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Sample records for ac applied field

  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. 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. Variation in energy stored and dissipated in type-II superconductor in applied ac magnetic field with relative phase of two sinusoidal components of the field

    NASA Astrophysics Data System (ADS)

    Janů, Zdeněk; Chagovets, Tymofiy

    2017-01-01

    We show that both the energy stored and dissipated by a system with hysteretic nonlinearity in an applied field varies with the relative phase of the sinusoidal components of the field, even if the magnitude of these components, and thus an effective value of the field, are kept constant. The explored system is a type-II superconductor in the critical state subjected to a time varying applied magnetic field. Complete analytical expressions for hysteresis loops, determined from basic physical phenomena, are known for this system. A theoretically predicted variation in the energy is in good agreement with our experimental measurements.

  4. Gate-opening gas adsorption and host-guest interacting gas trapping behavior of porous coordination polymers under applied AC electric fields.

    PubMed

    Kosaka, Wataru; Yamagishi, Kayo; Zhang, Jun; Miyasaka, Hitoshi

    2014-09-03

    The gate-opening adsorption behavior of the one-dimensional chain compound [Ru2(4-Cl-2-OMePhCO2)4(phz)] (1; 4-Cl-2-OMePhCO2(-) = 4-chloro-o-anisate; phz = phenazine) for various gases (O2, NO, and CO2) was electronically monitored in situ by applying ac electric fields to pelletized samples attached to a cryostat, which was used to accurately control the temperature and gas pressure. The gate-opening and -closing transitions induced by gas adsorption/desorption, respectively, were accurately monitored by a sudden change in the real part of permittivity (ε'). The transition temperature (TGO) was also found to be dependent on the applied temperature and gas pressure according to the Clausius-Clapeyron equation. This behavior was also observed in the isostructural compound [Rh2(4-Cl-2-OMePhCO2)4(phz)] (2), which exhibited similar gate-opening adsorption properties, but was not detected in the nonporous gate-inactive compound [Ru2(o-OMePhCO2)4(phz)] (3). Furthermore, the imaginary part of permittivity (ε″) effectively captured the electronic perturbations of the samples induced by the introduced guest molecules. Only the introduction of NO resulted in the increase of the sample's electronic conductivity for 1 and 3, but not for 2. This behavior indicates that electronic host-guest interactions were present, albeit very weak, at the surface of sample 1 and 3, i.e., through grain boundaries of the sample, which resulted in perturbation of the conduction band of this material's framework. This technique involving the in situ application of ac electric fields is useful not only for rapidly monitoring gas sorption responses accompanied by gate-opening/-closing structural transitions but also potentially for the development of molecular framework materials as chemically driven electronic devices.

  5. Effect of the magnetic material on AC losses in HTS conductors in AC magnetic field carrying AC transport current

    NASA Astrophysics Data System (ADS)

    Wan, Xing-Xing; Huang, Chen-Guang; Yong, Hua-Dong; Zhou, You-He

    2015-11-01

    This paper presents an investigation on the AC losses in several typical superconducting composite conductors using the H-formulation model. A single superconducting strip with ferromagnetic substrate or cores and a stack of coated conductors with ferromagnetic substrates are studied. We consider all the coated conductors carrying AC transport currents and simultaneously exposed to perpendicular AC magnetic fields. The influences of the amplitude, frequency, phase difference and ferromagnetic materials on the AC losses are investigated. The results show that the magnetization losses of single strip and stacked strips have similar characteristics. The ferromagnetic substrate can increase the magnetization loss at low magnetic field, and decrease the loss at high magnetic field. The ferromagnetic substrate can obviously increase the transport loss in stacked strips. The trends of total AC losses of single strip and stacked strips are similar when they are carrying current or exposed to a perpendicular magnetic field. The effect of the frequency on the total AC losses of single strip is related to the amplitude of magnetic field. The AC losses decrease with increasing frequency in low magnetic field region while increase in high magnetic field region. As the phase difference changes, there is a periodic variation for the AC losses. Moreover, when the strip is under only the transport current and magnetic field, the ferromagnetic cores will increase the AC losses for large transport current or field.

  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. Transport signatures in topological systems coupled to ac fields

    NASA Astrophysics Data System (ADS)

    Ruocco, Leonard; Gómez-León, Álvaro

    2017-02-01

    We study the transport properties of a topological system coupled to an ac electric field by means of Floquet-Keldysh formalism. We consider a semi-infinite chain of dimers coupled to a semi-infinite metallic lead and obtain the density of states and current when the system is out of equilibrium. Our formalism is nonperturbative and allows us to explore, in the thermodynamic limit, a wide range of regimes for the ac field, arbitrary values of the coupling strength to the metallic contact and corrections to the wide-band limit (WBL). We find that hybridization with the contact can change the dimerization phase, and that the current dependence on the field amplitude can be used to discriminate between them. We also show the appearance of side bands and nonequilibrium zero-energy modes, characteristic of the Floquet systems. Our results directly apply to the stability of nonequilibrium topological phases, when transport measurements are used for their detection.

  8. Electric field and losses at AC self field mode in MF composites

    SciTech Connect

    Fukui, S.; Hlasnik, I.; Tsukamoto, O.; Amemiya, N. ); Polak, M.; Kottman, P. . Inst. of Electrical Engineering)

    1994-07-01

    Studies of the current-voltage characteristics of typical superconducting wires under static and dynamic conditions up to 50 Hz frequency have revealed much higher instantaneous local loss power densities in an external DC magnetic field than those which occur by magnetization in a transverse AC magnetic field. In this paper, the measured loss characteristics are compared with theoretical ones derived from the critical state model, and the self field AC loss are also estimated. Possible errors that can result by applying the critical state model are discussed.

  9. 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.

  10. 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.

  11. Measurements of AC Loss In Second-Generation HTS Tapes in a DC Magnetic Field

    NASA Astrophysics Data System (ADS)

    Osofsky, M. S.; Soulen, R. J.; Gubser, D. U.; Datta, T.

    2008-03-01

    The successful application of superconductivity to motors and other power system components depends on the characterization and subsequent minimization of the ac loss in the superconductor used for fabrication of the component. The superconductive component, excited by an ac power source, may be exposed to large dc magnetic fields and/or ac fields. To further complicate the situation, the transport properties of the tapes are strongly dependent on the angle between the applied field and the YBCO c-axis (normal to the tape surface). We report on measurements of the transport ac loss of a YBaCuO tape at 65 K, at several frequencies, in applied dc fields of 1-3 T with the field parallel and perpendicular to the tape normal.

  12. AC losses in a HTS coil carrying DC current in AC external magnetic field

    NASA Astrophysics Data System (ADS)

    Ogawa, J.; Zushi, Y.; Fukushima, M.; Tsukamoto, O.; Suzuki, E.; Hirakawa, M.; Kikukawa, K.

    2003-10-01

    We electrically measured AC losses in a Bi2223/Ag-sheathed pancake coil excited by a DC current in AC external magnetic field. Losses in the coil contain two kinds of loss components that are the magnetization losses and dynamic resistance losses. In the measurement, current leads to supply a current to the coil were specially arranged to suppress electromagnetic coupling between the coil current and the AC external magnetic field. A double pick-up coils method was used to suppress a large inductive voltage component contained in voltage signal for measuring the magnetization losses. It was observed that the magnetization losses were dependent on the coil current and that a peak of a curve of the loss factor vs. amplitude of the AC external magnetic field shifted to lower amplitude of the AC magnetic field as the coil current increased. This result suggests the full penetration magnetic field of the coil tape decreases as the coil current increases. The dynamic resistance losses were measured by measuring a DC voltage appearing between the coil terminals. It was observed that the DC voltage appearing in the coil subject to the AC external magnetic field was much larger than that in the coil subject to DC magnetic field.

  13. AC-electric field dependent electroformation of giant lipid vesicles.

    PubMed

    Politano, Timothy J; Froude, Victoria E; Jing, Benxin; Zhu, Yingxi

    2010-08-01

    Giant vesicles of larger than 5 microm, which have been of intense interest for their potential as drug delivery vehicles and as a model system for cell membranes, can be rapidly formed from a spin-coated lipid thin film under an electric field. In this work, we explore the AC-field dependent electroformation of giant lipid vesicles in aqueous media over a wide range of AC-frequency from 1 Hz to 1 MHz and peak-to-peak field strength from 0.212 V/mm to 40 V/mm between two parallel conducting electrode surfaces. By using fluorescence microscopy, we perform in-situ microscopic observations of the structural evolution of giant vesicles formed from spin-coated lipid films under varied uniform AC-electric fields. The real-time observation of bilayer bulging from the lipid film, vesicle growth and fusing further examine the critical role of AC-induced electroosmotic flow of surrounding fluids for giant vesicle formation. A rich AC-frequency and field strength phase diagram is obtained experimentally to predict the AC-electroformation of giant unilamellar vesicles (GUVs) of l-alpha-phosphatidylcholine, where a weak dependence of vesicle size on AC-frequency is observed at low AC-field voltages, showing decreased vesicle size with a narrowed size distribution with increased AC-frequency. Formation of vesicles was shown to be constrained by an upper field strength of 10 V/mm and an upper AC-frequency of 10 kHz. Within these parameters, giant lipid vesicles were formed predominantly unilamellar and prevalent across the entire electrode surfaces.

  14. 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.

  15. AC loss evaluation of an HTS insert for high field magnet cooled by cryocoolers

    NASA Astrophysics Data System (ADS)

    Kajikawa, Kazuhiro; Awaji, Satoshi; Watanabe, Kazuo

    2016-12-01

    AC losses in a high temperature superconducting (HTS) insert coil for 25-T cryogen-free superconducting magnet during its initial energization are numerically calculated under the assumption of slab approximation. The HTS insert consisting of 68 single pancakes wound using coated conductors generates a central magnetic field of 11.5 T in addition to the contribution of 14.0 T from a set of low temperature superconducting (LTS) outsert coils. Both the HTS insert and the LTS coils are cooled using cryocoolers, and energized simultaneously up to the central field of 25.5 T with a constant ramp rate for 60 min. The influences of the magnitudes and orientations of locally applied magnetic fields, magnetic interactions between turns and transport currents flowing in the windings are taken into account in the calculations of AC losses. The locally applied fields are separated into axial and radial components, and the individual contributions of these field components to the AC losses are simply summed up to obtain the total losses. The AC losses due to the axial fields become major in the beginning of energization, whereas the total losses monotonically increase with time after the AC losses due to the radial fields become major.

  16. Total AC losses in twisted and untwisted multifilamentary Bi-2223 superconducting tapes carrying AC transport current in AC longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Amemiya, Naoyuki; Jin, Feng; Jiang, Zhenan; Shirai, Shunsuke; ten Haken, Bennie; Rabbers, Jan-Jaap; Ayai, Naoki; Hayashi, Kazuhiko

    2003-03-01

    In some electrical apparatuses, superconducting tapes are exposed to the longitudinal magnetic field. In this work, AC losses were measured in twisted and untwisted Bi-2223 tapes carrying AC transport current in the AC longitudinal magnetic field. In twisted tapes, the transport, magnetization and total losses depend on the relative direction of the longitudinal magnetic field to the direction of the transport current, while the field direction does not influence the AC loss characteristics in untwisted tapes. In the Z-twisted tapes, the total AC loss is larger in the longitudinal magnetic field that is anti-parallel to the transport current than in the longitudinal magnetic field of another direction. Numerical analysis shows that this field direction dependence of the total AC loss results from the change in the current distribution. In the longitudinal magnetic field that is anti-parallel to the transport current, the total AC loss in the Z-twisted tape is more than that in the untwisted tape. This dependence on the field direction is reversed in S-twisted tapes. It is to be noted that the twist increases the total AC loss in a longitudinal magnetic field of a certain direction, while it reduces the AC loss in the transverse magnetic field.

  17. 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

  18. Trapping of Rb Atoms by ac Electric Fields

    SciTech Connect

    Schlunk, Sophie; Marian, Adela; Geng, Peter; Meijer, Gerard; Schoellkopf, Wieland; Mosk, Allard P.

    2007-06-01

    We demonstrate trapping of an ultracold gas of neutral atoms in a macroscopic ac electric trap. Three-dimensional confinement is obtained by switching between two saddle-point configurations of the electric field. Stable trapping is observed in a narrow range of switching frequencies around 60 Hz. The dynamic confinement of the atoms is directly visualized at different phases of the ac switching cycle. We observe about 10{sup 5} Rb atoms in the 1 mm{sup 3} large and several microkelvins deep trap with a lifetime of approximately 5 s.

  19. 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.

  20. 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)

  1. The photon: EM fields, electrical potentials, and AC charge

    NASA Astrophysics Data System (ADS)

    Meulenberg, A.; Hudgins, W. R.; Penland, R. F.

    2015-09-01

    Photons are here considered to be resonant oscillations (solitons) in four dimensions (space/time) of an undefined `field' otherwise generally existing at a local energy minimum. The photons' constituent EM fields result in elevated energy, and therefore potentials, within that field. It is in the context of the standing waves of and between photons that the EM fields and potentials lead to a description of alternating (AC) `currents' (of some form) of unquantized alternating `charge' (of some sort). The main topic of this paper is the alternating charge.

  2. Theoretical and experimental study of meniscus behavior under AC electric field for Electrohydrodynamic (EHD) jetting

    NASA Astrophysics Data System (ADS)

    Tran, Si Bui Quang; Byun, Doyoung

    2009-11-01

    The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Furthermore, the analytical simulation about the oscillation of an anchored edge hemispherical meniscus located on a conductive flat plate under a uniform ac electric field is presented. The mutual interaction between the electric field and the hydrodynamics is iteratively solved. As a result, the simulation can calculate the meniscus shapes, contours of voltage outside the meniscus and the velocity profile of liquid inside the meniscus during the period of the oscillation according to the applied frequency. Based on the present theory, one can predict the oscillation mode with a certain applied frequency. The present theory can also be applied to investigate the oscillation of a free conductive drop in a uniform ac electric field.

  3. Electric-Field Instrument With Ac-Biased Corona Point

    NASA Technical Reports Server (NTRS)

    Markson, R.; Anderson, B.; Govaert, J.

    1993-01-01

    Measurements indicative of incipient lightning yield additional information. New instrument gives reliable readings. High-voltage ac bias applied to needle point through high-resistance capacitance network provides corona discharge at all times, enabling more-slowly-varying component of electrostatic potential of needle to come to equilibrium with surrounding air. High resistance of high-voltage coupling makes instrument insensitive to wind. Improved corona-point instrument expected to yield additional information assisting in safety-oriented forecasting of lighting.

  4. SQUIDs De-fluxing Using a Decaying AC Magnetic Field

    SciTech Connect

    Matlashov, Andrei Nikolaevich; Semenov, Vasili Kirilovich; Anderson, Bill

    2016-06-08

    Flux trapping is the Achilles’ heel of all superconductor electronics. The most direct way to avoid flux trapping is a prevention of superconductor circuits from exposure to magnetic fields. Unfortunately this is not feasible if the circuits must be exposed to a strong DC magnetic field even for a short period of time. For example, such unavoidable exposures take place in superparamagnetic relaxation measurements (SPMR) and ultra-low field magnetic resonance imaging (ULF MRI) using unshielded thin-film SQUID-based gradiometers. Unshielded SQUIDs stop working after being exposed to DC magnetic fields of only a few Gauss in strength. In this paper we present experimental results with de-fluxing of planar thin-film LTS SQUID-based gradiometers using a strong decaying AC magnetic field. We used four commercial G136 gradiometers for SPMR measurements with up to a 10 mT magnetizing field. Strong 12.9 kHz decaying magnetic field pulses reliably return SQUIDs to normal operation 50 ms after zeroing the DC magnetizing field. This new AC de-fluxing method was also successfully tested with seven other different types of LTS SQUID sensors and has been shown to dissipate extremely low energy.

  5. 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.

  6. 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.

  7. The Feasibility of Applying AC Driven Low-Temperature Plasma for Multi-Cycle Detonation Initiation

    NASA Astrophysics Data System (ADS)

    Zheng, Dianfeng

    2016-11-01

    Ignition is a key system in pulse detonation engines (PDE). As advanced ignition methods, nanosecond pulse discharge low-temperature plasma ignition is used in some combustion systems, and continuous alternating current (AC) driven low-temperature plasma using dielectric barrier discharge (DBD) is used for the combustion assistant. However, continuous AC driven plasmas cannot be used for ignition in pulse detonation engines. In this paper, experimental and numerical studies of pneumatic valve PDE using an AC driven low-temperature plasma igniter were described. The pneumatic valve was jointly designed with the low-temperature plasma igniter, and the numerical simulation of the cold-state flow field in the pneumatic valve showed that a complex flow in the discharge area, along with low speed, was beneficial for successful ignition. In the experiments ethylene was used as the fuel and air as oxidizing agent, ignition by an AC driven low-temperature plasma achieved multi-cycle intermittent detonation combustion on a PDE, the working frequency of the PDE reached 15 Hz and the peak pressure of the detonation wave was approximately 2.0 MPa. The experimental verifications of the feasibility in PDE ignition expanded the application field of AC driven low-temperature plasma. supported by National Natural Science Foundation of China (No. 51176001)

  8. Photon-assisted field emission from a Si tip at addition of an AC low voltage

    NASA Astrophysics Data System (ADS)

    Zaporozhchenko, A. V.; Chernov, S. V.; Odnodvorets, L. V.; Stetsenko, B. V.; Nepijko, S. A.; Elmers, H. J.; Schönhense, G.

    2015-07-01

    We investigated the field emission current from a p-type silicon tip with large resistivity of 4 × 103 Ω cm for light illumination with a photon energy of 1.3 eV and tip-anode voltages of 0.7-5.0 kV. Additional AC voltage with amplitude 30-60 V and frequency varying in the range of 10-107 Hz was applied to the tip which resulted in variations of emission current. We investigated the dependence of this phenomenon on the AC signal parameters, light intensity and temperature. The resonant-like frequency dependence of the emission current is because the tip acts as a driven plasmonic resonator. The results represent an important step forward for the development of high-frequency display systems based on electron field emission.

  9. AC conductivity of a niobium thin film in a swept magnetic field.

    PubMed

    Tsindlekht, M I; Genkin, V M; Gazi, S; Chromik, S

    2013-02-27

    We report results of measurements of the ac conductivity of a Nb superconducting thin film in a swept dc magnetic field. In the mixed state the swept dc field creates vortices at the film surface which pass through the film and form the observed ac conductivity. Vortex rate generation does not depend on the value of the dc field and there is a large plateau-like region of dc magnetic fields where the dissipation is approximately constant. A proposed phenomenological model describes quite well the main features of the ac response in these fields, including its dependency on the sweep rate, ac amplitude, frequency, and value of the second and third harmonics.

  10. AC field-induced polymer electroluminescence with single wall carbon nanotubes.

    PubMed

    Sung, Jinwoo; Choi, Yeon Sik; Kang, Seok Ju; Cho, Sung Hwan; Lee, Tae-Woo; Park, Cheolmin

    2011-03-09

    We developed a high-performance field-induced polymer electroluminescence (FPEL) device consisting of four stacked layers: a top metal electrode/thin solution-processed nanocomposite film of single wall carbon nanotubes (SWNTs) and a fluorescent polymer/insulator/transparent bottom electrode working under an alternating current (AC) electric field. A small amount of SWNTs that were highly dispersed in the fluorescent polymer matrix by a conjugate block copolymer dispersant significantly enhanced EL, and we were able to realize an SWNT-FPEL device with a light emission of approximately 350 cd/m(2) at an applied voltage of ±25 V and an AC frequency of 300 kHz. The brightness of the SWNT-FPEL device is much greater than those of other AC-based organic or even inorganic ELs that generally require at least a few hundred volts. Light is emitted from our SWNT-FPEL device because of the sequential injection of field-induced holes and then electron carriers through ambipolar carbon nanotubes under an AC field, followed by exciton formation in the conjugated organic layer. Field-induced bipolar charge injection provides great material design freedom for our devices; the energy level does not have to be aligned between the electrode and the emission layer, and the balance of the carrier injected and transported can be altered in contrast to that in conventional organic light-emitting diodes, leading to an extremely cost-effective and unified device architecture that is applicable to all red-green-blue fluorescent polymers.

  11. AC electric field induced dipole-based on-chip 3D cell rotation.

    PubMed

    Benhal, Prateek; Chase, J Geoffrey; Gaynor, Paul; Oback, Björn; Wang, Wenhui

    2014-08-07

    The precise rotation of suspended cells is one of the many fundamental manipulations used in a wide range of biotechnological applications such as cell injection and enucleation in nuclear transfer (NT) cloning. Noticeably scarce among the existing rotation techniques is the three-dimensional (3D) rotation of cells on a single chip. Here we present an alternating current (ac) induced electric field-based biochip platform, which has an open-top sub-mm square chamber enclosed by four sidewall electrodes and two bottom electrodes, to achieve rotation about the two axes, thus 3D cell rotation. By applying an ac potential to the four sidewall electrodes, an in-plane (yaw) rotating electric field is generated and in-plane rotation is achieved. Similarly, by applying an ac potential to two opposite sidewall electrodes and the two bottom electrodes, an out-of-plane (pitch) rotating electric field is generated and rolling rotation is achieved. As a prompt proof-of-concept, bottom electrodes were constructed with transparent indium tin oxide (ITO) using the standard lift-off process and the sidewall electrodes were constructed using a low-cost micro-milling process and then assembled to form the chip. Through experiments, we demonstrate rotation of bovine oocytes of ~120 μm diameter about two axes, with the capability of controlling the rotation direction and the rate for each axis through control of the ac potential amplitude, frequency, and phase shift, and cell medium conductivity. The maximum observed rotation rate reached nearly 140° s⁻¹, while a consistent rotation rate reached up to 40° s⁻¹. Rotation rate spectra for zona pellucida-intact and zona pellucida-free oocytes were further compared and found to have no effective difference. This simple, transparent, cheap-to-manufacture, and open-top platform allows additional functional modules to be integrated to become a more powerful cell manipulation system.

  12. Applied-field MPD thruster geometry effects

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.

    1991-01-01

    Eight MPD thruster configurations were used to study the effects of applied field strength, propellant, and facility pressure on thruster performance. Vacuum facility background pressures higher than approx. 0.12 Pa were found to greatly influence thruster performance and electrode power deposition. Thrust efficiency and specific impulse increased monotonically with increasing applied field strength. Both cathode and anode radii fundamentally influenced the efficiency specific impulse relationship, while their lengths influence only the magnitude of the applied magnetic field required to reach a given performance level. At a given specific impulse, large electrode radii result in lower efficiencies for the operating conditions studied. For all test conditions, anode power deposition was the largest efficiency loss, and represented between 50 and 80 pct. of the input power. The fraction of the input power deposited into the anode decreased with increasing applied field and anode radii. The highest performance measured, 20 pct. efficiency at 3700 seconds specific impulse, was obtained using hydrogen propellant.

  13. Propelling and spinning of microsheets in nematic liquid crystals driven by ac electric field

    NASA Astrophysics Data System (ADS)

    Rasna, M. V.; Ramudu, U. V.; Chandrasekar, R.; Dhara, Surajit

    2017-01-01

    Dynamics of microparticles in isotropic liquids by transducing the energy of an applied electric field have been studied for decades. Recently, such studies in anisotropic media like liquid crystals have opened up new perspectives in colloid science. Here, we report studies on ac-electric-field-driven dynamics of microsheets in nematic liquid crystals. In planar aligned liquid crystals, with negative dielectric anisotropy, the microsheets are propelled parallel to the director. A steady spinning of the microsheets is observed in homeotropic cells with positive dielectric anisotropy liquid crystals. The velocity of propelling and the angular frequency of spinning depends on the amplitude and the frequency of the applied electric field. The electrokinetic studies of anisotropic microparticles are important as they are potential for applications in microfluidics and in areas where the controlled transport or rotation is required.

  14. 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

    2011-05-04

    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.

  15. 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.

  16. The thermoelectric power of Al-0.99 wt.% Fe alloys in the AC magnetic field

    NASA Astrophysics Data System (ADS)

    Lan, Qing; Zhang, Jianfeng; Liu, Xuan; Le, Qichi; Yin, Siqi; Liu, Yiting; Cui, Jianzhong

    2017-04-01

    The melt structure of Al-0.99 wt.% Fe alloys in the AC magnetic field have been studied with thermoelectric power by the four-point probe technique and microstructure with the liquid quenching method. The melt temperature is in the range of 913 K–1013 K. The thermoelectric power increases due to the AC magnetic field and decreases after the AC magnetic field stops, then keeps stable. Some characteristic parameters of thermoelectric power in the recovery process are used to represent the variation of melt structure. The α-Al phase refinement in the AC magnetic field is attributed to the persistent variation of melt structure. The persistent variation of thermoelectric power can be used to characterize the variation of the α-Al phase size. The hardness increases and the diffraction peaks of some planes reduce, which can reflect the uniform and disorder melt structure in the AC magnetic field.

  17. 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.

  18. The movement of actin-myosin biomolecular linear motor under AC electric fields: an experimental study.

    PubMed

    Lee, Yongkuk; Famouri, Parviz

    2013-03-15

    The role of actin-myosin as a biomolecular linear motor is considered a transport system at nanoscale because of their size, efficiency and functionality. To utilize the ability to transport, it is essential to control the random movement of actin filaments (F-actin) on myosin coated substrate. In the presence of an alternating current (AC) electric field, the direction of F-actin movement is regulated by electro-orientation torque and, as a result, its movement is perpendicularly toward the electrode edges. Our data confirm such aligned movement is proportional to the strength of applied electric field. Interestingly, the aligned movement is found frequency-dependent and the electrothermal effect is observed by means of the velocity measurement of aligned F-actin movement. The findings in this study may provide constructive information for manipulating actin-myosin nanotransport system to build functional nanodevices in future work.

  19. Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

    NASA Astrophysics Data System (ADS)

    Yan, Xinzhu; Li, Jian; Li, Licheng; Huang, Zhengyong; Wang, Feipeng; Wei, Yuan

    2016-10-01

    In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

  20. 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.

  1. 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.

  2. Applied Electric Fields and the Aggregation of Highly Charged Proteins

    NASA Astrophysics Data System (ADS)

    Nemzer, Louis; Flanders, Bret; Sorensen, Christopher

    2011-03-01

    The abnormal aggregation of misfolded proteins is associated with the onset of Alzheimer's disease, along with other neurodegenerative disorders, and there is increasing evidence that prefibrillar clusters, rather than fully-formed amyloid plaques, are primarily responsible. Therefore, weakly invasive methods, such as dynamic light scattering, which can probe the size distribution and structure factor of early nuclei and proto-aggregate clusters, can serve an important role in understanding this process, and may lead to insights regarding future therapeutic interventions. Here we study a highly charged model protein, lysozyme, under the influence of applied AC and DC fields in an effort to evaluate general models of protein aggregation, including the coarse-grained ``patchy protein'' method of visualizing charge heterogeneity. This anisotropy in the interprotein interaction can lead to frustrated crystalline order, resulting in low density phases. Dynamic measurements of the size distribution and structure factor can reveal local ordering, hierarchical clustering, and fractal properties of the aggregates. Early results show that applied fields affect early cluster growth by modulating local protein and counterion concentrations, in addition to their influence on protein alignment.

  3. 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.

  4. Applied-field magnetoplasmadynamic engine developments

    NASA Technical Reports Server (NTRS)

    Goodfellow, K. D.; Pivirotto, T. J.; Polk, J. E.

    1992-01-01

    There are potential space exploration missions which may significantly benefit from the use of electric propulsion at power levels of hundreds of kilowatts. The applied magnetic field MPD thruster is potentially capable of efficient, high specific impulse operation in this power range. This paper describes current experimental and analytical efforts to further the development of such a thruster and presents the latest results. In particular, efforts to measure, simultaneously, the thrust developed by the archead and by the electromagnet, and to evaluate the effect of a diffuser on vacuum tank back pressure, are presented and discussed. It was found that with ammonia vapor as propellant, the vacuum tank pressure was reduced from 8 to 4.9 Pa at a power level of 80 kW. This pressure decrease is expected to become greater as the power and applied field are increased. Also, the development of a cathode/plasma interaction model for determining the heat loads to the cathode as functions of the various free stream plasma parameters is presented. This model is combined with a cathode thermal model in order to provide a complete and integrated picture of MPD thruster cathode operation. Several computational examples are used to illustrate the combined model.

  5. 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.

  6. Quantum system driven by incoherent a.c fields: Multi-crossing Landau Zener dynamics

    NASA Astrophysics Data System (ADS)

    Jipdi, M. N.; Fai, L. C.; Tchoffo, M.

    2016-10-01

    The paper investigates the multi-crossing dynamics of a Landau-Zener (LZ) system driven by two sinusoidal a.c fields applying the Dynamic Matrix approach (DMA). The system is shown to follow one-crossing and multi-crossing dynamics for low and high frequency regime respectively. It is shown that in low frequency regime, the resonance phenomenon occurs and leads to the decoupling of basis states; the effective gap vanishes and then the complete blockage of the system. For high frequency, the system achieves multi-crossing dynamics with two fictitious crossings; the system models a Landau-Zener-Stückelberg (LZS) interferometer with critical parameters that tailor probabilities. The system is then shown to depend only on the phase that permits the easiest control with possible application in implementing logic gates.

  7. 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.

  8. 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.

  9. 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.

  10. Nonlinear dynamics of Josephson vortices in a film screen under dc and ac magnetic fields

    NASA Astrophysics Data System (ADS)

    Sheikhzada, A.; Gurevich, A.

    2014-11-01

    We present detailed numerical simulations of Josephson vortices in a long Josephson junction perpendicular to a thin film screen under strong dc and ac magnetic fields. By solving the sine-Gordon equation, we calculated the threshold magnetic field for penetration of fluxons as a function of frequency, and the power dissipated by oscillating fluxons as functions of the ac field amplitude and frequency. We considered the effects of superimposed ac and dc fields, and a bi-harmonic magnetic field resulting in a vortex ratchet dynamics. The results were used to evaluate the contribution of weak-linked grain boundaries to the nonlinear surface resistance of polycrystalline superconductors under strong electromagnetic fields, particularly thin film screens and resonator cavities.

  11. Numerical simulations of electromagnetic behavior and AC loss in rectangular bulk superconductor with an elliptical flaw under AC magnetic fields

    NASA Astrophysics Data System (ADS)

    Xia, Jing; Zhou, Youhe

    2015-07-01

    This paper presents a finite element model based on the H-formulation to solve the electromagnetic behavior and AC loss in rectangular bulk superconductor with an elliptical flaw in AC external field condition. Both the interior flaw and the edge flaw are considered. A modified E-J power law which is valid for an arbitrary current density range is adopted in order to predict the strong local enhancement of the current density in the vicinity of the flaw tip. The results for the usual E-J power law are calculated for comparison as well. The simulation results show that the existence of the flaw significantly blocks the flow of the induced current and forces the current to redistribute around it. Meanwhile, the strong local enhancement of the current density is observed in the vicinity of the flaw tip. Furthermore, the influences of the size and position of the flaw on the local enhancement of the current density in the vicinity of the flaw tip are investigated. In addition, it is found that the influence of the flaw on the AC loss of the sample is slight for both cases of the interior flaw and the edge flaw.

  12. Dynamics of particle chain formation in a liquid polymer under ac electric field: modeling and experiments

    NASA Astrophysics Data System (ADS)

    Belijar, G.; Valdez-Nava, Z.; Diaham, S.; Laudebat, L.; Jones, T. B.; Lebey, T.

    2017-01-01

    Polymer/ceramic composite materials are of great interest for their many potential applications because of their ability to combine at least two properties of the constitutive elements: particles and matrix. In most cases, such enhanced properties are required only in one direction. Orthotropic materials can be elaborated by applying an ac electric field to form particle chain structures in the direction of the electric field due to the dielectrophoretic interactions affecting the particles. However, there is still a lack in the understanding of the impact of the structures on the properties of the material. The aim of this study is to propose a predictive model for the evolution of the permittivity during the chain formation, by including micro- and macroscopic phenomena. The chaining model is based on dipole-dipole interactions and the dielectric permittivity is computed through a finite element method. In parallel, an experimental study is performed with online permittivity measurements of composites during chaining. The developed model is able to predict the experimental results from 1 vol% while taking into account parameters such as the resin viscosity and permittivity and the transient evolution of the applied electric field. The formation of particle chains inside a material has applications in many domains such as electrorheological fluids, anisotropic composites, self-recovery materials etc. Such a developed model is a valuable tool for the tailoring of materials.

  13. Simulational studies of epitaxial semiconductor superlattices: Quantum dynamical phenomena in ac and dc electric fields

    SciTech Connect

    Reynolds, Joseph

    1997-10-08

    Using high-accuracy numerical methods the author investigates the dynamics of independent electrons in both ideal and realistic superlattices subject to arbitrary ac and/or dc electric fields. For a variety of superlattice potentials, optically excited initial wave packets, and combinations of ac and dc electric fields, he numerically solves the time-dependent Schroedinger equation. In the case of ideal periodic superlattice potentials, he investigates a long list of dynamical phenomena involving multiple miniband transitions and time-dependent electric fields. These include acceleration effects associated with interminiband transitions in strong fields, Zener resonances between minibands, dynamic localization with ac fields, increased single-miniband transport with an auxiliary resonant ac field, and enhanced or suppressed interminiband probability exchange using an auxiliary ac field. For all of the cases studied, the resulting time-dependent wave function is analyzed by projecting the data onto convenient orthonormal bases. This allows a detailed comparison with approximately analytic treatments. In an effort to explain the rapid decay of experimentally measured Bloch oscillation (BO) signals the author incorporates a one-dimensional representation of interface roughness (IR) into their superlattice potential. He shows that as a result of IR, the electron dynamics can be characterized in terms of many discrete, incommensurate frequencies near the Block frequency. Chapters 2, 3, 4 and 5 have been removed from this report and will be processed separately.

  14. Range Detection of the Extremely Low-Frequency Magnetic Field Produced by Laptop's AC Adapter

    NASA Astrophysics Data System (ADS)

    Brodić, Darko; Amelio, Alessia

    2017-02-01

    Human exposure to extremely low frequency magnetic field represents a risk to their health. This paper takes into consideration the level of an extremely low-frequency magnetic field between 30 and 300 Hz emitted by an AC laptop adapter. The experiment consists of testing 17 different AC adapters for laptops. During the testing, laptops are operated in a normal operating conditions as well as under heavy load. The magnetic field measurement is conducted in the area around the AC adapter. Obtained data is evaluated according to the critical level of the magnetic field proposed by safety standards. Furthermore, data is classified by a K-medians method in order to determine the critical levels of the magnetic field exposure in the nearby area of the AC adapter. Obtained classifications are evaluated according to safety standards, giving a critical analysis of magnetic field areas at risk. Due to emission of a very strong magnetic field in certain areas, a recommendation for safety use of the AC adapter is proposed.

  15. 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

  16. 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

  17. 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.

  18. Angular dependence of direct current decay in a closed YBCO double-pancake coil under external AC magnetic field and reduction by magnetic shielding

    NASA Astrophysics Data System (ADS)

    Geng, J.; Zhang, H.; Li, C.; Zhang, X.; Shen, B.; Coombs, T. A.

    2017-03-01

    High T c superconducting (HTS) coils are ideal candidates in the use of high field magnets. HTS coils carrying a direct current, however, suffer a non-negligible loss when they are exposed to an external AC magnetic field. Although this phenomenon is well known, no study concerning AC magnetic field angular dependence of direct current decay has ever been shown. In this work, we experimentally investigate the direct current decay characteristics in a closed double pancake coil made of a YBCO coated conductor under external AC field. AC field of different angles with respect to the coil plane is applied. Results show that the current decay rate presents a strong angular dependence. The fastest decay occurs when the field is parallel to the coil plane, in which case the surface of the tape in the outermost layer experiences most flux variation. To reduce the decay rate, we propose wrapping superconducting tapes around the outermost layer of the coil to shield external AC field. This method significantly reduces direct current decay rate under parallel field, without affecting the perpendicular self-field of the coil.

  19. Particle segregation in suspensions subject to high-gradient ac electric fields

    NASA Astrophysics Data System (ADS)

    Dussaud, Anne D.; Khusid, Boris; Acrivos, Andreas

    2000-11-01

    An experimental and theoretical study is described dealing with the dielectrophoretic motion of individual particles in a static as well as in a flowing suspension subject to high-gradient ac electric fields. The experiments were performed on very dilute suspensions of neutrally buoyant hollow ceramic spheres in a specially designed device in which the electric-field lines and the dielectrophoretic force were along the plane perpendicular to the streamlines of the main flow. Upon application of a high-gradient field (˜several kV/mm) to a quiescent suspension, the particles were found to move away from the electrodes and then to concentrate above the grounded electrodes, forming a distinct boundary between the clean fluid and the remaining suspension. This same field, when applied to a flowing suspension, caused the particles to concentrate within thin stripes parallel to the flow above the grounded electrodes and to travel with the suspending fluid within these stripes. The theoretical model for the particle motion included only the dielectrophoretic force and the viscous drag, and required no fitting parameters because the particle polarizability was calculated independently by measuring the concentration dependence of the complex permittivity of the suspension in a spatially uniform electric field of low strength (˜several V/mm). The computed particle motions and pattern formations were found to be in a good agreement with the experimental data. These results demonstrate that the expression for the dielectrophoretic force which employs the value of the particle polarization measured in fields of low strength can be used for describing the particle motions in fields of high strength. This approach enables one to model a broad range of electro-hydrodynamic phenomena in suspensions irrespective of whether or not they are perfectly insulating or perfectly conducting.

  20. 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.

  1. 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…

  2. Pure Parallel Near-UV Observations with WFPC2 within High-Latitude ACS Survey Fields

    NASA Astrophysics Data System (ADS)

    Gardner, Jonathan

    2002-07-01

    In anticipation of the allocation of ACS high-latitude imaging survey{s}, we request a modification of the default pure parallel program for those WFPC2 parallels that fall within the ACS survey field. Rather than duplicate the red bands which will be done much better with ACS, we propose to observe in the near-ultraviolet F300W filter. These data will enable study of the rest-frame ultraviolet morphology of galaxies at 0ACS.

  3. 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.

  4. Effect of carbon substitution on low magnetic field AC losses in MgB 2 single crystals

    NASA Astrophysics Data System (ADS)

    Ciszek, M.; Rogacki, K.; Karpiński, J.

    2011-11-01

    The DC magnetization and AC magnetic susceptibilities were measured for MgB2 single crystals, unsubstituted and carbon substituted with the composition of Mg(B0.94C0.06)2. AC magnetic losses were derived from the AC susceptibility data as a function of the AC amplitude and the DC bias magnetic field. From the DC magnetization loops critical current densities were derived as a function of temperature and DC field. Results show that the substitution with carbon decreases critical current densities at low external magnetic fields, in contrast to the well known effect of an increase of the critical current densities at higher magnetic fields.

  5. 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.

  6. Total AC loss characteristics of untwisted and twisted Bi-2223 multifilamentary tapes and interaction between self and external magnetic fields

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenan; Amemiya, Naoyuki; Ayai, Naoki; Hayashi, Kazuhiko

    2004-11-01

    The authors have electrically measured the total AC losses of untwisted and twisted Bi-2223 multifilamentary tapes in AC parallel and perpendicular transverse magnetic fields. The magnetization and transport losses in the untwisted and twisted Bi-2223 multifilamentary tapes carrying an AC transport current in AC parallel and perpendicular transverse magnetic fields were measured independently to obtain the total AC loss. The total AC losses of both the untwisted and twisted Bi-2223 multifilamentary tapes in a parallel transverse magnetic field are approximately equal to the sum of the transport loss without the external magnetic field and the magnetization loss without the transport current. In particular, the total AC loss of the twisted tape in a parallel transverse magnetic field is in good agreement with this sum. On the other hand, the total AC losses of both the untwisted and twisted Bi-2223 multifilamentary tapes in a perpendicular transverse magnetic field are larger than the sum of the transport loss without any external magnetic field and the magnetization loss without transport current. The total AC loss of the twisted tape in a parallel transverse magnetic field can be predicted by the sum of the magnetization loss using the slab model for an equivalent filament thickness and the transport loss given by Norris for a superconductor with an elliptical cross section.

  7. Why an ac magnetic field shifts the irreversibility line in type-II superconductors.

    PubMed

    Brandt, Ernst Helmut; Mikitik, Grigorii P

    2002-07-08

    We show that for a thin superconducting strip placed in a transverse dc magnetic field--the typical geometry of experiments with high-T(c) superconductors--the application of a weak ac magnetic field perpendicular to the dc field generates a dc voltage in the strip. This voltage leads to the decay of the critical currents circulating in the strip, and eventually the equilibrium state of the superconductor is established. This relaxation is not due to thermally activated flux creep but to the "walking" motion of vortices in the two-dimensional critical state of the strip with in-plane ac field. Our theory explains the shaking effect that was used for detecting phase transitions of the vortex lattice in superconductors.

  8. Structure in the DC and AC electric fields associated with the dayside cusp region

    NASA Technical Reports Server (NTRS)

    Maynard, N. C.

    1985-01-01

    The cusp region as seen in the AC and DC electric fields is one of intense variation. The intensity peaks within the soft particle precipitation. The only AC signal that appears to be unique to the cusp is broadband ULF-ELF magnetic noise. Other types of emissions are also found at other local times at high latitudes. The pattern of these signals, especially that of ULF-ELF broadband electrostatic noise (BEN), distinguishes the cusp region from other regions. BEN signatures are indicators of magnetosheath-like soft particle precipitation but not necessarily of open field lines. In addition, large spike-like features in the DC electric field are seen near local magnetic noon which appear to be related to the large convective electric fields that have been observed at the magnetopause. These features are not necessarily tied to convection reversals, but may appear within broader regions of zonal convective flow.

  9. Calculation of the ac to dc resistance ratio of conductive nonmagnetic straight conductors by applying FEM simulations

    NASA Astrophysics Data System (ADS)

    Riba, Jordi-Roger

    2015-09-01

    This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductor configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. Alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications, as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is not usually analyzed in detail in undergraduate and even in graduate studies. To address this, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations.

  10. Comprehensive analysis of particle motion under non-uniform AC electric fields in a microchannel.

    PubMed

    Oh, Jonghyun; Hart, Robert; Capurro, Jorge; Noh, Hongseok Moses

    2009-01-07

    AC electrokinetics is rapidly becoming a foundational tool for lab-on-a-chip systems due to its versatility and the simplicity of the components capable of generating them. Predicting the behavior of fluids and particles under non-uniform AC electric fields is important for the design of next generation devices. Though there are several important phenomena that contribute to the overall behavior of particles and fluids, current predictive techniques consider special conditions where only a single phenomenon may be considered. We report a 2D numerical simulation, using COMSOL Multiphysics, which incorporates the three major AC electrokinetic phenomena (dielectrophoresis, AC electroosmosis and electrothermal effect) and is valid for a wide range of operational conditions. Corroboration has been performed using experimental conditions that mimic those of the simulation and shows good qualitative agreement. Furthermore, a broad range of experiments has been performed using four of the most widely reported devices under varying conditions in order to show their behavior as it relates to the simulation. The large number of experimental conditions reported, together with the comprehensive numerical simulation, will help provide guidelines for scientists and engineers interested in incorporating AC electrokinetics into their lab-on-a-chip systems.

  11. New perspectives on the dynamics of AC and DC plasma arcs exposed to cross-fields

    NASA Astrophysics Data System (ADS)

    Abdo, Youssef; Rohani, Vandad; Cauneau, François; Fulcheri, Laurent

    2017-02-01

    Interactions between an arc and external fields are crucially important for the design and the optimization of modern plasma torches. Multiple studies have been conducted to help better understand the behavior of DC and AC current arcs exposed to external and ‘self-induced’ magnetic fields, but the theoretical foundations remain very poorly explored. An analytical investigation has therefore been carried out in order to study the general behavior of DC and AC arcs under the effect of random cross-fields. A simple differential equation describing the general behavior of a planar DC or AC arc has been obtained. Several dimensionless numbers that depend primarily on arc and field parameters and the main arc characteristics (temperature, electric field strength) have also been determined. Their magnitude indicates the general tendency pattern of the arc evolution. The analytical results for many case studies have been validated using an MHD numerical model. The main purpose of this investigation was deriving a practical analytical model for the electric arc, rendering possible its stabilization and control, and the enhancement of the plasma torch power.

  12. An Actual Design of AC Filter for Static Var Compensator and Verification Results from the Field Test

    NASA Astrophysics Data System (ADS)

    Tamura, Yuji; Takasaki, Shinji; Irokawa, Shoichi; Takeda, Hideo; Takagi, Kikuo; Noro, Yasuhiro; Ametani, Akihiro

    AC filter design method for SVC and HVDC is commonly known in the relevant CIGRE technical brochure and IEC technical report. However the conventional method requires many iterative calculations of the harmonic voltages and currents until the calculation results become within the regulation levels by changing filter parameters based on the experience. In this respect, a new improved design method is proposed, which enables efficient evaluation on the complex impedance plane to confirm as to whether the proposed filter impedance is in the permissible range. In an actual project of Okuura SVC of Kyusyu Electric Power Co., Inc., the new method was applied to the AC filter design. This paper describes on the actual procedure of the AC filter design with the new method, the actual references of the harmonic performance calculation, and the field test measurement results on Okuura SVC. The calculation results and the filed measurement results are consistent with each other, thus the validity of the new design method is verified on its accuracy and effectiveness.

