now capable of modeling antenna structures in 3-D. Although LLNL`s interest in plasma processing has diminished, we have certainly added to LLNL`s capabilities. Interestingly, we have already found another application, the magnetic behavior of read/write heads in the magnetic storage industry, that can make use of many of the computational methods described here, rewarding us again for maintaining a strong core competency in low-frequency EM plasmas.

  10. Polarization of low-frequency electromagnetic radiation in the lobes of Jupiter's magnetotail

    NASA Technical Reports Server (NTRS)

    Moses, S. L.; Kennel, C. F.; Coroniti, F. V.; Scarf, F. L.; Kurth, W. S.

    1987-01-01

    The plasma wave instruments on the Voyager spacecraft have detected intense electromagnetic radiation within the lobes of Jupiter's magnetic tail down to the lowest frequency of the detector (10 Hz). During a yaw maneuver performed by Voyager 1 in the lobe of the Jovian magnetotail, a modulation appeared in the amplitudes of waves detected in the 10-, 17.8- and 31.1-Hz channels of the plasma wave analyzer, well below the local electron cyclotron frequency of 260 Hz. The lowest amplitudes occurred when the antenna axis was most nearly parallel to the magnetic field. Wave amplitudes in the 56.2-Hz and higher frequency channels remained nearly constant during the maneuver. From the cold-plasma theory of electromagnetic waves, it is concluded that the plasma frequency was between the 56.2- and 31.1-Hz channels where the parallel-polarized component of the spectrum cuts off. This implies a tail-lobe density between 0.000032 and 0.000015/cu cm. The left-hand cutoff frequency would then be below 10 Hz, consistent with either the Z-mode (L, X) or whistlers (R-mode) in the modulated channels.

  11. Noninvasive low-frequency electromagnetic stimulation of the left stellate ganglion reduces myocardial infarction-induced ventricular arrhythmia

    PubMed Central

    Wang, Songyun; Zhou, Xiaoya; Huang, Bing; Wang, Zhuo; Zhou, Liping; Wang, Menglong; Yu, Lilei; Jiang, Hong

    2016-01-01

    Noninvasive magnetic stimulation has been widely used in autonomic disorders in the past few decades, but few studies has been done in cardiac diseases. Recently, studies showed that low-frequency electromagnetic field (LF-EMF) might suppress atrial fibrillation by mediating the cardiac autonomic nervous system. In the present study, the effect of LF-EMF stimulation of left stellate ganglion (LSG) on LSG neural activity and ventricular arrhythmia has been studied in an acute myocardium infarction canine model. It is shown that LF-EMF stimulation leads to a reduction both in the neural activity of LSG and in the incidence of ventricular arrhythmia. The obtained results suggested that inhibition of the LSG neural activity might be the causal of the reduction of ventricular arrhythmia since previous studies have shown that LSG hyperactivity may facilitate the incidence of ventricular arrhythmia. LF-EMF stimulation might be a novel noninvasive substitute for the existing implant device-based electrical stimulation or sympathectomy in the treatment of cardiac disorders. PMID:27470078

  12. [Modulation of Ca(2+)-Dependent Proteiolysis under the Action of Weak Low-Frequency Magnetic Fields].

    PubMed

    Kantserova, N P; Lysenko, L A; Ushakova, N V; Krylov, V V; Nemova, N N

    2015-01-01

    The study aimed to determine the molecular targets of magnetic fields in living objects. Time-dependent effects of weak low-frequency magnetic field tuned to the parametric resonance for calcium ions were studied on model organisms (fish, whelk). The dynamics of Ca(2+)-dependent proteinase activity under the exposure to magnetic fields with given parameters was determined and minimal time of exposure in order to achieve inactivation of these proteinases was find out as well. As hyperactivation of Ca(2+)-dependent proteinases is a basis of degenerative pathology development the therapeutic potential of weak low-frequency magnetic fields enabling to modulate Ca(2+)-dependent proteinase activity is supported. PMID:27125027

  13. Experimental investigation of the start-up phase during direct chill and low frequency electromagnetic casting of 6063 aluminum alloy processes

    NASA Astrophysics Data System (ADS)

    Wang, Xiangjie; Zhang, Haitao; Zhao, Zhihao; Zhu, Qingfeng; Wang, Gaosong; Jiang, Huixue; Cui, Jianzhong

    2010-06-01

    On the basis of conventional hot-top casting and Casting, Refining and Electromagnetic process, a lower frequency electromagnetic field was applied during the conventional hot-top casting process. Nine thermocouples (type K) were introduced into the metal to study the temperature profile in the ingot during the start-up phase of casting process. The experimental results show that under the effect of the low frequency electromagnetic filed, the heat transfer is changed greatly and the film boiling disappears, which could restrain the formation of fine subsurface cracks; the sump is shallow, and the macrostructure of the ingot butt is fine during the start-up phase of direct chill casting process.

  14. Exposure assessment of extremely low frequency electric fields in Tehran, Iran, 2010.

    PubMed

    Nassiri, Parvin; Esmaeilpour, Mohammad Reza Monazzam; Gharachahi, Ehsan; Haghighat, Gholamali; Yunesian, Masoud; Zaredar, Narges

    2013-01-01

    Extremely Low-Frequency (ELF) electric and magnetic fields belonging to the nonionizing electromagnetic radiation spectrum have a frequency of 50 - 60 Hz. All people are exposed to a complex set of electric and magnetic fields that spread throughout the environment. The current study was carried out to assess people's exposure to an ELF electric field in the Tehran metropolitan area in 2010. The measurement of the electronic fields was performed using an HI-3604 power frequency field strength measurement device. A total number of 2,753 measurements were performed. Afterward, the data obtained were transferred to the base map using Arc View Version 3.2 and Arc Map Version 9.3. Finally, an interpolation method was applied to expand the intensity of the electric field to the entire city. Based on the results obtained, the electric field was divided into three parts with various intensities including 0-5 V m, 5-15 V m, and >15 V m. It should be noted that the status of high voltage transmission lines, electric substations, and specific points including schools and hospitals were also marked on the map. Minimum and maximum electric field intensities were measured tantamount to 0.31 V m and 19.80 V m, respectively. In all measurements, the electric field was much less than the amount provided in the ICNIRP Guide. The results revealed that 141 hospitals and 6,905 schools are situated in an area with electric field intensity equal to 0-5 V m, while 15 hospitals and 95 schools are located in zones of 5-15 V m and more than 15 V m. Examining high voltage transmission lines and electric substations in Tehran and its suburbs suggested that the impact of the lines on the background electric field of the city was low. Accordingly, 0.97 km of Tehran located on the city border adjacent to the high voltage transmission lines have an electric field in the range of 5 to 15 V m. The noted range is much lower than the available standards. In summary, it can be concluded that the public

  15. Electromagnetic scattering by a triaxial homogeneous penetrable ellipsoid: Low-frequency derivation and testing of the localized nonlinear approximation

    NASA Astrophysics Data System (ADS)

    Perrusson, G.; Lambert, M.; Lesselier, D.; Charalambopoulos, A.; Dassios, G.

    2000-03-01

    The field resulting from the illumination by a localized time-harmonic low-frequency source (typically a magnetic dipole) of a voluminous lossy dielectric body placed in a lossy dielectric embedding is determined within the framework of the localized nonlinear approximation by means of a low-frequency Rayleigh analysis. It is sketched (1) how one derives a low-frequency series expansion in positive integral powers of (jk), where k is the embedding complex wavenumber, of the depolarization dyad that relates the background electric field to the total electric field inside the body; (2) how this expansion is used to determine the magnetic field resulting outside the body and how the corresponding series expansion of this field, up to the power 5 in (jk), follows once the series expansion of the incident electric field in the body volume is known up to the same power; and (3) how the needed nonzero coefficients of the depolarization dyad (up to the power 3 in (jk)) are obtained, for a general triaxial ellipsoid and after careful reduction for the geometrically degenerate geometries, with the help of the elliptical harmonic theory. Numerical results obtained by this hybrid low-frequency approach illustrate its capability to provide accurate magnetic fields at low computational cost, in particular, in comparison with a general purpose method-of-moments code.

  16. Very low frequency (VLF) measurements and theoretical study of seismo-electromagnetic phenomena

    NASA Astrophysics Data System (ADS)

    Eichelberger, Hans; Schwingenschuh, Konrad; Wolbang, Daniel; Besser, Bruno P.; Rozhnoi, Alexander; Solovieva, Maria; Biagi, Pier Francesco; Stachel, Manfred; Prattes, Gustav; Boudjada, Mohammed Y.; Aydogar, Özer; Zehetleitner, Sigrid; Grill, Claudia; Jernej, Irmgard

    2016-04-01

    In this study we compare amplitude and phase measurements, obtained by our very low frequency (VLF) receiver station, with analytical and numerical investigations of the VLF paths from the transmitter to the receiver. Particular interest is on variations of electrical conductivity profiles related to natural phenomena, e.g. due to earthquakes. Beside the well known seasonal and diurnal influences on the Earth-ionosphere VLF waveguide, the robust detection of an anomalous behavior is a major goal of the VLF station. This operational VLF monitoring system, continuously working since 2009, is complemented with ground based ultra low frequency (ULF) measurements from the South European Geomagnetic Array (SEGMA) multi station magnetometer chain. The VLF measurements enable the remote detection of numerous natural and man made variations, simulation of the transmitter-receiver links further constrain the source area where the waveguide modifications originate, other parameters can be included.

  17. Low-frequency electromagnetic plasma waves at comet P/Grigg-Skjellerup: Overview and spectral characteristics

    NASA Technical Reports Server (NTRS)

    Glassmeier, Karl-Heinz; Neubauer, Fritz M.

    1993-01-01

    Large-amplitude electromagnetic plasma waves are one of the dominant features of the solar wind-comet interaction. Wave characteristics strongly depend on parameters such as the solar wind flow and Alfven velocities and the angle between flow and interplanetary magnetic field as well as the production rate. With respect to the latter the flyby of the spacecraft Giotto at comet P/Griff-Skjellerup provides a unique possibility to study such waves in further detail. Pickup ion-related wave signatures have been observed up to a distance of 600,000 km from the nucleus. Peak spectral power in the spacecraft frame of reference occurs at frequencies mainly somewhat below the water group ion gyrofrequency. From this the waves are determined to be mainly left-hand polarized waves, causing one-sided pitch angle diffusion outbound. The wave activity strongly increases close to the comet; upstream it exhibits a quadratic dependence on the water group pickup ion free energy. Furthermore, a phenomenological study of the wave characteristics provides a unique description of the fine-structure of the interaction region. Indications of steepened magnetosonic waves have been found in the outbound magnetosheath region.

  18. Balloon observations of ultra-low-frequency waves in the electric field above the South Pole

    SciTech Connect

    Liao, B.; Benbrrook, J.R.; Bering E.A. III; Byrne, G.J.; Theall, J.R. )

    1988-01-01

    The physics of ultra-low-frequency waves in the magnetosphere, near the cusp and in the polar cap, is important because this region is one where ultra-low-frequency wave energy from the magnetopause can most easily enter the magnetosphere. During the 1985-1986 South Pole balloon campaign, eight stratospheric balloon payloads were launched from Amundsen-Scott Station, South Geographic Pole, Antarctica, to record data on ultra-low-frequency waves. The payloads were instrumented with three-axis double-probe electric field detectors and X-ray scintillation counters. This paper concentrates on the third flight of this series, which was launched at 2205 universal time on 21 December 1985. Good data were received from the payload until the transmitter failed at 0342 universal time on 22 December. During most of the four hours that the balloon was afloat, an intense ultra-low-frequency wave event was in progress. The electric-field data from this period have been examined in detail and compared with magnetic field data, obtained with ground-based fluxgate and induction magnetometers to determine the characteristics of the waves. After float was reached, the electric-field data in figure 1 show large-amplitude, quasi-periodic fluctuations suggesting the presence of intense ultra-low-frequency wave activity. In conclusion, the electric-field signature observed from flight 3 appears to have been essentially an electrostatic event or possibly a short-wavelength hydromagnetic wave with a varying and interesting polarization character. The authors are continuing the analysis of the data to determine the source of the observed ultra-low-frequency waves.

  19. Inhibition of Angiogenesis Mediated by Extremely Low-Frequency Magnetic Fields (ELF-MFs)

    PubMed Central

    Delle Monache, Simona; Angelucci, Adriano; Sanità, Patrizia; Iorio, Roberto; Bennato, Francesca; Mancini, Fabrizio; Gualtieri, Giancaterino; Colonna, Rosella Cardigno

    2013-01-01

    The formation of new blood vessels is an essential therapeutic target in many diseases such as cancer, ischemic diseases, and chronic inflammation. In this regard, extremely low-frequency (ELF) electromagnetic fields (EMFs) seem able to inhibit vessel growth when used in a specific window of amplitude. To investigate the mechanism of anti-angiogenic action of ELF-EMFs we tested the effect of a sinusoidal magnetic field (MF) of 2 mT intensity and frequency of 50 Hz on endothelial cell models HUVEC and MS-1 measuring cell status and proliferation, motility and tubule formation ability. MS-1 cells when injected in mice determined a rapid tumor-like growth that was significantly reduced in mice inoculated with MF-exposed cells. In particular, histological analysis of tumors derived from mice inoculated with MF-exposed MS-1 cells indicated a reduction of hemangioma size, of blood-filled spaces, and in hemorrhage. In parallel, in vitro proliferation of MS-1 treated with MF was significantly inhibited. We also found that the MF-exposure down-regulated the process of proliferation, migration and formation of tubule-like structures in HUVECs. Using western blotting and immunofluorescence analysis, we collected data about the possible influence of MF on the signalling pathway activated by the vascular endothelial growth factor (VEGF). In particular, MF exposure significantly reduced the expression and activation levels of VEGFR2, suggesting a direct or indirect influence of MF on VEGF receptors placed on cellular membrane. In conclusion MF reduced, in vitro and in vivo, the ability of endothelial cells to form new vessels, most probably affecting VEGF signal transduction pathway that was less responsive to activation. These findings could not only explain the mechanism of anti-angiogenic action exerted by MFs, but also promote the possible development of new therapeutic applications for treatment of those diseases where excessive angiogenesis is involved. PMID:24244477

  20. Comparison of Ground-Penetrating Radar and Low-Frequency Electromagnetic Sounding for Detection and Characterization of Groundwater on Mars

    NASA Technical Reports Server (NTRS)

    Grimm, R. E.

    2003-01-01

    Two orbital, ground-penetrating radars, MARSIS and SHARAD, are scheduled for Mars flight, with detection of groundwater a high priority. While these radars will doubtlessly provide significant new information on the subsurface of Mars, thin films of adsorbed water in the cryosphere will strongly attenuate radar signals and prevent characterization of any true aquifers, if present. Scattering from 10-m scale layering or wavelength-size regolith heterogeneities will also degrade radar performance. Dielectric contrasts are sufficiently small for low-porosity, deep aquifers that groundwater cannot be reliably identified. In contrast, low-frequency (mHz-kHz) soundings are ideally suited to groundwater detection due to their great depths of penetration and the high electrical conductivity (compared to cold, dry rock) of groundwater. A variety of low-frequency methods span likely ranges of mass, volume, and power resources, but all require acquisition at or near the planetary surface. Therefore the current generation of orbital radars will provide useful global reconnaissance for subsequent targeted exploration at low frequency. Introduction: Electromagnetic (EM) methods

  1. Generation of low-frequency electrostatic and electromagnetic waves as nonlinear consequences of beam-plasma interactions

    SciTech Connect

    Umeda, Takayuki

    2008-06-15

    Nonlinear evolution of the electron two-stream instability in a current-carrying plasma is examined by using a two-dimensional electromagnetic particle-in-cell simulation. Formation of electron phase-space holes is observed as an early nonlinear consequence of electron-beam-plasma interactions. Lower-hybrid waves, electrostatic, and electromagnetic whistler mode waves are also excited by different mechanisms during the ensuing nonlinear wave-particle interactions. It is shown by the present computer simulation with a large simulation domain and a long simulation time that these low-frequency waves can disturb the electrostatic equilibrium of electron phase-space holes, suggesting that the lifetime of electron phase-space holes sometimes becomes shorter in a current-carrying plasma.

  2. Low frequency noise characteristics in multilayer WSe2 field effect transistor

    NASA Astrophysics Data System (ADS)

    Cho, In-Tak; Kim, Jong In; Hong, Yoonki; Roh, Jeongkyun; Shin, Hyeonwoo; Baek, Geun Woo; Lee, Changhee; Hong, Byung Hee; Jin, Sung Hun; Lee, Jong-Ho

    2015-01-01

    This paper investigates the low-frequency noise properties of multilayer WSe2 field effect transistors (FETs) in subthreshold, linear, and saturation regime. The measured noise power spectral density of drain current (SID) shows that the low-frequency noise in multilayer WSe2 FET fits well to a 1/fγ power law with γ ˜ 1 in the frequency range of 10 Hz-200 Hz. From the dependence of SID on the drain current, carrier mobility fluctuation is considered as a dominant low frequency noise mechanism from all operation regimes in multilayer WSe2 FET. Extracted Hooge's parameter in this study is within the value of 0.12, comparable to those of the transition metal dichalcogenide FETs in recent reports.

  3. New generalized dispersion relation for low-frequency electromagnetic waves in Hall-magnetohydrodynamic dusty plasmas

    SciTech Connect

    Shukla, Padma Kant; Kourakis, Ioannis; Stenflo, Lennart

    2005-10-31

    A generalized linear theory for electromagnetic waves in a homogeneous dusty magnetoplasma is presented. The waves described are characterized by a frequency which is much smaller (larger) than the electron gyrofrequency (dust plasma and dust gyrofrequencies), and a long wavelength (in comparison with the ion gyroradius and the electron skin depth). The generalized Hall-magnetohydrodynamic (GH-MHD) equations are derived by assuming massive charged dust macroparticles to be immobile, and Fourier transformed to obtain a general dispersion relation. The latter is analyzed to understand the influence of immobile charged dust grains on various electromagnetic wave modes in a magnetized dusty plasma.

  4. Introducing Electromagnetic Field Momentum

    ERIC Educational Resources Information Center

    Hu, Ben Yu-Kuang

    2012-01-01

    I describe an elementary way of introducing electromagnetic field momentum. By considering a system of a long solenoid and line charge, the dependence of the field momentum on the electric and magnetic fields can be deduced. I obtain the electromagnetic angular momentum for a point charge and magnetic monopole pair partially through dimensional…

  5. Formation of osteoclast-like cells is suppressed by low frequency, low intensity electric fields.

    PubMed

    Rubin, J; McLeod, K J; Titus, L; Nanes, M S; Catherwood, B D; Rubin, C T

    1996-01-01

    With use of a solenoid to generate uniform time-varying electric fields, the effect of extremely low frequency electric fields on osteoclast-like cell formation stimulated by 1,25(OH)2D3 was studied in primary murine marrow culture. Recruitment of osteoclast-like cells was assessed by counting multinuclear, tartrate-resistant acid phosphatase positive cells on day 8 of culture. A solenoid was used to impose uniform time-varying electric fields on cells; sham exposures were performed with an identical solenoid with a null net electric field. During the experiments, both solenoids heated interiorly to approximately 1.5 degrees C above ambient incubator temperature. As a result of the heating, cultures in the sham solenoid formed more osteoclast-like cells than those on the incubator shelf (132 +/- 12%). For this reason, cells exposed to the sham solenoid were used for comparison with cultures exposed to the active coil. Marrow cells were plated at 1.4 x 10(6)/cm2 in square chamber dishes and exposed to 60 Hz electric fields at 9.6 muV/cm from days 1 to 8. Field exposure inhibited osteoclast-like cell recruitment by 17 +/- 3% as compared with sham exposure (p < 0.0001). Several variables, including initial cell plating density, addition of prostaglandin E2 to enhance osteoclast-like cell recruitment, and field parameters, were also assessed. In this secondary series, extremely low frequency fields inhibited osteoclast-like cell formation by 24 +/- 4% (p < 0.0001), with their inhibitory effect consistent throughout all variations in protocol. These experiments demonstrate that extremely low intensity, low frequency sinusoidal electric fields suppress the formation of osteoclast-like cells in marrow culture. The in vitro results support in vivo findings that demonstrate that electric fields inhibit the onset of osteopenia and the progression of osteonecrosis; this suggests that extremely low frequency fields may inhibit osteoclast recruitment in vivo. PMID:8618169

  6. Generation of low-frequency electric and magnetic fields during large- scale chemical and nuclear explosions

    SciTech Connect

    Adushkin, V.V.; Dubinya, V.A.; Karaseva, V.A.; Soloviev, S.P.; Surkov, V.V.

    1995-06-01

    We discuss the main parameters of the electric field in the surface layer of the atmosphere and the results of the investigations of the natural electric field variations. Experimental investigations of the electromagnetic field for explosions in air are presented. Electromagnetic signals generated by underground nuclear and chemical explosions are discussed and explosions for 1976--1991 are listed. Long term anomalies of the earth`s electromagnetic field in the vicinity of underground explosions were also investigated. Study of the phenomenon of the irreversible shock magnetization showed that in the zone nearest to the explosion the quasistatic magnetic field decreases in inverse proportion to the distance.

  7. Low-frequency electromagnetic waves in a Hall-magnetohydrodynamic plasma with charged dust macroparticles

    SciTech Connect

    Shukla, P.K.; Kourakis, I.; Stenflo, L.

    2005-02-01

    A linear theory for intermediate-frequency [much smaller (larger) than the electron gyrofrequency (dust plasma and dust gyrofrequencies)], long wavelength (in comparison with the ion gyroradius and the electron skin depth) electromagnetic waves in a multicomponent, homogeneous electron-ion-dust magnetoplasma is presented. For this purpose, the generalized Hall-magnetohydrodynamic (GH-MHD) equations are derived for the case with immobile charged dust macroparticles. The GH-MHD equations in a quasineutral plasma consist of the ion continuity equation, the generalized ion momentum equation, and Faraday's law with the Hall term. The GH-MHD equations are Fourier transformed and combined to obtain a general dispersion relation. The latter is analyzed to understand the influence of immobile charged dust grains on various electromagnetic wave modes in a magnetized dusty plasma.

  8. Instabilities of low frequency, parallel propagating electromagnetic waves in the earth's foreshock region

    NASA Technical Reports Server (NTRS)

    Sentman, D. D.; Edmiston, J. P.; Frank, L. A.

    1981-01-01

    An instability analysis is presented for parallel and antiparallel propagating electromagnetic waves generated by reflected and diffuse suprathermal ions upstream of the earth's bow shock. Calculations are performed on the basis of upstream particle observations made by the ISEE 1 Quadrispheric Lepedea instrument and low-energy electron measurements made by the ISEE 1 electron spectrometer for a single period. The electromagnetic dispersion relation is computed and the unstable modes and growth times of the fastest growing waves are determined. It is found that the reflected ions destabilize the plasma most strongly at a wave frequency 0.1 that of the ion gyrofrequency by a resonant ion beam instability for waves propagating upstream and by a nonresonant firehose-like instability for waves propagating downstream. The diffuse ions also destabilize the plasma most strongly at the same frequency by means of resonant instabilities of both right- and left-hand polarized waves propagating away from the bow shock.

  9. Effects of low frequency waves and spiky electric fields in the magnetotail

    NASA Technical Reports Server (NTRS)

    Cattell, C.; Bennett, T.; Sigsbee, K.; Streed, T.; Mozer, F. S.; Roth, I.; Tsuruda, K.; Yamamoto, T.; Okada, T.; Kokubun, S.

    1996-01-01

    Intense low frequency waves and large amplitude spiky electric fields are commonly observed in the active magnetotail. These fields are of dynamic significance for substorms because the amplitude of the waves is large enough to provide the dissipation necessary for reconnection. The waves modify the trajectories of ions in the magnetotail, resulting in enhanced energization and pitch angle scattering in comparison with the trajectories obtained without waves. The spikes may represent the nonlinear evolution of the waves. Observations are presented of low frequency waves and spiky electric fields measured in the plasma sheet. The relationship between the waves and the spikes is compared to wave evolution theories. The Lundquist number is evaluated for the magnetotail based on the wave observations and previously published studies of the current sheet scale sizes. The effects of the waves on the ion trajectories are discussed using the results from a particle tracing code.

  10. Low frequency electrostatic and electromagnetic modes of ultracold magnetized nonuniform dense plasmas

    SciTech Connect

    Saleem, H.; Ahmad, Ali; Khan, S. A.

    2008-09-15

    A coupled linear dispersion relation for the basic electrostatic and electromagnetic waves in the ultracold nonuniform magnetized dense plasmas has been obtained which interestingly is analogous to the classical case. The scales of macroscopic phenomena and the interparticle quantum interactions are discussed. It is important to point out that hydrodynamic models cannot take into account strong quantum effects and they are not applicable to very dense plasmas. The analysis is presented with applications to dense plasmas which are relevant to both laboratory and astrophysical environments.

  11. Enhanced electroporation in plant tissues via low frequency pulsed electric fields: influence of cytoplasmic streaming.

    PubMed

    Asavasanti, Suvaluk; Stroeve, Pieter; Barrett, Diane M; Jernstedt, Judith A; Ristenpart, William D

    2012-01-01

    Pulsed electric fields (PEF) are known to be effective at permeabilizing plant tissues. Prior research has demonstrated that lower pulse frequencies induce higher rates of permeabilization, but the underlying reason for this response is unclear. Intriguingly, recent microscopic observations with onion tissues have also revealed a correlation between PEF frequency and the subsequent speed of intracellular convective motion, i.e., cytoplasmic streaming. In this paper, we investigate the effect of cytoplasmic streaming on the efficacy of plant tissue permeabilization via PEF. Onion tissue samples were treated with Cytochalasin B, a known inhibitor of cytoplasmic streaming, and changes in cellular integrity and viability were measured over a wide range of frequencies and field strengths. We find that at low frequencies (f < 1 Hz), the absence of cytoplasmic streaming results in a 19% decrease in the conductivity disintegration index compared with control samples. Qualitatively, similar results were observed using a microscopic cell viability assay. The results suggest that at low frequencies convection plays a statistically significant role in distributing more conductive fluid throughout the tissue, making subsequent pulses more efficacious. The key practical implication is that PEF pretreatment at low frequency can increase the rate of tissue permeabilization in dehydration or extraction processes, and that the treatment will be most effective when cytoplasmic streaming is most active, i.e., with freshly prepared plant tissues. PMID:22246974

  12. FR II radio galaxies at low frequencies – I. Morphology, magnetic field strength and energetics

    PubMed Central

    Harwood, Jeremy J.; Croston, Judith H.; Intema, Huib T.; Stewart, Adam J.; Ineson, Judith; Hardcastle, Martin J.; Godfrey, Leith; Best, Philip; Brienza, Marisa; Heesen, Volker; Mahony, Elizabeth K.; Morganti, Raffaella; Murgia, Matteo; Orrú, Emanuela; Röttgering, Huub; Shulevski, Aleksandar; Wise, Michael W.

    2016-01-01

    Due to their steep spectra, low-frequency observations of Fanaroff–Riley type II (FR II) radio galaxies potentially provide key insights in to the morphology, energetics and spectrum of these powerful radio sources. However, limitations imposed by the previous generation of radio interferometers at metre wavelengths have meant that this region of parameter space remains largely unexplored. In this paper, the first in a series examining FR IIs at low frequencies, we use LOFAR (LOw Frequency ARray) observations between 50 and 160 MHz, along with complementary archival radio and X-ray data, to explore the properties of two FR II sources, 3C 452 and 3C 223. We find that the morphology of 3C 452 is that of a standard FR II rather than of a double-double radio galaxy as had previously been suggested, with no remnant emission being observed beyond the active lobes. We find that the low-frequency integrated spectra of both sources are much steeper than expected based on traditional assumptions and, using synchrotron/inverse-Compton model fitting, show that the total energy content of the lobes is greater than previous estimates by a factor of around 5 for 3C 452 and 2 for 3C 223. We go on to discuss possible causes of these steeper-than-expected spectra and provide revised estimates of the internal pressures and magnetic field strengths for the intrinsically steep case. We find that the ratio between the equipartition magnetic field strengths and those derived through synchrotron/inverse-Compton model fitting remains consistent with previous findings and show that the observed departure from equipartition may in some cases provide a solution to the spectral versus dynamical age disparity. PMID:27284270

  13. FR II radio galaxies at low frequencies - I. Morphology, magnetic field strength and energetics

    NASA Astrophysics Data System (ADS)

    Harwood, Jeremy J.; Croston, Judith H.; Intema, Huib T.; Stewart, Adam J.; Ineson, Judith; Hardcastle, Martin J.; Godfrey, Leith; Best, Philip; Brienza, Marisa; Heesen, Volker; Mahony, Elizabeth K.; Morganti, Raffaella; Murgia, Matteo; Orrú, Emanuela; Röttgering, Huub; Shulevski, Aleksandar; Wise, Michael W.

    2016-06-01

    Due to their steep spectra, low-frequency observations of Fanaroff-Riley type II (FR II) radio galaxies potentially provide key insights in to the morphology, energetics and spectrum of these powerful radio sources. However, limitations imposed by the previous generation of radio interferometers at metre wavelengths have meant that this region of parameter space remains largely unexplored. In this paper, the first in a series examining FR IIs at low frequencies, we use LOFAR (LOw Frequency ARray) observations between 50 and 160 MHz, along with complementary archival radio and X-ray data, to explore the properties of two FR II sources, 3C 452 and 3C 223. We find that the morphology of 3C 452 is that of a standard FR II rather than of a double-double radio galaxy as had previously been suggested, with no remnant emission being observed beyond the active lobes. We find that the low-frequency integrated spectra of both sources are much steeper than expected based on traditional assumptions and, using synchrotron/inverse-Compton model fitting, show that the total energy content of the lobes is greater than previous estimates by a factor of around 5 for 3C 452 and 2 for 3C 223. We go on to discuss possible causes of these steeper-than-expected spectra and provide revised estimates of the internal pressures and magnetic field strengths for the intrinsically steep case. We find that the ratio between the equipartition magnetic field strengths and those derived through synchrotron/inverse-Compton model fitting remains consistent with previous findings and show that the observed departure from equipartition may in some cases provide a solution to the spectral versus dynamical age disparity.

  14. [Nonionizing radiation and electromagnetic fields].

    PubMed

    Bernhardt, J H

    1991-01-01

    Nonionising radiation comprises all kinds of radiation and fields of the electromagnetic spectrum where biological matter is not ionised, as well as mechanical waves such as infrasound and ultrasound. The electromagnetic spectrum is subdivided into individual sections and includes: Static and low-frequency electric and magnetic fields including technical applications of energy with mains frequency, radio frequency fields, microwaves and optic radiation (infrared, visible light, ultraviolet radiation including laser). The following categories of persons can be affected by emissions by non-ionising radiation: Persons in the environment and in the household, workers, patients undergoing medical diagnosis or treatment. If the radiation is sufficiently intense, or if the fields are of appropriate strength, a multitude of effects can occur (depending on the type of radiation), such as heat and stimulating or irritating action, inflammations of the skin or eyes, changes in the blood picture, burns or in some cases cancer as a late sequel. The ability of radiation to penetrate into the human body, as well as the types of interaction with biological tissue, with organs and organisms, differs significantly for the various kinds of nonionising radiation. The following aspects of nonionising radiation are discussed: protection of humans against excessive sunlight rays when sunbathing and when exposed to UV radiation (e.g. in solaria); health risks of radio and microwaves (safety of microwave cookers and mobile radio units); effects on human health by electric and magnetic fields in everyday life. PMID:1837859

  15. Low frequency wave at the meniscus of a continuous caster generated by a DC magnetic field

    NASA Astrophysics Data System (ADS)

    Etay, J.; Delannoy, Y.

    2003-12-01

    A continuous casting system for steel has been studied under a continuous magnetic field with the help of physical and numerical models. The behaviour of the free surface and the internal flow has been investigated experimentally on a mercury model, representing at the scale one third a typical casting head. A specific numerical model has been used to describe the effect of the horizontal magnetic field on the mean flow. For experiments with a magnetic field, a wave was observed at the mercury surface, travelling from one side of the mould to the other. With the help of a numerical model, this low frequency instability was related to the recirculating flow created by the nozzle. An analysis is proposed, based on the bidimensionalisation generated by the magnetic field and by self sustained oscillations of the upper recirculating flow. All other fluctuations of the free surface level are damped by the magnetic field. Tables 2, Figs 5, Refs 8.

  16. In vitro investigation of eddy current effect on pacemaker operation generated by low frequency magnetic field.

    PubMed

    Babouri, A; Hedjeidj, A

    2007-01-01

    This paper presents in vitro investigation of the eddy current induction effects to the cardiac pacemaker exposed to low frequency magnetic fields. The method used in this study is based to the interaction by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. In this article we present experimental results, analytical calculations and numerical simulations using the finite element method. PMID:18003302

  17. Low frequency electric field variations during HF transmissions on a mother-daughter rocket

    NASA Technical Reports Server (NTRS)

    Rosenberg, T. J.; Maynard, M. C.; Holtet, J. A.; Karlsen, N. O.; Egeland, A.; Moe, T. E.; Troim, J.

    1977-01-01

    HF wave propagation experiments were conducted on Mother-Daughter rockets in the polar ionosphere. Swept frequency transmissions from the Mother, nominally covering the range from 0.5 to 5 MHz in both CW and pulse modes, are received by the Daughter. In the most recent rocket of the series, the Mother also contained an AC electric field spectrometer covering the frequency range from 10 Hz to 100 kHz in four decade bands. The low frequency response of the ionosphere with respect to waves emitted from the onboard HF transmitter is examined.

  18. Hazard zoning around electric substations of petrochemical industries by stimulation of extremely low-frequency magnetic fields.

    PubMed

    Hosseini, Monireh; Monazzam, Mohammad Reza; Farhang Matin, Laleh; Khosroabadi, Hossein

    2015-05-01

    Electromagnetic fields in recent years have been discussed as one of the occupational hazards at workplaces. Hence, control and assessment of these physical factors is very important to protect and promote the health of employees. The present study was conducted to determine hazard zones based on assessment of extremely low-frequency magnetic fields at electric substations of a petrochemical complex in southern Iran, using the single-axis HI-3604 device. In measurement of electromagnetic fields by the single-axis HI-3604 device, the sensor screen should be oriented in a way to be perpendicular to the field lines. Therefore, in places where power lines are located in different directions, it is required to keep the device towards three axes of x, y, and z. For further precision, the measurements should be repeated along each of the three axes. In this research, magnetic field was measured, for the first time, in three axes of x, y, and z whose resultant value was considered as the value of magnetic field. Measurements were done based on IEEE std 644-1994. Further, the spatial changes of the magnetic field surrounding electric substations were stimulated using MATLAB software. The obtained results indicated that the maximum magnetic flux density was 49.90 μT recorded from boiler substation, while the minimum magnetic flux density of 0.02 μT was measured at the control room of the complex. As the stimulation results suggest, the spaces around incoming panels, transformers, and cables were recognized as hazardous zones of indoor electric substations. Considering the health effects of chronic exposure to magnetic fields, it would be possible to minimize exposure to these contaminants at workplaces by identification of risky zones and observation of protective considerations. PMID:25877640

  19. Plasma filamentation and shock wave enhancement in microwave rockets by combining low-frequency microwaves with external magnetic field

    NASA Astrophysics Data System (ADS)

    Takahashi, Masayuki; Ohnishi, Naofumi

    2016-08-01

    A filamentary plasma is reproduced based on a fully kinetic model of electron and ion transports coupled with electromagnetic wave propagation. The discharge plasma transits from discrete to diffusive patterns at a 110-GHz breakdown, with decrease in the ambient pressure, because of the rapid electron diffusion that occurs during an increase in the propagation speed of the ionization front. A discrete plasma is obtained at low pressures when a low-frequency microwave is irradiated because the ionization process becomes more dominant than the electron diffusion, when the electrons are effectively heated by the low-frequency microwave. The propagation speed of the plasma increases with decrease in the incident microwave frequency because of the higher ionization frequency and faster plasma diffusion resulting from the increase in the energy-absorption rate. An external magnetic field is applied to the breakdown volume, which induces plasma filamentation at lower pressures because the electron diffusion is suppressed by the magnetic field. The thrust performance of a microwave rocket is improved by the magnetic fields corresponding to the electron cyclotron resonance (ECR) and its higher-harmonic heating, because slower propagation of the ionization front and larger energy-absorption rates are obtained at lower pressures. It would be advantageous if the fundamental mode of ECR heating is coupled with a lower frequency microwave instead of combining the higher-harmonic ECR heating with the higher frequency microwave. This can improve the thrust performance with smaller magnetic fields even if the propagation speed increases because of the decrease in the incident microwave frequency.

  20. Imaging of the interaction of low frequency electric fields with biological tissues by optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Peña, Adrian F.; Devine, Jack; Doronin, Alexander; Meglinski, Igor

    2014-03-01

    We report the use of conventional Optical Coherence Tomography (OCT) for visualization of propagation of low frequency electric field in soft biological tissues ex vivo. To increase the overall quality of the experimental images an adaptive Wiener filtering technique has been employed. Fourier domain correlation has been subsequently applied to enhance spatial resolution of images of biological tissues influenced by low frequency electric field. Image processing has been performed on Graphics Processing Units (GPUs) utilizing Compute Unified Device Architecture (CUDA) framework in the frequencydomain. The results show that variation in voltage and frequency of the applied electric field relates exponentially to the magnitude of its influence on biological tissue. The magnitude of influence is about twice more for fresh tissue samples in comparison to non-fresh ones. The obtained results suggest that OCT can be used for observation and quantitative evaluation of the electro-kinetic changes in biological tissues under different physiological conditions, functional electrical stimulation, and potentially can be used non-invasively for food quality control.

  1. Infrared thermography based defect detection in ferromagnetic specimens using a low frequency alternating magnetic field

    NASA Astrophysics Data System (ADS)

    Lahiri, B. B.; Bagavathiappan, S.; Soumya, C.; Mahendran, V.; Pillai, V. P. M.; Philip, John; Jayakumar, T.

    2014-05-01

    A new active infrared thermography based technique is proposed for defect detection in ferromagnetic specimens using a low frequency alternating magnetic field induced heating. The test specimens (four mild steel specimens with artificial rectangular slots of 8.0, 5.0, 3.3 and 3.0 mm depths) are magnetized using a low frequency alternating magnetic field and by using an infrared camera, the surface temperature is remotely monitored in real time. An alternating magnetic field induces an eddy current in the specimen which increases the specimen temperature due to the Joule's heating. The experimental results show a thermal contrast in the defective region that decays exponentially with the defect depth. The observed thermal contrast is attributed to the reduction in induction heating due to the leakage of magnetic flux caused by magnetic permeability gradient in the defective region. The proposed technique is suitable for rapid non-contact wide area inspection of ferromagnetic materials and offers several advantages over the conventional active thermography techniques like fast direct heating, no frequency optimization, no dependence on the surface absorption coefficient and penetration depth.

  2. Introducing electromagnetic field momentum

    NASA Astrophysics Data System (ADS)

    Yu-Kuang Hu, Ben

    2012-07-01

    I describe an elementary way of introducing electromagnetic field momentum. By considering a system of a long solenoid and line charge, the dependence of the field momentum on the electric and magnetic fields can be deduced. I obtain the electromagnetic angular momentum for a point charge and magnetic monopole pair partially through dimensional analysis and without using vector calculus identities or the need to evaluate integrals. I use this result to show that linear and angular momenta are conserved for a charge in the presence of a magnetic dipole when the dipole strength is changed.

  3. Review of russian literature on biological action of DC and low-frequency AC magnetic fields.

    PubMed

    Zhadin, M N

    2001-01-01

    This review considers the Russian scientific literature on the influence of weak static and of low-frequency alternating magnetic fields on biological systems. The review covers the most interesting works and the main lines of investigation during the period 1900 to the present. Shown here are the historical roots, beginning with the ideas of V. Vernadsky and A. Chizhevsky, which led in the field of Russian biology to an increasing interest in magnetic fields, based on an intimate connection between solar activity and life on the Earth, and which determined the peculiar development of Russian magnetobiology. The variety of studies on the effects of magnetic storms and extremely low-frequency, periodic variations of the geomagnetic field on human beings and animals as well as on social phenomena are described. The diverse experiments involving artificial laboratory magnetic fields acting on different biological entities under different conditions are also considered. A series of theoretical advances are reviewed that have paved the way for a step-by-step understanding of the mechanisms of magnetic field effects on biological systems. The predominantly unfavorable influence of magnetic fields on living beings is shown, but the cases of favorable influence of magnetic fields on human beings and lower animals are demonstrated as well. The majority of Russian investigations in this area of science has been unknown among the non-Russian speaking audience for many reasons, primarily because of a language barrier. Therefore, it is hoped that this review may be of interest to the international scientific community. PMID:11122491

  4. Cancer incidence among welders: possible effects of exposure to extremely low frequency electromagnetic radiation (ELF) and to welding fumes.

    PubMed Central

    Stern, R M

    1987-01-01

    Epidemiological studies of cancer incidence among welders disclose a pooled total of 146 cases of leukemia observed versus 159.46 expected, a risk ratio of 0.92, and 40 cases of acute leukemia observed versus 43.39 expected, a risk ratio of 0.92. For respiratory tract cancer, the pooled total is 1789 cases observed versus 1290.7 expected, a risk ratio of 1.39. Most electric welders are exposed to extremely low frequency electromagnetic radiation (ELF) (magnetic flux densities of up to 100,000 microT), a suspected leukemogen, and to concentrated metallic aerosols (up to 200 mg/m3), which can contain the putative respiratory tract carcinogens Cr(VI) and Ni. The two exposures are usually coincident, since welding with an electric current produces welding fumes. The observation of an excess risk for respiratory tract cancer strongly suggests significant exposure both to fumes and to ELF. The absence of increased risk for all leukemia or for acute leukemia among ELF-exposed welders does not support the hypothesis that the observed excess risk for leukemia or acute leukemia among workers in the electrical trades is due to their ELF exposure, which on the average is lower than that of welders. PMID:3447902

  5. NATURAL-FIELD AND VERY LOW-FREQUENCY TIPPER PROFILE INTERPRETATION OF CONTACTS.

    USGS Publications Warehouse

    Labson, Victor F.; Becker, Alex

    1987-01-01

    Anomalous vertical magnetic field (tipper) profiles acquired using natural or very low-frequency (VLF) radio transmitter sources can be interpreted simply and rapidly for a number of geologic settings. The relations between computed numerical models, and outcropping dipping and buried vertical contacts are presented. In this paper in a series of interpretation charts. Use of the tipper phase in the analysis minimizes the effect of transmitter azimuth in the VLF case. Two examples illustrate the application to field data. An audiofrequency natural-field tipper profile over a conductive bed in a north-central Washington State metasedimentary sequence demonstrates the interpretation procedure for a dipping contact. VLF profiles over covered basement faults in Ontario demonstrate the application for a buried vertical contact. In both cases the quick results are in agreement with the much more laborious trial-and-error matching to two-dimensional models.

  6. Characterization of extremely low frequency magnetic fields from diesel, gasoline and hybrid cars under controlled conditions.

