Science.gov

Sample records for ac field amplitude

  1. Modified Solenoid Coil That Efficiently Produces High Amplitude AC Magnetic Fields With Enhanced Uniformity for Biomedical Applications

    PubMed Central

    Bordelon, David E.; Goldstein, Robert C.; Nemkov, Valentin S.; Kumar, Ananda; Jackowski, John K.; DeWeese, Theodore L.; Ivkov, Robert

    2014-01-01

    In this paper, we describe a modified solenoid coil that efficiently generates high amplitude alternating magnetic fields (AMF) having field uniformity (≤10%) within a 125-cm3 volume of interest. Two-dimensional finite element analysis (2D-FEA) was used to design a coil generating a targeted peak AMF amplitude along the coil axis of ~100 kA/m (peak-to-peak) at a frequency of 150 kHz while maintaining field uniformity to >90% of peak for a specified volume. This field uniformity was realized by forming the turns from cylindrical sections of copper plate and by adding flux concentrating rings to both ends of the coil. Following construction, the field profile along the axes of the coil was measured. An axial peak field value of 95.8 ± 0.4 kA/m was measured with 650 V applied to the coil and was consistent with the calculated results. The region of axial field uniformity, defined as the distance over which field ≥90% of peak, was also consistent with the simulated results. We describe the utility of such a device for calorimetric measurement of nanoparticle heating for cancer therapy and for magnetic fluid hyperthermia in small animal models of human cancer. PMID:25392562

  2. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  3. The amplitude of quantum field theory

    SciTech Connect

    Medvedev, B.V. ); Pavlov, V.P.; Polivanov, M.K. ); Sukhanov, A.D. )

    1989-05-01

    General properties of the transition amplitude in axiomatic quantum field theory are discussed. Bogolyubov's axiomatic method is chosen as the variant of the theory. The axioms of this method are analyzed. In particular, the significance of the off-shell extension and of the various forms of the causality condition are examined. A complete proof is given of the existence of a single analytic function whose boundary values are the amplitudes of all channels of a process with given particle number.

  4. Variation of Magnetic Particle Imaging Tracer Performance With Amplitude and Frequency of the Applied Magnetic Field

    PubMed Central

    Khandhar, Amit P.; Kemp, Scott J.; Ota, Satoshi; Nakamura, Kosuke; Takemura, Yasushi; Krishnan, Kannan M.

    2015-01-01

    The magnetic response of magnetic particle imaging (MPI) tracers varies with the slew rate of the applied magnetic field, as well as with the tracer's average magnetic core size. Currently, 25 kHz and 20 mT/μ0 drive fields are common in MPI, but lower field amplitudes may be necessary for patient safety in future designs. We studied how several different sizes of monodisperse MPI tracers behaved under different drive field amplitude and frequency, using magnetic particle spectrometry and ac hysteresis for drive field conditions at 16, 26, and 40 kHz, with field amplitudes from 5 to 40 mT/μ0. We observed that both field amplitude and frequency can influence the tracer behavior, but that the magnetic behavior is consistent when the slew rate (the product of field amplitude and frequency) is consistent. However, smaller amplitudes provide a correspondingly smaller field of view, sometimes resulting in excitation of a minor hysteresis loop. PMID:26023242

  5. ac driving amplitude dependent systematic error in scanning Kelvin probe microscope measurements: Detection and correction

    SciTech Connect

    Wu Yan; Shannon, Mark A.

    2006-04-15

    The dependence of the contact potential difference (CPD) reading on the ac driving amplitude in scanning Kelvin probe microscope (SKPM) hinders researchers from quantifying true material properties. We show theoretically and demonstrate experimentally that an ac driving amplitude dependence in the SKPM measurement can come from a systematic error, and it is common for all tip sample systems as long as there is a nonzero tracking error in the feedback control loop of the instrument. We further propose a methodology to detect and to correct the ac driving amplitude dependent systematic error in SKPM measurements. The true contact potential difference can be found by applying a linear regression to the measured CPD versus one over ac driving amplitude data. Two scenarios are studied: (a) when the surface being scanned by SKPM is not semiconducting and there is an ac driving amplitude dependent systematic error; (b) when a semiconductor surface is probed and asymmetric band bending occurs when the systematic error is present. Experiments are conducted using a commercial SKPM and CPD measurement results of two systems: platinum-iridium/gap/gold and platinum-iridium/gap/thermal oxide/silicon are discussed.

  6. Extending membrane pore lifetime with AC fields: A modeling study

    NASA Astrophysics Data System (ADS)

    Garner, Allen L.; Bogdan Neculaes, V.

    2012-07-01

    AC (sinusoidal) fields with frequencies from kilohertz to gigahertz have been used for gene delivery. To understand the impact of AC fields on electroporation dynamics, we couple a nondimensionalized Smoluchowski equation to an exact representation of the cell membrane voltage obtained solving the Laplace equation. The slope of the pore energy function, dφ/dr, with respect to pore radius is critical in predicting pore dynamics in AC fields because it can vary from positive, inducing pore shrinkage, to negative, driving pore growth. Specifically, the net sign of the integral of dφ/dr over time determines whether the average pore size grows (negative), shrinks (positive), or oscillates (zero) indefinitely about a steady-state radius, rss. A simple analytic relationship predicting the amplitude of the membrane voltage necessary for this behavior agrees well with simulation for frequencies from 500 kHz to 5 MHz for rss < 10 nm. For larger pore size (rss > 10 nm), dφ/dr oscillates about a negative value, suggesting that a net creation of pores may be necessary to maintain a constant pore size. In both scenarios, the magnitude of rss depends only upon the amplitude of the membrane voltage and not directly upon the applied field frequency other than the relationship between the amplitudes of the applied field and membrane voltage.

  7. Manipulating Flames with AC Electric Fields

    NASA Astrophysics Data System (ADS)

    Bishop, Kyle

    2013-11-01

    Time-oscillating electric fields applied to plasmas present in flames create steady flows of gas capable of shaping, directing, enhancing, or even extinguishing flames. Interestingly, electric winds induced by AC electric fields can be stronger that those due to static fields of comparable magnitude. Furthermore, unlike static fields, the electric force due to AC fields is localized near the surface of the flame. Consequently, the AC response depends only on the local field at the surface of the flame - not on the position of the electrodes used to generate the field. These results suggest that oscillating electric fields can be used to manipulate and control combustion processes at a distance. To characterize and explain these effects, we investigate a simple experimental system comprising a laminar methane-air flame positioned between two parallel-plate electrodes. We quantify both the electric and hydrodynamic response of the flame as a function of frequency and magnitude of the applied field. A theoretical model shows how steady gas flows emerge from the time-averaged electrical force due to the field-induced motion of ions generated within the flame and by their disappearance by recombination. These results provide useful insights into the application of AC fields to direct combustion processes.

  8. Electrohydrodynamic instabilities in thin viscoelastic films: AC and DC fields

    NASA Astrophysics Data System (ADS)

    Espin, Leonardo; Corbett, Andrew; Kumar, Satish; Kumar Research Group Team

    2012-11-01

    Electrohydrodynamic instabilities in thin liquid films are a promising route for the self-assembly of well-defined topographical features on the surfaces of materials. Here, we study the effect of viscoelasticity on these instabilities under the influence of AC and DC electric fields. Viscoelasticity is incorporated via a Jeffreys model and both perfect and leaky dielectric materials are considered. In the case of DC fields, asymptotic methods are employed to shed light on the nature of a singularity that arises when solvent viscosity is neglected (i.e., the Maxwell-fluid limit). In the case of AC fields, we apply a numerical procedure based on Floquet theory to determine the maximum growth rate and corresponding wavenumber as a function of the oscillation amplitude and frequency. Elasticity is found to increase both the maximum growth rate and the corresponding wavenumber, with the effects being the most pronounced when the oscillation period is comparable to the fluid relaxation time.

  9. Topological field theory amplitudes for A N-1 fibration

    NASA Astrophysics Data System (ADS)

    Iqbal, Amer; Khan, Ahsan Z.; Qureshi, Babar A.; Shabbir, Khurram; Shehper, Muhammad A.

    2015-12-01

    We study the partition function N=1 5D U( N) gauge theory with g adjoint hypermultiplets and show that for massless adjoint hypermultiplets it is equal to the partition function of a two dimensional topological field on a genus g Riemann surface. We describe the topological field theory by its amplitudes associated with cap, propagator and pair of pants. These basic amplitudes are open topological string amplitudes associated with certain Calabi-Yau threefolds in the presence of Lagrangian branes.

  10. AC Magnetic Field Frequency Dependence of Magnetoacoustic Emission

    NASA Technical Reports Server (NTRS)

    Namkung, M.; Wincheski, B.; Fulton, J. P.; DeNale, R.

    1992-01-01

    Our recent study has proved a strong correlation between the low-frequency AC applied magnetic field amplitude dependence of the asymmetry of the magnetoacoustic emission (MAE) burst and the strength of the domain wall-defect interaction in iron-base ferromagnets. For the present study the AC magnetic field frequency dependence of the asymmetry has been investigated in the range of 1 to 200 Hz. When represented by the third moment of the rectified acoustic emission pulses, the asymmetry becomes a bell-shaped function of frequency with its center located around 25 Hz. This experiment has been performed with low carbon, high yield stress steel specimens of three different levels of domain wall-defect interaction strength. The results show that the increase in the interaction strength causes a vertical down shift of the asymmetry in the entire frequency range investigated.

  11. Frequency and amplitude responses of ac susceptibility in high temperature superconductors [rapid communication

    NASA Astrophysics Data System (ADS)

    Liu, S. L.; Wu, G. J.; Xu, X. B.; Wu, J.; Shao, H. M.; Cai, Y. M.; Jin, X. C.

    2005-05-01

    According to the scaling function of vortex glass phase transition, a general description for the peak temperatures TP of frequency- and amplitude-dependent ac susceptibility has been deduced for high temperature superconductors. The description can be written as lnω0ωPBnhacμ=A(1-tP)q. This description is in good agreement of the experiments in our melt-textured YBCO and Pb doped Hg-1234 ceramic superconductors. The values of the exponents are estimated to be q=3/2 and n=1. And the comparison of our description with YBCO single crystal also sounds excellent.

  12. Resonant transport through a carbon nanotube junction exposed to an ac field.

    PubMed

    Shafranjuk, S E

    2011-12-14

    The electron transport through a carbon nanotube (CNT) double barrier junction exposed to an external electromagnetic field is studied. The electron spectrum in the quantum well (QW) formed by the junction bears relativistic features. We examine how the ac field affects the level quantization versus the ac field parameters and chirality. We find that the transport through the junction changes dramatically versus the ac field frequency and amplitude. These changes are pronounced in the junction's differential conductance, which allows judgment about the role of relativistic effects in the CNT QW structures. PMID:22109843

  13. Development and application of setup for ac magnetic field in neutron scattering experiments.

    PubMed

    Klimko, Sergey; Zhernenkov, Kirill; Toperverg, Boris P; Zabel, Hartmut

    2010-10-01

    We report on a new setup developed for neutron scattering experiments in periodically alternating magnetic fields at the sample position. The assembly consisting of rf generator, amplifier, wide band transformer, and resonance circuit. It allows to generate homogeneous ac magnetic fields over a volume of a few cm(3) and variable within a wide range of amplitudes and frequencies. The applicability of the device is exemplified by ac polarized neutron reflectometry (PNR): a new method established to probe remagnetization kinetics in soft ferromagnetic films. Test experiments with iron films demonstrate that the ac field within the accessible range of frequencies and amplitudes produces a dramatic effect on the PNR signal. This shows that the relevant ac field parameters generated by the device match well with the scales involved in the remagnetization processes. Other possible applications of the rf unit are briefly discussed. PMID:21034083

  14. Development and application of setup for ac magnetic field in neutron scattering experiments

    SciTech Connect

    Klimko, Sergey; Zhernenkov, Kirill; Toperverg, Boris P.; Zabel, Hartmut

    2010-10-15

    We report on a new setup developed for neutron scattering experiments in periodically alternating magnetic fields at the sample position. The assembly consisting of rf generator, amplifier, wide band transformer, and resonance circuit. It allows to generate homogeneous ac magnetic fields over a volume of a few cm{sup 3} and variable within a wide range of amplitudes and frequencies. The applicability of the device is exemplified by ac polarized neutron reflectometry (PNR): a new method established to probe remagnetization kinetics in soft ferromagnetic films. Test experiments with iron films demonstrate that the ac field within the accessible range of frequencies and amplitudes produces a dramatic effect on the PNR signal. This shows that the relevant ac field parameters generated by the device match well with the scales involved in the remagnetization processes. Other possible applications of the rf unit are briefly discussed.

  15. Effective Field Theories from Soft Limits of Scattering Amplitudes

    NASA Astrophysics Data System (ADS)

    Cheung, Clifford; Kampf, Karol; Novotny, Jiri; Trnka, Jaroslav

    2015-06-01

    We derive scalar effective field theories—Lagrangians, symmetries, and all—from on-shell scattering amplitudes constructed purely from Lorentz invariance, factorization, a fixed power counting order in derivatives, and a fixed order at which amplitudes vanish in the soft limit. These constraints leave free parameters in the amplitude which are the coupling constants of well-known theories: Nambu-Goldstone bosons, Dirac-Born-Infeld scalars, and Galilean internal shift symmetries. Moreover, soft limits imply conditions on the Noether current which can then be inverted to derive Lagrangians for each theory. We propose a natural classification of all scalar effective field theories according to two numbers which encode the derivative power counting and soft behavior of the corresponding amplitudes. In those cases where there is no consistent amplitude, the corresponding theory does not exist.

  16. Effective Field Theories from Soft Limits of Scattering Amplitudes.

    PubMed

    Cheung, Clifford; Kampf, Karol; Novotny, Jiri; Trnka, Jaroslav

    2015-06-01

    We derive scalar effective field theories-Lagrangians, symmetries, and all-from on-shell scattering amplitudes constructed purely from Lorentz invariance, factorization, a fixed power counting order in derivatives, and a fixed order at which amplitudes vanish in the soft limit. These constraints leave free parameters in the amplitude which are the coupling constants of well-known theories: Nambu-Goldstone bosons, Dirac-Born-Infeld scalars, and Galilean internal shift symmetries. Moreover, soft limits imply conditions on the Noether current which can then be inverted to derive Lagrangians for each theory. We propose a natural classification of all scalar effective field theories according to two numbers which encode the derivative power counting and soft behavior of the corresponding amplitudes. In those cases where there is no consistent amplitude, the corresponding theory does not exist. PMID:26196613

  17. Field-dependence of AC susceptibility in titanomagnetites

    USGS Publications Warehouse

    Jackson, M.; Moskowitz, B.; Rosenbaum, J.; Kissel, Catherie

    1998-01-01

    AC susceptibility measurements as a function of field amplitude Hac and of frequency show a strong field dependence for a set of synthetic titanomagnetites (Fe3-xTixO4) and for certain basalts from the SOH-1 Hawaiian drill hole and from Iceland. In-phase susceptibility is constant below fields of about 10-100 A/m, and then increases by as much as a factor of two as Hsc is increased to 2000 A/m. Both the initial field-independent susceptibilities and field-dependence of susceptibility are systematically related to composition: initial susceptibility is 3 SI for a single-crystal sphere of TMO (x = 0) and decreases with increasing titanium content; field-dependence is nearly zero for TM0 and increases systematically to a maximum near TM60 (x = 0.6). This field dependence can in some cases be mistaken for frequency dependence, and leaf to incorrect interpretations of magnetic grain size and composition when titanomagnetite is present.

  18. Hierarchical assembly of anisotropic particles in AC electric fields

    NASA Astrophysics Data System (ADS)

    Torres Diaz, Isaac; Rupp, Bradley; Hua, Xiaoqing; Yang, Yuguang; Bevan, Michael A.

    Hierarchical microstructures composed of colloids are of great interest for technological applications and advanced materials such as metamaterials and microfluidic devices. The dynamics of spherical colloidal particles has been analyzed previously for several systems, and has led to the control of the formation of perfect crystals using AC electric fields. However, spherical particles do not have a dependence on its orientation as anisotropic particles. Recently, researchers reported experiments showing the capabilities of anisotropic particles to assemble in different configurations, yet a detailed understanding of the mechanism and control is lacking. This work shows both theoretical and experimental results of the control of a colloidal system composed of anisotropic colloidal particles with a tri-axial ellipsoidal shape subjected to a non-uniform electric field close to a planar wall. We show that particles pack into different structures and orientations as a function of the applied electric field amplitude and frequency by taking into account dipole-field, dipole-dipole, and colloidal interactions. This analysis provides a theoretical framework for the equilibrium and non-equilibrium structures that can be formed via field mediated interaction, which are validated by experimental microscopy results, and can ultimately be used to engineer the hierarchical assembly of anisotropic particles.

  19. Time-asymptotic field amplitudes in nonlinear Landau damping

    SciTech Connect

    Buchanan, M.; Kirkitelos, P.; Dorning, J.J. )

    1993-01-01

    The behavior of an electrostatic plasma wave of initial amplitude Ei in a collisionless electron plasma depends crucially on the ratio [delta] = [gamma]L/[omega]B, where [gamma]L is the damping coefficient calculated from linear plasma kinetic theory and [omega]B = (ekEi/m)[sup 1/2] is the [open quotes]bounce[close quotes] frequency for trapped electrons. For sufficiently small E[sub i], i.e., [delta] [much gt] 1, the wave damps away completely; conversely, a wave of large initial amplitude, for which [delta] [much lt] 1, saturates at a finite final amplitude due to the nonlinear effects of particle trapping. In this paper, we report results concerning the transition region [delta] [approximately] 0(1), which separates these two regimes. For the case of weak damping, i.e., [vert bar][gamma]L/[omega]p[vert bar][much lt]1, where [omega]p is the plasma frequency, we calculate analytically the critical value [delta][sub i,e] below which complete damping occurs and derive the first explicit analytic relationship between E[sub i] and E[sub f], the time-asymptotic amplitude, for E[sub i] above the critical value E[sub i,c] = (m,ek)([gamma]L/[delta][sub i,c]). The results predict an interesting phenomenon - a finite jump [delta]E in the final field amplitude as E[sub i] is increased through E[sub i,c]. We have corroborated the reality of this phenomenon through large-scale numerical simulations of the Vlasov-Poisson system, carried out using the spectral splitting code of Klimas. These important new results establish a detailed picture of the fundamental transition between linear and nonlinear Landau damping and, in particular, show that the onset of essentially nonlinear behavior occurs very abruptly as the initial wave amplitude increases through its critical value.

  20. Regularized adelic formulas for string and superstring amplitudes in one-class quadratic fields

    NASA Astrophysics Data System (ADS)

    Vladimirov, V. S.

    2010-09-01

    We obtain regularized adelic formulas for gamma and beta functions for fields of rational numbers and the one-class quadratic fields and arbitrary quasicharacters (ramified or not). We consider applications to four-tachyon tree string amplitudes, generalized Veneziano amplitudes (open string), perturbed Virasoro amplitudes (closed string), massless four-particle tree open and closed superstring amplitudes, Ramond-Neveu-Schwarz superstring amplitudes, and charged heterotic superstring amplitudes. We establish certain relations between different string and superstring amplitudes.

  1. De Wijk gas field: Reservoir mapping with amplitude anomalies

    SciTech Connect

    Bruijn, B. )

    1993-09-01

    De Wijk field, discovered in 1949, is located in the northeastern part of Netherlands. The main gas accumulation is contained in cretaceous and Triassic sandstone reservoirs trapped in a broad salt-induced structure of around 80 km[sup 2] areal extent. The field contains gas in the tertiary, Chalk, Zechstein 2 Carbonate, and Carboniferous reservoirs as well. De Wijk field is unique in the Netherlands as most gas-producing reservoirs in the Cretaceous/Triassic are of no commercial interest. Post-depositional leaching has positively affected the reservoir properties of the Triassic formations subcropping below the Cretaceous unconformity. Optimum, interpretation of 3-D seismic data acquired in 1989 resulted in spectacular displays highlighting the uniqueness of the field. Most gas-bearing reservoirs are expressed on seismic by amplitude anomalies. Various attribute-measurement techniques show the effect of gas fill, leaching, and sand distribution in the various reservoirs.

  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. Effect of electric-field fluctuations on rotational revival amplitudes

    NASA Astrophysics Data System (ADS)

    Pearson, Andrew J.; Antonsen, Thomas M.

    2009-11-01

    We study numerically the behavior of rotational revivals in a molecular gas when subject to the fluctuating electric field of a background plasma. We model a molecule using a rigid rotor Hamiltonian and couple it to an electric field using permanent and induced multipole interaction terms. The evolution of the density matrix for the molecule is calculated for a short intense laser pulse, followed by a fluctuating background electric field. A broad superposition of angular momentum eigenstates of a molecule is created by the laser field, and the result of an ensemble average over initial molecular orientation is a set of recurring peaks in the probability density for observing a particular orientation—the so-called “rotational revivals.” The fluctuating background field is created using the dressed particle technique, and the result is a loss of coherence between the phases of the various basis states of the molecule, which causes a decreasing amplitude for subsequent alignment peaks. Modern short-pulse lasers operate with sufficient intensity to make this effect relevant to experiments in molecular alignment.

  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. Critical field measurements in superconductors using ac inductive techniques

    NASA Astrophysics Data System (ADS)

    Campbell, S. A.; Ketterson, J. B.; Crabtree, G. W.

    1983-09-01

    The ac in-phase and out-of-phase response of type II superconductors is discussed in terms of dc magnetization curves. Hysteresis in the dc magnetization is shown to lead to a dependence of the ac response on the rate at which an external field is swept. This effect allows both Hc1 and Hc2 to be measured by ac techniques. A relatively simple mutual inductance bridge for making such measurements is described in the text, and factors affecting bridge sensitivity are discussed in the Appendix. Data for the magnetic superconductor ErRh4B4 obtained using this bridge are reported.

  6. AC electric field induced droplet deformation in a microfluidic T-junction.

    PubMed

    Xi, Heng-Dong; Guo, Wei; Leniart, Michael; Chong, Zhuang Zhi; Tan, Say Hwa

    2016-08-01

    We present for the first time an experimental study on the droplet deformation induced by an AC electric field in droplet-based microfluidics. It is found that the deformation of the droplets becomes stronger with increasing electric field intensity and frequency. The measured electric field intensity dependence of the droplet deformation is consistent with an early theoretical prediction for stationary droplets. We also proposed a simple equivalent circuit model to account for the frequency dependence of the droplet deformation. The model well explains our experimental observations. In addition, we found that the droplets can be deformed repeatedly by applying an amplitude modulation (AM) signal. PMID:27173587

  7. Two-level systems driven by large-amplitude fields

    SciTech Connect

    Ashhab, S.; Johansson, J. R.; Zagoskin, A. M.; Nori, Franco

    2007-06-15

    We analyze the dynamics of a two-level system subject to driving by large-amplitude external fields, focusing on the resonance properties in the case of driving around the region of avoided level crossing. In particular, we consider three main questions that characterize resonance dynamics: (1) the resonance condition (2) the frequency of the resulting oscillations on resonance, and (3) the width of the resonance. We identify the regions of validity of different approximations. In a large region of the parameter space, we use a geometric picture in order to obtain both a simple understanding of the dynamics and quantitative results. The geometric approach is obtained by dividing the evolution into discrete time steps, with each time step described by either a phase shift on the basis states or a coherent mixing process corresponding to a Landau-Zener crossing. We compare the results of the geometric picture with those of a rotating wave approximation. We also comment briefly on the prospects of employing strong driving as a useful tool to manipulate two-level systems.

  8. Aligned Immobilization of Proteins Using AC Electric Fields.

    PubMed

    Laux, Eva-Maria; Knigge, Xenia; Bier, Frank F; Wenger, Christian; Hölzel, Ralph

    2016-03-01

    Protein molecules are aligned and immobilized from solution by AC electric fields. In a single-step experiment, the enhanced green fluorescent proteins are immobilized on the surface as well as at the edges of planar nanoelectrodes. Alignment is found to follow the molecules' geometrical shape with their longitudinal axes parallel to the electric field. Simultaneous dielectrophoretic attraction and AC electroosmotic flow are identified as the dominant forces causing protein movement and alignment. Molecular orientation is determined by fluorescence microscopy based on polarized excitation of the proteins' chromophores. The chromophores' orientation with respect to the whole molecule supports X-ray crystal data. PMID:26779699

  9. Exchange anisotropy determined by magnetic field dependence of ac susceptibility

    NASA Astrophysics Data System (ADS)

    Rodríguez-Suárez, R. L.; Vilela Leão, L. H.; de Aguiar, F. M.; Rezende, S. M.; Azevedo, A.

    2003-10-01

    ac susceptibility measurements of ferromagnetic/antiferromagnetic (FM/AF) bilayers are usually performed as a function of the temperature. In this work we describe measurements of transverse biased ac susceptibility (χt) of FM/AF bilayers as a function of the applied magnetic field H0. The measurements were carried out at room temperature by means of an ac magneto-optical Kerr effect susceptometer. The χt-1(H0) dependence, at the saturation magnetization regime, exhibits a linear behavior with the applied field parallel and perpendicular to the exchange bias direction. The linear extrapolation of χt-1 versus H0 cuts the abscissa at asymmetrical values of field due to the exchange bias coupling. The inverse susceptibility is calculated in the saturation regime by a model, which takes into account the free energy of both layers plus a term corresponding to the interfacial coupling. The exchange coupling field (HE) and uniaxial anisotropy (HU) are extracted from the best fit to the experimental results. The results obtained are crosschecked by those obtained from ferromagnetic resonance (FMR) and dc magnetometry. The measurements of the exchange bias and the uniaxial field in all of the three analyzed bilayers gave values that are consistently lower when measured by FMR than those obtained by ac and dc magnetometry. It is argued that the apparently discrepant values of HE and HU, obtained by different techniques, might be explained by existence of unstable AF grains at the AF/FM interface.

  10. AC Electrostatic Field Study : Final Report.

    SciTech Connect

    Lebby, Gary L.

    1990-08-28

    The phenomenon of fast transients propagating to the outer sheath of a gas insulated substation (GIS) during switching and disconnect operations as well as the distortion of the electric field gradient around an electric transmission line in the presence of field measuring equipment are examples of electrostatic and electromagnetic field problems that are very much on the minds of both power engineers and maintenance personnel alike. Maintenance personnel working on high voltage equipment want to know the areas that have the highest electric field strength gradients and they want to reduce the risk of being shocked when touching a conventionally 60 Hz grounded GIS enclosure due to fast transients initiated by faults and switching operations. In studying these phenomena during the performance period of this grant, tower configurations for the electric field strength gradient measurements were tested with the ESURF3D program acquired from BPA and gas insulated substation test pole (GISTP) models were tested using the Alternative Transients Program (ATP) version Electromagnets Transients Program (EMTP). The results of these two modeling paradigms are presented in this report not as the last word on these subjects, but as a couple of the many ways one can approach two classical electromagnetic waves problems. 19 refs., 13 figs., 3 tabs.

  11. AC-field-induced quantum phase transitions in density of states

    NASA Astrophysics Data System (ADS)

    Yang, Kai-Hua; Liu, Kai-Di; Wang, Huai-Yu; Qin, Chang-Dong

    2016-02-01

    We investigate the joint effects of the intralead electron interaction and an external alternating gate voltage on the time-averaged local density of states (DOSs) of a quantum dot coupled to two Luttinger-liquid leads in the Kondo regime. A rich dependence of the DOSs on the driving amplitude and intralead interaction is demonstrated. We show that the feature is quite different for different interaction strengths in the presence of the ac field. It is shown that the photon-assisted transport processes cause an additional splitting of the Kondo peak or dip, which exhibits photon-assisted single-channel (1CK) or two-channel Kondo (2CK) physics behavior. The phase transition between photon-assisted 1CK and 2CK physics occurs when the interaction strength is moderately strong. The inelastic channels associated with photon-assisted electron tunneling can dominate electron transport for weak interaction when the ac amplitude is greater than the frequency by one order of magnitude. In the limit of strong interaction the DOSs scale as a power-law behavior which is strongly affected by the ac field.

  12. On the field theory expansion of superstring five point amplitudes

    NASA Astrophysics Data System (ADS)

    Boels, Rutger H.

    2013-11-01

    A simple recursive expansion algorithm for the integrals of tree level superstring five point amplitudes in a flat background is given which reduces the expansion to simple symbol(ic) manipulations. This approach can be used for instance to prove the expansion is maximally transcendental to all orders and to verify several conjectures made in recent literature to high order. Closed string amplitudes follow from these open string results by the KLT relations. To obtain insight into these results in particular the maximal R-symmetry violating amplitudes (MRV) in type IIB superstring theory are studied. The obtained expansion of the open string amplitudes reduces the analysis for MRV amplitudes to the classification of completely symmetric polynomials of the external legs, up to momentum conservation. Using Molien's theorem as a counting tool this problem is solved by constructing an explicit nine element basis for this class. This theorem may be of wider interest: as is illustrated at higher points it can be used to calculate dimensions of polynomials of external momenta invariant under any finite group for in principle any number of legs, up to momentum conservation. In the closed (or mixed) case this follows after application of the Kawai-Lewellen-Tye [1] relations (or their analogons [2,3]).

  13. Study of mechanisms of electric field-induced DNA transfection. II. Transfection by low-amplitude, low-frequency alternating electric fields.

    PubMed

    Xie, T D; Tsong, T Y

    1990-10-01

    Electroporation for DNA transfection generally uses short intense electric pulses (direct current of kilovolts per centimeter, microseconds to milliseconds), or intense dc shifted radio-frequency oscillating fields. These methods, while remarkably effective, often cause death of certain cell populations. Previously it was shown that a completely reversible, high ionic permeation state of membranes could be induced by a low-frequency alternating electric field (ac) with a strength one-tenth, or less, of the critical breakdown voltage of the cell membrane (Teissie, J., and T. Y. Tsong. 1981. J. Physiol. (Paris). 77:1043-1053). We report the transfection of E. coli (JM105) by plasmid PUC18 DNA, which carries an ampicillin-resistance gene, using low-amplitude, low-frequency ac fields. E. coli transformants confer the ampicillin resistance and the efficiency of the transfection can be conveniently assayed by counting colonies in a selection medium containing ampicillin. For the range of ac fields employed (peak-to-peak amplitude 50-200 V/cm, frequency 0.1 Hz-1 MHz, duration 1-100 s), 100% of the E. coli survived the electric field treatment. Transfection efficiencies varied with field strength and frequency, and as high as 1 x 10(5)/micrograms DNA was obtained with a 200 V/cm square wave, 1 Hz ac field, 30 s exposure time, when the DNA/cell ratio was 50-75. Control samples gave a background transfection of much less than 10/micrograms DNA. With a square wave ac field, the transfection efficiency showed a frequency window: the optimal frequency was 1 Hz with a 200 V/cm field, and was approximately 0.1 Hz with a 50 V/cm field. Transfection efficiency varied with the waveform: square wave > sine wave > triangle wave. If the DNA was added after the ac field was turned off, transfection efficiency was reduced to the background level within 1 min. The field intensity used in this study was low and insufficient to cause electric breakdown of cell membranes. Thus, DNA

  14. Disk relations for tree amplitudes in minimal coupling theory of gauge field and gravity

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Xin; Du, Yi-Jian; Ma, Qian

    2010-07-01

    KLT relations on S factorize closed string amplitudes into product of open string tree amplitudes. The field theory limits of KLT factorization relations hold in minimal coupling theory of gauge field and gravity. In this paper, we consider the field theory limits of relations on D. Though the relations on D and KLT factorization relations hold on worldsheets with different topologies, we find the field theory limits of D relations also hold in minimal coupling theory of gauge field and gravity. We use the D relations to give three- and four-point tree amplitudes where gluons are minimally coupled to gravitons. We also give a further discussion on general tree amplitudes in minimal coupling theory of gauge field and gravity. In general, any tree amplitude with M gravitons in addition to N gluons can be given by pure-gluon tree amplitudes with N+2M legs.

  15. Gravity and Yang-Mills Amplitude Relations in Field Theory

    NASA Astrophysics Data System (ADS)

    Søndergaard, Thomas

    2011-07-01

    We review some recent work in the famous Kawai-Lewellen-Tye (KLT) relations. Especially we present a compact way of writing down the general n-point relation. We also look at an extra feature of these relations which were only very recently realized, and leads to new relations among gauge-theory amplitudes.

  16. ``Superfast'' and ``Hyperfast'' Electrophoresis in DC and AC Electric Fields

    NASA Astrophysics Data System (ADS)

    Demekhin, Evgeny; Korovyakovsky, Alex

    2006-11-01

    Movement of a small conducting spherical granule in an electrolyte solution under force of DC and AC fields is considered. The problem is described by strongly coupled nonlinear PDE system. The fact that it has two small parameters, the ratio of the ion double layer to the diffusion layer and the ratio of the diffusion layer to the granule's diameter, makes the problem unique and extremely difficult to solve. This is the reason why only solutions for some particular cases have been known. In this work for the first time, combining asymptotic and numerical methods, a complete theory of electrophoresis in DC and AC fields is developed. By special decomposition method the system is transformed to new variables. Analytical solution in the inner region results in the nonlinear Smoluchowski slip velocity. In the intermediate region convection-diffusion equation is solved numerically. In tern, the intermediate solution is matched with the outer solution of Laplace equation to complete the statement. For a strong DC field (``superfast'' electrophoresis) the theory predicts, in agreement with experiments, the granule's velocity to be proportional to the granule's size and squared external field; there is a large elongated vortex behind the granule and a small one near its equator. There is an excellent agreement with available experimental data. Granule's velocity for AC field becomes even larger than for DC, it has a maximum with respect to the field's frequency (``hyperfast'' electrophoresis).

  17. Dependence of seismoelectric amplitudes on water content - a field study

    NASA Astrophysics Data System (ADS)

    Strahser, M. H. P.; Matthey, P.-D.; Jouniaux, L.; Sailhac, P.

    2009-04-01

    In porous saturated media, seismic compressional waves can cause seismoelectric and seismoelectromagnetic signals through electrokinetic coupling. It has been observed that these measureable signals also occur in partially saturated media, but the theory is largely unknown for these circumstances. Seismoelectromagnetic tomography is expected to combine the sensitivity of electrical properties to water-content and permeability, to the high spatial resolution of seismic surveys. A better understanding of the physical processes and a reliable quantification of the conversion between seismic and electric energy are necessary and need to take into account the effect of water-content, especially for shallow subsurface investigations. In order to quantify seismoelectric signals with changing water content, we repeated seismoelectric and seismic measurements on the same profile in the Vosges Mountains during several months. The electrical resistivity was also monitored to take into account the water-content variations. We show that an exponential relation can be established between the seismoelectric amplitudes normalized with the seismic amplitudes and the resistivity which in turn is related to the saturation: Increasing resistivity (decreasing water content) leads to decreasing normalized seismoelectric amplitudes. These results imply that the electrokinetic coefficient should increase with water-saturation, as measured in laboratory, but not predicted by theory. This work was funded by CNRS and Université Louis Pasteur de Strasbourg.

  18. AC Electric Field Communication for Human-Area Networking

    NASA Astrophysics Data System (ADS)

    Kado, Yuichi; Shinagawa, Mitsuru

    We have proposed a human-area networking technology that uses the surface of the human body as a data transmission path and uses an AC electric field signal below the resonant frequency of the human body. This technology aims to achieve a “touch and connect” intuitive form of communication by using the electric field signal that propagates along the surface of the human body, while suppressing both the electric field radiating from the human body and mutual interference. To suppress the radiation field, the frequency of the AC signal that excites the transmitter electrode must be lowered, and the sensitivity of the receiver must be raised while reducing transmission power to its minimally required level. We describe how we are developing AC electric field communication technologies to promote the further evolution of a human-area network in support of ubiquitous services, focusing on three main characteristics, enabling-transceiver technique, application-scenario modeling, and communications quality evaluation. Special attention is paid to the relationship between electro-magnetic compatibility evaluation and regulations for extremely low-power radio stations based on Japan's Radio Law.

  19. Large amplitude middle atmospheric electric fields - Fact or fiction?

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.; Siefring, C. L.; Pfaff, R. F., Jr.

    1983-01-01

    An analysis of the measurements of large apparent dc fields in the middle atmosphere, previously gathered by two sounding rockets, shows these fields to be spurious. In the case of one of the rockets, the evidence presented suggests that the measured electric fields, aligned with the rocket's velocity vector, may be due to a negatively charged wake. A comparison of measurements made by various electric field booms also suggests that the insulating boom coatings in one experiment may have affected the results obtained. It is recommended that insulating coatings should not be used at mesospheric altitudes, because of the detrimental effects that frictional charging may have.

  20. The attenuation of the levitation force of HTS bulk exposed to AC magnetic field on the above NdFeB guideway

    NASA Astrophysics Data System (ADS)

    Liu, Minxian; Wang, Yan

    2012-01-01

    In the present High Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So it is required to study the characteristics of levitation force of the HTS bulk affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which AC magnetic field generated by an electromagnet is used to simulate the time-varying magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC field, and the attenuation is increased with the amplitude of the AC field, but the attenuation is almost independent of the frequency the AC magnetic field.

  1. Lipid Bilayer Vesicle Dynamics in AC Electric Fields

    NASA Astrophysics Data System (ADS)

    McConnell, Lane; Vlahovska, Petia; Miksis, Michael

    2014-11-01

    Vesicles are closed, fluid-filled lipid bilayers which are mechanically similar to biological cells and which undergo shape transitions in the presence of electric fields. Here we model the vesicle membrane as an infinitely thin, capacitive, area-incompressible interface with the surrounding fluids acting as charge-advecting leaky dielectrics. We then implement the boundary integral method to numerically investigate the dynamics of a vesicle in various AC electric field profiles. Our numerical results are then compared with recent small deformation theory and experimental data. We also note our observation of a new theoretical vesicle behavior that has yet to be observed experimentally.

  2. Reconstruction of far-field tsunami amplitude distributions from earthquake sources

    USGS Publications Warehouse

    Geist, Eric L.; Parsons, Thomas E.

    2016-01-01

    The probability distribution of far-field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones. Tsunami amplitude distributions at tide gauge stations follow a similar functional form, well described by a tapered Pareto distribution that is parameterized by a power-law exponent and a corner amplitude. Distribution parameters are first established for eight tide gauge stations in the Pacific, using maximum likelihood estimation. A procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps: (1) define the distribution of seismic moment at subduction zones; (2) establish a source-station scaling relation from regression analysis; (3) transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone; and (4) mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station. The tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies. In comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation, the reconstructed distributions consistently exhibit higher corner amplitude values, implying that in most cases, the empirical catalogs are too short to include the largest amplitudes. Because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog, it is less susceptible to the effects of record-breaking events and more indicative of the actual distribution of tsunami amplitudes.

  3. Reconstruction of Far-Field Tsunami Amplitude Distributions from Earthquake Sources

    NASA Astrophysics Data System (ADS)

    Geist, Eric L.; Parsons, Tom

    2016-04-01

    The probability distribution of far-field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones. Tsunami amplitude distributions at tide gauge stations follow a similar functional form, well described by a tapered Pareto distribution that is parameterized by a power-law exponent and a corner amplitude. Distribution parameters are first established for eight tide gauge stations in the Pacific, using maximum likelihood estimation. A procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps: (1) define the distribution of seismic moment at subduction zones; (2) establish a source-station scaling relation from regression analysis; (3) transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone; and (4) mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station. The tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies. In comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation, the reconstructed distributions consistently exhibit higher corner amplitude values, implying that in most cases, the empirical catalogs are too short to include the largest amplitudes. Because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog, it is less susceptible to the effects of record-breaking events and more indicative of the actual distribution of tsunami amplitudes.

  4. Determining the True Polarity and Amplitude of Synaptic Currents Underlying Gamma Oscillations of Local Field Potentials

    PubMed Central

    Makarov, Valeri A.; Herreras, Oscar

    2013-01-01

    Fluctuations in successive waves of oscillatory local field potentials (LFPs) reflect the ongoing processing of neuron populations. However, their amplitude, polarity and synaptic origin are uncertain due to the blending of electric fields produced by multiple converging inputs, and the lack of a baseline in standard AC-coupled recordings. Consequently, the estimation of underlying currents by laminar analysis yields spurious sequences of inward and outward currents. We devised a combined analytical/experimental approach that is suitable to study laminated structures. The approach was essayed on an experimental oscillatory LFP as the Schaffer-CA1 gamma input in anesthetized rats, and it was verified by parallel processing of model LFPs obtained through a realistic CA1 aggregate of compartmental units. This approach requires laminar LFP recordings and the isolation of the oscillatory input from other converging pathways, which was achieved through an independent component analysis. It also allows the spatial and temporal components of pathway-specific LFPs to be separated. While reconstructed Schaffer-specific LFPs still show spurious inward/outward current sequences, these were clearly stratified into distinct subcellular domains. These spatial bands guided the localized delivery of neurotransmitter blockers in experiments. As expected, only Glutamate but not GABA blockers abolished Schaffer LFPs when applied to the active but not passive subcellular domains of pyramidal cells. The known chemical nature of the oscillatory LFP allowed an empirical offset of the temporal component of Schaffer LFPs, such that following reconstruction they yield only sinks or sources at the appropriate sites. In terms of number and polarity, some waves increased and others decreased proportional to the concomitant inputs in native multisynaptic LFPs. Interestingly, the processing also retrieved the initiation time for each wave, which can be used to discriminate afferent from

  5. Collapse of DNA in a.c. electric fields

    PubMed Central

    Zhou, Chunda; Reisner, Walter W.; Staunton, Rory J.; Ashan, Amir; Austin, Robert H.; Riehn, Robert

    2013-01-01

    We report that double-stranded DNA collapses in presence of a.c. electric fields at frequencies of a few hundred Hertz, and does not stretch as commonly assumed. In particular, we show that confinement-stretched DNA can collapse to about one quarter of its equilibrium length. We propose that this effect is based on finite relaxation times of the counterion cloud, and the subsequent partitioning of the molecule into mutually attractive units. We discuss alternative models of those attractive units. PMID:21770604

  6. Measurement of the light-field amplitude-correlation function through joint photon-count distributions.

    NASA Technical Reports Server (NTRS)

    Furcinitti, P.; Kuppenheimer, J. D.; Narducci, L. M.; Tuft , R. A.

    1972-01-01

    When an amplitude-stabilized He-Ne laser beam is scattered by a rotating ground glass with small surface inhomogeneities, the probability density of the instantaneous scattered-wave amplitude is Gaussian. In this paper, we suggest the use of the joint photon-count probability distribution to measure the absolute value of the electric-field amplitude-correlation function for random Gaussian light fields, and report the results of an experiment in which the Gaussian field is produced by scattering a light beam through a rotating ground glass. This procedure offers an alternative to other conventional methods, such as self-beating spectroscopy and irradiance-correlation techniques. The correlation time of the scattered-field amplitude in the present experiment has been measured with an accuracy of approximately 0.8%.

  7. Coherence-population-trapping transients induced by an ac magnetic field

    NASA Astrophysics Data System (ADS)

    Margalit, L.; Rosenbluh, M.; Wilson-Gordon, A. D.

    2012-06-01

    Coherent-population-trapping transients induced by an ac magnetic field are investigated theoretically for a realistic three-level Λ system in the D1 line of 87Rb. The contributions to the transient probe absorption from the various subsystems that compose the realistic atomic system are examined and the absorption of each Λ subsystem is compared to that of a simple Λ system. The population redistribution due to optical pumping is shown to be the dominant cause of the difference between the contributions of the various subsystems to the oscillatory character of the probe absorption. We also discuss the series of transients that reappear every half-cycle time of a modulated magnetic field when the system is in two-photon resonance, and we study the transient behavior as a function of the probe detuning. The effect of a buffer gas on the amplitude and shape of the transients is considered.

  8. Adèlic formulas for string amplitudes in fields of algebraic numbers

    NASA Astrophysics Data System (ADS)

    Vladimirov, V. S.; Sapuzhak, T. M.

    1996-06-01

    On the basis of the analysis on adèle groups (Tate's formula) for any field of algebraic numbers, a regularization of infinite adèlic products of gamma and beta functions of local fields is proposed. The formulas obtained are applied to representations of the four-point crossing symmetric Veneziano and Virasoro-Shapiro amplitudes through regularized adèlic products of the corresponding string (open and closed, resp.) amplitudes.

  9. Effect of amplitude correlations on coherence in the local field potential.

    PubMed

    Srinath, Ramanujan; Ray, Supratim

    2014-08-15

    Neural activity across the brain shows both spatial and temporal correlations at multiple scales, and understanding these correlations is a key step toward understanding cortical processing. Correlation in the local field potential (LFP) recorded from two brain areas is often characterized by computing the coherence, which is generally taken to reflect the degree of phase consistency across trials between two sites. Coherence, however, depends on two factors-phase consistency as well as amplitude covariation across trials-but the spatial structure of amplitude correlations across sites and its contribution to coherence are not well characterized. We recorded LFP from an array of microelectrodes chronically implanted in the primary visual cortex of monkeys and studied correlations in amplitude across electrodes as a function of interelectrode distance. We found that amplitude correlations showed a similar trend as coherence as a function of frequency and interelectrode distance. Importantly, even when phases were completely randomized between two electrodes, amplitude correlations introduced significant coherence. To quantify the contributions of phase consistency and amplitude correlations to coherence, we simulated pairs of sinusoids with varying phase consistency and amplitude correlations. These simulations confirmed that amplitude correlations can significantly bias coherence measurements, resulting in either over- or underestimation of true phase coherence. Our results highlight the importance of accounting for the correlations in amplitude while using coherence to study phase relationships across sites and frequencies. PMID:24790174

  10. AC magnetic field losses in BSCCO-2223 superconducting tapes

    SciTech Connect

    Lelovic, M.; Mench, S.; Deis, T.

    1997-09-01

    The AC magnetic losses at power frequencies (60 Hz) were investigated for mono- and multifilament Ag-sheathed (Bi, Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (BSCCO-2223) tapes with similar transport critical current (I{sub c}) values at 77 K. The multifilament sample exhibited higher losses than the monofilament under the same conditions. Loss peaks are discussed in terms of intergranular, intragranular and eddy current losses. Because of BSCCO`s anisotropy, field orientation has a large effect on the magnitude of these peaks, even at relatively small angles. Losses for fields applied parallel to the c-axis of the textured BSCCO grains are larger by more than one order of magnitude than those applied perpendicular.

  11. Generation of longitudinally polarized terahertz pulses with field amplitudes exceeding 2 kV/cm

    SciTech Connect

    Cliffe, M. J. Rodak, A.; Graham, D. M.; Jamison, S. P.

    2014-11-10

    We demonstrate the generation of near-single cycle longitudinally polarized terahertz radiation using a large-area radially biased photoconductive antenna with a longitudinal field amplitude in excess of 2 kV/cm. The 76 mm diameter antenna was photo-excited by a 0.5 mJ amplified near-infrared femtosecond laser system and biased with a voltage of up to 100 kV applied over concentric electrodes. Amplitudes for both the transverse and longitudinal field components of the source were measured using a calibrated electro-optic detection scheme. By tightly focusing the radiation emitted from the photoconductive antenna, we obtained a maximum longitudinal field amplitude of 2.22 kV/cm with an applied bias field of 38.5 kV/cm.

  12. Electrohydrodynamics of suspension of liquid drops in AC fields

    NASA Astrophysics Data System (ADS)

    Abdul Halim, Md.; Esmaeeli, Asghar

    2012-11-01

    Manipulation of liquid drops by an externally applied electric field is currently the focus of increased attention because of its relevance in a broad range of industrial processes. The effect of a uniform DC electric field on a solitary drop is well studied; however, less is know about the impact of electric field on suspension of liquid drops, and very little information is available on the impact of AC field on a single or a suspension of drops. Here we report the results of Direct Numerical Simulations of electrohydrodynamics of suspension of liquid drops. The governing equations are solved using a front tracking/finite difference technique, in conjunction with Taylor's leaky dielectric model. The imposed electric potential comprises of two parts, a time-independent base and a time-dependent part. The goal is to explore the relative importance of these two components in setting the statistically steady state behavior of the suspension. To this end, we report the results of three sets of simulations, where (i) the time-dependent part act as a perturbation on the base potential, (ii) the two components are of the same order, and (iii) the time-dependent part is much larger than the base potential. The problem is studied as a function of the governing nondimensional parameters.

  13. Absorption of ac fields in amorphous indium-oxide films

    NASA Astrophysics Data System (ADS)

    Ovadyahu, Z.

    2014-08-01

    Absorption data from applied ac fields in Anderson-localized amorphous indium-oxide (InxO) films are shown to be frequency and disorder dependent. The absorption shows a roll-off at a frequency which is much lower than the electron-electron scattering rate of the material when it is in the diffusive regime. This is interpreted as evidence for discreteness of the energy spectrum of the deeply localized regime. This is consistent with recent many-body localization scenarios. As the metal-insulator transition is approached, the absorption shifts to higher frequencies. Comparing with the previously obtained results on the crystalline version of indium-oxide (In2O3-x) implies a considerably higher inelastic electron-phonon scattering rate in the amorphous material. The range over which the absorption versus frequency decreases may indicate that a wide distribution of localization length is a common feature in these systems.

  14. Influence of the ac magnetic field frequency on the magnetoimpedance of amorphous wire

    NASA Astrophysics Data System (ADS)

    Chen, A. P.; García, C.; Zhukov, A.; Domínguez, L.; Blanco, J. M.; González, J.

    2006-05-01

    Experimental and theoretical studies on the influence of ac magnetic field frequency on the axial diagonal (ζzz) and off-diagonal (ζphiz) components of the magnetoimpedance (MI) tensor in (Co0.94Fe0.06)72.5Si12.5B15 amorphous wires have been performed. The frequency (f) of an ac current flowing along the wire was varied from 1 to 20 MHz with the current amplitude less than 15 mA. In order to enhance the ζphiz component, the amorphous wire was submitted to torsion annealing for developing and preserving a helical magnetic anisotropy in the surface of the wire. The experimental measurements show that the value of the impedance is proportional to the square-root of the ac current frequency, \\sqrt f , in the vicinity of Hex < HK and this increase is due to the contribution of the resistance (real part of the impedance). The measurements also indicate that the peaks of the MI curve shift slightly towards higher field values with increasing f. In a theoretical study the magnetoimpedance expressions ζzz and ζphiz have been deduced using the Faraday law in combination with the solutions of the Maxwell and Landau-Lifshitz-Gilbert (LLG) equations. By analysing quantitatively the spectra of ζzz and ζphiz, the phenomenon of the shift in the peaks of the MI curve with f has been considered as a characteristic of the helical anisotropy in the domain structure of the wire surface.

  15. Constructive and destructive interferences of Stark resonances induced by an ac field in atomic hydrogen

    SciTech Connect

    Pawlak, Mariusz; Bylicki, Miroslaw; Moiseyev, Nimrod; Sindelka, Milan

    2010-12-15

    We study theoretically the problem of a hydrogen atom exposed both to a static dc field and to a monochromatic ac field. We show that, in the presence of an ac field, a constructive (or destructive) interference occurs between the excited (Rydberg) Stark resonance states and the hydrogenic ground state. This mechanism is responsible for dramatic enhancement (or suppression) of the corresponding photoionization rates.

  16. AC Electric Field Activated Shape Memory Polymer Composite

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

    2011-01-01

    Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

  17. Universal features of particle motion in ac electric fields

    NASA Astrophysics Data System (ADS)

    Niemeyer, L.; Seeger, M.

    2015-11-01

    Mobile particles present as contaminants in high voltage gas insulated switchgear (GIS) may constitute a risk for insulation failure. The understanding of their motion in the electric field of the insulation gap is therefore essential for quality control in manufacturing, commissioning and in service monitoring. Published research on particle motion in ac electric fields has shown that this rather complex process depends on numerous parameters, many of which remain unknown under practical conditions. This renders modelling, generalization of experimental data and practical application difficult. The scope of this paper therefore is to develop a unified description of particle motion which minimizes the number of controlling parameters, enables the comparison of experimental data and allows simple interpretation relations to be derived. This is achieved by making the controlling equations dimensionless with an appropriate choice of reference values and by using simplifying assumptions for the specific conditions prevailing in GIS. The resulting generalized description of the process can then be summarized in the form of 2D patterns (dynamic maps). Approximate scaling relations are derived between specific features of these patterns and particle-related parameters. A reference case is discussed in detail. The non-linear character of the equation of motion suggests that the particle motion may be a deterministic process with chaotic features. This is confirmed by a preliminary chaos-theoretical analysis of the process.

  18. 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

  19. Concentrating membrane proteins using asymmetric traps and AC electric fields.

    PubMed

    Cheetham, Matthew R; Bramble, Jonathan P; McMillan, Duncan G G; Krzeminski, Lukasz; Han, Xiaojun; Johnson, Benjamin R G; Bushby, Richard J; Olmsted, Peter D; Jeuken, Lars J C; Marritt, Sophie J; Butt, Julea N; Evans, Stephen D

    2011-05-01

    Membrane proteins are key components of the plasma membrane and are responsible for control of chemical ionic gradients, metabolite and nutrient transfer, and signal transduction between the interior of cells and the external environment. Of the genes in the human genome, 30% code for membrane proteins (Krogh et al. J. Mol. Biol.2001, 305, 567). Furthermore, many FDA-approved drugs target such proteins (Overington et al. Nat. Rev. Drug Discovery 2006, 5, 993). However, the structure-function relationships of these are notably sparse because of difficulties in their purification and handling outside of their membranous environment. Methods that permit the manipulation of membrane components while they are still in the membrane would find widespread application in separation, purification, and eventual structure-function determination of these species (Poo et al. Nature 1977, 265, 602). Here we show that asymmetrically patterned supported lipid bilayers in combination with AC electric fields can lead to efficient manipulation of charged components. We demonstrate the concentration and trapping of such components through the use of a "nested trap" and show that this method is capable of yielding an approximately 30-fold increase in the average protein concentration. Upon removal of the field, the material remains trapped for several hours as a result of topographically restricted diffusion. Our results indicate that this method can be used for concentrating and trapping charged membrane components while they are still within their membranous environment. We anticipate that our approach could find widespread application in the manipulation and study of membrane proteins. PMID:21476549

  20. In vitro cytotoxicity of Selol-loaded magnetic nanocapsules against neoplastic cell lines under AC magnetic field activation

    NASA Astrophysics Data System (ADS)

    Falqueiro, A. M.; Siqueira-Moura, M. P.; Jardim, D. R.; Primo, F. L.; Morais, P. C.; Mosiniewicz-Szablewska, E.; Suchocki, P.; Tedesco, A. C.

    2012-04-01

    The goals of this study are to evaluate invitro compatibility of magnetic nanomaterials and their therapeutic potential against cancer cells. Highly stable ionic magnetic fluid sample (maghemite, γ-Fe2O3) and Selol were incorporated into polymeric nanocapsules by nanoprecipitation method. The cytotoxic effect of Selol-loaded magnetic nanocapsules was assessed on murine melanoma (B16-F10) and oral squamous cell carcinoma (OSCC) cell lines following AC magnetic field application. The influence of different nanocapsules on cell viability was investigated by colorimetric MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. In the absence of AC magnetic field Selol-loaded magnetic nanocapsules, containing 100 µg/mL Selol plus 5 × 1012 particle/mL, showed antitumoral activity of about 50% on B16-F10 melanoma cells while OSCC carcinoma cells demonstrated drug resistance at all concentrations of Selol and magnetic fluid (range of 100-500 µg/mL Selol and 5 × 1012-2.5 × 1013 particle/mL). On the other hand, under AC applied fields (1 MHz and 40 Oe amplitude) B16-F10 cell viability was reduced down to 40.5% (±3.33) at the highest concentration of nanoencapsulated Selol. The major effect, however, was observed on OSCC cells since the cell viability drops down to about 33.3% (±0.38) under application of AC magnetic field. These findings clearly indicate that the Selol-loaded magnetic nanocapsules present different toxic effects on neoplastic cell lines. Further, the cytotoxic effect was maximized under AC magnetic field application on OSCC, which emphasizes the effectiveness of the magnetohyperthermia approach.

  1. Analyze and experiment on AC magnetic field's effect to fiber optic gyroscopes in compact stabilization control systems

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Mao, Yao; Tian, Jing; Li, Zhijun

    2015-10-01

    Fiber optic gyroscopes (FOG) are getting more and more attention in areas such as stabilization control systems as they are all solid state and have a wide bandwidth. In stabilization systems that require wide bandwidth control, motors are usually used as actuating mechanism for active disturbance restrain. Voice coil motors (VCMs) are usually used in compact stabilization systems that require large torque and fast response. However, AC magnetic field, which can affect the output of FOG due to Faraday effect, will be generated during operation of VCMs. The frequency range affected by the AC magnetic field to the FOG's output is the same as VCMs drive signal frequency range, which is also exactly the stabilization system's working range. Therefore the effect of the AC magnetic field to FOGs must be evaluated to verify the feasibility of a stable system design that uses both FOGs and VCMs. In this article, the basic structure and operating principle of stabilization system is introduced. The influence of AC magnetic field to FOG is theoretically analyzed. The magnetic field generated by VCMs is numerically simulated based on the theory deduction of the magnetic field near energized wires. To verify the influence of the VCM generated magnetic field to the FOGs in practical designs, a simplified random fiber coil model is built for it's hard to accurately test the exact polarize axis's twisting rate in a fiber coil. The influence to the FOG's output of different random coil model is simulated and the result shows a same trend that the influence of the VCM's magnetic field to the FOG is reduced as the distance between the VCM and the FOG increasing. The influence of a VCM to a FOG with the same parameters is experimentally tested. In the Fourier transformed FOG data the same frequency point as the VCM drive signal frequency can be read. The result fit simulated result that as the distance increases, the influence decreases. The amplitude of the frequency point is just

  2. 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.

  3. Absorption of ac fields in amorphous indium-oxide films

    SciTech Connect

    Ovadyahu, Z.

    2014-08-20

    Absorption data from applied ac fields in Anderson-localized amorphous indium-oxide (In{sub x}O) films are shown to be frequency and disorder dependent. The absorption shows a roll-off at a frequency which is much lower than the electron-electron scattering rate of the material when it is in the diffusive regime. This is interpreted as evidence for discreteness of the energy spectrum of the deeply localized regime. This is consistent with recent many-body localization scenarios. As the metal-insulator transition is approached, the absorption shifts to higher frequencies. Comparing with the previously obtained results on the crystalline version of indium-oxide (In{sub 2}O{sub 3−x}) implies a considerably higher inelastic electron-phonon scattering rate in the amorphous material. The range over which the absorption versus frequency decreases may indicate that a wide distribution of localization length is a common feature in these systems.

  4. Particle Agglomeration in Bipolar Barb Agglomerator Under AC Electric Field

    NASA Astrophysics Data System (ADS)

    Huang, Chao; Ma, Xiuqin; Sun, Youshan; Wang, Meiyan; Zhang, Changping; Lou, Yueya

    2015-04-01

    The development of an efficient technology for removing fine particles in flue gas is essential as the haze is becoming more and more serious. To improve agglomeration effectiveness of fine particles, a dual zone electric agglomeration device consisting of a charging chamber and an agglomeration chamber with bipolar barb electrodes was developed. The bipolar barb electric agglomerator with a polar distance of 200 mm demonstrates good agglomeration effectiveness for particles with a size less than 8.0 μm under applied AC electric field. An optimal condition for achieving better agglomeration effectiveness was found to be as follows: flue gas flow velocity of 3.00 m/s, particle concentration of 2.00 g/m3, output voltage of 35 kV and length of the barb of 16 mm. In addition, 4.0-6.0 μm particles have the best effectiveness with the variation of particle volume occupancy of -3.2. supported by the Key Technology R&D Program of Hebei, China (No. 13211207D)

  5. Use of amplitude vs offset seismic techniques to delineate subtle stratigraphic traps - Three field studies

    SciTech Connect

    Holton, J.E.; Lausten, C.D.; Blott, J.E. )

    1989-09-01

    Three stratigraphically trapped Wyoming fields which were previously held to be seismically invisible have been examined using amplitude vs. offset seismic techniques. This technology examines the seismic signature changes which take place as a function of source and receiver distance. Such signature changes are directly related to lithology and can be predicted in models and confirmed by the actual data. Two oil fields are located in the Powder River basin: Hartzog Draw and Coyote Creek. The third field, Dripping Rock, is a gas field in the Washakie basin of southwestern Wyoming. The fields produce from sands of the Shannon, Dakota, and Almond formations, respectively. All three fields lack significant velocity differences between the reservoir and trap facies. This results in an inability to delineate the sands using conventional seismic techniques. Amplitude vs. offset techniques, however, present easily identifiable anomalies which reliably delineate the extent of the reservoir sands in each of the cases. Amplitude vs. offset technology has been used successfully in numerous exploratory and development situations throughout the Rocky Mountains and other areas of the US and Canada. It has proven to be a very reliable technique to explore subtle stratigraphic plays which remain relatively immature in mature basins.