  13. Upper critical field and AC-Susceptibility studies on FeTe0.5Se0.5 superconductor

    NASA Astrophysics Data System (ADS)

    Zargar, Rayees A.; Pal, Anand; Hafiz, A. K.; Awana, V. P. S.

    2015-06-01

    In this study we present synthesis and characterization of FeTe0.5Se0.5 sample that has been prepared by solid state reaction route by encapsulation of stoichiometric high purity (5N) ingredients in an evacuated quartz tube at 750 °C. The resultant compound is crystallized in single phase tetragonal structure with space group P4/nmm, having lattice parameters a = 3.792(1) Å and c = 6.0081(3) Å. The studied compound is superconducting at below 13K in both magnetic and transport measurements. Further superconductivity is barely affected by external applied magnetic field, giving rise to upper critical field of above 180 Tesla at 0 K. The sample is studied extensively for AC susceptibility measurements in superconducting state. The AC drive field and frequency are varied from 1-13 Oe and 33-9999 Hz respectively. It is concluded that though the grain boundaries of this superconductor are mainly metallic the minor (undetectable in XRD) foreign phases and the role of porosity cannot be ruled out completely. This is because both frequency and amplitude affects slightly the superconductivity coupling temperature of the grains.

  14. Magnetohydrodynamic flow of generalized Maxwell fluids in a rectangular micropump under an AC electric field

    NASA Astrophysics Data System (ADS)

    Zhao, Guangpu; Jian, Yongjun; Chang, Long; Buren, Mandula

    2015-08-01

    By using the method of separation of variables, an analytical solution for the magnetohydrodynamic (MHD) flow of the generalized Maxwell fluids under AC electric field through a two-dimensional rectangular micropump is reduced. By the numerical computation, the variations of velocity profiles with the electrical oscillating Reynolds number Re, the Hartmann number Ha, the dimensionless relaxation time De are studied graphically. Further, the comparison with available experimental data and relevant researches is presented.

  15. 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.

  16. 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.

  17. AC field induced-charge electroosmosis over leaky dielectric blocks embedded in a microchannel.

    PubMed

    Zhao, Cunlu; Yang, Chun

    2011-02-01

    An effective electrical boundary condition is formulated to describe AC field-driven induced-charge electrokinetic (ICEK) phenomena at the interface between a liquid and a leaky dielectric solid. Since most materials in reality possess finite dielectric and conductive properties, i.e. leaky dielectric, the present boundary condition can be used to describe the induced zeta potential on a leaky dielectric surface with consideration of both bond charges (due to polarization) and free charges (due to conduction). Two well-known limiting cases, i.e. the perfectly dielectric and the perfectly conducting wall boundary conditions can be recovered from the present formulation. Utilizing the derived boundary condition, we obtain analytical solutions in closed form for the AC field-driven induced-charge electroosmosis (ICEO) over two symmetric leaky dielectric blocks embedded in the walls of an infinitely long microchannel. Two important factors for the induced zeta potential are identified to respectively account for the polarization charges and the free charges, and their effects on AC field-driven ICEO oscillating flow patterns are analyzed. It is found that the flow patterns exhibit two counter-rotating vortices, which can be deformed, relocated, eliminated and even reverse their rotating directions. It is very promising that such temporary evolution of flow patterns can possibly induce chaotic advection which can enhance microfluidic mixing.

  18. Dynamical band flipping in fermionic lattice systems: an ac-field-driven change of the interaction from repulsive to attractive.

    PubMed

    Tsuji, Naoto; Oka, Takashi; Werner, Philipp; Aoki, Hideo

    2011-06-10

    We show theoretically that the sudden application of an appropriate ac field to correlated lattice fermions flips the band structure and effectively switches the interaction from repulsive to attractive. The nonadiabatically driven system is characterized by a negative temperature with a population inversion. We numerically demonstrate the converted interaction in an ac-driven Hubbard model with the nonequilibrium dynamical mean-field theory solved by the continuous-time quantum Monte Carlo method. Based on this, we propose an efficient ramp-up protocol for ac fields that can suppress heating, which leads to an effectively attractive Hubbard model with a temperature below the superconducting transition temperature of the equilibrium system.

  19. 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.

  20. Electro-worming: The behaviors of Caenorhabditis (C.) elegans in DC and AC electric fields

    NASA Astrophysics Data System (ADS)

    Chuang, Han-Sheng; Raizen, David M.; Dabbish, Nooreen; Bau, Haim H.

    2011-09-01

    The video showcases how C. elegans worms respond to DC and AC electrical stimulations. Gabel et al (2007) demonstrated that in the presence of DC and low frequency AC fields, worms of stage L2 and larger propel themselves towards the cathode. Rezai et al (2010) have demonstrated that this phenomenon, dubbed electrotaxis, can be used to control the motion of worms. In the video, we reproduce Rezai's experimental results. Furthermore, we show, for the first time, that worms can be trapped with high frequency, nonuniform electric fields. We studied the effect of the electric field on the nematode as a function of field intensity and frequency and identified a range of electric field intensities and frequencies that trap worms without apparent adverse effect on their viability. Worms tethered by dielectrophoresis (DEP) avoid blue light, indicating that at least some of the nervous system functions remain unimpaired in the presence of the electric field. DEP is useful to dynamically confine nematodes for observations, sort them according to size, and separate dead worms from live ones.

  1. 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.

  2. 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.

  3. 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.

  4. AC losses in perpendicular external magnetic fields in ring bundle barrier multifilamentary BSCCO(2223) tapes with a central resistive barrier

    NASA Astrophysics Data System (ADS)

    Eckelmann, H.; Krelaus, J.; Nast, R.; Goldacker, W.

    2001-06-01

    For the most common AC frequencies, the main components of the AC losses in multifilamentary Bi(2223) tapes are caused by both hysteresis and coupling losses. These losses can be reduced by increasing the matrix resistivity, applying a twist to the filaments and by the use of a conductor design optimised for a practical application. In the ring bundle barrier (RBB) conductor design we have bundles of filaments which are twisted around a central resistive core. The RBB structure was prepared via the powder in tube assemble and react (PITAR) route . In these tapes six bundles of seven filaments are twisted around a resistive layer of a mixture of 50% SrCO 3 and 50% SrZrO 3 in the centre of the tape. A series of tapes with twist lengths down to 3.4 mm was prepared. We present the measured AC losses of these tapes in external perpendicular magnetic fields. By using existing models, a description of the losses in the low Ḃ range was possible, leading to a separation into hysteresis, eddy current and coupling current losses. The frequency dependent loss contribution is dominated by the coupling current losses, from which the coupling current decay time constant, the effective permeability, the matrix resistivity and the critical Ḃc for filament coupling were extracted. In tapes with a twist length below 5 mm the typical loss behaviour for decoupled filaments is observed at frequencies up to 500 Hz. Compared to the untwisted tapes, a loss reduction of up to 70% for low field amplitudes (below 10 mT) was achieved.

  5. Development of dielectrophoresis separator with an insulating porous membrane using DC-Offset AC Electric Fields.

    PubMed

    Hakoda, Masaru

    2016-09-01

    Our previous studies revealed that the dielectrophoresis method is effective for separating cells having different dielectric properties. The purpose of this study was to evaluate the separation characteristics of two kinds of cells by direct current (DC) voltage offset/alternating current (AC) voltage using an insulating porous membrane dielectrophoretic separator. The separation device gives dielectrophoretic (DEP) force and electrophoretic (EP) force to dispersed particles by applying the DC-offset AC voltage. This device separates cells of different DEP properties by adopting a structure in which only the parallel plate electrodes and the insulating porous membrane are disposed in the flow path through which the cell-suspension flows. The difference in the retention ratios of electrically homogeneous 4.5 μm or 20.0 μm diameter standard particles was a maximum of 82 points. Furthermore, the influences of the AC voltage or offset voltage on the retention ratios of mouse hybridoma 3-2H3 cells and horse red blood cells (HRBC) were investigated. The difference in the retention ratio of the two kinds of cells was a maximum of 56 points. The separation efficiency of this device is expected to be improved by changing the device shape, number of pores, and pore placement. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1292-1300, 2016.

  6. 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.

  7. Geometric effects in applied-field MPD thrusters

    NASA Technical Reports Server (NTRS)

    Myers, R. M.; Mantenieks, M.; Sovey, James S.

    1990-01-01

    Three applied-field magnetoplasmadynamic (MPD) thruster geometries were tested with argon propellant to establish the influence of electrode geometry on thruster performance. The thrust increased approximately linearly with anode radius, while the discharge and electrode fall voltages increased quadratically with anode radius. All these parameters increased linearly with applied-field strength. Thrust efficiency, on the other hand, was not significantly influenced by changes in geometry over the operating range studied, though both thrust and thermal efficiencies increased monotonically with applied field strength. The best performance, 1820 sec I(sub sp) at 20 percent efficiency, was obtained with the largest radius anode at the highest discharge current (1500 amps) and applied field strength (0.4 Tesla).

  8. Geometric effects in applied-field MPD thrusters

    NASA Technical Reports Server (NTRS)

    Myers, R. M.; Mantenieks, M.; Sovey, J.

    1990-01-01

    Three applied-field magnetoplasmadynamic (MPD) thruster geometries were tested with argon propellant to establish the influence of electrode geometry on thruster performance. The thrust increased approximately linearly with anode radius, while the discharge and electrode fall voltages increased quadratically with anode radius. All these parameters increased linearly with applied-field strength. Thrust efficiency, on the other hand, was not significantly influenced by changes in geometry over the operating range studied, though both thrust and thermal efficiencies increased monotonically with applied field strength. The best performance, 1820 sec I (sub sp) at 20 percent efficiency, was obtained with the largest radius anode at the highest discharge current (1500 amps) and applied field strength (0.4 Tesla).

  9. A preliminary characterization of applied-field MPD thruster plumes

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Wehrle, David; Vernyi, Mark; Biaglow, James; Reese, Shawn

    1991-01-01

    Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied field magnetohydrodynamic thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no measurable impact on the plume characteristics. For all cases studied the plume was highly ionized, though spectral lines of neutral species were always present. Centerline electron densities and temperatures ranged from 2 times 10 (exp 18) to 8 times 10 (exp 18) m(exp -3) and from 7500 to 20,000 K, respectively. The plume was strongly confined by the magnetic field, with radial density gradients increasing monotonically with applied field strength. Plasma potential measurements show a strong effect of the magnetic field on the electrical conductivity and indicate the presence of radial current conduction in the plume.

  10. A preliminary characterization of applied-field MPD thruster plumes

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Wehrle, David; Vernyi, Mark; Biaglow, James; Reese, Shawn

    1991-01-01

    Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied-field MPD thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no measurable impact on the plume characteristics. For all cases studied the plume was highly ionized, though spectral lines of neutral species were always present. Centerline electron densities and temperatures ranged from 2 x 10 to the 18th to 8 x 10 to the 18th cu m and from 7500 to 20,000 K, respectively. The plume was strongly confined by the magnetic field, with radial density gradients increasing monotonically with applied field strength. Plasma potential measurements show a strong effect of the magnetic field on the electrical conductivity and indicate the presence of radial current conduction in the plume.

  11. Periodicals in the Field of Applied Linguistics. An International Survey.

    ERIC Educational Resources Information Center

    Okreglak, Ludmila, Comp.; Taylor, Marcia E., Comp.

    This volume lists and classifies journal literature in the field of applied linguistics. More than 200 periodicals are cited. Although emphasis is placed on publications dealing with language teaching, journals concerned with other aspects of applied linguistics are also included. The entries are arranged in alphabetical order, with foreign…

  12. Deep Vadose Zone Applied Field Research Initiative (DVZ AFRI) - Overview

    SciTech Connect

    2011-02-01

    The Deep Vadoze Zone Applied Field Research Initiative (DVZ AFRI) was established to protect water resources and to address the challenge of preventing contamination in the deep vadose zone from reaching groundwater. This factsheet provides an overview of the initiative and the approach to integrate basic science and needs-driven applied research activities with cleanup operations.

  13. Reversal of a body image disorder (macrosomatognosia) in Parkinson's disease by treatment with AC pulsed electromagnetic fields.

    PubMed

    Sandyk, R

    1998-02-01

    Macrosomatognosia refers to a disorder of the body image in which the patient perceives a part or parts of his body as disproportionately large. Macrosomatognosia has been associated with lesions in the parietal lobe, particularly the right parietal lobe, which integrates perceptual-sensorimotor functions concerned with the body image. It has been observed most commonly in patients with paroxysmal cerebral disorders such as epilepsy and migraine. The Draw-a-Person-Test has been employed in neuropsychological testing to identify disorders of the body image. Three fully medicated elderly Parkinsonian patients who exhibited, on the Draw-a-Person Test, macrosomatognosia involving the upper limbs are presented. In these patients spontaneous drawing of the figure of a man demonstrated disproportionately large arms. Furthermore, it was observed that the arm affected by tremor or, in the case of bilateral tremor, the arm showing the most severe tremor showed the greatest abnormality. This association implies that dopaminergic mechanisms influence neuronal systems in the nondominant right parietal lobe which construct the body image. After receiving a course of treatments with AC pulsed electromagnetic fields (EMFs) in the picotesla flux density applied transcranially, these patients' drawings showed reversal of the macrosomatognosia. These findings demonstrate that transcranial applications of AC pulsed EMFs affect the neuronal systems involved in the construction of the human body image and additionally reverse disorders of the body image in Parkinsonism which are related to right parietal lobe dysfunction.

  14. Spectral response of atmospheric electric field measurements near AC high voltage power lines

    NASA Astrophysics Data System (ADS)

    Silva, H. G.; Matthews, J. C.; Wright, M. D.; Shallcross, D. E.

    2015-10-01

    To understand the influence of corona ion emission on the atmospheric electrical field, measurements were made near to two AC high voltage power lines. A JCI 131 field-mill recorded the atmospheric electric field over one year. Meteorological measurements were also taken. The data series is divided in four zones (dependent on wind direction): whole zones, Z0; zone 1, Z1; zone 2, Z2; zone 3, Z3. Z3 is the least affected by corona ion emission and for that reason it is used as a reference against Z1 and Z2, which are strongly influenced by this phenomena. Analysis was undertaken for all weather days and dry days only. The Lomb-Scargle strategy developed for unevenly spaced time-series is used to calculate the spectral response of the aforementioned zones. Only frequencies above 1 minute are considered.

  15. Field Crop Nutrition--Applied Science Concepts. Student Manual.

    ERIC Educational Resources Information Center

    Miller, Charles R.

    This manual is designed to help agricultural education students to determine and provide the proper kinds and amounts of nutrients for the field crops they produce. The manual provides many learning situations regarding field crops--for example, determining nutrient needs, diagnosing nutrient shortages, and selecting and applying fertilizer and…

  16. DC and AC Electric Field Measurements by Spin-Plane Double Probes Onboard MMS

    NASA Astrophysics Data System (ADS)

    Lindqvist, P. A.; Marklund, G. T.; Khotyaintsev, Y. V.; Ergun, R. E.; Goodrich, K.; Torbert, R. B.; Argall, M. R.; Nakamura, R.

    2015-12-01

    The four spacecraft of the NASA Magnetospheric Multiscale mission (MMS) were launched on 12 March 2015 into a 1.2 x 12 Re equatorial orbit to study energy conversion processes in Earth's magnetosphere. After a 5-month commissioning period the first scientific phase starts on 1 September as the orbit enters the dusk magnetopause region. The Spin-plane Double Probe electric field instrument (SDP), part of the electric and magnetic fields instrument suite FIELDS, measures the electric field in the range 0.3 - 500 mV/m with a continuous time resolution up to 8192 samples/s. The instrument features adjustable bias currents and guard voltages to optimize the measurement performance. SDP also measures the spacecraft potential, which can be controlled by the Active Spacecraft Potential Control (ASPOC) ion emitter, and under certain conditions can be used to determine plasma density. We present observations of DC and AC electric fields in different plasma regions covered by MMS since launch including the night side flow braking region, reconnection regions at the dusk and dayside magnetopause, and in the magnetosheath. We compare the electric field measurements by SDP to other, independent determinations of the electric field, in particular by the Electron Drift Instrument (EDI), in order to assess the accuracy of the electric field measurement under different plasma conditions. We also study the influence of the currents emitted by ASPOC and EDI on the SDP measurements.

  17. Tuning polymer nanocomposite morphology: AC electric field manipulation of epoxy-montmorillonite (clay) suspensions

    SciTech Connect

    Koerner,H.; Jacobs, D.; Tomlin, D.; Busbee, J.; Vaia, R.

    2004-01-01

    The next revolutionary leap forward for polymer nano-'composites' necessitates the development of tools to transform the currently random or ill-defined nanoscale morphologies into compositionally and spatially engineered hierarchal structures, paralleling that underpinning conventional continuous fiber reinforced composites and enabling experimental verification of morphology-mechanical property correlations. Here in, utilization of AC electric fields of modest strength (1-10 V/micron) is demonstrated as a general approach to align organically modified layered silicates (OLS) parallel to the electric field-enhancing CTE, modulus and optical clarity in the reinforced direction. Interfacial polarization arising from electrophoric motion of the organic-modifier on the layer surface induces a dipole parallel to the plane of the layer, which couples to the external field. Comparably, application of a static magnetic field (0.5-2 T) induces alignment of the layers parallel or perpendicular to the field, depending on the chemical composition of the OLS. The impact of field magnitude, field frequency, dielectric permittivity and magnetic permeability of the system is discussed to elucidate the molecular characteristics of induced dipole formation and establish the limits of the process.

  18. Tuning Polymer Nanocomposite Morphology: Magnetic and AC Electric Field Manipulation of Epoxy - Montmorillonite (Clay) Suspensions

    NASA Astrophysics Data System (ADS)

    Vaia, Richard; Koerner, Hilmar; Jacobs, J. David; Busbee, John; Hampton, Edwin; Dean, Derrick

    2004-03-01

    The next revolutionary leap forward for polymer nano-'composites' necessitates the development of tools to transform the currently random or ill-defined nanoscale morphologies into compositionally and spatially engineered hierarchal structures, paralleling that underpinning conventional continuous fiber reinforced composites and enabling experimental verification of morphology-mechanical property correlations. Here in, utilization of AC electric fields of modest strength (1-10 V/micron) is demonstrated as a general approach to align organically modified layered silicates (OLS) parallel to the electric field - enhancing CTE, modulus and optical clarity in the reinforced direction. Interfacial polarization arising from electrophoric motion of the organic-modifier on the layer surface induces a dipole parallel to the plane of the layer, which couples to the external field. Comparably, application of a static magnetic field (0.5-2 T) induces alignment of the layers parallel or perpendicular to the field, depending on the chemical composition of the OLS. The impact of field magnitude, field frequency, dielectric permittivity and magnetic permeability of the system is discussed to elucidate the molecular characteristics of induced dipole formation and establish the limits of the process.

  19. Boson mapping techniques applied to constant gauge fields in QCD

    NASA Technical Reports Server (NTRS)

    Hess, Peter Otto; Lopez, J. C.

    1995-01-01

    Pairs of coordinates and derivatives of the constant gluon modes are mapped to new gluon-pair fields and their derivatives. Applying this mapping to the Hamiltonian of constant gluon fields results for large coupling constants into an effective Hamiltonian which separates into one describing a scalar field and another one for a field with spin two. The ground state is dominated by pairs of gluons coupled to color and spin zero with slight admixtures of color zero and spin two pairs. As color group we used SU(2).

  20. 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.

  1. 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.

  2. Effect of interaction between AC electric field and phonon oscillation of metal cluster on tip-growth of carbon nanotube

    NASA Astrophysics Data System (ADS)

    Saeidi, Mohammadreza

    2015-06-01

    The paper reports effect of interaction between AC electric field and metal cluster sitting at tip end of the carbon nanotube (CNT) on CNT tip-growth in CVD theoretically. For this purpose, a theoretical model based on phonon oscillations of the metal catalyst and influence of AC electric field on these oscillations is presented. Results show that there is an optimum AC electric field which optimizes growth of ultra-long CNTs. Then it is demonstrated that, in comparison with CNTs in the absence of field, CNTs under optimum electric field grow more. In addition, relation between optimum temperature and amplitude of AC electric field is investigated and it is shown that increasing electric field leads to higher optimum temperature. Finally, Investigation of effect of catalyst type on optimum electric field demonstrates the optimum field for various catalysts is different due to their different characteristics including van der Waals interaction with carbon, atomic mass and number of free charge carriers per each atom. All results are discussed and interpreted.

  3. Thermodynamics of the Stockmayer fluid in an applied field

    NASA Astrophysics Data System (ADS)

    Elfimova, Ekaterina A.; Ivanov, Alexey O.; Sindt, Julien O.; Camp, Philip J.

    2015-12-01

    The thermodynamic properties of the Stockmayer fluid in an applied field are studied using theory and computer simulation. Theoretical expressions for the second and third virial coefficients are obtained in terms of the dipolar coupling constant (λ, measuring the strength of dipolar interactions as compared to thermal energy) and dipole-field interaction energy (α, being proportional to the applied field strength). These expressions are tested against numerical results obtained by Mayer sampling calculations. The expression for the second virial coefficient contains terms up to λ4, and is found to be accurate over realistic ranges of dipole moment and temperature, and over the entire range of the applied field strength (from zero to infinity). The corresponding expression for the third virial coefficient is truncated at λ3, and is not very accurate: higher order terms are very difficult to calculate. The virial coefficients are incorporated in to a thermodynamic theory based on a logarithmic representation of the Helmholtz free energy. This theory is designed to retain the input virial coefficients, and account for some higher order terms in the sense of a resummation. The compressibility factor is obtained from the theory and compared to results from molecular dynamics simulations with a typical value λ = 1. Despite the mathematical approximations of the virial coefficients, the theory captures the effects of the applied field very well. Finally, the vapour-liquid critical parameters are determined from the theory, and compared to published simulation results; the agreement between the theory and simulations is good.

  4. Enhanced proton acceleration in an applied longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Arefiev, A.; Toncian, T.; Fiksel, G.

    2016-10-01

    Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic field impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the laser energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT-level magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The possibility of improving characteristics of laser-driven proton beams using such fields is a strong motivation for further development of laser-driven magnetic field capabilities.

  5. Anode power deposition in applied-field MPD thrusters

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Soulas, George C.

    1992-01-01

    Anode power deposition is the principal performance limiter of magnetoplasmadynamic (MPD) thrusters. Current thrusters lose between 50 and 70 percent of the input power to the anode. In this work, anode power deposition was studied for three cylindrical applied magnetic field thrusters for a range of argon propellant flow rates, discharge currents, and applied-field strengths. Between 60 and 95 percent of the anode power depositions resulted from electron current conduction into the anode, with cathode radiation depositing between 5 and 35 percent of the anode power, and convective heat transfer from the hot plasma accounting for less than 5 percent. While the fractional anode power loss decreased with increasing applied-field strength and anode size, the magnitude of the anode power increased. The rise in anode power resulted from a linear rise in the anode fall voltage with applied-field strength and anode radius. The anode fall voltage also rose with decreasing propellant flow rate. The trends indicate that the anode fall region is magnetized, and suggest techniques for reducing the anode power loss in MPD thrusters.

  6. Anode power deposition in applied-field MPD thrusters

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Soulas, George C.

    1992-01-01

    Anode power deposition is the principle performance limiter of magnetoplasmadynamic (MPD) thrusters. Current thrusters lose between 50 and 70 percent of the input power to the anode. In this work, anode power deposition was studied for three cylindrical applied magnetic field thrusters for a range of argon propellant flow rates, discharge currents, and applied-field strengths. Between 60 and 95 percent of the anode power deposition resulted from electron current conduction into the anode, with cathode radiation depositing between 5 and 35 percent of the anode power, and convective heat transfer from the hot plasma accounting for less than 5 percent. While the fractional anode power loss decreased with increasing applied-field strength and anode size, the magnitude of the anode power increased. The rise in anode power resulted from a linear rise in the anode fall voltage with applied-field strength and anode radius. The anode fall voltage also rose with decreasing propellant flow rate. The trends indicate that the anode fall region is magnetized, and suggest techniques for reducing the anode power loss in MPD thrusters.

  7. Comprehensive analysis of human cells motion under an irrotational AC electric field in an electro-microfluidic chip.

    PubMed

    Vaillier, Clarisse; Honegger, Thibault; Kermarrec, Frédérique; Gidrol, Xavier; Peyrade, David

    2014-01-01

    AC electrokinetics is a versatile tool for contact-less manipulation or characterization of cells and has been widely used for separation based on genotype translation to electrical phenotypes. Cells responses to an AC electric field result in a complex combination of electrokinetic phenomena, mainly dielectrophoresis and electrohydrodynamic forces. Human cells behaviors to AC electrokinetics remain unclear over a large frequency spectrum as illustrated by the self-rotation effect observed recently. We here report and analyze human cells behaviors in different conditions of medium conductivity, electric field frequency and magnitude. We also observe the self-rotation of human cells, in the absence of a rotational electric field. Based on an analytical competitive model of electrokinetic forces, we propose an explanation of the cell self-rotation. These experimental results, coupled with our model, lead to the exploitation of the cell behaviors to measure the intrinsic dielectric properties of JURKAT, HEK and PC3 human cell lines.

  8. Comprehensive Analysis of Human Cells Motion under an Irrotational AC Electric Field in an Electro-Microfluidic Chip

    PubMed Central

    Kermarrec, Frédérique; Gidrol, Xavier; Peyrade, David

    2014-01-01

    AC electrokinetics is a versatile tool for contact-less manipulation or characterization of cells and has been widely used for separation based on genotype translation to electrical phenotypes. Cells responses to an AC electric field result in a complex combination of electrokinetic phenomena, mainly dielectrophoresis and electrohydrodynamic forces. Human cells behaviors to AC electrokinetics remain unclear over a large frequency spectrum as illustrated by the self-rotation effect observed recently. We here report and analyze human cells behaviors in different conditions of medium conductivity, electric field frequency and magnitude. We also observe the self-rotation of human cells, in the absence of a rotational electric field. Based on an analytical competitive model of electrokinetic forces, we propose an explanation of the cell self-rotation. These experimental results, coupled with our model, lead to the exploitation of the cell behaviors to measure the intrinsic dielectric properties of JURKAT, HEK and PC3 human cell lines. PMID:24736275

  9. 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.

  10. 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.

  11. HST Imagery of the Kepler Field-of-view Acquired with the WFPC2 and with the ACS

    NASA Astrophysics Data System (ADS)

    Verner, Ekaterina; Bruhweiler, F.; Kondo, Y.; Borucki, W. J.; Koch, D.; Batalha, N.; Kepler Team

    2010-01-01

    Hubble Space Telescope (HST) imagery of four fields in the large Kepler Field-of-View (FOV) acquired with the WFPC2 and four reference star fields on the Galactic Equator with the ACS have been obtained and analyzed. The detected stars in the 18th to 26th magnitude range and the faint galaxies represent background objects to targets for the Kepler FOV. The WFPC2 dataset using the F606W filter consisted of dithered images. This dithering technique included a "multidrizzle” algorithm to enhance signal-to-noise and resolution in the four WFPC2 fields. As comparison fields, the HST/ACS data were acquired in the F606W and the F812W filters with total exposure time of 14340 sec. In the reduced WFPC and ACS images, we used SEXTRACTOR to identify stars and their positions in the sky, then the PYRAF and STSDAS/photometry packages to measure star magnitudes. We have created catalogs of the observed stars as well as generated V-I versus V color diagrams for the ACS observed fields. This information reveals stellar statistics as well as photometrical properties for individual stars and binary systems. The analysis of these WFPC2 and ACS images are essential to ascertain the level of photometric uncertainty in Kepler photometry used to search for transits of earth-like planets. The WFPC2 imagery for KEPLER FOV data show noticeable contributions from faint background galaxies not seen in the ACS dataset obtained at the Galactic Equator. This work has been supported through a Guest Observer program grant, GO-10166, from the Space Telescope Science Institute.

  12. Spontaneous AC Field Induced Mechanical Rotation in Magnetostrictive FeSiB-Based Wires Subjected to Thermal Treatments

    DTIC Science & Technology

    2001-04-01

    MAGNETOSTRICTIVE FeSiB-BASED WIRES SUBJECTED TO THERMAL TREATMENTS V.Raposo1 2, A.Mitra1," 3 and M.Vizquez 1 1 Instituto de Ciencia de Materiales de Madrid...INTRODUCTION The mechanical rotation of Fe base amorphous wires with bistable magnetic behavior when subjected to an alternating AC field of several kHz...The aim of this work has been to study the AC field induced rotation of Feyy.5 Si7 .5B 15 and Fe 73.5 Si]3.5B9Cu1 Nb3 amorphous wires exhibiting large

  13. Nanomaterial-assisted PCR based on thermal generation from magnetic nanoparticles under high-frequency AC magnetic fields

    NASA Astrophysics Data System (ADS)

    Higashi, Toshiaki; Minegishi, Hiroaki; Echigo, Akinobu; Nagaoka, Yutaka; Fukuda, Takahiro; Usami, Ron; Maekawa, Toru; Hanajiri, Tatsuro

    2015-08-01

    Here the authors present a nanomaterial-assisted PCR technique based on the use of thermal generation from magnetic nanoparticles (MNPs) under AC magnetic fields. In this approach, MNPs work as internal nano thermal generators to realize PCR thermal cycling. In order to suppress the non-specific absorption of DNA synthetic enzymes, MNPs are decorated with bovine serum albumin (BSA), forming BSA/MNP complexes. Under high-frequency AC magnetic fields, these complexes work as internal nano thermal generators, thereby producing the typical temperature required for PCR thermal cycling, and perform all the reaction processes of PCR amplification in the place of conventional PCR thermal cyclers.

  14. 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.

  15. 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.

  16. Concentration-tuned interactions and structures in flowing suspensions under a gradient AC electric field

    NASA Astrophysics Data System (ADS)

    Tada, Shigeru; Qiu, Zhiyong; Shen, Yan

    2016-11-01

    In this study, numerical simulations of suspensions of Al2O3 particles in corn oil at various volume fractions were performed to explore the mechanisms involved in the electro-mechanical behavior of positive polarized particles suspended in an insulated suspending medium traveling through a rotating flow channel while exposed to a nonuniform AC electric field. A theoretical model was developed to simulate the trajectories of individual particles under the action of dielectrophoretic (DEP), dipole-dipole interparticle, viscous, and gravitational forces in a laminar flow. The results demonstrated that particles began to aggregate along the edges of electrodes with electric field application. New particles coming from more distant regions then gradually joined the vertices of particle aggregates, leading to the growth of chain-like clusters along the electric field gradient. Predictions showed good agreement with the results observed in a previous experiment. The new findings of this study are that the DEP force always tends to confine particles near the electrode edges, whereas the clustering of particles on the electrodes arises from the competition between particle interaction due to the DEP force and the long-range dipole-dipole interparticle interaction with neighboring particles. This process became more apparent with higher volume fractions of particle.

  17. A low frequency MEMS energy harvester scavenging energy from magnetic field surrounding an AC current-carrying wire

    NASA Astrophysics Data System (ADS)

    Olszewski, Oskar Z.; Houlihan, Ruth; Mathewson, Alan; Jackson, Nathan

    2016-10-01

    This paper reports on a low frequency piezoelectric energy harvester that scavenges energy from a wire carrying an AC current. The harvester is described, fabricated and characterized. The device consists of a silicon cantilever with integrated piezoelectric capacitor and proof-mass that incorporates a permanent magnet. When brought close to an AC current carrying wire, the magnet couples to the AC magnetic field from a wire, causing the cantilever to vibrate and generate power. The measured average power dissipated across an optimal resistive load was 1.5 μW. This was obtained by exciting the device into mechanical resonance using the electro-magnetic field from the 2 A source current. The measurements also reveal that the device has a nonlinear response that is due to a spring hardening mechanism.

  18. Enhanced proton acceleration in an applied longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Toncian, Toma; Arefiev, Alexey; Fiksel, Gennady

    2016-10-01

    Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the laser energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The predicted improved characteristics of laser-driven proton beams would be critical for a number of applications. The work was supported by U.S. Department of Energy - National Nuclear Security Administration Cooperative Agreement No. DE-NA0002008. HPC resources were provided by the Texas Advanced Computing Center at The University of Texas.

  19. Frequency Domain Analysis of Beat-Less Control Method for Converter-Inverter Driving Systems Applied to AC Electric Cars

    NASA Astrophysics Data System (ADS)

    Kimura, Akira

    In inverter-converter driving systems for AC electric cars, the DC input voltage of an inverter contains a ripple component with a frequency that is twice as high as the line voltage frequency, because of a single-phase converter. The ripple component of the inverter input voltage causes pulsations on torques and currents of driving motors. To decrease the pulsations, a beat-less control method, which modifies a slip frequency depending on the ripple component, is applied to the inverter control. In the present paper, the beat-less control method was analyzed in the frequency domain. In the first step of the analysis, transfer functions, which revealed the relationship among the ripple component of the inverter input voltage, the slip frequency, the motor torque pulsation and the current pulsation, were derived with a synchronous rotating model of induction motors. An analysis model of the beat-less control method was then constructed using the transfer functions. The optimal setting of the control method was obtained according to the analysis model. The transfer functions and the analysis model were verified through simulations.

  20. Influence of AC external magnetic field on guidance force relaxation between HTS bulk and NdFeB guideway

    NASA Astrophysics Data System (ADS)

    Zhang, Longcai; Wang, Suyu; Wang, Jiasu; Zheng, Jun

    2007-12-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to time-varying external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. So it is required to study whether the guidance force of the bulks is influenced by the inhomogeneity. In this paper, we studied the characteristics of the guidance force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experiment results, it was found that the guidance force was decreased with the application of the AC external magnetic field, and the decay increased with the amplitude and was almost independent of the frequency.

  1. Degradation of Cry1Ac protein within transgenic Bacillus thuringiensis rice tissues under field and laboratory conditions.

    PubMed

    Li, Yunhe; Wu, Kongming; Zhang, Yongjun; Yuan, Guohui

    2007-10-01

    To clarify the environmental fate of the Cry1Ac protein from Bacillus thuringiensis subsp. kurstaki (Bt) contained in transgenic rice plant stubble after harvest, degradation was monitored under field conditions using an enzyme-linked immunosorbent assay. In stalks, Cry1Ac protein concentration decreased rapidly to 50% of the initial amount during the first month after harvest; subsequently, the degradation decreased gradually reaching 21.3% when the experiment was terminated after 7 mo. A similar degradation pattern of the Cry1Ac protein was observed in rice roots. However, when the temperature increased in April of the following spring, protein degradation resumed, and no protein could be detected by the end of the experiment. In addition, a laboratory experiment was conducted to study the persistence of Cry1Ac protein released from rice tissue in water and paddy soil. The protein released from leaves degraded rapidly in paddy soil under flooded conditions during the first 20 d and plateaued until the termination of this trial at 135 d, when 15.3% of the initial amount was still detectable. In water, the Cry1Ac protein degraded more slowly than in soil but never entered a relatively stable phase as in soil. The degradation rate of Cry1Ac protein was significantly faster in nonsterile water than in sterile water. These results indicate that the soil environment can increase the degradation of Bt protein contained in plant residues. Therefore, plowing a field immediately after harvest could be an effective method for decreasing the persistence of Bt protein in transgenic rice fields.

  2. Magneto-electric response of iron garnet film micromagnetic structure on combined action of AC and DC electric field

    NASA Astrophysics Data System (ADS)

    Koronovskyy, Vadim; Vakyla, Yuri

    2015-11-01

    Changes in the domain structure of epitaxial ferrite-garnet films under joint action of DC and AC electric fields and DC magnetic field were investigated by the optical polarimetry method. The effect of broadening of the domain wall image was found under specified combined influences. The investigations revealed that visual manifestation of the effect strongly depends on the curvature of the domain walls and the orientation of the magnetic field relative to the sample plane. Analyzing our results, we note that reaction of the domain structure to influence of external electric fields was caused by changing the magnetic anisotropy parameters of ferrite garnets in an electric field. [Figure not available: see fulltext.

  3. Electric current quadratic in an applied electric field

    NASA Astrophysics Data System (ADS)

    Deyo, Eric

    The theory of the photogalvanic effect in a low frequency electric field is developed. We complete the semiclassical theory of the effect in bulk samples lacking inversion symmetry, taking into account contributions from the asymmetry of scattering, the shift current, and the effect of Berry's phase. We consider the effect in such samples both in the presence and absence of a constant magnetic field. It is found that by experimentally measuring this effect, that Berry's curvature and the average shift of the center of mass of an electron during a scattering event can be extracted. We also investigate the magnetic field dependence of the part of the electrical current which is quadratic in voltage in mesoscopic conductors. We find that the part of the current which is quadratic in bias voltage, and linear in an applied magnetic field can be related to the effective electron-electron interaction strength. We also find that in the case when the magnetic field is oriented parallel to the plane of a two dimensional sample, that the spin-orbit scattering rate can be measured.

  4. Protein kinase C activity is altered in HL60 cells exposed to 60 Hz AC electric fields

    SciTech Connect

    Holian, O.; Reyes, H.M.; Attar, B.M.; Walter, R.J.; Astumian, R.D.; Lee, R.C.

    1996-12-31

    The authors examined the effects of electric fields (EFs) on the activity and subcellular distribution of protein kinase C (PKC) of living HL60 cells. Sixty Hertz AC sinusoidal EFs (1.5--1,000 mV/cm p-p) were applied for 1 h to cells (10{sup 7}/ml) in Teflon chambers at 37 C in the presence or absence of 2 {micro}M phorbol 12-myristate 13-acetate (PMA). PMA stimulation alone evoked intracellular translocation of PKC from the cytosolic to particulate fractions. In cells that were exposed to EFs (100--1,000 mV/cm) without PMA, a loss of PKC activity from the cytosol, but no concomitant rise in particulate PKC activity, was observed. In the presence of PMA, EFs (33--330 mV/cm) also accentuated the expected loss of PKC activity from the cytosol and augmented the rise in PKC activity in the particulate fraction. These data show that EFs alone or combined with PMA promote down-regulation of cytosolic PKC activity similar to that evoked by mitogens and tumor promoters but that it does not elicit the concomitant rise in particulate activity seen with those agents.

  5. 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.

  6. Near-field optical taper antennas fabricated with a highly replicable ac electrochemical etching method

    NASA Astrophysics Data System (ADS)

    Kharintsev, Sergey S.; Noskov, Alexey I.; Hoffmann, Günter G.; Loos, Joachim

    2011-01-01

    This paper describes a novel chemical etching method to fabricate high quality near-field optical antennas—tapered metallic tips—from gold wire in a reproducible way for optically probing a specimen on the nanoscale. A new type of an electrochemical cell is introduced and different dc and ac etching regimes are studied in detail. The formation and dynamics of a meniscus around a gold wire immersed in an electrolyte when supplying a square wave voltage are considered. We show that in situ etching current kinetics allows one to improve a yield of tips with a well-defined geometry up to 95% by filtering these on the basis of a cutoff current and a power spectrum of etching current fluctuations. As a quantitative measure for estimating the yield we introduce a probability to find tips with curvature radii falling in the range of interest. Testing the tips for a plasmonic effect is implemented with tip-enhanced Raman spectroscopy and sub-wavelength imaging of a thin fullerene film.

  7. 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.

  8. 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.

  9. δ-FeOOH: a superparamagnetic material for controlled heat release under AC magnetic field

    NASA Astrophysics Data System (ADS)

    Chagas, Poliane; da Silva, Adilson Cândido; Passamani, Edson Caetano; Ardisson, José Domingos; de Oliveira, Luiz Carlos Alves; Fabris, José Domingos; Paniago, Roberto M.; Monteiro, Douglas Santos; Pereira, Márcio César

    2013-04-01

    Experimental evidences on its in vitro use reveal that δ-FeOOH is a material that release-controlled amount of heat if placed under an AC magnetic field. δ-FeOOH nanoparticles were prepared by precipitating Fe(OH)2 in alkaline solution followed by fast oxidation with H2O2. XRD and 57Fe Mössbauer spectroscopy data confirmed that δ-FeOOH is indeed the only iron-bearing compound in the produced sample. TEM images evidence that the averaged particle sizes for this δ-FeOOH sample is 23 nm. Magnetization measurements indicate that these δ-FeOOH particles behave superparamagnetically at 300 K; its saturation magnetization was found to be 13.2 emu g-1; the coercivity and the remnant magnetization were zero at 300 K. The specific absorption rate values at 225 kHz were 2.1, 6.2, and 34.2 W g-1, under 38, 64, and 112 mT, respectively. The release rate of heat can be directly controlled by changing the mass of δ-FeOOH nanoparticles. In view of these findings, the so-prepared δ-FeOOH is a real alternative to be further tested as a material for medical practices in therapies involving magnetic hyperthermia as in clinical oncology.

  10. On the influence of applied fields on spinel formation

    SciTech Connect

    KORTE,C.; FARER,J.K.; RAVISHANKAR,N.; MICHAEL,JOSEPH R.; SCHMALZRIED,J.; CARTER,C.B.

    2000-04-04

    Interfaces play an important role in determining the effect of electric fields on the mechanism of the formation spinel by solid-state reaction. The reaction occurs by the movement of phase boundaries but the rate of this movement can be affected by grain boundaries in the reactants or in the reaction product. Only by understanding these relationships will it be possible to engineer their behavior. As a particular example of such a study, MgIn{sub 2}O{sub 4} can be formed by the reaction between single-crystal MgO substrate and a thin film of In{sub 2}O{sub 3} with or without an applied electric field. High-resolution backscattered electron (BSE) imaging and electron backscattered diffraction (EBSD) in a scanning electron microscope (SEM) has been used to obtain complementary chemical and crystallographic information.

  11. Nonlinear dependence of complex plasma parameters on applied electric field

    SciTech Connect

    Sodha, M. S.; Mishra, S. K.; Misra, Shikha

    2011-02-15

    This paper presents an analysis of the effect of an applied static or alternating electric field on the electron density and temperature, charge on the particles, the electron collision frequency, the electronic conductivity, and the coefficient of electron diffusion in a complex plasma (i) when not illuminated by light, which can cause photoelectric emission from the particles, and (ii) when so illuminated. A parametric analysis based on computations for some typical sets of parameters has also been made. The significance of this work to (i) the disappearance of a polar mesospheric summer echoes structure by radio wave and (ii) magneto-hydrodynamic (MHD) power generation has also been indicated. The time dependence of the various parameters after the application of the electric field has also been discussed.

  12. The virtual fields method applied to spalling tests on concrete

    NASA Astrophysics Data System (ADS)

    Pierron, F.; Forquin, P.

    2012-08-01

    For one decade spalling techniques based on the use of a metallic Hopkinson bar put in contact with a concrete sample have been widely employed to characterize the dynamic tensile strength of concrete at strain-rates ranging from a few tens to two hundreds of s-1. However, the processing method mainly based on the use of the velocity profile measured on the rear free surface of the sample (Novikov formula) remains quite basic and an identification of the whole softening behaviour of the concrete is out of reach. In the present paper a new processing method is proposed based on the use of the Virtual Fields Method (VFM). First, a digital high speed camera is used to record the pictures of a grid glued on the specimen. Next, full-field measurements are used to obtain the axial displacement field at the surface of the specimen. Finally, a specific virtual field has been defined in the VFM equation to use the acceleration map as an alternative `load cell'. This method applied to three spalling tests allowed to identify Young's modulus during the test. It was shown that this modulus is constant during the initial compressive part of the test and decreases in the tensile part when micro-damage exists. It was also shown that in such a simple inertial test, it was possible to reconstruct average axial stress profiles using only the acceleration data. Then, it was possible to construct local stress-strain curves and derive a tensile strength value.

  13. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

    DOEpatents

    Chaffin, R.J.; Dawson, L.R.; Fritz, I.J.; Osbourn, G.C.; Zipperian, T.E.

    1984-04-19

    In a field-effect transistor comprising a semiconductor having therein a source, a drain, a channel and a gate in operational relationship, there is provided an improvement wherein said semiconductor is a superlattice comprising alternating quantum well and barrier layers, the quantum well layers comprising a first direct gap semiconductor material which in bulk form has a certain bandgap and a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, the barrier layers comprising a second semiconductor material having a bandgap wider than that of said first semiconductor material, wherein the layer thicknesses of said quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice having a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, and wherein the thicknesses of said quantum well layers are selected to provide a superlattice curve of electron velocity versus applied electric field whereby, at applied electric fields higher than that at which the maximum electron velocity occurs in said first material when in bulk form, the electron velocities are higher in said superlattice than they are in said first semiconductor material in bulk form.

  14. 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

  15. 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.

  16. Improved analog and AC performance with increased noise immunity using nanotube junctionless field effect transistor (NJLFET)

    NASA Astrophysics Data System (ADS)

    Rewari, Sonam; Nath, Vandana; Haldar, Subhasis; Deswal, S. S.; Gupta, R. S.