    PubMed

    Hareuveny, Ronen; Sudan, Madhuri; Halgamuge, Malka N; Yaffe, Yoav; Tzabari, Yuval; Namir, Daniel; Kheifets, Leeka

    2015-02-01

    This study characterizes extremely low frequency (ELF) magnetic field (MF) levels in 10 car models. Extensive measurements were conducted in three diesel, four gasoline, and three hybrid cars, under similar controlled conditions and negligible background fields. Averaged over all four seats under various driving scenarios the fields were lowest in diesel cars (0.02 μT), higher for gasoline (0.04-0.05 μT) and highest in hybrids (0.06-0.09 μT), but all were in-line with daily exposures from other sources. Hybrid cars had the highest mean and 95th percentile MF levels, and an especially large percentage of measurements above 0.2 μT. These parameters were also higher for moving conditions compared to standing while idling or revving at 2500 RPM and higher still at 80 km/h compared to 40 km/h. Fields in non-hybrid cars were higher at the front seats, while in hybrid cars they were higher at the back seats, particularly the back right seat where 16%-69% of measurements were greater than 0.2 μT. As our results do not include low frequency fields (below 30 Hz) that might be generated by tire rotation, we suggest that net currents flowing through the cars' metallic chassis may be a possible source of MF. Larger surveys in standardized and well-described settings should be conducted with different types of vehicles and with spectral analysis of fields including lower frequencies due to magnetization of tires. PMID:25647323

  7. Characterization of Extremely Low Frequency Magnetic Fields from Diesel, Gasoline and Hybrid Cars under Controlled Conditions

    PubMed Central

    Hareuveny, Ronen; Sudan, Madhuri; Halgamuge, Malka N.; Yaffe, Yoav; Tzabari, Yuval; Namir, Daniel; Kheifets, Leeka

    2015-01-01

    This study characterizes extremely low frequency (ELF) magnetic field (MF) levels in 10 car models. Extensive measurements were conducted in three diesel, four gasoline, and three hybrid cars, under similar controlled conditions and negligible background fields. Averaged over all four seats under various driving scenarios the fields were lowest in diesel cars (0.02 μT), higher for gasoline (0.04–0.05 μT) and highest in hybrids (0.06–0.09 μT), but all were in-line with daily exposures from other sources. Hybrid cars had the highest mean and 95th percentile MF levels, and an especially large percentage of measurements above 0.2 μT. These parameters were also higher for moving conditions compared to standing while idling or revving at 2500 RPM and higher still at 80 km/h compared to 40 km/h. Fields in non-hybrid cars were higher at the front seats, while in hybrid cars they were higher at the back seats, particularly the back right seat where 16%–69% of measurements were greater than 0.2 μT. As our results do not include low frequency fields (below 30 Hz) that might be generated by tire rotation, we suggest that net currents flowing through the cars’ metallic chassis may be a possible source of MF. Larger surveys in standardized and well-described settings should be conducted with different types of vehicles and with spectral analysis of fields including lower frequencies due to magnetization of tires. PMID:25647323

  8. CHARACTERISTICS OF TRANSVERSE ELECTRIC AND MAGNETIC FIELD TRANSMISSION CELLS AT EXTREMELY LOW FREQUENCIES

    EPA Science Inventory

    Transverse electric and magnetic field cells are often designed to subject samples to electromagnetic radiation of intrinsic impedance (E/H) that is the same as in free space, 377 ohms. Earlier work has shown this value to be correct for the RF region. In the study, measurements ...

  9. Emerging issues in extremely-low-frequency electric and magnetic field health research

    SciTech Connect

    Kavet, R.I.; Banks, R.S.

    1986-04-01

    Concern has increased over potential consequences of exposure to electric and magnetic fields of extremely low frequency (0-100 Hz), particularly from power transmission and distribution. Also at issue are electrical environments in homes and workplaces. Until recently, research focused on the electric, rather than the magnetic, field; now, both are under extensive investigation. A review of research to date indicates the following: Electric and magnetic fields can produce effects in vitro, with the locus of field interaction believed to be at the cell membrane. Chronic in vivo electric field exposure fails to produce effects except in behavior, neurophysiology, endocrinology, and, possibly, fetal development. The extrapolation of these animal data to humans requires further research. The epidemiological literature has, in some cases, reported an association between increased cancer rates and putative field exposure. Exposure assessments indicate that, in all likelihood, human exposures to 60-Hz electric fields of the magnitudes found under transmission lines are very infrequent; assessments are continuing to characterize exposure to 60-Hz magnetic fields and to measure the field frequency spectra found in residential and workplace settings. The public health issues emerging from this research focus on fetal development and on the initiation or promotion of cancer. It is critical to reduce existing uncertainties in order to enable valid risk assessment.

  10. Induction of chondrogenic differentiation of human adipose-derived stem cells by low frequency electric field

    PubMed Central

    Mardani, Mohammad; Roshankhah, Shiva; Hashemibeni, Batool; Salahshoor, Mohammadreza; Naghsh, Erfan; Esfandiari, Ebrahim

    2016-01-01

    Background: Since when the cartilage damage (e.g., with the osteoarthritis) it could not be repaired in the body, hence for its reconstruction needs cell therapy. For this purpose, adipose-derived stem cells (ADSCs) is one of the best cell sources because by the tissue engineering techniques it can be differentiated into chondrocytes. Chemical and physical inducers is required order to stem cells to chondrocytes differentiating. We have decided to define the role of electric field (EF) in inducing chondrogenesis process. Materials and Methods: A low frequency EF applied the ADSCs as a physical inducer for chondrogenesis in a 3D micromass culture system which ADSCs were extracted from subcutaneous abdominal adipose tissue. Also enzyme-linked immunosorbent assay, methyl thiazolyl tetrazolium, real time polymerase chain reaction and flowcytometry techniques were used for this study. Results: We found that the 20 minutes application of 1 kHz, 20 mv/cm EF leads to chondrogenesis in ADSCs. Although our results suggest that application of physical (EF) and chemical (transforming growth factor-β3) inducers at the same time, have best results in expression of collagen type II and SOX9 genes. It is also seen EF makes significant decreased expression of collagens type I and X genes. Conclusion: The low frequency EF can be a good motivator to promote chondrogenic differentiation of human ADSCs. PMID:27308269

  11. [Biological and health effects on electric and magnetic fields at extremely low frequencies].

    PubMed

    Torregrossa, M V

    2005-01-01

    While the enormous benefits of using electricity in everyday life and health care are unquestioned, during the past 20 years the general public has become increasingly concerned about potential adverse health effects of exposure to electric and magnetic fields at extremely low frequencies (ELF). Such exposures arise mainly from the transmission and use of electrical energy at the power frequencies of 50/60 Hz. The international scientific community is addressing the associated health issues through in vitro, in vivo and epidemiological studies, although present research results are often contradictory. The purpose of this paper is to provide information about the possible impacts of exposure to electric and magnetic field at ELF frequencies on health within the community and the workplace. Information comes from recent research studies on this subject and from epidemiological pooled studies recently reviewed by eminent authorities. PMID:16353681

  12. Electromagnetic fields in cased borehole

    SciTech Connect

    Lee, Ki Ha; Kim, Hee Joon; Uchida, Toshihiro

    2001-07-20

    Borehole electromagnetic (EM) measurements, using fiberglass-cased boreholes, have proven useful in oil field reservoir characterization and process monitoring (Wilt et al., 1995). It has been presumed that these measurements would be impossible in steel-cased wells due to the very large EM attenuation and phase shifts. Recent laboratory and field studies have indicated that detection of EM signals through steel casing should be possible at low frequencies, and that these data provide a reasonable conductivity image at a useful scale. Thus, we see an increased application of this technique to mature oilfields, and an immediate extension to geothermal industry as well. Along with the field experiments numerical model studies have been carried out for analyzing the effect of steel casing to the EM fields. The model used to be an infinitely long uniform casing embedded in a homogeneous whole space. Nevertheless, the results indicated that the formation signal could be accurately recovered if the casing characteristics were independently known (Becker et al., 1998; Lee el al., 1998). Real steel-cased wells are much more complex than the simple laboratory models used in work to date. The purpose of this study is to develop efficient numerical methods for analyzing EM fields in realistic settings, and to evaluate the potential application of EM technologies to cross-borehole and single-hole environment for reservoir characterization and monitoring.

  13. Parametric Excitation of Very Low Frequency (VLF) Electromagnetic Whistler Waves by Transformation of Lower Oblique Resonance Waves on Density Perturbations in the Vicinity of a Loop VLF Antenna

    NASA Astrophysics Data System (ADS)

    Kim, T.; Sotnikov, V.; Main, D.; Mishin, E.; Gershenzon, N.

    2015-11-01

    Concept of a parametric antenna in the ionospheric plasma is analyzed. Such antennas are capable of exciting electromagnetic radiation fields, specifically the creation of whistler waves generated at the very low frequency (VLF) range, which are also capable of propagating large distances away from the source region. The mechanism of whistler wave generation is considered a parametric interaction of quasi-electrostatic low oblique resonance (LOR) oscillations excited by conventional loop antenna. The transformation of LOR waves on quasi-neutral density perturbations generated by a dipole antenna gives rise to electromagnetic whistler waves on combination frequencies. In this approach extended plasma volume around a loop antenna represents a parametric antenna. Simulation to demonstrate excitation and spatial structure of VLF waves excited by a loop antenna using a PIC code LSP will be presented as well. Possible applications including the wave-particle interactions to mitigate performance anomalies of Low Earth Orbit (LEO) satellites, active space experiments, communication via VLF waves, and modification experiments in the ionosphere will be discussed.

  14. Microscopic origin of low frequency noise in MoS{sub 2} field-effect transistors

    SciTech Connect

    Ghatak, Subhamoy; Jain, Manish; Ghosh, Arindam; Mukherjee, Sumanta; Sarma, D. D.

    2014-09-01

    We report measurement of low frequency 1/f noise in molybdenum di-sulphide (MoS{sub 2}) field-effect transistors in multiple device configurations including MoS{sub 2} on silicon dioxide as well as MoS{sub 2}-hexagonal boron nitride (hBN) heterostructures. All as-fabricated devices show similar magnitude of noise with number fluctuation as the dominant mechanism at high temperatures and density, although the calculated density of traps is two orders of magnitude higher than that at the SiO{sub 2} interface. Measurements on the heterostructure devices with vacuum annealing and dual gated configuration reveals that along with the channel, metal-MoS{sub 2} contacts also play a significant role in determining noise magnitude in these devices.

  15. Pilot study of extremely low frequency magnetic fields emitted by transformers in dwellings. Social aspects.

    PubMed

    Zaryabova, Victoria; Shalamanova, Tsvetelina; Israel, Michel

    2013-06-01

    A large number of epidemiologic studies examining the potential effect of residential exposure to extremely-low frequency (ELF) magnetic fields and childhood leukemia have been published. Two pooled analyses [Ahlbom A, Day N, Feychting M, Roman E, Skinner J, Dockerty J, Linet M, et al. (2000). A pooled analysis of magnetic fields and childhood leukaemia. Br J Cancer. 83(5):692-698; Greenland S, Sheppard AR, Kaune WT, Poole C, Kelsh AM (2000). A pooled analysis of magnetic fields, wire codes, and childhood leukemia. Epidemiology. 11(6):624-634], which included the major epidemiologic studies on ELF magnetic fields and childhood leukemia showed twofold increase in childhood leukemia risk in association with residential ELF exposure above 0.3-0.4 μT. Based on "limited" epidemiologic evidence linking ELF exposure to childhood leukemia and "inadequate evidence" for carcinogenicity of ELF in rodent bioassays, the International Agency for Research on Cancer (IARC) classified ELF magnetic fields as a possible human carcinogen (2B classification) [International Agency for Research on Cancer (IARC) (2002). Non-ionizing radiation, Part 1: Static and extremely low-frequency (ELF) electric and magnetic fields. IARC monographs on the evaluation of carcinogenic risks to humans. Vol. 80. IARC Press: Lyon], confirmed by WHO on the basis of studies published after 2000 [World Health Organization. Extremely low frequency fields. In: 238 Environmental health criteria, Geneva: WHO; 2007]. The analysis of more recent studies of ELF magnetic fields and childhood leukemia had small findings and propose methodological improvements concerning the uncertainties in epidemiological approaches and exposure assessment, bias in selection of controls [Kheifets L, Oksuzyan S (2008). Exposure assessment and other challenges in non-ionizing radiation studies of childhood leukaemia. Radiat Prot Dosimetry. 132(2):139-147]. By the end of 2010, 37 countries had been identified for possible participation

  16. Comparative dosimetry for children and rodents exposed to extremely low-frequency magnetic fields.

    PubMed

    Gong, Yijian; Capstick, Myles; Dasenbrock, Clemens; Fedrowitz, Maren; Cobaleda, Cesar; Sánchez-García, Isidro; Kuster, Niels

    2016-07-01

    We describe a method to correlate E-fields induced by exposure to extremely low frequency magnetic fields in laboratory mice and rats during in vivo experiments to those induced in children. Four different approaches of mapping relative dose rates between humans and rodents are herein proposed and analyzed. Based on these mapping methods and volume averaging guidelines published by the International Commission on Non-Ionizing Radiation Protection (ICNRP) in 2010, maximum and median induced field values for whole body and for tissues of children and rodents were evaluated and compared. Median induced electric fields in children younger than 10 years old are in the range 5.9-8.5 V/m per T (±0.4 dB). Maximum induced electric fields, generally in the skin, are between 48 V/m and 228 V/m per T (±4 dB). To achieve induced electric fields of comparable magnitude in rodents, external magnetic field must be increased by a factor of 4.0 (±2.6 dB) for rats and 7.4 (±1.8 dB) for mice. Meanwhile, to achieve comparable magnetic field dose in rodents, ratio is close to one. These induced field dose rates for children and rodents can be used to quantifiably compare experimental data from in vivo studies with data on exposure of children from epidemiological studies, such as for leukemia. Bioelectromagnetics. 37:310-322, 2016. © 2016 Wiley Periodicals, Inc. PMID:27176719

  17. Investigation of exposure to Extremely Low Frequency (ELF) magnetic and electric fields: Ongoing animal studies

    SciTech Connect

    Anderson, L.E.

    1994-03-01

    There is now convincing evidence from a large number of laboratories, that exposure to extremely low frequency (ELF) magnetic and electric fields produces biological responses in animals. Many of the observed effects appear to be directly or indirectly associated with the neural or neuroendocrine systems. Such effects include increased neuronal excitability, chemical and hormonal changes in the nervous system, altered behavioral responses, some of which are related to sensing the presence of the field, and changes in endogenous biological rhythms. Additional indices of general physiological status appear relatively unaffected by exposure, although effects have occasionally been described in bone growth and fracture repair, reproduction and development, and immune system function. A major current emphasis in laboratory research is to determine whether or not the reported epidemiological studies that suggest an association between EMF exposure and risk of cancer are supported in studies using animal models. Three major challenges exist for ongoing research: (1) knowledge about the mechanisms underlying observed bioeffects is incomplete, (2) researchers do not as yet understand what physical aspects of exposure produce biological responses, and (3) health consequences resulting from ELF exposure are unknown. Although no animal studies clearly demonstrate deleterious effects of ELF fields, several are suggestive of potential health impacts. From the perspective of laboratory animal studies, this paper will discuss biological responses to ELF magnetic and/or electric field exposures.

  18. Increased Sensitivity of Magnetoelectric Sensors at Low Frequencies Using Magnetic Field Modulation

    NASA Astrophysics Data System (ADS)

    Petrie, Jonathan; Viehland, Dwight; Gray, David; Mandal, Sanjay; Sreenivasulu, Gollapudi; Srinivasan, Gopalan; Edelstein, Alan

    2012-02-01

    Magnetoelectric (ME) laminate sensors are vector magnetometers that can detect pT magnetic fields at 1 kHz, although sensitivity may be reduced at lower frequencies. These passive sensors consist of alternating layers of magnetostrictive and piezoelectric materials. A magnetic field causes the magnetostrictive layer to strain the piezoelectric material and create measurable charge. We have shownootnotetextTo be published in Journal of Applied Physics. that since the strain response is a nonlinear function of the bias field, sweeping the magnetic bias on the magnetostrictive layer can modulate the ME response and increase the operating frequency of the sensor. This upward shift lowers the 1/f noise and increases the signal amplitude if the new operating frequency is near a mechanical resonance mode of the sensor. Using this modulation technique, the low frequency sensitivity has been improved by more than an order of magnitude and we have achieved a detectivity of 7 pT/Hz at1 Hz. In addition to increasing the magnetic signal frequency, we can use magnetic modulation to increase the operating frequency of acoustic signals detected by these sensors. This occurs because the ME sensors are nonlinear devices. In these cases using magnetic field modulation, the signal appears as sidebands around the modulation frequency.

  19. Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields.

    PubMed

    Paffi, Alessandra; Camera, Francesca; Lucano, Elena; Apollonio, Francesca; Liberti, Micaela

    2016-06-21

    An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform's size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257-65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke's brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz. PMID:27223143

  20. Time resolved dosimetry of human brain exposed to low frequency pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Paffi, Alessandra; Camera, Francesca; Lucano, Elena; Apollonio, Francesca; Liberti, Micaela

    2016-06-01

    An accurate dosimetry is a key issue to understanding brain stimulation and related interaction mechanisms with neuronal tissues at the basis of the increasing amount of literature revealing the effects on human brain induced by low-level, low frequency pulsed magnetic fields (PMFs). Most literature on brain dosimetry estimates the maximum E field value reached inside the tissue without considering its time pattern or tissue dispersivity. Nevertheless a time-resolved dosimetry, accounting for dispersive tissues behavior, becomes necessary considering that the threshold for an effect onset may vary depending on the pulse waveform and that tissues may filter the applied stimulatory fields altering the predicted stimulatory waveform’s size and shape. In this paper a time-resolved dosimetry has been applied on a realistic brain model exposed to the signal presented in Capone et al (2009 J. Neural Transm. 116 257–65), accounting for the broadband dispersivity of brain tissues up to several kHz, to accurately reconstruct electric field and current density waveforms inside different brain tissues. The results obtained by exposing the Duke’s brain model to this PMF signal show that the E peak in the brain is considerably underestimated if a simple monochromatic dosimetry is carried out at the pulse repetition frequency of 75 Hz.

  1. The embryonic development of Xenopus laevis under a low frequency electric field.

    PubMed

    Boga, Ayper; Binokay, Secil; Emre, Mustafa; Sertdemir, Yasar

    2012-06-01

    The aim of this study was to determine the effects of a low frequency electric field on the early embryonic development of frogs. The embryos of African clawed toads, Xenopus laevis, were exposed to a 20-μA electric current during the cleavage stages. The developmental processes of embryos during and after electric field exposure were monitored for teratogenic effects. All the embryos continuously exposed to the electric field died without undergoing any developmental processes. However, when the embryos were exposed to the electric field for 20-min periods (four times/over 2 d), the embryos developed into both normal tadpoles (70 %) and malformed tadpoles with light edema, reduced pigmentation, or axial anomalies, such as crooked tails. After exposure, the control embryos were at development stage 35.5 (2 d 2 h), while the normal embryos of the assay group were at developmental stage 41(3 d 4 h). There was a 1 d 2 h difference between the two developmental stages, revealing the importance of that time period for embryogenesis. In conclusion, the effects of electric current on Xenopus embryos are dependent on the initial developmental stage and the duration of exposure. PMID:22723004

  2. Sleep quality and general health status of employees exposed to extremely low frequency magnetic fields in a petrochemical complex

    PubMed Central

    2014-01-01

    Background Advances in science and technology of electrical equipment, despite increasing human welfare in everyday life, have increased the number of people exposed to Electro-Magnetic Fields (EMFs). Because of possible adverse effects on the health of exposed individuals, the EMFs have being the center of attention. This study was performed to determine possible correlation between Extremely Low Frequency Electro-Magnetic Fields (ELF EMFs) and sleep quality and public health of those working in substation units of a petrochemical complex in southern Iran. Materials and method To begin with, magnetic flux density was measured at different parts of a Control Building and two substations in accordance with IEEE std 644–1994. Subsequently, the questionnaires “Pittsburgh Sleep Quality Index” (PSQI) and “General Health Quality (GHQ)” were used to investigate relationship between ELF exposure level and sleep quality and public health, respectively. Both questionnaires were placed at disposal of a total number of 40 workers at the complex. The filled out questionnaires were analyzed by T-test, Duncan and the Chi-square tests. Results The obtained results revealed that 28% of those in case group suffered from poor health status and 61% were diagnosed with a sleep disorder. However, all members in control group were in good health condition and only 4.5% of them had undesirable sleep quality. Conclusion In spite of a significant difference between the case and control groups in terms of sleep quality and general health, no significant relationship was found between the exposure level and sleep quality and general health. It is worth noting that the measured EMF values were lower than the standard limits recommended by American Conference of Industrial Hygienists (ACGIH). However, given the uncertainties about the pathogenic effects caused by exposure to ELF EMFs, further epidemiological studies and periodic testing of personnel working in high voltage substations

  3. Electromagnetic Field Penetration Studies

    NASA Technical Reports Server (NTRS)

    Deshpande, M.D.

    2000-01-01

    A numerical method is presented to determine electromagnetic shielding effectiveness of rectangular enclosure with apertures on its wall used for input and output connections, control panels, visual-access windows, ventilation panels, etc. Expressing EM fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, integral equations with aperture tangential electric fields as unknown variables are obtained by enforcing the continuity of tangential electric and magnetic fields across the apertures. Using the Method of Moments, the integral equations are solved for unknown aperture fields. From these aperture fields, the EM field inside a rectangular enclosure due to external electromagnetic sources are determined. Numerical results on electric field shielding of a rectangular cavity with a thin rectangular slot obtained using the present method are compared with the results obtained using simple transmission line technique for code validation. The present technique is applied to determine field penetration inside a Boeing-757 by approximating its passenger cabin as a rectangular cavity filled with a homogeneous medium and its passenger windows by rectangular apertures. Preliminary results for, two windows, one on each side of fuselage were considered. Numerical results for Boeing-757 at frequencies 26 MHz, 171-175 MHz, and 428-432 MHz are presented.

  4. Satellite-borne study of seismic phenomena by low frequency magnetic field observations

    NASA Astrophysics Data System (ADS)

    Schwingenschuh, Konrad; Magnes, Werner; Xuhui, Shen; Wang, Jindong; Pollinger, Andreas; Hagen, Christian; Prattes, Gustav; Eichelberger, Hans-Ulrich; Wolbang, Daniel; Boudjada, Mohammed Y.; Besser, Bruno P.; Rozhnoi, Alexander A.; Zhang, Tielong

    2015-04-01

    A combined scalar-vector magnetic field experiment will be flown on the upcoming CSES mission (China Seismo-Electromagnetic Satellite). Magnetic field data from DC to 30 Hz will be measured with an accuracy of about 10 pT. A fluxgate instrument will provide the 3 magnetic field components and a new type of an optically pumped magnetometer [see Pollinger, 2010] will measure the magnitude of the ambient magnetic field. The satellite will operate in a Sun synchronous polar orbit at an altitude of about 500 km and with an inclination of 97°. We present a model of magnetic field fluctuations in the upper ionosphere based on previous satellite observations and on a model of the lithospheric-atmospheric-ionospheric coupling. Pollinger et al., CDSM-a new scalar magnetometer, EGU General Assembly 2010

  5. Seizure entrainment with polarizing low-frequency electric fields in a chronic animal epilepsy model

    NASA Astrophysics Data System (ADS)

    Sunderam, Sridhar; Chernyy, Nick; Peixoto, Nathalia; Mason, Jonathan P.; Weinstein, Steven L.; Schiff, Steven J.; Gluckman, Bruce J.

    2009-08-01

    Neural activity can be modulated by applying a polarizing low-frequency (Lt100 Hz) electric field (PLEF). Unlike conventional pulsed stimulation, PLEF stimulation has a graded, modulatory effect on neuronal excitability, and permits the simultaneous recording of neuronal activity during stimulation suitable for continuous feedback control. We tested a prototype system that allows for simultaneous PLEF stimulation with minimal recording artifact in a chronic tetanus toxin animal model (rat) of hippocampal epilepsy with spontaneous seizures. Depth electrode local field potentials recorded during seizures revealed a characteristic pattern of field postsynaptic potentials (fPSPs). Sinusoidal voltage-controlled PLEF stimulation (0.5-25 Hz) was applied in open-loop cycles radially across the CA3 of ventral hippocampus. For stimulated seizures, fPSPs were transiently entrained with the PLEF waveform. Statistical significance of entrainment was assessed with Thomson's harmonic F-test, with 45/132 stimulated seizures in four animals individually demonstrating significant entrainment (p < 0.04). Significant entrainment for multiple presentations at the same frequency (p < 0.01) was observed in three of four animals in 42/64 stimulated seizures. This is the first demonstration in chronically implanted freely behaving animals of PLEF modulation of neural activity with simultaneous recording.

  6. Study on ultra-precision magnetic abrasive finishing process using low frequency alternating magnetic field

    NASA Astrophysics Data System (ADS)

    Wu, Jinzhong; Zou, Yanhua; Sugiyama, Hitoshi

    2015-07-01

    We proposed a new ultra-precision magnetic abrasive finishing (MAF) process using low frequency alternating magnetic field in this paper. Magnetic cluster themselves may produce the up and down movement change under alternating magnetic force. The movement may not only promote the dispersion of micro-magnetic particles, but also improve stirring effect and cross-cutting effects of the abrasives, achieving circulation and update to ensure the stability of grinding tools. This process is considered to be able to efficiently apply in ultra-precision finishing of plane and complicated micro-surfaces. In this study, we investigated the effects of alternating magnetic field on magnetic field distribution, finishing force and abrasive behavior. Furthermore, a set of experimental devices have been designed for finishing SUS304 stainless steel plate. The present work is aimed at understanding finishing particularity of this process and studying impacts of important process parameters namely grinding fluid, rotational speed of magnetic pole, current frequency on change in finish surface and material removal. Experimental results indicate that the process can realize ultra-precision finishing of plane by using oily grinding fluid. In the present research, the surface roughness of SUS304 stainless steel plate was improved from 240.24 nm to 4.38 nm by this process.

  7. Bifurcation in the equililbrium height of colloidal particles over an electrode in low frequency electric fields

    NASA Astrophysics Data System (ADS)

    Woehl, Taylor; Dutcher, Cari; Talken, Nicholas; Chen, Bing Jie; Ristenpart, William

    2013-11-01

    Colloidal particles are known to change their equilibrium height above an electrode in response to an applied AC electric field, partially due to a lift force caused by electrohydrodynamic (EHD) flow generated around each particle. Here we report the existence of an unexpected bifurcation in the equilibrium particle height in response to low frequency (~100 Hz) fields. Optical and confocal microscopy observations reveal that upon application of the field 40% of the particles rapidly move several particle diameters up from the electrode, while the remaining 60% move slightly down. Statistics compiled from repeated trials demonstrate that the probability of any particle moving up follows a binomial distribution, indicating that particle lift up is random and does not result from membership in a distinct subpopulation of particles. The observations provide strong evidence for the existence of a tertiary minimum in the interaction potential at a surprisingly large distance from the electrode. We present scaling arguments for the interaction potential in terms a balance between colloidal forces, EHD flow, dipole image attraction, and gravity, yielding a predicted interaction potential with a tertiary minimum that is qualitatively consistent with the observed bifurcation.

  8. Individual estimation of exposures to extremely low frequency magnetic fields in jobs commonly held by women.

    PubMed

    Deadman, J E; Infante-Rivard, C

    2002-02-15

    Exposures to extremely low frequency (ELF) magnetic fields have not been documented extensively in occupations besides the work environments of electric or telephone utilities. A 1980-1993 study of childhood acute lymphoblastic leukemia (ALL) in Québec, Canada, gathered detailed information about the occupations of 491 mothers of ALL cases and mothers of a similar number of healthy controls. This information was combined with published data on the intensities of ELF magnetic fields associated with sources or work environments to estimate ELF magnetic field exposures for a wide range of jobs commonly held by women. Estimated exposures for 61 job categories ranged from 0.03 to 0.68 microT; the 25th, 50th, and 75th percentiles were 0.135, 0.17, and 0.23 microT, respectively. By job category, the most highly exposed jobs (>0.23 microT) included bakery worker, cashier, cook and kitchen worker, electronics worker, residential and industrial sewing machine operator, and textile machine operator. By work environment, the most highly exposed job categories were electronics worker in an assembly plant (0.70 microT) and sewing machine operators in a textile factory (0.68 microT) and shoe factory (0.66 microT). These results provide new information on expected levels of exposure in a wide range of jobs commonly held by women. PMID:11836202

  9. Proca and electromagnetic fields

    SciTech Connect

    Hillion, P.; Quinnerz, S.

    1986-07-01

    In the framework of the proper orthochronous Lorentz group, the old connection is revived between the electromagnetic field characterized by a self-dual tensor and a traceless second-rank spinor obeying the Proca equation. The relationship between this spinor and the Hertz potential also considered as a self-dual tensor is emphasized. The extension of this formalism to meet the covariance under the full Lorentz group is also discussed.

  10. Medical applications of electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Lai, Henry C.; Singh, Narendra P.

    2010-04-01

    In this article, we describe two possible applications of low-intensity non-ionizing electromagnetic fields (EMF) for the treatment of malaria and cancer, respectively. In malaria treatment, a low-intensity extremely-low frequency magnetic field can be used to induce vibration of hemozoin, a super-paramagnetic polymer particle, inside malaria parasites. This disturbance could cause free radical and mechanical damages leading to the death of the parasite. This concept has been tested in vitro on malaria parasites and found to be effective. This may provide a low cost effective treatment for malaria infection in humans. The rationale for cancer treatment using low-intensity EMF is based on two concepts that have been well established in the literature: (1) low-intensity non-thermal EMF enhances cytotoxic free radicals via the iron-mediated Fenton reaction; and (2) cancer cells have higher amounts of free iron, thus are more susceptible to the cytotoxic effects of EMF. Since normal cells contain minimal amount of free iron, the effect would be selectively targeting cancer cells. Thus, no adverse side effect would be expected as in traditional chemotherapy and radiation therapy. This concept has also been tested on human cancer cell and normal cells in vitro and proved to be feasible.

  11. Weak extremely-low-frequency magnetic fields and regeneration in the planarian Dugesia tigrina

    SciTech Connect

    Jenrow, K.A.; Smith, C.H.; Liboff, A.R.

    1995-06-01

    Extremely-low-frequency (ELF), low-intensity magnetic fields have been shown to influence cell signaling processes in a variety of systems, both in vivo and in vitro. Similar effects have been demonstrated for nervous system development and neurite outgrowth. The authors report that regeneration in planaria, which incorporates many of these processes, is also affected by ELF magnetic fields. The rate of cephalic regeneration, reflected by the mean regeneration time (MRT), for planaria populations regenerating under continuous exposure to combined DC (78.4 {mu}T) and AC (60.0 Hz at 10.0 {mu}T{sub peak}) magnetic fields applied in parallel was found to be significantly delayed (P {much_lt} 0.001) by 48 {+-} 1 h relative to two different types of control populations (MRT {minus}140 {+-} 12 h). One control population was exposed to only the AC component of this field combination, while the other experienced only the ambient geomagnetic field. All measurements were conducted in a low-gradient, low-noise magnetics laboratory under well-maintained temperature conditions. This delay in regeneration was shown to be dependent on the planaria having a fixed orientation with respect to the magnetic field vectors. Results also indicate that this orientation-dependent transduction process does not result from Faraday induction but is consistent with a Ca{sup 2+} cyclotron resonance mechanism. Data interpretation also permits the tentative conclusion that the effect results from an inhibition of events at an early stage in the regeneration process before the onset of proliferation and differentiation.

  12. Potential therapeutic mechanism of extremely low-frequency high-voltage electric fields in cells.

    PubMed

    Kim, Ka-Eun; Park, Soon-Kwon; Nam, Sang-Yun; Han, Tae-Jong; Cho, Il-Young

    2016-05-18

    The aim of this survey was to provide background theory based on previous research to elucidate the potential pathway by which medical devices using extremely low-frequency high-voltage electric fields (ELF-HVEF) exert therapeutic effects on the human body, and to increase understanding of the AC high-voltage electrotherapeutic apparatus for consumers and suppliers of the relevant devices. Our review revealed that an ELF field as weak as 1-10 μ V/m can induce diverse alterations of membrane proteins such as transporters and channel proteins, including changes in Ca + + binding to a specific site of the cell surface, changes in ion (e.g., Ca + + ) influx or efflux, and alterations in the ligand-receptor interaction. These alterations then induce cytoplasmic responses within cells (Ca + + , cAMP, kinases, etc.) that can have impacts on cell growth, differentiation, and other functional properties by promoting the synthesis of macromolecules. Moreover, increased cytoplasmic Ca + + involves calmodulin-dependent signaling and consequent Ca + + /calmodulin-dependent stimulation of nitric oxide synthesis. This event in turn induces the nitric oxide-cGMP-protein kinase G pathway, which may be an essential factor in the observed physiological and therapeutic responses. PMID:26684400

  13. A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

    NASA Astrophysics Data System (ADS)

    del Moral, A.; Azanza, María J.

    2015-03-01

    A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate ("frequency"), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca2+ Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD-CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD-CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B0 ≅0.2-15 mT) AC-MF of frequency fM=50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation.

  14. Effects of extremely low frequency magnetic field on production of mannatide by α-hemolytic Streptococcus.

    PubMed

    Zhang, Jialan; Xu, Cui; Wan, Yunlei; Gao, Mengxiang

    2016-07-01

    The effect of the extremely low frequency magnetic field (ELF-MF) on biomass and mannatide production by α-hemolytic Streptococcus in liquid-state fermentation culture medium was studied during shake flask culture. Magnetic field (MF) inductions, exposure times, and exposure periods varied in a range of 0-1.5 mT, 0-16 h, and six periods of incubation time, respectively. Results showed both biomass and mannatide production increased significantly at MF induction 0.4, 0.6, and 0.9 mT and decreased at both 1.2 and 1.5 mT. Biomass increased by exposure for initial and middle stages of fermentation. Mannatide production increased significantly at 4-8, 8-12, and 17-21 h. Peak yield of biomass and mannatide production increased by 10.7% and 14.0% at 25 and 27 h of incubation at 0.6 mT MF induction and exposure to 8-12 h of incubation time, compared with the control experiment, respectively. ELF-MF could also enhance the growth rate and mannatide production rate of α-hemolytic Streptococcus. However, ELF-MF did not alter α-hemolytic Streptococcus cell growth and mannatide metabolizing regulation or fermentation pattern. Mannatide production was not associated with cellular growth but rather only partially associated. Bioelectromagnetics. 37:331-337, 2016. © 2016 Wiley Periodicals, Inc. PMID:27271865

  15. Progress in Evaluating Potential EM Earthquake Precursors: Comparison of Independent Ultra Low-Frequency Electro-Magnetic (ULFEM) Systems

    NASA Astrophysics Data System (ADS)

    Chen, B.; Glen, J. M. G.; Klemperer, S. L.; Christman, L.; Bleier, T.; Dunson, J. C.; DeKlotz, M.

    2014-12-01

    Ultra-low frequency anomalies in the magnetic and electric fields have been reported prior to several earthquakes. Because most prominent ULFEM anomalies have thus far only been observed on individual stations, some authors have argued that some of these anomalies have an instrumental cause, rather than being earthquake precursors. Two independent ULFEM networks are presently operating in the greater San Francisco Bay Area; one managed by the U.S. Geological Survey (USGS) and Stanford University and the other by QuakeFinder (QF).The case that these anomalies are not instrumental would be strengthened by a demonstration that identical anomalies are seen on the two networks, despite their different components (magnetometers, digitizers and telemetry). A detailed comparison of the two systems will allow data from each of the two networks to be used to confirm anomalies and to evaluate potential precursor signals. To provide this comparison, the USGS-Stanford and QF acquired data on two independent ULFEM systems at the USGS-Stanford ULFEM station located at the Jasper Ridge Biological Preserve, CA, from March 31-May 13, 2014. The two systems were set up~50m from each other and away from potential sources of noise. Both systems recorded the magnetic field with induction coils oriented along the three cardinal directions aligned with magnetic north. The results of this experiment reveal that the two systems have very similar response functions and comparable noise and drift characteristics. Both complex "noise" (a, b) and single discrete pulses (c, d) were recorded with essentially identical characteristics by the two systems. We also found, in a few instances, where the signals were observed on one system but were absent on the other, clearly indicating either internal system noise or reflecting extremely local site phenomena affecting a single system. Future efforts will involve analyses of pulses, spectral characteristics, correlation coefficients and noise.

  16. Radial evolution of the high/low frequency breakpoint in magnetic field spectra

    NASA Technical Reports Server (NTRS)

    Feynman, J.; Ruzmaikin, A.; Smith, E. J.

    1995-01-01

    The spectra of magnetic field variations in the solar wind show different behavior in two frequency regions; a high frequency region in which the spectral exponent is about -5/3 and a low frequency region in which it is typically -1. The two types of variations must arise from different processes and a clue to the relationship between the spectral regions lies in understanding the behavior of the breakpoint between the spectral regions. Studies of the average behavior of spectra have shown that the break point occurs at about 3.5 hours at 1 AU. It is also known that, on average, the breakpoint occurs at lower frequencies with larger heliocentric distances. Ideally however, instead of the average properties of the spectra, we would like to know how the breakpoint evolves in particular samples of the solar wind as they propagate to larger heliocentric distances. In the study reported here we take advantage of the fact that, in 1974, Pioneer 10 (4.4 AU) and Pioneer 11 (5.6 AU) were close to being co-aligned and being aligned with the Earth. Solar wind observed at Earth can be closely matched with solar wind later observed at P10 and P11. We here compare the breakpoint observed at Earth with that observed at Pioneers 10 and 11 for matched samples of the wind.

  17. A newly designed experimental system for exposure of mammalian cells to extremely low frequency magnetic fields.

    PubMed

    Miyakoshi, J; Ohtsu, S; Tatsumi-Miyajima, J; Takebe, H

    1994-03-01

    To examine the biological effects of extremely low frequency magnetic field (ELFMF), we have designed and manufactured a new equipment for long-term and high-density exposure of cells to ELFMF. The ELFMF exposure system consists of a generator of magnets with a built-in CO2 incubator, an alternating current (AC) power supply, a gas compressor and a thermocontroller for the incubator, and a cooling unit for the magnets. The CO2 incubator made of acrylic resin is inserted into the inner-space of the silicon steel strip-cores. In this system, the temperature of the incubator is maintained at 37 +/- 0.5 degrees C. The maximum magnetic flux density on the exposure area of the incubator is 500 mT (T; tesla) at a current of 556 Arms (rms; root mean square) at 50 Hz. The long-term (up to 120 hr) exposure of 400 mT ELFMF did not affect the growth of both HL60RG and CCRF-CEM cells originated from human leukemia. The post-X-irradiation exposure of 400 mT ELFMF for 2 hr also did not affect the radiation sensitivity of GM0637 and TAT2SF cells originated from a normal human and an ataxia telangiectasia patient. PMID:8057268

  18. Low-frequency noise in MoSe2 field effect transistors

    NASA Astrophysics Data System (ADS)

    Das, Suprem R.; Kwon, Jiseok; Prakash, Abhijith; Delker, Collin J.; Das, Saptarshi; Janes, David B.

    2015-02-01

    One of the important performance metrics of emerging nanoelectronic devices, including low dimensional Field Effect Transistors (FETs), is the magnitude of the low-frequency noise. Atomically thin 2D semiconductor channel materials such as MoX2 (X ≡ S, Se) have shown promising transistor characteristics such as ION/IOFF ratio exceeding 106 and low IOFF, making them attractive as channel materials for next generation nanoelectronic devices. However, MoS2 FETs demonstrated to date exhibit high noise levels under ambient conditions. In this letter, we report at least two orders of magnitude smaller values of Hooge parameter in a back-gated MoSe2 FET (10 atomic layers) with nickel S/D contacts and measured at atmospheric pressure and temperature. The channel dominated regime of noise was extracted from the total noise spectrum and is shown to follow a mobility fluctuation model with 1/f dependence. The low noise in MoSe2 FETs is comparable to other 1D nanoelectronic devices such as carbon nanotube FETs (CNT-FETs) and paves the way for use in future applications in precision sensing and communications.

  19. Low-frequency noise in MoSe{sub 2} field effect transistors

    SciTech Connect

    Das, Suprem R. E-mail: janes@purdue.edu; Kwon, Jiseok; Prakash, Abhijith; Janes, David B. E-mail: janes@purdue.edu; Delker, Collin J.; Das, Saptarshi

    2015-02-23

    One of the important performance metrics of emerging nanoelectronic devices, including low dimensional Field Effect Transistors (FETs), is the magnitude of the low-frequency noise. Atomically thin 2D semiconductor channel materials such as MoX{sub 2} (X ≡ S, Se) have shown promising transistor characteristics such as I{sub ON}/I{sub OFF} ratio exceeding 10{sup 6} and low I{sub OFF}, making them attractive as channel materials for next generation nanoelectronic devices. However, MoS{sub 2} FETs demonstrated to date exhibit high noise levels under ambient conditions. In this letter, we report at least two orders of magnitude smaller values of Hooge parameter in a back-gated MoSe{sub 2} FET (10 atomic layers) with nickel S/D contacts and measured at atmospheric pressure and temperature. The channel dominated regime of noise was extracted from the total noise spectrum and is shown to follow a mobility fluctuation model with 1/f dependence. The low noise in MoSe{sub 2} FETs is comparable to other 1D nanoelectronic devices such as carbon nanotube FETs (CNT-FETs) and paves the way for use in future applications in precision sensing and communications.

  20. [Antitumor and Radioprotective Action of a Low-frequency Turbulent Magnetic Field].

