Science.gov

Sample records for amplitude-modulated electromagnetic fields

  1. Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies

    PubMed Central

    Zimmerman, Jacquelyn W.; Jimenez, Hugo; Pennison, Michael J.; Brezovich, Ivan; Morgan, Desiree; Mudry, Albert; Costa, Frederico P.; Barbault, Alexandre; Pasche, Boris

    2013-01-01

    In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF) electromagnetic fields (EMF), which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration allows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue- and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer. PMID:24206915

  2. Absorption line CW EPR using an amplitude modulated longitudinal field.

    PubMed

    Fedin, Matvey; Gromov, Igor; Schweiger, Arthur

    2004-11-01

    In standard continuous wave electron paramagnetic resonance (CW-EPR) experiments, the first derivative of absorption lines is detected. This type of a line shape is caused by the magnetic field modulation and is usually an undesired feature, since the sensitivity of CW-EPR drastically decreases with increasing linewidth. A new approach is introduced, which allows for the measurement of absorption line EPR spectra in systems with broad inhomogeneous lines. The method makes use of multiple-photon transitions that are induced in spin systems when a transverse microwave and a longitudinal radio frequency field are simultaneously applied. The absorption lines are obtained by using amplitude modulation of the radio frequency field and slight saturation of the spectral lines. The basics of the new approach are discussed and experimental examples are given. PMID:15504685

  3. Plasma based optical guiding of an amplitude-modulated electromagnetic beam

    NASA Astrophysics Data System (ADS)

    Singh, Mamta; Gupta, D. N.

    2015-06-01

    We propose the stronger optical guiding of an electromagnetic beam in a plasma by considering the amplitude modulation of the fundamental beam. With the advent of high power source of electromagnetic radiation, the electron velocity in a plasma may become quite large (comparable to the light velocity in free space). Thus, the effect of relativistic mass variation must be taken into account. The relativistic effect of the laser propagation in a plasma leads to self-focusing because of the dielectric constant of a plasma being an increasing function of the intensity. The ponderomotive force of the laser beam pushes the electrons out of the region of high intensity, which reduces the local electron density and increases the plasma dielectric function further, leading to even more selffocusing of the laser. In this work, we consider a short pulse laser of finite spot size as an amplitude modulation in time. Our findings show an efficient optical guiding mechanism based on amplitude modulation signal propagation in plasmas. Medium nonlinearity becomes stronger if an amplitude modulated beam is introduced, which contributes significantly in laser guiding in plasmas. Furthermore, the rate of laser self-focusing is increased with modulation index due the fact of stronger Kerr effect. The study related to amplitude modulated optical signal may be useful for communication technology.

  4. Amplitude modulation detection by human listeners in sound fields

    PubMed Central

    Zahorik, Pavel; Kim, Duck O.; Kuwada, Shigeyuki; Anderson, Paul W.; Brandewie, Eugene; Srinivasan, Nirmal

    2011-01-01

    The temporal modulation transfer function (TMTF) approach allows techniques from linear systems analysis to be used to predict how the auditory system will respond to arbitrary patterns of amplitude modulation (AM). Although this approach forms the basis for a standard method of predicting speech intelligibility based on estimates of the acoustical modulation transfer function (MTF) between source and receiver, human sensitivity to AM as characterized by the TMTF has not been extensively studied under realistic listening conditions, such as in reverberant sound fields. Here, TMTFs (octave bands from 2 – 512 Hz) were obtained in 3 listening conditions simulated using virtual auditory space techniques: diotic, anechoic sound field, reverberant room sound field. TMTFs were then related to acoustical MTFs estimated using two different methods in each of the listening conditions. Both diotic and anechoic data were found to be in good agreement with classic results, but AM thresholds in the reverberant room were lower than predictions based on acoustical MTFs. This result suggests that simple linear systems techniques may not be appropriate for predicting TMTFs from acoustical MTFs in reverberant sound fields, and may be suggestive of mechanisms that functionally enhance modulation during reverberant listening. PMID:22822417

  5. Velocity-Field Measurements of an Axisymmetric Separated Flow Subjected to Amplitude-Modulated Excitation

    NASA Technical Reports Server (NTRS)

    Trosin, Barry James

    2007-01-01

    Active flow control was applied at the point of separation of an axisymmetric, backward-facing-step flow. The control was implemented by employing a Helmholtz resonator that was externally driven by an amplitude-modulated, acoustic disturbance from a speaker located upstream of the wind tunnel. The velocity field of the separating/reattaching flow region downstream of the step was characterized using hotwire velocity measurements with and without flow control. Conventional statistics of the data reveal that the separating/reattaching flow is affected by the imposed forcing. Triple decomposition along with conditional averaging was used to distinguish periodic disturbances from random turbulence in the fluctuating velocity component. A significant outcome of the present study is that it demonstrates that amplitude-modulated forcing of the separated flow alters the flow in the same manner as the more conventional method of periodic excitation.

  6. Sensitive detection of vortex-core resonance using amplitude-modulated magnetic field

    NASA Astrophysics Data System (ADS)

    Cui, Xiaomin; Hu, Shaojie; Hidegara, Makoto; Yakata, Satoshi; Kimura, Takashi

    2015-12-01

    Understanding and manipulating the dynamic properties of the magnetic vortices stabilized in patterned ferromagnetic structures are of great interest owing to the superior resonant features with the high thermal stability and their flexible tunability. So far, numerous methods for investigating the dynamic properties of the magnetic vortex have been proposed and demonstrated. However, those techniques have some regulations such as spatial resolution, experimental facility and sensitivity. Here, we develop a simple and sensitive method for investigating the vortex-core dynamics by using the electrically separated excitation and detection circuits. We demonstrate that the resonant oscillation of the magnetic vortex induced by the amplitude- modulated alternating-sign magnetic field is efficiently picked up by the lock-in detection with the modulated frequency. By extending this method, we also investigate the size dependence and the influence of the magneto-static interaction in the resonant property of the magnetic vortex.

  7. Two-level atom driven by an intense amplitude-modulated field

    NASA Astrophysics Data System (ADS)

    Rudolph, Terry; Freedhoff, Helen

    1998-05-01

    We have calculated the entangled eigenstates (dressed states) and spectra of a two-level atom driven by an intense amplitude-modulated field of modulation frequency delta, for both weak and strong modulation amplitudes. The spectra arising with weak modulation are best described by comparison with those of the monochromatically driven atom: For the fluorescence and near-resonance absorption spectra, the central component of the Mollow triplet is unaffected, while the sideband lines are replaced by multiplets with spacing delta and intensity dependent on the ratio of the modulation amplitude to its frequency; in the Autler-Townes spectrum, each line is similarly replaced by a multiplet. For strong modulation, we describe the spectra by comparison with those which arise for an equal amplitude bichromatic (AM with suppressed carrier) driving field: The central lines of the fluorescence and near-resonance absorption multiplets are split into triplet features, while all other lines, as well of those of the Autler-Townes spectra, are split into doublets, with doublet splitting proportional to the amplitude of the carrier frequency. All spectra agree completely with the spectra calculated by numerically solving the optical Bloch equations for the system.

  8. Amplitude modulation detection by human listeners in reverberant sound fields: Effects of prior listening exposure

    PubMed Central

    Zahorik, Pavel; Anderson, Paul W.

    2013-01-01

    Previous work [Zahorik et al., POMA, 15, 050002 (2012)] has reported that for both broadband and narrowband noise carrier signals in a simulated reverberant sound field, human sensitivity to amplitude modulation (AM) is higher than would be predicted based on the acoustical modulation transfer function (MTF) of the listening environment. These results may be suggestive of mechanisms that functionally enhance modulation in reverberant listening, although many details of this enhancement effect are unknown. Given recent findings that demonstrate improvements in speech understanding with prior exposure to reverberant listening environments, it is of interest to determine whether listening exposure to a reverberant room might also influence AM detection in the room, and perhaps contribute to the AM enhancement effect. Here, AM detection thresholds were estimated (using an adaptive 2-alternative forced-choice procedure) in each of two listening conditions: one in which consistent listening exposure to a particular room was provided, and a second that intentionally disrupted listening exposure by varying the room from trial-to-trial. Results suggest that consistent prior listening exposure contributes to enhanced AM sensitivity in rooms. [Work supported by the NIH/NIDCD.] PMID:24163718

  9. Effects of weak microwave fields amplitude modulated at ELF on EEG of symmetric brain areas in rats

    SciTech Connect

    Vorobyov, V.V.; Galchenko, A.A.; Kukushkin, N.I.; Akoev, I.G.

    1997-06-01

    Averaged electroencephalogram (EEG) frequency spectra were studied in eight unanesthetized and unmyorelaxed adult male rats with chronically implanted carbon electrodes in symmetrical somesthetic areas when a weak microwave field, amplitude-modulated at extremely low frequency (ELF) was applied. Intermittent field exposure was used. Hemispheric asymmetry in frequency spectra of an ongoing EEG was characterized by a power decrease in the 1.5--3 Hz range on the left hemisphere and by a power decrease in the 10--14 and 20--30 Hz ranges on the right hemisphere. No differences between control and exposure experiments were shown under these routines of data averaging. Significant elevations of EEG asymmetry in 10--14 Hz range were observed during the first 20 s after four from five onsets of the MW field, when averaged spectra were obtained for every 10 s. Under neither control nor pre- and post-exposure conditions was this effect observed. These results are discussed with respect to interaction of MW fields with the EEG generators.

  10. Surface plasmon transmission through discontinuous conducting surfaces: Plasmon amplitude modulation by grazing scattered fields

    NASA Astrophysics Data System (ADS)

    Mayoral-Astorga, L. A.; Gaspar-Armenta, J. A.; Ramos-Mendieta, F.

    2016-04-01

    We have studied numerically the diffraction of a surface plasmon polariton (SPP) when it encounters a wide multi-wavelength slit in conducting films. As a jump process a SPP is excited beyond the slit by wave scattering at the second slit edge. The exciting radiation is produced when the incident SPP collapses at the first slit edge. We have found that the transmitted SPP supports inherent and unavoidable interference with grazing scattered radiation; the spatial modulation extends to the fields in the diffraction region where a series of low intensity spots arises. We demonstrate that the SPP generated on the second slab depends on the frequency but not on the wave vector of the collapsed SPP; a SPP is transmitted even when the two metals forming the slit are different. The numerical results were obtained using the Finite Difference Time Domain (FDTD) method with a grid size λ/100.

  11. Amplitude modulation detection by human listeners in reverberant sound fields: Carrier bandwidth effects and binaural versus monaural comparison

    PubMed Central

    Zahorik, Pavel; Kim, Duck O.; Kuwada, Shigeyuki; Anderson, Paul W.; Brandewie, Eugene; Collecchia, Regina; Srinivasan, Nirmal

    2012-01-01

    Previous work [Zahorik et al., POMA, 12, 050005 (2011)] has reported that for a broadband noise carrier signal in a simulated reverberant sound field, human sensitivity to amplitude modulation (AM) is higher than would be predicted based on the broadband acoustical modulation transfer function (MTF) of the listening environment. Interpretation of this result was complicated by the fact that acoustical MTFs of rooms are often quite different for different carrier frequency regions, and listeners may have selectively responded to advantageous carrier frequency regions where the effective acoustic modulation loss due to the room was less than indicated by a broadband acoustic MTF analysis. Here, AM sensitivity testing and acoustic MTF analyses were expanded to include narrowband noise carriers (1-octave and 1/3-octave bands centered at 4 kHz), as well as monaural and binaural listening conditions. Narrowband results were found to be consistent with broadband results: In a reverberant sound field, human AM sensitivity is higher than indicated by the acoustical MTFs. The effect was greatest for modulation frequencies above 32 Hz and was present whether the stimulation was monaural or binaural. These results are suggestive of mechanisms that functionally enhance modulation in reverberant listening. PMID:23437416

  12. 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.

  13. Amplitude Modulator Chassis

    SciTech Connect

    Erbert, G

    2009-09-01

    The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 ps apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.

  14. Treating Cancer with Amplitude-Modulated Electromagnetic Fields: A Potential Paradigm Shift, Again?

    EPA Science Inventory

    The Zimmerman et al. (2011) study published here, coupled with the group's two preceding papers (Barbault et al. (2009), Costa et al. (2011)), identify a potential modality for treating tumors at a dramatic reduction in trauma and cost. This set of clinical and explanatory labora...

  15. 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 ...

  16. Pulse amplitude modulated chlorophyll fluorometer

    SciTech Connect

    Greenbaum, Elias; Wu, Jie

    2015-12-29

    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  17. 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…

  18. 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.

  19. Self-demodulation of amplitude-modulated signal components in amplitude-modulated bone-conducted ultrasonic hearing

    NASA Astrophysics Data System (ADS)

    Ito, Kazuhito; Nakagawa, Seiji

    2015-07-01

    A novel hearing aid system utilizing amplitude-modulated bone-conducted ultrasound (AM-BCU) is being developed for use by profoundly deaf people. However, there is a lack of research on the acoustic aspects of AM-BCU hearing. In this study, acoustic fields in the ear canal under AM-BCU stimulation were examined with respect to the self-demodulation effect of amplitude-modulated signal components generated in the ear canal. We found self-demodulated signals with an audible sound pressure level related to the amplitude-modulated signal components of bone-conducted ultrasonic stimulation. In addition, the increases in the self-demodulated signal levels at low frequencies in the ear canal after occluding the ear canal opening, i.e., the positive occlusion effect, indicate the existence of a pathway by which the self-demodulated signals pass through the aural cartilage and soft tissue, and radiate into the ear canal.

  20. Graphene based plasmonic terahertz amplitude modulator operating above 100 MHz

    NASA Astrophysics Data System (ADS)

    Jessop, D. S.; Kindness, S. J.; Xiao, L.; Braeuninger-Weimer, P.; Lin, H.; Ren, Y.; Ren, C. X.; Hofmann, S.; Zeitler, J. A.; Beere, H. E.; Ritchie, D. A.; Degl'Innocenti, R.

    2016-04-01

    The terahertz (THz) region of the electromagnetic spectrum holds great potential in many fields of study, from spectroscopy to biomedical imaging, remote gas sensing, and high speed communication. To fully exploit this potential, fast optoelectronic devices such as amplitude and phase modulators must be developed. In this work, we present a room temperature external THz amplitude modulator based on plasmonic bow-tie antenna arrays with graphene. By applying a modulating bias to a back gate electrode, the conductivity of graphene is changed, which modifies the reflection characteristics of the incoming THz radiation. The broadband response of the device was characterized by using THz time-domain spectroscopy, and the modulation characteristics such as the modulation depth and cut-off frequency were investigated with a 2.0 THz single frequency emission quantum cascade laser. An optical modulation cut-off frequency of 105 ± 15 MHz is reported. The results agree well with a lumped element circuit model developed to describe the device.

  1. 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.

  2. 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.

  3. Generation of nondiffracting quasi-circular polarization beams using an amplitude modulated phase hologram.

    PubMed

    Yuan, G H; Wei, S B; Yuan, X-C

    2011-08-01

    We propose an approach to the generation of nondiffracting quasi-circularly polarized beams by a highly focusing azimuthally polarized beam using an amplitude modulated spiral phase hologram. Numerical verifications are implemented in the calculation of the electromagnetic fields and Poynting vector field near the focus based on the vector diffraction theory, and the polarization of the wavefront near the focal plane is analyzed in detail by calculating the Stokes polarization parameters. It is found that the electric field, magnetic field, and Poynting vector field can simultaneously be uniform and nondiverging over a relatively long axial range of ~7.23λ. In the transverse plane, the ellipticity and azimuthal angle of the local polarization ellipse varies from point to point. No polarization singularity and phase singularity are found at the beam center, which makes the bright spot possible. PMID:21811334

  4. Tailoring quantum superpositions with linearly polarized amplitude-modulated light

    SciTech Connect

    Pustelny, S.; Koczwara, M.; Cincio, L.; Gawlik, W.

    2011-04-15

    Amplitude-modulated nonlinear magneto-optical rotation is a powerful technique that offers a possibility of controllable generation of given quantum states. In this paper, we demonstrate creation and detection of specific ground-state magnetic-sublevel superpositions in {sup 87}Rb. By appropriate tuning of the modulation frequency and magnetic-field induction the efficiency of a given coherence generation is controlled. The processes are analyzed versus different experimental parameters.

  5. 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.

  6. 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.

  7. 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

  8. Evaluation of the electromagnetic field level emitted by medium frequency AM broadcast stations.

    PubMed

    Licitra, G; Bambini, S; Barellini, A; Monorchio, A; Rogovich, A

    2004-01-01

    In order to estimate the level of the electromagnetic field produced by telecommunication systems, different computational techniques can be employed whose complexity depends on the accuracy of the final results. In this paper, we present the validation of a code based on the method of moments that allows us to analyse the electromagnetic field emitted by radio-communication systems operating at medium frequencies. The method is able to provide an accurate estimate of the levels of electromagnetic field produced by this type of device and, consequently, it can be used as a method for verifying the compliance of the system with the safe exposure level regulations and population protection laws. Some numerical and experimental results are shown relevant to an amplitude modulated (AM) radio transmitter, together with the results of a forthcoming system that will be operative in the near future. PMID:15550708

  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. 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…

  11. 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.

  12. 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.

  13. Shaping symmetric Airy beam through binary amplitude modulation for ultralong needle focus

    SciTech Connect

    Fang, Zhao-Xiang; Gong, Lei; Ren, Yu-Xuan; Vaveliuk, Pablo; Chen, Yue; Lu, Rong-De

    2015-11-28

    Needle-like electromagnetic field has various advantages for the applications in high-resolution imaging, Raman spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device. Such amplitude modulation technique is able to shape traditional Airy beams, SABs, as well as the dynamic transition modes between the one-dimensional and two-dimensional (2D) symmetric Airy modes. The created 2D SAB was characterized through measurement of the propagating fields with one of the four main lobes blocked by an opaque mask. The 2D SAB was verified to exhibit self-healing property against propagation with the obstructed major lobe reconstructed after a certain distance. We further produced an elongated focal line by concentrating the SAB via lenses with different NAs and achieved an ultralong longitudinal needle focus. The produced long needle focus will be applied in optical, chemical, and biological sciences.

  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. [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

  16. 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

  17. Amplitude Modulation Mode of Scanning Ion Conductance Microscopy.

    PubMed

    Li, Peng; Liu, Lianqing; Yang, Yang; Zhou, Lei; Wang, Dong; Wang, Yuechao; Li, Guangyong

    2015-08-01

    Live-cell imaging at the nanoscale resolution is a hot research topic in the field of life sciences for the direct observation of cellular biological activity. Scanning ion conductance microscopy (SICM) is one of the few effective imaging tools for live-cell imaging at the nanoscale resolution. However, there are various problems in existing scanning modes. The hopping and AC modes suffer from low speed, whereas the DC mode is prone to instability because of the DC drift and external electrical interference. In this article, we propose an amplitude modulation (AM) mode of SICM, which employs an AC voltage to enhance the stability and improve the scanning speed. In this AM mode, we introduce a capacitance compensation method to eliminate capacitance effect and use the amplitude of the AC current component to control the tip movement. Experimental results on polydimethylsiloxane samples verify the validity of the AM mode and demonstrate an improved performance of both speed and stability of this new mode. PMID:25759185

  18. Modulator-free quadrature amplitude modulation signal synthesis

    NASA Astrophysics Data System (ADS)

    Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O'Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan

    2014-12-01

    The ability to generate high-speed on-off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5 Gbit s-1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on-off-keyed 10 Gbit s-1 systems and is absolutely prohibitive for today’s (>)100 Gbit s-1 coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions.

  19. Modulator-free quadrature amplitude modulation signal synthesis

    PubMed Central

    Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O’Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan

    2014-01-01

    The ability to generate high-speed on–off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5 Gbit s−1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on–off-keyed 10 Gbit s−1 systems and is absolutely prohibitive for today’s (>)100 Gbit s−1 coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions. PMID:25523757

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Amplitude modulation reduces loudness adaptation to high-frequency tones.

    PubMed

    Wynne, Dwight P; George, Sahara E; Zeng, Fan-Gang

    2015-07-01

    Long-term loudness perception of a sound has been presumed to depend on the spatial distribution of activated auditory nerve fibers as well as their temporal firing pattern. The relative contributions of those two factors were investigated by measuring loudness adaptation to sinusoidally amplitude-modulated 12-kHz tones. The tones had a total duration of 180 s and were either unmodulated or 100%-modulated at one of three frequencies (4, 20, or 100 Hz), and additionally varied in modulation depth from 0% to 100% at the 4-Hz frequency only. Every 30 s, normal-hearing subjects estimated the loudness of one of the stimuli played at 15 dB above threshold in random order. Without any amplitude modulation, the loudness of the unmodulated tone after 180 s was only 20% of the loudness at the onset of the stimulus. Amplitude modulation systematically reduced the amount of loudness adaptation, with the 100%-modulated stimuli, regardless of modulation frequency, maintaining on average 55%-80% of the loudness at onset after 180 s. Because the present low-frequency amplitude modulation produced minimal changes in long-term spectral cues affecting the spatial distribution of excitation produced by a 12-kHz pure tone, the present result indicates that neural synchronization is critical to maintaining loudness perception over time. PMID:26233027

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. [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

  14. 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.

  15. Extending single molecule fluorescence observation time by amplitude-modulated excitation

    PubMed Central

    Kisley, Lydia; Chang, Wei-Shun; Cooper, David; Mansur, Andrea P; Landes, Christy F

    2014-01-01

    We present a hardware-based method that can improve single molecule fluorophore observation time by up to 1500% and super-localization by 47% for the experimental conditions used. The excitation was modulated using an acousto-optic modulator (AOM) synchronized to the data acquisition and inherent data conversion time of the detector. The observation time and precision in super-localization of four commonly used fluorophores were compared under modulated and traditional continuous excitation, including direct total internal reflectance excitation of Alexa 555 and Cy3, non-radiative Förster resonance energy transfer (FRET) excited Cy5, and direct epi-fluorescence wide field excitation of Rhodamine 6G. The proposed amplitude-modulated excitation does not perturb the chemical makeup of the system or sacrifice signal and is compatible with multiple types of fluorophores. Amplitude-modulated excitation has practical applications for any fluorescent study utilizing an instrumental setup with time-delayed detectors. PMID:24587894

  16. Quantitative security evaluation of optical encryption using hybrid phase- and amplitude-modulated keys.

    PubMed

    Sarkadi, Tamás; Koppa, Pál

    2012-02-20

    In the increasing number of system approaches published in the field of optical encryption, the security level of the system is evaluated by qualitative and empirical methods. To quantify the security of the optical system, we propose to use the equivalent of the key length routinely used in algorithmic encryption. We provide a calculation method of the number of independent keys and deduce the binary key length for optical data encryption. We then investigate and optimize the key length of the combined phase- and amplitude-modulated key encryption in the holographic storage environment, which is one of the promising solutions for the security enhancement of single- and double-random phase-encoding encryption and storage systems. We show that a substantial growth of the key length can be achieved by optimized phase and amplitude modulation compared to phase-only encryption. We also provide experimental confirmation of the model results. PMID:22358164

  17. 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

  18. Symbol rate identification for auxiliary amplitude modulation optical signal

    NASA Astrophysics Data System (ADS)

    Wei, Junyu; Dong, Zhi; Huang, Zhiping; Zhang, Yimeng

    2016-09-01

    In this paper, we creatively propose and demonstrate a method for symbol rate identification (SRI) of auxiliary amplitude modulation (AAM) optical signal based on asynchronous delay-tap sampling (ADTS) and average magnitude difference function (AMDF). The method can accurately estimate symbol rate and has large transmission impairments tolerance. Furthermore, it can be realized in the digital signal processor (DSP) with low logical resources because of multiplication-free. In order to improve the accuracy of SRI, the peak to valley ratio (PTVR) of AMDF is introduced into our method for blind chromatic dispersion (CD) compensation. The results of the numerical simulations show that the overall maximum SRI error is smaller 0.079% for return-to-zero (RZ) on-off keying (OOK), RZ differential phase-shift keying (DPSK), RZ differential quadrature phase-shift keying (DQPSK) and RZ 16-ary quadrature amplitude modulation (QAM) with 50% duty cycles.

  19. Amplitude Modulation in the ZZ Ceti Star GD 244

    NASA Astrophysics Data System (ADS)

    Bognár, Zs.; Paparó, M.; Molnár, L.; Plachy, E.; Sódor, Á.

    2015-06-01

    Previous studies of GD 244 revealed seven pulsation frequencies (two doublets and three single periods) in the light variations of the star. The data obtained at McDonald Observatory between 2003 and 2006, and our additional measurements in 2006 and 2007 at Konkoly Observatory, allow the investigation of the long-term pulsational behaviour of GD 244. We found that the 307.1 s period component of one of the doublets show long-term, periodic amplitude modulation with a time scale of ˜ 740 days. Possible explanations are that nonlinear resonant mode coupling is operating among the rotationally split frequency components, or two modes, unresolved in the yearly data are excited at ˜ 307.1 s. This is the first time that such long-term periodic amplitude modulation is published on a ZZ Ceti star.

  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. 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.

  2. 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.

  3. 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.

  4. Focusing through a turbid medium by amplitude modulation with genetic algorithm

    NASA Astrophysics Data System (ADS)

    Dai, Weijia; Peng, Ligen; Shao, Xiaopeng

    2014-05-01

    Multiple scattering of light in opaque materials such as white paint and human tissue forms a volume speckle field, will greatly reduce the imaging depth and degrade the imaging quality. A novel approach is proposed to focus light through a turbid medium using amplitude modulation with genetic algorithm (GA) from speckle patterns. Compared with phase modulation method, amplitude modulation approach, in which the each element of spatial light modulator (SLM) is either zero or one, is much easier to achieve. Theoretical and experimental results show that, the advantage of GA is more suitable for low the signal to noise ratio (SNR) environments in comparison to the existing amplitude control algorithms such as binary amplitude modulation. The circular Gaussian distribution model and Rayleigh Sommerfeld diffraction theory are employed in our simulations to describe the turbid medium and light propagation between optical devices, respectively. It is demonstrated that the GA technique can achieve a higher overall enhancement, and converge much faster than others, and outperform all algorithms at high noise. Focusing through a turbid medium has potential in the observation of cells and protein molecules in biological tissues and other structures in micro/nano scale.

  5. 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.

  6. 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.

  7. 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.

  8. Light focusing through strongly scattering media by binary amplitude modulation

    NASA Astrophysics Data System (ADS)

    Huang, Hui-ling; Sun, Cun-zhi; Chen, Zi-yang; Pu, Ji-xiong

    2015-07-01

    Based on the angular spectrum method and the circular Gaussian distribution (CGD) model of scattering media, we numerically simulate light focusing through strongly scattering media. A high contrast focus in the target area is produced by using feedback optimization algorithm with binary amplitude modulation. It is possible to form the focusing with one focus or multiple foci at arbitrary areas. The influence of the number of square segments of spatial light modulation on the enhancement factor of intensity is discussed. Simulation results are found to be in good agreement with theoretical analysis for light refocusing.

  9. Amplitude Modulation in the δ Sct star KIC 7106205

    NASA Astrophysics Data System (ADS)

    Bowman, Dominic. M.; Kurtz, Donald W.

    2015-09-01

    The δ Sct star KIC 7106205 showed amplitude modulation in a single p mode, whilst all other p and g modes remained stable in amplitude and phase over 1470 d of the Kepler dataset. The data were divided into 30 time bins of equal length and a series of consecutive Fourier transforms was calculated. A fixed frequency, calculated from a least-squares fit of all data, allowed amplitude and phase for every mode in each time bin to be tracked. The missing p mode energy was not transferred to any other visible modes.

  10. Superposed pulse amplitude modulation for visible light communication.

    PubMed

    Li, J F; Huang, Z T; Zhang, R Q; Zeng, F X; Jiang, M; Ji, Y F

    2013-12-16

    We propose and experimentally demonstrate a novel modulation scheme called superposed pulse amplitude modulation (SPAM) which is low-cost, insensitive to non-linearity of light emitting diode (LED). Multiple optical pulses transmit parallelly from different spatial position in the LED array and overlap linearly in free space to realize SPAM. With LED arrangement, the experimental results show that using the modulation we proposed the data rate of 120 Mbit/s with BER 1 × 10(-3) can be achieved with an optical blue filter and RC post-equalization. PMID:24514674

  11. 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

  12. Detection and rate discrimination of amplitude modulation in electrical hearing.

    PubMed

    Chatterjee, Monita; Oberzut, Cherish

    2011-09-01

    Three experiments were designed to examine temporal envelope processing by cochlear implant (CI) listeners. In experiment 1, the hypothesis that listeners' modulation sensitivity would in part determine their ability to discriminate between temporal modulation rates was examined. Temporal modulation transfer functions (TMTFs) obtained in an amplitude modulation detection (AMD) task were compared to threshold functions obtained in an amplitude modulation rate discrimination (AMRD) task. Statistically significant nonlinear correlations were observed between the two measures. In experiment 2, results of loudness-balancing showed small increases in the loudness of modulated over unmodulated stimuli beyond a modulation depth of 16%. Results of experiment 3 indicated small but statistically significant effects of level-roving on the overall gain of the TMTF, but no impact of level-roving on the average shape of the TMTF across subjects. This suggested that level-roving simply increased the task difficulty for most listeners, but did not indicate increased use of intensity cues under more challenging conditions. Data obtained with one subject, however, suggested that the most sensitive listeners may derive some benefit from intensity cues in these tasks. Overall, results indicated that intensity cues did not play an important role in temporal envelope processing by the average CI listener. PMID:21895095

  13. 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.

  14. 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.

  15. Shuttle extravehicular activity signal processor pulse amplitude modulation decommutator

    NASA Technical Reports Server (NTRS)

    Noble, D. E.; Conrad, W. M.

    1974-01-01

    To provide data with long-term stability and accuracy, the pulse amplitude modulation (PAM) decommutator was synchronized to the PAM-return to zero wavetrain, and each channel was sampled with a common sample and hold circuit and digitized sequentially. The digital value of each channel was then scaled by the digital value of the calibration channels. The corrected digital value of each channel was stored for one complete frame and then transferred to the multiplexer-demultiplexer at a high rate in one block of serial digital data. A test model was built to demonstrate this design approach taken for the PAM decom and performance data was provided. The accuracies obtained with various signal to noise ratios are shown.

  16. Double-Referential Holography and Spatial Quadrature Amplitude Modulation

    NASA Astrophysics Data System (ADS)

    Zukeran, Keisuke; Okamoto, Atsushi; Takabayashi, Masanori; Shibukawa, Atsushi; Sato, Kunihiro; Tomita, Akihisa

    2013-09-01

    We proposed a double-referential holography (DRH) that allows phase-detection without external additional beams. In the DRH, phantom beams, prepared in the same optical path as signal beams and preliminary multiplexed in a recording medium along with the signal, are used to produce interference fringes on an imager for converting a phase into an intensity distribution. The DRH enables stable and high-accuracy phase detection independent of the fluctuations and vibrations of the optical system owing to medium shift and temperature variation. Besides, the collinear arrangement of the signal and phantom beams leads to the compactness of the optical data storage system. We conducted an experiment using binary phase modulation signals for verifying the DRH operation. In addition, 38-level spatial quadrature amplitude modulation signals were successfully reproduced with the DRH by numerical simulation. Furthermore, we verified that the distributed phase-shifting method moderates the dynamic range consumption for the exposure of phantom beams.

  17. Phonological awareness and sinusoidal amplitude modulation in phonological dislexia.

    PubMed

    Peñaloza-López, Yolanda; Herrera-Rangel, Aline; Pérez-Ruiz, Santiago J; Poblano, Adrián

    2016-04-01

    Objective Dyslexia is the difficulty of children in learning to read and write as results of neurological deficiencies. The objective was to test the Phonological awareness (PA) and Sinusoidal amplitude modulation (SAM) threshold in children with Phonological dyslexia (PD). Methods We performed a case-control, analytic, cross sectional study. We studied 14 children with PD and 14 control children from 7 to 11 years of age, by means of PA measurement and by SAM test. The mean age of dyslexic children was 8.39 years and in the control group was 8.15. Results Children with PD exhibited inadequate skills in PA, and SAM. We found significant correlations between PA and SAM at 4 Hertz frequency, and calculated regression equations that predicts between one-fourth and one-third of variance of measurements. Conclusion Alterations in PA and SAM found can help to explain basis of deficient language processing exhibited by children with PD. PMID:27097001

  18. 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).

  19. 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.

  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. Human Neuromagnetic Steady-State Responses to Amplitude-Modulated Tones, Speech, and Music

    PubMed Central

    Parkkonen, Lauri; Hari, Riitta

    2014-01-01

    Objectives: Auditory steady-state responses that can be elicited by various periodic sounds inform about subcortical and early cortical auditory processing. Steady-state responses to amplitude-modulated pure tones have been used to scrutinize binaural interaction by frequency-tagging the two ears’ inputs at different frequencies. Unlike pure tones, speech and music are physically very complex, as they include many frequency components, pauses, and large temporal variations. To examine the utility of magnetoencephalographic (MEG) steady-state fields (SSFs) in the study of early cortical processing of complex natural sounds, the authors tested the extent to which amplitude-modulated speech and music can elicit reliable SSFs. Design: MEG responses were recorded to 90-s-long binaural tones, speech, and music, amplitude-modulated at 41.1 Hz at four different depths (25, 50, 75, and 100%). The subjects were 11 healthy, normal-hearing adults. MEG signals were averaged in phase with the modulation frequency, and the sources of the resulting SSFs were modeled by current dipoles. After the MEG recording, intelligibility of the speech, musical quality of the music stimuli, naturalness of music and speech stimuli, and the perceived deterioration caused by the modulation were evaluated on visual analog scales. Results: The perceived quality of the stimuli decreased as a function of increasing modulation depth, more strongly for music than speech; yet, all subjects considered the speech intelligible even at the 100% modulation. SSFs were the strongest to tones and the weakest to speech stimuli; the amplitudes increased with increasing modulation depth for all stimuli. SSFs to tones were reliably detectable at all modulation depths (in all subjects in the right hemisphere, in 9 subjects in the left hemisphere) and to music stimuli at 50 to 100% depths, whereas speech usually elicited clear SSFs only at 100% depth. The hemispheric balance of SSFs was toward the right hemisphere

  3. 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.

  4. Measurement of the orbit fluctuation caused by an insertion device with the amplitude modulation method

    NASA Astrophysics Data System (ADS)

    Nakatani, T.; Agui, A.; Yoshigoe, A.; Matsushita, T.; Takao, M.; Aoyagi, H.; Takeuchi, M.; Tanaka, H.

    2004-05-01

    We have developed a new method to extract only the orbit fluctuation caused by changing magnetic field error of an insertion device (ID). This method consists of two main parts. (i) The orbit fluctuation is measured with modulating the error field of the ID by using the real-time beam position measuring system. (ii) The orbit fluctuation depending on the variation of the error field of the ID is extracted by the filter applying the Wavelet Transform. We call this approach the amplitude modulation method. This analysis technique was applied to measure the orbit fluctuation caused by the error field of APPLE-2 type undulator (ID23) installed in the SPring-8 storage ring. We quantitatively measured two kinds of the orbit fluctuation which are the static term caused by the magnetic field error and the dynamic term caused by the eddy current on the ID23 chamber.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. Amplitude modulated heterodyne reflectometer for density profile and density fluctuation profile measurements at W7-AS

    SciTech Connect

    Hirsch, M.; Hartfuss, H.; Geist, T.; de la Luna, E.

    1996-05-01

    A broadband heterodyne reflectometer operating in the frequency range 75{endash}110 GHz in extraordinary mode polarization is used at the W7-AS stellarator for both fast density profile determination and density fluctuation studies. The probing signal is amplitude modulated at a frequency 133 MHz using the envelope phase for profile evaluation and the carrier phase to determine the fluctuation information simultaneously. Separate Gaussian beam optics for final signal launch and detection permits a beam waist of about 2 cm at the reflecting layer in the plasma. Amplitude modulated detection is accomplished in the intermediate frequency part by synchronous detection after recovery of the carrier by narrow-band filtering. Voltage controlled solid state oscillators followed by active frequency multiplication allow to scan the full frequency band within less than 1 ms. For typical W7-AS operation the accessible density range is 1{times}10{sup 19} to 6{times}10{sup 19} m{sup {minus}3} for on axis magnetic field of 2.5 T and 4.5{times}10{sup 19} to 10{times}10{sup 19} m{sup {minus}3} for 1.25 T, respectively. The probed radial positions range between 0.2{lt}{ital r}/{ital a}{lt}1.1 depending on plasma conditions ({ital a}{approx_equal}17 cm). {copyright} {ital 1996 American Institute of Physics.}

  10. Discriminating Simulated Vocal Tremor Source Using Amplitude Modulation Spectra

    PubMed Central

    Carbonell, Kathy M.; Lester, Rosemary A.; Story, Brad H.; Lotto, Andrew J.

    2014-01-01

    Objectives/Hypothesis Sources of vocal tremor are difficult to categorize perceptually and acoustically. This paper describes a preliminary attempt to discriminate vocal tremor sources through the use of spectral measures of the amplitude envelope. The hypothesis is that different vocal tremor sources are associated with distinct patterns of acoustic amplitude modulations. Study Design Statistical categorization methods (discriminant function analysis) were used to discriminate signals from simulated vocal tremor with different sources using only acoustic measures derived from the amplitude envelopes. Methods Simulations of vocal tremor were created by modulating parameters of a vocal fold model corresponding to oscillations of respiratory driving pressure (respiratory tremor), degree of vocal fold adduction (adductory tremor) and fundamental frequency of vocal fold vibration (F0 tremor). The acoustic measures were based on spectral analyses of the amplitude envelope computed across the entire signal and within select frequency bands. Results The signals could be categorized (with accuracy well above chance) in terms of the simulated tremor source using only measures of the amplitude envelope spectrum even when multiple sources of tremor were included. Conclusions These results supply initial support for an amplitude-envelope based approach to identify the source of vocal tremor and provide further evidence for the rich information about talker characteristics present in the temporal structure of the amplitude envelope. PMID:25532813

  11. Population transfer by an amplitude-modulated pulse

    SciTech Connect

    Vitanov, N.V.; Yatsenko, L.P.; Bergmann, K.

    2003-10-01

    We propose a technique for coherent population inversion of a two-state system, which uses an amplitude-modulated pulse. In the modulation-free adiabatic basis, the modulation introduces oscillating interaction between the adiabatic states. In a second rotating-wave approximation picture, this oscillating interaction induces a pair of level crossings between the energies of the adiabatic states if the modulation frequency is chosen appropriately. By suitably offsetting the modulation with respect to the center of the pulse, one can make the modulation act only in the vicinity of one of these crossings. In a higher-order adiabatic basis, this crossing shows up as an avoided crossing between the energies of the higher-order adiabatic states. As a result robust and efficient population transfer can be achieved between the adiabatic states, and hence, between the original bare states. We derive analytically the conditions on the interaction parameters for this technique and verify them with numerical simulations. Possible experimental implementations are discussed.

  12. Automated force controller for amplitude modulation atomic force microscopy.

    PubMed

    Miyagi, Atsushi; Scheuring, Simon

    2016-05-01

    Atomic Force Microscopy (AFM) is widely used in physics, chemistry, and biology to analyze the topography of a sample at nanometer resolution. Controlling precisely the force applied by the AFM tip to the sample is a prerequisite for faithful and reproducible imaging. In amplitude modulation (oscillating) mode AFM, the applied force depends on the free and the setpoint amplitudes of the cantilever oscillation. Therefore, for keeping the applied force constant, not only the setpoint amplitude but also the free amplitude must be kept constant. While the AFM user defines the setpoint amplitude, the free amplitude is typically subject to uncontrollable drift, and hence, unfortunately, the real applied force is permanently drifting during an experiment. This is particularly harmful in biological sciences where increased force destroys the soft biological matter. Here, we have developed a strategy and an electronic circuit that analyzes permanently the free amplitude of oscillation and readjusts the excitation to maintain the free amplitude constant. As a consequence, the real applied force is permanently and automatically controlled with picoNewton precision. With this circuit associated to a high-speed AFM, we illustrate the power of the development through imaging over long-duration and at various forces. The development is applicable for all AFMs and will widen the applicability of AFM to a larger range of samples and to a larger range of (non-specialist) users. Furthermore, from controlled force imaging experiments, the interaction strength between biomolecules can be analyzed. PMID:27250433

  13. Demonstration of spot size reduction by focussing amplitude modulated radially polarized light on a photoresist

    NASA Astrophysics Data System (ADS)

    Ushakova, K.; van den Berg, Q. Y.; Pereira, S. F.; Urbach, H. P.

    2015-12-01

    Spot size reduction is demonstrated by printing focused spots from amplitude-modulated radially polarized light at the wavelength λ = 405 nm on a photoresist. Amplitude modulation is realized by ring illumination and by application of an optimized amplitude distribution function. Amplitude modulation is implemented via spatial light modulator, which is followed by a specially designed radial wire grid polarizer to obtain high-quality radially polarized light. Comparison between full and amplitude modulated apertures of the written focused spots on a photoresist is performed. Rigorous simulations based on the Richards-Wolf integral are made to confirm experimental data.

  14. 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.

  15. 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.

  16. Optical binary switch and amplitude modulator micromirror arrays

    NASA Astrophysics Data System (ADS)

    Kolesar, Edward S., Jr.; Allen, Peter B.; Boydston, Noah C.; Howard, Jeffrey T.; Ko, Simon Y.; Wilken, Josh M.

    1999-09-01

    Five types of micromirror arrays were designed and fabricated using a three-level, polysilicon, surface micromachined, micro-electromechanical systems (MEMS) process. The electrostatically deflectable micromirror designs included arrays of simple cantilever beams, torsion beams, tethered (piston-style) beams, circular membranes, and oval membranes. The smallest micromirror element was the simple cantilever beam, measuring 50 micrometer square. The largest micromirror element was the oval membrane; it possessed an active optical surface that was 320 micrometer by 920 micrometer. Each of the remaining micromirror designs have gold-coated polysilicon optical surfaces with geometries between these two limits. Electrostatically induced vertical deflections on the order of 2.75 micrometer were achieved. The torsion beam micromirror design exhibits both in-plane and out-of-plane deflection. The other micromirror designs only manifest in-plane deflections. The modeling phase focused on the microdynamical behavior of the torsion beam micromirror. The IntelliCADR finite element analysis program was used to generate a plot of the micromirror's deflection (d) versus applied direct current voltage (V). The data was least-squares fitted to the well- established V varies direct as d3/2 relationship. A resonant frequency analysis predicted an approximate switching speed of 6 microseconds. The reliability (number of operational cycles) of each micromirror design, when operated with a rectified 60 Hz alternating current (ac) signal, was measured to exceed more than 1 million flexure events. Experimental evidence supporting the potential for using micromirrors as binary optical switches and amplitude modulators is also addressed.

  17. Roles for Coincidence Detection in Coding Amplitude-Modulated Sounds

    PubMed Central

    Ashida, Go; Kretzberg, Jutta; Tollin, Daniel J.

    2016-01-01

    Many sensory neurons encode temporal information by detecting coincident arrivals of synaptic inputs. In the mammalian auditory brainstem, binaural neurons of the medial superior olive (MSO) are known to act as coincidence detectors, whereas in the lateral superior olive (LSO) roles of coincidence detection have remained unclear. LSO neurons receive excitatory and inhibitory inputs driven by ipsilateral and contralateral acoustic stimuli, respectively, and vary their output spike rates according to interaural level differences. In addition, LSO neurons are also sensitive to binaural phase differences of low-frequency tones and envelopes of amplitude-modulated (AM) sounds. Previous physiological recordings in vivo found considerable variations in monaural AM-tuning across neurons. To investigate the underlying mechanisms of the observed temporal tuning properties of LSO and their sources of variability, we used a simple coincidence counting model and examined how specific parameters of coincidence detection affect monaural and binaural AM coding. Spike rates and phase-locking of evoked excitatory and spontaneous inhibitory inputs had only minor effects on LSO output to monaural AM inputs. In contrast, the coincidence threshold of the model neuron affected both the overall spike rates and the half-peak positions of the AM-tuning curve, whereas the width of the coincidence window merely influenced the output spike rates. The duration of the refractory period affected only the low-frequency portion of the monaural AM-tuning curve. Unlike monaural AM coding, temporal factors, such as the coincidence window and the effective duration of inhibition, played a major role in determining the trough positions of simulated binaural phase-response curves. In addition, empirically-observed level-dependence of binaural phase-coding was reproduced in the framework of our minimalistic coincidence counting model. These modeling results suggest that coincidence detection of excitatory

  18. Auditory stream segregation using amplitude modulated bandpass noise.

    PubMed

    Nie, Yingjiu; Nelson, Peggy B

    2015-01-01

    The purpose of this study was to investigate the roles of spectral overlap and amplitude modulation (AM) rate for stream segregation for noise signals, as well as to test the build-up effect based on these two cues. Segregation ability was evaluated using an objective paradigm with listeners' attention focused on stream segregation. Stimulus sequences consisted of two interleaved sets of bandpass noise bursts (A and B bursts). The A and B bursts differed in spectrum, AM-rate, or both. The amount of the difference between the two sets of noise bursts was varied. Long and short sequences were studied to investigate the build-up effect for segregation based on spectral and AM-rate differences. Results showed the following: (1). Stream segregation ability increased with greater spectral separation. (2). Larger AM-rate separations were associated with stronger segregation abilities. (3). Spectral separation was found to elicit the build-up effect for the range of spectral differences assessed in the current study. (4). AM-rate separation interacted with spectral separation suggesting an additive effect of spectral separation and AM-rate separation on segregation build-up. The findings suggest that, when normal-hearing listeners direct their attention towards segregation, they are able to segregate auditory streams based on reduced spectral contrast cues that vary by the amount of spectral overlap. Further, regardless of the spectral separation they are able to use AM-rate difference as a secondary/weaker cue. Based on the spectral differences, listeners can segregate auditory streams better as the listening duration is prolonged-i.e., sparse spectral cues elicit build-up segregation; however, AM-rate differences only appear to elicit build-up when in combination with spectral difference cues. PMID:26300831

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Simulation of amplitude-modulated circularly polarized Alfven waves for beta less than one

    NASA Technical Reports Server (NTRS)

    Machida, S.; Spangler, S. R.; Goertz, C. K.

    1987-01-01

    The nonlinear properties of the amplitude-modulated circularly polarized Alfven wave are studied for beta less than one. The temporal behavior of the wave packet of the electromagnetic hybrid simulation is compared with a numerical solution of the derivative nonlinear Schroedinger (DNLS) equation. It is shown that the left-hand-polarized mode evolves into a shocklike structure due to the modulational instability. However, both cyclotron damping and a snowplow effect near the steepened wave packet suppress its further steepening, contrary to the predictions of the DNLS equation. For the right-hand mode, formation of the shock does not take place, and the initial time development is well described by the DNLS equation. The daughter Alfven wave and ion acoustic waves are excited due to the decay instability at a later time. Heating or acceleration of the particles takes place for both left- and right-hand waves. Energy transfer from the wave to the particles occurs effectively when substantial modulation in the wave amplitude is present.