    2016-12-01

    In this paper for the first time, the noise immunity and analog performance of nanotube junctionless field effect transistor (NJLFET) has been investigated. Small signal AC performance metrics namely Scattering parameters (S-parameters) have been analyzed along with analog parameters to validate the suitability of NJLFET for RFIC design. NJLFET performance is examined by comparing its performance with junctionless gate-all-around (JLGAA) MOSFET. It has been inferred that NJLFET has improved I on/ I off ratio directing improved digital performance at higher channel lengths, reduced channel resistance ( R ch) which enables the MOSFET to provide a low resistance path to current and improved early voltage ( V EA) which shows the capability for high-gain amplification and higher g m/ g d directing high intrinsic dc gain. Higher f Tmax for NJLFET has been observed posing its potential for terahertz applications. Higher gain transconductance frequency product makes NJLFET an ultimate device for high-speed switching applications. Higher maximum transducer power gain in NJLFET implies higher power gain than JLGAA MOSFET. Also, NJLFET exhibits lower harmonic distortion and it has been explained by significant reduction in third-order derivative of transconductance, g m3. Reduction in g m3 shows that NJLFET provides better linearity over JLGAA and is more suitable for RFIC design. Also the S-parameters namely S11, S12, S21 and S22 have been analyzed to verify the small signal performance. A lower magnitude for reflection coefficients S11 and S22 depicts minimum reflection and higher matching between ports in NJLFET than JLGAA MOSFET. Higher voltage gains S12 and S21 are present in NJLFET than its counterpart which shows the higher gains that can be achieved using nanotube architecture. The noise metrics which are noise figure and noise conductance show significant reduction for NJLFET justifying its noise immunity.

  17. Laser ablation with applied magnetic field for electric propulsion

    NASA Astrophysics Data System (ADS)

    Batishcheva, Alla; Batishchev, Oleg; Cambier, Jean-Luc

    2012-10-01

    Using ultrafast lasers with tera-watt-level power allows efficient ablation and ionization of solid-density materials [1], creating dense and hot (˜100eV) plasma. We propose ablating small droplets in the magnetic nozzle configurations similar to mini-helicon plasma source [2]. Such approach may improve the momentum coupling compared to ablation of solid surfaces and facilitate plasma detachment. Results of 2D modeling of solid wire ablation in the applied magnetic field are presented and discussed. [4pt] [1] O. Batishchev et al, Ultrafast Laser Ablation for Space Propulsion, AIAA technical paper 2008-5294, -16p, 44th JPC, Hartford, 2008.[0pt] [2] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

  18. Destruction of Emulsions by an AC Electric Field: Importance of Partial Merging

    NASA Astrophysics Data System (ADS)

    Thiam, Abdou Rachid; Bremond, Nicolas; Bibette, Jerome

    2010-03-01

    Electrocoalescence is basically the process of blending droplets by the application of an electric field. The approach is used in petroleum refineries for the separation of water in oil emulsions (that is, by coalescing water droplets), and more recently in biotechnology industry, for the fusion of micro reactors. In a first step, we will focus on the coalesce condition for two drops under a given electric field. Microfluidics offers a comfortable setup therefore, as we sought to span a range of initial conditions in terms of the distance between the droplets, their sizes, and also a region of the applied electric field. Thus, we could establish a stability diagram according to the initial conditions and droplets' composition, which displays three domains referred to as: coalescence, no coalescence and a third one of partial coalescence, where the droplets coalesce for a brief moment then separate right afterwards. We proceeded then by generalizing the setup to the case of a stream of droplets, and we found that the evolution of the stream can be predicted by the behaviour of the local pairs of droplets, as seen in the previous step. The main outcome of that study is the total destruction of an emulsion above a critical volume fraction for a given amplitude of electric field.

  19. 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

    2016-03-02

    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.

  20. 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

  1. 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.

  2. THE HST EXTREME DEEP FIELD (XDF): COMBINING ALL ACS AND WFC3/IR DATA ON THE HUDF REGION INTO THE DEEPEST FIELD EVER

    SciTech Connect

    Illingworth, G. D.; Magee, D.; Oesch, P. A.; Stiavelli, M.; Van Dokkum, P. G.; Trenti, M.; Carollo, C. M.; Gonzalez, V.

    2013-11-01

    The eXtreme Deep Field (XDF) combines data from 10 years of observations with the Hubble Space Telescope Advanced Camera for Surveys (ACS) and the Wide-Field Camera 3 Infra-Red (WFC3/IR) into the deepest image of the sky ever in the optical/near-IR. Since the initial observations of the Hubble Ultra-Deep Field (HUDF) in 2003, numerous surveys and programs, including supernovae follow-up, HUDF09, CANDELS, and HUDF12, have contributed additional imaging data across this region. However, these images have never been combined and made available as one complete ultra-deep image dataset. We combine them now with the XDF program. Our new and improved processing techniques provide higher quality reductions of the total dataset. All WFC3/IR and optical ACS data sets have been fully combined and accurately matched, resulting in the deepest imaging ever taken at these wavelengths, ranging from 29.1 to 30.3 AB mag (5σ in a 0.''35 diameter aperture) in 9 filters. The combined image therefore reaches to 31.2 AB mag 5σ (32.9 at 1σ) for a flat f {sub ν} source. The gains in the optical for the four filters done in the original ACS HUDF correspond to a typical improvement of 0.15 mag, with gains of 0.25 mag in the deepest areas. Such gains are equivalent to adding ∼130 to ∼240 orbits of ACS data to the HUDF. Improved processing alone results in a typical gain of ∼0.1 mag. Our 5σ (optical+near-IR) SExtractor catalogs reveal about 14,140 sources in the full field and about 7121 galaxies in the deepest part of the XDF.

  3. 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.

  4. 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.

  5. Ac irreversibility line of bismuth-based high temperature superconductors

    SciTech Connect

    Mehdaoui, A.; Beille, J.; Berling, D.; Loegel, B.; Noudem, J.G.; Tournier, R.

    1997-09-01

    We discuss the magnetic properties of lead doped Bi-2223 bulk samples obtained through combined magnetic melt texturing and hot pressing (MMTHP). The ac complex susceptibility measurements are achieved over a broad ac field range (1 Oe{lt}h{sub ac}{lt}100 Oe) and show highly anisotropic properties. The intergranular coupling is improved in the direction perpendicular to the applied stress and magnetic field direction, and an intragranular loss peak is observed for the first time. A comparison is made with other bismuth-based compounds and it is shown that the MMTHP process shifts the ac irreversibility line (ac IL) toward higher fields. It is also shown that all the ac IL{close_quote}s for quasi 2D bismuth-based compounds show a nearly quadratic temperature dependence and deviate therefore strongly from the linear behavior observed in quasi 3D compounds and expected from a critical state model.{copyright} {ital 1997 Materials Research Society.}

  6. 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.

  7. Quantum analysis applied to thermo field dynamics on dissipative systems

    SciTech Connect

    Hashizume, Yoichiro; Okamura, Soichiro; Suzuki, Masuo

    2015-03-10

    Thermo field dynamics is one of formulations useful to treat statistical mechanics in the scheme of field theory. In the present study, we discuss dissipative thermo field dynamics of quantum damped harmonic oscillators. To treat the effective renormalization of quantum dissipation, we use the Suzuki-Takano approximation. Finally, we derive a dissipative von Neumann equation in the Lindbrad form. In the present treatment, we can easily obtain the initial damping shown previously by Kubo.

  8. Semantic Data And Visualization Techniques Applied To Geologic Field Mapping

    NASA Astrophysics Data System (ADS)

    Houser, P. I. Q.; Royo-Leon, M.; Munoz, R.; Estrada, E.; Villanueva-Rosales, N.; Pennington, D. D.

    2015-12-01

    Geologic field mapping involves the use of technology before, during, and after visiting a site. Geologists utilize hardware such as Global Positioning Systems (GPS) connected to mobile computing platforms such as tablets that include software such as ESRI's ArcPad and other software to produce maps and figures for a final analysis and report. Hand written field notes contain important information and drawings or sketches of specific areas within the field study. Our goal is to collect and geo-tag final and raw field data into a cyber-infrastructure environment with an ontology that allows for large data processing, visualization, sharing, and searching, aiding in connecting field research with prior research in the same area and/or aid with experiment replication. Online searches of a specific field area return results such as weather data from NOAA and QuakeML seismic data from USGS. These results that can then be saved to a field mobile device and searched while in the field where there is no Internet connection. To accomplish this we created the GeoField ontology service using the Web Ontology Language (OWL) and Protégé software. Advanced queries on the dataset can be made using reasoning capabilities can be supported that go beyond a standard database service. These improvements include the automated discovery of data relevant to a specific field site and visualization techniques aimed at enhancing analysis and collaboration while in the field by draping data over mobile views of the site using augmented reality. A case study is being performed at University of Texas at El Paso's Indio Mountains Research Station located near Van Horn, Texas, an active multi-disciplinary field study site. The user can interactively move the camera around the study site and view their data digitally. Geologist's can check their data against the site in real-time and improve collaboration with another person as both parties have the same interactive view of the data.

  9. Cultivating Kuumba: Applying Art Based Strategies to Any Field

    ERIC Educational Resources Information Center

    Ellis, Auburn Elizabeth

    2015-01-01

    There are many contemporary issues to address in adult education. This paper explores art-based strategies and the utilization of creativity (Kuumba) to expand learning for global communities in any field of practice. Benefits of culturally grounded approaches to adult education are discussed. Images from ongoing field research can be viewed at…

  10. A Student Run Field Exercise in Applied Tourism Geography

    ERIC Educational Resources Information Center

    De Bres, Karen; Coomansingh, Johnny

    2006-01-01

    The purpose of this paper is to discuss the field project and the field experiences of 60 undergraduates in a lower level geography course. Cumulative based learning was the main teaching technique. The Eisenhower Center, the Dickinson County Historical Society Museum, and Old Abilene Town, a renovated/reconstructed frontier town, were selected…

  11. Applied fields for energy conservation, water treatment, and industrial applications. Final report

    SciTech Connect

    Reimers, R.S.; Bock, S.F.; White, L.E.

    1986-06-01

    A detailed evaluation was performed on the use of applied fields (nonionizing radiations, ultrasound, magnetic fields, etc.) for industrial waste treatment, wastewater treatment, and disinfection. Other industrial uses of applied fields and biological considerations were also studied. The evaluation was conducted in the following phases: literature review and personal contacts, papers from field and laboratory professionals, and a workshop with contributed papers. (DLC)

  12. Protective coatings for columbium applied in the field.

    NASA Technical Reports Server (NTRS)

    Carter, J.; Culp, J.

    1971-01-01

    The various aspects of field repair of columbium alloy panels with protective coatings designed as part of the Space Shuttle thermal protection system are examined. The field repair of the coatings is accomplished by employing ceramic cement repairs, and reapplying the fused slurry silicide coating. Techniques are described which improve the practicality of these repairs by employing torch heating. The repair coating quality is demonstrated by testing which simulates flight temperature, pressure, stress and acoustic vibration conditions as a function of time. Conclusions on the present status of field repair coatings are presented and recommendations are given for appropriate future activities relative to the use on an operational Space Shuttle system.

  13. Investigation of ac-magnetic field stimulated nanoelectroporation of magneto-electric nano-drug-carrier inside CNS cells

    PubMed Central

    Kaushik, Ajeet; Nikkhah-Moshaie, Roozbeh; Sinha, Raju; Bhardwaj, Vinay; Atluri, Venkata; Jayant, Rahul Dev; Yndart, Adriana; Kateb, Babak; Pala, Nezih; Nair, Madhavan

    2017-01-01

    In this research, we demonstrate cell uptake of magneto-electric nanoparticles (MENPs) through nanoelectroporation (NEP) using alternating current (ac)-magnetic field stimulation. Uptake of MENPs was confirmed using focused-ion-beam assisted transmission electron microscopy (FIB-TEM) and validated by a numerical simulation model. The NEP was performed in microglial (MG) brain cells, which are highly sensitive for neuro-viral infection and were selected as target for nano-neuro-therapeutics. When the ac-magnetic field optimized (60 Oe at 1 kHz), MENPs were taken up by MG cells without affecting cell health (viability > 92%). FIB-TEM analysis of porated MG cells confirmed the non-agglomerated distribution of MENPs inside the cell and no loss of their elemental and crystalline characteristics. The presented NEP method can be adopted as a part of future nanotherapeutics and nanoneurosurgery strategies where a high uptake of a nanomedicine is required for effective and timely treatment of brain diseases. PMID:28374799

  14. AC magnetic field-assisted method to develop porous carbon nanotube/conducting polymer composites for application in thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Chuang, Chun-Yu; Yang, Shu-Chian; Chang, Su-Hua; Yang, Ta-I.

    2015-04-01

    Thermoelectric materials are very effective in converting waste heat sources into useful electricity. Researchers are continuing to develop new polymeric thermoelectric materials. The segregated-network carbon nanotube (CNT)- polymer composites are most promising. Thus, the goal of this study is to develop novel porous CNT -polymer composites with improved thermoelectric properties. The research efforts focused on modifying the surface of the CNT with magnetic nanoparticles so that heat was released when subjecting to an AC magnetic field. Subsequently, polymers covered on the surface of the CNT were crosslinked. The porous CNT -polymer composites can be obtained by removing the un-crosslinked polymers. Polydimethylsiloxane polymer was utilized to investigate the effect of porosity and electrical conductivity on the thermoelectric properties of the composites. This AC magnetic field-assisted method to develop porous carbon nanotube/polymer composites for application in thermoelectric materials is introduced for the first time. The advantage of this method is that the electrical conductivity of the composites was high since we can easily to manipulate the CNT to form a conducting path. Another advantage is that the high porosity significantly reduced the thermal conductivity of the composites. These two advantages enable us to realize the polymer composites for thermoelectric applications. We are confident that this research will open a new avenue for developing polymer thermoelectric materials.

  15. The Transport Properties of Dilute Gases in Applied Fields.

    DTIC Science & Technology

    1979-03-01

    experimentally for pa ra ad ,i, a d diiama gnetic molecules, respectively, can aotually be measured "ore accurate!i than the transoort properties themselves... cross section de:pends on The angle 5 between the axis of rotation and the d-rection of motion. In the absence of a magnetic field, the direction of...precesses about the direction of the field. The collision cross section now chanoes periodically during the flight of the molecule, necessitating an

  16. 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.

  17. 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.

  18. A 65-kV insulated gate bipolar transistor switch applied in damped AC voltages partial discharge detection system.

    PubMed

    Jiang, J; Ma, G M; Luo, D P; Li, C R; Li, Q M; Wang, W

    2014-02-01

    Damped AC voltages detection system (DAC) is a productive way to detect the faults in power cables. To solve the problems of large volume, complicated structure and electromagnetic interference in existing switches, this paper developed a compact solid state switch based on electromagnetic trigger, which is suitable for DAC test system. Synchronous electromagnetic trigger of 32 Insulated Gate Bipolar Transistors (IGBTs) in series was realized by the topological structure of single line based on pulse width modulation control technology. In this way, external extension was easily achieved. Electromagnetic trigger and resistor-capacitor-diode snubber circuit were optimized to reduce the switch turn-on time and circular layout. Epoxy encapsulating was chosen to enhance the level of partial discharge initial voltage (PDIV). The combination of synchronous trigger and power supply is proposed to reduce the switch volume. Moreover, we have overcome the drawback of the electromagnetic interference and improved the detection sensitivity of DAC by using capacitor storage energy to maintain IGBT gate driving voltage. The experimental results demonstrated that the solid-state switch, with compact size, whose turn-on time was less than 400 ns and PDIV was more than 65 kV, was able to meet the actual demands of 35 kV DAC test system.

  19. A 65-kV insulated gate bipolar transistor switch applied in damped AC voltages partial discharge detection system

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Ma, G. M.; Luo, D. P.; Li, C. R.; Li, Q. M.; Wang, W.

    2014-02-01

    Damped AC voltages detection system (DAC) is a productive way to detect the faults in power cables. To solve the problems of large volume, complicated structure and electromagnetic interference in existing switches, this paper developed a compact solid state switch based on electromagnetic trigger, which is suitable for DAC test system. Synchronous electromagnetic trigger of 32 Insulated Gate Bipolar Transistors (IGBTs) in series was realized by the topological structure of single line based on pulse width modulation control technology. In this way, external extension was easily achieved. Electromagnetic trigger and resistor-capacitor-diode snubber circuit were optimized to reduce the switch turn-on time and circular layout. Epoxy encapsulating was chosen to enhance the level of partial discharge initial voltage (PDIV). The combination of synchronous trigger and power supply is proposed to reduce the switch volume. Moreover, we have overcome the drawback of the electromagnetic interference and improved the detection sensitivity of DAC by using capacitor storage energy to maintain IGBT gate driving voltage. The experimental results demonstrated that the solid-state switch, with compact size, whose turn-on time was less than 400 ns and PDIV was more than 65 kV, was able to meet the actual demands of 35 kV DAC test system.

  20. Infrared image denoising applied in infrared sound field measurement

    NASA Astrophysics Data System (ADS)

    Su, Zhiqiang; Shen, Guofeng

    2017-03-01

    The research made use of the heat property and explored the distribution of focused ultrasound field. In our experiments, we measured the distribution of heat sources, and then, calculated the distribution of focused ultrasound field via a liner relation. In the experiments, we got a series of infrared images with noise. It's such an important thing to find out a solution to get rid of the noise in those images in order to get an accurate focused ultrasound field distribution. So the investigation following is focused in finding out a filter which can remove most noise in the infrared charts and the distribution of ultrasound filed is not impacted. Experiments compared the effects of different filters by the index of - 6dB width of the temperature rise images. By this index, we can find out a filter which is the most suitable filter for keeping the distribution of focused ultrasound field in steady. All experiments, including simulations, semi-simulations and actual verification experiments used six filters to deal with the raw data to get -6dB width and signal to noise ratio. From the results of experiments, we drew a conclusion that gauss filter is the best to keep the distribution of focused ultrasound field in steady.

  1. 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…

  2. Comparison of performance of field applied girth weld coatings

    SciTech Connect

    Neal, D.

    1997-01-01

    A series of girth weld coatings was evaluated in cathodic disbonding and water immersion tests to determine their performance when applied over various levels of surface cleanliness. Tests were run at 77, 100, and 150 F (25, 38, and 66 C) for up to 90 days. Data show the performance of all the coatings is directly related to surface cleanliness, and there is a significant drop in performance over nonblast cleaned surfaces.

  3. Dynamic response of a blue phase to an applied field

    NASA Astrophysics Data System (ADS)

    Dolganov, V. K.; Heppke, G.; Kitzerow, H.-S.

    1992-10-01

    The dynamic response of the three-dimensionally ordered blue phases BPI and BPII to a step-function electric field was studied in a liquid crystal with negative dielectric anisotropy. A change of diffraction intensities, indicating the existence of two qualitatively different transformations of the structure, has been observed in a pulse electric field. Nous avons étudié la dynamique des propriétés électro-optiques pour les mésophases cubiques Phase Bleue I (BPI) et Phase Bleue II (BPII) dans un mélange avec une anisotropie diélectrique négative. Le changement des intensités des réflexions de Bragg sous l'influence d'un champ alternatif modulé indique deux transformations différentes de la structure des phases bleues.

  4. Simulated annealing algorithm applied in adaptive near field beam shaping

    NASA Astrophysics Data System (ADS)

    Yu, Zhan; Ma, Hao-tong; Du, Shao-jun

    2010-11-01

    Laser beam shaping is required in many applications for improving the efficiency of the laser systems. In this paper, the near field beam shaping based on the combination of simulated annealing algorithm and Zernike polynomials is demonstrated. Considering phase distribution can be represented by the expansion of Zernike polynomials, the problem of searching appropriate phase distribution can be changed into a problem of optimizing a vector made up of Zernike coefficients. The feasibility of this method is validated theoretically by translating the Gaussian beam into square quasi-flattop beam in the near field. Finally, the closed control loop system constituted by phase only liquid crystal spatial light modulator and simulated annealing algorithm is used to prove the validity of the technique. The experiment results show that the system can generate laser beam with desired intensity distributions.

  5. AC losses in multifilamentary Bi(2223) tapes with an interfilamentary resistive carbonate barrier

    NASA Astrophysics Data System (ADS)

    Eckelmann, H.; Quilitz, M.; Oomen, M.; Leghissa, M.; Goldacker, W.

    1998-12-01

    For the most common AC application frequencies, the main component of the AC losses in multifilamentary Bi(2223) tapes are caused by hysteresis- and coupling losses. These losses can be reduced enhancing the matrix resistivity and applying a twist to the filaments. We report on the AC loss properties of 37-filament tapes with AgAu (8 wt.%) matrix, and novel 19-filament tapes with SrCO 3 barriers between the filaments. We performed transport AC loss and magnetic AC loss measurements in parallel and perpendicular magnetic fields. Both kinds of tapes were also prepared with filament twists below a twist pitch of 20 mm. The influence of the different tape modifications on the AC loss behaviour is presented and compared with theoretical models to understand the effect of the resistive matrix. In the case of magnetic AC loss measurements, reduced AC losses due to decoupled filaments were observed for the twisted tapes with a resistive matrix in low parallel fields.

  6. Solidification processing of alloys using an applied electric field

    NASA Technical Reports Server (NTRS)

    Mckannan, Eugene C. (Inventor); Schmidt, Deborah D. (Inventor); Ahmed, Shaffiq (Inventor); Bond, Robert W. (Inventor)

    1990-01-01

    A method is provided for obtaining an alloy having an ordered microstructure which comprises the steps of heating the central portion of the alloy under uniform temperature so that it enters a liquid phase while the outer portions remain solid, applying a constant electric current through the alloy during the heating step, and solidifying the liquid central portion of the alloy by subjecting it to a temperature-gradient zone so that cooling occurs in a directional manner and at a given rate of speed while maintaining the application of the constant electric current through the alloy. The method of the present invention produces an alloy having superior characteristics such as reduced segregation. After subsequent precipitation by heat-treatment, the alloys produced by the present invention will have excellent strength and high-temperature resistance.

  7. Directional solidification processing of alloys using an applied electric field

    NASA Technical Reports Server (NTRS)

    McKannan, Eugene C. (Inventor); Schmidt, Deborah D. (Inventor); Ahmed, Shaffiq (Inventor); Bond, Robert W. (Inventor)

    1992-01-01

    A method is provided for obtaining an alloy having an ordered microstructure which comprises the steps of heating the central portion of the alloy under uniform temperature so that it enters a liquid phase while the outer portions remain solid, applying a constant electric current through the alloy during the heating step, and solidifying the liquid central portion of the alloy by subjecting it to a temperature-gradient zone so that cooling occurs in a directional manner and at a given rate of speed while maintaining the application of the constant electric current through the alloy. The method is particularly suitable for use with nickel-based superalloys. The method of the present invention produces an alloy having superior characteristics such as reduced segregation. After subsequent precipitation by heat-treatment, the alloys produced by the present invention will have excellent strength and high-temperature resistance.

  8. Hysteresis losses in MgB2 superconductors exposed to combinations of low AC and high DC magnetic fields and transport currents

    NASA Astrophysics Data System (ADS)

    Magnusson, N.; Abrahamsen, A. B.; Liu, D.; Runde, M.; Polinder, H.

    2014-11-01

    MgB2 superconductors are considered for generator field coils for direct drive wind turbine generators. In such coils, the losses generated by AC magnetic fields may generate excessive local heating and add to the thermal load, which must be removed by the cooling system. These losses must be evaluated in the design of the generator to ensure a sufficient overall efficiency. A major loss component is the hysteresis losses in the superconductor itself. In the high DC - low AC current and magnetic field region experimental results still lack for MgB2 conductors. In this article we reason towards a simplified theoretical treatment of the hysteresis losses based on available models in the literature with the aim of setting the basis for estimation of the allowable magnetic fields and current ripples in superconducting generator coils intended for large wind turbine direct drive generators. The resulting equations use the DC in-field critical current, the geometry of the superconductor and the magnitude of the AC magnetic field component as parameters. This simplified approach can be valuable in the design of MgB2 DC coils in the 1-4 T range with low AC magnetic field and current ripples.

  9. 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.

  10. In-situ X-ray diffraction combined with scanning AC nanocalorimetry applied to a Fe0.84Ni0.16 thin-film sample

    PubMed Central

    Gregoire, John M.; Xiao, Kechao; McCluskey, Patrick J.; Dale, Darren; Cuddalorepatta, Gayatri; Vlassak, Joost J.

    2013-01-01

    We combine the characterization techniques of scanning AC nanocalorimetry and x-ray diffraction to study phase transformations in complex materials system. Micromachined nanocalorimeters have excellent performance for high-temperature and high-scanning-rate calorimetry measurements. Time-resolved X-ray diffraction measurements during in-situ operation of these devices using synchrotron radiation provide unprecedented characterization of thermal and structural material properties. We apply this technique to a Fe0.84Ni0.16 thin-film sample that exhibits a martensitic transformation with over 350 K hysteresis, using an average heating rate of 85 K/s and cooling rate of 275 K/s. The apparatus includes an array of nanocalorimeters in an architecture designed for combinatorial studies. PMID:23825802

  11. Charged dendrimers under the action of AC electric fields: Breathing characteristics of molecular size, polarizations, and ion distributions

    NASA Astrophysics Data System (ADS)

    Das, Ashok K.; Hsiao, Pai-Yi

    2015-02-01

    Langevin dynamics simulations are performed to study the response of charged dendrimers in alternating current electric fields in 3:1 salt solutions. Time evolutions of molecular size show breathing characteristics which take saw-tooth-like patterns in square-wave electric fields and undulated sine-function ones in sine-wave fields. Detailed study reveals how the dendrimer and condensed ions oscillate in the electric fields, which result in polarization of the molecule. To effect a significant deformation of the dendrimer, the applied field amplitude must be larger than some critical strength Ecrit and the field frequency smaller than a threshold fcrit. The response behavior is characterized by two relaxation times in square-wave fields, both of which decrease linearly with the strong field strength larger than Ecrit. In sine-wave fields, the molecular size exhibits interesting hysteretic behavior in plotting the curves with the field variation. A Maxwell-Wagner type polarization theory is derived and proved by simulations, which connects fcrit with the strength of the applied electric field.

  12. Tools and setups for experiments with AC and rotating magnetic fields

    NASA Astrophysics Data System (ADS)

    Ponikvar, D.

    2010-09-01

    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 experiments and describes setups and tools which are easy to obtain and work with. Free software is offered to generate the required signals by a personal computer. The experiments can be implemented in introductory physics courses on electromagnetism for undergraduates or specialized courses at high schools.

  13. Deformation field validation and inversion applied to adaptive radiation therapy

    NASA Astrophysics Data System (ADS)

    Vercauteren, Tom; De Gersem, Werner; Olteanu, Luiza A. M.; Madani, Indira; Duprez, Fréderic; Berwouts, Dieter; Speleers, Bruno; De Neve, Wilfried

    2013-08-01

    Development and implementation of chronological and anti-chronological adaptive dose accumulation strategies in adaptive intensity-modulated radiation therapy (IMRT) for head-and-neck cancer. An algorithm based on Newton iterations was implemented to efficiently compute inverse deformation fields (DFs). Four verification steps were performed to ensure a valid dose propagation: intra-cell folding detection finds zero or negative Jacobian determinants in the input DF; inter-cell folding detection is implemented on the resolution of the output DF; a region growing algorithm detects undefined values in the output DF; DF domains can be composed and displayed on the CT data. In 2011, one patient with nonmetastatic head and neck cancer selected from a three phase adaptive DPBN study was used to illustrate the algorithms implemented for adaptive chronological and anti-chronological dose accumulation. The patient received three 18F-FDG-PET/CTs prior to each treatment phase and one CT after finalizing treatment. Contour propagation and DF generation between two consecutive CTs was performed in Atlas-based autosegmentation (ABAS). Deformable image registration based dose accumulations were performed on CT1 and CT4. Dose propagation was done using combinations of DFs or their inversions. We have implemented a chronological and anti-chronological dose accumulation algorithm based on DF inversion. Algorithms were designed and implemented to detect cell folding.

  14. Conditional random fields for pattern recognition applied to structured data

    SciTech Connect

    Burr, Tom; Skurikhin, Alexei

    2015-07-14

    Pattern recognition uses measurements from an input domain, X, to predict their labels from an output domain, Y. Image analysis is one setting where one might want to infer whether a pixel patch contains an object that is “manmade” (such as a building) or “natural” (such as a tree). Suppose the label for a pixel patch is “manmade”; if the label for a nearby pixel patch is then more likely to be “manmade” there is structure in the output domain that can be exploited to improve pattern recognition performance. Modeling P(X) is difficult because features between parts of the model are often correlated. Therefore, conditional random fields (CRFs) model structured data using the conditional distribution P(Y|X = x), without specifying a model for P(X), and are well suited for applications with dependent features. This paper has two parts. First, we overview CRFs and their application to pattern recognition in structured problems. Our primary examples are image analysis applications in which there is dependence among samples (pixel patches) in the output domain. Second, we identify research topics and present numerical examples.

  15. Conditional random fields for pattern recognition applied to structured data

    DOE PAGES

    Burr, Tom; Skurikhin, Alexei

    2015-07-14

    Pattern recognition uses measurements from an input domain, X, to predict their labels from an output domain, Y. Image analysis is one setting where one might want to infer whether a pixel patch contains an object that is “manmade” (such as a building) or “natural” (such as a tree). Suppose the label for a pixel patch is “manmade”; if the label for a nearby pixel patch is then more likely to be “manmade” there is structure in the output domain that can be exploited to improve pattern recognition performance. Modeling P(X) is difficult because features between parts of the modelmore » are often correlated. Therefore, conditional random fields (CRFs) model structured data using the conditional distribution P(Y|X = x), without specifying a model for P(X), and are well suited for applications with dependent features. This paper has two parts. First, we overview CRFs and their application to pattern recognition in structured problems. Our primary examples are image analysis applications in which there is dependence among samples (pixel patches) in the output domain. Second, we identify research topics and present numerical examples.« less

  16. Full-field optical coherence tomography apply in sphere measurements

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Li, Weiwei; li, Juncheng; Wang, Jingyu; Wang, Jianguo

    2016-10-01

    The geometry of a spherical surface, for example that of a precision optic, is completely determined by the radius -of-curvature at one point and the deviation from the perfect spherical form at all other points of the sphere. Full-field Optical Coherence Tomography (FF-OCT) is a parallel detection OCT technique that utilizes a 2D detector array. This technique avoids mechanical scanning in imaging optics, thereby speeding up the imaging process and enhancing the quality of images. The current paper presents an FF-OCT instrument that is designed to be used in sphere measurement with the principle of multiple delays (MD) OCT to evaluate the curvature and radius of curved objects in single-shot imaging. The optimum combination of the MD principle with the FF-OCT method was evaluated, and the radius of a metal ball was measured with this method. The generated 2n-1 contour lines were obtained by using an MDE with n delays in a single en-face OCT image. This method of measurement, it engaged in the measurement accuracy of spherical and enriches the means of measurement, to make a spherical scan techniques flexible application.

  17. Simulation and mathematical analyses of AC electric field driven apoptosis via microtubule disintegration

    NASA Astrophysics Data System (ADS)

    Tiwari, Pawan K.

    2015-09-01

    The moderate intensity alternating current electric fields with frequencies ranging between a few tens of kilohertz and a few tens of megahertz, also known as tumor treating fields (TTFs) are utilized as a modality in the electrotherapeutic treatment of the cancer cells. The application of sub-MHz TTF on the cancer cell results in the inducement of higher electric field at the furrow between the daughter cells, and such apoptosis stimulating phenomenon is investigated through the Maxwell two-dimensional (2D) finite element simulations. A furrow distance of the order of size of the nucleus accounts for the intense electric field inducement disintegrating the microtubule via the processes of its surface disruption and tubulin dimer detachment. A simulation and mathematical analyses of the microtubule disintegration mechanism is formulated to ascertain one of the factors causing an apoptosis of the cancer cells, and consequently checking their proliferation.

  18. Theoretical analysis of AC electric field transmission into biological tissue through frozen saline for electroporation.

    PubMed

    Xiao, Chunyan; Rubinsky, Boris

    2014-12-01

    An analytical model was used to explore the feasibility of sinusoidal electric field transmission across a frozen saline layer into biological tissue. The study is relevant to electroporation and permeabilization of the cell membrane by electric fields. The concept was analyzed for frequencies in the range of conventional electroporation frequencies and electric field intensity. Theoretical analysis for a variety of tissues show that the transmission of electroporation type electric fields through a layer of frozen saline into tissue is feasible and the behavior of this composite system depends on tissue type, frozen domain temperature, and frequency. Freezing could become a valuable method for adherence of electroporation electrodes to moving tissue surfaces, such as the heart in the treatment of atrial fibrillation or blood vessels for the treatment of restenosis.

  19. Huge ac magnetoresistance of La0.7Sr0.3MnO3 in sub-kilogauss magnetic fields

    NASA Astrophysics Data System (ADS)

    Mahendiran, Ramanathan; Rebello, Alwyn; Naik, Vinayak B.; Barik, Sujit Kumar

    2010-03-01

    We report radio frequency (f = 0.1 5 MHz) magnetotransport of La0.7Sr0.3MnO3 in sub kilogauss magnetic fields (H = 0-1 kG). We measured ac resistance (R) and reactance (X) simultaneously. In zero field, R decreases smoothly around the Curie temperature TC when f = 100 kHz, but it increases abruptly and shows a peak close to TC for f = 0.5-5 MHz. The peak decreases in amplitude, broadens and shifts downward in temperature as the bias field increases. The peak is completely suppressed under Hdc = 1 kOe when f = 0.5 MHz. A huge low-field ac magnetoresistance (δR/R = 40 %) and magnetoinductance (δX/X = 12 %) are found in a field of Hdc = 700 Oe and f = 2 MHz. We suggest that the observed ac magnetoresistance arises from the suppression of ac permeability and enhanced magnetic skin depth under a magnetic field. The dynamical magnetotransport reported here will be interesting from view points of fundamental physics and applications.

  20. An investigation of magnetic field effects on plume density and temperature profiles of an applied-field MPD thruster

    NASA Technical Reports Server (NTRS)

    Bullock, S. Ray; Myers, R. M.

    1994-01-01

    Applied-field magnetoplasmadynamic (MPD) thruster performance is below levels required for primary propulsion missions. While MPD thruster performance has been found to increase with the magnitude of the applied-field strength, there is currently little understanding of the impact of applied-field shape on thruster performance. The results of a study in which a single applied-field thruster was operated using three solenoidal magnets with diameters of 12.7, 15.2, and 30.4-cm are presented. Thruster voltage and anode power deposition were measured for each applied field shape over a range of field strengths. Plume electron number density and temperature distributions were measured using a Langmuir probe in an effort to determine the effect of field shape on plume confinement by the diverging magnetic-field for each of the three magnetic field shapes. Results show that the dependence of the measured thruster characteristics on field shape were non-monotonic and that the field shape had a significant effect on the plume density and temperature profiles.

  1. 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

  2. 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.

  3. Enhanced absorption performance of carbon nanostructure based metamaterials and tuning impedance matching behavior by an external AC electric field.

    PubMed

    Gholipur, Reza; Khorshidi, Zahra; Bahari, Ali

    2017-03-27

    Metamaterials have surprisingly broadened the range of available practical applications in new devices such as shielding, microwave absorbing, and novel antenna. More researches are related to the tuning DNG frequency bands of ordered or disordered metamaterials, and far less research has focused on the importance of impedance matching behavior, and is not effort and attention in adjusting the magnitude of negative permittivity values. This is particularly important if devices deal with low amplitude signals such as radio or TV antenna. The carbon/hafnium nickel oxide (C/Hf0.9Ni0.1Oy) nanocomposites with simultaneously negative permittivity and negative permeability, excellent metamaterial performance and good impedance matching could become an efficient alternative for the ordered metamaterials in wave-transparent, microwave absorbing, and solar energy harvesting fields. In this study, we prepared C/Hf0.9Ni0.1Oy nanocomposites by solvothermal method, and we clarified how the impedance matching and double negative (DNG) behaviors of C/Hf0.9Ni0.1Oy can be tuned by an external AC electric field created by electric quadrupole system. External electric field allows for the alignment of the well-dispersed nanoparticles of carbon with long-range orientations order. We believe that this finding broadens our understanding of moderate conductive material-based random metamaterials (MCMRMs), and provides a novel strategy for replacing high loss ordered or disordered metamaterials with MCMRMs.

  4. Scaling of 100 kW class applied-field MPD thrusters

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.

    1992-01-01

    Three cylindrical applied-field magnetoplasmadynamic thrusters were tested with argon propellant over a broad range of operating conditions to establish empirical scaling laws for thruster performance. Argon flow rates, discharge currents, and applied-field strengths were varied between 0.025 and 0.14 g/s, 750 to 2000 A, and 0.034 to 0.20T, respectively. The results showed that the thrust reached over five times the self-field value, and that thrust increased linearly with the product of discharge current and applied-field strength and quadratically with the anode radius. While increasing the propellant flow rate increased the thrust, it did not affect the rate of thrust increase with applied-field strength, and at low propellant flow rates the self-field thrust approached 30 percent of the measured thrust. The voltage increased linearly with applied-field strength but was insensitive to the discharge current. The rate of voltage increase with applied-field strength dependent on anode radius. Thruster efficiency increased monotonically with applied-field strength and propellant flow rate. Peak thruster efficiencies were insensitive to changes in anode radius. Electrode power loss and thruster efficiency measurements showed that while the electrode losses decreased with increasing anode radius the plasma losses increased. The opposite behaviors of electrode and plasma losses demonstrates the need to identify ways of independently controlling the thruster loss mechanisms.

  5. 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.

  6. 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

  7. Modeling of plasma processes in the slowly diverging magnetic fields at the exit of an applied-field magnetoplasmadynamic thruster

    NASA Astrophysics Data System (ADS)

    Li, Min; Tang, Hai-Bin; Ren, Jun-Xue; York, Thomas M.

    2013-10-01

    The performance of plasma thrusters with applied electric and magnetic fields can be enhanced by increasing the magnetic field strength, which is applied in the thrust chamber and the exit region propulsive plume. The ejected plasma which passes through a slowly diverging magnetic field will expand but can be restricted within the magnetic nozzle fields. To examine in detail the processes that occur, a new method with Particle-in-cell calculations is applied here. A two-dimensional axisymmetric particle dynamic code is used to model an AF-MPDT (Applied-field Magnetoplasmadynamic Thruster) for which extensive experimental data are available; it used Ar propellant and had applied magnetic coils of 101.5 mm radius and 153 mm length. From the results of the simulation study, it is found that total thrust increases linearly with magnetic field strength in the range of 0-0.1 T, but it decreases with increasing applied magnetic field up to 0.6 T. Thrust efficiency is found to increase to a maximum of 8.4% when B = 0.1 T; further, the peak value of nozzle efficiency reaches 91% at a moderate magnetic field (0.3 T). In detail, it is found that distributions of plasma density (1014-1015 m-3) that form in the magnetic nozzle demonstrate a significant pattern of concentration up to fields of B = 0.3 T where ions begin to be magnetized. However, azimuthal velocities of ions behave differently with different degrees of magnetization, i.e., weakly magnetized ions follow rotating electrons in a right-handed direction, while fully magnetized ions revolve in left-handed direction due to electromagnetic forces. Notably, a feedback effect on total magnetic field due to plasma motion identified in other studies is not found to be present in the working conditions of the AF-MPDT examined here.

  8. Current Transport and Onset-Related Phenomena in an MPD Thruster Modified by Applied Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Moeller, Robert Carlos

    This work investigated the effects of tailored, externally-applied magnetic fields on current transport and near-anode processes in the plasma discharge of a magnetoplasmadynamic thruster (MPDT). Electrical and plasma diagnostics were used to determine whether applied magnetic fields could mitigate the effects of the "onset" phenomena, including large-amplitude terminal voltage fluctuations and high anode fall voltages associated with unstable operation and anode erosion. A new MPDT was developed and operated with quasi-steady 1 ms pulses from 36 kW to 3.3 MW with argon propellant. Three magnetic configurations studied included self-field operation (without external electromagnets) and two applied poloidal magnetic fields. One configuration used magnetic field lines tangential to the anode lip (and intersecting the anode further upstream) and the other created a magnetic cusp intersecting the anode downstream. The influence of the applied fields on the discharge current streamlines, current densities, and key plasma properties (electron temperature, number density, and plasma potential) was studied. Key findings included that the current pattern and current densities redistributed to follow the applied magnetic field lines. Also, the anode fall voltage was substantially reduced with both applied fields over a large range of currents (and eliminated at 8 kA). These results occurred because applied magnetic field lines intersecting the anode provided a high conductivity path and reduced the local electric field required to sustain the radial current densities. The applied fields reduced the amplitude and frequency of the terminal voltage fluctuations (up to 49%) over a broad range of currents and also decreased transients in the ion saturation current, which suggest reduction of current filamentation and surface-eroding anode spots. Additionally, the cusp field reduced mean terminal voltages over the entire range of discharge currents (up to 31%), and the tangential

  9. 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

  10. Photoconductivity in AC-driven modulated two-dimensional electron gas in a perpendicular magnetic field.

    PubMed

    Torres, Manuel; Kunold, Alejandro

    2006-04-26

    In this work we study the microwave photoconductivity of a two-dimensional electron system (2DES) in the presence of a magnetic field and a two-dimensional modulation (2D). The model includes the microwave and Landau contributions in a non-perturbative exact way; the periodic potential is treated perturbatively. The Landau-Floquet states provide a convenient base with respect to which the lattice potential becomes time dependent, inducing transitions between the Landau-Floquet levels. Based on this formalism, we provide a Kubo-like formula that takes into account the oscillatory Floquet structure of the problem. The total longitudinal conductivity and resistivity exhibit strong oscillations, determined by ϵ = ω/ω(c), with ω the radiation frequency and ω(c) the cyclotron frequency. The oscillations follow a pattern with minima centred at [Formula: see text], and maxima centred at [Formula: see text], where j = 1,2,3..., δ∼1/5 is a constant shift and l is the dominant multipole contribution. Negative resistance states (NRSs) develop as the electron mobility and the intensity of the microwave power are increased. These NRSs appear in a narrow window region of values of the lattice parameter (a), around a∼l(B), where l(B) is the magnetic length. It is proposed that these phenomena may be observed in artificially fabricated arrays of periodic scatterers at the interface of ultraclean GaAs /Al(x)Ga(1-x)As heterostructures.

  11. Chemical reduction synthesis and ac field effect of iron based core-shell magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Balakrishnan, Srinivasan; Bonder, Michael J.; Hadjipanayis, George C.

    2009-12-01

    High magnetization nanoparticles coated with a biocompatible polymer have attracted considerable interest in recent times as potential materials for biomedical applications associated with targeted drug delivery, detection and the treatment of cancer. This paper considers the use of sodium borohydride reduction of metal salts to form Fe based nanoparticles coated with carboxyl terminated polyethylene glycol (cPEG). By mixing the reactants in a Y-junction, the synthesis produces uniform nanoparticles in the size range 10-20 nm with a core-shell structure. The particles are subsequently coated with a 1-3 nm thick layer of cPEG. These nanoparticles are soft ferromagnets with Hc = 400 Oe. Exciting these nanoparticles with a 4 Oe, 500 kHz alternating magnetic field leads to particle heating with a maximal increase in the saturation temperature as the particle size is decreased. For the largest particles considered here, the temperature reaches 35 °C with a 10 mg sample mass whilst for the smallest nanoparticles considered the temperature exceeds 40 °C.

  12. Difficulties in applying numerical simulations to an evaluation of occupational hazards caused by electromagnetic fields.

    PubMed

    Zradziński, Patryk

    2015-01-01

    Due to the various physical mechanisms of interaction between a worker's body and the electromagnetic field at various frequencies, the principles of numerical simulations have been discussed for three areas of worker exposure: to low frequency magnetic field, to low and intermediate frequency electric field and to radiofrequency electromagnetic field. This paper presents the identified difficulties in applying numerical simulations to evaluate physical estimators of direct and indirect effects of exposure to electromagnetic fields at various frequencies. Exposure of workers operating a plastic sealer have been taken as an example scenario of electromagnetic field exposure at the workplace for discussion of those difficulties in applying numerical simulations. The following difficulties in reliable numerical simulations of workers' exposure to the electromagnetic field have been considered: workers' body models (posture, dimensions, shape and grounding conditions), working environment models (objects most influencing electromagnetic field distribution) and an analysis of parameters for which exposure limitations are specified in international guidelines and standards.

  13. Difficulties in applying numerical simulations to an evaluation of occupational hazards caused by electromagnetic fields

    PubMed Central

    Zradziński, Patryk

    2015-01-01

    Due to the various physical mechanisms of interaction between a worker's body and the electromagnetic field at various frequencies, the principles of numerical simulations have been discussed for three areas of worker exposure: to low frequency magnetic field, to low and intermediate frequency electric field and to radiofrequency electromagnetic field. This paper presents the identified difficulties in applying numerical simulations to evaluate physical estimators of direct and indirect effects of exposure to electromagnetic fields at various frequencies. Exposure of workers operating a plastic sealer have been taken as an example scenario of electromagnetic field exposure at the workplace for discussion of those difficulties in applying numerical simulations. The following difficulties in reliable numerical simulations of workers’ exposure to the electromagnetic field have been considered: workers’ body models (posture, dimensions, shape and grounding conditions), working environment models (objects most influencing electromagnetic field distribution) and an analysis of parameters for which exposure limitations are specified in international guidelines and standards. PMID:26323781

  14. The Response of Starch/gelatin/glycerin Aqueous Electrorheological Elastomer to Applied Electric Field

    NASA Astrophysics Data System (ADS)

    Gao, Lingxiang; Zhao, Xiaopeng

    The aqueous ER elastomers, containing crude organic starch particles which dispersed in gelatin/glycerin/water matrix, were prepared with or without the applied DC electric field. The responses of the composite systems to the electric field were tested by the compression modulus and resistance of the elastomers. The result shows that they are enhanced and controlled evidently under an applied DC electric field. The strongest responses appear at 25% weight fraction of starch. In addition, the increment modulus of the elastomer increases with the strength of the applied field within 0.5~1.5 kV/mm, while after the field is stronger than 1.5 kV/mm it doesn't increase with field, appearing "saturation".