  6. Bordered surfaces, off-shell amplitudes, sewing, and string field theory

    NASA Astrophysics Data System (ADS)

    Carlip, Steven

    1989-04-01

    These lectures will deal with the current status of the sewing problem. The rationale for this approach is that any nonperturbative string theory must reproduce the Polyakov path integral as a perturbation series. If our experience in ordinary field theory is a guide, and admittedly it may not be, the terms in such a perturbation series, like Feynman diagrams, are likely to be built up from simple vertices and propagators, which can themselves be represented as (off-shell) Polyakov amplitudes. Hence an understanding of how to put together simple components into more complicated world sheet amplitudes is likely to give us much-needed information about the structure of nonperturbative string theory. To understand sewing, we must first understand the building blocks, off-shell Polyakov amplitudes. This is the subject of my first lecture. Next, we will explore the sewing of conformal field theories at a fixed conformal structure, that is, the reconstruction of correlation functions for a fixed surface (Sigma) from those on a pair of surfaces (Sigma)(sub 1) and (Sigma)(sub 2) obtained by cutting (Sigma) along a closed curve. We will then look at the problem of sewing amplitudes, integrals of correlation functions over moduli space. This will necessitate an understanding of how to build the moduli space of a complicated surface from simpler moduli spaces. Finally, we will briefly examine vertices and string field theories.

  7. Bordered surfaces, off-shell amplitudes, sewing, and string field theory

    SciTech Connect

    Carlip, S.

    1989-04-01

    These lectures will deal with the current status of the sewing problem. The rationale for this approach is that any nonperturbative string theory must reproduce the Polyakov path integral as a perturbation series. If our experience in ordinary field theory is a guide --- and admittedly it may not be --- the terms in such a perturbation series, like Feynman diagrams, are likely to be built up from simple ''vertices'' and ''propagators,'' which can themselves be represented as (off-shell) Polyakov amplitudes. Hence an understanding of how to put together simple components into more complicated world sheet amplitudes is likely to give us much-needed information about the structure of nonperturbative string theory. To understand sewing, we must first understand the building blocks, off-shell Polyakov amplitudes. This is the subject of my first lecture. Next, we will explore the sewing of conformal field theories at a fixed conformal structure, that is, the reconstruction of correlation functions for a fixed surface /Sigma/ from those on a pair of surfaces /Sigma//sub 1/ and /Sigma//sub 2/ obtained by cutting /Sigma/ along a closed curve. We will then look at the problem of sewing amplitudes, integrals of correlation functions over moduli space. This will necessitate an understanding of how to build the moduli space of a complicated surface from simpler moduli spaces. Finally, we will briefly examine vertices and string field theories. 48 refs., 10 figs.

  8. Absorption and Attenuation Coefficients Using the WET Labs ac-s in the Mid-Atlantic Bight: Field Measurements and Data Analysis

    NASA Technical Reports Server (NTRS)

    Ohi, Nobuaki; Makinen, Carla P.; Mitchell, Richard; Moisan, Tiffany A.

    2008-01-01

    Ocean color algorithms are based on the parameterization of apparent optical properties as a function of inherent optical properties. WET Labs underwater absorption and attenuation meters (ac-9 and ac-s) measure both the spectral beam attenuation [c (lambda)] and absorption coefficient [a (lambda)]. The ac-s reports in a continuous range of 390-750 nm with a band pass of 4 nm, totaling approximately 83 distinct wavelengths, while the ac-9 reports at 9 wavelengths. We performed the ac-s field measurements at nine stations in the Mid-Atlantic Bight from water calibrations to data analysis. Onboard the ship, the ac-s was calibrated daily using Milli Q-water. Corrections for the in situ temperature and salinity effects on optical properties of water were applied. Corrections for incomplete recovery of the scattered light in the ac-s absorption tube were performed. The fine scale of spectral and vertical distributions of c (lambda) and a (lambda) were described from the ac-s. The significant relationships between a (674) and that of spectrophotometric analysis and chlorophyll a concentration of discrete water samples were observed.

  9. Edge pinch instability of liquid metal sheet in a transverse high-frequency ac magnetic field.

    PubMed

    Priede, Jānis; Etay, Jacqueline; Fautrelle, Yves

    2006-06-01

    We analyze the linear stability of the edge of a thin liquid metal layer subject to a transverse high-frequency ac magnetic field. The layer is treated as a perfectly conducting liquid sheet that allows us to solve the problem analytically for both a semi-infinite geometry with a straight edge and a thin disk of finite radius. It is shown that the long-wave perturbations of a straight edge are monotonically unstable when the wave number exceeds the critical value k(c) = F0/(gamma l0), which is determined by the linear density of the electromagnetic force F0 acting on the edge, the surface tension gamma, and the effective arclength of edge thickness l0. Perturbations with wavelength shorter than critical are stabilized by the surface tension, whereas the growth rate of long-wave perturbations reduces as similar to k for k --> 0. Thus, there is the fastest growing perturbation with the wave number k max = 2/3 k(c). When the layer is arranged vertically, long-wave perturbations are stabilized by the gravity, and the critical perturbation is characterized by the capillary wave number k(c) = square root of (g rho/gamma), where g is the acceleration due to gravity and rho is the density of metal. In this case, the critical linear density of electromagnetic force is F(0,c) = 2k(c)l0 gamma, which corresponds to the critical current amplitude I(0,c) = 4 square root of (pi k(c) l0L gamma/mu 0) when the magnetic field is generated by a straight wire at the distance L directly above the edge. By applying the general approach developed for the semi-infinite sheet, we find that a circular disk of radius R0 placed in a transverse uniform high-frequency ac magnetic field with the induction amplitude B0 becomes linearly unstable with respect to exponentially growing perturbation with the azimuthal wave number m = 2 when the magnetic Bond number exceeds Bm(c) = B(0)2 R(0)2 / (2 mu 0 l0 gamma) = 3 pi. For Bm > Bm(c), the wave number of the fastest growing perturbation is m(max) = [2

  10. The magnetisation profiles and ac magnetisation losses in a single layer YBCO thin film caused by travelling magnetic field waves

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Coombs, Timothy

    2015-05-01

    This paper studies the magnetisation and ac magnetisation losses caused by a travelling magnetic wave on a single-layer YBCO thin film. This work provides thorough investigations on how the critical magnetic field gradient has been changed by the application of a travelling wave. Several conditions were studied such as zero-field cooling (ZFC), field cooling (FC) and a delta-shaped trapped field. It was found that the travelling wave tends to attenuate the existing critical magnetic field gradients in all these conditions. This interesting magnetic behaviour can be well predicted by the finite element (FEM) software with the E-J power law and Maxwell’s equations. The numerical simulations show that the existing critical current density has been compromised after applying the travelling wave. The magnetisation profile caused by the travelling wave is very different from the standing wave, while the magnetisation based on the standing wave can be interpreted by the Bean model and constant current density assumption. Based on the numerical method, which has reliability that has been solidly proven in the study, we have extended the study to the ac magnetisation losses. Comparisons were made between the travelling wave and the standing wave for this specific YBCO sample. It was found that by applying the magnetic wave of the same amplitude, the ac magnetisation loss caused by the travelling wave is about 1/3 of that caused by the standing wave. These results are helpful in understanding the general magnetism problems and ac magnetisation loss in the travelling magnetic wave conditions such as inside a high temperature superconducting (HTS) rotating machine, etc.

  11. Patterns driven by combined ac and dc electric fields in nematic liquid crystals.

    PubMed

    Krekhov, Alexei; Decker, Werner; Pesch, Werner; Eber, Nándor; Salamon, Péter; Fekete, Balázs; Buka, Agnes

    2014-05-01

    The effect of superimposed ac and dc electric fields on the formation of electroconvection and flexoelectric patterns in nematic liquid crystals was studied. For selected ac frequencies, an extended standard model of the electrohydrodynamic instabilities was used to characterize the onset of pattern formation in the two-dimensional parameter space of the magnitudes of the ac and dc electric field components. Numerical as well as approximate analytical calculations demonstrate that depending on the type of patterns and on the ac frequency, the combined action of ac and dc fields may either enhance or suppress the formation of patterns. The theoretical predictions are qualitatively confirmed by experiments in most cases. Some discrepancies, however, seem to indicate the need to extend the theoretical description. PMID:25353815

  12. Direction detectable static magnetic field imaging by frequency-modulated magnetic force microscopy with an AC magnetic field driven soft magnetic tip

    NASA Astrophysics Data System (ADS)

    Saito, Hitoshi; Ito, Ryoichi; Egawa, Genta; Li, Zhenghua; Yoshimura, Satoru

    2011-04-01

    Direction detectable static magnetic field imaging, which directly distinguishes the up and down direction of static perpendicular magnetic field from a sample surface and the polarity of magnetic charges on the surface, was demonstrated for CoCrPt-SiO2 perpendicular magnetic recording media based on a frequency-modulated magnetic force microscopy (FM-MFM), which uses a frequency modulation of the cantilever oscillation induced by an alternating force from the tip-sample magnetic interaction. In this study, to generate the alternating force, we used a NiFe soft magnetic tip driven by the ac magnetic field of a soft ferrite core and imaged the direction and the amplitude of the static magnetic field from the recorded bits. This method enables measurement of the static magnetic field near a sample surface, which is masked by short range forces of the surface. The present method will be effective in analyzing the microscopic magnetic domain structure of hard magnetic samples.

  13. Large amplitude free vibrations of Timoshenko beams at higher modes using coupled displacement field method

    NASA Astrophysics Data System (ADS)

    Krishna Bhaskar, K.; Meera Saheb, K.

    2015-12-01

    A simple but accurate continuum solution for the shear flexible beam problem using the energy method involves in assuming suitable single term admissible functions for the lateral displacement and total rotation. This leads to two non-linear temporal differential equations in terms of the lateral displacement and the total rotation and are difficult, if not impossible, to solve to obtain the large amplitude fundamental frequencies of beams as a function of the amplitude and slenderness ratios of the vibrating beam. This situation can be avoided if one uses the concept of coupled displacement field where in the fields for lateral displacement and the total rotation are coupled through the static equilibrium equation. In this paper the lateral displacement field is assumed and the field for the total rotation is evaluated through the coupling equation. This approach leads to only one undetermined coefficient which can easily be used in the principle of conservation of total energy of the vibrating beam at a given time, neglecting damping. Finally, through a number of algebraic manipulations, one gets a nonlinear equation of Duffing type which can be solved using any standard method. To demonstrate the simplicity of the method discussed above the problem of large amplitude free vibrations of a uniform shear flexible hinged beam at higher modes with ends immovable to move axially has been solved. The numerical results obtained from the present formulation are in very good agreement with those obtained through finite element and other continuum methods for the fundamental mode, thus demonstrating the efficacy of the proposed method. Also some interesting observations are made with variation of frequency Vs amplitude at different modes.

  14. Dynamic Resistance of YBCO-Coated Conductors in Applied AC Fields with DC Transport Currents and DC Background Fields

    SciTech Connect

    Duckworth, Robert C; Zhang, Yifei; Ha, Tam T; Gouge, Michael J

    2011-01-01

    In order to predict heat loads in future saturable core fault-current-limiting devices due to ac fringing fields, dynamic resistance in YBCO-coated conductors was measured at 77 K in peak ac fields up to 25 mT at 60 Hz and in dc fields up to 1 T. With the sample orientation set such that the conductor face was either parallel or perpendicular to the ac and dc applied fields, the dynamic resistance was measured at different fractions of the critical current to determine the relationship between the dc transport current and the applied fields. With respect to field orientation, the dynamic resistance for ac fields that were perpendicular to the conductor face was significantly higher than when the ac fields were parallel to the conductor face. It was also observed that the dynamic resistance: (1) increased with increasing fraction of the dc transport current to the critical current, (2) was proportional to the inverse of the critical current, and (3) demonstrated a linear dependence with the applied ac field once a threshold field was exceeded. This functional behavior was consistent with a critical state model for the dynamic resistance, but discrepancies in absolute value of the dynamic resistance suggested that further theoretical development is needed.

  15. Frequency characteristics of field electron emission from long carbon nanofilaments/nanotubes in a weak AC electric field

    NASA Astrophysics Data System (ADS)

    Izrael'yants, K. R.; Orlov, A. P.; Musatov, A. L.; Blagov, E. V.

    2016-05-01

    Frequency characteristics of field electron emission from long carbon nanofilaments/nanotubes in strong dc and weak ac electric fields have been investigated. A series of narrow peaks with a quality factor of up to 1100 has been discovered in the frequency range of hundreds of kilohertz. The analysis has shown that these peaks are probably associated with mechanical oscillations of the carbon nanofilaments/nanotubes driven by the ac electric field.

  16. Simultaneous ac and dc magnetic field measurements in residential areas: Implications for resonance theories of biological effects

    SciTech Connect

    Wong, P.S.; Sastre, A.

    1995-10-01

    The goal of this study was to obtain data that could be used to evaluate the applicability of ``resonance`` theories of biological effects in residential settings. The authors first describe a measurement system which allows the study of ac and dc magnetic fields simultaneously in space and in time. Sample measurements were taken near two power lines, two objects and in two residential homes. The results show that the earth`s (dc) magnetic field was unaffected near power lines. The compass orientation of the power line influenced the relative values of the ac components parallel and perpendicular to the dc field. The electric heating system greatly affected the ac field levels in the home, causing the levels to increase from less than 1 mG to a maximum of 7.5 mG during heating. The magnitudes of the dc field in the two homes varied from about 380 to 650 mG, with the larger variations near metallic or magnetic objects such as the refrigerator or a metallic air duct. The earth`s field was elevated above its natural level within a distance of 8 feet from a subcompact passenger car, e.g., the level changed from about 540 to 1,100 mG beside the headlight. A steel chair changed the earth`s field by up to 60 mG within a distance of one foot. These results suggest that some of the narrow ``resonances`` described in laboratory studies may be difficult to observe against the variations in do field amplitude and direction resulting from the presence of everyday metallic objects.

  17. Amplitude Metrics for Field Retrieval with Hard-Edged and Uniformly Illuminated Apertures. Section 7.2

    NASA Technical Reports Server (NTRS)

    Thurman, Samuel T.; DeRosa, Ryan; Fienup, James R.

    2009-01-01

    In field retrieval, the amplitude and phase of the generalized pupil function for an optical system are estimated from multiple defocused measurements of the system point-spread function. A baseline field reconstruction algorithm optimizing a data consistency metric is described. Additionally, two metrics specifically designed to incorporate a priori knowledge about pupil amplitude for hard-edged and uniformly illuminated aperture systems are given. Experimental results demonstrate the benefit of using these amplitude metrics in addition to the baseline metric

  18. Decay Characteristics of Levitation Force of YBCO Bulk Exposed to AC Magnetic Field above NdFeB Guideway

    NASA Astrophysics Data System (ADS)

    Liu, Minxian; Lu, Yiyun; Wang, Suyu; Ma, Guangtong

    2011-04-01

    The superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the nonuniformity of the magnetic field along the movement direction above the NdFeB guideway is inevitable due to the assembly error and inhomogeneity of the material property of the NdFeB magnet. So it is required to study the characteristics of levitation force of the bulks affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we will study the characteristics of the levitation force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet is used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experimental results, it has found that the levitation force is decreasing with the application of the AC external magnetic field, and the decay increasing with the amplitude of the applied magnetic field and is almost independent of the frequency.

  19. C/NOFS Observations of AC Electric Field Fields Associated with Equatorial Spread-F

    NASA Technical Reports Server (NTRS)

    Pfaff, R.; Liebrecht, C.

    2009-01-01

    The Vector Electric Field Investigation (VEFI) on the C/NOFS equatorial satellite provides a unique data set in which to acquire detailed knowledge of irregularities associated with the equatorial ionosphere and in particular with spread-F depletions. We present vector AC electric field observations, primarily gathered within the ELF band (1 Hz to 250 Hz) on C/NOFS that address a variety of key questions regarding how plasma irregularities, from meter to kilometer scales, are created and evolve. The data will be used to explore the anisotropy/isotropy of the waves, their wavelength and phase velocity, as well as their spectral distributions. When analyzed in conjunction with the driving DC electric fields and detailed plasma number density measurements, the combined data reveal important information concerning the instability mechanisms themselves. We also present high resolution, vector measurements of intense lower hybrid waves that have been detected on numerous occasions by the VEFI burst memory VLF electric field channels.

  20. Measurement of a microwave field amplitude beyond the standard quantum limit

    NASA Astrophysics Data System (ADS)

    Penasa, M.; Gerlich, S.; Rybarczyk, T.; Métillon, V.; Brune, M.; Raimond, J. M.; Haroche, S.; Davidovich, L.; Dotsenko, I.

    2016-08-01

    We report a quantum measurement beyond the standard quantum limit (SQL) for the amplitude of a small displacement acting on a cavity field. This measurement uses as a resource an entangled mesoscopic state, prepared by the resonant interaction of a circular Rydberg atom with a field stored in a superconducting cavity. We analyze the measurement process in terms of Fisher information and prove that it is, in principle, optimal. The experimental precision achieved, 2.4 dB below the SQL, is well understood in terms of experimental imperfections. This method could be transposed to other systems, particularly to circuit QED, for the precise measurement of weak forces acting on oscillators.

  1. Nonlinear magnetization relaxation of superparamagnetic nanoparticles in superimposed ac and dc magnetic bias fields

    NASA Astrophysics Data System (ADS)

    Titov, Serguey V.; Déjardin, Pierre-Michel; El Mrabti, Halim; Kalmykov, Yuri P.

    2010-09-01

    The nonlinear ac response of the magnetization M(t) of a uniaxially anisotropic superparamagnetic nanoparticle subjected to both ac and dc bias magnetic fields of arbitrary strengths and orientations is determined by averaging Gilbert’s equation augmented by a random field with Gaussian white-noise properties in order to calculate exactly the relevant statistical averages. It is shown that the magnetization dynamics of the uniaxial particle driven by a strong ac field applied at an angle to the easy axis of the particle (so that the axial symmetry is broken) alters drastically leading to different nonlinear effects due to coupling of the thermally activated magnetization reversal mode with the precessional modes of M(t) via the driving ac field.

  2. 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.

  3. Strong-field cyclotron scattering. I - Scattering amplitudes and natural line width

    NASA Astrophysics Data System (ADS)

    Graziani, Carlo

    1993-07-01

    The introduction of resonance line width into the QED cyclotron scattering amplitudes is considered. It is shown that the width arises from loop corrections to the electron propagator, which also bring about shifts in the Landau energy levels. A formalism is developed that allows the dressed electron propagator to be derived. It is shown that the states of Herold et al. (1982) and of Sokolov and Ternov (1968), which diagonalize the component of the magnetic moment operator parallel to the external magnetic field, are appropriate for calculation of the scattering amplitudes, whereas the states of Johnson and Lippmann (1949) are not. In addition, it is shown that the Breit-Wigner broadening approximation E tends to E - i(Gamma)/2 is consistent with the perturbation-theoretic order of the calculation, if the former basis states are chosen, but not the latter.

  4. Inhomogeneous superconductor in an a.c. field: Application to the pseudogap region

    SciTech Connect

    Ovchinnikov, Yu.N.; Kresin, V.Z.

    2002-02-01

    The behavior of an inhomogeneous superconductor in an external a.c. field is studied. General equations describing the a.c. response are formulated. Special attention is paid to the case of a layered conductor containing superconducting ''islands''. A system of this type displays ''pseudogap'' properties. The surface impedance Z is evaluated. It is shown that the ReZ {ne} |ImZ| and their difference {Delta}Z {proportional_to} {omega}{sup -1/2}, {omega} is the frequency of the a.c. field.

  5. Effect of Interfacial Resistance on AC Loss as a Function of Applied AC Field in YBCO Filamentary Conductors

    SciTech Connect

    Duckworth, Robert C; List III, Frederick Alyious; Zhang, Yifei

    2009-01-01

    To reduce ac loss in Y-Ba-Cu-O (YBCO) coated conductors while maintaining current sharing between filaments, an attempt was made to introduce an interfacial resistance between the YBCO filaments and a continuous silver cap layer. The YBCO filaments were produced via laser scribing of MOCVD YBCO films deposited on standard Ion Beam Assisted Deposition (IBAD) templates. After laser scribing, the filaments were exposed to air at room temperature to degrade the YBCO surface. A three micron thick silver cap layer was then and each sample was oxygen annealed at different temperature to produce different interface resistance at the interface between the silver and YBCO. Measurements of the ac loss was measured as a function of applied perpendicular field and frequency revealed a correlation between the reduction in coupling loss and the oxygen annealing temperature.

  6. Modeling of finite-amplitude sound beams: second order fields generated by a parametric loudspeaker.

    PubMed

    Yang, Jun; Sha, Kan; Gan, Woon-Seng; Tian, Jing

    2005-04-01

    The nonlinear interaction of sound waves in air has been applied to sound reproduction for audio applications. A directional audible sound can be generated by amplitude-modulating the ultrasound carrier with an audio signal, then transmitting it from a parametric loudspeaker. This brings the need of a computationally efficient model to describe the propagation of finite-amplitude sound beams for the system design and optimization. A quasilinear analytical solution capable of fast numerical evaluation is presented for the second-order fields of the sum-, difference-frequency and second harmonic components. It is based on a virtual-complex-source approach, wherein the source field is treated as an aggregation of a set of complex virtual sources located in complex distance, then the corresponding fundamental sound field is reduced to the computation of sums of simple functions by exploiting the integrability of Gaussian functions. By this result, the five-dimensional integral expressions for the second-order sound fields are simplified to one-dimensional integrals. Furthermore, a substantial analytical reduction to sums of single integrals also is derived for an arbitrary source distribution when the basis functions are expressible as a sum of products of trigonometric functions. The validity of the proposed method is confirmed by a comparison of numerical results with experimental data previously published for the rectangular ultrasonic transducer. PMID:16060510

  7. Magnetic flux penetration into twisted multifilamentary coated superconductors subjected to ac transverse magnetic fields

    NASA Astrophysics Data System (ADS)

    Amemiya, Naoyuki; Sato, Susumu; Ito, Takeshi

    2006-12-01

    ac losses in superconductors are generated by the magnetic flux and current penetration into them. To reveal the magnetic flux and current penetration processes in twisted multifilamentary coated superconductors in which the thin superconductor layer is subdivided into filaments and then twisted as a whole for ac loss reduction, a theoretical model for electromagnetic field analysis was developed based on the power law E-J (electric-field-current-density) characteristic for the superconductor and a thin strip approximation of the conductor. The developed theoretical model was implemented into a numerical code using the finite element method to calculate and visualize the current and magnetic flux distributions. The magnetization losses in twisted multifilamentary coated superconductors exposed to ac transverse magnetic fields were calculated from the temporal evolutions of the current distribution to demonstrate the effect of the twisted multifilamentary architecture on ac loss reduction.

  8. An energy stable, hexagonal finite difference scheme for the 2D phase field crystal amplitude equations

    NASA Astrophysics Data System (ADS)

    Guan, Zhen; Heinonen, Vili; Lowengrub, John; Wang, Cheng; Wise, Steven M.

    2016-09-01

    In this paper we construct an energy stable finite difference scheme for the amplitude expansion equations for the two-dimensional phase field crystal (PFC) model. The equations are formulated in a periodic hexagonal domain with respect to the reciprocal lattice vectors to achieve a provably unconditionally energy stable and solvable scheme. To our knowledge, this is the first such energy stable scheme for the PFC amplitude equations. The convexity of each part in the amplitude equations is analyzed, in both the semi-discrete and fully-discrete cases. Energy stability is based on a careful convexity analysis for the energy (in both the spatially continuous and discrete cases). As a result, unique solvability and unconditional energy stability are available for the resulting scheme. Moreover, we show that the scheme is point-wise stable for any time and space step sizes. An efficient multigrid solver is devised to solve the scheme, and a few numerical experiments are presented, including grain rotation and shrinkage and grain growth studies, as examples of the strength and robustness of the proposed scheme and solver.

  9. Calorimetric method of ac loss measurement in a rotating magnetic field.

    PubMed

    Ghoshal, P K; Coombs, T A; Campbell, A M

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-T(c) superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines. PMID:20687748

  10. Calorimetric method of ac loss measurement in a rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-Tc superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  11. Calorimetric method of ac loss measurement in a rotating magnetic field

    SciTech Connect

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-15

    A method is described for calorimetric ac-loss measurements of high-T{sub c} superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  12. Spectroscopic method for measuring plasma magnetic fields having arbitrary distributions of direction and amplitude.

    PubMed

    Stambulchik, E; Tsigutkin, K; Maron, Y

    2007-06-01

    An approach for measurements of magnetic fields, based on the comparison of the magnetic-field-induced contributions to the line shapes of different fine-structure components of an atomic multiplet, is proposed and experimentally demonstrated. Contrary to the methods based on detecting an anisotropy in either the emitted radiation or in the dispersion properties of the medium, the present method is applicable when the field direction or amplitude vary significantly in the region viewed or during the time of observation. The technique can be used even when the line shapes are Stark or Doppler dominated. It has potential applications in laser-matter interactions, plasmas driven by high-current pulses, and astrophysics. PMID:17677852

  13. Influence of size distribution and field amplitude on specific loss power

    NASA Astrophysics Data System (ADS)

    Boskovic, M.; Goya, G. F.; Vranjes-Djuric, S.; Jovic, N.; Jancar, B.; Antic, B.

    2015-03-01

    Herein we present the results of specific loss power (SLP) analysis of polydisperse water based ferrofluids, Fe3O4/PEG200 and Fe3O4/PEG6000, with average Fe3O4 particle size of 9 nm and 11 nm, respectively. Specific loss power was measured in alternating magnetic field of various amplitudes and at fixed frequency of 580.5 kHz. Maximum SLP values acquired were 195 W/g for Fe3O4/PEG200 and 60 W/g for Fe3O4/PEG6000 samples. The samples were labeled as superparamagnetic by magnetization measurements, but SLP field dependence showed deviation from the behavior predicted by the commonly employed linear response theory. The scope of this theory for both samples with wide particle size distribution is discussed. Deviation from the expected behavior is explained by referring to polydisperse nature of the samples and field dependent relaxation rates.

  14. THE SOLAR WIND AND INTERPLANETARY FIELD DURING VERY LOW AMPLITUDE SUNSPOT CYCLES

    SciTech Connect

    Wang, Y.-M.; Sheeley, N. R. Jr. E-mail: neil.sheeley@nrl.navy.mil

    2013-02-10

    Cosmogenic isotope records indicate that a solar-cycle modulation persists through extended periods of very low sunspot activity. One immediate implication is that the photospheric field during such grand minima did not consist entirely of ephemeral regions, which produce a negligible amount of open magnetic flux, but continued to have a large-scale component originating from active regions. Present-day solar and heliospheric observations show that the solar wind mass flux and proton density at the coronal base scale almost linearly with the footpoint field strength, whereas the wind speed at Earth is uncorrelated with the latter. Thus a factor of {approx}4-7 reduction in the total open flux, as deduced from reconstructions of the interplanetary magnetic field (IMF) during the Maunder Minimum, would lead to a similar decrease in the solar wind densities, while leaving the wind speeds largely unchanged. We also demonstrate that a decrease in the strengths of the largest active regions during grand minima will reduce the amplitude of the Sun's equatorial dipole relative to the axial component, causing the IMF strength to peak near sunspot minimum rather than near sunspot maximum, a result that is consistent with the phase shift observed in the {sup 10}Be record during the Maunder Minimum. Finally, we discuss the origin of the 5 yr periodicity sometimes present in the cosmogenic isotope data during low and medium amplitude cycles.

  15. Electric field in an AC dielectric barrier discharge overlapped with a nanosecond pulse discharge

    NASA Astrophysics Data System (ADS)

    Goldberg, Benjamin M.; Shkurenkov, Ivan; Adamovich, Igor V.; Lempert, Walter R.

    2016-08-01

    The effect of ns discharge pulses on the AC barrier discharge in hydrogen in plane-to-plane geometry is studied using time-resolved measurements of the electric field in the plasma. The AC discharge was operated at a pressure of 300 Torr at frequencies of 500 and 1750 Hz, with ns pulses generated when the AC voltage was near zero. The electric field vector is measured by ps four-wave mixing technique, which generates coherent IR signal proportional to the square of electric field. Absolute calibration was done using an electrostatic (sub-breakdown) field applied to the discharge electrodes, when no plasma was generated. The results are compared with one-dimensional kinetic modeling of the AC discharge and the nanosecond pulse discharge, predicting behavior of both individual micro-discharges and their cumulative effect on the electric field distribution in the electrode gap, using stochastic averaging based on the experimental micro-discharge temporal probability distribution during the AC period. Time evolution of the electric field in the AC discharge without ns pulses, controlled by a superposition of random micro-discharges, exhibits a nearly ‘flat top’ distribution with the maximum near breakdown threshold, reproduced quite well by kinetic modeling. Adding ns pulse discharges on top of the AC voltage waveform changes the AC discharge behavior in a dramatic way, inducing transition from random micro-discharges to a more regular, near-1D discharge. In this case, reproducible volumetric AC breakdown is produced at a well-defined moment after each ns pulse discharge. During the reproducible AC breakdown, the electric field in the plasma exhibits a sudden drop, which coincides in time with a well-defined current pulse. This trend is also predicted by the kinetic model. Analysis of kinetic modeling predictions shows that this effect is caused by large-volume ionization and neutralization of surface charges on the dielectrics by ns discharge pulses. The present

  16. Study of effect of AC and DC magnetic fields on growth of Pisum sativum seeds

    NASA Astrophysics Data System (ADS)

    Bahar, Mahmood; Yasaie Mehrjardi, Yasaman; Sojoodi, Jaleh; Bayani, Hosien; Kazem Salem, Mohammad

    2013-08-01

    This paper concentrates on the effect of the AC and DC magnetic fields on plant growth. The effect of AC magnetic field with intensities of 2.25, 1.66 and 1.49 mT and DC magnetic field with intensities of 3.6, 2.41 and 2.05 mT in exposure durations of 2, 4, 6, 8, 10 and 12 min on two groups of dry and wet Pisum sativum seedlings was studied. In each experiment 10 seeds were used; the experiments were repeated three times for each group and there was a sham exposed group for comparison purposes. The light cycle was 12 h light/12 h darkness and the temperature was 25 ± 1° C. The index of growth is considered to be the root and stem elongation on the sixth day. It was observed that AC magnetic field has a positive effect on the growth in all durations and intensities. Moreover, it is highlighted that during the experiments, the mean growth of dry seedlings significantly increased by a factor of 11 in AC magnetic field with the lowest intensity of 1.49 mT (p < 0.05). It was also shown that AC magnetic fields had a more positive effect on the growth of plants in comparison to DC magnetic fields.

  17. Acquisition of Cry1Ac Protein by Non-Target Arthropods in Bt Soybean Fields

    PubMed Central

    Yu, Huilin; Romeis, Jörg; Li, Yunhe; Li, Xiangju; Wu, Kongming

    2014-01-01

    Soybean tissue and arthropods were collected in Bt soybean fields in China at different times during the growing season to investigate the exposure of arthropods to the plant-produced Cry1Ac toxin and the transmission of the toxin within the food web. Samples from 52 arthropod species/taxa belonging to 42 families in 10 orders were analysed for their Cry1Ac content using enzyme-linked immunosorbent assay (ELISA). Among the 22 species/taxa for which three samples were analysed, toxin concentration was highest in the grasshopper Atractomorpha sinensis and represented about 50% of the concentration in soybean leaves. Other species/taxa did not contain detectable toxin or contained a concentration that was between 1 and 10% of that detected in leaves. These Cry1Ac-positive arthropods included a number of mesophyll-feeding Hemiptera, a cicadellid, a curculionid beetle and, among the predators, a thomisid spider and an unidentified predatory bug belonging to the Anthocoridae. Within an arthropod species/taxon, the Cry1Ac content sometimes varied between life stages (nymphs/larvae vs. adults) and sampling dates (before, during, and after flowering). Our study is the first to provide information on Cry1Ac-expression levels in soybean plants and Cry1Ac concentrations in non-target arthropods in Chinese soybean fields. The data will be useful for assessing the risk of non-target arthropod exposure to Cry1Ac in soybean. PMID:25110881

  18. Achieving High Performance in AC-Field Driven Organic Light Sources

    PubMed Central

    Xu, Junwei; Carroll, David L.; Smith, Gregory M.; Dun, Chaochao; Cui, Yue

    2016-01-01

    Charge balance in organic light emitting structures is essential to simultaneously achieving high brightness and high efficiency. In DC-driven organic light emitting devices (OLEDs), this is relatively straight forward. However, in the newly emerging, capacitive, field-activated AC-driven organic devices, charge balance can be a challenge. In this work we introduce the concept of gating the compensation charge in AC-driven organic devices and demonstrate that this can result in exceptional increases in device performance. To do this we replace the insulator layer in a typical field-activated organic light emitting device with a nanostructured, wide band gap semiconductor layer. This layer acts as a gate between the emitter layer and the voltage contact. Time resolved device characterization shows that, at high-frequencies (over 40 kHz), the semiconductor layer allows for charge accumulation in the forward bias, light generating part of the AC cycle and charge compensation in the negative, quiescent part of the AC cycle. Such gated AC organic devices can achieve a non-output coupled luminance of 25,900 cd/m2 with power efficiencies that exceed both the insulator-based AC devices and OLEDs using the same emitters. This work clearly demonstrates that by realizing balanced management of charge, AC-driven organic light emitting devices may well be able to rival today’s OLEDs in performance. PMID:27063414

  19. Achieving High Performance in AC-Field Driven Organic Light Sources.

    PubMed

    Xu, Junwei; Carroll, David L; Smith, Gregory M; Dun, Chaochao; Cui, Yue

    2016-01-01

    Charge balance in organic light emitting structures is essential to simultaneously achieving high brightness and high efficiency. In DC-driven organic light emitting devices (OLEDs), this is relatively straight forward. However, in the newly emerging, capacitive, field-activated AC-driven organic devices, charge balance can be a challenge. In this work we introduce the concept of gating the compensation charge in AC-driven organic devices and demonstrate that this can result in exceptional increases in device performance. To do this we replace the insulator layer in a typical field-activated organic light emitting device with a nanostructured, wide band gap semiconductor layer. This layer acts as a gate between the emitter layer and the voltage contact. Time resolved device characterization shows that, at high-frequencies (over 40 kHz), the semiconductor layer allows for charge accumulation in the forward bias, light generating part of the AC cycle and charge compensation in the negative, quiescent part of the AC cycle. Such gated AC organic devices can achieve a non-output coupled luminance of 25,900 cd/m(2) with power efficiencies that exceed both the insulator-based AC devices and OLEDs using the same emitters. This work clearly demonstrates that by realizing balanced management of charge, AC-driven organic light emitting devices may well be able to rival today's OLEDs in performance. PMID:27063414

  20. Achieving High Performance in AC-Field Driven Organic Light Sources

    NASA Astrophysics Data System (ADS)

    Xu, Junwei; Carroll, David L.; Smith, Gregory M.; Dun, Chaochao; Cui, Yue

    2016-04-01

    Charge balance in organic light emitting structures is essential to simultaneously achieving high brightness and high efficiency. In DC-driven organic light emitting devices (OLEDs), this is relatively straight forward. However, in the newly emerging, capacitive, field-activated AC-driven organic devices, charge balance can be a challenge. In this work we introduce the concept of gating the compensation charge in AC-driven organic devices and demonstrate that this can result in exceptional increases in device performance. To do this we replace the insulator layer in a typical field-activated organic light emitting device with a nanostructured, wide band gap semiconductor layer. This layer acts as a gate between the emitter layer and the voltage contact. Time resolved device characterization shows that, at high-frequencies (over 40 kHz), the semiconductor layer allows for charge accumulation in the forward bias, light generating part of the AC cycle and charge compensation in the negative, quiescent part of the AC cycle. Such gated AC organic devices can achieve a non-output coupled luminance of 25,900 cd/m2 with power efficiencies that exceed both the insulator-based AC devices and OLEDs using the same emitters. This work clearly demonstrates that by realizing balanced management of charge, AC-driven organic light emitting devices may well be able to rival today’s OLEDs in performance.

  1. Acquisition of Cry1Ac protein by non-target arthropods in Bt soybean fields.

    PubMed

    Yu, Huilin; Romeis, Jörg; Li, Yunhe; Li, Xiangju; Wu, Kongming

    2014-01-01

    Soybean tissue and arthropods were collected in Bt soybean fields in China at different times during the growing season to investigate the exposure of arthropods to the plant-produced Cry1Ac toxin and the transmission of the toxin within the food web. Samples from 52 arthropod species/taxa belonging to 42 families in 10 orders were analysed for their Cry1Ac content using enzyme-linked immunosorbent assay (ELISA). Among the 22 species/taxa for which three samples were analysed, toxin concentration was highest in the grasshopper Atractomorpha sinensis and represented about 50% of the concentration in soybean leaves. Other species/taxa did not contain detectable toxin or contained a concentration that was between 1 and 10% of that detected in leaves. These Cry1Ac-positive arthropods included a number of mesophyll-feeding Hemiptera, a cicadellid, a curculionid beetle and, among the predators, a thomisid spider and an unidentified predatory bug belonging to the Anthocoridae. Within an arthropod species/taxon, the Cry1Ac content sometimes varied between life stages (nymphs/larvae vs. adults) and sampling dates (before, during, and after flowering). Our study is the first to provide information on Cry1Ac-expression levels in soybean plants and Cry1Ac concentrations in non-target arthropods in Chinese soybean fields. The data will be useful for assessing the risk of non-target arthropod exposure to Cry1Ac in soybean. PMID:25110881

  2. Resonant tunneling of interacting electrons in an AC electric field

    SciTech Connect

    Elesin, V. F.

    2013-11-15

    The problem of the effect of electron-electron interaction on the static and dynamic properties of a double-barrier nanostructure (resonant tunneling diode (RTD)) is studied in terms of a coherent tunneling model, which includes a set of Schrödinger and Poisson equations with open boundary conditions. Explicit analytical expressions are derived for dc and ac potentials and reduced (active and reactive) currents in the quasi-classical approximation over a wide frequency range. These expressions are used to analyze the frequency characteristics of RTD. It is shown that the interaction can radically change the form of these expressions, especially in the case of a hysteretic I-V characteristic. In this case, the active current and the ac potentials can increase sharply at both low and high frequencies. For this increase to occur, it is necessary to meet quantum regime conditions and to choose a proper working point in the I-V characteristic of RTD. The possibility of appearance of specific plasma oscillations, which can improve the high-frequency characteristics of RTD, is predicted. It is found that the active current can be comparable with the resonant dc current of RTD.

  3. Rapid computation of the amplitude and phase of tightly focused optical fields distorted by scattering particles.

    PubMed

    Ranasinghesagara, Janaka C; Hayakawa, Carole K; Davis, Mitchell A; Dunn, Andrew K; Potma, Eric O; Venugopalan, Vasan

    2014-07-01

    We develop an efficient method for accurately calculating the electric field of tightly focused laser beams in the presence of specific configurations of microscopic scatterers. This Huygens-Fresnel wave-based electric field superposition (HF-WEFS) method computes the amplitude and phase of the scattered electric field in excellent agreement with finite difference time-domain (FDTD) solutions of Maxwell's equations. Our HF-WEFS implementation is 2-4 orders of magnitude faster than the FDTD method and enables systematic investigations of the effects of scatterer size and configuration on the focal field. We demonstrate the power of the new HF-WEFS approach by mapping several metrics of focal field distortion as a function of scatterer position. This analysis shows that the maximum focal field distortion occurs for single scatterers placed below the focal plane with an offset from the optical axis. The HF-WEFS method represents an important first step toward the development of a computational model of laser-scanning microscopy of thick cellular/tissue specimens. PMID:25121440

  4. Rapid computation of the amplitude and phase of tightly focused optical fields distorted by scattering particles

    PubMed Central

    Ranasinghesagara, Janaka C.; Hayakawa, Carole K.; Davis, Mitchell A.; Dunn, Andrew K.; Potma, Eric O.; Venugopalan, Vasan

    2014-01-01

    We develop an efficient method for accurately calculating the electric field of tightly focused laser beams in the presence of specific configurations of microscopic scatterers. This Huygens–Fresnel wave-based electric field superposition (HF-WEFS) method computes the amplitude and phase of the scattered electric field in excellent agreement with finite difference time-domain (FDTD) solutions of Maxwell’s equations. Our HF-WEFS implementation is 2–4 orders of magnitude faster than the FDTD method and enables systematic investigations of the effects of scatterer size and configuration on the focal field. We demonstrate the power of the new HF-WEFS approach by mapping several metrics of focal field distortion as a function of scatterer position. This analysis shows that the maximum focal field distortion occurs for single scatterers placed below the focal plane with an offset from the optical axis. The HF-WEFS method represents an important first step toward the development of a computational model of laser-scanning microscopy of thick cellular/tissue specimens. PMID:25121440

  5. Efficacy of an AC sinusoidal electric field for apoptosis induction in lung carcinoma cells (A549)

    NASA Astrophysics Data System (ADS)

    Park, Hyoun-Hyang; Lee, Seung S.; Hoon Lee, Dae

    2012-08-01

    An AC sinusoidal electric field was applied to lung carcinoma cells for the induction of apoptosis. The occurrence of apoptosis was determined by analysis of Annexin V/PI and DNA fragmentation. Additional evidence of apoptosis was confirmed by caspase-3 cleavage and disruption of mitochondrial membrane potential. These results demonstrated that the expression of apoptosis can be controlled by varying the magnitude and the duration of the field, and that the application of an AC electric field can stimulate the apoptosis via mitochondria-mediated pathway.

  6. Exploiting SENTINEL-1 Amplitude Data for Glacier Surface Velocity Field Measurements: Feasibility Demonstration on Baltoro Glacier

    NASA Astrophysics Data System (ADS)

    Nascetti, A.; Nocchi, F.; Camplani, A.; Di Rico, C.; Crespi, M.

    2016-06-01

    The leading idea of this work is to continuously retrieve glaciers surface velocity through SAR imagery, in particular using the amplitude data from the new ESA satellite sensor Sentinel-1 imagery. These imagery key aspects are the free access policy, the very short revisit time (down to 6 days with the launch of the Sentinel-1B satellite) and the high amplitude resolution (up to 5 m). In order to verify the reliability of the proposed approach, a first experiment has been performed using Sentinel-1 imagery acquired over the Karakoram mountain range (North Pakistan) and Baltoro and other three glaciers have been investigated. During this study, a stack of 11 images acquired in the period from October 2014 to September 2015 has been used in order to investigate the potentialities of the Sentinel-1 SAR sensor to retrieve the glacier surface velocity every month. The aim of this test was to measure the glacier surface velocity between each subsequent pair, in order to produce a time series of the surface velocity fields along the investigated period. The necessary coregistration procedure between the images has been performed and subsequently the glaciers areas have been sampled using a regular grid with a 250 × 250 meters posting. Finally the surface velocity field has been estimated, for each image pair, using a template matching procedure, and an outlier filtering procedure based on the signal to noise ratio values has been applied, in order to exclude from the analysis unreliable points. The achieved velocity values range from 10 to 25 meters/month and they are coherent to those obtained in previous studies carried out on the same glaciers and the results highlight that it is possible to have a continuous update of the glacier surface velocity field through free Sentinel-1 imagery, that could be very useful to investigate the seasonal effects on the glaciers fluid-dynamics.

  7. Field of Bachelor's Degree in the United States: 2009. American Community Survey Reports. ACS-18

    ERIC Educational Resources Information Center

    Siebens, Julie; Ryan, Camille L.

    2012-01-01

    This report provides information on fields of bachelor's degrees in the United States using data from the 2009 American Community Survey (ACS). It includes estimates of fields of bachelor's degree by demographic characteristics including age, sex, race, Hispanic origin, nativity, and educational attainment. This report also looks at geographic and…

  8. Inviscid evolution of large amplitude filaments in a uniform gravity field

    SciTech Connect

    Angus, J. R.; Krasheninnikov, S. I.

    2014-11-15

    The inviscid evolution of localized density stratifications under the influence of a uniform gravity field in a homogeneous, ambient background is studied. The fluid is assumed to be incompressible, and the stratification, or filament, is assumed to be initially isotropic and at rest. It is shown that the center of mass energy can be related to the center of mass position in a form analogous to that of a solid object in a gravity field g by introducing an effective gravity field g{sub eff}, which is less than g due to energy that goes into the background and into non-center of mass motion of the filament. During the early stages of the evolution, g{sub eff} is constant in time and can be determined from the solution of a 1D differential equation that depends on the initial, radially varying density profile of the filament. For small amplitude filaments such that ρ{sub 0} ≪ 1, where ρ{sub 0} is the relative amplitude of the filament to the background, the early stage g{sub eff} scales linearly with ρ{sub 0}, but as ρ{sub 0}→∞, g{sub eff}→g and is thus independent of ρ{sub 0}. Fully nonlinear simulations are performed for the evolution of Gaussian filaments, and it is found that the time t{sub max}, which is defined as the time for the center of mass velocity to reach its maximum value U{sub max}, occurs very soon after the constant acceleration phase and so U{sub max}≈g{sub eff}(t=0)t{sub max}. The simulation results show that U{sub max}∼1/t{sub max}∼√(ρ{sub 0}) for ρ{sub 0} ≪ 1, in agreement with theory and results from previous authors, but that U{sub max} and t{sub max} both scale approximately with √(ρ{sub 0}) for ρ{sub 0} ≫ 1. The fact that U{sub max} and t{sub max} have the same scaling with ρ{sub 0} for large amplitude filaments is in agreement with the theory presented in this paper.

  9. Regulation of endothelial MAPK/ERK signalling and capillary morphogenesis by low-amplitude electric field

    PubMed Central

    Sheikh, Abdul Q.; Taghian, Toloo; Hemingway, Bryan; Cho, Hongkwan; Kogan, Andrei B.; Narmoneva, Daria A.

    2013-01-01

    Low-amplitude electric field (EF) is an important component of wound-healing response and can promote vascular tissue repair; however, the mechanisms of action on endothelium remain unclear. We hypothesized that physiological amplitude EF regulates angiogenic response of microvascular endothelial cells via activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway. A custom set-up allowed non-thermal application of EF of high (7.5 GHz) and low (60 Hz) frequency. Cell responses following up to 24 h of EF exposure, including proliferation and apoptosis, capillary morphogenesis, vascular endothelial growth factor (VEGF) expression and MAPK pathways activation were quantified. A db/db mouse model of diabetic wound healing was used for in vivo validation. High-frequency EF enhanced capillary morphogenesis, VEGF release, MEK-cRaf complex formation, MEK and ERK phosphorylation, whereas no MAPK/JNK and MAPK/p38 pathways activation was observed. The endothelial response to EF did not require VEGF binding to VEGFR2 receptor. EF-induced MEK phosphorylation was reversed in the presence of MEK and Ca2+ inhibitors, reduced by endothelial nitric oxide synthase inhibition, and did not depend on PI3K pathway activation. The results provide evidence for a novel intracellular mechanism for EF regulation of endothelial angiogenic response via frequency-sensitive MAPK/ERK pathway activation, with important implications for EF-based therapies for vascular tissue regeneration. PMID:22993248

  10. Bipartite field theories: from D-brane probes to scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Franco, Sebastián

    2012-11-01

    We introduce and initiate the investigation of a general class of 4d, {N}=1 quiver gauge theories whose Lagrangian is defined by a bipartite graph on a Riemann surface, with or without boundaries. We refer to such class of theories as Bipartite Field Theories (BFTs). BFTs underlie a wide spectrum of interesting physical systems, including: D3-branes probing toric Calabi-Yau 3-folds, their mirror configurations of D6-branes, cluster integrable systems in (0 + 1) dimensions and leading singularities in scattering amplitudes for {N}=4 SYM. While our discussion is fully general, we focus on models that are relevant for scattering amplitudes. We investigate the BFT perspective on graph modifications, the emergence of Calabi-Yau manifolds (which arise as the master and moduli spaces of BFTs), the translation between square moves in the graph and Seiberg duality and the identification of dual theories by means of the underlying Calabi-Yaus, the phenomenon of loop reduction and the interpretation of the boundary operator for cells in the positive Grassmannian as higgsing in the BFT. We develop a technique based on generalized Kasteleyn matrices that permits an efficient determination of the Calabi-Yau geometries associated to arbitrary graphs. Our techniques allow us to go beyond the planar limit by both increasing the number of boundaries of the graphs and the genus of the underlying Riemann surface. Our investigation suggests a central role for Calabi-Yau manifolds in the context of leading singularities, whose full scope is yet to be uncovered.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  12. Encouragement of Enzyme Reaction Utilizing Heat Generation from Ferromagnetic Particles Subjected to an AC Magnetic Field

    PubMed Central

    Suzuki, Masashi; Aki, Atsushi; Mizuki, Toru; Maekawa, Toru; Usami, Ron; Morimoto, Hisao

    2015-01-01

    We propose a method of activating an enzyme utilizing heat generation from ferromagnetic particles under an ac magnetic field. We immobilize α-amylase on the surface of ferromagnetic particles and analyze its activity. We find that when α-amylase/ferromagnetic particle hybrids, that is, ferromagnetic particles, on which α-amylase molecules are immobilized, are subjected to an ac magnetic field, the particles generate heat and as a result, α-amylase on the particles is heated up and activated. We next prepare a solution, in which α-amylase/ferromagnetic particle hybrids and free, nonimmobilized chitinase are dispersed, and analyze their activities. We find that when the solution is subjected to an ac magnetic field, the activity of α-amylase immobilized on the particles increases, whereas that of free chitinase hardly changes; in other words, only α-amylase immobilized on the particles is selectively activated due to heat generation from the particles. PMID:25993268

  13. 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.

  14. Fiber - Optic Devices as Temperature Sensors for Temperature Measurements in AC Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Rablau, Corneliu; Lafrance, Joseph; Sala, Anca

    2007-10-01

    We report on the investigation of several fiber-optic devices as potential sensors for temperature measurements in AC magnetic fields. Common temperature sensors, such as thermocouples, thermistors or diodes, will create random and/or systematic errors when placed in a magnetic field. A DC magnetic field is susceptible to create a systematic offset to the measurement, while in an AC magnetic field of variable frequency random errors which cannot be corrected for can also be introduced. Fiber-Bragg-gratings and thin film filters have an inherent temperature dependence. Detrimental for their primary applications, the same dependence allows one to use such devices as temperature sensors. In an AC magnetic field, they present the advantage of being immune to electromagnetic interference. Moreover, for fiber-Bragg-gratings, the shape factor and small mass of the bare-fiber device make it convenient for temperature measurements on small samples. We studied several thin-film filters and fiber-Bragg-gratings and compared their temperature measurement capabilities in AC magnetic fields of 0 to 150 Gauss, 0 to 20 KHz to the results provided by off-the-shelf thermocouples and thermistor-based temperature measurement systems.

  15. ACS Flat Field Corrections from Observations of 47 Tucanae

    NASA Astrophysics Data System (ADS)

    Mack, J.; Bohlin, R. C.; Gilliland, R. L.; van der Marel, R.; Blakeslee, J. P.; de Marchi, G.

    2002-12-01

    The uniformity of the WFC and HRC detector response has been assessed using multiple dithered pointings of 47 Tucanae. By placing the same stars over different portions of the detector and measuring relative changes in brightness, low frequency spatial variations in the response of each detector have been measured. The original WFC and HRC laboratory flat fields produce photometric errors of 5 to 18 percent from corner-to-corner. The required low-order correction (L-flat) has been applied to the lab flats, and new flat fields have been delivered for use in the calibration pipeline. Initial results suggest the photometric response for a given star is now the same to 1 for any position in the field of view. As a further test, the improved flat fields are compared with observations of the bright earth at UV wavelengths (F330W) and with skyflats from ERO data at long wavelengths (F775W).

  16. Superposition of an AC field improves the discrimination between peptides in nanopore analysis.

    PubMed

    Jakova, Elisabet; Lee, Jeremy S

    2015-07-21

    In standard nanopore analysis a constant DC voltage is used to electrophoretically drive small molecules and peptides towards a pore. Superposition of an AC voltage at particular frequencies causes molecules to oscillate as they approach the pore which can alter the event parameters, the blockade current (I) and blockade time (T). Four peptides with similar structures were studied. Alpha-helical peptides A10 (FmocDDA10KK), A14, A18 and retro-inverso A10. It was shown that the ratio of translocations to bumping events could be manipulated by a combination of AC voltages and frequencies. In particular, A10 could be studied without interference from retro-inverso A10. Similarly, a large, intrinsically disordered protein of 140 amino acids, α-synuclein, which translocates the pore readily in a DC field could be prevented from doing so by application of an AC field of 200 mV at 100 MHz. PMID:25699656

  17. Study of DC and AC electric field effect on Pisum sativum seeds growth

    NASA Astrophysics Data System (ADS)

    Mahmood, Bahar; Jaleh, Sojoodi; Yasaman, Yasaie

    2014-07-01

    In this research the effect of electric field on two groups of wet and dry Pisum sativum seeds growth was studied. To generate the required electric field a parallel-plate capacitor with round copper plates of 30 cm diameter was used. The experiments were performed once in fixed exposure duration of 8 min in variable DC electric field of 0.25-1.5 kV/m. The other experiments were performed in variable fields of 50-125 kV/m in fixed exposure duration of 8 min, in two groups of AC and DC electric fields. The experiments were repeated three times. In each experiment 10 seeds were used and there was a sham exposed group for comparison, too. After application of electric field, the seeds were kept for six days in the same growth chamber with the temperature of 25 ± 1 °C and 12 h light/12 h darkness. On the 6th day length of stems and height of roots were measured. After doing statistical analysis, in low intensities of DC electric field, the highest significant increase of mean growth (The average of stem length and the height of roots) was seen in 1.5 kV/m in wet seeds. In high intensities of DC and AC electric fields, the highest significant increase of mean growth was seen in AC electric field of 100 kV/m in wet seeds.

  18. 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

  19. Revisiting the pion leading-twist distribution amplitude within the QCD background field theory

    NASA Astrophysics Data System (ADS)

    Zhong, Tao; Wu, Xing-Gang; Wang, Zhi-Gang; Huang, Tao; Fu, Hai-Bing; Han, Hua-Yong

    2014-07-01

    We study the pion leading-twist distribution amplitude (DA) within the framework of Shifman-Vainshtein-Zakharov sum rules under the background field theory. To improve the accuracy of the sum rules, we expand both the quark propagator and the vertex (z.D↔)n of the correlator up to dimension-six operators in the background field theory. The sum rules for the pion DA moments are obtained, in which all condensates up to dimension-six have been taken into consideration. Using the sum rules, we obtain ⟨ξ2⟩|1 GeV=0.338±0.032, ⟨ξ4⟩|1GeV=0.211±0.030 and ⟨ξ6⟩|1GeV=0.163±0.030. It is shown that the dimension-six condensates shall provide sizable contributions to the pion DA moments. We show that the first Gegenbauer moment of the pion leading-twist DA is a2π|1 GeV=0.403±0.093, which is consistent with those obtained in the literature within errors but prefers a larger central value as indicated by lattice QCD predictions.

  20. AC Electric Field-Induced Trapping of Microparticles in Pinched Microconfinements.

    PubMed

    Dey, Ranabir; Shaik, Vaseem Akram; Chakraborty, Debapriya; Ghosal, Sandip; Chakraborty, Suman

    2015-06-01

    The trapping of charged microparticles under confinement in a converging-diverging microchannel, under a symmetric AC field of tunable frequency, is studied. We show that at low frequencies, the trapping characteristics stem from the competing effects of positive dielectrophoresis and the linear electrokinetic phenomena of electroosmosis and electrophoresis. It is found, somewhat unexpectedly, that electroosmosis and electrophoresis significantly affect the concentration profile of the trapped analyte, even for a symmetric AC field. However, at intermediate frequencies, the microparticle trapping mechanism is predominantly a consequence of positive dielectrophoresis. We substantiate our experimental results for the microparticle concentration distribution, along the converging-diverging microchannel, with a detailed theoretical analysis that takes into account all of the relevant frequency-dependent electrokinetic phenomena. This study should be useful in understanding the response of biological components such as cells to applied AC fields. Moreover, it will have potential applications in the design of efficient point-of-care diagnostic devices for detecting biomarkers and also possibly in some recent strategies in cancer therapy using AC fields. PMID:25954982

  1. Experimental investigation of impulsive magnetic reconnection induced by large amplitude electromagnetic fluctuations in the presence of a guide field

    NASA Astrophysics Data System (ADS)

    Kuwahata, Akihiro; Inomoto, Michiaki; Yanai, Ryoma; Ono, Yasushi

    2015-11-01

    Impulsive enhancement of magnetic reconnection is one of the potential candidates to invoke various explosive events observed in nature and laboratory plasmas. In TS-3 laboratory experiment with a guide field of Bguide /Brec = 1-2.5, impulsive growth of the reconnection electric field was observed just behind the onset of large-amplitude electromagnetic fluctuations (f = 1.5-2 fci and the amplitude was 0.1Brec). It was found that both the fluctuation amplitude and the enhanced reconnection electric field during the fluctuation period showed positive correlation with the guide field. The normalized reconnection rate of about 0.03 before the onset of fluctuations was reasonably comparable with the classical reconnection rate of Sweet-Parker model. However, the reconnection rate rose up to 0.11 after the fluctuations onset, suggesting that the transition from slow steady reconnection to fast impulsive reconnection took place. Since the fluctuation amplitude was so large that the nonlinear terms of the induced electric field was not negligible. The electric field enhancement due to the nonlinear contribution from the observed fluctuation was 650 V/m, which showed good agreement with the experimentally observed electric field increment of about 800 V/m.

  2. AC current distribution and losses in multifilamentary superconductors exposed to longitudinal magnetic field

    SciTech Connect

    Le Naour, S.; Lacaze, A.; Laumond, Y.; Estop, P.; Verhaege, T.

    1996-07-01

    The current distribution and also AC losses, in a multifilamentary superconductor carrying a transport current, are influenced by the self and the external magnetic field. By using the Maxwell equations, a model has been developed in order to calculate the temporal evolution of current distribution in a single wire exposed or not to external magnetic field. This model is based on the actual relationship of electrical field E with current density J and takes into account the twist pitch of the wire. AC losses are calculated by adding all local losses through the cross section. This paper presents calculations of the influence of the cable twist coupled with the longitudinal magnetic field, and also gives some ideas how to decrease losses.

  3. 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

  4. Stability of the ACS CCD: geometry, flat fielding, photometry

    NASA Astrophysics Data System (ADS)

    De Marchi, Guido

    2002-07-01

    A moderately crowded stellar field, located 6' West of the centre of the cluster 47 Tuc, is observed repeatedly {every three weeks with the WFC, every other month with the HRC} in various filters, spending 1 orbit per epoch. Different filters will be used every time, so that over the course of the year all filters will have been employed at least twice. The most common filters will be checked more frequently. The same field has been observed in the course of the SMOV phase and the positions and magnitudes of the most prominent stars have been accurately measured. Although the field is neither a proper astrometric nor a proper photometric standard one, the positions and magnitudes of the objects in it can be used to monitor any local and large scale variations in the platescale and sensitivity of the detectors. It should be noted that for the filters which have already been used during the SMOV phase it will be sufficient to take one single image, without CR-SPLIT, since the exposure time is always short {20-30 sec} and there will be so many stars that the few of them which are affected by cosmic rays can be discarded as outliers in the photometry. For narrow and medium band filters not exercised on this target in the SMOV phase, however, a baseline will have to be set. This expenditure of time will apply to the current cycle only. At variance with the approach used in SMOV, there is no need for large telescope slews to place the same objects on opposite sides of the detectors, thence allowing the programme to remain compact and efficient. All exposure level parameters are set to their default values, except for the amplifier gain of the WFC exposures in the F606W band, which will be collected with the gain value of 2 for the WFC for compatibility with the SMOV observations. The exposure time is typically 30 seconds for the WFC, 60 sec for the HRC. No attempt will be made to attain a predefined or the same orientation on the sky amongst different epochs. Typically

  5. Numerical and theoretical evaluations of AC losses for single and infinite numbers of superconductor strips with direct and alternating transport currents in external AC magnetic field

    NASA Astrophysics Data System (ADS)

    Kajikawa, K.; Funaki, K.; Shikimachi, K.; Hirano, N.; Nagaya, S.

    2010-11-01

    AC losses in a superconductor strip are numerically evaluated by means of a finite element method formulated with a current vector potential. The expressions of AC losses in an infinite slab that corresponds to a simple model of infinitely stacked strips are also derived theoretically. It is assumed that the voltage-current characteristics of the superconductors are represented by Bean’s critical state model. The typical operation pattern of a Superconducting Magnetic Energy Storage (SMES) coil with direct and alternating transport currents in an external AC magnetic field is taken into account as the electromagnetic environment for both the single strip and the infinite slab. By using the obtained results of AC losses, the influences of the transport currents on the total losses are discussed quantitatively.

  6. On the angle between the average interplanetary magnetic field and the propagation direction of plane large amplitude Alfven waves

    NASA Technical Reports Server (NTRS)

    Lichtenstein, B. R.; Sonett, C. P.