    PubMed

    Rybakov, Y L

    2016-01-01

    The results of experimental studies on the biological effects and mechanisms of action of antitumor and radio modifying weak low-frequency turbulent magnetic field (TMF) on tumor objects of different levels of integration are presented. The studies have been conducted in the Russian Cancer Research Center named after Blokhin of the Russian Academy of Medical Sciences using the methods and criteria applied for the evaluation of antitumor efficacy of new drugs and impacts. Studies of the direct TMP action on tumor cells demonstrate the inhibitory effect on the DNA synthesis, also shown is the ability of TMP to induce apoptosis. It has been shown that exposure to TMF increases the functional activity of phagocytes, which manifests itself in increased level of non-specific resistance of the organism to the tumor process, and represents one of the possible mechanisms of the antitumor action. The discovered radio modifying effect of TMP opens the prospects for its use in combination with radiotherapy. Possible hypotheses about biophysical mechanisms of the established biological effects of TMP are presented. The presence in this physical factor of its own antitumor activity can be of interest for further research. PMID:27534069

  1. Suppression of Low-Frequency Electronic Noise in Polymer Nanowire Field-Effect Transistors.

    PubMed

    Lezzi, Francesca; Ferrari, Giorgio; Pennetta, Cecilia; Pisignano, Dario

    2015-11-11

    The authors report on the reduction of low-frequency noise in semiconductor polymer nanowires with respect to thin-films made of the same organic material. Flicker noise is experimentally investigated in polymer nanowires in the range of 10-10(5) Hz by means of field-effect transistor architectures. The noise in the devices is well described by the Hooge empirical model and exhibits an average Hooge constant, which describes the current power spectral density of fluctuations, suppressed by 1-2 orders of magnitude compared to thin-film devices. To explain the Hooge constant reduction, a resistor network model is developed, in which the organic semiconducting nanostructures or films are depicted through a two-dimensional network of resistors with a square-lattice structure, accounting for the different anisotropy and degree of structural disorder of the active nanowires and films. Results from modeling agree well with experimental findings. These results support enhanced structural order through size-confinement in organic nanostructures as effective route to improve the noise performance in polymer electronic devices. PMID:26479330

  2. Children's Personal Exposure Measurements to Extremely Low Frequency Magnetic Fields in Italy.

    PubMed

    Liorni, Ilaria; Parazzini, Marta; Struchen, Benjamin; Fiocchi, Serena; Röösli, Martin; Ravazzani, Paolo

    2016-01-01

    Extremely low frequency magnetic fields (ELF-MFs) exposure is still a topic of concern due to their possible impact on children's health. Although epidemiological studies claimed an evidence of a possible association between ELF-MF above 0.4 μT and childhood leukemia, biological mechanisms able to support a causal relationship between ELF-MF and this disease were not found yet. To provide further knowledge about children's ELF-MF exposure correlated to children's daily activities, a measurement study was conducted in Milan (Italy). Eighty-six children were recruited, 52 of whom were specifically chosen with respect to the distance to power lines and built-in transformers to oversample potentially highly exposed children. Personal and bedroom measurements were performed for each child in two different seasons. The major outcomes of this study are: (1) median values over 24-h personal and bedroom measurements were <3 μT established by the Italian law as the quality target; (2) geometric mean values over 24-h bedroom measurements were mostly <0.4 μT; (3) seasonal variations did not significantly influence personal and bedroom measurements; (4) the highest average MF levels were mostly found at home during the day and outdoors; (5) no significant differences were found in the median and geometric mean values between personal and bedroom measurements, but were found in the arithmetic mean. PMID:27258295

  3. Children’s Personal Exposure Measurements to Extremely Low Frequency Magnetic Fields in Italy

    PubMed Central

    Liorni, Ilaria; Parazzini, Marta; Struchen, Benjamin; Fiocchi, Serena; Röösli, Martin; Ravazzani, Paolo

    2016-01-01

    Extremely low frequency magnetic fields (ELF-MFs) exposure is still a topic of concern due to their possible impact on children’s health. Although epidemiological studies claimed an evidence of a possible association between ELF-MF above 0.4 μT and childhood leukemia, biological mechanisms able to support a causal relationship between ELF-MF and this disease were not found yet. To provide further knowledge about children’s ELF-MF exposure correlated to children’s daily activities, a measurement study was conducted in Milan (Italy). Eighty-six children were recruited, 52 of whom were specifically chosen with respect to the distance to power lines and built-in transformers to oversample potentially highly exposed children. Personal and bedroom measurements were performed for each child in two different seasons. The major outcomes of this study are: (1) median values over 24-h personal and bedroom measurements were <3 μT established by the Italian law as the quality target; (2) geometric mean values over 24-h bedroom measurements were mostly <0.4 μT; (3) seasonal variations did not significantly influence personal and bedroom measurements; (4) the highest average MF levels were mostly found at home during the day and outdoors; (5) no significant differences were found in the median and geometric mean values between personal and bedroom measurements, but were found in the arithmetic mean. PMID:27258295

  4. Effect of weak, interrupted sinusoidal low frequency magnetic field on neural regeneration in rats: functional evaluation.

    PubMed

    Bervar, Marijan

    2005-07-01

    A study of the effect of weak, interrupted sinusoidal low frequency magnetic field (ISMF) stimulation on regeneration of the rat sciatic nerve was carried out. In the experiment, 60 Wistar rats were used: 24 rats underwent unilateral sciatic nerve transection injury and immediate surgical nerve repair, 24 rats underwent unilateral sciatic nerve crush injury, and the remaining 12 rats underwent a sham surgery. Half of the animals (n = 12) with either sciatic nerve lesion were randomly chosen and exposed between a pair of Helmholtz coils for 3 weeks post-injury, 4 h/day, to an interrupted (active period to pause ratio = 1.4 s/0.8 s) sinusoidal 50 Hz magnetic field of 0.5 mT. The other half of the animals (n = 12) and six rats with sham surgery were used for two separate controls. Functional recovery was followed for 6 weeks for the crush injuries and 7(1/2) months for the transection injuries by video assisted footprint analysis in static conditions and quantified using a recently revised static sciatic index (SSI) formula. We ascertained that the magnetic field influence was weak, but certainly detectable in both injury models. The accuracy of ISMF influence detection, determined by the one-way repeated measures ANOVA test, was better for the crush injury model: F(1, 198) = 9.0144, P = .003, than for the transection injury model: F(1, 198) = 6.4826, P = .012. The Student-Newman-Keuls range test for each response day yielded significant differences (P < .05) between the exposed and control groups early in the beginning of functional recovery and later on from the points adjacent to the beginning of the plateau, or 95% of functional recovery, and the end of observation. These differences probably reflect the ISMF systemic effect on the neuron cell bodies and increased and more efficient reinnervation of the periphery. PMID:15887258

  5. Functional brain measurements within the prefrontal area on pseudo-"blindsight" induced by extremely low frequency electromagnetic stimulations

    NASA Astrophysics Data System (ADS)

    Nakagawa, Hidenori; Ueno, Shoogo

    2015-05-01

    For evaluating the effects of phosphene as pseudo-blindsight closely, we used functional near-infrared spectroscopy to investigate whether or not the phosphene appearance itself substantially affects the hemodynamic responses of the prefrontal area. Seven healthy volunteers ranging in age from 22 to 72 participated in the visual stimulation experiments. First, we examined the influences of electromagnetic stimulations at around the threshold (10 mT) for a blindsight-like phosphene on the responses. According to the results of the aged volunteers, we found the possibility that the delay in the phosphene perception might be caused by aging beyond a certain age. In the results of our measurements using the stimulation of 50 mT, no significant difference in the perception delay for all the volunteers could be detected. When the field strength was decreased from 50 mT to the threshold in steps of 10 mT, the results obtained at the threshold are equivalent to that obtained at 50 mT. Our data strongly support the hypothesis that pseudo-blindsight induced by electromagnetic stimulation of above 50 mT is able to excite all the volunteers' retinal photoreceptor cells provisionally. Hence the continuous stimulations for a long period of time might gradually activate synaptic plasticity on the neural network of the retina.

  6. MESSENGER Magnetic Field Observations of Upstream Ultra-Low Frequency Waves at Mercury

    NASA Technical Reports Server (NTRS)

    Le, G.; Chi, P. J.; Boardsen, S.; Blanco-Cano, X.; Anderosn, B. J.; Korth, H.

    2012-01-01

    The region upstream from a planetary bow shock is a natural plasma laboratory containing a variety of wave particle phenomena. The study of foreshocks other than the Earth's is important for extending our understanding of collisionless shocks and foreshock physics since the bow shock strength varies with heliocentric distance from the Sun, and the sizes of the bow shocks are different at different planets. The Mercury's bow shock is unique in our solar system as it is produced by low Mach number solar wind blowing over a small magnetized body with a predominately radial interplanetary magnetic field. Previous observations of Mercury upstream ultra-low frequency (ULF) waves came exclusively from two Mercury flybys of Mariner 10. The MESSENGER orbiter data enable us to study of upstream waves in the Mercury's foreshock in depth. This paper reports an overview of upstream ULF waves in the Mercury's foreshock using high-time resolution magnetic field data, 20 samples per second, from the MESSENGER spacecraft. The most common foreshock waves have frequencies near 2 Hz, with properties similar to the I-Hz waves in the Earth's foreshock. They are present in both the flyby data and in every orbit of the orbital data we have surveyed. The most common wave phenomenon in the Earth's foreshock is the large-amplitude 30-s waves, but similar waves at Mercury have frequencies at near 0.1 Hz and occur only sporadically with short durations (a few wave cycles). Superposed on the "30-s" waves, there are spectral peaks at near 0.6 Hz, not reported previously in Mariner 10 data. We will discuss wave properties and their occurrence characteristics in this paper.

  7. What Message Should Health Educators Give regarding Electromagnetic Fields?

    ERIC Educational Resources Information Center

    Al-Khamees, Nedaa A.

    2008-01-01

    The possibility of extremely low frequency electromagnetic fields (ELF EMF) causing a number of medical conditions and common symptoms remains a concern and presents somewhat of a quandary to health educators in view of conflicting results. This study investigated the relationship of a number of EMF sources to reported symptoms in an attempt to,…

  8. Safety of Exposure From Extremely Low Frequency Magnetic Fields During Prenatal Ultrasound Examinations in Clinicians and Pregnant Women.

    PubMed

    Park, Jee Soo; Kim, Deok Won; Chung, Jai Won; Kwon, Ja-Young; Park, Yong Won; Cho, Hee Young

    2015-07-01

    Investigations into the safety of ultrasonography in pregnancy have focused on the potential harm of ultrasound itself. However, no data have been published regarding the electromagnetic fields that ultrasound devices might produce. This study is the first to measure extremely low-frequency magnetic field (ELF-MF) exposure of clinicians and pregnant women during prenatal ultrasound examinations in the examination room from 2 different ultrasound devices and compare them with ELF-MFs during patient consultation in the consulting room.The ELF-MF intensities that clinicians and pregnant women were exposed to were measured every 10 seconds for 40 prenatal ultrasound examinations using Philips iU22 or Accuvix V20 Prestige machines and 20 patient consultations in a consulting room using portable ELF-MF measurement devices. The mean ELF-MF exposure of both clinicians and pregnant women was 0.18 ± 0.06 mG during prenatal ultrasound examination. During patient consultation, the mean ELF-MF exposures of clinicians and pregnant women were 0.10 ± 0.01 and 0.11 ± 0.01 mG, respectively. Mean ELF-MF exposures during prenatal ultrasound examination were significantly higher than those during patient consultations (P < 0.001 by Mann-Whitney U test).Our results provide basic reference data on the ELF-MF exposure of both clinicians and pregnant women during prenatal ultrasound monitoring from 2 different ultrasound devices and patient consultation, all of which were below 2 mG, the most stringent level considered safe in many studies, thus relieving any anxiety of clinicians and pregnant women regarding potential risks of ELF-MFs. PMID:26200630

  9. Cancer risk assessment of extremely low frequency electric and magnetic fields: a critical review of methodology.

    PubMed Central

    McCann, J

    1998-01-01

    This review provides a discussion of cancer risk assessment methodology pertinent to developing a strategy for extremely low frequency electric and magnetic fields (EMF). Approaches taken for chemical agents or ionizing radiation in six key topic areas are briefly reviewed, and then those areas are examined from the perspective of EMF, identifying issues to be addressed in developing a risk assessment strategy. The following recommendations are offered: 1) risk assessment should be viewed as an iterative process that informs an overall judgment as to health risk and consists of a complex of related activities incorporating both positive and negative data, tumor and nontumor end points, and human and nonhuman sources of information; 2) a hazard identification resulting in a conclusion of weak or null effects, such as may be associated with EMF, will need to assign significant weight to animal cancer bioassays conducted under defined exposure conditions as well as to human epidemiologic studies; 3) a default factor to account for possible age differences in sensitivity to carcinogenesis should be included in an EMF risk assessment; 4) lack of evidence of dose response and the apparent lack of DNA reactivity of EMF suggest that a safety (or uncertainty) factor or margin of exposure type of risk characterization may be most appropriate; and 5) an EMF risk assessment should permit at least tentative conclusions to be reached as to the limits of carcinogenic risk from exposure to EMF, and should also define an efficient research agenda aimed at clarifying uncertainties appropriate to a more complete assessment. PMID:9799185

  10. Exposure of surgeons to extremely low-frequency magnetic fields during laparoscopic and robotic surgeries.

    PubMed

    Park, Jee Soo; Chung, Jai Won; Kim, Nam Kyu; Cho, Min Soo; Kang, Chang Moo; Choi, Soo Beom; Kim, Deok Won

    2015-02-01

    The development of new medical electronic devices and equipment has increased the use of electrical apparatuses in surgery. Many studies have reported the association of long-term exposure to extremely low-frequency magnetic fields (ELF-MFs) with diseases or cancer. Robotic surgery has emerged as an alternative tool to overcome the disadvantages of conventional laparoscopic surgery. However, there has been no report regarding how much ELF-MF surgeons are exposed to during laparoscopic and robotic surgeries. In this observational study, we aimed to measure and compare the ELF-MFs that surgeons are exposed to during laparoscopic and robotic surgery.The intensities of the ELF-MFs surgeons are exposed to were measured every 4 seconds for 20 cases of laparoscopic surgery and 20 cases of robotic surgery using portable ELF-MF measuring devices with logging capability.The mean ELF-MF exposures were 0.6 ± 0.1 mG for laparoscopic surgeries and 0.3 ± 0.0 mG for robotic surgeries (significantly lower with P < 0.001 by Mann-Whitney U test).Our results show that the ELF-MF exposure levels of surgeons in both robotic and conventional laparoscopic surgery were lower than 2 mG, which is the most stringent level considered safe in many studies. However, we should not overlook the effects of long-term ELF-MF exposure during many surgeries in the course of a surgeon's career. PMID:25674758

  11. Effect of extremely low frequency magnetic fields on cell proliferation and gene expression.

    PubMed

    Lee, Hyung Chul; Hong, Mi-Na; Jung, Seung Hee; Kim, Bong Cho; Suh, Young Ju; Ko, Young-Gyu; Lee, Yun-Sil; Lee, Byeong-Yoon; Cho, Yeun-Gyu; Myung, Sung-Ho; Lee, Jae-Seon

    2015-10-01

    Owing to concerns regarding possible effects of extremely low frequency magnetic fields (ELF-MF) on human health, many studies have been conducted to elucidate whether ELF-MF can induce modifications in biological processes. Despite this, controversies regarding effects of ELF-MF are still rife. In this study, we investigated biological effects of ELF-MF on MCF10A, MCF7, Jurkat, and NIH3T3 cell lines. ELF-MF with a magnetic flux density of 1 mT at 60 Hz was employed to stimulate cells for 4 or 16 h, after which the effects of ELF-MF on cell proliferation, cell death, cell viability, and DNA synthesis rates were assessed. Whereas Jurkat and NIH3T3 cells showed no consistent variation in cell number, cell viability, and DNA synthesis rate, MCF10A and MCF7 cells showed consistent and significant decreases in cell number, cell viability, and DNA synthesis rates. However, there was no effect of ELF-MF on cell death in any of tested cell lines. Next, to investigate the effect of ELF-MF on gene expression, we exposed MCF7 cells to 2 mT at 60 Hz for 16 h and examined transcriptional responses by using gene expression array. We found a gene, PMAIP1, that exhibited statistically significant variation using two-fold cut-off criteria and certified its expression change by using semi-quantitative and quantitative reverse transcription polymerase chain reaction. From these results, we concluded that ELF-MF could induce the delay of cell cycle progression in MCF7 and MCF10A cells in a cell context-specific manner and could up-regulate PMAIP1 in MCF7 cells. PMID:26239017

  12. Locating narrow bipolar events with single-station measurement of low-frequency magnetic fields

    NASA Astrophysics Data System (ADS)

    Zhang, Hongbo; Lu, Gaopeng; Qie, Xiushu; Jiang, Rubin; Fan, Yanfeng; Tian, Ye; Sun, Zhuling; Liu, Mingyuan; Wang, Zhichao; Liu, Dongxia; Feng, Guili

    2016-06-01

    We developed a method to locate the narrow bipolar events (NBEs) based on the single-station measurement of low-frequency (LF, 40-500 kHz) magnetic fields. The direction finding of a two-axis magnetic sensor provides the azimuth of NBEs relative to the measurement site; the ionospheric reflection pairs in the lightning sferics are used to determine the range and height. We applied this method to determine the three-dimensional (3D) locations of 1475 NBEs with magnetic signals recorded during the SHandong Artificially Triggered Lightning Experiment (SHATLE) in summer of 2013. The NBE detections are evaluated on a storm basis by comparing with radar observations of reflectivity and lightning data from the World Wide Lightning Location Network (WWLLN) for two mesoscale convective systems (MCSs) of different sizes. As revealed by previous studies, NBEs are predominately produced in the convective regions with relatively strong radar echo (with composite reflectivity ≥30 dBZ), although not all the convections with high reflectivity and active lightning production are in favor of NBE production. The NBEs located by the single-station magnetic method also exhibit the distinct segregation in altitude for positive and negative NBEs, namely positive NBEs are mainly produced between 7 km and 15 km, while negative NBEs are predominantly produced above 14 km. In summary, the results of comparison generally show that the single-station magnetic method can locate NBEs with good reliability, although the accuracy of 3D location remains to be evaluated with the traditional multi-station method based on the time-of-arrival technique. This method can be applied to track the motion of storm convection within 800 km, especially when they move out to ocean beyond the detection range (typically <400 km) of meteorological radars, making it possible to study NBEs in oceanic thunderstorms for which the location with multiple ground-based stations is usually not feasible.

  13. Eruption of permanent dentition in rhesus monkeys exposed to ELF (extremely low frequency) fields. Interim report

    SciTech Connect

    David, T.D.; Harris, G.A.; Bley, J.A. Jr

    1983-04-01

    In a study initiated to determine the biological effects of ELF electric and magnetic fields associated with a submarine communications system ELF-exposed male rhesus monkeys gained weight at a slightly faster rate than control males. In order to obtain sufficient data on the physiological effects of electromagnetic fields, a second ELF study was initiated. Whereas the first study was initiated with wild-caught young adult animals, the second study utilized colony-bred animals beginning at 30 days of age. The emphasis of the second study was to substantiate previous findings and determine the underlying mechanisms involved. As in the first study, 30 primates (male and female) were exposed to the ELF electric and magnetic fields, and 30 control animals received the same care and treatment, but were not exposed. This report deals with the development of the permanent teeth relative to ELF exposure and sex. A consistent trend noted was that the teeth of female animals erupted at a slightly earlier age than males. However, no significant differences due to ELF exposure or sex were detected.

  14. [Health effects of electromagnetic fields].

    PubMed

    Röösli, Martin

    2013-12-01

    Use of electricity causes extremely low frequency magnetic fields (ELF-MF) and wireless communication devices emit radiofrequency electromagnetic fields (RF-EMF). Average ELF-MF exposure is mainly determined by high voltage power lines and transformers at home or at the workplace, whereas RF-EMF exposure is mainly caused by devices operating close to the body (mainly mobile and cordless phones). Health effects of EMF are controversially discussed. The IARC classified ELF-MF and RF-EMF as possible carcinogenic. Most consistent epidemiological evidence was found for an association between ELF-MF and childhood leukaemia. If causal, 1 - 4 percent of all childhood leukaemia cases could be attributed to ELF-MF. Epidemiological research provided some indications for an association between ELF-MF and Alzheimer's diseases as well as amyotrophic lateral sclerosis, although not entirely consistent. Regarding mobile phones and brain tumours, some studies observed an increased risk after heavy or long term use on the one hand. On the other hand, brain tumour incidence was not found to have increased in the last decade in Sweden, England or the US. Acute effects of RF-EMF on non-specific symptoms of ill health seem unlikely according to randomized and double blind provocation studies. However, epidemiological research on long term effects is still limited. Although from the current state of the scientific knowledge a large individual health risk from RF-EMF exposure is unlikely, even a small risk would have substantial public health relevance because of the widespread use of wireless communication technologies. PMID:24297859

  15. Interactions between electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Schwan, H. P.

    1985-02-01

    We applied for this grant to support a workshop at Erice, Italy. This workshop has been commonly called Erice School and the main subject of this workshop is the interaction of electromagnetic fields with biological cells and molecules. The grant from ONR enabled us to invite American scientists to participants in this workshop and deliver scientific papers. The duration of the Erice School was ten days. Therefore, we had sufficient time to discuss the problems of electromagnetic radiations. Vigorous discussions took place during official sessions and during private conversations. The participants of this workshop are mostly those who have been active in the research on bioelectromagnetics, but there are some numbers of speakers who discussed the basic electrical and magnetic properties of polyelectrolytes, biological membranes and tissue. The workshop was unique in that there were participants with a variety of training backgrounds. This enabled us to exchange the information between applied scientists and basic scientists. Also, active exchanges of opinions took place between biological scientists and physical scientists.

  16. Macroscopic vacuum effects in an inhomogeneous and nonstationary electromagnetic field

    SciTech Connect

    Gal'tsov, D.V.; Nikitina, N.S.

    1983-04-01

    Macroscopic effects of vacuum polarization by a strong nonuniform and nonstationary fields, which are kinematically forbidden in the case of a uniform magnetic field, are considered. Calculations are perfomed for the deflection of a light beam in the field of a magnetic dipole, for the production of photon pairs by an inclined rotator, and for doubling and modulation of the frequency in scattering of low-frequency electromagnetic waves by the magnetic field of an inclined rotator.

  17. REVIEWS OF TOPICAL PROBLEMS: Natural and man-made low-frequency magnetic fields as a potential health hazard

    NASA Astrophysics Data System (ADS)

    Ptitsyna, N. G.; Villoresi, G.; Dorman, L. I.; Iucci, N.; Tyasto, Marta I.

    1998-07-01

    Is human health affected by low-frequency low-intensity environmental magnetic fields? There is much diehard evidence that it is. For this reason irregular, spectrally complex ULF (0-10 Hz) magnetic fields have recently come under scrutiny, typical of natural geomagnetic perturbations or electric transportation. Recent work shows that such fields do affect the nervous system and may even cause heart attacks.

  18. Low frequency magnetic field suppression in an atomic spin co-magnetometer with a large electron magnetic field

    NASA Astrophysics Data System (ADS)

    Fang, Jiancheng; Chen, Yao; Zou, Sheng; Liu, Xuejing; Hu, Zhaohui; Quan, Wei; Yuan, Heng; Ding, Ming

    2016-03-01

    In a K-Rb-21Ne co-magnetometer, the Rb electron magnetic field which is experienced by the nuclear spin is about 100 times larger than that of the K in a K-3He co-magnetometer. The large electron magnetic field which is neglected in the K-3He co-magnetometer coupled Bloch equations model is considered here in the K-Rb-21Ne co-magnetometer to study the low frequency magnetic field suppression effect. Theoretical analysis and experimental results shows that in the K-Rb-21Ne spin co-magnetometer, not only the nuclear spin but also the large electron spin magnetic field compensate the external magnetic field noise. By comparison, only the 3He nuclear spins mainly compensate the external magnetic field noise in a K-3He co-magnetometer. With this study, in addition to just increasing the magnetic field of the nuclear spins, we can suppress the magnetic field noise by increasing the density of the electron spin. We also studied how the magnetic field suppression effect relates to the scale factor of the K-Rb-21Ne co-magnetometer and we compared the scale factor with that of the K-3He co-magnetometer. Lastly, we show the sensitivity of our co-magnetometer. The magnetic field noise, the air density fluctuation noise and pumping power optimization are studied to improve the sensitivity of the co-magnetometer.

  19. Severe Cognitive Dysfunction and Occupational Extremely Low Frequency Magnetic Field Exposure among Elderly Mexican Americans

    PubMed Central

    Davanipour, Zoreh; Tseng, Chiu-Chen; Lee, Pey-Jiuan; Markides, Kyriakos S.; Sobel, Eugene

    2014-01-01

    Aims This report is the first study of the possible relationship between extremely low frequency (50–60 Hz, ELF) magnetic field (MF) exposure and severe cognitive dysfunction. Earlier studies investigated the relationships between MF occupational exposure and Alzheimer’s disease (AD) or dementia. These studies had mixed results, depending upon whether the diagnosis of AD or dementia was performed by experts and upon the methodology used to classify MF exposure. Study Design Population-based case-control. Place and Duration of Study Neurology and Preventive Medicine, Keck School of Medicine, University of Southern California, 2 years. Methodology The study population consisted of 3050 Mexican Americans, aged 65+, enrolled in Phase 1 of the Hispanic Established Population for the Epidemiologic Study of the Elderly (H-EPESE) study. Mini-Mental State Exam (MMSE) results, primary occupational history, and other data were collected. Severe cognitive dysfunction was defined as an MMSE score below 10. The MF exposure methodology developed and used in earlier studies was used. Results Univariate odds ratios (OR) were 3.4 (P< .03; 95% CI: 1.3–8.9) for high and 1.7 (P=.27; 95% CI: 0.7–4.1) for medium or high (M/H) MF occupations. In multivariate main effects models, the results were similar. When interaction terms were allowed in the models, the interactions between M/H or high occupational MF exposure and smoking history or age group were statistically significant, depending upon whether two (65–74, 75+) or three (65–74, 75–84, 85+) age groups were considered, respectively. When the analyses were limited to subjects aged 75+, the interactions between M/H or high MF occupations and a positive smoking history were statistically significant. Conclusion The results of this study indicate that working in an occupation with high or M/H MF exposure may increase the risk of severe cognitive dysfunction. Smoking and older age may increase the deleterious effect of MF

  20. The influence of low frequency of external electric field on nucleation enhancement of hen egg-white lysozyme (HEWL)

    NASA Astrophysics Data System (ADS)

    Pan, Weichun; Xu, Haixing; Zhang, Rui; Xu, Jin; Tsukamoto, Katsuo; Han, Jianzhong; Li, Ang

    2015-10-01

    Protein crystal nucleation processes are drawing increasing interests in both academic and industrial communities. Electric field is a promising means, due to its versatility and easy application, among various external fields that may lead to controllable desired protein crystal nucleation. Different from literature reported experimental and theoretical studies that examined the effects of high frequency electric fields; this work was focused on the low frequency range. For this purpose, Hen-White Lysozyme crystal nucleation from its aqueous solution was used as the model system. We found by experiments that the nucleation rate is non-monotonously dependent on electric field frequency less than 1 kHz, which may be ascribed to the mutual orientation modification between neighbor protein molecules induced by the external low frequency, and is different from the case of high frequencies that influence the intermolecular interactions.

  1. Low-frequency Imaging of Fields at High Galactic Latitude with the Murchison Widefield Array 32 Element Prototype

    NASA Astrophysics Data System (ADS)

    Williams, Christopher L.; Hewitt, Jacqueline N.; Levine, Alan M.; de Oliveira-Costa, Angelica; Bowman, Judd D.; Briggs, Frank H.; Gaensler, B. M.; Hernquist, Lars L.; Mitchell, Daniel A.; Morales, Miguel F.; Sethi, Shiv K.; Subrahmanyan, Ravi; Sadler, Elaine M.; Arcus, Wayne; Barnes, David G.; Bernardi, Gianni; Bunton, John D.; Cappallo, Roger C.; Crosse, Brian W.; Corey, Brian E.; Deshpande, Avinash; deSouza, Ludi; Emrich, David; Goeke, Robert F.; Greenhill, Lincoln J.; Hazelton, Bryna J.; Herne, David; Kaplan, David L.; Kasper, Justin C.; Kincaid, Barton B.; Koenig, Ronald; Kratzenberg, Eric; Lonsdale, Colin J.; Lynch, Mervyn J.; McWhirter, S. Russell; Morgan, Edward H.; Oberoi, Divya; Ord, Stephen M.; Pathikulangara, Joseph; Prabu, Thiagaraj; Remillard, Ronald A.; Rogers, Alan E. E.; Anish Roshi, D.; Salah, Joseph E.; Sault, Robert J.; Udaya Shankar, N.; Srivani, K. S.; Stevens, Jamie B.; Tingay, Steven J.; Wayth, Randall B.; Waterson, Mark; Webster, Rachel L.; Whitney, Alan R.; Williams, Andrew J.; Wyithe, J. Stuart B.

    2012-08-01

    The Murchison Widefield Array (MWA) is a new low-frequency, wide-field-of-view radio interferometer under development at the Murchison Radio-astronomy Observatory in Western Australia. We have used a 32 element MWA prototype interferometer (MWA-32T) to observe two 50° diameter fields in the southern sky, covering a total of ~2700 deg2, in order to evaluate the performance of the MWA-32T, to develop techniques for epoch of reionization experiments, and to make measurements of astronomical foregrounds. We developed a calibration and imaging pipeline for the MWA-32T, and used it to produce ~15' angular resolution maps of the two fields in the 110-200 MHz band. We perform a blind source extraction using these confusion-limited images, and detect 655 sources at high significance with an additional 871 lower significance source candidates. We compare these sources with existing low-frequency radio surveys in order to assess the MWA-32T system performance, wide-field analysis algorithms, and catalog quality. Our source catalog is found to agree well with existing low-frequency surveys in these regions of the sky and with statistical distributions of point sources derived from Northern Hemisphere surveys; it represents one of the deepest surveys to date of this sky field in the 110-200 MHz band.

  2. LOW-FREQUENCY IMAGING OF FIELDS AT HIGH GALACTIC LATITUDE WITH THE MURCHISON WIDEFIELD ARRAY 32 ELEMENT PROTOTYPE

    SciTech Connect

    Williams, Christopher L.; Hewitt, Jacqueline N.; Levine, Alan M.; De Oliveira-Costa, Angelica; Hernquist, Lars L.; Bernardi, Gianni; Bowman, Judd D.; Briggs, Frank H.; Gaensler, B. M.; Mitchell, Daniel A.; Subrahmanyan, Ravi; Sadler, Elaine M.; Morales, Miguel F.; Sethi, Shiv K.; Arcus, Wayne; Crosse, Brian W.; Barnes, David G.; Bunton, John D.; Cappallo, Roger C.; Corey, Brian E.; and others

    2012-08-10

    The Murchison Widefield Array (MWA) is a new low-frequency, wide-field-of-view radio interferometer under development at the Murchison Radio-astronomy Observatory in Western Australia. We have used a 32 element MWA prototype interferometer (MWA-32T) to observe two 50 Degree-Sign diameter fields in the southern sky, covering a total of {approx}2700 deg{sup 2}, in order to evaluate the performance of the MWA-32T, to develop techniques for epoch of reionization experiments, and to make measurements of astronomical foregrounds. We developed a calibration and imaging pipeline for the MWA-32T, and used it to produce {approx}15' angular resolution maps of the two fields in the 110-200 MHz band. We perform a blind source extraction using these confusion-limited images, and detect 655 sources at high significance with an additional 871 lower significance source candidates. We compare these sources with existing low-frequency radio surveys in order to assess the MWA-32T system performance, wide-field analysis algorithms, and catalog quality. Our source catalog is found to agree well with existing low-frequency surveys in these regions of the sky and with statistical distributions of point sources derived from Northern Hemisphere surveys; it represents one of the deepest surveys to date of this sky field in the 110-200 MHz band.

  3. Enzyme-functionalized gold-coated magnetite nanoparticles as novel hybrid nanomaterials: synthesis, purification and control of enzyme function by low-frequency magnetic field.

    PubMed

    Majouga, Alexander; Sokolsky-Papkov, Marina; Kuznetsov, Artem; Lebedev, Dmitry; Efremova, Maria; Beloglazkina, Elena; Rudakovskaya, Polina; Veselov, Maxim; Zyk, Nikolay; Golovin, Yuri; Klyachko, Natalia; Kabanov, Alexander

    2015-01-01

    The possibility of remotely inducing a defined effect on NPs by means of electromagnetic radiation appears attractive. From a practical point of view, this effect opens horizons for remote control of drug release systems, as well as modulation of biochemical functions in cells. Gold-coated magnetite nanoparticles are perfect candidates for such application. Herein, we have successfully synthesized core-shell NPs having magnetite cores and gold shells modified with various sulphur containing ligands and developed a new, simple and robust procedure for the purification of the resulting nanoparticles. The carboxylic groups displayed at the surface of the NPs were utilized for NP conjugation with a model enzyme (ChT). In the present study, we report the effect of the low-frequency AC magnetic field on the catalytic activity of the immobilized ChT. We show that the enzyme activity decreases upon exposure of the NPs to the field. PMID:25460600

  4. Estimating the power law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic data

    NASA Astrophysics Data System (ADS)

    Beskardes, G. D.; Weiss, C. J.; Everett, M. E.

    2013-12-01

    Electromagnetic methods of geophysical exploration are a reflection of the spatio-temporal variability in ground conductivity, a macroscopic physical property that is a function of lithology, pore-scale surface chemistry, fracture networks, and the presence and distribution of fluids and partial melts. As such, the bulk electrical properties of some representative elementary volume within the subsurface derive from the macroscopic effect of charge buildup and current pathways across a range of length scales within. Quantifying this relationship between multiscale electrical properties and the observed geophysical data is a critical step toward meaningful geologic interpretation. Previously we presented evidence of near-surface electromagnetic data whose small scale fluctuations are both repeatable and fractally distributed -- an observation that supports the notion of a spatially hierarchical Earth. Bounded by the end member cases from homogenized isotropic and anisotropic media, we present numerical modeling results from textured and spatially-correlated, stochastic geologic media, demonstrating that the electromagnetic response is a power law distribution similar to that seen in the earlier observational data, rather than a smooth response polluted with Gaussian noise as is commonly assumed. Furthermore, we show that such power law behavior is dependent on correlation length within the medium and that the power law distribution of Earth conductivity can be estimated from that of the observed electromagnetic data.

  5. Kinetic theory of low-frequency cross-field instability in a weakly ionized plasma. I

    SciTech Connect

    Dimant, Y.S.; Sudan, R.N.

    1995-04-01

    A consistent kinetic theory is developed for the description of electrons under conditions of a low-frequency two-stream {bold E}{times}{bold B} instability in collisionally dominated, weakly ionized plasmas. Starting from the Boltzmann collision integral, a simplified kinetic equation for the electron distribution function has been derived, which takes into account strong pitch-angle scattering of electrons by neutrals, velocity dependence of the electron--neutral collision frequency, etc. Linearized equations describing small oscillations of the electron distribution function and ion density are presented. For the asymptotic case of short waves, the dispersion relation of the {bold E}{times}{bold B} instability has been obtained and analyzed under conditions typical for the lower ionosphere. Under certain conditions, the rigorous kinetic consideration yields substantial changes in results compared to previous theories. The general approach may be applied to other linear and nonlinear low-frequency processes in a weakly ionized plasma. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  6. Coherent hybrid electromagnetic field imaging

    DOEpatents

    Cooke, Bradly J.; Guenther, David C.

    2008-08-26

    An apparatus and corresponding method for coherent hybrid electromagnetic field imaging of a target, where an energy source is used to generate a propagating electromagnetic beam, an electromagnetic beam splitting means to split the beam into two or more coherently matched beams of about equal amplitude, and where the spatial and temporal self-coherence between each two or more coherently matched beams is preserved. Two or more differential modulation means are employed to modulate each two or more coherently matched beams with a time-varying polarization, frequency, phase, and amplitude signal. An electromagnetic beam combining means is used to coherently combine said two or more coherently matched beams into a coherent electromagnetic beam. One or more electromagnetic beam controlling means are used for collimating, guiding, or focusing the coherent electromagnetic beam. One or more apertures are used for transmitting and receiving the coherent electromagnetic beam to and from the target. A receiver is used that is capable of square-law detection of the coherent electromagnetic beam. A waveform generator is used that is capable of generation and control of time-varying polarization, frequency, phase, or amplitude modulation waveforms and sequences. A means of synchronizing time varying waveform is used between the energy source and the receiver. Finally, a means of displaying the images created by the interaction of the coherent electromagnetic beam with target is employed.

  7. Kinetic theory of low-frequency cross-field instability in a weakly ionized plasma. II

    SciTech Connect

    Dimant, Y.S.; Sudan, R.N.

    1995-04-01

    The consistent kinetic approach developed in Paper I [Ya. S. Dimant and R. N. Sudan, Phys. Plasmas {bold 2}, 1157 (1995)] is applied to obtain the general dispersion relation of the two-stream {bold E}{times}{bold B} instability in collisionally dominated weakly ionized plasmas for wave frequencies small compared to the ion--neutral collision frequency. This dispersion relation covers the whole low-frequency band from the asymptotic short-wave limit studied in Paper I to the long-wave limit. Previous theories employing simplified kinetic theory or fluid equations for electron behavior are only correct in the long-wave limit. The principal new results are that the threshold conditions for this instability and the growth rates are altered from those predicted by earlier simplified theories. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  8. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOEpatents

    Epstein, A.J.; Morin, B.G.

    1998-10-13

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors. 21 figs.

  9. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOEpatents

    Epstein, Arthur J.; Morin, Brian G.

    1998-01-01

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors.

  10. Near-field Observations of Very-low-frequency Earthquakes on the San Andreas Fault

    NASA Astrophysics Data System (ADS)

    Peña-Castro, A. F.; Harrington, R. M.; Cochran, E. S.

    2015-12-01

    Fault rupture at varying time scales has been detected in multiple subduction zones, e.g., in slow-slip events (SSEs), very-low-frequency earthquakes (VLFEs), and low-frequency earthquakes (LFEs) or tectonic tremor. However, only LFEs or tremor have been identified and studied in detail along strike-slip faults, like the San Andreas Fault (SAF). Here, we present evidence for VLFEs on the SAF near Parkfield, California. Using data from permanent broadband stations and a temporary deployment of 13 broadband stations installed in 2010-2011 near Cholame, California, we detect 5 VLFEs, with 1 VLFE occurring unambiguosly when there is visible tremor activity. We check that the signals we detect are local by confirming that they appear only on stations within a 70 km radius, and removing time periods when teleseismic events occur, as identified in the global Centroid Moment Tensor (CMT) and the Northern California Seismic Network (NCSN) catalogs. VLFEs have to-date been observed to only occur simultaneously in time and space with tremor activity, but our detections suggests that VLFEs can occur independent of tremor along strike-slip faults. This may indicate that the slipping patches that produce slow earthquakes in transform faults have different mechanical properties than the patches in subducting plates, althought it does not rule out that VLFEs are only observed with tremor in subduction zones simply due to detection methods. An approximate estimation of the apparent velocity, based on a grid-search location using variance reduction, suggests that the observed phase velocity of the VLFEs is ~ 3km/s, corresponding to surface waves. We perform a focal mechanism inversion with a grid search to find a more precise location, depth and orientation of the VLFEs. These results provide new insight into the behavior of the SAF and more generally contribute to an improved understanding of transform fault systems.

  11. Sounding of Groundwater Through Conductive Media in Mars Analog Environments Using Transient Electromagnetics and Low Frequency GPR.

    NASA Astrophysics Data System (ADS)

    Jernsletten, J. A.; Heggy, E.

    2004-05-01

    INTRODUCTION: This study compares the use of (diffusive) Transient Electromagnetics (TEM) for sounding of subsurface water in conductive Mars analog environments to the use of (propagative) Ground-Penetrating Radar (GPR) for the same purpose. We show data from three field studies: 1) Radar sounding data (GPR) from the Nubian aquifer, Bahria Oasis, Egypt; 2) Diffusive sounding data (TEM) from Pima County, Arizona; and 3) Shallower sounding data using the Fast-Turnoff TEM method from Peña de Hierro in the Rio Tinto area, Spain. The latter is data from work conducted under the auspices of the Mars Analog Research and Technology Experiment (MARTE). POTENTIAL OF TEM: A TEM survey was carried out in Pima County, Arizona, in January 2003. Data was collected using 100 m Tx loops, a ferrite-cored magnetic coil Rx antenna, and a sounding frequency of 16 Hz. The dataset has ~500 m depth of investigation, shows a ~120 m depth to the water table (confirmed by several USGS test wells in the area), and a conductive (~20-40 Ω m) clay-rich soil above the water table. The Rio Tinto Fast-Turnoff TEM data was collected using 40 m Tx loops, 10 m Rx loops, and a 32 Hz sounding frequency. Note ~200 m depth of investigation and a conductive high at ~80 m depth (interpreted as water table). Data was also collected using 20 m Tx loops (10 m Rx loops) in other parts of the area. Note ~50 m depth of investigation and a conductive high at ~15 m depth (interpreted as subsurface water flow under mine tailings matching surface flows seen coming out from under the tailings, and shown on maps). Both of these interpretations were roughly confirmed by preliminary results from the MARTE ground truth drilling campaign carried out in September and October 2003. POTENTIAL OF GPR: A GPR experiment was carried out in February 2003 in the Bahria Oasis in the western Egyptian desert, using a 2 MHz monostatic GPR, mapping the Nubian Aquifer at depths of 100-900 m, beneath a thick layer of homogenous marine

  12. Basic Restriction and Reference Level in Anatomically-based Japanese Models for Low-Frequency Electric and Magnetic Field Exposures

    NASA Astrophysics Data System (ADS)

    Takano, Yukinori; Hirata, Akimasa; Fujiwara, Osamu

    Human exposed to electric and/or magnetic fields at low frequencies may cause direct effect such as nerve stimulation and excitation. Therefore, basic restriction is regulated in terms of induced current density in the ICNIRP guidelines and in-situ electric field in the IEEE standard. External electric or magnetic field which does not produce induced quantities exceeding the basic restriction is used as a reference level. The relationship between the basic restriction and reference level for low-frequency electric and magnetic fields has been investigated using European anatomic models, while limited for Japanese model, especially for electric field exposures. In addition, that relationship has not well been discussed. In the present study, we calculated the induced quantities in anatomic Japanese male and female models exposed to electric and magnetic fields at reference level. A quasi static finite-difference time-domain (FDTD) method was applied to analyze this problem. As a result, spatially averaged induced current density was found to be more sensitive to averaging algorithms than that of in-situ electric field. For electric and magnetic field exposure at the ICNIRP reference level, the maximum values of the induced current density for different averaging algorithm were smaller than the basic restriction for most cases. For exposures at the reference level in the IEEE standard, the maximum electric fields in the brain were larger than the basic restriction in the brain while smaller for the spinal cord and heart.

  13. Neural network technique for identifying prognostic anomalies from low-frequency electromagnetic signals in the Kuril-Kamchatka region

    NASA Astrophysics Data System (ADS)

    Popova, I.; Rozhnoi, A.; Solovieva, M.; Levin, B.; Chebrov, V.

    2016-03-01

    In this paper, we suggest a technique for forecasting seismic events based on the very low and low frequency (VLF and LF) signals in the 10 to 50 Hz band using the neural network approach, specifically, the error back-propagation method (EBPM). In this method, the solution of the problem has two main stages: training and recognition (forecasting). The training set is constructed from the combined data, including the amplitudes and phases of the VLF/LF signals measured in the monitoring of the Kuril-Kamchatka region and the corresponding parameters of regional seismicity. Training the neural network establishes the internal relationship between the characteristic changes in the VLF/LF signals a few days before a seismic event and the corresponding level of seismicity. The trained neural network is then applied in a prognostic mode for automated detection of the anomalous changes in the signal which are associated with seismic activity exceeding the assumed threshold level. By the example of several time intervals in 2004, 2005, 2006, and 2007, we demonstrate the efficiency of the neural network approach in the short-term forecasting of earthquakes with magnitudes starting from M ≥ 5.5 from the nighttime variations in the amplitudes and phases of the LF signals on one radio path. We also discuss the results of the simultaneous analysis of the VLF/LF data measured on two partially overlapping paths aimed at revealing the correlations between the nighttime variations in the amplitude of the signal and seismic activity.

  14. Extremely low-frequency magnetic fields can impair spermatogenesis recovery after reversible testicular damage induced by heat.

    PubMed

    Tenorio, Bruno Mendes; Ferreira Filho, Moisés Bonifacio Alves; Jimenez, George Chaves; de Morais, Rosana Nogueira; Peixoto, Christina Alves; Nogueira, Romildo de Albuquerque; da Silva Junior, Valdemiro Amaro

    2014-06-01

    Male infertility is often related to reproductive age couples experiencing fertility-related issues. Men may have fertility problems associated with reversible testicular damage. Considering that men have been increasingly exposed to extremely low-frequency magnetic fields generated by the production, distribution and use of electricity, this study analyzed whether 60 Hz and 1 mT magnetic field exposure may impair spermatogenesis recovery after reversible testicular damage induced by heat shock using rats as an experimental model. Adult male rats were subjected to a single testicular heat shock (HS, 43 °C for 12 min) and then exposed to the magnetic field for 15, 30 and 60 d after HS. Magnetic field exposure during the spermatogenesis recovery induced changes in testis components volume, cell ultrastructure and histomorphometrical parameters. Control animals had a reestablished and active spermatogenesis at 60 d after heat shock, while animals exposed to magnetic field still showed extensive testicular degeneration. Magnetic field exposure did not change the plasma testosterone. In conclusion, extremely low-frequency magnetic field may be harmful to fertility recovery in males affected by reversible testicular damage. PMID:23781997

  15. Self-dual electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Chubykalo, Andrew E.; Espinoza, Augusto; Kosyakov, B. P.