  15. Size dependent heating ability of CoFe2O4 nanoparticles in AC magnetic field for magnetic nanofluid hyperthermia

    NASA Astrophysics Data System (ADS)

    Çelik, Özer; Can, Musa Mutlu; Firat, Tezer

    2014-03-01

    We investigated the size dependent magnetic properties and heating mechanism of spinel CoFe2O4 nanoparticles, which synthesized using the nonhydrolytic thermal decomposition method. The size of CoFe2O4 nanoparticles was arranged with the variation of solvent type, reflux time, and reflux temperature. The optimum size range was determined for magnetic fluid hyperthermia. The particles with 9.9 ± 0.3 nm average diameter have the highest heating ability in the AC magnetic field having 3.2 kA/m amplitude and 571 kHz frequency. The maximum specific absorption rate of 22 W/g was obtained for 9.9 ± 0.3 nm sized CoFe2O4 nanoparticles. The calculations and experimental results showed the dominancy of Brownian relaxation at the heat production of synthesized 9.9 ± 0.3 nm nanoparticles. In contrary, the magneto-heating in 5.4 ± 0.2 nm particles mainly originated from Neel relaxation.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Friability of spray-applied fireproofing and thermal insulations: field evaluation of prototype test devices

    SciTech Connect

    Rossiter, W.J.; Roberts, W.E.; Mathey, R.G.

    1989-03-01

    The report describes results of the third and final phase of a study conducted for the General Services Administration (GSA) to develop a field-test method to measure the friability of spray-applied fireproofing and thermal-insulation materials. Field tests were conducted on 17 fibrous and 2 cementitious spray-applied materials to assess surface and bulk compression/shear, indentation, abrasion, and impact properties. The tests were performed using prototype devices developed in an earlier phase of the study. As expected, the field specimens displayed varying response to dislodgment or indentation in the tests. The field tests confirmed that the goal of the study had been achieved.

  18. Calculation of externally applied electric field intensity for disruption of cancer cell proliferation.

    PubMed

    Sardari, Dariush; Verga, Nicolae

    2010-06-01

    It is already known that electrostatic, magnetostatic, extremely low-frequency electric fields, and pulsed electric field could be utilized in cancer treatment. The healing effect depends on frequency and amplitude of electric field. In the present work, a simple theoretical model is developed to estimate the intensity of electrostatic field that damages a living cell during division. By this model, it is shown that magnification of electric field in the bottleneck of dividing cell is enough to break chemical bounds between molecules by an avalanche process. Our model shows that the externally applied electric field of 4 V/cm intensity is able to hurt a cancer cell at the dividing stage.

  19. Electrorheology of Dispersions of BaxSr(1-x)TiO3 in Silicone Oil Under AC or DC Electric Field

    NASA Astrophysics Data System (ADS)

    Luz, Glauber M. S.; Bombard, Antonio J. F.; Brito, Silvio L. M.; Gouvêa, Douglas; Vieira, Sheila L.

    2012-07-01

    Electrorheology (ER) of ferroelectric materials such as nanometric BaTiO3 is still not fully understood. In this paper, nanoparticles of BaxSr(1-x)TiO3 (where x = 0.8, 0.9 or 1.0) were synthesized using the method of Pechini, calcinated at 950°C, and after, lixiviated under pH 1 or pH 5. A controlled stress rheometer (MCR-301) was used to make the ER characterization of dispersions made of Bax Ti1-xO3 in silicone oil (30% w/w), where (a) shear stress as a function of DC electric field (under constant shear rate) or (b) shear stress as a function of shear rate (under constant AC or DC electric field) were measured. We observed that electrophoresis occurred under electric field DC, creating a concentration gradient which induced phase separation in ER fluid. On the other hand, under AC fields above 1 kV/mm, the ER effect is stronger than for DC field, and almost without electrophoresis. Furthermore, there is an AC frequency, dependent on the disperse phase, where the ER effect has a maximum.

  20. Deep Vadose Zone–Applied Field Research Initiative Fiscal Year 2012 Annual Report

    SciTech Connect

    Wellman, Dawn M.; Truex, Michael J.; Johnson, Timothy C.; Bunn, Amoret L.; Golovich, Elizabeth C.

    2013-03-14

    This annual report describes the background of the Deep Vadose Zone-Applied Field Research Initiative, and some of the programmatic approaches and transformational technologies in groundwater and deep vadose zone remediation developed during fiscal year 2012.

  1. Behavioral recovery induced by applied electric fields after spinal cord hemisection in guinea pig

    SciTech Connect

    Borgens, R.B.; Blight, A.R.; McGinnis, M.E.

    1987-10-16

    Applied electric fields were used to promote axonal regeneration in spinal cords of adult guinea pigs. A propriospinal intersegmental reflex (the cutaneous trunci muscle reflex) was used to test lateral tract function after hemisection of the thoracic spinal cord. An electrical field (200 microvolts per millimeter, cathode rostral) applied across the lesion led to functional recovery of the cutaneous trunci muscle reflex in 25 percent of experimental animals, whereas the functional deficit remained in control animals, which were implanted with inactive stimulators.

  2. Dependence of neoclassical toroidal viscosity on the poloidal spectrum of applied nonaxisymmetric fields

    SciTech Connect

    Logan, Nikolas C.; Park, Jong -Kyu; Paz-Soldan, Carloa; Lanctot, Matthew J.; Smith, Sterling P.; Burrell, K. H.

    2016-02-05

    This paper presents a single mode model that accurately predicts the coupling of applied nonaxisymmetric fields to the plasma response that induces neoclassical toroidal viscosity (NTV) torque in DIII-D H-mode plasmas. The torque is measured and modeled to have a sinusoidal dependence on the relative phase of multiple nonaxisymmetric field sources, including a minimum in which large amounts of nonaxisymmetric drive is decoupled from the NTV torque. This corresponds to the coupling and decoupling of the applied field to a NTV-driving mode spectrum. Modeling using the perturbed equilibrium nonambipolar transport (PENT) code confirms an effective single mode coupling between the applied field and the resultant torque, despite its inherent nonlinearity. Lastly, the coupling to the NTV mode is shown to have a similar dependence on the relative phasing as that of the IPEC dominant mode, providing a physical basis for the efficacy of this linear metric in predicting error field correction optima in NTV dominated regimes.

  3. Long period preservation of marine products using electrostatic field

    NASA Astrophysics Data System (ADS)

    Okumura, Takamasa; Yaegashi, Taro; Yamada, Kazuki; Ito, Takanori; Takahashi, Katsuyuki; Aisawa, Sumio; Takaki, Koichi; Yamazaki, Shigeyoshi; Syuto, Bunei

    2016-07-01

    The effect of an AC electric field on the freshness of marine products was experimentally investigated. An AC voltage of 10 kV with 50 Hz in frequency was generated with a transformer and applied to a plane electrode set in an incubator. The biological material was the gonad of purple sea urchin. The AC electric field with 50 Hz in frequency was applied to the gonad at -1 °C for 7 days. Freshness was evaluated by measuring protein release and lactate dehydrogenase (LDH) activity. The results showed that the protein release and LDH activity in the gonad were suppressed by applying the AC electric field, compared with that without the AC electric field. Moreover, the gonad was treated with the AC electric field at -5 °C for 3 days and then preserved at 0 °C for 1 day without the field. This electrical field treatment of the gonad prolonged the freshness date for more than 10 days under 4 °C preservation condition. In addition, the permeability of the cell membrane was suppressed by applying the AC electric field. Concerning the relationship between permeability and AC electric field, the conformational change of bovine serum albumin (BSA) induced by the AC electric field was evaluated on the basis of UV absorption spectra. The results revealed that the secondary and/or higher-order structure gradually changes with preservation period. The conformational change of the BSA molecule was induced by applying the AC electric field.

  4. Fundamental mathematical model shows that applied electrical field enhances chemotherapy delivery to tumors.

    PubMed

    Moarefian, Maryam; Pascal, Jennifer A

    2016-02-01

    Biobarriers imposed by the tumor microenvironment create a challenge to deliver chemotherapeutics effectively. Electric fields can be used to overcome these biobarriers in the form of electrochemotherapy, or by applying an electric field to tissue after chemotherapy has been delivered systemically. A fundamental understanding of the underlying physical phenomena governing tumor response to an applied electrical field is lacking. Building upon the work of Pascal et al. [1], a mathematical model that predicts the fraction of tumor killed due to a direct current (DC) applied electrical field and chemotherapy is developed here for tumor tissue surrounding a single, straight, cylindrical blood vessel. Results show the typical values of various parameters related to properties of the electrical field, tumor tissue and chemotherapy drug that have the most significant influence on the fraction of tumor killed. We show that the applied electrical field enhances tumor death due to chemotherapy and that the direction and magnitude of the applied electrical field have a significant impact on the fraction of tumor killed.

  5. Magnetic memory signals variation induced by applied magnetic field and static tensile stress in ferromagnetic steel

    NASA Astrophysics Data System (ADS)

    Huang, Haihong; Yang, Cheng; Qian, Zhengchun; Han, Gang; Liu, Zhifeng

    2016-10-01

    Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, Hp(y), induced by applied magnetic fields with different intensities measured through the tensile tests. The Hp(y), its slope coefficient KS and maximum gradient Kmax changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of Hp(y) and its slope coefficient KS increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, Hp(y) and KS reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of Hp(y) instead of changing the signal curve‧s profile; and the magnitude of Hp(y), KS, Kmax and the change rate of KS increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials.

  6. Nonlinear modal interaction in HVDC/AC power systems with dc power modulation

    SciTech Connect

    Ni, Y.X.; Vittal, V.; Kliemann, W.; Fouad, A.A.

    1996-11-01

    In this paper investigation of nonlinear modal interaction using the normal form of vector fields technique is extended to HVDC/AC power systems with dc power modulation. The ac-dc interface equations are solved to form a state space model with second order approximation. Using the normal form technique, the system`s nonlinear dynamic characteristics are obtained. The proposed approach is applied to a 4-generator HVDC/AC test power system, and compare with the time domain solution.

  7. AC Electric Field Enhances Cryopreservation Efficiency of Sprague-Dawley Rat Liver During a Slow Freezing Procedure.

    PubMed

    Ma, Ya H; Qin, Guo F; Li, Jing; Ding, Gui R; Xu, Sheng L; Zhou, Yan; Guo, Guo Z

    2016-02-01

    Slow freezing coupled with an AC electric field (ACEF) has been demonstrated to miniaturize the ice crystals of a 0.9% (w/v) NaCl solution in a prior study. The aim of this study was to assess the effect of ACEF on Sprague-Dawley (SD) rat liver in vitro during the slow cooling procedure. SD rat liver exposed to an oscillating electric field was frozen in a programmed freezer initially down to -30°C at a cooling rate of -1°C/min and continuing down to -80°C at a cooling rate of -5°C/min. The cryovials were finally transferred into liquid nitrogen for 7 days. The frequency range was 0-20 MHz, and peak field strength was 1,000 V/m. For the sham and electric-exposed groups, the freezing solution consisted of 0%, 2.5%, 5.0%, 7.5%, or 10% (v/v) dimethyl sulfoxide (DMSO) Dulbecco's modified Eagles' medium culture solution, and fresh tissue was selected as the control group. The changes in cell survival rate, adenosine triphosphate (ATP) content, and morphology of fresh and frozen-thawed liver tissue were examined. Compared with the sham group with 5.0% DMSO, the result showed that slow freezing coupled with 2.45 MHz or 5 MHz ACEF significantly increased the relative survival rate by 43.27% and 26.31% (P < 0.001), respectively. However, ACEF exposure increased the ATP content compared with the sham group. Especially in 5% and 10% DMSO with 2.45 MHz ACEF exposure, the ATP content approximated the fresh group (7.3 ± 2.7 nmol/piece), corresponding to 94.52% and 80.82%. In addition, the cellular membrane and some organelles (e.g., mitochondria) in the electric-exposed group appeared to be more intact according to the transmission electron microscopy images. The underlying mechanism might be that the ACEF affects the formation and growth of the ice crystallization, and thus inhibits cryoinjury. These results show that ACEF would provide an efficient method for cryopreservation banking with a low concentration of CPA during the slow freezing process.

  8. Dynamic performance of a disk-type magnetorheological fluid damper under AC excitation

    NASA Astrophysics Data System (ADS)

    Zhu, Changsheng

    2005-02-01

    It is shown that the dynamic behaviour of a disk-type magnetorheological (MR) fluid damper developed on shear mode for rotational machinery can be controlled by application of an external DC magnetic field produced by a low voltage electromagnetic coil and that the disk-type MR fluid damper can effectively attenuate the rotor vibration. In this paper, the dynamic behaviour of the disk-type MR fluid damper for attenuating rotor vibration under AC sinusoidal magnetic field is experimentally studied on a flexible rotor. It is shown that as the frequency of applied AC sinusoidal magnetic field increases, the capability of the disk-type MR fluid damper to attenuate rotor vibration significantly reduces. There is a maximum frequency of AC sinusoidal magnetic field for a given applied magnetic field strength to realize the MR effect. When the frequency of AC sinusoidal magnetic field is over the maximum frequency, the MR activity almost completely disappears and the dynamic behaviour of the disk-type MR fluid dampers under a high frequency AC magnetic field is the same as that without magnetic field. For a given sinusoidal magnetic field frequency, there is also a minimum AC sinusoidal magnetic field to active the MR effect. In the rotor vibration control of view, it is not necessary to use the AC power supply for disk-type MR fluid dampers.

  9. Towards high concentration enhancement of microfluidic temperature gradient focusing of sample solutes using combined AC and DC field induced Joule heating.

    PubMed

    Ge, Zhengwei; Wang, Wei; Yang, Chun

    2011-04-07

    It is challenging to continuously concentrate sample solutes in microfluidic channels. We present an improved electrokinetic technique for enhancing microfluidic temperature gradient focusing (TGF) of sample solutes using combined AC and DC field induced Joule heating effects. The introduction of an AC electric field component services dual functions: one is to produce Joule heat for generating temperature gradient; the other is to suppress electroosmotic flow. Consequently the required DC voltages for achieving sample concentration by Joule heating induced TGF are reduced, thereby leading to smaller electroosmotic flow (EOF) and thus backpressure effects. As a demonstration, the proposed technique can lead to concentration enhancement of sample solutes of more than 2500-fold, which is much higher than the existing literature reported microfluidic concentration enhancement by utilizing the Joule heating induced TGF technique.

  10. Second-order nonlinear susceptibility in quantum dot structure under applied electric field

    NASA Astrophysics Data System (ADS)

    Abdullah, M.; Noori, Farah T. Mohammed; Al-Khursan, Amin H.

    2015-06-01

    A model for quantum dot (QD) subbands, when the dots are in the form of quantum disks, under applied electric field was stated. Then, subbands of dots with different disk radii and heights were calculated under applied field. The competition between the shift due to confinement by field and the size was shown for subbands. Second-order nonlinear susceptibility in quantum dots (QDs) was derived using density matrix theory which is, then, simulated using the calculated subbands. Both interband (IB) and intersubband (ISB) transitions were discussed. High second-order susceptibility in QDs was predicted. The results show a reduction in the susceptibility with the applied field while the peak wavelength was mainly relates to energy difference between subbands. A good match between theory and laboratory experiments was observed. Laboratory experiments at terahertz region might be possible using valence intersubband which is important in many device applications.

  11. Synthesis and Characteristics of FePt Nanoparticle Films Under In Situ-Applied Magnetic Field.

    PubMed

    Qian, Xu; Gao, Mo-Yun; Li, Ai-Dong; Zhou, Xiao-Yu; Liu, Xiao-Jie; Cao, Yan-Qiang; Li, Chen; Wu, Di

    2016-12-01

    In situ external magnetic field was applied during the synthesis of FePt nanoparticles via a chemical solution method. FePt nanoparticle films were prepared on Si by a drop-coating method with and without a magnetic field. Annealing at 700 °C in reductive atmosphere was explored to obtain ferromagnetic FePt L10 phase. The effect of in situ-applied magnetic field on the structure, morphology, and magnetic properties of FePt nanoparticle films was characterized. It is found that the applied magnetic field during the chemical synthesis of FePt nanoparticles plays a key role in the crystallinity and magnetic property of FePt nanoparticle films. As-synthesized FePt nanoparticles under the magnetic field are monodispersed and can be self-assembled over a larger area by a dropping method. The applied magnetic field during the synthesis of FePt nanoparticles not only significantly improves the nanoparticles' c-axis preferred orientation but also benefits the phase transition of FePt nanoparticles from face-centered cubic to face-centered tetragonal structure during the annealing process. The FePt nanoparticle films derived under magnetic field also show some magnetic anisotropy.

  12. Synthesis and Characteristics of FePt Nanoparticle Films Under In Situ-Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Qian, Xu; Gao, Mo-Yun; Li, Ai-Dong; Zhou, Xiao-Yu; Liu, Xiao-Jie; Cao, Yan-Qiang; Li, Chen; Wu, Di

    2016-07-01

    In situ external magnetic field was applied during the synthesis of FePt nanoparticles via a chemical solution method. FePt nanoparticle films were prepared on Si by a drop-coating method with and without a magnetic field. Annealing at 700 °C in reductive atmosphere was explored to obtain ferromagnetic FePt L10 phase. The effect of in situ-applied magnetic field on the structure, morphology, and magnetic properties of FePt nanoparticle films was characterized. It is found that the applied magnetic field during the chemical synthesis of FePt nanoparticles plays a key role in the crystallinity and magnetic property of FePt nanoparticle films. As-synthesized FePt nanoparticles under the magnetic field are monodispersed and can be self-assembled over a larger area by a dropping method. The applied magnetic field during the synthesis of FePt nanoparticles not only significantly improves the nanoparticles' c-axis preferred orientation but also benefits the phase transition of FePt nanoparticles from face-centered cubic to face-centered tetragonal structure during the annealing process. The FePt nanoparticle films derived under magnetic field also show some magnetic anisotropy.

  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. Effect of Externally Applied Perturbation Fields on Alfvénic MHD Activity in the NSTX Tokamak

    NASA Astrophysics Data System (ADS)

    Bortolon, Alessandro

    2014-10-01

    Observations from NSTX demonstrate that externally applied magnetic perturbations (MP) can alter the dynamic of beam driven Alfvén modes. Bursting Global Alfvén Eigenmodes (GAE, n = 7-9, 400-700 kHz) respond to pulses of static n = 3 fields (δB/B ~ 0.01 at the plasma edge) reducing mode amplitude, bursting period and frequency sweep by a factor of 2-3 [Bortolon et al., Phys. Rev. Lett. 110, 265008 (2013)]. Similar MP attenuate the amplitude of continuous Toroidal Alfvén Eigenmodes (TAE, n = 2-3, 50-90 kHz). Calculations of the perturbed beam-ion distribution function, considering MP from ideal or resistive plasma response, confirm an enhanced fast-ion transport consistent with a reduced drive for the GAE. At the same time, MP can also affect the Alfvén stability by altering the structure of Alfvén continua through modification of the kinetic profiles or introducing toroidal coupling as result of the broken axisymmetry. Computations of the n = 2 Alfvén continuum for NSTX equilibria with n = 3 MP show strong modification of the TAE continuum near the plasma edge, where coupling between n = 2 and n = 5 continuum modes reduces the gap, providing an additional damping for TAE modes extending in this region. DOE Contracts No. DE-FG02-06ER54867, DE-AC02-09CH11466.

  15. Fluorescence modulation in single CdSe quantum dots by moderate applied electric fields

    SciTech Connect

    LeBlanc, Sharonda J.; McClanahan, Mason R.; Moyer, Tully; Moyer, Patrick J.; Jones, Marcus

    2014-01-21

    Single molecule time-resolved fluorescence spectroscopy of CdSe/ZnS core-shell quantum dots (QDs) under the influence of moderate applied electric fields reveals distributed emission from states which are neither fully on nor off and pronounced changes in the excited state decay. The data suggest that a 54 kV/cm applied electric field causes small perturbations to the QD surface charge distribution, effectively increasing the surface trapping probability and resulting in the appearance of gray states. We present simultaneous blinking and fluorescence decay results for two sets of QDs, with and without an applied electric field. Further kinetic modeling analysis suggests that a single trapped charged cannot be responsible for a blinking off event.

  16. Inhibition of root elongation in microgravity by an applied electric field

    NASA Technical Reports Server (NTRS)

    Wolverton, C.; Mullen, J. L.; Aizawa, S.; Yoshizaki, I.; Kamigaichi, S.; Mukai, C.; Shimazu, T.; Fukui, K.; Evans, M. L.; Ishikawa, H.

    1999-01-01

    Roots grown in an applied electric field demonstrate a bidirectional curvature. To further understand the nature of this response and its implications for the regulation of differential growth, we applied an electric field to roots growing in microgravity. We found that growth rates of roots in microgravity were higher than growth rates of ground controls. Immediately upon application of the electric field, root elongation was inhibited. We interpret this result as an indication that, in the absence of a gravity stimulus, the sensitivity of the root to an applied electric stimulus is increased. Further space experiments are required to determine the extent to which this sensitivity is shifted. The implications of this result are discussed in relation to gravitropic signaling and the regulation of differential cell elongation in the root.

  17. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

    DOEpatents

    Chaffin, R.J.; Dawson, L.R.; Fritz, I.J.; Osbourn, G.C.; Zipperian, T.E.

    1987-06-08

    A field effect transistor comprises a semiconductor having a source, a drain, a channel and a gate in operational relationship. The semiconductor is a strained layer superlattice comprising alternating quantum well and barrier layers, the quantum well layers and barrier layers being selected from the group of layer pairs consisting of InGaAs/AlGaAs, InAs/InAlGaAs, and InAs/InAlAsP. The layer thicknesses of the quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice which has a superlattice conduction band energy level structure in k-vector space. The layer thicknesses of the quantum well layers are selected to provide a superlattice L/sub 2D/-valley which has a shape which is substantially more two-dimensional than that of said bulk L-valley. 2 figs.

  18. The second harmonic generation in symmetrical and asymmetrical Gaussian potential quantum wells with applied electric field

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Chen, Ni; Mo, Hua; Zhang, Yan; Zhang, Zhi-Hai

    2015-12-01

    A detailed investigation of the second harmonic generation in symmetrical and asymmetrical Gaussian potential quantum wells under the influence of applied electric field by using the compact-density-matrix approach and the finite difference method. The results show that the second-harmonic generation susceptibility obtained in two cases can reach the magnitude of 10-4 m/V, which depend dramatically on the applied electric field and the structural parameters. Finally, the resonant peak and its corresponding to the resonant energy are also taken into account.

  19. Performance of a 100 kW class applied field MPD thruster

    NASA Technical Reports Server (NTRS)

    Mantenieks, Maris A.; Sovey, James S.; Myers, Roger M.; Haag, Thomas W.; Raitano, Paul; Parkes, James E.

    1989-01-01

    Performance of a 100 kW, applied field magnetoplasmadynamic (MPD) thruster was evaluated and sensitivities of discharge characteristics to arc current, mass flow rate, and applied magnetic field were investigated. Thermal efficiencies as high as 60 percent, thrust efficiencies up to 21 percent, and specific impulses of up to 1150 s were attained with argon propellant. Thrust levels up to 2.5 N were directly measured with an inverted pendulum thrust stand at discharge input powers up to 57 kW. It was observed that thrust increased monotonically with the product of arc current and magnet current.

  20. 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.

  1. The Effect of Time Modulation of the Applied Fields on an RFP

    NASA Astrophysics Data System (ADS)

    Phillips, J. A.; Baker, D. A.; Gribble, R. F.

    1997-11-01

    Improved behavior of the original z-pinch has been achieved by applying different constraints. These include the following: adding a toroidal field, using a conducting shell, reversing the toroidal magnetic field near the wall, and improving shell designs giving lower field errors. Recently, reduced fluctuations and increased energy confinement have been reported(J.C. Sarff et. al., Phys. Plasmas 2, 2440 (1995).) on MST by applying a time varying poloidal voltage to the toroidal field circuit (pulsed poloidal current drive PPCD). An analogous reduction in the low frequency sawteeth was observed when oscillating field current drive OFCD(K.F. Schoenberg et. al., J. Appl. Phys. 56,2519 (1984).) was applied to ZT- 40M. It was suggested this is a manifestation of a dynamic stabilization(J.A. Phillips, D.A. Baker & R.F. Gribble, Nucl. Fusion 35, 935 (1995).). We examine the OFCD data further to document the effect of the modulation of the poloidal and toroidal voltages on the fluctuation level and the dissipative component of the power input. Comparisons with corresponding MST results are made. Past ZT-40M data( L.C. Burkhardt & J.A.Phillips, LANL Rpt., LA-8753-MS(1981).)are also investigated to examine the time variation of the applied poloidal voltage affects current density profile.

  2. Scaling and applied field studies of MPD thrusters with laser diagnostics

    NASA Technical Reports Server (NTRS)

    York, Thomas M.

    1992-01-01

    The topics are presented in viewgraph form and include the following: self-field magnetoplasmadynamics; 1/4-scale applied-field MPD; scaling of arcs and MPD-arcs; magnetic nozzle studies; advanced diagnostic techniques needed for obtaining particle velocity, temperature, and current distributions in plasma thrusters; nonintrusive laser diagnostics for arcs and MPD-arcs; and schematic of multi-beam interferometer for electron density profile determination.

  3. 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.

  4. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

    DOEpatents

    Chaffin, deceased, Roger J.; Dawson, Ralph; Fritz, Ian J.; Osbourn, Gordon C.; Zipperian, Thomas E.

    1989-01-01

    A field effect transistor comprises a semiconductor having a source, a drain, a channel and a gate in operational relationship. The semiconductor is a strained layer superlattice comprising alternating quantum well and barrier layers, the quantum well layers and barrier layers being selected from the group of layer pairs consisting of InGaAs/AlGaAs, InAs/InAlGaAs, and InAs/InAlAsP. The layer thicknesses of the quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice which has a superlattice conduction band energy level structure in k-vector space which includes a lowest energy .GAMMA.-valley and a next lowest energy L-valley, each k-vector corresponding to one of the orthogonal directions defined by the planes of said layers and the directions perpendicular thereto. The layer thicknesses of the quantum well layers are selected to provide a superlattice L.sub.2D -valley which has a shape which is substantially more two-dimensional than that of said bulk L-valley.

  5. Experimental study of loss mechanisms of AgAu/PbBi-2223 tapes with twisted filaments under perpendicular AC magnetic fields at power frequencies

    NASA Astrophysics Data System (ADS)

    Martínez, E.; Yang, Y.; Beduz, C.; Huang, Y. B.

    2000-05-01

    AC losses under perpendicular AC fields have been measured at 77 K and power frequencies for multifilamentary AgAu (10 wt.%)/Bi-2223 tapes with filaments twisted at different pitches. Using simultaneous measurements of the first and higher harmonics of the voltage induced in the pick-up coil, the main loss contributions (superconductor and coupling current losses) have been obtained separately. At power frequencies, twisting produces the desired uncoupling of the filaments at fields lower than the coupling field, which has also been determined experimentally. In the uncoupled-filament regime, the superconductor losses are reduced strongly with respect to the untwisted tapes. The reduction of the total loss with twisting is also observed. However, due to the important contribution of the coupling current losses for this field orientation, a very small pitch (<5 mm) is necessary for a considerably lower loss than that of untwisted tapes. The dependence of the coupling field and coupling current losses on the twist pitch has been analysed and compared with the theoretical predictions.

  6. Applied DC magnetic fields cause alterations in the time of cell divisions and developmental abnormalities in early sea urchin embryos

    SciTech Connect

    Levin, M.; Ernst, S.G.

    1997-05-01

    Most work on magnetic field effects focuses on AC fields. The present study demonstrates that exposure to medium-strength (10 mT--0.1 T) static magnetic fields can alter the early embryonic development of two species of sea urchin embryos. Batches of fertilized eggs from two species of urchin were exposed to fields produced by permanent magnets. Samples of the continuous cultures were scored for the timing of the first two cell divisions, time of hatching, and incidence of exogastrulation. It was found that static fields delay the onset of mitosis in both species by an amount dependent on the exposure timing relative to fertilization. The exposure time that caused the maximum effect differed between the two species. Thirty millitesla fields, but not 15 mT fields, caused an eightfold increase in the incidence of exogastrulation in Lytechinus pictus, whereas neither of these fields produced exogastrulation in Strongylocentrotus purpuratus.

  7. The tunable electronic structure and optic absorption properties of phosphorene by a normally applied electric field

    NASA Astrophysics Data System (ADS)

    Yang, Mou; Duan, Hou-Jian; Wang, Rui-Qiang

    2016-10-01

    We studied the electronic structure and optical absorption properties of phosphorene (a monolayer black phosphorus) under a normally applied electric field. The electric field enlarges the energy gap, weakens the effective mass anisotropy, and increases the effective mass component along the armchair direction (x-direction) for both conduction and valence bands but provides little change to the component along the zigzag direction (y-direction). The band edge optical absorption is completely polarized in the x-direction, and decreases when increasing the electric field. If the exciting frequency is beyond the energy gap, the absorption for the y-polarized light becomes nonzero, but the absorption is still highly polarized.

  8. An industrial light-field camera applied for 3D velocity measurements in a slot jet

    NASA Astrophysics Data System (ADS)

    Seredkin, A. V.; Shestakov, M. V.; Tokarev, M. P.

    2016-10-01

    Modern light-field cameras have found their application in different areas like photography, surveillance and quality control in industry. A number of studies have been reported relatively low spatial resolution of 3D profiles of registered objects along the optical axis of the camera. This article describes a method for 3D velocity measurements in fluid flows using an industrial light-field camera and an alternative reconstruction algorithm based on a statistical approach. This method is more accurate than triangulation when applied for tracking small registered objects like tracer particles in images. The technique was used to measure 3D velocity fields in a turbulent slot jet.

  9. Development of Home Economics Curriculum Materials and Their Use in a Field Study of Applied Nutrition.

    ERIC Educational Resources Information Center

    Jolley, Margaret Virginia

    To improve students' food habits through teacher training in newer teaching methods as applied to nutrition, curriculum materials based on four basic nutrition concepts were developed, pilot tested, evaluated, and revised. Ten Louisiana home economics teachers were given inservice training, and they field tested the curriculum materials using 425…

  10. Vortex configuration in the presence of local magnetic field and locally applied stress

    NASA Astrophysics Data System (ADS)

    Wissberg, Shai; Kremen, Anna; Shperber, Yishai; Kalisky, Beena

    2017-02-01

    Vortex configuration is determined by the repulsive interaction, which becomes dominant with increasing vortex density, by the pinning potential, and by other considerations such as the local magnetic fields, currents flowing in the sample, or as we showed recently, by local stress applied on the sample. In this work we describe different ways to control vortex configuration using scanning SQUID microscopy.

  11. Crystal Field Theory and the Angular Overlap Model Applied to Hydrides of Main Group Elements.

    ERIC Educational Resources Information Center

    Moore, E. A.

    1990-01-01

    Described is how crystal field theory and the angular overlap model can be applied to very simple molecules which can then be used to introduce such concepts as bonding orbitals, MO diagrams, and Walsh diagrams. The main-group compounds are used as examples and a switch to the transition metal complexes. (KR)

  12. Redistribution of mobile surface charges of an oil droplet in water in applied electric field.

    PubMed

    Li, Mengqi; Li, Dongqing

    2016-10-01

    Most researches on oil droplets immersed in aqueous solutions assume that the surface charges of oil droplets are, similar to that of solid particles, immobile and distributed uniformly under external electric field. However, the surface charges at the liquid-liquid interface are mobile and will redistribute under external electric field. This paper studies the redistribution of surface charges on an oil droplet under the influence of the external electrical field. Analytical expressions of the local zeta potential on the surface of an oil droplet after the charge redistribution in a uniform electrical field were derived. The effects of the initial zeta potential, droplet radius and strength of applied electric field on the surface charge redistribution were studied. In analogy to the mobile surface charges, the redistribution of Al2O3-passivated aluminum nanoparticles on the oil droplet surface was observed under applied electrical field. Experimental results showed that these nanoparticles moved and accumulated towards one side of the oil droplet under electric field. The redistribution of the nanoparticles is in qualitative agreement with the redistribution model of the mobile surface charges developed in this work.

  13. 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.

  14. Applied field and total dose dependence of trapped charge buildup in MOS devices

    SciTech Connect

    Krantz, R.J.; Aukerman, L.W.; Zietlow, T.C.

    1987-12-01

    A rate equation for charge buildup which includes carrier sweep out, geminate recombination, hole/electron trapping, and effects of internal fields is developed. The first moment of the resulting charge distribution is calculated to yield the midgap voltage shift as a function of irradiation time. The initial midgap voltage shift per dose and the maximum midgap voltage shift are derived. The field dependence of these quantities is shown to be a consequence of the field dependence of the hole/electron capture cross sections and geminate recombination escape probability. The results of this formulation show that the E/sup -1/2/ decrease in the midgap shift per dose with field described in the literature is due to the decrease of the hole capture cross section with increasing applied field. The theory is validated by comparison with experimental results obtained on 225 A thermal oxide on p-type silicon test capacitors irradiated under bias at room temperature.

  15. Biodegradation of phenol: a comparative study with and without applying magnetic fields.

    PubMed

    Jung, J; Sanji, B; Godbole, S; Sofer, S

    1993-01-01

    The objective of this work was to study the effect of magnetic fields on the rate of phenol biodegradation using immobilized activated sludge. A recirculation flow bioreactor employing immobilized bacterial beads was used with phenol as the substrate to study the biodegradation process. This study was conducted by applying separately the north pole and the south pole magnetic fields to the bioreactor. Rate of dissolved oxygen consumption, phenol concentration and extracellular protein concentration were the parameters monitored during the process. It was observed that by applying a magnetic south pole to the process, biodegradation in the form of biological oxidation was enhanced. A 30% increase in biodegradation rate was obtained by applying a magnetic south pole of strength of 0.45 Tesla to the bioreactor with immobilized microbial beads as compared to the control. Magnetic north pole irradiation inhibited this type of biooxidation. This process has potential for biological treatment of organic wastes.

  16. Investigation of microflow reversal by ac electrokinetics in orthogonal electrodes for micropump design.

    PubMed

    Yang, Kai; Wu, Jie

    2008-04-04

    Orthogonal electrodes have been reported to produce high velocity microflows when excited by ac signals, showing potential for micropumping applications. This paper investigates the microflow reversal phenomena in such orthogonal electrode micropumps. Three types of microflow fields were observed by changing the applied electric signals. Three ac electrokinetic processes, capacitive electrode polarization, Faradaic polarization, and the ac electrothermal effect, are proposed to explain the different flow patterns, respectively. The hypotheses were corroborated by impedance analysis, numerical simulations, and velocity measurements. The investigation of microflow reversal can improve the understanding of ac electrokinetics and hence effectively manipulate fluids.

  17. Magnetic structure in the zero-applied-field reentrant superconductor ErNi1.96Fe0.04B2C0.99

    NASA Astrophysics Data System (ADS)

    Alleno, E.; Godart, C.; André, G.; Dhar, S. K.; Pattalwar, S. M.; Bonville, P.; Nagarajan, R.; Gupta, L. C.

    2003-12-01

    ErNi1.96Fe0.04B2C0.99 is superconducting at Tc=7.3 K and is shown to partially reenter the normal state between 5.5 and 5.7 K in zero applied field by means of ac-susceptibility (χ'ac) and resistivity measurements. Specific heat (Cp) measurements give a magnetic ordering temperature TN=5.7±0.2 K. Powder neutron diffraction measurements showed that the Er3+ magnetic moments adopt below TN=5.9±0.2 K a transverse modulated structure along the a axis (q=0.559a*). Observation of third-order and fifth-order harmonics indicates a squaring of the structure at lower temperature (8.2μB at 1.4 K). Although even-order peaks could not be detected in the neutron data, a weak ferromagnetic transition at TWFM=2.2 K could be directly evidenced by magnetic susceptibility measurements and Cp measurements and indirectly evidenced in the thermal variations of the intensity of the first-order magnetic peaks (Iq), the magnetic coherence length (ξm), and the magnetic wave vector (q). The magnetic structure of ErNi1.96Fe0.04B2C0.99 is nearly identical to that of the parent compound ErNi2B2C. Precise comparison between the temperature variations of Iq, ξm, and χ'ac shows that the transverse a*-modulated magnetic structure is responsible for the reentrant behavior between 5.5 and 5.7 K. Although it is still pair breaking below 5.5 K, it coexists with superconductivity. 57Fe Mössbauer spectra display no broadening in the temperature range where the reentrant behavior is observed, showing that the transferred hyperfine field at the Fe site, if any, is smaller than 2 kOe.

  18. Dependence of neoclassical toroidal viscosity on the poloidal spectrum of applied nonaxisymmetric fields

    DOE PAGES

    Logan, Nikolas C.; Park, Jong -Kyu; Paz-Soldan, Carloa; ...

    2016-02-05

    This paper presents a single mode model that accurately predicts the coupling of applied nonaxisymmetric fields to the plasma response that induces neoclassical toroidal viscosity (NTV) torque in DIII-D H-mode plasmas. The torque is measured and modeled to have a sinusoidal dependence on the relative phase of multiple nonaxisymmetric field sources, including a minimum in which large amounts of nonaxisymmetric drive is decoupled from the NTV torque. This corresponds to the coupling and decoupling of the applied field to a NTV-driving mode spectrum. Modeling using the perturbed equilibrium nonambipolar transport (PENT) code confirms an effective single mode coupling between themore » applied field and the resultant torque, despite its inherent nonlinearity. Lastly, the coupling to the NTV mode is shown to have a similar dependence on the relative phasing as that of the IPEC dominant mode, providing a physical basis for the efficacy of this linear metric in predicting error field correction optima in NTV dominated regimes.« less

  19. Fabrication of superconducting tunnel junctions with embedded coil for applying magnetic field

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Kenji; Nakagawa, Hiroshi; Aoyagi, Masahiro; Naruse, Masato; Myoren, Hiroaki; Taino, Tohru

    2016-11-01

    We have proposed and demonstrated a superconducting tunnel junction (STJ) with an embedded coil for applying a magnetic field. The STJ was fabricated on the coil, which was embedded in a Si substrate. The coil in the Si substrate consists of superconducting microstrip lines and applies a magnetic field to the STJ to suppress the dc Josephson current. The embedded coil was designed with a line and space of 3 μm and a thickness of 120 nm. To planarize the coil, we employed chemical mechanical polishing (CMP) in our fabrication process. In this STJ, the maximum current of the embedded coil was 28 mA, which corresponded to the maximum magnetic field of 11.76 mT.

  20. The second-harmonic generation susceptibility in semiparabolic quantum wells with applied electric field

    NASA Astrophysics Data System (ADS)

    Yuan, Jian-Hui; Zhang, Yan; Mo, Hua; Chen, Ni; Zhang, Zhihai

    2015-12-01

    The second-harmonic generation susceptibility in semiparabolic quantum wells with applied electric field is investigated theoretically. For the same topic studied by Zhang and Xie [Phys. Rev. B 68 (2003) 235315] [1], some new and reliable results are obtained by us. It is easily observed that the second harmonic generation susceptibility decreases and the blue shift of the resonance is induced with increasing of the frequencies of the confined potential. Moreover, a transition from a two-photon resonance to two single-photon resonances will appear adjusted by the frequencies of the confined potential. Similar results can also be obtained by controlling the applied electric field. Surprisingly, the second harmonic generation susceptibility is weakened in the presence of the electric field, which is in contrast to the conventional case. Finally, the resonant peak and its corresponding resonant energy are also taken into account.

  1. Peculiarities of the time evolution of magnetoresistance of granular HTSC in a constant applied magnetic field

    NASA Astrophysics Data System (ADS)

    Balaev, D. A.; Dubrovskiy, A. A.; Shaykhutdinov, K. A.; Popkov, S. I.; Petrov, M. I.

    2008-08-01

    The time evolution of the magnetoresistance of bulk YBCO + CuO composites at T=4.2 K in constant applied magnetic fields was studied to clarify the mechanism of hysteretic behavior of magnetoresistance R(H) of granular HTSC. The composites represent "model" granular HTSC with weakened Josephson coupling between superconducting (YBCO) crystallites. It was found for the first time that on the ascending branch of R(H) dependence, the resistance at H=const decreased with time while on the descending branch, the resistance increased with time in an applied constant magnetic field. In the range of low magnetic fields (below the minimum point of the descending branch of the R(H) dependence), the resistance at H=const decreased again. Similar measurements performed on pure polycrystalline YBCO at T=77.4 K have shown that the behavior of evolution of resistance with time is similar to that observed for the composite. This proves the peculiarity of time evolution of magnetoresistance to be a common feature of granular HTSCs. The behavior revealed is well described by the model of granular HTSC, where the intergrain media is in an effective magnetic field which is the superposition of the external field and the field induced by superconducting grains. The time evolution of resistance reflects the time relaxation of magnetization of HTSC grains due to the intragrain flux creep processes.

  2. Terahertz Radiation from Laser Created Plasma by Applying a Transverse Static Electric Field

    NASA Astrophysics Data System (ADS)

    Fukuda, Takuya; Katahira, Koji; Yugami, Noboru; Sentoku, Yasuhiko; Sakagami, Hitoshi; Nagatomo, Hideo

    2016-10-01

    Terahertz (THz) radiation, which is emitted in narrow cone in the forward direction from laser created plasma has been observed by N.Yugami et al.. Additionally, Löffler et al. have observed that a significantly increased THz emission intensity in the forward direction when the transverse static electric field is applied to the plasma. The purpose of our study is to derive the mechanism of the THz radiation from laser created plasma by applying the transverse static electric field. To study the radiation mechanism, we conducted 2D-PIC simulation. With the static electric field of 10 kV/cm and gas density of 1020 cm-3, we obtain 1.2 THz single cycle pulse radiation, whose intensity is 1.3 ×105 W/cm2. The magnetic field called ``picket fence mode'' is generated in the laser created plasma. At the boundary surface between the plasma and vacuum, the magnetic field is canceled because eddy current flows. We conclude that the temporal behavior of the magnetic field at the boundary surface radiates the THz wave.

  3. Heat generation ability in AC magnetic field of nano MgFe2O4-based ferrite powder prepared by bead milling

    NASA Astrophysics Data System (ADS)

    Hirazawa, Hideyuki; Aono, Hiromichi; Naohara, Takashi; Maehara, Tsunehiro; Sato, Mitsunori; Watanabe, Yuji

    2011-03-01

    Nanosized MgFe2O4-based ferrite powder having heat generation ability in an AC magnetic field was prepared by bead milling and studied for thermal coagulation therapy applications. The crystal size and the particle size significantly decreased by bead milling. The heat generation ability in an AC magnetic field improved with the milling time, i.e. a decrease in crystal size. However, the heat generation ability decreased for excessively milled samples with crystal sizes of less than 5.5 nm. The highest heat ability (ΔT=34 °C) in the AC magnetic field (370 kHz, 1.77 kA/m) was obtained for fine MgFe2O4 powder having a ca. 6 nm crystal size (the samples were milled for 6-8 h using 0.1 mm ϕ beads). The heat generation of the samples was closely related to hysteresis loss, a B-H magnetic property. The reason for the high heat generation properties of the samples milled for 6-8 h using 0.1 mm ϕ beads was ascribed to the increase in hysteresis loss by the formation of a single domain. Moreover, the improvement in heating ability was obtained by calcination of the bead-milled sample at low temperature. In this case, the maximum heat generation (ΔT=41 °C) ability was obtained for a ca. 11 nm crystal size sample was prepared by crystal growth during the sample calcination. On the other hand, the ΔT value for Mg0.5Ca0.5Fe2O4 was synthesized using a reverse precipitation method decreased by bead milling.

  4. Drop Migration and Demixing of Biphasic Aqueous Systems in an Applied Electric Field

    NASA Astrophysics Data System (ADS)

    Todd, Paul; Raghavarao, Karumanchi S. M. S.

    1999-11-01

    Applying an electric field to a demixing emulsion of poly(ethylene glycol)(PEG) and dextran (or maltodextrin) in phosphate-buffered aqueous solution shortens the demixing time up to 6 fold. Phosphate ions partition into the dextran-rich phase imparting a small electrical potential between the phases. PEG-rich drops migrate cathodally, and their electrophoretic mobility is directly proportional to their radius and increases with increased ionization of phosphate. An electric field, either parallel or antiparallel to the gravity vector, can enhance demixing. A theory consistent with these observations states that drops move due to external and internal electroosmotic flow (tractor treading). Enhanced demixing in an electric field whose polarity opposes buoyancy is thought to be caused by initial increased drop growth during retardation by the electric field so that the drop becomes more buoyant. However, at infinite internal drop viscosity the theory does not extrapolate to the result for solid colloid particles.

  5. 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.

  6. Capture and emission of electrons in quantum wells under applied electric field

    NASA Astrophysics Data System (ADS)

    Vinter, B.; Luc, F.; Bois, P.; Thibaudeau, L.; Rosencher, E.