    1979-01-01

    The paper shows that the experimentally observed close alignment of magnetic field minimum variance direction with the average magnetic field for Alfven waves in the solar wind is consistent with theoretically predicted properties of plane large amplitude Alfven waves in the MHD approximation. The theoretical properties of these Alfven waves constrain the time averaged magnetic field to cluster around the direction of minimum variance, which is aligned with the wave normal. Thus, spacecraft magnetometer observations in the solar wind of minimum variance directions strongly peaked about the average magnetic field direction are consistent with plane large amplitude Alfven waves which have wave normals aligned with the directions of minimum variance. This does not imply that geometrical hydromagnetic calculations for Alfven wave propagation direction in the solar wind are incorrect, but there is a discrepancy between geometrical hydromagnetics theory and observations that IMF minimum variance directions tend to be aligned with the ideal Parker spiral instead of the radial direction.

  7. Propagation of magnetic avalanches in Mn12Ac at high field sweep rates.

    PubMed

    Decelle, W; Vanacken, J; Moshchalkov, V V; Tejada, J; Hernández, J M; Macià, F

    2009-01-16

    Time-resolved measurements of the magnetization reversal in single crystals of Mn12Ac in pulsed magnetic fields, at magnetic field sweep rates from 1.5 kT/s up to 7 kT/s, suggest a new process that cannot be scaled onto a deflagrationlike propagation driven by heat diffusion. The sweep rate dependence of the propagation velocity, increasing from a few 100 m/s up to the speed of sound in Mn12Ac, indicates the existence of two new regimes at the highest sweep rates, with a transition around 4 kT/s that can be understood as a magnetic deflagration-to-detonation transition. PMID:19257315

  8. ac-Field-induced fluid pumping in microsystems with asymmetric temperature gradients.

    PubMed

    Holtappels, Moritz; Stubbe, Marco; Gimsa, Jan

    2009-02-01

    We present two different designs of electrohydrodynamic micropumps for microfluidic systems. The micropumps have no movable parts, and their simple design allows for fabrication by microsystems technology. The pumps are operated by ac voltages from 1 to 60 V and were tested with aqueous solutions in the conductivity range of 1-112 mS m(-1). The pump effect is induced by an ac electric field across a fluid medium with an inhomogeneous temperature distribution. It is constant over a wide range of the ac field frequency with a conductivity-dependent drop-off at high frequencies. The temperature-dependent conductivity and permittivity distributions in the fluid induce space charges that interact with the electric field and induce fluid motion. The temperature distribution can be generated either by Joule heating in the medium or by external heating. We present experimental results obtained with two prototypes featuring Joule heating and external heating by a heating filament. Experimental and numerical results are compared with an analytical model. PMID:19391842

  9. Theoretical study of electromagnetic electron cyclotron waves in the presence of AC field in Uranian magnetosphere

    NASA Astrophysics Data System (ADS)

    Pandey, R. S.; Kaur, Rajbir

    2015-10-01

    Electromagnetic electron cyclotron (EMEC) waves with temperature anisotropy in the magnetosphere of Uranus have been studied in present work. EMEC waves are investigated using method of characteristic solution by kinetic approach, in presence of AC field. In 1986, Voyager 2 encounter with Uranus revealed that magnetosphere of Uranus exhibit non-Maxwellian high-energy tail distribution. So, the dispersion relation, real frequency and growth rate are evaluated using Lorentzian Kappa distribution function. Effect of temperature anisotropy, AC frequency and number density of particles is found. The study is also extended to oblique propagation of EMEC waves in presence and absence of AC field. Through comprehensive mathematical analysis it is found that when EMEC wave propagates parallel to intrinsic magnetic field of Uranus, its growth is more enhanced than in case of oblique propagation. Results are also discussed in context to magnetosphere of Earth and also gives theoretical explanation to existence of high energetic particles observed by Voyager 2 in the magnetosphere of Uranus. The results can present a further insight into the nature of electron-cyclotron instability condition for the whistler mode waves in the outer radiation belts of Uranus or other space plasmas.

  10. Super-resolution high sensitivity AC Magnetic Field Imaging with NV Centers in Diamond

    NASA Astrophysics Data System (ADS)

    Bauch, Erik; Jaskula, Jean-Christophe; Trifonov, Alexei; Walsworth, Ronald

    2015-05-01

    The Nitrogen-Vacancy center in diamond (NV center), a defect consisting of a nitrogen atom next to a missing atom, has been successfully applied to sense magnetic field, electric field, temperature and can also be used as fluorescence marker and single photon emitter. We will present super-resolution imaging of NV centers and simultaneous sensing of AC magnetic fields with high sensitivity. To demonstrate the applicability of super-resolution magnetic field imaging, we resolve several NV centers with an optical resolution smaller than 20 nm and probe locally the gradient of a externally applied magnetic field. Additionally, we demonstrate the detection of magnetic field signals from 1H protons with subdiffraction image resolution. We will also show that our super-resolution magnetometer will benefit from a new readout method based on a spin-to-charge mapping that we have developed to increase the readout contrast.

  11. Keratinocyte galvanotaxis in combined DC and AC electric fields supports an electromechanical transduction sensing mechanism.

    PubMed

    Hart, Francis X; Laird, Mhairi; Riding, Aimie; Pullar, Christine E

    2013-02-01

    Sedentary keratinocytes at the edge of a skin wound migrate into the wound, guided by the generation of an endogenous electric field (EF) generated by the collapse of the transepithelial potential. The center of the wound quickly becomes more negative than the surrounding tissue and remains the cathode of the endogenous EF until the wound is completely re-epithelialized. This endogenous guidance cue can be studied in vitro. When placed in a direct current (DC) EF of physiological strength, 100 V/m, keratinocytes migrate directionally toward the cathode in a process known as galvanotaxis. Although a number of membrane-bound (e.g., epidermal growth factor receptor (EGFR), integrins) and cytosolic proteins (cAMP, ERK, PI3K) are known to play a role in the downstream signaling mechanisms underpinning galvanotaxis, the initial sensing mechanism for this response is not understood. To investigate the EF sensor, we studied the migration of keratinocytes in a DC EF of 100 V/m, alternating current (AC) EFs of 40 V/m at either 1.6 or 160 Hz, and combinations of DC and AC EFs. In the AC EFs alone, keratinocytes migrated randomly. The 1.6 Hz AC EF combined with the DC EF suppressed the direction of migration but had no effect on speed. In contrast, the 160 Hz AC EF combined with the DC EF did not affect the direction of migration but increased the migration speed compared to the DC EF alone. These results can be understood in terms of an electromechanical transduction model, but not an electrodiffusion/osmosis or a voltage-gated channel model. PMID:22907479

  12. On estimating attenuation from the amplitude of the spectrally whitened ambient seismic field

    NASA Astrophysics Data System (ADS)

    Weemstra, Cornelis; Westra, Willem; Snieder, Roel; Boschi, Lapo

    2014-06-01

    Measuring attenuation on the basis of interferometric, receiver-receiver surface waves is a non-trivial task: the amplitude, more than the phase, of ensemble-averaged cross-correlations is strongly affected by non-uniformities in the ambient wavefield. In addition, ambient noise data are typically pre-processed in ways that affect the amplitude itself. Some authors have recently attempted to measure attenuation in receiver-receiver cross-correlations obtained after the usual pre-processing of seismic ambient-noise records, including, most notably, spectral whitening. Spectral whitening replaces the cross-spectrum with a unit amplitude spectrum. It is generally assumed that cross-terms have cancelled each other prior to spectral whitening. Cross-terms are peaks in the cross-correlation due to simultaneously acting noise sources, that is, spurious traveltime delays due to constructive interference of signal coming from different sources. Cancellation of these cross-terms is a requirement for the successful retrieval of interferometric receiver-receiver signal and results from ensemble averaging. In practice, ensemble averaging is replaced by integrating over sufficiently long time or averaging over several cross-correlation windows. Contrary to the general assumption, we show in this study that cross-terms are not required to cancel each other prior to spectral whitening, but may also cancel each other after the whitening procedure. Specifically, we derive an analytic approximation for the amplitude difference associated with the reversed order of cancellation and normalization. Our approximation shows that an amplitude decrease results from the reversed order. This decrease is predominantly non-linear at small receiver-receiver distances: at distances smaller than approximately two wavelengths, whitening prior to ensemble averaging causes a significantly stronger decay of the cross-spectrum.

  13. Analysis of resistance to Cry1Ac in field-collected pink bollworm, Pectinophora gossypiella (Lepidoptera:Gelechiidae), populations.

    PubMed

    Ojha, Abhishek; Sree, K Sowjanya; Sachdev, Bindiya; Rashmi, M A; Ravi, K C; Suresh, P J; Mohan, Komarlingam S; Bhatnagar, Raj K

    2014-01-01

    High survivorship of pink bollworrm, Pectinophora gossypiella in bolls of Bollgard® cotton hybrids and resistance to Cry1Ac protein, expressed in Bollgard cotton were reported in field-populations collected from the state of Gujarat (western India) in 2010. We have found Cry1Ac-resistance in pink bollworm populations sourced from Bollgard and non-Bt cotton fields in the adjoining states of Maharashtra and Madhya Pradesh in Central India. Further, we observed reduced binding of labeled Cry1Ac protein to receptors localized on the brush-border membrane of pink bollworm larval strains with high tolerance to Cry1Ac. These strains were sourced from Bollgard and conventional cotton fields. A pooled Cry1Ac-resistant strain, further selected on Cry1Ac diet also showed significantly reduced binding to Cry1Ac protein. The reduced binding of Cry1Ac to receptors could be an underlying mechanism for the observed resistance in pink bollworm populations feeding on Bollgard hybrids. PMID:25523173

  14. Spin superconductivity and ac-Josephson effect in Graphene system under strong magnetic field

    NASA Astrophysics Data System (ADS)

    Liu, Haiwen; Jiang, Hua; Sun, Qing-Feng; Xie, X. C.; Collaborative Innovation Center of Quantum Matter, Beijing, China Collaboration

    We study the spin superconductivity in Graphene system under strong magnetic field. From the microscopically Gor'kov method combined with the Aharonov-Casher effect, we derive the effective Landau-Ginzburg free energy and analyze the time evolution of order parameter, which is confirmed to be the off-diagonal long range order. Meanwhile, we compare the ground state of spin superconductivity to the canted-antiferromagnetic state, and demonstrate the equivalence between these two states. Moreover, we give out the pseudo-field flux quantization condition of spin supercurrent, and propose an experimental measurable ac-Josephson effect of spin superconductivity in this system.

  15. Dynamic melting and impurity particle tracking in continuously adjustable AC magnetic field

    NASA Astrophysics Data System (ADS)

    Bojarevics, V.; Pericleous, K.

    2016-07-01

    The analysis of semi-levitation melting is extended to account for the presence of particles (impurities, broken metal dendrite agglomerates, bubbles) during the full melting cycle simulated numerically using the pseudo-spectral schemes. The AC coil is dynamically moving with the melt front progress, while the generated Joule heat serves to enhance the melting rate. The electromagnetic force is decomposed into the time average and the oscillating parts. The time average effects on the particle transport are investigated previously using approximations derived for a locally uniform magnetic field. This paper presents expressions for the skin-layer type of the AC force containing also the pulsating part which contributes to the particle drag by the ‘history’ and ‘added mass’ contributions. The intense turbulence in the bulk of molten metal additionally contributes to the particle dispersion. The paper attempts to demonstrate the importance of each of the mentioned effects onto the particle transport during the melting until the final pouring stage. The method could be extended to similar AC field controlled melting/solidification processes.

  16. Small-amplitude magnetic Rayleigh-Taylor instability growth in cylindrical liners and Z-pinches imploded in an axial magnetic field

    NASA Astrophysics Data System (ADS)

    Velikovich, A. L.; Giuliani, J. L.; Clark, R. W.; Mikitchuk, D.; Kroupp, E.; Maron, Y.; Fisher, A.; Schmit, P. F.

    2014-10-01

    Recent progress in developing the MagLIF approach to pulsed-power driven inertial confinement fusion has stimulated the interest in observation and mitigation of the magnetic Rayleigh-Taylor instability (MRTI) of liners and Z-pinches imploded in an axial magnetic field. Theoretical analysis of these issues is particularly important because direct numerical simulation of the MRTI development is challenging due to intrinsically 3D helical structure of the fastest-growing modes. We review the analytical small-amplitude theory of the MRTI perturbation development and the weakly nonlinear theory of MRTI mode interaction, emphasizing basic physics, opportunity for 3D code verification against exact analytical solutions, and stabilization criteria. The theory is compared to the experimental results obtained at Weizmann Institute with gas-puff Z pinches and on the Z facility at Sandia with solid liners imploded in an axial magnetic field. Work supported by the US DOE/NNSA, and by the US-Israel Binational Science Foundation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  17. Identification of boundaries in the cometary environment from AC electric field measurements

    NASA Astrophysics Data System (ADS)

    Mogilevsky, M.; Mikhailov, Y.; Molchanov, O.; Grard, R.; Pedersen, A.; Trotignon, J. G.; Beghin, C.; Formisano, V.; Shapiro, V.; Shevchenko, V.

    1986-12-01

    Electric fields are measured with the AVP-V experiment in the frequency range 8 Hz - 300 kHz. The field amplitude increases significantly, first at a distance of 2×105km, then at distances of 1.2 - 1.5×105km, and 5 - 7×104km from the nucleus. These phenomena have been observed both on VEGA-1 and VEGA-2. The electric field measurements are compared with data obtained from dust and plasma experiments; possible mechanisms responsible for the existence of these boundaries are discussed.

  18. The ac and dc electric field meters developed for the US Department of Energy

    NASA Technical Reports Server (NTRS)

    Kirkham, H.; Johnston, A.; Jackson, S.; Sheu, K.

    1987-01-01

    Two space-potential electric field meters developed at the Jet Propulsion Laboratory under the auspices of the U.S. Department of Energy are described. One of the meters was designed to measure dc fields, the other ac fields. Both meters use fiber optics to couple a small measuring probe to a remote readout device, so as to minimize field perturbation due to the presence of the probe. By using coherent detection, it has been possible to produce instruments whose operating range extends from about 10 V/m up to about 2.5 kV/cm, without the need for range switching on the probe. The electrical and mechanical design of both meters are described in detail. Data from laboratory tests are presented, as well as the results of the tests at the National Bureau of Standards and the Electric Power Research Institute's High Voltage Transmission Research Facility.

  19. Hot electrons injection in carbon nanotubes under the influence of quasi-static ac-field

    NASA Astrophysics Data System (ADS)

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-07-01

    The theory of hot electrons injection in carbon nanotubes (CNTs) where both dc electric field (Ez), and a quasi-static ac field exist simultaneously (i.e. when the frequency ω of ac field is much less than the scattering frequency v (ω ≪ v or ωτ ≪ 1, v =τ-1) where τ is relaxation time) is studied. The investigation is done theoretically by solving semi-classical Boltzmann transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density versus dc field (Ez) applied along the axis of the CNTs in the presence and absence of hot electrons reveal ohmic conductivity initially and finally negative differential conductivity (NDC) provided ωτ ≪ 1 (i.e. quasi- static case). With strong enough axial injection of the hot electrons, there is a switch from NDC to positive differential conductivity (PDC) about Ez ≥ 75 kV / cm and Ez ≥ 140 kV / cm for a zigzag CNT and an armchair CNT respectively. Thus, the most important tough problem for NDC region which is the space charge instabilities can be suppressed due to the switch from the NDC behaviour to the PDC behaviour predicting a potential generation of terahertz radiations whose applications are relevance in current-day technology, industry, and research.

  20. Self-field ac losses in biaxially aligned Y{endash}Ba{endash}Cu{endash}O tape conductors

    SciTech Connect

    Iijima, Y.; Hosaka, M.; Sadakata, N.; Saitoh, T.; Kohno, O.; Takeda, K.

    1997-11-01

    Self-field ac losses were measured by the conventional ac four-probe method in biaxially aligned Y{endash}Ba{endash}Cu{endash}O tapes using polycrystalline Hastelloy tapes with textured yttria-stabilized-zirconia buffer layers. The ac losses increased in proportion to the fourth power of transport current in the high J{sub c} sample, and agreed well with Norris{close_quote} equation for thin strip conductors. However, the low J{sub c} sample had rather higher losses than Norris{close_quote} prediction, suggesting excessive magnetic flux penetration caused by percolated current paths. The results confirmed Norris{close_quote} prediction of the low ac losses for thin strip conductors, and indicated the importance of removing percolated structures of current paths to avoid higher ac losses than the theoretical predictions based on uniform conductors. {copyright} {ital 1997 American Institute of Physics.}

  1. Dynamics of atom-field probability amplitudes in a coupled cavity system with Kerr non-linearity

    SciTech Connect

    Priyesh, K. V.; Thayyullathil, Ramesh Babu

    2014-01-28

    We have investigated the dynamics of two cavities coupled together via photon hopping, filled with Kerr non-linear medium and each containing a two level atom in it. The evolution of various atom (field) state probabilities of the coupled cavity system in two excitation sub space are obtained numerically. Detailed analysis has been done by taking different initial conditions of the system, with various coupling strengths and by varying the susceptibility of the medium. The role of susceptibility factor, on the dynamics atom field probability has been examined. In a coupled cavity system with strong photon hopping it is found that the susceptibility factor modifies the behaviour of probability amplitudes.

  2. Stretching of long DNA molecules in the microvortex induced by laser and ac electric field

    NASA Astrophysics Data System (ADS)

    Nakano, Michihiko; Kurita, Hirofumi; Komatsu, Jun; Mizuno, Akira; Katsura, Shinji

    2006-09-01

    A microvortex is generated around an infrared laser focus where an intense ac electric field is applied. The authors used this optoelectrostatic microvortex for stretching individual long DNAs. When λ-or T4-phage DNA molecules were introduced into the optoelectrostatic microvortex, they were stretched around the laser focus. In addition, especially for longer T4 DNA molecules, it was possible to keep it in stretching form for more than 30s. Using this method, length of DNA molecules can be measured without fixing to a substrate. This method can be applied to DNA molecules longer than about 10μm.

  3. Dependence of the amplitude of Pc5-band magnetic field variations on the solar wind and solar activity

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazue; Yumoto, Kiyohumi; Claudepierre, Seth G.; Sanchez, Ennio R.; Troshichev, Oleg A.; Janzhura, Alexander S.

    2012-04-01

    We have studied the dependence of the amplitude of magnetic field variations in the Pc5 band (1.6-6.7 mHz) on the solar wind and solar activity. Solar wind parameters considered are the bulk velocity Vsw and the variation of the solar wind dynamic pressure δPsw. The solar activity dependence is examined by contrasting observations made in 2001 (solar activity maximum) and 2006 (solar activity declining phase). We calculated hourly Pc5 amplitude using data from geostationary satellites at L = 6.8 and ground stations covering 1 < L < 9. The amplitude is positively correlated with both Vsw and δPsw, but the degree of correlation varies with L and magnetic local time. As measured by the correlation coefficient, the amplitude dependence on both Vsw and δPsw is stronger on the dayside than on the nightside, and the dependence on Vsw (δPsw) tends to be stronger at higher (lower) L, with the relative importance of the two solar wind parameters switching at L ˜ 5. We attribute the Vsw control to the Kelvin-Helmholtz instability on the magnetopause, occurring both at high and low latitudes, and the δPsw control to buffeting of the magnetosphere by variation of solar wind dynamic pressure. The GOES amplitude is higher at the solar maximum at all local times and the same feature is seen on the ground in the dawn sector at L > 6. A radial shift of the fast mode wave turning point, associated with the solar cycle variation of magnetosphere mass density, is a possible cause of this solar activity dependence.

  4. Magnetic fluid hyperthermia (MFH): Cancer treatment with AC magnetic field induced excitation of biocompatible superparamagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Jordan, Andreas; Scholz, Regina; Wust, Peter; Fähling, Horst; Felix, Roland

    1999-07-01

    The story of hyperthermia with small particles in AC magnetic fields started in the late 1950s, but most of the studies were unfortunately conducted with inadequate animal systems, inexact thermometry and poor AC magnetic field parameters, so that any clinical implication was far behind the horizon. More than three decades later, it was found, that colloidal dispersions of superparamagnetic (subdomain) iron oxide nanoparticles exhibit an extraordinary specific absorption rate (SAR [ W/ g]), which is much higher at clinically tolerable H 0 f combinations in comparison to hysteresis heating of larger multidomain particles. This was the renaissance of a cancer treatment method, which has gained more and more attention in the last few years. Due to the increasing number of randomized clinical trials preferentially in Europe with conventional E-field hyperthermia systems, the general medical and physical experience in hyperthermia application is also rapidly growing. Taking this increasing clinical experience carefully into account together with the huge amount of new biological data on heat response of cells and tissues, the approach of magnetic fluid hyperthermia (MFH) is nowadays more promising than ever before. The present contribution reviews the current state of the art and some of the future perspectives supported by advanced methods of the so-called nanotechnology.

  5. AC transport in p-Ge/GeSi quantum well in high magnetic fields

    SciTech Connect

    Drichko, I. L.; Malysh, V. A.; Smirnov, I. Yu.; Golub, L. E.; Tarasenko, S. A.; Suslov, A. V.; Mironov, O. A.; Kummer, M.; Känel, H. von

    2014-08-20

    The contactless surface acoustic wave technique is implemented to probe the high-frequency conductivity of a high-mobility p-Ge/GeSi quantum well structure in the regime of integer quantum Hall effect (IQHE) at temperatures 0.3–5.8 K and magnetic fields up to 18 T. It is shown that, in the IQHE regime at the minima of conductivity, holes are localized and ac conductivity is of hopping nature and can be described within the “two-site” model. The analysis of the temperature and magnetic-field-orientation dependence of the ac conductivity at odd filing factors enables us to determine the effective hole g-factor, |g{sub zz}|≈4.5. It is shown that the in-plane component of the magnetic field leads to a decrease in the g-factor as well as increase in the cyclotron mass, which is explained by orbital effects in the complex valence band of germanium.

  6. Enhancement of the thermoelectric figure of merit in a quantum dot due to external ac field

    NASA Astrophysics Data System (ADS)

    Chen, Qiao; Wang, Zhi-yong; Xie, Zhong-Xiang

    2013-08-01

    We investigate the figure of merit of a quantum dot (QD) system irradiated with an external microwave filed by nonequilibrium Green's function (NGF) technique. Results show that the frequency of microwave field influence the figure of merit ZT significantly. At low temperature, a sharp peak can be observed in the figure of merit ZT as the frequency of ac field increases. As the frequency varies, several zero points and resonant peaks emerge in the figure of merit ZT. By adjusting the frequency of the microwave field, we can obtain high ZT. The figure of merit ZT increases with the decreasing of linewidth function Γ. In addition, Wiedemann-Franz law does not hold, particularly in the low frequency region due to multi-photon emission and absorption. Some novel thermoelectric properties are also found in two-level QD system.

  7. Orientation and Pearl-Chain Formation of Paramecia Induced by AC Electric Field

    NASA Astrophysics Data System (ADS)

    Hatakeyama, Toyomasa; Tanji, Ayafumi; Yagi, Hiroshi

    1987-11-01

    Paramecium deciliated with ethanol is able to orient itself in a parallel (positive orientation) or perpendicular direction (negative orientation) to an AC electric field, depending upon the applied frequency. We found that this turnover frequency is between 1 and 10 MHz in a non-electrolyte solution for the cells. The cells also aggregate with one another by the mutual dielectrophoresis in the electric field, provided the distance between the two cells is shorter than about half their length. The two critical field intensities for the orientation and for the aggregation cannot be clearly distinguished. Consequently, when the cell density in the solution is sufficiently high, a positive or negative pearl-chain of the cells is formed, depending upon the applied frequency.

  8. Test Results of the AC Field Measurements of Fermilab Booster Corrector Magnets

    SciTech Connect

    DiMarco, E.Joseph; Harding, D.J.; Kashikhin, V.S.; Kotelnikov, S.K.; Lamm, M.J.; Makulski, A.; Nehring, R.; Orris, D.F.; Schlabach, P.; Sylvester, C.; Tartaglia, Michael Albert; /Fermilab

    2008-06-25

    Multi-element corrector magnets are being produced at Fermilab that enable correction of orbits and tunes through the entire cycle of the Booster, not just at injection. The corrector package includes six different corrector elements--normal and skew orientations of dipole, quadrupole, and sextupole--each independently powered. The magnets have been tested during typical AC ramping cycles at 15Hz using a fixed coil system to measure the dynamic field strength and field quality. The fixed coil is comprised of an array of inductive pick-up coils around the perimeter of a cylinder which are sampled simultaneously at 100 kHz with 24-bit ADC's. The performance of the measurement system and a summary of the field results are presented and discussed.

  9. From earthquake size to far-field tsunami amplitude: development of a simple formula and application to DART buoy data

    NASA Astrophysics Data System (ADS)

    Okal, Emile A.; Reymond, Dominique; Hébert, Hélène

    2014-01-01

    We derive a simple formula relating tsunami amplitude in the far field to seismic moment, distance and azimuth from propagating rupture. Our formula is obtained from a comparison of a set of 4650 Pacific-wide simulations, computed for a series of sources spread over 10 subduction zones and four order of magnitudes in seismic moments. Our simulations are run both for a real grid reproducing the true bathymetry of the Pacific Basin and for an idealized one featuring a constant depth of 4000 m and no shorelines. This enables us to study and model separately the influence on the final amplitude of a tsunami wave of effects such as directivity and irregular bathymetry. The contribution of source size directivity and propagation over the sphere are studied using the constant-depth simulations. The influence of distance does not require any dispersive term and is properly modelled by geometrical spreading on the sphere. The directivity term, described classically in the frequency domain by Ben-Menahem & Rosenman can be approximated in the time domain by a moment-dependent linear regression as a function of azimuth. Finally, and after an allowance is made for the effect of receiver bathymetry using Green's law, the effect of irregular bathymetry is found to be generally defocusing, and can be modelled as a linear regression with distance. Once an estimate of the seismic moment of the parent earthquake is known, and under the assumption of a subduction mechanism along a fault of known azimuth, the resulting formula allows to forecast far-field tsunami amplitudes on the high seas. We use a data set of 116 tsunami amplitudes recorded at 51 past and present DART buoys following 21 tsunamigenic events to compare the estimates predicted by our algorithm to the amplitudes actually recorded. The average values of the residuals are 0.00 ± 0.25 logarithmic units, and 0.02 ± 0.20 at distances greater than 20°. An important aspect of our algorithm is that it correctly predicts the

  10. Mimicking Dirac fields in curved spacetime with fermions in lattices with non-unitary tunneling amplitudes

    NASA Astrophysics Data System (ADS)

    Minář, Jiří; Grémaud, Benoît

    2015-04-01

    In this paper we show that a Dirac Hamiltonian in a curved background spacetime can be interpreted, when discretized, as a tight-binding Hamiltonian with non-unitary tunneling amplitudes. We find the form of the non-unitary tunneling matrices in terms of the metric tensor. The main motivation behind this exercise is the feasibility of such Hamiltonians by means of laser-assisted tunnelings in cold atomic experiments. The mapping thus provides a physical interpretation of such Hamiltonians. We demonstrate the use of the mapping on the example of a time-dependent metric in 2+1 dimensions. Studying the spin dynamics, we find qualitative agreement with known theoretical predictions, namely particle pair creation in an expanding Universe.

  11. Far-field sub-diffraction focusing lens based on binary amplitude-phase mask for linearly polarized light.

    PubMed

    Chen, Gang; Zhang, Kun; Yu, Anping; Wang, Xianyou; Zhang, Zhihai; Li, Yuyan; Wen, Zhongquan; Li, Chen; Dai, Luru; Jiang, Senling; Lin, Feng

    2016-05-16

    Planar lenses are attractive photonic devices due to its minimized size and easy to integrate. However, planar lenses designed in traditional ways are restricted by the diffraction limit. They have difficulties in further reducing the focal spot size beyond the diffraction limit. Super-oscillation provides a possible way to solve the problem. However, lenses based on super-oscillation have always been affected by huge sidelobes, which resulted in limited field of view and difficulties in real applications. To address the problem, in the paper, a far-field sub-diffraction lens based on binary amplitude-phase mask was demonstrated under illumination of linearly polarized plane wave at wavelength 632.8 nm. The lens realized a long focal length of 148λ (94 µm), and the full width at half maximum of the focal line was 0.406λ, which was super-oscillatory. More important is that such a flat lens has small sidelobes and wide field of view. Within the measured range of [-132λ, + 120λ], the maximum sidelobe observed on the focal plane was less than 22% of the central peak. Such binary amplitude-phase planar lens can also be extended to long focal length far-field sub-diffraction focusing lens for other spectrum ranges. PMID:27409922

  12. Fokker-Planck equation with arbitrary dc and ac fields: continued fraction method.

    PubMed

    Lee, Chee Kong; Gong, Jiangbin

    2011-07-01

    The continued fraction method (CFM) is used to solve the Fokker-Planck equation with arbitrary dc and ac fields. With an appropriate choice of basis functions, the Fokker-Planck equation is converted into a set of linear algebraic equations with short-ranged coupling and then CFM is implemented to obtain numerical solutions with high efficiency. Both a proposed perturbative CFM and the numerically exact matrix CFM are used to study the nonlinear response of driven systems, with their results compared to assess the validity regime of the perturbative approach. The proposed perturbative CFM approach needs scalar quantities only and hence is more efficient within its validity regime. Two nonlinear systems of different nature are used as examples: molecular dipole (rotational Brownian motion) and particle in a periodic potential (translational Brownian motion). The associated full dynamics is presented in the compact form of hysteresis loops. It is observed that as the strength of an AC driving field increases, pronounced nonlinear effects are manifested in the deformation of the hysteresis loops. PMID:21867110

  13. Modeling of Nanoparticle-Mediated Electric Field Enhancement Inside Biological Cells Exposed to AC Electric Fields

    NASA Astrophysics Data System (ADS)

    Tiwari, Pawan K.; Kang, Sung Kil; Kim, Gon Jun; Choi, Jun; Mohamed, A.-A. H.; Lee, Jae Koo

    2009-08-01

    We present in this article the effect of alternating electric field at kilohertz (kHz) and megahertz (MHz) frequencies on the biological cells in presence and absence of nanoparticles. The induced electric field strength distribution in the region around cell membrane and nucleus envelope display different behavior at kHz and MHz frequencies. The attachment of gold nanoparticles (GNPs), especially gold nanowires around the surface of nucleus induce enhanced electric field strengths. The induced field strengths are dependent on the length of nanowire and create varying field regions when the length of nanowire is increased from 2 to 4 µm. The varying nanowire length increased the induced field strengths inside nucleoplasm and region adjacent to the nucleus in the cytoplasm. We investigated a process of electrostatic disruption of nucleus membrane when the induced electric field strength across the nucleus exceeds its tensile strength.

  14. Field Evolved Resistance in Helicoverpa armigera (Lepidoptera: Noctuidae) to Bacillus thuringiensis Toxin Cry1Ac in Pakistan

    PubMed Central

    Alvi, Anwaar H. K.; Sayyed, Ali H.; Naeem, Muhammad; Ali, Muhammad

    2012-01-01

    Helicoverpa armigera (Hübner) is one of the most destructive pests of several field and vegetable crops, with indiscriminate use of insecticides contributing to multiple instances of resistance. In the present study we assessed whether H. armigera had developed resistance to Bt cotton and compared the results with several conventional insecticides. Furthermore, the genetics of resistance was also investigated to determine the inheritance to Cry1Ac resistance. To investigate the development of resistance to Bt cotton, and selected foliar insecticides, H. armigera populations were sampled in 2010 and 2011 in several cotton production regions in Pakistan. The resistance ratios (RR) for Cry1Ac, chlorpyrifos, profenofos, cypermethrin, spinosad, indoxacarb, abamectin and deltamethrin were 580-fold, 320-, 1110-, 1950-, 200-, 380, 690, and 40-fold, respectively, compared with the laboratory susceptible (Lab-PK) population. Selection of the field collected population with Cry1Ac in 2010 for five generations increased RR to 5440-fold. The selection also increased RR for deltamethrin, chlorpyrifos, profenofos, cypermethrin, spinosad, indoxacarb, abamectin to 125-folds, 650-, 2840-, 9830-, 370-, 3090-, 1330-fold. The estimated LC50s for reciprocal crosses were 105 µg/ml (Cry1Ac-SEL female × Lab-PK male) and 81 g µg/ml (Lab-PK female × Cry1Ac-SEL male) suggesting that the resistance to Cry1Ac was autosomal; the degree of dominance (DLC) was 0.60 and 0.57 respectively. Mixing of enzyme inhibitors significantly decreased resistance to Cry1Ac suggesting that the resistance to Cry1Ac and other insecticides tested in the present study was primarily metabolic. Resistance to Cry1Ac was probably due to a single but unstable factor suggesting that crop rotation with non-Bt cotton or other crops could reduce the selection pressure for H. armigera and improve the sustainability of Bt cotton. PMID:23077589

  15. Field evolved resistance in Helicoverpa armigera (Lepidoptera: Noctuidae) to Bacillus thuringiensis toxin Cry1Ac in Pakistan.

    PubMed

    Alvi, Anwaar H K; Sayyed, Ali H; Naeem, Muhammad; Ali, Muhammad

    2012-01-01

    Helicoverpa armigera (Hübner) is one of the most destructive pests of several field and vegetable crops, with indiscriminate use of insecticides contributing to multiple instances of resistance. In the present study we assessed whether H. armigera had developed resistance to Bt cotton and compared the results with several conventional insecticides. Furthermore, the genetics of resistance was also investigated to determine the inheritance to Cry1Ac resistance. To investigate the development of resistance to Bt cotton, and selected foliar insecticides, H. armigera populations were sampled in 2010 and 2011 in several cotton production regions in Pakistan. The resistance ratios (RR) for Cry1Ac, chlorpyrifos, profenofos, cypermethrin, spinosad, indoxacarb, abamectin and deltamethrin were 580-fold, 320-, 1110-, 1950-, 200-, 380, 690, and 40-fold, respectively, compared with the laboratory susceptible (Lab-PK) population. Selection of the field collected population with Cry1Ac in 2010 for five generations increased RR to 5440-fold. The selection also increased RR for deltamethrin, chlorpyrifos, profenofos, cypermethrin, spinosad, indoxacarb, abamectin to 125-folds, 650-, 2840-, 9830-, 370-, 3090-, 1330-fold. The estimated LC(50s) for reciprocal crosses were 105 µg/ml (Cry1Ac-SEL female × Lab-PK male) and 81 g µg/ml (Lab-PK female × Cry1Ac-SEL male) suggesting that the resistance to Cry1Ac was autosomal; the degree of dominance (D(LC)) was 0.60 and 0.57 respectively. Mixing of enzyme inhibitors significantly decreased resistance to Cry1Ac suggesting that the resistance to Cry1Ac and other insecticides tested in the present study was primarily metabolic. Resistance to Cry1Ac was probably due to a single but unstable factor suggesting that crop rotation with non-Bt cotton or other crops could reduce the selection pressure for H. armigera and improve the sustainability of Bt cotton. PMID:23077589

  16. Measurements on magnetized GdBCO pellets subjected to small transverse ac magnetic fields at very low frequency: Evidence for a slowdown of the magnetization decay

    NASA Astrophysics Data System (ADS)

    Fagnard, Jean-Francois; Kirsch, Sébastien; Morita, Mitsuru; Teshima, Hidekazu; Vanderheyden, Benoit; Vanderbemden, Philippe

    2015-05-01

    Due to their ability to trap large magnetic inductions, superconducting bulk materials can be used as powerful permanent magnets. The permanent magnetization of such materials, however, can be significantly affected by the application of several cycles of a transverse variable magnetic field. In this work, we study, at T = 77 K, the long term influence of transverse ac magnetic fields of small amplitudes (i.e. much smaller than the full penetration field) on the axial magnetization of a bulk single grain superconducting GdBCO pellet over a wide range of low frequencies (1 mHz-20 Hz). Thermocouples are placed against the pellet surface to probe possible self-heating of the material during the experiments. A high sensitivity cryogenic Hall probe is placed close to the surface to record the local magnetic induction normal to the surface. The results show first that, for a given number of applied triangular transverse cycles, higher values of dBapp/dt induce smaller magnetization decays. An important feature of practical interest is that, after a very large number of cycles which cause the loss of a substantial amount of magnetization (depending on the amplitude and the frequency of the field), the rate of the magnetization decay goes back to its initial value, corresponding to the relaxation of the superconducting currents due to flux creep only. In the amplitude and frequency range investigated, the thermocouples measurements and a 2D magneto-thermal modelling show no evidence of sufficient self-heating to affect the magnetization so that the effect of the transverse magnetic field cycles on the trapped magnetic moment is only attributed to a redistribution of superconducting currents in the volume of the sample and not to a thermal effect.

  17. Nonlinear elastic effects in phase field crystal and amplitude equations: Comparison to ab initio simulations of bcc metals and graphene

    NASA Astrophysics Data System (ADS)

    Hüter, Claas; Friák, Martin; Weikamp, Marc; Neugebauer, Jörg; Goldenfeld, Nigel; Svendsen, Bob; Spatschek, Robert

    2016-06-01

    We investigate nonlinear elastic deformations in the phase field crystal model and derived amplitude equation formulations. Two sources of nonlinearity are found, one of them is based on geometric nonlinearity expressed through a finite strain tensor. This strain tensor is based on the inverse right Cauchy-Green deformation tensor and correctly describes the strain dependence of the stiffness for anisotropic and isotropic behavior. In isotropic one- and two-dimensional situations, the elastic energy can be expressed equivalently through the left deformation tensor. The predicted isotropic low-temperature nonlinear elastic effects are directly related to the Birch-Murnaghan equation of state with bulk modulus derivative K'=4 for bcc. A two-dimensional generalization suggests K2D '=5 . These predictions are in agreement with ab initio results for large strain bulk deformations of various bcc elements and graphene. Physical nonlinearity arises if the strain dependence of the density wave amplitudes is taken into account and leads to elastic weakening. For anisotropic deformation, the magnitudes of the amplitudes depend on their relative orientation to the applied strain.

  18. ac losses and field and current density distribution during a full cycle of a stack of superconducting tapes

    NASA Astrophysics Data System (ADS)

    Yuan, Weijia; Campbell, A. M.; Coombs, T. A.

    2010-05-01

    Starting from an existing model by Clem et al., this paper has analyzed how the current density and magnetic field distribution of a stack of superconducting tapes with ac transport currents or applied fields will change in a full cycle. This paper assumes when the ac current or field starts to change in the other direction, a new penetrated region will begin to penetrate from the superconductor surface. If we assume Jc is constant in the critical region, this paper demonstrates that the Claassen formula (7) can be used to calculate the exact ac losses. If Jc depends on local Bz, we can use Eq. (9) to quickly predict the ac losses. This approach does not need to calculate a complete ac cycle. This saves considerably computation time while gives a result which is in close agreement with that calculated from a complete ac cycle. The calculation method can be applied for calculating a superconducting pancake coil if the coil radius is much larger than the tape width.

  19. Accelerated Detection of Viral Particles by Combining AC Electric Field Effects and Micro-Raman Spectroscopy

    PubMed Central

    Tomkins, Matthew Robert; Liao, David Shiqi; Docoslis, Aristides

    2015-01-01

    A detection method that combines electric field-assisted virus capture on antibody-decorated surfaces with the “fingerprinting” capabilities of micro-Raman spectroscopy is demonstrated for the case of M13 virus in water. The proof-of-principle surface mapping of model bioparticles (protein coated polystyrene spheres) captured by an AC electric field between planar microelectrodes is presented with a methodology for analyzing the resulting spectra by comparing relative peak intensities. The same principle is applied to dielectrophoretically captured M13 phage particles whose presence is indirectly confirmed with micro-Raman spectroscopy using NeutrAvidin-Cy3 as a labeling molecule. It is concluded that the combination of electrokinetically driven virus sampling and micro-Raman based signal transduction provides a promising approach for time-efficient and in situ detection of viruses. PMID:25580902

  20. Theoretical study on the amplitude ratio of the seismoelectric field to the Stoneley wave and the formation tortuosity estimation from seismoelectric logs

    NASA Astrophysics Data System (ADS)

    Guan, Wei; Yin, Chenggang; Wang, Jun; Cui, Naigang; Hu, Hengshan; Wang, Zhi

    2015-12-01

    Seismoelectric logging has potential applications in exploring the porous formation characteristics. In this study, we theoretically address how the amplitudes of the Stoneley wave and its accompanying borehole seismoelectric field depend on the porous formation parameters such as porosity, permeability and tortuosity. We calculate the ratio of the electric field amplitude to the pressure amplitude (REP amplitude) for the low-frequency Stoneley wave of different formations and find that the REP amplitude is sensitive to porosity and tortuosity but insensitive to permeability. To confirm this conclusion, we derive the approximate expression of the REP amplitude in the wavenumber-frequency domain which shows that the REP amplitude is dependent on tortuosity but independent of permeability. This contradicts the result concluded by previous researchers from experiments that the REP amplitude is directly proportional to the permeability. The reason is probably attributed to the fact that the rock samples with different permeabilities typically have different tortuosities. Since the REP amplitude is sensitive to tortuosity, we propose a method of estimating formation tortuosity from seismoelectric logs. It is implemented by using the REP amplitude and the wavenumber of the Stoneley wave at a given frequency when the porosity and the pore fluid viscosity and salinity are known. We test the method by estimating the tortuosities from the synthetic seismoelectric waveforms in different formations. The result shows that the errors relative to the input tortuosities are lower than 5.0 per cent without considering the uncertainties of other input parameters.

  1. AC electric field induced dielectrophoretic assembly behavior of gold nanoparticles in a wide frequency range

    NASA Astrophysics Data System (ADS)

    Liu, Weiyu; Wang, Chunhui; Ding, Haitao; Shao, Jinyou; Ding, Yucheng

    2016-05-01

    In this work, we focus on frequency-dependence of pearl chain formations (PCF) of gold nanoparticles driven by AC dielectrophoresis (DEP), especially in a low field-frequency range, where induced double-layer charging effect at ideally polarizable surfaces on particle DEP behavior and surrounding liquid motion need not be negligible. As field frequency varies, grown features of DEP assembly structures ranging from low-frequency non-bridged gap to high-frequency single gold nanoparticle-made nanowires bridging the electrodes are demonstrated experimentally. Specifically, at 10 kHz, a kind of novel channel-like structure with parallel opposing banks is formed at the center of interelectrode gap. In stark contrast, at 1 MHz, thin PCF with diameter of 100 nm is created along the shortest distance of the isolation spacing. Moreover, a particular conductive path of nanoparticle chains is produced at 1 MHz in a DEP device embedded with multiple floating electrodes. A theoretical framework taking into account field-induced double-layer polarization at both the particle/electrolyte and electrode/electrolyte interface is developed to correlate these experimental observations with induced-charge electrokinetic (ICEK) phenomenon. And a RC circuit model is helpful in accounting for the formation of this particular non-bridged channel-like structure induced by a low-frequency AC voltage. As compared to thin PCF formed at high field frequency that effectively short circuits the electrode pair, though it is difficult for complete PCF bridging to occur at low frequency, the non-bridged conducting microstructure has potential to further miniaturize the size of electrode gap fabricated by standard micromachining process and may find useful application in biochemical sensing.

  2. Human aquaporin 4 gating dynamics in dc and ac electric fields: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Garate, J.-A.; English, Niall J.; MacElroy, J. M. D.

    2011-02-01

    Water self-diffusion within human aquaporin 4 has been studied using molecular dynamics (MD) simulations in the absence and presence of external ac and dc electric fields. The computed diffusive (pd) and osmotic (pf) permeabilities under zero-field conditions are (0.718 ± 0.24) × 10-14 cm3 s-1 and (2.94 ± 0.47) × 10-14 cm3 s-1, respectively; our pf agrees with the experimental value of (1.50 ± 0.6) × 10-14 cm3 s-1. A gating mechanism has been proposed in which side-chain dynamics of residue H201, located in the selectivity filter, play an essential role. In addition, for nonequilibrium MD in external fields, it was found that water dipole orientation within the constriction region of the channel is affected by electric fields (e-fields) and that this governs the permeability. It was also found that the rate of side-chain flipping motion of residue H201 is increased in the presence of e-fields, which influences water conductivity further.

  3. Experimental study of the ponderomotive effects of a large amplitude microwave field on a magnetized electron beam

    SciTech Connect

    Hadjoudj, Y.; Pierre, T.; Heuraux, S.; Leclert, G.

    1995-11-01

    Charged particles propagating in an inhomogeneous large amplitude microwave field experience a nonlinear force called the ponderomotive force. This effect can be theoretically evaluated either from the single particle or the fluid theories. For magnetized particles, these two descriptions predict quite different behaviors. A previous experiment [J. Vaclavik {ital et} {ital al}., Phys. Fluids {bold 29}, 2034 (1986)] has shown results in agreement with the fluid theory. Here, an experiment with a magnetized electron beam is described, which brings out a ponderomotive deflection in agreement with the single particle theory. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  4. Single-cycle Terahertz Pulses with >0.2 V/A Field Amplitudes via Coherent Transition Radiation

    SciTech Connect

    Daranciang, Dan; Goodfellow, John; Fuchs, Matthias; Wen, Haidan; Ghimire, Shambhu; Reis, David A.; Loos, Henrik; Fisher, Alan S.; Lindenberg, Aaron M.; /Stanford U. Materials Sci. Dept. /SIMES, Stanford /SLAC, PULSE

    2012-02-15

    We demonstrate terahertz pulses with field amplitudes exceeding 0.2 V/{angstrom} generated by coherent transition radiation. Femtosecond, relativistic electron bunches generated at the Linac Coherent Light Source are passed through a beryllium foil, and the emitted radiation is characterized as a function of the bunch duration and charge. Broadband pulses centered at a frequency of 10 THz with energies of 140 {mu}J are measured. These far-below-bandgap pulses drive a nonlinear optical response in a silicon photodiode, with which we perform nonlinear autocorrelations that yield information regarding the terahertz temporal profile. Simulations of the spatiotemporal profile agree well with experimental results.

  5. Large-amplitude electric fields in the inner magnetosphere: Van Allen Probes observations of subauroral polarization streams

    NASA Astrophysics Data System (ADS)

    Califf, S.; Li, X.; Wolf, R. A.; Zhao, H.; Jaynes, A. N.; Wilder, F. D.; Malaspina, D. M.; Redmon, R.

    2016-06-01

    The subauroral polarization stream (SAPS) is an important magnetosphere-ionosphere (MI) coupling phenomenon that impacts a range of particle populations in the inner magnetosphere. SAPS studies often emphasize ionospheric signatures of fast westward flows, but the equatorial magnetosphere is also affected through strong radial electric fields in the dusk sector. This study focuses on a period of steady southward interplanetary magnetic field (IMF) during the 29 June 2013 geomagnetic storm where the Van Allen Probes observe a region of intense electric fields near the plasmapause over multiple consecutive outbound duskside passes. We show that the large-amplitude electric fields near the equatorial plane are consistent with SAPS by investigating the relationship between plasma sheet ion and electron boundaries, associated field-aligned currents, and the spatial location of the electric fields. By incorporating high-inclination DMSP data we demonstrate the spatial and temporal variability of the SAPS region, and we suggest that discrete, earthward propagating injections are driving the observed strong electric fields at low L shells in the equatorial magnetosphere. We also show the relationship between SAPS and plasmasphere erosion, as well as a possible correlation with flux enhancements for 100s keV electrons.

  6. Large amplitude oscillation of magnetization in spin-torque oscillator stabilized by field-like torque

    SciTech Connect

    Taniguchi, Tomohiro Kubota, Hitoshi; Imamura, Hiroshi; Tsunegi, Sumito

    2015-05-07

    Oscillation frequency of spin torque oscillator with a perpendicularly magnetized free layer and an in-plane magnetized pinned layer is theoretically investigated by taking into account the field-like torque. It is shown that the field-like torque plays an important role in finding the balance between the energy supplied by the spin torque and the dissipation due to the damping, which results in a steady precession. The validity of the developed theory is confirmed by performing numerical simulations based on the Landau-Lifshitz-Gilbert equation.

  7. Large amplitude oscillation of magnetization in spin-torque oscillator stabilized by field-like torque

    NASA Astrophysics Data System (ADS)

    Taniguchi, Tomohiro; Tsunegi, Sumito; Kubota, Hitoshi; Imamura, Hiroshi

    2015-05-01

    Oscillation frequency of spin torque oscillator with a perpendicularly magnetized free layer and an in-plane magnetized pinned layer is theoretically investigated by taking into account the field-like torque. It is shown that the field-like torque plays an important role in finding the balance between the energy supplied by the spin torque and the dissipation due to the damping, which results in a steady precession. The validity of the developed theory is confirmed by performing numerical simulations based on the Landau-Lifshitz-Gilbert equation.

  8. Adelic formulae for the gamma and beta functions of completions of algebraic number fields, and applications of them to string amplitudes

    NASA Astrophysics Data System (ADS)

    Vladimirov, Vasilii S.

    1996-02-01

    On the basis of analysis on the adele group (the Tate formula) of an algebraic number field, a regularization is constructed for the divergent adelic products of the gamma and beta functions of all (non-isomorphic) completions of this field. The formulae obtained are applied to representations of the four-point crossing-symmetric Veneziano amplitudes and Virasoro-Shapiro amplitudes in terms of regularized adelic products of string amplitudes (for open or closed strings) corresponding to all non-Archimedean completions of the algebraic number field under consideration.

  9. Large amplitude spin torque vortex oscillations at zero external field using a perpendicular spin polarizer

    SciTech Connect

    Dussaux, A.; Rache Salles, B.; Jenkins, A. S.; Bortolotti, P.; Grollier, J.; Cros, V.; Fert, A.; Khvalkovskiy, A. V.; Kubota, H.; Fukushima, A.; Yakushiji, K.; Yuasa, S.

    2014-07-14

    We investigate the microwave response of a spin transfer vortex based oscillator in a magnetic tunnel junction with an in-plane reference layer combined with a spin valve with an out-of-plane magnetization spin polarizing layer. The main advantage of this perpendicular spin polarizer is to induce a large spin transfer force even at zero magnetic field, thus leading to a record emitted power (up to 0.6 μW) associated to a very narrow spectral linewidth of a few hundreds of kHz. The characteristics of this hybrid vortex based spin transfer nano-oscillator obtained at zero field and room temperature are of great importance for applications based on rf spintronic devices as integrated and tunable microwave source and/or microwave detector.

  10. Near-Forward Rescattering Photoelectron Holography in Strong-Field Ionization: Extraction of the Phase of the Scattering Amplitude.

    PubMed

    Zhou, Yueming; Tolstikhin, Oleg I; Morishita, Toru

    2016-04-29

    We revisit the concept of near-forward rescattering strong-field photoelectron holography introduced by Y. Huismans et al. [Science 331, 61 (2011)]. The recently developed adiabatic theory is used to show how the phase of the scattering amplitude for near-forward rescattering of an ionized electron by the parent ion is encoded in and can be read out from the corresponding interference pattern in photoelectron momentum distributions (PEMDs) produced in the ionization of atoms and molecules by intense laser pulses. A procedure to extract the phase is proposed. Its application to PEMDs obtained by solving the time-dependent Schrödinger equation for a model atom yields results in good agreement with scattering calculations. This establishes a novel general approach to extracting structural information from strong-field observables capable of providing time-resolved imaging of ultrafast processes. PMID:27176518

  11. Near-Forward Rescattering Photoelectron Holography in Strong-Field Ionization: Extraction of the Phase of the Scattering Amplitude

    NASA Astrophysics Data System (ADS)

    Zhou, Yueming; Tolstikhin, Oleg I.; Morishita, Toru

    2016-04-01

    We revisit the concept of near-forward rescattering strong-field photoelectron holography introduced by Y. Huismans et al. [Science 331, 61 (2011)]. The recently developed adiabatic theory is used to show how the phase of the scattering amplitude for near-forward rescattering of an ionized electron by the parent ion is encoded in and can be read out from the corresponding interference pattern in photoelectron momentum distributions (PEMDs) produced in the ionization of atoms and molecules by intense laser pulses. A procedure to extract the phase is proposed. Its application to PEMDs obtained by solving the time-dependent Schrödinger equation for a model atom yields results in good agreement with scattering calculations. This establishes a novel general approach to extracting structural information from strong-field observables capable of providing time-resolved imaging of ultrafast processes.

  12. Mesoscopic turbulence and local order in Janus particles self-propelling under an ac electric field

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Daiki; Sano, Masaki

    2015-11-01

    To elucidate mechanisms of mesoscopic turbulence exhibited by active particles, we experimentally study turbulent states of nonliving self-propelled particles. We realize an experimental system with dense suspensions of asymmetrical colloidal particles (Janus particles) self-propelling on a two-dimensional surface under an ac electric field. Velocity fields of the Janus particles in the crowded situation can be regarded as a sort of turbulence because it contains many vortices and their velocities change abruptly. Correlation functions of their velocity field reveal the coexistence of polar alignment and antiparallel alignment interactions, which is considered to trigger mesoscopic turbulence. Probability distributions of local order parameters for polar and nematic orders indicate the formation of local clusters with particles moving in the same direction. A broad peak in the energy spectrum of the velocity field appears at the spatial scales where the polar alignment and the cluster formation are observed. Energy is injected at the particle scale and conserved quantities such as energy could be cascading toward the larger clusters.

  13. Mesoscopic turbulence and local order in Janus particles self-propelling under an ac electric field.

    PubMed

    Nishiguchi, Daiki; Sano, Masaki

    2015-11-01

    To elucidate mechanisms of mesoscopic turbulence exhibited by active particles, we experimentally study turbulent states of nonliving self-propelled particles. We realize an experimental system with dense suspensions of asymmetrical colloidal particles (Janus particles) self-propelling on a two-dimensional surface under an ac electric field. Velocity fields of the Janus particles in the crowded situation can be regarded as a sort of turbulence because it contains many vortices and their velocities change abruptly. Correlation functions of their velocity field reveal the coexistence of polar alignment and antiparallel alignment interactions, which is considered to trigger mesoscopic turbulence. Probability distributions of local order parameters for polar and nematic orders indicate the formation of local clusters with particles moving in the same direction. A broad peak in the energy spectrum of the velocity field appears at the spatial scales where the polar alignment and the cluster formation are observed. Energy is injected at the particle scale and conserved quantities such as energy could be cascading toward the larger clusters. PMID:26651697

  14. Deformation and Interaction of Droplet Pairs in a Microchannel Under ac Electric Fields

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodong; Song, Yongxin; Li, Dongqing; Hu, Guoqing

    2015-08-01

    The deformation and interaction of a droplet pair in an electric field determine the success of droplet coalescence. Electric intensity and initial droplet separation are crucial parameters in this process. In this work, a combined theoretical and numerical analysis is performed to study the electrohydrodynamics of confined droplet pairs in a rectangular microchannel under ac electric fields. We develop a theoretical model to predict the relationship between critical electric intensity and droplet separation. A geometrical model relating the initial droplet separation to the cone angle is also established to determine the critical separation for partial coalescence. These models are validated by comparisons with existing experimental observations. According to the initial separation and electric intensity, five regimes of droplet interactions are classified by direct numerical simulations, namely noncoalescence, coalescence, partial coalescence, ejection after coalescence, and ejection with partial coalescence. According to their controlling mechanisms, the five regimes are distinguished by three well-defined boundaries. The detailed dynamics of the partial coalescence phenomenon is resolved when the droplet separation exceeds the critical value. A dynamic liquid bridge between the droplets is sustained by the competition between surface tension and electric stress. The dynamics of ejected microjets at the exterior ends are also addressed to show their responses to the oscillating electric field. The full understanding of the droplet dynamics under electric fields can be used to predict the droplet fusion behaviors and thus to facilitate the design of droplet-based microfluidic devices.

  15. Standard and nonstandard nematic electrohydrodynamic convection in the presence of asymmetric ac electric fields

    NASA Astrophysics Data System (ADS)

    Low, Jonathan; Hogan, S. John

    2008-10-01

    In planar nematic electrohydrodynamic convection (EHC), a microscopic liquid crystal cell is driven by a homogeneous ac electric field, which, if strong enough, causes the fluid to destabilize into a regular pattern-forming state. We consider asymmetric electric fields E(t)=E(t+T)≠-E(t+T/2) , which leads to the possibility of three different types of instabilities at onset: conductive, dielectric, and subharmonic. The first two are already well known as they are easily produced when the system is driven by symmetric electric fields; the third can only occur when the electric field symmetry is broken. We present theoretical results on EHC using linear stability analysis and Floquet theory. We consider rigid and free boundary conditions, extending the model to two Fourier modes in the vertical plane, the inclusion of flexoelectricity, and using standard (nematic electric conductivity σa>0 and dielectric anisotorpy γa<0 ) and nonstandard (σa<0) material parameters. We make full use of a three-dimensional linear model where two mutually perpendicular planar wave numbers q and p can be varied. Our results show that there is a qualitative difference between the boundary conditions used, which is also dependent on how many vertical Fourier modes were used in the model. We have obtained threshold values favoring oblique rolls in subharmonic and dielectric regimes in parameter space. For the nonstandard EHC parameter values, both conduction and subharmonic regimes disappear and only the dielectric threshold exists.

  16. The effect of dissipation on the torque and force experienced by nanoparticles in an AC field

    NASA Astrophysics Data System (ADS)

    Claro, F.; Fuchs, R.; Robles, P.; Rojas, R.

    2015-09-01

    We discuss the force and torque acting on spherical particles in an ensemble in the presence of a uniform AC electric field. We show that for a torque causing particle rotation to appear the particle must be absorptive. Our proof includes all electromagnetic excitations, which in the case of two or more particles gives rise to one or more resonances in the spectrum of force and torque depending on interparticle distance. Several peaks are found in the force and torque between two spheres at small interparticle distances, which coalesce to just one as the separation grows beyond three particle radii. We also show that in the presence of dissipation the force on each particle is nonconservative and may not be derived from the classical interaction potential energy as has been done in the past.

  17. External dc bias field effects in the nonlinear ac stationary response of permanent dipoles in a uniaxial potential

    NASA Astrophysics Data System (ADS)

    Wei, Nijun; Coffey, William T.; Déjardin, Pirre-Michel; Kalmykov, Yuri P.

    External dc bias field effects on the nonlinear dielectric relaxation and dynamic Kerr effect of a system of permanent dipoles in a uniaxial mean field potential are studied via the rotational Brownian motion model. Postulated in terms of the infinite hierarchy of differential-recurrence equations for the statistical moments (the expectation value of the Legendre polynomials), the dielectric and Kerr effect ac stationary responses may be evaluated for arbitrary dc bias field strength via perturbation theory in the ac field. We have given two complementary approaches for treating the nonlinear effects. The first is based on perturbation theory allowing one to calculate the nonlinear ac stationary responses using powerful matrix methods. The second approach based on the accurate two-mode approximation [D.A. Garanin, Phys. Rev. E. 54, 3250 (1996)] effectively generalizes the existing results for dipolar systems in superimposed ac and dc fields to a mean field potential. The results apply both to nonlinear dielectric relaxation and dynamic Kerr effect of nematics and to magnetic birefringence relaxation of ferrofluids. Furthermore, the given methods of the solution of infinite hierarchies of multi-term recurrence relations are quite general and can be applied to analogous nonlinear response problems.

  18. 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.

  19. Effects of low-intensity AC and/or DC electromagnetic fields on cell attachment and induction of apoptosis

    SciTech Connect

    Blumenthal, N.C.; Ricci, J.; Breger, L.; Zychlinsky, A.; Solomon, H.; Chen, G.G.; Kuznetsov, D.; Dorfman, R.

    1997-05-01

    Rat tendon fibroblast (RTF) and rat bone marrow (RBM) osteoprogenitor cells were cultured and exposed to AC and/or DC magnetic fields in a triaxial Helmholtz coil in an incubator for up to 13 days. The AC fields were at 60 and 1,000 Hz and up to 0.25 mT peak to peak, and the DC fields were up to 0.25 mT. At various combinations of field strengths and frequencies, AC and/or DC fields resulted in extensive detachment of preattached cells and prevented the normal attachment of cells not previously attached to substrates. In addition, the fields resulted in altered cell morphologies. When RTF and RBM cells were removed from the fields after several days of exposure, they partially reattached and assumed more normal morphologies. An additional set of experiments described in the Appendix corroborates these findings and also shows that low-frequency EMF also initiates apoptosis, i.e., programmed cell death, at the onset of cell detachment. Taken together, these results suggest that the electromagnetic fields result in significant alterations in cell metabolism and cytoskeleton structure. Further work is required to determine the relative effect of the electric and magnetic fields on these phenomena. The research has implications for understanding the role of fields in affecting bone healing in fracture nonunions, in cell detachment in cancer metastasis, and in the effect of EMF on organisms generally.

  20. High-Resolution ac Measurements of the Hall Effect in Organic Field-Effect Transistors

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Yi, H. T.; Podzorov, V.