  7. Signal detection in amplitude-modulated maskers. II. Processing in the songbird's auditory forebrain.

    PubMed

    Nieder, A; Klump, G M

    2001-03-01

    In the natural environment, acoustic signals have to be detected in ubiquitous background noise. Temporal fluctuations of background noise can be exploited by the auditory system to enhance signal detection, especially if spectral masking components are coherently amplitude modulated across several auditory channels (a phenomenon called 'comodulation masking release'). In this study of neuronal mechanisms of masking release in the primary auditory forebrain (field L) of awake European starlings (Sturnus vulgaris), we determined and compared neural detection thresholds for 20-ms probe tones presented in a background of sinusoidally amplitude modulated (10-Hz) noise maskers. Responses of a total of 34 multiunit clusters were recorded via radiotelemetry with chronically implanted microelectrodes from unrestrained birds. For maskers consisting of a single noise band centred around the recording site's characteristic frequency, a substantial reduction in detection threshold (21 dB on average) was found when probe tones were presented during envelope dips rather than during envelope peaks. Such effects could also explain results obtained for masking protocols where the on-frequency noise band was presented together with excitatory or inhibitory flanking bands that were either coherently modulated (in-phase) or incoherently modulated (phase-shifted). Generally, masking release for probe tones in maskers with flanking bands extending beyond the frequency range of a cell cluster's excitatory tuning curve was not substantially improved. Only some of the neurophysiological results are in agreement with behavioural data from the same species if only the average population response is considered. A subsample of individual neurons, however, could account for behavioural thresholds. PMID:11264677

  8. ERP responses to processing prosodic phrasing of sentences in amplitude modulated noise.

    PubMed

    Carroll, Rebecca; Ruigendijk, Esther

    2016-02-01

    Intonation phrase boundaries (IPBs) were hypothesized to be especially difficult to process in the presence of an amplitude modulated noise masker because of a potential rhythmic competition. In an event-related potential study, IPBs were presented in silence, stationary, and amplitude modulated noise. We elicited centro-parietal Closure Positive Shifts (CPS) in 23 young adults with normal hearing at IPBs in all acoustic conditions, albeit with some differences. CPS peak amplitudes were highest in stationary noise, followed by modulated noise, and lowest in silence. Both noise types elicited CPS delays, slightly more so in stationary compared to amplitude modulated noise. These data suggest that amplitude modulation is not tantamount to a rhythmic competitor for prosodic phrasing but rather supports an assumed speech perception benefit due to local release from masking. The duration of CPS time windows was, however, not only longer in noise compared to silence, but also longer for amplitude modulated compared to stationary noise. This is interpreted as support for additional processing load associated with amplitude modulation for the CPS component. Taken together, processing prosodic phrasing of sentences in amplitude modulated noise seems to involve the same issues that have been observed for the perception and processing of segmental information that are related to lexical items presented in noise: a benefit from local release from masking, even for prosodic cues, and a detrimental additional processing load that is associated with either stream segregation or signal reconstruction. PMID:26776233

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Beating frequency and amplitude modulation of the piano tone due to coupling of tones

    NASA Astrophysics Data System (ADS)

    Cartling, Bo

    2005-04-01

    The influence on a piano tone from weak coexcitation of damped adjacent tones due to coupling via the bridge is studied. The frequency and amplitude modulation of the sound resulting from coexcitation of one strong and one or two weak tones is analyzed. One weak tone causes frequency and amplitude modulation of the sound, and two weak tones produce beating frequency and amplitude modulation, where the beatings of the two modulations are of opposite phase. By digital recording of the sound of piano tones, the appearance of these phenomena is verified. The audibility of the observed frequency and amplitude modulation is discussed in terms of previously determined detection thresholds. The beating character of both frequency and amplitude modulations, however, distinguishes the phenomena from those previously studied and prompts further psychoacoustic investigations. It is shown that detuning of unison strings may significantly increase the frequency deviation of the frequency modulation in conjunction with affected amplitude modulation. The modulatory effects of coupling to adjacent tones therefore may possibly be utilized in the tuning process. A coupling of tones analogous to the situation in a piano may arise in other stringed musical instruments transferring string vibrations to a soundboard via a bridge. .

  19. Beating frequency and amplitude modulation of the piano tone due to coupling of tones.

    PubMed

    Cartling, Bo

    2005-04-01

    The influence on a piano tone from weak coexcitation of damped adjacent tones due to coupling via the bridge is studied. The frequency and amplitude modulation of the sound resulting from coexcitation of one strong and one or two weak tones is analyzed. One weak tone causes frequency and amplitude modulation of the sound, and two weak tones produce beating frequency and amplitude modulation, where the beatings of the two modulations are of opposite phase. By digital recording of the sound of piano tones, the appearance of these phenomena is verified. The audibility of the observed frequency and amplitude modulation is discussed in terms of previously determined detection thresholds. The beating character of both frequency and amplitude modulations, however, distinguishes the phenomena from those previously studied and prompts further psychoacoustic investigations. It is shown that detuning of unison strings may significantly increase the frequency deviation of the frequency modulation in conjunction with affected amplitude modulation. The modulatory effects of coupling to adjacent tones therefore may possibly be utilized in the tuning process. A coupling of tones analogous to the situation in a piano may arise in other stringed musical instruments transferring string vibrations to a soundboard via a bridge. PMID:15898666

  20. 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

  1. 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.

  2. 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

  3. 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

  4. 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.

  5. Micro-antennas for the phase and amplitude modulation of terahertz wave

    NASA Astrophysics Data System (ADS)

    He, Jingwen; Wang, Sen; Zhang, Yan

    2015-11-01

    Based on the localized surface plasmons (LSPs), a series of C-shaped slits antennas are designed to modulate the phase and amplitude of the cross-polarized transmitted wave in THz waveband. By adjusting the structure parameters of the antenna unit, arbitrary phase and amplitude modulation of the cross-polarized THz wave can be obtained. The C-shaped slit antenna units are designed at two operating frequencies f=0.8 THz and f=1.0 THz using a commercial software package (Lumerical Solutions), which is based on the finite-difference time-domain method. According to the simulated results, principles for modulating the phase and amplitude of THz wave are summarized as follows. Firstly, the operating wavelength depends on the effective length of the antenna and the operating wavelength increases as the effective length increases; Secondly, the phase of the cross-polarized wave can be modulated from 0 to 2π by changing the opening angle of the split; Thirdly, the amplitude transmittance of the cross-polarized wave can be changed from the extinction state to the maximum value by rotating the symmetry axis of the C-shaped slit. These principles can be used to direct the design of the field modulator in any other working frequency.

  6. Anti-ship missile tracking with a chirped amplitude modulation ladar

    NASA Astrophysics Data System (ADS)

    Redman, Brian C.; Stann, Barry L.; Ruff, William C.; Giza, Mark M.; Aliberti, Keith; Lawler, William B.

    2004-09-01

    Shipboard infrared search and track (IRST) systems can detect sea-skimming anti-ship missiles at long ranges. Since IRST systems cannot measure range and velocity, they have difficulty distinguishing missiles from slowly moving false targets and clutter. ARL is developing a ladar based on its patented chirped amplitude modulation (AM) technique to provide unambiguous range and velocity measurements of targets handed over to it by the IRST. Using the ladar's range and velocity data, false alarms and clutter objects will be distinguished from valid targets. If the target is valid, it's angular location, range, and velocity, will be used to update the target track until remediation has been effected. By using an array receiver, ARL's ladar can also provide 3D imagery of potential threats in support of force protection. The ladar development program will be accomplished in two phases. In Phase I, currently in progress, ARL is designing and building a breadboard ladar test system for proof-of-principle static platform field tests. In Phase II, ARL will build a brassboard ladar test system that will meet operational goals in shipboard testing against realistic targets. The principles of operation for the chirped AM ladar for range and velocity measurements, the ladar performance model, and the top-level design for the Phase I breadboard are presented in this paper.

  7. 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.

  8. Responses to amplitude modulated infrared stimuli in the guinea pig inferior colliculus

    PubMed Central

    Richter, Claus-Peter; Young, Hunter

    2014-01-01

    Responses of units in the central nucleus of the inferior colliculus of the guinea pig were recorded with tungsten electrodes. The set of data presented here is limited to high stimulus levels. The effect of changing the modulation frequency and the modulation depth was explored for acoustic and laser stimuli. The selected units responded to sinusoidal amplitude modulated (AM) tones, AM trains of clicks, and AM trains of laser pulses with a modulation of their spike discharge. At modulation frequencies of 20 Hz, some units tended to respond with 40 Hz to the acoustic stimuli, but only at 20 Hz for the trains of laser pulses. For all modes of stimulation the responses revealed a dominant response to the first cycle of the modulation, with decreasing number of action potential during successive cycles. While amplitude modulated tone bursts and amplitude modulated trains of acoustic clicks showed similar patterns, the response to trains of laser pulses was different. PMID:25075264

  9. 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).

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. Multilevel phase and amplitude modulation method for holographic memories with programmable phase modulator

    NASA Astrophysics Data System (ADS)

    Honma, Satoshi; Sekiguchi, Toru

    2014-09-01

    The utilization of spatial quadrature amplitude modulation (SQAM) signals with amplitude and phase modulation is a simple method used to improve storage capacity in a holographic data storage system. We propose a multilevel phase and amplitude modulation method for holographic memories with a programmable phase modulator (PPM). In this method, holographic page data is recorded by a two-step exposure process for different phase-modulated data. There is no need to adjust the positions of spatial light modulators (SLM) with high accuracy because we use only one spatial modulator. We estimate the quality of 16 SQAM signals produced by our technique.

  15. Diffusion-induced periodic transition between oscillatory modes in amplitude-modulated patterns

    SciTech Connect

    Tang, Xiaodong; He, Yuxiu; Wang, Shaorong; Gao, Qingyu; Epstein, Irving R.; Wang, Qun

    2014-06-15

    We study amplitude-modulated waves, e.g., wave packets in one dimension, overtarget spirals and superspirals in two dimensions, under mixed-mode oscillatory conditions in a three-variable reaction-diffusion model. New transition zones, not seen in the homogeneous system, are found, in which periodic transitions occur between local 1{sup N−1} and 1{sup N} oscillations. Amplitude-modulated complex patterns result from periodic transition between (N − 1)-armed and N-armed waves. Spatial recurrence rates provide a useful guide to the stability of these modulated patterns.

  16. 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.

  17. Visualizing electromagnetic fields at the nanoscale by single molecule localization.

    PubMed

    Steuwe, Christian; Erdelyi, Miklos; Szekeres, G; Csete, M; Baumberg, Jeremy J; Mahajan, Sumeet; Kaminski, Clemens F

    2015-05-13

    Coupling of light to the free electrons at metallic surfaces allows the confinement of electric fields to subwavelength dimensions, far below the optical diffraction limit. While this is routinely used to manipulate light at the nanoscale, in electro-optic devices and enhanced spectroscopic techniques, no characterization technique for imaging the underlying nanoscopic electromagnetic fields exists, which does not perturb the field or employ complex electron beam imaging. Here, we demonstrate the direct visualization of electromagnetic fields on patterned metallic substrates at nanometer resolution, exploiting a strong "autonomous" fluorescence-blinking behavior of single molecules within the confined fields allowing their localization. Use of DNA-constructs for precise positioning of fluorescence dyes on the surface induces this distance-dependent autonomous blinking thus completely obviating the need for exogenous agents or switching methods. Mapping such electromagnetic field distributions at nanometer resolution aids the rational design of nanometals for diverse photonic applications. PMID:25915093

  18. EFFECTS OF CONTINUOUS-WAVE, PULSED, AND SINUSOIDAL-AMPLITUDE-MODULATED MICROWAVES ON BRAIN ENERGY METABOLISM

    EPA Science Inventory

    A comparison of the effects of continuous wave, sinusoidal-amplitude modulated, and pulsed square-wave-modulated 591-MHz microwave exposures on brain energy metabolism was made in male Sprague Dawley rats (175-225g). Brain NADH fluorescence, adensine triphosphate (ATP) concentrat...

  19. A Simple Approximation for the Symbol Error Rate of Triangular Quadrature Amplitude Modulation

    NASA Astrophysics Data System (ADS)

    Duy, Tran Trung; Kong, Hyung Yun

    In this paper, we consider the error performance of the regular triangular quadrature amplitude modulation (TQAM). In particular, using an accurate exponential bound of the complementary error function, we derive a simple approximation for the average symbol error rate (SER) of TQAM over Additive White Gaussian Noise (AWGN) and fading channels. The accuracy of our approach is verified by some simulation results.

  20. Radar transponder operation with compensation for distortion due to amplitude modulation

    DOEpatents

    Ormesher, Richard C.; Tise, Bertice L.; Axline, Jr., Robert M.

    2011-01-04

    In radar transponder operation, a variably delayed gating signal is used to gate a received radar pulse and thereby produce a corresponding gated radar pulse for transmission back to the source of the received radar pulse. This compensates for signal distortion due to amplitude modulation on the retransmitted pulse.

  1. Nonlinear electromagnetic fields as a source of universe acceleration

    NASA Astrophysics Data System (ADS)

    Kruglov, S. I.

    2016-04-01

    A model of nonlinear electromagnetic fields with a dimensional parameter β is proposed. From PVLAS experiment the bound on the parameter β was obtained. Electromagnetic fields are coupled with the gravitation field and we show that the universe accelerates due to nonlinear electromagnetic fields. The magnetic universe is considered and the stochastic magnetic field is a background. After inflation the universe decelerates and approaches to the radiation era. The range of the scale factor, when the causality of the model and a classical stability take place, was obtained. The spectral index, the tensor-to-scalar ratio, and the running of the spectral index were estimated which are in approximate agreement with the Planck, WMAP, and BICEP2 data.

  2. Electromagnetic waves in optical fibres in a magnetic field

    NASA Astrophysics Data System (ADS)

    Gorelik, V. S.; Burdanova, M. G.

    2016-03-01

    A new method is reported of recording the secondary radiation of luminescent substances based on the use of capillary fibres of great length. Theoretical analysis of the dispersion curves of electromagnetic radiation in capillary fibres doped with erbium ions Er3+ has been established. The Lorentz model is used for describing the dispersion properties of electromagnetic waves in a homogeneous medium doped with rare-earth ions. The dispersion dependencies of polariton and axion-polariton waves in erbium nitrate hydrate are determined on the basis of the model of the interaction between electromagnetic waves and the resonance electronic states of erbium ions in the absence and presence of a magnetic field.

  3. Amplitude modulation in δ Sct stars: statistics from an ensemble study of Kepler targets

    NASA Astrophysics Data System (ADS)

    Bowman, Dominic M.; Kurtz, Donald W.; Breger, Michel; Murphy, Simon J.; Holdsworth, Daniel L.

    2016-08-01

    We present the results of a search for amplitude modulation of pulsation modes in 983 δ Sct stars, which have effective temperatures between 6400 ≤ Teff ≤ 10 000 K in the Kepler Input Catalogue and were continuously observed by the Kepler Space Telescope for 4 yr. We demonstrate the diversity in pulsational behaviour observed, in particular non-linearity, which is predicted for δ Sct stars. We analyse and discuss examples of δ Sct stars with constant amplitudes and phases; those that exhibit amplitude modulation caused by beating of close-frequency pulsation modes; those that exhibit pure amplitude modulation (with no associated phase variation); those that exhibit phase modulation caused by binarity; and those that exhibit amplitude modulation caused by non-linearity. Using models and examples of individual stars, we demonstrate that observations of the changes in amplitude and phase of pulsation modes can be used to distinguish among the different scenarios. We find that 603 δ Sct stars (61.3 per cent) exhibit at least one pulsation mode that varies significantly in amplitude over 4 yr. Conversely, many δ Sct stars have constant pulsation amplitudes so short-length observations can be used to determine precise frequencies, amplitudes and phases for the most coherent and periodic δ Sct stars. It is shown that amplitude modulation is not restricted to a small region on the HR diagram, therefore not necessarily dependent on stellar parameters such as Teff or log g. Our catalogue of 983 δ Sct stars will be useful for comparisons to similar stars observed by K2 and TESS, because the length of the 4-yr Kepler data set will not be surpassed for some time.

  4. Hierarchical effects of task engagement on amplitude modulation encoding in auditory cortex.

    PubMed

    Niwa, Mamiko; O'Connor, Kevin N; Engall, Elizabeth; Johnson, Jeffrey S; Sutter, M L

    2015-01-01

    We recorded from middle lateral belt (ML) and primary (A1) auditory cortical neurons while animals discriminated amplitude-modulated (AM) sounds and also while they sat passively. Engagement in AM discrimination improved ML and A1 neurons' ability to discriminate AM with both firing rate and phase-locking; however, task engagement affected neural AM discrimination differently in the two fields. The results suggest that these two areas utilize different AM coding schemes: a "single mode" in A1 that relies on increased activity for AM relative to unmodulated sounds and a "dual-polar mode" in ML that uses both increases and decreases in neural activity to encode modulation. In the dual-polar ML code, nonsynchronized responses might play a special role. The results are consistent with findings in the primary and secondary somatosensory cortices during discrimination of vibrotactile modulation frequency, implicating a common scheme in the hierarchical processing of temporal information among different modalities. The time course of activity differences between behaving and passive conditions was also distinct in A1 and ML and may have implications for auditory attention. At modulation depths ≥ 16% (approximately behavioral threshold), A1 neurons' improvement in distinguishing AM from unmodulated noise is relatively constant or improves slightly with increasing modulation depth. In ML, improvement during engagement is most pronounced near threshold and disappears at highly suprathreshold depths. This ML effect is evident later in the stimulus, and mainly in nonsynchronized responses. This suggests that attention-related increases in activity are stronger or longer-lasting for more difficult stimuli in ML. PMID:25298387

  5. Hierarchical effects of task engagement on amplitude modulation encoding in auditory cortex

    PubMed Central

    Niwa, Mamiko; O'Connor, Kevin N.; Engall, Elizabeth; Johnson, Jeffrey S.

    2014-01-01

    We recorded from middle lateral belt (ML) and primary (A1) auditory cortical neurons while animals discriminated amplitude-modulated (AM) sounds and also while they sat passively. Engagement in AM discrimination improved ML and A1 neurons' ability to discriminate AM with both firing rate and phase-locking; however, task engagement affected neural AM discrimination differently in the two fields. The results suggest that these two areas utilize different AM coding schemes: a “single mode” in A1 that relies on increased activity for AM relative to unmodulated sounds and a “dual-polar mode” in ML that uses both increases and decreases in neural activity to encode modulation. In the dual-polar ML code, nonsynchronized responses might play a special role. The results are consistent with findings in the primary and secondary somatosensory cortices during discrimination of vibrotactile modulation frequency, implicating a common scheme in the hierarchical processing of temporal information among different modalities. The time course of activity differences between behaving and passive conditions was also distinct in A1 and ML and may have implications for auditory attention. At modulation depths ≥ 16% (approximately behavioral threshold), A1 neurons' improvement in distinguishing AM from unmodulated noise is relatively constant or improves slightly with increasing modulation depth. In ML, improvement during engagement is most pronounced near threshold and disappears at highly suprathreshold depths. This ML effect is evident later in the stimulus, and mainly in nonsynchronized responses. This suggests that attention-related increases in activity are stronger or longer-lasting for more difficult stimuli in ML. PMID:25298387

  6. Heteronuclear refocusing by nonlinear phase and amplitude modulation on a single transmitter channel.

    PubMed

    Moore, Jay; Colón, Raul D; Tadanki, Sasidhar; Waddell, Kevin W

    2014-08-01

    The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins ((13)C and (1)H) at 12mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128kHz ((13)C) and 510kHz ((1)H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as

  7. Suppression and control of leakage field in electromagnetic helical microwiggler

    SciTech Connect

    Ohigashi, N.; Tsunawaki, Y.; Imasaki, K.

    1995-12-31

    Shortening the period of electromagnetic wiggler introduces both the radical increase of the leakage field and the decrease of the field in the gap region. The leakage field is severer problem in planar electromagnetic wiggler than in helical wiggler. Hence, in order to develop a short period electromagnetic wiggler, we have adopted {open_quotes}three poles per period{close_quotes} type electromagnetic helical microwiggler. In this work, we inserted the permanent magnet (PM) blocks with specific magnetized directions in the space between magnetic poles, for suppressing the leakage field flowing out from a pole face to the neighboring pole face. These PM-blocks must have higher intrinsic coersive force than saturation field of pole material. The gap field due to each pole is adjustable by controlling the leakage fields, that is, controlling the position of each iron screw set in each retainer fixing the PM-blocks. At present time, a test wiggler with period 7.8mm, periodical number 10 and gap length 4.6mm has been manufactured. Because the ratio of PM-block aperture to gap length is important parameter to suppress the leakage field, the parameter has been surveyed experimentally for PM-blocks with several dimensions of aperture. The field strength of 3-5kG (K=0.2-0.4) would be expected in the wiggler.

  8. Invited commentary: electromagnetic fields and cancer in railway workers.

    PubMed

    Savitz, D A

    2001-05-01

    The ideal study of occupational exposure to electromagnetic fields and cancer risk would have a clear exposure source, historically stable exposures, and comparable groups of exposed and unexposed workers. Cohorts of railway workers have marked exposure contrasts and limited job changes and provide marginally adequate study sizes, but there have been important changes in their exposures over time, and the field frequency involved is unusual. The results of Minder and Pfluger's study (Am J Epidemiol 2001;153:825--35) add modest support for an association between electromagnetic field exposure and leukemia. However, given the large size and high quality of a number of previous studies of occupational electromagnetic field exposure and cancer, additional studies similar to past ones are unlikely to yield important new insights. PMID:11323312

  9. Analytical model for electromagnetic cascades in rotating electric field

    SciTech Connect

    Nerush, E. N.; Bashmakov, V. F.; Kostyukov, I. Yu.

    2011-08-15

    Electromagnetic cascades attract a lot of attention as an important quantum electrodynamics effect that will reveal itself in various electromagnetic field configurations at ultrahigh intensities. We study cascade dynamics in rotating electric field analytically and numerically. The kinetic equations for the electron-positron plasma and gamma-quanta are formulated. The scaling laws are derived and analyzed. For the cascades arising far above the threshold the dependence of the cascade parameters on the field frequency is derived. The spectra of high-energy cascade particles are calculated. The analytical results are verified by numerical simulations.

  10. External Field QED on Cauchy Surfaces for Varying Electromagnetic Fields

    NASA Astrophysics Data System (ADS)

    Deckert, D.-A.; Merkl, F.

    2016-03-01

    The Shale-Stinespring Theorem (J Math Mech 14:315-322, 1965) together with Ruijsenaar's criterion (J Math Phys 18(4):720-737, 1977) provide a necessary and sufficient condition for the implementability of the evolution of external field quantum electrodynamics between constant-time hyperplanes on standard Fock space. The assertion states that an implementation is possible if and only if the spatial components of the external electromagnetic four-vector potential {A_μ} are zero. We generalize this result to smooth, space-like Cauchy surfaces and, for general {A_μ} , show how the second-quantized Dirac evolution can always be implemented as a map between varying Fock spaces. Furthermore, we give equivalence classes of polarizations, including an explicit representative, that give rise to those admissible Fock spaces. We prove that the polarization classes only depend on the tangential components of {A_μ} w.r.t. the particular Cauchy surface, and show that they behave naturally under Lorentz and gauge transformations.

  11. External Field QED on Cauchy Surfaces for Varying Electromagnetic Fields

    NASA Astrophysics Data System (ADS)

    Deckert, D.-A.; Merkl, F.

    2016-08-01

    The Shale-Stinespring Theorem (J Math Mech 14:315-322, 1965) together with Ruijsenaar's criterion (J Math Phys 18(4):720-737, 1977) provide a necessary and sufficient condition for the implementability of the evolution of external field quantum electrodynamics between constant-time hyperplanes on standard Fock space. The assertion states that an implementation is possible if and only if the spatial components of the external electromagnetic four-vector potential {A_μ} are zero. We generalize this result to smooth, space-like Cauchy surfaces and, for general {A_μ}, show how the second-quantized Dirac evolution can always be implemented as a map between varying Fock spaces. Furthermore, we give equivalence classes of polarizations, including an explicit representative, that give rise to those admissible Fock spaces. We prove that the polarization classes only depend on the tangential components of {A_μ} w.r.t. the particular Cauchy surface, and show that they behave naturally under Lorentz and gauge transformations.

  12. Aharonov-Bohm oscillations, quantum decoherence and amplitude modulation in mesoscopic InGaAs/InAlAs rings.

    PubMed

    Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B

    2013-10-30

    Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms. PMID:24096892

  13. Health Effects of Electromagnetic Fields: A Review of Literature.

    ERIC Educational Resources Information Center

    White, George L.; And Others

    1995-01-01

    Current evidence suggests that the effects of electromagnetic fields (EMF) disturb cell homeostasis at very low intensities by influencing discrete intracellular magnetic fields. The article reviews current research about the health effects of EMF, examining historical implications, childhood studies, adult studies, and popular press reports, and…

  14. Quaternionic Analysis of Generalized Electromagnetic Fields of Superluminal Dyons

    SciTech Connect

    Bisht, P. S.; Negi, O. P. S.

    2008-04-21

    Superluminal electromagnetic fields of dyons are described in T{sup 4}--space and Quaternion formulation of various quantum equations is derived. It is shown that on passing from subluminal to superluminal realm via quaternion the theory of dyons becomes the Tachyonic dyons. Corresponding field Equations of Tachyonic dyons are derived in consistent, compact and simpler form.

  15. 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.

  16. On guided versus deflected fields in controlled-source electromagnetics

    NASA Astrophysics Data System (ADS)

    Swidinsky, Andrei

    2015-06-01

    The detection of electrically resistive targets in applied geophysics is of interest to the hydrocarbon, mining and geotechnical industries. Elongated thin resistive bodies have been extensively studied in the context of offshore hydrocarbon exploration. Such targets guide electromagnetic fields in a process which superficially resembles seismic refraction. On the other hand, compact resistive bodies deflect current in a process which has more similarities to diffraction and scattering. The response of a real geological structure is a non-trivial combination of these elements-guiding along the target and deflection around its edges. In this note the electromagnetic responses of two end-member models are compared: a resistive layer, which guides the electromagnetic signal, and a resistive cylinder, which deflects the fields. Results show that the response of a finite resistive target tends to saturate at a much lower resistivity than a resistive layer, under identical survey configurations. Furthermore, while the guided electromagnetic fields generated by a buried resistive layer contain both anomalous horizontal and vertical components, the process of electromagnetic deflection from a buried resistive cylinder creates mainly anomalous vertical fields. Finally, the transmitter orientation with respect to the position of a finite body is an important survey parameter: when the distance to the target is much less than the host skin depth, a transmitter pointing towards the resistive cylinder will produce a stronger signal than a transmitter oriented azimuthally with respect to the cylinder surface. The opposite situation is observed when the distance to the target is greater than the host skin depth.

  17. Quantum processes in short and intensive electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Titov, A. I.; Kämpfer, Burkhard; Hosaka, Atsushi; Takabe, Hideaki

    2016-05-01

    This work provides an overview of our recent results in studying two most important and widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g. laser) wave field or generalized Breit-Wheeler process, and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. We show that the probabilities of particle production in both processes are determined by interplay of two dynamical effects, where the first one is related to the shape and duration of the pulse and the second one is non-linear dynamics of the interaction of charged fermions with a strong electromagnetic field. We elaborate suitable expressions for the production probabilities and cross sections, convenient for studying evolution of the plasma in presence of strong electromagnetic fields.

  18. Integral equations for the electromagnetic field in dielectrics

    NASA Astrophysics Data System (ADS)

    Mostowski, Jan; Załuska-Kotur, Magdalena A.

    2016-09-01

    We study static the electric field and electromagnetic waves in dielectric media. In contrast to the standard approach, we use, formulate and solve integral equations for the field. We discuss the case of an electrostatic field of a point charge placed inside a dielectric; the integral equation approach allows us to find and interpret the dielectric constant in terms of molecular polarizability. Next we discuss propagation of electromagnetic waves using the same integral equation approach. We derive the dispersion relation and find the reflection and transmission coefficients at the boundary between the vacuum and the dielectric. The present approach supplements the standard approach based on macroscopic Maxwell equations and contributes to better a understanding of some electromagnetic effects.

  19. The effect of pulsed electromagnetic field therapy on food sensitivity.

    PubMed

    Monro, Jean A; Puri, Basant K

    2015-01-01

    Owing to the involvement of the immune system in the etiology of food sensitivity, and because pulsed electromagnetic field therapy is associated with beneficial immunologic changes, it was hypothesized that pulsed electromagnetic fields may have a beneficial effect on food sensitivity. A small pilot study was carried out in patients suffering from food sensitivity, with the antigen leukocyte antibody test being employed to index the degree of food sensitivity in terms of the number of foods to which each patient reacted. It was found that a 1-week course of pulsed electromagnetic field therapy, consisting of one hour's treatment per day, resulted in a reduction in the mean number of reactive foods of 10.75 (p < 0.05). On the basis of these results, a larger study is warranted. PMID:24712751

  20. Biological effects of electromagnetic fields and recently updated safety guidelines for strong static magnetic fields.

    PubMed

    Yamaguchi-Sekino, Sachiko; Sekino, Masaki; Ueno, Shoogo

    2011-01-01

    Humans are exposed daily to artificial and naturally occurring magnetic fields that originate from many different sources. We review recent studies that examine the biological effects of and medical applications involving electromagnetic fields, review the properties of static and pulsed electromagnetic fields that affect biological systems, describe the use of a pulsed electromagnetic field in combination with an anticancer agent as an example of a medical application that incorporates an electromagnetic field, and discuss the recently updated safety guidelines for static electromagnetic fields. The most notable modifications to the 2009 International Commission on Non-Ionizing Radiation Protection guidelines are the increased exposure limits, especially for those who work with or near electromagnetic fields (occupational exposure limits). The recommended increases in exposure were determined using recent scientific evidence obtained from animal and human studies. Several studies since the 1994 publication of the guidelines have examined the effects on humans after exposure to high static electromagnetic fields (up to 9.4 tesla), but additional research is needed to ascertain further the safety of strong electromagnetic fields. PMID:21441722

  1. Electromagnetic signature in holographic plasma with B field

    NASA Astrophysics Data System (ADS)

    Bu, Yanyan

    2013-01-01

    We explore the effect of a magnetic field on the electromagnetic signature in QCD-like plasma by taking the AdS/CFT approach. Concretely, we choose two QCD gravity dual models to do comparative studies: the D4/D6 and D3/D7 models. The magnetic field is simulated by a spatial component of the flavor U(1) gauge field in the bulk side. For both models, we plot the spectral function and photoemission rate for lightlike momenta as well as the ac conductivity. Due to the presence of the magnetic field, the rotational symmetry is partially broken. Therefore, we plot the spectral function and photoemission rate with spatial momentum parallel or perpendicular to the magnetic field, respectively. We find that the magnetic field induces an anisotropic feature in the electromagnetic signature. To be specific, when the emitted photons from the plasma are moving along the magnetic field, the electromagnetic signature is weakened as the magnetic field is increasing; on the contrary, when the produced photons move perpendicular to the magnetic field, the magnetic field has the effect of amplifying the electromagnetic signature. This should have a relationship with the anisotropic feature of the photon signal observed in heavy-ion collision experiments. This anisotropic characteristic can also be observed in the ac conductivity of the holographic plasma. In the infrared regime of the frequency, the magnetic field suppresses the ac conductivity (along the direction perpendicular to the magnetic field) and likely gives a pseudogap structure. However, the ac conductivity along the magnetic field is enhanced due to the presence of the magnetic field.

  2. Electromagnetic instabilities attributed to a cross-field ion drift

    NASA Technical Reports Server (NTRS)

    Chang, C. L.; Wong, H. K.; Wu, C. S.

    1990-01-01

    Instabilities due to a cross-field ion flow are reexamined by including the electromagnetic response of the ions, which has been ignored in existing discussions. It is found that this effect can lead to significant enhancement of the growth rate. Among the new results, a purely growing, electromagnetic unstable mode with a wave vector k parallel to the ambient magnetic field is found. The plasma configuration under consideration is similar to that used in the discussion of the well-known modified-two-stream instability. This instability has a growth rate faster than the ion cyclotron frequency, and is not susceptible to high-plasma-beta stabilization.

  3. Near-field thermal electromagnetic transport: An overview

    NASA Astrophysics Data System (ADS)

    Edalatpour, Sheila; DeSutter, John; Francoeur, Mathieu

    2016-07-01

    A general near-field thermal electromagnetic transport formalism that is independent of the size, shape and number of heat sources is derived. The formalism is based on fluctuational electrodynamics, where fluctuating currents due to thermal agitation are added to Maxwell's curl equations, and is thus valid for heat sources in local thermodynamic equilibrium. Using a volume integral formulation, it is shown that the proposed formalism is a generalization of the classical electromagnetic scattering framework in which thermal emission is implicitly assumed to be negligible. The near-field thermal electromagnetic transport formalism is afterwards applied to a problem involving three spheres with size comparable to the wavelength, where all multipolar interactions are taken into account. Using the thermal discrete dipole approximation, it is shown that depending on the dielectric function, the presence of a third sphere slightly affects the spatial distribution of power absorbed compared to the two-sphere case. A transient analysis shows that despite a non-uniform spatial distribution of power absorbed, the sphere temperature remains spatially uniform at any instant due to the fact that the thermal resistance by conduction is much smaller than the resistance by radiation. The formalism proposed in this paper is general, and could be used as a starting point for adapting solution methods employed in traditional electromagnetic scattering problems to near-field thermal electromagnetic transport.

  4. Coulomb field in a constant electromagnetic background

    NASA Astrophysics Data System (ADS)

    Adorno, T. C.; Gitman, D. M.; Shabad, A. E.

    2016-06-01

    Nonlinear Maxwell equations are written up to the third-power deviations from a constant-field background, valid within any local nonlinear electrodynamics including QED with a Euler-Heisenberg (EH) effective Lagrangian. The linear electric response to an imposed static finite-sized charge is found in the vacuum filled by an arbitrary combination of constant and homogeneous electric and magnetic fields. The modified Coulomb field and corrections to the total charge and to the charge density are given in terms of derivatives of the effective Lagrangian with respect to the field invariants. These are specialized for the EH Lagrangian.

  5. 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.

  6. Amplitude modulation following response in children as a clinical audiometric tool.

    PubMed

    Mauer, G; Döring, W H; Hamacher, V; Bell, C

    1997-11-01

    The current study was designed to investigate the clinical application of amplitude modulation following response (AMFR) in cochlear implant candidates. A new digital signal processor (DSP)-assisted PC-based hardware and software was developed to perform both simultaneous generation of amplitude-modulated stimuli and the recording, and synchronized signal processing of the electrode signals. Our first results show that AMFR can be recorded in adults as well as in children without any contamination by response-like stimulus artifacts. Very high sound pressure levels can be applied, allowing frequency-specific assessment of residual hearing. Response threshold detection, using spectral analysis, proved to be superior compared to visual evaluation of average time waveforms. PMID:9391622

  7. Miniature Surface Plasmon Polariton Amplitude Modulator by Beat Frequency and Polarization Control.

    PubMed

    Chang, Cheng-Wei; Lin, Chu-En; Yu, Chih-Jen; Yeh, Ting-Tso; Yen, Ta-Jen

    2016-01-01

    The miniaturization of modulators keeps pace for the compact devices in optical applications. Here, we present a miniature surface plasmon polariton amplitude modulator (SPPAM) by directing and interfering surface plasmon polaritons on a nanofabricated chip. Our results show that this SPPAM enables two kinds of modulations. The first kind of modulation is controlled by encoding angular-frequency difference from a Zeeman laser, with a beat frequency of 1.66 MHz; the second of modulation is validated by periodically varying the polarization states from a polarization generator, with rotation frequencies of 0.5-10 k Hz. In addition, the normalized extinction ratio of our plasmonic structure reaches 100. Such miniaturized beat-frequency and polarization-controlled amplitude modulators open an avenue for the exploration of ultrasensitive nanosensors, nanocircuits, and other integrated nanophotonic devices. PMID:27558516

  8. Miniature Surface Plasmon Polariton Amplitude Modulator by Beat Frequency and Polarization Control

    PubMed Central

    Chang, Cheng-Wei; Lin, Chu-En; Yu, Chih-Jen; Yeh, Ting-Tso; Yen, Ta-Jen

    2016-01-01

    The miniaturization of modulators keeps pace for the compact devices in optical applications. Here, we present a miniature surface plasmon polariton amplitude modulator (SPPAM) by directing and interfering surface plasmon polaritons on a nanofabricated chip. Our results show that this SPPAM enables two kinds of modulations. The first kind of modulation is controlled by encoding angular-frequency difference from a Zeeman laser, with a beat frequency of 1.66 MHz; the second of modulation is validated by periodically varying the polarization states from a polarization generator, with rotation frequencies of 0.5–10 k Hz. In addition, the normalized extinction ratio of our plasmonic structure reaches 100. Such miniaturized beat-frequency and polarization-controlled amplitude modulators open an avenue for the exploration of ultrasensitive nanosensors, nanocircuits, and other integrated nanophotonic devices. PMID:27558516

  9. Cross correlation analysis of plasma perturbation in amplitude modulated reactive dusty plasmas

    NASA Astrophysics Data System (ADS)

    Ito, Teppei; Soejima, Masahiro; Yamashita, Daisuke; Seo, Hyunwoong; Itagaki, Naho; Koga, Kazunori; Shiratani, Masaharu; Kobayashi, Tatsuya; Inagaki, Shigeru

    2015-09-01

    Interactions between plasmas and nano-interface are one of the most important issues in plasma processing. We have studied effects of plasma perturbation on growth of nanoparticles in amplitude modulated reactive dusty plasmas and have clarified that amplitude modulation (AM) leads to suppression of growth of nanoparticles [1]. Here we report results of cross correlation analysis of time evolution of laser light scattering intensity from nanoparticles in reactive plasmas. Experiments were carried out using a capacitively-coupled rf discharge reactor with a two-dimensional laser light scattering (LLS) system. We employed Ar +DM-DMOS discharge plasmas to generate nanoparticles. The peaks at higher harmonics and subharmonics in spectra of laser light scattering intensity were detected, suggesting nonlinear coupling between plasma and nanoparticle amount. We found high cross correlation t between waves at AM frequency and its higher harmonics. Namely, perturbation at fAM closely correlates with those at higher harmonics.

  10. 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.

  11. 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.

  12. Hydrostatic Vibratory Drive of the Test Stand for Excitation of the Amplitude-Modulated Vibrations

    NASA Astrophysics Data System (ADS)

    Nizhegorodov, A. I.; Gavrilin, A. N.; Moyzes, B. B.

    2016-01-01

    The article reviews the problems arising during the development of the test stand hydrostatic vibratory drive, which synthesize controlled amplitude-modulated vibrations required testing of vibration strength and vibrostability of technological devices. The newly developed modification can adequately simulate the transport vibration and vibration of the operating power-supply units of technological machinery vibration by means of implementing of a continuous frequency spectrum of the vibration exposure in the desired frequency range.

  13. Quantitative measurement of tip-sample interactions in amplitude modulation atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Hölscher, H.

    2006-09-01

    The author introduces an algorithm for the reconstruction of the tip-sample interactions in amplitude modulation atomic force microscopy ("tapping mode"). The method is based on the recording of amplitude and phase versus distance curves and allows the reconstruction of tip-sample force and energy dissipation as a function of the actual tip-sample distance. The proposed algorithm is verified by a numerical simulation and applied to a silicon sample in ambient conditions.

  14. Flexible quadrature amplitude modulation with semiconductor optical amplifier and electroabsorption modulator.

    PubMed

    Schrenk, Bernhard; Dris, Stefanos; Bakopoulos, Paraskevas; Lazarou, Ioannis; Voigt, Karsten; Zimmermann, Lars; Avramopoulos, Hercules

    2012-08-01

    Optical quadrature amplitude modulation (QAM) is experimentally demonstrated with a low-complexity modulator based on a semiconductor optical amplifier and electroabsorption modulator. Flexible amplitude/phase format transmission is achieved. The applicability of octary QAM for coherent optical access networks with sustainable 3 Gb/s per-user bandwidth is investigated for a long reach of 100 km, and its compatibility with a potentially high split is verified. PMID:22859139

  15. Field intercomparisons of electromagnetic current meters

    NASA Astrophysics Data System (ADS)

    Guza, R. T.; Clifton, M. C.; Rezvani, F.

    1988-08-01

    In order to assess the performance of current meters within and near the surf zone, data from biaxial electromagnetic current meters with spherical and open frame probe geometries were intercompared. One bottom-mounted flow meter of each type was deployed in a mean depth of 7.0 m for 17 days, and two sensors of each type were deployed in a mean depth of 2.0 m for 5 days. Sensors in the shallow deployment were frequently in the surf zone. Hourly averaged mean flows measured by different sensor types are highly correlated, averaging above 0.98. The largest difference between measured mean flows is a constant bias, typically about 3.0 cm/s, which is roughly equal to the estimated accuracy of the sensor offset calibrations. Root-mean-square deviations from this constant bias are less than 2.0 cm/s, and are contributed to by errors in both gain calibration and sensor orientation. Comparisons of measured (surface gravity wave) oscillatory currents were made both between current meter types and with velocities inferred from the application of linear theory to pressure sensor data. Correlations between time series of UTrms (the rms total oscillatory velocity for a 1-hour record) were all above 0.99 in 7.0-m depth and averaged 0.95 for the shallow deployment. The average UTrms ratio (over all hour-long records) was within 1.0 ±0.07 for all current meter pairs in both deployments, which is consistent with the estimated 5% uncertainties in the flow meter gain calibration. Typical fluctuations of the UTrms ratio of any spherical and open frame sensor pair about its mean ratio, indicative of flow meter gain distortions probably associated with variations in the hydrodynamic environment, were less than 0.04 for any one deployment. Ratios of UTrms from both deployments taken together suggest that the open frame sensor overresponds, relative to the spherical probe, by about 5% at low (about 10.0 cm/s) total (mean + UTrms) speeds, and underresponds by about 5% at higher total

  16. Amplitude modulation of streamwise velocity fluctuations in the roughness sublayer: evidence from large-eddy simulations

    NASA Astrophysics Data System (ADS)

    Awasthi, Ankit; Anderson, William

    2015-11-01

    Large-scale motions in the logarithmic region of turbulent boundary layers amplitude modulate the viscous sublayer (Marusic et al., 2010: Science; Mathis et al., 2009: J. Fluid Mech.). This finding has promising implications for large-eddy simulation of wall-bounded turbulence at high Reynolds number (wherein the turbulence integral length exhibits linear proportionality with wall-normal elevation). Existing amplitude modulation studies have addressed smooth wall flows, though high Reynolds number rough wall flows are ubiquitous. Under such conditions, roughness-scale vortices ablate the viscous sublayer and result in the roughness sublayer. The roughness sublayer depth scales with aggregate element height, k, and is typically 2k ~ 3k. Above this, Townsend's Hypothesis dictates that the logarithmic layer is unaffected by the roughness sublayer. Here, we present large-eddy simulation results of turbulent channel flow over rough walls. We follow the decoupling procedure of Mathis et al., 2009: J. Fluid Mech., and present evidence that outer-layer dynamics amplitude modulate the roughness sublayer. Below the roughness element height, we report enormous sensitivity to element proximity. Above the elements, but within the roughness sublayer, topography dependence rapidly declines. This work was supported by the Air Force Office of Scientific Research, Turbulence and Transition Program (PM: Dr. R. Ponnoppan) under Grant # FA9550-14-1-0101. Computational resources were provided by the Texas Adv. Comp. Center at the Univ. of Texas.

  17. Systematic and quantitative analysis of residual amplitude modulation in Pound-Drever-Hall frequency stabilization

    NASA Astrophysics Data System (ADS)

    Shen, Hui; Li, Liufeng; Bi, Jin; Wang, Jia; Chen, Lisheng

    2015-12-01

    We theoretically analyze the effects of two primary mechanisms of residual amplitude modulation, estimate the resulting frequency instabilities, and discuss relevant experimental countermeasures, providing useful information that are beneficial for the development of ultrastable optical oscillators as well as many precision experiments relying on stable lasers. A Pound-Drever-Hall signal comprising contributions from the birefringence of the electro-optic crystal is derived and used to examine the birefringence-related amplitude modulation and the resultant frequency offset in terms of various experimental parameters. The combined effect of the crystal birefringence and pararsitic étalons is further investigated by dividing the étalons into three representative categories according to their locations in the optical path. The analysis shows that introducing a resonant optical cavity only scales the birefringence-generated amplitude modulation by a constant, thereby lending strong support to the active control scheme using a separate detection path. When a parasitic étalon is added, the active control scheme can still suppress the resultant instability except for the parasitic étalon that is located closely in front of the optical cavity. In this case the étalon produces rather large frequency instability and therefore should be avoided. In addition, numerical calculations are performed to assess the impact of a special situation where the front and end surfaces of an ultrastable optical cavity are potential sources of the parasitic étalon that can strongly couple with the cavity.

  18. A physically motivated quantization of the electromagnetic field

    NASA Astrophysics Data System (ADS)

    Bennett, Robert; Barlow, Thomas M.; Beige, Almut

    2016-01-01

    The notion that the electromagnetic field is quantized is usually inferred from observations such as the photoelectric effect and the black-body spectrum. However accounts of the quantization of this field are usually mathematically motivated and begin by introducing a vector potential, followed by the imposition of a gauge that allows the manipulation of the solutions of Maxwell’s equations into a form that is amenable for the machinery of canonical quantization. By contrast, here we quantize the electromagnetic field in a less mathematically and more physically motivated way. Starting from a direct description of what one sees in experiments, we show that the usual expressions of the electric and magnetic field observables follow from Heisenberg’s equation of motion. In our treatment, there is no need to invoke the vector potential in a specific gauge and we avoid the commonly used notion of a fictitious cavity that applies boundary conditions to the field.

  19. Electromagnetic field generation by explosion in the ionosphere

    NASA Astrophysics Data System (ADS)

    Sorokin, V. M.; Sergeev, I. Yu.; Yaschenko, A. K.

    2006-01-01

    Interpolation model of the shock wave excited by explosion in the ionosphere is obtained. Basic criteria of the model are the correspondence to exact solutions for strong shock waves, the extrapolating to small Mach numbers and the agreement with experimental data. It allows obtaining the spatial-temporal distribution of thermodynamic functions and gas velocity behind the shock wave front. The model can be used for determination of the shock related electric current and the perturbation of ionosphere conductivity tensor. Calculations of electromagnetic field distribution in front of the shock wave related to explosion have shown the oscillatory structure of the field perturbation in the vicinity of the magnetic force line corresponding to the center of explosion. In the plane perpendicular to external magnetic field the perturbation has a form of pulse dispersed according to diffusion law. The oscillation frequency and the phase velocity of electromagnetic field perturbation decrease with increase of the propagation angle relatively to geomagnetic field direction.

  20. 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,…

  1. 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.