    1994-06-01

    Important characteristics of Quantum Well Infrared Photodetectors are determined almost entirely by the photoionization rate of electrons out of the Quantum Well (QW) and the recapture into the QWs. To elucidate these processes microscopically we have made structures in which the QWs are isolated from one contact by a completely blocking barrier, so that the steady state current vanishes. The transient current induced by photoionization out of the QWs gives a direct measurement of the photoionization cross section and the escape probability of a photoexcited electron. We have found that the variation of the latter with the electric field may be described by a simple barrier lowering model combined with statistical fluctuation of the QW width. The capture process has been studied by impedance spectroscopy in samples containing only one well. The capture velocity thus measured is found to decrease with increasing applied electric field but within experimental uncertainties it does not depend on the width of the well for well widths between 3 and 7.5 nm. Theoretical results on optical phonon mediated transitions in the applied field from barrier to well states show a generally good agreement with experiment at low fields but less dependence on the field.

  7. The Effect of Rotating a Faraday Disc Perpendicular to an Applied Magnetic Field Theory and Experiment

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Grugel, Richard N.

    2003-01-01

    A magnetohydrodynamic model that examines the effect of rotating an electrically conducting cylinder with a uniform external magnetic field applied orthogonal to its axis is presented. Noting a simple geometry, it can be classified as a fundamental dynamo problem. For the case of an infinitely long cylinder, an analytical solution is obtained and analyzed in detail. A semi-analytical model was developed that considers a finite cylinder. Experimental data from a spinning brass wheel in the presence of Earth's magnetic field were compared to the proposed theory and found to fit well.

  8. Solar coronal magnetic fields derived using seismology techniques applied to omnipresent sunspot waves

    NASA Astrophysics Data System (ADS)

    Jess, David B.; Reznikova, Veronika E.; Ryans, Robert S. I.; Christian, Damian J.; Keys, Peter H.; Mathioudakis, Mihalis; Mackay, Duncan H.; Krishna Prasad, S.; Banerjee, Dipankar; Grant, Samuel D. T.; Yau, Sean; Diamond, Conor

    2016-02-01

    Sunspots on the surface of the Sun are the observational signatures of intense manifestations of tightly packed magnetic field lines, with near-vertical field strengths exceeding 6,000 G in extreme cases. It is well accepted that both the plasma density and the magnitude of the magnetic field strength decrease rapidly away from the solar surface, making high-cadence coronal measurements through traditional Zeeman and Hanle effects difficult as the observational signatures are fraught with low-amplitude signals that can become swamped with instrumental noise. Magneto-hydrodynamic (MHD) techniques have previously been applied to coronal structures, with single and spatially isolated magnetic field strengths estimated as 9-55 G (refs ,,,). A drawback with previous MHD approaches is that they rely on particular wave modes alongside the detectability of harmonic overtones. Here we show, for the first time, how omnipresent magneto-acoustic waves, originating from within the underlying sunspot and propagating radially outwards, allow the spatial variation of the local coronal magnetic field to be mapped with high precision. We find coronal magnetic field strengths of 32 +/- 5 G above the sunspot, which decrease rapidly to values of approximately 1 G over a lateral distance of 7,000 km, consistent with previous isolated and unresolved estimations. Our results demonstrate a new, powerful technique that harnesses the omnipresent nature of sunspot oscillations to provide magnetic field mapping capabilities close to a magnetic source in the solar corona.

  9. Magnetic AC loss of a mono-Sr0.6K0.4Fe2As2 tape/Ag in perpendicular field

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Zhang, Guomin; Yu, Hui; Huang, Miaomiao; Yuan, Weijia

    2016-12-01

    The magnetic AC losses of monofilament Sr0.6K0.4Fe2As2/Ag tapes are measured in the temperature range between 20 K and 30 K both in perpendicular and parallel field. The loss, measured by the standard magnetization technique, is determined from the area of the hysteresis loop using a vibrating sample magnetometer (VSM) in a cyclic field of amplitude up to 7 T. The results in perpendicular field are compared to that of the parallel-field loss and theoretical calculation of magnetization loss at various temperatures. There is a reasonable agreement between the theoretical model and the experimental results even in high field. The magnetic critical current density (Jc) of the tape, obtained by the magnetic hysteresis measurements M(H), are investigated in two field directions and in the temperature range from 5 K to 30 K. The comparison between the magnetic Jc in both field directions and the transport Jc of the tape are also done at various temperatures and fields. The anisotropy of Jc (Γ = Jcab /Jcc) is very small.

  10. Evaluation of Lipton-Glicksman-Kurz Model for Free Dendritic Growth Under an Applied Electric Field

    NASA Astrophysics Data System (ADS)

    Nasresfahani, Mohamad Reza; Niroumand, Behzad; Kermanpur, Ahmad

    2017-02-01

    The present research investigates the ability of the Lipton-Glicksman-Kurz (LGK) model in predicting dendritic growth velocity under an applied electric field. In order to solve the LGK model, the stability criterion, σ*, was first calculated. It was found that σ* was not constant and was reduced by applying the electric field and decreasing the growth velocity. The decrease in the σ* means the increase in the possibility of formation of side branches in the dendrites as well as the hills in the interface. The growth velocities predicted by the model were less than those obtained experimentally. This could be due to the failure of the LGK model to consider convection. The results showed that, by changing the distribution coefficient, the accuracy of the model could increase. Despite some differences in the point-to-point comparison between the model results, the predicted general trend was correct.

  11. Applied-field MPD thruster performance with hydrogen and argon propellants

    NASA Astrophysics Data System (ADS)

    Myers, Roger M.

    1993-10-01

    A single thruster geometry with argon and hydrogen propellants under the same operating conditions was tested to determine the effects of propellant choice on thruster performance and power deposition. It is found that operating on hydrogen extended the stable operating range to higher values of applied magnetic field range. The extended operating range resulted in a factor of two increase in peak efficiency with hydrogen, with a peak measured performance of 3700-s specific impulse at 20 percent efficiency.

  12. Enhancing Tc in field-doped fullerenes by applying uniaxial stress

    NASA Astrophysics Data System (ADS)

    Koch, Erik

    2002-08-01

    Capitalizing on the two-dimensional nature of superconductivity in field-effect doped C60, we show that it should be possible to increase the transition temperature Tc by applying uniaxial stress perpendicular to the gate electrode. This method not only holds the promise of substantially enhancing Tc (by about 30 K per GPa), but also provides a sensitive check of the current understanding of superconductivity in the doped fullerenes.

  13. Anomalously large electro-optic Pockels effect at the air-water interface with an electric field applied parallel to the interface

    NASA Astrophysics Data System (ADS)

    Suzuki, Yuto; Osawa, Kengo; Yukita, Shunpei; Kobayashi, Takayoshi; Tokunaga, Eiji

    2016-05-01

    The optical Pockels effect was observed at the air-water interface by electromodulation spectroscopy. When an AC electric field of frequency f was applied parallel to a water surface between Pt electrodes, the field induced a change in the transmitted light intensity synchronized at 1f proportional to the field strength. The 1f signals dominated over 2f signals by one order of magnitude and the signal disappeared when the electrodes were completely immersed under the water surface, strongly suggesting that the observed phenomena were due to the Pockels effect at the air-water interface. The Pockels coefficient was estimated to be | r | = 1.4 × 105 pm/V, which is much larger than that at the solid-water interface. However, this is unusual because the parallel electric field does not induce the break in inversion symmetry required for the appearance of the Pockels effect. The electrowetting effect was experimentally ruled out as a mechanism for the Pockels effect, and this made the existence of a field perpendicular to the surface, although extremely weak, the most likely explanation.

  14. Domain states in the zero-temperature diluted antiferromagnet in an applied field

    NASA Astrophysics Data System (ADS)

    Glaser, A.; Jones, A. C.; Duxbury, P. M.

    2005-05-01

    We use Bethe lattice calculations, directed models, and exact optimization methods to find percolating antiferromagnetic, ferromagnetic, and domain-state structures in the diluted antiferromagnet in an applied field (DAFF). Based on these calculations, the ground-state structures occuring on simple cubic and body-centered-cubic lattices are presented for the full range of site dilution, 0⩽c⩽1 , and applied magnetic field, 0⩽H⩽∞ . Ground-state phase boundaries are identified by the onset of several different types of extensive clusters: the antiferromagnet phase boundary, where one giant antiferromagnetic cluster emerges; the domain-state (DS) boundary where two antiphase giant antiferromagnetic clusters emerge; and a phase boundary where a giant ferromagnetic cluster emerges. We find that there is an “intermediate” concentration regime in which the DS has the lowest energy so that in the ground state, there is an intermediate regime between the paramagnetic phase and the ordered antiferromagnet. We compare our results to local mean-field theory and Monte Carlo studies of the DAFF and to recent results on the ground-state structure of the random-field Ising model. In this context we discuss the relevance of the ground-state structures we calculate to the thermodynamic phase diagram and the dynamics of the DAFF.

  15. Nonlinear optical rectification in laterally-coupled quantum well wires with applied electric field

    NASA Astrophysics Data System (ADS)

    Liu, Guanghui; Guo, Kangxian; Zhang, Zhongmin; Hassanbadi, Hassan; Lu, Liangliang

    2017-03-01

    Nonlinear optical rectification coefficient χ0(2) in laterally-coupled AlxGa1-xAs/GaAs quantum well wires with an applied electric field is theoretically investigated using the effective mass approximation as well as the numerical energy levels and wavefunctions of electrons. We find that χ0(2) is greatly influenced by the electric field as well as both the distance and the radius of the coupled system. A blue shift of χ0(2) with increasing electric field is exhibited while a red shift followed by a blue shift with increasing distance or radius is exhibited. A nonmonotonic behavior can be found in the resonant peak values of χ0(2) along with the increase of the electric field, the distance or the radius. One or two of the following physical mechanisms: the increased localization of the ground and first-excited states, the reduced coupling and the reduced quantum confinement effect are applied to elucidate the results above. Our results play a potential role in infrared photodetectors based on the coupled system.

  16. Collective migration exhibits greater sensitivity but slower dynamics of alignment to applied electric fields

    PubMed Central

    Lalli, Mark L.; Asthagiri, Anand R.

    2015-01-01

    During development and disease, cells migrate collectively in response to gradients in physical, chemical and electrical cues. Despite its physiological significance and potential therapeutic applications, electrotactic collective cell movement is relatively less well understood. Here, we analyze the combined effect of intercellular interactions and electric fields on the directional migration of non-transformed mammary epithelial cells, MCF-10A. Our data show that clustered cells exhibit greater sensitivity to applied electric fields but align more slowly than isolated cells. Clustered cells achieve half-maximal directedness with an electric field that is 50% weaker than that required by isolated cells; however, clustered cells take ∼2-4 fold longer to align. This trade-off in greater sensitivity and slower dynamics correlates with the slower speed and intrinsic directedness of collective movement even in the absence of an electric field. Whereas isolated cells exhibit a persistent random walk, the trajectories of clustered cells are more ballistic as evidenced by the superlinear dependence of their mean square displacement on time. Thus, intrinsically-directed, slower clustered cells take longer to redirect and align with an electric field. These findings help to define the operating space and the engineering trade-offs for using electric fields to affect cell movement in biomedical applications. PMID:26692908

  17. Magnetic field on fouling control of ultrafiltration membranes applied in treatment of a synthetic textile effluent.

    PubMed

    Carlesso, Franciele; Zin, Guilherme; de Souza, Selene M A G U; Luccio, Marco Di; de Souza, Antonio A U; Oliveira, J Vladimir

    2016-01-01

    Membrane performance is decreased by fouling, reducing permeate flux and membrane lifespan. This paper assesses ultrafiltration of a model textile effluent assisted by permanent magnetic field as an alternative to improve the water permeability recovery. Ultrafiltration was performed in a tangential module and model solutions, composed of carboxymethylcellulose (CMC) and sodium sulphate (Na2SO4). The feed was permeated through 30 kDa polysulphone membrane with and without the presence of a permanent magnetic field of 0.41 T, perpendicular to the membrane surface. Magnetic induction (MI) of feed solution was also investigated by recirculation of the feed stream through the magnetic field for 3 h. The increase in feed concentration did not affect permeate flux, while the presence of salt resulted in a severe flux decline. Effective water permeability recovery was obtained when the magnetic field was applied in the ultrafiltration process, although the MI of the CMC and Na2SO4 solutions also caused some enhancement in permeability recovery. Scanning electron microscopy images showed differences between the assays done with and without the presence of magnetic field. The magnetic field application in ultrafiltration of CMC and Na2SO4 solutions has proved to be an attractive alternative for improving the permeability recovery.

  18. A Validation Study of the General Amber Force Field Applied to Energetic Molecular Crystals

    NASA Astrophysics Data System (ADS)

    Bergh, Magnus; Caleman, Carl

    2016-01-01

    Molecula dynamics is a well-established tool to computationally study molecules. However, to reach predictive capability at the level required for applied research and design, extensive validation of the available force fields is pertinent. Here we present a study of density, isothermal compressibility and coefficients of thermal expansion of four energetic materials (FOX-7, RDX, CL-20 and HMX) based on molecular dynamics simulations with the General Amber Force Field (GAFF), and compare the results to experimental measurements from the literature. Furthermore, we quantify the accuracy of the calculated properties through hydrocode simulation of a typical impact scenario. We find that molecular dynamics simulations with generic and computationally efficient force fields may be used to understand and estimate important physical properties of nitramine-like energetic materials.

  19. Directional solidification of Bi-Mn alloys using an applied magnetic field

    NASA Technical Reports Server (NTRS)

    Decarlo, J. L.; Pirich, R. G.

    1987-01-01

    Off-eutectic compositions of Bi-Mn were directionally solidified in applied transverse magnetic fields up to 3 kG, to determine the effects on thermal and solutal convection. Plane front directional solidification of eutectic and near-eutectic Bi-Mn results in a two-phase rodlike morphology consisting of ferromagnetic MnBi rods in a Bi solid solution matrix. Compositions of either side of the eutectic were studied in growth orientations vertically up and down. Temperature gradient was monitored during growth by means of an in-situ thermocouple. For Bi-rich compositions, the magnetic field appeared to increase mixing as determined from thermal, morphological, chemical, and magnetic analyses. For Mn-rich compositions, morphological and chemical analyses suggest some reduction in mixing due to application of the magnetic force. The capability for carrying out directional solidification of Bi-Mn in high longitudinal magnetic fields was established.

  20. Astroid Curves for a Synthetic Antiferromagnetic Stack in AN Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Forrester, D. M.; Kovacs, E.; Kürten, K. E.; Kusmartsev, F. V.

    The interaction of two magnetic particles separated by an interlayer is illustrated through the "astroid" curves that represent regions in the magnetic field plane where different numbers of minima associated with stable or metastable states may exist. For a single particle, we describe the astroid curves of the Stoner-Wohlfarth model. The case of two particles is then examined and found to be much more complicated. The energy landscape of the two-particle system contains ferromagnetic, antiferromagnetic and canting states that emerge in response to the level of applied magnetic field. Because of this, up to four energy minima can exist in the system, depending upon the strength of the magnetic field and the material properties of the particles.

  1. Astroid Curves for a Synthetic Antiferromagnetic Stack in AN Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    Forrester, D. M.; Kovacs, E.; Kürten, K. E.; Kusmartsev, F. V.

    2010-12-01

    The interaction of two magnetic particles separated by an interlayer is illustrated through the "astroid" curves that represent regions in the magnetic field plane where different numbers of minima associated with stable or metastable states may exist. For a single particle, we describe the astroid curves of the Stoner-Wohlfarth model. The case of two particles is then examined and found to be much more complicated. The energy landscape of the two-particle system contains ferromagnetic, antiferromagnetic and canting states that emerge in response to the level of applied magnetic field. Because of this, up to four energy minima can exist in the system, depending upon the strength of the magnetic field and the material properties of the particles.

  2. Applying a polynomial formula to photon beam output and equivalent square field.

    PubMed

    Chen, F S

    1990-01-01

    The polynomial formula proposed by Chen [Med. Phys. 15, 348 (1988)] in calculating the electron beam output from a Therac 20 linear accelerator has been applied to generating the output factor of various machines with photon energies ranging from 100 kVp to 18 MeV. The calculated outputs are within 1% of the measured values. This formula can be very useful to the physicist in preparing an output table of photon beams or electron beams for a therapeutic unit. An equation is derived from this formula to calculate the equivalent square. The derivation shows that only under special circumstances is the equivalent square field equivalent to 2ab/(a + b); otherwise the equivalent square field depends on the formula's parameters as well as the sides of the rectangular field. These parameters, in turn, are dependent on the photon energy, the medium irradiated, and the collimator design.

  3. Applying a polynomial formula to photon beam output and equivalent square field

    SciTech Connect

    Chen, F. )

    1990-05-01

    The polynomial formula proposed by Chen (Med. Phys. {bold 15}, 348 (1988)) in calculating the electron beam output from a Therac 20 linear accelerator has been applied to generating the output factor of various machines with photon energies ranging from 100 kVp to 18 MeV. The calculated outputs are within 1% of the measured values. This formula can be very useful to the physicist in preparing an output table of photon beams or electron beams for a therapeutic unit. An equation is derived from this formula to calculate the equivalent square. The derivation shows that only under special circumstances is the equivalent square field equivalent to 2{ital ab}/({ital a}+{ital b}); otherwise the equivalent square field depends on the formula's parameters as well as the sides of the rectangular field. These parameters, in turn, are dependent on the photon energy, the medium irradiated, and the collimator design.

  4. Interaction of atomized colloid with an ac electric field in a dielectric barrier discharge reactor used for deposition of nanocomposite coatings

    NASA Astrophysics Data System (ADS)

    Profili, Jacopo; Dap, Simon; Levasseur, Olivier; Naude, Nicolas; Belinger, Antoine; Stafford, Luc; Gherardi, Nicolas

    2017-02-01

    Nanocomposite thin films can be obtained by polymerization of a colloidal solution in a dielectric barrier discharge (DBD) at atmospheric pressure. In such a process, the dispersion of nanoparticles into the matrix is driven by the charging, transport, and deposition dynamics of the atomized colloid. This work examines the interaction of atomized TiO2 nanoparticles with ac electric fields in a plane-to-plane dielectric barrier discharge reactor. Experiments are performed with the discharge off to examine transport and deposition phenomena over a wide range of experimental conditions with a fixed particle charge distribution. Scanning electron microscopy reveals that the size distribution of TiO2 nanoparticles collected at different locations along the substrate surface placed on the bottom electrode of the DBD reactor can judiciously be controlled by varying the amplitude and frequency of the ac electric field. These results are also compared to the predictions of a simple particle motion model accounting for the electrostatic force, the gravitational force, and the neutral drag force in the laminar flow. It is found that while the initial charge distribution of atomized particles strongly influences the total deposition yield, its maximal position on the substrate, and the width of the deposited area, the initial size distribution of the particles at the entrance of the reactor mostly changes the size distribution at each position along the substrate surface.

  5. Development of an applied-magnetic-field diode for ion-beam-transport experiments

    SciTech Connect

    Young, F.C.; Neri, J.M.; Boller, J.R.

    1996-12-31

    An applied-magnetic-field ion diode (ABD) is being developed to study the transport of intense ion beams for light-ion inertial confinement fusion. Initially, the beam from this diode will be used to test the concept of self-pinched transport (SPT). The design goal is diode operation at 1.5 MV and 250-kA total current on the Gamble 2 generator at NRL. For SPT experiments, the beam is extracted from the diode and focused into a transport channel. The ATHETA code is used to calculate B-field configurations in the diode and ion-beam trajectories. Shaping of the anode surface to aim the beam and to counteract focusing due to self B-field and solenoidal-lens effects results in a convex anode surface. Most of the beam can be focused within a spot size of 1.4-cm diameter at 65 cm from the anode. The B-field is generated with inner and outer cathode coils connected in series and driven by a 100-{micro}s risetime, 50-kA pulse. A shunt inductor in parallel with the outer coil is used to control the ratio of the currents in the two coils. To cancel flux penetration of the aluminum anode by the main B-field, a current pulse of opposite polarity with a 1-ms risetime is applied prior to the main pulse. This current is adjusted to place the B-field separatrix on the ion emission surface in the diode gap, accounting for anode plasma expansion. A grooved-anode flashover source is planned for initial experiments. Preliminary results are presented.

  6. Influence of Tailored Applied Magnetic Fields on High-Power MPD Thruster Current Transport and Onset-Related Phenomena

    NASA Technical Reports Server (NTRS)

    Moeller, Robert C.; Polk, James E.

    2013-01-01

    This work investigated the effects of tailored, externally-applied magnetic fields on current transport and near-anode processes in the plasma discharge of a magnetoplasmadynamic thruster (MPDT). Electrical and plasma diagnostics were used to investigate how localized applied magnetic fields could mitigate the effects of the "onset" phenomena, including large-amplitude terminal voltage fluctuations and high anode fall voltages associated with unstable operation and anode erosion. An MPDT with a multi-channel hollow cathode was developed and tested with quasi-steady pulses of 1 millisecond duration at power levels of 36 kilowatts (20 volts, 1800 amperes) to 3.3 milliwatts (255 volts, 13.1 kiloamperes) with argon propellant in three different magnetic configurations: self-field, applied B field tangential to the anode lip near the exit plane, and applied cusp B field. The current pattern and current densities redistributed to follow the applied poloidal magnetic field lines, which created increased conduction paths to the anode. Also, the anode fall voltage was substantially reduced with both applied B field topologies over a large range of currents. For example, at 10.7 kiloamperes, the cusp applied magnetic field decreased anode fall voltages from 45-83 volts down to 15 volts or lower along much of the anode. The amplitude and frequency of the voltage fluctuations were also reduced over a broad range of currents with the applied fields. E.g., the standard deviations of the fluctuations were lowered by 37-49 percent at 8-9 kiloamperes. In addition, decreases in the mean terminal voltages as large as 31 percent were measured with the applied magnetic fields. These effects are shown to be associated with the increased current conduction along the applied magnetic field lines in the near-anode region. These results also suggest a reduction in frequency and intensity of current-concentrating filaments and anode spots, which contribute to erosion. Overall, both applied

  7. Influence of the maximum applied magnetic field on the angular dependence of Magnetic Barkhausen Noise in API5L steels

    NASA Astrophysics Data System (ADS)

    Martínez-Ortiz, P.; Pérez-Benítez, J. A.; Espina-Hernández, J. H.; Caleyo, F.; Mehboob, N.; Grössinger, R.; Hallen, J. M.

    2016-03-01

    This work studies the influence of the maximum applied magnetic field on the angular dependence of the energy of the Magnetic Barkhausen Noise signal in three different API5L pipeline steels. The results show that the shape of the angular dependence of the Magnetic Barkhausen Noise energy changes with the increase of the amplitude of the applied magnetic field. This phenomenon is a consequence of the presence of unlike magnetization processes at different magnitudes of the applied magnetic field. The outcomes reveal the importance of controlling the value of the maximum applied field as parameter for the improvement of the MBN angular dependence measurements.

  8. Field and laboratory studies on the impact of two Bt rice lines expressing a fusion protein Cry1Ab/1Ac on aquatic organisms.

    PubMed

    Wang, Yongmo; Huang, Jiacheng; Hu, Huawei; Li, Jianhong; Liu, Biao; Zhang, Guoan

    2013-06-01

    Genetically modified (GM) rice expressing Bt toxins is at the edge of commercial release in China. However, little information is available concerning the impact of Bt rice on aquatic organisms which are abundant in paddy field. A two-year study was conducted to assess the effects of two GM rice lines expressing a fusion protein Cry1Ab/1Ac (Bt rice) on three groups of zooplankton, rotifers, cladocerans and copepods in field conditions. Multi-factor ANOVA revealed that the population densities of rotifers, cladocerans and copepods in paddy field varied significantly between years and rice developmental stages, but did not differ significantly between Bt and non-Bt rice treatments. In all the field investigations, only one significant difference was found on copepods in the tillering stage of 2009, but the difference was not related to the presence of the Cry toxin. Under open-air conditions, we simulated the farming practice of straw mulch, using Bt rice straw as a food source for the water flea Daphnia hyalina. After one and two months of culture, the density of D. hyalina did not differ between Bt rice treatments and non-Bt rice treatments. A laboratory experiment found that purified Bt toxins Cry1Ab and Cry1Ac had no toxic effect on D. hyalina even in the treatment in which the Bt toxin concentration was as high as 2500ng/ml. Those above results indicate that the two Bt rice lines have no negative effect on the three groups of zooplankton. However, further studies are needed to compare the effects of Bt rice and non-Bt rice on the paddy zooplankton community in the context of integrated pest management which includes the use of pesticides.

  9. Longitudinal wave function control in single quantum dots with an applied magnetic field

    NASA Astrophysics Data System (ADS)

    Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai

    2015-01-01

    Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.

  10. Longitudinal wave function control in single quantum dots with an applied magnetic field.

    PubMed

    Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai

    2015-01-27

    Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.

  11. Effect of applied magnetic field on sound transmission loss of MR-based sandwich panels

    NASA Astrophysics Data System (ADS)

    Hemmatian, Masoud; Sedaghati, Ramin

    2017-02-01

    This study aims to investigate the sound transmission loss (STL) capability of sandwich panels treated with Magnetorheological (MR) fluids at low frequencies. An experimental setup has been designed to investigate the effect of the intensity of applied magnetic field on the natural frequencies and STL of a clamped circular panel. It is shown that the fundamental natural frequency of the MR sandwich panel increases in proportion to the applied magnetic field. In addition, the STL of the panel at the resonance frequency increases as the magnetic field is amplified. Furthermore, the classical plate theory and Ritz method have been utilized to develop the governing equations of motion of the finite multilayered circular panels comprising two elastic face sheets and MR fluid core layer. The radiated sound power from the panel is derived using Rayleigh integral as a function of the transverse velocity of the panel which is subsequently used to evaluate the STL. The theoretical study is validated comparing the simulation results with the experimental measurements. Experimental and analytical parametric study have also been conducted to study the effect of the core layers’ thickness on the natural frequency and the STL of sandwich panel.

  12. Evidence of Toroidally Localized Turbulence with Applied 3D Fields in the DIII-D Tokamak.

    PubMed

    Wilcox, R S; Shafer, M W; Ferraro, N M; McKee, G R; Zeng, L; Rhodes, T L; Canik, J M; Paz-Soldan, C; Nazikian, R; Unterberg, E A

    2016-09-23

    New evidence indicates that there is significant 3D variation in density fluctuations near the boundary of weakly 3D tokamak plasmas when resonant magnetic perturbations are applied to suppress transient edge instabilities. The increase in fluctuations is concomitant with an increase in the measured density gradient, suggesting that this toroidally localized gradient increase could be a mechanism for turbulence destabilization in localized flux tubes. Two-fluid magnetohydrodynamic simulations find that, although changes to the magnetic field topology are small, there is a significant 3D variation of the density gradient within the flux surfaces that is extended along field lines. This modeling agrees qualitatively with the measurements. The observed gradient and fluctuation asymmetries are proposed as a mechanism by which global profile gradients in the pedestal could be relaxed due to a local change in the 3D equilibrium. These processes may play an important role in pedestal and scrape-off layer transport in ITER and other future tokamak devices with small applied 3D fields.

  13. RAPID COMMUNICATION: High performance superconducting wire in high applied magnetic fields via nanoscale defect engineering

    NASA Astrophysics Data System (ADS)

    Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L.; Cantoni, Claudia

    2008-09-01

    High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3-5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 µm thick YBa2Cu3O7-δ (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm-1 and 65.4 kA cm-2, respectively.

  14. High Performance Superconducting Wire in High Applied Magnetic Fields via Nanoscale Defect Engineering

    SciTech Connect

    Goyal, Amit; Wee, Sung Hun; Zuev, Yuri L; Cantoni, Claudia

    2008-01-01

    High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3 5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 m thick YBa2Cu3O7− (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm−1 and 65.4 kA cm−2, respectively.

  15. Quantum correlated cluster mean-field theory applied to the transverse Ising model.

    PubMed

    Zimmer, F M; Schmidt, M; Maziero, Jonas

    2016-06-01

    Mean-field theory (MFT) is one of the main available tools for analytical calculations entailed in investigations regarding many-body systems. Recently, there has been a surge of interest in ameliorating this kind of method, mainly with the aim of incorporating geometric and correlation properties of these systems. The correlated cluster MFT (CCMFT) is an improvement that succeeded quite well in doing that for classical spin systems. Nevertheless, even the CCMFT presents some deficiencies when applied to quantum systems. In this article, we address this issue by proposing the quantum CCMFT (QCCMFT), which, in contrast to its former approach, uses general quantum states in its self-consistent mean-field equations. We apply the introduced QCCMFT to the transverse Ising model in honeycomb, square, and simple cubic lattices and obtain fairly good results both for the Curie temperature of thermal phase transition and for the critical field of quantum phase transition. Actually, our results match those obtained via exact solutions, series expansions or Monte Carlo simulations.

  16. Evidence of toroidally localized turbulence with applied 3D fields in the DIII-D tokamak

    DOE PAGES

    Wilcox, R. S.; Shafer, M. W.; Ferraro, N. M.; ...

    2016-09-21

    New evidence indicates that there is significant 3D variation in density fluctuations near the boundary of weakly 3D tokamak plasmas when resonant magnetic perturbations are applied to suppress transient edge instabilities. The increase in fluctuations is concomitant with an increase in the measured density gradient, suggesting that this toroidally localized gradient increase could be a mechanism for turbulence destabilization in localized flux tubes. Two-fluid magnetohydrodynamic simulations find that, although changes to the magnetic field topology are small, there is a significant 3D variation of the density gradient within the flux surfaces that is extended along field lines. This modeling agreesmore » qualitatively with the measurements. The observed gradient and fluctuation asymmetries are proposed as a mechanism by which global profile gradients in the pedestal could be relaxed due to a local change in the 3D equilibrium. In conclusion, these processes may play an important role in pedestal and scrape-off layer transport in ITER and other future tokamak devices with small applied 3D fields.« less

  17. Evidence of toroidally localized turbulence with applied 3D fields in the DIII-D tokamak

    SciTech Connect

    Wilcox, R. S.; Shafer, M. W.; Ferraro, N. M.; McKee, G. R.; Zeng, L.; Rhodes, T. L.; Canik, J. M.; Paz-Soldan, C.; Nazikian, R.; Unterberg, E. A.

    2016-09-21

    New evidence indicates that there is significant 3D variation in density fluctuations near the boundary of weakly 3D tokamak plasmas when resonant magnetic perturbations are applied to suppress transient edge instabilities. The increase in fluctuations is concomitant with an increase in the measured density gradient, suggesting that this toroidally localized gradient increase could be a mechanism for turbulence destabilization in localized flux tubes. Two-fluid magnetohydrodynamic simulations find that, although changes to the magnetic field topology are small, there is a significant 3D variation of the density gradient within the flux surfaces that is extended along field lines. This modeling agrees qualitatively with the measurements. The observed gradient and fluctuation asymmetries are proposed as a mechanism by which global profile gradients in the pedestal could be relaxed due to a local change in the 3D equilibrium. In conclusion, these processes may play an important role in pedestal and scrape-off layer transport in ITER and other future tokamak devices with small applied 3D fields.

  18. The practice of prediction: What can ecologists learn from applied, ecology-related fields?

    USGS Publications Warehouse

    Pennekamp, Frank; Adamson, Matthew; Petchey, Owen L; Poggiale, Jean-Christophe; Aguiar, Maira; Kooi, Bob W.; Botkin, Daniel B.; DeAngelis, Don

    2016-01-01

    The pervasive influence of human induced global environmental change affects biodiversity across the globe, and there is great uncertainty as to how the biosphere will react on short and longer time scales. To adapt to what the future holds and to manage the impacts of global change, scientists need to predict the expected effects with some confidence and communicate these predictions to policy makers. However, recent reviews found that we currently lack a clear understanding of how predictable ecology is, with views seeing it as mostly unpredictable to potentially predictable, at least over short time frames. However, in applied, ecology-related fields predictions are more commonly formulated and reported, as well as evaluated in hindsight, potentially allowing one to define baselines of predictive proficiency in these fields. We searched the literature for representative case studies in these fields and collected information about modeling approaches, target variables of prediction, predictive proficiency achieved, as well as the availability of data to parameterize predictive models. We find that some fields such as epidemiology achieve high predictive proficiency, but even in the more predictive fields proficiency is evaluated in different ways. Both phenomenological and mechanistic approaches are used in most fields, but differences are often small, with no clear superiority of one approach over the other. Data availability is limiting in most fields, with long-term studies being rare and detailed data for parameterizing mechanistic models being in short supply. We suggest that ecologists adopt a more rigorous approach to report and assess predictive proficiency, and embrace the challenges of real world decision making to strengthen the practice of prediction in ecology.

  19. Directing migration of endothelial progenitor cells with applied DC electric fields.

    PubMed

    Zhao, Zhiqiang; Qin, Lu; Reid, Brian; Pu, Jin; Hara, Takahiko; Zhao, Min

    2012-01-01

    Naturally-occurring, endogenous electric fields (EFs) have been detected at skin wounds, damaged tissue sites and vasculature. Applied EFs guide migration of many types of cells, including endothelial cells to migrate directionally. Homing of endothelial progenitor cells (EPCs) to an injury site is important for repair of vasculature and also for angiogenesis. However, it has not been reported whether EPCs respond to applied EFs. Aiming to explore the possibility to use electric stimulation to regulate the progenitor cells and angiogenesis, we tested the effects of direct-current (DC) EFs on EPCs. We first used immunofluorescence to confirm the expression of endothelial progenitor markers in three lines of EPCs. We then cultured the progenitor cells in EFs. Using time-lapse video microscopy, we demonstrated that an applied DC EF directs migration of the EPCs toward the cathode. The progenitor cells also align and elongate in an EF. Inhibition of vascular endothelial growth factor (VEGF) receptor signaling completely abolished the EF-induced directional migration of the progenitor cells. We conclude that EFs are an effective signal that guides EPC migration through VEGF receptor signaling in vitro. Applied EFs may be used to control behaviors of EPCs in tissue engineering, in homing of EPCs to wounds and to an injury site in the vasculature.

  20. Applying LED in full-field optical coherence tomography for gastrointestinal endoscopy

    NASA Astrophysics Data System (ADS)

    Yang, Bor-Wen; Wang, Yu-Yen; Juan, Yu-Shan; Hsu, Sheng-Jie

    2015-08-01

    Optical coherence tomography (OCT) has become an important medical imaging technology due to its non-invasiveness and high resolution. Full-field optical coherence tomography (FF-OCT) is a scanning scheme especially suitable for en face imaging as it employs a CMOS/CCD device for parallel pixels processing. FF-OCT can also be applied to high-speed endoscopic imaging. Applying cylindrical scanning and a right-angle prism, we successfully obtained a 360° tomography of the inner wall of an intestinal cavity through an FF-OCT system with an LED source. The 10-μm scale resolution enables the early detection of gastrointestinal lesions, which can increase detection rates for esophageal, stomach, or vaginal cancer. All devices used in this system can be integrated by MOEMS technology to contribute to the studies of gastrointestinal medicine and advanced endoscopy technology.

  1. 100-kW class applied-field MPD thruster component wear

    NASA Astrophysics Data System (ADS)

    Mantenieks, Maris A.; Myers, Roger M.

    1993-01-01

    Component erosion and material deposition sites were identified and analyzed during tests of various configurations of 100 kW class, applied-field, water-cooled magnetoplasmadynamic (MPD) thrusters. Severe erosion of the cathode and the boron nitride insulator was observed for the first series of tests, which was significantly decreased by reducing the levels of propellant contamination. Severe erosion of the copper anode resulting from sputtering by the propellant was also observed. This is the first observation of this phenomenon in MPD thrusters. The anode erosion indicates that development of long life MPD thrusters requires the use of light gas propellants such as hydrogen, deuterium, or lithium.

  2. 100-kW class applied-field thruster component wear

    NASA Astrophysics Data System (ADS)

    Mantenieks, Maris A.; Myers, Roger M.

    1993-01-01

    Component erosion and material deposition sites were identified and analyzed during tests of various configurations of 100 kW class, applied-field, water-cooled magnetoplasmadynamic (MPD) thrusters. Severe erosion of the cathode and the boron nitride insulator was observed for the first series of tests, which was significantly decreased by reducing the levels of propellant contamination. Severe erosion of the copper anode resulting from sputtering by the propellant was also observed. This is the first observation of this phenomenon in MPD thrusters. The anode erosion indicates that development of long life MPD thrusters requires the use of light gas propellants such as hydrogen, deuterium, or lithium.

  3. Reorientation Response of Magnetic Microspheres Attached to Gold Electrodes Under an Applied Magnetic Field

    NASA Astrophysics Data System (ADS)

    De Los Santos Valladares, L.; Dominguez, A. Bustamante; Aguiar, J. Albino; Reeve, R. M.; Mitrelias, T.; Langford, R. M.; Azuma, Y.; Barnes, C. H. W.; Majima, Y.

    2013-08-01

    In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current-voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C8H18S2), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution.

  4. Monitoring fibroblast behavior in tissue culture with an applied electric field.

    PubMed Central

    Giaever, I; Keese, C R

    1984-01-01

    Mammalian fibroblasts have been cultured on evaporated gold electrodes subjected to an alternating electric field at 4000 Hz. The system consists of a large (approximately equal to 2 cm2) and a small (approximately equal to 3 X 10(-4) cm2) electrode bathed in tissue culture medium. The applied electric field produces a voltage drop at the boundary between the solution and the small electrode of a few mV at a current density of a few mA/cm2. The small population of cells that attach and spread on this electrode have a marked effect on the measured impedance and also cause it to fluctuate with time. The amplitude of these fluctuations is greatly reduced by cytochalasin B (10 microM), suggesting they are a consequence of cell movement. Images PMID:6587391

  5. Rupture of nanoscaled water sheets in the presence of an applied electric field

    NASA Astrophysics Data System (ADS)

    Gopan, Nandu

    2016-12-01

    Understanding the behaviour of water sheets is relevant in numerous areas, such as thin film coating and atomisation. The rupture of planar liquid sheets are interesting due to the fact that they are objects of co-dimension 1. Previous work seems to suggest that a generic route to liquid structure fragmentation is via liquid sheets. The interplay between inertia, surface tension and viscosity is crucial in determining the dynamics of liquid sheets at a macro scale. At the nanoscale, where thermal fluctuations are expected to play a dominant role, the dynamics become more interesting. The stability and rupture dynamics of nanoscaled water sheets, at constant temperature, are studied using constrained molecular dynamics (MD) simulations. The SPC/E potential with long range electrostatics is used to simulate water molecules. The effect of an applied electric field on the stability of the nanoscaled water sheet forms the focus of this study. The effect of the initial configuration is studied by changing the random seed values used for velocity initialisation. The effect of sheet thickness on the rupture dynamics is also explored. It is seen that when large electric fields (5 V/nm) act across very thin sheets (1 layer), then breakup into multiple ellipsoidal structures is a possibility, and the response of the fluid structure to the applied electric field is non-linear. Furthermore, it is seen that Taylor's predictions for the critical electric field intensity, based on classical electro-hydrodynamics for the onset of instability in macroscopic drops, scales surprisingly well for the case of nanoscaled sheets.

  6. 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.

  7. Synthesis of Micelles Guided Magnetite (Fe3O4) Hollow Spheres and their application for AC Magnetic Field Responsive Drug Release.

    PubMed

    Mandal Goswami, Madhuri

    2016-10-31

    This paper reports on synthesis of hollow spheres of magnetite, guided by micelles and their application in drug release by the stimulus responsive technique. Here oleyelamine micelles are used as the core substance for the formation of magnetite nano hollow spheres (NHS). Diameter and shell thickness of NHS have been changed by changing concentration of the micelles. Mechanism of NHS formation has been established by investigating the aliquot collected at different time during the synthesis of NHS. It has been observed that oleyelamine as micelles play an important role to generate hollow-sphere particles of different diameter and thickness just by varying its amount. Structural analysis was done by XRD measurement and morphological measurements, SEM and TEM were performed to confirm the shape and size of the NHS. FTIR measurement support the formation of magnetite phase too. Frequency dependent AC magnetic measurements and AC magnetic field stimulated drug release event by these particles provide a direction of the promising application of these NHS for better cancer treatment in near future. Being hollow &porous in structure and magnetic in nature, such materials will also be useful in other applications such as in removal of toxic materials, magnetic separation etc.

  8. Synthesis of Micelles Guided Magnetite (Fe3O4) Hollow Spheres and their application for AC Magnetic Field Responsive Drug Release

    PubMed Central

    Mandal Goswami, Madhuri

    2016-01-01

    This paper reports on synthesis of hollow spheres of magnetite, guided by micelles and their application in drug release by the stimulus responsive technique. Here oleyelamine micelles are used as the core substance for the formation of magnetite nano hollow spheres (NHS). Diameter and shell thickness of NHS have been changed by changing concentration of the micelles. Mechanism of NHS formation has been established by investigating the aliquot collected at different time during the synthesis of NHS. It has been observed that oleyelamine as micelles play an important role to generate hollow-sphere particles of different diameter and thickness just by varying its amount. Structural analysis was done by XRD measurement and morphological measurements, SEM and TEM were performed to confirm the shape and size of the NHS. FTIR measurement support the formation of magnetite phase too. Frequency dependent AC magnetic measurements and AC magnetic field stimulated drug release event by these particles provide a direction of the promising application of these NHS for better cancer treatment in near future. Being hollow & porous in structure and magnetic in nature, such materials will also be useful in other applications such as in removal of toxic materials, magnetic separation etc. PMID:27796329

  9. Synthesis of Micelles Guided Magnetite (Fe3O4) Hollow Spheres and their application for AC Magnetic Field Responsive Drug Release

    NASA Astrophysics Data System (ADS)

    Mandal Goswami, Madhuri

    2016-10-01

    This paper reports on synthesis of hollow spheres of magnetite, guided by micelles and their application in drug release by the stimulus responsive technique. Here oleyelamine micelles are used as the core substance for the formation of magnetite nano hollow spheres (NHS). Diameter and shell thickness of NHS have been changed by changing concentration of the micelles. Mechanism of NHS formation has been established by investigating the aliquot collected at different time during the synthesis of NHS. It has been observed that oleyelamine as micelles play an important role to generate hollow-sphere particles of different diameter and thickness just by varying its amount. Structural analysis was done by XRD measurement and morphological measurements, SEM and TEM were performed to confirm the shape and size of the NHS. FTIR measurement support the formation of magnetite phase too. Frequency dependent AC magnetic measurements and AC magnetic field stimulated drug release event by these particles provide a direction of the promising application of these NHS for better cancer treatment in near future. Being hollow & porous in structure and magnetic in nature, such materials will also be useful in other applications such as in removal of toxic materials, magnetic separation etc.

  10. [Negative air ions generated by plants upon pulsed electric field stimulation applied to soil].

    PubMed

    Wu, Ren-ye; Deng, Chuan-yuan; Yang, Zhi-jian; Weng, Hai-yong; Zhu, Tie-jun-rong; Zheng, Jin-gui

    2015-02-01

    This paper investigated the capacity of plants (Schlumbergera truncata, Aloe vera var. chinensis, Chlorophytum comosum, Schlumbergera bridgesii, Gymnocalycium mihanovichii var. friedrichii, Aspidistra elatior, Cymbidium kanran, Echinocactus grusonii, Agave americana var. marginata, Asparagus setaceus) to generate negative air ions (NAI) under pulsed electric field stimulation. The results showed that single plant generated low amounts of NAI in natural condition. The capacity of C. comosum and G. mihanovichii var. friedrichii generated most NAI among the above ten species, with a daily average of 43 ion · cm(-3). The least one was A. americana var. marginata with the value of 19 ion · cm(-3). When proper pulsed electric field stimulation was applied to soil, the NAI of ten plant species were greatly improved. The effect of pulsed electric field u3 (average voltage over the pulse period was 2.0 x 10(4) V, pulse frequency was 1 Hz, and pulse duration was 50 ms) was the greatest. The mean NAI concentration of C. kanran was the highest 1454967 ion · cm(-3), which was 48498.9 times as much as that in natural condition. The lowest one was S. truncata with the value of 34567 ion · cm(-3), which was 843.1 times as much as that in natural condition. The capacity of the same plants to generate negative air ion varied extremely under different intensity pulsed electric fields.

  11. Tissue heterogeneity as a mechanism for localized neural stimulation by applied electric fields

    NASA Astrophysics Data System (ADS)

    Miranda, P. C.; Correia, L.; Salvador, R.; Basser, P. J.

    2007-09-01

    We investigate the heterogeneity of electrical conductivity as a new mechanism to stimulate excitable tissues via applied electric fields. In particular, we show that stimulation of axons crossing internal boundaries can occur at boundaries where the electric conductivity of the volume conductor changes abruptly. The effectiveness of this and other stimulation mechanisms was compared by means of models and computer simulations in the context of transcranial magnetic stimulation. While, for a given stimulation intensity, the largest membrane depolarization occurred where an axon terminates or bends sharply in a high electric field region, a slightly smaller membrane depolarization, still sufficient to generate action potentials, also occurred at an internal boundary where the conductivity jumped from 0.143 S m-1 to 0.333 S m-1, simulating a white-matter-grey-matter interface. Tissue heterogeneity can also give rise to local electric field gradients that are considerably stronger and more focal than those impressed by the stimulation coil and that can affect the membrane potential, albeit to a lesser extent than the two mechanisms mentioned above. Tissue heterogeneity may play an important role in electric and magnetic 'far-field' stimulation.

  12. 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.