    2016-03-01

    We describe a high resolving power technique for Hall-effect measurements, efficient in determining Hall mobility and carrier density in organic field-effect transistors and other low-mobility systems. We utilize a small low-frequency ac magnetic field (Brms<0.25 T ) and a phase-sensitive (lock-in) detection of Hall voltage, with the necessary corrections for Faraday induction. This method significantly enhances the signal-to-noise ratio and eliminates the necessity of using high magnetic fields in Hall-effect studies. With the help of this method, we are able to obtain the Hall mobility and carrier density in organic transistors with a mobility as low as μ ˜0.3 cm2 V-1 s-1 by using a compact desktop apparatus and low magnetic fields. We find a good agreement between Hall-effect and electric-field-effect measurements, indicating that, contrary to the common belief, certain organic semiconductors with mobilities below 1 cm2 V-1 s-1 can still exhibit a fully developed, band-semiconductor-like Hall effect, with the Hall mobility and carrier density matching those obtained in longitudinal transistor measurements. This suggests that, even when μ <1 cm2 V-1 s-1 , charges in organic semiconductors can still behave as delocalized coherent carriers. This technique paves the way to ubiquitous Hall-effect studies in a wide range of low-mobility materials and devices, where it is typically very difficult to resolve the Hall effect even in very high dc magnetic fields.

  1. 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.

  2. Effect of n = 3 perturbation field amplitudes below the ELM triggering threshold on edge and SOL transport in NSTX

    DOE PAGESBeta

    J. M. Canik; Lore, J. D.; Ahn, J. -W.; Bortolon, A.; Fredrickson, E. D.; Jaworski, M. A.; Kramer, G. J.; Maingi, R.; McLean, A. G.; Scotti, F.; et al

    2013-01-12

    Here, the pulsed application of n = 3 magnetic perturbation fields with amplitudes below that which triggers ELMs results in distinct, transient responses observable on several edge and divertor diagnostics in NSTX. We refer to these responses as Sub-Threshold Edge Perturbations (STEPs). An analysis of edge measurements suggests that STEPs result in increased transport in the plasma edge and scrape-off layer, which leads to augmentation of the intrinsic strike point splitting due to error fields, i.e., an intensification of the helical divertor footprint flux pattern. These effects are much smaller in magnitude than those of triggered ELMs, and are observedmore » for the duration of the field perturbation measured internal to the vacuum vessel. In addition, STEPs are correlated with changes to the MHD activity, along with transient reductions in the neutron production rate. Ideally the STEPs could be used to provide density control and prevent impurity accumulation, in the same manner that on-demand ELM triggering is used on NSTX, without the impulsive divertor fluxes and potential for damage to plasma facing components associated with ELMs.« less

  3. Generation of zonal flow and magnetic field by finite-amplitude waves in the ionospheric E-layer

    NASA Astrophysics Data System (ADS)

    Kahlon, Laila; Kaladze, Tamaz

    2016-07-01

    We review the generation of zonal flow and magnetic field by coupled electromagnetic (EM) ULF waves in the Earth's ionospheric E layer. It is shown that under the typical ionospheric E-layer conditions different planetary low-frequency waves can couple with each other. Propagation of coupled internal-gravity-Alfvén (CIGA), coupled Rossby-Khantadze (CRK) and coupled Rossby-Alfvén-Khantadze (CRAK) waves is revealed and studied. A set of appropriate equations describing the nonlinear interaction of such waves with sheared zonal flow is derived. The conclusion on the instability of short wavelength turbulence of such coupled waves with respect to the excitation of low-frequency and large-scale perturbation of the sheared zonal flow and sheared magnetic field is deduced. The nonlinear mechanism of the instability is based on the parametric triple interaction of finite amplitude coupled waves leading to the inverse energy cascade toward the longer wavelength. The possibility of generation of the intense mean magnetic field is shown. Obtained growth rates are discussed for each case of the considered coupled waves.

  4. Post-Flash Calibration Darks for the Advanced Camera for Surveys Wide Field Channel (ACS/WFC)

    NASA Astrophysics Data System (ADS)

    Ogaz, S.; Anderson, J.; Golimowski, D.

    2015-06-01

    We present a summary and analysis of the changes made to the ACS/WFC dark reference files. As of January 15, 2015 the ACS team has begun to produce post- flashed dark reference files for the Wide Field Channel (WFC). This change was made to combat the charge transfer efficiency (CTE) losses caused by radiation damage that the two WFC CCDs have suffered since being put into orbit by artificially increasing the background in the dark images. This has resulted in several changes to the reference file pipeline, and an improved calibration dark.

  5. Thermodynamics of the Mn12-ac molecule in a skew magnetic field at T \\gtrsim 21 K

    NASA Astrophysics Data System (ADS)

    Rojas, Onofre; Thomaz, M. T.; Corrêa Silva, E. V.; de Souza, S. M.

    2009-01-01

    We derive the high-temperature expansion of the Helmholtz free energy of the quantum and classical models for the Mn12-ac molecule in the presence of a skew magnetic field, including the transverse term in the Hamiltonians, for T \\gtrsim 21 K. In this region of temperature, we show that the transverse term can give a measurable contribution to the x component of the magnetization. We obtain the specific heat per site of a powder sample of Mn12-ac under a constant magnetic field. For strong skew magnetic fields (h/D>1), the specific heat differs up to 20% from its value of a crystal sample under purely longitudinal magnetic fields. Finally, we obtain that in the limit T \\rightarrow \\infty , the values of the classical and quantum specific heat differ; in particular, for \\vec {h}= \\vec 0 this difference is 0.96%.

  6. Study of the Dependence on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

    NASA Technical Reports Server (NTRS)

    Bandler, Simon

    2011-01-01

    At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in the AC bias configuration. For x-ray photons at 6keV the AC biased pixel shows a best energy resolution of 3.7eV, which is about a factor of 2 worse than the energy resolution observed in identical DC-biased pixels. To better understand the reasons of this discrepancy, we investigated the detector performance as a function of temperature, bias working point and applied magnetic field. A strong periodic dependence of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recent weak-link behaviour observed inTES microcalorimeters.

  7. Production Of Multi-magnetron Plasma By Using Polyphase Ac Glow Discharge In An Improved Multi-pole Magnetic Field

    NASA Astrophysics Data System (ADS)

    Matsumoto, Kazunori; Motoki, Kentaro; Miyamoto, Masahiro; Uetani, Yasuhiro

    1998-10-01

    Effects of an improved multi-pole magnetic field on a plasma production generated by a polyphase ac glow discharge with multiple electrodes have been investigated. Conventional configuration of the multi-pole magnetic filed has been modified to suppress plasma losses at both ends of the chamber due to ExB drift motion. The modified multi-pole magnetic field has enabled us to produce a multiple magnetron-plasma at a considerably low pressure less than mTorr. The low temperature plasma has been widely used as the fine processing technology of a dry etching and as the thin film formation technology of a sputtering coating. Large-scale plasmas which can be generated at a low gas-pressure have been desired for more wider dry etching and greater sputter coating. The purpose of this study is to develop a large-scale and low-cost plasma generator by using a polyphase ac power source with the low frequency. In this session, we will present the experimental result as to a multiple magnetron-plasma generated in the modified twenty-four poles magnetic field by using the twenty-four-phase ac power source with the commercial electric power frequency of 60Hz. The ac power is supplied to twenty-four electrodes which are fixed to the water-cooled chamber-wall through sheet insulators so that the electrodes can be cooled indirectly.

  8. Effects of AC/DC magnetic fields, frequency, and nanoparticle aspect ratio on cellular transfection of gene vectors

    NASA Astrophysics Data System (ADS)

    Ford, Kris; Mair, Lamar; Fisher, Mike; Rowshon Alam, Md.; Juliano, Rudolph; Superfine, Richard

    2008-10-01

    In order to make non-viral gene delivery a useful tool in the study and treatment of genetic disorders, it is imperative that these methodologies be further refined to yield optimal results. Transfection of magnetic nanoparticles and nanorods are used as non-viral gene vectors to transfect HeLa EGFP-654 cells that stably express a mutated enhanced green fluorescent protein (EGFP) gene. We deliver antisense oligonucleotides to these cells designed to correct the aberrant splicing caused by the mutation in the EGFP gene. We also transfect human bronchial endothelial cells and immortalized WI-38 lung cells with pEGFP-N1 vectors. To achieve this we bind the genes to magnetic nanoparticles and nanorods and introduce magnetic fields to effect transfection. We wish to examine the effects of magnetic fields on the transfection of these particles and the benefits of using alternating (AC) magnetic fields in improving transfection rates over direct (DC) magnetic fields. We specifically look at the frequency dependence of the AC field and particle aspect ratio as it pertains to influencing transfection rate. We posit that the increase in angular momentum brought about by the AC field and the high aspect ratio of the nanorod particles, is vital to generating the force needed to move the particle through the cell membrane.

  9. Mathematical approximations for the amplitude of the fundamental mode field (LP01) of a dispersion shifted fiber at six wavelengths

    NASA Astrophysics Data System (ADS)

    Lamarche, Louis

    2009-06-01

    Hydro-Quebec optical network includes more than 5,000 km of optical ground wires [1] (OPGW) using dispersion shifted fibers (SMF-DSTM) [2]-[3]. This paper provides a model of the index profile for a typical reference fiber and the mathematical approximations of the amplitude of the LP01 mode at six important wavelengths (1.31, 1.41, 1.45, 1.48, 1.55, 1.625 μm). The fiber model has a triangular core and a quadratic ring shape. The weakly guided mode is obtained using the variational principle [4] implemented using an algorithm based on a Laguerre-Gauss-Bessel approximation of the field [5]. We modeled the wavelength dependence of the index of refraction of germanium doped silica using an experimental formula [6]. A comprehensive algorithm was developed to compute the normalized damping factor W and the normalized propagation constant U in the variational algorithm. The mode field diameter, group velocity and chromatic dispersion were also computed at the above wavelengths.

  10. 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

  11. Oblique electromagnetic electron cyclotron waves for Kappa distribution with AC field in planetary magnetospheres

    NASA Astrophysics Data System (ADS)

    Pandey, R. S.; Kaur, Rajbir

    2015-08-01

    The dispersion relation for obliquely propagating relativistic electromagnetic electron cyclotron (EMEC) waves in collision-less magnetoplasma is obtained. Investigations for EMEC waves in magnetosphere of Jupiter, Saturn and Uranus have been done, in presence of perpendicular AC electric field for Kappa distribution function. The relativistic temporal growth rate is calculated using method of characteristic solution. Using the data provided by spacecrafts like Cassini, Voyager 1 and 2, while exploring the magnetosphere of Jupiter, Saturn and Uranus, is used to plot graphs showing growth rate being effected by various parameters. Comprehensive parametric analysis have been done at different radial distances of the planets. It is concluded that beside huge difference in magnetospheric configuration, temperature anisotropy remains the main source of energy in case of Jupiter and Uranus. While studying EMEC waves in magnetosphere of Saturn, it is inferred that growth rate attains maximum magnitude when angle of propagation increases. Also, the results and its interpretations explain how the growth of EMEC wave modifies in different magnetospheric conditions.

  12. Generation of liquid metal structures of high aspect ratio by application of an ac magnetic field

    NASA Astrophysics Data System (ADS)

    Andreev, Oleg; Pothérat, Alban; Thess, André

    2010-06-01

    We study how the shape of parts obtained through the LASER cladding process can be controlled by application of an ac magnetic field by means of two simple physical models: a numerical and an experimental one. More specifically, we show that straight metallic joints of high aspect ratio can be obtained by using inductors of triangular cross-section that concentrate electromagnetic forces at the bottom of the joint. The effect is first demonstrated on a numerical model for an infinitely long joint such as: we illustrate how the joint shape can be controlled by varying the inclination of the inductor and for a magnetic Bond number Bom=60 (which measures the ratio of electromagnetic to capillary forces), we obtain a joint of aspect ratio up to 7.2. We further find that inductor angles in the range 15°-25° lead to joint side faces that are close to vertical. These findings are then verified experimentally by placing a liquid metal drop in a purpose built inductor of triangular cross-section. We find a good agreement between the theoretical prediction of our two-dimensional model and the real three-dimensional drop. For the highest magnetic Bond number our generator could deliver, Bom=20.19, we achieved a drop aspect ratio of 2.73.

  13. Mean-field dispersion-induced spatial synchrony, oscillation and amplitude death, and temporal stability in an ecological model.

    PubMed

    Banerjee, Tanmoy; Dutta, Partha Sharathi; Gupta, Anubhav

    2015-05-01

    One of the most important issues in spatial ecology is to understand how spatial synchrony and dispersal-induced stability interact. In the existing studies it is shown that dispersion among identical patches results in spatial synchrony; on the other hand, the combination of spatial heterogeneity and dispersion is necessary for dispersal-induced stability (or temporal stability). Population synchrony and temporal stability are thus often thought of as conflicting outcomes of dispersion. In contrast to the general belief, in this present study we show that mean-field dispersion is conducive to both spatial synchrony and dispersal-induced stability even in identical patches. This simultaneous occurrence of rather conflicting phenomena is governed by the suppression of oscillation states, namely amplitude death (AD) and oscillation death (OD). These states emerge through spatial synchrony of the oscillating patches in the strong-coupling strength. We present an interpretation of the mean-field diffusive coupling in the context of ecology and identify that, with increasing mean-field density, an open ecosystem transforms into a closed ecosystem. We report on the occurrence of OD in an ecological model and explain its significance. Using a detailed bifurcation analysis we show that, depending on the mortality rate and carrying capacity, the system shows either AD or both AD and OD. We also show that the results remain qualitatively the same for a network of oscillators. We identify a new transition scenario between the same type of oscillation suppression states whose geneses differ. In the parameter-mismatched case, we further report on the direct transition from OD to AD through a transcritical bifurcation. We believe that this study will lead to a proper interpretation of AD and OD in ecology, which may be important for the conservation and management of several communities in ecosystems. PMID:26066241

  14. Mean-field dispersion-induced spatial synchrony, oscillation and amplitude death, and temporal stability in an ecological model

    NASA Astrophysics Data System (ADS)

    Banerjee, Tanmoy; Dutta, Partha Sharathi; Gupta, Anubhav

    2015-05-01

    One of the most important issues in spatial ecology is to understand how spatial synchrony and dispersal-induced stability interact. In the existing studies it is shown that dispersion among identical patches results in spatial synchrony; on the other hand, the combination of spatial heterogeneity and dispersion is necessary for dispersal-induced stability (or temporal stability). Population synchrony and temporal stability are thus often thought of as conflicting outcomes of dispersion. In contrast to the general belief, in this present study we show that mean-field dispersion is conducive to both spatial synchrony and dispersal-induced stability even in identical patches. This simultaneous occurrence of rather conflicting phenomena is governed by the suppression of oscillation states, namely amplitude death (AD) and oscillation death (OD). These states emerge through spatial synchrony of the oscillating patches in the strong-coupling strength. We present an interpretation of the mean-field diffusive coupling in the context of ecology and identify that, with increasing mean-field density, an open ecosystem transforms into a closed ecosystem. We report on the occurrence of OD in an ecological model and explain its significance. Using a detailed bifurcation analysis we show that, depending on the mortality rate and carrying capacity, the system shows either AD or both AD and OD. We also show that the results remain qualitatively the same for a network of oscillators. We identify a new transition scenario between the same type of oscillation suppression states whose geneses differ. In the parameter-mismatched case, we further report on the direct transition from OD to AD through a transcritical bifurcation. We believe that this study will lead to a proper interpretation of AD and OD in ecology, which may be important for the conservation and management of several communities in ecosystems.

  15. Low-amplitude, high-frequency electromagnetic field exposure causes delayed and reduced growth in Rosa hybrida.

    PubMed

    Grémiaux, Alexandre; Girard, Sébastien; Guérin, Vincent; Lothier, Jérémy; Baluška, František; Davies, Eric; Bonnet, Pierre; Vian, Alain

    2016-01-15

    It is now accepted that plants perceive high-frequency electromagnetic field (HF-EMF). We wondered if the HF-EMF signal is integrated further in planta as a chain of reactions leading to a modification of plant growth. We exposed whole small ligneous plants (rose bush) whose growth could be studied for several weeks. We performed exposures at two different development stages (rooted cuttings bearing an axillary bud and 5-leaf stage plants), using two high frequency (900MHz) field amplitudes (5 and 200Vm(-1)). We achieved a tight control on the experimental conditions using a state-of-the-art stimulation device (Mode Stirred Reverberation Chamber) and specialized culture-chambers. After the exposure, we followed the shoot growth for over a one-month period. We observed no growth modification whatsoever exposure was performed on the 5-leaf stage plants. When the exposure was performed on the rooted cuttings, no growth modification was observed on Axis I (produced from the elongation of the axillary bud). Likewise, no significant modification was noted on Axis II produced at the base of Axis I, that came from pre-formed secondary axillary buds. In contrast, Axis II produced at the top of Axis I, that came from post-formed secondary buds consistently displayed a delayed and significant reduced growth (45%). The measurements of plant energy uptake from HF-EMF in this exposure condition (SAR of 7.2 10(-4)Wkg(-1)) indicated that this biological response is likely not due to thermal effect. These results suggest that exposure to electromagnetic field only affected development of post-formed organs. PMID:26643955

  16. Depinning of flux lines and AC losses in magnet-superconductor levitation system

    SciTech Connect

    Terentiev, A. N.; Hull, J. R.; De Long, L. E.

    1999-11-29

    The AC loss characteristics of a magnet-superconductor system were studied with the magnet fixed to the free end of an oscillating cantilever located near a stationary melt-textured YBCO pellet. Below a threshold AC field amplitude {approx}2Oe, the dissipation of the oscillator is amplitude-independent, characteristic of a linear, non-hysteretic regime. Above threshold,dissipation increases with amplitude, reflecting the depinning and hysteretic motion of flux lines. The threshold AC field is an order of magnitude higher than that measured for the same YBCO material via AC susceptometry in a uniform DC magnetic field, A partial lock-in of flux lines between YBCO ab planes is proposed as the mechanism for the substantial increase of the depinning threshold.

  17. Amplitude death and synchronized states in nonlinear time-delay systems coupled through mean-field diffusion

    NASA Astrophysics Data System (ADS)

    Banerjee, Tanmoy; Biswas, Debabrata

    2013-12-01

    We explore and experimentally demonstrate the phenomena of amplitude death (AD) and the corresponding transitions through synchronized states that lead to AD in coupled intrinsic time-delayed hyperchaotic oscillators interacting through mean-field diffusion. We identify a novel synchronization transition scenario leading to AD, namely transitions among AD, generalized anticipatory synchronization (GAS), complete synchronization (CS), and generalized lag synchronization (GLS). This transition is mediated by variation of the difference of intrinsic time-delays associated with the individual systems and has no analogue in non-delayed systems or coupled oscillators with coupling time-delay. We further show that, for equal intrinsic time-delays, increasing coupling strength results in a transition from the unsynchronized state to AD state via in-phase (complete) synchronized states. Using Krasovskii-Lyapunov theory, we derive the stability conditions that predict the parametric region of occurrence of GAS, GLS, and CS; also, using a linear stability analysis, we derive the condition of occurrence of AD. We use the error function of proper synchronization manifold and a modified form of the similarity function to provide the quantitative support to GLS and GAS. We demonstrate all the scenarios in an electronic circuit experiment; the experimental time-series, phase-plane plots, and generalized autocorrelation function computed from the experimental time series data are used to confirm the occurrence of all the phenomena in the coupled oscillators.

  18. Scale-dependent Normalized Amplitude and Weak Spectral Anisotropy of Magnetic Field Fluctuations in the Solar Wind Turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Tu, Chuanyi; Marsch, Eckart; He, Jiansen; Wang, Linghua

    2016-01-01

    Turbulence in the solar wind was recently reported to be anisotropic, with the average power spectral index close to -2 when sampling parallel to the local mean magnetic field B0 and close to -5/3 when sampling perpendicular to the local B0. This result was widely considered to be observational evidence for the critical balance theory (CBT), which is derived by making the assumption that the turbulence strength is close to one. However, this basic assumption has not yet been checked carefully with observational data. Here we present for the first time the scale-dependent magnetic-field fluctuation amplitude, which is normalized by the local B0 and evaluated for both parallel and perpendicular sampling directions, using two 30-day intervals of Ulysses data. From our results, the turbulence strength is evaluated as much less than one at small scales in the parallel direction. An even stricter criterion is imposed when selecting the wavelet coefficients for a given sampling direction, so that the time stationarity of the local B0 is better ensured during the local sampling interval. The spectral index for the parallel direction is then found to be -1.75, whereas the spectral index in the perpendicular direction remains close to -1.65. These two new results, namely that the value of the turbulence strength is much less than one in the parallel direction and that the angle dependence of the spectral index is weak, cannot be explained by existing turbulence theories, like CBT, and thus will require new theoretical considerations and promote further observations of solar-wind turbulence.

  19. SQUID sensor with additional compensation module for operation in an AC applied field

    NASA Astrophysics Data System (ADS)

    Della Penna, S.; Cianflone, F.; Del Gratta, C.; Erné, S. N.; Granata, C.; Pasquarelli, A.; Pentiricci, A.; Pizzella, V.; Russo, M.; Romani, G. L.

    2006-06-01

    A possible implementation of an in-vivo SQUID susceptometer able to estimate the liver iron concentration of humans uses a low frequency applied field together with a lock-in detection. The room-temperature magnetising coils and the detection coils are designed to minimize their mutual coupling. Nevertheless, deviation from ideal behaviour causes a residual signal in the detection coil, with an amplitude significantly larger than the patient's. In addition low frequency noise is added by any relative displacement of the magnetising and sensing coils. Thus, we designed a SQUID sensor using a compact compensating module to be used in a multichannel SQUID susceptometer. The sensor consists of two second order axial gradiometers, wounded one inside the other on the same support. The sensing channel is larger than the compensation channel which is only sensitive to the residual signal. Each gradiometer is coupled to a dc SQUID with parallel washer configuration. The output of the compensation channel is A/D converted and is processed by an adaptive algorithm running on a real time unit. The compensation signal is coupled to the sensing channel by an additional feedback loop. The performances of a prototype module will be presented.

  20. Angular Dependence of Transport AC Losses in Superconducting Wire with Position-Dependent Critical Current Density in a DC Magnetic Field

    NASA Astrophysics Data System (ADS)

    Su, Xing-liang; Xiong, Li-ting; Gao, Yuan-wen; Zhou, You-he

    2013-07-01

    Transport AC losses play a very important role in high temperature superconductors (HTSs), which usually carry AC transport current under applied magnetic field in typical application-like conditions. In this paper, we propose the analytical formula for transport AC losses in HTS wire by considering critical current density of both inhomogeneous and anisotropic field dependent. The angular dependence of critical current density is described by effective mass theory, and the HTS wire has inhomogeneous distribution cross-section of critical current density. We calculate the angular dependence of normalized AC losses under different DC applied magnetic fields. The numerical results of this formula agree well with the experiment data and are better than the results of Norris formula. This analytical formula can explain the deviation of experimental transport current losses from the Norris formula and apply to calculate transport AC losses in realistic practical condition.

  1. Calorimetric AC loss measurement of MgB2 superconducting tape in an alternating transport current and direct magnetic field

    NASA Astrophysics Data System (ADS)

    See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

    2012-11-01

    Applications of MgB2 superconductors in electrical engineering have been widely reported, and various studies have been made to define their alternating current (AC) losses. However, studies on the transport losses with an applied transverse DC magnetic field have not been conducted, even though this is one of the favored conditions in applications of practical MgB2 tapes. Methods and techniques used to characterize and measure these losses have so far been grouped into ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present a new approach to mounting the sample and employ the calorimetric method to accurately determine the losses in the concurrent application of AC transport current and DC magnetic fields that are likely to be experienced in practical devices such as generators and motors. This technique provides great simplification compared to the pickup coil and lock-in amplifier methods and is applied to a long length (˜10 cm) superconducting tape. The AC loss data at 20 and 30 K will be presented in an applied transport current of 50 Hz under external DC magnetic fields. The results are found to be higher than the theoretical predictions because of the metallic fraction of the tape that contributes quite significantly to the total losses. The data, however, will allow minimization of losses in practical MgB2 coils and will be used in the verification of numerical coil models.

  2. Annual variations of the amplitude characteristic of the noise magnetic field in the ELF frequency range based on the results of high-latitude observations

    NASA Astrophysics Data System (ADS)

    Pchelkin, V. V.

    2014-09-01

    The annual variation of a number of amplitude characteristics of the noise electromagnetic field in the frequency range near the first Schumann resonance (and in particular the mean values of the modulus of horizontal magnetic components and parameters of the distribution function of noise pulses over amplitudes) was obtained and analyzed based on the results of three-year measurements performed at the high-latitude magnetic observatory Lovozero. The summer increase in mean and median values of the magnetic component of noises associated with electrical storms and the lack of annual variations of the exponent that empirically describes the distribution of amplitudes of noise signals were found. The relationship between the seasonal (winter/summer in the northern hemisphere) increase in the mean value of the modulus of the horizontal magnetic field component and seasonal increase in the global number of lightning discharges is shown by the correlation of the results of satellite observations and measurements of the magnetic component.

  3. Effect of electric field configuration on streamer and partial discharge phenomena in a hydrocarbon insulating liquid under AC stress

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Liu, Q.; Wang, Z. D.

    2016-05-01

    This paper concerns pre-breakdown phenomena, including streamer characteristics from a fundamental perspective and partial discharge (PD) measurements from an industrial perspective, in a hydrocarbon insulating liquid. The aim was to investigate the possible changes of the liquid’s streamer and PD characteristics and their correlations when the uniformity of the AC electric field varies. In the experiments, a plane-to-plane electrode system incorporating a needle protrusion was used in addition to a needle-to-plane electrode system. When the applied electric field became more uniform, fewer radial branches occurred and streamer propagation towards the ground electrode was enhanced. The transition from streamer propagation dominated breakdown in divergent fields to streamer initiation dominated breakdown in uniform fields was evidenced. Relationships between streamer and PD characteristics were established, which were found to be electric field dependent. PD of the same apparent charge would indicate longer streamers if the electric field is more uniform.

  4. Superconductor-Mediated Modification of Gravity? AC Motor Experiments with Bulk YBCO Disks in Rotating Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Koczor, Ronald J.; Roberson, Rick

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. Podkietnov, et al (Podkietnov, E. and Nieminen, R. (1992) A Possibility of Gravitational Force Shielding by Bulk YBa2 Cu3 O7-x Superconductor, Physica C, C203:441-444.) have indicated that rotating AC fields play an essential role in their observed distortion of combined gravity and barometric pressure readings. We report experiments on large (15 cm diameter) bulk YBCO ceramic superconductors placed in the core of a three-phase, AC motor stator. The applied rotating field produces up to a 12,000 revolutions per minute magnetic field. The field intensity decays rapidly from the maximum at the outer diameter of the superconducting disk (less than 60 Gauss) to the center (less than 10 Gauss). This configuration was applied with and without a permanent DC magnetic field levitating the superconducting disk, with corresponding gravity readings indicating an apparent increase in observed gravity of less than 1 x 10(exp -6)/sq cm, measured above the superconductor. No effect of the rotating magnetic field or thermal environment on the gravimeter readings or on rotating the superconducting disk was noted within the high precision of the observation. Implications for propulsion initiatives and power storage flywheel technologies for high temperature superconductors will be discussed for various spacecraft and satellite applications.

  5. Role of peroxide in AC electrical field exposure effects on Friend murine erythroleukemia cells during dielectrophoretic manipulations

    PubMed Central

    Wang, Xujing; Yang, Jun; Gascoyne, Peter R.C.

    2009-01-01

    The effects of AC field exposure on the viability and proliferation of mammalian cells under conditions appropriate for their dielectrophoretic manipulation and sorting were investigated using DS19 murine erythroleukemia cells as a model system. The frequency range 100 Hz-10 MHz and medium conductivities of 10 mS/m, 30 mS/m and 56 mS/m were studied for fields generated by applying signals of up to 7V peak to peak (p-p) to a parallel electrode array having equal electrode widths and gaps of 100 μm. Between 1 kHz and 10 MHz, cell viability after up to 40 min of field exposure was found to be above 95% and cells were able to proliferate. However, cell growth lag phase was extended with decreasing field frequency and with increasing voltage, medium conductivity and exposure duration. Modified growth behavior was not passed on to the next cell passage, indicating that field exposure did not cause permanent alterations in cell proliferation characteristics. Cell membrane potentials induced by field exposure were calculated and shown to be well below values typically associated with cell damage. Furthermore, medium treated by field exposure and then added to untreated cells produced the same modifications of growth as exposing cells directly, and these modifications occurred only when the electrode polarization voltage exceeded a threshold of ~0.4 V p-p. These findings suggested that electrochemical products generated during field exposure were responsible for the changes in cell growth. Finally, it was found that hydrogen peroxide was produced when sugar-containing media were exposed to fields and that normal cell growth could be restored by addition of catalase to the medium, whether or not field exposure occurred in the presence of cells. These results show that AC fields typically used for dielectrophoretic manipulation and sorting of cells do not damage DS19 cells and that cell alterations arising from electrochemical effects can be completely mitigated. PMID

  6. Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

    NASA Technical Reports Server (NTRS)

    Gottardi, L.; Bruijn, M.; denHartog, R.; Hoevers, H.; deKorte, P.; vanderKuur, J.; Linderman, M.; Adams, J.; Bailey, C.; Bandler, S.; Chervenak, J.; Eckart, M.; Finkbeiner, F.; Kelley, R.; Kilbourne, C.; Porter, F.; Sadlier, J.; Smith, S.

    2012-01-01

    At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Delta E(sub FWHM) = 3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterized the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter.

  7. Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy.

    PubMed

    Li, Xiang; Lu, Wei; Song, Yiming; Wang, Yuxin; Chen, Aiying; Yan, Biao; Yoshimura, Satoru; Saito, Hitoshi

    2016-01-01

    Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 × 10(-20) A m(2), respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution. PMID:26932357

  8. Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy

    PubMed Central

    Li, Xiang; Lu, Wei; Song, Yiming; Wang, Yuxin; Chen, Aiying; Yan, Biao; Yoshimura, Satoru; Saito, Hitoshi

    2016-01-01

    Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 × 10−20 A m2, respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution. PMID:26932357

  9. Quantitatively probing the magnetic behavior of individual nanoparticles by an AC field-modulated magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Lu, Wei; Song, Yiming; Wang, Yuxin; Chen, Aiying; Yan, Biao; Yoshimura, Satoru; Saito, Hitoshi

    2016-03-01

    Despite decades of advances in magnetic imaging, obtaining direct, quantitative information with nanometer scale spatial resolution remains an outstanding challenge. Current approaches, for example, Hall micromagnetometer and nitrogen-vacancy magnetometer, are limited by highly complex experimental apparatus and a dedicated sample preparation process. Here we present a new AC field-modulated magnetic force microscopy (MFM) and report the local and quantitative measurements of the magnetic information of individual magnetic nanoparticles (MNPs), which is one of the most iconic objects of nanomagnetism. This technique provides simultaneously a direct visualization of the magnetization process of the individual MNPs, with spatial resolution and magnetic sensitivity of about 4.8 nm and 1.85 × 10-20 A m2, respectively, enabling us to separately estimate the distributions of the dipolar fields and the local switching fields of individual MNPs. Moreover, we demonstrate that quantitative magnetization moment of individual MNPs can be routinely obtained using MFM signals. Therefore, it underscores the power of the AC field-modulated MFM for biological and biomedical applications of MNPs and opens up the possibility for directly and quantitatively probing the weak magnetic stray fields from nanoscale magnetic systems with superior spatial resolution.

  10. The use of field dependence of AC susceptibility for the interpretation of magnetic mineralogy and magnetic fabrics in the HSDP-2 basalts, Hawaii [rapid communication

    NASA Astrophysics Data System (ADS)

    Vahle, Carsten; Kontny, Agnes

    2005-09-01

    We applied the field dependence parameter χHd (%) = [( k300A/m - k30A/m) / k300A/m] × 100 given by de Wall for the subaerial and submarine basalts drilled by the 3109 m deep HSDP-2 borehole on Hawaii in order to verify the hypothesis that mainly composition controls the field dependence of AC susceptibility in titanomagnetite of natural occurrences. When we used this parameter, our data showed a significant scattering compared to data presented in earlier studies. In addition to composition, the effect of measurement temperature, grain size and anisotropy on the field dependent susceptibility were examined and found to be critical. The impact of grain size is weaker than the other effects. It cannot be totally excluded that the observed effects arise indirectly through an overlap of the other effects for the investigated basalts. The most important factor for the variation of field dependence is the degree of oxidation, causing a modification of the titanomagnetite composition or formation of titanomaghemite, and the mixing of Ti-rich with Ti-poor titanomagnetites, which strongly reduces the χHd parameter. Field dependence is not only related to titanomagnetite composition, especially for intermediate titanomagnetites with TCs between 100 and 300 °C. Temperature dependent susceptibility measurements at different field amplitudes for these intermediate types showed at constant geometry of the k( T) curve great differences in susceptibility, resulting in significant changes of the field dependence parameter over the temperature interval from - 100 to 260 °C. Therefore variations of the ambient measurement temperatures are able to influence the field dependence. The second important effect is the degree of particle shape and alignment, which controls the field dependence in different orientations especially for the intermediate titanomagnetite, which is intensively intergrown with elongated hemoilmenite grains. As a consequence, samples with higher degrees of

  11. Zonal flows and magnetic fields driven by large-amplitude Rossby-Alfvén-Khantadze waves in the E-layer ionosphere

    NASA Astrophysics Data System (ADS)

    Kaladze, T. D.; Horton, W.; Kahlon, L. Z.; Pokhotelov, O.; Onishchenko, O.

    2013-12-01

    waves and vortices in the weakly ionized ionospheric E layer are dominated by the Hall conductivity that couples the Rossby and Alfvén dynamics giving rise to what are called Rossby-Alfvén-Khantadze electromagnetic structures. At finite amplitudes we show that the nonlinearities in the dynamics generate sheared zonal-flow velocities and zonal magnetic field fluctuations. The zonal-flow mechanism is based on the parametric excitation of the zonal variations through three-wave mode coupling in the planetary-scale waves. The coupled dynamics of the nonlinear 3-D incompressible flows and the magnetic field fluctuations are derived and used to derive the structure and growth rates for the zonal flows and zonal magnetic fields. Large-amplitude planetary waves are shown to drive up magnetic fluctuations up to 100 nT.

  12. Resonant vibration of a droplet located on a superhydrophobic surface under the vertical and horizontal ac field

    NASA Astrophysics Data System (ADS)

    Higashiyama, Y.; Ohuchi, T.; Sugimoto, T.

    2015-10-01

    A water droplet under an ac electric field with resonant frequency changes drastically its shape repeating extension and shrinkage, alternatively. To develop an electrostatic mixing method of small amount of liquid, resonant vibrating motion of a water droplet was investigated. Both horizontal and vertical fields were applied to the droplet placed on a super-hydrophobic plate with a contact angle of 150 degrees. From the video images of the droplet, the degree of deformation of the droplet shape was evaluated by deformation rate. Under the two-directional electric field, the deformation ratio at shrinkage was increased significantly. The height of the droplet varies from 1.2 to 1.8 times larger than that of the original droplet during vibrating motion. Furthermore, the deformation rate at shrinkage varies with time periodically due to rotating motion of the droplet. The vertical electric field might be effective to cause the turbulent flow inside of the droplet.

  13. Refining the Search for Suitable KBOs: Calibration of the HST/ACS Wide Field Camera Ramp Filters.

    NASA Astrophysics Data System (ADS)

    Trafton, Laurence M.

    2014-11-01

    After the New Horizons flyby of Pluto, the spacecraft will travel on to fly by one or more KBO objects. These are yet to be determined; searches are currently underway to locate suitable candidates. Once some candidates are identified, further observations are likely in order to decide on the actual targets; e.g., spectra or narrow-band observations vs. rotational phase to determine the presence of frozen volatiles. With its wide field, clear and broad band B and I filters, and its suite of medium band filters (9% FWHM), the ACS WFC camera on board HST is useful for searches over the CCD wavelength range. Moreover, its suite of narrow band (2%) ramp filters, which are also distributed over this wavelength range, are potentially useful for identifying the signature of spectral features, such as solid methane bands, for KBOs as dim as V = +25. However, the transmission of these ramp filters is uncertain since it was never calibrated. We report the calibration of 9 ACS/WFC ramp filters at 15 selected central wavelengths. A comparison of the calibrated transmissions to the existing uncalibrated ramp filters is presented. Corrective flats have been submitted for insertion into the ACS data reduction pipeline.This program was supported through HST-AR-10981.01-A.

  14. Observation of amplitude and phase in ridge and photonic crystal waveguides operating at 1.55 microm by use of heterodyne scanning near-field optical microscopy.

    PubMed

    Tortora, P; Abashin, M; Märki, I; Nakagawa, W; Vaccaro, L; Salt, M; Herzig, H P; Levy, U; Fainman, Y

    2005-11-01

    We apply heterodyne scanning near-field optical microscopy (SNOM) to observe with subwavelength resolution the amplitude and phase of optical fields propagating in several microfabricated waveguide devices operating around the 1.55 microm wavelength. Good agreement between the SNOM measurements and predicted optical mode propagation characteristics in standard ridge waveguides demonstrates the validity of the method. In situ observation of the subwavelength-scale distribution and propagation of optical fields in straight and 90 degrees bend photonic crystal waveguides facilitates a more detailed understanding of the optical performance characteristics of these devices and illustrates the usefulness of the technique for investigating nanostructured photonic devices. PMID:16279458

  15. Field_ac: a research project on ocean modelling in coastal areas. The experience in the Catalan Sea.

    NASA Astrophysics Data System (ADS)

    Grifoll, Manel; Pallarès, Elena; Tolosana-Delgado, Raimon; Fernandez, Juan; Lopez, Jaime; Mosso, Cesar; Hermosilla, Fernando; Espino, Manuel; Sanchez-Arcilla, Agustín

    2013-04-01

    The EU founded Field_ac project has investigated during the last three years methods and strategies for improving operational services in coastal areas. The objective has been to generate added value for shelf and regional scale predictions from GMES Marine Core Services. In this sense the experience in the Catalan Sea site has allowed to combine high-resolution numerical modeling tools nested into regional GMES services, data from intensive field campaigns or local observational networks and remote sensing products. Multi-scale coupled models have been implemented to evaluate different temporal and spatial scales of the dominant physical processes related with waves, currents, continental/river discharges or sediment transport. In this sense the experience of the Field_ac project in the Catalan Sea has permit to "connect" GMES marine core service results to the coastal (local) anthropogenic forcing (e.g. causes of morphodynamic evolution and ecosystem degradation) and will support a knowledge-based assessment of decisions in the coastal zone. This will contribute to the implementation of EU directives (e.g., the Water Framework Directive for water quality at beaches near harbour entrances or the Risk or Flood Directives for waves and sea-level at beach/river-mouth scales).

  16. Dc to ac field conversion due to leaky-wave excitation in a plasma slab behind an ionization front

    NASA Astrophysics Data System (ADS)

    Kostin, V. A.; Vvedenskii, N. V.

    2015-03-01

    We present a way for generating coherent tunable electromagnetic radiation through dc to ac field conversion by an ionization front. The conversion is caused by the excitation of leaky waves behind the transversely limited ionization front propagating in a uniform electrostatic field. This differs significantly from the well-known dc-to-ac-radiation-converter models which consider Doppler-like frequency conversion by a transversely unlimited ionization front propagating in a spatially periodic electric field. We explore the dispersion properties and excitation of these leaky waves radiated through the transverse plasma boundary at the Cherenkov angle to the direction of propagation of a superluminal ionization front as dependent on the parameters of the plasma produced and on the speed of the ionization front. It is shown that not only the center frequency but also the duration and waveform of the generated pulse may significantly depend on the speed of the ionization front. The results indicate the possibility of using such converters based on planar photoconductive antennas to create sources of microwave and terahertz radiation with controllable waveforms that are transformed from video to radio pulse when the angle of incident ionizing radiation is tuned.

  17. ANALYSIS OF THE STRUCTURE OF MAGNETIC FIELDS THAT INDUCED INHIBITION OF STIMULATED NEURITE OUTGROWTH

    EPA Science Inventory

    The important experiments showing nonlinear amplitude dependences of the neurite outgrowth in pheochromocytoma nerve cells due to ELF magnetic field exposure had been carried out in a nonuniform ac magnetic field. The nonuniformity entailed larger than expected variances in magne...

  18. Experimental investigation of an inversion technique for the determination of broadband duct mode amplitudes by the use of near-field sensor arrays.

    PubMed

    Castres, Fabrice O; Joseph, Phillip F

    2007-08-01

    This paper is an experimental investigation of an inverse technique for deducing the amplitudes of the modes radiated from a turbofan engine, including schemes for stablizing the solution. The detection of broadband modes generated by a laboratory-scaled fan inlet is performed using a near-field array of microphones arranged in a geodesic geometry. This array geometry is shown to allow a robust and accurate modal inversion. The sound power radiated from the fan inlet and the coherence function between different modal amplitudes are also presented. The knowledge of such modal content is useful in helping to characterize the source mechanisms of fan broadband noise generation, for determining the most appropriate mode distribution model for duct liner predictions, and for making sound power measurements of the radiated sound field. PMID:17672635

  19. Analysis of the effect of medium and membrane conductance on the amplitude and kinetics of membrane potentials induced by externally applied electric fields.

    PubMed Central

    Lojewska, Z; Farkas, D L; Ehrenberg, B; Loew, L M

    1989-01-01

    The kinetics and amplitudes of membrane potential induced by externally applied electric field pulses are determined for a spherical lipid bilayer using a voltage-sensitive dye. Several experimental parameters were systematically varied. These included the incorporation of gramicidin into the membrane to alter its conductivity and the variation of the external electrolyte conductivity via changes in salt concentration. The ability of the solution to Laplace's equation for a spherical dielectric shell to quantitatively describe the membrane potential induced on a lipid bilayer could thus be critically evaluated. Both the amplitude and the kinetics of the induced potential were consistent with the predictions of this simple model, even at the extremes of membrane conductance or electrolyte concentration. The success of the experimental approach for this system encourages its application to more complex problems such as electroporation and the influences of external electric fields in growth and development. PMID:2752081

  20. Inductive heat property of Fe3O4/polymer composite nanoparticles in an ac magnetic field for localized hyperthermia.

    PubMed

    Zhao, Dong-Lin; Zhang, Hai-Long; Zeng, Xian-Wei; Xia, Qi-Sheng; Tang, Jin-Tian

    2006-12-01

    The magnetite (Fe(3)O(4)) nanoparticles were prepared by coprecipitation of Fe(3+) and Fe(2+) with an aqueous NaOH solution. The Fe(3)O(4)/polyaniline (PANI) magnetic composite nanoparticles with a core-shell structure with a diameter of 30-50 nm were prepared via an in situ polymerization of aniline in an aqueous solution containing the Fe(3)O(4) magnetic fluid. The inductive heat property of Fe(3)O(4)/PANI composite nanoparticles in an alternating current (ac) magnetic field was investigated. The potential of Fe(3)O(4)/PANI nanoparticles was evaluated for localized hyperthermia treatment of cancers. The saturation magnetization, M(s), and coercivity, H(c), are 50.05 emu g(-1) and 137 Oe for Fe(3)O(4) nanoparticles and 26.34 emu g(-1) and 0 Oe for Fe(3)O(4)/PANI composite nanoparticles, respectively. Exposed in the ac magnetic field for 29 min, the temperatures of physiological saline suspensions containing Fe(3)O(4) nanoparticles or Fe(3)O(4)/PANI composite nanoparticles are 63.6 degrees C and 52.4 degrees C, respectively. The Fe(3)O(4)/PANI composite nanoparticles would be useful as good thermoseeds for localized hyperthermia treatment of cancers. PMID:18458406

  1. Applied AC and DC magnetic fields cause alterations in the mitotic cycle of early sea urchin embryos

    SciTech Connect

    Levin, M.; Ernst, S.G.

    1995-09-01

    This study demonstrates that exposure to 60 Hz magnetic fields (3.4--8.8 mt) and magnetic fields over the range DC-600 kHz (2.5--6.5 mT) can alter the early embryonic development of sea urchin embryos by inducing alterations in the timing of the cell cycle. Batches of fertilized eggs were exposed to the fields produced by a coil system. Samples of the continuous cultures were taken and scored for cell division. The times of both the first and second cell divisions were advanced by ELF AC fields and by static fields. The magnitude of the 60 Hz effect appears proportional to the field strength over the range tested. the relationship to field frequency was nonlinear and complex. For certain frequencies above the ELF range, the exposure resulted in a delay of the onset of mitosis. The advance of mitosis was also dependent on the duration of exposure and on the timing of exposure relative to fertilization.

  2. Reentrant ac Magnetic Susceptibility in Josephson-Junction Arrays

    SciTech Connect

    Araujo-Moreira, F.M.; Barbara, P.; Cawthorne, A.B.; Lobb, C.J.

    1997-06-01

    We have measured the complex ac magnetic susceptibility of unshunted Josephson-junction arrays as a function of temperature T , amplitude of the excitation field h{sub ac} , and external magnetic field H{sub dc} . For small h{sub ac} Meissner screening occurs. For larger h{sub ac} , however, the screening is reentrant in T . This reentrance is not thermodynamic but dynamic and arises from the paramagnetic contribution of multijunction loops. This result gives an alternative explanation of the paramagnetic Meissner effect observed in granular superconductors. Experimental results are in agreement with a simplified model based on a single loop containing four junctions. {copyright} {ital 1997} {ital The American Physical Society}

  3. Retrieving both phase and amplitude information of Green's functions by ambient seismic wave field cross-correlation: A case study with a limestone mine induced seismic event

    NASA Astrophysics Data System (ADS)

    Kwak, S.; Song, S. G.; Kim, G.; Shin, J. S.

    2015-12-01

    Recently many seismologists have paid attention to ambient seismic field, which is no more referred as noise and called as Earth's hum, but as useful signal to understand subsurface seismic velocity structure. It has also been demonstrated that empirical Green's functions can be constructed by retrieving both phase and amplitude information from ambient seismic field (Prieto and Beroza 2008). The constructed empirical Green's functions can be used to predict strong ground motions after focal depth and double-couple mechanism corrections (Denolle et al. 2013). They do not require detailed subsurface velocity model and intensive computation for ground motion simulation. In this study, we investigate the capability of predicting long period surface waves by the ambient seismic wave field with a seismic event of Mw 4.0, which occurred with a limestone mine collapse in South Korea on January 31, 2015. This limestone-mine event provides an excellent opportunity to test the efficiency of the ambient seismic wave field in retrieving both phase and amplitude information of Green's functions due to the single force mechanism of the collapse event. In other words, both focal depth and double-couple mechanism corrections are not required for this event. A broadband seismic station, which is about 5.4 km away from the mine event, is selected as a source station. Then surface waves retrieved from the ambient seismic wave field cross-correlation are compared with those generated by the event. Our preliminary results show some potential of the ambient seismic wave field in retrieving both phase and amplitude of Green's functions from a single force impulse source at the Earth's surface. More comprehensive analysis by increasing the time length of stacking may improve the results in further studies. We also aim to investigate the efficiency of retrieving the full empirical Green's functions with the 2007 Mw 4.6 Odaesan earthquake, which is one of the strongest earthquakes occurred

  4. Study of the heating characteristics and mechanisms of magnetic nanoparticles over a wide range of frequencies and amplitudes of an alternating magnetic field

    NASA Astrophysics Data System (ADS)

    Seki, A.; Kita, E.; Isaka, D.; Kikuchi, Y.; Suzuki, K. Z.; Horiuchi, A.; Kishimoto, M.; Yanagihara, H.; Oda, T.; Ohkohchi, N.; Ikehata, H.; Nagano, I.

    2014-06-01

    An effective approach to gaining an understanding of the mechanism of heat generation for magnetic hyperthermia from nanomagnet suspensions is to perform heating tests over a wide frequency range. We constructed a heating test apparatus by using ferrite field cores with air gaps for low frequencies and solenoids for high frequencies. Magnetic field amplitudes up to 600 Oe (400 Oe) can be generated for frequencies lower than 500 kHz (800 kHz). Heat generation tests were performed for ferromagnetic nano-platelets and Co-doped Fe3O4 nanoparticles over a wide range of frequencies.

  5. HST/ACS Observations of RR Lyrae Stars in Six Ultra-Deep Fields of M31

    NASA Technical Reports Server (NTRS)

    Jeffery, E. J.; Smith, E.; Brown, T. M.; Sweigart, A. V.; Kalirai, J. S.; Ferguson, H. C.; Guhathakurta, P.; Renzini, A.; Rich, R. M.

    2010-01-01

    We present HST/ACS observations of RR Lyrae variable stars in six ultra deep fields of the Andromeda galaxy (M31), including parts of the halo, disk, and giant stellar stream. Past work on the RR Lyrae stars in M31 has focused on various aspects of the stellar populations that make up the galaxy s halo, including their distances and metallicities. This study builds upon this previous work by increasing the spatial coverage (something that has been lacking in previous studies) and by searching for these variable stars in constituents of the galaxy not yet explored. Besides the 55 RR Lyrae stars we found in our initial field located 11kpc from the galactic nucleus, we find additional RR Lyrae stars in four of the remaining five ultra deep fields as follows: 21 in the disk, 24 in the giant stellar stream, 3 in the halo field 21kpc from the galactic nucleus, and 5 in one of the halo fields at 35kpc. No RR Lyrae were found in the second halo field at 35kpc. The RR Lyrae populations of these fields appear to mostly be of Oosterhoff I type, although the 11kpc field appears to be intermediate or mixed. We will discuss the properties of these stars including period and reddening distributions. We calculate metallicities and distances for the stars in each of these fields using different methods and compare the results, to an extent that has not yet been done. We compare these methods not just on RR Lyrae in our M31 fields, but also on a data set of Milky Way field RR Lyrae stars.

  6. HST/ACS OBSERVATIONS OF RR LYRAE STARS IN SIX ULTRA-DEEP FIELDS OF M31

    SciTech Connect

    Jeffery, E. J.; Smith, E.; Brown, T. M.; Kalirai, J. S.; Ferguson, H. C.; Sweigart, A. V.; Rich, R. M.

    2011-05-15

    We present HST/ACS observations of RR Lyrae variable stars in six ultra-deep fields of the Andromeda galaxy (M31), including parts of the halo, disk, and giant stellar stream. Past work on the RR Lyrae stars in M31 has focused on various aspects of the stellar populations that make up the galaxy's halo, including their distances and metallicities. This study builds upon this previous work by increasing the spatial coverage (something that has been lacking in previous studies) and by searching for these variable stars in constituents of the galaxy not yet explored. Besides the 55 RR Lyrae stars we found in our initial field located 11 kpc from the galactic nucleus, we find additional RR Lyrae stars in four of the remaining five ultra-deep fields as follows: 21 in the disk, 24 in the giant stellar stream, three in the halo field 21 kpc from the galactic nucleus, and five in one of the halo fields at 35 kpc. No RR Lyrae stars were found in the second halo field at 35 kpc. The RR Lyrae populations of these fields appear to be mostly of Oosterhoff I type, although the 11 kpc field appears to be intermediate or mixed. We will discuss the properties of these stars including period and reddening distributions. We calculate metallicities and distances for the stars in each of these fields using different methods and compare the results, to an extent that has not yet been done. We compare these methods not just on RR Lyrae stars in our M31 fields, but also on a data set of Milky Way field RR Lyrae stars.

  7. A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade.

    PubMed

    Ochoukov, R; Bobkov, V; Faugel, H; Fünfgelder, H; Noterdaeme, J-M

    2015-11-01

    A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k(//)) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k(tor)). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k(//) as strap phasing is moved away from the dipole configuration. This result is the opposite of the k(tor) trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k(//), as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue. PMID

  8. A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Ochoukov, R.; Bobkov, V.; Faugel, H.; Fünfgelder, H.; Noterdaeme, J.-M.

    2015-11-01

    A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k//) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (ktor). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k// as strap phasing is moved away from the dipole configuration. This result is the opposite of the ktor trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k//, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas' operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to address this issue.

  9. Strong-field cyclotron scattering. I - Scattering amplitudes and natural line width. [in spectra of accretion-powered X-ray pulsars

    NASA Technical Reports Server (NTRS)

    Graziani, Carlo

    1993-01-01

    The introduction of resonance line width into the QED cyclotron scattering amplitudes is considered. It is shown that the width arises from loop corrections to the electron propagator, which also bring about shifts in the Landau energy levels. A formalism is developed that allows the dressed electron propagator to be derived. It is shown that the states of Herold et al. (1982) and of Sokolov and Ternov (1968), which diagonalize the component of the magnetic moment operator parallel to the external magnetic field, are appropriate for calculation of the scattering amplitudes, whereas the states of Johnson and Lippmann (1949) are not. In addition, it is shown that the Breit-Wigner broadening approximation E tends to E - i(Gamma)/2 is consistent with the perturbation-theoretic order of the calculation, if the former basis states are chosen, but not the latter.

  10. RHIC AC DIPOLE DESIGN AND CONSTRUCTION.

    SciTech Connect

    BAI,M.; METH,M.; PAI,C.; PARKER,B.; PEGGS,S.; ROSER,T.; SANDERS,R.; TRBOJEVIC,D.; ZALTSMAN,A.

    2001-06-18

    Two ac dipoles with vertical and horizontal magnetic field have been proposed at RHIC for applications in linear and non-linear beam dynamics and spin manipulations. A magnetic field amplitude of 380 Gm is required to produce a coherent oscillation of 5 times the rms beam size at the top energy. We take the ac dipole frequency to be 1.0% of the revolution frequency away from the betatron frequency. To achieve the strong magnetic field with minimum power loss, an air-core magnet with two seven turn winding of low loss Litz wire resonating at 64 kHz is designed. The system is also designed to allow one to connect the two magnet winding in series to resonate at 37 kHz for the spin manipulation. Measurements of a half length prototype magnet are also presented.

  11. Tools and Setups for Experiments with AC and Rotating Magnetic Fields

    ERIC Educational Resources Information Center

    Ponikvar, D.

    2010-01-01

    A rotating magnetic field is the basis for the transformation of electrical energy to mechanical energy. School experiments on the rotating magnetic field are rare since they require the use of specially prepared mechanical setups and/or relatively large, three-phase power supplies to achieve strong magnetic fields. This paper proposes several…

  12. Influence of electrical fields (AC and DC) on phytoremediation of metal polluted soils with rapeseed (Brassica napus) and tobacco (Nicotiana tabacum).

    PubMed

    Bi, Ran; Schlaak, Michael; Siefert, Eike; Lord, Richard; Connolly, Helen

    2011-04-01

    The combined use of electrokinetic remediation and phytoremediation to decontaminate soil polluted with heavy metals has been demonstrated in a laboratory-scale experiment. The plants species selected were rapeseed and tobacco. Three kinds of soil were used: un-contaminated soil from forest area (S1), artificially contaminated soil with 15mgkg(-1) Cd (S2) and multi-contaminated soil with Cd, Zn and Pb from an industrial area (S3). Three treatment conditions were applied to the plants growing in the experimental vessels: control (no electrical field), alternating current electrical field (AC, 1Vcm(-1)) and direct current electrical field (DC, 1Vcm(-1)) with switching polarity every 3h. The electrical fields were applied for 30d for rapeseed and 90d for tobacco, each experiment had three replicates. After a total of 90d growth for rapeseed and of 180d for tobacco, the plants were harvested. The pH variation from anode to cathode was eliminated by switching the polarity of the DC field. The plants reacted differently under the applied electrical field. Rapeseed biomass was enhanced under the AC field and no negative effect was found under DC field. However, no enhancement of the tobacco biomass under the AC treatment was found. The DC field had a negative influence on biomass production on tobacco plants. In general, Cd content was higher in both species growing in S2 treated with AC field compared to the control. Metal uptake (Cd, Cu, Zn and Pb) per rapeseed plant shoot was enhanced by the application of AC field in all soils. PMID:21237480

  13. Ac loss characteristics of YBCO superconducting tapes fabricated by TFA-MOD technique

    NASA Astrophysics Data System (ADS)

    Iwakuma, Masataka; Nigo, Masahiro; Inoue, Daisuke; Miyamoto, Naoya; Kiss, Takanobu; Funaki, Kazuo; Iijima, Yasuhiro; Saitoh, Takashi; Izumi, Teruo; Yamada, Yutaka; Shiohara, Yuu

    2005-10-01

    We investigated the ac loss properties of a YBCO superconducting tape fabricated by TFA-MOD technique. The thickness of the YBCO layer is 1.2 μm. A 6-tape stack of 50 mm in length and 10 mm in width was inserted into a saddle-shaped pickup coil. The ac loss was measured at 35-77 K by applying an external ac magnetic field. The magnetic field angle was changed by rotating the sample stack around its longitudinal axis. The effective penetration field, which corresponds to the breaking point of an ac loss curve, decreased with increasing field angle though it was much smaller than that which was estimated for a superconducting slab with the same thickness as the width of a tape. As a result, the ac loss increased monotonically with an increasing field angle against the wide surface for any amplitude. The observed field angular dependence of the ac loss agreed with the theoretically predicted one by using the observed ac losses in perpendicular magnetic field. Anyway the ac loss for a larger amplitude than the effective penetration field was proportional to the critical current density and the projective width of a tape in the direction of the applied magnetic field for any field angle and any temperature as well known. In addition we estimated the magnetic field, B, dependence of the critical current, Ic, from the observed magnetization curves. It was shown that zero-field Ic appeared to be a linear function of temperature and Ic-B characteristics was scaled with zero-field Ic. We also discussed a difference in Ic-B characteristics and its temperature dependence between TFA-MOD tapes and IBAD-PLD ones.

  14. Tevatron AC dipole system

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.

  15. Linearity of the Faraday-rotation-type ac magnetic-field sensor with a ferrimagnetic or ferromagnetic rotator film

    NASA Astrophysics Data System (ADS)

    Mori, Hiroshi; Asahara, Yousuke

    1996-03-01

    We analyze the linearity and modulation depth of ac magnetic-field sensors or current sensors, using a ferrimagnetic or ferromagnetic film as the Faraday rotator and employing the detection of only the zeroth-order optical diffraction component from the rotator. It is theoretically shown that for this class of sensor the condition of a constant modulation depth and that of a constant ratio error give an identical series of curves for the relationship between Faraday rotation angle greater than or equals V and polarizer/analyzer relative angle Phi . We give some numerical examples to demonstrate the usefulness of the result with reference to a rare-earth iron garnet film as the rotator.

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

    PubMed

    Zhadin, M N

    2001-01-01

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

  17. A slowly rotating coil system for AC field measurements of Fermilab booster correctors

    SciTech Connect

    Velev, G.; DiMarco, J.; Harding, David J.; Kashikhin, V.; Lamm, Michael J.; Schlabach, P.; Tartaglia, Michael Albert; Tompkins, John C.; /Fermilab

    2007-06-01

    A method for measurement of rapidly changing magnetic fields has been developed and applied to the testing of new room temperature corrector packages designed for the Fermilab Booster Synchrotron. The method is based on fast digitization of a slowly rotating tangential coil probe, with analysis combining the measured coil voltages across a set of successive magnet current cycles. This paper presents results on the field quality measured for the normal and skew dipole, quadrupole, and sextupole elements in several of these corrector packages.

  18. Generation and development of small-amplitude disturbances in a laminar boundary layer in the presence of an acoustic field

    NASA Technical Reports Server (NTRS)

    Kachanov, Y. S.; Kozlov, V. V.; Levchenko, V. Y.

    1985-01-01

    A low-turbulence subsonic wind tunnel was used to study the influence of acoustic disturbances on the development of small sinusoidal oscillations (Tollmien-Schlichting waves) which constitute the initial phase of turbulent transition. It is found that acoustic waves propagating opposite to the flow generate vibrations of the model (plate) in the flow. Neither the plate vibrations nor the acoustic field itself have any appreciable influence on the stability of the laminar boundary layer. The influence of an acoustic field on laminar boundary layer disturbances is limited to the generation of Tollmien-Schlichting waves at the leading-edge of the plate.

  19. Seismic texture and amplitude analysis of large scale fluid escape pipes using time lapses seismic surveys: examples from the Loyal Field (Scotland, UK)

    NASA Astrophysics Data System (ADS)

    Maestrelli, Daniele; Jihad, Ali; Iacopini, David; Bond, Clare

    2016-04-01

    Fluid escape pipes are key features of primary interest for the analysis of vertical fluid flow and secondary hydrocarbon migration in sedimentary basin. Identified worldwide (Løset et al., 2009), they acquired more and more importance as they represent critical pathways for supply of methane and potential structure for leakage into the storage reservoir (Cartwright & Santamarina, 2015). Therefore, understanding their genesis, internal characteristics and seismic expression, is of great significance for the exploration industry. Here we propose a detailed characterization of the internal seismic texture of some seal bypass system (e.g fluid escape pipes) from a 4D seismic survey (released by the BP) recently acquired in the Loyal Field. The seal by pass structure are characterized by big-scale fluid escape pipes affecting the Upper Paleogene/Neogene stratigraphic succession in the Loyal Field, Scotland (UK). The Loyal field, is located on the edge of the Faroe-Shetland Channel slope, about 130 km west of Shetland (Quadrants 204/205 of the UKCS) and has been recently re-appraised and re developed by a consortium led by BP. The 3D detailed mapping analysis of the full and partial stack survey (processed using amplitude preservation workflows) shows a complex system of fluid pipe structure rooted in the pre Lista formation and developed across the paleogene and Neogene Units. Geometrical analysis show that pipes got diameter varying between 100-300 m and a length of 500 m to 2 km. Most pipes seem to terminate abruptly at discrete subsurface horizons or in diffuse termination suggesting multiple overpressured events and lateral fluid migration (through Darcy flows) across the overburden units. The internal texture analysis of the large pipes, (across both the root and main conduit zones), using near, medium and far offset stack dataset (processed through an amplitude preserved PSTM workflow) shows a tendency of up-bending of reflection (rather than pulls up artefacts

  20. Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

    NASA Astrophysics Data System (ADS)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

  1. A new B-dot probe-based diagnostic for amplitude, polarization, and wavenumber measurements of ion cyclotron range-of frequency fields on ASDEX Upgrade

    SciTech Connect

    Ochoukov, R.; Bobkov, V.; Faugel, H.; Fünfgelder, H.; Noterdaeme, J.-M.