  2. Fractional effective action at strong electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Kleinert, Hagen; Strobel, Eckhard; Xue, She-Sheng

    2013-07-01

    In 1936, Weisskopf [K. Dan. Vidensk. Selsk. Mat. Fys. Medd. XIV (1936)] showed that for vanishing electric or magnetic fields the strong-field behavior of the one-loop Euler-Heisenberg effective Lagrangian of quantum electro dynamics (QED) is logarithmic. Here we generalize this result for different limits of the Lorentz invariants E→2-B→2 and B→·E→. The logarithmic dependence can be interpreted as a lowest-order manifestation of an anomalous power behavior of the effective Lagrangian of QED, with critical exponents δ=e2/(12π) for spinor QED, and δS=δ/4 for scalar QED.

  3. Charged and Electromagnetic Fields from Relativistic Quantum Geometry

    NASA Astrophysics Data System (ADS)

    Arcodía, Marcos; Bellini, Mauricio

    2016-06-01

    In the Relativistic Quantum Geometry (RQG) formalism recently introduced, was explored the possibility that the variation of the tensor metric can be done in a Weylian integrable manifold using a geometric displacement, from a Riemannian to a Weylian integrable manifold, described by the dynamics of an auxiliary geometrical scalar field $\\theta$, in order that the Einstein tensor (and the Einstein equations) can be represented on a Weyl-like manifold. In this framework we study jointly the dynamics of electromagnetic fields produced by quantum complex vector fields, which describes charges without charges. We demonstrate that complex fields act as a source of tetra-vector fields which describe an extended Maxwell dynamics.

  4. Electromagnetic fields from mobile phone base station - variability analysis.

    PubMed

    Bienkowski, Pawel; Zubrzak, Bartlomiej

    2015-09-01

    The article describes the character of electromagnetic field (EMF) in mobile phone base station (BS) surroundings and its variability in time with an emphasis on the measurement difficulties related to its pulse and multi-frequency nature. Work also presents long-term monitoring measurements performed recently in different locations in Poland - small city with dispersed building development and in major polish city - dense urban area. Authors tried to determine the trends in changing of EMF spectrum analyzing daily changes of measured EMF levels in those locations. Research was performed using selective electromagnetic meters and also EMF meter with spectrum analysis. PMID:26444202

  5. [Clinical monitoring in areas of exposure to radiofrequency electromagnetic fields].

    PubMed

    Suvorov, I M

    2013-01-01

    Clinical syndromes induced by high intensity radiofrequency electromagnetic field chronic exposure are described. Persons injured by occupational exposure have been observed central nervous system changes in diencephalic syndrome form, cardio-vascular system changes revealed in atherosclerosis, isch(a)emic heart disease and coronary insufficiency rapid progressive expansion. General public living in territory of radar station exposure zone different functional disorders have been identified: vegetative dystonia (asthenovegetative syndrome), thrombocytopenia, decrease of blood coagulation index, and thyroid gland function changes. Observed diseases clinical variability may be determined by electromagnetic exposure characteristics. PMID:23785812

  6. Beta decay and other processes in strong electromagnetic fields

    SciTech Connect

    Akhmedov, E. Kh.

    2011-09-15

    We consider effects of the fields of strong electromagnetic waves on various characteristics of quantum processes. After a qualitative discussion of the effects of external fields on the energy spectra and angular distributions of the final-state particles as well as on the total probabilities of the processes (such as decay rates and total cross sections), we present a simple method of calculating the total probabilities of processes with production of nonrelativistic charged particles. Using nuclear {beta} decay as an example, we study the weak- and strong-field limits, as well as the field-induced {beta} decay of nuclei stable in the absence of the external fields, both in the tunneling and multiphoton regimes. We also consider the possibility of accelerating forbidden nuclear {beta} decays by lifting the forbiddeness due to the interaction of the parent or daughter nuclei with the field of a strong electromagnetic wave. It is shown that for currently attainable electromagnetic fields all effects on total {beta}-decay rates are unobservably small.

  7. Computational electromagnetics: the physics of smooth versus oscillatory fields.

    PubMed

    Chew, W C

    2004-03-15

    This paper starts by discussing the difference in the physics between solutions to Laplace's equation (static) and Maxwell's equations for dynamic problems (Helmholtz equation). Their differing physical characters are illustrated by how the two fields convey information away from their source point. The paper elucidates the fact that their differing physical characters affect the use of Laplacian field and Helmholtz field in imaging. They also affect the design of fast computational algorithms for electromagnetic scattering problems. Specifically, a comparison is made between fast algorithms developed using wavelets, the simple fast multipole method, and the multi-level fast multipole algorithm for electrodynamics. The impact of the physical characters of the dynamic field on the parallelization of the multi-level fast multipole algorithm is also discussed. The relationship of diagonalization of translators to group theory is presented. Finally, future areas of research for computational electromagnetics are described. PMID:15306509

  8. Electromagnetic Field Effects in Semiconductor Crystal Growth

    NASA Technical Reports Server (NTRS)

    Dulikravich, George S.

    1996-01-01

    This proposed two-year research project was to involve development of an analytical model, a numerical algorithm for its integration, and a software for the analysis of a solidification process under the influence of electric and magnetic fields in microgravity. Due to the complexity of the analytical model that was developed and its boundary conditions, only a preliminary version of the numerical algorithm was developed while the development of the software package was not completed.

  9. Motion of trapped electrons in gyro-resonant electromagnetic field

    NASA Astrophysics Data System (ADS)

    Hafizi, B.; Aamodt, R. E.

    1987-12-01

    It is shown that the phase space of magnetically trapped electrons in plasmas interacting with gyro-resonant electromagnetic waves is divided into two parts. In one, as a particle gains energy its turning point moves towards the region of weaker magnetic field; in the other, energy gain results in the turning point moving towards the region of stronger magnetic field, with possible detrapping. Present address: Lodestar Research Corporation, P.O. Box 4545, Boulder, CO 80306, USA

  10. Numerical Analysis of Electromagnetic Fields in Multiscale Model

    NASA Astrophysics Data System (ADS)

    Ma, Ji; Fang, Guang-You; Ji, Yi-Cai

    2015-04-01

    Modeling technique for electromagnetic fields excited by antennas is an important topic in computational electromagnetics, which is concerned with the numerical solution of Maxwell's equations. In this paper, a novel hybrid technique that combines method of moments (MoM) with finite-difference time-domain (FDTD) method is presented to handle the problem. This approach employed Huygen's principle to realize the hybridization of the two classical numerical algorithms. For wideband electromagnetic data, the interpolation scheme is used in the MoM based on the dyadic Green's function. On the other hand, with the help of equivalence principle, the scattered electric and magnetic fields on the Huygen's surface calculated by MoM are taken as the sources for FDTD. Therefore, the electromagnetic fields in the environment can be obtained by employing finite-difference time-domain method. Finally, numerical results show the validity of the proposed technique by analyzing two canonical samples. Supported in part by China Postdoctoral Science Foundation under Grant No. 201M550839, and in part by the Key Research Program of the Chinese Academy of Sciences under Grant No. KGZD-EW-603

  11. Proton Radiography as an electromagnetic field and density perturbation diagnostic

    SciTech Connect

    Mackinnon, A; Patel, P; Town, R; Edwards, M; Phillips, T; Lerner, S; Price, D; Hicks, D; Key, M; Hatchett, S; Wilks, S; King, J; Snavely, R; Freeman, R; Boehlly, T; Koenig, M; Martinolli, E; Lepape, S; Benuzzi-Mounaix, A; Audebert, P; Gauthier, J; Borghesi, M; Romagnani, L; Toncian, T; Pretzler, G; Willi, O

    2004-04-15

    Laser driven proton beams have been used to diagnose transient fields and density perturbations in laser produced plasmas. Grid deflectometry techniques have been applied to proton radiography to obtain precise measurements of proton beam angles caused by electromagnetic fields in laser produced plasmas. Application of proton radiography to laser driven implosions has demonstrated that density conditions in compressed media can be diagnosed with MeV protons. This data has shown that proton radiography can provide unique insight into transient electromagnetic fields in super critical density plasmas and provide a density perturbation diagnostics in compressed matter . PACS numbers: 52.50.Jm, 52.40.Nk, 52.40.Mj, 52.70.Kz

  12. Electromagnetic biaxial vector scanner using radial magnetic field.

    PubMed

    Han, Aleum; Cho, Ah Ran; Ju, Suna; Ahn, Si-Hong; Bu, Jong-Uk; Ji, Chang-Hyeon

    2016-07-11

    We present an electromagnetic biaxial vector-graphic scanning micromirror. In contrast to conventional electromagnetic actuators using linear magnetic field, proposed device utilizes a radial magnetic field and uniquely designed current paths to enable the 2 degree-of-freedom scanning motion. As the radial field is generated by concentrically assembled magnets placed under the scanner die, large driving torque can be generated without the aid of hermetic packaging and relatively small device volume can be achieved. Mechanical half scan angle of 6.43° and 4.20° have been achieved at DC current of 250mA and 350mA for horizontal and vertical scans, respectively. Forced actuation along both scan axes has been realized by feedback control. PMID:27410851

  13. 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

  14. Biological effects and exposure criteria for radiofrequency electromagnetic fields

    SciTech Connect

    Not Available

    1986-01-01

    This report, which begins with a discussion of fundamental studies at the molecular level, presents a review of the subject matter covered in NCRP Report No. 67 on mechanisms of interaction of radiofrequency electromagnetic (RFEM) fields with tissue. The discussion continues to progressively larger scales of interaction, beginning with macromolecular and cellular effects, chromosomal and mutagenic effects, and carcinogenic effects. The scope of the subject matter is then expanded to include systemic effects such as those on reproduction, growth, and development, hematopoiesis and immunology, endocrinology and autonomic nervous function, cardiovascular effects and cerebrovascular effects. The interaction of electromagnetic fields with the central nervous system and special senses is also discussed. Also included are epidemiological studies, a discussion of thermoregulation, and a history of therapeutic applications of RFEM fields. The report concludes with human exposure criteria and rationale.

  15. The electromagnetic force field, fluid flow field and temperature profiles in levitated metal droplets

    NASA Technical Reports Server (NTRS)

    El-Kaddah, N.; Szekely, J.

    1982-01-01

    A mathematical representation was developed for the electromagnetic force field, the flow field, the temperature field (and for transport controlled kinetics), in a levitation melted metal droplet. The technique of mutual inductances was employed for the calculation of the electromagnetic force field, while the turbulent Navier - Stokes equations and the turbulent convective transport equations were used to represent the fluid flow field, the temperature field and the concentration field. The governing differential equations, written in spherical coordinates, were solved numerically. The computed results were in good agreement with measurements, regarding the lifting force, and the average temperature of the specimen and carburization rates, which were transport controlled.

  16. Controlling Electromagnetic Field by Graded Meta-materials

    NASA Astrophysics Data System (ADS)

    Sun, Lei

    Metamaterials , i.e. artificial materials with electromagnetic properties not readily available in nature, have become a major research topic in both scientific and engineering communities. Being different from conventional materials, metamaterials possess peculiar electromagnetic properties, e.g. negative refractive index, depending on their structures. In particular, metamaterials form a basis for achieving cloaking device that makes an object invisible or transparency to the probing electromagnetic wave. This topic has significant impact on various fields ranging from optics, medicine, biology to nanotechnology. Several cloaking techniques have been proposed by different research groups, namely, anomalous localized resonance, transformation optics, and scattering cancellation, etc. Each of them has its own advantages and disadvantages. For instance, the limitation in working frequency is a primary disadvantage of them. This thesis is concentrated on controlling electromagnetic field by graded metamaterials, i.e, metamaterials with graded structures, with the objective to realize the broadband electromagnetic transparency by extending the working frequency. Regarding the limitations of existing cloaking techniques, we propose the graded model based on the scattering cancellation technique, because it does not rely on resonant phenomena, and is fairly robust to relatively high variations of the shape and electromagnetic properties of the cloaked object. We modify the original Mie theory and Rayleigh scattering theory to deal with the graded metamaterial structures, and calculate the scattering cross section of graded isotropic and anisotropic spherical structures, an alytically and numerically. For the graded isotropic spherical structure, we achieve the exact analytic expressions for both full-wave and Rayleigh scattering cross sections, within our modified Mie theory and Rayleigh scattering theory. The numerical studies on the scattering cross sections clearly

  17. Effect of current focusing on the sensitivity of inferior colliculus neurons to amplitude-modulated stimulation.

    PubMed

    George, Shefin S; Shivdasani, Mohit N; Fallon, James B

    2016-09-01

    In multichannel cochlear implants (CIs), current is delivered to specific electrodes along the cochlea in the form of amplitude-modulated pulse trains, to convey temporal and spectral cues. Our previous studies have shown that focused multipolar (FMP) and tripolar (TP) stimulation produce more restricted neural activation and reduced channel interactions in the inferior colliculus (IC) compared with traditional monopolar (MP) stimulation, suggesting that focusing of stimulation could produce better transmission of spectral information. The present study explored the capability of IC neurons to detect modulated CI stimulation with FMP and TP stimulation compared with MP stimulation. The study examined multiunit responses of IC neurons in acutely deafened guinea pigs by systematically varying the stimulation configuration, modulation depth, and stimulation level. Stimuli were sinusoidal amplitude-modulated pulse trains (carrier rate of 120 pulses/s). Modulation sensitivity was quantified by measuring modulation detection thresholds (MDTs), defined as the lowest modulation depth required to differentiate the response of a modulated stimulus from an unmodulated one. Whereas MP stimulation showed significantly lower MDTs than FMP and TP stimulation (P values <0.05) at stimulation ≤2 dB above threshold, all stimulation configurations were found to have similar modulation sensitivities at 4 dB above threshold. There was no difference found in modulation sensitivity between FMP and TP stimulation. The present study demonstrates that current focusing techniques such as FMP and TP can adequately convey amplitude modulation and are comparable to MP stimulation, especially at higher stimulation levels, although there may be some trade-off between spectral and temporal fidelity with current focusing stimulation. PMID:27306672

  18. Radiotelephone with reduced electromagnetic field in human head

    NASA Astrophysics Data System (ADS)

    King, Ronold W. P.

    1995-01-01

    The quarter-wave monopole base driven over a circular ground plane with a finite radius has applications in over-the-horizon radar and on surveillance aircraft. A new use, for which the analysis is given in this paper, is as an over-the-head-mounted antenna for cellular telephones. With this design, the electromagnetic field in the head and the associated specific absorption rate of electromagnetic energy are greatly reduced when compared with the conventional hand-held transceiver. A complete analysis is carried out of the electromagnetic field on the surface of the head and throughout its interior when the head is modeled as a cylinder with the electrical properties of the brain enclosed in a wall with the thickness and electrical properties of the skull. Graphs and tables are provided that give the field in the air on the surface of the head and in the skull and brain. The far field is also determined. The results are compared with those obtained with the hand-held radiotelephone (King, 1995).

  19. Electromagnetic fields in the exterior of an oscillating relativistic star - II. Electromagnetic damping

    NASA Astrophysics Data System (ADS)

    Rezzolla, Luciano; Ahmedov, Bobomurat J.

    2016-07-01

    An important issue in the asteroseismology of compact and magnetized stars is the determination of the dissipation mechanism which is most efficient in damping the oscillations when these are produced. In a linear regime and for low-multipolarity modes, these mechanisms are confined to either gravitational-wave or electromagnetic losses. We here consider the latter and compute the energy losses in the form of Poynting fluxes, Joule heating and Ohmic dissipation in a relativistic oscillating spherical star with a dipolar magnetic field in vacuum. While this approach is not particularly realistic for rapidly rotating stars, it has the advantage that it is fully analytic and that it provides expressions for the electric and magnetic fields produced by the most common modes of oscillation both in the vicinity of the star and far away from it. In this way, we revisit and extend to a relativistic context the classical estimates of McDermott et al. Overall, we find that general-relativistic corrections lead to electromagnetic damping time-scales that are at least one order of magnitude smaller than in Newtonian gravity. Furthermore, with the only exception of g (gravity) modes, we find that f (fundamental), p (pressure), i (interface) and s (shear) modes are suppressed more efficiently by gravitational losses than by electromagnetic ones.

  20. Cochlear hearing loss and the detection of sinusoidal versus random amplitude modulation.

    PubMed

    Grose, John H; Porter, Heather L; Buss, Emily; Hall, Joseph W

    2016-08-01

    This study assessed the effect of cochlear hearing loss on detection of random and sinusoidal amplitude modulation. Listeners with hearing loss and normal-hearing listeners (eight per group) generated temporal modulation transfer functions (TMTFs) for envelope fluctuations carried by a 2000-Hz pure tone. TMTFs for the two groups were similar at low modulation rates but diverged at higher rates presumably because of differences in frequency selectivity. For both groups, detection of random modulation was poorer than for sinusoidal modulation at lower rates but the reverse occurred at higher rates. No evidence was found that cochlear hearing loss, per se, affects modulation detection. PMID:27586778

  1. VizieR Online Data Catalog: Kepler δ Sct stars amplitude modulation (Bowman+, 2016)

    NASA Astrophysics Data System (ADS)

    Bowman, D. M.; Kurtz, D. W.; Breger, M.; Murphy, S. J.; Holdsworth, D. L.

    2016-06-01

    We searched for amplitude modulation of pulsation modes in δ Sct stars observed by the Kepler Space Telescope. The number of pulsation modes out of a maximum of twelve that have constant amplitudes and variable amplitudes are given in the columns NoMod and AMod, respectively, along with stellar parameters from Huber et al. (2014, Cat. J/ApJS/211/2). Table 1 is the full version for all 983 δ Sct stars the abridged version of the paper. (1 data file).

  2. Effects of noise and electromagnetic fields on reproductive outcomes.

    PubMed Central

    Meyer, R E; Aldrich, T E; Easterly, C E

    1989-01-01

    Much public health research has been directed to studies of cancer risks due to chemical agents. Recently, increasing attention has been given to adverse reproductive outcomes as another, shorter-term biologic indicator of public health impact. Further, several low-level ubiquitous physical agents have been implicated recently as possibly affecting human health. These physical factors (noise and electromagnetic fields) represent difficult topics for research with epidemiologic study methods. This paper provides a brief review of the published data related to the risk of adverse reproductive outcomes and exposure to noise or electromagnetic fields. The discussion includes ideas for possible biologic mechanisms, considerations for exposure assessment, and suggestions for epidemiologic research. PMID:2667980

  3. Controversies related to electromagnetic field exposure on peripheral nerves.

    PubMed

    Say, Ferhat; Altunkaynak, Berrin Zuhal; Coşkun, Sina; Deniz, Ömür Gülsüm; Yıldız, Çağrı; Altun, Gamze; Kaplan, Arife Ahsen; Kaya, Sefa Ersan; Pişkin, Ahmet

    2016-09-01

    Electromagnetic field (EMF) is a pervasive environmental presence in modern society. In recent years, mobile phone usage has increased rapidly throughout the world. As mobile phones are generally held close to the head while talking, studies have mostly focused on the central and peripheral nervous system. There is a need for further research to ascertain the real effect of EMF exposure on the nervous system. Several studies have clearly demonstrated that EMF emitted by cell phones could affect the systems of the body as well as functions. However, the adverse effects of EMF emitted by mobile phones on the peripheral nerves are still controversial. Therefore, this review summarizes current knowledge on the possible positive or negative effects of electromagnetic field on peripheral nerves. PMID:26718608

  4. Reflection-type spatial amplitude modulation of visible light based on a sub-wavelength plasmonic absorber.

    PubMed

    Hwang, Chi-Young; Yi, Yoonsik; Choi, Choon-Gi

    2016-03-01

    We present a method for reflection-type spatial amplitude modulation using a sub-wavelength plasmonic absorber structure that can operate in the visible region. We utilize a pixelated array of absorbing elements based on a two-dimensional sub-wavelength metal grating, and the reflectance of each pixel is controlled by simple structural modification. For the purpose of validation, numerical simulations were performed on an amplitude modulation hologram fabricated using our method. PMID:26974098

  5. 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.

  6. Immune Response to Electromagnetic Fields through Cybernetic Modeling

    NASA Astrophysics Data System (ADS)

    Godina-Nava, J. J.; Segura, M. A. Rodríguez; Cadena, S. Reyes; Sierra, L. C. Gaitán

    2008-08-01

    We study the optimality of the humoral immune response through a mathematical model, which involves the effect of electromagnetic fields over the large lymphocytes proliferation. Are used the so called cybernetic variables in the context of the matching law of microeconomics or mathematical psychology, to measure the large lymphocytes population and to maximize the instantaneous antibody production rate in time during the immunologic response in order to most efficiently inactivate the antigen.

  7. 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.

  8. 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.

  9. Immune Response to Electromagnetic Fields through Cybernetic Modeling

    SciTech Connect

    Godina-Nava, J. J.; Segura, M. A. Rodriguez; Cadena, S. Reyes; Sierra, L. C. Gaitan

    2008-08-11

    We study the optimality of the humoral immune response through a mathematical model, which involves the effect of electromagnetic fields over the large lymphocytes proliferation. Are used the so called cybernetic variables in the context of the matching law of microeconomics or mathematical psychology, to measure the large lymphocytes population and to maximize the instantaneous antibody production rate in time during the immunologic response in order to most efficiently inactivate the antigen.

  10. Opinion on potential health effects of exposure to electromagnetic fields.

    PubMed

    2015-09-01

    In January 2015, the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) published its final opinion on "Potential health effects of exposure to electromagnetic fields." The purpose of this document was to update previous SCENIHR opinions in the light of recently available information since then, and to give special consideration to areas that had not been dealt with in the previous opinions or in which important knowledge gaps had been identified. PMID:26179386

  11. FLASH requirements for the high intensity radiated field electromagnetic environment

    NASA Astrophysics Data System (ADS)

    Murdock, John K.

    1995-05-01

    The worldwide proliferation of high intensity emitting sources and the more electric aircraft increase the intensity of the Electromagnetic Environment (EME) in which aircraft must operate. A FLASH program HIRF (High Intensity Radiated Field) EME requirement is derived to cover both commercial and military fixed and rotary wing aircraft. This requirement is derived from the radiated susceptibility requirement documents of both the FAA and U.S. military. Specific test data and analysis will show that we can meet this requirement.

  12. Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR.

    PubMed

    Basse, Kristoffer; Shankar, Ravi; Bjerring, Morten; Vosegaard, Thomas; Nielsen, Niels Chr; Nielsen, Anders B

    2016-09-01

    We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization ((RESPIRATION)CP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer. In this description, it becomes transparent that the main attribute leading to non-ideal performance is a fictitious field along the rf field axis, which is generated from second-order cross terms arising mainly between chemical shift tensors and themselves. This insight is useful for the development of improved recoupling experiments. We discuss the validity of this approach and present quaternion calculations to determine the effective resonance conditions in a combined rf field and chemical shift offset interaction frame transformation. Based on this, we derive a broad-banded version of the (RESPIRATION)CP experiment. The new sequence is experimentally verified using SNNFGAILSS amyloid fibrils where simultaneous (15)N → (13)CO and (15)N → (13)Cα coherence transfer is demonstrated on high-field NMR instrumentation, requiring great offset stability. PMID:27608995

  13. Electron-ion collision operator in strong electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Fraiman, Gennadiy; Balakin, Alexey

    2012-10-01

    The pair electron-ion collision operator is found for the kinetic equation describing the one-particle drift distribution in strong electromagnetic fields [1]. The pair collisions are studied under the conditions when the oscillation velocity of an electron driven by an external electromagnetic wave is much larger than the electron drift velocity. The operator is presented in the Boltzmann form and describes collisions with both small and large changes of the particle momentum. In contrast with the Landau collision operator, which describes diffusion in the momentum space, the collision operator that we propose describes a new and very important effect, namely, Coulomb attraction of a wave-driven oscillating electron to an ion due to multiple returns of the electron to the same ion. This effect leads to a large increase of the collision cross-section of electron-ion collisions in strong laser fields, to increased efficiency of the Joule heating in plasma, to the generation of fast electrons through e-i collisions, etc. [4pt] [1] A. A. Balakin and G. M. Fraiman, Electron-ion collision operator in strong electromagnetic fields, EPL 93, 35001 (2011).

  14. Measurement of radiofrequency electromagnetic fields in and around ambulances.

    PubMed

    Boivin, W S; Boyd, S M; Coletta, J A; Neunaber, L M

    1997-01-01

    Electromagnetic interference (EMI) with medical devices can threaten patient safety. More information is needed regarding circumstances in health care environments in which electromagnetic (EM) field strengths are expected to be high, such as emergency/transport. In ambulances medical devices and communications equipment must function properly in close proximity. This study characterized EM fields in and around ambulances under realistic conditions. Two types of ambulances were surveyed: the advanced life support (ALS) unit and the basic life support (BLS) unit. The surveys were conducted on-site using the ambulance mobile radio as the primary source of EM energy. Broadband field-strength measurements were collected at various locations in and around the ambulance to map interior and exterior EM field distributions. Nine ambulances were surveyed. In addition to the transmitter power and frequency, the field strengths measured were shown to be dependent upon the shielding provided by the ambulance roof and proximity of the measurement probe to the antenna. Field-strength measurements frequently exceeded the 3 V/m standard immunity level for devices set by the IEC Standard 601-1-2. The results indicate that the ambulance environment presents a considerable challenge to medical devices specifically used for emergency medical care. In order to assure their proper operation, medical devices used for transport emergency care must be able to withstand exposure to EM field strengths comparable to those reported in this study. PMID:9099436

  15. Offshore windmills and the effects of electromagnetic fields on fish.

    PubMed

    Ohman, Marcus C; Sigray, Peter; Westerberg, Håkan

    2007-12-01

    With the large scale developments of offshore windpower the number of underwater electric cables is increasing with various technologies applied. A wind farm is associated with different types of cables used for intraturbine, array-to-transformer, and transformer-to-shore transmissions. As the electric currents in submarine cables induce electromagnetic fields there is a concern of how they may influence fishes. Studies have shown that there are fish species that are magneto-sensitive using geomagnetic field information for the purpose of orientation. This implies that if the geomagnetic field is locally altered it could influence spatial patterns in fish. There are also physiological aspects to consider, especially for species that are less inclined to move as the exposure could be persistent in a particular area. Even though studies have shown that magnetic fields could affect fish, there is at present limited evidence that fish are influenced by the electromagnetic fields that underwater cables from windmills generate. Studies on European eel in the Baltic Sea have indicated some minor effects. In this article we give an overview on the type of submarine cables that are used for electric transmissions in the sea. We also describe the character of the magnetic fields they induce. The effects of magnetic fields on fish are reviewed and how this may relate to the cables used for offshore wind power is discussed. PMID:18240676

  16. Comparison of saltation, amplitude modulation, and a hybrid method of vibrotactile stimulation.

    PubMed

    Raisamo, Jukka; Raisamo, Roope; Surakka, Veikko

    2013-01-01

    Illusory vibrotactile movement can be used to provide directional tactile information on the skin. Our research question was how the presentation method affects the perception of vibrotactile movement. Illusion of vibrotactile mediolateral movement was elicited to a left dorsal forearm to investigate cognitive and emotional experiences to vibrotactile stimulation. Eighteen participants were presented with stimuli delivered to a linearly aligned row of three vibrotactile actuators. Three presentation methods were used--saltation, amplitude modulation, and a hybrid method--to form 12 distinct patterns of movement. First, the stimuli were compared pairwise using a two-alternative forced-choice procedure (same-different judgments). Second, the stimuli were rated using three nine-point bipolar scales measuring the continuity, pleasantness, and arousal of each stimulus. The stimuli presented with the amplitude modulation method were rated significantly more continuous and pleasant, and less arousing. Strong correlations between the cognition-related scale of continuity and the emotion-related scales of pleasantness and arousal were found: More continuous stimuli were rated more pleasant and less arousing. PMID:24808403

  17. NOTE ON TRAVEL TIME SHIFTS DUE TO AMPLITUDE MODULATION IN TIME-DISTANCE HELIOSEISMOLOGY MEASUREMENTS

    SciTech Connect

    Nigam, R.; Kosovichev, A. G. E-mail: sasha@quake.stanford.ed

    2010-01-10

    Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times have not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is artificially suppressed by a spatial function, and using numerical simulations that the amplitude modulations in combination with the phase-speed filtering may cause systematic shifts of acoustic travel times. To understand the properties of this procedure, we derive an analytical expression for the cross-covariance of a signal that has been modulated locally by a spatial function that has azimuthal symmetry and then filtered by a phase-speed filter typically used in time-distance helioseismology. Comparing this expression to the Gabor wavelet fitting formula without this effect, we find that there is a shift in the travel times that is introduced by the amplitude modulation. The analytical model presented in this paper can be useful also for interpretation of travel time measurements for the non-uniform distribution of oscillation amplitude due to observational effects.

  18. The influence of practice on the detectability of auditory sinusoidal amplitude modulation

    NASA Astrophysics Data System (ADS)

    Fitzgerald, Matthew B.; Wright, Beverly A.

    2002-05-01

    The capacity to detect fluctuations in sound amplitude influences the perception of many everyday sounds, including speech. Here, the influence of practice on this ability was investigated. Between two testing sessions, one group of nine listeners who were tested on the detection of sinusoidal amplitude modulation (SAM) improved by about 0.7 dB on each of five conditions (300 trials/condition). Nine other listeners participated in these same sessions, but between them, practiced 4320 trials detecting the presence of 80-Hz SAM with a 3- to 4-kHz narrow-band carrier. Only three of these listeners, who had among the highest initial detection thresholds on the trained condition, improved during this training phase. These learners subsequently improved at untrained modulation rates (30 and 150 Hz) with the trained carrier, but not at the trained modulation rate with untrained carriers (0.5-1.5 kHz and 0-5 kHz). These data suggest that (1) at some stage, modulation processing is more linked to the carrier spectrum than to the modulation rate, and (2) while most normal-hearing listeners reach their best modulation-detection performance with minimal experience, listeners with high initial thresholds benefit from extended practice. Thus, training may aid populations that have difficulty detecting amplitude modulation. [Work supported by NIDCD.

  19. Dynamic enhancement of autofocusing property for symmetric Airy beam with exponential amplitude modulation

    NASA Astrophysics Data System (ADS)

    Liu, Weiwei; Lu, Yao; Gong, Lei; Chu, Xiuxiang; Xue, Guosheng; Ren, Yuxuan; Zhong, Mincheng; Wang, Ziqiang; Zhou, Jinhua; Li, Yinmei

    2016-07-01

    A symmetric Airy beam (SAB) autofocuses during free space propagation. Such autofocusing SAB is useful in optical manipulation and biomedical imaging. However, its inherently limited autofocusing property may degrade the performance of the SAB in those applications. To enhance the autofocus, a symmetric apodization mask was proposed to regulate the SAB. In combination with the even cubic phase that shapes the SAB, this even exponential function mask with an adjustable parameter regulates the contribution of different frequency spectral components to the SAB. The propagation properties of this new amplitude modulated SAB (AMSAB) were investigated both theoretically and experimentally. Simulation shows that the energy distribution and autofocusing property of an AMSAB can be adjusted by the exponential amplitude modulation. Especially, the beam energy will be more concentrated in the central lobe once the even cubic phase is modulated by the mask with a higher proportion of high-frequency spectral components. Consequently, the autofocusing property and axial gradient force of AMSABs are efficiently enhanced. The experimental generation and characterization for AMSABs were implemented by modulating the collimated beam with a phase-only spatial light modulator. The experimental results well supported the theoretical predictions. With the ability to enhance the autofocus, the proposed exponential apodization modulation will make SAB more powerful in various applications, including optical trapping, fluorescence imaging and particle acceleration.

  20. Identification-Based Closed-Loop NMES Limb Tracking With Amplitude-Modulated Control Input.

    PubMed

    Cheng, Teng-Hu; Wang, Qiang; Kamalapurkar, Rushikesh; Dinh, Huyen T; Bellman, Matthew; Dixon, Warren E

    2016-07-01

    An upper motor neuron lesion (UMNL) can be caused by various neurological disorders or trauma and leads to disabilities. Neuromuscular electrical stimulation (NMES) is a technique that is widely used for rehabilitation and restoration of motor function for people suffering from UMNL. Typically, stability analysis for closed-loop NMES ignores the modulated implementation of NMES. However, electrical stimulation must be applied to muscle as a modulated series of pulses. In this paper, a muscle activation model with an amplitude modulated control input is developed to capture the discontinuous nature of muscle activation, and an identification-based closed-loop NMES controller is designed and analyzed for the uncertain amplitude modulated muscle activation model. Semi-global uniformly ultimately bounded tracking is guaranteed. The stability of the closed-loop system is analyzed with Lyapunov-based methods, and a pulse frequency related gain condition is obtained. Experiments are performed with five able-bodied subjects to demonstrate the interplay between the control gains and the pulse frequency, and results are provided which indicate that control gains should be increased to maintain stability if the stimulation pulse frequency is decreased to mitigate muscle fatigue. For the first time, this paper brings together an analysis of the controller and modulation scheme. PMID:26241989

  1. Interactive coding of visual spatial frequency and auditory amplitude-modulation rate.

    PubMed

    Guzman-Martinez, Emmanuel; Ortega, Laura; Grabowecky, Marcia; Mossbridge, Julia; Suzuki, Satoru

    2012-03-01

    Spatial frequency is a fundamental visual feature coded in primary visual cortex, relevant for perceiving textures, objects, hierarchical structures, and scenes, as well as for directing attention and eye movements. Temporal amplitude-modulation (AM) rate is a fundamental auditory feature coded in primary auditory cortex, relevant for perceiving auditory objects, scenes, and speech. Spatial frequency and temporal AM rate are thus fundamental building blocks of visual and auditory perception. Recent results suggest that crossmodal interactions are commonplace across the primary sensory cortices and that some of the underlying neural associations develop through consistent multisensory experience such as audio-visually perceiving speech, gender, and objects. We demonstrate that people consistently and absolutely (rather than relatively) match specific auditory AM rates to specific visual spatial frequencies. We further demonstrate that this crossmodal mapping allows amplitude-modulated sounds to guide attention to and modulate awareness of specific visual spatial frequencies. Additional results show that the crossmodal association is approximately linear, based on physical spatial frequency, and generalizes to tactile pulses, suggesting that the association develops through multisensory experience during manual exploration of surfaces. PMID:22326023

  2. Study of the optimal duty cycle and pumping rate for square-wave amplitude-modulated Bell–Bloom magnetometers

    NASA Astrophysics Data System (ADS)

    Mei-Ling, Wang; Meng-Bing, Wang; Gui-Ying, Zhang; Kai-Feng, Zhao

    2016-06-01

    We theoretically and experimentally study the optimal duty cycle and pumping rate for square-wave amplitude-modulated Bell–Bloom magnetometers. The theoretical and the experimental results are in good agreement for duty cycles and corresponding pumping rates ranging over 2 orders of magnitude. Our study gives the maximum field response as a function of duty cycle and pumping rate. Especially, for a fixed duty cycle, the maximum field response is obtained when the time averaged pumping rate, which is the product of pumping rate and duty cycle, is equal to the transverse relaxation rate in the dark. By using a combination of small duty cycle and large pumping rate, one can increase the maximum field response by up to a factor of 2 or π/2, relative to that of the sinusoidal modulation or the 50% duty cycle square-wave modulation respectively. We further show that the same pumping condition is also practically optimal for the sensitivity due to the fact that the signal at resonance is insensitive to the fluctuations of pumping rate and duty cycle. Project supported by the National Natural Science Foundation of China (Grant No. 11074050).

  3. Electro-Magnetic Fields and Plasma in the Cosmos

    SciTech Connect

    Scott, Donald E.

    2006-03-21

    It is becoming widely recognized that a majority of baryons in the cosmos are in the plasma state. But, fundamental disagreements about the properties and behavior of electro-magnetic fields in these plasmas exist between the science of modern astronomy and the experimentally verified laws of electrical engineering and physics. Some astronomers claim that magnetic fields can be open-ended - that they begin on or beneath the Sun's surface and extend outward to infinity. Astrophysicists have claimed that galactic magnetic fields begin and end on molecular clouds. Electrical engineers, most physicists, and the pioneers in electromagnetic field theory disagree - magnetic fields have no beginning or end. Since these two viewpoints are mutually exclusive, both cannot be correct; one must be completely false. Many astrophysicists claim that magnetic fields are 'frozen into' electric plasma. We also examine the basis for this claim. It has been shown to be incorrect in the laboratory. The hypothetical 'magnetic merging' mechanism is also reviewed in light of both theoretical and experimental investigations. The cause of large-scale filamentation in the cosmos is also simply revealed by experimental results obtained in plasma laboratories.

  4. Reconstruction of velocity fields in electromagnetic flow tomography.

    PubMed

    Lehtikangas, Ossi; Karhunen, Kimmo; Vauhkonen, Marko

    2016-06-28

    Electromagnetic flow meters (EMFMs) are the gold standard in measuring flow velocity in process industry. The flow meters can measure the mean flow velocity of conductive liquids and slurries. A drawback of this approach is that the velocity field cannot be determined. Asymmetric axial flows, often encountered in multiphase flows, pipe elbows and T-junctions, are problematic and can lead to serious systematic errors. Recently, electromagnetic flow tomography (EMFT) has been proposed for measuring velocity fields using several coils and a set of electrodes attached to the surface of the pipe. In this work, a velocity field reconstruction method for EMFT is proposed. The method uses a previously developed finite-element-based computational forward model for computing boundary voltages and a Bayesian framework for inverse problems. In the approach, the vz-component of the velocity field along the longitudinal axis of the pipe is estimated on the pipe cross section. Different asymmetric velocity fields encountered near pipe elbows, solids-in-water flows in inclined pipes and in stratified or multiphase flows are tested. The results suggest that the proposed reconstruction method could be used to estimate velocity fields in complicated pipe flows in which the conventional EMFMs have limited accuracy. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185961

  5. 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

  6. Nonminimally coupled gravitational and electromagnetic fields: pp-wave solutions

    SciTech Connect

    Dereli, Tekin; Sert, Oezcan

    2011-03-15

    We give the Lagrangian formulation of a generic nonminimally extended Einstein-Maxwell theory with an action that is linear in the curvature and quadratic in the electromagnetic field. We derive the coupled field equations by a first-order variational principle using the method of Lagrange multipliers. We look for solutions describing plane-fronted Einstein-Maxwell waves with parallel rays. We give a family of exact pp-wave solutions associated with a partially massless spin-2 photon and a partially massive spin-2 graviton.

  7. Topological thermal Casimir effect for spinor and electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bezerra, V. B.

    2015-12-01

    We obtain the thermal corrections to the Casimir energy for the neutrino and electromagnetic fields in Einstein and closed Friedmann universes containing a static, infinitely straight and thin cosmic string. The Casimir free energy is also obtained as well as their low and high temperature limits. It is shown that the vacuum energies associated with these fields, in the background considered, are given simply by the vacuum energies in the absence of the cosmic string multiplied by a factor that codifies the presence of this topological defect.

  8. Time-Domain Computation Of Electromagnetic Fields In MMICs

    NASA Technical Reports Server (NTRS)

    Lansing, Faiza S.; Rascoe, Daniel L.

    1995-01-01

    Maxwell's equations solved on three-dimensional, conformed orthogonal grids by finite-difference techniques. Method of computing frequency-dependent electrical parameters of monolithic microwave integrated circuit (MMIC) involves time-domain computation of propagation of electromagnetic field in response to excitation by single pulse at input terminal, followed by computation of Fourier transforms to obtain frequency-domain response from time-domain response. Parameters computed include electric and magnetic fields, voltages, currents, impedances, scattering parameters, and effective dielectric constants. Powerful and efficient means for analyzing performance of even complicated MMIC.

  9. Electromagnetic field properties in the vicinity of a massive wormhole

    SciTech Connect

    Novikov, I. D.; Shatskiy, A. A.

    2011-12-15

    It is proved that not only massless but also traversable massive wormholes can have electromagnetic 'hair.' An analysis is also presented of the passage from a traversable wormhole to the limit of a Reissner-Nordstroem black hole, with the corresponding disappearance of 'hair.' A general method is developed for solving stationary axisymmetric Maxwell's equations in the field of a massive, spherically symmetric wormhole. As a particular example of application of the method, a solution is found to the axisymmetric magnetostatic problem for a current loop in the field of the Bronnikov-Ellis-Morris-Thorne wormhole.

  10. Spectrum of classes of point emitters of electromagnetic wave fields.

    PubMed

    Castañeda, Román

    2016-09-01

    The spectrum of classes of point emitters has been introduced as a numerical tool suitable for the design, analysis, and synthesis of non-paraxial optical fields in arbitrary states of spatial coherence. In this paper, the polarization state of planar electromagnetic wave fields is included in the spectrum of classes, thus increasing its modeling capabilities. In this context, optical processing is realized as a filtering on the spectrum of classes of point emitters, performed by the complex degree of spatial coherence and the two-point correlation of polarization, which could be implemented dynamically by using programmable optical devices. PMID:27607498

  11. Electromagnetic plasma wave emissions from the auroral field lines

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1978-01-01

    The most important types of auroral radio emissions are reviewed. Particular attention is given to the following four types of electromagnetic emissions: auroral hiss, saucers, ELF noise bands, and auroral kilometric radiation. It is shown that the auroral hiss and auroral kilometric radiation are generated along the auroral field lines relatively close to the earth, at radial distances in the range of 2.5-5 earth radii, probably in direct association with auroral-particle acceleration by parallel electric fields. The auroral hiss appears to be generated by amplified Cerenkov radiation. Several mechanisms are proposed for the auroral kilometric radiation, usually involving the intermediate generation of electrostatic waves by the precipitating electrons.

  12. Electromagnetic field properties in the vicinity of a massive wormhole

    NASA Astrophysics Data System (ADS)

    Novikov, I. D.; Shatskiy, A. A.

    2011-12-01

    It is proved that not only massless but also traversable massive wormholes can have electromagnetic "hair." An analysis is also presented of the passage from a traversable wormhole to the limit of a Reissner-Nordström black hole, with the corresponding disappearance of "hair." A general method is developed for solving stationary axisymmetric Maxwell's equations in the field of a massive, spherically symmetric wormhole. As a particular example of application of the method, a solution is found to the axisymmetric magnetostatic problem for a current loop in the field of the Bronnikov-Ellis-Morris-Thorne wormhole.

  13. Electromagnetic field evolution in relativistic heavy-ion collisions

    SciTech Connect

    Voronyuk, V.; Toneev, V. D.; Cassing, W.; Bratkovskaya, E. L.; Konchakovski, V. P.; Voloshin, S. A.

    2011-05-15

    The hadron string dynamics (HSD) model is generalized to include the creation and evolution of retarded electromagnetic fields as well as the influence of the magnetic and electric fields on the quasiparticle propagation. The time-space structure of the fields is analyzed in detail for noncentral Au + Au collisions at {radical}(s{sub NN})=200 GeV. It is shown that the created magnetic field is highly inhomogeneous, but in the central region of the overlapping nuclei it changes relatively weakly in the transverse direction. For the impact parameter b=10 fm, the maximal magnetic field - perpendicularly to the reaction plane - is obtained of order eB{sub y}/m{sub {pi}}{sup 2}{approx}5 for a very short time {approx}0.2 fm/c, which roughly corresponds to the time of a maximal overlap of the colliding nuclei. We find that at any time, the location of the maximum in the eB{sub y} distribution correlates with that of the energy density of the created particles. In contrast, the electric field distribution, being also highly inhomogeneous, has a minimum in the center of the overlap region. Furthermore, the field characteristics are presented as a function of the collision energy and the centrality of the collisions. To explore the effect of the back reaction of the fields on hadronic observables, a comparison of HSD results with and without fields is exemplified. Our actual calculations show no noticeable influence of the electromagnetic fields--created in heavy-ion collisions--on the effect of the electric charge separation with respect to the reaction plane.

  14. Cardiac torsion and electromagnetic fields: the cardiac bioinformation hypothesis.

    PubMed

    Burleson, Katharine O; Schwartz, Gary E

    2005-01-01

    Although in physiology the heart is often referred to as a simple piston pump, there are in fact two additional features that are integral to cardiac physiology and function. First, the heart as it contracts in systole, also rotates and produces torsion due to the structure of the myocardium. Second, the heart produces a significant electromagnetic field with each contraction due to the coordinated depolarization of myocytes producing a current flow. Unlike the electrocardiogram, the magnetic field is not limited to volume conduction and extends outside the body. The therapeutic potential for interaction of this cardioelectromagnetic field both within and outside the body is largely unexplored. It is our hypothesis that the heart functions as a generator of bioinformation that is central to normative functioning of body. The source of this bioinformation is based on: (1) vortex blood flow in the left ventricle; (2) a cardiac electromagnetic field and both; (3) heart sounds; and (4) pulse pressure which produce frequency and amplitude information. Thus, there is a multidimensional role for the heart in physiology and biopsychosocial dynamics. Recognition of these cardiac properties may result in significant implications for new therapies for cardiovascular disease based on increasing cardiac energy efficiency (coherence) and bioinformation from the cardioelectromagnetic field. Research studies to test this hypothesis are suggested. PMID:15823696

  15. Electromagnetic field exposure dosimeter. Final report, September 1992-May 1993

    SciTech Connect

    Feaga, A.C.; Hilliard, M.P.; Link, R.

    1994-07-28

    The growing concern about adverse health effects caused by electromagnetic radiation prompted the ideas for this dosimeter. Data have been presented that link prolonged exposure to electromagnetic radiation from power lines to leukemia and some types of cancer. At present, though, there is a lack of recording instrumentation to measure the prolonged exposure of an individual; thus, it is not possible to correlate properly the amount of exposure or dose to health effects. With the recent advances in small, low-power devices, a small measuring device can be developed. Once this is built, a large data base can be obtained to help correlate electromagnetic field exposure to health conditions. The objective of this project is to develop an instrument which can measure electromagnetic fields over a prolonged period of time. The instrument would be small, say about the size of a radio Walkman, and would be worn throughout the day while taking data, as the individual goes about normal activities. A PC would be used to retrieve the data from the instrument at the end of the day. The dosimeter comprises a triaxial ferrite-loaded coil sensor, a set of amplifiers and filters, analog-to-digital converters, a microcontroller, and random access data memory. The signals from the sensor are filtered into three frequency ranges: one to measure 60-Hz exposure and two harmonics, another to measure high-energy pulsed energy, and a third frequency range to record the activity level of the individual. The signals from the filters are digitized and read into a microcontroller. The microcontroller performs a few calculations and controls the flow of the data to either random access memory or to a computer. A computer is used to retrieve the data from the dosimeter, and can store and display the measured data.

  16. Instability-driven electromagnetic fields in coronal plasmasa)

    NASA Astrophysics Data System (ADS)

    Manuel, M. J.-E.; Li, C. K.; Séguin, F. H.; Sinenian, N.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D.; Hager, J. D.; Betti, R.; Hu, S. X.; Delettrez, J.; Meyerhofer, D. D.

    2013-05-01

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. Séguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser-irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of ˜210 μm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature and density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.