  13. Embryonic zebrafish neuronal growth is not affected by an applied electric field in vitro.

    PubMed

    Cormie, Peter; Robinson, Kenneth R

    2007-01-10

    Naturally occurring electric fields (EFs) have been implicated in cell guidance during embryonic development and adult wound healing. Embryonic Xenopus laevis neurons sprout preferentially towards the cathode, turn towards the cathode, and migrate faster towards the cathode in the presence of an external EF in vitro. A recent Phase 1 clinical trial has investigated the effects of oscillating EFs on human spinal cord regeneration. The purpose of this study was to investigate whether embryonic zebrafish neurons respond to an applied EF, and thus extend this research into another vertebrate system. Neural tubes of zebrafish embryos (16-17 somites) were dissected and dissociated neuroblasts were plated onto laminin-coated glass. A 100 mV/mm EF was applied to cell cultures for 4 or 20 h and the responses of neurons to the applied EFs were investigated. After 4h in an EF neurites were significantly shorter than control neurites. No other statistically significant effects were observed. After 20 h, control and EF-exposed neurites were no different in length. No length difference was seen between cathodally- and anodally-sprouted neurites. Application of an EF did not affect the average number of neurons in a chamber. Growth cones did not migrate preferentially towards either pole of the EF and no asymmetry was seen in neurite sprout sites. We conclude that zebrafish neurons do not respond to a 100 mV/mm applied EF in vitro. This suggests that neurons of other vertebrate species may not respond to applied EFs in the same ways as Xenopus laevis neurons.

  14. Combined AC electroosmosis and dielectrophoresis for controlled rotation of microparticles

    PubMed Central

    Walid Rezanoor, Md.; Dutta, Prashanta

    2016-01-01

    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

  15. The behaviors of ferromagnetic nano-particles in and around blood vessels under applied magnetic fields

    NASA Astrophysics Data System (ADS)

    Nacev, A.; Beni, C.; Bruno, O.; Shapiro, B.

    2011-03-01

    In magnetic drug delivery, therapeutic magnetizable particles are typically injected into the blood stream and magnets are then used to concentrate them to disease locations. The behavior of such particles in-vivo is complex and is governed by blood convection, diffusion (in blood and in tissue), extravasation, and the applied magnetic fields. Using physical first-principles and a sophisticated vessel-membrane-tissue (VMT) numerical solver, we comprehensively analyze in detail the behavior of magnetic particles in blood vessels and surrounding tissue. For any blood vessel (of any size, depth, and blood velocity) and tissue properties, particle size and applied magnetic fields, we consider a Krogh tissue cylinder geometry and solve for the resulting spatial distribution of particles. We find that there are three prototypical behaviors (blood velocity dominated, magnetic force dominated, and boundary-layer formation) and that the type of behavior observed is uniquely determined by three non-dimensional numbers (the magnetic-Richardson number, mass Péclet number, and Renkin reduced diffusion coefficient). Plots and equations are provided to easily read out which behavior is found under which circumstances (Figs. 5-8). We compare our results to previously published in-vitro and in-vivo magnetic drug delivery experiments. Not only do we find excellent agreement between our predictions and prior experimental observations, but we are also able to qualitatively and quantitatively explain behavior that was previously not understood.

  16. High-temperature tensile deformation behavior of aluminum oxide with and without an applied electric field

    NASA Astrophysics Data System (ADS)

    Campbell, James

    1998-12-01

    Ceramics are usually considered to be brittle, but under certain conditions some ceramics exhibit a large degree of ductility. They are fine-grained and exhibit superplastic behavior when deformed at high temperatures and low stresses. Whereas superplasticity gives enhanced ductility to metals, it may be the only method for imparting large plasticity to ceramics. Electric fields have been shown to increase ductility, reduce flow stress and reduce cavitation in the superplastic forming of 7475 Al and yttria-stabilized zirconia. Thus, the concurrent application of an electric field may give improved superplastic properties and increased plasticity to a marginally ductile ceramic such as aluminum oxide (alpha-alumina). Fine-grained alumina tensile specimens, formed by dry pressing and sintering a spray-dried powder, were tested in tension at high temperature with and without an electric field of 300 V/cm. Constant strain rate, strain rate cycling and stress relaxation tests were performed. The effects of an electric field on the ductility, flow stress, cavitation and parameters of the Weertman-Dorn deformation equation were measured. Without an electric field, the following deformation parameters were found: the stress exponent n = 2.2, the grain size exponent p = 1.9, the activation energy Q = 490 kJ/mol and the threshold stress sigmao ≈ 0 MPa, indicating structural superplasticity where grain boundary sliding is the predominant deformation mode and was likely accommodated by the motion of grain boundary dislocations. An electric field of 300 V/cm gave a Joule heating temperature increase of ˜30°C and caused the alumina to swell 5--25% (increasing with time), even while under no applied stress, thereby reducing its ductility and flow stress. After correcting for Joule heating and swelling there was still a significant flow stress reduction produced by the field and the following deformation parameters were found: n = 2.2, p = 1.9, Q = 950 kJ/mol and sigmao ≈ 0

  17. Deep Vadose Zone-Applied Field Research Initiative Fiscal Year 2011 Annual Report

    SciTech Connect

    Wellman, Dawn M.; Johnson, Timothy C.; Smith, Ronald M.; Truex, Michael J.; Matthews, Hope E.

    2011-10-01

    This annual report describes the background of the Deep Vadose Zone-Applied Field Research Initiative, and some of the programmatic approaches and transformational technologies in groundwater and deep vadose zone remediation developed during fiscal year 2011. The Department of Energy (DOE) Office of Technology Innovation and Development's (OTID) mission is to transform science into viable solutions for environmental cleanup. In 2010, OTID developed the Impact Plan, Science and Technology to Reduce the Life Cycle Cost of Closure to outline the benefits of research and development of the lifecycle cost of cleanup across the DOE complex. This plan outlines OTID's ability to reduce by $50 billion, the $200 billion life-cycle cost in waste processing, groundwater and soil, nuclear materials, and deactivation and decommissioning. The projected life-cycle costs and return on investment are based on actual savings realized from technology innovation, development, and insertion into remedial strategies and schedules at the Fernald, Mound, and Ashtabula sites. To achieve our goals, OTID developed Applied Field Research Initiatives to facilitate and accelerate collaborative development and implementation of new tools and approaches that reduce risk, cost and time for site closure. The primary mission of the Deep Vadose Zone-Applied Field Research Initiative (DVZ-AFRI) is to protect our nation's water resources, keeping them clean and safe for future generations. The DVZ-AFRI was established for the DOE to develop effective, science-based solutions for remediating, characterizing, monitoring, and predicting the behavior and fate of deep vadose zone contamination. Subsurface contaminants include radionuclides, metals, organics, and liquid waste that originated from various sources, including legacy waste from the nation's nuclear weapons complexes. The DVZ-AFRI project team is translating strategy into action by working to solve these complex challenges in a collaborative

  18. Tuning the energy gap of bilayer α-graphyne by applying strain and electric field

    NASA Astrophysics Data System (ADS)

    Yang, Hang; Wu, Wen-Zhi; Jin, Yu; Wan-Lin, Guo

    2016-02-01

    Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing University of Aeronautics and Astronautics (NUAA) Fundamental Research Funds, China (Grant No. NP2015203), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

  19. Old concepts, new molecules and current approaches applied to the bacterial nucleotide signalling field

    PubMed Central

    2016-01-01

    Signalling nucleotides are key molecules that help bacteria to rapidly coordinate cellular pathways and adapt to changes in their environment. During the past 10 years, the nucleotide signalling field has seen much excitement, as several new signalling nucleotides have been discovered in both eukaryotic and bacterial cells. The fields have since advanced quickly, aided by the development of important tools such as the synthesis of modified nucleotides, which, combined with sensitive mass spectrometry methods, allowed for the rapid identification of specific receptor proteins along with other novel genome-wide screening methods. In this review, we describe the principle concepts of nucleotide signalling networks and summarize the recent work that led to the discovery of the novel signalling nucleotides. We also highlight current approaches applied to the research in the field as well as resources and methodological advances aiding in a rapid identification of nucleotide-specific receptor proteins. This article is part of the themed issue ‘The new bacteriology’. PMID:27672152

  20. Nutrient Status and Contamination Risks from Digested Pig Slurry Applied on a Vegetable Crops Field

    PubMed Central

    Zhang, Shaohui; Hua, Yumei; Deng, Liangwei

    2016-01-01

    The effects of applied digested pig slurry on a vegetable crops field were studied. The study included a 3-year investigation on nutrient characteristics, heavy metals contamination and hygienic risks of a vegetable crops field in Wuhan, China. The results showed that, after anaerobic digestion, abundant N, P and K remained in the digested pig slurry while fecal coliforms, ascaris eggs, schistosoma eggs and hookworm eggs were highly reduced. High Cr, Zn and Cu contents in the digested pig slurry were found in spring. Digested pig slurry application to the vegetable crops field led to improved soil fertility. Plant-available P in the fertilized soils increased due to considerable increase in total P content and decrease in low-availability P fraction. The As content in the fertilized soils increased slightly but significantly (p = 0.003) compared with control. The Hg, Zn, Cr, Cd, Pb, and Cu contents in the fertilized soils did not exceed the maximum permissible contents for vegetable crops soils in China. However, high Zn accumulation should be of concern due to repeated applications of digested pig slurry. No fecal coliforms, ascaris eggs, schistosoma eggs or hookworm eggs were detected in the fertilized soils. PMID:27058548

  1. The drift field model applied to the lithium-containing silicon solar cell

    NASA Technical Reports Server (NTRS)

    Godlewski, M. P.; Baraona, C. R.; Brandhorst, H. W., Jr.

    1973-01-01

    The drift field model used by Wolf to calculate the short-circuit current was extended to permit calculations of the open-circuit voltage and the maximum power under conditions of illumination of either tungsten (2800 C) source or AMO sunlight. Voltages were calculated using an expression for the drift field diode saturation current derived here. The model, applied to the oxygen rich (C-13 group) lithium solar cells, was used to calculate the pre-and post-electron bombardment trends for lithium gradients in the range of 10 to the 18th power to 10 to the 19th power Li/cm to the 4th power. Published experimental data characterizing these cells were used to tailor the model. The calculated trends are in reasonable agreement with the empirical data of Faith. Diffusion length degradation and carrier removal effects were sufficient to predict the cell performance up to 3 x 10 to the 14th power e/sq cm. Beyond this fluence it was necessary to include drift field removal effects.

  2. Translocation of closed polymers through a nanopore under an applied external field

    NASA Astrophysics Data System (ADS)

    Jiang, Shao-Chuan; Zhang, Lin-Xi; Xia, A.-Gen; Chen, Hong-Ping; Cheng, Jun

    2010-01-01

    The dynamic behaviours of the translocations of closed circular polymers and closed knotted polymers through a nanopore, under the driving of an applied field, are studied by three-dimensional Langevin dynamics simulations. The power-law scaling of the translocation time τ with the chain length N and the distribution of translocation time are investigated separately. For closed circular polymers, a crossover scaling of translocation time with chain length is found to be τ simeq Nα, with the exponent α varying from α = 0.71 for relatively short chains to α = 1.29 for longer chains under driving force F = 5. The scaling behaviour for longer chains is in good agreement with experimental results, in which the exponent α = 1.27 for the translocation of double-strand DNA. The distribution of translocation time D(τ) is close to a Gaussian function for duration time τ < τp and follows a falling exponential function for duration time τ > τp. For closed knotted polymers, the scaling exponent α is 1.27 for small field force (F = 5) and 1.38 for large field force (F = 10). The distribution of translocation time D(τ) remarkably features two peaks appearing in the case of large driving force. The interesting result of multiple peaks can conduce to the understanding of the influence of the number of strands of polymers in the pore at the same time on translocation dynamic process and scaling property.

  3. 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

  4. Equilibrium intermediate-state patterns in a type-I superconducting slab in an arbitrarily oriented applied magnetic field

    DOE PAGES

    Clem, John; Prozorov, Ruslan; Wijngaarden, Rinke J.

    2013-09-04

    The equilibrium topology of superconducting and normal domains in flat type-I superconductors is investigated. Important improvements with respect to previous work are that (1) the energy of the external magnetic field, as deformed by the presence of superconducting domains, is calculated in the same way for three different topologies and (2) calculations are made for arbitrary orientation of the applied field. A phase diagram is presented for the minimum-energy topology as a function of applied field magnitude and angle. For small (large) applied fields, normal (superconducting) tubes are found, while for intermediate fields, parallel domains have a lower energy. Themore » range of field magnitudes for which the superconducting-tubes structure is favored shrinks when the field is more in-plane oriented.« less

  5. Equilibrium intermediate-state patterns in a type-I superconducting slab in an arbitrarily oriented applied magnetic field

    SciTech Connect

    Clem, John; Prozorov, Ruslan; Wijngaarden, Rinke J.

    2013-09-04

    The equilibrium topology of superconducting and normal domains in flat type-I superconductors is investigated. Important improvements with respect to previous work are that (1) the energy of the external magnetic field, as deformed by the presence of superconducting domains, is calculated in the same way for three different topologies and (2) calculations are made for arbitrary orientation of the applied field. A phase diagram is presented for the minimum-energy topology as a function of applied field magnitude and angle. For small (large) applied fields, normal (superconducting) tubes are found, while for intermediate fields, parallel domains have a lower energy. The range of field magnitudes for which the superconducting-tubes structure is favored shrinks when the field is more in-plane oriented.

  6. Comparison of AC electronic monitoring and field data for estimating tolerance to Empoasca kraemeri (Homoptera: Cicadellidae) in common bean genotypes.

    PubMed

    Serrano, M S; Backus, E A; Cardona, C

    2000-12-01

    Two methods for estimating the tolerance of common bean genotypes to Empoasca kraemeri Ross & Moore were compared, using a yield trial carried out at Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia, versus stylet penetration tactics measured by AC electronic feeding monitors. A stylet penetration index was devised based on principal component scores of three penetration tactics identified (pulsing laceration, cell rupturing, and lancing sap ingestion), combined with knowledge of the hopperburn symptoms caused by each tactic. Tolerant genotypes, as classified by the CIAT yield index, showed significantly more unprotected yield and lower hopperburn scores than the susceptible control. They also induced performance of less pulsing laceration (the tactic considered most damaging to the plant), and more of the other two, mitigating tactics, especially cell rupturing. When index values were calculated for each genotype, stylet penetration index values matched those of the yield index for three out of five genotypes: two EMP-coded tolerant lines ('EMP 385' and 'EMP 392') and the susceptible control 'BAT 41'. Thus, for these three genotypes, all subsequent hoppereburn symptoms are predictable by the type of feeding behavior performed on them. 'Porrillo Sintético' and 'EMP 84', considered borderline genotypes by the yield index, were overestimated and underestimated respectively, by the stylet penetration index. We postulate that, for these two genotypes, plant physiological responses to feeding (either compensatory or heightened sensitivity, respectively) synergize with type of feeding performed to generate the overall hopperburn condition. This multivariate analysis of electronic monitoring data was successfully used to devise an index of resistance. The implications of using the stylet penetration index and the advantages of using electronic monitoring in a bean-breeding program are discussed.

  7. Seismic Traveltime Tomography Applied to Data from Miranga Field, Reconcavo Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Bassrei, A.; Rodrigues, V.

    2015-12-01

    The growing global demand for hydrocarbons has tested the limits of oil exploration and exploitation technologies. Within the seismic methods, tomography is an alternative for the high resolution characterization of reservoirs, enabling a more efficient recovery of new as well as mature fields. In this work, seismic traveltime tomography in the transmission mode was applied to real data from the Miranga Field, Reconcavo Basin, State of Bahia, Brazil. This basin represents a landmark of oil exploration in Brazil and has been intensively studied since the 1950s. Today, the Reconcavo Basin is still the principal oil producer in the State of Bahia, but there is a demand for new technologies, especially for mature fields, to improve hydrocarbon recovery. The objective is to estimate the two-dimensional velocity distribution in the region between the two wells. We have used linearized inversion through the Levenberg-Marquardt scheme. The input data in the system are the traveltimes between the sources and the receivers and the distances propagated by each ray connecting such sources and receivers. Both inputs are provided through acoustic forward modeling. The conjugate gradient algorithm with regularization through derivative matrices was used as an inverse procedure. The tomographic inversion is an ill-posed problem because the existence, uniqueness and stability conditions are not completely satisfied. The linear system is regularized by derivative matrices derived to minimize the instability. This regularization procedure has a crucially important parameter called regularization parameter lambda. For the selection of lambda we used L-curve and Theta-curve. The estimated tomograms were consistent with previous geological knowledge of the area and the P-wave velocity range was consistent. The results showed that traveltime tomography is feasible for the characterization of reservoirs with a high rate of vertical change, similar to the Miranga Field.

  8. Activation of Schwann cells in vitro by magnetic nanocomposites via applied magnetic field

    PubMed Central

    Liu, Zhongyang; Huang, Liangliang; Liu, Liang; Luo, Beier; Liang, Miaomiao; Sun, Zhen; Zhu, Shu; Quan, Xin; Yang, Yafeng; Ma, Teng; Huang, Jinghui; Luo, Zhuojing

    2015-01-01

    Schwann cells (SCs) are attractive seed cells in neural tissue engineering, but their application is limited by attenuated biological activities and impaired functions with aging. Therefore, it is important to explore an approach to enhance the viability and biological properties of SCs. In the present study, a magnetic composite made of magnetically responsive magnetic nanoparticles (MNPs) and a biodegradable chitosan–glycerophosphate polymer were prepared and characterized. It was further explored whether such magnetic nanocomposites via applied magnetic fields would regulate SC biological activities. The magnetization of the magnetic nanocomposite was measured by a vibrating sample magnetometer. The compositional characterization of the magnetic nanocomposite was examined by Fourier-transform infrared and X-ray diffraction. The tolerance of SCs to the magnetic fields was tested by flow-cytometry assay. The proliferation of cells was examined by a 5-ethynyl-2-deoxyuridine-labeling assay, a PrestoBlue assay, and a Live/Dead assay. Messenger ribonucleic acid of BDNF, GDNF, NT-3, and VEGF in SCs was assayed by quantitative real-time polymerase chain reaction. The amount of BDNF, GDNF, NT-3, and VEGF secreted from SCs was determined by enzyme-linked immunosorbent assay. It was found that magnetic nanocomposites containing 10% MNPs showed a cross-section diameter of 32.33±1.81 µm, porosity of 80.41%±0.72%, and magnetization of 5.691 emu/g at 8 kOe. The 10% MNP magnetic nanocomposites were able to support cell adhesion and spreading and further promote proliferation of SCs under magnetic field exposure. Interestingly, a magnetic field applied through the 10% MNP magnetic scaffold significantly increased the gene expression and protein secretion of BDNF, GDNF, NT-3, and VEGF. This work is the first stage in our understanding of how to precisely regulate the viability and biological properties of SCs in tissue-engineering grafts, which combined with additional

  9. Activation of Schwann cells in vitro by magnetic nanocomposites via applied magnetic field.

    PubMed

    Liu, Zhongyang; Huang, Liangliang; Liu, Liang; Luo, Beier; Liang, Miaomiao; Sun, Zhen; Zhu, Shu; Quan, Xin; Yang, Yafeng; Ma, Teng; Huang, Jinghui; Luo, Zhuojing

    2015-01-01

    Schwann cells (SCs) are attractive seed cells in neural tissue engineering, but their application is limited by attenuated biological activities and impaired functions with aging. Therefore, it is important to explore an approach to enhance the viability and biological properties of SCs. In the present study, a magnetic composite made of magnetically responsive magnetic nanoparticles (MNPs) and a biodegradable chitosan-glycerophosphate polymer were prepared and characterized. It was further explored whether such magnetic nanocomposites via applied magnetic fields would regulate SC biological activities. The magnetization of the magnetic nanocomposite was measured by a vibrating sample magnetometer. The compositional characterization of the magnetic nanocomposite was examined by Fourier-transform infrared and X-ray diffraction. The tolerance of SCs to the magnetic fields was tested by flow-cytometry assay. The proliferation of cells was examined by a 5-ethynyl-2-deoxyuridine-labeling assay, a PrestoBlue assay, and a Live/Dead assay. Messenger ribonucleic acid of BDNF, GDNF, NT-3, and VEGF in SCs was assayed by quantitative real-time polymerase chain reaction. The amount of BDNF, GDNF, NT-3, and VEGF secreted from SCs was determined by enzyme-linked immunosorbent assay. It was found that magnetic nanocomposites containing 10% MNPs showed a cross-section diameter of 32.33±1.81 µm, porosity of 80.41%±0.72%, and magnetization of 5.691 emu/g at 8 kOe. The 10% MNP magnetic nanocomposites were able to support cell adhesion and spreading and further promote proliferation of SCs under magnetic field exposure. Interestingly, a magnetic field applied through the 10% MNP magnetic scaffold significantly increased the gene expression and protein secretion of BDNF, GDNF, NT-3, and VEGF. This work is the first stage in our understanding of how to precisely regulate the viability and biological properties of SCs in tissue-engineering grafts, which combined with additional

  10. Activity recognition in planetary navigation field tests using classification algorithms applied to accelerometer data.

    PubMed

    Song, Wen; Ade, Carl; Broxterman, Ryan; Barstow, Thomas; Nelson, Thomas; Warren, Steve

    2012-01-01

    Accelerometer data provide useful information about subject activity in many different application scenarios. For this study, single-accelerometer data were acquired from subjects participating in field tests that mimic tasks that astronauts might encounter in reduced gravity environments. The primary goal of this effort was to apply classification algorithms that could identify these tasks based on features present in their corresponding accelerometer data, where the end goal is to establish methods to unobtrusively gauge subject well-being based on sensors that reside in their local environment. In this initial analysis, six different activities that involve leg movement are classified. The k-Nearest Neighbors (kNN) algorithm was found to be the most effective, with an overall classification success rate of 90.8%.

  11. Electron transport in fast dielectric liquids at high applied electric fields

    SciTech Connect

    Faidas, H.; McCorkle, D.L. . Dept. of Physics); Christophorou, L.G. )

    1990-01-01

    The drift velocity, w, of excess electrons as a function of the applied uniform electric field, E, in liquid 2,2-dimethylpropane (TMC), tetramethylsilane (TMS), tetramethylgermanium (TMG), tetramethyltin (TMT), 2,2,4,4-tetramethylpentane (TMP) and in mixtures of TMS with TMP (mole ratio M = 1.31/1) and n-pentane (M = 102/1, 17/1, and 5.6/1) has been measured for E-values up to {approximately}10{sup 5} V cm{sup {minus}1}. The thermal electron mobility in the above liquids is 71.5, 119.3, 114.7, 85.7, 31.8, 39.1, 118, 85, and 47.6 cm{sup 2} s{sup {minus}1} V{sup {minus}1}, respectively. 8 refs., 2 figs., 1 tab.

  12. Tokamak equilibria and edge stability when non-axisymmetric fields are applied

    NASA Astrophysics Data System (ADS)

    Ham, C. J.; Chapman, I. T.; Simpson, J.; Suzuki, Y.

    2015-05-01

    Tokamaks are traditionally viewed as axisymmetric devices. However this is not always true, for example in the presence of saturated instabilities, error fields, or resonant magnetic perturbations (RMPs) applied for edge localized mode (ELM) control. We use the VMEC code (Hirshman and Whitson 1983 Phys. Fluids 26 3553) to calculate three dimensional equilibria by energy minimization for tokamak plasmas. MAST free boundary equilibria have been calculated with profiles for plasma pressure and current derived from two dimensional reconstruction. It is well known that ELMs will need to be controlled in ITER to prevent damage that may limit the lifetime of the machine (Loarte et al 2003 Plasma Phys. Control. Fusion 45 1549). ELM control has been demonstrated on several tokamaks including MAST (Kirk et al 2013 Nucl. Fusion 53 043007). However the application of RMPs causes the plasma to gain a displacement or corrugation (Liu et al 2011 Nucl. Fusion 51 083002). Previous work has shown that the phase and size of these corrugations is in agreement with experiment (Chapman et al 2012 Plasma Phys. Control. Fusion 54 105013). The interaction of these corrugations with the plasma control system (PCS) may cause high heat loads at certain toroidal locations if care is not taken (Chapman et al 2014 Plasma Phys. Control. Fusion 56 075004). VMEC assumes nested flux surfaces but this assumption has been relaxed in other stellarator codes. These codes allow equilibria where magnetic islands and stochastic regions can form. We show some initial results using the HINT2 code (Suzuki et al 2006 Nucl. Fusion 46 L19). The Mercier stability of VMEC equilibria with RMPs applied is calculated. The geodesic curvature contribution can be strongly influenced by helical Pfirsch-Schlüter currents driven by the applied RMPs. ELM mitigation is not fully understood but one of the factors that influences peeling-ballooning stability, which is linked to ELMs, is a three dimensional corrugation of the

  13. The Application of Intensive Longitudinal Methods to Investigate Change: Stimulating the Field of Applied Family Research.

    PubMed

    Bamberger, Katharine T

    2016-03-01

    The use of intensive longitudinal methods (ILM)-rapid in situ assessment at micro timescales-can be overlaid on RCTs and other study designs in applied family research. Particularly, when done as part of a multiple timescale design-in bursts over macro timescales-ILM can advance the study of the mechanisms and effects of family interventions and processes of family change. ILM confers measurement benefits in accurately assessing momentary and variable experiences and captures fine-grained dynamic pictures of time-ordered processes. Thus, ILM allows opportunities to investigate new research questions about intervention effects on within-subject (i.e., within-person, within-family) variability (i.e., dynamic constructs) and about the time-ordered change process that interventions induce in families and family members beginning with the first intervention session. This paper discusses the need and rationale for applying ILM to family intervention evaluation, new research questions that can be addressed with ILM, example research using ILM in the related fields of basic family research and the evaluation of individual-based interventions. Finally, the paper touches on practical challenges and considerations associated with ILM and points readers to resources for the application of ILM.

  14. Applying simulation model to uniform field space charge distribution measurements by the PEA method

    SciTech Connect

    Liu, Y.; Salama, M.M.A.

    1996-12-31

    Signals measured under uniform fields by the Pulsed Electroacoustic (PEA) method have been processed by the deconvolution procedure to obtain space charge distributions since 1988. To simplify data processing, a direct method has been proposed recently in which the deconvolution is eliminated. However, the surface charge cannot be represented well by the method because the surface charge has a bandwidth being from zero to infinity. The bandwidth of the charge distribution must be much narrower than the bandwidths of the PEA system transfer function in order to apply the direct method properly. When surface charges can not be distinguished from space charge distributions, the accuracy and the resolution of the obtained space charge distributions decrease. To overcome this difficulty a simulation model is therefore proposed. This paper shows their attempts to apply the simulation model to obtain space charge distributions under plane-plane electrode configurations. Due to the page limitation for the paper, the charge distribution originated by the simulation model is compared to that obtained by the direct method with a set of simulated signals.

  15. The Application of Intensive Longitudinal Methods to Investigate Change: Stimulating the Field of Applied Family Research

    PubMed Central

    Bamberger, Katharine T.

    2015-01-01

    The use of intensive longitudinal methods (ILM)—rapid in situ assessment at micro timescales—can be overlaid on RCTs and other study designs in applied family research. Especially when done as part of a multiple timescale design—in bursts over macro timescales, ILM can advance the study of the mechanisms and effects of family interventions and processes of family change. ILM confers measurement benefits in accurately assessing momentary and variable experiences and captures fine-grained dynamic pictures of time-ordered processes. Thus, ILM allows opportunities to investigate new research questions about intervention effects on within-subject (i.e., within-person, within-family) variability (i.e., dynamic constructs) and about the time-ordered change process that interventions induce in families and family members beginning with the first intervention session. This paper discusses the need and rationale for applying ILM to intervention evaluation, new research questions that can be addressed with ILM, example research using ILM in the related fields of basic family research and the evaluation of individual-based (rather than family-based) interventions. Finally, the paper touches on practical challenges and considerations associated with ILM and points readers to resources for the application of ILM. PMID:26541560

  16. DEEP VADOSE ZONE APPLIED FIELD RESEARCH CENTER: TRANSFORMATIONAL TECHNOLOGY DEVELOPMENT FOR ENVIRONMENTAL REMEDIATION

    SciTech Connect

    Wellman, Dawn M.; Triplett, Mark B.; Freshley, Mark D.; Truex, Michael J.; Gephart, Roy E.; Johnson, Timothy C.; Chronister, Glen B.; Gerdes, Kurt D.; Chamberlain, Skip; Marble, Justin; Ramirez, Rosa

    2011-02-27

    DOE-EM, Office of Groundwater and Soil Remediation and DOE Richland, in collaboration with the Hanford site and Pacific Northwest National Laboratory, have established the Deep Vadose Zone Applied Field Research Center (DVZ-AFRC). The DVZ-AFRC leverages DOE investments in basic science from the Office of Science, applied research from DOE EM Office of Technology Innovation and Development, and site operation (e.g., site contractors [CH2M HILL Plateau Remediation Contractor and Washington River Protection Solutions], DOE-EM RL and ORP) in a collaborative effort to address the complex region of the deep vadose zone. Although the aim, goal, motivation, and contractual obligation of each organization is different, the integration of these activities into the framework of the DVZ-AFRC brings the resources and creativity of many to provide sites with viable alternative remedial strategies to current baseline approaches for persistent contaminants and deep vadose zone contamination. This cooperative strategy removes stove pipes, prevents duplication of efforts, maximizes resources, and facilitates development of the scientific foundation needed to make sound and defensible remedial decisions that will successfully meet the target cleanup goals for one of DOE EM's most intractable problems, in a manner that is acceptable by regulators.

  17. The generalized 20/80 law using probabilistic fractals applied to petroleum field size

    USGS Publications Warehouse

    Crovelli, R.A.

    1995-01-01

    Fractal properties of the Pareto probability distribution are used to generalize "the 20/80 law." The 20/80 law is a heuristic law that has evolved over the years into the following rule of thumb for many populations: 20 percent of the population accounts for 80 percent of the total value. The general p100/q100 law in probabilistic form is defined with q as a function of p, where p is the population proportion and q is the proportion of total value. Using the Pareto distribution, the p100/q100 law in fractal form is derived with the parameter q being a fractal, where q unexpectedly possesses the scale invariance property. The 20/80 law is a special case of the p100/q100 law in fractal form. The p100/q100 law in fractal form is applied to petroleum fieldsize data to obtain p and q such that p100% of the oil fields greater than any specified scale or size in a geologic play account for q100% of the total oil of the fields. The theoretical percentages of total resources of oil using the fractal q are extremely close to the empirical percentages from the data using the statistic q. Also, the empirical scale invariance property of the statistic q for the petroleum fieldsize data is in excellent agreement with the theoretical scale invariance property of the fractal q. ?? 1995 Oxford University Press.

  18. Convective Effects During Diffusivity Measurements in Liquids with An Applied Magnetic Field

    NASA Technical Reports Server (NTRS)

    Khine, Yu Yu; Banish, R. Michael; Alexander, J. Iwan D.

    2003-01-01

    Convective contamination of self-diffusion experiments with an applied magnetic field is considered using a two-dimensional axisymmetric model. Constant, uniform, and an additional non-uniform heat fluxes are imposed along the sidewall of the cylinder while constant heat loss occurs through the top and bottom. In this model, due to a very small thermal Peclet number, convective heat transfer is neglected, and the flow is steady and inertialess. Time-dependent concentration is solved for various values of the mass Peclet number, Pe(sub m), (the ratio between the convective transport rate and the diffusive transport rate) and different magnetic field strengths represented by the Hartmann number Ha. Normalized values of these diffusivities vs. effective Pe(sub m) are presented for different imposed temperature profiles. In all cases, the diffusivity value obtained through the simulated measurement increases as the effective Pe(sub m) increases. The numerical results suggest that an additional periodic flux, or hot and cold spots, can significantly decrease the convective contamination in our geometry.

  19. E-field-ratio telluric techniques applied to cavity detection for OSI operations

    SciTech Connect

    Didwall, E.M.; Wilt, M.J.

    1983-04-01

    Verification of compliance to a Comprehensive Test Ban Treaty (CTBT) may require an On-Site Inspection (OSI) of an area in the USSR where an underground nuclear test may have been conducted. As one of the possible technologies that may be applied by an OSI team, the E-field-ratio telluric method for cavity detection is examined. This method utilizes naturally occurring earth currents which are induced by ionospheric and tropospheric electromagnetic activity - no electric field source is provided by the user, thus reducing equipment requirements. Two test surveys were made at the Nevada Test Site. Underground cavities at these locations are expected to have lateral extents of the order of a few 10's of meters and depths less than 300 meters. Telluric measurements indicate that an electrically resistive anomaly exists where the cavity is expected. The anomaly associated with the cavity could be detected even when the survey line did not cross directly over the expected cavity location. Although these experiments do not define the limitations of the method, they do show strong evidence that cavities and chimney formations from an underground nuclear explosion can be detected. Specific goals for further research are suggested.

  20. Ionization at a solid-water interface in an applied electric field: Charge regulation

    NASA Astrophysics Data System (ADS)

    Okamoto, Ryuichi; Onuki, Akira

    2016-09-01

    We investigate ionization at a solid-water interface in an applied electric field. We attach an electrode to a dielectric film bearing silanol or carboxyl groups with an areal density Γ0, where the degree of dissociation α is determined by the proton density in water close to the film. We show how α depends on the density n0 of NaOH in water and the surface charge density σm on the electrode. For σm > 0, the protons are expelled away from the film, leading to an increase in α. In particular, in the range 0 < σm < eΓ0, self-regulation occurs to realize α ≅ σm/eΓ0 for n0 ≪ nc, where nc is 0.01 mol/L for silica surfaces and is 2 × 10-5 mol/L for carboxyl-bearing surfaces. We also examine the charge regulation with decreasing the cell thickness H below the Debye length κ-1, where a crossover occurs at the Gouy-Chapman length. In particular, when σm ˜ eΓ0 and H ≪ κ-1, the surface charges remain only partially screened by ions, leading to a nonvanishing electric field in the interior.

  1. Interaction of a particle bed with a droplet under an applied electric field

    NASA Astrophysics Data System (ADS)

    Ireland, P. M.; Webber, G. B.; Jarrett, E. D.; Galvin, K. P.

    2015-10-01

    Transport of dry solid particles to a liquid is relevant to a number of emerging applications, including ‘liquid marbles’. We report experiments where the transport of dry particles to a pendent water droplet is driven by an external electric field. Both hydrophilic and hydrophobic materials (silica, PMMA) were studied. For silica particles (hydrophilic, poorly conductive), a critical applied voltage initiated transfer, in the form of a rapid ‘avalanche’ of a large number of particles. The particle-loaded drop then detached, producing a metastable spherical agglomerate. Pure PMMA particles did not display this ‘avalanche’ behaviour, and when added to silica particles, appeared to cause aggregation and change the nature of the transfer mechanism. This paper is largely devoted to the avalanche process, in which deformation of the drop and radial compaction of the particle bed due to the electric field are thought to have played a central role. Since no direct contact is required between the bed and the drop, we hope to produce liquid marble-type aggregates with layered structures incorporating hydrophilic particles, which has not previously been possible.

  2. Currents, magnetization and AC-losses of YBa 2Cu 3O 7 superconductors in rapidly changing magnetic fields

    NASA Astrophysics Data System (ADS)

    Kwasnitza, K.; Plotzner, V.; Waldmann, M.; Widmer, E.

    1988-06-01

    In YBa 2Cu 3O 7 samples of different shape time dependent magnetization currents were induced at 4.2K by the application of rapid magnetic field changes. This contactless method allows the study of the intergrain and intragrain currents in the resistive flux flow state.

  3. Theory of dielectrophoresis and aggregation in suspensions of highly polarized particles subjected to high-gradient AC electric fields

    NASA Astrophysics Data System (ADS)

    Jacqmin, David; Khusid, Boris; Acrivos, Andreas

    2001-11-01

    The proposed mathematical model of electro-hydrodynamic phenomena consists of strongly coupled field and flow equations supplemented by constitutive equations for the dielectric polarization and the field-induced contribution to the energy and stresses in a suspension in the presence of a time-varying electric field. The suspension is viewed as an effective Newtonian fluid with a concentration-dependent viscosity. The long-range hydrodynamic interactions of the particles subjected to shear are incorporated through the concentration dependence of the suspension viscosity, the hindrance function in the expression for the particle settling velocity, and the shear-induced diffusion of the particles. For the electric energy and stress, we employed the constitutive equations of our microscopic theory for the case of strong electric energy dissipation. The equation for the total particle flux includes the flux induced by the electric force exerted on a particle due to the gradient of its chemical potential in a spatially non-uniform electric field, the flux generated by the buoyancy force, and the particle shear-diffusion. We consider the specific case of low particle Reynolds numbers which is relevant to our current experiments. We investigated the situation of "heterogeneous aggregation" when the field-induced phase transitions occur in a thin layer adjacent to the electrodes. By comparing our theoretical predictions with the results of experiments on a rotating channel, we demonstrated that the model is capable of predicting a wide range of physical processes in a suspension of highly polarizable particles, in particular, the formation of highly concentrated particle layers on both the high-voltage and the grounded electrodes.

  4. Headquarters, 172nd Military Airlift Group Mississippi Air National Guard, A.C. Thompson Field, Jackson, Mississippi

    DTIC Science & Technology

    1988-07-01

    Leverett silt loam is moderate and available water capacity is high. This soil series is very strongly acid to medium acid throughout, except in areas...is very strongly acid to medium acid throughout except in areas where lime has been applied to the surface layer. The surface runoff is slow and’the...detergent (monyl phenol ethylene oxide condensate), sodium dodecyl ]benzene sulphonate , and water. Not a priority pollutant. ALUVrI-,M - A general term for

  5. Applying a Bayesian Approach to Identification of Orthotropic Elastic Constants from Full Field Displacement Measurements

    NASA Astrophysics Data System (ADS)

    Gogu, C.; Yin, W.; Haftka, R.; Ifju, P.; Molimard, J.; Le Riche, R.; Vautrin, A.

    2010-06-01

    A major challenge in the identification of material properties is handling different sources of uncertainty in the experiment and the modelling of the experiment for estimating the resulting uncertainty in the identified properties. Numerous improvements in identification methods have provided increasingly accurate estimates of various material properties. However, characterizing the uncertainty in the identified properties is still relatively crude. Different material properties obtained from a single test are not obtained with the same confidence. Typically the highest uncertainty is associated with respect to properties to which the experiment is the most insensitive. In addition, the uncertainty in different properties can be strongly correlated, so that obtaining only variance estimates may be misleading. A possible approach for handling the different sources of uncertainty and estimating the uncertainty in the identified properties is the Bayesian method. This method was introduced in the late 1970s in the context of identification [1] and has been applied since to different problems, notably identification of elastic constants from plate vibration experiments [2]-[4]. The applications of the method to these classical pointwise tests involved only a small number of measurements (typically ten natural frequencies in the previously cited vibration test) which facilitated the application of the Bayesian approach. For identifying elastic constants, full field strain or displacement measurements provide a high number of measured quantities (one measurement per image pixel) and hence a promise of smaller uncertainties in the properties. However, the high number of measurements represents also a major computational challenge in applying the Bayesian approach to full field measurements. To address this challenge we propose an approach based on the proper orthogonal decomposition (POD) of the full fields in order to drastically reduce their dimensionality. POD is

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. Effects of Soil Salinity on the Expression of Bt Toxin (Cry1Ac) and the Control Efficiency of Helicoverpa armigera in Field-Grown Transgenic Bt Cotton

    PubMed Central

    Luo, Jun-Yu; Zhang, Shuai; Peng, Jun; Zhu, Xiang-Zhen; Lv, Li-Min; Wang, Chun-Yi; Li, Chun-Hua; Zhou, Zhi-Guo; Cui, Jin-Jie

    2017-01-01

    An increasing area of transgenic Bacillus thuringiensis (Bt) cotton is being planted in saline-alkaline soil in China. The Bt protein level in transgenic cotton plants and its control efficiency can be affected by abiotic stress, including high temperature, water deficiency and other factors. However, how soil salinity affects the expression of Bt protein, thus influencing the control efficiency of Bt cotton against the cotton bollworm (CBW) Helicoverpa armigera (Hübner) in the field, is poorly understood. Our objective in the present study was to investigate the effects of soil salinity on the expression of Bt toxin (Cry1Ac) and the control efficiency of Helicoverpa armigera in field-grown transgenic Bt cotton using three natural saline levels (1.15 dS m-1 [low soil-salinity], 6.00 dS m-1 [medium soil-salinity] and 11.46 dS m-1 [high soil-salinity]). We found that the Bt protein content in the transgenic Bt cotton leaves and the insecticidal activity of Bt cotton against CBW decreased with the increasing soil salinity in laboratory experiments during the growing season. The Bt protein content of Bt cotton leaves in the laboratory were negatively correlated with the salinity level. The CBW populations were highest on the Bt cotton grown in medium-salinity soil instead of the high-salinity soil in field conditions. A possible mechanism may be that the relatively high-salinity soil changed the plant nutritional quality or other plant defensive traits. The results from this study may help to identify more appropriate practices to control CBW in Bt cotton fields with different soil salinity levels. PMID:28099508

  12. Effects of Soil Salinity on the Expression of Bt Toxin (Cry1Ac) and the Control Efficiency of Helicoverpa armigera in Field-Grown Transgenic Bt Cotton.

    PubMed

    Luo, Jun-Yu; Zhang, Shuai; Peng, Jun; Zhu, Xiang-Zhen; Lv, Li-Min; Wang, Chun-Yi; Li, Chun-Hua; Zhou, Zhi-Guo; Cui, Jin-Jie

    2017-01-01

    An increasing area of transgenic Bacillus thuringiensis (Bt) cotton is being planted in saline-alkaline soil in China. The Bt protein level in transgenic cotton plants and its control efficiency can be affected by abiotic stress, including high temperature, water deficiency and other factors. However, how soil salinity affects the expression of Bt protein, thus influencing the control efficiency of Bt cotton against the cotton bollworm (CBW) Helicoverpa armigera (Hübner) in the field, is poorly understood. Our objective in the present study was to investigate the effects of soil salinity on the expression of Bt toxin (Cry1Ac) and the control efficiency of Helicoverpa armigera in field-grown transgenic Bt cotton using three natural saline levels (1.15 dS m-1 [low soil-salinity], 6.00 dS m-1 [medium soil-salinity] and 11.46 dS m-1 [high soil-salinity]). We found that the Bt protein content in the transgenic Bt cotton leaves and the insecticidal activity of Bt cotton against CBW decreased with the increasing soil salinity in laboratory experiments during the growing season. The Bt protein content of Bt cotton leaves in the laboratory were negatively correlated with the salinity level. The CBW populations were highest on the Bt cotton grown in medium-salinity soil instead of the high-salinity soil in field conditions. A possible mechanism may be that the relatively high-salinity soil changed the plant nutritional quality or other plant defensive traits. The results from this study may help to identify more appropriate practices to control CBW in Bt cotton fields with different soil salinity levels.

  13. Characterizing and calibrating a large Helmholtz coil at low ac magnetic field levels with peak magnitudes below the earth's magnetic field

    NASA Astrophysics Data System (ADS)

    Schill, Robert A.; Hoff, Karin

    2001-06-01

    Characterizing and calibrating a low impedance large Helmholtz coil generating 60 Hz magnetic fields with amplitudes well below the earth's magnetic field is difficult and imprecise when coil shielding is not available and noise is an issue. Parameters influencing the calibration process such as temperature and coil impedance need to be figured in the calibration process. A simple and reliable calibration technique is developed and used to measure low amplitude fields over a spatial grid using a standard Hall effect probe gaussmeter. These low amplitude fields are typically hard or impossible to detect in the presence of background fields when using the gaussmeter in the conventional manner. Standard deviations of two milligauss and less have been achieved over a spatial grid in a uniform field region. Theoretical and measured fields are compared yielding reasonable agreement for a large coil system designed and built for bioelectromagnetic experiments at the University of Nevada at Las Vegas using simple tools. Theoretical results need to be compared with and adjusted in accord with measurements taken over a large parameter space within the design constraints of the coil. Magnetic field measurements made over a four year period are shown to be consistent. Characterizing and calibrating large Helmholtz coils can be performed with rulers, levels, plumb lines, and inexpensive gaussmeters.

  14. Simulation study on structure of water in aqueous solutions confined between graphene electrodes under very high applied electric field

    NASA Astrophysics Data System (ADS)

    Leuty, Gary; Tsige, Mesfin; Talapatra, Saikat

    2011-03-01

    Arising from questions regarding electric double-layer capacitors utilizing graphene electrodes and aqueous electrolyte (KOH solution), atomistic MD simulations of electrolyte confined between graphene electrodes were performed to understand the behavior of electrolyte as a function of electric field strength and solution concentration, from pure water to 6M KOH. It was noted that the strength of the electric field had a demonstrable effect on the structure of pure water between the electrodes (as has previously been seen in highly confined multilayer water systems), creating regularly spaced channels and densely packed sheets of highly ordered molecules. We also saw a clear effect due to the presence of electrolyte ions and their separation from the water due to the action of the field; different field strengths appear to greatly alter the distribution of ions, which in turn affects the structure and ordering of the water. Time dependence in the strength of the electric field was also studied to determine what effect, if any, it has on induced structure. Authors gratefully acknowledge support from the ACS Petroleum Research Fund and the National Science Foundation.

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

    PubMed

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

    2015-01-09

    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 °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.

  16. 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.