    2015-11-15

    A new B-dot probe-based diagnostic has been installed on an ASDEX Upgrade tokamak to characterize ion cyclotron range-of frequency (ICRF) wave generation and interaction with magnetized plasma. The diagnostic consists of a field-aligned array of B-dot probes, oriented to measure fast and slow ICRF wave fields and their field-aligned wavenumber (k{sub //}) spectrum on the low field side of ASDEX Upgrade. A thorough description of the diagnostic and the supporting electronics is provided. In order to compare the measured dominant wavenumber of the local ICRF fields with the expected spectrum of the launched ICRF waves, in-air near-field measurements were performed on the newly installed 3-strap ICRF antenna to reconstruct the dominant launched toroidal wavenumbers (k{sub tor}). Measurements during a strap current phasing scan in tokamak discharges reveal an upshift in k{sub //} as strap phasing is moved away from the dipole configuration. This result is the opposite of the k{sub tor} trend expected from in-air near-field measurements; however, the near-field based reconstruction routine does not account for the effect of induced radiofrequency (RF) currents in the passive antenna structures. The measured exponential increase in the local ICRF wave field amplitude is in agreement with the upshifted k{sub //}, as strap phasing moves away from the dipole configuration. An examination of discharges heated with two ICRF antennas simultaneously reveals the existence of beat waves at 1 kHz, as expected from the difference of the two antennas’ operating frequencies. Beats are observed on both the fast and the slow wave probes suggesting that the two waves are coupled outside the active antennas. Although the new diagnostic shows consistent trends between the amplitude and the phase measurements in response to changes applied by the ICRF antennas, the disagreement with the in-air near-field measurements remains. An electromagnetic model is currently under development to

  2. Simulation of fluid flow induced by opposing ac magnetic fields in a continuous casting mold

    SciTech Connect

    Chang, F.C.; Hull, J.R.; Beitelman, L.

    1995-07-01

    A numerical simulation was performed for a novel electromagnetic stirring system employing two rotating magnetic fields. The system controls stirring flow in the meniscus region of a continuous casting mold independently from the stirring induced within the remaining volume of the mold by a main electromagnetic stirrer (M-EMS). This control is achieved by applying to the meniscus region an auxiliary electromagnetic field whose direction of rotation is opposite to that of the main magnetic field produced by the M-EMS. The model computes values and spatial distributions of electromagnetic parameters and fluid flow in the stirred pools of mercury in cylindrical and square geometries. Also predicted are the relationships between electromagnetics and fluid flows pertinent to a dynamic equilibrium of the opposing stirring swirls in the meniscus region. Results of the numerical simulation compared well with measurements obtained from experiments with mercury pools.

  3. AC field measurements of Fermilab Booster correctors using a rotating coil system

    SciTech Connect

    Velev, G.V.; DiMarco, J.; Harding, D.J.; Kashikhin, V.; Lamm, M.; Makulski, A.; Orris, D.; Schlabach, P.; Sylvester, C.; Tartaglia, M.; Tompkins, J.; /Fermilab

    2006-07-01

    The first prototype of a new corrector package for the Fermilab Booster Synchrotron is presently in production. This water-cooled package includes normal and skew dipole, quadrupole and sextupole elements to control orbit, tune and chromaticity of the beam over the full range of Booster energies (0.4-8 GeV). These correctors operate at the 15 Hz excitation cycle of the main synchrotron magnets, but must also make more rapid excursions, in some cases even switching polarity in approximately 1 ms at transition crossing. To measure the dynamic field changes during operation, a new method based on a relatively slow rotating coil system is proposed. The method pieces together the measured voltages from successive current cycles to reconstruct the field harmonics. This paper describes the method and presents initial field quality measurements from a Tevatron corrector.

  4. Compression and acceleration of electron bunches to high energies in the interference field of intense laser pulses with tilted amplitude fronts: concept and modelling

    SciTech Connect

    Korobkin, V V; Romanovsky, Mikhail Yu; Trofimov, V A; Shiryaev, O B

    2013-03-31

    A new concept of accelerating electrons by laser radiation is proposed, namely, direct acceleration by a laser field under the conditions of interference of several relativistic-intensity laser pulses with amplitude fronts tilted by the angle 45 Degree-Sign with respect to the phase fronts. Due to such interference the traps moving with the speed of light arise that capture the electrons, produced in the process of ionisation of low-density gas by the same laser radiation. The modelling on the basis of solving the relativistic Newton equation with the appropriate Lorenz force shows that these traps, moving in space, successively collect electrons from the target, compress the resulting electron ensemble in all directions up to the dimensions smaller than the wavelength of the laser radiation and accelerate it up to the energies of the order of a few GeV per electron. (extreme light fields and their applications)

  5. A Fast-sampling, Planar Array for Measuring the AC Field of Fermilab Pulsed Extraction Magnets

    SciTech Connect

    DiMarco, E.Joseph; Johnstone, C.; Kiemschies, O.; Kotelnikov, S.K.; Lamm, M.J.; Makulski, A.; Nehring, R.; Orris, D.F.; Russell, A.D.; Tartaglia, Michael Albert; Velev, G.; /Fermilab

    2008-06-25

    A system employing a planar array of inductive pick-up coils has been developed for measurements of the rapidly changing dipole field in pulsed extraction magnets for the Fermilab MuCool project. The magnets are of C-type and deigned to support a peak field of 0.65 T during 8.33 millisecond half-sine pulse at a 15 Hz repetition rate. The coils of the measurement system are fabricated on a single, 97.5 mm wide, 2-layer circuit board. The array of coils is simultaneously sampled at data rates of up to 100 kHz with 10 kHz bandwidth using 24-bit ADC's. A detailed overview of the system and data analysis is presented, along with a characterization of results and system performance.

  6. Hiding objects in AC magnetic fields of power grid frequency by two-shell ferromagnetic/superconducting cloak

    NASA Astrophysics Data System (ADS)

    Šouc, J.; Solovyov, M.; Gömöry, F.

    2016-07-01

    Performance of magnetic cloak made from commercially available materials has been tested by verifying its ability to suppress the magnetic signatures of metallic and ferromagnetic objects. The range of magnetic field amplitudes from 0.1 to 10 mT and frequencies around 50-60 Hz were used. The cloak combines the inner tube from high-temperature superconductor that should be cooled by liquid nitrogen, with the outer tube made from MnZn ferrite powder mixed in plastic matter. Superconductor is in the form of tapes wound in helical manner on a round former. Such design is promising when the objects with dimensions reaching several centimeters should be cloaked. Performance of the small model manufactured following this design was demonstrated by observing ˜20 times reduction of the magnetic signature of metallic or ferromagnetic objects.

  7. Formation of 85Rb2 ultracold molecules via photoassociation by two-color laser fields modulating the Gaussian amplitude

    NASA Astrophysics Data System (ADS)

    Huang, Yin; Zhang, Wei; Wang, Gao-Ren; Xie, Ting; Cong, Shu-Lin

    2012-10-01

    The formations of 85Rb2 molecules via photoassociation (PA) steered by two-color laser fields are explored theoretically in order to find an efficient and robust PA scheme. The PA processes steered by the PA pulses modulated by two Gaussian pulses and by two chirped pulses are discussed and compared in detail. The two pulses are coherent in the picosecond range and reach their maxima at the same time. The influences of the linear chirp rate, the frequency difference between two pulses, and the phase shift of the modulated envelope with respect to the maximum of the Gaussian envelope on the PA process are investigated. The yield of photoassociated molecules on vibrational levels with a binding energy of >1.0 cm-1 with respect to the 5S+5P1/2 dissociation limit can apparently be enhanced by choosing proper pulse parameters. Especially, the two-color laser field modulated by two chirped pulses can raise the PA efficiency on one side, and weaken the dependence of the PA process on phase shift on the other side.

  8. 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

  9. Electro-phoretic rotation and orientation of polarizable spheroidal particles in AC fields

    NASA Astrophysics Data System (ADS)

    Miloh, Touvia; Goldstein, Ben Weis

    2015-02-01

    A theoretical study is provided for determining the angular rotation rate of an ideally polarized (metallic) spheroidal particle freely suspended in a symmetric electrolyte under general alternating current ambient electric excitations. In particular, we discuss cases of electro-rotation (ROT) and electro-orientation (EOR) of such nano/micro particles incited by two orthogonal electric field components which may be out of phase. The analysis is carried under the Poisson-Nernst-Planck approximation and the "weak" field model. The analytic expressions thus obtained are valid for a conducting prolate spheroid with arbitrary eccentricity including the limiting cases of isotropic spheres and infinitely long cylindrical rods. The total dipolophoretic (DIP) angular velocity is decomposed from contributions due to dielectrophoresis (DEP) induced by the dipole-moment within the particle and by the induced-charge electrophoresis (ICEP) mechanism near the conducting surface. It is demonstrated that the explicit expressions for the DIP angular velocities reduce to the well-known ROT solution for the sphere as well as to the recently found expressions (based on slender-body approximation) for both ROT and EOR of metal nanowires [Arcenegui et al., "Electro-orientation and electrorotation of metal nanowires," Phys. Rev. E 88(6), 063018 (2013)]. Some comparisons with available experimental data are also provided for slender spheroidal geometries including a detailed discussion of DEP and ICEP effects and their relative contributions to the overall DIP rotational velocity.

  10. AC electric field for rapid assembly of nanostructured polyaniline onto microsized gap for sensor devices.

    PubMed

    La Ferrara, Vera; Rametta, Gabriella; De Maria, Antonella

    2015-07-01

    Interconnected network of nanostructured polyaniline (PANI) is giving strong potential for enhancing device performances than bulk PANI counterparts. For nanostructured device processing, the main challenge is to get prototypes on large area by requiring precision, low cost and high rate assembly. Among processes meeting these requests, the alternate current electric fields are often used for nanostructure assembling. For the first time, we show the assembly of nanostructured PANI onto large electrode gaps (30-60 μm width) by applying alternate current electric fields, at low frequencies, to PANI particles dispersed in acetonitrile (ACN). An important advantage is the short assembly time, limited to 5-10 s, although electrode gaps are microsized. That encouraging result is due to a combination of forces, such as dielectrophoresis (DEP), induced-charge electrokinetic (ICEK) flow and alternate current electroosmotic (ACEO) flow, which speed up the assembly process when low frequencies and large electrode gaps are used. The main achievement of the present study is the development of ammonia sensors created by direct assembling of nanostructured PANI onto electrodes. Sensors exhibit high sensitivity to low gas concentrations as well as excellent reversibility at room temperature, even after storage in air. PMID:26009866

  11. Frequency-dependent electrodeformation of giant phospholipid vesicles in AC electric field

    PubMed Central

    2010-01-01

    A model of vesicle electrodeformation is described which obtains a parametrized vesicle shape by minimizing the sum of the membrane bending energy and the energy due to the electric field. Both the vesicle membrane and the aqueous media inside and outside the vesicle are treated as leaky dielectrics, and the vesicle itself is modeled as a nearly spherical shape enclosed within a thin membrane. It is demonstrated (a) that the model achieves a good quantitative agreement with the experimentally determined prolate-to-oblate transition frequencies in the kilohertz range and (b) that the model can explain a phase diagram of shapes of giant phospholipid vesicles with respect to two parameters: the frequency of the applied alternating current electric field and the ratio of the electrical conductivities of the aqueous media inside and outside the vesicle, explored in a recent paper (S. Aranda et al., Biophys J 95:L19–L21, 2008). A possible use of the frequency-dependent shape transitions of phospholipid vesicles in conductometry of microliter samples is discussed. PMID:21886342

  12. DC-like Phase Space Manipulation and Particle Acceleration Using Chirped AC Fields

    SciTech Connect

    P.F. Schmit and N.J. Fisch

    2009-06-17

    Waves in plasmas can accelerate particles that are resonant with the wave. A DC electric field also accelerates particles, but without a resonance discrimination, which makes the acceleration mechanism profoundly different. We investigate the effect on a Hamiltonian distribution of an accelerating potential waveform, which could, for example, represent the average ponderomotive effect of two counterpropagating electromagnetic waves. In particular, we examine the apparent DC-like time-asymptotic response of the distribution in regimes where the potential structure is accelerated adiabatically. A highly resonant population within the distribution is always present, and we characterize its nonadiabatic response during wave-particle resonance using an integral method in the noninertial reference frame moving with the wave. Finally, we show that in the limit of infinitely slow acceleration of the wave, these highly resonant particles disappear and the response

  13. MAVEN observations of magnetic flux ropes with a strong field amplitude in the Martian magnetosheath during the ICME passage on 8 March 2015

    NASA Astrophysics Data System (ADS)

    Hara, Takuya; Luhmann, Janet G.; Halekas, Jasper S.; Espley, Jared R.; Seki, Kanako; Brain, David A.; Hasegawa, Hiroshi; McFadden, James P.; Mitchell, David L.; Mazelle, Christian; Harada, Yuki; Livi, Roberto; DiBraccio, Gina A.; Connerney, John E. P.; Andersson, Lailla; Jakosky, Bruce M.

    2016-05-01

    We present initial results of strong field amplitude flux ropes observed by Mars Atmosphere and Volatile EvolutioN (MAVEN) mission around Mars during the interplanetary coronal mass ejection (ICME) passage on 8 March 2015. The observed durations were shorter than 5 s and the magnetic field magnitudes peaked above 80 nT, which is a few times stronger than those usually seen in the magnetosheath barrier. These are the first unique observations that MAVEN detected such flux ropes with a strong field at high altitudes (>5000 km). Across these structures, MAVEN coincidentally measured planetary heavy ions with energies higher than a few keV. The spatial properties inferred from the Grad-Shafranov equation suggest that the speed of the structure can be estimated at least an order of magnitude faster than those previously reported quiet-time counterparts. Hence, the space weather event like the ICME passage can be responsible for generating the observed strong field, fast-traveling flux ropes.

  14. Long-range doublon transfer in a dimer chain induced by topology and ac fields.

    PubMed

    Bello, M; Creffield, C E; Platero, G

    2016-01-01

    The controlled transfer of particles from one site of a spatial lattice to another is essential for many tasks in quantum information processing and quantum communication. In this work we study how to induce long-range transfer between the two ends of a dimer chain, by coupling states that are localized just on the chain's end-points. This has the appealing feature that the transfer occurs only between the end-points - the particle does not pass through the intermediate sites-making the transfer less susceptible to decoherence. We first show how a repulsively bound-pair of fermions, known as a doublon, can be transferred from one end of the chain to the other via topological edge states. We then show how non-topological surface states of the familiar Shockley or Tamm type can be used to produce a similar form of transfer under the action of a periodic driving potential. Finally we show that combining these effects can produce transfer by means of more exotic topological effects, in which the driving field can be used to switch the topological character of the edge states, as measured by the Zak phase. Our results demonstrate how to induce long range transfer of strongly correlated particles by tuning both topology and driving. PMID:26932406

  15. Long-range doublon transfer in a dimer chain induced by topology and ac fields

    NASA Astrophysics Data System (ADS)

    Bello, M.; Creffield, C. E.; Platero, G.

    2016-03-01

    The controlled transfer of particles from one site of a spatial lattice to another is essential for many tasks in quantum information processing and quantum communication. In this work we study how to induce long-range transfer between the two ends of a dimer chain, by coupling states that are localized just on the chain’s end-points. This has the appealing feature that the transfer occurs only between the end-points - the particle does not pass through the intermediate sites-making the transfer less susceptible to decoherence. We first show how a repulsively bound-pair of fermions, known as a doublon, can be transferred from one end of the chain to the other via topological edge states. We then show how non-topological surface states of the familiar Shockley or Tamm type can be used to produce a similar form of transfer under the action of a periodic driving potential. Finally we show that combining these effects can produce transfer by means of more exotic topological effects, in which the driving field can be used to switch the topological character of the edge states, as measured by the Zak phase. Our results demonstrate how to induce long range transfer of strongly correlated particles by tuning both topology and driving.

  16. Long-range doublon transfer in a dimer chain induced by topology and ac fields

    PubMed Central

    Bello, M.; Creffield, C. E.; Platero, G.

    2016-01-01

    The controlled transfer of particles from one site of a spatial lattice to another is essential for many tasks in quantum information processing and quantum communication. In this work we study how to induce long-range transfer between the two ends of a dimer chain, by coupling states that are localized just on the chain’s end-points. This has the appealing feature that the transfer occurs only between the end-points – the particle does not pass through the intermediate sites–making the transfer less susceptible to decoherence. We first show how a repulsively bound-pair of fermions, known as a doublon, can be transferred from one end of the chain to the other via topological edge states. We then show how non-topological surface states of the familiar Shockley or Tamm type can be used to produce a similar form of transfer under the action of a periodic driving potential. Finally we show that combining these effects can produce transfer by means of more exotic topological effects, in which the driving field can be used to switch the topological character of the edge states, as measured by the Zak phase. Our results demonstrate how to induce long range transfer of strongly correlated particles by tuning both topology and driving. PMID:26932406

  17. Direct simulation of phase delay effects on induced-charge electro-osmosis under large ac electric fields.

    PubMed

    Sugioka, Hideyuki

    2016-08-01

    The standard theory of induced-charge electro-osmosis (ICEO) often overpredicts experimental values of ICEO velocities. Using a nonsteady direct multiphysics simulation technique based on the coupled Poisson-Nernst-Planck and Stokes equations for an electrolyte around a conductive cylinder subject to an ac electric field, we find that a phase delay effect concerning an ion response provides a fundamental mechanism for electrokinetic suppression. A surprising aspect of our findings is that the phase delay effect occurs even at much lower frequencies (e.g., 50 Hz) than the generally believed charging frequency of an electric double layer (typically, 1 kHz) and it can decrease the electrokinetic velocities in one to several orders. In addition, we find that the phase delay effect may also cause a change in the electrokinetic flow directions (i.e., flow reversal) depending on the geometrical conditions. We believe that our findings move toward a more complete understanding of complex experimental nonlinear electrokinetic phenomena. PMID:27627362

  18. Shape change and physical properties of giant phospholipid vesicles prepared in the presence of an AC electric field.

    PubMed

    Mathivet, L; Cribier, S; Devaux, P F

    1996-03-01

    Giant unilamellar vesicles with diameters ranging from 10 to 60 microns were obtained by the swelling of phospholipid bilayers in water in the presence of an AC electric field. This technique leads to a homogeneous population of perfectly spherical and unilamellar vesicles, as revealed by phase-contrast optical microscopy and freeze-fracture electron microscopy. Freshly prepared vesicles had a high surface tension with no visible surface undulations. Undulations started spontaneously after several hours of incubation or were triggered by the application of a small osmotic pressure. Partially deflated giant vesicles could undergo further shape change if asymmetrical bilayers were formed by adding lyso compounds to the external leaflet or by imposing a transmembrane pH gradient that selectively accumulates on one leaflet phosphatidylglycerol. Fluorescence photobleaching with 7-nitrobenz-2-oxa-1,3-diazol-4-yl-labeled phospholipids or labeled dextran trapped within the vesicles enabled the measurement of the membrane continuity in the dumbbell-shaped vesicles. In all instances phospholipids diffused from one lobe to the other, but soluble dextran sometimes was unable to traverse the neck. This suggests that the diameter of the connecting neck may be variable. PMID:8785271

  19. Intensive microgravity field campaign dedicated to the search of low to medium amplitude hydrological signals: a case study in Southwest Niger

    NASA Astrophysics Data System (ADS)

    Hinderer, J.; Pfeffer, J.; Champollion, C.; Favreau, G.; Cappelaere, B.; Mouyen, M.; Boucher, M.; Nazoumou, Y.; Oi, M.; Robert, O.; Le Moigne, N.; Deroussi, S.; Demarty, J.; Benarrosh, N.

    2011-12-01

    Terrestrial gravity measurements allow detecting temporal gravity changes in the μGal (absolute free fall gravimeters) to the 0.1 μGal (relative superconducting gravimeters) ranges. However small amplitude signals due to the Earth rotation or deep mass transfers are often masked by hydrological processes occurring in the surroundings of the gravity station. Due to the sharp variability of the water storage at local scale, fundamental questions about the relevance of the gravity measurements could not be studied at a single station; the evaluation of the gravity response to water storage changes needs spatially and temporally distributed measurements. For this study, we investigated the dynamic variations of the water storage at the subcatchment scale (< 1km) by an intensive microgravity field campaign coupled to hydrodynamic data. Weekly microgravity surveys were carried out over 16 stations located in the small Wankama catchment in Southwest Niger. The repetitions over the microgravity network enabled to take 801 relative gravity measurement points, during three months of the rainy season in 2009. Accuracies in the 3 - 5 μGal range were achieved showing that even in difficult field conditions, modern relative gravimeters and careful data processing allow retrieving low amplitude hydrological signals. Gravity changes, measured in the vicinity of a temporary pond, display a significant spatial variability (standard deviation of 5.3 μGal). The analysis of auxiliary hydrodynamic data suggests that the heterogeneity of the water storage in the vadose zone is the main reason for the dispersion of the gravity values at local scale. This experiment evidences the ability of time lapse microgravity survey to detect the intraseasonal variations of the water storage in Sahelian Africa. Besides, this study shows that significant gravity changes occur at subcatchment scale, which should be taken into account for scaling issue such as satellite gravimetry validation or

  20. Observation of multi-scale oscillation of laminar lifted flames with low-frequency AC electric fields

    SciTech Connect

    Ryu, S.K.; Kim, Y.K.; Kim, M.K.; Won, S.H.; Chung, S.H.

    2010-01-15

    The oscillation behavior of laminar lifted flames under the influence of low-frequency AC has been investigated experimentally in coflow jets. Various oscillation modes were existed depending on jet velocity and the voltage and frequency of AC, especially when the AC frequency was typically smaller than 30 Hz. Three different oscillation modes were observed: (1) large-scale oscillation with the oscillation frequency of about 0.1 Hz, which was independent of the applied AC frequency, (2) small-scale oscillation synchronized to the applied AC frequency, and (3) doubly-periodic oscillation with small-scale oscillation embedded in large-scale oscillation. As the AC frequency decreased from 30 Hz, the oscillation modes were in the order of the large-scale oscillation, doubly-periodic oscillation, and small-scale oscillation. The onset of the oscillation for the AC frequency smaller than 30 Hz was in close agreement with the delay time scale for the ionic wind effect to occur, that is, the collision response time. Frequency-doubling behavior for the small-scale oscillation has also been observed. Possible mechanisms for the large-scale oscillation and the frequency-doubling behavior have been discussed, although the detailed understanding of the underlying mechanisms will be a future study. (author)

  1. Effect of n = 3 perturbation field amplitudes below the ELM triggering threshold on edge and SOL transport in NSTX

    SciTech Connect

    J. M. Canik; Lore, J. D.; Ahn, J. -W.; Bortolon, A.; Fredrickson, E. D.; Jaworski, M. A.; Kramer, G. J.; Maingi, R.; McLean, A. G.; Scotti, F.; Soukhanovskii, V. A.; Tritz, K.

    2013-01-12

    Here, the pulsed application of n = 3 magnetic perturbation fields with amplitudes below that which triggers ELMs results in distinct, transient responses observable on several edge and divertor diagnostics in NSTX. We refer to these responses as Sub-Threshold Edge Perturbations (STEPs). An analysis of edge measurements suggests that STEPs result in increased transport in the plasma edge and scrape-off layer, which leads to augmentation of the intrinsic strike point splitting due to error fields, i.e., an intensification of the helical divertor footprint flux pattern. These effects are much smaller in magnitude than those of triggered ELMs, and are observed for the duration of the field perturbation measured internal to the vacuum vessel. In addition, STEPs are correlated with changes to the MHD activity, along with transient reductions in the neutron production rate. Ideally the STEPs could be used to provide density control and prevent impurity accumulation, in the same manner that on-demand ELM triggering is used on NSTX, without the impulsive divertor fluxes and potential for damage to plasma facing components associated with ELMs.

  2. Substorm statistics: Occurrences and amplitudes

    SciTech Connect

    Borovsky, J.E.; Nemzek, R.J.

    1994-05-01

    The occurrences and amplitudes of substorms are statistically investigated with the use of three data sets: the AL index, the Los Alamos 3-satellite geosynchronous energetic-electron measurements, and the GOES-5 and -6 geosynchronous magnetic-field measurements. The investigation utilizes {approximately} 13,800 substorms in AL, {approximately} 1400 substorms in the energetic-electron flux, and {approximately} 100 substorms in the magnetic field. The rate of occurrence of substorms is determined as a function of the time of day, the time of year, the amount of magnetotail bending, the orientation of the geomagnetic dipole, the toward/away configuration of the IMF, and the parameters of the solar wind. The relative roles of dayside reconnection and viscous coupling in the production of substorms are assessed. Three amplitudes are defined for a substorms: the jump in the AL index, the peak of the >30-keV integral electron flux at geosynchronous orbit near midnight, and the angle of rotation of the geosynchronous magnetic field near midnight. The substorm amplitudes are statistically analyzed, the amplitude measurements are cross correlated with each other, and the substorm amplitudes are determined as functions of the solar-wind parameters. Periodically occurring and randomly occurring substorms are analyzed separately. The energetic-particle-flux amplitudes are consistent with unloading and the AL amplitudes are consistent with direct driving plus unloading.

  3. Roebel assembled coated conductor cables (RACC): Ac-Losses and current carrying potential

    NASA Astrophysics Data System (ADS)

    Frank, A.; Heller, R.; Goldacker, W.; Kling, A.; Schmidt, C.

    2008-02-01

    Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature in the range 50-77 K. Ac-field applications require cables with low ac-losses and hence twisting of the individual strands. We solved this problem using the Roebel technique. Short lengths of Roebel bar cables were prepared from industrial DyBCO and YBCO-CC. Meander shaped tapes of 4 or 5 mm width with twist pitches of 123 or 127 mm were cut from the 10 or 12 mm wide CC tapes using a specially designed tool. Eleven or twelve of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac-field were measured as a function of frequency and field amplitude as well as the coupling current decay time constant. We discuss the results in terms of available theories and compare measured time constants in transverse field with measured coupling losses. Finally the potential of this cable type for ac-use is discussed with respect to ac-losses and current carrying capability.

  4. AC losses and heat removal in three-dimensional winding pack of Samsung superconducting test facility under pulsed magnetic field operation

    NASA Astrophysics Data System (ADS)

    Wang, Qiuliang; Seong Yoon, Cheon; Baang, Sungkeun; Kim, Myungkyu; Park, Hyunki; Kim, Yongjin; Lee, Sangil; Kim, Keeman

    2001-04-01

    The Samsung superconducting test facility (SSTF) will be operated under the highly pulsed field to simulate the operating conditions of KSTAR. An analysis has been performed to study the transient heat removal characteristics and temperature margin for the main, blip and compensating coils in the SSTF. This method is based on a quasi-three-dimensional model, which the thermal coupling of turn-to-turn, pancake-to-pancake and channel-to-channel is taken into account, to simulate the conductor temperature rise and the thermal expansion of supercritical helium due to the high AC losses under the pulsed field. The local AC losses, which include coupling loss, eddy current loss and hysteresis loss in the cable-in-conduit conductor, are estimated. The temperature margin, mass flow rate, distribution of AC losses are studied under the given operating scenario. The mass flow reduction and peak temperature rise depending on the inlet pressure and inlet position of CICC are studied. It is shown that the initial mass flow rate remarkably influences on the peak temperature of superconducting strands. The large mass flow rate can reduce the temperature rise when the inlet of helium is located at the high field region. By contrast, because of heat induced flow to improve the cooling condition of the superconducting strands, the small initial mass flow rate results in the low peak temperature in strands when the inlet of helium is located at the low field region.

  5. The wave magnetic field amplitude threshold for nonlinear trapping of energetic gyroresonant and Landau resonant electrons by nonducted VLF waves in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Bell, T. F.

    1986-01-01

    A recently developed theory is used to calculate the wave magnetic field amplitude threshold, B-tau, necessary to allow the nonlinear trapping of energetic gyroresonant and Landau resonant electrons by VLF whistler mode waves in the magnetosphere propagating at an arbitrary angle, psi, with respect to the earth's magnetic field. A detailed raytracing study is carried out to establish the variation of psi with position along each magnetic shell in the range L = 2-5 and for frequencies 5-17.8 kHz. It is found that the minimum values of B-tau along each L shell generally occur at points of second-order resonance. In general, for nonducted fixed frequency signals there is only one point of second-order resonance on each L shell, and this is located within a few degrees of the magnetic equator. However, over a narrow range of L, there are as many as three points of second-order resonance and as many as three associated minima in B-tau. At least one of these points is located more than 10 deg from the magnetic equator.

  6. Adding flexibility to the "particles-on-a-sphere" model for large-amplitude motion: POSflex force field for protonated methane

    NASA Astrophysics Data System (ADS)

    Uhl, Felix; Walewski, Łukasz; Forbert, Harald; Marx, Dominik

    2014-09-01

    The so-called "particles-on-a-sphere" (POS) model has been introduced a while ago in order to describe in simple terms large-amplitude motion of polyatomic hydrides, XHn. The POS model of protonated methane, CH_5^+, has been shown to capture well the essence of the fluxional nature of this enigmatic floppy molecule. Here, we extend this model to the POSflex force field by adding flexibility to the C-H bonds, which are constrained to a common fixed bond length in the original model. This makes the present model extremely efficient for computer simulation, including path integral molecular dynamics in order to assess the crucial quantum effects on nuclear motion at low temperatures. Moreover, the POSflex force field can be conveniently used to study microsolvation effects upon combining it with intermolecular pair potentials to account for solute-solvent interactions. Upon computing static properties as well as thermal and quantum fluctuation effects at ambient and low temperatures, respectively, it is shown that the POSflex model is very well suited to describe the structural properties of bare CH_5^+, including hydrogen scrambling and thus fluxionality in the first place. The far- to mid-infrared spectrum up to the bending band is roughly described, whereas the model fails to account for the well-structured stretching band by construction.

  7. Adding flexibility to the “particles-on-a-sphere” model for large-amplitude motion: POSflex force field for protonated methane

    SciTech Connect

    Uhl, Felix; Walewski, Łukasz; Forbert, Harald; Marx, Dominik

    2014-09-14

    The so-called “particles-on-a-sphere” (POS) model has been introduced a while ago in order to describe in simple terms large-amplitude motion of polyatomic hydrides, XH{sub n}. The POS model of protonated methane, CH{sub 5}{sup +}, has been shown to capture well the essence of the fluxional nature of this enigmatic floppy molecule. Here, we extend this model to the POSflex force field by adding flexibility to the C–H bonds, which are constrained to a common fixed bond length in the original model. This makes the present model extremely efficient for computer simulation, including path integral molecular dynamics in order to assess the crucial quantum effects on nuclear motion at low temperatures. Moreover, the POSflex force field can be conveniently used to study microsolvation effects upon combining it with intermolecular pair potentials to account for solute-solvent interactions. Upon computing static properties as well as thermal and quantum fluctuation effects at ambient and low temperatures, respectively, it is shown that the POSflex model is very well suited to describe the structural properties of bare CH{sub 5}{sup +}, including hydrogen scrambling and thus fluxionality in the first place. The far- to mid-infrared spectrum up to the bending band is roughly described, whereas the model fails to account for the well-structured stretching band by construction.

  8. Magnetic-field dependence of Brownian and Néel relaxation times

    NASA Astrophysics Data System (ADS)

    Dieckhoff, Jan; Eberbeck, Dietmar; Schilling, Meinhard; Ludwig, Frank

    2016-01-01

    The investigation of the rotational dynamics of magnetic nanoparticles in magnetic fields is of academic interest but also important for applications such as magnetic particle imaging where the particles are exposed to magnetic fields with amplitudes of up to 25 mT. We have experimentally studied the dependence of Brownian and Néel relaxation times on ac and dc magnetic field amplitude using ac susceptibility measurements in the frequency range between 2 Hz and 9 kHz for field amplitudes up to 9 mT. As samples, single-core iron oxide nanoparticles with core diameters between 20 nm and 30 nm were used either suspended in water-glycerol mixtures or immobilized by freeze-drying. The experimentally determined relaxation times are compared with theoretical models. It was found that the Néel relaxation time decays much faster with increasing field amplitude than the Brownian one. Whereas the dependence of the Brownian relaxation time on the ac and dc field amplitude can be well explained with existing theoretical models, a proper model for the dependence of the Néel relaxation time on ac field amplitude for particles with random distribution of easy axes is still lacking. The extrapolation of the measured relaxation times of the 25 nm core diameter particles to a 25 mT ac field with an empirical model predicts that the Brownian mechanism clearly co-determines the dynamics of magnetic nanoparticles in magnetic particle imaging applications, in agreement with magnetic particle spectroscopy data.

  9. A.C. Susceptibility in MAGNESIUM(1+T)TITANIUM(T)IRON(2 -2T)OXYGEN(4) Near the Breakdown of Ferrimagnetic Order

    NASA Astrophysics Data System (ADS)

    Lautzenhiser, Frans Peter

    1990-01-01

    The complex a.c. susceptibility _ {Xac} in t = 0.45 and 0.5 powder samples of the ferrimagnetic magnesium-titanium-iron oxide spinel have been measured. Frequency, a.c. amplitude, and d.c. field were varied with temperatures ranging from 5K to above the ferrimagnetic Neel temperature T _{N} (285K and 225K, respectively). For fixed frequency f, temperature T, and a.c. amplitude H _{ac}, a monotonic decrease in _{Xac} with increasing d.c. field, characteristic of superparamagnetism (SPM), was seen over the range of field 0.5 Oe < H_{dc} < 65 Oe. The derivative -d_ {Xac}/dH_{ dc} shows a sharp peak near T _{p} = 225K in the t = 0.45 sample. For fixed f, H_{dc}, and T, an increase in _ {Xac} with H_ {ac} was observed over the range of amplitudes 10^{-3} Oe < H_{ac } < 10 Oe. At 200Hz, this nonlinear a.c. response reaches a peak at T_{ac} = 55K and 70K in the t = 0.45 and 0.5 samples respectively. The peak temperature T_{ac} is reduced by lowering f. This frequency dependence is seen neither in the ferrimagnetic Neel temperature nor in the broad peaks of the a.c. susceptibility which occur near T = 0.8T_{N}. Although similar to a SPM blocking transition, the transition at T_{ac} is interpreted as a spin glass freezing temperature. The samples used in this study were previously analyzed by Brand et al. (J. Phys. F 15 1987 (1985).) using d.c. susceptibility and Mossbauer effect measurements.

  10. Automated ac galvanomagnetic measurement system

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Espy, P. N.

    1985-01-01

    An automated, ac galvanomagnetic measurement system is described. Hall or van der Pauw measurements in the temperature range 10-300 K can be made at a preselected magnetic field without operator attendance. Procedures to validate sample installation and correct operation of other system functions, such as magnetic field and thermometry, are included. Advantages of ac measurements are discussed.

  11. DNA- and AC electric field-assisted assembly of two-dimensional colloidal photonic crystals and their controlled defect insertion

    NASA Astrophysics Data System (ADS)

    Kim, Sejong

    Photonic crystals (PC) are structures in which the refractive index is a periodic function in space. The ability of photonic crystals to localize and manipulate electromagnetic waves has attracted considerable attention from the scientific community. The self-assembly of monodisperse micrometer scale colloidal spheres into hexagonal closed-packed colloidal crystals provides a simple, fast, and cheap materials chemistry approach to PCs. Employing DNA supramolecular recognition, 2-dimensional (2D) photonic crystal monolayer was fabricated with monodisperse polystyrene colloidal microspheres. Amine-terminated DNA oligomers were covalently attached onto carboxy-decorated microspheres and enabled their DNA-functionalization while preserving their colloidal stability and organization properties. Following a capillary-force-assisted organization of DNA-decorated microspheres into close-packed 2D opaline arrays, the first monolayer was immobilized by DNA hybridization. Insertion of vacancies at predetermined sites within the lattice of colloidal crystals is a prerequisite in order to realize high-quality, opaline-based photonic devices. The previously obtained DNA-hybridization type binding of 2D-opaline arrays provides a heat-sensitive "adhesive" between substrate and microspheres within a surrounding aqueous medium that enables tuning the hybridization strength of DNA linker as well as a mechanism to facilitate the removal of unbound microspheres. Focusing a laser beam onto a single microsphere of the opaline array induces localized heating that enables the microsphere to detach, leaving behind vacancies. By repeating this process, line vacancies were successfully obtained. The effects of salt concentration, laser power, light-absorbing dyes, DNA length and refractive index mismatch were investigated and found to correlate with heat-induced DNA dehybridization. In addition, AC (alternating current) electrokinetic force was also utilized to obtain assembly of colloidal

  12. AC/RF Superconductivity

    SciTech Connect

    Ciovati, Gianluigi

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  13. AC evidence of a field tuned 2D superconductor-metal transition in a low-disorder InOx film

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Pan, Lidong; Wen, Jiajia; Kim, Minsoo; Ganapathy, Sambandamurthy; Armitage, Peter

    2013-03-01

    Employing microwave spectroscopy, we investigated the field tuned quantum phase transition between the superconducting and the resistive states in a low-disorder amorphous InOx film in the frequency range of 0.05 to 16 GHz. Our AC measurements are explicitly sensitive to the critical slowing down of the characteristic frequency scales approaching a transition. The relevant frequency scale of superconducting fluctuations approaches zero at a field Bsm far below the field Bcross where different isotherms of resistance as a function of magnetic field cross each other. The phase stiffness at the lowest frequency vanishes from the superconducting side at B ~Bsm , while the high frequency limit extrapolates to zero near Bcross. Our data are consistent with a scenario where Bsm is the true quantum critical point for a transition from a superconductor to an anomalous metal, while Bcross only signifies a crossover to a regime where superconducting correlations make a vanishing contribution to both AC and DC transport measurements in the low-disorder limit.

  14. Domain Motion of Ferroelectricity of Bi2SrTa2O9 Single Crystals under an AC-Voltage Electric Field

    NASA Astrophysics Data System (ADS)

    Machida, Akio; Nagasawa, Naomi; Ami, Takaaki; Suzuki, Masayuki

    1999-02-01

    A novel phenomenon, which increases the remanent polarization of Bi2SrTa2O9 single crystals, a promising candidate for ferroelectric random access memories (FeRAM), has been identified. The single crystals, grown in vapor phases using the self-flux method, have a composition characterized asBixSryTa2O9 (x=2.08±0.09, y=1.04±0.06). Incontrast to BixSryTa2O9 (x=1.91±0.05, y=1.27±0.08) single crystals grown by the self-flux method, the coercive field of the present single crystals is smaller. Observing optical anisotropy in the c-plane, we found that this material has a paraelectric phase, which might originate from the partial distortion of the crystal. After voltage was applied, the paraelectric phase disappeared and the crystal became a ferroelectric domain structure. Measuring the electrical properties in the c-plane, the remanent polarization of the Bi2SrTa2O9 single crystal was increased by applying ac-voltage. One-hour annealing over the Curie temperature also produced a paraelectric phase in the crystal but it was confirmed that this paraelectric phase can also be decreased by applying ac-voltage. Using this ac-voltage application, we can clearly observe the domain structure of BiSTa single crystal for the first time.

  15. Amplitude inversion of fast and slow converted waves for fracture characterization of the Montney Formation in Pouce Coupe field, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    MacFarlane, Tyler L.

    The Montney Formation of western Canada is one of the largest economically viable gas resource plays in North America with reserves of 449TCF. As an unconventional tight gas play, the well development costs are high due to the hydraulic stimulations necessary for economic success. The Pouce Coupe research project is a multidisciplinary collaboration between the Reservoir Characterization Project (RCP) and Talisman Energy Inc. with the objective of understanding the reservoir to enable the optimization of well placement and completion design. The work in this thesis focuses on identifying the natural fractures in the reservoir that act as the delivery systems for hydrocarbon flow to the wellbore. Characterization of the Montney Formation at Pouce Coupe is based on time-lapse multicomponent seismic surveys that were acquired before and after the hydraulic stimulation of two horizontal wells. Since shear-wave velocities and amplitudes of the PS-waves are known to be sensitive to near-vertical fractures, I utilize isotropic simultaneous seismic inversions on azimuthally-sectored PS1 and PS2 data sets to obtain measurements of the fast and slow shear-velocities. Specifically, I analyze two orthogonal azimuths that are parallel and perpendicular to the strike of the dominant fracture system in the field. These volumes are used to approximate the shear-wave splitting parameter (gamma(s*)) that is closely related to crack density. Since crack density has a significant impact on defining the percolation zone, the work presented in this thesis provides information that can be utilized to reduce uncertainty in the reservoirs fracture model. Isotropic AVO inversion of azimuthally limited PS-waves demonstrates sufficient sensitivity to detect contrast between the anisotropic elastic properties of the reservoir and is capable of identifying regions with high crack density. This is supported by integration with spinner production logs, hydraulic stimulation history of the field

  16. Ac magnetotransport in La 0.7Sr 0.3Mn 0.95Fe 0.05O 3 at low dc magnetic fields

    NASA Astrophysics Data System (ADS)

    Barik, S. K.; Mahendiran, R.

    2011-12-01

    We report the ac electrical response of La 0.7Sr 0.3Mn 1- xFe xO 3(x=0.05) as a function of temperature, magnetic field (H) and frequency of radio frequency ( rf) current ( f=0.1-20 MHz). The ac impedance (Z) was measured while rf current directly passes through the sample as well as in a coil surrounding the sample. It is found that with increasing frequency of the rf current, Z(T) shows an abrupt increase accompanied by a peak at the ferromagnetic Curie temperature. The peak decreases in magnitude and shifts down with increasing value of H. We find a magnetoimpedance of ΔZ/Z=-21% for ΔH=500 Oe at f=1 MHz around room temperature when the rf current flows directly through the sample and ΔZ/Z=-65.9% when the rf current flows through a coil surrounding the sample. It is suggested that the magnetoimpedance observed is a consequence of suppression of transverse permeability which enhances skin depth for current flow. Our results indicate that the magnetic field control of high frequency impedance of manganites is more useful than direct current magnetoresistance for low-field applications.

  17. Calculating scattering amplitudes efficiently

    SciTech Connect

    Dixon, L.

    1996-01-01

    We review techniques for more efficient computation of perturbative scattering amplitudes in gauge theory, in particular tree and one- loop multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color and helicity information to decompose amplitudes into smaller gauge-invariant pieces, and (2) exploiting the analytic properties of these pieces, namely their cuts and poles. Other useful tools include recursion relations, special gauges and supersymmetric rearrangements. 46 refs., 11 figs.

  18. Gravity and Yang-Mills amplitude relations

    SciTech Connect

    Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Soendergaard, Thomas; FengBo

    2010-11-15

    Using only general features of the S matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.

  19. RHIC spin flipper AC dipole controller

    SciTech Connect

    Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.

    2011-03-28

    The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.

  20. Rotational Brownian dynamics simulations of non-interacting magnetized ellipsoidal particles in d.c. and a.c. magnetic fields

    NASA Astrophysics Data System (ADS)

    Sánchez, Jorge H.; Rinaldi, Carlos

    2009-10-01

    The rotational Brownian motion of magnetized tri-axial ellipsoidal particles (orthotropic particles) suspended in a Newtonian fluid, in the dilute suspension limit, under applied d.c. and a.c. magnetic fields was studied using rotational Brownian dynamics simulations. The algorithm describing the change in the suspension magnetization was obtained from the stochastic angular momentum equation using the fluctuation-dissipation theorem and a quaternion formulation of orientation space. Simulation results are in agreement with the Langevin function for equilibrium magnetization and with single-exponential relaxation from equilibrium at small fields using Perrin's effective relaxation time. Dynamic susceptibilities for ellipsoidal particles of different aspect ratios were obtained from the response to oscillating magnetic fields of different frequencies and described by Debye's model for the complex susceptibility using Perrin's effective relaxation time. Simulations at high equilibrium and probe fields indicate that Perrin's effective relaxation time continues to describe relaxation from equilibrium and response to oscillating fields even beyond the small field limit.

  1. Comparison of AC losses, magnetic field/current distributions and critical currents of superconducting circular pancake coils and infinitely long stacks using coated conductors

    NASA Astrophysics Data System (ADS)

    Yuan, Weijia; Campbell, A. M.; Hong, Z.; Ainslie, M. D.; Coombs, T. A.

    2010-08-01

    A model is presented for calculating the AC losses, magnetic field/current density distribution and critical currents of a circular superconducting pancake coil. The assumption is that the magnetic flux lines will lie parallel to the wide faces of tapes in the unpenetrated area of the coil. Instead of using an infinitely long stack to approximate the circular coil, this paper gives an exact circular coil model using elliptic integrals. A new efficient numerical method is introduced to yield more accurate and fast computation. The computation results are in good agreement with the assumptions. For a small value of the coil radius, there is an asymmetry along the coil radius direction. As the coil radius increases, this asymmetry will gradually decrease, and the AC losses and penetration depth will increase, but the critical current will decrease. We find that if the internal radius is equal to the winding thickness, the infinitely long stack approximation overestimates the loss by 10% and even if the internal radius is reduced to zero, the error is still only 60%. The infinitely long stack approximation is therefore adequate for most practical purposes. In addition, the comparison result shows that the infinitely long stack approximation saves computation time significantly.

  2. Dynamic characteristics of double-barrier nanostructures with asymmetric barriers of finite height and widths in a strong ac electric field

    SciTech Connect

    Chuenkov, V. A.

    2013-12-15

    The theory of the interaction of a monoenergetic flow of injected electrons with a strong high-frequency ac electric field in resonant-tunneling diode (RTD) structures with asymmetric barriers of finite height and width is generalized. In the quasi-classical approximation, electron wavefunctions and tunneling functions in the quantum well and barriers are found. Analytical expressions for polarization currents in RTDs are derived in both the general case and in a number of limiting cases. It is shown that the polarization currents and radiation power in RTDs with asymmetric barriers strongly depend on the ratio of the probabilities of electron tunneling through the emitter and collector barriers. In the quantum mode, when δ = ε − ε{sub r} = ħω ≪ Γ (ε is the energy of electrons injected in the RTD, ħ is Planck’s constant, ω is the ac field frequency, ε{sub r} and Γ are the energy and width of the resonance level, respectively), the active polarization current in a field of E ≈ 2.8ħω/ea (e is the electron charge and a is the quantum-well width) reaches a maximum equal in magnitude to 84% of the direct resonant current, if the probability of electron tunneling through the emitter barrier is much higher than that through the collector barrier. The radiation-generation power at frequencies of ω = 10{sup 12}–10{sup 13} s{sup −1} can reach 10{sup 5}–10{sup 6} W/cm{sup 2} in this case.

  3. Fiber Materials AC Impedance Characteristics and Principium Analysis

    NASA Astrophysics Data System (ADS)

    Wang, Jianjun; Li, Xiaofeng

    With an invariable amplitude and variable frequency inspiriting, impedance of fiber materials rapidly decrease at first and then increase speedy followed with increasing of signal frequency. For the impedance curve of frequency is section of bathtub, this phenomenon is defined as alternating current electric conductive bathtub effect of fiber material. With analysis tools,of circuit theory and medium polarization theory, the phenomenon can be deeply detected that in AC electric field there are four different kind of currents in fiber material: absorbing current, conductance current, charging current and superficial current. With more analyzing it's discovered this phenomenon can be explained by medium polarize theory. Make using of fiber AC electric conductivity bathtub effect, fast testing equipment on fiber moisture regain can be invent, and disadvantages of conventional impedance technique, such as greatness test error and electrode polarization easily. This paper affords directions to design novel speediness fiber moisture test equipments in theory.

  4. Experimental observation of further frequency upshift from dc to ac radiation converter with perpendicular dc magnetic field

    PubMed

    Higashiguchi; Yugami; Gao; Niiyama; Sasaki; Takahashi; Ito; Nishida

    2000-11-20

    A frequency upshift of a short microwave pulse is generated by the interaction between a relativistic underdense ionization front and a periodic electrostatic field with a perpendicular dc magnetic field. When the dc magnetic field is applied, further frequency upshift of 3 GHz is observed with respect to an unmagnetized case which has typically a GHz range. The radiation frequency depends on both the plasma density and the strength of the dc magnetic field, i.e., the plasma frequency and the cyclotron frequency. The frequency of the emitted radiation is in reasonable agreement with the theoretical values. PMID:11082591

  5. Large amplitude drop shape oscillations

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Wang, T. G.

    1982-01-01

    An experimental study of large amplitude drop shape oscillation was conducted in immiscible liquids systems and with levitated free liquid drops in air. In liquid-liquid systems the results indicate the existence of familiar characteristics of nonlinear phenomena. The resonance frequency of the fundamental quadrupole mode of stationary, low viscosity Silicone oil drops acoustically levitated in water falls to noticeably low values as the amplitude of oscillation is increased. A typical, experimentally determined relative frequency decrease of a 0.5 cubic centimeters drop would be about 10% when the maximum deformed shape is characterized by a major to minor axial ratio of 1.9. On the other hand, no change in the fundamental mode frequency could be detected for 1 mm drops levitated in air. The experimental data for the decay constant of the quadrupole mode of drops immersed in a liquid host indicate a slight increase for larger oscillation amplitudes. A qualitative investigation of the internal fluid flows for such drops revealed the existence of steady internal circulation within drops oscillating in the fundamental and higher modes. The flow field configuration in the outer host liquid is also significantly altered when the drop oscillation amplitude becomes large.

  6. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Greenblatt, M.H.

    1958-03-25

    This patent pertains to pulse amplitude analyzers for sorting and counting a serles of pulses, and specifically discloses an analyzer which ls simple in construction and presents the puise height distribution visually on an oscilloscope screen. According to the invention, the pulses are applied to the vertical deflection plates of an oscilloscope and trigger the horizontal sweep. Each pulse starts at the same point on the screen and has a maximum amplitude substantially along the same vertical line. A mask is placed over the screen except for a slot running along the line where the maximum amplitudes of the pulses appear. After the slot has been scanned by a photocell in combination with a slotted rotating disk, the photocell signal is displayed on an auxiliary oscilloscope as vertical deflection along a horizontal time base to portray the pulse amplitude distribution.

  7. PULSE AMPLITUDE ANALYSERS

    DOEpatents

    Lewis, I.A.D.

    1956-05-15

    This patent pentains to an electrical pulse amplitude analyzer, capable of accepting input pulses having a separation between adjacent pulses in the order of one microsecond while providing a large number of channels of classification. In its broad aspect the described pulse amplitude analyzer utilizes a storage cathode ray tube und control circuitry whereby the amplitude of the analyzed pulses controls both the intensity and vertical defiection of the beam to charge particular spots in horizontal sectors of the tube face as the beam is moved horizontally across the tube face. As soon as the beam has swept the length of the tube the information stored therein is read out by scanning individually each horizontal sector corresponding to a certain range of pulse amplitudes and applying the output signal from each scan to separate indicating means.

  8. Two large-amplitude motions in triatomic molecules. Force field of the 1B2 (1A') state of SO2

    NASA Astrophysics Data System (ADS)

    Mezey, Paul G.; Ramachandra Rao, Ch. V. S.

    1980-01-01

    A program has been developed to calculate the energy levels associated with the two large-amplitude stretching vibrations ν1 and ν3 of a bent triatomic molecule in which the ν3 oscillation occurs in a double minimum potential. Employing the two large-amplitude Hamiltonian H0s(ρ1,ρ3) obtained earlier by Brand and Rao. [J. Mol. Spectrosc., 61, 360 (1976)], the vibrational energy levels (v1,v3even/odd) of SO2 molecule in its 1B2 (1A') excited state are calculated. The nine parameters of the potential function V0(ρ1,ρ3) are then adjusted to give a least-square fit to the 12 observed vibrational term values corresponding to the levels (v1,v3even) of S16O2 and S18O2. A three-dimensional picture of the potential surface V0(ρ1,ρ3) using the final set of force constants is also presented. The saddle point of this surface is at (ρO1=1.5525 Å, ρO3=0.0 Å) and the absolute minima occur at (ρe1=1.5644 Å, ρe3=±0.0745 Å). Barrier height, i.e., the height of the saddle point above the absolute minima, is 140 cm-1.

  9. Topics in Scattering Amplitudes

    NASA Astrophysics Data System (ADS)

    Dennen, Tristan Lucas

    In Part 1, we combine on-shell methods with the six-dimensional helicity formalism of Cheung and O'Connell to construct tree-level and multiloop scattering amplitudes. As a nontrivial multiloop example, we confirm that the recently constructed four-loop four-point amplitude of N=4 super-Yang-Mills theory, including nonplanar contributions, is valid for dimensions less than or equal to six. We demonstrate that the tree-level amplitudes of maximal super-Yang-Mills theory in six dimensions, when stripped of their overall momentum and supermomentum delta functions, are covariant with respect to the six-dimensional dual conformal group. We demonstrate that this property is also present for loop amplitudes. In Part 2, we explore consequences of the recently discovered duality between color and kinematics, which states that kinematic numerators in a diagrammatic expansion of gauge-theory amplitudes can be arranged to satisfy Jacobi-like identities in one-to-one correspondence to the associated color factors. The related squaring relations express gravity amplitudes in terms of gauge-theory ingredients. We then present a Yang-Mills Lagrangian whose diagrams through five points manifestly satisfy the duality between color and kinematics. Finally, we compute the coefficient of the potential three-loop divergence in pure N=4 supergravity and show that it vanishes, contrary to expectations from symmetry arguments.

  10. Low field AC susceptibility study of intergranular critical current density in Mg-substituted CuBa2Ca3Cu4O12-y high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Agarwal, S. K.; Kumaraswamy, B. V.

    2005-05-01

    Measurements of the a.c.susceptibility (χ=χ‧+iχ″) have been made on the Mg substituted high TC superconducting system, CuBa2(MgxCa1-x)3Cu4O12-y (Cu-1234) with x=0, 0.10 & 0.20, at different values of the a.c.field amplitude. Estimates of the intergranular critical current density(JC) made from the field dependent χ″-T curves show an improvement in the Mg-substituted Cu-1234 system. Results have been analysed in the light of the crystal structure and the superconducting anisotropy factor (γ=ξab/ξc) of the Cu-1234 system. Lower superconducting anisotropy emanating from Mg substitution has been found to be significant, resulting in better superconducting properties.

  11. Constant-amplitude, frequency- independent phase shifter

    NASA Technical Reports Server (NTRS)

    Deboo, G. J.

    1971-01-01

    Electronic circuit using operational amplifiers provides output with constant phase shift amplitude, with respect to sinusoidal input, over wide range of frequencies. New circuit includes field effect transistor, Q, operational amplifiers, A1 and A2, and phase detector.

  12. Chaotic dynamics and basin erosion in nanomagnets subject to time-harmonic magnetic fields

    NASA Astrophysics Data System (ADS)

    d'Aquino, M.; Quercia, A.; Serpico, C.; Bertotti, G.; Mayergoyz, I. D.; Perna, S.; Ansalone, P.

    2016-04-01

    Magnetization dynamics in uniformly magnetized particles subject to time-harmonic (AC) external fields is considered. The study is focused on the behavior of the AC-driven dynamics close to saddle equilibria. It happens that such dynamics has chaotic nature at moderately low power level, due to the heteroclinic tangle phenomenon which is produced by the combined effect of AC-excitations and saddle type dynamics. By using analytical theory for the threshold AC excitation amplitudes necessary to create the heteroclinic tangle together with numerical simulations, we quantify and show how the tangle produces the erosion of the safe basin around the stable equilibria.

  13. Tevatron optics measurements using an AC dipole

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is a device to study beam optics of hadron synchrotrons. It can produce sustained large amplitude oscillations with virtually no emittance growth. A vertical AC dipole for the Tevatron is recently implemented and a maximum oscillation amplitude of 2{sigma} (4{sigma}) at 980 GeV (150 GeV) is achieved [1]. When such large oscillations are measured with the BPM system of the Tevatron (20 {micro}m resolution), not only linear but even nonlinear optics can be directly measured. This paper shows how to measure {beta} function using an AC dipole and the result is compared to the other measurement. The paper also shows a test to detect optics changes when small changes are made in the Tevatron. Since an AC dipole is nondestructive, it allows frequent measurements of the optics which is necessary for such an test.

  14. dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots.

    PubMed

    Tsindlekht, M I; Genkin, V M; Felner, I; Zeides, F; Katz, N; Gazi, Š; Chromik, Š; Dobrovolskiy, O V; Sachser, R; Huth, M

    2016-06-01

    dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above H c1, but in fields lower than H c1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures above [Formula: see text] and [Formula: see text] the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near H c3. This similarity does not exist at low fields in a swept mode. PMID:27143621

  15. Universal dielectric loss in glass from simultaneous bias and microwave fields.

    PubMed

    Burin, Alexander L; Khalil, Moe S; Osborn, Kevin D

    2013-04-12

    We derive the ac dielectric loss in glasses due to resonant processes created by two-level systems and a swept electric field bias. It is shown that at sufficiently large ac fields and bias sweep rates, the nonequilibrium loss tangent created by the two fields approaches a universal maximum determined by the bare linear dielectric permittivity. In addition, this nonequilibrium loss tangent is derived for a range of bias sweep rates and ac amplitudes. A predicted loss function can be understood in a Landau-Zener theory and used to extract the two-level system density, dipole moment, and relaxation rate. PMID:25167300

  16. Micromagnetic study of phase-locking in spin-transfer nano-oscillators driven by currents and ac fields

    NASA Astrophysics Data System (ADS)

    d'Aquino, M.; Serpico, C.; Bonin, R.; Bertotti, G.; Mayergoyz, I. D.

    2011-04-01

    The magnetization dynamics of a spin-transfer nano-oscillator is studied for a system subject to the combined action of dc spin-polarized electric current and microwave circularly polarized applied field. The uniform mode theory is developed for a spin-valve with an arbitrary orientation of the polarizer. The theory enables one to predict the control parameters for the synchronization between the magnetization self-oscillation and the external microwave field. Full micromagnetic simulations are performed with the predicted control parameters, and they demonstrate the hysteretic nature of the synchronization in very good agreement with the theory.

  17. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  18. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  19. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  20. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  1. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  2. Rock formation characterization for CO2-EOR and carbon geosequestration; 3D seismic amplitude and coherency anomalies, Wellington Field, Kansas, USA

    USGS Publications Warehouse

    Ohl, D.; Raef, A.; Watnef, L.; Bhattacharya, S.

    2011-01-01

    In this paper, we present a workflow for a Mississipian carbonates characterization case-study integrating post-stack seismic attributes, well-logs porosities, and seismic modeling to explore relating changes in small-scale "lithofacies" properties and/or sub-seismic resolution faulting to key amplitude and coherency 3D seismic attributes. The main objective of this study is to put emphasis on reservoir characterization that is both optimized for and subsequently benefiting from pilot tertiary CO2-EOR in preparation for future carbon geosequestration in a depleting reservoir and a deep saline aquifer. The extracted 3D seismic coherency attribute indicated anomalous features that can be interpreted as a lithofacies change or a sub-seismic resolution faulting. A 2D finite difference modeling has been undertaken to understand and potentially build discriminant attributes to map structural and/or lithofacies anomalies of interest especially when embarking upon CO2-EOR and/or carbon sequestration monitoring and management projects. ?? 2011 Society of Exploration Geophysicists.

  3. Does the temperature dependence at constant volume of the hyperfine field of heavy impurities in ferromagnetic metals depend explicitly upon the amplitude of lattice vibrations?

    NASA Astrophysics Data System (ADS)

    Riedi, P. C.; Webber, G. D.

    1983-12-01

    Lattice dynamics seem to have little effect on the temperature dependence of the hyperfine field of pure iron and nickel and of most impurities in these metals but it is shown that Au in iron may be an exception to this rule. The hyperfine fields of other heavy impurities ( FeRu, FeIr, NiPt) were found to have a normal temperature dependence.

  4. Reinforcing Saccadic Amplitude Variability

    ERIC Educational Resources Information Center

    Paeye, Celine; Madelain, Laurent

    2011-01-01

    Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…

  5. Field Performance of Bt Eggplants (Solanum melongena L.) in the Philippines: Cry1Ac Expression and Control of the Eggplant Fruit and Shoot Borer (Leucinodes orbonalis Guenée).