  17. Instability-driven electromagnetic fields in coronal plasmas

    DOE PAGESBeta

    Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; Sinenian, N.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D.; Hager, J. D.; Betti, R.; Hu, S. X.; et al

    2013-04-15

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of 210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature andmore » density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.« less

  18. Instability-driven electromagnetic fields in coronal plasmas

    SciTech Connect

    Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; Sinenian, N.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D.; Hager, J. D.; Betti, R.; Hu, S. X.; Delettrez, J.; Meyerhofer, D. D.

    2013-04-15

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of 210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature and density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.

  19. Instability-driven electromagnetic fields in coronal plasmas

    SciTech Connect

    Manuel, M. J.-E.; Li, C. K.; Séguin, F. H.; Sinenian, N.; Frenje, J. A.; Casey, D. T.; Petrasso, R. D.; Hager, J. D.; Betti, R.; Hu, S. X.; Delettrez, J.; Meyerhofer, D. D.

    2013-05-15

    Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. Séguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser-irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of ∼210 μm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature and density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.

  20. Cosmological magnetic fields from inflation in extended electromagnetism

    SciTech Connect

    Beltran Jimenez, Jose; Maroto, Antonio L.

    2011-01-15

    In this work we consider an extended electromagnetic theory in which the scalar state which is usually eliminated by means of the Lorenz condition is allowed to propagate. This state has been shown to generate a small cosmological constant in the context of standard inflationary cosmology. Here we show that the usual Lorenz gauge-breaking term now plays the role of an effective electromagnetic current. Such a current is generated during inflation from quantum fluctuations and gives rise to a stochastic effective charge density distribution. Because of the high electric conductivity of the cosmic plasma after inflation, the electric charge density generates currents which give rise to both vorticity and magnetic fields on sub-Hubble scales. Present upper limits on vorticity coming from temperature anisotropies of the CMB are translated into lower limits on the present value of cosmic magnetic fields. We find that, for a nearly scale invariant vorticity spectrum, magnetic fields B{sub {lambda}>}10{sup -12} G are typically generated with coherence lengths ranging from subgalactic scales up to the present Hubble radius. Those fields could act as seeds for a galactic dynamo or even account for observations just by collapse and differential rotation of the protogalactic cloud.

  1. Dark energy and cosmic magnetic fields: electromagnetic relics from inflation

    NASA Astrophysics Data System (ADS)

    Jiménez, Jose Beltrán; Maroto, Antonio L.

    We consider an extended electromagnetic theory in which the scalar state which is usually eliminated be means of the Lorenz condition is allowed to propagate. On super-Hubble scales, such a state is given by the temporal component of the electromagnetic potential and contributes as an effective cosmological constant to the energy-momentum tensor. Its initial amplitude is set by quantum fluctuations generated during inflation and it is shown that the predicted value for the cosmological constant agrees with observations provided inflation took place at the electroweak scale. We also consider more general theories including non-minimal couplings to the space-time curvature in the presence of the temporal electromagnetic background. We show that both in the minimal and non-minimal cases, the modified Maxwell's equations include new effective current terms which can generate magnetic fields from sub-galactic scales up to the present Hubble horizon. The corresponding amplitudes could be enough to seed a galactic dynamo or even to account for observations just by collapse and differential rotation in the protogalactic cloud.

  2. Application of nano material for shielding power-frequency electromagnetic field

    NASA Astrophysics Data System (ADS)

    Li, Hualiang; Li, Li; Liu, Jiawen

    2015-07-01

    Only limited data are available on shielding electromagnetic field exposure in professional work. In our paper, we studied the electromagnetic field intensity in 500 kV substations, and explored influence of nanomaterial in high voltage laboratory simulation. Moreover, the results of nano-fabrics material for shielding power frequency electromagnetic field indicated that, both shielding fabrics can almost completely shield the electric field, but have weak shielding effectiveness against magnetic field.

  3. Potential sensitivities in frequency modulation and heterodyne amplitude modulation Kelvin probe force microscopes

    PubMed Central

    2013-01-01

    In this paper, the potential sensitivity in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM) and heterodyne amplitude modulation (AM) modes. We showed theoretically that the minimum detectable contact potential difference (CPD) in FM-KPFM is higher than in heterodyne AM-KPFM. We experimentally confirmed that the signal-to-noise ratio in FM-KPFM is lower than that in heterodyne AM-KPFM, which is due to the higher minimum detectable CPD dependence in FM-KPFM. We also compared the corrugations in the local contact potential difference on the surface of Ge (001), which shows atomic resolution in heterodyne AM-KPFM. In contrast, atomic resolution cannot be obtained in FM-KPFM under the same experimental conditions. The higher potential resolution in heterodyne AM-KPFM was attributed to the lower crosstalk and higher potential sensitivity between topographic and potential measurements. PMID:24350866

  4. The effect of temporal asymmetry on amplitude modulation detection using pure-tone carriers (L).

    PubMed

    Shen, Yi; Lentz, Jennifer J

    2011-11-01

    The effect of temporal asymmetry on amplitude modulation detection was studied using sawtooth modulators with rising (ramped) or falling (damped) temporal envelopes within each period of modulation. For pure-tone carriers, damped modulation was more detectable than ramped modulation for a 5-kHz carrier (by a threshold difference of 3.2 dB on average) but not for a 1-kHz carrier. The threshold difference obtained at 5 kHz between the ramped and damped modulators was consistent across modulation rates (8-128 Hz). This carrier frequency dependence suggests that the effect of temporally asymmetry on modulation detection originates from envelope-based, within-channel mechanisms. PMID:22087889

  5. Improvement in underwater phase measurement of an amplitude-modulated laser beam by polarimetric techniques.

    PubMed

    Bartolini, L; De Dominicis, L; Fornetti, G; Francucci, M; Guarneri, M; Poggi, C; Ricci, R

    2007-06-01

    The phase of the amplitude-modulated radiation reflected by a Lambertian target immersed in water was measured by using a linearly and circularly polarized sounding laser beam. Different values of the water extinction coefficient in the range of 0.06 - 2 m(-1) were realized by adding skim milk as a scattering element. It is shown that very efficient rejection of optical noise, resulting in reliable phase measurements, is accomplished with a cross-polarized and copolarized detection scheme for linear and circular polarization, respectively. The experiment demonstrates that phase measurements are very sensitive to optical noise suppression and that, as far as single scattering is the main involved mechanism, significant improvements can be achieved by adopting a polarization control on both the transmitter and the receiver stages of the apparatus. PMID:17546135

  6. Tip radius preservation for high resolution imaging in amplitude modulation atomic force microscopy

    SciTech Connect

    Ramos, Jorge R.

    2014-07-28

    The acquisition of high resolution images in atomic force microscopy (AFM) is correlated to the cantilever's tip shape, size, and imaging conditions. In this work, relative tip wear is quantified based on the evolution of a direct experimental observable in amplitude modulation atomic force microscopy, i.e., the critical amplitude. We further show that the scanning parameters required to guarantee a maximum compressive stress that is lower than the yield/fracture stress of the tip can be estimated via experimental observables. In both counts, the optimized parameters to acquire AFM images while preserving the tip are discussed. The results are validated experimentally by employing IgG antibodies as a model system.

  7. Instrument Reflections and Scene Amplitude Modulation in a Polychromatic Microwave Quadrature Interferometer

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Jones, Jonathan E.; Chavers, Greg

    2003-01-01

    A polychromatic microwave quadrature interferometer has been characterized using several laboratory plasmas. Reflections between the transmitter and the receiver have been observed, and the effects of including reflection terms in the data reduction equation have been examined. An error analysis which includes the reflections, modulation of the scene beam amplitude by the plasma, and simultaneous measurements at two frequencies has been applied to the empirical database, and the results are summarized. For reflection amplitudes around 1096, the reflection terms were found to reduce the calculated error bars for electron density measurements by about a factor of 2. The impact of amplitude modulation is also quantified. In the complete analysis, the mean error bar for high- density measurements is 7.596, and the mean phase shift error for low-density measurements is 1.2". .

  8. Monocular 3D see-through head-mounted display via complex amplitude modulation.

    PubMed

    Gao, Qiankun; Liu, Juan; Han, Jian; Li, Xin

    2016-07-25

    The complex amplitude modulation (CAM) technique is applied to the design of the monocular three-dimensional see-through head-mounted display (3D-STHMD) for the first time. Two amplitude holograms are obtained by analytically dividing the wavefront of the 3D object to the real and the imaginary distributions, and then double amplitude-only spatial light modulators (A-SLMs) are employed to reconstruct the 3D images in real-time. Since the CAM technique can inherently present true 3D images to the human eye, the designed CAM-STHMD system avoids the accommodation-convergence conflict of the conventional stereoscopic see-through displays. The optical experiments further demonstrated that the proposed system has continuous and wide depth cues, which enables the observer free of eye fatigue problem. The dynamic display ability is also tested in the experiments and the results showed the possibility of true 3D interactive display. PMID:27464184

  9. Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids

    PubMed Central

    Jaafar, Miriam; Cuenca, Mariano; Melcher, John; Raman, Arvind

    2012-01-01

    Summary We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode. PMID:22563531

  10. Response of a coupled two-spin system to on-resonance amplitude modulated RF pulses

    NASA Astrophysics Data System (ADS)

    Zhou, Jinyuan; Ye, Chaohui; Sanctuary, B. C.

    A weakly scalar-coupled two-spin system subjected to two amplitude modulated RF pulses on exact resonance is treated by means of the rotation operator approach. The theory presented here enables coherence evolution to be evaluated by the routine procedure and to be expressed in analytical form. The evolution behaviour from the equilibrium state is discussed in some detail. It is shown that the application of rotation matrix and quaternion elements clarifies evolution expressions. The numerical calculation is performed by way of quaternions. Examples of BURP (band-selective, uniform response, purephase) and sinc-shaped RF pulses are given and the case of time-symmetrical RF pulses is analysed further.

  11. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    SciTech Connect

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-15

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized {sup 208-210}Fr ion beams at beam energies of 5 keV and intensities of 10{sup 5} s{sup -1}. Efficient neutralization ({>=}80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  12. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    NASA Astrophysics Data System (ADS)

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized F208-210r ion beams at beam energies of 5 keV and intensities of 105 s-1. Efficient neutralization (≥80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  13. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers.

    PubMed

    Sell, J F; Gulyuz, K; Sprouse, G D

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized (208-210)Fr ion beams at beam energies of 5 keV and intensities of 10(5) s(-1). Efficient neutralization (> or = 80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate. PMID:20059132

  14. Minimising the effect of nanoparticle deformation in intermittent contact amplitude modulation atomic force microscopy measurements

    NASA Astrophysics Data System (ADS)

    Babic, Bakir; Lawn, Malcolm A.; Coleman, Victoria A.; Jämting, Åsa K.; Herrmann, Jan

    2016-06-01

    The results of systematic height measurements of polystyrene (PS) nanoparticles using intermittent contact amplitude modulation atomic force microscopy (IC-AM-AFM) are presented. The experimental findings demonstrate that PS nanoparticles deform during AFM imaging, as indicated by a reduction in the measured particle height. This deformation depends on the IC-AM-AFM imaging parameters, material composition, and dimensional properties of the nanoparticles. A model for nanoparticle deformation occurring during IC-AM-AFM imaging is developed as a function of the peak force which can be calculated for a particular set of experimental conditions. The undeformed nanoparticle height can be estimated from the model by extrapolation to zero peak force. A procedure is proposed to quantify and minimise nanoparticle deformation during IC-AM-AFM imaging, based on appropriate adjustments of the experimental control parameters.

  15. Multielectrode distributed feedback laser for pure frequency modulation and chirping suppressed amplitude modulation

    NASA Astrophysics Data System (ADS)

    Yoshikuni, Yuzo; Motosugi, George

    1987-04-01

    A new concept for operation of distributed feedback lasers with multielectrodes is proposed, and its capability for amplitude or frequency modulation is demonstrated. The device has electrically separated electrodes so that carrier density distribution along the laser cavity can be controlled artificially by adjusting the current distribution for each electrode. The lasing frequency can be controlled by changing the current ratio applied to the electrodes. Frequency modulation experiments disclose that neither frequency modulation efficiency nor phase delay depend on modulation frequency. It turned out that the frequency shift under modulation showed blue shift or red shift, depending on bias current distribution and the position of the modulation applied electrode. Using these characteristics, chirping suppressed amplitude modulation and frequency modulation with constant output power are realized.

  16. An Optimization of Pulsed ElectroMagnetic Fields Study

    NASA Technical Reports Server (NTRS)

    Goodwin, Thomas J.

    2006-01-01

    To date, in our research we have focused on the use of normal human neuronal progenitor (NHNP) cells because of their importance in human nervous system regeneration, development and maintenance, but we have developed 2-D and 3-D bioreactors that can accommodate any cell line. In this Project, we will include the use of tissues important for physiological regeneration: Human osteoblasts or chondrocytes, and vascular cells. Our initial results with the NHNP cells were quite startling using extremely low-level electromagnetic fields (5 microtesla at 10Hz; 6mA). The low-amplitude, rapidly time-varying electromagnetic fields exert a very potent effect on the proliferation, morphology, and gene expression of the cells in culture, both in standard 2-dimensional culture plates as well as cells organized into 3-dimensional tissue-like assemblies (TLAs) in a 3D bioreactor. We have replicated our preliminary results many, many times, have analyzed the gene expression using gene arrays (followed by Luminex analysis for protein production), and have monitored cell proliferation, orientation, morphology, and glucose metabolism, and we are confident that we have a stable and reliable model to study the control of high-level cellular processes by application of low-amplitude, time varying electromagnetic fields (TVEMF) (1, 2). In additional studies at the University of Michigan, we have been able to generate functional in vitro engineered mammalian skeletal muscle, and have employed nerve-muscle co-culture techniques to promote axonal sprouting. We believe that nearly all tissues, in particular, neural, are susceptible to the influences of low-level TVEMF.

  17. Coding of amplitude-modulated signals in the cochlear nucleus of a grass frog

    NASA Astrophysics Data System (ADS)

    Bibikov, N. G.

    2002-07-01

    To study the mechanisms that govern the coding of temporal features of complex sound signals, responses of single neurons located in the dorsal nucleus of the medulla oblongata (the cochlear nucleus) of a curarized grass frog ( Rana temporaria) to pure tone bursts and amplitude modulated tone bursts with a modulation frequency of 20 Hz and modulation depths of 10 and 80% were recorded. The carrier frequency was equal to the characteristic frequency of a neuron, the average signal level was 20 30 dB above the threshold, and the signal duration was equal to ten full modulation periods. Of the 133 neurons studied, 129 neurons responded to 80% modulated tone bursts by discharges that were phase-locked with the envelope waveform. At this modulation depth, the best phase locking was observed for neurons with the phasic type of response to tone bursts. For tonic neurons with low characteristic frequencies, along with the reproduction of the modulation, phase locking with the carrier frequency of the signal was observed. At 10% amplitude modulation, phasic neurons usually responded to only the onset of a tone burst. Almost all tonic units showed a tendency to reproduce the envelope, although the efficiency of the reproduction was low, and for half of these neurons, it was below the reliability limit. Some neurons exhibited a more efficient reproduction of the weak modulation. For almost half of the neurons, a reliable improvement was observed in the phase locking of the response during the tone burst presentation (from the first to the tenth modulation period). The cooperative histogram of a set of neurons responding to 10% modulated tone bursts within narrow ranges of frequencies and intensities retains the information on the dynamics of the envelope variation. The data are compared with the results obtained from the study of the responses to similar signals in the acoustic midbrain center of the same object and also with the psychophysical effect of a differential

  18. Stream segregation in the perception of sinusoidally amplitude-modulated tones.

    PubMed

    Dolležal, Lena-Vanessa; Beutelmann, Rainer; Klump, Georg M

    2012-01-01

    Amplitude modulation can serve as a cue for segregating streams of sounds from different sources. Here we evaluate stream segregation in humans using ABA- sequences of sinusoidally amplitude modulated (SAM) tones. A and B represent SAM tones with the same carrier frequency (1000, 4000 Hz) and modulation depth (30, 100%). The modulation frequency of the A signals (f(modA)) was 30, 100 or 300 Hz, respectively. The modulation frequency of the B signals was up to four octaves higher (Δf(mod)). Three different ABA- tone patterns varying in tone duration and stimulus onset asynchrony were presented to evaluate the effect of forward suppression. Subjects indicated their 1- or 2-stream percept on a touch screen at the end of each ABA- sequence (presentation time 5 or 15 s). Tone pattern, f(modA), Δf(mod), carrier frequency, modulation depth and presentation time significantly affected the percentage of a 2-stream percept. The human psychophysical results are compared to responses of avian forebrain neurons evoked by different ABA- SAM tone conditions [1] that were broadly overlapping those of the present study. The neurons also showed significant effects of tone pattern and Δf(mod) that were comparable to effects observed in the present psychophysical study. Depending on the carrier frequency, modulation frequency, modulation depth and the width of the auditory filters, SAM tones may provide mainly temporal cues (sidebands fall within the range of the filter), spectral cues (sidebands fall outside the range of the filter) or possibly both. A computational model based on excitation pattern differences was used to predict the 50% threshold of 2-stream responses. In conditions for which the model predicts a considerably larger 50% threshold of 2-stream responses (i.e., larger Δf(mod) at threshold) than was observed, it is unlikely that spectral cues can provide an explanation of stream segregation by SAM. PMID:22984436

  19. Detection thresholds for amplitude modulations of tones in budgerigar, rabbit, and human.

    PubMed

    Carney, Laurel H; Ketterer, Angela D; Abrams, Kristina S; Schwarz, Douglas M; Idrobo, Fabio

    2013-01-01

    Envelope fluctuations of complex sounds carry information that is -essential for many types of discrimination and for detection in noise. To study the neural representation of envelope information and mechanisms for processing of this temporal aspect of sounds, it is useful to identify an animal model that can -sensitively detect amplitude modulations (AM). Low modulation frequencies, which dominate speech sounds, are of particular interest. Yet, most animal -models studied previously are relatively insensitive to AM at low modulation -frequencies. Rabbits have high thresholds for low-frequency modulations, -especially for tone carriers. Rhesus macaques are less sensitive than humans to low-frequency -modulations of wideband noise (O'Conner et al. Hear Res 277, 37-43, 2011). Rats and -chinchilla also have higher thresholds than humans for amplitude -modulations of noise (Kelly et al. J Comp Psychol 120, 98-105, 2006; Henderson et al. J Acoust Soc Am 75, -1177-1183, 1984). In contrast, the budgerigar has thresholds for AM detection of wideband noise similar to those of human listeners at low -modulation frequencies (Dooling and Searcy. Percept Psychophys 46, 65-71, 1981). A -one-interval, two-alternative operant conditioning procedure was used to estimate AM -detection thresholds for 4-kHz tone carriers at low modulation -frequencies (4-256 Hz). Budgerigar thresholds are comparable to those of human subjects in a comparable task. Implications of these comparative results for temporal coding of complex sounds are discussed. Comparative results for masked AM detection are also presented. PMID:23716245

  20. Detection Thresholds for Amplitude Modulations of Tones in Budgerigar, Rabbit, and Human

    PubMed Central

    Ketterer, Angela D.; Abrams, Kristina S.; Schwarz, Douglas M.; Idrobo, Fabio

    2015-01-01

    Envelope fluctuations of complex sounds carry information that is essential for many types of discrimination and for detection in noise. To study the neural representation of envelope information and mechanisms for processing of this temporal aspect of sounds, it is useful to identify an animal model that can sensitively detect amplitude modulations (AM). Low modulation frequencies, which dominate speech sounds, are of particular interest. Yet, most animal models studied previously are relatively insensitive to AM at low modulation frequencies. Rabbits have high thresholds for low-frequency modulations, especially for tone carriers. Rhesus macaques are less sensitive than humans to low-frequency modulations of wideband noise (O’Conner et al. Hear Res 277, 37–43, 2011). Rats and chinchilla also have higher thresholds than humans for amplitude modulations of noise (Kelly et al. J Comp Psychol 120, 98–105, 2006; Henderson et al. J Acoust Soc Am 75, 1177–1183, 1984). In contrast, the budgerigar has thresholds for AM detection of wideband noise similar to those of human listeners at low modulation frequencies (Dooling and Searcy. Percept Psychophys 46, 65–71, 1981). A one-interval, two-alternative operant conditioning procedure was used to estimate AM detection thresholds for 4-kHz tone carriers at low modulation frequencies (4–256 Hz). Budgerigar thresholds are comparable to those of human subjects in a comparable task. Implications of these comparative results for temporal coding of complex sounds are discussed. Comparative results for masked AM detection are also presented. PMID:23716245

  1. 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.

  2. Bray-Liebhafsky oscillatory reaction in the radiofrequency electromagnetic field

    NASA Astrophysics Data System (ADS)

    Stanisavljev, Dragomir R.; Velikić, Zoran; Veselinović, Dragan S.; Jacić, Nevena V.; Milenković, Maja C.

    2014-09-01

    Oscillatory Bray-Liebhafsky (BL) reaction is capacitively coupled with the electromagnetic radiation in the frequency range 60-110 MHz. Because of the specific reaction dynamics characterized by several characteristic parameters (induction period, period between chemical oscillations and their amplitude) it served as a good model system for the investigation of the effects of radiofrequent (RF) radiation. RF power of up to 0.2 W did not produce observable changes of the BL reaction parameters in the limit of the experiment reproductivity. Results indicate that, under the given experimental conditions, both dissipative and reactive properties of the solution are not considerably coupled with the RF electrical field.

  3. Accuracy Improvement in Magnetic Field Modeling for an Axisymmetric Electromagnet

    NASA Technical Reports Server (NTRS)

    Ilin, Andrew V.; Chang-Diaz, Franklin R.; Gurieva, Yana L.; Il,in, Valery P.

    2000-01-01

    This paper examines the accuracy and calculation speed for the magnetic field computation in an axisymmetric electromagnet. Different numerical techniques, based on an adaptive nonuniform grid, high order finite difference approximations, and semi-analitical calculation of boundary conditions are considered. These techniques are being applied to the modeling of the Variable Specific Impulse Magnetoplasma Rocket. For high-accuracy calculations, a fourth-order scheme offers dramatic advantages over a second order scheme. For complex physical configurations of interest in plasma propulsion, a second-order scheme with nonuniform mesh gives the best results. Also, the relative advantages of various methods are described when the speed of computation is an important consideration.

  4. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Marutschke, Christoph; Walters, Deron; Cleveland, Jason; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

    2014-08-01

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic—yet decisive—question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface.

  5. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy.

    PubMed

    Marutschke, Christoph; Walters, Deron; Walters, Deron; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

    2014-08-22

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic - yet decisive - question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface. PMID:25074402

  6. Electromagnetic field tapering using all-dielectric gradient index materials

    PubMed Central

    Yi, Jianjia; Piau, Gérard-Pascal; de Lustrac, André; Burokur, Shah Nawaz

    2016-01-01

    The concept of transformation optics (TO) is applied to control the flow of electromagnetic fields between two sections of different dimensions through a tapering device. The broadband performance of the field taper is numerically and experimentally validated. The taper device presents a graded permittivity profile and is fabricated through three-dimensional (3D) polyjet printing technology using low-cost all-dielectric materials. Calculated and measured near-field mappings are presented in order to validate the proposed taper. A good qualitative agreement is obtained between full-wave simulations and experimental tests. Such all-dielectric taper paves the way to novel types of microwave devices that can be easily fabricated through low-cost additive manufacturing processes. PMID:27464989

  7. Electromagnetic effects in an applied-field magnetoplasmadynamic thruster

    SciTech Connect

    Arakawa, Y.; Sasoh, A. Tohoku University, Sendai, )

    1992-02-01

    Experimental and analytical studies have been conducted on the performance and thrust production mechanisms of an applied-field magnetoplasmadynamic thruster. The thruster was able to run with a high-thruster performance due to large electromagnetic effects related to the applied magnetic field. Using hydrogen, helium, and argon as the propellant, over 20 percent thrust efficiency was obtained over a wide specific impulse range from 1000 to 7000 s at input power levels between 2.2 and 15.9 kW. From the measurements of performance characteristics and current densities in the acceleration region, and by a theoretical analysis, it is found that the thruster operation is characterized by a parameter, B-squared/m (B: applied magnetic field strength, m: propellant mass flow rate). 9 refs.

  8. Electromagnetic field tapering using all-dielectric gradient index materials.

    PubMed

    Yi, Jianjia; Piau, Gérard-Pascal; de Lustrac, André; Burokur, Shah Nawaz

    2016-01-01

    The concept of transformation optics (TO) is applied to control the flow of electromagnetic fields between two sections of different dimensions through a tapering device. The broadband performance of the field taper is numerically and experimentally validated. The taper device presents a graded permittivity profile and is fabricated through three-dimensional (3D) polyjet printing technology using low-cost all-dielectric materials. Calculated and measured near-field mappings are presented in order to validate the proposed taper. A good qualitative agreement is obtained between full-wave simulations and experimental tests. Such all-dielectric taper paves the way to novel types of microwave devices that can be easily fabricated through low-cost additive manufacturing processes. PMID:27464989

  9. Electromagnetic field tapering using all-dielectric gradient index materials

    NASA Astrophysics Data System (ADS)

    Yi, Jianjia; Piau, Gérard-Pascal; de Lustrac, André; Burokur, Shah Nawaz

    2016-07-01

    The concept of transformation optics (TO) is applied to control the flow of electromagnetic fields between two sections of different dimensions through a tapering device. The broadband performance of the field taper is numerically and experimentally validated. The taper device presents a graded permittivity profile and is fabricated through three-dimensional (3D) polyjet printing technology using low-cost all-dielectric materials. Calculated and measured near-field mappings are presented in order to validate the proposed taper. A good qualitative agreement is obtained between full-wave simulations and experimental tests. Such all-dielectric taper paves the way to novel types of microwave devices that can be easily fabricated through low-cost additive manufacturing processes.

  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. External Electromagnetic Fields of Slowly Rotating Relativistic Magnetized NUT Stars

    NASA Astrophysics Data System (ADS)

    Ahmedov, B. J.; Khugaev, A. V.

    2006-08-01

    Analytic general relativistic expressions for the electromagnetic fields external to a slowly-rotating magnetized NUT star with non-vanishing gravitomagnetic charge have been presented. Solutions for the electric and magnetic fields have been found after separating the Maxwell equations in the external background spacetime of a slowly rotating NUT star into angular and radial parts in the lowest order approximation in specific angular momentum and NUT parameter . The relativistic star is considered isolated and in vacuum, with different models for stellar magnetic field: i) monopolar magnetic field and ii) dipolar magnetic field aligned with the axis of rotation. It has been shown that the general relativistic corrections due to the dragging of reference frames and gravitomagnetic charge are not present in the form of the magnetic fields but emerge only in the form of the electric fields. In particular, it has been obtained that the frame-dragging and gravitomagnetic charge provide an additional induced electric field which is analogous to the one introduced by the rotation of the star in the flat spacetime limit.

  13. Basics of quantum field theory of electromagnetic interaction processes in single-layer graphene

    NASA Astrophysics Data System (ADS)

    Hieu Nguyen, Van

    2016-09-01

    The content of this work is the study of electromagnetic interaction in single-layer graphene by means of the perturbation theory. The interaction of electromagnetic field with Dirac fermions in single-layer graphene has a peculiarity: Dirac fermions in graphene interact not only with the electromagnetic wave propagating within the graphene sheet, but also with electromagnetic field propagating from a location outside the graphene sheet and illuminating this sheet. The interaction Hamiltonian of the system comprising electromagnetic field and Dirac fermions fields contains the limits at graphene plane of electromagnetic field vector and scalar potentials which can be shortly called boundary electromagnetic field. The study of S-matrix requires knowing the limits at graphene plane of 2-point Green functions of electromagnetic field which also can be shortly called boundary 2-point Green functions of electromagnetic field. As the first example of the application of perturbation theory, the second order terms in the perturbative expansions of boundary 2-point Green functions of electromagnetic field as well as of 2-point Green functions of Dirac fermion fields are explicitly derived. Further extension of the application of perturbation theory is also discussed.

  14. Underwater three-dimensional imaging with an amplitude-modulated laser radar at a 405 nm wavelength.

    PubMed

    Bartolini, Luciano; De Dominicis, Luigi; de Collibus, Mario Ferri; Fornetti, Giorgio; Guarneri, Massimiliano; Paglia, Emiliano; Poggi, Claudio; Ricci, Roberto

    2005-11-20

    We report the results of underwater imaging with an amplitude-modulated single-mode laser beam and miniaturized piezoactuator-based scanning system. The basic elements of the device are a diode laser source at 405 nm with digital amplitude modulation and a microscanning system realized with a small-aperture aspheric lens mounted on a pair of piezoelectric translators driven by sawtooth waveforms. The system has been designed to be a low-weight and rugged imaging device suitable to operate at medium range (approximately 10 m) in clear seawater as also demonstrated by computer simulation of layout performance. In the controlled laboratory conditions a submillimeter range accuracy has been obtained at a laser amplitude modulation frequency of 36.7 MHz. PMID:16318184

  15. Introduction to Electromagnetic Fields and Geodesics in a Tokamak

    NASA Astrophysics Data System (ADS)

    Sharma, Stephen

    Photons mediate electromagnetic radiation such that electric and magnetic particles obey the principle of least action from the applied fields. Elastic and inelastic collisions arise after summation of Lagrangian geodesics. In the case of reacting tritium and deuterium, energy is released in the form of electromagnetic radiation, neutrons, and alpha particles. Within fusion tokamaks, alpha particle energies determine if a self sustaining reaction--or ignition--will proceed. If particle mean free path is confined by electric and magnetic fields, then fusion occurs at higher frequencies. If temperature is increased and particle velocity is increased, then collision frequency increases. Modeling the nucleons as polarizable quark dielectric liquid drops increases differentiation between scattering events and fusion. When the cross section of two reactant liquid drops is coincident, fusion occurs. If cross sections do not overlap sufficiently, Coulomb scattering occurs. One strives for understanding of geometric approaches to solving for reactants' cross sections and fusion collision frequency in order to determine power output per particle and critical density of reactants.

  16. Field evaluation of an electromagnetic current meter based vertical profiler

    NASA Astrophysics Data System (ADS)

    Hamblin, P. F.; Marmoush, Y. M. R.; Boyce, F. M.; Smith, A. A.

    1987-10-01

    A current profiler consisting of a vertical array of three electromagnetic current meters has been evaluated through an intercomparison of the three sensors, with reference to nearby current and wave data and by comparison to recent laboratory performance tests (Aubrey and Trowbridge, 1985). Mean flow estimates are too uncertain and variable to allow bottom boundary layer shear stress to be estimated by the conventional logarithmic law method. As well as unexplained sudden shifts in the mean speed response, the comparison with vector-averaged current meter data indicates possible long-term reduction in response due to fouling of the sensors by biological growth. The directional response was less sensitive to fouling effects. The oscillatory response on one occasion after field deployment for 17 days indicates a reduction in response from 41 to 45% at a period of oscillation of 3 s in a combined steady and oscillatory flow field. This study demonstrates that despite careful laboratory calibration, electromagnetic current meters are not at present suitable for quantitative study of dynamics of sediment resuspension in near-bottom shallow-water environments.

  17. Theory of a ring laser. [electromagnetic field and wave equations

    NASA Technical Reports Server (NTRS)

    Menegozzi, L. N.; Lamb, W. E., Jr.

    1973-01-01

    Development of a systematic formulation of the theory of a ring laser which is based on first principles and uses a well-known model for laser operation. A simple physical derivation of the electromagnetic field equations for a noninertial reference frame in uniform rotation is presented, and an attempt is made to clarify the nature of the Fox-Li modes for an open polygonal resonator. The polarization of the active medium is obtained by using a Fourier-series method which permits the formulation of a strong-signal theory, and solutions are given in terms of continued fractions. It is shown that when such a continued fraction is expanded to third order in the fields, the familiar small-signal ring-laser theory is obtained.

  18. Electromagnetic field triggered drug and chemical delivery via liposomes

    DOEpatents

    Liburdy, R.P.

    1993-03-02

    The present invention relates to a system and to a method of delivering a drug to a preselected target body site of a patient, comprising the steps of encapsulating the chemical agent within liposomes, essentially temperature insensitive, i.e. not having a specific predetermined phase transition temperature within the specific temperature range of drug administration; administering the liposomes to the target body site; and subjecting the target body site to nonionizing electromagnetic fields in an area of the preselected target body in order to release the chemical agent from the liposomes at a temperature of between about +10 and 65 C. The invention further relates to the use of the liposomes to bind to the surface of or to enter target tissue or an organ in a living system, and, when subjected to a nonionizing field, to release a drug from the liposomes into the target site.

  19. Electromagnetic field triggered drug and chemical delivery via liposomes

    DOEpatents

    Liburdy, Robert P.

    1993-01-01

    The present invention relates to a system and to a method of delivering a drug to a preselected target body site of a patient, comprising the steps of encapsulating the chemical agent within liposomes, essentially temperature insensitive, i.e. not having a specific predetermined phase transition temperature within the specific temperature range of drug administration; administering the liposomes to the target body site; and subjecting the target body site to nonionizing electromagnetic fields in an area of the preselected target body in order to release said chemical agent from the liposomes at a temperature of between about +10 and 65.degree. C. The invention further relates to the use of said liposomes to bind to the surface of or to enter target tissue or an organ in a living system, and, when subjected to a nonionizing field, to release a drug from the liposomes into the target site.

  20. Photon merging and splitting in electromagnetic field inhomogeneities

    NASA Astrophysics Data System (ADS)

    Gies, Holger; Karbstein, Felix; Seegert, Nico

    2016-04-01

    We investigate photon merging and splitting processes in inhomogeneous, slowly varying electromagnetic fields. Our study is based on the three-photon polarization tensor following from the Heisenberg-Euler effective action. We put special emphasis on deviations from the well-known constant field results, also revisiting the selection rules for these processes. In the context of high-intensity laser facilities, we analytically determine compact expressions for the number of merged/split photons as obtained in the focal spots of intense laser beams. For the parameter range of typical petawatt class laser systems as pump and probe, we provide estimates for the numbers of signal photons attainable in an actual experiment. The combination of frequency upshifting, polarization dependence and scattering off the inhomogeneities renders photon merging an ideal signature for the experimental exploration of nonlinear quantum vacuum properties.

  1. Acceleration of adiabatic quantum dynamics in electromagnetic fields

    SciTech Connect

    Masuda, Shumpei; Nakamura, Katsuhiro

    2011-10-15

    We show a method to accelerate quantum adiabatic dynamics of wave functions under electromagnetic field (EMF) by developing the preceding theory [Masuda and Nakamura, Proc. R. Soc. London Ser. A 466, 1135 (2010)]. Treating the orbital dynamics of a charged particle in EMF, we derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states in any desired short time. The scheme is consolidated by describing a way to overcome possible singularities in both the additional phase and driving potential due to nodes proper to wave functions under EMF. As explicit examples, we exhibit the fast forward of adiabatic squeezing and transport of excited Landau states with nonzero angular momentum, obtaining the result consistent with the transitionless quantum driving applied to the orbital dynamics in EMF.

  2. Electromagnetic plasma wave emissions from the auroral field lines

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1977-01-01

    The most important types of auroral radio emissions are reviewed, both from a historical perspective as well as considering the latest results. Particular emphasis is placed on four types of electromagnetic emissions which are directly associated with the plasma on the auroral field lines. These emissions are (1) auroral hiss, (2) saucers, (3) ELF noise bands, and (4) auroral kilometric radiation. Ray tracing and radio direction finding measurements indicate that both the auroral hiss and auroral kilometric radiation are generated along the auroral field lines relatively close to the earth, at radial distances from about 2.5 to 5 R sub e. For the auroral hiss the favored mechanism appears to be amplified Cerenkov radiation. For the auroral kilometric radiation several mechanisms have been proposed, usually involving the intermediate generation of electrostatic waves by the precipitating electrons.

  3. Electromagnetic field limits set by the V-Curve.

    SciTech Connect

    Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Hudson, Howard Gerald

    2014-07-01

    When emitters of electromagnetic energy are operated in the vicinity of sensitive components, the electric field at the component location must be kept below a certain level in order to prevent the component from being damaged, or in the case of electro-explosive devices, initiating. The V-Curve is a convenient way to set the electric field limit because it requires minimal information about the problem configuration. In this report we will discuss the basis for the V-Curve. We also consider deviations from the original V-Curve resulting from inductive versus capacitive antennas, increases in directivity gain for long antennas, decreases in input impedance when operating in a bounded region, and mismatches dictated by transmission line losses. In addition, we consider mitigating effects resulting from limited antenna sizes.

  4. 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

  5. Simultaneous Electromagnetic Tracking and Calibration for Dynamic Field Distortion Compensation.

    PubMed

    Sadjadi, Hossein; Hashtrudi-Zaad, Keyvan; Fichtinger, Gabor

    2016-08-01

    Electromagnetic (EM) tracking systems are highly susceptible to field distortion. The interference can cause measurement errors up to a few centimeters in clinical environments, which limits the reliability of these systems. Unless corrected for, this measurement error imperils the success of clinical procedures. It is therefore fundamental to dynamically calibrate EM tracking systems and compensate for measurement error caused by field distorting objects commonly present in clinical environments. We propose to combine a motion model with observations of redundant EM sensors and compensate for field distortions in real time. We employ a simultaneous localization and mapping technique to accurately estimate the pose of the tracked instrument while creating the field distortion map. We conducted experiments with six degrees-of-freedom motions in the presence of field distorting objects in research and clinical environments. We applied our approach to improve the EM tracking accuracy and compared our results to a conventional sensor fusion technique. Using our approach, the maximum tracking error was reduced by 67% for position measurements and by 64% for orientation measurements. Currently, clinical applications of EM trackers are hampered by the adverse distortion effects. Our approach introduces a novel method for dynamic field distortion compensation, independent from preoperative calibrations or external tracking devices, and enables reliable EM navigation for potential applications. PMID:26595908

  6. A. A. Ukhtomskii`s dominance principle of brain activity in the perception of electromagnetic fields

    SciTech Connect

    Kholodov, Yu.A.

    1994-07-01

    Preliminary instruction of the subject plays an important role in the perception of weak electromagnetic fields acting on the hand. Active attention to a potential effect amplifies a brain state that can be called caution dominance and arises spontaneously with a {open_quotes}placebo{close_quotes} or an electromagnetic field. The radar principle of brain operation is discussed among the physiological mechanisms through which electromagnetic fields act on an organism.

  7. A. A. Ukhtomskii's dominance principle of brain activity in the perception of electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Kholodov, Yu. A.

    1994-01-01

    Preliminary instruction of the subject plays an important role in the perception of weak electromagnetic fields acting on the hand. Active attention to a potential effect amplifies a brain state that can be called caution dominance and arises spontaneously with a “placebo” or an electromagnetic field. The radar principle of brain operation is discussed among the physiological mechanisms through which electromagnetic fields act on an organism.

  8. Mechanisms of biological effects of radiofrequency electromagnetic fields: an overview

    SciTech Connect

    Erwin, D.N.

    1988-11-01

    Manmade sources of electromagnetic (EM) fields, and therefore human exposures to them, continue to increase. Public concerns stem from the effects reported in the literature, the visibility of the sources, and somewhat from confusion between EM fields and ionizing radiation. Protecting humans from the real hazards and allaying groundless fears requires a self-consistent body of scientific data concerning effects of the fields, levels of exposures which cause those effects, and which effects are deleterious (or beneficial or neutral). With that knowledge, appropriate guidelines for safety can be devised, while preserving the beneficial uses of radiofrequency radiation (RFR) energy for military or civilian purposes. The task is monumental because of the large and growing number of biological endpoints and the infinite array of RFR exposure conditions under which those endpoints might be examined. The only way to reach this goal is to understand the mechanisms by which EM fields interact with tissues. As in other fields of science, a mechanistic understanding of RFR effects will enable scientists to generalize from a selected few experiments to derive the laws of RFR bioeffects. This article gives an overview of present knowledge of those mechanisms and the part that the USAF School of Aerospace Medicine has played in expanding that knowledge. 91 references.

  9. 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.

  10. Setting prudent public health policy for electromagnetic field exposures.

    PubMed

    Carpenter, David O; Sage, Cindy

    2008-01-01

    Electromagnetic fields (EMF) permeate our environment, coming both from such natural sources as the sun and from manmade sources like electricity, communication technologies and medical devices. Although life on earth would not be possible without sunlight, increasing evidence indicates that exposures to the magnetic fields associated with electricity and to communication frequencies associated with radio, television, WiFi technology, and mobile cellular phones pose significant hazards to human health. The evidence is strongest for leukemia from electricity-frequency fields and for brain tumors from communication-frequency fields, yet evidence is emerging for an association with other diseases as well, including neurodegenerative diseases. Some uncertainty remains as to the mechanism(s) responsible for these biological effects, and as to which components of the fields are of greatest importance. Nevertheless, regardless of whether the associations are causal, the strengths of the associations are sufficiently strong that in the opinion of the authors, taking action to reduce exposures is imperative, especially for the fetus and children. Inaction is not compatible with the Precautionary Principle, as enunciated by the Rio Declaration. Because of ubiquitous exposure, the rapidly expanding development of new EMF technologies and the long latency for the development of such serious diseases as brain cancers, the failure to take immediate action risks epidemics of potentially fatal diseases in the future. PMID:18763539

  11. Neurometric amplitude-modulation detection threshold in the guinea-pig ventral cochlear nucleus.

    PubMed

    Sayles, Mark; Füllgrabe, Christian; Winter, Ian M

    2013-07-01

    Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (∼5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation

  12. Neurometric amplitude-modulation detection threshold in the guinea-pig ventral cochlear nucleus

    PubMed Central

    Sayles, Mark; Füllgrabe, Christian; Winter, Ian M

    2013-01-01

    Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (∼5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation

  13. Electromagnetic Form Factors of Hadrons in Quantum Field Theories

    SciTech Connect

    Dominguez, C. A.

    2008-10-13

    In this talk, recent results are presented of calculations of electromagnetic form factors of hadrons in the framework of two quantum field theories (QFT), (a) Dual-Large N{sub c} QCD (Dual-QCD{sub {infinity}}) for the pion, proton, and {delta}(1236), and (b) the Kroll-Lee-Zumino (KLZ) fully renormalizable Abelian QFT for the pion form factor. Both theories provide a QFT platform to improve on naive (tree-level) Vector Meson Dominance (VMD). Dual-QCD{sub {infinity}} provides a tree-level improvement by incorporating an infinite number of zero-width resonances, which can be subsequently shifted from the real axis to account for the time-like behaviour of the form factors. The renormalizable KLZ model provides a QFT improvement of VMD in the framework of perturbation theory. Due to the relative mildness of the {rho}{pi}{pi} coupling, and the size of loop suppression factors, the perturbative expansion is well defined in spite of this being a strong coupling theory. Both approaches lead to considerable improvements of VMD predictions for electromagnetic form factors, in excellent agreement with data.

  14. Cross-spectrally pure light, cross-spectrally pure fields and statistical similarity in electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Chen, Jingjing; Lu, RongSheng; Chen, Feinan; Li, Jia

    2014-08-01

    This paper describes the concept of cross-spectrally pure light, implications of statistical similarity of an optical field on its cross-spectral purity and cross-spectrally pure fields. First, the concept of cross-spectral purity of light is analysed in the space-frequency domain by taking into account the vectorial nature of the radiation, and the conditions and reduction formula are obtained. Then, by utilizing statistical similarity, the relationship between cross-spectral purity and spatial coherence is explored in the electromagnetic field. Last, the conditions for cross-spectrally pure fields are discussed, the polychromatic plane wave and the far field produced by a planar, secondary, stochastic electromagnetic source are studied as examples, and moreover, the relationship between cross-spectral purity and spatial coherence, which we have drawn, is verified during the study.

  15. Effects of Pulse Electromagnetic Field on Corrosion Resistance of Al-5 % Cu Alloy

    NASA Astrophysics Data System (ADS)

    Wang, B.; Tang, L. D.; Qi, J. G.; Wang, J. Z.

    2013-03-01

    It was investigated that corrosion resistance of Al-5 % Cu alloy was influenced by pulse electromagnetic field (PEMF). The morphologies were observed by scanning election microscopy (SEM). The corrosion behaviors were investigated by potentiodynamic polarization tests and immersion tests. The results indicated that corrosion resistance of samples could be increased by using pulse electromagnetic field, moreover, the optimum parameter of pulse electromagnetic field in this experiment was showed as follows: 500 V, 3 Hz, 30 s. Decreasing the quantity of eutectic in grain boundaries and refining the grains were main causations for increasing corrosion resistance of Al-5 % Cu alloy with pulse electromagnetic field.

  16. Impact of the strong electromagnetic field on the QCD effective potential for homogeneous Abelian gluon field configurations

    SciTech Connect

    Galilo, Bogdan V.; Nedelko, Sergei N.

    2011-11-01

    The one-loop quark contribution to the QCD effective potential for the homogeneous Abelian gluon field in the presence of an external strong electromagnetic field is evaluated. The structure of extrema of the potential as a function of the angles between chromoelectric, chromomagnetic, and electromagnetic fields is analyzed. In this setup, the electromagnetic field is considered as an external one while the gluon field represents domain structured nonperturbative gluon configurations related to the QCD vacuum in the confinement phase. Two particularly interesting gluon configurations, (anti-)self-dual and crossed orthogonal chromomagnetic and chromoelectric fields, are discussed specifically. Within this simplified framework it is shown that the strong electromagnetic fields can play a catalyzing role for a deconfinement transition. At the qualitative level, the present consideration can be seen as a highly simplified study of an impact of the electromagnetic fields generated in relativistic heavy ion collisions on the strongly interacting hadronic matter.

  17. Using strong electromagnetic fields to control x-ray processes.

    SciTech Connect

    Young, L.; Buth, C.; Dunford, R. W.; Ho, P.; Kanter, E. P.; Kraessig, B.; Peterson, E. R.; Rohringer, N.; Santra, R.; Southworth, S. H.

    2010-06-01

    Exploration of a new ultrafast-ultrasmall frontier in atomic and molecular physics has begun. Not only is is possible to control outer-shell electron dynamics with intense ultrafast optical lasers, but now control of inner-shell processes has become possible by combining intense infrared/optical lasers with tunable sources of X-ray radiation. This marriage of strong-field laser and X-ray physics has led to the discovery of methods to control reversibly resonant X-ray absorption in atoms and molecules on ultrafast timescales. Using a strong optical dressing field, resonant X-ray absorption in atoms can be markedly suppressed, yielding an example of electromagnetically induced transparency for x rays. Resonant X-ray absorption can also be controlled in molecules using strong non-resonant, polarized laser fields to align the framework of a molecule, and therefore its unoccupied molecular orbitals to which resonant absorption occurs. At higher laser intensities, ultrafast field ionization produces an irreversible change in X-ray absorption. Finally, the advent of X-ray free electron lasers enables first exploration of non-linear X-ray processes.

  18. 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.