    2010-08-01

    We demonstrate the utility of self-dual fields in electrodynamics. Stable configurations of free electromagnetic fields can be represented as superpositions of standing waves, each possessing zero Poynting vector and zero orbital angular momentum. The standing waves are themselves superpositions of self-dual and anti-self-dual solutions. The idea of self-duality provides additional insights into the geometrical and spectral properties of stable electromagnetic configurations, such as those responsible for the formation of ball lightning.

  16. New experimental technique for detecting the effect of low-frequency electric fields on enzyme structure

    SciTech Connect

    Greco, G. Jr.; Gianfreda, L.; d'Ambrosio, G.; Massa, R.; Scaglione, A.; Scarfi, M.R. )

    1990-01-01

    A new experimental approach has been developed to determine kinetic and thermodynamic parameters of the inactivation of an enzyme under labile conditions both with and without exposure to electrical currents as sources of perturbation. Studies were undertaken to investigate if low-frequency electric currents can accelerate the thermal inactivation of an enzyme through interactions with dipole moments in enzymatic molecules and through related mechanical stresses. The experiments were conducted with the enzyme acid phosphatase. The enzyme was exposed to a 50-Hz current at different densities (10 to 60 mA/cm2 rms) or to a sinusoidal or square-wave current at an average density of 3 mA/cm2 and frequencies from, respectively, 50 Hz to 20 kHz and 500 pulses per second (pps) to 50,000 pps. Positive-control experiments were performed in the presence of a stabilizer or a deactivator. The results indicate that the technique is sensitive to conformational changes that otherwise may be impossible to detect. However, exposure to electric currents under the experimental conditions described herein showed no effects of the currents.

  17. New experimental technique for detecting the effect of low-frequency electric fields on enzyme structure.

    PubMed

    Greco, G; Gianfreda, L; d'Ambrosio, G; Massa, R; Scaglione, A; Scarfi, M R

    1990-01-01

    A new experimental approach has been developed to determine kinetic and thermodynamic parameters of the inactivation of an enzyme under labile conditions both with and without exposure to electrical currents as sources of perturbation. Studies were undertaken to investigate if low-frequency electric currents can accelerate the thermal inactivation of an enzyme through interactions with dipole moments in enzymatic molecules and through related mechanical stresses. The experiments were conducted with the enzyme acid phosphatase. The enzyme was exposed to a 50-Hz current at different densities (10 to 60 mA/cm2 rms) or to a sinusoidal or square-wave current at an average density of 3 mA/cm2 and frequencies from, respectively, 50 Hz to 20 kHz and 500 pulses per second (pps) to 50,000 pps. Positive-control experiments were performed in the presence of a stabilizer or a deactivator. The results indicate that the technique is sensitive to conformational changes that otherwise may be impossible to detect. However, exposure to electric currents under the experimental conditions described herein showed no effects of the currents. PMID:2346508

  18. Preliminary Analysis of Observations on the Ultra-Low Frequency Electric Field in the Beijing Region

    NASA Astrophysics Data System (ADS)

    Zhuang, Jiancang; Vere-Jones, David; Guan, Huaping; Ogata, Yosihiko; Ma, Li

    2005-06-01

    This paper presents a preliminary analysis of observations on ultra-low frequency ground electric signals from stations operated by the China Seismological Bureau over the last 20 years. A brief description of the instrumentation, operating procedures and data processing procedures is given. The data analyzed consists of estimates of the total strengths (cumulated amplitudes) of the electric signals during 24-hour periods. The thresholds are set low enough so that on most days a zero observation is returned. Non-zero observations are related to electric and magnetic storms, occasional man-made electrical effects, and, apparently, some pre-, co-, or postseismic signals. The main purpose of the analysis is to investigate the extent that the electric signals can be considered as preseismic in character. For this purpose the electric signals from each of five stations are jointly analyzed with the catalogue of local earthquakes within circular regions around the selected stations. A version of Ogata’s Lin-Lin algorithm is used to estimate and test the existence of a pre-seismic signal. This model allows the effect of the electric signals to be tested, even after allowing for the effects of earthquake clustering. It is found that, although the largest single effect influencing earthquake occurrence is the clustering tendency, there remains a significant preseismic component from the electrical signals. Additional tests show that the apparent effect is not postseismic in character, and persists even under variations of the model and the time periods used in the analysis. Samples of the data are presented and the full data sets have been made available on local websites.

  19. Systemic Effects of Electromagnetic Fields in Patients with Myocardial Infarction

    NASA Astrophysics Data System (ADS)

    Cañedo-Dorantes, L.; Valle, L.; Uruchurtu, E.; Medel, A.; García-Mayen, F.; Serrano-Luna, G.

    2003-09-01

    Healing of acute myocardial infarction (AMI) is associated with inflammatory response, which promotes healing and scar formation. Activation of a local inflammatory response in patients with sequel of AMI could have an important role to enhance angiogenesis and regeneration of hibernating myocardial tissue. Chronic arterial leg ulcers have a similar etiology, and healing has been promoted by exposure to extremely low frequency electromagnetic fields (ELF). We report the evolution of three AMI patients with sequel of AMI that were exposed to ELF.

  20. Electromagnetic fields and public health.

    PubMed Central

    Aldrich, T E; Easterly, C E

    1987-01-01

    A review of the literature is provided for the topic of health-related research and power frequency electromagnetic fields. Minimal evidence for concern is present on the basis of animal and plant research. General observation would accord with the implication that there is no single and manifest health effect as the result of exposure to these fields. There are persistent indications, however, that these fields have biologic activity, and consequently, there may be a deleterious component to their action, possibly in the presence of other factors. Power frequency electromagnetic field exposures are essentially ubiquitous in modern society, and their implications in the larger perspective of public health are unclear at this time. Electromagnetic fields represent a methodological obstacle for epidemiologic studies and a quandary for risk assessment; there is need for more data. PMID:3319560

  1. An estimate of the magnetic field strength associated with a solar coronal mass ejection from low frequency radio observations

    SciTech Connect

    Sasikumar Raja, K.; Ramesh, R.; Hariharan, K.; Kathiravan, C.; Wang, T. J.

    2014-11-20

    We report ground based, low frequency heliograph (80 MHz), spectral (85-35 MHz), and polarimeter (80 and 40 MHz) observations of drifting, non-thermal radio continuum associated with the 'halo' coronal mass ejection that occurred in the solar atmosphere on 2013 March 15. The magnetic field strengths (B) near the radio source were estimated to be B ≈ 2.2 ± 0.4 G at 80 MHz and B ≈ 1.4 ± 0.2 G at 40 MHz. The corresponding radial distances (r) are r ≈ 1.9 R {sub ☉} (80 MHz) and r ≈ 2.2 R {sub ☉} (40 MHz).

  2. On a low-frequency relaxation in (K, Li)TaO3 crystals: an influence of the bias field

    NASA Astrophysics Data System (ADS)

    Turik, A. V.

    2002-01-01

    The low-frequency or π dielectric relaxation in (K, Li)TaO3 crystals is considered. An analysis of available experimental data on the influence of the bias field on the relaxation frequency enabled a value of the dipole moment of flipping polar elements to be determined for the first time. It is affirmed that they are most probably pairs of rigidly coupled dipoles (dimers) created by off-centre Li ions. The asymmetry changing the Arrhenius law for the mean relaxation time is emphasized and discussed. The dimer concentration and the dimer contribution to the dielectric permittivity are estimated.

  3. Effects of low frequency electric fields on synaptic integration in hippocampal CA1 pyramidal neurons: implications for power line emissions

    PubMed Central

    Cavarretta, Francesco; Carnevale, Nicholas T.; Tegolo, Domenico; Migliore, Michele

    2014-01-01

    The possible cognitive effects of low frequency external electric fields (EFs), such as those generated by power lines, are poorly understood. Their functional consequences for mechanisms at the single neuron level are very difficult to study and identify experimentally, especially in vivo. The major open problem is that experimental investigations on humans have given inconsistent or contradictory results, making it difficult to estimate the possible effects of external low frequency electric fields on cognitive functions. Here we investigate this issue with realistic models of hippocampal CA1 pyramidal neurons. Our findings suggest how and why EFs, with environmentally observed frequencies and intensities far lower than what is required for direct neural activation, can perturb dendritic signal processing and somatic firing of neurons that are crucially involved in cognitive tasks such as learning and memory. These results show that individual neuronal morphology, ion channel dendritic distribution, and alignment with the electric field are major determinants of overall effects, and provide a physiologically plausible explanation of why experimental findings can appear to be small and difficult to reproduce, yet deserve serious consideration. PMID:25346660

  4. Searching for Low-Frequency Radio Transients from Supernovae

    NASA Astrophysics Data System (ADS)

    Tsai-Wei, Jr.; Cutchin, Sean; Kothari, Manthan; Schmitt, Christian; Kavic, Michael; Simonetti, John

    2011-10-01

    Supernovae events may be accompanied by prompt emission of a low-frequency electromagnetic transient. These transient events are created by the interaction of a shock wave of charged particles created by SN core-collapse with a stars ambient magnetic field. Such events can be detected in low-frequency radio array. Here we discuss an ongoing search for such events using two radio arrays: the Long Wavelength Array (LWA) and Eight-meter-wavelength Transient Array (ETA).

  5. Weak extremely-low-frequency magnetic field-induced regeneration anomalies in the planarian, Dugesia tigrina

    SciTech Connect

    Jenrow, K.A.; Smith, C.H.; Liboff, A.R.

    1996-12-31

    The authors recently reported that cephalic regeneration in the planarian Dugesia tigrina was significantly delayed in populations exposed continuously to combined parallel DC and AC magnetic fields. This effect was consistent with hypotheses suggesting an underlying resonance phenomenon. The authors report here, in a parallel series of investigations on the same model system, that the incidence of regeneration anomalies presenting as tumor-like protuberances also increases significantly (P < .001) in association with exposure to weak 60 Hz magnetic fields, with peak intensities ranging between 1.0 and 80.0 {micro}T. These anomalies often culminate in the complete disaggregation of the organism. Similar to regeneration rate effects, the incidence of regeneration anomalies is specifically dependent upon the planaria possessing a fixed orientation with respect to the applied magnetic field vectors. However, unlike the regeneration rate effects, the AC magnetic field alone, in the absence of any measurable DC field, is capable of producing these anomalies. Moreover, the incidence of regeneration anomalies follows a clear dose-response relationship as a function of AC magnetic field intensity, with the threshold for induced electric field intensity estimated at 5 {micro} V/m. The addition of either 51.1 or 78.4 {micro}T DC magnetic fields, applied in parallel combination with the AC field, enhances the appearance of anomalies relative to the 60 Hz AC field alone, but only at certain AC field intensities. Thus, whereas the previous study of regeneration rate effects appeared to involve exclusively resonance interactions, the regeneration anomalies reported here appear to result primarily from Faraday induction coupling.

  6. Control of low-frequency plasma instabilities by a nonuniform radial electric field

    SciTech Connect

    Komori, A.; Watanabe, K.; Kawai, Y.

    1988-01-01

    Flute instability of a magnetoplasma is generated and controlled experimentally by a nonuniform weak radial electric field. Six concentric electrodes, biased separately, are used to change the radial electric field. The instability, which is different from the velocity shear flute instability, is observed in a plasma with well-type potential and hill-type density profiles.

  7. Childhood leukemia and residential exposure to weak extremely low frequency magnetic fields

    SciTech Connect

    Feychting, M.; Ahlbom, A.

    1995-03-01

    There is no known mechanism by which magnetic fields of the type generated by high voltage power lines can play a role in cancer development. Nevertheless, epidemiologic research has rather consistently found associations between residential magnetic field exposure and cancer. This is most evident for leukemia in children. 18 refs., 1 tab.

  8. Vital functions of organisms in infra-low frequency magnetic fields 3. The embryogeny of mammals

    SciTech Connect

    Khizhenkov, P.K.; Bilobrov, V.M.; Zinkevich, I.I.; Zyablitsev, S.V.

    1994-10-01

    Results are presented of the experimental studies of the effect of variable (rotary) magnetic fields H at f = 6.5 Hz on the reproduction function of rats. It is shown that a pregnancy does not occur when mating takes place under the action of the field H. In the second quarter of pregnancy, the effect of the field is characterized by an increase of the mass of the body and of the internal organs of the new-born rats, among which, the growth of gemmae, spleen and of the thymus gland are particularly significant. The relative composition of the white blood cells changes as well.

  9. What Are Electromagnetic Fields?

    MedlinePlus

    ... with distance from it. Conductors such as metal shield them very effectively. Other materials, such as building ... with distance from the source. Most building materials shield electric fields to some extent. Magnetic fields arise ...

  10. Note: Enhanced energy harvesting from low-frequency magnetic fields utilizing magneto-mechano-electric composite tuning-fork.

    PubMed

    Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

    2015-06-01

    A magnetic-field energy harvester using a low-frequency magneto-mechano-electric (MME) composite tuning-fork is proposed. This MME composite tuning-fork consists of a copper tuning fork with piezoelectric Pb(Zr(1-x)Ti(x))O3 (PZT) plates bonded near its fixed end and with NdFeB magnets attached at its free ends. Due to the resonance coupling between fork prongs, the MME composite tuning-fork owns strong vibration and high Q value. Experimental results show that the proposed magnetic-field energy harvester using the MME composite tuning-fork exhibits approximately 4 times larger maximum output voltage and 7.2 times higher maximum power than the conventional magnetic-field energy harvester using the MME composite cantilever. PMID:26133877

  11. Note: Enhanced energy harvesting from low-frequency magnetic fields utilizing magneto-mechano-electric composite tuning-fork

    NASA Astrophysics Data System (ADS)

    Yang, Aichao; Li, Ping; Wen, Yumei; Yang, Chao; Wang, Decai; Zhang, Feng; Zhang, Jiajia

    2015-06-01

    A magnetic-field energy harvester using a low-frequency magneto-mechano-electric (MME) composite tuning-fork is proposed. This MME composite tuning-fork consists of a copper tuning fork with piezoelectric Pb(Zr1-xTix)O3 (PZT) plates bonded near its fixed end and with NdFeB magnets attached at its free ends. Due to the resonance coupling between fork prongs, the MME composite tuning-fork owns strong vibration and high Q value. Experimental results show that the proposed magnetic-field energy harvester using the MME composite tuning-fork exhibits approximately 4 times larger maximum output voltage and 7.2 times higher maximum power than the conventional magnetic-field energy harvester using the MME composite cantilever.

  12. Efficient compensation of low-frequency magnetic field disturbances in NMR with fluxgate sensors.

    PubMed

    Kazimierczuk, Krzysztof; Koźmiński, Wiktor

    2005-06-01

    A simple stabilization scheme of B(0) magnetic field fluctuations is described. The method is based on external measurements of time dependent magnetic field fluctuations by fluxgate sensors and generation of a compensating correction current in a coil mounted directly on an NMR magnet. It is shown that such an approach efficiently eliminates relatively slow magnetic field variations with frequency up to approximately 100 Hz. In combination with a standard (2)H field-frequency lock system, the method enables acquisition of reproducible lineshapes and dramatically improves overall performance of a high resolution NMR spectrometer. The presented solution might substitute for the internal lock system in these case where deuterium lock is not available. PMID:15862246

  13. Evaluating alternative exposure indices in epidemiologic studies on extremely low-frequency magnetic fields

    SciTech Connect

    Juutilainen, J.; Hatfield, T.; Laeaerae, E.

    1996-05-01

    Choosing the right exposure index for epidemiological studies on 50--60 Hz magnetic fields is difficult due to the lack of knowledge about critical exposure parameters for the biological effects of magnetic fields. This paper uses data from a previously published epidemiological investigation on early pregnancy loss (EPL) to study the methods of evaluating the exposure-response relationship of 50 Hz magnetic fields. Two approaches were used. The first approach was to apply generalized additive modeling to suggest the functional form of the relationship between EPL data with eight alternative exposure indices: the 24 h average of magnetic field strength, three indices measuring the proportion of time above specified thresholds, and four indices measuring the proportion of time within specified intensity windows. Because the original exposure data included only spot measurements, estimates for the selected exposure indices were calculated indirectly form the spot measurements using empirical nonlinear equations derived from 24 h recording in 60 residences. The results did not support intensity windows, and a threshold-type dependence on field strength appeared to be more plausible than a linear relationship. In addition, the study produced data suggesting that spot measurements may be used as surrogates for other exposure indices besides the time average field strength. No final conclusions should be drawn from this study alone, but the authors hope that this exercise stimulates evaluation of alternative exposure indices in other planned and ongoing epidemiological studies.

  14. Physical aspects of magnetic hyperthermia: Low-frequency ac field absorption in a magnetic colloid

    NASA Astrophysics Data System (ADS)

    L. Raikher, Yu.; Stepanov, V. I.

    2014-11-01

    A uniaxially anisotropic superparamagnetic particle suspended in a viscous fluid and subjected to an ac field is considered. Consistently taking into account both internal (Néel) and external (Brownian) magnetic relaxations, a simple expression for the dynamic susceptibility is obtained. This result, with regard to the ac field energy absorption, is compared to the common heuristic approach. This is done for a model polydisperse colloid containing maghemite nanoparticles, which are assumed to posses either bulk or surface magnetic anisotropy. It is shown that viscous losses caused by the particle motion in a fluid matrix make important contribution to the full magnetic response of a ferrocolloid and, thus, its ability to absorb the ac field energy. The obtained exact expression, which takes in both dissipation mechanisms, paves the way to correct optimization of the nanoparticle-mediated heating effect.

  15. An investigation into the vector ellipticity of extremely low frequency magnetic fields from appliances in UK homes.

    PubMed

    Ainsbury, Elizabeth A; Conein, Emma; Henshaw, Denis L

    2005-07-01

    Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0-3000 Hz magnetic fields, produced by 226 domestic mains-fed appliances of 32 different types, were carried out in 16 homes in Worcestershire in the summer of 2004. Magnetic field strengths were low, with average (RMS) values of 0.03 +/- 0.02 microT across all residences. In contrast, background field ellipticities were high, on average 47 +/- 11%. Microwave and electric ovens produced the highest ellipticities: mean respective values of 21 +/- 21% and 21 +/- 17% were observed 20 cm away from these appliances. There was a negative correlation between field strength and field polarization, which we attribute to the higher relative field contribution close to each individual (single-phase) appliance. The measurements demonstrate that domestic magnetic fields are extremely complex and cannot simply be characterized by traditional measurements such as time-weighted average or peak exposure levels. We conclude that ellipticity should become a relevant metric for future epidemiological studies of health and ELF-MF exposure. PMID:15972990

  16. An investigation into the vector ellipticity of extremely low frequency magnetic fields from appliances in UK homes

    NASA Astrophysics Data System (ADS)

    Ainsbury, Elizabeth A.; Conein, Emma; Henshaw, Denis L.

    2005-07-01

    Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0-3000 Hz magnetic fields, produced by 226 domestic mains-fed appliances of 32 different types, were carried out in 16 homes in Worcestershire in the summer of 2004. Magnetic field strengths were low, with average (RMS) values of 0.03 ± 0.02 µT across all residences. In contrast, background field ellipticities were high, on average 47 ± 11%. Microwave and electric ovens produced the highest ellipticities: mean respective values of 21 ± 21% and 21 ± 17% were observed 20 cm away from these appliances. There was a negative correlation between field strength and field polarization, which we attribute to the higher relative field contribution close to each individual (single-phase) appliance. The measurements demonstrate that domestic magnetic fields are extremely complex and cannot simply be characterized by traditional measurements such as time-weighted average or peak exposure levels. We conclude that ellipticity should become a relevant metric for future epidemiological studies of health and ELF-MF exposure. This work is supported by the charity CHILDREN with LEUKAEMIA, registered charity number 298405.

  17. Induced electric fields in workers near low-frequency induction heating machines.

    PubMed

    Kos, Bor; Valič, Blaž; Kotnik, Tadej; Gajšek, Peter

    2014-04-01

    Published data on occupational exposure to induction heating equipment are scarce, particularly in terms of induced quantities in the human body. This article provides some additional information by investigating exposure to two such machines-an induction furnace and an induction hardening machine. Additionally, a spatial averaging algorithm for measured fields we developed in a previous publication is tested on new data. The human model was positioned at distances where measured values of magnetic flux density were above the reference levels. All human exposure was below the basic restriction-the lower bound of the 0.1 top percentile induced electric field in the body of a worker was 0.193 V/m at 30 cm from the induction furnace. PMID:24203794

  18. Low-frequency 1/f noise in the interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Matthaeus, W. H.; Goldstein, M. L.

    1986-01-01

    Spacecraft observations of the interplanetary magnetic field at 1 AU are shown to have frequency spectra with a 1/f dependence in the range 2.7-80 microHz. It is suggested that the 1/f spectrum results from the superposition of uncorrelated samples of solar surface turbulence that have log-normal distributions of correlation lengths corresponding to a scale-invariant distribution of correlation times over an appropriate range of parameters.

  19. Study on Electric field assisted low frequency (20 kHz) ultrasonic spray

    NASA Astrophysics Data System (ADS)

    Chae, Ilkyeong; Seong, Baekhoon; Marten, Darmawan; Byun, Doyoung

    2015-11-01

    Ultrasonic spray is one of the fabulous techniques to discharge small size of droplets because it utilizes ultrasonic vibration on nozzle. However, spray patterns and size of ejected droplet is hardly controlled in conventional ultrasonic spray method. Therefore, here we present electric field assisted ultrasonic spray, which combined conventional technique with electric field in order to control spray pattern and droplet size precisely. Six kinds of various liquid (D.I water, Ethanol, Acetone, Iso-propanol, Toluene, Hexane) with various dielectric constants were used to investigate the mechanism of this method. Also, PIV (Particle Image Velocimetry) was used and various variables were obtained including spray angle, amplitude of liquid vibration, current, and size distribution of ejected droplets. Our electric field assisted ultrasonic spray show that the standard deviation of atomized droplet was decreased up to 39.6%, and it shows the infinite possibility to be utilized in various applications which require precise control of high transfer efficiency. This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2014-023284).

  20. Low-Frequency Sound Field Control in a Reverberant Room with a Single Active Controller Source.

    NASA Astrophysics Data System (ADS)

    Bullock, John Drayton, Jr.

    The operation of a single active controller source in a reverberant room has been investigated. The system consists of a controlled transducer source and a near-source microphone, with electronics arranged as a closed feedback loop. The controller system responds to a single source placed arbitrarily in the room. A theoretical analysis is presented based on the two port model of the controller transducer interfaced to an equivalent description of the reverberant room. The room acoustic transfer impedances between the active controller, room exciter source, near controller pressure sensor, and an arbitrary point in the reverberant sound field are described by a Green's function model. To minimize resonant effects of the controller piston diaphragm, a second control feedback loop using a diaphragm mounted accelerometer was added to the pressure control loop. Examples of the controller system operation were drawn from a computer model. Experimental data were gathered in a test reverberation room at the Applied Research Laboratory of The Pennsylvania State University. This investigation has brought forth three factors which define the limits on wide band control loop gain. They are (i) the position of an accelerometer on the controller diaphragm, (ii) the spacing between the controller and pressure sensor microphone, and (iii) the first mode frequency and the Q of the controller diaphragm. These system and transducer constraints can introduce instability in the control system. The controller system operation in the room has been modeled as a lumped element ideal piston using a flow graph representation. Additional loops on the graph are used to represent non-ideal transducer aberrations, and to define the pressure at various points in the room. Four cases for controller operation have been defined based on the proximity of the room source, the pressure sensor, and the controller. Two of these are important for practical applications: (i) the sensor microphone and

  1. Magnetoreception in laboratory mice: sensitivity to extremely low-frequency fields exceeds 33 nT at 30 Hz

    PubMed Central

    Prato, Frank S.; Desjardins-Holmes, Dawn; Keenliside, Lynn D.; DeMoor, Janice M.; Robertson, John A.; Thomas, Alex W.

    2013-01-01

    Magnetoreception in the animal kingdom has focused primarily on behavioural responses to the static geomagnetic field and the slow changes in its magnitude and direction as animals navigate/migrate. There has been relatively little attention given to the possibility that weak extremely low-frequency magnetic fields (wELFMF) may affect animal behaviour. Previously, we showed that changes in nociception under an ambient magnetic field-shielded environment may be a good alternative biological endpoint to orientation measurements for investigations into magnetoreception. Here we show that nociception in mice is altered by a 30 Hz field with a peak amplitude more than 1000 times weaker than the static component of the geomagnetic field. When mice are exposed to an ambient magnetic field-shielded environment 1 h a day for five consecutive days, a strong analgesic (i.e. antinociception) response is induced by day 5. Introduction of a static field with an average magnitude of 44 µT (spatial variability of ±3 µT) marginally affects this response, whereas introduction of a 30 Hz time-varying field as weak as 33 nT has a strong effect, reducing the analgesic effect by 60 per cent. Such sensitivity is surprisingly high. Any purported detection mechanisms being considered will need to explain effects at such wELFMF. PMID:23365198

  2. Magnetic Nanoparticle Quantitation with Low Frequency Magnetic Fields: Compensating for Relaxation Effects

    PubMed Central

    Weaver, John B.; Zhang, Xiaojuan; Kuehlert, Esra; Toraya-Brown, Seiko; Reeves, Daniel B.; Perreard, Irina M.; Fiering, Steven N.

    2013-01-01

    Quantifying the number of nanoparticles present in tissue is central to many in vivo and in vitro applications. Magnetic nanoparticles can be detected with high sensitivity both in vivo and in vitro using the harmonics of their magnetization produced in a sinusoidal magnetic field. However, relaxation effects damp the magnetic harmonics rendering them of limited use in quantitation. We show that an accurate measure of the number of nanoparticles can be made by correcting for relaxation effects. Correction for relaxation reduced errors of 50% for larger nanoparticles in high relaxation environments to 2%. The result is a method of nanoparticle quantitation capable of in vivo and in vitro applications including histopathology assays, quantitative imaging, drug delivery and thermal therapy preparation. PMID:23867287

  3. Low-frequency electron dynamics in the near field of a Hall effect thruster

    SciTech Connect

    Albarede, L.; Mazouffre, S.; Bouchoule, A.; Dudeck, M.

    2006-06-15

    Time-resolved electrostatic probe measurements were performed in the near field of a SPT100-ML Hall effect thruster in order to investigate electron properties changes on a microsecond time scale. Such measurements allow one to monitor the electron temperature T{sub e}, the electron density n{sub e}, as well as the plasma potential V{sub p} during a time period that corresponds to one cycle of a breathing-type plasma oscillation with f{approx_equal}15-30 kHz. Although T{sub e}(t) stays constant in time, n{sub e}(t) and V{sub p}(t) oscillate with the discharge current waveform frequency. The observed time delay between n{sub e} and anode discharge current (Id{sub a}) waveforms, which is of approximately 7 {mu}s, is linked to the ion transit time from the ionization layer to the probed near-field region. The same time gap is measured between V{sub p}(t) and Id{sub a}(t), however V{sub p}(t) and n{sub e}(t) are in phase opposition. The electron density reaches its highest value at the very moment ions are ejected out of the thruster discharge chamber, which also corresponds to the instant the cathode potential is the most negative. Such a behavior images the need for ion beam neutralization. Further, it is shown that there is a strong correlation between the electron dynamics and the presence of high frequency (HF) plasma oscillations in the megahertz range: HF fluctuations are the strongest when n{sub e} is the highest.

  4. Explanations, Education, and Electromagnetic Fields.

    ERIC Educational Resources Information Center

    Friedman, Sharon M.

    Explaining complex scientific and environmental subjects in the mass media is difficult to do, particularly under such constraints as short deadlines and lack of space or time. When a scientific controversy and human health risk are involved, this becomes an even harder task to accomplish. The subject of electromagnetic fields (EMF) involves…

  5. The courts and electromagnetic fields

    SciTech Connect

    Freeman, M. )

    1990-07-19

    This article examines the recent development in eminent domain cases involving power transmission line rights of way, the issue of fear of the mythical buyer. The author feels that the fear of electrocution or of the possible cancer-inducing effects of electromagnetic fields is greatly influencing court decisions in these cases. The results could be more expensive rights of way acquisition by utilities.

  6. Above-Threshold Ionization of Quasiperiodic Structures by Low-Frequency Laser Fields

    NASA Astrophysics Data System (ADS)

    Catoire, F.; Bachau, H.

    2015-10-01

    We investigate the theoretical problem of the photoelectron cutoff change in periodical structures induced by an infrared laser field. We use a one-dimensional Kronig-Penney potential including a finite number of wells, and the analysis is fulfilled by resolving the time-dependent Schrödinger equation. The electron spectra, calculated for an increasing number of wells, clearly show that a plateau quickly appears as the periodic nature of the potential builds up, even at a moderate intensity (10 TW /cm2 ). Varying the intensity from 10 to 30 TW /cm2 we observe a net increase of both the yield and accessible energy range of the ionization spectrum. In order to gain insight into the dynamics of the system at these intensities, we use an analytical approach, based on exact solutions of the full Hamiltonian in a periodic potential. We show that the population transfers efficiently from lower to upper bands when the Bloch and laser frequencies become comparable. The model leads to a quantitative prediction of the intensity range where ionization enters the nonperturbative regime. Moreover, it reveals the physics underlying the increase of the photoelectron energy cutoff at moderate intensities, as observed experimentally.

  7. Physiologic regulation in electromagnetic fields

    SciTech Connect

    Michaelson, S.M.

    1982-01-01

    Electromagnetic fields have been demonstrated to elicit thermoregulatory responses, neuroendocrine, neurochemical modulations, and behavioral reactions. These physiologic regulatory processes are exquisitely tuned, interrelated functions that constitute sensitive indicators of organismic responses to radiofrequency energy absorption (the radiofrequency portion of the electromagnetic spectrum includes as one part microwaves). Assessment of the integration and correlation of these functions relative to the thermal inputs and homeokinetic reactions of the individual subjected to radiofrequency energy should permit differentiation between potential hazards that might compromise the individual's ability to maintain normal physiologic function and effects that are compensated by physiologic redundancy.

  8. Analysis of extremely low frequency brain magnetic fields associated with short-term memory and recognition processes (abstract)

    NASA Astrophysics Data System (ADS)

    Yoshida, Hideki; Ueno, Shoogo; Cheyne, Douglas; Weinberg, Harold

    1996-04-01

    One of the advantages of neural magnetic measurement using a dc-SQUID machine is to measure magnetic fields associated with the direct current or the extremely low frequencial components of neural electric activities. In this study, the order of four tones is memorized by the subject and compared with that of another four tones. The extremely slow magnetic fields were observed by using this paradigm. Two kinds of tones (two octaves apart: the 1046.5 Hz tone and the 261.6 Hz tone) were used. A male subject memorized the order of four tones chosen randomly. After 1.4 s rest, the other four tones were presented. The subject discriminated the order of the first tones from that of the last tones in the forward order. When another long (1 s) tone was presented 2.4 s later, the subject was to push either a true or a false button. Pushing the true button meant the order of the first four tones was the same as that of the last in the forward order. Pushing the false button meant the order was not the same. The whole-cortex 64 channels of MEG data were digitized with a sampling frequency of 125 Hz, and filtered (zero phase shift, low pass digital filter with a cutoff at 20 Hz). In comparison with the control wave, the wave during memorizing clearly includes very low frequency components. We observed that the intensities of the power spectral components at 0.5 Hz during memorizing and recognition is higher than that of the control power spectral components, and tried to make the topographies using the differences between the power spectral components at 0.5 Hz during memory and recognition and the control power spectral components. Because the memory processes affect the very low frequency components of MEG, the current dipole source models are made from the data filtered below 0.5 Hz. We observed that the memory processes affected the very low frequency components of MEG. We estimated the current dipole sources using MEG data below 0.5 Hz.

  9. Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L'Aquila regarding regional geotechnical information

    NASA Astrophysics Data System (ADS)

    Prattes, G.; Schwingenschuh, K.; Eichelberger, H. U.; Magnes, W.; Boudjada, M.; Stachel, M.; Vellante, M.; Villante, U.; Wesztergom, V.; Nenovski, P.

    2011-07-01

    This work presents ground based Ultra Low Frequency (ULF) magnetic field measurements in the frequency range from 10-15 mHz from 1 January 2008 to 14 April 2009. In this time period a strong earthquake series hit the Italian Abruzzo region around L'Aquila with the main stroke of magnitude M = 6.3 on 6 April 2009. In the frame of the South European Geomagnetic Array (SEGMA), a European collaboration runs ULF fluxgate instruments providing continuously magnetic field data recorded in mid- and south Europe. The main scientific objective is the investigation of signal variations due to seismic activity and the discrimination between other natural and human influences. The SEGMA station closest to the L'Aquila earthquake epicenter is L'Aquila observatory located in the epicenter region. For the scientific analysis we extract the nighttime period from 22:00-02:00 UT and determine the power spectral density (PSD) of the horizontal (H) and vertical (Z) magnetic field components and the standardized polarization ratio (Z) over (H). To discriminate local emissions from global geomagnetic effects, data from three SEGMA stations in distances up to 630 km from the epicenter region are analyzed and further compared to the independent global geomagnetic ∑ Kp index. Apart from indirect ionospheric effects, electromagnetic noise could be originated in the lithosphere due to tectonic mechanisms in the earthquake focus. To estimate the amplitude of assumed lithospheric electromagnetic noise emissions causing anomalies in the PSD of the (Z) component, we consider magnetotelluric calculations of the electric crust conductivity in the L'Aquila region. Results found at L'Aquila observatory are interpreted with respect to the lithosphere electrical conductivity in the local observatory region, the ∑ Kp index, and further in a multi station analysis. Possible seismic related ULF anomalies occur ~2 weeks before the main stroke.

  10. Difficulties in applying numerical simulations to an evaluation of occupational hazards caused by electromagnetic fields.

    PubMed

    Zradziński, Patryk

    2015-01-01

    Due to the various physical mechanisms of interaction between a worker's body and the electromagnetic field at various frequencies, the principles of numerical simulations have been discussed for three areas of worker exposure: to low frequency magnetic field, to low and intermediate frequency electric field and to radiofrequency electromagnetic field. This paper presents the identified difficulties in applying numerical simulations to evaluate physical estimators of direct and indirect effects of exposure to electromagnetic fields at various frequencies. Exposure of workers operating a plastic sealer have been taken as an example scenario of electromagnetic field exposure at the workplace for discussion of those difficulties in applying numerical simulations. The following difficulties in reliable numerical simulations of workers' exposure to the electromagnetic field have been considered: workers' body models (posture, dimensions, shape and grounding conditions), working environment models (objects most influencing electromagnetic field distribution) and an analysis of parameters for which exposure limitations are specified in international guidelines and standards. PMID:26323781

  11. Difficulties in applying numerical simulations to an evaluation of occupational hazards caused by electromagnetic fields

    PubMed Central

    Zradziński, Patryk

    2015-01-01

    Due to the various physical mechanisms of interaction between a worker's body and the electromagnetic field at various frequencies, the principles of numerical simulations have been discussed for three areas of worker exposure: to low frequency magnetic field, to low and intermediate frequency electric field and to radiofrequency electromagnetic field. This paper presents the identified difficulties in applying numerical simulations to evaluate physical estimators of direct and indirect effects of exposure to electromagnetic fields at various frequencies. Exposure of workers operating a plastic sealer have been taken as an example scenario of electromagnetic field exposure at the workplace for discussion of those difficulties in applying numerical simulations. The following difficulties in reliable numerical simulations of workers’ exposure to the electromagnetic field have been considered: workers’ body models (posture, dimensions, shape and grounding conditions), working environment models (objects most influencing electromagnetic field distribution) and an analysis of parameters for which exposure limitations are specified in international guidelines and standards. PMID:26323781

  12. Numerical study of induced current perturbations in the vicinity of excitable cells exposed to extremely low frequency magnetic fields

    NASA Astrophysics Data System (ADS)

    Hassan, Noha; Chatterjee, Indira; Publicover, Nelson G.; Craviso, Gale L.

    2003-10-01

    Realistic three-dimensional cell morphologies were modelled to determine the current density induced in excitable cell culture preparations exposed to 60 Hz magnetic fields and to identify important factors that can influence the responses of cells to these fields. Cell morphologies representing single spherical adrenal chromaffin cells, single elongated smooth muscle cells and chromaffin cell aggregates in a Petri dish containing culture medium were modelled using the finite element method. The computations for a spherical cell revealed alterations in the magnitude and spatial distribution of the induced current density in the immediate vicinity of the cell. Maxima occurred at the equatorial sides and minima at the poles. Proximity of cells to each other as well as cell aggregate shape, size and orientation with respect to the induced current influenced the magnitude and spatial distribution of the induced current density. For an elongated cell, effects on the induced current density were highly dependent on cell orientation with respect to the direction of the induced current. These results provide novel insights into the perturbations in induced current that occur in excitable cell culture preparations and lay a foundation for understanding the mechanisms of interaction with extremely low frequency magnetic fields at the tissue level.

  13. Electromagnetic Fields, Oxidative Stress, and Neurodegeneration

    PubMed Central

    Consales, Claudia; Merla, Caterina; Marino, Carmela; Benassi, Barbara

    2012-01-01

    Electromagnetic fields (EMFs) originating both from both natural and manmade sources permeate our environment. As people are continuously exposed to EMFs in everyday life, it is a matter of great debate whether they can be harmful to human health. On the basis of two decades of epidemiological studies, an increased risk for childhood leukemia associated with Extremely Low Frequency fields has been consistently assessed, inducing the International Agency for Research on Cancer to insert them in the 2B section of carcinogens in 2001. EMFs interaction with biological systems may cause oxidative stress under certain circumstances. Since free radicals are essential for brain physiological processes and pathological degeneration, research focusing on the possible influence of the EMFs-driven oxidative stress is still in progress, especially in the light of recent studies suggesting that EMFs may contribute to the etiology of neurodegenerative disorders. This review synthesizes the emerging evidences about this topic, highlighting the wide data uncertainty that still characterizes the EMFs effect on oxidative stress modulation, as both pro-oxidant and neuroprotective effects have been documented. Care should be taken to avoid methodological limitations and to determine the patho-physiological relevance of any alteration found in EMFs-exposed biological system. PMID:22991514

  14. Binary black holes' effects on electromagnetic fields.

    PubMed

    Palenzuela, Carlos; Anderson, Matthew; Lehner, Luis; Liebling, Steven L; Neilsen, David

    2009-08-21

    In addition to producing gravitational waves, the dynamics of a binary black hole system could induce emission of electromagnetic radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We here study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as a possible enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves. PMID:19792706

  15. Effect of exposure to extremely low frequency magnetic fields on melatonin levels in calves is seasonally dependent.

    PubMed

    Kolbabová, Tereza; Pascal Malkemper, E; Bartoš, Luděk; Vanderstraeten, Jacques; Turčáni, Marek; Burda, Hynek

    2015-01-01

    The question of health effects of extremely low frequency (50/60 Hz) magnetic fields (ELFMF) has been widely discussed, but the mechanisms of interaction of these fields with biological systems for intensities relevant to human and animal exposure are still under question. The melatonin (MLT) hypothesis suggests that exposure to ELFMF might decrease MLT production thereby promoting cancerogenesis. So far, most studies of MLT secretion under exposure to ELFMF reported negative or inconsistent results. Here, we measured salivary MLT in 1-2 months old cattle calves exposed to 50 Hz-MF in the hundreds of nT-range. We found an inhibitory effect of the ELFMF upon MLT secretion in winter (in accordance with the MLT hypothesis). In contrast, in summer, MLT concentration was increased by ELFMF exposure (contrary to the MLT hypothesis). The inhibitory effect in winter was much stronger than the positive effect in summer. We hypothesize that this season-dependent effect upon MLT synthesis might by mediated by an effect of ELFMF upon the serotonin metabolism and conclude that future tests of ELFMF effects should also measure serotonin levels and consider association with the seasonal effects (photoperiod or temperature) during the exposure. PMID:26381579

  16. Monitoring of interaction of low-frequency electric field with biological tissues upon optical clearing with optical coherence tomography.

    PubMed

    Peña, Adrián F; Doronin, Alexander; Tuchin, Valery V; Meglinski, Igor

    2014-08-01

    The influence of a low-frequency electric field applied to soft biological tissues ex vivo at normal conditions and upon the topical application of optical clearing agents has been studied by optical coherence tomography (OCT). The electro-kinetic response of tissues has been observed and quantitatively evaluated by the double correlation OCT approach, utilizing consistent application of an adaptive Wiener filtering and Fourier domain correlation algorithm. The results show that fluctuations, induced by the electric field within the biological tissues are exponentially increased in time. We demonstrate that in comparison to impedance measurements and the mapping of the temperature profile at the surface of the tissue samples, the double correlation OCT approach is much more sensitive to the changes associated with the tissues' electro-kinetic response. We also found that topical application of the optical clearing agent reduces the tissues' electro-kinetic response and is cooling the tissue, thus reducing the temperature induced by the electric current by a few degrees. We anticipate that dcOCT approach can find a new application in bioelectrical impedance analysis and monitoring of the electric properties of biological tissues, including the resistivity of high water content tissues and its variations. PMID:25104408

  17. Effect of exposure to extremely low frequency magnetic fields on melatonin levels in calves is seasonally dependent

    PubMed Central

    Kolbabová, Tereza; Pascal Malkemper, E.; Bartoš, Luděk; Vanderstraeten, Jacques; Turčáni, Marek; Burda, Hynek

    2015-01-01

    The question of health effects of extremely low frequency (50/60 Hz) magnetic fields (ELFMF) has been widely discussed, but the mechanisms of interaction of these fields with biological systems for intensities relevant to human and animal exposure are still under question. The melatonin (MLT) hypothesis suggests that exposure to ELFMF might decrease MLT production thereby promoting cancerogenesis. So far, most studies of MLT secretion under exposure to ELFMF reported negative or inconsistent results. Here, we measured salivary MLT in 1–2 months old cattle calves exposed to 50 Hz-MF in the hundreds of nT-range. We found an inhibitory effect of the ELFMF upon MLT secretion in winter (in accordance with the MLT hypothesis). In contrast, in summer, MLT concentration was increased by ELFMF exposure (contrary to the MLT hypothesis). The inhibitory effect in winter was much stronger than the positive effect in summer. We hypothesize that this season-dependent effect upon MLT synthesis might by mediated by an effect of ELFMF upon the serotonin metabolism and conclude that future tests of ELFMF effects should also measure serotonin levels and consider association with the seasonal effects (photoperiod or temperature) during the exposure. PMID:26381579

  18. Leukaemia, brain tumours and exposure to extremely low frequency magnetic fields: cohort study of Swiss railway employees

    PubMed Central

    Röösli, Martin; Lörtscher, Manfred; Egger, Matthias; Pfluger, Dominik; Schreier, Nadja; Lörtscher, Emanuel; Locher, Peter; Spoerri, Adrian; Minder, Christoph

    2007-01-01

    Aims To investigate the relationship between extremely low frequency magnetic field (ELF‐MF) exposure and mortality from leukaemia and brain tumour in a cohort of Swiss railway workers. Methods 20 141 Swiss railway employees with 464 129 person‐years of follow‐up between 1972 and 2002 were studied. Mortality rates for leukaemia and brain tumour of highly exposed train drivers (21 μT average annual exposure) were compared with medium and low exposed occupational groups (i.e. station masters with an average exposure of 1 μT). In addition, individual cumulative exposure was calculated from on‐site measurements and modelling of past exposures. Results The hazard ratio (HR) for leukaemia mortality of train drivers was 1.43 (95% CI 0.74 to 2.77) compared with station masters. For myeloid leukaemia the HR of train drivers was 4.74 (95% CI 1.04 to 21.60) and for Hodgkin's disease 3.29 (95% CI 0.69 to 15.63). Lymphoid leukaemia, non‐Hodgkin's disease and brain tumour mortality were not associated with magnetic field exposure. Concordant results were obtained from analyses based on individual cumulative exposure. Conclusions Some evidence of an exposure–response association was found for myeloid leukaemia and Hodgkin's disease, but not for other haematopoietic and lymphatic malignancies and brain tumours. PMID:17525094

  19. Effect of Zr on microstructures and mechanical properties of an Al-Mg-Si-Cu-Cr alloy prepared by low frequency electromagnetic casting

    SciTech Connect

    Meng, Yi Cui, Jianzhong; Zhao, Zhihao; He, Lizi

    2014-06-01

    The Al-1.6Mg-1.2Si-1.1Cu-0.15Cr (all in wt. %) alloys with and without Zr addition prepared by low frequency electromagnetic casting process were investigated by using the optical microscope, scanning electron microscope and transmission electron microscope equipped with energy dispersive analytical X-ray. The effects of Al{sub 3}Zr phases on the microstructures and mechanical properties during solidification, homogenization, hot extrusion and solid solution were studied. The results show that Al{sub 3}Zr phases reduce the grain size by ∼ 29% and promote the formation of an equiaxed grain structure during solidification. Numerous spherical Al{sub 3}Zr dispersoids with 35–60 nm in diameters precipitate during homogenization, and these fine dispersoids change little during subsequent hot extrusion and solid solution. Adding 0.15 wt. % Zr results in no recrystallization after hot extrusion and partial recrystallization after solid solution, while the recrystallized grain size is 400–550 μm in extrusion direction in the Zr-free alloy. In addition, adding 0.15 wt. % Zr can obviously promote Q′ phase precipitation, while the β″ phases are predominant in the alloy without Zr. Adding 0.15 wt. % Zr, the ultimate tensile strength of the T6 treated alloy increases by 45 MPa, while the elongation remains about 16.7%. - Highlights: • Minor Zr can refine as-cast grains of the LFEC Al-Mg-Si-Cu-Cr alloy. • L1{sub 2} Al{sub 3}Zr phases with 35–60 nm in diameter precipitate during homogenization. • L1{sub 2} and DO{sub 22} Al{sub 3}Zr phases result in partial recrystallization after solid solution. • Minor Zr can promote the precipitation of Q′ phases. • Mechanical properties of Al-Mg-Si-Cu-Cr-Zr alloy are higher than those of AA7005.