    PubMed

    Hautea, Desiree M; Taylo, Lourdes D; Masanga, Anna Pauleen L; Sison, Maria Luz J; Narciso, Josefina O; Quilloy, Reynaldo B; Hautea, Randy A; Shotkoski, Frank A; Shelton, Anthony M

    2016-01-01

    Plants expressing Cry proteins from the bacterium, Bacillus thuringiensis (Bt), have become a major tactic for controlling insect pests in maize and cotton globally. However, there are few Bt vegetable crops. Eggplant (Solanum melongena) is a popular vegetable grown throughout Asia that is heavily treated with insecticides to control the eggplant fruit and shoot borer, Leucinodes orbonalis (EFSB). Herein we provide the first publicly available data on field performance in Asia of eggplant engineered to produce the Cry1Ac protein. Replicated field trials with five Bt eggplant open-pollinated (OP) lines from transformation event EE-1 and their non-Bt comparators were conducted over three cropping seasons in the Philippines from 2010-2012. Field trials documented levels of Cry1Ac protein expressed in plants and evaluated their efficacy against the primary target pest, EFSB. Cry1Ac concentrations ranged from 0.75-24.7 ppm dry weight with the highest in the terminal leaves (or shoots) and the lowest in the roots. Cry1Ac levels significantly increased from the vegetative to the reproductive stage. Bt eggplant lines demonstrated excellent control of EFSB. Pairwise analysis of means detected highly significant differences between Bt eggplant lines and their non-Bt comparators for all field efficacy parameters tested. Bt eggplant lines demonstrated high levels of control of EFSB shoot damage (98.6-100%) and fruit damage (98.1-99.7%) and reduced EFSB larval infestation (95.8-99.3%) under the most severe pest pressure during trial 2. Moths that emerged from larvae collected from Bt plants in the field and reared in their Bt eggplant hosts did not produce viable eggs or offspring. These results demonstrate that Bt eggplant lines containing Cry1Ac event EE-1 provide outstanding control of EFSB and can dramatically reduce the need for conventional insecticides. PMID:27322533

  6. Field Performance of Bt Eggplants (Solanum melongena L.) in the Philippines: Cry1Ac Expression and Control of the Eggplant Fruit and Shoot Borer (Leucinodes orbonalis Guenée)

    PubMed Central

    Hautea, Desiree M.; Taylo, Lourdes D.; Masanga, Anna Pauleen L.; Sison, Maria Luz J.; Narciso, Josefina O.; Quilloy, Reynaldo B.; Hautea, Randy A.; Shotkoski, Frank A.; Shelton, Anthony M.

    2016-01-01

    Plants expressing Cry proteins from the bacterium, Bacillus thuringiensis (Bt), have become a major tactic for controlling insect pests in maize and cotton globally. However, there are few Bt vegetable crops. Eggplant (Solanum melongena) is a popular vegetable grown throughout Asia that is heavily treated with insecticides to control the eggplant fruit and shoot borer, Leucinodes orbonalis (EFSB). Herein we provide the first publicly available data on field performance in Asia of eggplant engineered to produce the Cry1Ac protein. Replicated field trials with five Bt eggplant open-pollinated (OP) lines from transformation event EE-1 and their non-Bt comparators were conducted over three cropping seasons in the Philippines from 2010–2012. Field trials documented levels of Cry1Ac protein expressed in plants and evaluated their efficacy against the primary target pest, EFSB. Cry1Ac concentrations ranged from 0.75–24.7 ppm dry weight with the highest in the terminal leaves (or shoots) and the lowest in the roots. Cry1Ac levels significantly increased from the vegetative to the reproductive stage. Bt eggplant lines demonstrated excellent control of EFSB. Pairwise analysis of means detected highly significant differences between Bt eggplant lines and their non-Bt comparators for all field efficacy parameters tested. Bt eggplant lines demonstrated high levels of control of EFSB shoot damage (98.6–100%) and fruit damage (98.1–99.7%) and reduced EFSB larval infestation (95.8–99.3%) under the most severe pest pressure during trial 2. Moths that emerged from larvae collected from Bt plants in the field and reared in their Bt eggplant hosts did not produce viable eggs or offspring. These results demonstrate that Bt eggplant lines containing Cry1Ac event EE-1 provide outstanding control of EFSB and can dramatically reduce the need for conventional insecticides. PMID:27322533

  7. Specific absorption rate dependence on temperature in magnetic field hyperthermia measured by dynamic hysteresis losses (ac magnetometry)

    NASA Astrophysics Data System (ADS)

    Garaio, Eneko; Sandre, Olivier; Collantes, Juan-Mari; Garcia, Jose Angel; Mornet, Stéphane; Plazaola, Fernando

    2015-01-01

    Magnetic nanoparticles (NPs) are intensively studied for their potential use for magnetic hyperthermia, a treatment that has passed a phase II clinical trial against severe brain cancer (glioblastoma) at the end of 2011. Their heating power, characterized by the ‘specific absorption rate (SAR)’, is often considered temperature independent in the literature, mainly because of the difficulties that arise from the measurement methodology. Using a dynamic magnetometer presented in a recent paper, we measure here the thermal dependence of SAR for superparamagnetic iron oxide (maghemite) NPs of four different size-ranges corresponding to mean diameters around 12 nm, 14 nm, 15 nm and 16 nm. The article reports a parametrical study extending from 10 to 60 {}^\\circ C in temperature, from 75 to 1031 kHz in frequency, and from 2 to 24 kA m-1 in magnetic field strength. It was observed that SAR values of smaller NPs decrease with temperature whereas for the larger sample (16 nm) SAR values increase with temperature. The measured variation of SAR with temperature is frequency dependent. This behaviour is fully explained within the scope of linear response theory based on Néel and Brown relaxation processes, using independent magnetic measurements of the specific magnetization and the magnetic anisotropy constant. A good quantitative agreement between experimental values and theoretical values is confirmed in a tri-dimensional space that uses as coordinates the field strength, the frequency and the temperature.

  8. Mixed Brownian alignment and Néel rotations in superparamagnetic iron oxide nanoparticle suspensions driven by an ac field

    PubMed Central

    Shah, Saqlain A.; Reeves, Daniel B.; Ferguson, R. Matthew; Weaver, John B.

    2015-01-01

    Superparamagnetic iron oxide nanoparticles with highly nonlinear magnetic behavior are attractive for biomedical applications like magnetic particle imaging and magnetic fluid hyperthermia. Such particles display interesting magnetic properties in alternating magnetic fields and here we document experiments that show differences between the magnetization dynamics of certain particles in frozen and melted states. This effect goes beyond the small temperature difference (ΔT ~ 20 °C) and we show the dynamics to be a mixture of Brownian alignment of the particles and Néel rotation of their moments occurring in liquid particle suspensions. These phenomena can be modeled in a stochastic differential equation approach by postulating log-normal distributions and partial Brownian alignment of an effective anisotropy axis. We emphasize that precise particle-specific characterization through experiments and nonlinear simulations is necessary to predict dynamics in solution and optimize their behavior for emerging biomedical applications including magnetic particle imaging. PMID:26504371

  9. Extension of a regularizing algorithm for the determination of equilibrium geometry and force field of free molecules from joint use of electron diffraction, molecular spectroscopy and ab initio data on systems with large-amplitude oscillatory motion

    NASA Astrophysics Data System (ADS)

    Kochikov, I. V.; Tarasov, Yu. I.; Spiridonov, V. P.; Kuramshina, G. M.; Yagola, A. G.; Saakjan, A. S.; Popik, M. V.; Samdal, S.

    1999-08-01

    The previously developed integrated algorithm for the joint treatment of gas-phase electron diffraction and vibrational spectroscopic data is extended to include systems with large-amplitude oscillatory motion. In addition, the treatment is augmented by the inclusion of microwave rotational constants. As in the previous work, the analysis of data from experimental sources is guided by quantum mechanical molecular geometry and force field optimization results. The computed force field matrix can be corrected empirically with the aid of suitable scale factors. Centrifugal distortion corrections to interatomic distances are included. The standard deviations of the parameters determined and the correlation coefficients can now be estimated. The principal design of the developed computer program is outlined, and some methodological problems associated with diffraction analysis of molecules with large-amplitude motion are discussed. To provide an example of a problem susceptible to attack by the present method an account is made of the re-analysis of diffraction data for 4-fluorobenzaldehyde collected earlier on the Balzers apparatus in Oslo.

  10. Change in the microhardness of nonmagnetic crystals after their exposure to the Earth's magnetic field and AC pump field in the EPR scheme

    NASA Astrophysics Data System (ADS)

    Alshits, V. I.; Darinskaya, E. V.; Koldaeva, M. V.; Petrzhik, E. A.

    2012-02-01

    Changes in the microhardness of ZnO, triglycine sulfate (TGS), and potassium acid phthalate (KAP) crystals after their exposure to crossed ultralow magnetic fields, i.e., the Earth's field B Earth ≈ 50 μT and the alternating-current field tilde B ≈ 3 μ T orthogonal to it, have been revealed. In ZnO crystals, the microhardness increases, whereas in TGS and KAP, it decreases. A maximum change (10-15%) is reached within 1-3 h after magnetic treatment; then, the microhardness gradually recovers to its initial value for the first day. After a sufficient pause, the effect is completely reproduced under the same conditions. The resonant frequency of the pump field tilde B corresponds to the EPR condition with a g-factor close to two. The magnetic memory exhibits a strong anisotropy: for each of the crystals, a direction is found, which, being coincident with the Earth's magnetic field vector B Earth, causes complete or partial suppression of the effect. In ZnO and TGS crystals, these are symmetry axes 6 and 2, respectively. In the KAP crystal, it is the direction in the cleavage plane orthogonal the 2 axis. Possible physical mechanisms of the observed phenomena have been discussed.

  11. 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.

  12. Self-Rotation of Cells in an Irrotational AC E-Field in an Opto-Electrokinetics Chip

    PubMed Central

    Chau, Long-Ho; Liang, Wenfeng; Cheung, Florence Wing Ki; Liu, Wing Keung; Li, Wen Jung; Chen, Shih-Chi; Lee, Gwo-Bin

    2013-01-01

    The use of optical dielectrophoresis (ODEP) to manipulate microparticles and biological cells has become increasingly popular due to its tremendous flexibility in providing reconfigurable electrode patterns and flow channels. ODEP enables the parallel and free manipulation of small particles on a photoconductive surface on which light is projected, thus eliminating the need for complex electrode design and fabrication processes. In this paper, we demonstrate that mouse cells comprising melan-a cells, RAW 267.4 macrophage cells, peripheral white blood cells and lymphocytes, can be manipulated in an opto-electrokinetics (OEK) device with appropriate DEP parameters. Our OEK device generates a non-rotating electric field and exerts a localized DEP force on optical electrodes. Hitherto, we are the first group to report that among all the cells investigated, melan-a cells, lymphocytes and white blood cells were found to undergo self-rotation in the device in the presence of a DEP force. The rotational speed of the cells depended on the voltage and frequency applied and the cells' distance from the optical center. We discuss a possible mechanism for explaining this new observation of induced self-rotation based on the physical properties of cells. We believe that this rotation phenomenon can be used to identify cell type and to elucidate the dielectric and physical properties of cells. PMID:23320067

  13. Mask-assisted deterministic phase-amplitude retrieval from a single far-field intensity diffraction pattern: two experimental proofs of principle using visible light.

    PubMed

    Podorov, Sergey G; Bishop, Alexis I; Paganin, David M; Pavlov, Konstantin M

    2011-06-01

    We recently developed a simple closed-form algorithm, which allows one to reconstruct the complex scalar wavefield at the exit surface of a sample, from the intensity of its far-field coherent diffraction pattern which is obtained in the presence of a suitable object-plane mask. In the first variant of this algorithm, the sample is contained within a uniformly illuminated sharp rectangular aperture in which at least one transverse dimension is at least twice that of the object. In the second variant, the sample is uniformly illuminated and is transversely displaced from an opaque rectangular mask in the object plane. For both variants, the far-field diffraction pattern is first Fourier transformed and then differentiated with respect to both transverse coordinates, in order to deterministically yield a series of independent reconstructions of the sample. Here we give an experimental demonstration of each of these two variants of our technique, using visible light. PMID:21664548

  14. China Amplitude Tomography

    NASA Astrophysics Data System (ADS)

    Hearn, T. M.

    2014-12-01

    Modern data from the China Bulletin and temporary network deployments has been used to update amplitude tomography using ML and MS seismic amplitudes. This work builds on the results of Hearn et al., 2008. ML attenuation estimates are much better resolved due to the inclusion of subnet data. We find that the trade-off between geometrical spreading and attenuation estimates are well constrained; however, both of these parameters have significant trade-off with the frequency dependence of attenuation. Maps of attenuation using the ML amplitudes are similar to those of Lg attenuation found by other authors suggesting that ML attenuation estimates form a suitable proxy for Lg attenuation estimates. We are now able to associate high attenuation directly with the Longmen Shan and the Qilian Shan mountains and also, where resolved, with the Kunlun Shan, Altyn Tag, and Tian Shan mountains. Grabens around the Ordos Platform also show high attenuation. Basins, however, do not in general show high attenuation. The main exception to this is the Bohai Basin. We conclude that the ML waveforms, like the Lg waveforms, interrogate the entire crustal column and are most sensitive to tectonically active structures and rapid changes in crustal structure. Data from MS data do not include subnet readings and do not have the resolution that was obtained with the ML data. Nonetheless, features are similar with the exception that basins appear more highly attenuative.

  15. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Gray, G.W.; Jensen, A.S.

    1957-10-22

    A pulse-height analyzer system of improved design for sorting and counting a series of pulses, such as provided by a scintillation detector in nuclear radiation measurements, is described. The analyzer comprises a main transmission line, a cathode-ray tube for each section of the line with its deflection plates acting as the line capacitance; means to bias the respective cathode ray tubes so that the beam strikes a target only when a prearranged pulse amplitude is applied, with each tube progressively biased to respond to smaller amplitudes; pulse generating and counting means associated with each tube to respond when the beam is deflected; a control transmission line having the same time constant as the first line per section with pulse generating means for each tube for initiating a pulse on the second transmission line when a pulse triggers the tube of corresponding amplitude response, the former pulse acting to prevent successive tubes from responding to the pulse under test. This arrangement permits greater deflection sensitivity in the cathode ray tube and overcomes many of the disadvantages of prior art pulse-height analyzer circuits.

  16. Electron acceleration and emission in a field of a plane and converging dipole wave of relativistic amplitudes with the radiation reaction force taken into account

    SciTech Connect

    Bashinov, Aleksei V; Gonoskov, Arkady A; Kim, A V; Marklund, Mattias; Mourou, G; Sergeev, Aleksandr M

    2013-04-30

    A comparative analysis is performed of the electron emission characteristics as the electrons move in laser fields with ultra-relativistic intensity and different configurations corresponding to a plane or tightly focused wave. For a plane travelling wave, analytical expressions are derived for the emission characteristics, and it is shown that the angular distribution of the radiation intensity changes qualitatively even when the wave intensity is much less than that in the case of the radiation-dominated regime. An important conclusion is drawn that the electrons in a travelling wave tend to synchronised motion under the radiation reaction force. The characteristic features of the motion of electrons are found in a converging dipole wave, associated with the curvature of the phase front and nonuniformity of the field distribution. The values of the maximum achievable longitudinal momenta of electrons accelerated to the centre, as well as their distribution function are determined. The existence of quasi-periodic trajectories near the focal region of the dipole wave is shown, and the characteristics of the emission of both accelerated and oscillating electrons are analysed. (extreme light fields and their applications)

  17. Electrical Characteristics, Electrode Sheath and Contamination Layer Behavior of a Meso-Scale Premixed Methane-Air Flame Under AC/DC Electric Fields

    NASA Astrophysics Data System (ADS)

    Chen, Qi; Yan, Limin; Zhang, Hao; Li, Guoxiu

    2016-05-01

    Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC (0-4300 V, 0-500 Hz) and DC (0-3300 V) electric fields were studied. I-V curves were measured under different experimental conditions to estimate the magnitude of the total current 100-102 μA, the electron density 1015-1016 m‑3 and further the power dissipation ≤ 0.7 W in the reaction zone. At the same time, the meso-scale premixed flame conductivity 10‑4-10‑3 Ω‑1·m‑1 as a function of voltage and frequency was experimentally obtained and was believed to represent a useful order-of magnitude estimate. Moreover, the influence of the collision sheath relating to Debye length (31–98 μm) and the contamination layer of an active electrode on measurements was discussed, based on the combination of simulation and theoretical analysis. As a result, the electrode sheath dimension was evaluated to less than 0.5 mm, which indicated a complex effect of the collision sheath on the current measurements. The surface contamination effect of an active electrode was further analyzed using the SEM imaging method, which showed elements immigration during the contamination layer formation process. supported by National Natural Science Foundation of China (No. 51376021), and the Fundamental Research Fund for Major Universities (No. 2013JBM079)

  18. Attenuation of Mouse Melanoma by A/C Magnetic Field after Delivery of Bi-Magnetic Nanoparticles by Neural Progenitor Cells

    PubMed Central

    Rachakatla, Raja Shekar; Balivada, Sivasai; Seo, Gwi-Moon; Myers, Carl B; Wang, Hongwang; Samarakoon, Thilani N.; Dani, Raj; Pyle, Marla; Kroh, Franklin O.; Walker, Brandon; Leaym, Xiaoxuan; Koper, Olga B.; Chikan, Viktor; Bossmann, Stefan H.; Tamura, Masaaki; Troyer, Deryl L.

    2010-01-01

    Localized magnetic hyperthermia as a treatment modality for cancer has generated renewed interest, particularly if it can be targeted to the tumor site. We examined whether tumor-tropic neural progenitor cells (NPCs) could be utilized as cell delivery vehicles for achieving preferential accumulation of core/shell iron/iron oxide magnetic nanoparticles (MNPs) within a mouse model of melanoma. We developed aminosiloxane-porphyrin functionalized MNPs, evaluated cell viability and loading efficiency, and transplanted neural progenitor cells loaded with this cargo into mice with melanoma. NPCs were efficiently loaded with core/shell Fe/Fe3O4 MNPs with minimal cytotoxicity; the MNPs accumulated as aggregates in the cytosol. The NPCs loaded with MNPs could travel to subcutaneous melanomas, and after A/C (alternating current) magnetic field (AMF) exposure, the targeted delivery of MNPs by the cells resulted in a measurable regression of the tumors. The tumor attenuation was significant (p<0.05) a short time (24 hours) after the last of three AMF exposures. PMID:21058696

  19. Helicity amplitudes on the light-front

    NASA Astrophysics Data System (ADS)

    Cruz Santiago, Christian A.

    Significant progress has been made recently in the field of helicity amplitudes. Currently there are on-shell recursion relations with shifted complex momenta, geometric interpretations of amplitudes and gauge invariant off-shell amplitudes. All this points to helicity amplitudes being a rich field with much more to say. In this work we take initial steps in understanding amplitudes through the light-front formalism for the first time. We begin by looking at crossing symmetry. In the light-front it is not obvious that crossing symmetry should be present as there are non-local energy denominators that mix energies of different states. Nevertheless, we develop a systematic approach to relate, for example, 1 → N gluon processes to 2 → N -- 1 processes. Using this method, we give a perturbative proof of crossing symmetry on the light-front. One important caveat is that the proof requires the amplitudes to be on-shell. We also saw that the analytic continuation from outgoing to incoming particle produces a phase that's dependent on the choice of polarizations. Next, we reproduce the Parke-Taylor amplitudes. For this purpose we found a recursion relation for an off-shell object called the fragmentation function. This recursion relies on the factorization property of the fragmentation functions, and it becomes apparent that this recursion is the light-front analog of the Berends-Giele recursion relation. We also found this object's connection to off-shell and on-shell amplitudes. The solution for the off-shell amplitude, which does reproduce the Parke-Taylor amplitudes in the on-shell limit, turns out to be very interesting. It can be written as a linear sum of off-shell objects with the same structure as MHV amplitudes. Finally, we look at the Wilson line approach to generate gauge invariant off-shell amplitudes. It turns out that the exact same recursion relation appears on both frameworks, thereby providing the interpretation that our recursion relation has it

  20. Investigation of Spiral Bevel Gear Condition Indicator Validation via AC-29-2C Using Fielded Rotorcraft HUMS Data

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.; Wade, Daniel R.; Antolick, Lance J.; Thomas, Josiah

    2014-01-01

    This report presents the analysis of gear condition indicator data collected on a helicopter when damage occurred in spiral bevel gears. The purpose of the data analysis was to use existing in-service helicopter HUMS flight data from faulted spiral bevel gears as a Case Study, to better understand the differences between HUMS data response in a helicopter and a component test rig, the NASA Glenn Spiral Bevel Gear Fatigue Rig. The reason spiral bevel gear sets were chosen to demonstrate differences in response between both systems was the availability of the helicopter data and the availability of a test rig that was capable of testing spiral bevel gear sets to failure. The objective of the analysis presented in this paper was to re-process helicopter HUMS data with the same analysis techniques applied to the spiral bevel rig test data. The damage modes experienced in the field were mapped to the failure modes created in the test rig. A total of forty helicopters were evaluated. Twenty helicopters, or tails, experienced damage to the spiral bevel gears in the nose gearbox. Vibration based gear condition indicators data was available before and after replacement. The other twenty tails had no known anomalies in the nose gearbox within the time frame of the datasets. These twenty tails were considered the baseline dataset. The HUMS gear condition indicators evaluated included gear condition indicators (CI) Figure of Merit 4 (FM4), Root Mean Square (RMS) or Diagnostic Algorithm 1 (DA1) and +/- 3 Sideband Index (SI3). Three additional condition indicators, not currently calculated on-board, were calculated from the archived data. These three indicators were +/- 1 Sideband Index (SI1), the DA1 of the difference signal (DiffDA1) and the peak-to-peak of the difference signal (DP2P). Results found the CI DP2P, not currently available in the on-board HUMS, performed the best, responding to varying levels of damage on thirteen of the fourteen helicopters evaluated. Two

  1. The effect of surface grain reversal on the AC losses of sintered Nd-Fe-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Moore, Martina; Roth, Stefan; Gebert, Annett; Schultz, Ludwig; Gutfleisch, Oliver

    2015-02-01

    Sintered Nd-Fe-B magnets are exposed to AC magnetic fields in many applications, e.g. in permanent magnet electric motors. We have measured the AC losses of sintered Nd-Fe-B magnets in a closed circuit arrangement using AC fields with root mean square-values up to 80 mT (peak amplitude 113 mT) over the frequency range 50 to 1000 Hz. Two magnet grades with different dysprosium content were investigated. Around the remanence point the low grade material (1.7 wt% Dy) showed significant hysteresis losses; whereas the losses in the high grade material (8.9 wt% Dy) were dominated by classical eddy currents. Kerr microscopy images revealed that the hysteresis losses measured for the low grade magnet can be mainly ascribed to grains at the sample surface with multiple domains. This was further confirmed when the high grade material was subsequently exposed to DC and AC magnetic fields. Here a larger number of surface grains with multiple domains are also present once the step in the demagnetization curve attributed to the surface grain reversal is reached and a rise in the measured hysteresis losses is evident. If in the low grade material the operating point is slightly offset from the remanence point, such that zero field is not bypassed, its AC losses can also be fairly well described with classical eddy current theory.

  2. Producing directed migration with correlated atoms in a tilted ac-driven lattice

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Yang, Shi-Jie

    2016-06-01

    The correlated atoms in a tilted optical lattice driven by an ac field are studied within the Hubbard model. By making use of both photon-assisted tunneling and coherent destructive tunneling effects, we can move a pair of strongly correlated atoms in the lattice via manipulating the global amplitude of the driving field. We propose a scheme for creating entanglement between the particle pair and a single particle through interacting oscillations. Our model may provide a new building block for investigating quantum computing and quantum information processing with ultracold atoms in optical lattices.

  3. Ion trajectory simulations of axial ac dipolar excitation in the Orbitrap

    NASA Astrophysics Data System (ADS)

    Wu, Guangxiang; Noll, Robert J.; Plass, Wolfgang R.; Hu, Qizhi; Perry, Richard H.; Cooks, R. Graham

    2006-07-01

    The newly developed version of the multi-particle ion trajectory simulation program, ITSIM 6.0, was applied to simulate ac dipolar excitation of ion axial motion in the Orbitrap. The Orbitrap inner and outer electrodes were generated in AutoCAD, a 3D drawing program. The electrode geometry was imported into the 3D field solver COMSOL; the field array was then imported into ITSIM 6.0. Ion trajectories were calculated by solving Newton's equations using Runge-Kutta integration methods. Compared to the analytical solution, calculated radial components of the field at the device's "equator" (z = 0) were within 0.5% and calculated axial components midway between the inner and outer electrodes were within 0.2%. The experiments simulated here involved the control of axial motion of ions in the Orbitrap by the application of dipolar ac signals to the split outer electrodes, as described in a recently published paper from this laboratory [Hu et al., J. Phys. Chem. A 110 (2006) 2682]. In these experiments, ac signal was applied at the axial resonant frequency of a selected ion. Axial excitation and eventual ion ejection resulted when the ac was in phase with, i.e., had 0° phase relative to ion axial motion. De-excitation of ion axial motion until the ions were at z = 0 and at rest with respect to the z-axis resulted if the applied ac was out of phase with ion motion, with re-excitation of ion axial motion occurring if the dipolar ac was continued beyond this point. Both de-excitation and re-excitation could be achieved mass-selectively and depended on the amplitude and duration (number of cycles) of the applied ac. The effects of ac amplitude, frequency, phase relative to ion motion, and bandwidth of applied waveform were simulated. All simulation results were compared directly with the experimental data and good agreement was observed. Such ion motion control experiments and their simulation provide the possibility to improve Orbitrap performance and to develop tandem mass

  4. AC susceptibility study at the inter- and intragranular properties in (Bi,Pb):2223 superconductor

    SciTech Connect

    Pop, A.V.; Ciurchea, D.; Ilonca, G.; Deltour, R.; Harabor, A.

    1997-11-20

    The temperature and amplitude of AC field dependencies of both inter- and intragranular T{sub p} and T{sub g} temperatures of the imaginary peaks of {chi}{double_prime} has been studied for a sintered single phase (Bi,Pb):2223 superconductor. The AC field dependencies for T{sub p} and T{sub g} and the relation between inter- and intragrain force densities were discussed by using Mueller critical-state model. From the {chi}{double_prime} curve, the values of intergrain magnetic critical current density J{sub cJ} was obtained via the application of Beans` critical state model. J{sub cJ}(T) dependence near {Tc} agree with the assumption of SNS intergrain junctions.

  5. Calibration of low-temperature ac susceptometers with a copper cylinder standard

    SciTech Connect

    Chen, D.-X.; Skumryev, V.

    2010-02-15

    A high-quality low-temperature ac susceptometer is calibrated by comparing the measured ac susceptibility of a copper cylinder with its eddy-current ac susceptibility accurately calculated. Different from conventional calibration techniques that compare the measured results with the known property of a standard sample at certain fixed temperature T, field amplitude H{sub m}, and frequency f, to get a magnitude correction factor, here, the electromagnetic properties of the copper cylinder are unknown and are determined during the calibration of the ac susceptometer in the entire T, H{sub m}, and f range. It is shown that the maximum magnitude error and the maximum phase error of the susceptometer are less than 0.7% and 0.3 deg., respectively, in the region T=5-300 K and f=111-1111 Hz at H{sub m}=800 A/m, after a magnitude correction by a constant factor as done in a conventional calibration. However, the magnitude and phase errors can reach 2% and 4.3 deg. at 10 000 and 11 Hz, respectively. Since the errors are reproducible, a large portion of them may be further corrected after a calibration, the procedure for which is given. Conceptual discussions concerning the error sources, comparison with other calibration methods, and applications of ac susceptibility techniques are presented.

  6. Efficacy of Soybean's Event DAS-81419-2 Expressing Cry1F and Cry1Ac to Manage Key Tropical Lepidopteran Pests Under Field Conditions in Brazil.

    PubMed

    Marques, L H; Castro, B A; Rossetto, J; Silva, O A B N; Moscardini, V F; Zobiole, L H S; Santos, A C; Valverde-Garcia, P; Babcock, J M; Rule, D M; Fernandes, O A

    2016-08-01

    Bacillus thuringiensis (Bt) event DAS-81419-2 (Conkesta technology) in soybean, Glycine max (L.) Merrill, expresses Cry1F and Cry1Ac proteins to provide protection from feeding by several lepidopteran pests. A total of 27 field experiments across nine locations were conducted from 2011 to 2015 in southern and central Brazil to characterize the efficacy of DAS-81419-2 soybean infested with Anticarsia gemmatalis Hübner (Lepidoptera: Erebidae), Chrysodeixis includens (Walker) (Lepidoptera: Noctuidae), Heliothis virescens (F.) (Lepidoptera: Noctuidae), and Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) during vegetative (V4) and reproductive (R2 and R4) crop developmental stages. The efficacy of DAS-81419-2 was compared to that of a non-Bt isogenic variety managed with or without applications of commercial foliar insecticides for lepidopteran control. DAS-81419-2 soybean consistently experienced defoliation levels of 0.5% or less (compared with 20.05-56.74% in the non-Bt, nonsprayed treatment) and larval survival of < 0.1% in all four species across the vegetative and reproductive plant stages evaluated. The efficacy of DAS-81419-2 was significantly higher than commercial foliar insecticides applied to the non-Bt variety. DAS-81419-2 soybeans containing two highly effective Bt proteins are expected to be a more robust IRM tool compared to single-trait Bt technologies. The consistent efficacy of DAS-81419-2 soybeans across years, locations, and crop stages suggests that it will be a valuable product for management of hard-to-control key lepidopteran pests in South American soybean production. PMID:27401112

  7. Experimental investigation of the critical magnetic fields of transition metal superconductors

    NASA Technical Reports Server (NTRS)

    Mcevoy, J. P.

    1973-01-01

    The isothermal magnetic transitions of a type 2 superconductor have been studied by AC susceptibility techniques as a function of the amplitude and frequency of the exciting field. The field variation of the complex susceptibility was used to determine the critical fields. The research was planned to clarify the determination (both experimentally and theoretically) of the maximum field at which the superconductive phase spontaneously nucleates in the bulk and on the surface of the metal.

  8. PULSE AMPLITUDE DISTRIBUTION RECORDER

    DOEpatents

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  9. ACS Quicklook PDF products

    NASA Astrophysics Data System (ADS)

    Suchkov, Anatoly

    1999-12-01

    This report details the features of the ACS quicklook PDF products produced by the HST data pipeline. The requirements closely follow the design of paper products recommended by the Data Quality Committee, with appropriate changes required to fully support ACS.

  10. Superconductor coil geometry and ac losses

    NASA Technical Reports Server (NTRS)

    Pierce, T. V., Jr.; Zapata, R. N.

    1976-01-01

    An empirical relation is presented which allows simple computation of volume-averaged winding fields from central fields for coils of small rectangular cross sections. This relation suggests that, in certain applications, ac-loss minimization can be accomplished by use of low winding densities, provided that hysteresis losses are independent of winding density. The ac-loss measurements on coils wound of twisted multifilamentary composite superconductors show no significant dependence on ac losses on winding density, thus permitting the use of winding density as an independent design parameter in loss minimization.

  11. Ac-loss measurement of a DyBCO-Roebel assembled coated conductor cable (RACC)

    NASA Astrophysics Data System (ADS)

    Schuller, S.; Goldacker, W.; Kling, A.; Krempasky, L.; Schmidt, C.

    2007-10-01

    Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature around 50-77 K, which is a crucial precondition for economical cooling costs. We prepared a short length of a Roebel bar cable made of industrial DyBCO coated conductor (Theva Company, Germany). Meander shaped tapes of 4 mm width with a twist pitch of 122 mm were cut from 10 mm wide CC tapes using a specially designed tool. Eleven of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac field were measured as a function of frequency and field amplitude in transverse and parallel field orientations. In addition, the coupling current time constant of the sample was directly measured.

  12. On the Period-Amplitude and Amplitude-Period Relationships

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    Examined are Period-Amplitude and Amplitude-Period relationships based on the cyclic behavior of the 12-month moving averages of monthly mean sunspot numbers for cycles 0.23, both in terms of Fisher's exact tests for 2x2 contingency tables and linear regression analyses. Concerning the Period-Amplitude relationship (same cycle), because cycle 23's maximum amplitude is known to be 120.8, the inferred regressions (90-percent prediction intervals) suggest that its period will be 131 +/- 24 months (using all cycles) or 131 +/- 18 months (ignoring cycles 2 and 4, which have the extremes of period, 108 and 164 months, respectively). Because cycle 23 has already persisted for 142 months (May 1996 through February 2008), based on the latter prediction, it should end before September 2008. Concerning the Amplitude-Period relationship (following cycle maximum amplitude versus preceding cycle period), because cycle 23's period is known to be at least 142 months, the inferred regressions (90-percent prediction intervals) suggest that cycle 24's maximum amplitude will be about less than or equal to 96.1 +/- 55.0 (using all cycle pairs) or less than or equal to 91.0 +/- 36.7 (ignoring statistical outlier cycle pairs). Hence, cycle 24's maximum amplitude is expected to be less than 151, perhaps even less than 128, unless cycle pair 23/24 proves to be a statistical outlier.

  13. Field evaluation of soybean engineered with a synthetic cry1Ac transgene for resistance to corn earworm, soybean looper, velvetbean caterpillar (Lepidoptera: Noctuidae), and lesser cornstalk borer (Lepidoptera: Pyralidae).

    PubMed

    Walker, D R; All, J N; McPherson, R M; Boerma, H R; Parrott, W A

    2000-06-01

    A transgenic line of the soybean 'Jack', Glycine max (L.) Merrill, expressing a synthetic cry1Ac gene from Bacillus thuringiensis variety kurstaki (Jack-Bt), was evaluated for resistance to four lepidopteran pests in the field. Jack-Bt and genotypes serving as susceptible and resistant controls were planted in field cages and artificially infested with larvae of corn earworm, Helicoverpa zea (Boddie), and velvetbean caterpillar, Anticarsia gemmatalis (Hübner), in 1996, 1997, and 1998, and also with soybean looper, Pseudoplusia includens (Walker), in 1996. Susceptible controls included Jack (1996-1998), 'Cobb' (1996), and Jack-HPH (1996). GatIR 81-296 was used as the resistant control in all 3 yr. Compared with untransformed Jack, Jack-Bt showed three to five times less defoliation from corn earworm and eight to nine times less damage from velvetbean caterpillar. Defoliation of GatIR 81-296 was intermediate between that of Jack and Jack-Bt for corn earworm, and similar to that of Jack for velveltbean caterpillar. Jack-Bt exhibited significant, but lower resistance to soybean looper. Jack-Bt also showed four times greater resistance than Jack to natural infestations of lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), in conventional field plots at two locations in 1998. Data from these experiments suggest that expression of this cry1Ac construct in soybean should provide adequate levels of resistance to several lepidopteran pests under field conditions. PMID:10902306

  14. Cooling Floor AC Systems

    NASA Astrophysics Data System (ADS)

    Jun, Lu; Hao, Ding; Hong, Zhang; Ce, Gao Dian

    The present HVAC equipments for the residential buildings in the Hot-summer-and-Cold-winter climate region are still at a high energy consuming level. So that the high efficiency HVAC system is an urgently need for achieving the preset government energy saving goal. With its advantage of highly sanitary, highly comfortable and uniform of temperature field, the hot-water resource floor radiation heating system has been widely accepted. This paper has put forward a new way in air-conditioning, which combines the fresh-air supply unit and such floor radiation system for the dehumidification and cooling in summer or heating in winter. By analyze its advantages and limitations, we found that this so called Cooling/ Heating Floor AC System can improve the IAQ of residential building while keep high efficiency quality. We also recommend a methodology for the HVAC system designing, which will ensure the reduction of energy cost of users.

  15. dc and ac magnetic properties of thin-walled Nb cylinders with and without a row of antidots

    NASA Astrophysics Data System (ADS)

    Tsindlekht, M. I.; Genkin, V. M.; Felner, I.; Zeides, F.; Katz, N.; Gazi, Š.; Chromik, Š.; Dobrovolskiy, O. V.; Sachser, R.; Huth, M.

    2016-06-01

    dc and ac magnetic properties of two thin-walled superconducting Nb cylinders with a rectangular cross-section are reported. Magnetization curves and the ac response were studied on as-prepared and patterned samples in magnetic fields parallel to the cylinder axis. A row of micron-sized antidots (holes) was made in the film along the cylinder axis. Avalanche-like jumps of the magnetization are observed for both samples at low temperatures for magnetic fields not only above H c1, but in fields lower than H c1 in the vortex-free region. The positions of the jumps are not reproducible and they change from one experiment to another, resembling vortex lattice instabilities usually observed for magnetic fields larger than H c1. At temperatures above 0.66{{T}\\text{c}} and 0.78{{T}\\text{c}} the magnetization curves become smooth for the patterned and the as-prepared samples, respectively. The magnetization curve of a reference planar Nb film in the parallel field geometry does not exhibit jumps in the entire range of accessible temperatures. The ac response was measured in constant and swept dc magnetic field modes. Experiment shows that ac losses at low magnetic fields in a swept field mode are smaller for the patterned sample. For both samples the shapes of the field dependences of losses and the amplitude of the third harmonic are the same in constant and swept field near H c3. This similarity does not exist at low fields in a swept mode.

  16. Initial tests of an AC dipole for the Tevatron

    SciTech Connect

    Miyamoto, R.; Jansson, A.; Kopp, S.; Syphers, M.; /Fermilab

    2006-06-01

    The AC dipole is a device to diagnose transverse motions of a beam. It can achieve large-amplitude oscillations without two inevitable problems of conventional kicker/pinger magnets: decoherence and emittance growth. While not the first synchrotron to operate with an AC dipole, the Tevatron can now make use of its recently upgraded BPM system, providing unprecedented resolution for use with an AC dipole, to measure both linear and nonlinear properties of the accelerator. Plans are to provide AC dipole systems for both transverse degrees of freedom. Preliminary tests have been done using an audio power amplifier with an existing vertical pinger magnet, producing oscillation amplitudes up to 2{sigma} at 150 GeV. In this paper, we will present the configuration of this system. We also show the analysis of a first few data sets, including the direct measurement of beta functions at BPM locations.

  17. Magnetization AC losses in MgB2 wires made by IMD process

    NASA Astrophysics Data System (ADS)

    Kováč, J.; Šouc, J.; Kováč, P.; Hušek, I.

    2015-01-01

    Magnetization AC losses of MgB2 superconductors with one and four filaments made by an internal magnesium diffusion (IMD) into boron process were measured and analyzed. For AC loss measurement a system based on a calibration-free method was used. Short samples of MgB2 wires were exposed to an external magnetic field with amplitudes up to 0.07 T, frequencies up to 1200 Hz, and a temperature range between 15 K and 40 K. A strong effect of eddy current losses was found in single-core wire containing pure copper sheath, which was proved by the same wire measurement after Cu etching. The impact of coupling current losses in non-twisted four-filament wire and the decoupling effect after twisting were observed. Coupling current losses in a low-frequency region were effectively reduced in agreement with theoretical assumption. The degradation of transport currents due to torsion stress by twisting was taken into account and the normalized AC losses of MgB2 wires made by IMD and powder-in-tube processes were compared. It appears that the IMD process is more perspective for AC applications due to much higher current densities and smaller degradation of current-carrying capability by twisting.

  18. Amplitudes of MHD Waves in Sunspots

    NASA Astrophysics Data System (ADS)

    Norton, Aimee Ann; Cally, Paul; Baldner, Charles; Kleint, Lucia; Tarbell, Theodore D.; De Pontieu, Bart; Scherrer, Philip H.; Rajaguru, Paul

    2016-05-01

    The conversion of p-modes into MHD waves by strong magnetic fields occurs mainly in the sub-photospheric layers. The photospheric signatures of MHD waves are weak due to low amplitudes at the beta=1 equipartion level where mode-conversion occurs. We report on small amplitude oscillations observed in the photosphere with Hinode SOT/SP in which we analyze time series for sunspots ARs 12186 (11.10.2014) and 12434 (17.10.2015). No significant magnetic field oscillations are recovered in the umbra or penumbra in the ME inversion. However, periodicities in the inclination angle are found at the umbral/penumbral boundary with 5 minute periods. Upward propagating waves are indicated in the intensity signals correlated between HMI and AIA at different heights. We compare SP results with the oscillations observed in HMI data. Simultaneous IRIS data shows transition region brightening above the umbral core.

  19. CHY formula and MHV amplitudes

    NASA Astrophysics Data System (ADS)

    Du, Yi-Jian; Teng, Fei; Wu, Yong-Shi

    2016-05-01

    In this paper, we study the relation between the Cachazo-He-Yuan (CHY) formula and the maximal-helicity-violating (MHV) amplitudes of Yang-Mills and gravity in four dimensions. We prove that only one special rational solution of the scattering equations found by Weinzierl supports the MHV amplitudes. Namely, localized at this solution, the integrated CHY formula produces the Parke-Taylor formula for MHV Yang-Mills amplitudes as well as the Hodges formula for MHV gravitational amplitudes, with an arbitrary number of external gluons/gravitons. This is achieved by developing techniques, in a manifestly Möbius covariant formalism, to explicitly compute relevant reduced Pfaffians/determinants. We observe and prove two interesting properties (or identities), which facilitate the computations. We also check that all the other ( n - 3)! - 1 solutions to the scattering equations do not support the MHV amplitudes, and prove analytically that this is indeed true for the other special rational solution proposed by Weinzierl, that actually supports the anti-MHV amplitudes. Our results reveal a mysterious feature of the CHY formalism that in Yang-Mills and gravity theory, solutions of scattering equations, involving only external momenta, somehow know about the configuration of external polarizations of the scattering amplitudes.

  20. Subleading soft factor for string disk amplitudes

    NASA Astrophysics Data System (ADS)

    Schwab, Burkhard U. W.

    2014-08-01

    We investigate the behavior of superstring disk scattering amplitudes in the presence of a soft external momentum at finite string tension. We prove that there are no α'-corrections to the field theory form of the subleading soft factor S (1). At the end of this work, we also comment on the possibility to find the corresponding subleading soft factors in closed string theory using our result and the KLT relations.

  1. Off-shell CHY amplitudes

    NASA Astrophysics Data System (ADS)

    Lam, C. S.; Yao, York-Peng

    2016-06-01

    The Cachazo-He-Yuan (CHY) formula for on-shell scattering amplitudes is extended off-shell. The off-shell amplitudes (amputated Green's functions) are Möbius invariant, and have the same momentum poles as the on-shell amplitudes. The working principles which drive the modifications to the scattering equations are mainly Möbius covariance and energy momentum conservation in off-shell kinematics. The same technique is also used to obtain off-shell massive scalars. A simple off-shell extension of the CHY gauge formula which is Möbius invariant is proposed, but its true nature awaits further study.

  2. Tree-level amplitudes in the nonlinear sigma model

    NASA Astrophysics Data System (ADS)

    Kampf, Karol; Novotný, Jirí; Trnka, Jaroslav

    2013-05-01

    We study in detail the general structure and further properties of the tree-level amplitudes in the SU( N) nonlinear sigma model. We construct the flavor-ordered Feynman rules for various parameterizations of the SU( N) fields U ( x), write down the Berends-Giele relations for the semi-on-shell currents and discuss their efficiency for the amplitude calculation in comparison with those of renormalizable theories. We also present an explicit form of the partial amplitudes up to ten external particles. It is well known that the standard BCFW recursive relations cannot be used for reconstruction of the the on-shell amplitudes of effective theories like the SU( N) nonlinear sigma model because of the inappropriate behavior of the deformed on-shell amplitudes at infinity. We discuss possible generalization of the BCFW approach introducing "BCFW formula with subtractions" and with help of Berends-Giele relations we prove particular scaling properties of the semi-on-shell amplitudes of the SU( N) nonlinear sigma model under specific shifts of the external momenta. These results allow us to define alternative deformation of the semi-on-shell amplitudes and derive BCFW-like recursion relations. These provide a systematic and effective tool for calculation of Goldstone bosons scattering amplitudes and it also shows the possible applicability of on-shell methods to effective field theories. We also use these BCFW-like relations for the investigation of the Adler zeroes and double soft limit of the semi-on-shell amplitudes.

  3. CAMORRA: A C++ library for recursive computation of particle scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Kleiss, R.; van den Oord, G.

    2011-02-01

    We present a new Monte Carlo tool that computes full tree-level matrix elements in high-energy physics. The program accepts user-defined models and has no restrictions on the process multiplicity. To achieve acceptable performance, CAMORRA evaluates the matrix elements in a recursive way by combining off-shell currents. Furthermore, CAMORRA can be used to compute amplitudes involving continuous color and helicity final states. Program summaryProgram title: CAMORRA Catalogue identifier: AEHN_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHN_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL version 2 No. of lines in distributed program, including test data, etc.: 252 572 No. of bytes in distributed program, including test data, etc.: 1 711 469 Distribution format: tar.gz Programming language: C++ Computer: All Operating system: Tested on Linux and Mac OS, but should work on any system Classification: 4.4 Nature of problem: Current recursive matrix element computation programs are confined to standard model amplitudes, whereas many new physics signatures and backgrounds at hadron colliders are associated with multi-parton final states. Solution method: The library applies the Berends-Giele/Caravaglios-Moretti recursive algorithm in a generic way applicable to a wide range of quantum field theories. It allows the user to define a new physics model and consequently compute its predicted scattering amplitudes with exponential growth of the computing time with process multiplicity rather than factorial growth. Restrictions: There are no built-in restrictions on process complexity. Unusual features: CAMORRA can cope with Majorana fermions. Running time: A ten-gluon amplitude typically takes 9 ms per event.

  4. Positive amplitudes in the amplituhedron

    NASA Astrophysics Data System (ADS)

    Arkani-Hamed, Nima; Hodges, Andrew; Trnka, Jaroslav

    2015-08-01

    The all-loop integrand for scattering amplitudes in planar SYM is determined by an "amplitude form" with logarithmic singularities on the boundary of the amplituhedron. In this note we provide strong evidence for a new striking property of the superamplitude, which we conjecture to be true to all loop orders: the amplitude form is positive when evaluated inside the amplituhedron. The statement is sensibly formulated thanks to the natural "bosonization" of the superamplitude associated with the amplituhedron geometry. However this positivity is not manifest in any of the current approaches to scattering amplitudes, and in particular not in the cellulations of the amplituhedron related to on-shell diagrams and the positive grassmannian. The surprising positivity of the form suggests the existence of a "dual amplituhedron" formulation where this feature would be made obvious. We also suggest that the positivity is associated with an extended picture of amplituhedron geometry, with the amplituhedron sitting inside a co-dimension one surface separating "legal" and "illegal" local singularities of the amplitude. We illustrate this in several simple examples, obtaining new expressions for amplitudes not associated with any triangulations, but following in a more invariant manner from a global view of the positive geometry.

  5. A self-powered AC magnetic sensor based on piezoelectric nanogenerator

    NASA Astrophysics Data System (ADS)

    Yu, Aifang; Song, Ming; Zhang, Yan; Kou, Jinzong; Zhai, Junyi; Wang, Zhong Lin

    2014-11-01

    An AC magnetic field, which is a carrier of information, is distributed everywhere and is continuous. How to use and detect this field has been an ongoing topic over the past few decades. Conventional magnetic sensors are usually based on the Hall Effect, the fluxgate, a superconductor quantum interface or magnetoelectric or magnetoresistive sensing. Here, a flexible, simple, low-cost and self-powered active piezoelectric nanogenerator (NG) is successfully demonstrated as an AC magnetic field sensor at room temperature. The amplitude and frequency of a magnetic field can both be accurately sensed by the NG. The output voltage of the NG has a good linearity with a measured magnetic field. The detected minute magnetic field is as low as 1.2 × 10-7 tesla, which is 400 times greater than a commercial magnetic sensor that uses the Hall Effect. In comparison to the existing technologies, an NG is a room-temperature self-powered active sensor that is very simple and very cheap for practical applications.

  6. A self-powered AC magnetic sensor based on piezoelectric nanogenerator.

    PubMed

    Yu, Aifang; Song, Ming; Zhang, Yan; Kou, Jinzong; Zhai, Junyi; Lin Wang, Zhong

    2014-11-14

    An AC magnetic field, which is a carrier of information, is distributed everywhere and is continuous. How to use and detect this field has been an ongoing topic over the past few decades. Conventional magnetic sensors are usually based on the Hall Effect, the fluxgate, a superconductor quantum interface or magnetoelectric or magnetoresistive sensing. Here, a flexible, simple, low-cost and self-powered active piezoelectric nanogenerator (NG) is successfully demonstrated as an AC magnetic field sensor at room temperature. The amplitude and frequency of a magnetic field can both be accurately sensed by the NG. The output voltage of the NG has a good linearity with a measured magnetic field. The detected minute magnetic field is as low as 1.2 × 10(-7) tesla, which is 400 times greater than a commercial magnetic sensor that uses the Hall Effect. In comparison to the existing technologies, an NG is a room-temperature self-powered active sensor that is very simple and very cheap for practical applications. PMID:25333328

  7. Characterization of magnetic property depth profiles of surface-modified materials using a model-assisted swept frequency modulation field technique

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.

    2009-04-01

    This paper reports on a model-assisted approach to characterizing surface-modified materials whose magnetic properties vary continuously with depth. The technique involves measuring ac permeability profiles under a quasistatic biasing field superimposed with an ac modulation field of adjustable frequency and amplitude to control field penetration depth. A frequency dependent magnetic hysteresis model was used to model ac permeability profiles at different modulation field frequencies for direct comparison with measurement results. The approach was applied to characterize a series of surface hardened Fe-C samples. The depth dependence of the magnetic properties was determined by obtaining the best fits of the modeled ac permeability profiles to experimental data at multiple modulation frequencies. The midpoints of the inverted magnetic property profiles and the measured hardness profiles were found to be in agreement.

  8. The small amplitude magnetohydrodynamic Riemann problem

    NASA Technical Reports Server (NTRS)

    Wu, C. C.; Kennel, C. F.

    1993-01-01

    The small-amplitude MHD Riemann problem is studied using the Cohen-Kulsrud-Burgers equations. Unlike the coplanar Riemann problem, the evolution of noncoplanar Riemann problems is not self-similar and its flow structures could change in time. But its large-time behavior is very simple and a time-dependent 2 - 3 intermediate shock is always involved for the noncoplanar field rotations. The time-dependent 2 - 3 intermediate shock has a well-defined structure and exists for any degree of field rotation.

  9. ACS Data Handbook v.6.0

    NASA Astrophysics Data System (ADS)

    Gonzaga, S.; et al.

    2011-03-01

    ACS was designed to provide a deep, wide-field survey capability from the visible to near-IR using the Wide Field Camera (WFC), high resolution imaging from the near-UV to near-IR with the now-defunct High Resolution Camera (HRC), and solar-blind far-UV imaging using the Solar Blind Camera (SBC). The discovery efficiency of ACS's Wide Field Channel (i.e., the product of WFC's field of view and throughput) is 10 times greater than that of WFPC2. The failure of ACS's CCD electronics in January 2007 brought a temporary halt to CCD imaging until Servicing Mission 4 in May 2009, when WFC functionality was restored. Unfortunately, the high-resolution optical imaging capability of HRC was not recovered.

  10. Characteristics of ? multifilamentary wires for a.c. use developed by the bronze process using diffusion barrier techniques

    NASA Astrophysics Data System (ADS)

    Miura, Osuke; Matsumoto, Kaname; Tanaka, Yasuzo; Uno, Naoki

    1996-03-01

    0953-2048/9/3/015/img7 multifilamentary superconducting wires for a.c. use were developed by the bronze method using Cu diffusion barrier techniques. To reduce a.c. losses, the filament diameter was designed to be less than 0953-2048/9/3/015/img8 and the final resistivity of the bronze matrix was increased using a Cu alloy diffusion barrier with the addition of Si and Mn elements around the filaments. As a result, interfilamentary proximity coupling could be prevented until a filament spacing of 0953-2048/9/3/015/img9 and hysteresis losses for the wires reached lower values, from 0953-2048/9/3/015/img10 to 0953-2048/9/3/015/img11 at a magnetic field amplitude of 0.5 T under controlled reaction heat treatment. The perpendicular resistivity of the matrix between the filaments estimated from the coupling loss was about 0953-2048/9/3/015/img12, which was considerably less than the resistivity value of the matrix estimated after the reaction. This was thought to be due to an extreme reduction in Sn concentration between the filaments. Furthermore, a small a.c. coil was fabricated by winding a stranded cable fabricated in this way. The a.c. loss of the coil at 50 Hz in a central magnetic field of 0.5 T was 0953-2048/9/3/015/img13 and the a.c. quench current at 50 Hz was 195 A, which is about 10% lower than the critical current on the load line. This degradation was due to the temperature rise in the cable caused by a.c. loss.

  11. Differential equations, associators, and recurrences for amplitudes

    NASA Astrophysics Data System (ADS)

    Puhlfürst, Georg; Stieberger, Stephan

    2016-01-01

    We provide new methods to straightforwardly obtain compact and analytic expressions for ɛ-expansions of functions appearing in both field and string theory amplitudes. An algebraic method is presented to explicitly solve for recurrence relations connecting different ɛ-orders of a power series solution in ɛ of a differential equation. This strategy generalizes the usual iteration by Picard's method. Our tools are demonstrated for generalized hypergeometric functions. Furthermore, we match the ɛ-expansion of specific generalized hypergeometric functions with the underlying Drinfeld associator with proper Lie algebra and monodromy representations. We also apply our tools for computing ɛ-expansions for solutions to generic first-order Fuchsian equations (Schlesinger system). Finally, we set up our methods to systematically get compact and explicit α‧-expansions of tree-level superstring amplitudes to any order in α‧.

  12. Dependence of the ac loss on the aspect ratio in a cable in conduit conductor

    NASA Astrophysics Data System (ADS)

    Cau, F.; Bruzzone, P.

    2010-04-01

    The coupling current loss in rectangular superconducting cables is strictly dependent on their aspect ratio, which has an impact on the area linked by the field variation and consequently on the currents induced between strands. The relation between the ac loss and aspect ratio is studied with reference to the testing of three short cable in conduit conductor (CICC) samples at the SULTAN test facility. The first conductor is a 25 kA NbTi cable for the JT60-SA tokamak; the second is a 20 kA Nb3Sn cable for the HZB hybrid magnet. The last CICC is a 68 kA Nb3Sn cable with layout similar to that of the ITER toroidal field (TF) conductor (called the 'European toroidal field (EUTF) alternate'). All the samples are assembled with two conductor sections differing only in their orientation with respect to the external variable field. In the first and third samples, the cable of one leg is rotated by 90°, while in the HZB sample it is rotated by 45° with respect to the other leg. The ac loss is measured at the SULTAN test facility using a gas flow calorimetric method. A sample length of 39 cm is exposed to a sinusoidal field with an amplitude of ± 0.3 or ± 0.2 T (depending on the superconductor) and frequency variable in the range 0.1-0.8 Hz. A background field of 2 T perpendicular both to the sinusoidal field and to the sample axis is also applied. The ac loss is assessed by measuring the variation of the He enthalpy, assuming the metal enthalpy to be negligible. The loss curve for both legs is discussed in terms of the respective aspect ratios and the results, including data from former test campaigns, are compared with the aim of finding an analytical relation between the loss and the conductor dimensions.

  13. Shape of Pion Distribution Amplitude

    SciTech Connect

    Radyushkin, Anatoly

    2009-11-01

    A scenario is investigated in which the leading-twist pion distribution amplitude $\\varphi_\\pi (x)$ is approximated by the pion decay constant $f_\\pi$ for all essential values of the light-cone fraction $x$. A model for the light-front wave function $\\Psi (x, k_\\perp)$ is proposed that produces such a distribution amplitude and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination $ k_\\perp^2/x(1-x)$. It is shown that this model easily reproduces the fit of recent large-$Q^2$ BaBar data on the photon-pion transition form factor. Some aspects of scenario with flat pion distribution amplitude are discussed.

  14. OPE for all helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Basso, Benjamin; Caetano, João; Córdova, Lucía; Sever, Amit; Vieira, Pedro

    2015-08-01

    We extend the Operator Product Expansion (OPE) for scattering amplitudes in planar SYM to account for all possible helicities of the external states. This is done by constructing a simple map between helicity configurations and so-called charged pentagon transitions. These OPE building blocks are generalizations of the bosonic pentagons entering MHV amplitudes and they can be bootstrapped at finite coupling from the integrable dynamics of the color flux tube. A byproduct of our map is a simple realization of parity in the super Wilson loop picture.

  15. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  16. Trapped Field Attenuation Characteristics of HTS Bulk Magnet Exposed to External Traveling-Wave Magnetic Field in an HTSLSM

    NASA Astrophysics Data System (ADS)

    Jin, Jianxun; Zheng, Luhai

    Traveling-wave magnetic field generated by a linear motor is a typical AC time-varying field. In order to identify the trapped magnetic flux attenuation characteristics of the high temperature superconducting (HTS) bulk magnet exposed to the external traveling-wave field generated by the primary of a developed HTS linear synchronous motor (HTSLSM), relevant experiments have been carried out through a built measurement system. As results, the relationships between the trapped magnetic flux attenuation of the HTS bulk magnet and the amplitude, frequency and direction of the external traveling-wave magnetic field are experimentally obtained to allow the HTSLSM characteristics to be practically verified.

  17. High Frequency Amplitude Detector for GMI Magnetic Sensors

    PubMed Central

    Asfour, Aktham; Zidi, Manel; Yonnet, Jean-Paul

    2014-01-01

    A new concept of a high-frequency amplitude detector and demodulator for Giant-Magneto-Impedance (GMI) sensors is presented. This concept combines a half wave rectifier, with outstanding capabilities and high speed, and a feedback approach that ensures the amplitude detection with easily adjustable gain. The developed detector is capable of measuring high-frequency and very low amplitude signals without the use of diode-based active rectifiers or analog multipliers. The performances of this detector are addressed throughout the paper. The full circuitry of the design is given, together with a comprehensive theoretical study of the concept and experimental validation. The detector has been used for the amplitude measurement of both single frequency and pulsed signals and for the demodulation of amplitude-modulated signals. It has also been successfully integrated in a GMI sensor prototype. Magnetic field and electrical current measurements in open- and closed-loop of this sensor have also been conducted. PMID:25536003

  18. Renormalization of massless Feynman amplitudes in configuration space

    NASA Astrophysics Data System (ADS)

    Nikolov, Nikolay M.; Stora, Raymond; Todorov, Ivan

    2014-05-01

    A systematic study of recursive renormalization of Feynman amplitudes is carried out both in Euclidean and in Minkowski configuration spaces. For a massless quantum field theory (QFT), we use the technique of extending associate homogeneous distributions to complete the renormalization recursion. A homogeneous (Poincaré covariant) amplitude is said to be convergent if it admits a (unique covariant) extension as a homogeneous distribution. For any amplitude without subdivergences — i.e. for a Feynman distribution that is homogeneous off the full (small) diagonal — we define a renormalization invariant residue. Its vanishing is a necessary and sufficient condition for the convergence of such an amplitude. It extends to arbitrary — not necessarily primitively divergent — Feynman amplitudes. This notion of convergence is finer than the usual power counting criterion and includes cancellation of divergences.

  19. Toward complete pion nucleon amplitudes

    NASA Astrophysics Data System (ADS)

    Mathieu, V.; Danilkin, I. V.; Fernández-Ramírez, C.; Pennington, M. R.; Schott, D.; Szczepaniak, Adam P.; Fox, G.

    2015-10-01

    We compare the low-energy partial-wave analyses of π N scattering with high-energy data via finite-energy sum rules. We construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and reconstruct the real parts using dispersion relations.

  20. Toward complete pion nucleon amplitudes

    DOE PAGESBeta

    Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; Pennington, Michael R.; Schott, Diane M.; Szczepaniak, Adam P.; Fox, G.

    2015-10-05

    We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.

  1. Employing helicity amplitudes for resummation

    NASA Astrophysics Data System (ADS)

    Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Waalewijn, Wouter J.

    2016-05-01

    Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are directly given in terms of color-ordered helicity amplitudes. Using this basis allows one to seamlessly combine fixed-order helicity amplitudes at any order they are known with a resummation of higher-order logarithmic corrections. In particular, the virtual loop amplitudes can be employed in factorization theorems to make predictions for exclusive jet cross sections without the use of numerical subtraction schemes to handle real-virtual infrared cancellations. We also discuss matching onto SCET in renormalization schemes with helicities in 4- and d -dimensions. To demonstrate that our helicity operator basis is easy to use, we provide an explicit construction of the operator basis, as well as results for the hard matching coefficients, for p p →H +0 , 1, 2 jets, p p →W /Z /γ +0 , 1, 2 jets, and p p →2 , 3 jets. These operator bases are completely crossing symmetric, so the results can easily be applied to processes with e+e- and e-p collisions.

  2. N-loop string amplitude

    SciTech Connect

    Mandelstam, S.