  19. Could Radiotherapy Effectiveness Be Enhanced by Electromagnetic Field Treatment?

    PubMed Central

    Francisco, Artacho-Cordón; del Mar, Salinas-Asensio María; Irene, Calvente; Sandra, Ríos-Arrabal; Josefa, León; Elisa, Román-Marinetto; Nicolás, Olea; Isabel, Núñez María

    2013-01-01

    One of the main goals in radiobiology research is to enhance radiotherapy effectiveness without provoking any increase in toxicity. In this context, it has been proposed that electromagnetic fields (EMFs), known to be modulators of proliferation rate, enhancers of apoptosis and inductors of genotoxicity, might control tumor recruitment and, thus, provide therapeutic benefits. Scientific evidence shows that the effects of ionizing radiation on cellular compartments and functions are strengthened by EMF. Although little is known about the potential role of EMFs in radiotherapy (RT), the radiosensitizing effect of EMFs described in the literature could support their use to improve radiation effectiveness. Thus, we hypothesized that EMF exposure might enhance the ionizing radiation effect on tumor cells, improving the effects of RT. The aim of this paper is to review reports of the effects of EMFs in biological systems and their potential therapeutic benefits in radiotherapy. PMID:23867611

  20. The role of electromagnetic fields in neurological disorders.

    PubMed

    Terzi, Murat; Ozberk, Berra; Deniz, Omur Gulsum; Kaplan, Suleyman

    2016-09-01

    In the modern world, people are exposed to electromagnetic fields (EMFs) as part of their daily lives; the important question is "What is the effect of EMFs on human health?" Most previous studies are epidemiological, and we still do not have concrete evidence of EMF pathophysiology. Several factors may lead to chemical, morphological, and electrical alterations in the nervous system in a direct or indirect way. It is reported that non-ionizing EMFs have effects on animals and cells. The changes they bring about in organic systems may cause oxidative stress, which is essential for the neurophysiological process; it is associated with increased oxidization in species, or a reduction in antioxidant defense systems. Severe oxidative stress can cause imbalances in reactive oxygen species, which may trigger neurodegeneration. This review aims to detail these changes. Special attention is paid to the current data regarding EMFs' effects on neurological disease and associated symptoms, such as headache, sleep disturbances, and fatigue. PMID:27083321

  1. Annals of conflicting results: looking back on electromagnetic field research.

    PubMed Central

    Schoen, D

    1996-01-01

    Few environmental health issues are as contentious as the question of whether exposure to electromagnetic fields (EMFs) from power lines increases cancer risk. Among the many actors in this controversy, epidemiologists have played the leading role in raising the question and motivating research. Epidemiologic studies of the effects of exposure to power-line EMFs include the investigation by Dr. Gilles Thériault and colleagues into incidence rates of cancer among electric-utility workers in Quebec, Ontario and France. With the development of personal dosimeters to measure exposure to electric, magnetic and pulsed EMFs, occupational studies in the 1990s have made an important methodologic advance. But, as Thériault explains, improvements in assessing exposure have not yet translated into clear and consistent findings. Images p1444-a PMID:8943934

  2. Effects of electromagnetic fields on osteoporosis: A systematic literature review.

    PubMed

    Wang, Rong; Wu, Hua; Yang, Yong; Song, Mingyu

    2016-01-01

    Electromagnetic fields (EMFs) as a safe, effective and noninvasive treatment have been researched and used for many years in orthopedics, and the common use clinically is to promote fracture healing. The effects of EMFs on osteoporosis have not been well concerned. The balance between osteoblast and osteoclast activity as well as the balance between osteogenic differentiation and adipogenic differentiation of bone marrow mesenchymal stem cells plays an important role in the process of osteoporosis. A number of recent reports suggest that EMFs have a positive impact on the balances. In this review, we discuss the recent advances of EMFs in the treatment of osteoporosis from basic research to clinical study and introduce the possible mechanism. In addition, we presented future perspectives of application of EMFs for osteoporosis. PMID:27356174

  3. Electromagnetically induced transparency in a diamond spin ensemble enables all-optical electromagnetic field sensing.

    PubMed

    Acosta, V M; Jensen, K; Santori, C; Budker, D; Beausoleil, R G

    2013-05-24

    We use electromagnetically induced transparency (EIT) to probe the narrow electron-spin resonance of nitrogen-vacancy centers in diamond. Working with a multipass diamond chip at temperatures 6-30 K, the zero-phonon absorption line (637 nm) exhibits an optical depth of 6 and inhomogeneous linewidth of ~30 GHz FWHM. Simultaneous optical excitation at two frequencies separated by the ground-state zero-field splitting (2.88 GHz) reveals EIT resonances with a contrast exceeding 6% and FWHM down to 0.4 MHz. The resonances provide an all-optical probe of external electric and magnetic fields with a projected photon-shot-noise-limited sensitivity of 0.2 V/cm/√[Hz] and 0.1 nT/√[Hz], respectively. Operation of a prototype diamond-EIT magnetometer measures a noise floor of ~/<1 nT/√[Hz] for frequencies above 10 Hz and Allan deviation of 1.3±1.1 nT for 100 s intervals. The results demonstrate the potential of diamond-EIT devices for applications ranging from quantum-optical memory to precision measurement and tests of fundamental physics. PMID:23745875

  4. Amplitude-modulated stimuli reveal auditory-visual interactions in brain activity and brain connectivity

    PubMed Central

    Laing, Mark; Rees, Adrian; Vuong, Quoc C.

    2015-01-01

    The temporal congruence between auditory and visual signals coming from the same source can be a powerful means by which the brain integrates information from different senses. To investigate how the brain uses temporal information to integrate auditory and visual information from continuous yet unfamiliar stimuli, we used amplitude-modulated tones and size-modulated shapes with which we could manipulate the temporal congruence between the sensory signals. These signals were independently modulated at a slow or a fast rate. Participants were presented with auditory-only, visual-only, or auditory-visual (AV) trials in the fMRI scanner. On AV trials, the auditory and visual signal could have the same (AV congruent) or different modulation rates (AV incongruent). Using psychophysiological interaction analyses, we found that auditory regions showed increased functional connectivity predominantly with frontal regions for AV incongruent relative to AV congruent stimuli. We further found that superior temporal regions, shown previously to integrate auditory and visual signals, showed increased connectivity with frontal and parietal regions for the same contrast. Our findings provide evidence that both activity in a network of brain regions and their connectivity are important for AV integration, and help to bridge the gap between transient and familiar AV stimuli used in previous studies. PMID:26483710

  5. Amplitude modulation of sexy phrases is salient for song attractiveness in female canaries (Serinus canaria).

    PubMed

    Pasteau, Magali; Ung, Davy; Kreutzer, Michel; Aubin, Thierry

    2012-07-01

    Song discrimination and recognition in songbird species have usually been studied by measuring responses to song playbacks. In female canaries, Serinus canaria, copulation solicitation displays (CSDs) are used as an index of female preferences, which are related to song recognition. Despite the fact that many studies underline the role of song syntax in this species, we observed that short segments of songs (a few seconds long) are enough for females to discriminate between conspecific and heterospecific songs, whereas such a short duration is not sufficient to identify the syntax rules. This suggests that other cues are salient for song recognition. In this experiment, we investigated the influence of amplitude modulation (AM) on the responses (CSDs) of female canaries to song playbacks. We used two groups of females: (1) raised in acoustic isolation and (2) raised in normal conditions. When adult, we tested their preferences for sexy phrases with different AMs. We broadcast three types of stimuli: (1) songs with natural canary AM, (2) songs with AM removed, or (3) song with wren Troglodytes troglodytes AM. Results indicate that female canaries prefer and have predispositions for a song type with the natural canary AM. Thus, this acoustic parameter is a salient cue for song attractiveness. PMID:22476242

  6. Efficient amplitude-modulated pulses for triple- to single-quantum coherence conversion in MQMAS NMR.

    PubMed

    Colaux, Henri; Dawson, Daniel M; Ashbrook, Sharon E

    2014-08-01

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed "too challenging". PMID:25047226

  7. Photon-counting chirped amplitude modulation lidar using a smart premixing method.

    PubMed

    Zhang, Zijing; Zhang, Jianlong; Wu, Long; Zhang, Yong; Zhao, Yuan; Su, Jianzhong

    2013-11-01

    We proposed a new premixing method for photon-counting chirped amplitude modulation lidar (PCCAML). Earlier studies used the counting results of the returned signal detected by a Geiger mode avalanche photodiode detector (Gm-APD) to mix with the reference signal, called the postmixing method. We use an alternative method known as the premixing method, in which the reference signal is used to directly modulate the sampling gate width of the Gm-APD, and the mixing of the returned signal and the reference signal is completed before the Gm-APD. This premixing method is more flexible and may perform better than the postmixing method in terms of signal-to-noise ratio by cutting down a separated mixer commonly used in the postmixing lidar system. Furthermore, this premixing method lowers the demand for the sampling frequency of the Gm-APD. It allows the use of a much wider modulation bandwidth to improve the range accuracy and resolution. To the best of our knowledge, this is the first report to use the premixing method in the PCCAML system, which will benefit future lidar applications. PMID:24177101

  8. Active cancellation of residual amplitude modulation in a frequency-modulation based Fabry-Perot interferometer.

    PubMed

    Yu, Yinan; Wang, Yicheng; Pratt, Jon R

    2016-03-01

    Residual amplitude modulation (RAM) is one of the most common noise sources known to degrade the sensitivity of frequency modulation spectroscopy. RAM can arise as a result of the temperature dependent birefringence of the modulator crystal, which causes the orientation of the crystal's optical axis to shift with respect to the polarization of the incident light with temperature. In the fiber-based optical interferometer used on the National Institute of Standards and Technology calculable capacitor, RAM degrades the measured laser frequency stability and correlates with the environmental temperature fluctuations. We have demonstrated a simple approach that cancels out excessive RAM due to polarization mismatch between the light and the optical axis of the crystal. The approach allows us to measure the frequency noise of a heterodyne beat between two lasers individually locked to different resonant modes of a cavity with an accuracy better than 0.5 ppm, which meets the requirement to further determine the longitudinal mode number of the cavity length. Also, this approach has substantially mitigated the temperature dependency of the measurements of the cavity length and consequently the capacitance. PMID:27036752

  9. Amplitude modulation of hydromagnetic waves and associated rogue waves in magnetoplasmas.

    PubMed

    Sabry, R; Moslem, W M; Shukla, P K

    2012-09-01

    It is shown that the dynamics of amplitude-modulated compressional dispersive Alfvénic (CDA) waves in a collisional megnetoplasma is governed by a complex Ginzburg-Landau (CGL) equation. The nonlinear dispersion relation for the modulational instability of the CDA waves is derived and investigated numerically. It is found that the growth rate of the modulational instability decreases (increases) with the increase of the normalized electron-ion collision frequency α (the plasma β). The modulational instability criterion for the CGL equation is defined precisely and investigated numerically. The region of the modulational instability becomes narrower with the increase of α and β, indicating that the system dissipates the wave energy by collisions, and a stable CDA wave envelope packet in the form of a hole will be a dominant localized pulse. For a collisionless plasma, i.e., α=0, the CGL equation reduces to the standard nonlinear Schrödinger (NLS) equation. The latter is used to investigate the modulational (in)stability region for the CDA waves in a collisionless magnetoplasma. It is shown that, within unstable regions, a random set of nonlinearly interacting CDA perturbations leads to the formation of CDA rogue waves. In order to demonstrate that the characteristics of the CDA rogue waves are influenced by the plasma β, the relevant numerical analysis of the appropriate nonlinear solution of the NLS equation is presented. The application of our investigation to space and laboratory magnetoplasmas is discussed. PMID:23031035

  10. Neural correlates of behavioral amplitude modulation sensitivity in the budgerigar midbrain.

    PubMed

    Henry, Kenneth S; Neilans, Erikson G; Abrams, Kristina S; Idrobo, Fabio; Carney, Laurel H

    2016-04-01

    Amplitude modulation (AM) is a crucial feature of many communication signals, including speech. Whereas average discharge rates in the auditory midbrain correlate with behavioral AM sensitivity in rabbits, the neural bases of AM sensitivity in species with human-like behavioral acuity are unexplored. Here, we used parallel behavioral and neurophysiological experiments to explore the neural (midbrain) bases of AM perception in an avian speech mimic, the budgerigar (Melopsittacus undulatus). Behavioral AM sensitivity was quantified using operant conditioning procedures. Neural AM sensitivity was studied using chronically implanted microelectrodes in awake, unrestrained birds. Average discharge rates of multiunit recording sites in the budgerigar midbrain were insufficient to explain behavioral sensitivity to modulation frequencies <100 Hz for both tone- and noise-carrier stimuli, even with optimal pooling of information across recording sites. Neural envelope synchrony, in contrast, could explain behavioral performance for both carrier types across the full range of modulation frequencies studied (16-512 Hz). The results suggest that envelope synchrony in the budgerigar midbrain may underlie behavioral sensitivity to AM. Behavioral AM sensitivity based on synchrony in the budgerigar, which contrasts with rate-correlated behavioral performance in rabbits, raises the possibility that envelope synchrony, rather than average discharge rate, might also underlie AM perception in other species with sensitive AM detection abilities, including humans. These results highlight the importance of synchrony coding of envelope structure in the inferior colliculus. Furthermore, they underscore potential benefits of devices (e.g., midbrain implants) that evoke robust neural synchrony. PMID:26843608

  11. Quadrature amplitude modulation (QAM) using binary-driven coupling-modulated rings

    NASA Astrophysics Data System (ADS)

    Karimelahi, Samira; Sheikholeslami, Ali

    2016-05-01

    We propose and fully analyze a compact structure for DAC-free pure optical QAM modulation. The proposed structure is the first ring resonator-based DAC-free QAM modulator reported in the literature, to the best of our knowledge. The device consists of two segmented add-drop Mach Zehnder interferometer-assisted ring modulators (MZIARM) in an IQ configuration. The proposed architecture is investigated based on the parameters from SOI technology where various key design considerations are discussed. We have included the loss in the MZI arms in our analysis of phase and amplitude modulation using MZIARM for the first time and show that the imbalanced loss results in a phase error. The output level linearity is also studied for both QAM-16 and QAM-64 not only based on optimizing RF segment lengths but also by optimizing the number of segments. In QAM-16, linearity among levels is achievable with two segments while in QAM-64 an additional segment may be required.

  12. Efficient Amplitude-Modulated Pulses for Triple- to Single-Quantum Coherence Conversion in MQMAS NMR

    PubMed Central

    2014-01-01

    The conversion between multiple- and single-quantum coherences is integral to many nuclear magnetic resonance (NMR) experiments of quadrupolar nuclei. This conversion is relatively inefficient when effected by a single pulse, and many composite pulse schemes have been developed to improve this efficiency. To provide the maximum improvement, such schemes typically require time-consuming experimental optimization. Here, we demonstrate an approach for generating amplitude-modulated pulses to enhance the efficiency of the triple- to single-quantum conversion. The optimization is performed using the SIMPSON and MATLAB packages and results in efficient pulses that can be used without experimental reoptimisation. Most significant signal enhancements are obtained when good estimates of the inherent radio-frequency nutation rate and the magnitude of the quadrupolar coupling are used as input to the optimization, but the pulses appear robust to reasonable variations in either parameter, producing significant enhancements compared to a single-pulse conversion, and also comparable or improved efficiency over other commonly used approaches. In all cases, the ease of implementation of our method is advantageous, particularly for cases with low sensitivity, where the improvement is most needed (e.g., low gyromagnetic ratio or high quadrupolar coupling). Our approach offers the potential to routinely improve the sensitivity of high-resolution NMR spectra of nuclei and systems that would, perhaps, otherwise be deemed “too challenging”. PMID:25047226

  13. A role for amplitude modulation phase relationships in speech rhythm perception.

    PubMed

    Leong, Victoria; Stone, Michael A; Turner, Richard E; Goswami, Usha

    2014-07-01

    Prosodic rhythm in speech [the alternation of "Strong" (S) and "weak" (w) syllables] is cued, among others, by slow rates of amplitude modulation (AM) within the speech envelope. However, it is unclear exactly which envelope modulation rates and statistics are the most important for the rhythm percept. Here, the hypothesis that the phase relationship between "Stress" rate (∼2 Hz) and "Syllable" rate (∼4 Hz) AMs provides a perceptual cue for speech rhythm is tested. In a rhythm judgment task, adult listeners identified AM tone-vocoded nursery rhyme sentences that carried either trochaic (S-w) or iambic patterning (w-S). Manipulation of listeners' rhythm perception was attempted by parametrically phase-shifting the Stress AM and Syllable AM in the vocoder. It was expected that a 1π radian phase-shift (half a cycle) would reverse the perceived rhythm pattern (i.e., trochaic → iambic) whereas a 2π radian shift (full cycle) would retain the perceived rhythm pattern (i.e., trochaic → trochaic). The results confirmed these predictions. Listeners judgments of rhythm systematically followed Stress-Syllable AM phase-shifts, but were unaffected by phase-shifts between the Syllable AM and the Sub-beat AM (∼14 Hz) in a control condition. It is concluded that the Stress-Syllable AM phase relationship is an envelope-based modulation statistic that supports speech rhythm perception. PMID:24993221

  14. Practical loss tangent imaging with amplitude-modulated atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Proksch, Roger; Kocun, Marta; Hurley, Donna; Viani, Mario; Labuda, Aleks; Meinhold, Waiman; Bemis, Jason

    2016-04-01

    Amplitude-modulated (AM) atomic force microscopy (AFM), also known as tapping or AC mode, is a proven, reliable, and gentle imaging method with widespread applications. Previously, the contrast in AM-AFM has been difficult to quantify. AFM loss tangent imaging is a recently introduced technique that recasts AM mode phase imaging into a single term tan δ that includes both the dissipated and stored energy of the tip-sample interaction. It promises fast, versatile mapping of variations in near-surface viscoelastic properties. However, experiments to date have generally obtained values larger than expected for the viscoelastic loss tangent of materials. Here, we explore and discuss several practical considerations for AFM loss tangent imaging experiments. A frequent limitation to tapping in air is Brownian (thermal) motion of the cantilever. This fundamental noise source limits the accuracy of loss tangent estimation to approximately 0.01

  15. Wavelet analysis of pulse-amplitude-modulated chlorophyll fluorescence for differentiation of plant samples.

    PubMed

    Guo, Ya; Zhou, Yesen; Tan, Jinglu

    2015-04-01

    Pulse-amplitude-modulated (PAM) chlorophyll fluorescence (ChlF) from photosystem II (PSII) of plants has been routinely measured for the analysis of photosynthesis and environmental changes. PAM ChlF from PSII is non-stationary and has time-varying frequency characteristics; however, existing analysis of PAM ChlF has been limited to selected characteristic values in the time domain. Wavelet transform is recognized as an efficient tool for analyzing non-stationary signals. In this research, an attempt was made to analyze PAM ChlF through wavelet transform. Features of PAM ChlF signals were computed from wavelet decomposition to classify two tree species and to detect chilling and detachment stresses. The wavelet-based features were compared with the commonly-used maximal PSII efficiency Fv/Fm. Both the wavelet-based features and Fv/Fm could effectively classify two tree species, but the former showed superiority than the latter in detecting the stresses. Wavelet transform revealed chilling stress earlier than Fv/Fm and detected detachment stress Fv/Fm failed to show. The results show that wavelet transform is a useful technique for analysis of PAM ChlF. PMID:25665719

  16. Acousto-optic tomography using amplitude-modulated focused ultrasound and a near-IR laser

    SciTech Connect

    Yao Yong; Xing Da; He Yonghong; Ueda, Ken-ichi

    2001-11-30

    A novel tomographic method that can be applied in strongly scattering optical media is proposed. 1-MHz focused ultrasound is used to tag the scattering photons in the biological tissue; it carries a 10-KHz sinusoidal wave to act as a detection wave through amplitude-modulation (AM). The scattering photons that come from the focused zone carry the modulated information. Their optoelectronic signal is demodulated by real-time FFT. By detecting and discriminating ultrasound-modulated information carried by scattered photons, the optical tomographic images of the media simulating biological tissue and of a buried object are reconstructed by the AM spectral intensity. This ultrasound-tagged optical tomography can be applied to tissue structures with different optical parameters. For the first time, by using this method, we obtained the tomographic image of a 5 mm-wide soft rubber cube buried in a biological tissue-simulating media with a detecting depth of 30 mm. (laser applications and other topics in quantum electronics)

  17. Fast terahertz optoelectronic amplitude modulator based on plasmonic metamaterial antenna arrays and graphene

    NASA Astrophysics Data System (ADS)

    Jessop, David S.; Sol, Christian W. O.; Xiao, Long; Kindness, Stephen J.; Braeuninger-Weimer, Philipp; Lin, Hungyen; Griffiths, Jonathan P.; Ren, Yuan; Kamboj, Varun S.; Hofmann, Stephan; Zeitler, J. Axel; Beere, Harvey E.; Ritchie, David A.; Degl'Innocenti, Riccardo

    2016-02-01

    The growing interest in terahertz (THz) technologies in recent years has seen a wide range of demonstrated applications, spanning from security screening, non-destructive testing, gas sensing, to biomedical imaging and communication. Communication with THz radiation offers the advantage of much higher bandwidths than currently available, in an unallocated spectrum. For this to be realized, optoelectronic components capable of manipulating THz radiation at high speeds and high signal-to-noise ratios must be developed. In this work we demonstrate a room temperature frequency dependent optoelectronic amplitude modulator working at around 2 THz, which incorporates graphene as the tuning medium. The architecture of the modulator is an array of plasmonic dipole antennas surrounded by graphene. By electrostatically doping the graphene via a back gate electrode, the reflection characteristics of the modulator are modified. The modulator is electrically characterized to determine the graphene conductivity and optically characterization, by THz time-domain spectroscopy and a single-mode 2 THz quantum cascade laser, to determine the optical modulation depth and cut-off frequency. A maximum optical modulation depth of ~ 30% is estimated and is found to be most (least) sensitive when the electrical modulation is centered at the point of maximum (minimum) differential resistivity of the graphene. A 3 dB cut-off frequency > 5 MHz, limited only by the area of graphene on the device, is reported. The results agree well with theoretical calculations and numerical simulations, and demonstrate the first steps towards ultra-fast, graphene based THz optoelectronic devices.

  18. Digital services using quadrature amplitude modulation (QAM) over CATV analog DWDM system

    NASA Astrophysics Data System (ADS)

    Yeh, JengRong; Selker, Mark D.; Trail, J.; Piehler, David; Levi, Israel

    2000-04-01

    Dense Wavelength Division Multiplexing (DWDM) has recently gained great popularity as it provides a cost effective way to increase the transmission capacity of the existing fiber cable plant. For a long time, Dense WDM was exclusively used for baseband digital applications, predominantly in terrestrial long haul networks and in some cases in metropolitan and enterprise networks. Recently, the performance of DWDM components and frequency-stabilized lasers has substantially improved while the costs have down significantly. This makes a variety of new optical network architectures economically viable. The first commercial 8- wavelength DWDM system designed for Hybrid Fiber Coax networks was reported in 1998. This type of DWDM system utilizes Sub-Carrier Multiplexing (SCM) of Quadrature Amplitude Modulated (QAM) signals to transport IP data digital video broadcast and Video on Demand on ITU grid lightwave carriers. The ability of DWDM to provide scalable transmission capacity in the optical layer with SCM granularity is now considered by many to be the most promising technology for future transport and distribution of broadband multimedia services.

  19. Active cancellation of residual amplitude modulation in a frequency-modulation based Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Yu, Yinan; Wang, Yicheng; Pratt, Jon R.

    2016-03-01

    Residual amplitude modulation (RAM) is one of the most common noise sources known to degrade the sensitivity of frequency modulation spectroscopy. RAM can arise as a result of the temperature dependent birefringence of the modulator crystal, which causes the orientation of the crystal's optical axis to shift with respect to the polarization of the incident light with temperature. In the fiber-based optical interferometer used on the National Institute of Standards and Technology calculable capacitor, RAM degrades the measured laser frequency stability and correlates with the environmental temperature fluctuations. We have demonstrated a simple approach that cancels out excessive RAM due to polarization mismatch between the light and the optical axis of the crystal. The approach allows us to measure the frequency noise of a heterodyne beat between two lasers individually locked to different resonant modes of a cavity with an accuracy better than 0.5 ppm, which meets the requirement to further determine the longitudinal mode number of the cavity length. Also, this approach has substantially mitigated the temperature dependency of the measurements of the cavity length and consequently the capacitance.

  20. Extracting binaural information from simultaneous targets and distractors: Effects of amplitude modulation and asynchronous envelopes

    PubMed Central

    Stellmack, Mark A.; Byrne, Andrew J.; Viemeister, Neal F.

    2010-01-01

    When different components of a stimulus carry different binaural information, processing of binaural information in a target component is often affected. The present experiments examine whether such interference is affected by amplitude modulation and the relative phase of modulation of the target and distractors. In all experiments, listeners attempted to discriminate interaural time differences of a target stimulus in the presence of distractor stimuli with ITD=0. In Experiment 1, modulation of the distractors but not the target reduced interference between components. In Experiment 2, synthesized musical notes exhibited little binaural interference when there were slight asynchronies between different streams of notes (31 or 62 ms). The remaining experiments suggested that the reduction in binaural interference in the previous experiments was due neither to the complex spectra of the synthesized notes nor to greater detectability of the target in the presence of modulated distractors. These data suggest that this interference is reduced when components are modulated in ways that result in the target appearing briefly in isolation, not because of segregation cues. These data also suggest that modulation and asynchronies between modulators that might be encountered in real-world listening situations are adequate to reduce binaural interference to inconsequential levels. PMID:20815459

  1. Wireless multi-level terahertz amplitude modulator using active metamaterial-based spatial light modulation.

    PubMed

    Rout, Saroj; Sonkusale, Sameer

    2016-06-27

    The ever increasing demand for bandwidth in wireless communication systems will inevitably lead to the extension of operating frequencies toward the terahertz (THz) band known as the 'THz gap'. Towards closing this gap, we present a multi-level amplitude shift keying (ASK) terahertz wireless communication system using terahertz spatial light modulators (SLM) instead of traditional voltage mode modulation, achieving higher spectral efficiency for high speed communication. The fundamental principle behind this higher efficiency is the conversion of a noisy voltage domain signal to a noise-free binary spatial pattern for effective amplitude modulation of a free-space THz carrier wave. Spatial modulation is achieved using an an active metamaterial array embedded with pseudomorphic high-electron mobility (pHEMT) designed in a consumer-grade galium-arsenide (GaAs) integrated circuit process which enables electronic control of its THz transmissivity. Each array is assembled as individually controllable tiles for transmissive terahertz spatial modulation. Using the experimental data from our metamaterial based modulator, we show that a four-level ASK digital communication system has two orders of magnitude improvement in symbol error rate (SER) for a degradation of 20 dB in transmit signal-to-noise ratio (SNR) using spatial light modulation compared to voltage controlled modulation. PMID:27410614

  2. Wave-packet dynamics of noninteracting ultracold bosons in an amplitude-modulated parabolic optical lattice

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Tomotake; Watanabe, Shinichi

    2015-06-01

    The recent Aarhus experiment [Phys. Rev. A 88, 023620 (2013), 10.1103/PhysRevA.88.023620] produced wave packets by applying amplitude modulation to a trapped Bose-Einstein condensate (BEC) of 87Rb using an optical lattice. The present paper renders a theoretical account of this experimental production of wave packets and their subsequent time evolution, focusing on a one-dimensional noninteracting bosonic system as a fundamental starting point for accurate quantum analysis. Since experimental manipulation requires efficient wave-packet creation, we introduce the "single-Q Rabi model" to give a simple and reliable description of the interband transition. As a natural extension, we demonstrate enhancement of the wave-packet production by the "two-step Rabi oscillation method" using either one or two frequencies. The subsequent time evolution is affected by the intertwining of Bragg reflection and the Landau-Zener transition at each band gap, which is analyzed with the aid of a semiclassical theory [Phys. Rev. Lett. 110, 085302 (2013), 10.1103/PhysRevLett.110.085302].

  3. Performance of a Coded Non-Square Quadrature Amplitude Modulation Scheme over Fading Channels

    NASA Astrophysics Data System (ADS)

    Li, L.; Divsalar, D.; Dolinar, S.

    2004-02-01

    It is shown that a non-square (NS) 2^(2n+1)-ary quadrature amplitude modulation (QAM) can be decomposed into a single-parity-check (SPC) block encoder and a memoryless modulator with independent in-phase (I) and quadrature (Q) symbol mapping. When NS-2^(2n+1)-QAM is concatenated with a forward-error-correcting (FEC) code, iterative demodulation and decoding of the FEC code and the inherent SPC code of NS-2^(2n+1)-QAM exploits the modulation's inherent memory and its independent I- and Q-channel mapping and demapping. The capacity and the bit-/symbol-error-rate (BER/SER) performance of coded and uncoded NS-2^(2n+1)-QAM systems are given for both additive white Gaussian noise (AWGN) channels and Rayleigh fading channels and are compared to those of other conventional 2^(2n+1)-ary systems. Simulation results show that, with iterative demodulation and decoding, coded NS-8QAM outperforms three conventional 8-ary systems by at least 0.65 dB on AWGN channels and by at least 0.57 dB on Rayleigh fading channels at BER = 10^(-5), when the FEC code is a concatenation of (15,11) Hamming codes with rate-1 accumulator codes, while coded NS-32QAM outperforms standard 32QAM by about 0.45 dB on AWGN channels and by about 0.27 dB on Rayleigh fading channels.

  4. The Analysis for Activations in the Brain during Hearing the Amplitude-Modulated Tone by fMRI Measurement

    NASA Astrophysics Data System (ADS)

    Fukami, Tadanori; Shimada, Takamasa; Akatsuka, Takao; Saito, Yoichi

    In audiometry, ABR (Auditory Brainstem Response) is widely used. However, it shows low accuracy in low frequency band. Meanwhile, AMFR (Amplitude-Modulation-Following Response), the response during hearing an amplitude-modulated tone, has high frequency specificity and is brought to attention. As the first step to clinical application of AMFR, we investigated the activated areas in a brain when the subjects hear SAM tone (Sinusoidally Amplitude-Modulated tone) with both ears. We measured following two signals. One is the difference of BOLD (Blood Oxygenation Level Dependent) signal between hearing SAM tone vs. silence, the other is the difference of BOLD signal between hearing SAM tone vs. unmodulated tone. As a result, in the case of SAM vs. silence, the bilaterally auditory cortex (Broadmann Area 41, 42), the biratelally BA 10, left superior frontal gyrus and right superior temporal gyrus were activated (p<0.0037, uncorrected). In the case of SAM vs. unmodulated tone, the bilaterally superior frontal gyrus (BA 6) and precuneus (BA 7), neighboring area including the bilaterally inferior parietal lobule (BA 40), the bilaterally medial frontal gyrus and superior frontal gyrus were activated (p<0.021, uncorrected). Activations of visual perception due to eye-opened state were detected in some parts of activations. As a result, we inferred that modulated tone was recognized in the medial frontal gyrus and inferior parietal lobule was the part related to perception of amplitude-modulation.

  5. Reconfigurable optical quadrature amplitude modulation converter/encoder using a tunable complex coefficient optical tapped delay line.

    PubMed

    Khaleghi, Salman; Chitgarha, Mohammad Reza; Yilmaz, Omer F; Tur, Moshe; Haney, Michael W; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

    2013-05-15

    We experimentally demonstrate a reconfigurable optical converter/encoder for quadrature amplitude modulated (QAM) signals. The system utilizes nonlinear wavelength multicasting, conversion-dispersion delays, and simultaneous nonlinear multiplexing and sampling. We show baud rate tunability (31 and 20 Gbaud) and reconfigurable conversions from lower-order QAM signals to higher-order QAM signals (e.g., 64-QAM). PMID:23938882

  6. Paternal occupational exposure to electromagnetic fields and neuroblastoma in offspring

    SciTech Connect

    Wilkins, J.R. 3d.; Hundley, V.D. )

    1990-06-01

    Investigators in Texas have reported an association between paternal employment in jobs linked with exposure to electromagnetic fields and risk of neuroblastoma in offspring. In an attempt to replicate this finding, the authors conducted a case-control study in Ohio. A total of 101 incident cases of neuroblastoma were identified through the Columbus (Ohio) Children's Hospital Tumor Registry. All cases were born sometime during the period 1942-1967. From a statewide roster of birth certificates, four controls were selected for each case, with individual matching on the case's year of birth, race, and sex, and the mother's county of residence at the time of the (index) child's birth. Multiple definitions were employed to infer the potential for paternal occupational exposure to electromagnetic fields from the industry/occupation statements on the birth certificates. Case-control comparisons revealed adjusted odds ratios ranging in magnitude from 0.5 to 1.9. For two of the exposure definitions employed--both of which are similar to one used by the Texas investigators--the corresponding odds ratios were modestly elevated (odds ratios = 1.6 and 1.9). Notably, the magnitude of these odds ratios is not inconsistent with the Texas findings, where the exposure definition referred to yielded an odds ratio of 2.1. Because the point estimates in this study are imprecise, and because the biologic plausibility of the association is uncertain, the results reported here must be interpreted cautiously. However, the apparent consistency between two independent studies suggests that future evaluation of the association is warranted.

  7. Electromagnetic field and cylindrical compact objects in modified gravity

    NASA Astrophysics Data System (ADS)

    Yousaf, Z.; Bhatti, M. Zaeem ul Haq

    2016-05-01

    In this paper, we have investigated the role of different fluid parameters particularly electromagnetic field and f(R) corrections on the evolution of cylindrical compact object. We have explored the modified field equations, kinematical quantities and dynamical equations. An expression for the mass function has been found in comparison with the Misner-Sharp formalism in modified gravity, after which different mass-radius diagrams are drawn. The coupled dynamical transport equation have been formulated to discuss the role of thermoinertial effects on the inertial mass density of the cylindrical relativistic interior. Finally, we have presented a framework, according to which all possible solutions of the metric f(R)-Maxwell field equations coupled with static fluid can be written through set of scalar functions. It is found that modified gravity induced by Lagrangians f(R) = αR2, f(R) = αR2 - βR and f(R)=α R^2-β R/1+γ R are likely to host more massive cylindrical compact objects with smaller radii as compared to general relativity.

  8. Pseudo-gradient and Lagrangian boundary control system formulation of electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Jeltsema, Dimitri; van der Schaft, Arjan

    2007-09-01

    This paper describes an electromagnetic field analogue of the classical Brayton-Moser formulation. It is shown that Maxwell's curl equations constitute a pseudo-gradient system with respect to a single electromagnetic mixed-potential functional and a metric defined by the constitutive relations of the fields. Besides its use for the generation of power-based Lyapunov functionals for stability analysis and Poynting-like flow balances, the electromagnetic mixed-potential formulation suggests a family of alternative variational principles. This yields a novel Lagrangian boundary control system formulation admitting nonzero energy flow through the boundary. The corresponding symplectic Hamiltonian system is still associated with the total electromagnetic field energy.

  9. Electromagnetic induction tomography field experiment at Lost Hills, CA

    SciTech Connect

    Buettner, H. M.; Berryman, J. G.

    1998-11-03

    We have collected borehole to surface electromagnetic induction field data for a shallow steam injection that is underway at Mobil Oil' s Lost Hills-3 field in San Joaquin Valley. Earlier work had been done at the same site by Wilt et al. (1996). This site is an interesting test for techniques under development for environmental engineering, because it can be viewed as an excellent analog of a shallow environmental remediation using steam injection. Surface magnetic field data (vertical and radial fields, magnitude and phase) were collected using 18 receiver stations along two profiles which ran radially from the EM transmitter well from 5 m to 120 m. The data at each surface station were collected while the EM transmitter was raised slowly from a depth of 120 m to a final depth of 20 m. As part of this experiment, a calibration of the EM transmitter was also performed. Magnetic field data from Lost Hills were successfully collected, including both vertical and horizontal (surface radial) magnitude and phase data along a northerly profile and along a westerly profile. We have observed that the radial receiver data appear to be better behaved than the vertical receiver data, suggesting that these data may be less sensitive to environmental clutter (numerous metallic pipes crisscrossing the site at the surface) than are the vertical data. Some simple 1-D modeling has been done to confirm that the expected conductivity change in the steam zone should produce an observable anomaly in the measured data when comparing the pre-steam to the post-steam conditions. Results of this test were positive. Further analyses of these data making use of a new code developed in a companion paper are in progress and will presented separately.

  10. Modeling of interactions of electromagnetic fields with human bodies

    NASA Astrophysics Data System (ADS)

    Caputa, Krzysztof

    Interactions of electromagnetic fields with the human body have been a subject of scientific interest and public concern. In recent years, issues in power line field effects and those of wireless telephones have been in the forefront of research. Engineering research compliments biological investigations by quantifying the induced fields in biological bodies due to exposure to external fields. The research presented in this thesis aims at providing reliable tools, and addressing some of the unresolved issues related to interactions with the human body of power line fields and fields produced by handheld wireless telephones. The research comprises two areas, namely development of versatile models of the human body and their visualisation, and verification and application of numerical codes to solve selected problems of interest. The models of the human body, which are based on the magnetic resonance scans of the body, are unique and differ considerably from other models currently available. With the aid of computer software developed, the models can be arranged to different postures, and medical devices can be accurately placed inside them. A previously developed code for modeling interactions of power line fields with biological bodies has been verified by rigorous, quantitative inter-laboratory comparison for two human body models. This code has been employed to model electromagnetic interference (EMI) of the magnetic field with implanted cardiac pacemakers. In this case, the correct placement and representation of the pacemaker leads are critical, as simplified computations have been shown to result in significant errors. In modeling interactions of wireless communication devices, the finite difference time domain technique (FDTD) has become a de facto standard. The previously developed code has been verified by comparison with the analytical solution for a conductive sphere. While previously researchers limited their verifications to principal axes of the sphere

  11. SYSTEMS FOR EXPOSING MICE TO 2,450-MHZ ELECTROMAGNETIC FIELDS

    EPA Science Inventory

    Two systems for exposing mice to 2,450-MHz electromagnetic fields are described. In a waveguide system, four mice were placed in a Styrofoam cage and exposed dorsally to circularly polarized electromagnetic fields. The temperature and humidity in the mouse holder were kept consta...

  12. Piezo-drive circuits for amplitude-modulated locomoton for miniature wireless robots

    NASA Astrophysics Data System (ADS)

    Martel, Sylvain M.; Hunter, Ian W.

    2001-10-01

    Piezo-actuators due to their relatively high resonant frequencies and small deflections are ideally suited as accurate displacement transducers. As such, they have been used to implement the legs of the miniature wireless NanoWalker robot where step sizes in the order of a few tenths of nanometers are required for final positioning within the range of an embedded instrument designed to operate at the atomic scale. The relatively high capacitance combined with the high-drive voltage requirement of the actuators, impose constraints on the miniaturization of the electronics. The amplitude modulation scheme requires one amplifier per quadrant electrode on the piezo-legs. Although power amplifiers are suited to drive large capacitive loads with large signal amplitudes without stability problems, the quiescent current of the amplifiers requires several DC/DC converters of significant size. During locomotion, the sudden current increase occurring when high slew rate signals are used during the charging/discharging cycle of the capacitive loads at each walking step, causes the power rail voltage to drop, yielding a reduction in the amplitude of the deflections of the piezo-legs. To minimize the number of DC/DC converters, the slew rate requirement of the drive signal is reduced by an increase of the angular acceleration of the leg created by an initial static friction force with the walking surface. It is then suggested that further miniaturization of the embedded electronics can be achieved by adjusting the kinematic behavior of the piezo-legs with an appropriate mechanical design and the right friction coefficient through careful materials selection.

  13. Acoustic change responses to amplitude modulation: a method to quantify cortical temporal processing and hemispheric asymmetry

    PubMed Central

    Han, Ji Hye; Dimitrijevic, Andrew

    2015-01-01

    Objective: Sound modulation is a critical temporal cue for the perception of speech and environmental sounds. To examine auditory cortical responses to sound modulation, we developed an acoustic change stimulus involving amplitude modulation (AM) of ongoing noise. The AM transitions in this stimulus evoked an acoustic change complex (ACC) that was examined parametrically in terms of rate and depth of modulation and hemispheric symmetry. Methods: Auditory cortical potentials were recorded from 64 scalp electrodes during passive listening in two conditions: (1) ACC from white noise to 4, 40, 300 Hz AM, with varying AM depths of 100, 50, 25% lasting 1 s and (2) 1 s AM noise bursts at the same modulation rate. Behavioral measures included AM detection from an attend ACC condition and AM depth thresholds (i.e., a temporal modulation transfer function, TMTF). Results: The N1 response of the ACC was large to 4 and 40 Hz and small to the 300 Hz AM. In contrast, the opposite pattern was observed with bursts of AM showing larger responses with increases in AM rate. Brain source modeling showed significant hemispheric asymmetry such that 4 and 40 Hz ACC responses were dominated by right and left hemispheres respectively. Conclusion: N1 responses to the ACC resembled a low pass filter shape similar to a behavioral TMTF. In the ACC paradigm, the only stimulus parameter that changes is AM and therefore the N1 response provides an index for this AM change. In contrast, an AM burst stimulus contains both AM and level changes and is likely dominated by the rise time of the stimulus. The hemispheric differences are consistent with the asymmetric sampling in time hypothesis suggesting that the different hemispheres preferentially sample acoustic time across different time windows. Significance: The ACC provides a novel approach to studying temporal processing at the level of cortex and provides further evidence of hemispheric specialization for fast and slow stimuli. PMID:25717291

  14. Observer weighting of interaural cues in positive and negative envelope slopes of amplitude-modulated waveforms.

    PubMed

    Hsieh, I-Hui; Petrosyan, Agavni; Gonçalves, Óscar F; Hickok, Gregory; Saberi, Kourosh

    2011-07-01

    The auditory system can encode interaural delays in highpass-filtered complex sounds by phase locking to their slowly modulating envelopes. Spectrotemporal analysis of interaurally time-delayed highpass waveforms reveals the presence of a concomitant interaural level cue. The current study systematically investigated the contribution of time and concomitant level cues carried by positive and negative envelope slopes of a modified sinusoidally amplitude-modulated (SAM) high-frequency carrier. The waveforms were generated from concatenation of individual modulation cycles whose envelope peaks were extended by the desired interaural delay, allowing independent control of delays in the positive and negative modulation slopes. In experiment 1, thresholds were measured using a 2-interval forced-choice adaptive task for interaural delays in either the positive or negative modulation slopes. In a control condition, thresholds were measured for a standard SAM tone. In experiment 2, decision weights were estimated using a multiple-observation correlational method in a single-interval forced-choice task for interaural delays carried simultaneously by the positive, and independently, negative slopes of the modulation envelope. In experiment 3, decision weights were measured for groups of 3 modulation cycles at the start, middle, and end of the waveform to determine the influence of onset dominance or recency effects. Results were consistent across experiments: thresholds were equal for the positive and negative modulation slopes. Decision weights were positive and equal for the time cue in the positive and negative envelope slopes. Weights were also larger for modulations cycles near the waveform onset. Weights estimated for the concomitant interaural level cue were positive for the positive envelope slope and negative for the negative slope, consistent with exclusive use of time cues. PMID:21272630

  15. Resolving the contribution of the uncoupled phycobilisomes to cyanobacterial pulse-amplitude modulated (PAM) fluorometry signals.

    PubMed

    Acuña, Alonso M; Snellenburg, Joris J; Gwizdala, Michal; Kirilovsky, Diana; van Grondelle, Rienk; van Stokkum, Ivo H M

    2016-01-01

    Pulse-amplitude modulated (PAM) fluorometry is extensively used to characterize photosynthetic organisms on the slow time-scale (1-1000 s). The saturation pulse method allows determination of the quantum yields of maximal (F(M)) and minimal fluorescence (F(0)), parameters related to the activity of the photosynthetic apparatus. Also, when the sample undergoes a certain light treatment during the measurement, the fluorescence quantum yields of the unquenched and the quenched states can be determined. In the case of cyanobacteria, however, the recorded fluorescence does not exclusively stem from the chlorophyll a in photosystem II (PSII). The phycobilins, the pigments of the cyanobacterial light-harvesting complexes, the phycobilisomes (PB), also contribute to the PAM signal, and therefore, F(0) and F(M) are no longer related to PSII only. We present a functional model that takes into account the presence of several fluorescent species whose concentrations can be resolved provided their fluorescence quantum yields are known. Data analysis of PAM measurements on in vivo cells of our model organism Synechocystis PCC6803 is discussed. Three different components are found necessary to fit the data: uncoupled PB (PB(free)), PB-PSII complexes, and free PSI. The free PSII contribution was negligible. The PB(free) contribution substantially increased in the mutants that lack the core terminal emitter subunits allophycocyanin D or allophycocyanin F. A positive correlation was found between the amount of PB(free) and the rate constants describing the binding of the activated orange carotenoid protein to PB, responsible for non-photochemical quenching. PMID:25893897

  16. Hindlimb Movement in the Cat Induced by Amplitude-Modulated Stimulation Using Extra-Spinal Electrodes

    PubMed Central

    Tai, Changfeng; Wang, Jicheng; Shen, Bing; Wang, Xianchun; Roppolo, James R.; de Groat, William C.

    2010-01-01

    Hindlimb movement in the cat induced by electrical stimulation with an amplitude-modulated waveform of the dorsal surface of L5-S1 spinal cord or the L5-S1 dorsal/ventral roots was investigated before and after acute spinal cord transection at the T13-L1 level. Stimulation of the spinal cord or dorsal/ventral root at the same spinal segment induced similar movements including coordinated multi-joint flexion or extension. The induced movements changed from flexion to extension when the stimulation was moved from rostral (L5) to caudal (S1) spinal segments. Stimulation of a dorsal or ventral root on one side induced only ipsilateral hindlimb movement. However, stimulation on the dorsal surface of the spinal cord along the midline or across the spinal cord induced bilateral movements. The extension induced by stimulation of L7 dorsal root produced the largest ground reaction force that was strong enough to support body weight. Dorsal root stimulation induced a larger ground reaction force than ventral root stimulation and produced a more graded recruitment curve. Stepping at different speeds could be generated by combined stimulation of the rostral (L5) and the caudal (L6/L7) spinal segments with an appropriate timing between the different stimulation channels. Acute transection of the spinal cord did not change the responses indicating that the induced movements did not require the involvement of the supraspinal locomotor centers. The methods and the stimulation strategy developed in this study might be utilized to restore locomotor function after spinal cord injury. PMID:18369283

  17. Hindlimb movement in the cat induced by amplitude-modulated stimulation using extra-spinal electrodes

    NASA Astrophysics Data System (ADS)

    Tai, Changfeng; Wang, Jicheng; Shen, Bing; Wang, Xianchun; Roppolo, James R.; de Groat, William C.