  17. Trends of Abutment-Scour Prediction Equations Applied to 144 Field Sites in South Carolina

    USGS Publications Warehouse

    Benedict, Stephen T.; Deshpande, Nikhil; Aziz, Nadim M.; Conrads, Paul A.

    2006-01-01

    The U.S. Geological Survey conducted a study in cooperation with the Federal Highway Administration in which predicted abutment-scour depths computed with selected predictive equations were compared with field measurements of abutment-scour depth made at 144 bridges in South Carolina. The assessment used five equations published in the Fourth Edition of 'Evaluating Scour at Bridges,' (Hydraulic Engineering Circular 18), including the original Froehlich, the modified Froehlich, the Sturm, the Maryland, and the HIRE equations. An additional unpublished equation also was assessed. Comparisons between predicted and observed scour depths are intended to illustrate general trends and order-of-magnitude differences for the prediction equations. Field measurements were taken during non-flood conditions when the hydraulic conditions that caused the scour generally are unknown. The predicted scour depths are based on hydraulic conditions associated with the 100-year flow at all sites and the flood of record for 35 sites. Comparisons showed that predicted scour depths frequently overpredict observed scour and at times were excessive. The comparison also showed that underprediction occurred, but with less frequency. The performance of these equations indicates that they are poor predictors of abutment-scour depth in South Carolina, and it is probable that poor performance will occur when the equations are applied in other geographic regions. Extensive data and graphs used to compare predicted and observed scour depths in this study were compiled into spreadsheets and are included in digital format with this report. In addition to the equation-comparison data, Water-Surface Profile Model tube-velocity data, soil-boring data, and selected abutment-scour data are included in digital format with this report. The digital database was developed as a resource for future researchers and is especially valuable for evaluating the reasonableness of future equations that may be developed.

  18. Forced Magnetic Reconnection and Field Penetration of an Externally Applied Rotating Helical Magnetic Field in the TEXTOR Tokamak

    SciTech Connect

    Kikuchi, Y.; Finken, K. H.; Jakubowski, M.; Koslowski, H. R.; Kraemer-Flecken, A.; Lehnen, M.; Liang, Y.; Reiser, D.; Wolf, R. C.; Zimmermann, O.; Bock, M. F. M. de; Jaspers, R.; Matsunaga, G.

    2006-08-25

    The magnetic field penetration process into a magnetized plasma is of basic interest both for plasma physics and astrophysics. In this context special measurements on the field penetration and field amplification are performed by a Hall probe on the dynamic ergodic divertor (DED) on the TEXTOR tokamak and the data are interpreted by a two-fluid plasma model. It is observed that the growth of the forced magnetic reconnection by the rotating DED field is accompanied by a change of the plasma fluid rotation. The differential rotation frequency between the DED field and the plasma plays an important role in the process of the excitation of tearing modes. The momentum input from the rotating DED field to the plasma is interpreted by both a ponderomotive force at the rational surface and a radial electric field modified by an edge ergodization.

  19. 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

  20. 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

  1. 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.

  2. Therapeutic effects of whole-body devices applying pulsed electromagnetic fields (PEMF): a systematic literature review.

    PubMed

    Hug, Kerstin; Röösli, Martin

    2012-02-01

    Pulsed electromagnetic fields (PEMF) delivered by whole-body mats are promoted in many countries for a wide range of therapeutic applications and for enhanced well-being. However, neither the therapeutic efficacy nor the potential health hazards caused by these mats have been systematically evaluated. We conducted a systematic review of trials investigating the therapeutic effects of low-frequency PEMF devices. We were interested in all health outcomes addressed so far in randomized, sham-controlled, double-blind trials. In total, 11 trials were identified. They were focused on osteoarthritis of the knee (3 trials) or the cervical spine (1), fibromyalgia (1), pain perception (2), skin ulcer healing (1), multiple sclerosis-related fatigue (2), or heart rate variability and well-being (1). The sample sizes of the trials ranged from 12 to 71 individuals. The observation period lasted 12 weeks at maximum, and the applied magnetic flux densities ranged from 3.4 to 200 µT. In some trials sporadic positive effects on health were observed. However, independent confirmation of such singular findings was lacking. We conclude that the scientific evidence for therapeutic effects of whole-body PEMF devices is insufficient. Acute adverse effects have not been reported. However, adverse effects occurring after long-term application have not been studied so far. In summary, the therapeutic use of low-frequency whole-body PEMF devices cannot be recommended without more scientific evidence from high-quality, double-blind trials.

  3. Physiological response of rice (Oryza sativa L.) genotypes to elevated nitrogen applied under field conditions.

    PubMed

    Singh, Hukum; Verma, Amit; Ansari, Mohammad Wahid; Shukla, Alok

    2014-01-01

    Field experiment was conducted at G.B.P.U.A.T. Pantnagar, Uttarakhand, India in rainy season of 2008 and 2009 to study the impacts of increased nitrogen doses on growth dynamics, biomass partitioning, chaffy grain and nitrogen use efficiency in 4 rice genotypes viz., Vasumati, Tulsi, Kasturi and Krishna Hamsa. Four doses (N(0), N(50), N(100) and N(200) kg N ha(-1)) of nitrogen in the form of urea were applied in 3 split. Increased trend in growth dynamics during active tillering and flowering stage, and biomass partitioning at the time of active tillering and flowering stage was observed with respect to nitrogen doses. Chaffy grain number and chaffy grain weight per 5 panicles was significantly increased with enhancing nitrogen doses and was highest for Vasumati. Nitrogen use efficiency (NUE) was increased up to N(100) kg N ha(-1) and it was declined with rising nitrogen doses (N(200) kg N ha(-1)). The highest values for NUE was achieved by rice genotype Krishna Hamsa whereas lowest by Vasumati. In addition to this, a significant correlation between nitrogen doses and growth dynamics, biomass partitioning and chaffy grain was observed. These findings suggest that growth dynamics, biomass partitioning, chaffy grain could be enhanced by the input of high rate of nitrogen fertilizer but not nitrogen use efficiency. Therefore, this study is useful to screen most N efficient genotypes which can be strongly suggested to rice growers to enhance crop yield irrespective of use of high dose of N fertilizers.

  4. Implementation Plan for the Deep Vadose Zone-Applied Field Research Center

    SciTech Connect

    Wellman, Dawn M.; Truex, Michael J.; Freshley, Mark D.; Gephart, Roy E.; Triplett, Mark B.; Johnson, Timothy C.

    2011-02-11

    The Long-Range Deep Vadose Zone Program Plan was published in October 2010. It summarized the U.S. Department of Energy’s (DOE’s) state-of-knowledge about the contaminant remediation challenges facing the deep vadose zone (DVZ) beneath the Central Plateau of the Hanford Site and their approach to solving those challenges. Developing an implementation plan is the next step to address the knowledge and capabilities required to solve DVZ challenges when needed. This multi-year plan (FY-11 through FY-20) identifies the short to long-term research, management, and execution plans required to solve those problems facing the DVZ-Applied Field Research Center (DVZ-AFRC). The schedule supporting implementation overlies existing activities and milestones from Hanford’s DOE-Environmental Management (EM) end-user projects. Success relies upon multi-project teams focused on coordinated subsurface projects undertaken across the DOE Complex combined with facilitated, problem-focused, research investments implemented through the DVZ-AFRC.

  5. Superconducting shielded core reactor with reduced AC losses

    DOEpatents

    Cha, Yung S.; Hull, John R.

    2006-04-04

    A superconducting shielded core reactor (SSCR) operates as a passive device for limiting excessive AC current in a circuit operating at a high power level under a fault condition such as shorting. The SSCR includes a ferromagnetic core which may be either closed or open (with an air gap) and extends into and through a superconducting tube or superconducting rings arranged in a stacked array. First and second series connected copper coils each disposed about a portion of the iron core are connected to the circuit to be protected and are respectively wound inside and outside of the superconducting tube or rings. A large impedance is inserted into the circuit by the core when the shielding capability of the superconducting arrangement is exceeded by the applied magnetic field generated by the two coils under a fault condition to limit the AC current in the circuit. The proposed SSCR also affords reduced AC loss compared to conventional SSCRs under continuous normal operation.

  6. 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)

  7. Does the Rayleigh equation apply to evaluate field isotope data in contaminant hydrogeology?

    PubMed

    Abe, Yumiko; Hunkeler, Daniel

    2006-03-01

    Stable isotope data have been increasingly used to assess in situ biodegradation of organic contaminants in groundwater. The data are usually evaluated using the Rayleigh equation to evaluate whether isotope data follow a Rayleigh trend, to calculate the extent of contaminant biodegradation, or to estimate first-order rate constants. However, the Rayleigh equation was developed for homogeneous systems while in the subsurface, contaminants can migrate at different velocities due to physical heterogeneity. This paper presents a method to quantify the systematic effect that is introduced by applying the Rayleigh equation to field isotope data. For this purpose, the travel time distribution between source and sampling point is characterized by an analytical solution to the advection-dispersion equation. The systematic effect was evaluated as a function of the magnitude of physical heterogeneity, geometry of the contaminant plume, and degree of biodegradation. Results revealed that the systematic effect always leads to an underestimation of the actual values of isotope enrichment factors, the extent of biodegradation, or first-order rate constants, especially in the dispersion-dominant region representing a higher degree of physical heterogeneity. A substantial systematic effect occurs especially for the quantification of first-order rate constants (up to 50% underestimation of actual rate) while it is relatively small for quantification of the extent of biodegradation (< 5% underestimation of actual degree of biodegradation). The magnitude of the systematic effect is in the same range as the uncertainty due to uncertainty of the analytical data, of the isotope enrichment factor, and the average travel time.

  8. Markov random field-based clustering applied to the segmentation of masses in digital mammograms.

    PubMed

    Suliga, M; Deklerck, R; Nyssen, E

    2008-09-01

    In this paper we propose a new pixel clustering model applied to the analysis of digital mammograms. The clustering represents here the first step in a more general method and aims at the creation of a concise data-set (clusters) for automatic detection and classification of masses, which are typically among the first symptoms analysed in early diagnosis of breast cancer. For the purpose of this work, a set of mammographic images has been employed, that are 12-bit gray level digital scans and as such, are inherently inhomogeneous and affected by the noise resulting from the film scanning. The image pixels are described only by their intensity (gray level), therefore, the available information is limited to one dimension. We propose a Markov random field (MRF)-based technique that is suitable for performing clustering in an environment which is described by poor or limited data. The proposed method is a statistical classification model, that labels the image pixels based on the description of their statistical and contextual information. Apart from evaluating the pixel statistics, that originate from the definition of the K-means clustering scheme, the model expands the analysis by the description of the spatial dependence between pixels and their labels (context), hence leading to the reduction of the inhomogeneity of the output. Moreover, we define a probabilistic description of the model, that is characterised by a remarkable simplicity, such that its realisation can be easily and efficiently implemented in any high- or low-level programming language, thus allowing it to be run on virtually any kind of platform. Finally, we evaluate the algorithm against the classical K-means clustering routine. We point out similarities between the two methods and, moreover, show the advantages and superiority of the MRF scheme.

  9. Applied-field molecular dynamics study of a model calcium channel selectivity filter

    NASA Astrophysics Data System (ADS)

    Yang, Yan; Henderson, Douglas; Busath, David

    2003-03-01

    The calcium channel is thought to have a short selectivity filter containing charged glutamate side chains. This filter was modeled using an atomistic cylinder of length 10 Å in which were confined eight half-charged oxygen anions representing glutamate carboxylate oxygens. Current flow through the filter was computed using applied field nonequilibrium molecular dynamics simulations at various mole fractions of Na+ and Ca2+ in 2 M chloride solutions with simple point charge/extended model water. The filter was cation selective and had conductances in the range of those extrapolated from experimental results. For this model, unlike implicit solvent models at lower voltages and concentrations, the mole fraction behavior was not anomalous and cation binding was nonselective at 2.2 V. Perturbations of filter diameter and confined charge resulted in similar behaviors. At physiological voltages, mole fraction conductance behavior could not be reliably simulated in 100 ns runs, but nonselective cation binding persisted. Nevertheless, it is of interest that ion entry into the confinement region was limited by an energy barrier and at least, in the case of Ca2+, led to an increase in the energy of the other Ca2+ ion in the confinement region and prompt exit of one of them. The filter was most commonly occupied by 2 or 3 Na+ ions in pure Na+ solutions or 1 or 2 Ca2+ ions in pure Ca2+ solutions. For CaCl2 solution, the additional ion, if present, was most commonly stalled behind the entry barrier, i.e., within the channel filter but not yet having entered the confinement region. Thus, the simulations demonstrate the concept that entry of a new mobile Ca2+ ion into the selectivity filter serves to release the prior occupant that was tightly bound.

  10. Health-Economics Analyses Applied to ELF Electric and Magnetic Fields.

    PubMed

    Kandel, Shaiela; Swanson, John; Kheifets, Leeka

    2016-06-01

    Extremely low frequency electric and magnetic fields (ELF EMFs) are a common exposure for modern populations. The prevailing public-health protection paradigm is that quantitative exposure limits are based on the established acute effects, whereas the possible chronic effects are considered too uncertain for quantitative limits, but might justify precautionary measures. The choice of precautionary measures can be informed by a health-economics analysis (HEA). We consider four such analyses of precautionary measures that have been conducted at a national or state level in California, the Netherlands, the United Kingdom, and Israel. We describe the context of each analysis, examine how they deal with some of the more significant issues that arise, and present a comparison of the input parameters and assumptions used. The four HEAs are methodologically similar. The most significant qualitative choices that have to be made are what dose-response relationship to assume, what allowance if any to make for uncertainty, and, for a CBA only, what diseases to consider, and all four analyses made similar choices. These analyses suggest that, on the assumptions made, there are some low-cost measures, such as rephasing, that can be applied to transmission in some circumstances and that can be justifiable in cost-benefit terms, but that higher cost measures, such as undergrounding, become unjustifiable. Of the four HEAs, those in the United Kingdom and Israel were influential in determining the country's EMF policy. In California and Netherlands, the HEA may well have informed the debate, but the policy chosen did not stem directly from the HEA.

  11. Mitigation of cadmium and arsenic in rice grain by applying different silicon fertilizers in contaminated fields.

    PubMed

    Wang, Hong-Yan; Wen, Shi-Lin; Chen, Peng; Zhang, Lu; Cen, Kuang; Sun, Guo-Xin

    2016-02-01

    A field experiment was established to support the hypothesis that application of different silicon (Si) fertilizers can simultaneously reduce cadmium (Cd) and arsenic (As) concentration in rice grain. The "semi-finished product of Si-potash fertilizer" treatment at the high application of 9000 kg/ha (NP+S-KSi9000) significantly reduced the As concentration in rice grain by up to 20.1%, compared with the control. Si fertilization reduces the Cd concentration in rice considerably more than the As concentration. All Si fertilizers apart from sodium metasilicate (Na2SiO3) exhibited a high ability to reduce Cd concentration in rice grain. The Si-calcium (CaSi) fertilizer is the most effective in the mitigation of Cd concentration in rice grain. The CaSi fertilizer applied at 9000 kg/ha (NPK+CaSi9000) and 900 kg/ha (NPK+CaSi900) reduced the Cd concentration in rice grain about 71.5 and 48.0%, respectively, while the Si-potash fertilizer at 900 kg/ha (NP+KSi900), the semi-finished product of Si-potash fertilizer at both 900 kg/ha (NP+S-KSi900) and 9000 kg/ha (NP+S-KSi9000), and the rice straw (NPK+RS) treatments reduced the Cd concentration in rice grain about 42, 26.5, 40.7, and 23.1%, respectively. The results of this investigation demonstrated the potential effects of Si fertilizers in reducing Cd and As concentrations in rice grain.

  12. Hybrid immersed interface-immersed boundary methods for AC dielectrophoresis

    SciTech Connect

    Hossan, Mohammad Robiul; Dillon, Robert; Dutta, Prashanta

    2014-08-01

    Dielectrophoresis, a nonlinear electrokinetic transport mechanism, has become popular in many engineering applications including manipulation, characterization and actuation of biomaterials, particles and biological cells. In this paper, we present a hybrid immersed interface–immersed boundary method to study AC dielectrophoresis where an algorithm is developed to solve the complex Poisson equation using a real variable formulation. An immersed interface method is employed to obtain the AC electric field in a fluid media with suspended particles and an immersed boundary method is used for the fluid equations and particle transport. The convergence of the proposed algorithm as well as validation of the hybrid scheme with experimental results is presented. In this paper, the Maxwell stress tensor is used to calculate the dielectrophoretic force acting on particles by considering the physical effect of particles in the computational domain. Thus, this study eliminates the approximations used in point dipole methods for calculating dielectrophoretic force. A comparative study between Maxwell stress tensor and point dipole methods for computing dielectrophoretic forces are presented. The hybrid method is used to investigate the physics of dielectrophoresis in microfluidic devices using an AC electric field. The numerical results show that with proper design and appropriate selection of applied potential and frequency, global electric field minima can be obtained to facilitate multiple particle trapping by exploiting the mechanism of negative dielectrophoresis. Our numerical results also show that electrically neutral particles form a chain parallel to the applied electric field irrespective of their initial orientation when an AC electric field is applied. This proposed hybrid numerical scheme will help to better understand dielectrophoresis and to design and optimize microfluidic devices.

  13. AC Electrokinetics of Physiological Fluids for Biomedical Applications.

    PubMed

    Lu, Yi; Liu, Tingting; Lamanda, Ariana C; Sin, Mandy L Y; Gau, Vincent; Liao, Joseph C; Wong, Pak Kin

    2015-12-01

    Alternating current (AC) electrokinetics is a collection of processes for manipulating bulk fluid mass and embedded objects with AC electric fields. The ability of AC electrokinetics to implement the major microfluidic operations, such as pumping, mixing, concentration, and separation, makes it possible to develop integrated systems for clinical diagnostics in nontraditional health care settings. The high conductivity of physiological fluids presents new challenges and opportunities for AC electrokinetics-based diagnostic systems. In this review, AC electrokinetic phenomena in conductive physiological fluids are described followed by a review of the basic microfluidic operations and the recent biomedical applications of AC electrokinetics. The future prospects of AC electrokinetics for clinical diagnostics are presented.

  14. AC Electrokinetics of Physiological Fluids for Biomedical Applications

    PubMed Central

    Lu, Yi; Liu, Tingting; Lamanda, Ariana C.; Sin, Mandy L Y; Gau, Vincent; Liao, Joseph C.; Wong, Pak Kin

    2016-01-01

    AC electrokinetics is a collection of processes for manipulating bulk fluid mass and embedded objects with AC electric fields. The ability of AC electrokinetics to implement the major microfluidic operations, such as pumping, mixing, concentration and separation, makes it possible to develop integrated systems for clinical diagnostics in non-traditional healthcare settings. The high conductivity of physiological fluids presents new challenges and opportunities for AC electrokinetics based diagnostic systems. In this review, AC electrokinetic phenomena in conductive physiological fluids are described followed by a review of the basic microfluidic operations and the recent biomedical applications of AC electrokinetics. The future prospects of AC electrokinetics for clinical diagnostics are presented. PMID:25487557

  15. Dependences of microwave surface resistance of HTS thin films on applied dc magnetic fields parallel and normal to the substrate

    NASA Astrophysics Data System (ADS)

    Sato, K.; Sato, S.; Ichikawa, K.; Watanabe, M.; Honma, T.; Tanaka, Y.; Oikawa, S.; Saito, A.; Ohshima, S.

    2014-05-01

    We investigated the dc magnetic field and temperature dependences of microwave surface resistance (Rs) of high-temperature superconductor (HTS) films. Previously, we reported that the surface resistance RsRs(n) under a dc magnetic field applied normaly to the substrate increased when increasing the applied magnetic field. For NMR application, we have to examine the Rs(p) under the dc magnetic field parallel to the substrate. We measured the Rs(p) of the YBCO and DyBCO thin films with a thickness of 500 nm deposited on a MgO (100) substrate using the dielectric resonator method at 21.8 GHz, and a dc magnetic field of up to 5 T. In a zero magnetic field, the values of Rs(n) and Rs(p) were 0.35 mQ at 20 K. Under the dc magnetic field, the Rs(n) and the Rs(p) also increased with increasing magnetic field, however, the Rs(p) had a lower magnetic field dependence and the value was about 1/10 of that of the Rs(n). The Rs(p) at 16.4 T and at 700 MHz could be estimated by the two-fluid model. The Rs(p) value was about 1/2600 compared with that of copper at 20 K. As a result, we clarified that 500 nm thick YBCO and DyBCO thin films could provide advantages for NMR application.

  16. Studying the reversal mode of the magnetization vector versus applied field angle using generalized magneto-optical ellipsometry

    SciTech Connect

    Pufall, M. R.; Berger, A.

    1999-10-26

    The authors used the technique of vector Generalized Magneto-optical Ellipsometry to study the behavior of the magnetization vector of a 50 Co thin film as a function of external field magnitude and direction. With this method, which determines the both the direction and magnitude of the magnetization, averaged over the 1 mm incident laser beam, they were able to determine the relative contributions of magnetization rotation and domain formation to the reversal of M. The Co sample had a uniaxial in-plane anisotropy. The authors found that when the angle between the applied field and the easy axis was greater than {approximately} 40 degrees, the reversal occurred primarily by rotation of the magnetization, accompanied by a small reduction of the magnitude of M. In this angular region, the critical field-the field at which there is a large jump in the angle of M -- as a function of applied field angle followed a coherent rotation model. However, at applied field angles less than 40 degrees to the easy axis, they found a larger reduction in {vert_bar}M{vert_bar} occurring before and during the jump in the magnetization angle. The jump also occurred at fields much lower than those predicted by the coherent rotation model, indicating a reversal mode initiated by domain formation.

  17. Model channel ion currents in NaCl-extended simple point charge water solution with applied-field molecular dynamics.

    PubMed Central

    Crozier, P S; Henderson, D; Rowley, R L; Busath, D D

    2001-01-01

    Using periodic boundary conditions and a constant applied field, we have simulated current flow through an 8.125-A internal diameter, rigid, atomistic channel with polar walls in a rigid membrane using explicit ions and extended simple point charge water. Channel and bath currents were computed from 10 10-ns trajectories for each of 10 different conditions of concentration and applied voltage. An electric field was applied uniformly throughout the system to all mobile atoms. On average, the resultant net electric field falls primarily across the membrane channel, as expected for two conductive baths separated by a membrane capacitance. The channel is rarely occupied by more than one ion. Current-voltage relations are concentration dependent and superlinear at high concentrations. PMID:11720976

  18. Dose response of selected solid state detectors in applied homogeneous transverse and longitudinal magnetic fields

    SciTech Connect

    Reynolds, M.; Fallone, B. G.; Rathee, S.

    2014-09-15

    Purpose: MR-Linac devices under development worldwide will require standard calibration, commissioning, and quality assurance. Solid state radiation detectors are often used for dose profiles and percent depth dose measurements. The dose response of selected solid state detectors is therefore evaluated in varying transverse and longitudinal magnetic fields for this purpose. Methods: The Monte Carlo code PENELOPE was used to model irradiation of a PTW 60003 diamond detector and IBA PFD diode detector in the presence of a magnetic field. The field itself was varied in strength, and oriented both transversely and longitudinally with respect to the incident photon beam. The long axis of the detectors was oriented either parallel or perpendicular to the photon beam. The dose to the active volume of each detector in air was scored, and its ratio to dose with zero magnetic field strength was determined as the “dose response” in magnetic field. Measurements at low fields for both detectors in transverse magnetic fields were taken to evaluate the accuracy of the simulations. Additional simulations were performed in a water phantom to obtain few representative points for beam profile and percent depth dose measurements. Results: Simulations show significant dose response as a function of magnetic field in transverse field geometries. This response can be near 20% at 1.5 T, and it is highly dependent on the detectors’ relative orientation to the magnetic field, the energy of the photon beam, and detector composition. Measurements at low transverse magnetic fields verify the simulations for both detectors in their relative orientations to radiation beam. Longitudinal magnetic fields, in contrast, show little dose response, rising slowly with magnetic field, and reaching 0.5%–1% at 1.5 T regardless of detector orientation. Water tank and in air simulation results were the same within simulation uncertainty where lateral electronic equilibrium is present and expectedly

  19. Estimating the runaway diffusion coefficient in the TEXT tokamak from shift and externally applied resonant magnetic-field experiments

    SciTech Connect

    Catto, P.J.; Myra, J.R. ); Wang, P.W.; Wootton, A.J.; Bengtson, R.D. )

    1991-08-01

    Two techniques are employed on the TEXT tokamak (Nucl. Fusion {bold 29}, 547 (1989); {bold 30}, 167 (1990)) to measure the runaway diffusion coefficient {ital D}: (i) displacing the plasma column, and (ii) externally applying resonant magnetic fields. Model diffusion equations for the experiments are solved to obtain analytic predictions which then can be used to interpret the measurements. The initial transient response of the x-ray flux to the perturbing shift or applied magnetic field is used to measure a {ital D} of order 1 m{sup 2} sec{sup {minus}1} near the edge that decreases inward.

  20. Effects of an Applied Magnetic Field on the Directional Solidification of Hg(1-x)Zn(x)Se Alloys

    NASA Technical Reports Server (NTRS)

    Cobb, S. D.; Lehoczky, S. L.; Szofran, F. R.; Jones, K. S.

    1999-01-01

    Directionally solidified Hg(0.9)Zn(0.1)Se alloys were studied as an alternative to HgCdTe for the detection of electromagnetic radiation because of predicted improvements in lattice stability. Several boules were grown using a modified Bridgman-Stockbarger method and in an applied magnetic field. Axial compositional profiles showed mass transfer was primarily diffusion controlled. Radial compositional variations were greatly reduced when solidification occurred in an applied magnetic field. Microstructural characteristics and dislocation etch pit densities were greatly improved over HgTe based alloys. The extreme importance of processing conditions on defect generation was illustrated by comparing ampoule configurations and thermal profiles.

  1. Avoiding Tokamak Disruptions by Applying Static Magnetic Fields That Align Locked Modes with Stabilizing Wave-Driven Currents.

    PubMed

    Volpe, F A; Hyatt, A; La Haye, R J; Lanctot, M J; Lohr, J; Prater, R; Strait, E J; Welander, A

    2015-10-23

    Nonrotating ("locked") magnetic islands often lead to complete losses of confinement in tokamak plasmas, called major disruptions. Here locked islands were suppressed for the first time, by a combination of applied three-dimensional magnetic fields and injected millimeter waves. The applied fields were used to control the phase of locking and so align the island O point with the region where the injected waves generated noninductive currents. This resulted in stabilization of the locked island, disruption avoidance, recovery of high confinement, and high pressure, in accordance with the expected dependencies upon wave power and relative phase between the O point and driven current.

  2. Hands-On Teaching through a Student Field Project in Applied Geophysics.

    ERIC Educational Resources Information Center

    Klasner, John Samuel; Crockett, Jeffrey Jon; Horton, Kimberly Beth; Poe, Michele Daun; Wollert, Matthew Todd

    1992-01-01

    Describes the Proffit Mountain project, part of a senior-level class in applied geophysics that provides students with hands-on experience in applying principles and techniques learned in class. Students conduct magnetic, gravity, and radiometric studies over a diabase body which intrudes rhyolite at Proffitt Mountain in southeast Missouri.…

  3. Tunable Lamb wave band gaps in two-dimensional magnetoelastic phononic crystal slabs by an applied external magnetostatic field.

    PubMed

    Zhou, Changjiang; Sai, Yi; Chen, Jiujiu

    2016-09-01

    This paper theoretically investigates the band gaps of Lamb mode waves in two-dimensional magnetoelastic phononic crystal slabs by an applied external magnetostatic field. With the assumption of uniformly oriented magnetization, an equivalent piezomagnetic material model is used. The effects of magnetostatic field on phononic crystals are considered carefully in this model. The numerical results indicate that the width of the first band gap is significantly changed by applying the external magnetic field with different amplitude, and the ratio between the maximum and minimum gap widths reaches 228%. Further calculations demonstrate that the orientation of the magnetic field obviously affects the width and location of the first band gap. The contactless tunability of the proposed phononic crystal slabs shows many potential applications of vibration isolation in engineering.

  4. Voltage-controlled magnetization switching in MRAMs in conjunction with spin-transfer torque and applied magnetic field

    NASA Astrophysics Data System (ADS)

    Munira, Kamaram; Pandey, Sumeet C.; Kula, Witold; Sandhu, Gurtej S.

    2016-11-01

    Voltage-controlled magnetic anisotropy (VCMA) effect has attracted a significant amount of attention in recent years because of its low cell power consumption during the anisotropy modulation of a thin ferromagnetic film. However, the applied voltage or electric field alone is not enough to completely and reliably reverse the magnetization of the free layer of a magnetic random access memory (MRAM) cell from anti-parallel to parallel configuration or vice versa. An additional symmetry-breaking mechanism needs to be employed to ensure the deterministic writing process. Combinations of voltage-controlled magnetic anisotropy together with spin-transfer torque (STT) and with an applied magnetic field (Happ) were evaluated for switching reliability, time taken to switch with low error rate, and energy consumption during the switching process. In order to get a low write error rate in the MRAM cell with VCMA switching mechanism, a spin-transfer torque current or an applied magnetic field comparable to the critical current and field of the free layer is necessary. In the hybrid processes, the VCMA effect lowers the duration during which the higher power hungry secondary mechanism is in place. Therefore, the total energy consumed during the hybrid writing processes, VCMA + STT or VCMA + Happ, is less than the energy consumed during pure spin-transfer torque or applied magnetic field switching.

  5. Magneto-optical controlled transmittance alteration of PbS quantum dots by moderately applied magnetic fields at room temperature

    SciTech Connect

    Singh, Akhilesh K.; Barik, Puspendu; Ullrich, Bruno E-mail: bruno.ullrich@yahoo.com

    2014-12-15

    We observed changes of the transmitted monochromatic light passing through a colloidal PbS quantum dot film on glass owing to an applied moderate (smaller than 1 T) magnetic field under ambient conditions. The observed alterations show a square dependence on the magnetic field increase that cannot be achieved with bulk semiconductors. The findings point to so far not recognized application potentials of quantum dots.

  6. Magneto-optical controlled transmittance alteration of PbS quantum dots by moderately applied magnetic fields at room temperature

    NASA Astrophysics Data System (ADS)

    Singh, Akhilesh K.; Barik, Puspendu; Ullrich, Bruno

    2014-12-01

    We observed changes of the transmitted monochromatic light passing through a colloidal PbS quantum dot film on glass owing to an applied moderate (smaller than 1 T) magnetic field under ambient conditions. The observed alterations show a square dependence on the magnetic field increase that cannot be achieved with bulk semiconductors. The findings point to so far not recognized application potentials of quantum dots.

  7. The Study of Electron Coherence Effects in Metallic Systems with High Frequency AC Electric Fields: Weak Localization and Mesoscopic Photovoltaic Effects.

    NASA Astrophysics Data System (ADS)

    Liu, Jin

    We have studied the effect of a high-frequency microwave electric field on electron phase coherence in thin Sb films and wires. The phase coherence is monitored through the effect of weak localization on the conductance. Through careful experimental design, we were able to calibrate the high frequency electric field. The ac effect was separated from the Joule heating with either dc measurements or the application of a magnetic field. This has made it possible to make a detailed, quantitative comparison with the theory with no free parameters. We have found good agreements between the experiments and the theory for both one and two dimensional cases. We have used the simple dc heating experiment to study the electron heating effects in Sb films. The electron temperature was reflected in the resistance, as an especially striking manner, to be quite different from the lattice temperature. This experiment was also used to study the electron-phonon scattering time in thin Sb films in the temperature range 1-4K. The magnitude of the scattering time is in reasonable accord with the theory, while the temperature dependence is of the form tau_{E_{ph}} ~ T^{-alpha }, with alpha ~ 1.4. The value of alpha appears to be significantly smaller than predicted by the theory, and is not understood. We have also studied the high frequency heating effects of thin AuPd, AuFe, and Au films at low temperatures. The analysis of the experiments yield consistent results with the theory for AuPd films with high values of the sheet resistance. However, for low-sheet-resistance films of AuPd, AuFe, and Au, the analysis suggests either that Joule heating is suppressed at microwave frequencies (as compared with that found for the same field strength at lower frequencies), or that a microwave field enhances the contribution of electron-electron interactions to the resistance. Either of these results would be at odds with current theories. Another experiment in which we were involved was the

  8. Approaching to the ideal condition of plasma confinement by applying external resonant fields in IR-T1 tokamak

    NASA Astrophysics Data System (ADS)

    Meshkani, Sakineh; Ghoranneviss, Mahmood; Lafouti, Mansoureh

    2015-06-01

    For understanding the effect of resonant helical magnetic field (RHF) and bias on the edge plasma turbulent transport, the radial and poloidal electric field (Er, EP ), poloidal and toroidal magnetic field (BP, Br ) were detected by the Langmuir probe, magnetic probe and diamagnetic loop. The poloidal, toroidal and radial velocity (VP, Vr, Vt ) can be determined from the electric and magnetic field. In the present work, we have investigated the effect of the magnitude of bias (V bias = 200v, V bias = 320v) on Er, EP, BP, Bt, VP, Vr, Vt . Moreover, we applied RHF with L = 2, L = 3 and L = 2 and 3 and investigate the effect of the helical windings radius on above parameters. Also, the experiment was repeated by applying the positive biasing potentials and RHF's simultaneously. The results show that by applying bias to the plasma at t = 15 msec at r/a = 0.9, Er , BP and Bt increase while EP decreases. The best modification occurs at V bias = 200v. By applying RHF to the plasma, both the electric and magnetic field vary. Er reaches the highest in the presence of RHF with L = 3. The same results are obtained for BP, Bt, VP and Vt . While the inverse results are obtained for EP and Vr . Finally, RHF and bias are applied simultaneously to the plasma. With applied bias with V bias = 200v and RHF with L = 2 and 3, we reach to the ideal circumstance. The same results obtain in the situation with V bias = 320v and RHF with L = 2 and 3.

  9. Mustiscaling Analysis applied to field Water Content through Distributed Fiber Optic Temperature sensing measurements

    NASA Astrophysics Data System (ADS)

    Benitez Buelga, Javier; Rodriguez-Sinobas, Leonor; Sanchez, Raul; Gil, Maria; Tarquis, Ana M.

    2014-05-01

    signal variation, or to see at which scales signals are most correlated. This can give us an insight into the dominant processes An alternative to both of the above methods has been described recently. Relative entropy and increments in relative entropy has been applied in soil images (Bird et al., 2006) and in soil transect data (Tarquis et al., 2008) to study scale effects localized in scale and provide the information that is complementary to the information about scale dependencies found across a range of scales. We will use them in this work to describe the spatial scaling properties of a set of field water content data measured in an extension of a corn field, in a plot of 500 m2 and an spatial resolution of 25 cm. These measurements are based on an optics cable (BruggSteal) buried on a ziz-zag deployment at 30cm depth. References Bird, N., M.C. Díaz, A. Saa, and A.M. Tarquis. 2006. A review of fractal and multifractal analysis of soil pore-scale images. J. Hydrol. 322:211-219. Kravchenko, A.N., R. Omonode, G.A. Bollero, and D.G. Bullock. 2002. Quantitative mapping of soil drainage classes using topographical data and soil electrical conductivity. Soil Sci. Soc. Am. J. 66:235-243. Lark, R.M., A.E. Milne, T.M. Addiscott, K.W.T. Goulding, C.P. Webster, and S. O'Flaherty. 2004. Scale- and location-dependent correlation of nitrous oxide emissions with soil properties: An analysis using wavelets. Eur. J. Soil Sci. 55:611-627. Lark, R.M., S.R. Kaffka, and D.L. Corwin. 2003. Multiresolution analysis of data on electrical conductivity of soil using wavelets. J. Hydrol. 272:276-290. Lark, R. M. and Webster, R. 1999. Analysis and elucidation of soil variation using wavelets. European J. of Soil Science, 50(2): 185-206. Mandelbrot, B.B. 1982. The fractal geometry of nature. W.H. Freeman, New York. Percival, D.B., and A.T. Walden. 2000. Wavelet methods for time series analysis. Cambridge Univ. Press, Cambridge, UK. Tarquis, A.M., N.R. Bird, A.P. Whitmore, M.C. Cartagena, and

  10. Runoff and phosphorus loads from two Iowa fields with and without applied manure, 2000-2011

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the dynamics of field-edge runoff water quality and responses to changes in management practices and climate through monitoring will probably require decade-duration data sets. This study compared runoff volumes and phosphorus loads from two fields in central Iowa, where the glacial la...

  11. 3-D residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

    PubMed

    O'Brien, Kieran; Daducci, Alessandro; Kickler, Nils; Lazeyras, Francois; Gruetter, Rolf; Feiweier, Thorsten; Krueger, Gunnar

    2013-08-01

    Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3-D eddy current field induced. In this work, we aimed to predict, using linear response theory, the residual 3-D eddy current field required for geometric distortion correction based on phantom eddy current field measurements. The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to ~1 Hz. The model's performance was tested on diffusion weighted images of four normal volunteers, following distortion correction, the quality of the Stejskal-Tanner diffusion-weighted images was found to have comparable quality to image registration based corrections (FSL) at low b-values. Unlike registration techniques the correction was not hindered by low SNR at high b-values, and results in improved image quality relative to FSL. Characterization of the 3-D eddy current field with linear response theory enables the prediction of the 3-D eddy current field required to correct eddy current induced geometric distortions for a wide range of clinical and high b-value protocols.

  12. Quantifying the motion of magnetic particles in excised tissue: Effect of particle properties and applied magnetic field

    NASA Astrophysics Data System (ADS)

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-11-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 μm diameter) with four different coatings (starch, chitosan, lipid, and PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields.

  13. Estimation of decay rates for fecal indicator bacteria and bacterial pathogens in agricultural field-applied manure

    EPA Science Inventory

    Field-applied manure is an important source of pathogenic exposure in surface water bodies for humans and ecological receptors. We analyzed the persistence and decay of fecal indicator bacteria and bacterial pathogens from three sources (cattle, poultry, swine) for agricultural f...

  14. QUANTIFYING THE MOTION OF MAGNETIC PARTICLES IN EXCISED TISSUE: EFFECT OF PARTICLE PROPERTIES AND APPLIED MAGNETIC FIELD

    PubMed Central

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-01-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 µm diameter) with four different coatings (starch, chitosan, lipid, PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields. PMID:26120240

  15. Legal Linguistics as a Mutual Arena for Cooperation: Recent Developments in the Field of Applied Linguistics and Law

    ERIC Educational Resources Information Center

    Engberg, Jan

    2013-01-01

    This article reports on some of the recent projects and individual works in the field of Legal Linguistics as examples of cooperation between Applied Linguistics and law. The article starts by discussing relevant prototypical concepts of Legal Linguistics. Legal Linguistics scrutinizes interactions between human beings in the framework of legal…

  16. QUANTIFYING THE MOTION OF MAGNETIC PARTICLES IN EXCISED TISSUE: EFFECT OF PARTICLE PROPERTIES AND APPLIED MAGNETIC FIELD.

    PubMed

    Kulkarni, Sandip; Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi; Nacev, Alek; Depireux, Didier; Shimoji, Mika; Shapiro, Benjamin

    2015-11-01

    This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 µm diameter) with four different coatings (starch, chitosan, lipid, PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields.

  17. Two-beam coupling gain in undoped GaAs with applied dc electric field and moving grating

    NASA Technical Reports Server (NTRS)

    Liu, Duncan T. H.; Cheng, Li-Jen; Chiou, Arthur E.; Yeh, Pochi

    1989-01-01

    Experimental results of two-beam coupling gain efficiency in an undoped, semiinsulating GaAs crystal are reported. The highest gain coefficient measured is about 4.5/cm under the condition of an applied electric field of 13 kV/cm and a grating periodicity of 20 microns. The experimental results and theoretical calculations are in reasonable agreement with each other.

  18. Effect of application method, manure characteristics, weather and field conditions on ammonia volatilization from manure applied to arable land

    NASA Astrophysics Data System (ADS)

    Huijsmans, J. F. M.; Hol, J. M. G.; Vermeulen, G. D.

    To predict ammonia (NH 3) volatilization from field-applied manure, factors affecting volatilization following manure application need to be known. A database of field measurements in the Netherlands was analysed to identify these factors and to quantify their effects on the volatilization of NH 3 from liquid pig manure applied and incorporated on arable land. The combination and the statistical analysis of these data, together with the models that were designed, yielded valuable information about the factors that influence NH 3 volatilization, and about the magnitude of their effects when applying and incorporating manure on arable land. Factors analysed were application method, characteristics of the manure, weather and field conditions. The mean total volatilization, expressed as % of the total ammoniacal nitrogen (TAN) applied, was 68% for surface spreading, 17% for surface incorporation and 2% for deep placement. The volatilization rate increased with an increase in TAN content of the manure, manure application rate and air temperature. Wind speed had a substantial effect on the volatilization rate, only when manure was surface applied or surface incorporated. The results show that useful prediction of ammonia volatilization following manure application on arable land in the Netherlands is feasible on the basis of information about application method, characteristics of the manure and weather conditions.

  19. Effect of an applied magnetic field on the performance of a SIS receiver near 300 GHz

    NASA Technical Reports Server (NTRS)

    Mallison, W. H.; De Zafra, R. L.

    1992-01-01

    A superconductor-insulator-superconductor (SIS) receiver has been successfully constructed and tested for operation at 265 - 280 GHz using 1 micron/sq area Nb-AlO(x)-Nb tunnel junctions fabricated at Stony Brook. The best performance to date is a double sideband (DSB) receiver noise temperature of 129 K at 278 GHz. It is found that suppression of the Josephson pair currents with a magnetic field is essential for good performance and a stable dc bias point. Fields as high as 280 gauss have been used with no degradation of mixing performance. The improvement in the intermediate frequency output stability with progressively increasing magnetic fields is illustrated.

  20. AC Susceptibility of the Dipolar Spin Ice Dy2Ti2O7: Experiments and Monte Carlo Simulations

    NASA Astrophysics Data System (ADS)

    Takatsu, Hiroshi; Goto, Kazuki; Otsuka, Hiromi; Higashinaka, Ryuji; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Kadowaki, Hiroaki

    2013-10-01

    Experimental data of the frequency-dependent ac susceptibility [χac(ω)] for the dipolar spin ice Dy2Ti2O7 has been analyzed by Monte Carlo simulations on the basis of the single-spin-flip Metropolis algorithm. We have directly evaluated χac(ω) by applying an ac magnetic field. We found that this simulation reasonably reproduces the experimental behavior of χac(ω) in the temperature range from 0.6 to 1.0 K, where dilute magnetic monopoles diffusively move. The conversion factor from simulation time to real time, i.e., the rate of hopping of monopoles to nearest-neighbor sites, strongly depends on temperature.

  1. Nearest neighbor correlations in perpendicular artificial spin ice arrays in the presence of an applied field

    NASA Astrophysics Data System (ADS)

    Kempinger, Susan; Fraleigh, Robert; Lammert, Paul; Crespi, Vincent; Samarth, Nitin; Schiffer, Peter

    By studying the field dependent magnetization switching process in perpendicular artificial spin ice arrays arrays, we hope to gain insight in to the dynamical properties of interacting spin systems. To this end, we have used diffraction-limited Kerr imaging to study lithographically patterned arrays of single domain, nanoscale islands of Co/Pt multilayers. We can tune the interaction strength and introduce geometric frustration in to the patterned systems by changing the lattice spacing and geometry of the arrays. Using MOKE microscopy we are able to optically resolve, spatially isolate, and extract the switching field of each island in an array in the presence of an external field. These switching fields allow us to calculate the magnetization and nearest neighbor spin-spin correlation throughout a hysteresis loop. These quantities help us determine the effect of increased interactions and geometric frustration on the switching process of dipole coupled arrays. Funded by DOE.

  2. Simple lumped circuit model applied to field flatness tuning of four-rod radio frequency quadrupoles

    NASA Astrophysics Data System (ADS)

    Tan, C. Y.; Schmidt, J. S.; Schempp, A.

    2014-01-01

    The field flatness of any radio frequency quadrupole (RFQ) is an important parameter that needs to be carefully tuned because it can affect beam transmission efficiency. In four-rod RFQs, the heights of a set of tuning plates determine the quality of the field flatness. The goals of this paper are (a) to show that by using a lumped circuit model of a four-rod RFQ, the field flatness profile for any tuning plate height distribution can be quickly calculated, (b) to derive a perturbative solution of the model so that insights into the physics of the tuning process and its effects can be understood, and (c) to compare the predicted field profiles to measurements.

  3. The weak field approximation and the strong field approximation for a quantum mechanical two-state system with an applied time-dependent force

    NASA Astrophysics Data System (ADS)

    Ropiak, Cynthia Ann

    A semi-classical treatment of the two-state atom subjected to a time-dependent applied force leads to a set of two coupled, complex, first-order ordinary differential equations governing the time evolution of the system's state vector that are to date, not solvable in closed form. Contained in this paper is a demonstration of how the system is parameterized by a single variable Θ, which in turn reduces the problem to one real, nonlinear, second-order ordinary differential equation. Utilizing a non-standard perturbation expansion in the variable `A' (the Field Strength Parameter) on this reduction subsequently allows for both a first-order Weak Field Approximation and a first-order Strong Field Approximation. In addition, a technique is outlined for obtaining the full power series solution in the Weak Field Limit (|A|<< l). However, a detailed discussion of the power series solution as well as its consequences is deferred due to the fact that it is presently a collaborative work in progress between Dr. Robert L. Anderson and myself. When applied to the specific case of both resonant and near-resonant linearly polarized light incident on an atom, both the Weak Field Approximation and the Strong Field Approximation are shown to be in good agreement with numerically generated solutions for the probability amplitudes of the state vector. Furthermore, this new Weak Field Approximation reveals the defect in the ansatz of discarding the `rapidly oscillating' term in the traditional Rotating Wave Approximation. Finally, the resonance case of the first-order Weak Field Approximation is found to contain large-time behavior. This large-time behavior is extracted and the new approximation is referred to as the Long-Time Weak Field Approximation. The resonance power series solution is demonstrated to contain large-time behavior, which is found to reduce to the first-order Long-Time Weak Field Approximation, but again a detailed analysis of the power series is deferred.