  20. Finite element modeling of electromagnetic fields and waves using NASTRAN

    NASA Technical Reports Server (NTRS)

    Moyer, E. Thomas, Jr.; Schroeder, Erwin

    1989-01-01

    The various formulations of Maxwell's equations are reviewed with emphasis on those formulations which most readily form analogies with Navier's equations. Analogies involving scalar and vector potentials and electric and magnetic field components are presented. Formulations allowing for media with dielectric and conducting properties are emphasized. It is demonstrated that many problems in electromagnetism can be solved using the NASTRAN finite element code. Several fundamental problems involving time harmonic solutions of Maxwell's equations with known analytic solutions are solved using NASTRAN to demonstrate convergence and mesh requirements. Mesh requirements are studied as a function of frequency, conductivity, and dielectric properties. Applications in both low frequency and high frequency are highlighted. The low frequency problems demonstrate the ability to solve problems involving media inhomogeneity and unbounded domains. The high frequency applications demonstrate the ability to handle problems with large boundary to wavelength ratios.

  1. Electromagnetic fields mediate efficient cell reprogramming into a pluripotent state.

    PubMed

    Baek, Soonbong; Quan, Xiaoyuan; Kim, Soochan; Lengner, Christopher; Park, Jung-Keug; Kim, Jongpil

    2014-10-28

    Life on Earth is constantly exposed to natural electromagnetic fields (EMFs), and it is generally accepted that EMFs may exert a variety of effects on biological systems. Particularly, extremely low-frequency electromagnetic fields (EL-EMFs) affect biological processes such as cell development and differentiation; however, the fundamental mechanisms by which EMFs influence these processes remain unclear. Here we show that EMF exposure induces epigenetic changes that promote efficient somatic cell reprogramming to pluripotency. These epigenetic changes resulted from EMF-induced activation of the histone lysine methyltransferase Mll2. Remarkably, an EMF-free system that eliminates Earth's naturally occurring magnetic field abrogates these epigenetic changes, resulting in a failure to undergo reprogramming. Therefore, our results reveal that EMF directly regulates dynamic epigenetic changes through Mll2, providing an efficient tool for epigenetic reprogramming including the acquisition of pluripotency. PMID:25248035

  2. An estimate of the coronal magnetic field near a solar coronal mass ejection from low-frequency radio observations

    SciTech Connect

    Hariharan, K.; Ramesh, R.; Kishore, P.; Kathiravan, C.; Gopalswamy, N.

    2014-11-01

    We report ground-based, low-frequency (<100 MHz) radio imaging, spectral, and polarimeter observations of the type II radio burst associated with the solar coronal mass ejection (CME) that occurred on 2013 May 2. The spectral observations indicate that the burst has fundamental (F) and harmonic (H) emission components with split-band and herringbone structures. The imaging observations at 80 MHz indicate that the H component of the burst was located close to leading edge of the CME at a radial distance of r ≈ 2 R {sub ☉} in the solar atmosphere. The polarimeter observations of the type II burst, also at 80 MHz, indicate that the peak degree of circular polarization (dcp) corresponding to the emission generated in the corona ahead of and behind the associated MHD shock front are ≈0.05 ± 0.02 and ≈0.1 ± 0.01, respectively. We calculated the magnetic field B in the above two coronal regions by adopting the empirical relationship between the dcp and B for the harmonic plasma emission and the values are ≈(0.7-1.4) ± 0.2 G and ≈(1.4-2.8) ± 0.1 G, respectively.

  3. THE LOW-FREQUENCY CHARACTERISTICS OF PSR J0437–4715 OBSERVED WITH THE MURCHISON WIDE-FIELD ARRAY

    SciTech Connect

    Bhat, N. D. R.; Ord, S. M.; Tremblay, S. E.; Tingay, S. J.; Oronsaye, S.; Emrich, D.; Deshpande, A. A.; Van Straten, W.; Briggs, F.; Bernardi, G.; Bowman, J. D.; Cappallo, R. J.; Corey, B. E.; Goeke, R.; Hewitt, J. N.; Greenhill, L. J.; Kasper, J. C.; Hazelton, B. J.; Johnston-Hollitt, M.; Kaplan, D. L.; and others

    2014-08-20

    We report on the detection of the millisecond pulsar PSR J0437–4715 with the Murchison Wide-field Array (MWA) at a frequency of 192 MHz. Our observations show rapid modulations of pulse intensity in time and frequency that arise from diffractive scintillation effects in the interstellar medium (ISM), as well as prominent drifts of intensity maxima in the time-frequency plane that arise from refractive effects. Our analysis suggests that the scattering screen is located at a distance of ∼80-120 pc from the Sun, in disagreement with a recent claim that the screen is closer (∼10 pc). Comparisons with higher frequency data from Parkes reveal a dramatic evolution of the pulse profile with frequency, with the outer conal emission becoming comparable in strength to that from the core and inner conal regions. As well as demonstrating the high time resolution science capabilities currently possible with the MWA, our observations underscore the potential to conduct low-frequency investigations of timing-array millisecond pulsars, which may lead to increased sensitivity in the detection of nanoHertz gravitational waves via the accurate characterization of ISM effects.

  4. The effects of extremely low-frequency magnetic fields on melatonin and cortisol, two marker rhythms of the circadian system

    PubMed Central

    Touitou, Yvan; Selmaoui, Brahim

    2012-01-01

    In the past 30 years the concern that daily exposure to extremely low-frequency magnetic fields (ELF-EMF) (1 to 300 Hz) might be harmful to human health (cancer, neurobehavioral disturbances, etc) has been the object of debate, and has become a public health concern. This has resulted in the classification of ELF-EMF into category 2B, ie, agents that are “possibly carcinogenic to humans” by the International Agency for Research on Cancer. Since melatonin, a neurohormone secreted by the pineal gland, has been shown to possess oncostatic properties, a “melatonin hypothesis” has been raised, stating that exposure to EMF might decrease melatonin production and therefore might promote the development of breast cancer in humans. Data from the literature reviewed here are contradictory. In addition, we have demonstrated a lack of effect of ELF-EMF on melatonin secretion in humans exposed to EMF (up to 20 years' exposure) which rebuts the melatonin hypothesis. Currently, the debate concerns the effects of ELF-EMF on the risk of childhood leukemia in children chronically exposed to more than 0.4 μT. Further research is thus needed to obtain more definite answers regarding the potential deleterious effects of ELF-EMF. PMID:23393415

  5. Molecular basis underlying the biological effects elicited by extremely low-frequency magnetic field (ELF-MF) on neuroblastoma cells.

    PubMed

    Sulpizio, Marilisa; Falone, Stefano; Amicarelli, Fernanda; Marchisio, Marco; Di Giuseppe, Fabrizio; Eleuterio, Enrica; Di Ilio, Carmine; Angelucci, Stefania

    2011-12-01

    Extremely low-frequency magnetic fields (ELF-MFs) may affect human health because of the possible associations with leukemia but also with cancer, cardiovascular, and neurological disorders. In the present work, human SH-SY5Y neuroblastoma cells were exposed to a 50 Hz, 1 mT sinusoidal ELF-MF at three different times, that is, 5 days (T5), 10 days (T10), and 15 days (T15) and then the effects of ELF-MF on proteome expression and biological behavior were investigated. Through comparative analysis between treated and control samples, we analyzed the proteome changes induced by ELF-MF exposure. Nine new proteins resolved in sample after a 15-day treatment were involved in a cellular defense mechanism and/or in cellular organization and proliferation such as peroxiredoxin isoenzymes (2, 3, and 6), 3-mercaptopyruvate sulfurtransferase, actin cytoplasmatic 2, t-complex protein subunit beta, ropporin-1A, and profilin-2 and spindlin-1. Our results indicated that ELF-MFs exposure altered the proliferative status and other important cell biology-related parameters, such as cell growth pattern, and cytoskeletal organization. These findings support our hypothesis that ELF radiation could trigger a shift toward a more invasive phenotype. PMID:21826706

  6. Diffraction of high-intensity field in focal region as dynamics of nonlinear system with low-frequency dispersion

    NASA Astrophysics Data System (ADS)

    Rudenko, O. V.; Hedberg, C. M.

    2015-01-01

    The stationary profile in the focal region of a focused nonlinear acoustic wave is described. Three models following from the Khokhlov-Zabolotskaya (KZ) equation with three independent variables are used: (i) the simplified one-dimensional Ostrovsky-Vakhnenko equation, (ii) the system of equations for paraxial series expansion of the acoustic field in powers of transverse coordinates, and (iii) the KZ equation reduced to two independent variables. The structure of the last equation is analogous to the Westervelt equation. Linearization through the Legendre transformation and reduction to the well-studied Euler-Tricomi equation is shown. At high intensities the stationary profiles are periodic sequences of arc sections having singularities of derivative in their matching points. The occurrence of arc profiles was pointed out by Makov. These appear in different nonlinear systems with low-frequency dispersion. Profiles containing discontinuities (shock fronts) change their form while passing through the focal region and are non-stationary waves. The numerical estimations of maximum pressure and intensity in the focus agree with computer calculations and experimental measurements.

  7. Low-frequency magnetic fields do not aggravate disease in mouse models of Alzheimer's disease and amyotrophic lateral sclerosis

    PubMed Central

    Liebl, Martina P.; Windschmitt, Johannes; Besemer, Anna S.; Schäfer, Anne-Kathrin; Reber, Helmut; Behl, Christian; Clement, Albrecht M.

    2015-01-01

    Low-frequency magnetic fields (LF-MF) generated by power lines represent a potential environmental health risk and are classified as possibly carcinogenic by the World Health Organization. Epidemiological studies indicate that LF-MF might propagate neurodegenerative diseases like Alzheimer's disease (AD) or amyotrophic lateral sclerosis (ALS). We conducted a comprehensive analysis to determine whether long-term exposure to LF-MF (50 Hz, 1 mT) interferes with disease development in established mouse models for AD and ALS, namely APP23 mice and mice expressing mutant Cu/Zn-superoxide dismutase (SOD1), respectively. Exposure for 16 months did not aggravate learning deficit of APP23 mice. Likewise, disease onset and survival of SOD1G85R or SOD1G93A mice were not altered upon LF-MF exposure for ten or eight months, respectively. These results and an extended biochemical analysis of protein aggregation, glial activation and levels of toxic protein species suggests that LF-MF do not affect cellular processes involved in the pathogenesis of AD or ALS. PMID:25717019

  8. Healing of Chronic Wounds through Systemic Effects of Electromagnetic Fields

    NASA Astrophysics Data System (ADS)

    Cañedo, L.; Trigos, I.; García-Cantú, R.; Godina-Nava, J. J.; Serrano, G.

    2002-08-01

    Extremely low frequency electromagnetic fields (ELF) were configured to interact with peripheral blood mononuclear cells (PBMC). These ELF were applied in the arm to five patients with chronic wounds resistant to medical and surgical treatment. Wound healing began in all patients during the first two weeks after ELF exposure permiting their previously unresponsive chronic wounds to function as internal controls. All lesions were cured or healed >70% in less than four months. Systemic effects were explained by ELF activation of PBMC and their transportation through the blood to the affected site. This therapy is effective in selected patients with chronic wounds.

  9. Low-frequency internal waves in magnetized rotating stellar radiation zones. II. Angular momentum transport with a toroidal field

    NASA Astrophysics Data System (ADS)

    Mathis, S.; de Brye, N.

    2012-04-01

    Context. With the progress of observational constraints on dynamical processes in stars, it becomes necessary to understand the angular momentum and the rotation profile history. In this context, internal waves constitute an efficient transport mechanism over long distances in stellar radiation zones. Indeed, they could be one of the mechanisms responsible for the quasi-flat rotation profile of the solar radiative region up to 0.2 R⊙. Aims: Angular momentum transport induced by internal waves depends on the properties of their excitation regions and of their dissipation during propagation. Then, the bottom of convective envelopes (the top of convective cores, respectively) are differentially rotating magnetic layers while radiation zones may host fossil magnetic fields. It is therefore necessary to understand the modification of internal wave mechanisms by both rotation and magnetic fields. Methods: We continue our previous work by proceeding step by step. We analytically built a complete formalism that treats the angular momentum transport by internal waves while taking into account both the Coriolis acceleration and the Lorentz force in a non-perturbative way for an axisymmetric toroidal field. We assumed a uniform Alfvén frequency and a weak differential rotation to isolate the transport properties as a function of the Rossby and Elsasser numbers. Results: We examined the different possible approximations to describe low-frequency internal waves modified by the Coriolis acceleration and the Lorentz force in a deep spherical shell. The complete structure of these waves, which become magneto-gravito-inertial waves, is given assuming the quasi-linear approximation first in the adiabatic case and then in the dissipative one. Vertical and equatorial trapping phenomena appear that favor retrograde waves. The efficiency of the induced transport as a function of the Rossby and Elsasser numbers is then obtained. Conclusions: A complete study of the transport of

  10. Assessment of occupational risks to extremely low frequency magnetic fields: Validation of an empirical non-expert approach.

    PubMed

    El-Zein, Mariam; Deadman, Jan-Erik; Infante-Rivard, Claire

    2016-12-01

    The expert method of exposure assignment involves relying on chemists or hygienists to estimate occupational exposures using information collected on study subjects. Once the estimation method for a particular contaminant has been made available in the literature, it is not known whether a non-expert, briefly trained by an expert remaining available to answer ad hoc questions, can provide reliable exposure estimates. We explored this issue by comparing estimates of exposure to extremely low frequency magnetic fields (ELF-MF) obtained by an expert to those from a non-expert. Using a published exposure matrix, both the expert and non-expert independently calculated a weekly time-weighted average exposure for 208 maternal jobs by considering three main determinants: the work environment, magnetic field sources, and duration of use or exposure to given sources. Agreement between assessors was tested using the Bland-Altman 95% limits of agreement. The overall mean difference in estimates between the expert and non-expert was 0.004 μT (standard deviation 0.104). The 95% limits of agreement were - 0.20 μT and + 0.21 μT. The work environments and exposure sources were almost always similarly identified but there were differences in estimating exposure duration. This occurred mainly when information collected from study subjects was not sufficiently detailed. Our results suggest that following a short training period and the availability of a clearly described method for estimating exposures, a non-expert can cost-efficiently and reliably assign exposure, at least to ELF-MF. PMID:27413676

  11. The developmental effects of extremely low frequency electric fields on visual and somatosensory evoked potentials in adult rats.

    PubMed

    Gok, Deniz Kantar; Akpinar, Deniz; Hidisoglu, Enis; Ozen, Sukru; Agar, Aysel; Yargicoglu, Piraye

    2016-01-01

    The purpose of our study was to investigate the developmental effects of extremely low frequency electric fields (ELF-EFs) on visual evoked potentials (VEPs) and somatosensory-evoked potentials (SEPs) and to examine the relationship between lipid peroxidation and changes of these potentials. In this context, thiobarbituric acid reactive substances (TBARS) levels were determined as an indicator of lipid peroxidation. Wistar albino female rats were divided into four groups; Control (C), gestational (prenatal) exposure (Pr), gestational+ postnatal exposure (PP) and postnatal exposure (Po) groups. Pregnant rats of Pr and PP groups were exposed to 50 Hz electric field (EF) (12 kV/m; 1 h/day), while those of C and Po groups were placed in an inactive system during pregnancy. Following parturition, rats of PP and Po groups were exposed to ELF-EFs whereas rats of C and Pr groups were kept under the same experimental conditions without being exposed to any EF during 68 days. On postnatal day 90, rats were prepared for VEP and SEP recordings. The latencies of VEP components in all experimental groups were significantly prolonged versus C group. For SEPs, all components of PP group, P2, N2 components of Pr group and P1, P2, N2 components of Po group were delayed versus C group. As brain TBARS levels were significantly increased in Pr and Po groups, retina TBARS levels were significantly elevated in all experimental groups versus C group. In conclusion, alterations seen in evoked potentials, at least partly, could be explained by lipid peroxidation in the retina and brain. PMID:25496054

  12. Low-Frequency Radioastronomy Basics

    NASA Astrophysics Data System (ADS)

    Zarka, P.

    2011-04-01

    With the many large instruments in construction or in project, the present epoch corresponds to a renewal of low-frequency radioastronomy. The field will attract new researchers and students not expert of the radioastronomy techniques. With this audience in mind, we present here a very brief introduction to radioastronomy basics, including propagation and polarization of low-frequency radio waves as well as instrumental aspects. Basic formulas are given. The references and internet links will allow the interested reader to go further.

  13. Effects of Pulsed Electromagnetic Fields on Osteoporosis Model

    NASA Astrophysics Data System (ADS)

    Xiaowei, Yang; Liming, Wang; Guan, Z. C.; Yaou, Zhang; Xiangpeng, Wang

    The purpose of this paper was to investigate the preventive effects and long term effects of extremely low frequency pulsed electromagnetic fields (PEMFs), generated by circular coils and pulsed electromagnetic fields stimulators, on osteoporosis in bilaterally ovariectomized rats. In preventive experiment, thirty three-month old female Sprague-Dawley rats were randomly divided into three different groups: sham (SHAM), ovariectomy (OVX), PEMFs stimulation (PEMFs). All rats were subjected to bilaterally ovariectomy except those in SHAM group. The PEMFs group was exposed to pulsed electromagnetic fields with frequency 15 Hz, peak magnetic induction density 2.2mT and exposure time 2 hours per day. The bone mineral density (BMD) of vertebra and left femur were measured by dual energy X-ray absorptiometry at eighth week, twelfth week and sixteenth week after surgery. In long term effects experiment, forty four rats were randomly divided into sham (14 rats, SHAM), ovariectomy group (10 rats, OVX), 15Hz PEMFs group(10 rats, 15Hz) and 30Hz PEMFs group(10 rats, 30Hz) at twenty-sixth week after surgery. Rats in PEMFs groups were stimulated sixteen weeks. In preventive experiment, the Corrected BMD of vertebra and femur was significantly higher than that of OVX group after 16 weeks (P<0.001, P<0.001 respectively). In long term effects experiment, the vertebral BMD of 15Hz PEMFs group and 30Hz PEMFs group was significantly higher than that of OVX groups (P<0.01, P<0.05 respectively). The experimental results demonstrated that extremely low intensity, low frequency, single pulsed electromagnetic fields significantly slowed down the loss of corrected vertebral and femoral BMD in bilaterally ovariectomized rats and suggest that PEMFs may be beneficial in the treatment of osteoporosis.

  14. The sensitivity of children to electromagnetic fields.

    PubMed

    Kheifets, Leeka; Repacholi, Michael; Saunders, Rick; van Deventer, Emilie

    2005-08-01

    In today's world, technologic developments bring social and economic benefits to large sections of society; however, the health consequences of these developments can be difficult to predict and manage. With rapid advances in electromagnetic field (EMF) technologies and communications, children are increasingly exposed to EMFs at earlier and earlier ages. Consistent epidemiologic evidence of an association between childhood leukemia and exposure to extremely low frequency (ELF) magnetic fields has led to their classification by the International Agency for Research on Cancer as a "possible human carcinogen." Concerns about the potential vulnerability of children to radio frequency (RF) fields have been raised because of the potentially greater susceptibility of their developing nervous systems; in addition, their brain tissue is more conductive, RF penetration is greater relative to head size, and they will have a longer lifetime of exposure than adults. To evaluate information relevant to children's sensitivity to both ELF and RF EMFs and to identify research needs, the World Health Organization held an expert workshop in Istanbul, Turkey, in June 2004. This article is based on discussions from the workshop and provides background information on the development of the embryo, fetus, and child, with particular attention to the developing brain; an outline of childhood susceptibility to environmental toxicants and childhood diseases implicated in EMF studies; and a review of childhood exposure to EMFs. It also includes an assessment of the potential susceptibility of children to EMFs and concludes with a recommendation for additional research and the development of precautionary policies in the face of scientific uncertainty. PMID:16061584

  15. Extremely Low Frequency Magnetic Field (ELF-MF) Exposure Sensitizes SH-SY5Y Cells to the Pro-Parkinson's Disease Toxin MPP(.).

    PubMed

    Benassi, Barbara; Filomeni, Giuseppe; Montagna, Costanza; Merla, Caterina; Lopresto, Vanni; Pinto, Rosanna; Marino, Carmela; Consales, Claudia

    2016-08-01

    Parkinson's disease (PD) is a neurodegenerative disorder characterized by dopaminergic neuron loss, with an etiopathogenesis involving both genetic and environmental factors. The occupational/residential exposure to the electromagnetic fields has been recently associated with an increased risk of neurodegenerative diseases; it has been thus proposed that the extremely low frequency magnetic field (ELF-MF) may contribute to neurodegenerative etiopathogenesis, as its interaction with biological systems directly impairs redox homeostasis in specific areas of the brain. The molecular mechanisms elicited by ELF-MF, and their potential involvement in PD onset, still remain unclear. To this end, we set up a generator of ELF-MF able to stably and homogeneously reproduce environmental prolonged exposure to ELF-MF (50 Hz, 1 mT). Results obtained indicate that ELF-MF exposure alters cell response of SH-SY5Y cells to MPP(+). We demonstrate that ELF-MF does not affect per se survival, shape, and morphology of both proliferating and differentiated SH-SY5Y cells but significantly impairs redox homeostasis and thiol content, triggering an increase in protein carbonylation. As a result, toxicity of MPP(+), even at low doses, is highly enhanced in ELF-MF-exposed cells due to a significant increase in ROS levels, potentiation of oxidative damage, and induction of a caspase-dependent apoptosis. Pre-incubation with the thiol antioxidants N-acetyl-L-cysteine and GSH ethyl-ester significantly reduces the extent of oxidative damage and protects cells from death induced by the combined treatment ELF-MF/MPP(+). Taken overall, our results demonstrate the redox-based molecular interaction between ELF-MF and PD neurotoxins in vitro, and open a new scenario for defining the synergy of environmental factors in PD onset. PMID:26223801

  16. The history of early low frequency radio astronomy in Australia. 3: Ellis, Reber and the Cambridge field station near Hobart

    NASA Astrophysics Data System (ADS)

    George, Martin; Orchiston, Wayne; Slee, Bruce; Wielebinski, Richard

    2015-07-01

    Low frequency radio astronomy in Tasmania began with the arrival of Grote Reber to the State in 1954. After analysing ionospheric data from around the world, he concluded that Tasmania would be a very suitable place to carry out low frequency observations. Communications with Graeme Ellis in Tasmania, who had spent several years studying the ionosphere, led to a collaboration between the two in 1955 during which year they made observations at Cambridge, near Hobart. Their observations took place at four frequencies between 2.13 MHz and 0.52 MHz inclusive, with the results at the higher frequencies revealing a clear celestial component

  17. Link invariants of electromagnetic fields.

    PubMed

    von Bodecker, Hanno; Hornig, Gunnar

    2004-01-23

    The cross-helicity integral is known in fluid dynamics and plasma physics as a topological invariant which measures the mutual linkage of two divergence-free vector fields, e.g., magnetic fields, on a three-dimensional domain. Generalizing this concept, a new topological invariant is found which measures the mutual linkage of three closed two-forms, e.g., electromagnetic fields, on a four-dimensional domain. The integral is shown to detect a separation of the cross helicity between two of the fields with the help of the third field. It can be related to the triple linking number known in knot theory. Furthermore, it is shown that the well-known three-dimensional cross helicity and the new four-dimensional invariant are the first two examples of a series of topological invariants which are defined by n-1 field strengths F=dA on a simply connected n-dimensional manifold M(n). PMID:14753856

  18. Extremely low frequency alternating magnetic field-triggered and MRI-traced drug delivery by optimized magnetic zeolitic imidazolate framework-90 nanoparticles.

    PubMed

    Fang, Jie; Yang, Yong; Xiao, Wen; Zheng, Bingwen; Lv, Yun-Bo; Liu, Xiao-Li; Ding, Jun

    2016-02-14

    An extremely low frequency alternating magnetic field (ELF-AMF) was demonstrated to be able to effectively trigger drug release from carefully engineered magnetic ZIF-90 nanoparticles. The embedded Fe3O4 nanoparticles or alternatively Gd2O3 nanoparticles serve as effective MRI tracers for potential visualization of drug delivery to ensure drug delivery accuracy. PMID:26809987

  19. Quantization of Electromagnetic Fields in Cavities

    NASA Technical Reports Server (NTRS)

    Kakazu, Kiyotaka; Oshiro, Kazunori

    1996-01-01

    A quantization procedure for the electromagnetic field in a rectangular cavity with perfect conductor walls is presented, where a decomposition formula of the field plays an essential role. All vector mode functions are obtained by using the decomposition. After expanding the field in terms of the vector mode functions, we get the quantized electromagnetic Hamiltonian.

  20. Electromagnetic field and brain development.

    PubMed

    Kaplan, Suleyman; Deniz, Omur Gulsum; Önger, Mehmet Emin; Türkmen, Aysın Pınar; Yurt, Kıymet Kübra; Aydın, Işınsu; Altunkaynak, Berrin Zuhal; Davis, Devra

    2016-09-01

    Rapid advances in technology involve increased exposures to radio-frequency/microwave radiation from mobile phones and other wireless transmitting devices. As cell phones are held close to the head during talking and often stored next to the reproductive organs, studies are mostly focused on the brain. In fact, more research is especially needed to investigate electromagnetic field (EMF)'s effects on the central nervous system (CNS). Several studies clearly demonstrate that EMF emitted by cell phones could affect a range of body systems and functions. Recent work has demonstrated that EMF inhibit the formation and differentiation of neural stem cells during embryonic development and also affect reproductive and neurological health of adults that have undergone prenatal exposure. The aim of this review is to discuss the developing CNS and explain potential impacts of EMF on this system. PMID:26686296

  1. Field Evaluations of Low-Frequency SAFT-UT on Cast Stainless Steel and Dissimilar Metal Weld Components

    SciTech Connect

    Diaz, Aaron A.; Harris, R. V.; Doctor, Steven R.

    2008-11-01

    This report documents work performed at the Pacific Northwest National Laboratory (PNNL) in Richland, Washington, and at the Electric Power Research Institute's (EPRI) Nondestructive Examination (NDE) Center in Charlotte, North Carolina, on evalutating a low frequency ultrasonic inspection technique used for examination of cast stainless steel (CSS) and dissimilar metal (DMW) reactor piping components. The technique uses a zone-focused, multi-incident angle, low frequency (250-450 kHz) inspection protocol coupled with the synthetic aperture focusing technique (SAFT). The primary focus of this work is to provide information to the United States Nuclear Regulatory Commission on the utility, effectiveness and reliability of ultrasonic testing (UT) inspection techniques as related to the inservice ultrasonic inspection of coarse grained primary piping components in pressurized water reactors (PWRs).

  2. Crosswell electromagnetic tomography: System design considerations and field results

    SciTech Connect

    Wilt, M.J.; Alumbaugh, D.L.; Lee, K.H.; Deszcz-Pan, M.; Morrison, H.F.; Becker, A.

    1995-05-01

    Electrical conductivity is an important petroleum reservoir parameter because of its sensitivity to porosity, pore fluid type, and saturation. Although induction logs are widely used to obtain the conductivity near boreholes, the poor resolution offered by surface-based electrical and electromagnetic (EM) field systems has thus far limited obtaining this information in the region between boreholes. Low-frequency crosswell EM offers the promise of providing subsurface conductivity information at a much higher resolution than was previously possible. Researchers at Lawrence Livermore National Lab (LLNL), and Lawrence Berkeley Laboratories (LBL), together with an industrial consortium, recently began a program to conduct low-frequency crosswell EM surveys and develop suitable inversion techniques for interpreting the data. In developing the field instrumentation the authors used off-the-shelf components whenever possible, but custom-designed induction coil transmitters and receivers were built for the field experiments. The assembled field system has adequate power for moderate to high-resolution imaging, using boreholes spaced up to 500 m apart. The initial field experiment was undertaken in flat lying terrain at the British petroleum test site in Devine, Texas.

  3. Noninvasive valve monitor using alternating electromagnetic field

    DOEpatents

    Eissenberg, David M.; Haynes, Howard D.; Casada, Donald A.

    1993-01-01

    One or more electrical coils are carefully located on the outside of a valve body. An alternating current passing through the coil(s) results in an alternating electromagnetic field being transmitted into the valve body and valve internals. The electromagnetic field varies in intensity and polarity in the valve. As the position of a valve internal part is changed, the electromagnetic field throughout the valve body and its internals is altered. A passive receiver coil carefully located on the outside of the valve body detects the intensity of the electromagnetic field at that location as an induced electrical voltage in the coil. With the change in position of the valve internal part, there is a corresponding change in the induced voltage as a result of the alteration in the alternating electromagnetic field at that location. Changes in the voltage provide an indication of the position and motion of valve internals.

  4. Noninvasive valve monitor using alternating electromagnetic field

    DOEpatents

    Eissenberg, D.M.; Haynes, H.D.; Casada, D.A.

    1993-03-16

    One or more electrical coils are carefully located on the outside of a valve body. An alternating current passing through the coil(s) results in an alternating electromagnetic field being transmitted into the valve body and valve internals. The electromagnetic field varies in intensity and polarity in the valve. As the position of a valve internal part is changed, the electromagnetic field throughout the valve body and its internals is altered. A passive receiver coil carefully located on the outside of the valve body detects the intensity of the electromagnetic field at that location as an induced electrical voltage in the coil. With the change in position of the valve internal part, there is a corresponding change in the induced voltage as a result of the alteration in the alternating electromagnetic field at that location. Changes in the voltage provide an indication of the position and motion of valve internals.

  5. Study of mechanisms of electric field-induced DNA transfection. II. Transfection by low-amplitude, low-frequency alternating electric fields.

    PubMed

    Xie, T D; Tsong, T Y

    1990-10-01

    Electroporation for DNA transfection generally uses short intense electric pulses (direct current of kilovolts per centimeter, microseconds to milliseconds), or intense dc shifted radio-frequency oscillating fields. These methods, while remarkably effective, often cause death of certain cell populations. Previously it was shown that a completely reversible, high ionic permeation state of membranes could be induced by a low-frequency alternating electric field (ac) with a strength one-tenth, or less, of the critical breakdown voltage of the cell membrane (Teissie, J., and T. Y. Tsong. 1981. J. Physiol. (Paris). 77:1043-1053). We report the transfection of E. coli (JM105) by plasmid PUC18 DNA, which carries an ampicillin-resistance gene, using low-amplitude, low-frequency ac fields. E. coli transformants confer the ampicillin resistance and the efficiency of the transfection can be conveniently assayed by counting colonies in a selection medium containing ampicillin. For the range of ac fields employed (peak-to-peak amplitude 50-200 V/cm, frequency 0.1 Hz-1 MHz, duration 1-100 s), 100% of the E. coli survived the electric field treatment. Transfection efficiencies varied with field strength and frequency, and as high as 1 x 10(5)/micrograms DNA was obtained with a 200 V/cm square wave, 1 Hz ac field, 30 s exposure time, when the DNA/cell ratio was 50-75. Control samples gave a background transfection of much less than 10/micrograms DNA. With a square wave ac field, the transfection efficiency showed a frequency window: the optimal frequency was 1 Hz with a 200 V/cm field, and was approximately 0.1 Hz with a 50 V/cm field. Transfection efficiency varied with the waveform: square wave > sine wave > triangle wave. If the DNA was added after the ac field was turned off, transfection efficiency was reduced to the background level within 1 min. The field intensity used in this study was low and insufficient to cause electric breakdown of cell membranes. Thus, DNA

  6. Generating highly uniform electromagnetic field characteristics

    DOEpatents

    Crow, James T.

    1997-01-01

    An apparatus and method for generating homogenous electromagnetic fields within a volume. The homogeneity provided may be for magnetic and/or electric fields, and for field magnitude, radial gradient, or higher order radial derivative. The invention comprises conductive pathways oriented mirror symmetrically about a desired region of homogeneity. A corresponding apparatus and method is provided for substantially cancelling the electromagnetic field outside of the apparatus, comprising a second set of conductive pathways placed outside the first set.

  7. Generating highly uniform electromagnetic field characteristics

    DOEpatents

    Crow, J.T.

    1998-05-05

    An apparatus and method are disclosed for generating homogeneous electromagnetic fields within a volume. The homogeneity provided may be for magnetic and/or electric fields, and for field magnitude, radial gradient, or higher order radial derivative. The invention comprises conductive pathways oriented about a desired region of homogeneity. A corresponding apparatus and method is provided for substantially canceling the electromagnetic field outside of the apparatus, comprising a second set of conductive pathways placed outside the first set. 55 figs.

  8. Generating highly uniform electromagnetic field characteristics

    DOEpatents

    Crow, J.T.

    1998-02-10

    An apparatus and method for generating homogeneous electromagnetic fields within a volume is disclosed. The homogeneity provided may be for magnetic and/or electric fields, and for field magnitude, radial gradient, or higher order radial derivative. The invention comprises conductive pathways oriented mirror symmetrically about a desired region of homogeneity. A corresponding apparatus and method is provided for substantially canceling the electromagnetic field outside of the apparatus, comprising a second set of conductive pathways placed outside the first set. 39 figs.

  9. Generating highly uniform electromagnetic field characteristics

    DOEpatents

    Crow, James Terry

    1998-01-01

    An apparatus and method for generating homogenous electromagnetic fields within a volume. The homogeneity provided may be for magnetic and/or electric fields, and for field magnitude, radial gradient, or higher order radial derivative. The invention comprises conductive pathways oriented mirror symmetrically about a desired region of homogeneity. A corresponding apparatus and method is provided for substantially canceling the electromagnetic field outside of the apparatus, comprising a second set of conductive pathways placed outside the first set.

  10. Generating highly uniform electromagnetic field characteristics

    DOEpatents

    Crow, James T.

    1998-01-01

    An apparatus and method for generating homogenous electromagnetic fields within a volume. The homogeneity provided may be for magnetic and/or electric fields, and for field magnitude, radial gradient, or higher order radial derivative. The invention comprises conductive pathways oriented about a desired region of homogeneity. A corresponding apparatus and method is provided for substantially canceling the electromagnetic field outside of the apparatus, comprising a second set of conductive pathways placed outside the first set.

  11. Generating highly uniform electromagnetic field characteristics

    DOEpatents

    Crow, J.T.

    1997-06-24

    An apparatus and method are disclosed for generating homogeneous electromagnetic fields within a volume. The homogeneity provided may be for magnetic and/or electric fields, and for field magnitude, radial gradient, or higher order radial derivative. The invention comprises conductive pathways oriented mirror symmetrically about a desired region of homogeneity. A corresponding apparatus and method is provided for substantially canceling the electromagnetic field outside of the apparatus, comprising a second set of conductive pathways placed outside the first set. 26 figs.

  12. Technical specifications of low-frequency radio identification bedload tracking from field experiments: Differences in antennas, tags and operators

    NASA Astrophysics Data System (ADS)

    Arnaud, F.; Piégay, H.; Vaudor, L.; Bultingaire, L.; Fantino, G.

    2015-06-01

    Low-frequency passive integrated transponders (PIT tags) have been increasingly used for tracking bedload transport in gravel-bed rivers. Prior studies have reported high recovery rates in small streams, while recovery rates remained much lower in large systems, in large part because of the limited reading distance of the tags (< 1 m). Some laboratory tests have identified controlling factors for detection ranges (tag and antenna size, tag orientation, burial, submergence, etc.). Beyond these tests, improving our understanding of PIT tag functioning, using different equipment within different environments, is still needed in order to select the most suitable device for each geomorphic context. We address this knowledge gap with technical specifications for a low-frequency radio identification (RFID) device by working for the first time with real fluvial constraints, i.e., the gravel deposits and the aquatic channel. The three-dimensional detection envelopes of two types of tags and three types of antennas are quantified as well as the effect of practices (interoperator bias, battery power) on the detection. The interoperator variability and the intertag variability can be considered as negligible. The influence of burial in dry and water-saturated sediment and the influence of water immersion are shown to be minor. Finally, we summarize practical implications for RFID bedload tracking through these experiments.

  13. Induction of tamoxifen resistance in breast cancer cells by ELF electromagnetic fields

    SciTech Connect

    Girgert, Rainer . E-mail: rainer.girgert@med.uni-goettingen.de; Schimming, Hartmut; Koerner, Wolfgang; Gruendker, Carsten; Hanf, Volker

    2005-11-04

    The incidence of breast cancer in western societies has been rising ever since the Second World War. Besides the exposure to a multitude of new chemical compounds, electromagnetic field exposure has been linked to breast cancer through a radiation-mediated anti-melatonin pathway. We investigated, whether low-frequency electromagnetic field exposure interferes with the anti-estrogenic activity of tamoxifen. Two different clones of the breast cancer cell line MCF-7 were exposed to highly homogeneous 50 Hz electromagnetic fields and IC{sub 50} values were calculated from dose-response curves of tamoxifen at various field intensities. An intensity-dependent shift of tamoxifen dose-response curves to higher concentrations with a maximal response at 1.2 {mu}T was observed. Hypothetically, electromagnetic field exposure could contribute to tamoxifen resistance observed in breast cancer after long-term treatment.

  14. Propagation of a low-frequency rectangular pulse in seawater

    NASA Astrophysics Data System (ADS)

    King, Ronold W. P.

    1993-05-01

    As a necessary preliminary to the determination of the electromagnetic field scattered by a metal cylinder submerged in the ocean, the propagation of a low frequency pulse with a rectangular envelope is evaluated numerically as a function of the distance of travel. Graphs of the three component terms and their sum are shown for four distances. The very significant changes in shape and amplitude of the pulse are discussed.

  15. [Application of the pulsed low-frequency electrostatic field in the early rehabilitative treatment of patients following surgery for the correction of valgus deformation of the first toe].

    PubMed

    Razumov, A N; Li, A A; Kotenko, K V; Korchazhkina, N B; Orekhova, E M; Kazantsev, A B; Li, E A

    2010-01-01

    This paper describes the method and results of application of the pulsed low-frequency electrostatic field (PLFESF) to the lower extremities of the patients who underwent surgical treatment for the correction of valgus deformation of the first toe. The efficiency of the method used in the early period of rehabilitative treatment was estimated at 93.3% compared with 96.7% in the patients who were managed by the same therapy in combination with polyoxdonium. PMID:21086590

  16. The history of early low frequency radio astronomy in Australia. 4: Kerr, Shain, Higgins and the Hornsby Valley field station near Sydney

    NASA Astrophysics Data System (ADS)

    Orchiston, Wayne; Slee, Bruce; George, Martin; Wielebinski, Richard

    2015-11-01

    Between 1949 and 1952 the CSIR's Division of Radiophysics was a world leader in low frequency radio astronomy, through research conducted mainly by Alex Shain and Charlie Higgins at their Hornsby Valley field station near Sydney. In this paper we discuss the personnel, radio telescopes and research programs (mainly conducted at 9.15 and 18.3 MHz) associated with the Hornsby Valley site.

  17. Nanomechanical electric and electromagnetic field sensor

    DOEpatents

    Datskos, Panagiotis George; Lavrik, Nickolay

    2015-03-24

    The present invention provides a system for detecting and analyzing at least one of an electric field and an electromagnetic field. The system includes a micro/nanomechanical oscillator which oscillates in the presence of at least one of the electric field and the electromagnetic field. The micro/nanomechanical oscillator includes a dense array of cantilevers mounted to a substrate. A charge localized on a tip of each cantilever interacts with and oscillates in the presence of the electric and/or electromagnetic field. The system further includes a subsystem for recording the movement of the cantilever to extract information from the electric and/or electromagnetic field. The system further includes a means of adjusting a stiffness of the cantilever to heterodyne tune an operating frequency of the system over a frequency range.

  18. Exposure to electromagnetic fields and suicide among electric utility workers

    PubMed Central

    van Wijngaarden, Edwin; Savitz, David A; Kleckner, Robert C; Cai, Jianwen; Loomis, Dana

    2000-01-01

    Objective To examine mortality from suicide in relation to estimated exposure to extremely low-frequency electromagnetic fields in a cohort of138,905 male electric utility workers. Methods Case-control sampling, which included 536 deaths from suicide and 5,348 eligible controls. Exposure was classified based on work in the most common jobs with increased exposure to magnetic fields and indices of cumulative exposure to magnetic fields based on a measurement survey. Results Suicide mortality was increased relative to work in exposed jobs and with indices of exposure to magnetic fields. Increased odds ratios (ORs) were found for years of employment as an electrician (OR, 2.18; 95% confidence interval [CI], 1.25-3.80) or line worker(OR, 1.59; 95% CI, 1.18-2.14), whereas a decreased OR was found for power plant operators (OR, 0.67; 95% CI, 0.33-1.40). A dose-response gradient withexposure to magnetic fields was found for exposure in the previous year, with a mortality OR of 1.70 (95% CI, 1.00-2.90) in the highest exposure category.Stronger associations, with ORs in the range of 2.12 to 3.62, were found for men younger than 50 years. Conclusions These data provide evidence for an association between occupational electromagnetic fields and suicide that warrants further evaluation. A plausible mechanism related to melatonin and depression provides a direction for additional laboratory research and epidemiologic evaluation. PMID:10924428

  19. Study of low-frequency-acoustic- and seismic-wave energy propagation on the shelf

    NASA Astrophysics Data System (ADS)

    Rutenko, A. N.; Manul'chev, D. S.; Solov'ev, A. A.