    2008-06-01

    Hindlimb movement in the cat induced by electrical stimulation with an amplitude-modulated waveform of the dorsal surface of the L5-S1 spinal cord or the L5-S1 dorsal/ventral roots was investigated before and after acute spinal cord transection at the T13-L1 level. Stimulation of the spinal cord or dorsal/ventral root at the same spinal segment induced similar movements including coordinated multi-joint flexion or extension. The induced movements changed from flexion to extension when the stimulation was moved from rostral (L5) to caudal (S1) spinal segments. Stimulation of a dorsal or ventral root on one side induced only ipsilateral hindlimb movement. However, stimulation on the dorsal surface of the spinal cord along the midline or across the spinal cord induced bilateral movements. The extension induced by stimulation of L7 dorsal root produced the largest ground reaction force that was strong enough to support body weight. Dorsal root stimulation induced a larger ground reaction force than ventral root stimulation and produced a more graded recruitment curve. Stepping at different speeds could be generated by combined stimulation of the rostral (L5) and the caudal (L6/L7) spinal segments with an appropriate timing between the different stimulation channels. Acute transection of the spinal cord did not change the responses indicating that the induced movements did not require the involvement of the supraspinal locomotor centers. The methods and the stimulation strategy developed in this study might be utilized to restore locomotor function after spinal cord injury.

  18. Age-Related Changes in Processing Simultaneous Amplitude Modulated Sounds Assessed Using Envelope Following Responses.

    PubMed

    Parthasarathy, Aravindakshan; Lai, Jesyin; Bartlett, Edward L

    2016-04-01

    Listening conditions in the real world involve segregating the stimuli of interest from competing auditory stimuli that differ in their sound level and spectral content. It is in these conditions of complex spectro-temporal processing that listeners with age-related hearing loss experience the most difficulties. Envelope following responses (EFRs) provide objective neurophysiological measures of auditory processing. EFRs were obtained to two simultaneous sinusoidally amplitude modulated (sAM) tones from young and aged Fischer-344 rats. One was held at a fixed suprathreshold sound level (sAM1FL) while the second varied in sound level (sAM2VL) and carrier frequency. EFR amplitudes to sAM1FL in the young decreased with signal-to-noise ratio (SNR), and this reduction was more pronounced when the sAM2VL carrier frequency was spectrally separated from sAM1FL. Aged animals showed similar trends, while having decreased overall response amplitudes compared to the young. These results were replicated using an established computational model of the auditory nerve. The trends observed in the EFRs were shown to be due to the contributions of the low-frequency tails of high-frequency neurons, rather than neurons tuned to the sAM1FL carrier frequency. Modeling changes in threshold and neural loss reproduced some of the changes seen with age, but accuracy improved when combined with an additional decrease representing synaptic loss of auditory nerve neurons. Sound segregation in this case derives primarily from peripheral processing, regardless of age. Contributions by more central neural mechanisms are likely to occur only at low SNRs. PMID:26905273

  19. Mechanics of interaction and atomic-scale wear of amplitude modulation atomic force microscopy probes.

    PubMed

    Vahdat, Vahid; Grierson, David S; Turner, Kevin T; Carpick, Robert W

    2013-04-23

    Wear is one of the main factors that hinders the performance of probes for atomic force microscopy (AFM), including for the widely used amplitude modulation (AM-AFM) mode. Unfortunately, a comprehensive scientific understanding of nanoscale wear is lacking. We have developed a protocol for conducting consistent and quantitative AM-AFM wear experiments. The protocol involves controlling the tip-sample interaction regime during AM-AFM scanning, determining the tip-sample contact geometry, calculating the peak repulsive force and normal stress over the course of the wear test, and quantifying the wear volume using high-resolution transmission electron microscopy imaging. The peak repulsive tip-sample interaction force is estimated from a closed-form equation accompanied by an effective tip radius measurement procedure, which combines transmission electron microscopy and blind tip reconstruction. The contact stress is estimated by applying Derjaguin-Müller-Toporov contact mechanics model and also numerically solving a general contact mechanics model recently developed for the adhesive contact of arbitrary axisymmetric punch shapes. We discuss the important role that the assumed tip shape geometry plays in calculating both the interaction forces and the contact stresses. Contact stresses are significantly affected by the tip geometry while the peak repulsive force is mainly determined by experimentally controlled parameters, specifically, the free oscillation amplitude and amplitude ratio. The applicability of this protocol is demonstrated experimentally by assessing the performance of diamond-like carbon-coated and silicon-nitride-coated silicon probes scanned over ultrananocrystalline diamond substrates in repulsive mode AM-AFM. There is no sign of fracture or plastic deformation in the case of diamond-like carbon; wear could be characterized as a gradual atom-by-atom process. In contrast, silicon nitride wears through removal of the cluster of atoms and plastic

  20. Differential pulse amplitude modulation for multiple-input single-output OWVLC

    NASA Astrophysics Data System (ADS)

    Yang, S. H.; Kwon, D. H.; Kim, S. J.; Son, Y. H.; Han, S. K.

    2015-01-01

    White light-emitting diodes (LEDs) are widely used for lighting due to their energy efficiency, eco-friendly, and small size than previously light sources such as incandescent, fluorescent bulbs and so on. Optical wireless visible light communication (OWVLC) based on LED merges lighting and communications in applications such as indoor lighting, traffic signals, vehicles, and underwater communications because LED can be easily modulated. However, physical bandwidth of LED is limited about several MHz by slow time constant of the phosphor and characteristics of device. Therefore, using the simplest modulation format which is non-return-zero on-off-keying (NRZ-OOK), the data rate reaches only to dozens Mbit/s. Thus, to improve the transmission capacity, optical filtering and pre-, post-equalizer are adapted. Also, high-speed wireless connectivity is implemented using spectrally efficient modulation methods: orthogonal frequency division multiplexing (OFDM) or discrete multi-tone (DMT). However, these modulation methods need additional digital signal processing such as FFT and IFFT, thus complexity of transmitter and receiver is increasing. To reduce the complexity of transmitter and receiver, we proposed a novel modulation scheme which is named differential pulse amplitude modulation. The proposed modulation scheme transmits different NRZ-OOK signals with same amplitude and unit time delay using each LED chip, respectively. The `N' parallel signals from LEDs are overlapped and directly detected at optical receiver. Received signal is demodulated by power difference between unit time slots. The proposed scheme can overcome the bandwidth limitation of LEDs and data rate can be improved according to number of LEDs without complex digital signal processing.

  1. Electromagnetic fluid drift turbulence in static ergodic magnetic fields

    SciTech Connect

    Reiser, D.; Scott, B.

    2005-12-15

    Numerical simulations of three-dimensional nonlinear electromagnetic fluid drift turbulence in a tokamak plasma with externally applied stochastic magnetic-field perturbations are presented. The contributions to the radial particle transport due to nonlinearities arising from ExB advection and magnetic flutter are investigated for perturbation fields of varying strengths in the cases of low and high collisionalities. The perturbation strength is varied to study the physics for Chirikov parameters above 1. In all the cases considered a significant increase of ExB transport is found. A static contribution in the density and velocity perturbations contributes significantly to the total radial ExB transport. For low collisionality, the external perturbation leads to enhanced density and velocity fluctuations over a broad range in the toroidal wave-number spectrum, resulting in an enhanced turbulent flux. For high collisionality, the density fluctuations stay roughly the same and the velocity fluctuations are increased in an intermediate range of the toroidal wave number spectrum, separated from the maximum of the density fluctuations, thus leaving the turbulent flux almost unchanged.

  2. Electromagnetically induced transparency resonances inverted in magnetic field

    SciTech Connect

    Sargsyan, A.; Sarkisyan, D. E-mail: david@ipr.sci.am; Pashayan-Leroy, Y.; Leroy, C.; Cartaleva, S.; Wilson-Gordon, A. D.; Auzinsh, M.

    2015-12-15

    The phenomenon of electromagnetically induced transparency (EIT) is investigated in a Λ-system of the {sup 87}Rb D{sub 1} line in an external transverse magnetic field. Two spectroscopic cells having strongly different values of the relaxation rates γ{sub rel} are used: an Rb cell with antirelaxation coating (L ∼ 1 cm) and an Rb nanometric- thin cell (nanocell) with a thickness of the atomic vapor column L = 795 nm. For the EIT in the nanocell, we have the usual EIT resonances characterized by a reduction in the absorption (dark resonance (DR)), whereas for the EIT in the Rb cell with an antirelaxation coating, the resonances demonstrate an increase in the absorption (bright resonances (BR)). We suppose that such an unusual behavior of the EIT resonances (i.e., the reversal of the sign from DR to BR) is caused by the influence of an alignment process. The influence of alignment strongly depends on the configuration of the coupling and probe frequencies as well as on the configuration of the magnetic field.

  3. 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

  4. Rapid magnetic microfluidic mixer utilizing AC electromagnetic field.

    PubMed

    Wen, Chih-Yung; Yeh, Cheng-Peng; Tsai, Chien-Hsiung; Fu, Lung-Ming

    2009-12-01

    This paper presents a novel simple micromixer based on stable water suspensions of magnetic nanoparticles (i.e. ferrofluids). The micromixer chip is built using standard microfabrication and simple soft lithography, and the design can be incorporated as a subsystem into any chemical microreactor or a miniaturized biological sensor. An electromagnet driven by an AC power source is used to induce transient interactive flows between a ferrofluid and Rhodamine B. The alternative magnetic field causes the ferrofluid to expand significantly and uniformly toward Rhodamine B, associated with a great number of extremely fine fingering structures on the interface in the upstream and downstream regions of the microchannel. These pronounced fingering patterns, which have not been observed by other active mixing methods utilizing only magnetic force, increase the mixing interfacial length dramatically. Along with the dominant diffusion effects occurring around the circumferential regions of the fine finger structures, the mixing efficiency increases significantly. The miscible fingering instabilities are observed and applied in the microfluidics for the first time. This work is carried with a view to developing functionalized ferrofluids that can be used as sensitive pathogen detectors and the present experimental results demonstrate that the proposed micromixer has excellent mixing capabilities. The mixing efficiency can be as high as 95% within 2.0 s and a distance of 3.0 mm from the inlet of the mixing channel, when the applied peak magnetic field is higher than 29.2 Oe and frequency ranges from 45 to 300 Hz. PMID:19921677

  5. The influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction

    NASA Astrophysics Data System (ADS)

    Papadopoulos, D.

    2012-01-01

    The interaction between gravitational and electromagnetic waves in the presence of a static magnetic field is studied. The field strength of the static field is allowed to surpass the Schwinger critical field, such that the quantum electrodynamical (QED) effects of vacuum polarization and magnetization are significant. Equations governing the interaction are derived and analyzed. It turns out that the energy conversion from gravitational to electromagnetic waves can be significantly altered due to the QED effects. The consequences of our results are discussed.

  6. Influence of strong field vacuum polarization on gravitational-electromagnetic wave interaction

    SciTech Connect

    Forsberg, M.; Brodin, G.; Papadopoulos, D.

    2010-07-15

    The interaction between gravitational and electromagnetic waves in the presence of a static magnetic field is studied. The field strength of the static field is allowed to surpass the Schwinger critical field, such that the QED effects of vacuum polarization and magnetization are significant. Equations governing the interaction are derived and analyzed. It turns out that the energy conversion from gravitational to electromagnetic waves can be significantly altered due to the QED effects. The consequences of our results are discussed.

  7. Pentoxifylline and electromagnetic field improved bone fracture healing in rats

    PubMed Central

    Atalay, Yusuf; Gunes, Nedim; Guner, Mehmet Dervis; Akpolat, Veysi; Celik, Mustafa Salih; Guner, Rezzan

    2015-01-01

    Background The aim of this study was to evaluate the effects of a phosphodiesterase inhibitor pentoxifylline (PTX), electromagnetic fields (EMFs), and a mixture of both materials on bone fracture healing in a rat model. Materials and methods Eighty male Wistar rats were randomly divided into four groups: Group A, femur fracture model with no treatment; Group B, femur fracture model treated with PTX 50 mg/kg/day intraperitoneal injection; Group C, femur fracture model treated with EMF 1.5±0.2 Mt/50 Hz/6 hours/day; and Group D, femur fracture model treated with PTX 50 mg/kg/day intraperitoneal injection and EMF 1.5±0.2 Mt/50 Hz/6 hours/day. Results Bone fracture healing was significantly better in Group B and Group C compared to Group A (P<0.05), but Group D did not show better bone fracture healing than Group A (P>0.05). Conclusion It can be concluded that both a specific EMF and PTX had a positive effect on bone fracture healing but when used in combination, may not be beneficial. PMID:26388687

  8. Pulsed electromagnetic field may accelerate in vitro endochondral ossification.

    PubMed

    Wang, Jue; Tang, Na; Xiao, Qiang; Zhang, Li; Li, Yu; Li, Juan; Wang, Jun; Zhao, Zhihe; Tan, Lijun

    2015-01-01

    Recapitulation of embryonic endochondral bone formation is a promising alternative approach to bone tissue engineering. However, the time-consuming process is one of the reasons the approach is unpractical. Here, we aimed at accelerating the in vitro endochondral ossification process of tissue engineering by using a pulsed electromagnetic field (PEMF). The rat bone marrow-derived stem cells were chondrogenic or hypertrophic differentiated in a three-dimensional pellet culture system, and treated with different intensities of PEMF (1, 2, and 5 mT with modulation frequency 750 Hz, carrier frequency 75 Hz and a duty ratio of 0.8, 3 h/day for 4 weeks). The effects of PEMF on hypertrophy and endochondral ossification were assessed by safranin O staining, immunohistochemistry, and quantitative real-time polymerase chain reaction. The results suggest that PEMF at 1, 2, and 5 mT may inhibit the maintenance of the cartilaginous phenotype and increase cartilage-specific extracellular matrix degradation in the late stage of chondrogenic differentiation. In addition, among the three different intensities, only PEMF at 1 mT directed the differentiation of chondrogenic-induced stem cell pellets to the hypertrophic stage and promoted osteogenic differentiation. Our findings provide the feasibility to optimize the process of in vitro endochondral ossification with PEMF stimulation. PMID:25358461

  9. 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.

  10. On the solar cycle dependence of the amplitude modulation characterizing the mid-latitude sporadic E layer diurnal periodicity

    NASA Astrophysics Data System (ADS)

    Pezzopane, M.; Pignalberi, A.; Pietrella, M.

    2016-01-01

    Spectral analyses are employed to investigate how the diurnal periodicity of the critical frequency of the sporadic E (Es) layer varies with solar activity. The study is based on ionograms recorded at the ionospheric station of Rome (41.8°N, 12.5°E), Italy, from 1976 to 2009, a period of time covering three solar cycles. It was confirmed that the diurnal periodicity is always affected by an amplitude modulation with periods of several days, which is the proof that Es layers are affected indirectly by planetary waves through their nonlinear interaction with atmospheric tides at lower altitudes. The most striking features coming out from this study is however that this amplitude modulation is greater for high-solar activity than for low-solar activity.

  11. Phase-space representation and polarization domains of random electromagnetic fields.

    PubMed

    Castaneda, Roman; Betancur, Rafael; Herrera, Jorge; Carrasquilla, Juan

    2008-08-01

    The phase-space representation of stationary random electromagnetic fields is developed by using electromagnetic spatial coherence wavelets. The propagation of the field's power and states of spatial coherence and polarization results from correlations between the components of the field vectors at pairs of points in space. Polarization domains are theoretically predicted as the structure of the field polarization at the observation plane. In addition, the phase-space representation provides a generalization of the Poynting theorem. Theoretical predictions are examined by numerically simulating the Young experiment with electromagnetic waves. The experimental implementation of these results is a current subject of research. PMID:18670539

  12. Age-related shifts in distortion product otoacoustic emissions peak-ratios and amplitude modulation spectra.

    PubMed

    Lai, Jesyin; Bartlett, Edward L

    2015-09-01

    Amplitude modulation (AM) is an important temporal cue for precise speech and complex sound recognition. However, functional decline of the auditory periphery as well as degradation of central auditory processing due to aging can reduce the salience and resolution of temporal cues. Age-related deficits in central temporal processing have previously been observed at more rapid AM frequencies and various AM depths. These centrally observed changes result from cochlear changes compounded with changes along the ascending auditory pathway. In fact, a decrease in ability to detect temporally modulated sounds accurately could originate from changes in cochlear filtering properties and in cochlear mechanics due to aging. Nonetheless, few studies have examined cochlear mechanisms in AM detection. To assess integrity of the mechanical properties of the auditory periphery, distortion product otoacoustic emissions (DPOAEs) are a tool commonly used in clinics and in research. In this study, we measured DPOAEs to reveal age-related changes in peak f2/f1 ratio and degradation in AM detection by basilar membrane vibration. Two tones (f1 and f2, f2 > f1) at various f2/f1 ratios and simultaneous presentation of one AM and one pure tone were used as stimuli to evoke DPOAEs. In addition of observing reduced DPOAE amplitudes and steeper slopes in the input-output DPOAE functions, higher peak f2/f1 ratios and broader f2/f1 tuning were also observed in aged animals. Aged animals generally had lower distortion product (DP) and first sideband (SB 1) responses evoked by an f1 pure tone and an f2 AM tone, regardless of whether the AM frequency was 45 Hz or 128 Hz. SB 1 thresholds, which corresponds to the smallest stimulus AM depth that can induce cochlear vibrations at the DP generator locus, were higher in aged animals as well. The results suggest that age-related changes in peak f2/f1 ratio and AM detection by basilar membrane vibration are consistent with a reduction in endocochlear

  13. Age-related Shifts in Distortion Product Otoacoustic Emissions Peak-ratios and Amplitude Modulation Spectra

    PubMed Central

    Lai, Jesyin; Bartlett, Edward L.

    2015-01-01

    Amplitude modulation (AM) is an important temporal cue for precise speech and complex sound recognition. However, functional decline of the auditory periphery as well as degradation of central auditory processing due to aging can reduce the salience and resolution of temporal cues. Age-related deficits in central temporal processing have previously been observed at more rapid AM frequencies and various AM depths. These centrally observed changes result from cochlear changes compounded with changes along the ascending auditory pathway. In fact, a decrease in ability to detect temporally modulated sounds accurately could originate from changes in cochlear filtering properties and in cochlear mechanics due to aging. Nonetheless, few studies have examined cochlear mechanisms in AM detection. To assess integrity of the mechanical properties of the auditory periphery, distortion product otoacoustic emissions (DPOAEs) are a tool commonly used in clinics and in research. In this study, we measured DPOAEs to reveal age-related changes in peak f2/f1 ratio and degradation in AM detection by basilar membrane vibration. Two tones (f1 and f2, f2>f1) at various f2/f1 ratios and simultaneous presentation of one AM and one pure tone were used as stimuli to evoke DPOAEs. In addition of observing reduced DPOAE amplitudes and steeper slopes in the input-output DPOAE functions, higher peak f2/f1 ratios and broader f2/f1 tuning were also observed in aged animals. Aged animals generally had lower distortion product (DP) and first sideband (SB 1) responses evoked by an f1 pure tone and an f2 AM tone, regardless of whether the AM frequency was 45 Hz or 128 Hz. SB 1 thresholds, which corresponds to the smallest stimulus AM depth that can induce cochlear vibrations at the DP generator locus, were higher in aged animals as well. The results suggest that age-related changes in peak f2/f1 ratio and AM detection by basilar membrane vibration are consistent with a reduction in endocochlear

  14. Analysis of frequency noise in ultra-stable optical oscillators with active control of residual amplitude modulation

    NASA Astrophysics Data System (ADS)

    Li, Liufeng; Shen, Hui; Bi, Jin; Wang, Chun; Lv, Shasha; Chen, Lisheng

    2014-12-01

    Two 1,064-nm Nd:YAG lasers frequency stabilized by high-finesse optical cavities are developed to investigate various noise mechanisms in ultra-stable optical oscillators. Active control of residual amplitude modulation using a separate sensing path is implemented and its effectiveness in the presence of a resonant optical cavity is theoretically analyzed and experimentally verified by measuring the rejection ratios in optical heterodyne beat between a perturbed laser and a stable reference. Laser frequency noises originated from vibration, residual amplitude modulation, quantum-limited shot noise, and electronic noise are experimentally analyzed. With active control, residual amplitude modulation is suppressed to below 1 × 10-6 at 0.02-1,000 s, reaching a minimum of 2 × 10-7 at ~2 s. A frequency stability of 2 × 10-15 is obtained from 0.1 to 10 s, and the optical heterodyne beat of the two Nd:YAG lasers shows 1-Hz linewidth with a measurement time of 4.096 s. In addition, the experimentally determined linewidths agree well with the calculation according to a simplified relationship between the linewidth and the underlying flicker noise that modulates the laser frequency.

  15. Analysis of frequency noise in ultra-stable optical oscillators with active control of residual amplitude modulation

    NASA Astrophysics Data System (ADS)

    Li, Liufeng; Shen, Hui; Bi, Jin; Wang, Chun; Lv, Shasha; Chen, Lisheng

    2014-09-01

    Two 1,064-nm Nd:YAG lasers frequency stabilized by high-finesse optical cavities are developed to investigate various noise mechanisms in ultra-stable optical oscillators. Active control of residual amplitude modulation using a separate sensing path is implemented and its effectiveness in the presence of a resonant optical cavity is theoretically analyzed and experimentally verified by measuring the rejection ratios in optical heterodyne beat between a perturbed laser and a stable reference. Laser frequency noises originated from vibration, residual amplitude modulation, quantum-limited shot noise, and electronic noise are experimentally analyzed. With active control, residual amplitude modulation is suppressed to below 1 × 10-6 at 0.02-1,000 s, reaching a minimum of 2 × 10-7 at ~2 s. A frequency stability of 2 × 10-15 is obtained from 0.1 to 10 s, and the optical heterodyne beat of the two Nd:YAG lasers shows 1-Hz linewidth with a measurement time of 4.096 s. In addition, the experimentally determined linewidths agree well with the calculation according to a simplified relationship between the linewidth and the underlying flicker noise that modulates the laser frequency.

  16. The Dirac equation in an external electromagnetic field: symmetry algebra and exact integration

    NASA Astrophysics Data System (ADS)

    Breev, A. I.; Shapovalov, A. V.

    2016-01-01

    Integration of the Dirac equation with an external electromagnetic field is explored in the framework of the method of separation of variables and of the method of noncommutative integration. We have found a new type of solutions that are not obtained by separation of variables for several external electromagnetic fields. We have considered an example of crossed electric and magnetic fields of a special type for which the Dirac equation admits a nonlocal symmetry operator.

  17. Idiopathic environmental intolerance attributed to electromagnetic fields: a content analysis of British newspaper reports.

    PubMed

    Eldridge-Thomas, Buffy; Rubin, G James

    2013-01-01

    Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) is a controversial condition in which people describe symptoms following exposure to electromagnetic fields from everyday electrical devices. However, double-blind experiments have found no convincing evidence that electromagnetic fields cause these symptoms. In this study, we assessed whether recent newspaper reporting in the UK reflected this scientific evidence. We searched a database of newspaper articles to identify all those that contained IEI-EMF related keywords and selected a random sample of 60 for content analysis. For our primary outcomes, we assessed how many articles mainly or wholly presented an electromagnetic cause for IEI-EMF and how many discussed unproven treatments for the condition such as strategies intended to reduce exposure to electromagnetic fields or the use of complementary and alternative therapies. We also assessed whether the type of information source used by a newspaper article (e.g. scientist, person with IEI-EMF, politician) or the type of newspaper (broadsheet, tabloid, local or regional) was associated with either outcome. Of the 60 articles, 43 (71.7%) presented a mainly electromagnetic cause, compared to 13 (21.7%) which presented mainly non-electromagnetic causes and 4 (6.7%) which did not discuss a cause. 29 (48.3%) did not mention any potential treatment, while 24 (40.0%) mentioned eletromagnetic field related strategies and 12 (20.0%) mentioned complementary or alternative therapies. Articles which quoted someone with IEI-EMF were significantly more likely to report an electromagnetic cause and to present unproven treatments. Those which used a scientist as a source were more likely to present a non-electromagnetic cause for the condition. The widespread poor reporting we identified is disappointing and has the potential for to encourage more people to misattribute their symptoms to electromagnetic fields. Scientists should remain engaged

  18. Idiopathic Environmental Intolerance Attributed to Electromagnetic Fields: A Content Analysis of British Newspaper Reports

    PubMed Central

    Eldridge-Thomas, Buffy; Rubin, G James

    2013-01-01

    Idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) is a controversial condition in which people describe symptoms following exposure to electromagnetic fields from everyday electrical devices. However, double-blind experiments have found no convincing evidence that electromagnetic fields cause these symptoms. In this study, we assessed whether recent newspaper reporting in the UK reflected this scientific evidence. We searched a database of newspaper articles to identify all those that contained IEI-EMF related keywords and selected a random sample of 60 for content analysis. For our primary outcomes, we assessed how many articles mainly or wholly presented an electromagnetic cause for IEI-EMF and how many discussed unproven treatments for the condition such as strategies intended to reduce exposure to electromagnetic fields or the use of complementary and alternative therapies. We also assessed whether the type of information source used by a newspaper article (e.g. scientist, person with IEI-EMF, politician) or the type of newspaper (broadsheet, tabloid, local or regional) was associated with either outcome. Of the 60 articles, 43 (71.7%) presented a mainly electromagnetic cause, compared to 13 (21.7%) which presented mainly non-electromagnetic causes and 4 (6.7%) which did not discuss a cause. 29 (48.3%) did not mention any potential treatment, while 24 (40.0%) mentioned eletromagnetic field related strategies and 12 (20.0%) mentioned complementary or alternative therapies. Articles which quoted someone with IEI-EMF were significantly more likely to report an electromagnetic cause and to present unproven treatments. Those which used a scientist as a source were more likely to present a non-electromagnetic cause for the condition. The widespread poor reporting we identified is disappointing and has the potential for to encourage more people to misattribute their symptoms to electromagnetic fields. Scientists should remain engaged

  19. 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.

  20. More on the covariant retarded Green's function for the electromagnetic field in de Sitter spacetime

    SciTech Connect

    Higuchi, Atsushi; Lee, Yen Cheong; Nicholas, Jack R.

    2009-11-15

    In a recent paper 2 it was shown in examples that the covariant retarded Green's functions in certain gauges for electromagnetism and linearized gravity can be used to reproduce field configurations correctly in spite of the spacelike nature of past infinity in de Sitter spacetime. In this paper we extend the work of Ref. 2 concerning the electromagnetic field and show that the covariant retarded Green's function with an arbitrary value of the gauge parameter reproduces the electromagnetic field from two opposite charges at antipodal points of de Sitter spacetime.

  1. Dynamic model for electromagnetic field and heating patterns in loaded cylindrical cavities

    SciTech Connect

    Tian, Y.L.; Black, W.M.; Sa`adaldin, H.S.; Ahmad, I.; Silberglitt, R.

    1995-07-01

    An analytical solution for the electromagnetic fields in a cylindrical cavity, partially filled with a cylindrical dielectric has been recently reported. A program based on this solution has been developed and combined with the authors` previous program for heat transfer analysis. The new software has been used to simulate the dynamic temperature profiles of microwave heating and to investigate the role of electromagnetic field in heating uniformity and stability. The effects of cavity mode, cavity dimension, the dielectric properties of loads on electromagnetic field and heating patterns can be predicted using this software.

  2. 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.

  3. 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.

  4. 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.

  5. Nucleon electromagnetic form factors on the lattice and in chiral effective field theory

    SciTech Connect

    Goeckeler, M.; Hemmert, T.R.; Horsley, R.; Pleiter, D.; Rakow, P.E.L.; Schaefer, A.; Schierholz, G.

    2005-02-01

    We compute the electromagnetic form factors of the nucleon in quenched lattice QCD, using nonperturbatively improved Wilson fermions, and compare the results with phenomenology and chiral effective field theory.

  6. Control of the frozen geometric quantum correlation by applying the time-dependent electromagnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Mei; Xu, Jing-Bo; Yu, You-Hong

    2016-04-01

    We investigate how the time-dependent electromagnetic field affects the sudden transitions of the geometric quantum correlation for two qubits each coupled to its own dissipative environment, and two qubits uniformly coupled to a common dissipative environment, respectively. It is shown that the sudden transitions of the geometric quantum correlation in both cases can be controlled by making use of time-dependent electromagnetic field and, in addition, the frozen time during which the geometric quantum correlation remains constant can be lengthened.

  7. Amyotrophic lateral sclerosis and occupational exposure to electromagnetic fields

    SciTech Connect

    Davanipour, Z.; Sobel, E.; Bowman, J.D.; Qian, Z.; Will, A.D.

    1997-03-01

    In an hypothesis-generating case-control study of amyotrophic lateral sclerosis, lifetime occupational histories were obtained. The patients (n = 28) were clinic based. The occupational exposure of interest in this report is electromagnetic fields (EMFs). This is the first and so far the only exposure analyzed in this study. Occupational exposure up to 2 years prior to estimated disease symptom onset was used for construction of exposure indices for cases. Controls (n = 32) were blood and nonblood relatives of cases. Occupational exposure for controls was through the same age as exposure for the corresponding cases. Twenty (71%) cases and 28 (88%) controls had at least 20 years of work experience covering the exposure period. The occupational history and task data were used to classify blindly each occupation for each subject as having high, medium/high, medium, medium/low, or low EMF exposure, based primarily on data from an earlier and unrelated study designed to obtain occupational EMF exposure information on workers in ``electrical`` and ``nonelectrical`` jobs. By using the length of time each subject spent in each occupation through the exposure period, two indices of exposure were constructed: total occupational exposure (E{sub 1}) and average occupational exposure (E{sub 2}). For cases and controls with at least 20 years of work experience, the odds ratio (OR) for exposure at the 75th percentile of the E{sub 1} case exposure data relative to minimum exposure was 7.5 (P < 0.02; 95% CI, 1.4--38.1) and the corresponding OR for E{sub 2} was 5.5 (P < 0.02; 95% CI, 1.3--22.5). For all cases and controls, the ORs were 2.5 (P < 0.1; 95% CI, 0.9--8.1) for E{sub 1} and 2.3 (P = 0.12; 95% CI, 0.8--6.6) for E{sub 2}. This study should be considered an hypothesis-generating study. Larger studies, using incident cases and improved exposure assessment, should be undertaken.

  8. Influence of electromagnetic field on soliton-mediated charge transport in biological systems.

    PubMed

    Brizhik, Larissa

    2015-01-01

    It is shown that electromagnetic fields affect dynamics of Davydov's solitons which provide charge transport processes in macromolecules during metabolism of the system. There is a resonant frequency of the field at which it can cause the transition of electrons from bound soliton states into delocalised states. Such decay of solitons reduces the effectiveness of charge transport, and, therefore, inhibits redox processes. Solitons radiate their own electromagnetic field of characteristic frequency determined by their average velocity. This self-radiated field leads to synchronization of soliton dynamics and charge transport processes, and is the source of the coherence in the system. Exposition of the system to the oscillating electromagnetic field of the frequency, which coincides with the eigen-frequency of solitons can enhance eigen-radiation of solitons, and, therefore, will enhance synchronization of charge transpor, stimulate the redox processes and increase coherence in the system. Electromagnetic oscillating field causes also ratchet phenomenon of solitons, i.e., drift of solitons in macromolecules in the presence of unbiased periodic field. Such additional drift enhances the charge transport processes. It is shown that temperature facilitates the ratchet drift. In particular, temperature fluctuations lead to the lowering of the critical value of the intensity and period of the field, above which the drift of solitons takes place. Moreover, there is a stochastic resonance in the soliton dynamics in external electromagnetic fields. This means, that there is some optimal temperature at which the drift of solitons is maximal. PMID:26098523

  9. Electromagnetic field expressions in the wavenumber domain from both the horizontal and vertical electric dipoles

    NASA Astrophysics Data System (ADS)

    Li, Yuguo; Li, Gang

    2016-08-01

    In this paper, we present wavenumber domain (WD) electromagnetic field expressions at any depth in a layered conductivity earth due to both the horizontal and vertical electric dipoles, which can be buried anywhere within the layered earth. In modeling controlled-source electromagnetic (CSEM) responses for a 2D conductivity structure with a 3D source, it is very common to separate electromagnetic fields into a primary field and a secondary field to avoid the source singularity. This secondary field scheme requires WD background fields at any depth for a layered conductivity structure. To obtain primary electromagnetic fields in the WD, one can calculate quasi-analytical primary fields in the space domain (SD) and then transform them into the WD. However, this SD method is not a very efficient method of calculation. With the use of Schelkunoff potentials, we derive the quasi-analytic expressions for the electromagnetic fields in the WD, i.e. the WD method. Numerical tests indicate that the WD method can give results with the same accuracy as the SD method, and furthermore, the WD method is much faster than the SD method.

  10. 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.

  11. Linking the momentum of the electromagnetic field to the associated photons

    NASA Astrophysics Data System (ADS)

    Jakoby, Bernhard

    2013-11-01

    Considering the total force on matter in a dynamic electromagnetic field yields that, in contrast to the static case, the rate of change of mechanical momentum is not directly related to the integration of the Maxwell stress tensor but an additional term occurs, which can be interpreted as the rate of change of ‘electromagnetic momentum’. For beginners, the latter concept is hard to grasp in terms of a field theory. However, the electromagnetic momentum can readily be interpreted as the momentum of the photons associated with the electromagnetic field as presented in this paper. Even though the notion of photons is not required or included in Maxwellian electrodynamics, this relation may help students to get a better grip on the interpretation of momentum conservation in electrodynamics.

  12. Comparison of discrete multi-tone and pulse amplitude modulation for beyond 100 Gbps short-reach application

    NASA Astrophysics Data System (ADS)

    Nishihara, Masato; Kai, Yutaka; Tanaka, Toshiki; Takahara, Tomoo; Li, Lei; Yan, Weizhen; Liu, Bo; Tao, Zhenning; Rasmussen, Jens C.

    2013-12-01

    Advanced multi-level modulation is an attractive modulation technique for beyond 100 Gbps short reach optical transmission system. Above all, discrete multi-tone (DMT) technique and pulse amplitude modulation (PAM) technique are the strong candidates. We compared the 100 Gbps transmission characteristics of DMT and PAM by simulation and experiment. The comparison was done by using same devices and only the digital signal processing was changed. We studied the transmission distance dependence for 0.5 to 40 km and the impact of the frequency responses of the optical devices. Finally we discuss the features of the both modulation techniques.

  13. 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

  14. Electromagnetic Near Field Measurements of Two Critical Assemblies

    SciTech Connect

    Goettee, Jeffrey David

    2015-11-03

    The reactors employed, Godiva IV and WSMR Fast Burst Reactor, are described first. Then the point reactor kinetics model, electromagnetic potential, and the measurement of kinetics quantities are successively discussed. In summary, reactor power produces measurable electric energy. The electric signal mimics power curve for prompt burst operations - features in logarithmic derivatives match. The electric signature should be dependent on the power and not the derivative; therefore, steady-state modes should be measurable.

  15. Electromagnetic fields and anomalous transports in heavy-ion collisions-a pedagogical review.

    PubMed

    Huang, Xu-Guang

    2016-07-01

    The hot and dense matter generated in heavy-ion collisions may contain domains which are not invariant under P and CP transformations. Moreover, heavy-ion collisions can generate extremely strong magnetic fields as well as electric fields. The interplay between the electromagnetic field and triangle anomaly leads to a number of macroscopic quantum phenomena in these P- and CP-odd domains known as anomalous transports. The purpose of this article is to give a pedagogical review of various properties of the electromagnetic fields, the anomalous transport phenomena, and their experimental signatures in heavy-ion collisions. PMID:27275776

  16. Electromagnetic fields and anomalous transports in heavy-ion collisions—a pedagogical review

    NASA Astrophysics Data System (ADS)

    Huang, Xu-Guang

    2016-07-01

    The hot and dense matter generated in heavy-ion collisions may contain domains which are not invariant under P and CP transformations. Moreover, heavy-ion collisions can generate extremely strong magnetic fields as well as electric fields. The interplay between the electromagnetic field and triangle anomaly leads to a number of macroscopic quantum phenomena in these P- and CP-odd domains known as anomalous transports. The purpose of this article is to give a pedagogical review of various properties of the electromagnetic fields, the anomalous transport phenomena, and their experimental signatures in heavy-ion collisions.

  17. Theory of weak scattering of stochastic electromagnetic fields from deterministic and random media

    SciTech Connect

    Tong Zhisong; Korotkova, Olga

    2010-09-15

    The theory of scattering of scalar stochastic fields from deterministic and random media is generalized to the electromagnetic domain under the first-order Born approximation. The analysis allows for determining the changes in spectrum, coherence, and polarization of electromagnetic fields produced on their propagation from the source to the scattering volume, interaction with the scatterer, and propagation from the scatterer to the far field. An example of scattering of a field produced by a {delta}-correlated partially polarized source and scattered from a {delta}-correlated medium is provided.

  18. Terahertz Electromagnetic Fields (0.106 THz) Do Not Induce Manifest Genomic Damage In Vitro

    PubMed Central

    Hintzsche, Henning; Jastrow, Christian; Kleine-Ostmann, Thomas; Kärst, Uwe; Schrader, Thorsten; Stopper, Helga

    2012-01-01

    Terahertz electromagnetic fields are non-ionizing electromagnetic fields in the frequency range from 0.1 to 10 THz. Potential applications of these electromagnetic fields include the whole body scanners, which currently apply millimeter waves just below the terahertz range, but future scanners will use higher frequencies in the terahertz range. These and other applications will bring along human exposure to these fields. Up to now, only a limited number of investigations on biological effects of terahertz electromagnetic fields have been performed. Therefore, research is strongly needed to enable reliable risk assessment. Cells were exposed for 2 h, 8 h, and 24 h with different power intensities ranging from 0.04 mW/cm2 to 2 mW/cm2, representing levels below, at, and above current safety limits. Genomic damage on the chromosomal level was measured as micronucleus formation. DNA strand breaks and alkali-labile sites were quantified with the comet assay. No DNA strand breaks or alkali-labile sites were observed as a consequence of exposure to terahertz electromagnetic fields in the comet assay. The fields did not cause chromosomal damage in the form of micronucleus induction. PMID:23029508

  19. Influence of an electromagnetic field on the formation of wet metal foam

    NASA Astrophysics Data System (ADS)

    Heitkam, Sascha; Schwarz, Stephan; Santarelli, Claudio; Fröhlich, Jochen

    2013-03-01

    This paper presents a method of floating bubbles in liquid metal by applying an electromagnetic field. The aim of this method is to distribute the bubbles more homogeneously and to stop drainage in the generation process of metal foam. A horizontal electric current, combined with an orthogonal, horizontal magnetic field creates an upward Lorentz force that counteracts gravitational acceleration. Phase-resolving numerical simulations have been applied in order to investigate the complex behavior of a large number of bubbles exposed to these fields. Controlled by the strength of the electromagnetic fields, the bubbles can ascend more slowly, stagnate, or even descend. Due to the influence of the bubbles on the electric current, however, rotating flows are induced which prevent the bubbles from becoming immobile and induce an interesting mixing structure. Consequently, the applied electromagnetic field offers the opportunity to manipulate the bubble distribution and the drainage in the generation process of wet metal foam.

  20. Characterization and modeling of P-type electrosensory afferent responses to amplitude modulations in a wave-type electric fish.

    PubMed

    Nelson, M E; Xu, Z; Payne, J R

    1997-11-01

    The first stage of information processing in the electrosensory system involves the encoding of local changes in transdermal potential into trains of action potentials in primary electrosensory afferent nerve fibers. To develop a quantitative model of this encoding process for P-type (probability-coding) afferent fibers in the weakly electric fish Apteronotus leptorhynchus, we recorded single unit activity from electrosensory afferent axons in the posterior branch of the anterior lateral line nerve and analyzed responses to electronically generated sinusoidal amplitude modulations of the local transdermal potential. Over a range of AM frequencies from 0.1 to 200 Hz, the modulation transfer function of P-type afferents is high-pass in character, with a gain that increases monotonically up to AM frequencies of 100 Hz where it begins to roll off, and a phase advance with a range of 15-60 degrees. Based on quantitative analysis of the observed gain and phase characteristics, we present a computationally efficient model of P-type afferent response dynamics which accurately characterizes changes in afferent firing rate in response to amplitude modulations of the fish's own electric organ discharge over a wide range of AM frequencies relevant to active electrolocation. PMID:9373958

  1. Plane symmetric metrics associated with semi-plane symmetric electromagnetic fields in higher dimensions

    NASA Astrophysics Data System (ADS)

    Liang, Canbin; Tian, Guihua

    1994-11-01

    Electromagnetic fields yielding plane symmetric metrics in higher-dimensional spacetimes are exhausted and classified. It is shown that these EM fields must fall into one of the following two cases: (i)F it =F iz =0,i=1,...,n; (ii)Ftz=0. We give the general solution to the Einstein-Maxwell equations in higher dimensions corresponding to electromagnetic fields of case (ii) withF it =F iz , which covers all even-dimensional spacetimes as well as a subcase of odd-dimensional spacetimes.

  2. Quantum mechanical probability current as electromagnetic 4-current from topological EM fields

    NASA Astrophysics Data System (ADS)

    van der Mark, Martin B.

    2015-09-01

    Starting from a complex 4-potential A = αdβ we show that the 4-current density in electromagnetism and the probability current density in relativistic quantum mechanics are of identical form. With the Dirac-Clifford algebra Cl1,3 as mathematical basis, the given 4-potential allows topological solutions of the fields, quite similar to Bateman's construction, but with a double field solution that was overlooked previously. A more general nullvector condition is found and wave-functions of charged and neutral particles appear as topological configurations of the electromagnetic fields.

  3. Electrical engineers' perceptions on education - electromagnetic field theory and its connection to working life

    NASA Astrophysics Data System (ADS)

    Keltikangas, K.; Wallén, H.

    2010-10-01

    This paper investigates electrical engineers' perceptions on their education in Finland, with particular emphasis on the basic electromagnetic field theory courses and their applicability in working life, using two online surveys (n=99 and n=120). The answers show a reasonably good satisfaction with the electrical engineering studies in general, but limited practical usefulness of the field theory courses in working life. However, both respondent groups mentioned that electromagnetic field theory should belong to the basic electrical engineering curriculum, which suggests a need to strengthen the connections between the different topics in the curriculum to enable a better holistic understanding of electrical engineering.

  4. Proton radiography as an electromagnetic field and density perturbation diagnostic (invited)

    SciTech Connect

    Mackinnon, A.J.; Patel, P.K.; Town, R.P.; Edwards, M.J.; Phillips, T.; Lerner, S.C.; Price, D.W.; Hicks, D.; Key, M.H.; Hatchett, S.; Wilks, S.C.; Borghesi, M.; Romagnani, L.; Kar, S.; Toncian, T.; Pretzler, G.; Willi, O.; Koenig, M.; Martinolli, E.; Lepape, S.

    2004-10-01

    Laser driven proton beams have been used to diagnose transient fields and density perturbations in laser produced plasmas. Grid deflectometry techniques have been applied to proton radiography to obtain precise measurements of proton beam angles caused by electromagnetic fields in laser produced plasmas. Application of proton radiography to laser driven implosions has demonstrated that density conditions in compressed media can be diagnosed with million electron volt protons. This data has shown that proton radiography can provide unique insight into transient electromagnetic fields in super critical density plasmas and provide a density perturbation diagnostics in compressed matter.

  5. The electromagnetic field in conductive slabs and cylinders submitted to a harmonic longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Íñiguez, J.; Raposo, V.; Zazo, M.; García-Flores, A.; Hernández-Gómez, P.

    2009-11-01

    The analysis of the induced current distribution in conducting wires subjected to a harmonic axial voltage is important in designing many electrical devices such as transformers and transmission lines. The azimuthal magnetic field induces axial electric currents and therefore the impedance of the wire depends on the excitation frequency. The current density is increasingly confined to a thin layer at the boundary of the wire as the frequency increases. To minimize this effect at higher frequencies it is necessary to enhance the surface-to-volume ratio by using thin high-conductivity wires. The study of induction phenomena in conducting samples subjected to a harmonic longitudinal magnetic field has attracted less attention. The time-varying magnetic flux induces eddy currents, which flow perpendicularly to the axis of the sample. We study the electromagnetic field in samples of simple geometry, making the usual approximations in good conductors. The validity of our calculations extends to several GHz and allows us to propose a method for determining the electrical conductivity by measuring the phase angle of the complex mutual inductance between a primary coil, responsible for the external magnetic field, and a secondary winding around the sample.

  6. The nonextensive parameter for nonequilibrium electron gas in an electromagnetic field

    SciTech Connect

    Yu, Haining; Du, Jiulin

    2014-11-15

    The nonextensive parameter for nonequilibrium electron gas of the plasma in an electromagnetic field is studied. We exactly obtained an expression of the q-parameter based on Boltzmann kinetic theories for plasmas, where Coulombian interactions and Lorentz forces play dominant roles. We show that the q-parameter different from unity is related by an equation to temperature gradient, electric field strength, magnetic induction as well as overall bulk velocity of the gas. The effect of the magnetic field on the q-parameter depends on the overall bulk velocity. Thus the q-parameter for the electron gas in an electromagnetic field represents the nonequilibrium nature or nonisothermal configurations of the plasma with electromagnetic interactions. - Highlights: • An expression of the q-parameter is obtained for nonequilibrium plasma with electromagnetic interactions. • The q-parameter is related to temperature gradient, electric field strength, magnetic induction as well as overall bulk velocity of the plasma. • The q-parameter represents the nonequilibrium nature of the complex plasma with electromagnetic interactions.

  7. Exact Electromagnetic Fields Produced by a Finite Wire with Constant Current

    ERIC Educational Resources Information Center

    Jimenez, J. L.; Campos, I.; Aquino, N.

    2008-01-01

    We solve exactly the problem of calculating the electromagnetic fields produced by a finite wire with a constant current, by using two methods: retarded potentials and Jefimenko's formalism. One result in this particular case is that the usual Biot-Savart law of magnetostatics gives the correct magnetic field of the problem. We also show…

  8. FAST TRACK COMMUNICATION: Free form of the Foldy-Wouthuysen transformation in external electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Murguía, Gabriela; Raya, Alfredo

    2010-10-01

    We derive the exact Foldy-Wouthuysen transformation for Dirac fermions in a time-independent external electromagnetic field in the basis of the Ritus eigenfunctions, namely the eigenfunctions of the operator (γ sdot Π)2, with Πμ = pμ - eAμ. On this basis, the transformation acquires a free form involving the dynamical quantum numbers induced by the field.

  9. Dynamical localization of Dirac particles in electromagnetic fields with dominating magnetic potentials

    NASA Astrophysics Data System (ADS)

    Barbaroux, Jean-Marie; Mehringer, Josef; Stockmeyer, Edgardo; Taarabt, Amal

    2016-04-01

    We consider two-dimensional massless Dirac operators in a radially symmetric electromagnetic field. In this case the fields may be described by one-dimensional electric and magnetic potentials V and A. We show dynamical localization in the regime when lim r → ∞ ⁡ | V | / | A | < 1, where dense point spectrum occurs.

  10. 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.

  11. 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.

  12. Experimental research in aerodynamic control with electric and electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Braun, E. M.; Lu, F. K.; Wilson, D. R.