    1986-06-01

    Work on the derivation of an explicit perturbation series for string and superstring amplitudes is reviewed. The light-cone approach is emphasized, but some work on the Polyakov approach is also mentioned, and the two methods are compared. The calculation of the measure factor is outlined in the interacting-string picture. (LEW)

  3. Positivity of spin foam amplitudes

    NASA Astrophysics Data System (ADS)

    Baez, John C.; Christensen, J. Daniel

    2002-04-01

    The amplitude for a spin foam in the Barrett-Crane model of Riemannian quantum gravity is given as a product over its vertices, edges and faces, with one factor of the Riemannian 10j symbols appearing for each vertex, and simpler factors for the edges and faces. We prove that these amplitudes are always nonnegative for closed spin foams. As a corollary, all open spin foams going between a fixed pair of spin networks have real amplitudes of the same sign. This means one can use the Metropolis algorithm to compute expectation values of observables in the Riemannian Barrett-Crane model, as in statistical mechanics, even though this theory is based on a real-time (eiS) rather than imaginary-time e-S path integral. Our proof uses the fact that when the Riemannian 10j symbols are nonzero, their sign is positive or negative depending on whether the sum of the ten spins is an integer or half-integer. For the product of 10j symbols appearing in the amplitude for a closed spin foam, these signs cancel. We conclude with some numerical evidence suggesting that the Lorentzian 10j symbols are always nonnegative, which would imply similar results for the Lorentzian Barrett-Crane model.

  4. Constant-amplitude RC oscillator

    NASA Technical Reports Server (NTRS)

    Kerwin, W. J.; Westbrook, R. M.

    1970-01-01

    Sinusoidal oscillator has a frequency determined by resistance-capacitance /RC/ values of two charge control devices and a constant-amplitude voltage independent of frequency and RC values. RC elements provide either voltage-control, resistance-control, or capacitance-control of the frequency.

  5. ALOHA: Automatic libraries of helicity amplitudes for Feynman diagram computations

    NASA Astrophysics Data System (ADS)

    de Aquino, Priscila; Link, William; Maltoni, Fabio; Mattelaer, Olivier; Stelzer, Tim

    2012-10-01

    We present an application that automatically writes the HELAS (HELicity Amplitude Subroutines) library corresponding to the Feynman rules of any quantum field theory Lagrangian. The code is written in Python and takes the Universal FeynRules Output (UFO) as an input. From this input it produces the complete set of routines, wave-functions and amplitudes, that are needed for the computation of Feynman diagrams at leading as well as at higher orders. The representation is language independent and currently it can output routines in Fortran, C++, and Python. A few sample applications implemented in the MADGRAPH 5 framework are presented. Program summary Program title: ALOHA Catalogue identifier: AEMS_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: http://www.opensource.org/licenses/UoI-NCSA.php No. of lines in distributed program, including test data, etc.: 6094320 No. of bytes in distributed program, including test data, etc.: 7479819 Distribution format: tar.gz Programming language: Python2.6 Computer: 32/64 bit Operating system: Linux/Mac/Windows RAM: 512 Mbytes Classification: 4.4, 11.6 Nature of problem: An effcient numerical evaluation of a squared matrix element can be done with the help of the helicity routines implemented in the HELAS library [1]. This static library contains a limited number of helicity functions and is therefore not always able to provide the needed routine in the presence of an arbitrary interaction. This program provides a way to automatically create the corresponding routines for any given model. Solution method: ALOHA takes the Feynman rules associated to the vertex obtained from the model information (in the UFO format [2]), and multiplies it by the different wavefunctions or propagators. As a result the analytical expression of the helicity routines is obtained. Subsequently, this expression is

  6. NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE--FIELD STAFF TRAINING (RTI/ACS-AP-209-095)

    EPA Science Inventory

    This protocol covers training for NHEXAS project activities. All NHEXAS field technicians underwent training in order that they might carry out all of the field study duties they might be assigned. This training encompassed several subject areas including sample collection, data ...

  7. NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE--HANDLING QUALITY CONTROL SAMPLES IN THE FIELD (RTI/ACS-AP-209-090)

    EPA Science Inventory

    This protocol describes how quality control samples should be handled in the field, and was designed as a quick reference source for the field staff. The protocol describes quality control samples for air-VOCs, air-particles, water samples, house dust, soil, urine, blood, hair, a...

  8. AC loss in superconducting tapes and cables

    NASA Astrophysics Data System (ADS)

    Oomen, Marijn Pieter

    High-temperature superconductors are developed for use in power-transmission cables, transformers and motors. The alternating magnetic field in these devices causes AC loss, which is a critical factor in the design. The study focuses on multi-filament Bi-2223/Ag tapes exposed to a 50-Hz magnetic field at 77 K. The AC loss is measured with magnetic, electric and calorimetric methods. The results are compared to theoretical predictions based mainly on the Critical-State Model. The loss in high- temperature superconductors is affected by their characteristic properties: increased flux creep, high aspect ratio and inhomogeneties. Filament intergrowths and a low matrix resistivity cause a high coupling-current loss especially when the filaments are fully coupled. When the wide side of the tape is parallel to the external magnetic field, the filaments are decoupled by twisting. In a perpendicular field the filaments can be decoupled only by combining a short twist pitch with a transverse resistivity much higher than that of silver. The arrangement of the inner filaments determines the transverse resistivity. Ceramic barriers around the filaments cause partial decoupling in perpendicular magnetic fields at power frequencies. The resultant decrease in AC loss is greater than the accompanying decrease in critical current. With direct transport current in alternating magnetic field, the transport-current loss is well described with a new model for the dynamic resistance. The Critical- State Model describes well the magnetisation and total AC loss in parallel magnetic fields, at transport currents up to 0.7 times the critical current. When tapes are stacked face-to-face in a winding, the AC-loss density in perpendicular fields is greatly decreased due to the mutual shielding of the tapes. Coupling currents between the tapes in a cable cause an extra AC loss, which is reduced by a careful cable design. The total AC loss in complex devices with many tapes is generally well

  9. AC magnetohydrodynamic microfluidic switch

    SciTech Connect

    Lemoff, A V; Lee, A P

    2000-03-02

    A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.

  10. ACS Symposium Support

    SciTech Connect

    Kenneth D. Jordan

    2010-02-20

    The funds from this DOE grant were used to help cover the travel costs of five students and postdoctoral fellows who attended a symposium on 'Hydration: From Clusters to Aqueous Solutions' held at the Fall 2007 American Chemical Society Meeting in Boston, MA, August 19-23. The Symposium was sponsored by the Physical Chemistry Division, ACS. The technical program for the meeting is available at http://phys-acs.org/fall2007.html.

  11. Development of a hardware-based AC microgrid for AC stability assessment

    NASA Astrophysics Data System (ADS)

    Swanson, Robert R.

    As more power electronic-based devices enable the development of high-bandwidth AC microgrids, the topic of microgrid power distribution stability has become of increased interest. Recently, researchers have proposed a relatively straightforward method to assess the stability of AC systems based upon the time-constants of sources, the net bus capacitance, and the rate limits of sources. In this research, a focus has been to develop a hardware test system to evaluate AC system stability. As a first step, a time domain model of a two converter microgrid was established in which a three phase inverter acts as a power source and an active rectifier serves as an adjustable constant power AC load. The constant power load can be utilized to create rapid power flow transients to the generating system. As a second step, the inverter and active rectifier were designed using a Smart Power Module IGBT for switching and an embedded microcontroller as a processor for algorithm implementation. The inverter and active rectifier were designed to operate simultaneously using a synchronization signal to ensure each respective local controller operates in a common reference frame. Finally, the physical system was created and initial testing performed to validate the hardware functionality as a variable amplitude and variable frequency AC system.

  12. True amplitude prestack depth migration

    NASA Astrophysics Data System (ADS)

    Deng, Feng

    Reliable analysis of amplitude variation with offset (or with angle) requires accurate amplitudes from prestack migration. In routine seismic data processing, amplitude balancing and automatic gain control are often used to reduce amplitude lateral variations. However, these methods are empirical and lack a solid physical basis; thus, there are uncertainties that might produce erroneous conclusions, and hence cause economic loss. During wavefield propagation, geometrical spreading, intrinsic attenuation, transmission losses and the energy conversion significantly distort the wavefield amplitude. Most current true-amplitude migrations usually compensate only for geometrical spreading. A new prestack depth migration based on the framework of reverse-time migration in the time-space domain was developed in this dissertation with the aim of compensating all of the propagation effects in one integrated algorithm. Geometrical spreading is automatically included because of the use of full two-way wave extrapolation. Viscoelastic wave equations are solved to handle the intrinsic attenuation with a priori quality factor. Transmission losses for both up- and down-going waves are compensated using a two-pass, recursive procedure based on extracting the angle-dependent reflection/transmission coefficients from prestack migration. The losses caused by the conversion of energy from one elastic model to another are accounted for through elastic wave extrapolation; the influence of the S wave velocity contrast on the P wave reflection coefficient is implicitly included by using the Zoeppritz equations to describe the reflection and transmission at an elastic interface. Only smooth background models are assumed to be known. The contrasts/ratios of the model parameters can be estimated by fitting the compensated angle-dependent reflection coefficients obtained from data for multiple sources. This is one useful by-product of the algorithm. Numerical tests on both 2D and 3D scalar

  13. Single event AC - DC electrospraying

    NASA Astrophysics Data System (ADS)

    Stachewicz, U.; Dijksman, J. F.; Marijnissen, J. C. M.

    2008-12-01

    Electrospraying is an innovative method to deposit very small amounts of, for example, biofluids (far less than 1 p1) that include DNA or protein molecules. An electric potential is applied between a nozzle filled with liquid and a counter electrode placed at 1-2 millimeter distance from the nozzle. In our set-up we use an AC field superposed on a DC field to control the droplet generation process. Our approach is to create single events of electrospraying triggered by one single AC pulse. During this pulse, the equilibrium meniscus (determined by surface tension, static pressure and the DC field) of the liquid changes rapidly into a cone and subsequently into a jet formed at the cone apex. Next, the jet breaks-up into fine droplets and the spraying stops. The meniscus returns to its equilibrium shape again. So far we obtained a stable and reproducible single event process for ethanol and ethylene glycol with water using glass pipettes. The results will be used to generate droplets on demand in a controlled way and deposit them on a pre-defined place on the substrate.

  14. Randomized gap and amplitude estimation

    NASA Astrophysics Data System (ADS)

    Zintchenko, Ilia; Wiebe, Nathan

    2016-06-01

    We provide a method for estimating spectral gaps in low-dimensional systems. Unlike traditional phase estimation, our approach does not require ancillary qubits nor does it require well-characterized gates. Instead, it only requires the ability to perform approximate Haar random unitary operations, applying the unitary whose eigenspectrum is sought and performing measurements in the computational basis. We discuss application of these ideas to in-place amplitude estimation and quantum device calibration.

  15. Genus dependence of superstring amplitudes

    SciTech Connect

    Davis, Simon

    2006-11-15

    The problem of the consistency of the finiteness of the supermoduli space integral in the limit of vanishing super-fixed point distance and the genus-dependence of the integral over the super-Schottky coordinates in the fundamental region containing a neighborhood of |K{sub n}|=0 is resolved. Given a choice of the categories of isometric circles representing the integration region, the exponential form of bounds for superstring amplitudes is derived.

  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. Phase variation of hadronic amplitudes

    SciTech Connect

    Dedonder, J.-P.; Gibbs, W. R.; Nuseirat, Mutazz

    2008-04-15

    The phase variation with angle of hadronic amplitudes is studied with a view to understanding the underlying physical quantities that control it and how well it can be determined in free space. We find that unitarity forces a moderately accurate determination of the phase in standard amplitude analyses but that the nucleon-nucleon analyses done to date do not give the phase variation needed to achieve a good representation of the data in multiple scattering calculations. Models are examined that suggest its behavior near forward angles is related to the radii of the real and absorptive parts of the interaction. The dependence of this phase on model parameters is such that if these radii are modified in the nuclear medium (in combination with the change due to the shift in energy of the effective amplitude in the medium) then the larger magnitudes of the phase needed to fit the data might be attainable but only for negative values of the phase variation parameter.

  18. Lipid nanotube formation using space-regulated electric field above interdigitated electrodes.

    PubMed

    Bi, Hongmei; Fu, Dingguo; Wang, Lei; Han, Xiaojun

    2014-04-22

    Lipid nanotubes have great potential in biology and nanotechnology. Here we demonstrate a method to form lipid nanotubes using space-regulated AC electric fields above coplanar interdigitated electrodes. The AC electric field distribution can be regulated by solution height above the electrodes. The ratio of field component in x axis (Ex) to field component in z axis (Ez) increases dramatically at solution height below 50 μm; therefore, at lower solution height, the force from Ex predominantly drives lipids to form lipid nanotubes along with the electric field direction. The forces exerted on the lipid nanotube during its formation were analyzed in detail, and an equation was obtained to describe the relationship among nanotube length and field frequency, amplitude, and time. We believe that the presented approach opens a way to design and prepare nanoscale materials with unique structural and functional properties using space-regulated electric fields. PMID:24669822

  19. Electrostatic coalescence system with independent AC and DC hydrophilic electrodes

    DOEpatents

    Hovarongkura, A. David; Henry, Jr., Joseph D.

    1981-01-01

    An improved electrostatic coalescence system is provided in which independent AC and DC hydrophilic electrodes are employed to provide more complete dehydration of an oil emulsion. The AC field is produced between an AC electrode array and the water-oil interface wherein the AC electrode array is positioned parallel to the interface which acts as a grounded electrode. The emulsion is introduced into the AC field in an evenly distributed manner at the interface. The AC field promotes drop-drop and drop-interface coalescence of the water phase in the entering emulsion. The continuous oil phase passes upward through the perforated AC electrode array and enters a strong DC field produced between closely spaced DC electrodes in which small dispersed droplets of water entrained in the continuous phase are removed primarily by collection at hydrophilic DC electrodes. Large droplets of water collected by the electrodes migrate downward through the AC electrode array to the interface. All phase separation mechanisms are utilized to accomplish more complete phase separation.

  20. NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE--FIELD USE OF THE SAMPLE COLLECTION AND CUSTODY SOFTWARE (RTI/ACS-AP-209-086)

    EPA Science Inventory

    This procedure describes field use of the sample collection and custody software developed for this pilot study. This is an easy-to-use, spreadsheet-based, two-part sample collection and custody software package. The software is for use on laptop computers and defines the kinds a...

  1. NHEXAS PHASE I REGION 5 STUDY--STANDARD OPERATING PROCEDURE--SAMPLE CODING, LABELING, AND FIELD TRACKING PROCEDURES (RTI/ACS-AP-209-070)

    EPA Science Inventory

    This protocol defines the coding scheme, labeling procedures, and field tracking for samples collected in the NHEXAS Region 5 study. Unique sample codes were assigned to all personal, environmental, biological, and quality control samples. A label bearing the code in both bar cod...

  2. Development of a nano-tesla magnetic field shielded chamber and highly precise AC-susceptibility measurement coil at μK temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, Anil; Prakash, Om; Ramakrishanan, S.

    2014-04-01

    A special sample measurement chamber has been developed to perform experiments at ultralow temperatures and ultralow magnetic field. A high permeability material known as cryoperm 10 and Pb is used to shield the measurement space consisting of the signal detecting set-up and the sample. The detecting setup consists of a very sensitive susceptibility coil wound on OFHC Cu bobbin.

  3. A new AC susceptibility instrument for detecting frequency dependence over a wide range of frequencies

    NASA Astrophysics Data System (ADS)

    Kodama, K.

    2008-12-01

    A unique equipment was developed for measuring low-field AC susceptibility over a frequency spectrum ranging from 10 Hz to 4 kHz. The coil system consists of a primary coil for applying an excitation field, and a set of pickup coils linked in series and wound oppositely for compensation. The number of turns for the primary coil is 6,000 and that for the pickup coils is 4,400, using 0.1 mm thick copper wire, wound around a quartz-glass tube of 36 mm in diameter, allowing to measure conventional 10cc samples. The excitation field is produced by a commercial function generator with two independent outputs, capable of generating sinusoidal current with frequencies of 0 to 10 MHz. A mutual inductor coil is connected in series, to which the wave generator supplies, through the second output, a small current that can be adjusted in phase and magnitude to compensate the out-of-balance of the pickup coils. The resulting signal output voltage is fed to a digital rock-in amplifier. The AC frequency spans practically from 10 Hz to 4 kHz due to the limitation of the lock-in amplifier, but can be swept over the entire range with a constant amplitude of the applied field, which is changeable from 0.4 to 1.0 Oe. The outputs from the lock-in amplifier, in both magnitude and phase, are transferred to a PC to obtain the frequency dependence spectrum of both real and imaginary parts of AC susceptibility. The system calibration was made using a paramagnetic Gd2O3 powder as well as several natural samples that have ever been used for inter-laboratory calibrations.

  4. AC electric trapping of neutral atoms

    NASA Astrophysics Data System (ADS)

    Marian, Adela; Schlunk, Sophie; Schoellkopf, Wieland; Meijer, Gerard

    2008-05-01

    We have demonstrated trapping of ultracold ground-state ^87Rb atoms in a macroscopic ac electric trap [1]. Trapping by ac electric fields has been previously achieved for polar molecules [2], as well as Sr atoms on a chip [3], and recently for Rb atoms in a three-phase electric trap [4]. Similar to trapping of ions in a Paul trap, three-dimensional confinement in an ac electric trap is obtained by switching between two saddle-point configurations of the electric field. For the first time, this dynamic confinement is directly visualized with absorption images taken at different phases of the ac switching cycle. Stable electric trapping is observed in a narrow range of switching frequencies around 60 Hz, in agreement with trajectory calculations. In a typical experiment, about 3 x 10^5 Rb atoms are trapped with lifetimes on the order of 9 s and trap depths of about 10 μK. Additionally, we show that the atoms can be used to sensitively probe the electric fields in the trap by imaging the cloud while the fields are still on. References: 1. S. Schlunk et al., PRL 98, 223002 (2007) 2. H. L. Bethlem et al., PRA 74, 063403 (2006) 3. T. Kishimoto et al., PRL 96, 123001 (2006) 4. T. Rieger et al., PRL 99, 063001 (2007)

  5. Broadband metasurface holograms: toward complete phase and amplitude engineering.

    PubMed

    Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

    2016-01-01

    As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography. PMID:27615519

  6. Constraints on string resonance amplitudes

    NASA Astrophysics Data System (ADS)

    Cheung, Kingman; Liu, Yueh-Feng

    2005-07-01

    We perform a global analysis of the tree-level open-string amplitudes in the limit s≪M2S. Based on the present data from the Tevatron, HERA, and LEP 2, we set a lower limit on the string scale MS≥0.69 1.96 TeV at 95% confidence level for the Chan-Paton factors |T|=0-4. We also estimate the expected sensitivities at the CERN LHC, which can be as high as 19 TeV for |T|=4.

  7. Shape of the Hanle curve in spin-transport structures in the presence of an ac drive

    NASA Astrophysics Data System (ADS)

    Roundy, R. C.; Prestgard, M. C.; Tiwari, A.; Raikh, M. E.

    2014-11-01

    Resistance between two ferromagnetic electrodes coupled to a normal channel depends on their relative magnetizations. The spin-dependent component, R , of the resistance changes with magnetic field, B , normal to the directions of magnetizations. In the field of spin transport, this change, R (B ) , originating from the Larmour spin precession, is called the Hanle curve. We demonstrate that the shape of the Hanle curve evolves upon application of an ac drive and study this evolution theoretically as a function of the amplitude, B1, and frequency, ω , of the drive. If the distance between the electrodes, L , is smaller than the spin-diffusion length, λs, the prime effect of a weak circular-polarized drive is the shift of the center of the curve to the value of B for which the Larmour frequency, ωL, is ˜B12/ω . Magnetic resonance at ωL˜ω manifests itself in the derivative, d/R d B . For large L ≫λs the ac drive affects the Hanle curve if the drive amplitude exceeds the spin-relaxation rate, τs-1, i.e., at B1τs≳1 . The prime effect of the drive is the elimination of a minimum in R (B ) . A linearly polarized drive has a fundamentally different effect on the Hanle curve, affecting not its shape but rather its width.

  8. Berends-Giele recursion for double-color-ordered amplitudes

    NASA Astrophysics Data System (ADS)

    Mafra, Carlos R.

    2016-07-01

    Tree-level double-color-ordered amplitudes are computed using Berends-Giele recursion relations applied to the bi-adjoint cubic scalar theory. The standard notion of Berends-Giele currents is generalized to double-currents and their recursions are derived from a perturbiner expansion of linearized fields that solve the non-linear field equations. Two applications are given. Firstly, we prove that the entries of the inverse KLT matrix are equal to Berends-Giele double-currents (and are therefore easy to compute). And secondly, a simple formula to generate tree-level BCJ-satisfying numerators for arbitrary multiplicity is proposed by evaluating the field-theory limit of tree-level string amplitudes for various color orderings using double-color-ordered amplitudes.

  9. ac bidirectional motor controller

    NASA Technical Reports Server (NTRS)

    Schreiner, K.

    1988-01-01

    Test data are presented and the design of a high-efficiency motor/generator controller at NASA-Lewis for use with the Space Station power system testbed is described. The bidirectional motor driver is a 20 kHz to variable frequency three-phase ac converter that operates from the high-frequency ac bus being designed for the Space Station. A zero-voltage-switching pulse-density-modulation technique is used in the converter to shape the low-frequency output waveform.

  10. Combination frequencies in high-amplitude δ Scuti stars

    NASA Astrophysics Data System (ADS)

    Balona, L. A.

    2016-06-01

    Short-cadence observations of δ Scuti stars in the Kepler field are used to investigate the physical nature of high-amplitude δ Scuti stars (HADS). Although it is often mentioned that HADS are transition objects between classical Cepheids and δ Scuti stars, neither ground-based or space-based observations support this view. It is found that HADS occur randomly within the instability strip. The possibility that HADS may be defined by the presence of combination frequencies is discussed. There is a weak tendency for the number of combination frequencies to increase with increasing amplitude of the parent frequencies. However, even stars with very low amplitudes may have detectable combination frequencies. Very few parent modes have a period ratio appropriate to first-overtone and fundamental radial modes. It appears that a high amplitude, in itself, is not useful as a distinguishing feature of δ Scuti stars.

  11. Interplay between electron overheating and ac Josephson effect

    NASA Astrophysics Data System (ADS)

    De Cecco, A.; Le Calvez, K.; Sacépé, B.; Winkelmann, C. B.; Courtois, H.

    2016-05-01

    We study the response of high-critical-current proximity Josephson junctions to a microwave excitation. Electron overheating in such devices is known to create hysteretic dc voltage-current characteristics. Here we demonstrate that it also strongly influences the ac response. The interplay of electron overheating and ac Josephson dynamics is revealed by the evolution of the Shapiro steps with the microwave drive amplitude. Extending the resistively shunted Josephson junction model by including a thermal balance for the electronic bath coupled to phonons, a strong electron overheating is obtained.

  12. The magnetostrictive laser diode magnetometer for personal magnetic field dosimetry (abstract)

    NASA Astrophysics Data System (ADS)

    Chung, R.; Weber, R.; Jiles, D. C.

    1993-05-01

    This paper reports on the completion of a new type of magnetometer for personal magnetic field dosimetry.1,2 The instrument is a small 15 cm×10 cm×2.5 cm device which can be worn by the user. It utilizes the magnetostrictive response of a Tb-Dy-Fe sensor to measure the prevailing ac magnetic field amplitude. The results are stored using an on-board microprocessor which then integrates the field values to determine the total exposure ∫ Hmax(ω) dt over a given time period. The performance of this new device is reported for a range of ac field frequencies from 10 Hz to 30 kHz. It has been found that the sensitivity of the device is greatly enhanced by using a localized 16 kA/m dc bias field to operate the sensor at the condition of highest dλ/dH. The device can detect fields down the 5 μ T range, and by suitable signal processing, has been designed to give an output signal in both field amplitude and frequency. The device contains a rugged laser diode interferometer of the type used in compact disk audio systems, an AlNiCo permanent magnet to provide the bias field and a Tb0.3Dy0.7Fe1.9 magnetostrictive alloy sensors with strain amplitudes up to 1000 ppm.

  13. Optimized anisotropic magnetoelectric response of Fe61.6Co16.4Si10.8B11.2/PVDF/Fe61.6Co16.4Si10.8B11.2 laminates for AC/DC magnetic field sensing

    NASA Astrophysics Data System (ADS)

    Reis, S.; Silva, M. P.; Castro, N.; Correia, V.; Gutierrez, J.; Lasheras, A.; Lanceros-Mendez, S.; Martins, P.

    2016-05-01

    The anisotropic magnetoelectric (ME) effect on a Fe61.6Co16.4Si10.8B11.2/PVDF Fe61.6Co16.4Si10.8B11.2 laminate composite has been used for the development of a magnetic field sensor able to detect both the magnitude and direction of AC and DC magnetic fields. The accuracy (99% for both AC and DC sensors), linearity (92% for the DC sensor and 99% for the AC sensor) and reproducibility (99% for both sensors) indicate the suitability of the sensor for applications. Furthermore, the sensitivity of the Fe61.6Co16.4Si10.8B11.2/PVDF/Fe61.6Co16.4Si10.8B11.2 anisotropic magnetic sensor—15 and 1400 mV Oe‑1 for the DC and AC fields, respectively—are the highest reported in the literature for polymer-based ME materials. Such features, combined with its flexibility, versatility, light weight, low cost and low-temperature fabrication, lead to the suitability of the developed sensor for use in magnetic sensor applications.

  14. Involvement of membrane proteins and ion channels on the self-rotation of human cells in a non-rotating AC electric field.

    PubMed

    Vaillier, Clarisse; Honegger, Thibault; Kermarrec, Frédérique; Gidrol, Xavier; Peyrade, David

    2015-05-01

    Dielectrophoresis is a force that has been exploited in microsystems for label-free characterization and separation of cells, when their electrical signature is known. However, the polarization effect of cells at the transmembrane protein level is not well established. In this work, we have use the self-rotation effect of cells in a non-rotating field, known as the "Quincke effect," in order to measure the maximum rotation frequency (frotmax ) of different cell populations when modifying the composition of their membrane. We investigated the influence of active ionic transportation of membrane protein concentration on frotmax of HEK cells. Our results show that ionic transportation is responsible for the reduction of conductivity within the cytoplasm, which results in higher frotmax . However, the influence of the concentration of proteins in the membrane, achieved by silencing gene expression in cancer cells, changes significantly frotmax , which is not explained by the changes of ionic conductivity within the cell. PMID:25808576

  15. AC solar cell

    SciTech Connect

    Schutten, H.P.; Benjamin, J.A.; Lade, R.W.

    1986-03-18

    An AC solar cell is described comprising: a pair of PN junction type solar cells connected in antiparallel between a pair of main terminals; and means for electrically directing light alternatingly without mechanical movement on the PN junctions to generate an alternating potential across the main terminals.

  16. AC 67 Launch Video

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Live footage of the Unmanned Atlas Centaur (AC) 67 launch is presented on March 26, 1987 at the WESH television station in Florida. Lightning is shown after 49 seconds into the flight. The vehicle is totally destroyed due to a cloud-to-ground lightning flash.

  17. Investigation of Spiral Bevel Gear Condition Indicator Validation via AC-29-2C Combining Test Rig Damage Progression Data with Fielded Rotorcraft Data

    NASA Technical Reports Server (NTRS)

    Dempsey, Paula J.

    2015-01-01

    This is the final of three reports published on the results of this project. In the first report, results were presented on nineteen tests performed in the NASA Glenn Spiral Bevel Gear Fatigue Test Rig on spiral bevel gear sets designed to simulate helicopter fielded failures. In the second report, fielded helicopter HUMS data from forty helicopters were processed with the same techniques that were applied to spiral bevel rig test data. Twenty of the forty helicopters experienced damage to the spiral bevel gears, while the other twenty helicopters had no known anomalies within the time frame of the datasets. In this report, results from the rig and helicopter data analysis will be compared for differences and similarities in condition indicator (CI) response. Observations and findings using sub-scale rig failure progression tests to validate helicopter gear condition indicators will be presented. In the helicopter, gear health monitoring data was measured when damage occurred and after the gear sets were replaced at two helicopter regimes. For the helicopters or tails, data was taken in the flat pitch ground 101 rotor speed (FPG101) regime. For nine tails, data was also taken at 120 knots true airspeed (120KTA) regime. In the test rig, gear sets were tested until damage initiated and progressed while gear health monitoring data and operational parameters were measured and tooth damage progression documented. For the rig tests, the gear speed was maintained at 3500RPM, a one hour run-in was performed at 4000 in-lb gear torque, than the torque was increased to 8000 in-lbs. The HUMS gear condition indicator data evaluated included Figure of Merit 4 (FM4), Root Mean Square (RMS) or Diagnostic Algorithm 1(DA1), + 3 Sideband Index (SI3) and + 1 Sideband Index (SI1). These were selected based on their sensitivity in detecting contact fatigue damage modes from analytical, experimental and historical helicopter data. For this report, the helicopter dataset was reduced to

  18. Constructing Amplitudes from Their Soft Limits

    SciTech Connect

    Boucher-Veronneau, Camille; Larkoski, Andrew J.; /SLAC

    2011-12-09

    The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.

  19. New identities among gauge theory amplitudes

    NASA Astrophysics Data System (ADS)

    Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Feng, Bo; Søndergaard, Thomas

    2010-08-01

    Color-ordered amplitudes in gauge theories satisfy non-linear identities involving amplitude products of different helicity configurations. We consider the origin of such identities and connect them to the Kawai-Lewellen-Tye (KLT) relations between gravity and gauge theory amplitudes. Extensions are made to one-loop order of the full N = 4 super Yang-Mills multiplet.

  20. Gauge dependence in QED amplitudes in expanding de Sitter space

    NASA Astrophysics Data System (ADS)

    Nicolaevici, Nistor

    2016-04-01

    We consider first-order transition amplitudes in external fields in QED in the expanding de Sitter space and point out that they are gauge dependent quantities. We examine the gauge variations of the amplitudes assuming a decoupling of the interaction at large times, which allows to conclude that the source of the problem lies in the fact that the frequencies of the modes in the infinite future become independent of the comoving momenta. We show that a possibility to assure the gauge invariance of the external field amplitudes is to restrict to potentials which vanish sufficiently fast at infinite times, and briefly discuss a number of options in the face of the possible gauge invariance violation in the full interacting theory.

  1. Diffusive suppression of AC-Stark shifts in atomic magnetometers

    PubMed Central

    Sulai, I. A.; Wyllie, R.; Kauer, M.; Smetana, G. S.; Wakai, R. T.; Walker, T. G.

    2016-01-01

    In atomic magnetometers, the vector AC-Stark shift associated with circularly polarized light generates spatially varying effective magnetic fields, which limit the magnetometer response and serve as sources of noise. We describe a scheme whereby optically pumping a small subvolume of the magnetometer cell and relying on diffusion to transport polarized atoms allows a magnetometer to be operated with minimal sensitivity to the AC-Stark field. © 2013 Optical Society of America PMID:23503278

  2. Measurement of coupling resonance driving terms with the AC dipole

    SciTech Connect

    Miyamoto, R.

    2010-10-01

    Resonance driving terms for linear coupled betatron motion in a synchrotron ring can be determined from corresponding spectral lines of an excited coherent beam motion. An AC dipole is one of instruments to excite such a motion. When a coherent motion is excited with an AC dipole, measured Courant-Snyder parameters and betatron phase advance have apparent modulations, as if there is an additional quadrupole field at the location of the AC dipole. Hence, measurements of these parameters using the AC dipole require a proper interpretation of observed quantities. The situation is similar in measurements of resonance driving terms using the AC dipole. In this note, we derive an expression of coupled betatron motion excited with two AC dipoles in presence of skew quadrupole fields, discuss an impact of this quadrupole like effect of the AC dipole on a measurement of coupling resonance driving terms, and present an analytical method to determine the coupling resonance driving terms from quantities observed using the AC dipole.

  3. An AC constant-response method for electrophysiological measurements of spectral sensitivity functions.

    PubMed

    de Souza, J M; DeVoe, R D; Schoeps, C; Ventura, D F

    1996-10-01

    A number of methods have been used in the past to measure spectral sensitivity (S(lambda)) functions of electric responses in the visual system. We present here a microcomputer based, AC, constant-response method for automatic on-line measurement of S(lambda) in cells with or without a sustained tonic response. It is based on feedback adjustment of light intensity to obtain constant peak-to-peak amplitudes of response to a flickering stimulus as the spectrum is scanned between 300 and 700 nm in 4 nm steps. It combines the advantages of: (1) on-line presentation of S(lambda) curves; (2) constant light adaptation; (3) sampling of many points; and (4) fast data collection time. The system can be applied to sensitivity or threshold (e.g., S(lambda), dark adaptation, receptive field) measurements of any electrically recorded visual response. PMID:8912193

  4. Construction of Tunnel Diode Oscillator for AC Impedance Measurement

    NASA Astrophysics Data System (ADS)

    Shin, J. H.; Kim, E.

    2014-03-01

    We construct a tunnel diode oscillator (TDO) to study electromagnetic response of a superconducting thin film. Highly sensitive tunnel diode oscillators allow us to detect extremely small changes in electromagnetic properties such as dielectric constant, ac magnetic susceptibility and magnetoresistance. A tunnel diode oscillator is a self-resonant oscillator of which resonance frequency is primarily determined by capacitance and inductance of a resonator. Amplitude of the signal depends on the quality factor of the resonator. The change in the impedance of the sample electromagnetic coupled to one of inductors in the resonator alters impedance of the inductor, and leads to the shift in the resonance frequency and the change of the amplitude.

  5. The pulsed amplitude unit for the SLC

    SciTech Connect

    Rolfe, J.; Browne, M.J.; Jobe, R.K.

    1987-02-01

    There is a recurring requirement in the SLC for the control of devices such as magnets, phase shifters, and attenuators on a beam-by-beam basis. The Pulsed Amplitude Unit (PAU) is a single width CAMAC module developed for this purpose. It provides digitally programmed analog output voltages on a beam-by-beam basis. Up to 32 preprogrammed values of output voltage are available from the single analog output of the module, and any of these values can be associated with any of the 256 possible SLC beam definitions. A 12-bit Analog-to-Digital Converter (ADC) digitizes an analog input signal at the appropriate beam time and stores it in a buffer memory. This feature is normally used to monitor the response of the device being controlled by the PAU at each beam time. Initial application of the PAU is a part of the system that controls the output of Klystrons in the SLC. The PAU combines several different functions in a single module. In order to accommodate these functions in a single width CAMAC module, field programmed logic is used extensively. Field Programmable Logic Arrays, Programmed Array Logic, and a Field Programmable Logic Sequencer are employed.

  6. Crossed-magnetic-field experiments on stacked second generation superconducting tapes: Reduction of the demagnetization effects

    NASA Astrophysics Data System (ADS)

    Baghdadi, M.; Ruiz, H. S.; Coombs, T. A.

    2014-06-01

    The crossed-magnetic-field effect on the demagnetization factor of stacked second generation (2G) high temperature superconducting tapes is presented. The superconducting sample was initially magnetized along the c-axis by the field cooling magnetization method and after achieving the magnetic relaxation of the sample, an extensive set of experimental measurements for different amplitudes of an applied ac magnetic field parallel to the ab-plane was performed. On the one hand, a striking reduction of the demagnetization factor compared with the reported values for superconducting bulks is reported. On the other hand, the demagnetization factor increases linearly with the amplitude of the ac transverse magnetic field confirming the universal linear behavior for the magnetic susceptibility predicted by Brandt [Phys. Rev. B 54, 4246 (1996)]. The study has been also pursued at different frequencies of the ac transverse magnetic field in order to determine the influence of this parameter on the demagnetization factor measurements. We report an even lower demagnetization factor as long as the frequency of the transverse magnetic field increases. Thus, the significant reduction on the demagnetization factor that we have found by using stacked 2G-superconducting tapes, with higher mechanical strength compared with the one of superconducting bulks, makes to this configuration a highly attractive candidate for the future development of more efficient high-power density rotating machines and strong magnet applications.

  7. AC power systems handbook

    SciTech Connect

    Whitaker, J.

    1991-01-01

    Transient disturbances are what headaches are made of. Whatever you call them-spikes, surges, are power bumps-they can take your equipment down and leave you with a complicated and expensive repair job. Protection against transient disturbances is a science that demands attention to detail. This book explains how the power distribution system works, what can go wrong with it, and how to protect a facility against abnormalities. system grounding and shielding are covered in detail. Each major method of transient protection is analyzed and its relative merits discussed. The book provides a complete look at the critical elements of the ac power system. Provides a complete look at the ac power system from generation to consumption. Discusses the mechanisms that produce transient disturbances and how to protect against them. Presents diagrams to facilitate system design. Covers new areas, such as the extent of the transient disturbance problem, transient protection options, and stand-by power systems.

  8. Dynamic conductivity of ac-dc-driven graphene superlattice

    NASA Astrophysics Data System (ADS)

    Kukhar', E. I.; Kryuchkov, S. V.; Ionkina, E. S.

    2016-06-01

    The dynamic conductivity of graphene superlattice in the presence of ac electric field and dc electric field with longitudinal and transversal components with respect to superlattice axis was calculated. In the case of strong transversal component of dc field conductivity of graphene superlattice was shown to be such as if the electrons had got the effective mass. In the case of weak transversal component of dc field conductivity was shown to change its sign if the frequency of ac field was an integer multiple of half of Bloch frequency.

  9. Frequency and field dependent susceptibility of magnetite at low temperature

    NASA Astrophysics Data System (ADS)

    Özdemir, Özden; Dunlop, David J.; Jackson, Michael

    2009-01-01

    We report the temperature dependence of in-phase and quadrature susceptibilities, k' and k″, between 20 K and 300 K for a stoichiometric natural single crystal of magnetite. Measurements were made for amplitudes of the AC driving field ranging from H = 30 A/m to 2 kA/m and frequencies ranging from f = 40 Hz to 4 kHz. In cubic magnetite above the Verwey transition, TV = 120 K, k' is limited by self-demagnetization and does not vary greatly with T, H or f. As the crystal cools through TV and transforms to monoclinic structure, k' decreases by about a factor 2, with a further more gradual decrease of 10-20% in cooling from 40 to 20 K. Saturation remanence also drops sharply at T V but shows no further change in cooling below 40 K. Thus it appears that domain walls remain pinned throughout the 20-40 K range but small segments undergo reversible oscillations in an AC field, the amplitude of oscillation decreasing steadily with cooling below 40 K. In this same range, k″ reaches a peak, while the temperature at which k' decreases most rapidly changes with frequency. Both observations indicate that domain wall oscillations lag appreciably behind the driving field at very low temperature. Both k' and k″ increase markedly with increasing AC field amplitude below TV. The field dependence is particularly strong below 40 K. Analysis of the k'( f) data between 20 and 40 K based on an Arrhenius thermal activation equation gives a pre-exponential frequency factor f o ≈ 2.5 × 108 s-1 and an activation energy ΔE = 0.035 eV. The ΔE is appropriate for electron hopping but f o suggests an indirect mechanism for wall mobility related to changes in electron ordering within walls.

  10. Small-amplitude oscillatory shear magnetorheology of inverse ferrofluids.

    PubMed

    Ramos, Jose; de Vicente, Juan; Hidalgo-Alvarez, Roque

    2010-06-15

    A comprehensive investigation is performed on highly monodisperse silica-based inverse ferrofluids under small-amplitude oscillatory shear in the presence of external magnetic fields up to 1 T. The effect of particle volume fraction and continuous medium Newtonian viscosity is thoroughly investigated. Experimental results for storage modulus are used to validate existing micromechanical magnetorheological models assuming different particle-level field-induced structures. PMID:20345105

  11. Picosecond pulse shaping by spectral phase and amplitude manipulation.

    PubMed

    Heritage, J P; Weiner, A M; Thurston, R N

    1985-12-01

    The temporal profile of ultrashort optical pulses may be tailored by physically manipulating the phase and the amplitude of frequency components that are spatially dispersed within a grating pulse compressor. Arbitrary pulse shapes may be synthesized subject only to the usual restrictions imposed by finite bandwidth and spatial resolution. We demonstrate this technique by generating a burst of evenly spaced picosecond pulses, a pulse doublet with odd field symmetry, and a burst of evenly spaced pulse doublets with odd field symmetry. PMID:19730501

  12. Very low luminosity stars with very large amplitude flares

    SciTech Connect

    Schaefer, B.E. )

    1990-04-01

    CCD frames of CZ Cnc, KY Cep, the gamma-ray burster optical transient, and NSV 12006 are analyzed. Also studied are 549 archival photographic plates of the CZ Cnc field. These observations are compared with the data of Lovas (1976). Flare events on CZ Cnc are examined. Based on the data it is noted that CZ Cnc is a main-sequence star, has a magnitude of 16.1, a distance of 100 pc, occasional large-amplitude flares, and frequent flares with amplitudes greater than 4 mag. 36 refs.

  13. Very low luminosity stars with very large amplitude flares

    NASA Technical Reports Server (NTRS)

    Schaefer, Bradley E.

    1990-01-01

    CCD frames of CZ Cnc, KY Cep, the gamma-ray burster optical transient, and NSV 12006 are analyzed. Also studied are 549 archival photographic plates of the CZ Cnc field. These observations are compared with the data of Lovas (1976). Flare events on CZ Cnc are examined. Based on the data it is noted that CZ Cnc is a main-sequence star, has a magnitude of 16.1, a distance of 100 pc, occasional large-amplitude flares, and frequent flares with amplitudes greater than 4 mag.

  14. Recursive Construction of Higgs-Plus-Multiparton Loop Amplitudes:The Last of the \\phi-nite Loop Amplitudes

    SciTech Connect

    Berger, Carola F.; Del Duca, Vittorio; Dixon, Lance J.

    2006-08-18

    We consider a scalar field, such as the Higgs boson H, coupled to gluons via the effective operator H tr G{sub {mu}{nu}} G{sup {mu}{nu}} induced by a heavy-quark loop. We treat H as the real part of a complex field {phi} which couples to the self-dual part of the gluon field-strength, via the operator {phi} tr G{sub SD {mu}{nu}} G{sub SD}{sup {mu}{nu}}, whereas the conjugate field {phi} couples to the anti-self-dual part. There are three infinite sequences of amplitudes coupling {phi} to quarks and gluons that vanish at tree level, and hence are finite at one loop, in the QCD coupling. Using on-shell recursion relations, we find compact expressions for these three sequences of amplitudes and discuss their analytic properties.

  15. Role of fluctuations and nonlinearities on field emission nanomechanical self-oscillators

    NASA Astrophysics Data System (ADS)

    Barois, T.; Perisanu, S.; Vincent, P.; Purcell, S. T.; Ayari, A.

    2013-11-01

    A theoretical and experimental description of the threshold, amplitude, and stability of a self-oscillating nanowire in a field emission configuration is presented. Two thresholds for the onset of self-oscillation are identified, one induced by fluctuations of the electromagnetic environment and a second revealed by these fluctuations by measuring the probability density function of the current. The ac and dc components of the current and the phase stability are quantified. An ac to dc ratio above 100% and an Allan deviation of 1.3×10-5 at room temperature can be attained. Finally, it is shown that a simple nonlinear model cannot describe the equilibrium effective potential in the self-oscillating regime due to the high amplitude of oscillations.

  16. PtCu substrates subjected to AC and DC electric fields in a solution of benzene sulfonic acid-phenol as novel batteries and their use in glucose biofuel cells

    NASA Astrophysics Data System (ADS)

    Ammam, Malika; Fransaer, Jan

    2013-11-01

    We describe how bi-metal PtCu connected wires, immersed in a solution of benzene sulfonic acid (BSA)-phenol (P) or 2,2‧-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS)-phenol (P), then subjected to simultaneous alternating current (AC) and direct current (DC) electric fields generate power. We discovered that PtCu substrate covered by the deposit containing (BSA-PP-Pt-Cu), abbreviated as PtCu(BSA-PP-Pt-Cu) electrode, plays the role of a substantial anode and cathode. The latter was related to the formation of micro-batteries in the deposited film (BSA-PP-Pt-Cu) that are able to take or deliver electrons from the deposited Pt and Cu, respectively. PP-BSA plays probably the role of bridge for proton conduction in the formed micro-batteries. The power density of the fuel cell (FC)-based PtCu(BSA-PP-Pt-Cu) anode and PtCu(BSA-PP-Pt-Cu) cathode in phosphate buffer solution pH 7.4 at room temperature reaches ˜10.8 μW mm-2. Addition of enzymes, glucose oxidase at the anode and laccase at the cathode and, replacement of BSA by ABTS at the cathode in the deposited films increases the power density to 13.3 μW mm-2. This new procedure might be of great relevance for construction of a new generation of FCs operating at mild conditions or boost the power outputs of BFCs and make them suitable for diverse applications.

  17. S-duality and helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Colwell, Kitran; Terning, John

    2016-03-01

    We examine interacting Abelian theories at low energies and show that holomorphically normalized photon helicity amplitudes transform into dual amplitudes under SL(2, {Z} ) as modular forms with weights that depend on the number of positive and negative helicity photons and on the number of internal photon lines. Moreover, canonically normalized helicity amplitudes transform by a phase, so that even though the amplitudes are not duality invariant, their squares are duality invariant. We explicitly verify the duality transformation at one loop by comparing the amplitudes in the case of an electron and the dyon that is its SL(2, {Z} ) image, and extend the invariance of squared amplitudes order by order in perturbation theory. We demonstrate that S-duality is a property of all low-energy effective Abelian theories with electric and/or magnetic charges and see how the duality generically breaks down at high energies.

  18. Mammalian cycles: internally defined periods and interaction-driven amplitudes

    PubMed Central

    Krebs, CJ

    2015-01-01

    The cause of mammalian cycles—the rise and fall of populations over a predictable period of time—has remained controversial since these patterns were first observed over a century ago. In spite of extensive work on observable mammalian cycles, the field has remained divided upon what the true cause is, with a majority of opinions attributing it to either predation or to intra-species mechanisms. Here we unite the eigenperiod hypothesis, which describes an internal, maternal effect-based mechanism to explain the cycles’ periods with a recent generalization explaining the amplitude of snowshoe hare cycles in northwestern North America based on initial predator abundance. By explaining the period and the amplitude of the cycle with separate mechanisms, a unified and consistent view of the causation of cycles is reached. Based on our suggested theory, we forecast the next snowshoe hare cycle (predicted peak in 2016) to be of extraordinarily low amplitude. PMID:26339557

  19. Collinear limit of scattering amplitudes at strong coupling.

    PubMed

    Basso, Benjamin; Sever, Amit; Vieira, Pedro

    2014-12-31

    In this Letter, we consider the collinear limit of gluon scattering amplitudes in planar N=4 super-Yang-Mills theory at strong coupling. We argue that in this limit scattering amplitudes map into correlators of twist fields in the two dimensional nonlinear O(6) sigma model, similar to those appearing in recent studies of entanglement entropy. We provide evidence for this assertion by combining the intuition springing from the string world-sheet picture and the predictions coming from the operator product expansion series. One of the main implications of these considerations is that scattering amplitudes receive equally important contributions at strong coupling from both the minimal string area and its fluctuations in the sphere. PMID:25615305

  20. Mammalian cycles: internally defined periods and interaction-driven amplitudes.

    PubMed

    Ginzburg, L R; Krebs, C J

    2015-01-01

    The cause of mammalian cycles-the rise and fall of populations over a predictable period of time-has remained controversial since these patterns were first observed over a century ago. In spite of extensive work on observable mammalian cycles, the field has remained divided upon what the true cause is, with a majority of opinions attributing it to either predation or to intra-species mechanisms. Here we unite the eigenperiod hypothesis, which describes an internal, maternal effect-based mechanism to explain the cycles' periods with a recent generalization explaining the amplitude of snowshoe hare cycles in northwestern North America based on initial predator abundance. By explaining the period and the amplitude of the cycle with separate mechanisms, a unified and consistent view of the causation of cycles is reached. Based on our suggested theory, we forecast the next snowshoe hare cycle (predicted peak in 2016) to be of extraordinarily low amplitude. PMID:26339557

  1. Amplitude and polarization asymmetries in a ring laser

    NASA Technical Reports Server (NTRS)

    Campbell, L. L.; Buholz, N. E.

    1971-01-01

    Asymmetric amplitude effects between the oppositely directed traveling waves in a He-Ne ring laser are analyzed both theoretically and experimentally. These effects make it possible to detect angular orientations of an inner-cavity bar with respect to the plane of the ring cavity. The amplitude asymmetries occur when a birefringent bar is placed in the three-mirror ring cavity, and an axial magnetic field is applied to the active medium. A simplified theoretical analysis is performed by using a first order perturbation theory to derive an expression for the polarization of the active medium, and a set of self-consistent equations are derived to predict threshold conditions. Polarization asymmetries between the oppositely directed waves are also predicted. Amplitude asymmetries similar in nature to those predicted at threshold occur when the laser is operating in 12-15 free-running modes, and polarization asymmetry occurs simultaneously.

  2. Minimal Basis for Gauge Theory Amplitudes

    SciTech Connect

    Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Vanhove, Pierre

    2009-10-16

    Identities based on monodromy for integrations in string theory are used to derive relations between different color-ordered tree-level amplitudes in both bosonic and supersymmetric string theory. These relations imply that the color-ordered tree-level n-point gauge theory amplitudes can be expanded in a minimal basis of (n-3)exclamation amplitudes. This result holds for any choice of polarizations of the external states and in any number of dimensions.

  3. Cascaded phase-preserving multilevel amplitude regeneration.

    PubMed

    Roethlingshoefer, Tobias; Onishchukov, Georgy; Schmauss, Bernhard; Leuchs, Gerd

    2014-12-29

    The performance of cascaded in-line phase-preserving amplitude regeneration using nonlinear amplifying loop mirrors has been studied in numerical simulations. As an example of a spectrally efficient modulation format with two amplitude states and multiple phase states, the regeneration performance of a star-16QAM format, basically an 8PSK format with two amplitude levels, was evaluated. An increased robustness against amplified spontaneous emission and nonlinear phase noise was observed resulting in a significantly increased transmission distance. PMID:25607142

  4. Discontinuities of multi-Regge amplitudes

    NASA Astrophysics Data System (ADS)

    Fadin, V. S.

    2015-04-01

    In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for n-gluon amplitudes in the planar N = 4 SYM at n ≥ 6. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.

  5. THE ACS NEARBY GALAXY SURVEY TREASURY

    SciTech Connect

    Dalcanton, Julianne J.; Williams, Benjamin F.; Rosema, Keith; Gogarten, Stephanie M.; Christensen, Charlotte; Gilbert, Karoline; Hodge, Paul; Seth, Anil C.; Dolphin, Andrew; Holtzman, Jon; Skillman, Evan D.; Weisz, Daniel; Cole, Andrew; Girardi, Leo; Karachentsev, Igor D.; Olsen, Knut; Freeman, Ken; Gallart, Carme; De Jong, Roelof S. E-mail: ben@astro.washington.edu E-mail: stephanie@astro.washington.edu E-mail: fabio@astro.washington.edu E-mail: aseth@cfa.harvard.edu

    2009-07-15

    The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D < 4 Mpc). The survey volume encompasses 69 galaxies in diverse environments, including close pairs, small and large groups, filaments, and truly isolated regions. The galaxies include a nearly complete range of morphological types spanning a factor of {approx}10{sup 4} in luminosity and star formation rate. The survey data consist of images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST), supplemented with archival data and new Wide Field Planetary Camera 2 (WFPC2) imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. The new wide field imaging in ANGST reaches median 50% completenesses of m {sub F475W} = 28.0 mag, m {sub F606W} = 27.3 mag, and m {sub F814W} = 27.3 mag, several magnitudes below the tip of the red giant branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the structure in the red clump. The resulting photometric catalogs are publicly accessible and contain over 34 million photometric measurements of >14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.

  6. The plasma wave and quasi-static electric field instrument /PWI/ for dynamics Explorer-A

    NASA Technical Reports Server (NTRS)

    Shawhan, S. D.; Gurnett, D. A.; Odem, D. L.; Helliwell, R. A.; Park, C. G.

    1981-01-01

    It is explained that the Plasma Wave Instrument (PWI) on Dynamics Explorer-A measures both plasma wave phenomena and quasi-static electric fields. The quasi-static electric fields are measured parallel to the spin axis of the spacecraft in a range of 2 mV/m to 2 V/m and perpendicular to the spin axis 0.5 mV/m to 2 V/m at 16 samples/s. The ac electric field sensors include a 200-m tip-to-tip long wire antenna and a 0.6-m short electric antenna, both of which are perpendicular to the spin axis, and a 9-m tip-to-tip tubular antenna parallel to the spin axis. AC electric wave fields are measured over a frequency range of 1 Hz to 2 MHz and over an amplitude range of 0.03 microvolt/m to 100 mV/m.

  7. DVCS amplitude with kinematical twist-3 terms

    SciTech Connect

    Radyushkin, A.V.; Weiss, C.

    2000-08-01

    The authors compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude they include the operators of twist-3 which appear as total derivatives of twist-2 operators. The results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. They find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.

  8. Simulation of absolute amplitudes of ultrasound signals using equivalent circuits.

    PubMed

    Johansson, Jonny; Martinsson, Pär-Erik; Delsing, Jerker

    2007-10-01

    Equivalent circuits for piezoelectric devices and ultrasonic transmission media can be used to cosimulate electronics and ultrasound parts in simulators originally intended for electronics. To achieve efficient system-level optimization, it is important to simulate correct, absolute amplitude of the ultrasound signal in the system, as this determines the requirements on the electronics regarding dynamic range, circuit noise, and power consumption. This paper presents methods to achieve correct, absolute amplitude of an ultrasound signal in a simulation of a pulse-echo system using equivalent circuits. This is achieved by taking into consideration loss due to diffraction and the effect of the cable that connects the electronics and the piezoelectric transducer. The conductive loss in the transmission line that models the propagation media of the ultrasound pulse is used to model the loss due to diffraction. Results show that the simulated amplitude of the echo follows measured values well in both near and far fields, with an offset of about 10%. The use of a coaxial cable introduces inductance and capacitance that affect the amplitude of a received echo. Amplitude variations of 60% were observed when the cable length was varied between 0.07 m and 2.3 m, with simulations predicting similar variations. The high precision in the achieved results show that electronic design and system optimization can rely on system simulations alone. This will simplify the development of integrated electronics aimed at ultrasound systems. PMID:18019234

  9. Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS)

    PubMed Central

    Fehér, Kristoffer D.; Morishima, Yosuke

    2016-01-01

    Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to integrate cognitive neural processes. Transcranial alternating current stimulation (tACS) holds the promise to elucidate the causal link between specific frequencies of oscillatory brain activity and cognitive processes. Simultaneous electroencephalography (EEG) recording during tACS would offer an opportunity to directly explore immediate neurophysiological effects of tACS. However, it is not trivial to measure EEG signals during tACS, as tACS creates a huge artifact in EEG data. Here we explain how to set up concurrent tACS-EEG experiments. Two necessary considerations for successful EEG recording while applying tACS are highlighted. First, bridging of the tACS and EEG electrodes via leaking EEG gel immediately saturates the EEG amplifier. To avoid bridging via gel, the viscosity of the EEG gel is the most important parameter. The EEG gel must be viscous to avoid bridging, but at the same time sufficiently fluid to create contact between the tACS electrode and the scalp. Second, due to the large amplitude of the tACS artifact, it is important to consider using an EEG system with a high resolution analog-to-digital (A/D) converter. In particular, the magnitude of the tACS artifact can exceed 100 mV at the vicinity of a stimulation electrode when 1 mA tACS is applied. The resolution of the A/D converter is of importance to measure good quality EEG data from the vicinity of the stimulation site. By following these guidelines for the procedures and technical considerations, successful concurrent EEG recording during tACS will be realized. PMID:26862814

  10. Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS).

    PubMed

    Fehér, Kristoffer D; Morishima, Yosuke

    2016-01-01

    Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to integrate cognitive neural processes. Transcranial alternating current stimulation (tACS) holds the promise to elucidate the causal link between specific frequencies of oscillatory brain activity and cognitive processes. Simultaneous electroencephalography (EEG) recording during tACS would offer an opportunity to directly explore immediate neurophysiological effects of tACS. However, it is not trivial to measure EEG signals during tACS, as tACS creates a huge artifact in EEG data. Here we explain how to set up concurrent tACS-EEG experiments. Two necessary considerations for successful EEG recording while applying tACS are highlighted. First, bridging of the tACS and EEG electrodes via leaking EEG gel immediately saturates the EEG amplifier. To avoid bridging via gel, the viscosity of the EEG gel is the most important parameter. The EEG gel must be viscous to avoid bridging, but at the same time sufficiently fluid to create contact between the tACS electrode and the scalp. Second, due to the large amplitude of the tACS artifact, it is important to consider using an EEG system with a high resolution analog-to-digital (A/D) converter. In particular, the magnitude of the tACS artifact can exceed 100 mV at the vicinity of a stimulation electrode when 1 mA tACS is applied. The resolution of the A/D converter is of importance to measure good quality EEG data from the vicinity of the stimulation site. By following these guidelines for the procedures and technical considerations, successful concurrent EEG recording during tACS will be realized. PMID:26862814

  11. Nonlinear oscillations of a sessile drop on a hydrophobic surface induced by ac electrowetting

    NASA Astrophysics Data System (ADS)

    Lee, Joohee; Park, Jun Kwon; Hong, Jiwoo; Lee, Sang Joon; Kang, Kwan Hyoung; Hwang, Hyung Ju

    2014-09-01

    We examine the nature of ac electrowetting (EW)-driven axisymmetric oscillations of a sessile water drop on a dielectric substrate. In ac EW, small-amplitude oscillations of a drop differ from the Rayleigh linear modes of freely oscillating drops. In this paper, we demonstrate that changes in the time-averaged contact angle of the sessile drop attributed to the presence of an electric field and a solid substrate mainly caused this discrepancy. We combine the domain perturbation method with the Lindsted-Poincaré method to derive an asymptotic formula for resonant frequency. Theoretical analysis shows that the resonant frequency is a function of the time-averaged contact angle. Each mode of the resonance frequency is a linear function of ɛ1, which is the magnitude of the cosine of the time-averaged contact angle. The most dominant mode in this study, that is, the fundamental mode n =2, decreases linearly with ɛ1. The results of the theoretical model are compared with those of both the experiments and numerical simulations. The average resonant frequency deviation between the perturbation solutions and numerical simulations is 4.3%, whereas that between the perturbation solutions and the experiments is 1.8%.

  12. Controlling migration of a pair of correlated particles by doubly modulated fields

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Yang, Shi-Jie

    2016-01-01

    The resonant tunneling of correlated bosons in optical lattices is investigated in the presence of doubly modulated AC-fields. The effective hopping coefficients are density-dependent. We can make use of this property to control the migration of a pair of strongly interacting particles in one- or two-dimensional uniform lattices via properly manipulating the phases, frequencies and amplitudes of the driven fields. We design a bifurcating quantum motion of the pair in contrast to the coherent quantum walk of the correlated pair in the absence of external fields.

  13. 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.

  14. Identification of /sup 233/Ac

    SciTech Connect

    Chu, Y.Y.; Zhou, M.L.

    1983-09-01

    We report in this paper identification of the new isotope /sup 233/Ac. Uranium targets were irradiated with 28 GeV protons; after rapid retrieval of the target and separation of actinium from thorium, /sup 233/Ac was allowed to decay into the known /sup 233/Th daughter. Exhaustive chemical purification was employed to permit the identification of /sup 233/Th via its characteristic ..gamma.. radiations. The half-life derived for /sup 233/Ac from several experiments is 2.3 +- 0.3 min. The production cross section for /sup 233/Ac is 100 ..mu..b.

  15. Phase-locking of driven vortex lattices with transverse ac force and periodic pinning

    SciTech Connect

    Reichhardt, Charles; Kolton, Alejandro B.; Dominguez, Daniel; Gronbech-Jensen, Niels

    2001-10-01

    For a vortex lattice moving in a periodic array we show analytically and numerically that a new type of phase locking occurs in the presence of a longitudinal dc driving force and a transverse ac driving force. This phase locking is distinct from the Shapiro step phase locking found with longitudinal ac drives. We show that an increase in critical current and a fundamental phase-locked step width scale with the square of the driving ac amplitude. Our results should carry over to other systems such as vortex motion in Josephson-junction arrays.

  16. AC resistance measuring instrument

    DOEpatents

    Hof, P.J.

    1983-10-04

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument. 8 figs.

  17. AC Resistance measuring instrument

    DOEpatents

    Hof, Peter J.

    1983-01-01

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument.

  18. Phase-amplitude crosstalk in intensity modulated near infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Alford, K.; Wickramasinghe, Y.

    2000-05-01

    Near infrared spectroscopy (NIRS) instruments that rely on phase sensitive detection suffer from what is called "phase-amplitude crosstalk," i.e., the phase measured is dependent on the average light intensity entering the detector. Changes in detector rise time with input light intensity is the accepted explanation of this phenomenon. It is concluded here that an additional simple mechanism can cause phase-amplitude errors, particularly if the ratio of the ac component of the detected signal to the dc component is low. It is shown that the form of the phase distortion encountered during the development of a new phase sensitive NIR instrument can be modeled by assuming the presence of a synchronous interfering signal, due to rf coupling, at the detector output. This modeling allows a required margin between the detected signal of interest, i.e., the signal from the tissue and the interfering signal to be set in order to achieve a measured phase accuracy necessary to derive sufficiently accurate clinical parameters.

  19. Sewing relations and duality for BRST off-shell string tadpole amplitudes

    SciTech Connect

    Ordonez, C.R. ); Rey, S.; Rubin, M.A.; Zucchini, R.