    2013-05-01

    The paper presents the results of field and numerical studies on the features of low-frequency-acoustic- and seismic-wave energy propagation on the shelf of the Sea of Japan. Measurements were conducted with the Mollusk-07 autonomous vertical acousto-hydrophysical measurement system, an electromagnetic low-frequency resonance emitter, and a pulsed pneumoemitter lowered from the ship, as well as a shore-based resonance seismoemitter.

  20. Interaction of electromagnetic fields and biological tissues

    NASA Astrophysics Data System (ADS)

    Darshan Shrivastava, Bhakt; Barde, Ravindra; Mishra, Ashutosh; Phadke, S.

    2014-09-01

    This paper deals with the electromagnetic field interact in biological tissues. It is actually one of the important challenges for the electromagnetic field for the recent years. The experimental techniques are use in Broad-band Dielectric Measurement (BDM) with LCR meters. The authors used Bones and scales of Fish taken from Narmada River (Rajghat Dist. Barwani) as biological tissues. Experimental work carried out done in inter-university consortium (IUC) Indore. The major difficulties that appear are related to the material properties, to the effect of the electromagnetic problem and to the thermal model of the biological tissues.

  1. Extremely low frequency magnetic fields can either increase or decrease analgaesia in the land snail depending on field and light conditions.

    PubMed

    Prato, F S; Kavaliers, M; Thomas, A W

    2000-05-01

    Results of prior investigations with opioid peptide mediated antinociception or analgaesia have suggested that these extremely low frequency (ELF) magnetic field effects are described by a resonance mechanism rather than mechanisms based on either induced currents or magnetite. Here we show that ELF magnetic fields (141-414 microT peak) can, in a manner consistent with the predictions of Lednev's parametric resonance model (PRM) for the calcium ion, either (i) reduce, (ii) have no effect on, or (iii) increase endogenous opioid mediated analgaesia in the land snail, Cepaea nemoralis. When the magnetic fields were set to parameters for the predictions of the PRM for the potassium ion, opioid-peptide mediated analgaesia increased and there was evidence of antagonism by the K(+) channel blocker, glibenclamide. Furthermore, these effects were dependent on the presence of light; the effects were absent in the absence of light. These observed increases and decreases in opioid analgaesia are largely consistent with the predictions of Lednev's PRM. PMID:10797457

  2. Relativistic diffusive motion in thermal electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Haba, Z.

    2013-04-01

    We discuss relativistic dynamics in a random electromagnetic field which can be considered as a high temperature limit of the quantum electromagnetic field in a heat bath (cavity) moving with a uniform velocity w. We derive a diffusion approximation for the particle’s dynamics generalizing the diffusion of Schay and Dudley. It is shown that the Jüttner distribution is the equilibrium state of the diffusion.

  3. Narrow field electromagnetic sensor system and method

    DOEpatents

    McEwan, T.E.

    1996-11-19

    A narrow field electromagnetic sensor system and method of sensing a characteristic of an object provide the capability to realize a characteristic of an object such as density, thickness, or presence, for any desired coordinate position on the object. One application is imaging. The sensor can also be used as an obstruction detector or an electronic trip wire with a narrow field without the disadvantages of impaired performance when exposed to dirt, snow, rain, or sunlight. The sensor employs a transmitter for transmitting a sequence of electromagnetic signals in response to a transmit timing signal, a receiver for sampling only the initial direct RF path of the electromagnetic signal while excluding all other electromagnetic signals in response to a receive timing signal, and a signal processor for processing the sampled direct RF path electromagnetic signal and providing an indication of the characteristic of an object. Usually, the electromagnetic signal is a short RF burst and the obstruction must provide a substantially complete eclipse of the direct RF path. By employing time-of-flight techniques, a timing circuit controls the receiver to sample only the initial direct RF path of the electromagnetic signal while not sampling indirect path electromagnetic signals. The sensor system also incorporates circuitry for ultra-wideband spread spectrum operation that reduces interference to and from other RF services while allowing co-location of multiple electronic sensors without the need for frequency assignments. 12 figs.

  4. Narrow field electromagnetic sensor system and method

    DOEpatents

    McEwan, Thomas E.

    1996-01-01

    A narrow field electromagnetic sensor system and method of sensing a characteristic of an object provide the capability to realize a characteristic of an object such as density, thickness, or presence, for any desired coordinate position on the object. One application is imaging. The sensor can also be used as an obstruction detector or an electronic trip wire with a narrow field without the disadvantages of impaired performance when exposed to dirt, snow, rain, or sunlight. The sensor employs a transmitter for transmitting a sequence of electromagnetic signals in response to a transmit timing signal, a receiver for sampling only the initial direct RF path of the electromagnetic signal while excluding all other electromagnetic signals in response to a receive timing signal, and a signal processor for processing the sampled direct RF path electromagnetic signal and providing an indication of the characteristic of an object. Usually, the electromagnetic signal is a short RF burst and the obstruction must provide a substantially complete eclipse of the direct RF path. By employing time-of-flight techniques, a timing circuit controls the receiver to sample only the initial direct RF path of the electromagnetic signal while not sampling indirect path electromagnetic signals. The sensor system also incorporates circuitry for ultra-wideband spread spectrum operation that reduces interference to and from other RF services while allowing co-location of multiple electronic sensors without the need for frequency assignments.

  5. Observation of multi-scale oscillation of laminar lifted flames with low-frequency AC electric fields

    SciTech Connect

    Ryu, S.K.; Kim, Y.K.; Kim, M.K.; Won, S.H.; Chung, S.H.

    2010-01-15

    The oscillation behavior of laminar lifted flames under the influence of low-frequency AC has been investigated experimentally in coflow jets. Various oscillation modes were existed depending on jet velocity and the voltage and frequency of AC, especially when the AC frequency was typically smaller than 30 Hz. Three different oscillation modes were observed: (1) large-scale oscillation with the oscillation frequency of about 0.1 Hz, which was independent of the applied AC frequency, (2) small-scale oscillation synchronized to the applied AC frequency, and (3) doubly-periodic oscillation with small-scale oscillation embedded in large-scale oscillation. As the AC frequency decreased from 30 Hz, the oscillation modes were in the order of the large-scale oscillation, doubly-periodic oscillation, and small-scale oscillation. The onset of the oscillation for the AC frequency smaller than 30 Hz was in close agreement with the delay time scale for the ionic wind effect to occur, that is, the collision response time. Frequency-doubling behavior for the small-scale oscillation has also been observed. Possible mechanisms for the large-scale oscillation and the frequency-doubling behavior have been discussed, although the detailed understanding of the underlying mechanisms will be a future study. (author)

  6. The history of early low frequency radio astronomy in Australia. 5: Reber and the Kempton field station in Tasmania

    NASA Astrophysics Data System (ADS)

    George, Martin; Orchiston, Wayne; Wielebinski, Richard; Slee, Bruce

    2015-11-01

    After initially making low frequency observations with Graeme Ellis near Hobart, Tasmania, in 1955, Grote Reber returned to Tasmania to carry out further observations in 1956-1957 near Kempton, to the north of Hobart. He chose to investigate at 520 kHz, and used four dipoles, each about 670m long, about 300m apart and approximately 100m above a valley floor. Reber deduced that there was a celestial component which appeared to have a maximum, with an intensity he stated to be 4 × 10-20 Jy/sr, around right ascension 22 hours, declination -6°. By 1960, he had re-interpreted the results and concluded that the maximum emission actually came from a declination of about +42°, in the constellation of Cygnus. However, two decades later, he expressed doubt that he had actually observed cosmic emissions at all. In 1957, Reber briefly also made observations from Kempton at 143 kHz. One of us (MG) has visited the Kempton site on several occasions in recent years and has located artefacts that have remained relatively undisturbed for nearly 60 years.

  7. Development of Very Low Frequency Self-Nulling Probe for Inspection of Thick Layered Aluminum Structures

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Namkung, Min

    1998-01-01

    It is clear from simple skin depth considerations that steady state electromagnetic inspection of thick multi-layered conductors requires low frequency excitation. Conventional pickup sensors, however, lose sensitivity at lower frequencies. Giant magneto resistive materials offer a unique alternative for very low frequency electromagnetic NDE due to their high sensitivity to low frequency fields, small size, ease of use, and low cost. This paper outlines the development and testing of a Very Low Frequency Self-Nulling Probe incorporating a GMR sensor. The initial test results show flaw detectability at depths up to 1 cm in aluminum 2024. Optimization of the probe design based upon finite element modeling and GMR sensor characteristics (including hysteresis, linearity and saturation) is under way.

  8. Electromagnetic currents induced by color fields

    NASA Astrophysics Data System (ADS)

    Tanji, Naoto

    2015-12-01

    The quark production in classical color fields is investigated with a focus on the induction of an electromagnetic current by produced quarks. We show that the color SU(2) and the SU(3) theories lead significantly different results for the electromagnetic current. In uniform SU(2) color fields, the net electromagnetic current is not generated, while in SU(3) color fields the net current is induced depending on the color direction of background fields. Also the numerical study of the quark production in inhomogeneous color fields is done. Motivated by gauge field configurations provided by the color glass condensate framework, we introduce an ensemble of randomly distributed color electric fluxtubes. The spectrum of photons emitted from the quarks by a classical process is shown.

  9. Systemic effects of electromagnetic fields in epilepsy resistant to medical treatment

    NASA Astrophysics Data System (ADS)

    Cañedo, L.; García-Cantú, R.; Gonzalez, A.; Martinez-Mata, J.; Aguilar-Baturoni, U.; Martinez, M.; Serrano-Luna, G.; López García, E.

    2003-09-01

    Interaction between immune and nervous systems is intense. Immune alterations are present in various forms of epilepsy and seizures can be provoked or inhibited using strategies involving the immune system. Extremely low frequency electromagnetic fields (ELF) have been used to attenuate epileptic seizures and to activate immune cells. We used specifically configured ELF to activate immune cells peripherally and observe if they could participate in the attenuation of epileptic seizures. The results obtained support this hypothesis. Possible mechanisms are presented.

  10. Analgesic and behavioral effects of a 100 microT specific pulsed extremely low frequency magnetic field on control and morphine treated CF-1 mice.

    PubMed

    Shupak, Naomi M; Hensel, Jennifer M; Cross-Mellor, Shelly K; Kavaliers, Martin; Prato, Frank S; Thomas, Alex W

    2004-01-01

    Diverse studies have shown that magnetic fields can affect behavioral and physiological functions. Previously, we have shown that sinusoidal extremely low frequency magnetic fields and specific pulsed magnetic fields (Cnps) can produce alterations in the analgesia-related behavior of the land snail. Here, we have extended these studies to show an induction of analgesia in mice equivalent to a moderate dose of morphine (5 mg/kg), and the effect of both Cnp exposure and morphine injection on some open-field activity. Cnp exposure was found to prolong the response latency to a nociceptive thermal stimulus (hot plate). Cnp+morphine offset the increased movement activity found with morphine alone. These results suggest that pulsed magnetic fields can induce analgesic behavior in mice without the side effects often associated with opiates like morphine. PMID:14698475

  11. Electromagnetic field dynamics in Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Palenzuela, Carlos; Anderson, Matthew; Hirschmann, Eric; Lehner, Luis; Liebling, Steven; Neilsen, David; Motl, Patrick

    2011-04-01

    Neutron star mergers represent one of the most promising sources of gravitational waves (GW) within the bandwidth of advLIGO. In addition to GW, strong magnetic fields may offer the possibility of a characteristic electromagnetic signature allowing for concurrent detection. In this talk we present results from numerical evolutions of such mergers, studying the dynamics of both the gravitational and electromagnetic degrees of freedom.

  12. Electromagnetic fields in fractal continua

    NASA Astrophysics Data System (ADS)

    Balankin, Alexander S.; Mena, Baltasar; Patiño, Julián; Morales, Daniel

    2013-04-01

    Fractal continuum electrodynamics is developed on the basis of a model of three-dimensional continuum ΦD3⊂E3 with a fractal metric. The generalized forms of Maxwell equations are derived employing the local fractional vector calculus related to the Hausdorff derivative. The difference between the fractal continuum electrodynamics based on the fractal metric of continua with Euclidean topology and the electrodynamics in fractional space Fα accounting the fractal topology of continuum with the Euclidean metric is outlined. Some electromagnetic phenomena in fractal media associated with their fractal time and space metrics are discussed.

  13. Low frequency cultural noise

    NASA Astrophysics Data System (ADS)

    Sheen, Dong-Hoon; Shin, Jin Soo; Kang, Tae-Seob; Baag, Chang-Eob

    2009-09-01

    Abnormal cultural seismic noise is observed in the frequency range of 0.01-0.05 Hz. Cultural noise generated by human activities is generally observed in frequencies above 1 Hz, and is greater in the daytime than at night. The low-frequency noise presented in this paper exhibits a characteristic amplitude variation and can be easily identified from time domain seismograms in the frequency range of interest. The amplitude variation is predominantly in the vertical component, but the horizontal components also show variations. Low-frequency noise is markedly periodic, which reinforces its interpretation as cultural noise. Such noise is observed world-wide, but is limited to areas in the vicinity of railways. The amplitude variation in seismograms correlates strongly with railway timetables, and the waveform shows a wavelength shift associated with the Doppler effect, which indicates that the origin of seismic background noise in the frequency range 0.01-0.05 Hz is railways.

  14. A Further Investigation of the Effects of Extremely Low Frequency Magnetic Fields on Alkaline Phosphatase and Acetylcholinesterase.

    PubMed

    Silkstone, Gary; Wilson, Michael T

    2016-01-01

    Using a custom build spectrophotometer equipped with Helmholtz coils and designed to study the effects of magnetic fields on enzyme reactions in real-time we have investigated the influence of fields, from 100 μT to 10 mT and at a variety of field frequencies, on the membrane bound enzymes alkaline phosphatase and acetylcholinesterase. We have also employed other methods to apply a magnetic field, e.g. Biostim. In contrast to earlier reports we have been unable to detect any field effects on these enzymes under any field/frequency regime. We discuss possible reasons for the discrepancy between this and earlier work and note the particularly complex influence of small temperature changes that may confound analysis. PMID:26963611

  15. A Further Investigation of the Effects of Extremely Low Frequency Magnetic Fields on Alkaline Phosphatase and Acetylcholinesterase

    PubMed Central

    Silkstone, Gary; Wilson, Michael T.

    2016-01-01

    Using a custom build spectrophotometer equipped with Helmholtz coils and designed to study the effects of magnetic fields on enzyme reactions in real-time we have investigated the influence of fields, from 100 μT to 10 mT and at a variety of field frequencies, on the membrane bound enzymes alkaline phosphatase and acetylcholinesterase. We have also employed other methods to apply a magnetic field, e.g. Biostim. In contrast to earlier reports we have been unable to detect any field effects on these enzymes under any field/frequency regime. We discuss possible reasons for the discrepancy between this and earlier work and note the particularly complex influence of small temperature changes that may confound analysis. PMID:26963611

  16. Fundamental issues on electromagnetic fields (EMF).

    PubMed

    Novini, A

    1993-01-01

    This paper will examine the fundamental principals of Electromagnetic Field Radiation. The discussion will include: The basic physical characteristics of magnetic and electric fields, the numerous sources of EMF in our everyday lives, ways to detect and measure EMF accurately, what to look for in EMF instruments, and the issues and misconceptions on shielding and exposure reduction. PMID:8098895

  17. Ultra low frequency (ULF) electromagnetic anomalies associated with large earthquakes in Java Island, Indonesia by using wavelet transform and detrended fluctuation analysis

    NASA Astrophysics Data System (ADS)

    Febriani, F.; Han, P.; Yoshino, C.; Hattori, K.; Nurdiyanto, B.; Effendi, N.; Maulana, I.; Gaffar, E.

    2014-04-01

    Indonesia is one of the most seismically active regions in the world and mitigation of seismic hazard is important. It is reported that Ultra low frequency (ULF) geomagnetic anomalies are one of the most convincing phenomena preceding large earthquakes (EQs). In this paper we have analyzed geomagnetic data at Pelabuhan Ratu (PLR) (7.01° S, 106.56° E), Sukabumi, West Java, Indonesia, from 1 September 2008 to 31 October 2010. There are twelve moderate-large EQs (M ≥ 5) within 160 km from the station during the analyzed period. The largest one is the M =7.5 EQ (depth = 57 km, epicentral distance = 135 km, 2 September 2009) based on EQ catalog of Indonesian Meteorological, Climatological and Geophysical Agency (BMKG). To investigate the ULF geomagnetic anomalous variations preceding all the EQs, spectral density ratio at the frequency range of 0.01 ± 0.003 Hz based on wavelet transform (WT) and detrended fluctuation analysis (DFA) have been carried out. The spectral density ratio results show the enhancements a few weeks before the largest EQ. The enhancement persists about one week and reaches a maximum on 16 August 2009. At the same time, the result of the DFA presents the decrease of α value. For other EQs, there are no clear increases of the spectral density ratio with simultaneous decrease of α value. When these phenomena occur, the value of Dst index shows that there are no peculiar global geomagnetic activities at the low latitude region. The above results are suggestive of the relation between the detected anomalies and the largest EQ.

  18. Measurements of quasi-static and low-frequency electric fields with spherical double probes on the ISEE-1 spacecraft

    NASA Technical Reports Server (NTRS)

    Mozer, F. S.; Torbert, R. B.; Fahleson, U. V.; Falthammar, C. G.; Gonfalone, A.; Pedersen, A.

    1978-01-01

    The spherical double-probe electric-field experiment on the ISEE-1 spacecraft is described. It is shown that the instrument measures magnetospheric, magetosheath, and solar wind electric fields with a sensitivity well below one mV/m. Design features and diagnostic experiments performed in orbit to understand the instrument operation are discussed.

  19. Effect of low-frequency ambient magnetic fields on the control unit and RF head of a commercial SQUID magnetometer

    NASA Technical Reports Server (NTRS)

    Marcus, C. M.

    1984-01-01

    The control unit and RF head of the SHE model 330XRFSQUID system are shown to be sensitive to ambient ac magnetic fields below 1 HZ, which cause the appearance of false signals corresponding to a magnetometer signal of 0.000001 phi(0) per gauss of field applied. The control unit shows a sensitivity that is linear with frequency, suggesting that the signal is generated by Faraday induction. In contrast, the RF head response is independent of frequency and shows a strong second-harmonic coversion. This response may be due to the magnetic field sensitivity of the ferrite core inductor in the tuned amplifier of the RF head. These signals induced by ambient fields are a potential source of error in Stanford's Relativity Gyroscope experiment, which uses SQUID's on board a rolling satellite as part of the gyroscope readout system. The extent of the magnetic field sensitivity in these components necessitates the use of additional magnetic shielding aboard the satellite.

  20. Extremely low frequency alternating magnetic field-triggered and MRI-traced drug delivery by optimized magnetic zeolitic imidazolate framework-90 nanoparticles

    NASA Astrophysics Data System (ADS)

    Fang, Jie; Yang, Yong; Xiao, Wen; Zheng, Bingwen; Lv, Yun-Bo; Liu, Xiao-Li; Ding, Jun

    2016-02-01

    An extremely low frequency alternating magnetic field (ELF-AMF) was demonstrated to be able to effectively trigger drug release from carefully engineered magnetic ZIF-90 nanoparticles. The embedded Fe3O4 nanoparticles or alternatively Gd2O3 nanoparticles serve as effective MRI tracers for potential visualization of drug delivery to ensure drug delivery accuracy.An extremely low frequency alternating magnetic field (ELF-AMF) was demonstrated to be able to effectively trigger drug release from carefully engineered magnetic ZIF-90 nanoparticles. The embedded Fe3O4 nanoparticles or alternatively Gd2O3 nanoparticles serve as effective MRI tracers for potential visualization of drug delivery to ensure drug delivery accuracy. Electronic supplementary information (ESI) available: Experimental details; TEM and SEM images of ZIF-90 synthesized at different conditions and discussion; TEM images of Fe3O4 and Gd2O3 nanoparticles; XRD pattern of Gd2O3 nanoparticles; FT-IR spectra of ZIF-90, ZIF-90-RSA and RSA; DLS of ZIF-90-RSA; UV-Vis spectra of released 5-Fu; molecular models of ZIF-90 and 5-Fu. See DOI: 10.1039/c5nr08086j

  1. [The application of the pulsed low-frequency electrostatic field for the combined treatment of the children presenting with bronchial asthma].

    PubMed

    Ivanova, D A; Khan, M A; Lyan, N A; Mikitchenko, N A

    2015-01-01

    The objective of the present study was to develop a scientifically sound rationale for the application of the pulsed low-frequency electrostatic fields (PLIESF) for the combined treatment of the children presenting with bronchial asthma and the comparative assessment of the effectiveness of the use of this method either as monotherapy or together with therapeutic physical exercises based on the immediate and long-term results of the treatment. The dynamic clinical observations and special investigations were carried out on 101 children at the age varying from 5 to 15 years who suffered from bronchial asthma. PLIESF were shown to produce the beneficial effect on dynamics of clinical symptoms in the children manifested as the disappearance or reduced frequency of episodes of laborious respiration and the improvement of sputum discharge, auscultation picture, bronchial patency, and respiratory excursions of the chest. The application of PLIESF significantly increased the level of the general physical performance in the children with bronchial asthma, improved the functional conditions of the cardiovascular system, normalized both the cardiac rhythm and the heart rate. It was shown based on the analysis of the short-term and long-term outcomes of the treatment that the combined therapy with the use of the two physical factors, i.e. the pulsed low-frequency electrostatic fields and therapeutic physical exercises, ensures the significantly higher effectiveness of the treatment than the separate application of either of them. PMID:26595966

  2. Theory of high-order harmonic generation and attosecond pulse emission by a low-frequency elliptically polarized laser field

    SciTech Connect

    Strelkov, V. V.

    2006-07-15

    We present a quantum-mechanical theory of xuv generation by an elliptically polarized intense laser field. Our approach is valid when the Keldysh parameter {gamma} is about unity or less, and the driving ellipticity is less than {radical}(2){gamma}. After the photoionization the motion of the electronic wave packet along the major axis of the driving field polarization ellipse is described quasiclassically, whereas the motion in the transverse direction is considered fully quantum mechanically; we also find the condition that allows the reduction of the motion description to a quantum orbit in the polarization plane of the laser field. We use the ionization rate calculated via numerical solution of the three-dimensional Schroedinger equation (TDSE), and take into account the Coulomb modification of the free electronic wave packet. The predictions of our theory for xuv emission agree well with numerical and experimental results. We study the high harmonic intensities and phases as functions of the driving intensity and ellipticity, and also the ellipticity and the rotation angle of the harmonic field polarization ellipse as functions of the driving ellipticity. The atomic response is decomposed into the contributions of different quantum paths. This allows finding a straightforward explanation for the observed dependencies.

  3. Catalog of low frequency oscillations of the earth's magnetic field as observed at ATS-1 during January 1968

    NASA Technical Reports Server (NTRS)

    Cummings, W. D.; Lyons, D.

    1974-01-01

    A catalog of ATS-1 observed magnetic field oscillations is presented. The catalog holds only those events with a duration of at least ten minutes and with a frequency that remains roughly constant. Events are distinguished on the basis of the frequency of oscillations. A comparison was made between ATS-1 data and other ground and satellite magnetometer data.

  4. Solar and geomagnetic activity, extremely low frequency magnetic and electric fields and human health at the Earth's surface

    NASA Astrophysics Data System (ADS)

    Palmer, S. J.; Rycroft, M. J.; Cermack, M.

    2006-09-01

    The possibility that conditions on the Sun and in the Earth’s magnetosphere can affect human health at the Earth’s surface has been debated for many decades. This work reviews the research undertaken in the field of heliobiology, focusing on the effect of variations of geomagnetic activity on human cardiovascular health. Data from previous research are analysed for their statistical significance, resulting in support for some studies and the undermining of others. Three conclusions are that geomagnetic effects are more pronounced at higher magnetic latitudes, that extremely high as well as extremely low values of geomagnetic activity seem to have adverse health effects and that a subset of the population (10-15%) is predisposed to adverse health due to geomagnetic variations. The reported health effects of anthropogenic sources of electric and magnetic fields are also briefly discussed, as research performed in this area could help to explain the results from studies into natural electric and magnetic field interactions with the human body. Possible mechanisms by which variations in solar and geophysical parameters could affect human health are discussed and the most likely candidates investigated further. Direct effects of natural ELF electric and magnetic fields appear implausible; a mechanism involving some form of resonant absorption is more likely. The idea that the Schumann resonance signals could be the global environmental signal absorbed by the human body, thereby linking geomagnetic activity and human health is investigated. Suppression of melatonin secreted by the pineal gland, possibly via desynchronised biological rhythms, appears to be a promising contender linking geomagnetic activity and human health. There are indications that calcium ions in cells could play a role in one or more mechanisms. It is found to be unlikely that a single mechanism can explain all of the reported phenomena.

  5. Unmanned airborne vehicle (UAV): Flight testing and evaluation of two-channel E-field very low frequency (VLF) instrument

    SciTech Connect

    1998-12-01

    Using VLF frequencies, transmitted by the Navy`s network, for airborne remote sensing of the earth`s electrical, magnetic characteristics was first considered by the United States Geological Survey (USGS) around the mid 1970s. The first VLF system was designed and developed by the USGS for installation and operation on a single engine, fixed wing aircraft used by the Branch of Geophysics for geophysical surveying. The system consisted of five channels. Two E-field channels with sensors consisting of a fixed vertical loaded dipole antenna with pre-amp mounted on top of the fuselage and a gyro stabilized horizontal loaded dipole antenna with pre-amp mounted on a tail boom. The three channel magnetic sensor consisted of three orthogonal coils mounted on the same gyro stabilized platform as the horizontal E-field antenna. The main features of the VLF receiver were: narrow band-width frequency selection using crystal filters, phase shifters for zeroing out system phase variances, phase-lock loops for generating real and quadrature gates, and synchronous detectors for generating real and quadrature outputs. In the mid 1990s the Branch of Geophysics designed and developed a two-channel E-field ground portable VLF system. The system was built using state-of-the-art circuit components and new concepts in circuit architecture. Small size, light weight, low power, durability, and reliability were key considerations in the design of the instrument. The primary purpose of the instrument was for collecting VLF data during ground surveys over small grid areas. Later the system was modified for installation on a Unmanned Airborne Vehicle (UAV). A series of three field trips were made to Easton, Maryland for testing and evaluating the system performance.

  6. Radiated fields from an electromagnetic pulse simulator

    NASA Astrophysics Data System (ADS)

    Pelletier, M.; Delisle, G. Y.; Kashyap, S.

    Simulators of electromagnetic pulses allow generation within a limited time of very high-intensity fields such as those produced in a nuclear explosion. These fields can be radiated out of the test zone at a lower but nevertheless significant level; if the intensity of these fields is sufficiently high, damage to humans and electronic equipment can result. An evaluation of the potential danger of these simulator emissions requires knowledge of the amplitude, duration, and the energy of the radiated impulses. A technique is presented for calculating the fields radiated by a parallel-plane electromagnetic pulse simulator. The same method can also be applied to a rhombic type simulator. Sample numerical results are presented along with the calculations of the energy and power density and a discussion of the formation of the field in the frequency domain.

  7. Light-dependent and -independent behavioral effects of extremely low frequency magnetic fields in a land snail are consistent with a parametric resonance mechanism

    SciTech Connect

    Prato, F.S.; Thomas, A.W. |; Kavaliers, M.; Cullen, A.P.

    1997-05-01

    Exposure to extremely low frequency (ELF) magnetic fields has been shown to attenuate endogenous opioid peptide mediated antinociception or analgesia in the terrestrial pulmonate snail, Cepaea nemoralis. Here the authors examine the roles of light in determining this effect and address the mechanisms associated with mediating the effects of the ELF magnetic fields in both the presence and absence of light. Specifically, they consider whether the magnetic field effects involve an indirect induced electric current mechanism or a direct effect such as a parametric resonance mechanism (PRM). They exposed snails in both the presence and absence of light at three different frequencies (30, 60, and 120 Hz) with static field values (B{sub DC}) and ELF magnetic field amplitude (peak) and direction (B{sub AC}) set according to the predictions of the PRM for Ca{sup 2+}. Analgesia was induced in snails by injecting them with an enkephalinase inhibitor, which augments endogenous opioid (enkephalin) activity. They found that the magnetic field exposure reduced this opioid-induced analgesia significantly more if the exposure occurred in the presence rather than the absence of light. However, the percentage reduction in analgesia in both the presence and absence of light was not dependent on the ELF frequency. This finding suggests that in both the presence and the absence of light the effect of the ELF magnetic field was mediated by a direct magnetic field detection mechanism such as the PRM rather than an induced current mechanism.

  8. Gene transcription and electromagnetic fields

    SciTech Connect

    Henderson, A.S.

    1992-01-01

    Our overall aim is to obtain sufficient information to allow us to ultimately determine whether ELF EM field exposure is an initiating factor in neoplastic transformation and/or if exposure can mimic characteristics of the second-step counterpart in neoplastic disease. This aim is based on our previous findings that levels of some transcripts are increased in cells exposed to EM fields. While the research is basic in nature, the ramifications have bearing on the general safety of exposure to EM fields in industrial and everyday life. A large array of diverse biological effects are reported to occur as the result of exposure to elf EM fields, suggesting that the cell response to EM fields is at a basic level, presumably initiated by molecular and/or biophysical events at the cell membrane. The hypothesized route is a signal transduction pathway involving membrane calcium fluxes. Information flow resulting from signal transduction can mediate the induction of regulatory factors in the cell, and directly affect how transcription is regulated.

  9. Deep low-frequency radio observations of the NOAO Boötes field. I. Data reduction and catalog construction

    NASA Astrophysics Data System (ADS)

    Intema, H. T.; van Weeren, R. J.; Röttgering, H. J. A.; Lal, D. V.

    2011-11-01

    In this article we present deep, high-resolution radio interferometric observations at 153 MHz to complement the extensively studied NOAO Boötes field. We provide a description of the observations, data reduction and source catalog construction. From our single pointing GMRT observation of ~12 h we obtain a high-resolution (26″ × 22″) image of ~11.3 square degrees, fully covering the Boötes field region and beyond. The image has a central noise level of ~1.0 mJy beam-1, which rises to 2.0-2.5 mJy beam-1 at the field edge, placing it amongst the deepest ~150 MHz surveys to date. The catalog of 598 extracted sources is estimated to be ~92 percent complete for > 10 mJy sources, while the estimated contamination with false detections is < 1 percent. The low rms position uncertainty of 1.24″ facilitates accurate matching against catalogs at optical, infrared and other wavelengths. Differential source counts are determined down to ≲10 mJy. There is no evidence for flattening of the counts towards lower flux densities as observed in deep radio surveys at higher frequencies, suggesting that our catalog is dominated by the classical radio-loud AGN population that explains the counts at higher flux densities. Combination with available deep 1.4 GHz observations yields an accurate determination of spectral indices for 417 sources down to the lowest 153 MHz flux densities, of which 16 have ultra-steep spectra with spectral indices below -1.3. We confirm that flattening of the median spectral index towards low flux densities also occurs at this frequency. The detection fraction of the radio sources in NIR KS-band is found to drop with radio spectral index, which is in agreement with the known correlation between spectral index and redshift for brighter radio sources. Full Table 3 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/535/A38

  10. Influence of Electric, Magnetic, and Electromagnetic Fields on the Circadian System: Current Stage of Knowledge

    PubMed Central

    Żak, Arkadiusz

    2014-01-01

    One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms—two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields. PMID:25136557

  11. A high performing brain-machine interface driven by low-frequency local field potentials alone and together with spikes

    PubMed Central

    Stavisky, Sergey D.; Kao, Jonathan C.; Nuyujukian, Paul; Ryu, Stephen I.; Shenoy, Krishna V.

    2015-01-01

    Objective Brain-machine interfaces (BMIs) seek to enable people with movement disabilities to directly control prosthetic systems with their neural activity. Current high performance BMIs are driven by action potentials (spikes), but access to this signal often diminishes as sensors degrade over time. Decoding local field potentials (LFPs) as an alternative or complementary BMI control signal may improve performance when there is a paucity of spike signals. To date only a small handful of LFP decoding methods have been tested online; there remains a need to test different LFP decoding approaches and improve LFP-driven performance. There has also not been a reported demonstration of a hybrid BMI that decodes kinematics from both LFP and spikes. Here we first evaluate a BMI driven by the local motor potential (LMP), a low-pass filtered time-domain LFP amplitude feature. We then combine decoding of both LMP and spikes to implement a hybrid BMI. Approach Spikes and LFP were recorded from two macaques implanted with multielectrode arrays in primary and premotor cortex while they performed a reaching task. We then evaluated closed-loop BMI control using biomimetic decoders driven by LMP, spikes, or both signals together. Main Results LMP decoding enabled quick and accurate cursor control which surpassed previously reported LFP BMI performance. Hybrid decoding of both spikes and LMP improved performance when spikes signal quality was mediocre to poor. Significance These findings show that LMP is an effective BMI control signal which requires minimal power to extract and can substitute for or augment impoverished spikes signals. Use of this signal may lengthen the useful lifespan of BMIs and is therefore an important step towards clinically viable BMIs. PMID:25946198

  12. Finite difference calculations of current densities in a homogeneous model of a man exposed to extremely low frequency electric fields.

    PubMed

    Dimbylow, P J

    1987-01-01

    This paper presents three-dimensional finite difference calculations of induced current densities in a grounded, homogeneous, realistically human-shaped phantom. Comparison is made with published experimental values of current density at 60 Hz, measured in conducting saline manikins with their arms down by the side. The congruence between calculation and experiment gives confidence in the applicability of the numerical method and phantom shape to other configurations. The effect of raising both arms above the head is to reduce the current densities in the head and neck by approximately 50% and to increase those from the thorax downwards by 20-30%. A sensitivity analysis was performed on the shape and dimensions of the phantom, from a 45-kg, 1.5-m-tall person to a 140-kg, 1.9-m-tall person. When the phantom is grounded through both feet the current densities range from 50 to 90 microAm-2 in the head (all values for a 60-Hz, 1-kVm-1, vertical applied field), 70 to 140 microAm-2 in the thorax, 150 to 440 microAm-2 at the crotch, and 500 to 2,230 microAm-2 in the ankle. When grounded through only one foot the current densities at the crotch range from 400 to 1,000 microAm-2 and from 1,000 to 4,400 microAm-2 in the ankle of the grounded leg. Scale transformations of the short-circuit current with phantom height, weight, and surface area are confirmed. PMID:3122768

  13. A high performing brain-machine interface driven by low-frequency local field potentials alone and together with spikes

    NASA Astrophysics Data System (ADS)

    Stavisky, Sergey D.; Kao, Jonathan C.; Nuyujukian, Paul; Ryu, Stephen I.; Shenoy, Krishna V.

    2015-06-01

    Objective. Brain-machine interfaces (BMIs) seek to enable people with movement disabilities to directly control prosthetic systems with their neural activity. Current high performance BMIs are driven by action potentials (spikes), but access to this signal often diminishes as sensors degrade over time. Decoding local field potentials (LFPs) as an alternative or complementary BMI control signal may improve performance when there is a paucity of spike signals. To date only a small handful of LFP decoding methods have been tested online; there remains a need to test different LFP decoding approaches and improve LFP-driven performance. There has also not been a reported demonstration of a hybrid BMI that decodes kinematics from both LFP and spikes. Here we first evaluate a BMI driven by the local motor potential (LMP), a low-pass filtered time-domain LFP amplitude feature. We then combine decoding of both LMP and spikes to implement a hybrid BMI. Approach. Spikes and LFP were recorded from two macaques implanted with multielectrode arrays in primary and premotor cortex while they performed a reaching task. We then evaluated closed-loop BMI control using biomimetic decoders driven by LMP, spikes, or both signals together. Main results. LMP decoding enabled quick and accurate cursor control which surpassed previously reported LFP BMI performance. Hybrid decoding of both spikes and LMP improved performance when spikes signal quality was mediocre to poor. Significance. These findings show that LMP is an effective BMI control signal which requires minimal power to extract and can substitute for or augment impoverished spikes signals. Use of this signal may lengthen the useful lifespan of BMIs and is therefore an important step towards clinically viable BMIs.

  14. Low Frequency Sky Surveys

    NASA Astrophysics Data System (ADS)

    Lubin, Philip M.

    2015-08-01

    We propose to survey the sky from 10-100 GHz covering greater than 50% of the sky in intensity and polarizatiton. This will allow us to mep out the synchrotron and free - free background as well as the spinning dust component to sufficient sensitivity to allow detailed modeling and removal of the galactic foregrounds allowing for deeper polarization surveys searching for signatures of inflation. While most measurements have concentrated on the region above 100 GHz this reggion is more complex in dust contmination that originally thought. Dust is best measured at high frequencies but the atmosphere greatly hinders extremely deep dust surveys due to water vapor. Surveys ar low frequency will be complimentary to the higher frequency measurements.

  15. Relativistic diffusive motion in random electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Haba, Z.

    2011-08-01

    We show that the relativistic dynamics in a Gaussian random electromagnetic field can be approximated by the relativistic diffusion of Schay and Dudley. Lorentz invariant dynamics in the proper time leads to the diffusion in the proper time. The dynamics in the laboratory time gives the diffusive transport equation corresponding to the Jüttner equilibrium at the inverse temperature β-1 = mc2. The diffusion constant is expressed by the field strength correlation function (Kubo's formula).

  16. Exact quantization of a paraxial electromagnetic field

    SciTech Connect

    Aiello, A.; Woerdman, J. P.

    2005-12-15

    A nonperturbative quantization of a paraxial electromagnetic field is achieved via a generalized dispersion relation imposed on the longitudinal and the transverse components of the photon wave vector. This theoretical formalism yields a seamless transition between the paraxial- and the Maxwell-equation solutions. This obviates the need to introduce either ad hoc or perturbatively defined field operators. Moreover, our (exact) formalism remains valid beyond the quasimonochromatic paraxial limit.

  17. Spatiotemporal character of the Bobylev-Pikin flexoelectric instability in a twisted nematic bent-core liquid crystal exposed to very low frequency fields.

    PubMed

    Krishnamurthy, K S

    2014-05-01

    The Bobylev-Pikin striped-pattern state induced by a homogeneous electric field is a volume flexoelectric instability, originating in the midregion of a planarly aligned nematic liquid crystal layer. We find that the instability acquires a spatiotemporal character upon excitation by a low frequency (0.5 Hz) square wave field. This is demonstrated using a bent-core liquid crystal, initially in the 90°-twisted planar configuration. The flexoelectric modulation appears close to the cathode at each polarity reversal and, at low voltage amplitudes, decays completely as the field becomes steady. Correspondingly, at successive polarity changes, the stripe direction switches between the alignment directions at the two substrates. For large voltages, the stripes formed nearly along the alignment direction at the cathode gradually reorient toward the midplane director. These observations are generally attributed to inhomogeneous and time-dependent field conditions that come to exist after each polarity reversal. Polarity dependence of the instability is attributed to the formation of intrinsic double layers that bring about an asymmetry in surface fields. Momentary field elevation near the cathode following a voltage sign reversal and concomitant gradient flexoelectric polarization are considered the key factors in accounting for the surfacelike modulation observed at low voltages. PMID:25353816

  18. High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors

    NASA Astrophysics Data System (ADS)

    Giusi, G.; Giordano, O.; Scandurra, G.; Rapisarda, M.; Calvi, S.; Ciofi, C.

    2016-04-01

    Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz1/2, while DC performances are limited only by the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances.

  19. High sensitivity measurement system for the direct-current, capacitance-voltage, and gate-drain low frequency noise characterization of field effect transistors.

    PubMed

    Giusi, G; Giordano, O; Scandurra, G; Rapisarda, M; Calvi, S; Ciofi, C

    2016-04-01

    Measurements of current fluctuations originating in electron devices have been largely used to understand the electrical properties of materials and ultimate device performances. In this work, we propose a high-sensitivity measurement setup topology suitable for the automatic and programmable Direct-Current (DC), Capacitance-Voltage (CV), and gate-drain low frequency noise characterization of field effect transistors at wafer level. Automatic and programmable operation is particularly useful when the device characteristics relax or degrade with time due to optical, bias, or temperature stress. The noise sensitivity of the proposed topology is in the order of fA/Hz(1/2), while DC performances are limited only by the source and measurement units used to bias the device under test. DC, CV, and NOISE measurements, down to 1 pA of DC gate and drain bias currents, in organic thin film transistors are reported to demonstrate system operation and performances. PMID:27131690

  20. Visualization of circuit card electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Zwillinger, Daniel

    1995-01-01

    Circuit boards are used in nearly every electrical appliance. Most board failures cause differing currents in the circuit board traces and components. This causes the circuit board to radiate a differing electromagnetic field. Imaging this radiated field, which is equivalent to measuring the field, could be used for error detection. Using estimates of the fields radiated by a low power digital circuit board, properties of known materials, and available equipment, we determined how well the following technologies could be used to visualize circuit board electromagnetic fields (prioritized by promise): electrooptical techniques, magnetooptical techniques, piezoelectric techniques, thermal techniques, and electrodynamic force technique. We have determined that sensors using the electrooptical effect (Pockels effect) appear to be sufficiently sensitive for use in a circuit board imaging system. Sensors utilizing the magnetooptical effect may also be adequate for this purpose, when using research materials. These sensors appear to be capable of achieving direct broadband measurements. We also reviewed existing electromagnetic field sensors. Only one of the sensors (recently patented) was specifically designed for circuit board measurements.

  1. Electromagnetic fields of separable spacetimes

    NASA Astrophysics Data System (ADS)

    Gair, Jonathan R.; Lynden-Bell, Donald

    2007-03-01

    Carter derived the forms of the metric and the vector potentials of the spacetimes in which the relativistic Schrödinger equation for the motion of a charged particle separates. Here we show that on each 'spheroidal' surface a rotation rate, ω, exists such that relative to those rotating axes the electric and magnetic fields are parallel and orthogonal to the spheroid which is thus an equipotential in those axes. All the finite Carter separable systems without magnetic monopoles or gravomagnetic NUT monopoles have the same gyromagnetic ratio as the Dirac electron.

  2. Radiofrequency Electromagnetic Field Map of Timisoara

    NASA Astrophysics Data System (ADS)

    Stefu, N.; Solyom, I.; Arama, A.

    2015-12-01

    There are many electromagnetic field (EMF) sources nowadays acting simultaneously, especially in urban areas, making the theoretical estimation of electromagnetic power at ground level very difficult. This paper reports on EMF maps built with measurements collected in Timisoara, at various radiofrequencies. A grid of 15×15 squares was built (approximate resolution 400m x 400m) and measurements of the average and maximum values of the electric field E, magnetic field H and total power density S at 0.9, 1.8 and 2.4 GHz were collected in every node of the grid. Positions of the nodes in terms of latitude and longitude were also collected. Maps were built presenting the spatial distribution of the measured quantities over Timisoara. Potential influences of EMF on public health are discussed.