    2009-01-01

    Fifty years ago, publications began to discuss the possibilities of electromagnetic flow control (EMFC) to improve aerodynamic performance. This led to an era of research that focused on coupling the fundamentals of magnetohydrodynamics (MHD) with propulsion, control, and power generation systems. Unfortunately, very few designs made it past an exploratory phase as, among other issues, power consumption was unreasonably high. Recent proposed advancements in technology like the MARIAH hypersonic wind tunnel and the AJAX scramjet engine concepts have led to a new phase of MHD research in the aerospace industry, with many interdisciplinary applications. Compared with propulsion systems and channel flow accelerators, EMFC concepts applied to control surface aerodynamics have not seen the same level of advancement that may eventually produce a device that can be integrated with an aircraft or missile. The purpose of this paper is to review the overall feasibility of the different electric and EMFC concepts. Emphasis is placed on EMFC with high voltage ionization sources and experimental work.

  13. Lossy chaotic electromagnetic reverberation chambers: Universal statistical behavior of the vectorial field.

    PubMed

    Gros, J-B; Kuhl, U; Legrand, O; Mortessagne, F

    2016-03-01

    The effective Hamiltonian formalism is extended to vectorial electromagnetic waves in order to describe statistical properties of the field in reverberation chambers. The latter are commonly used in electromagnetic compatibility tests. As a first step, the distribution of wave intensities in chaotic systems with varying opening in the weak coupling limit for scalar quantum waves is derived by means of random matrix theory. In this limit the only parameters are the modal overlap and the number of open channels. Using the extended effective Hamiltonian, we describe the intensity statistics of the vectorial electromagnetic eigenmodes of lossy reverberation chambers. Finally, the typical quantity of interest in such chambers, namely, the distribution of the electromagnetic response, is discussed. By determining the distribution of the phase rigidity, describing the coupling to the environment, using random matrix numerical data, we find good agreement between the theoretical prediction and numerical calculations of the response. PMID:27078293

  14. Localization from near-source quasi-static electromagnetic fields

    SciTech Connect

    Mosher, J.C.

    1993-09-01

    A wide range of research has been published on the problem of estimating the parameters of electromagnetic and acoustical sources from measurements of signals measured at an array of sensors. In the quasi-static electromagnetic cases examined here, the signal variation from a point source is relatively slow with respect to the signal propagation and the spacing of the array of sensors. As such, the location of the point sources can only be determined from the spatial diversity of the received signal across the array. The inverse source localization problem is complicated by unknown model order and strong local minima. The nonlinear optimization problem is posed for solving for the parameters of the quasi-static source model. The transient nature of the sources can be exploited to allow subspace approaches to separate out the signal portion of the spatial correlation matrix. Decomposition techniques are examined for improved processing, and an adaptation of MUtiple SIgnal Characterization (MUSIC) is presented for solving the source localization problem. Recent results on calculating the Cramer-Rao error lower bounds are extended to the multidimensional problem here. This thesis focuses on the problem of source localization in magnetoencephalography (MEG), with a secondary application to thunderstorm source localization. Comparisons are also made between MEG and its electrical equivalent, electroencephalography (EEG). The error lower bounds are examined in detail for several MEG and EEG configurations, as well as localizing thunderstorm cells over Cape Canaveral and Kennedy Space Center. Time-eigenspectrum is introduced as a parsing technique for improving the performance of the optimization problem.

  15. Manipulating electromagnetic responses of metal wires at the deep subwavelength scale via both near- and far-field couplings

    SciTech Connect

    Tan, Wei; Sun, Yong; Chen, Hong; Wang, Zhi-Guo

    2014-03-03

    A hybrid coupling model containing both near- and far-field couplings is developed for radiating two-resonator structures. We demonstrate that the near- and far-field couplings make distinguished contributions to electromagnetic responses. Compared to the classical electromagnetically induced transparency configurations, the presence of far-field coupling provides more flexibility in tuning lineshapes. Planar metamaterials composed of metal wires are designed based on this model, and various electromagnetic responses are experimentally observed.

  16. Analysis and simulation research of electromagnetic field model in resistance spot welding

    NASA Astrophysics Data System (ADS)

    Xuan, Wenbo; Luo, Zhen; Li, Yang; Wang, Rui; Fan, Naifeng

    2010-12-01

    Resistance spot welding (RSW) has rarely been applied to the fields requiring high welding quality, as it is limited by the instability of welding quality and quality monitoring system. Inversion imaging of nugget is a new developing method of monitoring welding quality at this background. Before the inversion image, this paper does some researches on the electromagnetic forward problem by establishing the forward model and simulating its electromagnetic field. In order to verify the reliability of this model, this paper takes the magnetic field signals as example to carry out the spot welding experiments. By comparison, the data illustrates that this electromagnetic model is reliable within a certain distance range. Besides these, this paper also does some researches on the different patterns of Hall sensor array, in order to find the array pattern with smaller errors to carry out inversion imaging.

  17. Analysis and simulation research of electromagnetic field model in resistance spot welding

    NASA Astrophysics Data System (ADS)

    Xuan, Wenbo; Luo, Zhen; Li, Yang; Wang, Rui; Fan, Naifeng

    2011-05-01

    Resistance spot welding (RSW) has rarely been applied to the fields requiring high welding quality, as it is limited by the instability of welding quality and quality monitoring system. Inversion imaging of nugget is a new developing method of monitoring welding quality at this background. Before the inversion image, this paper does some researches on the electromagnetic forward problem by establishing the forward model and simulating its electromagnetic field. In order to verify the reliability of this model, this paper takes the magnetic field signals as example to carry out the spot welding experiments. By comparison, the data illustrates that this electromagnetic model is reliable within a certain distance range. Besides these, this paper also does some researches on the different patterns of Hall sensor array, in order to find the array pattern with smaller errors to carry out inversion imaging.

  18. [Electromagnetic fields in hospitals: wireless-LAN as a risk factor?].

    PubMed

    Oertle, M; Lehmann, H; Fritschi, P; Müller, M; Berz, R

    2006-06-01

    The actual level of exposure to non-ionizing radiation in Swiss hospitals is not well known. Therefore, the electromagnetic field of wireless LAN (WLAN) and other non-ionizing radiation sources in the publicly funded Hospital Thun (Switzerland), where WLAN supports bedside access to the computerized patient record for more than three years, has been measured. The results are compared to the international and national exposure limits for the general public. Nurse workplaces as well as patient rooms show exposure levels well below the legal (national and international) exposure limits. In the investigated patients' room the electromagnetic field of GSM and broadband cellular phone networks are dominant, whereas at the nurse workplace WLAN exposure is the most important source of exposure. The results of a questionnaire survey emphasize, that the hospital staff does not worry much about electromagnetic fields of new ICT technologies. PMID:16783890

  19. Growth stimulation of biological cells and tissue by electromagnetic fields and uses thereof

    NASA Technical Reports Server (NTRS)

    Wolf, David A. (Inventor); Goodwin, Thomas J. (Inventor)

    2004-01-01

    The present invention provides systems for growing two or three dimensional mammalian cells within a culture medium facilitated by an electromagnetic field, and preferably, a time varying electromagnetic field. The cells and culture medium are contained within a fixed or rotating culture vessel, and the electromagnetic field is emitted from at least one electrode. In one embodiment, the electrode is spaced from the vessel. The invention further provides methods to promote neural tissue regeneration by means of culturing the neural cells in the claimed system. In one embodiment, neuronal cells are grown within longitudinally extending tissue strands extending axially along and within electrodes comprising electrically conductive channels or guides through which a time varying electrical current is conducted, the conductive channels being positioned within a culture medium.

  20. Matter coupling to strong electromagnetic fields in two-level quantum systems with broken inversion symmetry.

    PubMed

    Kibis, O V; Slepyan, G Ya; Maksimenko, S A; Hoffmann, A

    2009-01-16

    We demonstrate theoretically the parametric oscillator behavior of a two-level quantum system with broken inversion symmetry exposed to a strong electromagnetic field. A multitude of resonance frequencies and additional harmonics in the scattered light spectrum as well as an altered Rabi frequency are predicted to be inherent to such systems. In particular, dipole radiation at the Rabi frequency appears to be possible. Since the Rabi frequency is controlled by the strength of the coupling electromagnetic field, the effect can serve for the frequency-tuned parametric amplification and generation of electromagnetic waves. Manifestation of the effect is discussed for III-nitride quantum dots with strong built-in electric field breaking the inversion symmetry. Terahertz emission from arrays of such quantum dots is shown to be experimentally observable. PMID:19257272

  1. Separation of particles, suspended in a conducting liquid, with the help of an alternating electromagnetic field

    SciTech Connect

    Korovin, V.M.

    1986-01-01

    The author studies MHD flow at low Reynolds numbers past a spherical particle with conductivity ..cap alpha../sub 1/ greater than or equal to0, moving in a viscous fluid at rest with conductivity ..cap alpha../sub 2/ not = ..cap alpha../sub 1/, filling the interior space of a long solenoid fed by an alternating current. It is shown that aside from the electromagnetic force calculated from the analog of Archimedes' principle, and from the Lorentz force arising from the interaction of eddy currents flowing in th particle with the magnetic field, the particle is also subjected to an electromagnetic propulsive force. A formula relating the local characteristics of the electromagnetic field with the velocity of the particle put into motion by the field but neglecting inertial effects is obtained.

  2. The effect of electromagnetic fields emitted by mobile phones on human sleep.

    PubMed

    Loughran, Sarah P; Wood, Andrew W; Barton, Julie M; Croft, Rodney J; Thompson, Bruce; Stough, Con

    2005-11-28

    Previous research has suggested that exposure to radiofrequency electromagnetic fields increases electroencephalogram spectral power in non-rapid eye movement sleep. Other sleep parameters have also been affected following exposure. We examined whether aspects of sleep architecture show sensitivity to electromagnetic fields emitted by digital mobile phone handsets. Fifty participants were exposed to electromagnetic fields for 30 min prior to sleep. Results showed a decrease in rapid eye movement sleep latency and increased electroencephalogram spectral power in the 11.5-12.25 Hz frequency range during the initial part of sleep following exposure. These results are evidence that mobile phone exposure prior to sleep may promote rapid eye movement sleep and modify the sleep electroencephalogram in the first non-rapid eye movement sleep period. PMID:16272890

  3. Growth Stimulation of Biological Cells and Tissue by Electromagnetic Fields and Uses Thereof

    NASA Technical Reports Server (NTRS)

    Wolf, David A. (Inventor); Goodwin, Thomas J. (Inventor)

    2002-01-01

    The present invention provides systems for growing two or three dimensional mammalian cells within a culture medium facilitated by an electromagnetic field, and preferably, a time varying electromagnetic field. The cells, and culture medium are contained within a fixed or rotating culture vessel, and the electromagnetic field is emitted from at least one electrode. In one embodiment, the electrode is spaced from the vessel. The invention further provides methods to promote neural tissue regeneration by means of culturing the neural cells in the claimed system. In one embodiment, neuronal cells are grown within longitudinally extending tissue strands extending axially along and within electrodes comprising electrically conductive channels or guides through which a time varying electrical current is conducted, the conductive channels being positioned within a culture medium.

  4. Particle Production in Strong Electromagnetic Fields in Relativistic Heavy-Ion Collisions

    DOE PAGESBeta

    Tuchin, Kirill

    2013-01-01

    I reviewmore » the origin and properties of electromagnetic fields produced in heavy-ion collisions. The field strength immediately after a collision is proportional to the collision energy and reaches ~ m π 2 at RHIC and ~ 10 m π 2 at LHC. I demonstrate by explicit analytical calculation that after dropping by about one-two orders of magnitude during the first fm/c of plasma expansion, it freezes out and lasts for as long as quark-gluon plasma lives as a consequence of finite electrical conductivity of the plasma. Magnetic field breaks spherical symmetry in the direction perpendicular to the reaction plane, and therefore all kinetic coefficients are anisotropic. I examine viscosity of QGP and show that magnetic field induces azimuthal anisotropy on plasma flow even in spherically symmetric geometry. Very strong electromagnetic field has an important impact on particle production. I discuss the problem of energy loss and polarization of fast fermions due to synchrotron radiation, consider photon decay induced by magnetic field, elucidate J / ψ dissociation via Lorentz ionization mechanism, and examine electromagnetic radiation by plasma. I conclude that all processes in QGP are affected by strong electromagnetic field and call for experimental investigation.« less

  5. A study on the discrete image method for calculation of transient electromagnetic fields in geological media

    NASA Astrophysics Data System (ADS)

    Meng, Qing-Xin; Pan, He-Ping; Luo, Miao

    2015-12-01

    We conducted a study on the numerical calculation and response analysis of a transient electromagnetic field generated by a ground source in geological media. One solution method, the traditional discrete image method, involves complex operation, and its digital filtering algorithm requires a large number of calculations. To solve these problems, we proposed an improved discrete image method, where the following are realized: the real number of the electromagnetic field solution based on the Gaver-Stehfest algorithm for approximate inversion, the exponential approximation of the objective kernel function using the Prony method, the transient electromagnetic field according to discrete image theory, and closed-form solution of the approximate coefficients. To verify the method, we tentatively calculated the transient electromagnetic field in a homogeneous model and compared it with the results obtained from the Hankel transform digital filtering method. The results show that the method has considerable accuracy and good applicability. We then used this method to calculate the transient electromagnetic field generated by a ground magnetic dipole source in a typical geoelectric model and analyzed the horizontal component response of the induced magnetic field obtained from the "ground excitation-stratum measurement" method. We reached the conclusion that the horizontal component response of a transient field is related to the geoelectric structure, observation time, spatial location, and others. The horizontal component response of the induced magnetic field reflects the eddy current field distribution and its vertical gradient variation. During the detection of abnormal objects, positions with a zero or comparatively large offset were selected for the drillhole measurements or a comparatively long observation delay was adopted to reduce the influence of the ambient field on the survey results. The discrete image method and forward calculation results in this paper

  6. 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

  7. [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

  8. Effects of randomizing phase on the discrimination between amplitude-modulated and quasi-frequency-modulated tones.

    PubMed

    Tabuchi, Hisaaki; Borucki, Ewa; Berg, Bruce G

    2012-08-01

    This study investigated the bandwidth of phase sensitivity. Subjects discriminated amplitude-modulated tones (AM), and quasi-frequency-modulated tones (QFM) in a two-interval, forced-choice task. An adaptive threshold procedure was used to estimate the modulation depth needed to discriminate the stimuli as a function of carrier and modulation frequency. Non-monotonicities in threshold-bandwidth functions were often observed at higher modulation frequencies. The results are discussed in terms of two potential cues: (1) waveform envelope, (2) cubic distortion products. In order to degrade the information obtained from auditory distortions, the phase for the carrier frequency was randomly sampled from a uniform distribution, which diminished the non-monotonicities with minimal effect at lower modulation frequencies. Model simulations demonstrated that phase randomization degrades distortion product cues with only a modest effect on temporal cues. Final results show that maximum bandwidths for phase sensitivity (BW(max)) were not proportional to carrier frequencies. PMID:22609773

  9. The effect of microphone wind noise on the amplitude modulation of wind turbine noise and its mitigation.

    PubMed

    Kendrick, Paul; von Hünerbein, Sabine; Cox, Trevor J

    2016-07-01

    Microphone wind noise can corrupt outdoor recordings even when wind shields are used. When monitoring wind turbine noise, microphone wind noise is almost inevitable because measurements cannot be made in still conditions. The effect of microphone wind noise on two amplitude modulation (AM) metrics is quantified in a simulation, showing that even at low wind speeds of 2.5 m/s errors of over 4 dBA can result. As microphone wind noise is intermittent, a wind noise detection algorithm is used to automatically find uncorrupted sections of the recording, and so recover the true AM metrics to within ±2/±0.5 dBA. PMID:27475217

  10. Composite Amplitude Modulated Phase Only Filter Based Detection and Tracking of the Back-Reflection of KDP Images

    SciTech Connect

    Awwal, A S; McClay, W A; Ferguson, S W; Candy, J V; Salmon, J T; Wegner, P J

    2004-08-26

    An algorithm for determining the position of the KDP back-reflection image was developed. It was compared to a centroid-based algorithm. While the algorithm based on centroiding exhibited a radial standard deviation of 9 pixels, the newly proposed algorithm based on classical matched filtering (CMF) and a Gaussian fit to correlation peak provided a radial standard deviation of less than 1 pixel. The speed of the peak detection was improved from an average of 5.5 seconds for Gaussian fit to 0.022 seconds by using a polynomial fit. The performance was enhanced even further by utilizing a composite amplitude modulated phase only filter; producing a radial standard deviation of 0.27 pixels. The proposed technique was evaluated on 900+ images with varying degrees of noise and image amplitude as well as real National Ignition Facility (NIF) images.

  11. Phase reduction of a limit cycle oscillator perturbed by a strong amplitude-modulated high-frequency force

    NASA Astrophysics Data System (ADS)

    Pyragas, Kestutis; Novičenko, Viktor

    2015-07-01

    The phase reduction method for a limit cycle oscillator subjected to a strong amplitude-modulated high-frequency force is developed. An equation for the phase dynamics is derived by introducing a new, effective phase response curve. We show that if the effective phase response curve is everywhere positive (negative), then an entrainment of the oscillator to an envelope frequency is possible only when this frequency is higher (lower) than the natural frequency of the oscillator. Also, by using the Pontryagin maximum principle, we have derived an optimal waveform of the perturbation that ensures an entrainment of the oscillator with minimal power. The theoretical results are demonstrated with the Stuart-Landau oscillator and model neurons.

  12. Imaging of biomaterials in liquids: a comparison between conventional and Q-controlled amplitude modulation ('tapping mode') atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Ebeling, D.; Hölscher, H.; Fuchs, H.; Anczykowski, B.; Schwarz, U. D.

    2006-04-01

    Lambda phage DNA and DPPC thin films are imaged in liquids by atomic force microscopy applying the amplitude modulation mode ('tapping mode') with active enhancement of the Q-factor by a 'Q-control' electronics. The topography of the resulting images is compared with images obtained without active Q-control. To enable a meaningful comparison, individual scan lines are alternately recorded with and without Q-factor enhancement using scan parameters optimized for each mode separately. As the major finding, significant height differences of topographical features are observed between the two modes. The heights measured with active Q-control are reproducibly higher compared to the ones observed without Q enhancement. This effect is attributed to the reduction of tip-sample forces by Q-control.

  13. Influence of electromagnetic field intensity on the metastable zone width of CaCO3 crystallization in circulating water

    NASA Astrophysics Data System (ADS)

    Wang, Jianguo; Liang, Yandong; Chen, Si

    2016-09-01

    In this study, changes in the metastable zone width of CaCO3 crystallization was determined through conductivity titration by altering electromagnetic field parameters applied to the circulating water system. The critical conductivity value and metastable zone curves of CaCO3 crystallization were determined under different solution concentrations and electromagnetic field intensities. Experimental results indicate that the effect of the electromagnetic field intensity on the critical conductivity value intensifies with the increase of solution concentration. Moreover, the metastable zone width of CaCO3 crystallization increases with the increase of electromagnetic field intensity within 200 Gs, thereby prolonging the induction period of nucleation.

  14. Electromagnetic and gravitational responses of two-dimensional noninteracting electrons in a background magnetic field

    NASA Astrophysics Data System (ADS)

    Abanov, Alexander G.; Gromov, Andrey

    2014-07-01

    We compute electromagnetic, gravitational, and mixed linear response functions of two-dimensional free fermions in an external quantizing magnetic field at an integer filling factor. The results are presented in the form of the effective action and as an expansion of currents and stresses in wave vectors and frequencies of the probing electromagnetic and metric fields. In addition to the well-studied U (1) Chern-Simons and Wen-Zee terms we find a gravitational Chern-Simons term that controls the correction to the Hall viscosity due to the background curvature. We relate the coefficient in front of the term with the chiral central charge.

  15. Effects of Electromagnetic Fields in Spinal Muscular Atrophy: A Case Report

    NASA Astrophysics Data System (ADS)

    Cañedo, L.; Martínez-Mata, J.; Serrano-Luna, G.

    2004-09-01

    Spinal Muscular Atrophy Type I is a disease that rapidly progress to death in early infancy. A case report of a child with Werdnig-Hoffmann disease Type I that recovered at three years of age after two years exposure to electromagnetic fields (ELF) is presented. The child is now eleven years old and with the exception of slightly abnormal gait, the muscle mass of tights and gluteus, high, weight and his everyday activities correspond to those of a normal child his age. Hypothetical explanations for the effects of the electromagnetic fields are discussed.

  16. Association between electromagnetic field exposure and abortion in pregnant women living in Tehran

    PubMed Central

    Abad, Masoumeh; Malekafzali, Hossein; Simbar, Masoumeh; Seyed Mosaavi, Hassan; Merghati Khoei, Effat

    2016-01-01

    Background: Health-related quality of life is affected by electromagnetic field exposure in each person everyday life. However, this is extremely controversial issue. Objective: Investigation of the associations between electromagnetic field exposure and miscarriage among women of Tehran. Materials and Methods: In this longitudinal study, 462 pregnant women with gestational age <12 wks from seven main regions of Tehran city in Iran with similar social and cultural status were participated. Women were interviewed face-to face to collect data. Reproductive information was collected using medical file recorded in those hospitals the subjects had delivery. The measuring device measured electromagnetic waves, Narda safety test solutions with valid calibration date at the entrance door of their houses. Results: A significant likelihood of miscarriage in women who exposed to significant level of electromagnetic wave. However, this association was not confirmed by Wald test. Conclusion: This study may not provide strong or consistent evidence that electromagnetic field exposure is associated or cause miscarriage. This issue may be due to small sample size in this study. PMID:27326421

  17. IMMUNOLOGIC EFFECTS OF ELECTROMAGNETIC FIELDS (1981-1983)

    EPA Science Inventory

    In vitro studies provide evidence that support and EM field induced thermal mechanism for immune effects. When proper control of culture temperatures has been achieved during in vitro exposure to EM fields, no alterations have been observed for a variety of immune cell functions....

  18. Electromagnetic field of fractal distribution of charged particles

    SciTech Connect

    Tarasov, Vasily E.

    2005-08-15

    Electric and magnetic fields of fractal distribution of charged particles are considered. The fractional integrals are used to describe fractal distribution. The fractional integrals are considered as approximations of integrals on fractals. Using the fractional generalization of integral Maxwell equation, the simple examples of the fields of homogeneous fractal distribution are considered. The electric dipole and quadrupole moments for fractal distribution are derived.

  19. DiPerna-Lions Flow for Relativistic Particles in an Electromagnetic Field

    NASA Astrophysics Data System (ADS)

    Jabin, P.-E.; Masmoudi, N.

    2015-09-01

    We show the existence and uniqueness of a DiPerna-Lions flow for relativistic particles subject to a Lorentz force in an electromagnetic field. The electric and magnetic fields solve the linear Maxwell system in the vacuum but for singular initial conditions which are only in the physical energy space. As the corresponding force field is only in L 2, we have to perform a careful analysis of the cancellations over a trajectory.

  20. Instability of a liquid metal surface in an electromagnetic field and relevance to EMC

    SciTech Connect

    Kageyama, R.; Evans, J.W.

    1996-10-01

    In electromagnetic casting (EMC) the surface of the molten metal, at the solidification front around the periphery of the melt pool, is not confirmed by a solid mold (as in, say, direct chill casting) but is free to move. Consequently disturbances of the melt surface are reflected in defects (waviness) in the solid ingot. The present paper examines the dynamics of a liquid metal surface in an electromagnetic field comparable to that of EMC. Numerical calculations of the flow of metal and motion of the melt surface have been accompanied by laboratory experiments in which a laser vibrometer has been used to measure the oscillations of the free surface of a mercury pool. Surface oscillations growth with increasing electromagnetic field strength in both the computations and the experiment, probably originating from the turbulent flow in the melt. The implications for EMC are discussed.

  1. 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.

  2. 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.

  3. Microfabricated sensors for the measurement of electromagnetic fields in biological tissues

    NASA Astrophysics Data System (ADS)

    Monberg, James; Henning, Albert K.

    1995-09-01

    Public awareness of the risks of exposure to electromagnetic radiation has grown over the past ten yeras. The effects of power lines on human and animal health have drawn particular attention. Some longitudinal studies of cancer rates near power lines show a significant correlation, while others show a null result. The studies have suffered from inadequate sensors for the measurement of electromagnetic radiation in vivo. In this work, we describe the design, construction, and testing of electrically passive, microfabricated single-pole antennas and coils. These sensors will be used in vivo to study the effects of electromagnetic radiation on animals. Our testing to date has been limited to in vitro studies of the magnetic field probes. Magnetic field pickup coils were fabricated with up to 100 turns, over a length of up to 1000 micrometers . Measurements were carried out with the sensors in air, and in water of various saline concentrations. Magnetic fields were applied using a Helmholtz coil. Both dc and ac fields were applied. The results indicate that small-area measurements of electromagnetic fields in vitro can be made successfully, provided adequate shielding and amplification are used.

  4. Controlling electromagnetic fields at boundaries of arbitrary geometries

    NASA Astrophysics Data System (ADS)

    Teo, Jonathon Yi Han; Wong, Liang Jie; Molardi, Carlo; Genevet, Patrice

    2016-08-01

    Rapid developments in the emerging field of stretchable and conformable photonics necessitate analytical expressions for boundary conditions at metasurfaces of arbitrary geometries. Here, we introduce the concept of conformal boundary optics: a design theory that determines the optical response for designer input and output fields at such interfaces. Given any object, we can realize coatings to achieve exotic effects like optical illusions and anomalous diffraction behavior. This approach is relevant to a broad range of applications from conventional refractive optics to the design of the next-generation of wearable optical components. This concept can be generalized to other fields of research where designer interfaces with nontrivial geometries are encountered.

  5. Nonequilibrium electromagnetics: Local and macroscopic fields and constitutive relationships

    SciTech Connect

    Baker-Jarvis, James; Kabos, Pavel; Holloway, Christopher L.

    2004-09-01

    We study the electrodynamics of materials using a Liouville-Hamiltonian-based statistical-mechanical theory. Our goal is to develop electrodynamics from an ensemble-average viewpoint that is valid for microscopic and nonequilibrium systems at molecular to submolecular scales. This approach is not based on a Taylor series expansion of the charge density to obtain the multipoles. Instead, expressions of the molecular multipoles are used in an inverse problem to obtain the averaging statistical-density function that is used to obtain the macroscopic fields. The advantages of this method are that the averaging function is constructed in a self-consistent manner and the molecules can either be treated as point multipoles or contain more microstructure. Expressions for the local and macroscopic fields are obtained, and evolution equations for the constitutive parameters are developed. We derive equations for the local field as functions of the applied, polarization, magnetization, strain density, and macroscopic fields.

  6. A Set of Computer Projects for an Electromagnetic Fields Class.

    ERIC Educational Resources Information Center

    Gleeson, Ronald F.

    1989-01-01

    Presented are three computer projects: vector analysis, electric field intensities at various distances, and the Biot-Savart law. Programing suggestions and project results are provided. One month is suggested for each project. (MVL)

  7. Guiding and collimating fast electron beam by the quasi-static electromagnetic field array

    SciTech Connect

    Wang, J.; Zhao, Z. Q.; He, W. H.; Dong, K. G.; Wu, Y. C.; Zhu, B.; Zhang, T. K.; Zhang, B.; Zhang, Z. M.; Gu, Y. Q.; Cao, L. H.

    2014-10-15

    A guidance and collimation scheme for fast electron beam in a traverse periodic quasi-static electromagnetic field array is proposed with the semi-analytic method and the particle-in-cell simulation. The sheath electric fields on the surfaces of nanowires and the magnetic fields around the nanowires form a traverse periodic quasi-static electromagnetic field array. Therefore, most of the fast electrons are confined at the nanowire surfaces and transport forward. More importantly, due to the divergent property of the beams, the magnitudes of the generated fields decrease with the target depth. The lateral momenta of the electrons convert into the forward momenta through Lorenz force, and they cannot recover their initial values. Therefore, the fast electrons can be guided and collimated efficiently in the gaps between the nanowires. In our particle-in-cell simulations, the observed guiding efficiency exceeds 80% compared with the reference target.

  8. Electromagnetic field exposure assessment in Europe radiofrequency fields (10 MHz-6 GHz).

    PubMed

    Gajšek, Peter; Ravazzani, Paolo; Wiart, Joe; Grellier, James; Samaras, Theodoros; Thuróczy, György

    2015-01-01

    Average levels of exposure to radiofrequency (RF) electromagnetic fields (EMFs) of the general public in Europe are difficult to summarize, as exposure levels have been reported differently in those studies in which they have been measured, and a large proportion of reported measurements were very low, sometimes falling below detection limits of the equipment used. The goal of this paper is to present an overview of the scientific literature on RF EMF exposure in Europe and to characterize exposure within the European population. A comparative analysis of the results of spot or long-term RF EMF measurements in the EU indicated that mean electric field strengths were between 0.08 V/m and 1.8 V/m. The overwhelming majority of measured mean electric field strengths were <1 V/m. It is estimated that <1% were above 6 V/m and <0.1% were above 20 V/m. No exposure levels exceeding European Council recommendations were identified in these surveys. Most population exposures from signals of radio and television broadcast towers were observed to be weak because these transmitters are usually far away from exposed individuals and are spatially sparsely distributed. On the other hand, the contribution made to RF exposure from wireless telecommunications technology is continuously increasing and its contribution was above 60% of the total exposure. According to the European exposure assessment studies identified, three population exposure categories (intermittent variable partial body exposure, intermittent variable low-level whole-body (WB) exposure and continuous low-level WB exposure) were recognized by the authors as informative for possible future risk assessment. PMID:23942394

  9. Strings: A possible alternative explanation for the Unification of Gravitation Field and Electromagnetic Field

    NASA Astrophysics Data System (ADS)

    Rivera, Susana

    Throughout the last century, since the last decades of the XIX century, until present day, there had been many attempts to achieve the unification of the Forces of Nature. First unification was done by James Clerk Maxwell, with his Electromagnetic Theory. Then Max Plank developed his Quantum Theory. In 1905, Albert Einstein gave birth to the Special Relativity Theory, and in 1916 he came out with his General Relativity Theory. He noticed that there was an evident parallelism between the Gravitational Force, and the Electromagnetic Force. So, he tried to unify these forces of Nature. But Quantum Theory interposed on his way. On the 1940’s it had been developed the Quantum Electrodynamics (QED), and with it, the unified field theory had an arise interest. On the 60’s and 70’s there was developed the Quantum Chromodynamics (QCD). Along with these theories came the discovery of the strong interaction force and weak interaction force. And though there had been many attempts to unify all these forces of the nature, it could only be achieved the Unification of strong interaction, weak interaction and Electromagnetic Force. On the late 80”s and throughout the last two decades, theories such as “super-string theory”, “or the “M-theory”, among others, groups of Scientists, had been doing grand efforts and finally they came out with the unification of the forces of nature, being the only limitation the use of more than 11 dimensions. Using an ingenious mathematical tool known as the super symmetries, based on the Kaluza - Klein work, they achieve this goal. The strings of these theories are in the rank of 10-33 m. Which make them undetectable. There are many other string theories. The GEUFT theory is based on the existence of concentrated energy lines, which vibrates, expands and contracts, submitting and absorbing energy, matter and antimatter, and which yields a determined geometry, that gives as a result the formation of stars, galaxies, nebulae, clusters

  10. On the electrodynamics of moving permanent dipoles in external electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Mansuripur, Masud

    2014-09-01

    The classical theory of electrodynamics is built upon Maxwell's equations and the concepts of electromagnetic field, force, energy and momentum, which are intimately tied together by Poynting's theorem and the Lorentz force law. Whereas Maxwell's macroscopic equations relate the electric and magnetic fields to their material sources (i.e., charge, current, polarization and magnetization), Poynting's theorem governs the flow of electromagnetic energy and its exchange between fields and material media, while the Lorentz law regulates the back-and-forth transfer of momentum between the media and the fields. The close association of momentum with energy thus demands that the Poynting theorem and the Lorentz law remain consistent with each other, while, at the same time, ensuring compliance with the conservation laws of energy, linear momentum, and angular momentum. This paper shows how a consistent application of the aforementioned laws of electrodynamics to moving permanent dipoles (both electric and magnetic) brings into play the rest-mass of the dipoles. The rest mass must vary in response to external electromagnetic fields if the overall energy of the system is to be conserved. The physical basis for the inferred variations of the rest-mass appears to be an interference between the internal fields of the dipoles and the externally applied fields. We use two different formulations of the classical theory in which energy and momentum relate differently to the fields, yet we find identical behavior for the restmass in both formulations.

  11. 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

  12. Electrical Engineers' Perceptions on Education--Electromagnetic Field Theory and Its Connection to Working Life

    ERIC Educational Resources Information Center

    Keltikangas, K.; Wallen, H.

    2010-01-01

    This paper investigates electrical engineers' perceptions on their education in Finland, with particular emphasis on the basic electromagnetic field theory courses and their applicability in working life, using two online surveys (n = 99 and n = 120). The answers show a reasonably good satisfaction with the electrical engineering studies in…

  13. Possible Mechanism of Action of the Electromagnetic Fields of Ultralow Frequency on G-protein

    SciTech Connect

    Nava, J. J. Godina; Segura, M. A. Rodriguez; Garcia, M. N. Jimenez; Cadena, M. S. Reyes

    2008-08-11

    Based in several clinical achievements and mathematical simulation of the immune sytem, previously studied, permit us to establish that a possible Mechanism of Action of ultralow frequency Electromagnetic Fields (ELF) is on G-protein as it has been proposed in specialized literature.

  14. Electron beam electromagnetic field interaction in one-dimensional coaxial vircator

    NASA Astrophysics Data System (ADS)

    Shao, H.; Liu, G. Z.; Yang, Z. F.

    2005-10-01

    A one-dimensional model of the interaction between an injected electron beam and an electromagnetic (EM) field inside a coaxial vircator is presented. The effects of the injected electron beam energy spread, anode absorption rate, feedback and injected current premodulation are analyzed. The EM-gains of interaction between the electron beam and TM01, TE11 modes are derived and discussed.

  15. EVALUATION OF THE POTENTIAL CARCINOGENICITY OF ELECTROMAGNETIC FIELDS (EXTERNAL REVIEW DRAFT)

    EPA Science Inventory

    The U.S. Environmental Protection Agency (EPA or Agency) is posting on this web site a draft document related to the potential adverse human health effects resulting from exposure to electromagnetic fields (EMF). This document was never finalized after EPA activities were discon...

  16. PHYSICAL FOUNDATIONS OF QUANTUM ELECTRONICS: Vector potential of the electromagnetic field of a photon

    NASA Astrophysics Data System (ADS)

    Makshantsev, B. I.; Makshantsev, V. B.

    2001-09-01

    A solution of D'Alembert's equation for the vector potential of an electromagnetic field is found in the form of a wave packet, which does not spread in time and space. The expression obtained for the vector potential of a photon is used for the solution of some problems.

  17. The Role of Angular Momentum in the Construction of Electromagnetic Multipolar Fields

    ERIC Educational Resources Information Center

    Tischler, Nora; Zambrana-Puyalto, Xavier; Molina-Terriza, Gabriel

    2012-01-01

    Multipolar solutions of Maxwell's equations are used in many practical applications and are essential for the understanding of light-matter interactions at the fundamental level. Unlike the set of plane wave solutions of electromagnetic fields, the multipolar solutions do not share a standard derivation or notation. As a result, expressions…

  18. Quaternionic Analysis and Formulation of Generalized Electromagnetic fields in Chiral Media

    SciTech Connect

    Bisht, P. S.; Negi, O. P. S.; Singh, Jivan

    2007-10-03

    The time dependent Dirac-Maxwell's Equations in presence of electric and magnetic sources are written in chiral media and the solutions for the classical problem are obtained in unique simple and consistent manner. The quaternion reformulation of generalized electromagnetic fields in chiral media has also been developed in compact, simple and consistent manner.

  19. Biological Effects of Weak Electromagnetic Field on Healthy and Infected Lime (Citrus aurantifolia) Trees with Phytoplasma

    PubMed Central

    Abdollahi, Fatemeh; Niknam, Vahid; Ghanati, Faezeh; Masroor, Faribors; Noorbakhsh, Seyyed Nasr

    2012-01-01

    Exposure to electromagnetic fields (EMF) has become an issue of concern for a great many people and is an active area of research. Phytoplasmas, also known as mycoplasma-like organisms, are wall-less prokaryotes that are pathogens of many plant species throughout the world. Effects of electromagnetic fields on the changes of lipid peroxidation, content of H2O2, proline, protein, and carbohydrates were investigated in leaves of two-year-old trees of lime (Citrus aurantifolia) infected by the Candidatus Phytoplasma aurantifoliae. The healthy and infected plants were discontinuously exposed to a 10 KHz quadratic EMF with maximum power of 9 W for 5 days, each 5 h, at 25°C. Fresh and dry weight of leaves, content of MDA, proline, and protein increased in both healthy and infected plants under electromagnetic fields, compared with those of the control plants. Electromagnetic fields decreased hydrogen peroxide and carbohydrates content in both healthy and infected plants compared to those of the controls. PMID:22649313

  20. A wave guide model of lightning currents and their electromagnetic field

    NASA Technical Reports Server (NTRS)

    Volland, H.

    1980-01-01

    Lightning channels are considered as resonant wave guides in which only standing resonant wave modes can be excited. Two types of discharging currents develop. Type 1 is an aperiodic wave; type 2 is a damped oscillation. The electromagnetic radiation field of both types of currents is calculated and compared with the observation.

  1. 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

  2. Apparent Paradoxes in Classical Electrodynamics: A Fluid Medium in an Electromagnetic Field

    ERIC Educational Resources Information Center

    Kholmetskii, A. L.; Yarman, T.

    2008-01-01

    In this paper we analyse a number of teaching paradoxes of classical electrodynamics, dealing with the relativistic transformation of energy and momentum for a fluid medium in an external electromagnetic field. In particular, we consider a moving parallel plate charged capacitor, where the electric attraction of its plates is balanced by the…

  3. ALTERATIONS IN CALCIUM ION ACTIVITY BY ELF AND RF ELECTROMAGNETIC FIELDS

    EPA Science Inventory



    Alterations in calcium ion activity by ELF and RF electromagnetic fields

    Introduction

    Calcium ions play many important roles in biological systems. For example, calcium ion activity can be used as an indicator of second-messenger signal-transduction processe...

  4. Interaction of electromagnetic fields with chondrocytes in gel culture

    NASA Astrophysics Data System (ADS)

    Grodzinsky, Alan J.; Buschmann, Michael D.; Gluzband, Yehezkiel A.

    1992-01-01

    The specific objectives of this research period were: (1) to quantify the effect of applied electric fields on chondrocyte metabolism, using a range of stimulation frequencies and amplitudes; (2) to compare the chondrocyte biosynthetic response to applied fields at early times in agarose gel culture before an extracellular matrix has accumulated and at later times after significant deposition of matrix around and between the cells; and (3) to begin to interpret the biosynthetic response to applied fields in terms of models of physical mechanisms. The results of these studies suggest that electric fields applied to chondrocytes in agarose can modulate the synthesis of proteoglycans and protein constituents. Biosynthesis may be inhibited or stimulated depending on the amplitude of the applied current density. In addition, the presence of extracellular matrix may enhance the ability of normal chondrocytes and cells in intact cartilage to respond to electric fields, although the presence of matrix was not required for the stimulatory response to be observed with Swarm rat chondrosarcoma cells.

  5. Gene transcription and electromagnetic fields. Final progress report

    SciTech Connect

    Henderson, A.S.

    1992-12-31

    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.

  6. Measurements and computations of electromagnetic fields in electric power substations

    SciTech Connect

    Daily, W.K. ); Dawalibi, F. )

    1994-01-01

    The magnetic fields generated by a typical distribution substation were measured and calculated based on a computer model which takes into account currents in the grounding systems, distribution feeder neutrals, overhead ground wires and induced currents in equipment structures and ground grid loops. Both measured and computer results indicate that magnetic fields are significantly influenced by ground currents, as well as induced currents in structures and ground system loops. All currents in the network modeled were computed, based on the measured currents impressed at the boundary points (ends of the conductor network). The agreement between the measured and computer values is good. Small differences were observed and are attributed mainly to uncertainties in the geometry of the network model and phase angles of some of the currents in the neutral conductors which were not measured in the field. Further measurements, including more accurate geometrical information and phase angles, are planned.

  7. Electromagnetic Near Field Measurements of Two Critical Assemblies

    NASA Astrophysics Data System (ADS)

    Goettee, Jeffrey; Goorley, Tim; Mayo, Douglas; Myers, William; Goda, Joetta; Sage, Frank

    2015-04-01

    Preliminary measurements of the fast metal nuclear reactors at the National Criticality Experiments Research Center (NCERC) and at White Sands Missile Range (WSMR) within the past year characterize the very near field environment of these critical assemblies. Both reactors are fast, highly enriched uranium metal reactors and can be operated in a burst mode above prompt supercritical. Initial measurements of the electric and the magnetic fields within the reactor cell are consistent between the two facilities, and begin to describe the dependance on distance and polarization as might be assumed from initial Monte Carlo modelling of these facilities. The amplitude and time variation of the electric and magnetic fields are consistent with burst time scales. The polarization is consistent with the geometry of the source and with Compton scattering from fission gammas as the dominant ionization mechanism. An overview of the two fast neutron sources and the excursion dynamics, the experimental details, and summary of the modelling calculations will be provided as background.

  8. Rayleigh-Taylor-Induced Electromagnetic Fields in Laser-Produced Plasmas

    NASA Astrophysics Data System (ADS)

    Manuel, Mario J.-E.

    Spontaneous electromagnetic fields can be important to the dynamic evolution of a plasma by directing heat flow as well as providing additional pressures on the conducting fluids through the Lorentz force. Electromagnetic fields are predicted to affect fluid behavior during the core-collapse of supernovae through generation of fields due to hydrodynamic instabilities. In the coronae of stars, self-generated magnetic fields lead to filamentary structure in the hot plasma. Recent experiments by Gregori et al. investigated sources of protogalactic magnetic fields generated by laser-produced shock waves. In inertial confinement fusion experiments, self-generated electromagnetic fields can also play a role and have recently become of great interest to the community. Present day laser facilities provide a unique opportunity to study spontaneous field-generation in these extreme environments under controlled conditions. Instability-induced electromagnetic fields were investigated using a novel monoenergetic-proton radiography system. Fusion protons generated by an 'exploding-pusher' implosion were used to probe laser-irradiated plastic foils with various preimposed surface perturbations. Imaging protons are sensitive to electromagnetic fields and density modulations in the plasma through the Lorentz force and Coulomb collisions, respectively. Corresponding x-ray radiographs of these targets provided mass density distributions and Coulomb effects on protons were assessed using a Monte Carlo code written using the Geant4 framework. Proton fluence distributions were recorded on CR-39 detectors and Fourier analyzed to infer path-integrated field strengths. Rayleigh-Taylor (RT) growth of preimposed surface perturbations generated magnetic fields by the RT-induced Biermann battery and were measured for the first time. Good data were obtained during linear growth and when compared to ideal calculations, demonstrated that field diffusion near the source played an important role

  9. Spectral domains for bosonic pair creation in static electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Lv, Q. Z.; Li, Y. J.; Grobe, R.; Su, Q.

    2016-04-01

    We study the emission spectrum of bosons created from the vacuum by combined static electric and magnetic fields. Depending on the spatial extension of the magnetic field, we find four regimes of pair creation, characterized by different growth behaviors of the number of the produced particles. We show that these regimes manifest themselves in the eigenenergy spectrum of the Klein-Gordon Hamiltonian. The regimes also lead to rather different kinetic energy spectra of the emitted bosons, whose peak positions can be obtained from a generalized Fano-like perturbative approach.

  10. Negative response of photosynthesis to natural and projected high seawater temperatures estimated by pulse amplitude modulation fluorometry in a temperate coral

    PubMed Central

    Caroselli, Erik; Falini, Giuseppe; Goffredo, Stefano; Dubinsky, Zvy; Levy, Oren

    2015-01-01

    Balanophyllia europaea is a shallow water solitary zooxanthellate coral, endemic to the Mediterranean Sea. Extensive field studies across a latitudinal temperature gradient highlight detrimental effects of rising temperatures on its growth, demography, and skeletal characteristics, suggesting that depression of photosynthesis at high temperatures might cause these negative effects. Here we test this hypothesis by analyzing, by means of pulse amplitude modulation fluorometry, the photosynthetic efficiency of B. europaea specimens exposed in aquaria to the annual range of temperatures experienced in the field (13, 18, and 28°C), and two extreme temperatures expected for 2100 as a consequence of global warming (29 and 32°C). The indicators of photosynthetic performance analyzed (maximum and effective quantum yield) showed that maximum efficiency was reached at 20.0–21.6°C, slightly higher than the annual mean temperature in the field (18°C). Photosynthetic efficiency decreased from 20.0 to 13°C and even more strongly from 21.6 to 32°C. An unusual form of bleaching was observed, with a maximum zooxanthellae density at 18°C that strongly decreased from 18 to 32°C. Chlorophyll a concentration per zooxanthellae cell showed an opposite trend as it was minimal at 18°C and increased from 18 to 32°C. Since the areal chlorophyll concentration is the product of the zooxanthellae density and its cellular content, these trends resulted in a homogeneous chlorophyll concentration per coral surface across temperature treatments. This confirms that B. europaea photosynthesis is progressively depressed at temperatures >21.6°C, supporting previous hypotheses raised by the studies on growth and demography of this species. This study also confirms the threats posed to this species by the ongoing seawater warming. PMID:26582993

  11. Negative response of photosynthesis to natural and projected high seawater temperatures estimated by pulse amplitude modulation fluorometry in a temperate coral.

    PubMed

    Caroselli, Erik; Falini, Giuseppe; Goffredo, Stefano; Dubinsky, Zvy; Levy, Oren

    2015-01-01

    Balanophyllia europaea is a shallow water solitary zooxanthellate coral, endemic to the Mediterranean Sea. Extensive field studies across a latitudinal temperature gradient highlight detrimental effects of rising temperatures on its growth, demography, and skeletal characteristics, suggesting that depression of photosynthesis at high temperatures might cause these negative effects. Here we test this hypothesis by analyzing, by means of pulse amplitude modulation fluorometry, the photosynthetic efficiency of B. europaea specimens exposed in aquaria to the annual range of temperatures experienced in the field (13, 18, and 28°C), and two extreme temperatures expected for 2100 as a consequence of global warming (29 and 32°C). The indicators of photosynthetic performance analyzed (maximum and effective quantum yield) showed that maximum efficiency was reached at 20.0-21.6°C, slightly higher than the annual mean temperature in the field (18°C). Photosynthetic efficiency decreased from 20.0 to 13°C and even more strongly from 21.6 to 32°C. An unusual form of bleaching was observed, with a maximum zooxanthellae density at 18°C that strongly decreased from 18 to 32°C. Chlorophyll a concentration per zooxanthellae cell showed an opposite trend as it was minimal at 18°C and increased from 18 to 32°C. Since the areal chlorophyll concentration is the product of the zooxanthellae density and its cellular content, these trends resulted in a homogeneous chlorophyll concentration per coral surface across temperature treatments. This confirms that B. europaea photosynthesis is progressively depressed at temperatures >21.6°C, supporting previous hypotheses raised by the studies on growth and demography of this species. This study also confirms the threats posed to this species by the ongoing seawater warming. PMID:26582993

  12. The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach

    ERIC Educational Resources Information Center

    Likar, A.; Razpet, N.