    1989-09-15

    Using a Becchi-Rouet-Stora-Tyutin- (BRST-)invariant first-quantized formalism for closed-bosonic-string theory, we construct amplitudes for closed-string tadpoles in the conformal gauge and discuss the connection with covariant string field theory in the Siegel gauge. We also show that the application of the sewing rules, previously found for propagators, to pairs of these tadpole amplitudes yields the Klein-bottle and annulus one-loop vacuum amplitudes as required by duality and factorization.

  20. Scattering amplitudes in gauge theories: progress and outlook Scattering amplitudes in gauge theories: progress and outlook

    NASA Astrophysics Data System (ADS)

    Roiban, Radu; Spradlin, Marcus; Volovich, Anastasia

    2011-11-01

    This issue aims to serve as an introduction to our current understanding of the structure of scattering amplitudes in gauge theory, an area which has seen particularly rapid advances in recent years following decades of steady progress. The articles contained herein provide a snapshot of the latest developments which we hope will serve as a valuable resource for graduate students and other scientists wishing to learn about the current state of the field, even if our continually evolving understanding of the subject might soon render this compilation incomplete. Why the fascination with scattering amplitudes, which have attracted the imagination and dedicated effort of so many physicists? Part of it stems from the belief, supported now by numerous examples, that unexpected simplifications of otherwise apparently complicated calculations do not happen by accident. Instead they provide a strong motivation to seek out an underlying explanation. The insight thereby gained can subsequently be used to make the next class of seemingly impossible calculations not only possible, but in some cases even trivial. This two-pronged strategy of exploring and exploiting the structure of gauge theory amplitudes appeals to a wide audience from formal theorists interested in mathematical structure for the sake of its own beauty to more phenomenologically-minded physicists eager to speed up the next generation of analysis software. Understandably it is the maximally supersymmetric 𝒩 = 4 Yang-Mills theory (SYM) which has the simplest structure and has correspondingly received the most attention. Rarely in theoretical physics are we fortunate enough to encounter a toy model which is simple enough to be solved completely yet rich enough to possess interesting non-trivial structure while simultaneously, and most importantly, being applicable (even if only as a good approximation) to a wide range of 'real' systems. The canonical example in quantum mechanics is of course the harmonic

  1. Phase-sensitive detection of both inductive and non-inductive ac voltages in ferromagnetic resonance

    NASA Astrophysics Data System (ADS)

    Weiler, Mathias; Shaw, Justin M.; Nembach, Hans T.; Schoen, Martin A.; Boone, Carl T.; Silva, Thomas J.

    2014-03-01

    Spin pumping causes significant damping in ultrathin ferromagnetic/normal metal (NM) multilayers via spin-current generation of both dc and ac character in the NM system. While the nonlinear dc component has been investigated in detail by utilization of the inverse spin Hall effect (iSHE) in NMs, much less is known about the linear ac component that is presumably much larger in the small-excitation limit. We measured generated ac voltages in a wide variety of Permalloy/NM multilayers via vector-network-analyzer ferromagnetic resonance. We employ a custom, impedance-matched, broadband microwave coupler that features a ferromagnetic thin film reference resonator to accurately compare ac voltage amplitudes and phases between varieties of multilayers. By use of the fact that inductive and ac iSHE signals are phase-shifted by π/2, we find that inductive signals are major contributors in all investigated samples. It is only by comparison of the phase and amplitude of the recorded ac voltages between multiple samples that we can extract the non-inductive contributions due to spin-currents. Voltages due to the ac iSHE in Permalloy(10nm)/platinum(5nm) bilayers are weaker than inductive signals, in agreement with calculations based upon recent theoretical predictions. M.W. acknowledges financial support by the German Academic Exchange service (DAAD).

  2. Wave-breaking amplitudes of relativistic upper-hybrid oscillations in a cold magnetized plasma

    NASA Astrophysics Data System (ADS)

    Karmakar, Mithun; Maity, Chandan; Chakrabarti, Nikhil

    2016-06-01

    A travelling wave solution is presented for relativistic upper-hybrid oscillations (RUHOs) in a cold magnetized plasma. An expression for the wave-breaking amplitudes of RUHOs is derived. The wave-breaking amplitudes of RUHOs are found to decrease with the increase of the strength of an ambient magnetic field. These results will be of relevance to the laboratory context of particle acceleration by wake-fields in which magnetic field plays a central role.

  3. Thermal cracking and amplitude dependent attenuation

    SciTech Connect

    Johnston, D.H.; Toksoez, M.N.

    1980-02-10

    The role of crack and grain boundary contacts in determining seismic wave attenuation in rock is investigated by examining Q as a function of thermal cycling (cracking) and wave strain amplitude. Q values are obtained using a longitudinal resonant bar technique in the 10- to 20-kHz range for maximum strain amplitudes varying from roughly 10/sup -8/ to 10/sup -5/. The samples studied include the Berea and Navajo sandstones, Plexiglas, Westerly granite, Solenhofen limestone, and Frederick diabase, the latter two relatively crack free in their virgin state. Measurements were made at room temperature and pressure in air. Q values for both sandstones are constant at low strains (<10/sup -6/) but decrease rapidly with amplitude at higher strains. There is no hysteresis of Q with amplitude. Q values for Plexiglas show no indication of amplitude dependent behavior. The granite, limestone, and diabase are thermally cycled at both fast and slow heating rates in order to induce cracking. Samples slowly cycled at 400/sup 0/C show a marked increase in Q that cannot be entirely explained by outgassing of volatiles. Cycling may also widen thin cracks and grain boundaries, reducing contact areas. Samples heated beyond 400/sup 0/C, or rapidly heated, result in generally decreasing Q values. The amplitude dependence of Q is found to be coupled to the effects of thermal cycling. For rock slowly cycled 400)C or less, the transition from low-amplitude contant Q to high-amplitude variable Q behavior decreases to lower amplitudes as a function of maximum temperature. Above 400/sup 0/C, and possibly in th rapidly heated samples also, the transition moves to higher amplitudes.

  4. AC Losses in the MICE Channel Magnets -- Is This a Curse or aBlessing?

    SciTech Connect

    Green, M.A.; Wu, H.; Wang, L.; Kai, L.L.; Jia, L.X.; Yang, S.Q.

    2008-01-31

    This report discusses the AC losses in the MICE channelmagnets during magnet charging and discharging. This report talks aboutthe three types of AC losses in the MICE magnets; the hysteretic AC lossin the superconductor, the coupling AC loss in the superconductor and theeddy current AC loss in the magnet mandrel and support structure. AClosses increase the heat load at 4 K. The added heat load increases thetemperature of the second stage of the cooler. In addition, AC losscontributes to the temperature rise between the second stage cold headand the high field point of the magnet, which is usually close to themagnet hot spot. These are the curses of AC loss in the MICE magnet thatcan limit the rate at which the magnet can be charge or discharged. Ifone is willing to allow some of the helium that is around the magnet toboil away during a magnet charge or discharge, AC losses can become ablessing. The boil off helium from the AC losses can be used to cool theupper end of the HTS leads and the surrounding shield. The AC losses arepresented for all three types of MICE magnets. The AC loss temperaturedrops within the coupling magnet are presented as an example of how boththe curse and blessing of the AC losses can be combined.

  5. The Joint Position-Amplitude Formulation for Hurricane State Estimation

    NASA Astrophysics Data System (ADS)

    Ravela, S.; Williams, J.; Emanuel, K.

    2008-12-01

    Classical formulations of data assimilation, whether sequential, ensemble-based or variational, are amplitude adjustment methods. Such approaches can perform poorly when forecast locations of weather systems are displaced from their observations. Compensating position errors by adjusting amplitudes can produce unacceptably 'distorted' states, adversely affecting analysis, verification and subsequent forecasts. There are many sources of position error. It is non-trivial to decompose position error into constituent sources and yet correcting position errors during assimilation can be essential for operationally predicting strong, localized weather events such as tropical cyclones. We will argue and show that if we assume a perfect world where forecast errors do not have position errors and have a Gaussian uncertainty, then in the real world, the bias or variance induced by position errors is the only reason for suboptimal performance of contemporary assimilation methods. Therefore, we propose a method that accounts for both position and amplitude errors using a variational approach. We show that the objective can be solved for position and amplitude decision variables using stochastic methods, thus corresponding with ensemble data assimilation. We then show that if an Euler-Lagrange approximation is made, can solve the objective nearly as well in two steps. This approach is entirely consistent with contemporary data assimilation practice. In the two-step approach, the first step is field alignment, where the current model state is aligned with observations by adjusting a continuous field of local displacements, subject to certain constraints. The second step is amplitude adjustment, where contemporary assimilation approaches are used. We will then demonstrate several choices of constraints on the displacement field, first starting with fluid-like viscous constraints and then proceeding to a multiscale wavelet representation that allows better balance in the

  6. Digital ac monitor

    DOEpatents

    Hart, George W.; Kern, Jr., Edward C.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

  7. Leading Wave Amplitude of a Tsunami

    NASA Astrophysics Data System (ADS)

    Kanoglu, U.

    2015-12-01

    Okal and Synolakis (EGU General Assembly 2015, Geophysical Research Abstracts-Vol. 17-7622) recently discussed that why the maximum amplitude of a tsunami might not occur for the first wave. Okal and Synolakis list observations from 2011 Japan tsunami, which reached to Papeete, Tahiti with a fourth wave being largest and 72 min later after the first wave; 1960 Chilean tsunami reached Hilo, Hawaii with a maximum wave arriving 1 hour later with a height of 5m, first wave being only 1.2m. Largest later waves is a problem not only for local authorities both in terms of warning to the public and rescue efforts but also mislead the public thinking that it is safe to return shoreline or evacuated site after arrival of the first wave. Okal and Synolakis considered Hammack's (1972, Ph.D. Dissertation, Calif. Inst. Tech., 261 pp., Pasadena) linear dispersive analytical solution with a tsunami generation through an uplifting of a circular plug on the ocean floor. They performed parametric study for the radius of the plug and the depth of the ocean since these are the independent scaling lengths in the problem. They identified transition distance, as the second wave being larger, regarding the parameters of the problem. Here, we extend their analysis to an initial wave field with a finite crest length and, in addition, to a most common tsunami initial wave form of N-wave as presented by Tadepalli and Synolakis (1994, Proc. R. Soc. A: Math. Phys. Eng. Sci., 445, 99-112). We compare our results with non-dispersive linear shallow water wave results as presented by Kanoglu et al. (2013, Proc. R. Soc. A: Math. Phys. Eng. Sci., 469, 20130015), investigating focusing feature. We discuss the results both in terms of leading wave amplitude and tsunami focusing. Acknowledgment: The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 603839 (Project ASTARTE - Assessment, Strategy and Risk

  8. Thermionic triode generates ac power

    NASA Technical Reports Server (NTRS)

    Kniazzeh, A. G. F.; Scharz, F. C.

    1970-01-01

    Electrostatic grid controls conduction cycle of thermionic diode to convert low dc output voltages to high ac power without undesirable power loss. An ac voltage applied to the grid of this new thermionic triode enables it to convert heat directly into high voltage electrical power.

  9. Vibration of low amplitude imaged in amplitude and phase by sideband versus carrier correlation digital holography.

    PubMed

    Verrier, N; Alloul, L; Gross, M

    2015-02-01

    Sideband holography can be used to get field images (E0 and E1) of a vibrating object for both the carrier (E0) and the sideband (E1) frequency with respect to vibration. Here we propose to record E0 and E1 sequentially and to image the product E1E0* or the correlation 〈E1E0*〉. We show that these quantities are insensitive to the phase related to the object roughness and directly reflect the phase of the mechanical motion. The signal to noise can be improved by averaging E1E0* over a neighbor pixel, yielding 〈E1E0*〉. Experimental validation is made with a vibrating cube of wood and a clarinet reed. At 2 kHz, vibrations of amplitude down to 0.01 nm are detected. PMID:25680060

  10. Finite-element simulations of hysteretic alternating current losses in a magnetically coated superconducting tubular wire subject to an oscillating transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Genenko, Y. A.; Rauh, H.; Kurdi, S.

    2015-06-01

    Numerical simulations of hysteretic ac losses in a tubular superconductor/paramagnet heterostructure subject to an oscillating transverse magnetic field are performed within the quasistatic approach, calling upon the COMSOL finite-element software package and exploiting magnetostatic-electrostatic analogues. It is shown that one-sided magnetic shielding of a thin, type-II superconducting tube by a coaxial paramagnetic support results in a slight increase of hysteretic ac losses as compared to those for a vacuum environment, when the support is placed inside; a spectacular shielding effect with a possible reduction of hysteretic ac losses by orders of magnitude, however, ensues, depending on the magnetic permeability and the amplitude of the applied magnetic field, when the support is placed outside.

  11. Stacked Optical Precursors from Amplitude and Phase Modulations

    SciTech Connect

    Chen, J. F.; Feng, L.; Loy, M. M. T.; Wong, G. K. L.; Du, Shengwang; Jeong, Heejeong

    2010-06-04

    We report the generation of stacked optical precursors from a laser beam whose amplitude or phase is modulated by sequenced on-off step waveforms. Making use of the constructive interference between the precursors produced from different steps, as well as the main field, we generate optical transient pulses having peak powers of eight times the input power with electromagnetically induced transparency in laser-cooled atoms.

  12. 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.

  13. A link representation for gravity amplitudes

    NASA Astrophysics Data System (ADS)

    He, Song

    2013-10-01

    We derive a link representation for all tree amplitudes in supergravity, from a recent conjecture by Cachazo and Skinner. The new formula explicitly writes amplitudes as contour integrals over constrained link variables, with an integrand naturally expressed in terms of determinants, or equivalently tree diagrams. Important symmetries of the amplitude, such as supersymmetry, parity and (partial) permutation invariance, are kept manifest in the formulation. We also comment on rewriting the formula in a GL( k)-invariant manner, which may serve as a starting point for the generalization to possible Grassmannian contour integrals.

  14. Amplitude- and rise-time-compensated filters

    DOEpatents

    Nowlin, Charles H.

    1984-01-01

    An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.

  15. Form factor and boundary contribution of amplitude

    NASA Astrophysics Data System (ADS)

    Huang, Rijun; Jin, Qingjun; Feng, Bo

    2016-06-01

    The boundary contribution of an amplitude in the BCFW recursion relation can be considered as a form factor involving boundary operator and unshifted particles. At the tree-level, we show that by suitable construction of Lagrangian, one can relate the leading order term of boundary operators to some composite operators of mathcal{N} = 4 superYang-Mills theory, then the computation of form factors is translated to the computation of amplitudes. We compute the form factors of these composite operators through the computation of corresponding double trace amplitudes.

  16. A dipole probe for electric field measurements in the LVPD

    NASA Astrophysics Data System (ADS)

    Srivastava, P. K.; Awasthi, L. M.; Ravi, G.; Kumar, Sunil; Mattoo, S. K.

    2016-01-01

    This paper describes the design, construction, and calibration of an electric dipole probe and demonstrates its capability by presenting results on the measurement of electric field excited by a ring electrode in the Large Volume Plasma Device (LVPD). It measures the electric field in vacuum and plasma conditions in a frequency range lying between 1-10 \\text{MHz} . The results show that it measures electric field ≥slant 2 mV cm-1 for frequency ≤slant 10 \\text{MHz} . The developed dipole probe works on the principle of amplitude modulation. The probe signal is transmitted through a carrier of 418 MHz, a much higher frequency than the available sources of noise present in the surrounding environment. The amplitude modulation concept of signal transmission is used to make the measurement; it is qualitatively better and less corrupted as it is not affected by the errors introduced by ac pickups. The probe is capable of measuring a variety of electric fields, namely (1) space charge field, (2) time varying field, (3) inductive field and (4) a mixed field containing both space charge and inductive fields. This makes it a useful tool for measuring electric fields in laboratory plasma devices.

  17. Light-Front Holography and Hadronization at the Amplitude Level

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy; Shrock, Robert

    2008-07-25

    The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. Light-front holography is a remarkable feature of AdS/CFT: it allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates and the behavior of the QCD coupling in the infrared. We suggest that the spatial support of QCD condensates is restricted to the interior of hadrons, since they arise due to the interactions of confined quarks and gluons. Chiral symmetry is thus broken in a limited domain of size 1=m{sub {pi}} in analogy to the limited physical extent of superconductor phases. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.

  18. Light-Front Holography and Hadronization at the Amplitude Level

    SciTech Connect

    Brodsky, Stanley J.; Teramond, Guy F. de; Shrock, Robert

    2008-10-13

    The correspondence between theories in anti-de Sitter space and conformal field theories in physical space-time leads to an analytic, semiclassical model for strongly-coupled QCD which has scale invariance at short distances and color confinement at large distances. Light-front holography is a remarkable feature of AdS/CFT: it allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time, thus providing a relativistic description of hadrons at the amplitude level. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates and the behavior of the QCD coupling in the infrared. We suggest that the spatial support of QCD condensates is restricted to the interior of hadrons, since they arise due to the interactions of confined quarks and gluons. Chiral symmetry is thus broken in a limited domain of size 1/m{sub {pi}}, in analogy to the limited physical extent of superconductor phases. A new method for computing the hadronization of quark and gluon jets at the amplitude level, an event amplitude generator, is outlined.

  19. Operation Method for AC Motor Control during Power Interruption in Direct AC/AC Converter System

    NASA Astrophysics Data System (ADS)

    Shizu, Keiichiro; Azuma, Satoshi

    Direct AC/AC converters have been studied due to their potential use in power converters with no DC-link capacitor, which can contribute to the miniaturization of power converters. However, the absence of a DC-link capacitor makes it difficult to control the AC motor during power interruption. First, this paper proposes a system that realizes AC motor control during power interruption by utilizing a clamp capacitor. In general, direct AC/AC converters have a clamp circuit consisting of a rectifier diode(s) and a clamp capacitor in order to avoid over-voltages. In the proposed system, there is an additional semiconductor switch reverse-parallel to the rectifier diode(s), and the clamp capacitor voltage can be utilized for AC motor control by turning on the additional switch. Second, this paper discusses an operation method for AC motor control and clamp capacitor voltage control during power interruption. In the proposed method “DC-link voltage control”, the kinetic energy in the AC motor is transformed into electrical energy and stored in the clamp capacitor; the clamp capacitor is therefore charged and the capacitor voltage is controlled to remain constant at an instruction value. Third, this paper discusses a switching operation during power interruption. A dead-time is introduced between the operation of turning off all switches on the rectifier side and the operation of turning on the additional switch, which prevents the occurrence of a short circuit between the interrupted power source and the clamp capacitor. Finally, experimental results are presented. During power interruptions, an output current was continuously obtained and the clamp capacitor voltage was maintained to be equal to the instruction value of the capacitor voltage. These results indicate that both AC motor control and capacitor voltage control were successfully achieved by using the proposed system.

  20. AC Zeeman potentials for atom chip-based ultracold atoms

    NASA Astrophysics Data System (ADS)

    Fancher, Charles; Pyle, Andrew; Ziltz, Austin; Aubin, Seth

    2015-05-01

    We present experimental and theoretical progress on using the AC Zeeman force produced by microwave magnetic near-fields from an atom chip to manipulate and eventually trap ultracold atoms. These AC Zeeman potentials are inherently spin-dependent and can be used to apply qualitatively different potentials to different spin states simultaneously. Furthermore, AC Zeeman traps are compatible with the large DC magnetic fields necessary for accessing Feshbach resonances. Applications include spin-dependent trapped atom interferometry and experiments in 1D many-body physics. Initial experiments and results are geared towards observing the bipolar detuning-dependent nature of the AC Zeeman force at 6.8 GHz with ultracold 87Rb atoms trapped in the vicinity of an atom chip. Experimental work is also underway towards working with potassium isotopes at frequencies of 1 GHz and below. Theoretical work is focused on atom chip designs for AC Zeeman traps produced by magnetic near-fields, while also incorporating the effect of the related electric near-fields. Electromagnetic simulations of atom chip circuits are used for mapping microwave propagation in on-chip transmission line structures, accounting for the skin effect, and guiding impedance matching.

  1. Effective string theory and QCD scattering amplitudes

    SciTech Connect

    Makeenko, Yuri

    2011-01-15

    QCD string is formed at distances larger than the confinement scale and can be described by the Polchinski-Strominger effective string theory with a nonpolynomial action, which has nevertheless a well-defined semiclassical expansion around a long-string ground state. We utilize modern ideas about the Wilson-loop/scattering-amplitude duality to calculate scattering amplitudes and show that the expansion parameter in the effective string theory is small in the Regge kinematical regime. For the amplitudes we obtain the Regge behavior with a linear trajectory of the intercept (d-2)/24 in d dimensions, which is computed semiclassically as a momentum-space Luescher term, and discuss an application to meson scattering amplitudes in QCD.

  2. Amplitude dynamics favors synchronization in complex networks

    PubMed Central

    Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia

    2016-01-01

    In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics. PMID:27108847

  3. The Hubble Legacy Archive ACS grism data

    NASA Astrophysics Data System (ADS)

    Kümmel, M.; Rosati, P.; Fosbury, R.; Haase, J.; Hook, R. N.; Kuntschner, H.; Lombardi, M.; Micol, A.; Nilsson, K. K.; Stoehr, F.; Walsh, J. R.

    2011-06-01

    A public release of slitless spectra, obtained with ACS/WFC and the G800L grism, is presented. Spectra were automatically extracted in a uniform way from 153 archival fields (or "associations") distributed across the two Galactic caps, covering all observations to 2008. The ACS G800L grism provides a wavelength range of 0.55-1.00 μm, with a dispersion of 40 Å/pixel and a resolution of ~80 Å for point-like sources. The ACS G800L images and matched direct images were reduced with an automatic pipeline that handles all steps from archive retrieval, alignment and astrometric calibration, direct image combination, catalogue generation, spectral extraction and collection of metadata. The large number of extracted spectra (73,581) demanded automatic methods for quality control and an automated classification algorithm was trained on the visual inspection of several thousand spectra. The final sample of quality controlled spectra includes 47 919 datasets (65% of the total number of extracted spectra) for 32 149 unique objects, with a median iAB-band magnitude of 23.7, reaching 26.5 AB for the faintest objects. Each released dataset contains science-ready 1D and 2D spectra, as well as multi-band image cutouts of corresponding sources and a useful preview page summarising the direct and slitless data, astrometric and photometric parameters. This release is part of the continuing effort to enhance the content of the Hubble Legacy Archive (HLA) with highly processed data products which significantly facilitate the scientific exploitation of the Hubble data. In order to characterize the slitless spectra, emission-line flux and equivalent width sensitivity of the ACS data were compared with public ground-based spectra in the GOODS-South field. An example list of emission line galaxies with two or more identified lines is also included, covering the redshift range 0.2 - 4.6. Almost all redshift determinations outside of the GOODS fields are new. The scope of science projects

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

    SciTech Connect

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

    1984-12-01

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

  5. Seismic directional beamforming using cosine amplitude distribution

    NASA Astrophysics Data System (ADS)

    Jiang, T.; Xu, X.; Song, J.; Jia, H.; Ge, L.

    2013-12-01

    o improve the signal-to-noise ratio in seismic exploration, we studied the method of time domain seismic beam-forming based on receiver array (TSBBRA). TSBBRA is useful to extract reflected waves from some target layers and decrease noise from other direction. When noise is strong enough, the control parameter of the method of TSBBRA need to be increased. It means that we have to use more raw records to form a directional seismic record. Therefore, the signal energy in beam is much denser, and the beam becomes narrower accordingly. When the beam can not cover the receiver array, the signal-to-noise ratios in different traces are quite unbalanced and average quality of data probably is still quite low. Therefore, this paper proposes seismic directional beamforming using the cosine amplitude distribution (SDBCAD). SDBCAD can adjust seismic beam shape by introducing cosine amplitude distribution, an amplitude weighting method, in the procedure of beamforming. We studied cosine amplitude weighting function, analyzed the characteristics of uniform and cosine amplitude distribution in beamforming, and compared directivity of beams from the two kind of amplitude pattern. It shows that the main beam of cosine-weighted amplitude is different from uniform distribution. The coverage of main beam from SDBCAD is wider than uniform amplitude, and the width of beam is varied with different number of cosine order. So we simulated the seismic raw record, and used TSBBRA and SDBCAD to process simulated data at the receiving array. The results show that SDBCAD can broaden directional beam, and the main beam from SDBCAD can cover the entire traces instead of partial coverage in TSBBRA. The average signal-to-noise ratio increased 0.2~4.5dB. It concludes that SDBCAD is competent to stretch beam reasonable, and it is useful to boost signal-to-noise ratio when beam from TSBBRA is too narrow to illuminate receiver array properly. Updated results will be presented at the meeting.

  6. Nucleon Distribution Amplitudes from Lattice QCD

    SciTech Connect

    Goeckeler, Meinulf; Kaltenbrunner, Thomas; Warkentin, Nikolaus; Horsley, Roger; Zanotti, James M.; Nakamura, Yoshifumi; Pleiter, Dirk; Schierholz, Gerrit; Rakow, Paul E. L.; Schaefer, Andreas; Stueben, Hinnerk

    2008-09-12

    We calculate low moments of the leading-twist and next-to-leading-twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature.

  7. Combined AC electroosmosis and dielectrophoresis for controlled rotation of microparticles.

    PubMed

    Walid Rezanoor, Md; Dutta, Prashanta

    2016-03-01

    Electrorotation is widely used for characterization of biological cells and materials using a rotating electric field. Generally, multiphase AC electric fields and quadrupolar electrode configuration are needed to create a rotating electric field for electrorotation. In this study, we demonstrate a simple method to rotate dielectrophoretically trapped microparticles using a stationary AC electric field. Coplanar interdigitated electrodes are used to create a linearly polarized nonuniform AC electric field. This nonuniform electric field is employed for dielectrophoretic trapping of microparticles as well as for generating electroosmotic flow in the vicinity of the electrodes resulting in rotation of microparticles in a microfluidic device. The rotation of barium titanate microparticles is observed in 2-propanol and methanol solvent at a frequency below 1 kHz. A particle rotation rate as high as 240 revolutions per minute is observed. It is demonstrated that precise manipulation (both rotation rate and equilibrium position) of the particles is possible by controlling the frequency of the applied electric field. At low frequency range, the equilibrium positions of the microparticles are observed between the electrode edge and electrode center. This method of particle manipulation is different from electrorotation as it uses induced AC electroosmosis instead of electric torque as in the case of electrorotation. Moreover, it has been shown that a microparticle can be rotated along its own axis without any translational motion. PMID:27014394

  8. Modelling ac ripple currents in HTS coated conductors

    NASA Astrophysics Data System (ADS)

    Xu, Zhihan; Grilli, Francesco

    2015-10-01

    Dc transmission using high temperature superconducting (HTS) coated conductors (CCs) offers a promising solution to the globally growing demand for effective, reliable and economic transmission of green energy up to the gigawatt level over very long distances. The credible estimation of the losses and thereby the heat dissipation involved, where ac ripples (introduced in rectification/ac-dc conversion) are viewed as a potential source of notable contribution, is highly essential for the rational design of practical HTS dc transmission cables and corresponding cryogenic systems to fulfil this demand. Here we report a targeted modelling study into the ac losses in a HTS CC subject to dc and ac ripple currents simultaneously, by solving Maxwell’s equations using the finite element method (FEM) in the commercial software package COMSOL. It is observed that the instantaneous loss exhibits only one peak per cycle in the HTS CC subject to sinusoidal ripples, given that the amplitude of the ac ripples is smaller than approximately 20% of that of the dc current. This is a distinct contrast to the usual observation of two peaks per cycle in a HTS CC subject to ac currents only. The unique mechanism is also revealed, which is directly associated with the finding that, around any local minima of the applied ac ripples, the critical state of -J c is never reached at the edges of the HTS CC, as it should be according to the Bean model. When running further into the longer term, it is discovered that the ac ripple loss of the HTS CC in full-wave rectification decays monotonically, at a speed which is found to be insensitive to the frequency of the applied ripples within our targeted situations, to a relatively low level of approximately 1.38 × 10-4 W m-1 in around 1.7 s. Comparison between this level and other typical loss contributions in a HTS dc cable implies that ac ripple currents in HTS CCs should only be considered as a minor source of dissipation in superconducting dc

  9. Twistor-strings and gravity tree amplitudes

    NASA Astrophysics Data System (ADS)

    Adamo, Tim; Mason, Lionel

    2013-04-01

    Recently we discussed how Einstein supergravity tree amplitudes might be obtained from the original Witten and Berkovits twistor-string theory when external conformal gravitons are restricted to be Einstein gravitons. Here we obtain a more systematic understanding of the relationship between conformal and Einstein gravity amplitudes in that twistor-string theory. We show that although it does not in general yield Einstein amplitudes, we can nevertheless obtain some partial twistor-string interpretation of the remarkable formulae recently been found by Hodges and generalized to all tree amplitudes by Cachazo and Skinner. The Hodges matrix and its higher degree generalizations encode the world sheet correlators of the twistor string. These matrices control both Einstein amplitudes and those of the conformal gravity arising from the Witten and Berkovits twistor-string. Amplitudes in the latter case arise from products of the diagonal elements of the generalized Hodges matrices and reduced determinants give the former. The reduced determinants arise if the contractions in the worldsheet correlator are restricted to form connected trees at MHV. The (generalized) Hodges matrices arise as weighted Laplacian matrices for the graph of possible contractions in the correlators and the reduced determinants of these weighted Laplacian matrices give the sum of the connected tree contributions by an extension of the matrix-tree theorem.

  10. High-sensitivity dc field magnetometer using nonlinear resonance magnetoelectric effect

    NASA Astrophysics Data System (ADS)

    Burdin, D. A.; Chashin, D. V.; Ekonomov, N. A.; Fetisov, Y. K.; Stashkevich, A. A.

    2016-05-01

    The design and operation principle of dc field magnetometer using nonlinear resonance magnetoelectric effect in a ferromagnetic-piezoelectric structure are described. It is shown that under action of ac pumping magnetic field the structure generates the output voltage containing higher harmonics whose amplitudes depend on the dc magnetic field. Best performance of the device is obtained if the signal of the third harmonics is used for the dc field measurement. The sensitivity can be considerably (by approximately three orders of magnitude) increased if advantage is taken of the acoustic resonance of the structure at this frequency. There exists the optimal pumping field ensuring the highest sensitivity. Further increasing of this field expands the range of measurable dc fields at the expense of deteriorated sensitivity. The magnetometer fabricated on the basis of a planar langatate-Metglas structure had sensitivity up to ~1 V/Oe and allowed detection of the fields as low as ~10-5 Oe.

  11. Relations between closed string amplitudes at higher-order tree level and open string amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Yi-Xin; Du, Yi-Jian; Ma, Qian

    2010-01-01

    KLT relations almost factorize closed string amplitudes on S by two open string tree amplitudes which correspond to the left- and the right-moving sectors. In this paper, we investigate string amplitudes on D and RP. We find that KLT factorization relations do not hold in these two cases. The relations between closed and open string amplitudes have new forms. On D and RP, the left- and the right-moving sectors are connected into a single sector. Then an amplitude with closed strings on D or RP can be given by one open string tree amplitude except for a phase factor. The relations depends on the topologies of the world-sheets. Under T-duality, the relations on D and RP give the amplitudes between closed strings scattering from D-brane and O-plane respectively by open string partial amplitudes. In the low energy limits of these two cases, the factorization relations for graviton amplitudes do not hold. The amplitudes for gravitons must be given by the new relations instead.

  12. DESIGN OF AN AC-DIPOLE FOR USE IN RHIC.

    SciTech Connect

    PARKER,B.; BAI,M.; JAIN,A.; MCINTYRE,G.; METH,M.; PEGGS,S.; ROSER,T.; SANDERS,R.; TRBOJEVIC,D.

    1999-03-29

    We present two options for implementing a pair of AC-dipoles in RHIC for spin flipping, measuring linear optical functions and nonlinear diagnostics. AC-dipoles are magnets that can be adiabatically excited and de-excited with a continuous sine-wave in order to coherently move circulating beam out to large betatron amplitudes without incurring emittance blow up [1]. The AGS already uses a similar device for getting polarized proton beams through depolarizing resonances [2]. By placing the magnets in the IP4 common beam region, two AC-dipoles are sufficient to excite both horizontal and vertical motion in both RHIC rings. While we initially investigated an iron-dominated magnet design using available steel tape cores; we now favor a new air coil plus ferrite design featuring mechanical frequency tuning, in order to best match available resources to demanding frequency sweeping requirements. Both magnet designs are presented here along with model magnet test results. The challenge is to make AC-dipoles available for year 2000 RHIC running.

  13. AC Loss Analysis on the Superconducting Coupling Magnet in MICE

    SciTech Connect

    Wu, Hong; Wang, Li; Green, Michael; Li, LanKai; Xu, FengYu; Liu, XiaoKun; Jia, LinXinag

    2008-07-08

    A pair of coupling solenoids is used in MICE experiment to generate magnetic field which keeps the muons within the iris of thin RF cavity windows. The coupling solenoids have a 1.5-meter inner diameter and will produce 7.4 T peak magnetic field. Three types of AC losses in coupling solenoid are discussed. The affect of AC losses on the temperature distribution within the cold mass during charging and rapid discharging process is analyzed also. The analysis result will be further confirmed by the experiment of the prototype solenoid for coupling solenoid, which will be designed, fabricated and tested at ICST.

  14. Ac traction gets on track

    SciTech Connect

    O`Connor, L.

    1995-09-01

    This article describes inverter-based ac traction systems which give freight locomotives greater adhesion, pulling power, and braking capacity. In the 1940s, dc traction replaced the steam engine as a source of train propulsion, and it has ruled the freight transportation industry ever since. But now, high-performance ac-traction systems, with their unprecedented levels of pulling power and adhesion, are becoming increasingly common on America`s freight railroads. In thousands of miles of demonstration tests, today`s ac-traction systems have outperformed traditional dc-motor driven systems. Major railroad companies are convinced enough of the benefits of ac traction to have integrated it into their freight locomotives.

  15. Observing rapid quasi-wave ionospheric disturbance using amplitude charts

    NASA Astrophysics Data System (ADS)

    Kurkin, Vladimir; Laryunin, Oleg; Podlesnyi, Alexey

    Data from vertical (quasi-vertical) sounding are traditionally used for determining a number of ionospheric parameters such as critical frequencies of E and F layers, peaks of these layers, and for reconstructing electron density profiles. In this respect, radio sounding is not used to its full capacity. Modern ionosondes provide additional information encoded in ionospheric echoes, including information on reflected-signal amplitude. The time dependence of the amplitude-frequency characteristic of reflected signal has been named "amplitude chart" (A-chart). Ionosondes used by the ISTP SB RAS Geophysical Observatory for constructing A-charts employ the frequency-modulated continuous-wave (FMCW) signal in a range 1.3-15 MHz. One-minute sounding interval allows a more detailed study of dynamic processes in the ionosphere. The ionosonde has a direct digital synthesizer and direct sampling receiver without automatic gain control (AGC). The absence of AGC and the high dynamic range enable determination of the relative field strength at a receiving point and registration of relative long-term variations in reflected-signal amplitude over the entire range of operating frequencies of the ionosonde. We have revealed that the passage of travelling ionospheric disturbances (TID) along with height-frequency distortion modulates amplitude characteristics of signal. The characteristic depth of the modulation reaches 40 dB. The pronounced alternate vertical stripes typical for A-charts are likely to be associated with focusing properties of TID. In order to examine the space-time structure of TID able to induce such a focusing of the radio waves, we performed ray tracing simulations. We used geometrical-optics approximation, took magneto-ionic effects into account and prescribed electron density to be a stratified electron density profile on which an undulating disturbance was superimposed. This work was supported by the RFBR grant №14-05-00259-а.

  16. Tectonic Tremor Source Amplitude in Northern Cascadia

    NASA Astrophysics Data System (ADS)

    Ulberg, C. W.; Creager, K. C.; Klaus, A. J.; Wech, A.

    2012-12-01

    Most studies of tectonic tremor have focused on tremor location and duration. We examine tremor source amplitude in northern Cascadia, and explore its importance in understanding the physical processes generating tremor and slow slip. In Cascadia, we observe a linear increase in tremor source amplitude during the approximately five-day initiation phase of episodic tremor and slip (ETS) events, apparently associated with a linear increase in the area where tremor is occurring. There is also mounting evidence that tremor amplitude during ETS events is strongly modulated by tidal stresses (e.g. Rubinstein et al, Science, 2008), including the most recent northern Cascadia ETS events of 2010 and 2011. This suggests a low coefficient of friction on the subduction interface. We will extend our existing amplitude catalog of the 2010 and 2011 Cascadia ETS events to include all of 2006 to 2012, incorporating multiple data sets and providing more insight into the spatial distribution of tremor, the initiation phase of ETS events, and tidal forcing of ETS and inter-ETS tremor. Tremor source amplitudes are estimated with a method similar to Maeda and Obara (JGR, 2009), using the proportional relationship between source amplitude and the root-mean square of band-limited (1.5 to 5.5 Hz) ground velocity for every 5-minute window. We use horizontal component seismograms from the CAFE (2006-2008) and Array of Arrays (2009-2011) experiments, as well as permanent PNSN stations. Tremor locations were determined using a waveform envelope cross-correlation method (Wech and Creager, GRL, 2008). We perform an inversion using these tremor locations and station ground velocities to determine the tremor source amplitude and station statics, taking into account geometric spreading and seismic attenuation.

  17. Radial convection of finite ion temperature, high amplitude plasma blobs

    SciTech Connect

    Wiesenberger, M. Kendl, A.; Madsen, J.

    2014-09-15

    We present results from simulations of seeded blob convection in the scrape-off-layer of magnetically confined fusion plasmas. We consistently incorporate high fluctuation amplitude levels and finite Larmor radius (FLR) effects using a fully nonlinear global gyrofluid model. This is in line with conditions found in tokamak scrape-off-layers (SOL) regions. Varying the ion temperature, the initial blob width, and the initial amplitude, we found an FLR dominated regime where the blob behavior is significantly different from what is predicted by cold-ion models. The transition to this regime is very well described by the ratio of the ion gyroradius to the characteristic gradient scale length of the blob. We compare the global gyrofluid model with a partly linearized local model. For low ion temperatures, we find that simulations of the global model show more coherent blobs with an increased cross-field transport compared to blobs simulated with the local model. The maximal blob amplitude is significantly higher in the global simulations than in the local ones. When the ion temperature is comparable to the electron temperature, global blob simulations show a reduced blob coherence and a decreased cross-field transport in comparison with local blob simulations.

  18. Full phase and amplitude control in computer-generated holography.

    PubMed

    Fratz, Markus; Fischer, Peer; Giel, Dominik M

    2009-12-01

    We report what we believe to be the first realization of a computer-generated complex-valued hologram recorded in a single film of photoactive polymer. Complex-valued holograms give rise to a diffracted optical field with control over its amplitude and phase. The holograms are generated by a one-step direct laser writing process in which a spatial light modulator (SLM) is imaged onto a polymer film. Temporal modulation of the SLM during exposure controls both the strength of the induced birefringence and the orientation of the fast axis. We demonstrate that complex holograms can be used to impart arbitrary amplitude and phase profiles onto a beam and thereby open new possibilities in the control of optical beams. PMID:19953153

  19. Phase-sensitive inductive detection of ac currents due to spin-pumping/inverse spin Hall effect in unpatterned Permalloy/Pt bilayers

    NASA Astrophysics Data System (ADS)

    Silva, Thomas; Nembach, Hans; Shaw, Justin; Karenowska, Alexy; Weiler, Mathias

    We present a new method to measure the ac inverse spin Hall effect at GHz frequencies. Unlike previous methods, our does not rely on any patterning or electrical contacts. We utilize phase-sensitive, broad-band, perpendicular-field ferromagnetic resonance to detect the ac current by the inverse spin Hall effect (iSHE) in Py/Pt bilayers. The iSHE component of the signal is non-linear in the excitation frequency; while the inductive FMR response scales linearly with frequency, the iSHE signal scales quadratically because the iSHE current itself is proportional to dm/dt. This differential gain affords us detection of previously unreported higher order contributions to the iSHE signal. We compare FMR measurements with a control samples that do not include the high spin-orbit layer, e.g. Pt. Data sets with and without Pt are normalized by the complex Polder susceptibility, which nullifies any effects due to differences in line-width and anisotropy. The complex ratio of the normalized inductive amplitudes is analyzed with a simple model that considers how the ac currents generated by the iSHE couple inductively back into the excitations waveguide. The linear iSHE signal agrees with previous reported values. The nonlinear iSHE signal is 3-4 orders of magnitude weaker, but is easily detected over the frequency range of 5-45 GHz

  20. AC electrophoretic deposition of organic-inorganic composite coatings.

    PubMed

    Yoshioka, T; Chávez-Valdez, A; Roether, J A; Schubert, D W; Boccaccini, A R

    2013-02-15

    Alternating current electrophoretic deposition (AC-EPD) of polyacrylic acid (PAA)-titanium oxide (TiO(2)) nanoparticle composites on stainless steel electrodes was investigated in basic aqueous solution. AC square wave with duty cycle of 80% was applied at a frequency of 1 kHz. FTIR-ATR spectra showed that both AC and direct current (DC) EPD successfully deposited PAA-TiO(2) composites. The deposition rate using AC-EPD was lower than that obtained in direct current DC-EPD. However, the microstructure and surface morphology of the deposited composite coatings were different depending on the type of electric field applied. AC-EPD applied for not more than 5 min led to smooth films without bubble formation, while DC-EPD for 1 min or more showed deposits with microstructural defects possibly as result of water electrolysis. AC-EPD was thus for the first time demonstrated to be a suitable technique to deposit organic-inorganic composite coatings from aqueous suspensions, showing that applying a square wave and frequency of 1 kHz leads to uniform PAA-TiO(2) composite coatings on conductive materials. PMID:23218240

  1. Sequential control by speed drive for ac motor

    NASA Astrophysics Data System (ADS)

    Barsoum, Nader

    2012-11-01

    The speed drive for ac motor is widely used in the industrial field to allow direct control for the speed and torque without any feedback from the motor shaft. By using the ABB ACS800 speed drive unit, the speed and torque can be controlled using sequential control method. Sequential control is one of the application control method provided in the ABB ACS800 Drive, where a set of events or action performed in a particular order one after the other to control the speed and torque of the ac motor. It was claimed that sequential control method is using the preset seven constant speeds being provided in ABB ACS800 drive to control the speed and torque in a continuous and sequential manner. The characteristics and features of controlling the speed and torque using sequential control method can be investigated by observing the graphs and curves plotted which are obtained from the practical result. Sequential control can run either in the Direct Torque Control (DTC) or Scalar motor control mode. By using sequential control method, the ABB ACS800 drive can be programmed to run the motor automatically according to the time setting of the seven preset constant speeds. Besides, the intention of this project is to generate a new form of the experimental set up.

  2. Quenching characteristics of a.c. superconducting coils

    NASA Astrophysics Data System (ADS)

    Akita, S.; Kasahara, H.; Torii, S.

    Quenching characteristics of two superconducting coils for a.c. use are investigated at different frequencies. One is impregnated with epoxy resin and the other is not. Both coils have experienced over 40 quenches in a.c. and d.c. The impregnated coil shows steady quenching currents for a.c. and the values are nearly the same as for d.c. On the other hand, quenching currents for a.c. in the non-impregnated coil are almost 80% of the trained-up d.c. quenching current and are scattered. Furthermore, the relationship between quenching currents and the estimated a.c. losses of the superconducting cable at the highest magnetic field point is investigated. According to the results of this investigation, the cause of quench in the impregnated coil is assumed to be the temperature rise of the winding due to a.c. losses, while the cause in the non-impregnated coil might be wire motion.

  3. The potential and electric field in the cochlear outer hair cell membrane

    PubMed Central

    Harland, Ben; Lee, Wen-han; Brownell, William E.; Sun, Sean X.; Spector, Alexander A.

    2015-01-01

    Outer hair cell electromechanics, critically important to mammalian active hearing, is driven by the cell membrane potential. The membrane protein prestin is a crucial component of the active outer hair cell’s motor. The focus of the paper is the analysis of the local membrane potential and electric field resulting from the interaction of electric charges involved. Here the relevant charges are the ions inside and outside the cell, lipid bilayer charges, and prestin-associated charges (mobile-transferred by the protein under the action of the applied field and stationary-relatively unmoved by the field). The electric potentials across and along the membrane are computed for the case of an applied DC-field. The local amplitudes and phases of the potential under different frequencies are analyzed for the case of a DC+AC-field. We found that the effect of the system of charges alters the electric potential and internal field, which deviate significantly from their traditional linear and constant distributions. Under DC+AC conditions, the strong frequency dependence of the prestin mobile charge has a relatively small effect on the amplitude and phase of the resulting potential. The obtained results can help in a better understanding and experimental verification of the mechanism of prestin performance. PMID:25687712

  4. The potential and electric field in the cochlear outer hair cell membrane.

    PubMed

    Harland, Ben; Lee, Wen-han; Brownell, William E; Sun, Sean X; Spector, Alexander A

    2015-05-01

    Outer hair cell electromechanics, critically important to mammalian active hearing, is driven by the cell membrane potential. The membrane protein prestin is a crucial component of the active outer hair cell's motor. The focus of the paper is the analysis of the local membrane potential and electric field resulting from the interaction of electric charges involved. Here the relevant charges are the ions inside and outside the cell, lipid bilayer charges, and prestin-associated charges (mobile-transferred by the protein under the action of the applied field, and stationary-relatively unmoved by the field). The electric potentials across and along the membrane are computed for the case of an applied DC-field. The local amplitudes and phases of the potential under different frequencies are analyzed for the case of a DC + AC-field. We found that the effect of the system of charges alters the electric potential and internal field, which deviate significantly from their traditional linear and constant distributions. Under DC + AC conditions, the strong frequency dependence of the prestin mobile charge has a relatively small effect on the amplitude and phase of the resulting potential. The obtained results can help in a better understanding and experimental verification of the mechanism of prestin performance. PMID:25687712

  5. Microwave Power Combiners for Signals of Arbitrary Amplitude

    NASA Technical Reports Server (NTRS)

    Conroy, Bruce; Hoppe, Daniel

    2009-01-01

    Schemes for combining power from coherent microwave sources of arbitrary (unequal or equal) amplitude have been proposed. Most prior microwave-power-combining schemes are limited to sources of equal amplitude. The basic principle of the schemes now proposed is to use quasi-optical components to manipulate the polarizations and phases of two arbitrary-amplitude input signals in such a way as to combine them into one output signal having a specified, fixed polarization. To combine power from more than two sources, one could use multiple powercombining stages based on this principle, feeding the outputs of lower-power stages as inputs to higher-power stages. Quasi-optical components suitable for implementing these schemes include grids of parallel wires, vane polarizers, and a variety of waveguide structures. For the sake of brevity, the remainder of this article illustrates the basic principle by focusing on one scheme in which a wire grid and two vane polarizers would be used. Wire grids are the key quasi-optical elements in many prior equal-power combiners. In somewhat oversimplified terms, a wire grid reflects an incident beam having an electric field parallel to the wires and passes an incident beam having an electric field perpendicular to the wires. In a typical prior equal-power combining scheme, one provides for two properly phased, equal-amplitude signals having mutually perpendicular linear polarizations to impinge from two mutually perpendicular directions on a wire grid in a plane oriented at an angle of 45 with respect to both beam axes. The wires in the grid are oriented to pass one of the incident beams straight through onto the output path and to reflect the other incident beam onto the output path along with the first-mentioned beam.

  6. Behavioral evidence that magnetic field effects in the land snail, Cepaea nemoralis, might not depend on magnetite or induced electric currents

    SciTech Connect

    Prato, F.S.; Kavaliers, M.; Carson, J.J.L.

    1996-05-01

    Although extremely low frequency (ELF) magnetic fields (< 300 Hz) appear to exert a variety of biological effects, the magnetic field sensing/transduction mechanism(s) remains to be established. Here, using the inhibitory effects of magnetic fields on endogenous opioid peptide-mediated analgesic response of the land snail, Cepaea nemoralis, the authors addressed the mechanism(s) of action of ELF magnetic fields. Indirect mechanisms involving both induced electric fields and direct magnetic field detection mechanisms (e.g., magnetite, parametric resonance) were evaluated. Snails were exposed to a static magnetic field (B{sub DC} = 78 {+-} 1 {micro}T) and a 60 Hz magnetic field (B{sub AC} = 299 {+-} 1 {micro}T peak) with the angle between the static and 60 Hz magnetic fields varied in eight steps between 0{degree} and 90{degree}. At 0{degree} and 90{degree}, the magnetic field reduced opioid-induced analgesia by approximately 20%, and this inhibition was increased to a maximum of 50% when the angle was between 50{degree} and 70{degree}. Because B{sub AC} was fixed in amplitude, direction, and frequency, any induced electric currents would be constant independent of the B{sub AC}/B{sub DC} angle. Also, an energy transduction mechanism involving magnetite should show greatest sensitivity at 90{degree}. Therefore, the energy transduction mechanism probably does not involve induced electric currents or magnetite. Rather, their results suggest a direct magnetic field detection mechanism consistent with the parametric resonance model proposed by Lednev.

  7. A description of seismic amplitude techniques

    NASA Astrophysics Data System (ADS)

    Shadlow, James

    2014-02-01

    The acquisition of seismic data is a non-invasive technique used for determining the sub surface geology. Changes in lithology and fluid fill affect the seismic wavelet. Analysing seismic data for direct hydrocarbon indicators (DHIs), such as full stack amplitude anomalies, or amplitude variation with offset (AVO), can help a seismic interpreter relate the geophysical response to real geology and, more importantly, to distinguish the presence of hydrocarbons. Inversion is another commonly used technique that attempts to tie the seismic data back to the geology. Much has been written about these techniques, and attempting to gain an understanding on the theory and application of them by reading through various journals can be quite daunting. The purpose of this paper is to briefly outline DHI analysis, including full stack amplitude anomalies, AVO and inversion and show the relationship between all three. The equations presented have been included for completeness, but the reader can pass over the mathematical detail.

  8. Periodic amplitude variations in Jovian continuum radiation

    NASA Astrophysics Data System (ADS)

    Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

    1986-12-01

    An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both 5 and 10 horus. Contrary to a plausible initial idea, the continuum amplitudes are not organized by the position of the observer relative to the dense plasma sheet. Instead, there seem to be perferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clocklike modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude solar wind alignment to the amplitude of the continuum radiation implies that the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.

  9. Connecting physical resonant amplitudes and lattice QCD

    NASA Astrophysics Data System (ADS)

    Bolton, Daniel R.; Briceño, Raúl A.; Wilson, David J.

    2016-06-01

    We present a determination of the isovector, P-wave ππ scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using mπ = 236 MeV. The finite volume spectra are described using extensions of Lüscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at mπ = 140 MeV. The scattering phase shift is found to agree with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a ρ-resonance pole at Eρ = [ 755 (2) (1) (20 -i/2 129 (3) (1) 7 1) ] MeV. The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.

  10. Cut-constructible part of QCD amplitudes

    SciTech Connect

    Britto, Ruth; Feng Bo; Mastrolia, Pierpaolo

    2006-05-15

    Unitarity cuts are widely used in analytic computation of loop amplitudes in gauge theories such as QCD. We expand upon the technique introduced in hep-ph/0503132 to carry out any finite unitarity cut integral. This technique naturally separates the contributions of bubble, triangle and box integrals in one-loop amplitudes and is not constrained to any particular helicity configurations. Loop momentum integration is reduced to a sequence of algebraic operations. We discuss the extraction of the residues at higher-order poles. Additionally, we offer concise algebraic formulas for expressing coefficients of three-mass triangle integrals. As an application, we compute all remaining coefficients of bubble and triangle integrals for nonsupersymmetric six-gluon amplitudes.

  11. Perturbative type II amplitudes for BPS interactions

    NASA Astrophysics Data System (ADS)

    Basu, Anirban

    2016-02-01

    We consider the perturbative contributions to the {{ R }}4, {D}4{{ R }}4 and {D}6{{ R }}4 interactions in toroidally compactified type II string theory. These BPS interactions do not receive perturbative contributions beyond genus three. We derive Poisson equations satisfied by these moduli dependent string amplitudes. These T-duality invariant equations have eigenvalues that are completely determined by the structure of the integrands of the multi-loop amplitudes. The source terms are given by boundary terms of the moduli space of Riemann surfaces corresponding to both separating and non-separating nodes. These are determined directly from the string amplitudes, as well as from U-duality constraints and logarithmic divergences of maximal supergravity. We explicitly solve these Poisson equations in nine and eight-dimensions.

  12. Connecting physical resonant amplitudes and lattice QCD

    NASA Astrophysics Data System (ADS)

    Bolton, Daniel R.; Briceño, Raúl A.; Wilson, David J.

    2016-06-01

    We present a determination of the isovector, P-wave ππ scattering phase shift obtained by extrapolating recent lattice QCD results from the Hadron Spectrum Collaboration using mπ = 236 MeV. The finite volume spectra are described using extensions of Lüscher's method to determine the infinite volume Unitarized Chiral Perturbation Theory scattering amplitude. We exploit the pion mass dependence of this effective theory to obtain the scattering amplitude at mπ = 140 MeV. The scattering phase shift is found to agree with experiment up to center of mass energies of 1.2 GeV. The analytic continuation of the scattering amplitude to the complex plane yields a ρ-resonance pole at Eρ = [ 755 (2) (1) (20 02) -i/2 129 (3) (1) (7 1) ] MeV. The techniques presented illustrate a possible pathway towards connecting lattice QCD observables of few-body, strongly interacting systems to experimentally accessible quantities.

  13. Total AC loss study of 2G HTS coils for fully HTS machine applications

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Yuan, Weijia; Kvitkovic, Jozef; Pamidi, Sastry

    2015-11-01

    The application of HTS coils for fully HTS machines has become a new research focus. In the stator of an electrical machine, HTS coils are subjected to a combination of an AC applied current and AC external magnetic field. There is a phase shift between the AC current and AC magnetic field. In order to understand and estimate the total AC loss of HTS coils for electrical machines, we designed and performed a calorimetric measurement for a 2G HTS racetrack coil. Our measurement indicates that the total AC loss is greatly influenced by the phase shift between the applied current and the external magnetic field when the magnetic field is perpendicular to the tape surface. When the applied current and the external magnetic field are in phase, the total AC loss is the highest. When there is a 90 degree phase difference, the total AC loss is the lowest. In order to explain this phenomenon, we employ H formulation and finite element method to model the 2G HTS racetrack coil. Our calculation agrees well with experimental measurements. Two parameters are defined to describe the modulation of the total AC loss in terms of phase difference. The calculation further reveals that the influence of phase difference varies with magnetic field direction. The greatest influence of phase difference is in the perpendicular direction. The study provides key information for large-scale 2G HTS applications, e.g. fully HTS machines and superconducting magnetic energy storage, where the total AC loss subjected to both applied currents and external magnetic fields is a critical parameter for the design.

  14. Amplitude for N-Gluon Superstring Scattering

    SciTech Connect

    Stieberger, Stephan; Taylor, Tomasz R.

    2006-11-24

    We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope {alpha}{sup '}. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in {alpha}{sup '}, for the so-called maximally helicity violating configurations, with N=4, 5 and N=6. We also obtain the leading O({alpha}{sup '2}) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.

  15. Microstrip amplitude-weighted wilkinson power dividers

    NASA Astrophysics Data System (ADS)

    Huck, K. D.

    1986-03-01

    Unequal-split reactive power dividers were examined for use in forming amplitude tapers for microstrip array antennas. Circuits with power ratios of up to 5.0 between arms were constructed on Rexolite substrate, for operation at 4.0 GHz and 7.5 GHz. The 4.0 GHz circuits were very accurate in forming the correct amplitude ratio between outputs, and in maintaining phase balance between outputs. Of those circuits designed for 7.5 GHz, only those with split ratios less than 2.5 worked correctly. This report includes a review of the theory, measured results, and recommendations for improved power dividers.

  16. Dual amplitude pulse generator for radiation detectors

    DOEpatents

    Hoggan, Jerry M.; Kynaston, Ronnie L.; Johnson, Larry O.

    2001-01-01

    A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.

  17. Modeling and Correcting the Time-Dependent ACS PSF

    NASA Technical Reports Server (NTRS)

    Rhodes, Jason; Massey, Richard; Albert, Justin; Taylor, James E.; Koekemoer, Anton M.; Leauthaud, Alexie

    2006-01-01

    The ability to accurately measure the shapes of faint objects in images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST) depends upon detailed knowledge of the Point Spread Function (PSF). We show that thermal fluctuations cause the PSF of the ACS Wide Field Camera (WFC) to vary over time. We describe a modified version of the TinyTim PSF modeling software to create artificial grids of stars across the ACS field of view at a range of telescope focus values. These models closely resemble the stars in real ACS images. Using 10 bright stars in a real image, we have been able to measure HST s apparent focus at the time of the exposure. TinyTim can then be used to model the PSF at any position on the ACS field of view. This obviates the need for images of dense stellar fields at different focus values, or interpolation between the few observed stars. We show that residual differences between our TinyTim models and real data are likely due to the effects of Charge Transfer Efficiency (CTE) degradation. Furthermore, we discuss stochastic noise that is added to the shape of point sources when distortion is removed, and we present MultiDrizzle parameters that are optimal for weak lensing science. Specifically, we find that reducing the MultiDrizzle output pixel scale and choosing a Gaussian kernel significantly stabilizes the resulting PSF after image combination, while still eliminating cosmic rays/bad pixels, and correcting the large geometric distortion in the ACS. We discuss future plans, which include more detailed study of the effects of CTE degradation on object shapes and releasing our TinyTim models to the astronomical community.

  18. Moderately nonlinear diffuse-charge dynamics under an ac voltage

    NASA Astrophysics Data System (ADS)

    Stout, Robert F.; Khair, Aditya S.

    2015-09-01

    The response of a symmetric binary electrolyte between two parallel, blocking electrodes to a moderate amplitude ac voltage is quantified. The diffuse charge dynamics are modeled via the Poisson-Nernst-Planck equations for a dilute solution of point-like ions. The solution to these equations is expressed as a Fourier series with a voltage perturbation expansion for arbitrary Debye layer thickness and ac frequency. Here, the perturbation expansion in voltage proceeds in powers of Vo/(kBT /e ) , where Vo is the amplitude of the driving voltage and kBT /e is the thermal voltage with kB as Boltzmann's constant, T as the temperature, and e as the fundamental charge. We show that the response of the electrolyte remains essentially linear in voltage amplitude at frequencies greater than the RC frequency of Debye layer charging, D /λDL , where D is the ion diffusivity, λD is the Debye layer thickness, and L is half the cell width. In contrast, nonlinear response is predicted at frequencies below the RC frequency. We find that the ion densities exhibit symmetric deviations from the (uniform) equilibrium density at even orders of the voltage amplitude. This leads to the voltage dependence of the current in the external circuit arising from the odd orders of voltage. For instance, the first nonlinear contribution to the current is O (Vo3) which contains the expected third harmonic but also a component oscillating at the applied frequency. We use this to compute a generalized impedance for moderate voltages, the first nonlinear contribution to which is quadratic in Vo. This contribution predicts a decrease in the imaginary part of the impedance at low frequency, which is due to the increase in Debye layer capacitance with increasing Vo. In contrast, the real part of the impedance increases at low frequency, due to adsorption of neutral salt from the bulk to the Debye layer.

  19. RG flow of AC conductivity in soft wall model of QCD

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Neha; Siwach, Sanjay

    2016-03-01

    We study the Renormalization Group (RG) flow of AC conductivity in soft wall model of holographic QCD. We consider the charged black hole metric and the explicit form of AC conductivity is obtained at the cutoff surface. We plot the numerical solution of conductivity flow as a function of radial coordinate. The equation of gauge field is also considered and the numerical solution is obtained for AC conductivity as a function of frequency. The results for AC conductivity are also obtained for different values of chemical potential and Gauss-Bonnet couplings.

  20. ac electroosmotic pumping induced by noncontact external electrodes

    PubMed Central

    Wang, Shau-Chun; Chen, Hsiao-Ping; Chang, Hsueh-Chia

    2007-01-01

    Electroosmotic (EO) pumps based on dc electroosmosis is plagued by bubble generation and other electrochemical reactions at the electrodes at voltages beyond 1 V for electrolytes. These disadvantages limit their throughput and offset their portability advantage over mechanical syringe or pneumatic pumps. ac electroosmotic pumps at high frequency (>100 kHz) circumvent the bubble problem by inducing polarization and slip velocity on embedded electrodes,1 but they require complex electrode designs to produce a net flow. We report a new high-throughput ac EO pump design based on induced-polarization on the entire channel surface instead of just on the electrodes. Like dc EO pumps, our pump electrodes are outside of the load section and form a cm-long pump unit consisting of three circular reservoirs (3 mm in diameter) connected by a 1×1 mm channel. The field-induced polarization can produce an effective Zeta potential exceeding 1 V and an ac slip velocity estimated as 1 mm∕sec or higher, both one order of magnitude higher than earlier dc and ac pumps, giving rise to a maximum throughput of 1 μl∕sec. Polarization over the entire channel surface, quadratic scaling with respect to the field and high voltage at high frequency without electrode bubble generation are the reasons why the current pump is superior to earlier dc and ac EO pumps. PMID:19693362