  3. Electromagnetic field of a linear antenna

    NASA Astrophysics Data System (ADS)

    Derby, Norman; Olbert, Stanislaw

    2008-11-01

    Animated computer simulations of the electric field of a radiating antenna can capture the attention of students in introductory electromagnetism courses and stimulate active discussions. The simulations raise questions not usually addressed in textbooks. In certain cases, some of the field lines appear to move toward the antenna, the speed of the field lines can change as they move, and the field lines exhibit strange behavior (circling or splitting) at certain points. Because their fields can be expressed in terms of elementary functions, animations of point dipole antennas are common, but animations showing the fields of antennas with more realistic lengths are not as common because analytical expressions for these fields are not as well known. We show that it is possible to derive analytical expressions in terms of elementary functions for the electromagnetic field of linear antennas of finite length. We draw attention to an open-source method for displaying the fine details within the field patterns and then give a general discussion of singular points and their motions, derive expressions for their location and phase velocity, and apply these results to some of the phenomena that are visible in visualizations of the fields of various antennas.

  4. Electromagnetic field induced biological effects in humans.

    PubMed

    Kaszuba-Zwolińska, Jolanta; Gremba, Jerzy; Gałdzińska-Calik, Barbara; Wójcik-Piotrowicz, Karolina; Thor, Piotr J

    2015-01-01

    Exposure to artificial radio frequency electromagnetic fields (EMFs) has increased significantly in recent decades. Therefore, there is a growing scientific and social interest in its influence on health, even upon exposure significantly below the applicable standards. The intensity of electromagnetic radiation in human environment is increasing and currently reaches astronomical levels that had never before experienced on our planet. The most influential process of EMF impact on living organisms, is its direct tissue penetration. The current established standards of exposure to EMFs in Poland and in the rest of the world are based on the thermal effect. It is well known that weak EMF could cause all sorts of dramatic non-thermal effects in body cells, tissues and organs. The observed symptoms are hardly to assign to other environmental factors occurring simultaneously in the human environment. Although, there are still ongoing discussions on non-thermal effects of EMF influence, on May 31, 2011--International Agency for Research on Cancer (IARC)--Agenda of World Health Organization (WHO) has classified radio electromagnetic fields, to a category 2B as potentially carcinogenic. Electromagnetic fields can be dangerous not only because of the risk of cancer, but also other health problems, including electromagnetic hypersensitivity (EHS). Electromagnetic hypersensitivity (EHS) is a phenomenon characterized by the appearance of symptoms after exposure of people to electromagnetic fields, generated by EHS is characterized as a syndrome with a broad spectrum of non-specific multiple organ symptoms including both acute and chronic inflammatory processes located mainly in the skin and nervous systems, as well as in respiratory, cardiovascular systems, and musculoskeletal system. WHO does not consider the EHS as a disease-- defined on the basis of medical diagnosis and symptoms associated with any known syndrome. The symptoms may be associated with a single source of EMF

  5. Electromagnetic unification of matter and force fields

    NASA Astrophysics Data System (ADS)

    John, Sarah

    2004-05-01

    Special relativity and quantum mechanics are descriptive of electromagnetic propagation in waveguides, with mass analogous to the cutoff frequency of a waveguide mode [S.John, Bull.Am.Phys.Soc. vol.39,no.2,1254 (1994)]. It is further postulated herein that all spin 1/2 matter (necessarily massive) and spin 1 force fields have their origin in the electromagnetic fields E and B. This concept is not new. Majorana, among others have obtained electromagnetic representations of Dirac-like equations valid for the zero-mass case. Here, the spinor representation of the Maxwell equations, as given by Sallhofer, is extended to oscillatory fields with propagation constant m to obtain, in the absence of charge and current densities, the coupled equation (M. hatp + β E)ψ = 0 , where M = diag[ M σ, M^* σ ] , β = offdiag[I,I] , ψ ^ = i ^dag ( σ. B0 ( p), σ. E_0(p)), and M=m+ip, with the energy-mass relation given by E^2 = M M . Further, it is shown that the interaction term of QED is a direct consequence of including the sources and currents of Maxwell equations. Qualitative field patterns for spin 1/2 and spin 1 states, such as the electron, neutrino, magnetic monopole, quarks, photon, and massive gauge bosons are suggested.

  6. Aspects of Interacting Electromagnetic and Torsion Fields

    NASA Astrophysics Data System (ADS)

    Gaete, Patricio; Helaÿel-Neto, José A.

    2011-01-01

    The interaction energy is studied for the coupling of axial torsion fields with photons in the presence of an external electromagnetic field. To this end, we compute the static quantum potential. Our discussion is carried out using the gauge-invariant but path-dependent variables formalism, which is alternative to the Wilson loop approach. Our results show that the static potential is a Yukawa correction to the usual static Coulomb potential. Interestingly, when this calculation is done by considering a mass term for the gauge field, the Coulombic piece disappears leading to a screening phase.

  7. Electromagnetic fields-Part 1; Biological effects

    SciTech Connect

    Nair, I.; Morgan, M.G. )

    1990-08-01

    It is known that low-frequency electric and magnetic fields can produce a variety of effects in biological systems. Pulsed magnetic fields, for instance, are used to mend broken bones, and other beneficial medical applications are being developed. But in more chronic and less controlled environments, can exposure to such fields also pose health risks No one knows. Today that possibility, however, requires serious consideration. Though present knowledge is fragmentary, and a coherent theory to explain the observations seems far off, the continuous presence of power-frequency fields in the modern environment makes potential health effects a matter of serious scientific and public health policy concern. That concern has focused on cancer - especially leukemia and brain tumors - and developmental abnormalities, and, to a lesser extent on endocrine and nervous system disorders, including chronic depression. The authors focus on 60-hertz fields, where the mechanism of interaction probably involves the cell membrane, is nonlinear, and may act by causing some cooperative phenomena among the components of the cell membrane.

  8. Analysis of Jovian low frequency radio emissions

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1985-01-01

    The density of ions in the Io plasma torus and the scattering of these ions by low frequency electromagnetic emissions detected by Voyager 1 were studied. The ion density profile was investigated using whistler dispersion measurements provided by the Voyager plasma instrument. The scale height and absolute density of H+ ions in the vicinity of the plasma torus were determined by combining the measured plasma densities with the whistler dispersion measurements. A theoretical analysis of the modes of propagation of low frequency electromagnetic emissions in the torus was undertaken. Polarization reversal effects and rough estimates of the ion diffusion coefficient were utilized. Numerical evaluation of the ion diffusion coefficients in the torus were made using the observed Voyager 1 wave intensities. Results show that the observed wave intensities produce significant ion diffusion effects in the ion torus.

  9. Polarization behavior of polystyrene particles under direct current and low-frequency (<1 kHz) electric fields in dielectrophoretic systems.

    PubMed

    Saucedo-Espinosa, Mario A; Rauch, Mallory M; LaLonde, Alexandra; Lapizco-Encinas, Blanca H

    2016-02-01

    The relative polarization behavior of micron and submicron polystyrene particles was investigated under direct current and very low frequency (<1 kHz) alternating current electric fields. Relative polarization of particles with respect to the suspending medium is expressed in terms of the Clausius-Mossotti factor, a parameter of crucial importance in dielectrophoretic-based operations. Particle relative polarization was studied by employing insulator-based dielectrophoretic (iDEP) devices. The effects of particle size, medium conductivity, and frequency (10-1000 Hz) of the applied electric potential on particle response were assessed through experiments and mathematical modeling with COMSOL Multiphysics(®). Particles of different sizes (100-1000 nm diameters) were introduced into iDEP devices fabricated from polydimethylsiloxane (PDMS) and their dielectrophoretic responses under direct and alternating current electric fields were recorded and analyzed in the form of images and videos. The results illustrated that particle polarizability and dielectrophoretic response depend greatly on particle size and the frequency of the electric field. Small particles tend to exhibit positive DEP at higher frequencies (200-1000 Hz), while large particles exhibit negative DEP at lower frequencies (20-200 Hz). These differences in relative polarization can be used for the design of iDEP-based separations and analysis of particle mixtures. PMID:26531799

  10. On electromagnetic field problems in inhomogeneous media

    NASA Technical Reports Server (NTRS)

    Mohsen, A.

    1973-01-01

    Analysis of electromagnetic fields in inhomogeneous media is of practical interest in general scattering and propagation problems and in the study of lenses. For certain types of inhomogeneities, the fields may be represented in terms of two scalars. In a general orthogonal coordinate system, these potentials satisfy second order differential equations. Exact solutions of these equations are known only for a few particular cases and in general, an approximate or numerical technique must be employed. The present work reviews and generalizes some of the main methods of attack of the problem. The results are presented in a form appropriate for numerical computation.

  11. Hamiltonian dynamics of the parametrized electromagnetic field

    NASA Astrophysics Data System (ADS)

    Barbero G, J. Fernando; Margalef-Bentabol, Juan; Villaseñor, Eduardo J. S.

    2016-06-01

    We study the Hamiltonian formulation for a parametrized electromagnetic field with the purpose of clarifying the interplay between parametrization and gauge symmetries. We use a geometric approach which is tailor-made for theories where embeddings are part of the dynamical variables. Our point of view is global and coordinate free. The most important result of the paper is the identification of sectors in the primary constraint submanifold in the phase space of the model where the number of independent components of the Hamiltonian vector fields that define the dynamics changes. This explains the non-trivial behavior of the system and some of its pathologies.

  12. Measurements on magnetized GdBCO pellets subjected to small transverse ac magnetic fields at very low frequency: Evidence for a slowdown of the magnetization decay

    NASA Astrophysics Data System (ADS)

    Fagnard, Jean-Francois; Kirsch, Sébastien; Morita, Mitsuru; Teshima, Hidekazu; Vanderheyden, Benoit; Vanderbemden, Philippe

    2015-05-01

    Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be significantly affected by the application of several cycles of a transverse variable magnetic field. In this work, we study, at T = 77 K, the long term influence of transverse ac magnetic fields of small amplitudes (i.e. much smaller than the full penetration field) on the axial magnetization of a bulk single grain superconducting GdBCO pellet over a wide range of low frequencies (1 mHz-20 Hz). Thermocouples are placed against the pellet surface to probe possible self-heating of the material during the experiments. A high sensitivity cryogenic Hall probe is placed close to the surface to record the local magnetic induction normal to the surface. The results show first that, for a given number of applied triangular transverse cycles, higher values of dBapp/dt induce smaller magnetization decays. An important feature of practical interest is that, after a very large number of cycles which cause the loss of a substantial amount of magnetization (depending on the amplitude and the frequency of the field), the rate of the magnetization decay goes back to its initial value, corresponding to the relaxation of the superconducting currents due to flux creep only. In the amplitude and frequency range investigated, the thermocouples measurements and a 2D magneto-thermal modelling show no evidence of sufficient self-heating to affect the magnetization so that the effect of the transverse magnetic field cycles on the trapped magnetic moment is only attributed to a redistribution of superconducting currents in the volume of the sample and not to a thermal effect.

  13. Theoretical limits on the threshold for the response of long cells to weak extremely low frequency electric fields due to ionic and molecular flux rectification.

    PubMed Central

    Weaver, J C; Vaughan, T E; Adair, R K; Astumian, R D

    1998-01-01

    Understanding exposure thresholds for the response of biological systems to extremely low frequency (ELF) electric and magnetic fields is a fundamental problem of long-standing interest. We consider a two-state model for voltage-gated channels in the membrane of an isolated elongated cell (Lcell = 1 mm; rcell = 25 micron) and use a previously described process of ionic and molecular flux rectification to set lower bounds for a threshold exposure. A key assumption is that it is the ability of weak physical fields to alter biochemistry that is limiting, not the ability of a small number of molecules to alter biological systems. Moreover, molecular shot noise, not thermal voltage noise, is the basis of threshold estimates. Models with and without stochastic resonance are used, with a long exposure time, texp = 10(4) s. We also determined the dependence of the threshold on the basal transport rate. By considering both spherical and elongated cells, we find that the lowest bound for the threshold is Emin approximately 9 x 10(-3) V m-1 (9 x 10(-5) V cm-1). Using a conservative value for the loop radius rloop = 0.3 m for induced current, the corresponding lower bound in the human body for a magnetic field exposure is Bmin approximately 6 x 10(-4) T (6 G). Unless large, organized, and electrically amplifying multicellular systems such as the ampullae of Lorenzini of elasmobranch fish are involved, these results strongly suggest that the biophysical mechanism of voltage-gated macromolecules in the membranes of cells can be ruled out as a basis of possible effects of weak ELF electric and magnetic fields in humans. PMID:9788920

  14. Effect of cyclophosphamide and electromagnetic fields on mouse bone marrow

    SciTech Connect

    Cadossi, R.; Zucchini, P.; Emilia, G.; Torelli, G. )

    1990-02-26

    The authors have previously shown that the exposure to low frequency pulsing electromagnetic fields (PEMF) of mice X-ray irradiated resulted in an increased damage to the bone marrow. The series of experiments here reported were designed to investigate the effect of PEMF exposure after intraperitoneum injection of 200mg/kg of cyclophosphamide (CY). Control mice were CY injected only; experimental mice were CY injected and then exposed to PEMF. Exposure to PEMF (24 hours/day) increased the rate of decline of white blood cells in peripheral blood. Spleen weight was statistically higher among control mice than among mice exposed to PEMF at day 6, 8 and 10 after CY injection. Spleen autoradiography proved to be higher among PEMF exposed mice than among controls at day 8 and 9 after CY injection. The grafting efficiency of the bone marrow obtained from control mice was higher than the grafting efficiency of the bone marrow recovered from mice exposed to PEMF. All these data indicate that the exposure to PEMF increases the cytotoxic effect of CY.

  15. The influence of anatomical and physiological parameters on the interference voltage at the input of unipolar cardiac pacemakers in low frequency electric fields

    NASA Astrophysics Data System (ADS)

    Joosten, S.; Pammler, K.; Silny, J.

    2009-02-01

    The problem of electromagnetic interference of electronic implants such as cardiac pacemakers has been well known for many years. An increasing number of field sources in everyday life and occupational environment leads unavoidably to an increased risk for patients with electronic implants. However, no obligatory national or international safety regulations exist for the protection of this patient group. The aim of this study is to find out the anatomical and physiological worst-case conditions for patients with an implanted pacemaker adjusted to unipolar sensing in external time-varying electric fields. The results of this study with 15 volunteers show that, in electric fields, variation of the interference voltage at the input of a cardiac pacemaker adds up to 200% only because of individual factors. These factors should be considered in human studies and in the setting of safety regulations.

  16. Vacuum birefringence in strong inhomogeneous electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Karbstein, Felix; Gies, Holger; Reuter, Maria; Zepf, Matt

    2015-10-01

    Birefringence is one of the fascinating properties of the vacuum of quantum electrodynamics (QED) in strong electromagnetic fields. The scattering of linearly polarized incident probe photons into a perpendicularly polarized mode provides a distinct signature of the optical activity of the quantum vacuum and thus offers an excellent opportunity for a precision test of nonlinear QED. Precision tests require accurate predictions and thus a theoretical framework that is capable of taking the detailed experimental geometry into account. We derive analytical solutions for vacuum birefringence which include the spatio-temporal field structure of a strong optical pump laser field and an x-ray probe. We show that the angular distribution of the scattered photons depends strongly on the interaction geometry and find that scattering of the perpendicularly polarized scattered photons out of the cone of the incident probe x-ray beam is the key to making the phenomenon experimentally accessible with the current generation of FEL/high-field laser facilities.

  17. Electromagnetic field emissions from underwater power cables

    NASA Astrophysics Data System (ADS)

    DiBiasio, Christopher

    This study is performed as a partial aid to a larger study that aims to determine if electromagnetic fields produced by underwater power cables have any effect on marine species. In this study, a new numerical method for calculating magnetic fields around subsea power cables is presented and tested. The numerical method is derived from electromagnetic theory, and the program, Matlab, is implemented in order to run the simulations. The Matlab code is validated by performing a series of tests in which the theoretical code is compared with other previously validated magnetic field solvers. Three main tests are carried out; two of these tests are physical and involve the use of a magnetometer, and the third is numerical and compares the code with another numerical model known as Ansys. The data produced by the Matlab code remains consistent with the measured values from both the magnetometer and the Ansys program; thus, the code is considered valid. The validated Matlab code can then be implemented into other parts of the study in order to plot the magnetic field around a specific power cable.

  18. Modulation of high- and low-frequency components of the cortical local field potential via nicotinic and muscarinic acetylcholine receptors in anesthetized mice

    PubMed Central

    Waters, Jack

    2013-01-01

    Release of acetylcholine (ACh) in neocortex is important for learning, memory and attention tasks. The primary source of ACh in neocortex is axons ascending from the basal forebrain. Release of ACh from these axons evokes changes in the cortical local field potential (LFP), including a decline in low-frequency spectral power that is often referred to as desynchronization of the LFP and is thought to result from the activation of muscarinic ACh receptors. Using channelrhodopsin-2, we selectively stimulated the axons of only cholinergic basal forebrain neurons in primary somatosensory cortex of the urethane-anesthetized mouse while monitoring the LFP. Cholinergic stimulation caused desynchronization and two brief increases in higher-frequency power at stimulus onset and offset. Desynchronization (1–6 Hz) was localized, extending ≤ 1 mm from the edge of stimulation, and consisted of both nicotinic and muscarinic receptor-mediated components that were inhibited by mecamylamine and atropine, respectively. Hence we have identified a nicotinic receptor-mediated component to desynchronization. The increase in higher-frequency power (>10 Hz) at stimulus onset was also mediated by activation of nicotinic and muscarinic receptors. However, the increase in higher-frequency power (10–20 Hz) at stimulus offset was evoked by activation of muscarinic receptors and inhibited by activation of nicotinic receptors. We conclude that the activation of nicotinic and muscarinic ACh receptors in neocortex exerts several effects that are reflected in distinct frequency bands of the cortical LFP in urethane-anesthetized mice. PMID:24155009

  19. Real-time magnetic nanothermometry: The use of magnetization of magnetic nanoparticles assessed under low frequency triangle-wave magnetic fields

    NASA Astrophysics Data System (ADS)

    Zhong, Jing; Liu, Wenzhong; Jiang, Ling; Yang, Ming; Morais, Paulo Cesar

    2014-09-01

    In this study, we propose and demonstrate the usefulness of employing time-varying magnetization of a magnetic nanoparticle (MNP) based sample, induced by low frequency (f = 25 Hz) triangular-wave magnetic field, to achieve the approach of real-time recording of magnetization curve, which allows precise and noninvasive temperature probing with real-time performance. Moreover, the present report introduces the design and performed the test of a detection system for accurate and real-time recording of the magnetization curve of MNP-based samples. We found that by employing the magnetization curve of a magnetic fluid sample containing magnetite nanoparticles of about 30 nm in diameter the accuracy of the temperature probing is about 0.32 K (0.1% relative accuracy), with response time of 1 s. Furthermore, an increase in response time from 1 to 8 s improves the accuracy of temperature probing from 0.32 to 0.20 K. Finally, we envisage that breakthroughs in clinical hyperthermia, targeted drug delivery and basic cell research can be accomplished while using the approach reported in this study.

  20. Transfer characteristics and low-frequency noise in single- and multi-layer MoS{sub 2} field-effect transistors

    SciTech Connect

    Sharma, Deepak; Motayed, Abhishek; Shah, Pankaj B.; Amani, Matin; Georgieva, Mariela; Glen Birdwell, A.; Dubey, Madan; Li, Qiliang; Davydov, Albert V.

    2015-10-19

    Leveraging nanoscale field-effect transistors (FETs) in integrated circuits depends heavily on its transfer characteristics and low-frequency noise (LFN) properties. Here, we report the transfer characteristics and LFN in FETs fabricated with molybdenum disulfide (MoS{sub 2}) with different layer (L) counts. 4L to 6L devices showed highest I{sub ON}-I{sub OFF} ratio (≈10{sup 8}) whereas LFN was maximum for 1L device with normalized power spectral density (PSD) ≈1.5 × 10{sup −5 }Hz{sup −1}. For devices with L ≈ 6, PSD was minimum (≈2 × 10{sup −8 }Hz{sup −1}). Further, LFN for single and few layer devices satisfied carrier number fluctuation (CNF) model in both weak and strong accumulation regimes while thicker devices followed Hooge's mobility fluctuation model in the weak accumulation regime and CNF model in strong accumulation regime, respectively. Transfer-characteristics and LFN experimental data are explained with the help of model incorporating Thomas-Fermi charge screening and inter-layer resistance coupling.

  1. The Effect of an Eextremely Low Frequency Magnetic Field on Larvae Production in the Parasite-Host System: Fasciola hepatica-Galba truncatula: a Preliminary Study.

    PubMed

    Kołodziejczyk, Lidia; Podraza, Wojciech; Gonet, Bolesław; Dzika, Ewa; Kosik-Bogacka, Danuta I

    2016-01-01

    The aim of this study was to determine the effect of an extremely low-frequency magnetic field (ELFMF) on the production of liver fluke larvae in a parasite-host system: Fasciola hepatica--Galba truncatula. Both F. hepatica eggs and F. hepatica-infected snails were exposed to an ELFMF (50 Hz, 2.0 mT) for 14 days and 36 days, respectively. F. hepatica-infected snails were divided into 4 groups, 10 specimens each. The snails of groups I and II were infected with F. hepatica larvae--miracidia obtained from control cultures, while the snails of groups III and IV were infected with miracidia reared from eggs that had been incubated in an ELFMF. After infection, the snails of groups II and IV were placed in an ELFMF, while those of groups I (control) and III were housed outside the ELFMF. At 36 days post-infection (dpi) there were no statistically significant differences between the number of F. hepatica larvae--cercariae and metacercariae, obtained from G. truncatula snails in the control group (group I) and the snail groups exposed to ELFMF (groups II, III and IV). However, a statistically significant difference between the average number of F. hepatica larvae in snail groups III and IV may indicate that the duration of exposure to ELFMF, i.e. embryogenesis period vs. the entire larval development, played a role in the production of F. hepatica larvae, and resulted in a reduction of their number. PMID:27172713

  2. Potent Stimulation of Blood Flow in Fingers of Volunteers after Local Short-Term Treatment with Low-Frequency Magnetic Fields from a Novel Device

    PubMed Central

    Funk, Richard H. W.; Knels, Lilla; Augstein, Antje; Marquetant, Rainer; Dertinger, Hermann F.

    2014-01-01

    A novel hand-held low-frequency magnetic stimulator (MagCell-SR) was tested for its ability to stimulate microcirculation in fingers of healthy volunteers. Blood flow during and after 5 minutes exposure was quantified using Laser Doppler Perfusion Imaging Technique. The device was positioned between the wrist and the dorsal part of the backhand. Because the increase in blood flow could be caused by a release of nitric oxide (NO) from the vascular endothelial cells we tested NO production with a fluorescence marker and quantified the measurements in cell cultures of human umbilical endothelial cells (HUVEC). Exposure increased blood flow significantly, persisted several minutes, and then disappeared gradually. In order to assess the effect of a static magnetic field, the measurements were also carried out with the device shutoff. Here, only a small increase in blood flow was noted. The application of the rotating MagCell-SR to the HUVEC cultures leads to a rapid onset and a significant increase of NO release after 15 minutes. Thus, frequencies between 4 and 12 Hz supplied by the device improve microcirculation significantly. Therefore, this device can be used in all clinical situations where an improvement of the microcirculation is useful like in chronic wound healing deficits. PMID:24963323

  3. Grouping of Experimental Conditions as an Approach to Evaluate Effects of Extremely Low-Frequency Magnetic Fields on Oxidative Response in in vitro Studies

    PubMed Central

    Mattsson, Mats-Olof; Simkó, Myrtill

    2014-01-01

    A large body of literature deals with biological effects of extremely low-frequency magnetic fields (ELF MFs) studied in vitro. Despite the multitude of studies, no coherent picture has evolved regarding the plausibility of effects at low-flux densities or regarding the interaction mechanisms. Here, we propose that ELF MF exposure in vitro causes changes in oxidative status as an early response. We tested this hypothesis by scrutinizing the literature and applying a grouping approach for analyzing relevant biological properties and exposure conditions. A total of 41 scientific original publications were analyzed for this purpose. The conclusion from the work is that ELF MF (modulated or unmodulated) consistently can influence the oxidative status, at or above 1 mT, in a broad range of cell types and independent of exposure duration. A response at lower flux densities is seen in certain studies, although not consistently. Further studies with stringent protocols for sham exposure, blinding, and statistical analysis as well as appropriate positive controls are needed to establish if true dose-relationships for effects on oxidative status exist. PMID:25229055

  4. Low-frequency noise in AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors

    NASA Astrophysics Data System (ADS)

    Le, Son Phuong; Ui, Toshimasa; Nguyen, Tuan Quy; Shih, Hong-An; Suzuki, Toshi-kazu

    2016-05-01

    Using aluminum titanium oxide (AlTiO, an alloy of Al2O3 and TiO2) as a high-k gate insulator, we fabricated and investigated AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors. From current low-frequency noise (LFN) characterization, we find Lorentzian spectra near the threshold voltage, in addition to 1/f spectra for the well-above-threshold regime. The Lorentzian spectra are attributed to electron trapping/detrapping with two specific time constants, ˜25 ms and ˜3 ms, which are independent of the gate length and the gate voltage, corresponding to two trap level depths of 0.5-0.7 eV with a 0.06 eV difference in the AlTiO insulator. In addition, gate leakage currents are analyzed and attributed to the Poole-Frenkel mechanism due to traps in the AlTiO insulator, where the extracted trap level depth is consistent with the Lorentzian LFN.

  5. Transfer characteristics and low-frequency noise in single- and multi-layer MoS2 field-effect transistors

    NASA Astrophysics Data System (ADS)

    Sharma, Deepak; Motayed, Abhishek; Shah, Pankaj B.; Amani, Matin; Georgieva, Mariela; Glen Birdwell, A.; Dubey, Madan; Li, Qiliang; Davydov, Albert V.

    2015-10-01

    Leveraging nanoscale field-effect transistors (FETs) in integrated circuits depends heavily on its transfer characteristics and low-frequency noise (LFN) properties. Here, we report the transfer characteristics and LFN in FETs fabricated with molybdenum disulfide (MoS2) with different layer (L) counts. 4L to 6L devices showed highest ION-IOFF ratio (≈108) whereas LFN was maximum for 1L device with normalized power spectral density (PSD) ≈1.5 × 10-5 Hz-1. For devices with L ≈ 6, PSD was minimum (≈2 × 10-8 Hz-1). Further, LFN for single and few layer devices satisfied carrier number fluctuation (CNF) model in both weak and strong accumulation regimes while thicker devices followed Hooge's mobility fluctuation model in the weak accumulation regime and CNF model in strong accumulation regime, respectively. Transfer-characteristics and LFN experimental data are explained with the help of model incorporating Thomas-Fermi charge screening and inter-layer resistance coupling.

  6. Electromagnetic fields on a quantum scale. I.

    PubMed

    Grimes, Dale M; Grimes, Craig A

    2002-10-01

    This is the first in a series of two articles, the second of which provides an exact electro-magnetic field description of photon emission, absorption, and radiation pattern. Photon energy exchanges are analyzed and shown to be the triggered, regenerative response of a non-local eigenstate electron. This first article presents a model-based, hidden variable analysis of quantum theory that provides the statistical nature of wave functions. The analysis uses the equations of classical electro-magnetism and conservation of energy while modeling an eigenstate electron as a nonlocal entity. Essential to the analysis are physical properties that were discovered and analyzed only after the historical interpretation of quantum mechanics was established: electron non-locality and the standing electro-magnetic energy that accompanies and encompasses an active, electrically small volume. The standing energy produces a driving radiation reaction force that, under certain circumstances, is many orders of magnitude larger than currently accepted values. These properties provide a sufficient basis for the Schrödinger equation as a descriptor of non-relativistic eigenstate electrons in or near equilibrium. The uncertainty principle follows, as does the exclusion principle. The analysis leads to atomic stability and causality in the sense that the status of physical phenomena at any instant specifies the status an instant later. PMID:12908293

  7. Calcium homeostasis and low-frequency magnetic and electric field exposure: A systematic review and meta-analysis of in vitro studies.

    PubMed

    Golbach, Lieke A; Portelli, Lucas A; Savelkoul, Huub F J; Terwel, Sofie R; Kuster, Niels; de Vries, Rob B M; Verburg-van Kemenade, B M Lidy

    2016-01-01

    Low frequency magnetic field (LF MF) exposure is recurrently suggested to have the ability to induce health effects in society. Therefore, in vitro model systems are used to investigate biological effects of exposure. LF MF induced changes of the cellular calcium homeostasis are frequently hypothesised to be the possible target, but this hypothesis is both substantiated and rejected by numerous studies in literature. Despite the large amount of data, no systematic analysis of in vitro studies has been conducted to address the strength of evidence for an association between LF MF exposure and calcium homeostasis. Our systematic review, with inclusion of 42 studies, showed evidence for an association of LF MF with internal calcium concentrations and calcium oscillation patterns. The oscillation frequency increased, while the amplitude and the percentage of oscillating cells remained constant. The intracellular calcium concentration increased (SMD 0.351, 95% CI 0.126, 0.576). Subgroup analysis revealed heterogeneous effects associated with the exposure frequency, magnetic flux density and duration. Moreover, we found support for the presence of MF-sensitive cell types. Nevertheless, some of the included studies may introduce a great risk of bias as a result of uncontrolled or not reported exposure conditions, temperature ranges and ambient fields. In addition, mathematical calculations of the parasitic induced electric fields (IEFs) disclosed their association with increased intracellular calcium. Our results demonstrate that LF MF might influence the calcium homeostasis in cells in vitro, but the risk of bias and high heterogeneity (I(2)>75%) weakens the analyses. Therefore any potential clinical implications await further investigation. PMID:26872872

  8. Safety Problems of Electric and Magnetic Fields and Experimental Magnetic Fusion Facilities 5.Electromagnetic Fields in the Workplace

    NASA Astrophysics Data System (ADS)

    Jonai, Hiroshi; Villanueva, Maria Beatriz G.

    The review addresses the concerns related to extremely low frequency electromagnetic fields (ELF/EMF) in workplaces. The exposure levels and epidemiological studies on cancer, the health effects of working with VDTs (visual display terminals), and the malfunction of cardiac pacemakers are described. The association of EMF exposure and cancer or disorders from VDT work cannot be considered conclusive. The information on the exposure level and effect of EMF on cardiac pacemakers should be disseminated in workplaces. Risk communication program on EMF is urgent for countermeasures against worker anxiety.

  9. Translation operator for finite dmensional electromagnetic fields

    SciTech Connect

    Howard, A.Q. Jr.

    1981-04-01

    Computation of electromagnetic fields in particular applications is usually accompanied by the adhoc assumption that the field contains a finite number of degrees of freedom. Herein, this assumption is made at the outset. It is shown that if an annular region between two closed surfaces contains no sources or sinks and is isotropic, lossless and homogeneous, a unique translation operator can be defined algebraically. Conservation of energy defines the translation operator T to within an arbitrary unitary transformation. The conditions of causality, unitarity and energy conservation are shown to uniquely determine T. Both scalar and vector fields are treated. In both of these cases, frequency and time domain transforms are computed. The transform T is compared with the analagous one as derived from the time domain Stratton-Chu Formulation. The application to a radiation condition boundary constraint on finite difference and finite element computations is discussed.

  10. Geometrization conditions for perfect fluids, scalar fields, and electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Krongos, D. S.; Torre, C. G.

    2015-07-01

    Rainich-type conditions giving a spacetime "geometrization" of matter fields in general relativity are reviewed and extended. Three types of matter are considered: perfect fluids, scalar fields, and electromagnetic fields. Necessary and sufficient conditions on a spacetime metric for it to be part of a perfect fluid solution of the Einstein equations are given. Formulas for constructing the fluid from the metric are obtained. All fluid results hold for any spacetime dimension. Geometric conditions on a metric which are necessary and sufficient for it to define a solution of the Einstein-scalar field equations and formulas for constructing the scalar field from the metric are unified and extended to arbitrary dimensions, to include a cosmological constant, and to include any self-interaction potential. Necessary and sufficient conditions on a four-dimensional spacetime metric for it to be an electrovacuum and formulas for constructing the electromagnetic field from the metric are generalized to include a cosmological constant. Both null and non-null electromagnetic fields are treated. A number of examples and applications of these results are presented.

  11. Investigating the impact of electromagnetic fields on human cells: A thermodynamic perspective

    NASA Astrophysics Data System (ADS)

    Lucia, Umberto; Ponzetto, Antonio; Deisboeck, Thomas S.

    2016-02-01

    The consequences of the interactions of electromagnetic waves, as used in conventional MRI technology, with human cells are not fully understood. To analyze these interactions, a novel thermodynamic approach is presented that is based on the relationship between electromagnetic and thermodynamic quantities. The theoretical results indicate that the waves' impact is largest at high magnetic field strengths and at low frequencies. This is the first step towards a clinically useful framework to quantitatively assess MRI impact including a potential trade-off between the desired increase in spatial resolution that higher magnetic field strengths yield for diagnostic purposes and the danger this may pose for cell membranes, and by extension, for the tissues investigated.

  12. Relationships among low-frequency local field potentials, spiking activity, and three-dimensional reach and grasp kinematics in primary motor and ventral premotor cortices

    PubMed Central

    Vargas-Irwin, Carlos E.; Truccolo, Wilson; Donoghue, John P.

    2011-01-01

    A prominent feature of motor cortex field potentials during movement is a distinctive low-frequency local field potential (lf-LFP) (<4 Hz), referred to as the movement event-related potential (mEP). The lf-LFP appears to be a global signal related to regional synaptic input, but its relationship to nearby output signaled by single unit spiking activity (SUA) or to movement remains to be established. Previous studies comparing information in primary motor cortex (MI) lf-LFPs and SUA in the context of planar reaching tasks concluded that lf-LFPs have more information than spikes about movement. However, the relative performance of these signals was based on a small number of simultaneously recorded channels and units, or for data averaged across sessions, which could miss information of larger-scale spiking populations. Here, we simultaneously recorded LFPs and SUA from two 96-microelectrode arrays implanted in two major motor cortical areas, MI and ventral premotor (PMv), while monkeys freely reached for and grasped objects swinging in front of them. We compared arm end point and grip aperture kinematics′ decoding accuracy for lf-LFP and SUA ensembles. The results show that lf-LFPs provide enough information to reconstruct kinematics in both areas with little difference in decoding performance between MI and PMv. Individual lf-LFP channels often provided more accurate decoding of single kinematic variables than any one single unit. However, the decoding performance of the best single unit among the large population usually exceeded that of the best single lf-LFP channel. Furthermore, ensembles of SUA outperformed the pool of lf-LFP channels, in disagreement with the previously reported superiority of lf-LFP decoding. Decoding results suggest that information in lf-LFPs recorded from intracortical arrays may allow the reconstruction of reach and grasp for real-time neuroprosthetic applications, thus potentially supplementing the ability to decode these same

  13. Extremely Low Frequency Magnetic Field (50 Hz, 0.5 mT) Reduces Oxidative Stress in the Brain of Gerbils Submitted to Global Cerebral Ischemia

    PubMed Central

    Rauš Balind, Snežana; Selaković, Vesna; Radenović, Lidija; Prolić, Zlatko; Janać, Branka

    2014-01-01

    Magnetic field as ecological factor has influence on all living beings. The aim of this study was to determine if extremely low frequency magnetic field (ELF-MF, 50 Hz, 0.5 mT) affects oxidative stress in the brain of gerbils submitted to 10-min global cerebral ischemia. After occlusion of both carotid arteries, 3-month-old gerbils were continuously exposed to ELF-MF for 7 days. Nitric oxide and superoxide anion production, superoxide dismutase activity and index of lipid peroxidation were examined in the forebrain cortex, striatum and hippocampus on the 7th (immediate effect of ELF-MF) and 14th day after reperfusion (delayed effect of ELF-MF). Ischemia per se increased oxidative stress in the brain on the 7th and 14th day after reperfusion. ELF-MF also increased oxidative stress, but to a greater extent than ischemia, only immediately after cessation of exposure. Ischemic gerbils exposed to ELF-MF had increased oxidative stress parameters on the 7th day after reperfusion, but to a lesser extent than ischemic or ELF-MF-exposed animals. On the 14th day after reperfusion, oxidative stress parameters in the brain of these gerbils were mostly at the control levels. Applied ELF-MF decreases oxidative stress induced by global cerebral ischemia and thereby reduces possible negative consequences which free radical species could have in the brain. The results presented here indicate a beneficial effect of ELF-MF (50 Hz, 0.5 mT) in the model of global cerebral ischemia. PMID:24586442

  14. Improvement of neurofeedback therapy for improved attention through facilitation of brain activity using local sinusoidal extremely low frequency magnetic field exposure.

    PubMed

    Zandi Mehran, Yasaman; Firoozabadi, Mohammad; Rostami, Reza

    2015-04-01

    Traditional neurofeedback (NF) is a training approach aimed at altering brain activity using electroencephalography (EEG) rhythms as feedback. In NF training, external factors such as the subjects' intelligence can have an effect. In contrast, a low-energy NF system (LENS) does not require conscious effort from the subject, which results in fewer attendance sessions. However, eliminating the subject role seems to eliminate an important part of the NF system. This study investigated the facilitating effect on the theta-to-beta ratio from NF training, using a local sinusoidal extremely low frequency magnetic field (LSELF-MF) versus traditional NF. Twenty-four healthy, intelligent subjects underwent 10 training sessions to enhance beta (15-18 Hz), and simultaneously inhibit theta (4-7 Hz) and high beta (22-30 Hz) activity, at the Cz point in a 3-boat-race video game. Each session consisted of 3 statuses, PRE, DURING, and POST. In the DURING status, the NF training procedure lasted 10 minutes. Subjects were led to believe that they would be exposed to a magnetic field during NF training; however, 16 of the subjects who were assigned to the experimental group were really exposed to 45 Hz-360 µT LSELF-MF at Cz. For the 8 other subjects, only the coil was located at the Cz point with no exposure. The duty cycle of exposure was 40% (2-second exposure and 3-second pause). The results show that the theta-to-beta ratio in the DURING status of each group differs significantly from the PRE and POST statuses. Between-group analysis shows that the theta-to-beta ratio in the DURING status of the experimental group is significantly (P < .001) lower than in the sham group. The result shows the effect of LSELF-MF on NF training. PMID:24939868

  15. Low-frequency wide-field fluorescence lifetime imaging using a high-power near-infrared light-emitting diode light source

    NASA Astrophysics Data System (ADS)

    Gioux, Sylvain; Lomnes, Stephen J.; Choi, Hak Soo; Frangioni, John V.

    2010-03-01

    Fluorescence lifetime imaging (FLi) could potentially improve exogenous near-infrared (NIR) fluorescence imaging, because it offers the capability of discriminating a signal of interest from background, provides real-time monitoring of a chemical environment, and permits the use of several different fluorescent dyes having the same emission wavelength. We present a high-power, LED-based, NIR light source for the clinical translation of wide-field (larger than 5 cm in diameter) FLi at frequencies up to 35 MHz. Lifetime imaging of indocyanine green (ICG), IRDye 800-CW, and 3,3'-diethylthiatricarbocyanine iodide (DTTCI) was performed over a large field of view (10 cm by 7.5 cm) using the LED light source. For comparison, a laser diode light source was employed as a gold standard. Experiments were performed both on the bench by diluting the fluorescent dyes in various chemical environments in Eppendorf tubes, and in vivo by injecting the fluorescent dyes mixed in Matrigel subcutaneously into CD-1 mice. Last, measured fluorescence lifetimes obtained using the LED and the laser diode sources were compared with those obtained using a state-of-the-art time-domain imaging system and with those previously described in the literature. On average, lifetime values obtained using the LED and the laser diode light sources were consistent, exhibiting a mean difference of 3% from the expected values and a coefficient of variation of 12%. Taken together, our study offers an alternative to laser diodes for clinical translation of FLi and explores the use of relatively low frequency modulation for in vivo imaging.

  16. Near-field radiofrequency electromagnetic exposure assessment.

    PubMed

    Rubtsova, Nina; Perov, Sergey; Belaya, Olga; Kuster, Niels; Balzano, Quirino

    2015-09-01

    Personal wireless telecommunication devices, such as radiofrequency (RF) electromagnetic field (EMF) sources operated in vicinity of human body, have possible adverse health effects. Therefore, the correct EMF assessment is necessary in their near field. According to international near-field measurement criteria, the specific absorption rate (SAR) is used for absorbed energy distribution assessment in tissue simulating liquid phantoms. The aim of this investigation is to validate the relationship between the H-field of incident EMF and absorbed energy in phantoms. Three typical wireless telecommunication system frequencies are considered (900, 1800 and 2450 MHz). The EMF source at each frequency is an appropriate half-wave dipole antenna and the absorbing medium is a flat phantom filled with the suitable tissue simulating liquid. Two methods for SAR estimation have been used: standard procedure based on E-field measured in tissue simulating medium and a proposed evaluation by measuring the incident H-field. Compared SAR estimations were performed for various distances between sources and phantom. Also, these research data were compared with simulation results, obtained by using finite-difference time-domain method. The acquired data help to determine the source near-field space characterized by the smallest deviation between SAR estimation methods. So, this region near the RF source is suitable for correct RF energy absorption assessment using the magnetic component of the RF fields. PMID:26444190

  17. Possible action mechanism of the electromagnetic fields in the liver cancer development: A mathematical proposal

    NASA Astrophysics Data System (ADS)

    Jiménez-García, Mónica Noemí; Godina-Nava, Juan José

    2012-02-01

    Currently it is known that electromagnetic field exposure can induce biological changes, although the precise effects and action mechanism of the interaction between the electromagnetic field and biological systems are not well understood. In this work we propose a possible action mechanism, concerning the effect that the extremely low frequency electromagnetic field exposure has on the early stage of liver cancer development. The model is developed studying the phenomena called oxidative stress that it appears after it is applied a carcinogenic agent used to induce hepatic cancer chemically in an experimental animal model. This physical-chemical process involves the movement of magnetic field dependent free charged particles, called free radicals. We will consider the use of the radical pairs theory as a framework, in which we will describe the spin density operator evolution by implementing the stochastic Liouville equation with hyperfine interaction. This describes how the selectivity of the interaction between spin states of the free radicals with the applied electromagnetic field, influences the development of pre-neoplastic lesions in the liver. AIP Publishing is retracting this article due to the substantial use of content in the Results and Conclusions section without proper citation of a previously published paper in Chemical Physics Letters 361 (2012) 219-225. This article is retracted from the scientific record with effect from 15 October 2015.

  18. Electromagnetic fields with vanishing scalar invariants

    NASA Astrophysics Data System (ADS)

    Ortaggio, Marcello; Pravda, Vojtěch

    2016-06-01

    We determine the class of p-forms {\\boldsymbol{F}} that possess vanishing scalar invariants (VSIs) at arbitrary order in an n-dimensional spacetime. Namely, we prove that {\\boldsymbol{F}} is a VSI if and only if if it is of type N, its multiple null direction {\\boldsymbol{\\ell }} is ‘degenerate Kundt’, and {\\pounds }{\\boldsymbol{\\ell }}{\\boldsymbol{F}}=0. The result is theory-independent. Next, we discuss the special case of Maxwell fields, both at the level of test fields and of the full Einstein-Maxwell equations. These describe electromagnetic non-expanding waves propagating in various Kundt spacetimes. We further point out that a subset of these solutions possesses a universal property, i.e. they also solve (virtually) any generalized (non-linear and with higher derivatives) electrodynamics, possibly also coupled to Einstein’s gravity.