    2009-01-01

    The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…

  13. Electromagnetic field interactions with the human body: Observed effects and theories

    NASA Technical Reports Server (NTRS)

    Raines, J. K.

    1981-01-01

    The effects of nonionizing electromagnetic (EM) field interactions with the human body were reported and human related studies were collected. Nonionizing EM fields are linked to cancer in humans in three different ways: cause, means of detection, and effective treatment. Bad and benign effects are expected from nonionizing EM fields and much more knowledge is necessary to properly categorize and qualify EM field characteristics. It is concluded that knowledge of the boundary between categories, largely dependent on field intensity, is vital to proper future use of EM radiation for any purpose and the protection of the individual from hazard.

  14. Calculation of electromagnetic fields induced on a geostationary satellite by an electrostatic discharge

    NASA Astrophysics Data System (ADS)

    Froger, E.; Marque, J. P.

    The electromagnetic response of an orbiting satellite to an electrostatic discharge is compared to that of the same object subjected (in a susceptibility test) to an injection current. In the absence of actual data, the comparison was performed on the basis of two numerical simulations: one using the GEODE particle code for the orbiting case, and the other using the ALICE code for a representative injection configuration. It is found that the evolution of the electromagnetic fields is controlled in particular by the particle emission rhythm, giving rise to an ejection flux 'slit' whose rise time is about several tens of nanoseconds.

  15. Investigation of Electromagnetic Field Threat to Fuel Tank Wiring of a Transport Aircraft

    NASA Technical Reports Server (NTRS)

    Ely, Jay J.; Nguyen, Truong X.; Dudley, Kenneth L.; Scearce, Stephen A.; Beck, Fred B.; Deshpande, Manohar D.; Cockrell, C. R.

    2000-01-01

    National Transportation Safety Board investigators have questioned whether an electrical discharge in the Fuel Quantity Indication System (FQIS) may have initiated the TWA-800 center wing tank explosion. Because the FQIS was designed to be incapable of producing such a discharge on its own, attention has been directed to mechanisms of outside electromagnetic influence. To support the investigation, the NASA Langley Research Center was tasked to study the potential for radiated electromagnetic fields from external radio frequency (RF) transmitters and passenger carried portable electronic devices (PEDs) to excite the FQIS enough to cause arcing, sparking or excessive heating within the fuel tank.

  16. Probing the spectral density of the surface electromagnetic fields through scattering of waveguide photons

    PubMed Central

    Chen, Guang-Yin

    2016-01-01

    The spectral density of the metal-surface electromagnetic fields will be strongly modified in the presence of a closely-spaced quantum emitter. In this work, we propose a feasible way to probe the changes of the spectral density through the scattering of the waveguide photon incident on the quantum emitter. The variances of the lineshape in the transmission spectra indicate the coherent interaction between the emitter and the pseudomode resulting from all the surface electromagnetic modes. We further investigate the quantum coherence between the emitter and the pseudomode of the metal-dielectric interface. PMID:26860197

  17. Effects of low-intensity pulsed electromagnetic fields on the early development of sea urchins

    SciTech Connect

    Falugi, C.; Grattarola, M.; Prestipino, G.

    1987-06-01

    The effects of weak electromagnetic signals on the early development of the sea urchin Paracentrotus lividus have been studied. The duration and repetition of the pulses were similar to those used for bone healing in clinical practice. A sequence of pulses, applied for a time ranging from 2 to 4 h, accelerates the cleavages of sea urchin embryo cells. This effect can be quantitatively assessed by determining the time shifts induced by the applied electromagnetic field on the completion of the first and second cleavages in a population of fertilized eggs. The exposed embryos were allowed to develop up to the pluteus stage, showing no abnormalities.

  18. The cavity electromagnetic field within the polarizable continuum model of solvation

    SciTech Connect

    Pipolo, Silvio; Department of Physics, University of Modena and Reggio Emilia, Modena ; Corni, Stefano; Cammi, Roberto

    2014-04-28

    Cavity field effects can be defined as the consequences of the solvent polarization induced by the probing electromagnetic field upon spectroscopies of molecules in solution, and enter in the definitions of solute response properties. The polarizable continuum model of solvation (PCM) has been extended in the past years to address the cavity-field issue through the definition of an effective dipole moment that couples to the external electromagnetic field. We present here a rigorous derivation of such cavity-field treatment within the PCM starting from the general radiation-matter Hamiltonian within inhomogeneous dielectrics and recasting the interaction term to a dipolar form within the long wavelength approximation. To this aim we generalize the Göppert-Mayer and Power-Zienau-Woolley gauge transformations, usually applied in vacuo, to the case of a cavity vector potential. Our derivation also allows extending the cavity-field correction in the long-wavelength limit to the velocity gauge through the definition of an effective linear momentum operator. Furthermore, this work sets the basis for the general PCM treatment of the electromagnetic cavity field, capable to describe the radiation-matter interaction in dielectric media beyond the long-wavelength limit, providing also a tool to investigate spectroscopic properties of more complex systems such as molecules close to large nanoparticles.

  19. The cavity electromagnetic field within the polarizable continuum model of solvation.

    PubMed

    Pipolo, Silvio; Corni, Stefano; Cammi, Roberto

    2014-04-28

    Cavity field effects can be defined as the consequences of the solvent polarization induced by the probing electromagnetic field upon spectroscopies of molecules in solution, and enter in the definitions of solute response properties. The polarizable continuum model of solvation (PCM) has been extended in the past years to address the cavity-field issue through the definition of an effective dipole moment that couples to the external electromagnetic field. We present here a rigorous derivation of such cavity-field treatment within the PCM starting from the general radiation-matter Hamiltonian within inhomogeneous dielectrics and recasting the interaction term to a dipolar form within the long wavelength approximation. To this aim we generalize the Göppert-Mayer and Power-Zienau-Woolley gauge transformations, usually applied in vacuo, to the case of a cavity vector potential. Our derivation also allows extending the cavity-field correction in the long-wavelength limit to the velocity gauge through the definition of an effective linear momentum operator. Furthermore, this work sets the basis for the general PCM treatment of the electromagnetic cavity field, capable to describe the radiation-matter interaction in dielectric media beyond the long-wavelength limit, providing also a tool to investigate spectroscopic properties of more complex systems such as molecules close to large nanoparticles. PMID:24784260

  20. The cavity electromagnetic field within the polarizable continuum model of solvation

    NASA Astrophysics Data System (ADS)

    Pipolo, Silvio; Corni, Stefano; Cammi, Roberto

    2014-04-01

    Cavity field effects can be defined as the consequences of the solvent polarization induced by the probing electromagnetic field upon spectroscopies of molecules in solution, and enter in the definitions of solute response properties. The polarizable continuum model of solvation (PCM) has been extended in the past years to address the cavity-field issue through the definition of an effective dipole moment that couples to the external electromagnetic field. We present here a rigorous derivation of such cavity-field treatment within the PCM starting from the general radiation-matter Hamiltonian within inhomogeneous dielectrics and recasting the interaction term to a dipolar form within the long wavelength approximation. To this aim we generalize the Göppert-Mayer and Power-Zienau-Woolley gauge transformations, usually applied in vacuo, to the case of a cavity vector potential. Our derivation also allows extending the cavity-field correction in the long-wavelength limit to the velocity gauge through the definition of an effective linear momentum operator. Furthermore, this work sets the basis for the general PCM treatment of the electromagnetic cavity field, capable to describe the radiation-matter interaction in dielectric media beyond the long-wavelength limit, providing also a tool to investigate spectroscopic properties of more complex systems such as molecules close to large nanoparticles.

  1. Conservation laws and symmetry transformations of the electromagnetic field with sources

    NASA Astrophysics Data System (ADS)

    Nienhuis, Gerard

    2016-02-01

    In classical electrodynamics, the universal conservation laws of energy, momentum, and angular momentum are expressed by well-known continuity equations for the densities of these quantities. In the presence of charges and currents source terms must be added. These terms describe the exchange of energy and (linear or angular) momentum between field and matter. Recently, other conserved quantities of the electromagnetic field have been introduced and discussed. Examples are the pseudoscalars chirality and helicity, which are related to the handedness of the field. Even though these quantities have no obvious definition for matter, their conservation laws can still be presented in the form of continuity equations with source terms added. We show that these terms shed light on the interaction of chiral light with matter. A different role of conserved quantities is that they generate symmetry transformations of the system. The spatial transformations translation and rotation of the radiation field are generated by differential operators acting on mode functions. These operators are identical in form to the operators for the momentum and angular momentum of a quantum particle with spin 1. Also, for the total helicity and spin angular momentum of the field such operators on mode functions can be identified. A quite different picture arises in a quantum description of the electromagnetic field. The operator nature of the conserved quantities then arises from the commutation rules of photon creation and annihilation operators. We analyze the relation between these two pictures of symmetry transformations of the electromagnetic field.

  2. Propagation of electromagnetic waves parallel to the magnetic field in the nightside Venus ionosphere

    NASA Astrophysics Data System (ADS)

    Huba, J. D.; Rowland, H. L.

    1993-03-01

    The propagation of electromagnetic waves parallel to the magnetic field in the nightside Venus ionosphere is presented in a theoretical and numerical analysis. The model assumes a source of electromagnetic radiation in the Venus atmosphere, such as that produced by lightning. Specifically addressed is wave propagation in the altitude range z = 130-160 km at the four frequencies detectable by the Pioneer Venus Orbiter Electric Field Detector: 100 Hz, 730 Hz, 5.4 kHz, and 30 kHz. Parameterizations of the wave intensities, peak electron density, and Poynting flux as a function of magnetic field are presented. The waves are found to propagate most easily in conditions of low electron density and high magnetic field. The results of the model are consistent with observational data.

  3. Beta Decay in the Field of an Electromagnetic Wave and Experiments on Measuring the Neutrino Mass

    SciTech Connect

    Dorofeev, O.F.; Lobanov, A.E.

    2005-06-01

    Investigations of the effect of an electromagnetic wave field on the beta-decay process are used to analyze the tritium-decay experimental data on the neutrino mass. It is shown that the electromagnetic wave can distort the beta spectrum, shifting the end point to the higher energy region. This phenomenon is purely classical and it is associated with the electron acceleration in the radiation field. Since strong magnetic fields exist in setups for precise measurement of the neutrino mass, the indicated field can appear owing to the synchrotron radiation mechanism. The phenomenon under consideration can explain the experimentally observed anomalies in the spectrum of the decay electrons; in particular, the effect of the 'negative square of the neutrino mass'.

  4. Propagation of electromagnetic waves parallel to the magnetic field in the nightside Venus ionosphere

    NASA Technical Reports Server (NTRS)

    Huba, J. D.; Rowland, H. L.

    1993-01-01

    The propagation of electromagnetic waves parallel to the magnetic field in the nightside Venus ionosphere is presented in a theoretical and numerical analysis. The model assumes a source of electromagnetic radiation in the Venus atmosphere, such as that produced by lightning. Specifically addressed is wave propagation in the altitude range z = 130-160 km at the four frequencies detectable by the Pioneer Venus Orbiter Electric Field Detector: 100 Hz, 730 Hz, 5.4 kHz, and 30 kHz. Parameterizations of the wave intensities, peak electron density, and Poynting flux as a function of magnetic field are presented. The waves are found to propagate most easily in conditions of low electron density and high magnetic field. The results of the model are consistent with observational data.

  5. Electromagnetic field analysis of septum magnet for APS positron accumulator ring

    SciTech Connect

    Yokoi, Toshiaki; Turner, L.R.

    1995-07-01

    This report consists of three parts. The first part describes a numerical analysis method for the electromagnetic field analysis of a septum magnet. A novel improvement to the treatment of exciting currents in the time-domain is proposed. The second part discusses numerical predictions of the electromagnetic characteristics of the APS PAR septum. The time variations of stray field and eddy currents are shown for three magnet designs. The last part explores how decreasing the septum material conductivity affects the stray field. The decrease of conductivity may be caused by an inadequate manufacturing of the septum material. The significance of a high quality septum, or flat interface between copper and iron, is emphasized from a point of view of stray field. An ideal method for joining two different metals without distortion, called HIP (Hot Isostatic Pressing), is introduced and recommended based on the authors` experience.

  6. Weak electromagnetic field admitting integrability in Kerr-NUT-(A)dS spacetimes

    NASA Astrophysics Data System (ADS)

    Kolář, Ivan; Krtouš, Pavel

    2015-06-01

    We investigate properties of higher-dimensional generally rotating black-hole spacetimes, so-called Kerr-NUT-(anti)-de Sitter spacetimes, as well as a family of related spaces which share the same explicit and hidden symmetries. In these spaces, we study a particle motion in the presence of a weak electromagnetic field and compare it with its operator analogies. First, we find general commutativity conditions for classical observables and for their operator counterparts, then we investigate a fulfillment of these conditions in the Kerr-NUT-(anti)-de Sitter and related spaces. We find the most general form of the weak electromagnetic field compatible with the complete integrability of the particle motion and the comutativity of the field operators. For such a field we solve the charged Hamilton-Jacobi and Klein-Gordon equations by separation of variables.

  7. Calcium displacement caused by electromagnetic fields. Final report, 1 November 1982-31 August 1989

    SciTech Connect

    Bond, J.D.; Jordan, C.A.

    1989-08-31

    This research effort was to determine theoretically a physical basis for the interaction of low-intensity externally applied electromagnetic fields with biological tissue. The primary aim of the investigation was to establish a molecular basis for the class of interactions commonly referred to as nonthermal effects of electromagnetic fields with biological systems. In particular, the biological structure of interest was the plasma membrane since it had been either directly or indirectly implicated in numerous experimental studies. It was demonstrated how a membrane undergoing a phase transition could qualitatively account for the release and/or uptake of divalent calcium ions. A characterization of changes in the structure of the membrane/electrolyte interface due to field induced changes in enzymatic activity was demonstrated. The role of critical phenomena was shown analytically to be able to account for the unique sensitivity of biomembranes to weak external field perturbations, and describe alterations in the passive transport of sodium ions in rabbit erythrocytes.

  8. Neurobehavioral effects of power-frequency electromagnetic fields.

    PubMed Central

    Paneth, N

    1993-01-01

    Some laboratory experiments have suggested that power-frequency electric and magnetic fields (EMF) may be capable of influencing calcium efflux from cell membranes, pineal function, and circadian rhythms. As yet, however, no consistent, replicable laboratory model has been developed for any of these effects. Most assessments of human volunteers exposed to EMF have been negative, but occasional effects on vigilance or alertness and some modest effects on circadian rhythmicity have been reported. Several carefully performed studies of workers occupationally exposed to high electric-field strengths have failed to find effects on behavior or cognitive functioning. Although the bulk of human research on the effects of EMF on cognitive performance is negative, there has been less assessment of behavior and psychiatric symptomatology. Because some studies, in both humans and animals, have described effects of EMF on circadian rhythms, future research might concentrate profitably on the assessment of EMF in relation to depression and other cyclically mediated psychiatric disorders. PMID:8206018

  9. Structure characteristics in industrially centrifugally cast 25Cr20Ni stainless steel tubes solidified under different electromagnetic field intensity

    SciTech Connect

    Wu, X.Q.; Yang, Y.S.; Zhang, J.S.; Jia, G.L.; Hu, Z.Q.

    1999-10-01

    The influences of different electromagnetic field intensities on the solidification structures of industrially centrifugally cast 25Cr20Ni stainless steel tubes have been investigated in detail. The results reveal that the electromagnetic field exerted during the centrifugal solidification causes a marked variation in the structures of the cast tubes. With an increase of the electromagnetic field intensity, the area fraction of the equiaxed structures in transverse sections of the cast tubes increases, and the macrostructures are gradually refined. The distribution of the eutectic carbides changes from the dendrite boundaries to the grain boundaries. However, an excessive electromagnetic field intensity gives rise to many intergranular cast defects formed along the inner walls of the centrifugally cast tubes. The effects of fluid flow induced by the electromagnetic field on the solidification process of the centrifugally cast tubes are the primary reason for the previously mentioned structure variations.

  10. Imaging Nanoscale Electromagnetic Near-Field Distributions Using Optical Forces.

    PubMed

    Huang, Fei; Tamma, Venkata Ananth; Mardy, Zahra; Burdett, Jonathan; Wickramasinghe, H Kumar

    2015-01-01

    We demonstrate the application of Atomic Force Microscopy (AFM) for mapping optical near-fields with nanometer resolution, limited only by the AFM probe geometry. By detecting the optical force between a gold coated AFM probe and its image dipole on a glass substrate, we profile the electric field distributions of tightly focused laser beams with different polarizations. The experimentally recorded focal force maps agree well with theoretical predictions based on a dipole-dipole interaction model. We experimentally estimate the aspect ratio of the apex of gold coated AFM probe using only optical forces. We also show that the optical force between a sharp gold coated AFM probe and a spherical gold nanoparticle of radius 15 nm, is indicative of the electric field distribution between the two interacting particles. Photo Induced Force Microscopy (PIFM) allows for background free, thermal noise limited mechanical imaging of optical phenomenon over wide range of wavelengths from Visible to RF with detection sensitivity limited only by AFM performance. PMID:26073331

  11. Continuum resonance induced electromagnetic torque by a rotating plasma response to static resonant magnetic perturbation field

    SciTech Connect

    Liu Yueqiang; Connor, J. W.; Cowley, S. C.; Ham, C. J.; Hastie, R. J.; Hender, T. C.

    2012-10-15

    A numerical study is carried out, based on a simple toroidal tokamak equilibrium, to demonstrate the radial re-distribution of the electromagnetic torque density, as a result of a rotating resistive plasma (linear) response to a static resonant magnetic perturbation field. The computed electromagnetic torque peaks at several radial locations even in the presence of a single rational surface, due to resonances between the rotating response, in the plasma frame, and both Alfven and sound continuum waves. These peaks tend to merge together to form a rather global torque distribution, when the plasma resistivity is large. The continuum resonance induced net electromagnetic torque remains finite even in the limit of an ideal plasma.

  12. The relativistic dynamics of a point charge in the field of a plane electromagnetic wave traveling in the direction of a uniform static magnetic field

    NASA Technical Reports Server (NTRS)

    Mitchell, T. P.

    1973-01-01

    The motion of a charged particle in electromagnetic fields of various geometric configurations and arising from a variety of sources is of intrinsic interest in electromagnetic theory. The particular configuration consisting of a plane wave propagating in the presence of a static uniform magnetic field whose direction is parallel to the wave normal is examined. The analysis presented here is treated within the context of classical electromagnetic theory. A numerical solution - at least to the approximate Lorentz-Dirac equation - is obtained.

  13. 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

  14. 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.

  15. Effects of Pulsed Electromagnetic Field on Differentiation of HUES-17 Human Embryonic Stem Cell Line

    PubMed Central

    Wu, Yi-Lin; Ma, Shi-Rong; Peng, Tao; Teng, Zeng-Hui; Liang, Xiang-Yan; Guo, Guo-Zhen; Zhang, Hai-Feng; Li, Kang-Chu

    2014-01-01

    Electromagnetic fields are considered to potentially affect embryonic development, but the mechanism is still unknown. In this study, human embryonic stem cell (hESC) line HUES-17 was applied to explore the mechanism of exposure on embryonic development to pulsed electromagnetic field (PEMF) for 400 pulses at different electric field intensities and the differentiation of HUES-17 cells was observed after PEMF exposure. The expression of alkaline phosphatase (AP), stage-specific embryonic antigen-3 (SSEA-3), SSEA-4 and the mRNA level and protein level of Oct4, Sox2 and Nanog in HUES-17 cells remained unchanged after PEMF exposure at the electric field intensities of 50, 100, 200 or 400 kV/m. Four hundred pulses PEMF exposure at the electric field intensities of 50, 100, 200 or 400 kV/m did not affect the differentiation of HUES-17 cells. The reason why electromagnetic fields affect embryonic development may be due to other mechanisms rather than affecting the differentiation of embryonic stem cells. PMID:25196518

  16. Effects of pulsed electromagnetic field on differentiation of HUES-17 human embryonic stem cell line.

    PubMed

    Wu, Yi-Lin; Ma, Shi-Rong; Peng, Tao; Teng, Zeng-Hui; Liang, Xiang-Yan; Guo, Guo-Zhen; Zhang, Hai-Feng; Li, Kang-Chu

    2014-01-01

    Electromagnetic fields are considered to potentially affect embryonic development, but the mechanism is still unknown. In this study, human embryonic stem cell (hESC) line HUES-17 was applied to explore the mechanism of exposure on embryonic development to pulsed electromagnetic field (PEMF) for 400 pulses at different electric field intensities and the differentiation of HUES-17 cells was observed after PEMF exposure. The expression of alkaline phosphatase (AP), stage-specific embryonic antigen-3 (SSEA-3), SSEA-4 and the mRNA level and protein level of Oct4, Sox2 and Nanog in HUES-17 cells remained unchanged after PEMF exposure at the electric field intensities of 50, 100, 200 or 400 kV/m. Four hundred pulses PEMF exposure at the electric field intensities of 50, 100, 200 or 400 kV/m did not affect the differentiation of HUES-17 cells. The reason why electromagnetic fields affect embryonic development may be due to other mechanisms rather than affecting the differentiation of embryonic stem cells. PMID:25196518

  17. Influence of constant, alternating and cyclotron low-intensity electromagnetic fields on fibroblast proliferative activity in vitro.

    PubMed

    Afinogenov, Gennadi; Afinogenova, Anna; Kalinin, Andrey

    2009-01-01

    Available data allow assuming the presence of stimulation of reparative processes under influence of low-intensity electromagnetic field, commensurable with a magnetic field of the Earth. Research of effects of low-intensity electromagnetic fields on fibroblast proliferative activity in human lungs in cell culture was performed.The influence of a constant electromagnetic field, an alternating electromagnetic field by frequency of 50 Hz and cyclotron electromagnetic field with identical intensity for all kinds of fields - 80 mcTl - on value of cellular mass and a correlation of live and dead cells in culture is investigated in three series of experiments. We used the universal electromagnetic radiator generating all three kinds of fields and supplied by a magnetometer which allows measuring the intensity of accurate within 0.1 mcTl including taking into account the Earth's magnetic field intensity.The peak value for stimulation cellular proliferation in the present experiences was two-hour influence by any of the specified kinds of electromagnetic fields. The irradiation by cyclotron electromagnetic field conducts positive dynamics in growth of live cells (up to 206+/-22%) and decreases the number of dead cells (down to 31+/-6%). Application of cyclotron magnetic fields promoted creation of optimum conditions for proliferation. As a result of researches we observed the reliable 30% increase of nitro-tetrazolium index (in nitro-tetrazolium blue test) after irradiation by cyclotron electromagnetic field in experience that testifies to strengthening of the cell breathing of living cells.In our opinion, it is necessary to pay attention not only to a pure gain of cells, but also to reduction of number dead cells that can be criterion of creation of optimum conditions for their specific development and valuable functioning. PMID:20204088

  18. Datta-and-Das spin transistor controlled by a high-frequency electromagnetic field

    NASA Astrophysics Data System (ADS)

    Sheremet, A. S.; Kibis, O. V.; Kavokin, A. V.; Shelykh, I. A.

    2016-04-01

    We developed the theory of spin dependent transport through a spin-modulator device (so-called Datta-and-Das spin transistor) in the presence of a high-frequency electromagnetic field (dressing field). Solving the Schrödinger problem for dressed electrons, we demonstrated that the field drastically modifies the spin transport. In particular, the dressing field leads to renormalization of spin-orbit coupling constants that varies conductivity of the spin transistor. The present effect paves the way for controlling the spin-polarized electron transport with light in prospective spin-optronic devices.

  19. 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.

  20. Electromagnetic induction by finite wavenumber source fields in 2-D lateral heterogeneities - The transverse electric mode

    NASA Technical Reports Server (NTRS)

    Hermance, J. F.

    1984-01-01

    Electromagnetic induction in a laterally homogeneous earth is analyzed in terms of a source field with finite dimensions. Attention is focused on a time-varying two-dimensional current source directed parallel to the strike of a two-dimensional anomalous structure within the earth, i.e., the E-parallel mode. The spatially harmonic source field is expressed as discontinuities in the magnetic (or electric) field of the current in the source. The model is applied to describing the magnetic gradients across megatectonic features, and may be used to predict the magnetic fields encountered by a satellite orbiting above the ionosphere.

  1. Electromagnetic superconductivity of vacuum induced by strong magnetic field: Numerical evidence in lattice gauge theory

    NASA Astrophysics Data System (ADS)

    Braguta, V. V.; Buividovich, P. V.; Chernodub, M. N.; Kotov, A. Yu.; Polikarpov, M. I.

    2012-12-01

    Using numerical simulations of quenched SU (2) gauge theory we demonstrate that an external magnetic field leads to spontaneous generation of quark condensates with quantum numbers of electrically charged ρ mesons if the strength of the magnetic field exceeds the critical value eBc = 0.927 (77) GeV2 or Bc = (1.56 ± 0.13) ṡ1016 Tesla. The condensation of the charged ρ mesons in strong magnetic field is a key feature of the magnetic-field-induced electromagnetic superconductivity of the vacuum.

  2. Dynamics of ionisation and entanglement in the 'atom + quantum electromagnetic field' system

    SciTech Connect

    Sharapova, P R; Tikhonova, O V

    2012-03-31

    The dynamics of a model Rydberg atom in a strong nonclassical electromagnetic field is investigated. The field-induced transitions to the continuum involving different numbers of photons (with intermediate states in the discrete spectrum) are taken into account and the specific features of ionisation in 'squeezed' field states are considered in comparison with the case of classical light. A significant decrease in the ionisation rate is found, which is caused by the interference stabilisation of the atomic system. The entanglement of the atomic and field subsystems, the temporal dynamics of the correlations found, and the possibility of measuring them are analysed.

  3. Numerical Modeling of Free Surface Dynamics of Melt in an Alternate Electromagnetic Field. Part II: Conventional Electromagnetic Levitation

    NASA Astrophysics Data System (ADS)

    Spitans, Sergejs; Baake, Egbert; Nacke, Bernard; Jakovics, Andris

    2016-02-01

    By means of external coupling between electromagnetic (EM) problem in ANSYS and hydrodynamic problem in FLUENT, a numerical model for the liquid metal free surface flow in an alternate EM field has been developed and verified in the first part of the article. Volume of Fluid ( VOF) algorithm has been used for tracking of free surface. In this work, improved performance of the model is presented. General validation of the VOF algorithm is performed by comparison of the calculated free oscillations of the liquid column to its analytical solution. The 3D/ VOF calculation of coupled EM field and free surface flow with Large Eddy Simulation turbulence description for the first time is applied for modeling of conventional EM levitation. Calculation results are compared with 2D/ VOF and 3D/ VOF models that use less precise k- ɛ and k- ω SST turbulence formulations. Obtained time-averaged droplet shapes are used for single-phase flow calculations with different turbulence models and free-slip/no-slip velocity conditions at the fixed free surface for validation of the flow. Meanwhile, series of levitation melting experiments are performed for verification of the simulated droplet shapes. In conclusion, parameter impact on the fully developed flow and the levitated droplet shape is discussed.

  4. An integrated program for amplitude-modulated RF pulse generation and re-mapping with shaped gradients.

    PubMed

    Matson, G B

    1994-01-01

    Efficient generation of amplitude modulated, frequency selective RF pulses has been demonstrated by the Shinnar-Le Roux (SLR) algorithm. In the present article, we provide an overview of a relatively comprehensive computer program that includes a version of the SLR algorithm and also incorporates an algorithm for re-mapping a selective RF pulse onto a new dwell time with modulated gradients. The re-mapping may be used to reduce SAR, or to shorten the RF pulse time by increasing the gradient and RF strength in regions where the original RF pulse amplitude was low. The program includes additional useful features including a Bloch equations algorithm, and pulse scaling, to enable examination of pulse profiles under a variety of conditions such as RF inhomogeneity and even nuclear relaxation. The program, MATPULSE, was developed with the MATLAB for Windows programming language and makes extensive use of the MATLAB graphical user interface (GUI) features to generate a user-friendly interface. A number of examples are provided to illustrate the capabilities of the MATPULSE program. PMID:7854027

  5. Toward automatic phenotyping of retinal images from genetically determined mono- and dizygotic twins using amplitude modulation-frequency modulation methods

    NASA Astrophysics Data System (ADS)

    Soliz, P.; Davis, B.; Murray, V.; Pattichis, M.; Barriga, S.; Russell, S.

    2010-03-01

    This paper presents an image processing technique for automatically categorize age-related macular degeneration (AMD) phenotypes from retinal images. Ultimately, an automated approach will be much more precise and consistent in phenotyping of retinal diseases, such as AMD. We have applied the automated phenotyping to retina images from a cohort of mono- and dizygotic twins. The application of this technology will allow one to perform more quantitative studies that will lead to a better understanding of the genetic and environmental factors associated with diseases such as AMD. A method for classifying retinal images based on features derived from the application of amplitude-modulation frequency-modulation (AM-FM) methods is presented. Retinal images from identical and fraternal twins who presented with AMD were processed to determine whether AM-FM could be used to differentiate between the two types of twins. Results of the automatic classifier agreed with the findings of other researchers in explaining the variation of the disease between the related twins. AM-FM features classified 72% of the twins correctly. Visual grading found that genetics could explain between 46% and 71% of the variance.

  6. Auditory Distance Coding in Rabbit Midbrain Neurons and Human Perception: Monaural Amplitude Modulation Depth as a Cue

    PubMed Central

    Zahorik, Pavel; Carney, Laurel H.; Bishop, Brian B.; Kuwada, Shigeyuki

    2015-01-01

    Mechanisms underlying sound source distance localization are not well understood. Here we tested the hypothesis that a novel mechanism can create monaural distance sensitivity: a combination of auditory midbrain neurons' sensitivity to amplitude modulation (AM) depth and distance-dependent loss of AM in reverberation. We used virtual auditory space (VAS) methods for sounds at various distances in anechoic and reverberant environments. Stimulus level was constant across distance. With increasing modulation depth, some rabbit inferior colliculus neurons increased firing rates whereas others decreased. These neurons exhibited monotonic relationships between firing rates and distance for monaurally presented noise when two conditions were met: (1) the sound had AM, and (2) the environment was reverberant. The firing rates as a function of distance remained approximately constant without AM in either environment and, in an anechoic condition, even with AM. We corroborated this finding by reproducing the distance sensitivity using a neural model. We also conducted a human psychophysical study using similar methods. Normal-hearing listeners reported perceived distance in response to monaural 1 octave 4 kHz noise source sounds presented at distances of 35–200 cm. We found parallels between the rabbit neural and human responses. In both, sound distance could be discriminated only if the monaural sound in reverberation had AM. These observations support the hypothesis. When other cues are available (e.g., in binaural hearing), how much the auditory system actually uses the AM as a distance cue remains to be determined. PMID:25834060

  7. Gas Phase Photoacoustic Spectroscopy in the long-wave IR using Quartz Tuning Forks and Amplitude Modulated Quantum Cascade Lasers

    SciTech Connect

    Wojcik, Michael D.; Phillips, Mark C.; Cannon, Bret D.

    2006-12-31

    A paper to accompany a 20 minute talk about the progress of a DARPA funded project called LPAS. ABSTRACT: We demonstrate the performance of a novel long-wave infrared photoacoustic laser absorbance spectrometer for gas-phase species using an amplitude modulated (AM) quantum cascade (QC) laser and a quartz tuning fork microphone. Photoacoustic signal was generated by focusing the output of a Fabry-Perot QC laser operating at 8.41 micron between the legs of a quartz tuning fork which served as a transducer for the transient acoustic pressure wave. The QC laser was modulated at the resonant frequency of the tuning fork (32.8 kHz). This sensor was calibrated using the infrared absorber Freon-134a by performing a simultanious absorption measurement using a 35 cm absorption cell. The NEAS of this instrument was determined to be 2 x 10^-8 W cm^-1 /Hz^1/2 and the fundamental sensitivity of this technique is limited by the noise floor of the tuning fork itself.

  8. Bi-stability of amplitude modulation AFM in air: deterministic and stochastic outcomes for imaging biomolecular systems.

    PubMed

    Santos, Sergio; Barcons, Victor; Font, Josep; Thomson, Neil H

    2010-06-01

    The dynamics of the oscillating microcantilever for amplitude modulation atomic force microscopy (AM AFM) operating in air is well understood theoretically but the experimental outcomes are still emerging. We use double-stranded DNA on mica as a model biomolecular system for investigating the connection between theory and experiment. A demonstration that the switching between the two cantilever oscillation states is stochastic in nature is achieved, and it can be induced by means of topographical anomalies on the surface. Whether one or the other attractor basin is accessed depends on the tip-sample separation history used to achieve the imaging conditions, and we show that the behaviour is reproducible when the tip is stable and well characterized. Emergence of background noise occurs in certain regions of parameter space regardless of whether two cantilever oscillation states coexist. The low state has been explored in detail and we note that at low to intermediate values of the free amplitude, noise-free imaging is achieved. The outcomes shown here are general and demonstrate that a thorough and systematic experimental approach in conjunction with standard modelling gives insight into the mechanisms behind image contrast formation in AM AFM in air. PMID:20453275

  9. Bounds and Simulation Results of 32-ary and 64-ary Quadrature Amplitude Modulation for Broadband-ISDN via Satellite

    NASA Technical Reports Server (NTRS)

    Kifle, Muli; Vanderaar, Mark

    1994-01-01

    Union bounds and Monte Carlo simulation Bit-Error-Rate (BER) performance results are presented for various 32-ary and 64-ary Quadrature Amplitude Modulation (QAM) schemes. Filtered and unfiltered modulation formats are compared for the best packing arrangement in peak power limited systems. It is verified that circular constellations which populate as many symbols as possible at the peak magnitude offer the best performance. For example: a 32-ary QAM scheme based on concentric circles offers about 1.05 dB better peak power improvement at a BER of 10(exp -6) over the scheme optimized for average power using triangular symbol packing. This peak power improvement increases to 1.25 dB for comparable 64-ary QAM schemes. This work serves as a precursor to determine the feasibility of a combined modem/codec that can accommodate Broadband Integrated Services Digital Network (B-ISDN) at a rate of 155.52 Mbps through typical transponder bandwidths of 36 MHz and 54 MHz.

  10. Correlation of neural responses in the cochlear nucleus with low-frequency noise amplitude modulation of a tonal signal

    NASA Astrophysics Data System (ADS)

    Bibikov, N. G.

    2014-09-01

    The responses of single neurons of the cochlear nucleus of a grass frog to long tonal signals amplitude-modulated by repeat intervals of low-frequency noise have been studied. The carrier frequency always corresponded to the characteristic frequency of the studied cell (a range of 0.2 kHz-2 kHz); the modulated signal was noise in the ranges 0-15 Hz, 0-50 Hz, or 0-150 Hz. We obtained the correlation functions of the cyclic histogram reflecting the change in probability of a neuron pulse discharge (spike) during the modulation period with the shape of the signal envelope in the same period. The form of the obtained correlation functions usually does not change qualitatively with a change in carrier level or modulation depth; however, this could essentially depend of the frequency component of the modulating function. In the majority of cases, comparison of the cyclic histogram of the reaction with only the current amplitude value does not adequately reveal the signal's time features that determine the reaction of a neuron. The response is also determined by the other sound features, primarily by the rate of the change in amplitude. The studied neurons differed among themselves, both in preference toward a certain range of modulated frequencies and in the features of the envelope that caused the cell's response.

  11. Amplitude-modulated ultrasound radiation force combined with phase-sensitive optical coherence tomography for shear wave elastography

    NASA Astrophysics Data System (ADS)

    Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Shen, Tueng T.; Wang, Ruikang K.; O'Donnell, Matthew

    2015-03-01

    Tissue stiffness can be measured from the propagation speed of shear waves. Acoustic radiation force (ARF) can generate shear waves by focusing ultrasound in tissue for ~100 μs. Safety considerations and electronics abilities limit ultrasound pressures. We previously presented shear wave elastography combining ARF and phase-sensitive optical coherence tomography (PhS-OCT) [1]. Here, we use amplitude-modulated ARF to enhance shear wave signal-to-noise ratio (SNR) at low pressures. Experiments were performed on tissue-mimicking phantoms. ARF was applied using a single-element transducer, driven by a 7.5 MHz, 3-ms, sine wave modulated in amplitude by a linear-swept frequency (1 to 7 kHz). Pressures between 1 to 3 MPa were tested. Displacements were tracked using PhS-OCT and numerically compressed using pulse compression methods detailed in previous work [2]. SNR was compared to that of 200-μs bursts. Stiffness maps were reconstructed using time-of-flight computations. 200-μs bursts give barely detectable displacements at 1 MPa (3.7 dB SNR). Pulse compression gives 36.2 dB at 1.5 MPa. In all cases with detectable displacements, shear wave speeds were determined in 5%-gelatin and 10%-gelatin phantoms and compared to literature values. Applicability to ocular tissues (cornea, intraocular lens) is under investigation.

  12. Method of Phase and Amplitude Modulation/Demodulation Using Datapages with Embedded Phase-Shift for Holographic Data Storage

    NASA Astrophysics Data System (ADS)

    Bunsen, Masatoshi; Umetsu, Shuhei; Takabayashi, Masanori; Okamoto, Atsushi

    2013-09-01

    A technique for the phase and amplitude detection of object beams with multivalued phase and amplitude modulation is proposed for holographic storage systems. Generally, the spatial distribution of the complex amplitude of the object beam can be precisely detected by phase-shifting interferometric measurements in which the phase of the reference wave for interferometry is temporally or spatially changed in the datapage retrieval process. On the other hand, our technique allows fast, accurate, and feasible phase and amplitude demodulations by preliminary embedding phase shift into the phase signal of the datapage during recording. This technique will significantly improve the data transfer rate and vibration tolerance of the holographic storage system because the complex amplitudes of the object beam carrying datapages can be detected by single-shot image capturing. The optical system for datapage replay will also be simplified because there is no need to use any phase-shifting device during data retrieval. The single-shot detection of the phase-modulated datapage is experimentally demonstrated.

  13. Amplitude modulation of quantum-ion-acoustic wavepackets in electron-positron-ion plasmas: Modulational instability, envelope modes, extreme waves

    SciTech Connect

    Rahman, Ata-ur-; Kerr, Michael Mc Kourakis, Ioannis; El-Taibany, Wael F.; Qamar, A.

    2015-02-15

    A semirelativistic fluid model is employed to describe the nonlinear amplitude modulation of low-frequency (ionic scale) electrostatic waves in an unmagnetized electron-positron-ion plasma. Electrons and positrons are assumed to be degenerated and inertialess, whereas ions are warm and classical. A multiscale perturbation method is used to derive a nonlinear Schrödinger equation for the envelope amplitude, based on which the occurrence of modulational instability is investigated in detail. Various types of localized ion acoustic excitations are shown to exist, in the form of either bright type envelope solitons (envelope pulses) or dark-type envelope solitons (voids, holes). The plasma configurational parameters (namely, the relativistic degeneracy parameter, the positron concentration, and the ionic temperature) are shown to affect the conditions for modulational instability significantly, in fact modifying the associated threshold as well as the instability growth rate. In particular, the relativistic degeneracy parameter leads to an enhancement of the modulational instability mechanism. Furthermore, the effect of different relevant plasma parameters on the characteristics (amplitude, width) of these envelope solitary structures is also presented in detail. Finally, the occurrence of extreme amplitude excitation (rogue waves) is also discussed briefly. Our results aim at elucidating the formation and dynamics of nonlinear electrostatic excitations in superdense astrophysical regimes.

  14. Probing the adsorption of weak acids on graphite using amplitude modulation-frequency modulation atomic force microscopy.

    PubMed

    Moustafa, Ahmed M A; Huang, Jun; McPhedran, Kerry N; Zeng, Hongbo; El-Din, Mohamed Gamal

    2015-03-17

    Recent thermodynamics calculations and adsorption isotherms showed that the adsorption of a self-assembled layer (SAL) of ionized weak acids to carbon was attributed to the negatively charged hydrogen bonding (-CAHB), yet the direct visualization and characterization of this adsorption behavior have not been reported. Here, an amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM) technique was applied to discriminate the adsorption of decanoic acids (DA) on highly ordered pyrolytic graphite (HOPG). Thermodynamics calculations revealed that the adsorption of SAL was driven by the formation of -CAHB with negatively charged functional groups of HOPG. Multilayer adsorption could occur over the adsorbed ionized SAL, leading to the development of aggregates. AM-FM AFM imaging showed that the adsorption of the DA molecules forming aggregates occurred only for the HOPG-functionalized steps, while DA molecules were found to adsorb over the entire functionalized HOPG surface after water-plasma treatment, as evident from the frequency shifts identified in AFM images. PMID:25710305

  15. Auditory distance coding in rabbit midbrain neurons and human perception: monaural amplitude modulation depth as a cue.

    PubMed

    Kim, Duck O; Zahorik, Pavel; Carney, Laurel H; Bishop, Brian B; Kuwada, Shigeyuki

    2015-04-01

    Mechanisms underlying sound source distance localization are not well understood. Here we tested the hypothesis that a novel mechanism can create monaural distance sensitivity: a combination of auditory midbrain neurons' sensitivity to amplitude modulation (AM) depth and distance-dependent loss of AM in reverberation. We used virtual auditory space (VAS) methods for sounds at various distances in anechoic and reverberant environments. Stimulus level was constant across distance. With increasing modulation depth, some rabbit inferior colliculus neurons increased firing rates whereas others decreased. These neurons exhibited monotonic relationships between firing rates and distance for monaurally presented noise when two conditions were met: (1) the sound had AM, and (2) the environment was reverberant. The firing rates as a function of distance remained approximately constant without AM in either environment and, in an anechoic condition, even with AM. We corroborated this finding by reproducing the distance sensitivity using a neural model. We also conducted a human psychophysical study using similar methods. Normal-hearing listeners reported perceived distance in response to monaural 1 octave 4 kHz noise source sounds presented at distances of 35-200 cm. We found parallels between the rabbit neural and human responses. In both, sound distance could be discriminated only if the monaural sound in reverberation had AM. These observations support the hypothesis. When other cues are available (e.g., in binaural hearing), how much the auditory system actually uses the AM as a distance cue remains to be determined. PMID:25834060

  16. Comparison of Cd, Cu, and Zn toxic effects on four marine phytoplankton by pulse-amplitude-modulated fluorometry.

    PubMed

    Miao, Ai-Jun; Wang, Wen-Xiong; Juneau, Philippe

    2005-10-01

    The toxic effects of Cd, Cu, and Zn on four different marine phytoplankton, Dunaliella tertiolecta, Prorocentrum minimum, Synechococcus sp., and Thalassiosira weissflogii, were examined by comparing the cell-specific growth rate, pulse-amplitude-modulated (PAM) parameters (maximum photosystem II quantum yield phiM and operational quantum yield phi'M, chlorophyll a content, and cellular metal concentration, over a 96-h period. The calculated no-observed-effect concentration (NOEC) based on both cell-specific growth rate and two PAM parameters (phiM and phi'M) were mostly identical. Thus, these PAM parameters and cell-specific growth rate were comparable in their sensitivities as the biomarkers for trace metal toxicity to marine phytoplankton. The cyanobacteria Synechococcus sp. was the most sensitive species among the four algal species tested because of its higher cell surface to volume ratio. The toxicity of the three tested metals followed the order of Cd > Cu > Zn based on the cellular metal concentration of the four algae at the NOEC. The cellular metal bioaccumulation followed the same Freundlich isotherm for each metal regardless of the algal species, indicating that the metal accumulation was a nonmetabolic process under high ambient metal concentrations and that the cell surface metal binding was comparable among the different species. For all the algae examined in our study, the bioaccumulation potentials of Cu and Zn were similar to each other, while the Cd bioaccumulation was much lower under environmentally realistic metal concentration. PMID:16268163

  17. Coherence-polarization properties of fields radiated from transversely periodic electromagnetic sources

    NASA Astrophysics Data System (ADS)

    Santarsiero, M.; de Sande, J. C. G.; Piquero, G.; Gori, F.

    2013-05-01

    Planar electromagnetic sources characterized by a periodic variation of their beam coherence-polarization matrix are investigated, as far as the polarization features of the radiated fields are concerned, within the framework of the paraxial approximation. A propagation scheme based on plane-wave decomposition leads to a longitudinal periodicity of the polarization properties of the field, thus extending the Talbot effect to the case of partially coherent electromagnetic sources. The polarization features of beams radiated from sources of this type are illustrated by means of simple examples. In particular, it is shown that completely unpolarized sources with uniform intensity profiles can be easily realized, for which the propagated field becomes perfectly polarized across some transverse planes, and vice versa.

  18. Electromagnetic field generated in model of human head by simplified telephone transceiver

    NASA Astrophysics Data System (ADS)

    King, Ronold W. P.

    1995-01-01

    Possible adverse effects of electromagnetic fields on the human body and especially on the nervous system and the brain are of increasing concern, particularly with reference to cellular telephone transceivers held close to the head. An essential step in the study of this problem is the accurate determination of the complete electromagnetic field penetrating through the skull into the brain. Simple analytical formulas are derived from the theory of the horizontal electric dipole over a layered region. These give the components of the electric and magnetic fields on the air-head surface, in the skin-skull layer, and throughout the brain in terms of a planar model with the dimensions and average electrical properties of the human head. The specific absorption rate (SAR) is also determined.

  19. Using the CAVE virtual-reality environment as an aid to 3-D electromagnetic field computation

    SciTech Connect

    Turner, L.R.; Levine, D.; Huang, M.; Papka, M; Kettunen, L.

    1995-08-01

    One of the major problems in three-dimensional (3-D) field computation is visualizing the resulting 3-D field distributions. A virtual-reality environment, such as the CAVE, (CAVE Automatic Virtual Environment) is helping to overcome this problem, thus making the results of computation more usable for designers and users of magnets and other electromagnetic devices. As a demonstration of the capabilities of the CAVE, the elliptical multipole wiggler (EMW), an insertion device being designed for the Advanced Photon Source (APS) now being commissioned at Argonne National Laboratory (ANL), wa made visible, along with its fields and beam orbits. Other uses of the CAVE in preprocessing and postprocessing computation for electromagnetic applications are also discussed.

  20. Electromagnetic waves destabilized by runaway electrons in near-critical electric fields

    SciTech Connect

    Komar, A.; Pokol, G. I.; Fueloep, T.

    2013-01-15

    Runaway electron distributions are strongly anisotropic in velocity space. This anisotropy is a source of free energy that may destabilize electromagnetic waves through a resonant interaction between the waves and the energetic electrons. In this work, we investigate the high-frequency electromagnetic waves that are destabilized by runaway electron beams when the electric field is close to the critical field for runaway acceleration. Using a runaway electron distribution appropriate for the near-critical case, we calculate the linear instability growth rate of these waves and conclude that the obliquely propagating whistler waves are most unstable. We show that the frequencies, wave numbers, and propagation angles of the most unstable waves depend strongly on the magnetic field. Taking into account collisional and convective damping of the waves, we determine the number density of runaways that is required to destabilize the waves and show its parametric dependences.