  19. Evaluation of chromosomal alteration in electrical workers occupationally exposed to low frequency of electro magnetic field (EMFs) in Coimbatore population, India.

    PubMed

    Balamuralikrishnan, Balasubramanian; Balachandar, Vellingiri; Kumar, Shanmugam Suresh; Stalin, Nattan; Varsha, Prakash; Devi, Subramaniam Mohana; Arun, Meyyazhagan; Manikantan, Pappuswamy; Venkatesan, Chinnakulandhai; Sasikala, Keshavarao; Dharwadkar, Shahnaz N

    2012-01-01

    Extremely low frequency electro magnetic fields (EMFs) have been classified as possibly carcinogenic to humans by the International Agency for Research on Cancer. An increased number of chromosomal alterations in peripheral lymphocytes are correlated with elevated incidence of cancer. The aim of the present study was to assess occupationally induced chromosomal damage in EMF workers exposed to low levels of radiation. We used conventional metaphase chromosome aberration (CA) analysis and the micronucleus (MN) assay as biological indicators of non ionizing radiation exposure. In the present study totally 70 subjects were selected including 50 exposed and 20 controls. Informed written consent was obtained from all participants and the study was performed in accordance with the Declaration of Helsinki and the approval of the local ethical committee. A higher degree of CA and MN was observed in exposed subjects compared to controls, the frequency of CA being significantly enhanced with long years of exposure (P<0.05). Moreover increase in CA and MN with age was noted in both exposed subjects and controls, but was significantly greater in the former. The results of this study demonstrated that a significant induction of cytogenetic damage in peripheral lymphocytes of workers occupationally exposed to EMFs in electric transformer and distribution stations. In conclusion, our findings suggest that EMFs possess genotoxic capability, as measured by CA and MN assays; CA analysis appeared more sensitive than other cytogenetic end-points. It can be concluded that chronic occupational exposure to EMFs may lead to an increased risk of genetic damage among electrical workers. PMID:22938490

  20. Exposure to an Extremely-Low-Frequency Magnetic Field Stimulates Adrenal Steroidogenesis via Inhibition of Phosphodiesterase Activity in a Mouse Adrenal Cell Line

    PubMed Central

    Kitaoka, Kazuyoshi; Kawata, Shiyori; Yoshida, Tomohiro; Kadoriku, Fumiya; Kitamura, Mitsuo

    2016-01-01

    Extremely low-frequency magnetic fields (ELF-MFs) are generated by power lines and household electrical devices. In the last several decades, some evidence has shown an association between ELF-MF exposure and depression and/or anxiety in epidemiological and animal studies. The mechanism underlying ELF-MF-induced depression is considered to involve adrenal steroidogenesis, which is triggered by ELF-MF exposure. However, how ELF-MFs stimulate adrenal steroidogenesis is controversial. In the current study, we investigated the effect of ELF-MF exposure on the mouse adrenal cortex-derived Y-1 cell line and the human adrenal cortex-derived H295R cell line to clarify whether the ELF-MF stimulates adrenal steroidogenesis directly. ELF-MF exposure was found to significantly stimulate adrenal steroidogenesis (p < 0.01–0.05) and the expression of adrenal steroid synthetic enzymes (p < 0.05) in Y-1 cells, but the effect was weak in H295R cells. Y-1 cells exposed to an ELF-MF showed significant decreases in phosphodiesterase activity (p < 0.05) and intracellular Ca2+ concentration (p < 0.01) and significant increases in intracellular cyclic adenosine monophosphate (cAMP) concentration (p < 0.001–0.05) and cAMP response element-binding protein phosphorylation (p < 0.05). The increase in cAMP was not inhibited by treatment with NF449, an inhibitor of the Gs alpha subunit of G protein. Our results suggest that ELF-MF exposure stimulates adrenal steroidogenesis via an increase in intracellular cAMP caused by the inhibition of phosphodiesterase activity in Y-1 cells. The same mechanism may trigger the increase in adrenal steroid secretion in mice observed in our previous study. PMID:27100201

  1. [Patient exposure to electromagnetic fields in magnetic resonance scanners: a review].

    PubMed

    Guibelalde del Castillo, E

    2013-12-01

    The use of non-ionizing electromagnetic fields in the low frequency end of the electromagnetic spectrum and static fields, radiofrequencies (RF), and microwaves is fundamental both in modern communication systems and in diagnostic medical imaging techniques like magnetic resonance imaging (MRI). The proliferation of these applications in recent decades has led to intense activity in developing regulations to guarantee their safety and to the establishment of guidelines and legal recommendations for the public, workers, and patients. In April 2012 it was foreseen that the European Parliament and Council would approve and publish a directive on the minimum health and safety requirements regarding the exposure of workers to the risks arising from electromagnetic fields, which would modify Directive 2004/40/EC. New studies related to the exposure to electromagnetic radiation and its impact on health published in recent years have led to a new postponement, and it is now foreseen that the directive will come into effect in October 2013. One of the most noteworthy aspects of the new version of the directive is the exclusion of the limits of occupational exposure to electromagnetic fields in the clinical use of MRI. In exchange for this exception, physicians and experts in protection against non-ionizing radiation are asked to make additional efforts to train workers exposed to non-ionizing radiation and to establish mechanisms to guarantee the correct application of non-ionizing electromagnetic fields in patients, along similar lines to the principles of justification and optimization established for ionizing radiation. On the basis of the most recently published studies, this article reviews some safety-related aspects to take into account when examining patients with MRI with high magnetic fields. PMID:24246885

  2. A new low-frequency backward mode in inhomogeneous plasmas

    SciTech Connect

    Vranjes, J.

    2014-07-15

    When an electromagnetic transverse wave propagates through an inhomogeneous plasma so that its electric field has a component in the direction of the background density gradient, there appears a disbalance of charge in every plasma layer, caused by the density gradient. Due to this, some additional longitudinal electric field component appears in the direction of the wave vector. This longitudinal field may couple with the usual electrostatic longitudinal perturbations like the ion acoustic, electron Langmuir, and ion plasma waves. As a result, these standard electrostatic waves are modified and in addition to this a completely new low-frequency mode appears. Some basic features of the coupling and modification of the ion acoustic wave, and properties of the new mode are discussed here, in ordinary electron-ion and in pair plasmas.

  3. Plant Responses to High Frequency Electromagnetic Fields

    PubMed Central

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre

    2016-01-01

    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  4. Plant Responses to High Frequency Electromagnetic Fields.

    PubMed

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre

    2016-01-01

    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  5. Measurement and analysis of electromagnetic fields from trams, trains and hybrid cars.

    PubMed

    Halgamuge, Malka N; Abeyrathne, Chathurika D; Mendis, Priyan

    2010-10-01

    Electricity is used substantially and sources of electric and magnetic fields are, unavoidably, everywhere. The transportation system is a source of these fields, to which a large proportion of the population is exposed. Hence, investigation of the effects of long-term exposure of the general public to low-frequency electromagnetic fields caused by the transportation system is critically important. In this study, measurements of electric and magnetic fields emitted from Australian trams, trains and hybrid cars were investigated. These measurements were carried out under different conditions, locations, and are summarised in this article. A few of the measured electric and magnetic field strengths were significantly lower than those found in prior studies. These results seem to be compatible with the evidence of the laboratory studies on the biological effects that are found in the literature, although they are far lower than international levels, such as those set up in the International Commission on Non-Ionising Radiation Protection guidelines. PMID:20554578

  6. Note on Inverse Bremsstrahlung in a Strong Electromagnetic Field

    DOE R&D Accomplishments Database

    Bethe, H. A.

    1972-09-01

    The collisional energy loss of an electron undergoing forced oscillation in an electromagnetic field behaves quite differently in the low and high intensity limits. ... It is shown that in the case of an electromagnetic field v {sub o} >> v {sub t} the rate of transfer is much slower, and actually decreases with the strength of the field.

  7. The Effect of Extremely Low Frequency Alternating Magnetic Field on the Behavior of Animals in the Presence of the Geomagnetic Field.

    PubMed

    Belova, Natalia A; Acosta-Avalos, Daniel

    2015-01-01

    It is known that the geomagnetic field can influence animal migration and homing. The magnetic field detection by animals is known as magnetoreception and it is possible due to two different transduction mechanisms: the first one through magnetic nanoparticles able to respond to the geomagnetic field and the second one through chemical reactions influenced by magnetic fields. Another behavior is the magnetic alignment where animals align their bodies to the geomagnetic field. It has been observed that magnetic alignment of cattle can be disrupted near electric power lines around the world. Experimentally, it is known that alternating magnetic fields can influence living beings, but the exact mechanism is unknown. The parametric resonance model proposes a mechanism to explain that effect on living beings and establishes that, in the presence of a constant magnetic field, molecules associated with biochemical reactions inside cells can absorb resonantly alternating magnetic fields with specific frequencies. In the present paper, a review is made about animal magnetoreception and the effects of alternating magnetic fields in living beings. It is suggested how alternating magnetic fields can interfere in the magnetic alignment of animals and a general conclusion is obtained: alternating magnetic field pollution can affect the magnetic sensibility of animals. PMID:26823664

  8. The Effect of Extremely Low Frequency Alternating Magnetic Field on the Behavior of Animals in the Presence of the Geomagnetic Field

    PubMed Central

    Belova, Natalia A.; Acosta-Avalos, Daniel

    2015-01-01

    It is known that the geomagnetic field can influence animal migration and homing. The magnetic field detection by animals is known as magnetoreception and it is possible due to two different transduction mechanisms: the first one through magnetic nanoparticles able to respond to the geomagnetic field and the second one through chemical reactions influenced by magnetic fields. Another behavior is the magnetic alignment where animals align their bodies to the geomagnetic field. It has been observed that magnetic alignment of cattle can be disrupted near electric power lines around the world. Experimentally, it is known that alternating magnetic fields can influence living beings, but the exact mechanism is unknown. The parametric resonance model proposes a mechanism to explain that effect on living beings and establishes that, in the presence of a constant magnetic field, molecules associated with biochemical reactions inside cells can absorb resonantly alternating magnetic fields with specific frequencies. In the present paper, a review is made about animal magnetoreception and the effects of alternating magnetic fields in living beings. It is suggested how alternating magnetic fields can interfere in the magnetic alignment of animals and a general conclusion is obtained: alternating magnetic field pollution can affect the magnetic sensibility of animals. PMID:26823664

  9. Truesdell invariance in relativistic electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Walwadkar, B. B.; Virkar, K. V.

    1984-01-01

    The Truesdell derivative of a contravariant tensor fieldX ab is defined with respect to a null congruencel a analogous to the Truesdell stress rate in classical continuum mechanics. The dynamical consequences of the Truesdell invariance with respect to a timelike vectoru a of the stress-energy tensor characterizing a charged perfect fluid with null conductivity are the conservation of pressure (p), charged density (e) an expansion-free flow, constancy of the Maxwell scalars, and vanishing spin coefficientsα+¯β = ¯σ - λ = τ = 0 (assuming freedom conditionsk = λ = ɛ ψ + ¯γ = 0). The electromagnetic energy momentum tensor for the special subcases of Ruse-Synge classification for typesA andB are described in terms of the spin coefficients introduced by Newman-Penrose.

  10. Production of flickering aurora and field-aligned electron flux by electromagnetic ion cyclotron waves

    NASA Technical Reports Server (NTRS)

    Temerin, M.; Mcfadden, J.; Boehm, M.; Carlson, C. W.; Lotko, W.

    1986-01-01

    Recent observations have suggested that flickering aurora is produced by a modulation of the field-aligned component of the electron flux within an auroral arc. It is proposed that a portion of the field-aligned electrons are of ionospheric origin and that these electrons are accelerated and their flux modulated by electromagnetic ion cyclotron waves that occur below the main acceleration region on auroral arc field lines. A model of the electromagnetic ion cyclotron wave shows that the parallel phase velocity of the wave increase as the wave propagates toward the ionosphere. A test particle calculation shows that ionospheric electrons trapped or reflected by the wave are accelerated to energies of several keV and that their flux is modulated at the wave frequency. The relative amplitudes of the model wave electric fields are consistent with the observations of small-scale low-frequency ionospheric and magnetospheric electric fields near auroral arcs of approximately 10 mV/m and 100 mV/m, respectively. The large-amplitude ion cyclotron waves also produce a ponderomotive force and a self-consistent ambipolar electric field. Energy considerations show that the downward energy flux in the electromagnetic ion cyclotron wave can be several percent of the total downward auroral electron energy flux.

  11. Developments and field tests of low-frequency portable acoustic transducers for a mobile exploration and time lapse experiment of a sea-bottom reservoir

    NASA Astrophysics Data System (ADS)

    Tsuruga, K.; Kasahara, J.; Hasada, Y.; Kondo, H.

    2013-12-01

    Depth, scale and resolutions of geophysical explorations for mineral resources are controlled by transmitted seismic energy and wavelength (frequency range). Most explorations in marine have been conducted by survey ship system with arrayed acoustic sources whose dominant frequency range is about 10 to 500 Hz. On the other hand, for shallow parts of sea bottom structure survey, some sub-bottom profilers with frequency range around 3.5kHz are used. To monitor a time lapse of a sea bottom reservoir such as an oil, gas, or methane hydrate reservoir as well as to exploit a mobile survey near a sea bottom by AUVs, it is necessary to use a broadband portable acoustic transducer with a dominant frequency range of 500 Hz to 5 kHz. We have been developing several types of portable acoustic transducers and a transmitting and recording system which is accurately controlled by a GPS clock (Tsuruga et al., 2012). In this pater, we report the new broadband acoustic portable transducers which have larger power than the original cylindrical acoustic transducers in a low frequency range (<5 kHz), partly funded by JOGMEC, and show the preliminary results of field tests at the shallow sea bottom around 32 m deep by means of the transducers and hydrophone receivers array. Each transducer repeatedly transmitted Chirp signals with a unit period of 500 msec in two frequency ranges of 0.5k-4.5kHz and 4k-16kHz . We stacked 500-ms data by 28 times to obtain a transfer function of each source-receiver pair in the time and frequency domains. The preliminary results suggest as the follows: (i) it is successful to broaden the frequency bandwidth (i.e., 2k-10kHz) by extending a geometrical resonance length of a cylindrical acoustic transducers, and (ii) the observation at the sea bottom with accurately controlled timing systems of transmitter and data-logger is very useful to identify the stable and/or unstable seismic phases, that is, waves propagating in a underground and/or in a sea water as

  12. Electromagnetic polarizabilities: Lattice QCD in background fields

    SciTech Connect

    W. Detmold, B.C. Tiburzi, A. Walker-Loud

    2012-04-01

    Chiral perturbation theory makes definitive predictions for the extrinsic behavior of hadrons in external electric and magnetic fields. Near the chiral limit, the electric and magnetic polarizabilities of pions, kaons, and nucleons are determined in terms of a few well-known parameters. In this limit, hadrons become quantum mechanically diffuse as polarizabilities scale with the inverse square-root of the quark mass. In some cases, however, such predictions from chiral perturbation theory have not compared well with experimental data. Ultimately we must turn to first principles numerical simulations of QCD to determine properties of hadrons, and confront the predictions of chiral perturbation theory. To address the electromagnetic polarizabilities, we utilize the background field technique. Restricting our attention to calculations in background electric fields, we demonstrate new techniques to determine electric polarizabilities and baryon magnetic moments for both charged and neutral states. As we can study the quark mass dependence of observables with lattice QCD, the lattice will provide a crucial test of our understanding of low-energy QCD, which will be timely in light of ongoing experiments, such as at COMPASS and HI gamma S.

  13. Mortality in workers exposed to electromagnetic fields

    SciTech Connect

    Milham, S. Jr.

    1985-10-01

    In an occupational mortality analysis of 486,000 adult male death records filed in Washington State in the years 1950-1982, leukemia and the non-Hodgkin's lymphomas show increased proportionate mortality ratios (PMRs) in workers employed in occupations with intuitive exposures to electromagnetic fields. Nine occupations of 219 were considered to have electric or magnetic field exposures. These were: electrical and electronic technicians, radio and telegraph operators, radio and television repairmen, telephone and power linemen, power station operators, welders, aluminum reduction workers, motion picture projectionists and electricians. There were 12,714 total deaths in these occupations. Eight of the nine occupations had PMR increases for leukemia (International Classification of Diseases (ICD), seventh revision 204) and seven of the nine occupations had PMR increases for the other lymphoma category (7th ICD 200.2, 202). The highest PMRs were seen for acute leukemia: (67 deaths observed, 41 deaths expected; PMR 162), and in the other lymphomas (51 deaths observed, 31 deaths expected; PMR 164). No increase in mortality was seen for Hodgkin's disease or multiple myeloma. These findings offer some support for the hypothesis that electric and magnetic fields may be carcinogenic.

  14. Inelastic deformation of conductive bodies in electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Altenbach, Holm; Morachkovsky, Oleg; Naumenko, Konstantin; Lavinsky, Denis

    2015-12-01

    Inelastic deformation of conductive bodies under the action of electromagnetic fields is analyzed. Governing equations for non-stationary electromagnetic field propagation and elastic-plastic deformation are presented. The variational principle of minimum of the total energy is applied to formulate the numerical solution procedure by the finite element method. With the proposed method, distributions of vector characteristics of the electromagnetic field and tensor characteristics of the deformation process are illustrated for the inductor-workpiece system within a realistic electromagnetic forming process.

  15. The early history of low frequency radio astronomy in Australia. 6: Michael Bessell and the University of Tasmania's Richmond field station near Hobart

    NASA Astrophysics Data System (ADS)

    George, Martin; Orchiston, Wayne; Slee, Bruce; Wielebinski, Richard

    2016-08-01

    Following some initial research in Tasmania between 1955 and 1957, notably by Graeme Ellis and Grote Reber, low frequency radio astronomy became a significant activity of the University of Tasmania from the early 1960s, with the main aims being to study the radio Milky Way and Jupiter's decametric emissions. Although locations very close to Hobart Airport were to see the majority of this work, in the early to mid-1960s low frequency antenna arrays were set up and used by the University at nearby Penna and Richmond. This paper describes the erection and use of the Richmond arrays, which in 1962-1963 operated at a site 1 km north of the town of Richmond, and at frequencies of 2.35, 1.55 and 1.03 MHz.

  16. Effect of non-ionizing electromagnetic field on the alteration of ovarian follicles in rats

    PubMed Central

    Ahmadi, Seyed Shahin; Khaki, Amir Afshin; Ainehchi, Nava; Alihemmati, Alireza; Khatooni, Azam Asghari; Khaki, Arash; Asghari, Ali

    2016-01-01

    Introduction In recent years, there has been an increase in the attention paid to safety effects, environmental and society’s health, extremely low frequency electromagnetic fields (ELF-EMF), and radio frequency electromagnetic fields (RF-EMF). The aim of this research was to determine the effect of EMF on the alteration of ovarian follicles. Methods In this experimental study at Tabriz Medical University in 2015, we did EMF exposures and assessed the alteration of rats’ ovarian follicles. Thirty three-month old rats were selected randomly from laboratory animals, and, after their ages and weights were determined, they were divided randomly into three groups. The control group consisted of 10 rats without any treatment, and they were kept in normal conditions. The second group of rats was influenced by a magnetic field of 50 Hz for eight weeks (three weeks intrauterine and five weeks ectopic). The third group of rats was influenced by a magnetic field of 50 Hz for 13 weeks (three weeks intrauterine and ten weeks ectopic). Samples were fixed in 10% buffered formaldehyde and cleared with Xylol and embedded in paraffin. After sectioning and staining, samples were studied by optic microscopy. Finally, SPSS version 17, were used for data analysis. Results EMF radiation increased the harmful effects on the formation of ovarian follicles and oocytes implantation. Studies on the effects of electromagnetic fields on ovarian follicles have shown that the nuclei of the oocytes become smaller and change shape. There were significant, harmful changes in the groups affected by electromagnetic waves. Atresia of ovarian follicles was significantly significant in both study groups compared to the control group (p < 0.05). Conclusion Exposure to electromagnetic fields during embryonic development can cause morphological changes in oocytes and affect the differentiation of oocytes and folliculogenesis, resulting in decreased ovarian reserve leading to infertility or reduced

  17. Children and adults exposed to low-frequency magnetic fields at the ICNIRP reference levels: theoretical assessment of the induced electric fields.

    PubMed

    Bakker, J F; Paulides, M M; Neufeld, E; Christ, A; Chen, X L; Kuster, N; van Rhoon, G C

    2012-04-01

    To avoid potentially adverse health effects, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined reference levels for time varying magnetic fields. Restrictions on the electric fields induced in the human body are provided based on biological response data for peripheral nerve stimulation and the induction of phosphenes. Numerical modeling is commonly used to assess the induced electric fields for various exposure configurations. The objective of this study was to assess the variations of the electric fields induced in children and adults and to compare the exposure at reference levels with the basic restrictions as function of anatomy. We used the scalar potential finite element method to calculate the induced electric fields in six children and two adults when exposed to uniform magnetic fields polarized in three orthogonal directions. We found that the induced electric fields are within the ICNIRP basic restrictions in nearly all cases. In PNS tissues, we found electric fields up to 95% (upper uncertainty limit due to discretization errors, k = 2) of the ICNIRP basic restrictions for exposures at the general public reference levels. For occupational reference levels, we found an over-exposure of maximum 79% (k = 2) in PNS tissues. We further found that the ICNIRP recommendations on spatial averaging in 2 × 2 × 2 mm³ contiguous tissue volumes and removal of peak values by the 99th percentile cause the results to depend strongly on the grid discretization step (i.e. an uncertainty of more than 50% at 2 mm) and the number of distinguished tissues in the anatomical models. The computational results obtained by various research institutes should be robust for different discretization settings and various anatomical models. Therefore, we recommend considering alternative routines for small anatomical structures such as non-contiguous averaging without taking the 99th percentile in future guidelines leading to consistent

  18. Children and adults exposed to low-frequency magnetic fields at the ICNIRP reference levels: theoretical assessment of the induced electric fields

    NASA Astrophysics Data System (ADS)

    Bakker, J. F.; Paulides, M. M.; Neufeld, E.; Christ, A.; Chen, X. L.; Kuster, N.; van Rhoon, G. C.

    2012-04-01

    To avoid potentially adverse health effects, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined reference levels for time varying magnetic fields. Restrictions on the electric fields induced in the human body are provided based on biological response data for peripheral nerve stimulation and the induction of phosphenes. Numerical modeling is commonly used to assess the induced electric fields for various exposure configurations. The objective of this study was to assess the variations of the electric fields induced in children and adults and to compare the exposure at reference levels with the basic restrictions as function of anatomy. We used the scalar potential finite element method to calculate the induced electric fields in six children and two adults when exposed to uniform magnetic fields polarized in three orthogonal directions. We found that the induced electric fields are within the ICNIRP basic restrictions in nearly all cases. In PNS tissues, we found electric fields up to 95% (upper uncertainty limit due to discretization errors, k = 2) of the ICNIRP basic restrictions for exposures at the general public reference levels. For occupational reference levels, we found an over-exposure of maximum 79% (k = 2) in PNS tissues. We further found that the ICNIRP recommendations on spatial averaging in 2 × 2 × 2 mm3 contiguous tissue volumes and removal of peak values by the 99th percentile cause the results to depend strongly on the grid discretization step (i.e. an uncertainty of more than 50% at 2 mm) and the number of distinguished tissues in the anatomical models. The computational results obtained by various research institutes should be robust for different discretization settings and various anatomical models. Therefore, we recommend considering alternative routines for small anatomical structures such as non-contiguous averaging without taking the 99th percentile in future guidelines leading to consistent

  19. The Universal C*-Algebra of the Electromagnetic Field

    NASA Astrophysics Data System (ADS)

    Buchholz, Detlev; Ciolli, Fabio; Ruzzi, Giuseppe; Vasselli, Ezio

    2016-02-01

    A universal C*-algebra of the electromagnetic field is constructed. It is represented in any quantum field theory which incorporates electromagnetism and expresses basic features of the field such as Maxwell's equations, Poincaré covariance and Einstein causality. Moreover, topological properties of the field resulting from Maxwell's equations are encoded in the algebra, leading to commutation relations with values in its center. The representation theory of the algebra is discussed with focus on vacuum representations, fixing the dynamics of the field.

  20. A nonstationary axially symmetric electromagnetic field in a moving sphere

    NASA Astrophysics Data System (ADS)

    Vestyak, V. A.; Tarlakovsky, D. V.

    2015-10-01

    Integral representations of series coefficients for components of an electromagnetic field with nuclei are formulated in the form of Green's functions. Approximate quasi-static analogs are used as these functions. An example of the translational motion of the sphere is presented. Explicit formulas for the components of the electromagnetic field are derived.

  1. A randomized, double-blind, placebo-controlled clinical trial using a low-frequency magnetic field in the treatment of musculoskeletal chronic pain

    PubMed Central

    Thomas, Alex W; Graham, Karissa; Prato, Frank S; McKay, Julia; Forster, Patricia Morley; Moulin, Dwight E; Chari, Sesh

    2007-01-01

    Exposure to a specific pulsed electromagnetic field (PEMF) has been shown to produce analgesic (antinociceptive) effects in many organisms. In a randomized, double-blind, sham-controlled clinical trial, patients with either chronic generalized pain from fibromyalgia (FM) or chronic localized musculoskeletal or inflammatory pain were exposed to a PEMF (400 μT) through a portable device fitted to their head during twice-daily 40 min treatments over seven days. The effect of this PEMF on pain reduction was recorded using a visual analogue scale. A differential effect of PEMF over sham treatment was noticed in patients with FM, which approached statistical significance (P=0.06) despite low numbers (n=17); this effect was not evident in those without FM (P=0.93; n=15). PEMF may be a novel, safe and effective therapeutic tool for use in at least certain subsets of patients with chronic, nonmalignant pain. Clearly, however, a larger randomized, double-blind clinical trial with just FM patients is warranted. PMID:18080043

  2. Inverse Problems of Low-Frequency Diagnostics of the Earth's Crust

    NASA Astrophysics Data System (ADS)

    Gaikovich, K. P.; Smirnov, A. I.

    2015-11-01

    We develop and test (in numerical simulation) methods of computer tomography of distributed under-surface inhomogeneities in the conductivity of a medium and for holography (i.e., reconstruction of the shape) of solid and uniformly composed subsurface objects in the context of the problems of multifrequency electromagnetic diagnostics of the Earth's crust structure in the extremely and ultra low frequency bands. The methods are based on solution of the inverse scattering problem using the results provided by multifrequency measurements of the distribution of complex amplitudes of the electromagnetic field on the surface of the medium under consideration.

  3. Assessment of Electromagnetic Fields at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Ficklen, Carter B.

    1995-01-01

    This report presents the results of an assessment of ElectroMagnetic Fields (EMF) completed at NASA Langley Research Center as part of the Langley Aerospace Research Summer Scholars Program. This project was performed to determine levels of electromagnetic fields, determine the significance of the levels present, and determine a plan to reduce electromagnetic field exposure, if necessary. This report also describes the properties of electromagnetic fields and their interaction with humans. The results of three major occupational epidemiological studies is presented to determine risks posed to humans by EMF exposure. The data for this report came from peer-reviewed journal articles and government publications pertaining to the health effects of electromagnetic fields.

  4. Non-thermal continuous and modulated electromagnetic radiation fields effects on sleep EEG of rats.

    PubMed

    Mohammed, Haitham S; Fahmy, Heba M; Radwan, Nasr M; Elsayed, Anwar A

    2013-03-01

    In the present study, the alteration in the sleep EEG in rats due to chronic exposure to low-level non-thermal electromagnetic radiation was investigated. Two types of radiation fields were used; 900 MHz unmodulated wave and 900 MHz modulated at 8 and 16 Hz waves. Animals has exposed to radiation fields for 1 month (1 h/day). EEG power spectral analyses of exposed and control animals during slow wave sleep (SWS) and rapid eye movement sleep (REM sleep) revealed that the REM sleep is more susceptible to modulated radiofrequency radiation fields (RFR) than the SWS. The latency of REM sleep increased due to radiation exposure indicating a change in the ultradian rhythm of normal sleep cycles. The cumulative and irreversible effect of radiation exposure was proposed and the interaction of the extremely low frequency radiation with the similar EEG frequencies was suggested. PMID:25685416

  5. Excitation of low-frequency waves by auroral electron beams

    NASA Technical Reports Server (NTRS)

    Lin, C. S.; Wong, H. K.; Koga, J.; Burch, J. L.

    1989-01-01

    The electron distribution functions measured by the Dynamics Explorer 1 satellite during an auroral pass in 1981 are used in a linear instability analysis of low-frequency electromagnetic and electrostatic waves near and below the hydrogen gyrofrequency. It is suggested that the low-frequency electric and magnetic noise in the auroral zone might be explained by O and H electromagnetic ion cyclotron waves excited by energetic electron beams. An instability analysis suggests that upward and downward streaming electrons throughout the central plasma sheet region provide the free energy for heating oxygen ion through oxygen electrostatic ion cyclotron waves.

  6. Industrialization, electromagnetic fields, and breast cancer risk.

    PubMed Central

    Kheifets, L I; Matkin, C C

    1999-01-01

    The disparity between the rates of breast cancer in industrialized and less-industrialized regions has led to many hypotheses, including the theory that exposure to light-at-night and/or electromagnetic fields (EMF) may suppress melatonin and that reduced melatonin may increase the risk of breast cancer. In this comprehensive review we consider strengths and weaknesses of more than 35 residential and occupational epidemiologic studies that investigated the association between EMF and breast cancer. Although most of the epidemiologic data do not provide strong support for an association between EMF and breast cancer, because of the limited statistical power as well as the possibility of misclassification and bias present in much of the existing data, it is not possible to rule out a relationship between EMF and breast cancer. We make several specific recommendations for future studies carefully designed to test the melatonin-breast cancer and EMF-breast cancer hypotheses. Future study designs should have sufficient statistical power to detect small to moderate associations; include comprehensive exposure assessments that estimate residential and occupational exposures, including shift work; focus on a relevant time period; control for known breast cancer risks; and pay careful attention to menopausal and estrogen receptor status. PMID:10229714

  7. Interpreting marine controlled source electromagnetic field behaviour with streamlines

    NASA Astrophysics Data System (ADS)

    Pethick, A. M.; Harris, B. D.

    2013-10-01

    Streamlines represent particle motion within a vector field as a single line structure and have been used in many areas of geophysics. We extend the concept of streamlines to interactive three dimensional representations of the coupled vector fields generated during marine controlled source electromagnetic surveys. These vector fields have measurable amplitudes throughout many hundreds of cubic kilometres. Electromagnetic streamline representation makes electromagnetic interactions within complex geo-electrical setting comprehensible. We develop an interface to rapidly compute and interactively visualise the electric and magnetic fields as streamlines for 3D marine controlled source electromagnetic surveys. Several examples highlighting how interactive use has value in marine controlled source electromagnetic survey design, interpretation and teaching are provided. The first videos of electric, magnetic and Poynting vector field streamlines are provided along with the first published example of the airwave represented as streamlines. We demonstrate that the electric field airwave is a circulating vortex moving down and out from the air-water interface towards the ocean floor. The use of interactive streamlines is not limited to marine controlled source electromagnetic methods. Streamlines provides a high level visualisation tool for interpreting the electric and magnetic field behaviour generated by a wide range of electromagnetic survey configurations for complex 3D geo-electrical settings.

  8. Observation of the acceleration by an electromagnetic field of nuclear beta decay

    NASA Astrophysics Data System (ADS)

    Reiss, H. R.

    2008-02-01

    Measurements are reported of the acceleration of the first-forbidden beta decay of 137Cs by exposure to intense, low-frequency electromagnetic fields. Two separate experiments were done: one in a coaxial cavity, and the other in a coaxial transmission line. The first showed an increase in the beta decay rate of (6.8±3.2)×10-4 relative to the natural rate, and the other resulted in an increase of (6.5±2.0)×10- 4. In addition, a Fourier analysis of the rate of 662 keV gamma emission following from the beta decay in the standing-wave experiment showed a clear indication of the frequency with which the external field was switched on and off. A simultaneously detected gamma emission from a placebo nucleus showed no such peak.

  9. Cellular response to exogenous electromagnetic fields. Annual report, October 1986-September 1987

    SciTech Connect

    Goodman, R.; Henderson, A.S.

    1987-09-21

    This research has determined that extremely-low-frequency (ELF) (100-Hz) electromagnetic (EM) fields induce alterations in transcription and translation in dipteran (Drosophila, Sciara) and human (HL60, IB4) cells. Transcriptional autoradiography and endoreplicated chromosomes, as well as analyses of sucrose density-gradient profiles, shows increased uptake of /sup 3/H uridine into RNA following exposure of cells to sinusoidal and asymmetric quasi-rectangular signals for time periods up to 60 minutes. Biochemical analyses (sucrose density gradients, oligo (d) T columns) have demonstrated that the RNA affected by signal stimulation is in the messenger-RNA size class. Quantitative and qualitative alterations also occur in polypeptide synthesis following EM-field stimulation. Major differences are noted from control among all sets analyzed with respect to new and augmented, as well as suppressed and deleted polypeptides. Using hybridization analysis, there is preliminary evidence that cell-specific transcripts are augmented.

  10. Electromagnetic field effects on cells of the immune system: The role of calcium signalling

    SciTech Connect

    Walleczek, J.

    1991-07-01

    During the past decade considerable evidence has accumulated demonstrating the exposures of cells of the immune system to relatively weak extremely-low-frequency (ELF) electromagnetic fields (< 300 Hz) can elicit cellular changes which might be relevant to in-vivo immune activity. However, knowledge about the underlying biological mechanisms by which weak fields induce cellular changes is still very limited. It is generally believed that the cell membrane and Ca{sup 2+} regulated activity is involved in bioactive ELF field-coupling to living systems. This article begins with a short review of the current state of knowledge concerning the effects of nonthermal levels of ELF electromagnetic fields on the biochemistry and activity of immune cells, and then closely examines new results which suggest a role for Ca{sup 2+} in the induction of these cellular field effects. Based on these findings it is proposed that membrane-mediated Ca{sup 2+} signalling processes are involved in the mediation of field effects on the immune system. 64 refs., 2 tabs.

  11. Algebraic structure of general electromagnetic fields and energy flow

    SciTech Connect

    Hacyan, Shahen

    2011-08-15

    Highlights: > Algebraic structure of general electromagnetic fields in stationary spacetime. > Eigenvalues and eigenvectors of the electomagnetic field tensor. > Energy-momentum in terms of eigenvectors and Killing vector. > Explicit form of reference frame with vanishing Poynting vector. > Application of formalism to Bessel beams. - Abstract: The algebraic structures of a general electromagnetic field and its energy-momentum tensor in a stationary space-time are analyzed. The explicit form of the reference frame in which the energy of the field appears at rest is obtained in terms of the eigenvectors of the electromagnetic tensor and the existing Killing vector. The case of a stationary electromagnetic field is also studied and a comparison is made with the standard short-wave approximation. The results can be applied to the general case of a structured light beams, in flat or curved spaces. Bessel beams are worked out as example.

  12. Influence of a multi-layered planetary ground on the propagation of ELF electromagnetic field pulses

    NASA Astrophysics Data System (ADS)

    Kulak, Andrzej; Mlynarczyk, Janusz; Kozakiewicz, Joanna

    2013-04-01

    Electrical discharges in planetary atmospheres generate short electromagnetic field pulses that propagate in ground-ionosphere waveguides over long distances as TEM waves. Due to waveguide dispersion the waveform of the ELF (Extremely Low Frequency) electromagnetic field pulses change significantly with the distance. Planetary crusts with a low electric conductivity have a particularly strong influence on ELF radiowave propagation in the ground-ionosphere waveguides due to the penetration of the ground by the wave's electromagnetic field. For a known distance from the source the waveform's shape allows investigating waveguide propagation properties. When the model of the lower ionosphere is known, contribution of the ground to the propagation parameters of the waveguide can be derived. A method based on this principle can be useful in a study of electrical properties of the ground especially on planets where the atmospheric discharges are not frequent enough to continuously generate Schumann resonances. In this work we present and analytical model of the ELF radiowave propagation in ground-ionosphere waveguides with multi-layered ground. We have developed equations that enable us to include different ground models in propagation equations using the concept of complex altitude. The model let us conclude that the influence of the ground on the ELF radiowave propagation is particularly strong when the field penetrates through a low conductivity layer of a planetary crust into a higher conductivity layer or the mantle, and a distinct boundary between the two layers leads to interferences in wave propagation in the upper layer and to a significant change in the propagation parameters of the ground-ionosphere waveguide. We envisage technical possibility of measurement of the magnetic field component of the electromagnetic waves generated by short electric discharges in the Martian atmosphere. The presented model can be useful in studies of ELF radiowave propagation on

  13. LOFAR, the low frequency array

    NASA Astrophysics Data System (ADS)

    Vermeulen, R. C.

    2012-09-01

    LOFAR, the Low Frequency Array, is a next-generation radio telescope designed by ASTRON, with antenna stations concentrated in the north of the Netherlands and currently spread into Germany, France, Sweden and the United Kingdom; plans for more LOFAR stations exist in several other countries. Utilizing a novel, phased-array design, LOFAR is optimized for the largely unexplored low frequency range between 30 and 240 MHz. Digital beam-forming techniques make the LOFAR system agile and allow for rapid re-pointing of the telescopes as well as the potential for multiple simultaneous observations. Processing (e.g. cross-correlation) takes place in the LOFAR BlueGene/P supercomputer, and associated post-processing facilities. With its dense core (inner few km) array and long (more than 1000 km) interferometric baselines, LOFAR reaches unparalleled sensitivity and resolution in the low frequency radio regime. The International LOFAR Telescope (ILT) is now issuing its first call for observing projects that will be peer reviewed and selected for observing starting in December. Part of the allocations will be made on the basis of a fully Open Skies policy; there are also reserved fractions assigned by national consortia in return for contributions from their country to the ILT. In this invited talk, the gradually expanding complement of operationally verified observing modes and capabilities are reviewed, and some of the exciting first astronomical results are presented.

  14. On Projecting Discretized Electromagnetic Fields with Unstructured Grids

    SciTech Connect

    Lee, Lie-Quan; Candel, Arno; Kabel, Andrea; Li, Zenghai; /SLAC

    2008-08-13

    A new method for projecting discretized electromagnetic fields on one unstructured grid to another grid is presented in this paper. Two examples are used for studying the errors of different projection methods. The analysis shows that the new method is very effective on balancing both the error of the electric field and that of the magnetic field (or curl of the electric field).

  15. Neutrino spin dynamics in dense matter and electromagnetic field

    NASA Astrophysics Data System (ADS)

    Arbuzova, E. V.; Lobanov, A. E.; Murchikova, E. M.

    2009-01-01

    A complete set of solutions to the Dirac-Pauli equation is derived for a massive neutrino that interacts with dense matter and a strong electromagnetic field. It is shown that these solutions may describe neutrino spin precession.

  16. Probing the electromagnetic field distribution within a metallic nanodisk.

    PubMed

    Meneses-Rodríguez, David; Ferreiro-Vila, Elías; Prieto, Patricia; Anguita, José; González, María U; García-Martín, José M; Cebollada, Alfonso; García-Martín, Antonio; Armelles, Gaspar

    2011-12-01

    A Co nanolayer is used as a local probe to evaluate the vertical inhomogeneous distribution of the electromagnetic (EM) field within a resonant metallic nanodisk. Taking advantage of the direct relation between the magneto-optical activity and the electromagnetic field intensity in the Co layer, it is shown that the nonuniform EM distribution within the nanodisk under plasmon resonant conditions has maximum values close to the upper and lower flat faces, and a minimum value in the middle. PMID:21972067

  17. Effects of Electromagnetic Fields on Fish and Invertebrates

    SciTech Connect

    Schultz, Irvin R.; Woodruff, Dana L.; Marshall, Kathryn E.; Pratt, William J.; Roesijadi, Guritno

    2010-10-13

    In this progress report, we describe the preliminary experiments conducted with three fish and one invertebrate species to determine the effects of exposure to electromagnetic fields. During fiscal year 2010, experiments were conducted with coho salmon (Onchrohychus kisutch), California halibut (Paralicthys californicus), Atlantic halibut (Hippoglossus hippoglossus), and Dungeness crab (Cancer magister). The work described supports Task 2.1.3: Effects on Aquatic Organisms, Subtask 2.1.3.1: Electromagnetic Fields.

  18. Magnetic fields and nonthermal electromagnetic radiation of stars

    NASA Astrophysics Data System (ADS)

    Kryvdyk, Volodymyr

    2016-07-01

    The results of the astrophysical observations of the magnetic fields and the nonthermal electromagnetic radiation of stars and the mechanisms generation of the nonthermal electromagnetic radiation from the magnetized stars of different spectral classes on the different stages their evolution are present. Results of observations allow to calculate the plasma parameters and the magnetic fields in areas around magnetized stars where is generated given radiation and their change during stellar evolution.

  19. Electromagnetic fields and potentials generated by massless charged particles

    SciTech Connect

    Azzurli, Francesco; Lechner, Kurt

    2014-10-15

    We provide for the first time the exact solution of Maxwell’s equations for a massless charged particle moving on a generic trajectory at the speed of light. In particular we furnish explicit expressions for the vector potential and the electromagnetic field, which were both previously unknown, finding that they entail different physical features for bounded and unbounded trajectories. With respect to the standard Liénard–Wiechert field the electromagnetic field acquires singular δ-like contributions whose support and dimensionality depend crucially on whether the motion is (a) linear, (b) accelerated unbounded, (c) accelerated bounded. In the first two cases the particle generates a planar shock-wave-like electromagnetic field traveling along a straight line. In the second and third cases the field acquires, in addition, a δ-like contribution supported on a physical singularity-string attached to the particle. For generic accelerated motions a genuine radiation field is also present, represented by a regular principal-part type distribution diverging on the same singularity-string. - Highlights: • First exact solution of Maxwell’s equations for massless charges in arbitrary motion. • Explicit expressions of electromagnetic fields and potentials. • Derivations are rigorous and based on distribution theory. • The form of the field depends heavily on whether the motion is bounded or unbounded. • The electromagnetic field contains unexpected Dirac-delta-function contributions.

  20. Calculating ultra-low-frequency wave power of the compressional magnetic field vs. L and time: multi-spacecraft analysis using the Van Allen probes, THEMIS and GOES

    NASA Astrophysics Data System (ADS)

    Sarris, Theodore E.; Li, Xinlin

    2016-06-01

    Ultra-low-frequency (ULF) pulsations are critical in radial diffusion processes of energetic particles, and the power spectral density (PSD) of these fluctuations is an integral part of the radial diffusion coefficients and of assimilative models of the radiation belts. Using simultaneous measurements from two Geostationary Operational Environmental Satellites (GOES) geosynchronous satellites, three satellites of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft constellation and the two Van Allen probes during a 10-day period of intense geomagnetic activity and ULF pulsations of October 2012, we calculate the PSDs of ULF pulsations at different L shells. By following the time history of measurements at different L it is shown that, during this time, ULF wave power is not enhanced uniformly throughout the magnetosphere but instead is mostly enhanced in the outer L shells, close to the magnetopause, and to a lesser extent in the inner magnetosphere, closer to the plasmapause. Furthermore, by using phase differences between two GOES geosynchronous satellite pairs, we estimate the daily-averaged distribution of power at different azimuthal wave numbers. These results can have significant implications in better defining the effect of radial diffusion in the phase space density of energetic particles for different wave numbers or L shell distributions of ULF power.