  4. Effect of graphene-oxide on the microstructure and charge carrier transport of polyaniline nanocomposites under low applied electric fields

    NASA Astrophysics Data System (ADS)

    Mombrú, Dominique; Romero, Mariano; Faccio, Ricardo; Mombrú, Álvaro W.

    2017-01-01

    We report a study on the preparation and characterization of polyaniline-graphene oxide (PANI-GO-X) nanocomposites focusing in the study of its structure, microstructure, and correlations with electrical transport properties under low applied electric fields. X-ray diffraction analysis showed evidence of graphene oxide (GO) blending between polyaniline fibers, and according to small angle X-ray scattering, the fractal dimensionality was quasi-one dimensional for all nanocomposites. Confocal Raman spectroscopy revealed that the addition of GO leads to a notorious decrease of the polaron population of polyaniline. A significant increase in resistivity was observed for PANI-GO-X nanocomposites with respect to pure polyaniline, in agreement with the decrease in the polaron population. The electrical transport mechanism could be explained by an Arrhenius behavior at high temperatures (T > 255 K) and a broad transition with a logarithmic dependence of the activation energy with temperature for the low temperature regime (T < 255 K). Additionally, an increase in the hopping transport dimensionality from quasi-1D to quasi-3D was observed for X = 7% GO nanocomposites. The transport properties, studied after the polarization using low applied electric fields, revealed the modification of the electrical transport at low temperatures. In addition, the electrical transport of PANI-GO-X nanocomposites followed a typical ln(σ) vs E1/2 Poole-Frenkel type dependence in the presence of low applied electric fields. At low temperatures, X = 7% GO nanocomposites showed a notorious increase in the Poole-Frenkel slope at low applied electric fields with respect to pure polyaniline. The enhancement on the electric response using low applied electric fields (E ˜ 2 V/cm) could be of great interest for the development of new organic electronic devices.

  5. Instantaneous velocity measurement of AC electroosmotic flows by laser induced fluorescence photobleaching anemometer with high temporal resolution

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Yang, Fang; Qiao, Rui; Wang, Guiren; Rui Qiao Collaboration

    2015-11-01

    Understanding the instantaneous response of flows to applied AC electric fields may help understand some unsolved issues in induced-charge electrokinetics and enhance performance of microfluidic devices. Since currently available velocimeters have difficulty in measuring velocity fluctuations with frequency higher than 1 kHz, most experimental studies so far focus only on the average velocity measurement in AC electrokinetic flows. Here, we present measurements of AC electroosmotic flow (AC-EOF) response time in microchannels by a novel velocimeter with submicrometer spatial resolution and microsecond temporal resolution, i.e. laser-induced fluorescence photobleaching anemometer (LIFPA). Several parameters affecting the AC-EOF response time to the applied electric signal were investigated, i.e. channel length, transverse position and solution conductivity. The experimental results show that the EOF response time under a pulsed electric field decreases with the reduction of the microchannel length, distance between the detection position to the wall and the conductivity of the solution. This work could provide a new powerful tool to measure AC electrokinetics and enhance our understanding of AC electrokinetic flows.

  6. Field site leaching from recycled concrete aggregates applied as sub-base material in road construction.

    PubMed

    Engelsen, Christian J; Wibetoe, Grethe; van der Sloot, Hans A; Lund, Walter; Petkovic, Gordana

    2012-06-15

    The release of major and trace elements from recycled concrete aggregates used in an asphalt covered road sub-base has been monitored for more than 4 years. A similar test field without an asphalt cover, directly exposed to air and rain, and an asphalt covered reference field with natural aggregates in the sub-base were also included in the study. It was found that the pH of the infiltration water from the road sub-base with asphalt covered concrete aggregates decreased from 12.6 to below pH 10 after 2.5 years of exposure, whereas this pH was reached within only one year for the uncovered field. Vertical temperature profiles established for the sub-base, could explain the measured infiltration during parts of the winter season. When the release of major and trace elements as function of field pH was compared with pH dependent release data measured in the laboratory, some similar pH trends were found. The field concentrations of Cd, Ni, Pb and Zn were found to be low throughout the monitoring period. During two of the winter seasons, a concentration increase of Cr and Mo was observed, possibly due to the use of de-icing salt. The concentrations of the trace constituents did not exceed Norwegian acceptance criteria for ground water and surface water Class II.

  7. Effects on wildlife of ethyl and methyl parathion applied to California rice fields

    USGS Publications Warehouse

    Custer, T.W.; Hill, E.F.; Ohlendorf, H.M.

    1985-01-01

    Selected rice fields on the Sacramento National Wildlife Refuge Complex were aerially sprayed one time during May or June 1982 with either ethyl (0.11 kg Al/ha) or methyl (0.84 kg AI/ha) parathion for control of tadpole shrimp, Triops longicaudatus. No sick or dead vertebrate wildlife were found or adjacent to the treated rice fields after spraying. Specimens of the following birds and mammals were assayed for brain cholinesterase (ChE) activity to determine exposure to either form of parathion; house mouse, Mus musculus; black-tailed jackrabbit, Lepus californicus; mallard, Anas platyrhynchos; ring-necked pheasant, Phasianus colchicus; American coot, Fulica americana; and red-winged blackbird, Agelaius phoeniceus. Both mice and pheasants from methyl parathion-treated fields had overall mean ChE activities that were significantly (P < 0.05) inhibited compared with controls, and 7, 40, 54 and 57% of individual blackbirds, pheasant, mice, and coots, respectively, had inhibited brain ChE activities (i.e., less than -2 SD of control mean). Although no overall species effect was detected for ethyl parathoid treatment, pheasants (43%), coots (33%), and mice (37%) had significantly inhibited brain ChE activities. Neither of the parathion treatment appeared acutely hazardous to wildlife in or adjacent to rice fields, but sufficient information on potential hazards was obtained to warrant caution in use of these chemicals, especially methyl parathion, in rice fields.

  8. Effects of wildlife of ethyl and methyl parathion applied to California USA rice fields

    USGS Publications Warehouse

    Custer, T.W.; Hill, E.F.; Ohlendorf, H.M.

    1985-01-01

    Selected rice fields on the Sacramento National Wildlife Refuge Complex were aerially sprayed one time during May or June 1982 with either ethyl (0.11 kg Al/ha) or methyl (0.84 kg AI/ha) parathion for control of tadpole shrimp, Triops longicaudatus. No sick or dead vertebrate wildlife were found or adjacent to the treated rice fields after spraying. Specimens of the following birds and mammals were assayed for brain cholinesterase (ChE) activity to determine exposure to either form of parathion; house mouse, Mus musculus; black-tailed jackrabbit, Lepus californicus; mallard, Anas platyrhynchos; ring-necked pheasant, Phasianus colchicus; American coot, Fulica americana; and red-winged blackbird, Agelaius phoeniceus. Both mice and pheasants from methyl parathion-treated fields had overall mean ChE activities that were significantly (P < 0.05) inhibited compared with controls, and 7, 40, 54 and 57% of individual blackbirds, pheasant, mice, and coots, respectively, had inhibited brain ChE activities (i.e., less than -2 SD of control mean). Although no overall species effect was detected for ethyl parathoid treatment, pheasants (43%), coots (33%), and mice (37%) had significantly inhibited brain ChE activities. Neither of the parathion treatment appeared acutely hazardous to wildlife in or adjacent to rice fields, but sufficient information on potential hazards was obtained to warrant caution in use of these chemicals, especially methyl parathion, in rice fields.

  9. Nacelle LiDAR online wind field reconstruction applied to feedforward pitch control

    NASA Astrophysics Data System (ADS)

    GUILLEMIN, F.; DOMENICO, D. DI; NGUYEN, N.; SABIRON, G.; BOQUET, M.; GIRARD, N.; COUPIAC, O.

    2016-09-01

    This paper presents innovative filtering and reconstruction techniques of nacelle LiDAR data, and exploitation of obtained wind anticipation capabilities for wind turbine control strategy. The implemented algorithms are applied under industrial constraints, on a MAIA EOLIS wind turbine, equipped with a LEOSPHERE 5-beams pulsed LiDAR, during experimental campaigns of SMARTEOLE collaborative project.

  10. Spherical Elementary Current Systems Method Applied to Geomagnetic Field Modeling for the Adriatic

    NASA Astrophysics Data System (ADS)

    Vujić, Eugen; Brkić, Mario

    2016-08-01

    The aim of this work was to derive an accurate regional model of geomagnetic components on the Adriatic. Data of north, east and vertical geomagnetic components at repeat stations and ground survey sites enclosing the Adriatic Sea were used to obtain a geomagnetic model at 2010.5 epoch. The core field was estimated by use of the global Enhanced Magnetic Model, while the crustal field by a mathematical technique for expanding vector systems on a sphere into basis functions, known as spherical elementary current systems method. The results of this method were presented and compared to the crustal field estimations by the Enhanced Magnetic Model. The maps of isolines of the regional model are also presented.

  11. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

    SciTech Connect

    Che, Xueke E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao; Shao, Tao E-mail: st@mail.iee.ac.cn

    2014-04-15

    Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

  12. Layer resolved magnetic domain imaging of epitaxial heterostructures in large applied magnetic fields

    NASA Astrophysics Data System (ADS)

    Zohar, S.; Choi, Y.; Love, D. M.; Mansell, R.; Barnes, C. H. W.; Keavney, D. J.; Rosenberg, R. A.

    2015-02-01

    We use X-ray Excited Luminescence Microscopy to investigate the elemental and layer resolved magnetic reversal in an interlayer exchange coupled (IEC) epitaxial Fe/Cr wedge/Co heterostructure. The transition from strongly coupled parallel Co-Fe reversal for Cr thickness tCr < 0.34 nm to weakly coupled layer independent reversal for tCr > 1.5 nm is punctuated at 0.34 < tCr < 1.5 nm by a combination of IEC guided domain wall motion and stationary zig zag domain walls. Domain walls nucleated at switching field minima are guided by IEC spatial gradients and collapse at switching field maxima.

  13. A procedure for specimen optimization applied to material testing in plasticity with the virtual fields method

    NASA Astrophysics Data System (ADS)

    Rossi, Marco; Badaloni, Michele; Lava, Pascal; Debruyne, Dimitri; Pierron, Fabrice

    2016-10-01

    The paper presents a numerical procedure to design an optimal geometry for specimens that will be used to identify the hardening behaviour of sheet metals with the virtual fields method (VFM). The procedure relies on a test simulator able to generate synthetic images similar to the ones obtained during an actual test. Digital image correlation (DIC) was used to achieve the strain field, then the constitutive parameters are identified with the VFM and compared with the reference ones. A parametric study was conducted on different types of notched specimens and an optimal configuration was identified eventually.

  14. Effects of an applied electric field on the vapor-liquid equilibria of water, methanol, and dimethyl ether.

    PubMed

    Maerzke, Katie A; Siepmann, J Ilja

    2010-04-01

    Gibbs ensemble Monte Carlo simulations are employed to examine the influence of moderately strong electric fields on the vapor-liquid coexistence curves and on structural and energetic properties of the saturated phases of water, methanol, and dimethyl ether. The application of an electric field of 0.1 V/A increases the critical temperature and normal boiling point by approximately 3% compared to the zero field case for all three compounds, whereas the critical density is found to decrease by 1% for methanol and dimethly ether and by 3% for water. For the special case of an electric field applied in only the liquid phase, these effects are magnified with a 4% increase in T(C) and a 13% decrease in rho(C). For the case of an electric field in only the vapor phase, the opposite effect is seen with a 4% decrease in T(C) and a 12% increase in rho(C). Structural analysis shows very little change in the radial distribution functions, but greatly increased orientational ordering with the application of an electric field. The orientational ordering effect is stronger in the liquid phase than in the vapor phase. An examination of the energetics reveals that, in the presence of an electric field, the interactions with the first and second solvation shells become less favorable but these are outweighed by a larger increase in the favorable long-range interactions with more distant molecules and the field.

  15. Applying Threshold Concepts Theory to an Unsettled Field: An Exploratory Study in Criminal Justice Education

    ERIC Educational Resources Information Center

    Wimshurst, Kerry

    2011-01-01

    Criminal justice education is a relatively new program in higher education in many countries, and its curriculum and parameters remain unsettled. An exploratory study investigated whether threshold concepts theory provided a useful lens by which to explore student understandings of this multidisciplinary field. Eight high-performing final-year…

  16. Environmental-sanitary risk analysis procedure applied to artificial turf sports fields.

    PubMed

    Ruffino, Barbara; Fiore, Silvia; Zanetti, Maria Chiara

    2013-07-01

    Owing to the extensive use of artificial turfs worldwide, over the past 10 years there has been much discussion about the possible health and environmental problems originating from styrene-butadiene recycled rubber. In this paper, the authors performed a Tier 2 environmental-sanitary risk analysis on five artificial turf sports fields located in the city of Turin (Italy) with the aid of RISC4 software. Two receptors (adult player and child player) and three routes of exposure (direct contact with crumb rubber, contact with rainwater soaking the rubber mat, inhalation of dusts and gases from the artificial turf fields) were considered in the conceptual model. For all the fields and for all the routes, the cumulative carcinogenic risk proved to be lower than 10(-6) and the cumulative non-carcinogenic risk lower than 1. The outdoor inhalation of dusts and gases was the main route of exposure for both carcinogenic and non-carcinogenic substances. The results given by the inhalation pathway were compared with those of a risk assessment carried out on citizens breathing gases and dusts from traffic emissions every day in Turin. For both classes of substances and for both receptors, the inhalation of atmospheric dusts and gases from vehicular traffic gave risk values of one order of magnitude higher than those due to playing soccer on an artificial field.

  17. From lab to field conditions: a pilot study on EEG methodology in applied sports sciences.

    PubMed

    Reinecke, Kirsten; Cordes, Marjolijn; Lerch, Christiane; Koutsandréou, Flora; Schubert, Michael; Weiss, Michael; Baumeister, Jochen

    2011-12-01

    Although neurophysiological aspects have become more important in sports and exercise sciences in the last years, it was not possible to measure cortical activity during performance outside a laboratory due to equipment limits or movement artifacts in particular. With this pilot study we want to investigate whether Electroencephalography (EEG) data obtained in a laboratory golf putting performance differ from a suitable putting task under field conditions. Therefore, parameters of the working memory (frontal Theta and parietal Alpha 2 power) were recorded during these two conditions. Statistical calculations demonstrated a significant difference only for Theta power at F4 regarding the two putting conditions "field" and "laboratory". These findings support the idea that brain activity patterns obtained under laboratory conditions are comparable but not equivalent to those obtained under field conditions. Additionally, we were able to show that the EEG methodology seems to be a reliable tool to observe brain activity under field conditions in a golf putting task. However, considering the still existing problems of movement artifacts during EEG measurements, eligible sports and exercises are limited to those being relatively motionless during execution. Further studies are needed to confirm these pilot results.

  18. Release 3 of the GOCE-only Gravity Field Model Applying the Time-wise Method

    NASA Astrophysics Data System (ADS)

    Brockmann, J.; Pail, R.; Mayer-Gürr, T.; Hoeck, E.; Krasbutter, I.; Fecher, T.; Schuh, W.; Mayrhofer, R.

    2011-12-01

    The release 3 of the time-wise global GOCE-only gravity field model, which has been processed as part of the GOCE High-Level Processing Facility, is based on data of the full nominal mission operation phase from November 2009 to April 2011. The time-wise processing strategy is based on the solution of full normal equations, where gravity field information from precise kinematic orbits is combined with the analysis of the gravity gradients. Special emphasis is given to a realistic stochastic modelling of the individual contributions, facilitating the consistent combination. The optimum relative weights are derived from variance component estimation. In this contribution, this new solution is compared with the previous two releases, in order to evaluate the improvements due to a substantially larger amount of input data, as well as with external gravity field information. Additionally, a performance prediction of the achievable final accuracy of GOCE-only gravity field models, provided that the satellite stays healthy in orbit at least until the end of the extended mission phase (December 2012), will be presented, and possible mission scenarios after 2012 and their impact on the performance will be discussed.

  19. FLEA: Fresnel-limited extraction algorithm applied to spectral phase interferometry for direct field reconstruction (SPIDER)

    NASA Astrophysics Data System (ADS)

    Pasquazi, Alessia; Peccianti, Marco; Azaña, José; Moss, David J.; Morandotti, Roberto

    2013-03-01

    We present a novel extraction algorithm for spectral phase interferometry for direct field reconstruction (SPIDER) for the so-called X-SPIDER configuration. Our approach largely extends the measurable time windows of pulses without requiring any modification to the experimental X-SPIDER set-up.

  20. Dynamics of low-density ultracold plasmas in externally applied electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Wilson, Truman M.

    The experiments described in this thesis were focused on the influence of external electric and magnetic fields and electron evaporation on the evolution of ultracold plasmas (UCPs). The UCPs were created from the photoionization of 85Rb which was first captured in a magneto-optical trap (MOT) and then magnetically trapped and transferred by a set of magnetic coils attached to a motorized translation stage to a region of the vacuum chamber with a set of electrodes. The first experiment studied the response of the UCP to sharp electric field pulses, which included 2 cycles of a sine wave pulse. These experiments showed a resonant response to the 2 cycles of rf that was density dependent, but was not a collision based mechanism. Instead, the response was caused by a rapid energy transfer to individual electrons through the collective motion of the electron cloud in the UCP. This density-dependent response allowed us to develop a technique for measuring the expansion rate of the UCPs in our system. It was also observed in second set of experiments that electron evaporation from the UCP had a significant effect on the amount of energy that was transferred to the ions to drive the UCP expansion. Model calculations show that we should expect electron evaporation to have a more significant influence on the UCP expansion rate at the relatively low densities of the UCPs that we create compared to other experiments. By modeling electron evaporation during expansion, our data are consistent with evaporation reducing the electron temperature significantly, which lowers the overall UCP expansion rate. In addition to these studies, we also performed an experiment in which it was observed that in the presence of a magnetic field there was a significant increase in the initial UCP expansion rate coupled with a deceleration of the ion expansion at later times in the UCP evolution. Our observations to date are consistent with the magnetic field influencing electron screening and UCP

  1. Dependence of electrical property on the applied magnetic fields in spin coated Fe(III)-Phorphyrin films

    NASA Astrophysics Data System (ADS)

    Utari; Kusumandari; Purnama, B.; Mudasir; Abraha, K.

    2016-11-01

    We report here on the experimental results of the effect of external magnetic field on the current flow in plane surface of Fe(III)-porphyrin thin layer. The deposition of the Fe(III)- porphyrin thin layer was done by spin coating method. The I-V characteristics of film were measured by means of two point probes. The sample of layer number N = 4 was used to evaluate the magnetic effect on the electrical currents. The ohmic characteristics of the I-V film measurement were obtained. The current decreases when magnetic field is applied to the system and saturated current is obtained at a given magnetic field. Here, the decrease in the current can be attributed to the recombination of carrier charge under the magnetic field. In addition, the magnitude of the saturated current is found to increase with the increase in the voltage used.

  2. Effect of external applied steady magnetic field on the morphology of laser welding joint of 4-mm 2024 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Zhan, Xiaohong; Zhou, Junjie; Sun, Weihua; Chen, Jicheng; Wei, Yanhong

    2017-01-01

    Additional external steady magnetic fields were applied to investigate the influence of a steady magnetic field aligned perpendicular to the welding direction during laser beam welding of 2024 aluminum alloy. The flow pattern in the molten pool and the weld seam geometry were significantly changed by the induced Lorentz force distribution in the liquid metal. It revealed that the application of a steady magnetic field to laser beam welding was helpful to the suppression of the characteristic wineglass-shape and the depth-to-width ratio because of the Marangoni convection. The microstructures and component distributions at various laser power and magnetic field intensity were analyzed too. It was indicated that the suppression of the Marangoni convection by Lorentz force was beneficial to accumulation of component and grain coarsening near the fusion line.

  3. Applying Erikson's wisdom to self-management practices of older adults: findings from two field studies.

    PubMed

    Perry, Tam E; Ruggiano, Nicole; Shtompel, Natalia; Hassevoort, Luke

    2015-04-01

    According to Erik Erikson's theory on the stages of human development, achieving wisdom later in life involves revisiting previous crises and renewing psychosocial accomplishments. However, few studies have used Erikson's theory as a framework for examining how older adults self-manage physical and mental health changes that commonly occur later in life. This article presents findings from two qualitative studies that demonstrate how older adults apply wisdom in new domains. Specifically, it was found that older adults (1) reasserted autonomy by initiating creative problem solving and (2) applied skills gained from productive activities earlier in life to new health-related problems that arise later in life. These findings highlight the importance of engaging older adults to repurpose their life skills and thus reapply wisdom to new areas of their lives. Implications for practice are discussed.

  4. Field Evaluation of Six Protective Coatings Applied to T56 Turbines after 1500 Hours Engine Use

    DTIC Science & Technology

    1991-06-01

    Six Coating Systems On First-stage Gas Turbine Blades In The Engines of a Long-Range Maritime Patrol Aircraft ", Surface and Coating Technology, 36...based coatings. They were applied to the first-stage turbine blades in the engines of two long range maritime patrol aircraft operated by the Royal...incorrect. These differently coated turbine - blades have in fact seen 1500 hours service in a T56 engine . The title and further reference in the text should

  5. High sensitivity microwave detection using a magnetic tunnel junction in the absence of an external applied magnetic field

    SciTech Connect

    Gui, Y. S.; Bai, L. H.; Hu, C.-M.; Xiao, Y.; Guo, H.; Hemour, S.; Zhao, Y. P.; Wu, K.; Houssameddine, D.

    2015-04-13

    In the absence of any external applied magnetic field, we have found that a magnetic tunnel junction (MTJ) can produce a significant output direct voltage under microwave radiation at frequencies, which are far from the ferromagnetic resonance condition, and this voltage signal can be increase by at least an order of magnitude by applying a direct current bias. The enhancement of the microwave detection can be explained by the nonlinear resistance/conductance of the MTJs. Our estimation suggests that optimized MTJs should achieve sensitivities for non-resonant broadband microwave detection of about 5000 mV/mW.

  6. Effect of an applied electric field on a weakly anchored non-planar Nematic Liquid Crystal (NLC) layer

    NASA Astrophysics Data System (ADS)

    Mema, Ensela; Cummings, Linda J.; Kondic, Lou

    We consider a mathematical model that consists of a NLC layer sandwiched between two parallel bounding plates, across which an external field is applied. We investigate its effect on the director orientation by considering the dielectric and flexoelectric contributions and varying parameters that represent the anchoring conditions and the electric field strength. In particular, we investigate possible director configurations that occur in weakly anchored and non-planar systems. We observe that non-planar anchoring angles destroy any hysteresis seen in a planar system by eliminating the fully vertical director configuration and the ''saturation threshold'' seen in weakly anchored planar Freedericksz cells. Supported by NSF Grant No. DMS-1211713.

  7. Continuous control of local magnetic moment by applied electric field in multiferroics Ba2CoGe2O7

    NASA Astrophysics Data System (ADS)

    Soda, Minoru; Hayashida, Shohei; Roessli, Bertrand; Mânsson, Martin; White, Jonathan S.; Matsumoto, Masashige; Shiina, Ryousuke; Masuda, Takatsugu

    2016-09-01

    Ba2CoGe2O7 exhibits a collinear-antiferromagnetic structure with the easy axis along <100 > directions and an antiferroelectric order with the polarization axis along the [001] direction. By applying the electric field the magnetic moment rotates from <100 > to [110] directions and, simultaneously, the antiferroelectric state changes to the ferroelectric state gradually. This magnetoelectric effect, i.e., continuous control of the local magnetic moment by the electric field, is quantitatively explained by the Hamiltonian including the dielectric energy.

  8. Advanced Electron Holography Applied to Electromagnetic Field Study in Materials Science.

    PubMed

    Shindo, Daisuke; Tanigaki, Toshiaki; Park, Hyun Soon

    2016-11-17

    Advances and applications of electron holography to the study of electromagnetic fields in various functional materials are presented. In particular, the development of split-illumination electron holography, which introduces a biprism in the illumination system of a holography electron microscope, enables highly accurate observations of electromagnetic fields and the expansion of the observable area. First, the charge distributions on insulating materials were studied by using split-illumination electron holography and including a mask in the illumination system. Second, the three-dimensional spin configurations of skyrmion lattices in a helimagnet were visualized by using a high-voltage holography electron microscope. Third, the pinning of the magnetic flux lines in a high-temperature superconductor YBa2 Cu3 O7-y was analyzed by combining electron holography and scanning ion microscopy. Finally, the dynamic accumulation and collective motions of electrons around insulating biomaterial surfaces were observed by utilizing the amplitude reconstruction processes of electron holography.

  9. Field trials of line transect methods applied to estimation of desert tortoise abundance

    USGS Publications Warehouse

    Anderson, David R.; Burnham, Kenneth P.; Lubow, Bruce C.; Thomas, L. E. N.; Corn, Paul Stephen; Medica, Philip A.; Marlow, R.W.

    2001-01-01

    We examine the degree to which field observers can meet the assumptions underlying line transect sampling to monitor populations of desert tortoises (Gopherus agassizii). We present the results of 2 field trials using artificial tortoise models in 3 size classes. The trials were conducted on 2 occasions on an area south of Las Vegas, Nevada, where the density of the test population was known. In the first trials, conducted largely by experienced biologists who had been involved in tortoise surveys for many years, the density of adult tortoise models was well estimated (-3.9% bias), while the bias was higher (-20%) for subadult tortoise models. The bias for combined data was -12.0%. The bias was largely attributed to the failure to detect all tortoise models on or near the transect centerline. The second trials were conducted with a group of largely inexperienced student volunteers and used somewhat different searching methods, and the results were similar to the first trials. Estimated combined density of subadult and adult tortoise models had a negative bias (-7.3%), again attributable to failure to detect some models on or near the centerline. Experience in desert tortoise biology, either comparing the first and second trials or in the second trial with 2 experienced biologists versus 16 novices, did not have an apparent effect on the quality of the data or the accuracy of the estimates. Observer training, specific to line transect sampling, and field testing are important components of a reliable survey. Line transect sampling represents a viable method for large-scale monitoring of populations of desert tortoise; however, field protocol must be improved to assure the key assumptions are met.

  10. Specific heat in KFe2As2 in zero and applied magnetic field

    NASA Astrophysics Data System (ADS)

    Kim, J. S.; Kim, E. G.; Stewart, G. R.; Chen, X. H.; Wang, X. F.

    2011-05-01

    The specific heat down to 0.08 K of the iron pnictide superconductor KFe2As2 was measured on a single-crystal sample with a residual resistivity ratio of ˜650, with a Tconset determined by a specific heat of 3.7 K. The zero-field normal-state specific heat divided by temperature, C/T, was extrapolated from above Tc to T=0 by insisting on agreement between the extrapolated normal-state entropy at Tc, Snextrap(Tc), and the measured superconducting-state entropy at Tc, Ssmeas(Tc), since for a second-order phase transition the two entropies must be equal. This extrapolation would indicate that this rather clean sample of KFe2As2 exhibits non-Fermi-liquid behavior; i.e., C/T increases at low temperatures, in agreement with the reported non-Fermi-liquid behavior in the resistivity. However, specific heat as a function of magnetic field shows that the shoulder feature around 0.7 K, which is commonly seen in KFe2As2 samples, is not evidence for a second superconducting gap as has been previously proposed but instead is due to an unknown magnetic impurity phase, which can affect the entropy balance and the extrapolation of the normal-state specific heat. This peak (somewhat larger in magnitude) with similar field dependence is also found in a less pure sample of KFe2As2, with a residual resistivity ratio of only 90 and Tconset=3.1 K. These data, combined with the measured normal-state specific heat in field to suppress superconductivity, allow the conclusion that an increase in the normal-state specific heat as T→0 is in fact not seen in KFe2As2; i.e., Fermi-liquid behavior is observed.

  11. Preferred Orientation of Rare Earth (RE)-Doped Alumina Crystallites by an Applied Magnetic Field

    DTIC Science & Technology

    2016-06-01

    studies of ceramic particles involve some form of colloidal processing; slip-casting, gel- casting, or tape casting, which gives particles the mobility of...of alumina by colloidal filtration in a strong magnetic field and sintering. Advanced Engineering Materials. 2001;3(7):490–492. Approved for...Journal of Colloid and Interface Science. 2012;375(1):203–212. 19. Makiya A, Shouji D, Tanaka S, Uchida N, Kimura T, Uematsu K. Grain oriented

  12. Current oscillation and chaotic dynamics in superlattices driven by crossed electric and magnetic fields.

    PubMed

    Wang, C; Cao, J C

    2005-03-01

    We have theoretically studied current oscillation and chaotic dynamics in doped GaAsAlAs superlattices driven by crossed electric and magnetic fields. When the superlattice system is driven by a dc voltage, a stationary or dynamic electric-field domain can be obtained. We carefully studied the electric-field-domain dynamics and current self-oscillation which both display different modes with the change of magnetic field. When an ac electric field is also applied to the superlattice, a typical nonlinear dynamic system is constructed with the ac amplitude, ac frequency, and magnetic field as the control parameters. Different nonlinear behaviors show up when we tune the control parameters.

  13. Transport properties of RPtBi (R = Gd, Dy, Tm, and Lu) under applied magnetic fields

    NASA Astrophysics Data System (ADS)

    Mun, Eundeok; Bud'Ko, Sergey; Canfield, Paul

    2015-03-01

    It has been suggested that the combination of strong spin-orbit coupling and noncentrosymmetric crystal structure make ternary Heusler compounds a strong candidate for 3D topological materials. The crystal structure of rare-earth platinum bismuth (RPtBi) half-Heusler compounds lacks an inversion symmetry, hence the material is a noncentrosymmeteric. The earlier electrical resistivity data of RPtBi revealed a systematic change from a small gap semiconductor for lighter rare-earth to metallic for heavier rare-earth compounds. The angle resolved photoemission spectroscopy showed a clear spin-orbit splitting of the surface bands that cross the Fermi surface. Here we present very large magnetic field dependences of transport properties in single crystals of RPtBi (R = Gd, Dy, Tm, and Lu). Successfully grown the high quality RPtBi single crystals reveal that a large non-saturating magnetoresistance (MR) of as high as 800 % at 2 K and over 300 % at 300 K under a moderate magnetic field of 14 T. In addition to the large MR, the samples exhibit pronounced temperature and magnetic field dependences of Hall coefficient and thermoelectric power. Obtained transport data suggest that the high hole and electron mobility dominate the magnetotransport.

  14. Enola Gay: an integrated modelling optical toolbox applied to a wide-field telescope

    NASA Astrophysics Data System (ADS)

    Schipani, P.; Perrotta, F.

    2008-07-01

    The integrated modelling approach is fundamental in telescopes design where it is necessary to merge different disciplines together. This paper describes the integration of optical ray-tracing capabilities within the Matlab computational environment. This approach allows to write automatic procedures to implement a huge number of computations, that are very unpractical to perform in interactive mode by ray tracing software packages. Data produced by computations are stored and automatically analyzed. One of the main benefits from this approach comes from the traceability of the work, that is intrinsically impossible when the optical designer works in interactive mode. The right procedure is built and tuned just the first time and the computation software is available for inspection and check. Furthermore computations and results are easily reproducible simply re-running Matlab scripts. An automatic approach is especially helpful in wide-field telescope projects where the optical quality has to be studied over a wide field of view. This leads to repeat the same computations many times in a number of fields. In interactive mode this would cause a significant waste of optical designer time to repeat many times the same manual procedures. The solution proposed here allows to save time and prevent occasional mistakes.

  15. Mechanism analysis of Magnetohydrodynamic heat shield system and optimization of externally applied magnetic field

    NASA Astrophysics Data System (ADS)

    Li, Kai; Liu, Jun; Liu, Weiqiang

    2017-04-01

    As a novel thermal protection technique for hypersonic vehicles, Magnetohydrodynamic (MHD) heat shield system has been proved to be of great intrinsic value in the hypersonic field. In order to analyze the thermal protection mechanisms of such a system, a physical model is constructed for analyzing the effect of the Lorentz force components in the counter and normal directions. With a series of numerical simulations, the dominating Lorentz force components are analyzed for the MHD heat flux mitigation in different regions of a typical reentry vehicle. Then, a novel magnetic field with variable included angle between magnetic induction line and streamline is designed, which significantly improves the performance of MHD thermal protection in the stagnation and shoulder areas. After that, the relationships between MHD shock control and MHD thermal protection are investigated, based on which the magnetic field above is secondarily optimized obtaining better performances of both shock control and thermal protection. Results show that the MHD thermal protection is mainly determined by the Lorentz force's effect on the boundary layer. From the stagnation to the shoulder region, the flow deceleration effect of the counter-flow component is weakened while the flow deflection effect of the normal component is enhanced. Moreover, there is no obviously positive correlation between the MHD shock control and thermal protection. But once a good Lorentz force's effect on the boundary layer is guaranteed, the thermal protection performance can be further improved with an enlarged shock stand-off distance by strengthening the counter-flow Lorentz force right after shock.

  16. Ammonia volatilization from field-applied animal slurry—the ALFAM model

    NASA Astrophysics Data System (ADS)

    Søgaard, H. T.; Sommer, S. G.; Hutchings, N. J.; Huijsmans, J. F. M.; Bussink, D. W.; Nicholson, F.

    A statistical analysis of European ammonia (NH 3) volatilization data (from Denmark, Italy, the Netherlands, Norway, Sweden, Switzerland and UK) collated in a database produced a model that is supported by theoretical considerations of the effect of explanatory variables (see www.alfam.dk). Volatilization could be described mathematically by a Michaelis-Menten-type equation, with the loss rates as the response variable ( R2=80%). Variables significantly affecting NH 3 volatilization throughout Europe are soil water content, air temperature, wind speed, slurry type, dry matter content of slurry, total ammoniacal nitrogen content of slurry (TAN=NH 3+NH 4+), application method and rate, slurry incorporation and measuring technique. The model was used to estimate the NH 3 volatilization from typical cattle and pig slurries applied in Italy, England, Norway and Denmark. Climate observations from the following three periods in year 2000 were used as input: (1) 1 week before the normal sowing time for spring crops, (2) mid-season, and (3) 1 week after harvesting. There was little difference in the total NH 3 volatilization from slurry applied in the three periods, principally due to interactions between soil water content and air temperature . The time from application to when 10% of the applied TAN was lost was similar for countries in the south and north of Europe, primarily due to the low wind speeds counteracting the effect of higher air temperatures at the southern location. To reduce NH 3 volatilization, the slurry should be incorporated faster in mid- and late-season than in the early spring, due to increasing air temperatures during the growing season.

  17. Friability of spray-applied fireproofing and thermal insulations: the basis for a field-test method

    SciTech Connect

    Rossiter, W.J.; Roberts, W.E.; Mathey, R.G.

    1987-12-01

    The investigation was Phase 1 of a two-part study to develop a test method that can be used in the field to measure the friability of spray-applied fireproofing and insulating materials containing asbestos fibers. Four test methods were selected; compression/shear, indentation, abrasion, and impact. For each of the four tests, mechanical devices were devised by modification of existing material test apparatus. A description of the test devices is given in the report.

  18. Fielding the magnetically applied pressure-shear technique on the Z accelerator (completion report for MRT 4519).

    SciTech Connect

    Alexander, C. Scott; Haill, Thomas A.; Dalton, Devon Gardner; Rovang, Dean Curtis; Lamppa, Derek C.

    2013-09-01

    The recently developed Magnetically Applied Pressure-Shear (MAPS) experimental technique to measure material shear strength at high pressures on magneto-hydrodynamic (MHD) drive pulsed power platforms was fielded on August 16, 2013 on shot Z2544 utilizing hardware set A0283A. Several technical and engineering challenges were overcome in the process leading to the attempt to measure the dynamic strength of NNSA Ta at 50 GPa. The MAPS technique relies on the ability to apply an external magnetic field properly aligned and time correlated with the MHD pulse. The load design had to be modified to accommodate the external field coils and additional support was required to manage stresses from the pulsed magnets. Further, this represents the first time transverse velocity interferometry has been applied to diagnose a shot at Z. All subsystems performed well with only minor issues related to the new feed design which can be easily addressed by modifying the current pulse shape. Despite the success of each new component, the experiment failed to measure strength in the samples due to spallation failure, most likely in the diamond anvils. To address this issue, hydrocode simulations are being used to evaluate a modified design using LiF windows to minimize tension in the diamond and prevent spall. Another option to eliminate the diamond material from the experiment is also being investigated.

  19. Electron and donor-impurity-related Raman scattering and Raman gain in triangular quantum dots under an applied electric field

    NASA Astrophysics Data System (ADS)

    Tiutiunnyk, Anton; Akimov, Volodymyr; Tulupenko, Viktor; Mora-Ramos, Miguel E.; Kasapoglu, Esin; Morales, Alvaro L.; Duque, Carlos Alberto

    2016-04-01

    The differential cross-section of electron Raman scattering and the Raman gain are calculated and analysed in the case of prismatic quantum dots with equilateral triangle base shape. The study takes into account their dependencies on the size of the triangle, the influence of externally applied electric field as well as the presence of an ionized donor center located at the triangle's orthocenter. The calculations are made within the effective mass and parabolic band approximations, with a diagonalization scheme being applied to obtain the eigenfunctions and eigenvalues of the x- y Hamiltonian. The incident and secondary (scattered) radiation have been considered linearly-polarized along the y-direction, coinciding with the direction of the applied electric field. For the case with an impurity center, Raman scattering with the intermediate state energy below the initial state one has been found to show maximum differential cross-section more than by an order of magnitude bigger than that resulting from the scheme with lower intermediate state energy. The Raman gain has maximum magnitude around 35 nm dot size and electric field of 40 kV/cm for the case without impurity and at maximum considered values of the input parameters for the case with impurity. Values of Raman gain of the order of up to 104cm-1 are predicted in both cases.

  20. Magnetic field applied to thermochemical non-equilibrium reentry flows in 2D - five species

    NASA Astrophysics Data System (ADS)

    Sávio de Góes Maciel, Edisson

    2015-07-01

    In this work, a study involving magnetic field actuation over reentry flows in thermochemical non-equilibrium is performed. The Euler and Navier-Stokes equations are studied. The proposed numerical algorithm is centred and second-order accurate. The hypersonic flow around a blunt body is simulated. Three time integration methods are tested. The reactive simulations involve Earth atmosphere of five species. The work of Gaitonde is the reference to couple the fluid dynamics and Maxwell equations of electromagnetism. The results have indicated that the Maciel scheme, using the Mavriplis dissipation model, yields the best prediction of the stagnation pressure.

  1. Effect of nonlinear absorption on electric field applied lead chloride by Z-scan technique

    SciTech Connect

    Rejeena, I.; Lillibai,; Nampoori, V. P. N.; Radhakrishnan, P.; Rahimkutty, M. H.

    2014-10-15

    The preparation, spectral response and optical nonlinearity of gel grown lead chloride single crystals subjected to electric field of 20V using parallel plate arrangements have been investigated. Optical band gap of the samples were determined using linear absorption spectra. Open aperture z-scan was employed for the determination of nonlinear absorption coefficient of PbCl{sub 2} solution. The normalized transmittance curve exhibits a valley shows reverse saturable absorption. The non linear absorption at different input fluences were recorded using a single Gaussian laser beam in tight focus geometry. The RSA nature of the sample makes it suitable for optical limiting applications.

  2. Some new methods in geomagnetic field modeling applied to the 1960 - 1980 epoch

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Estes, R. H.; Mead, G. H.

    1981-01-01

    The utilization of satellite and surface data together permitted the incorporation of a solution for the anomaly field at each observatory. The residuals of the observatory measurements to such models is commensurate with the actual measurment accuracy. Incorporation of the anomaly estimation enabled the inclusion of stable time derivatives of the spherical harmonic coefficients up to the third derivative. A spherical harmonic model is derived with degree and order 13 in its constant and first time derivative terms, six in its second derivative terms and four in its third derivative terms.

  3. Homotopic method applied to solving the flow field in a gas centrifuge

    NASA Astrophysics Data System (ADS)

    Zhang, Y. N.; Zeng, S.

    2016-09-01

    To investigate the flow field in a hyper-speed gas centrifuge, a hybrid difference scheme is used to discretize the axisymmetric Navier-Stokes equation. Source terms are included to simulate the injection and extraction of gas, also the mechanical drive of the scoops. The nonlinearity is obvious as the drive is strong. A Newton iteration used to solve the equation system becomes sensitive to the initial guess of the solution, which makes it difficult to converge. A homotopic method with self-adaptive steps is adopted to cope with this problem and to accelerate the iteration process. Numerical experiments simulating different strengths of scoop drive prove the effectiveness of the algorithm.

  4. Potential Pasture Nitrogen Concentrations and Uptake from Autumn or Spring Applied Cow Urine and DCD under Field Conditions.

    PubMed

    Moir, Jim; Cameron, Keith; Di, Hong

    2016-06-13

    Nitrogen (N) cycling and losses in grazed grassland are strongly driven by urine N deposition by grazing ruminants. The objective of this study was to quantify pasture N concentrations, yield and N uptake following autumn and spring deposition of cow urine and the effects of fine particle suspension (FPS) dicyandiamide (DCD). A field plot study was conducted on the Lincoln University dairy farm, Canterbury, New Zealand from May 2003 to May 2005. FPS DCD was applied to grazed pasture plots at 10 kg·ha(-1) in autumn and spring in addition to applied cow urine at a N loading rate of 1000 kg·N·ha(-1), with non-urine control plots. Pasture N ranged between 1.9 and 4.8% with higher concentrations from urine. Results indicated that urine consistently increased N concentrations for around 220 days post deposition (mid December/early summer) at which point concentrations dropped to background levels. In urine patches, pasture yield and annual N uptake were dramatically increased on average by 51% for autumn and 28% for spring applied urine, in both years, when DCD was applied. This field experiment provides strong evidence that annual pasture N uptake is more strongly influenced by high urine N deposition than pasture N concentrations. FPS DCD has the potential to result in very high N uptake in urine patches, even when they are autumn deposited.

  5. Potential Pasture Nitrogen Concentrations and Uptake from Autumn or Spring Applied Cow Urine and DCD under Field Conditions

    PubMed Central

    Moir, Jim; Cameron, Keith; Di, Hong

    2016-01-01

    Nitrogen (N) cycling and losses in grazed grassland are strongly driven by urine N deposition by grazing ruminants. The objective of this study was to quantify pasture N concentrations, yield and N uptake following autumn and spring deposition of cow urine and the effects of fine particle suspension (FPS) dicyandiamide (DCD). A field plot study was conducted on the Lincoln University dairy farm, Canterbury, New Zealand from May 2003 to May 2005. FPS DCD was applied to grazed pasture plots at 10 kg·ha−1 in autumn and spring in addition to applied cow urine at a N loading rate of 1000 kg·N·ha−1, with non-urine control plots. Pasture N ranged between 1.9 and 4.8% with higher concentrations from urine. Results indicated that urine consistently increased N concentrations for around 220 days post deposition (mid December/early summer) at which point concentrations dropped to background levels. In urine patches, pasture yield and annual N uptake were dramatically increased on average by 51% for autumn and 28% for spring applied urine, in both years, when DCD was applied. This field experiment provides strong evidence that annual pasture N uptake is more strongly influenced by high urine N deposition than pasture N concentrations. FPS DCD has the potential to result in very high N uptake in urine patches, even when they are autumn deposited. PMID:27304974

  6. 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.

  7. Point-wise and whole-field laser speckle intensity fluctuation measurements applied to botanical specimens

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Wang, Junlan; Wu, Xiaoping; Williams, Fred W.; Schmidt, Richard J.

    1997-12-01

    Based on multi-scattering speckle theory, the speckle fields generated by plant specimens irradiated by laser light have been studied using a pointwise method. In addition, a whole-field method has been developed with which entire botanical specimens may be studied. Results are reported from measurements made on tomato and apple fruits, orange peel, leaves of tobacco seedlings, leaves of shihu seedlings (a Chinese medicinal herb), soy-bean sprouts, and leaves from an unidentified trailing houseplant. Although differences where observed in the temporal fluctuations of speckles that could be ascribed to differences in age and vitality, the growing tip of the bean sprout and the shihu seedling both generated virtually stationary speckles such as were observed from boiled orange peel and from localised heat-damaged regions on apple fruit. Our results suggest that both the identity of the botanical specimen and the site at which measurements are taken are likely to critically affect the observation or otherwise of temporal fluctuations of laser speckles.

  8. Pulsed remote field eddy current technique applied to non-magnetic flat conductive plates

    NASA Astrophysics Data System (ADS)

    Yang, Binfeng; Zhang, Hui; Zhang, Chao; Zhang, Zhanbin

    2013-12-01

    Non-magnetic metal plates are widely used in aviation and industrial applications. The detection of cracks in thick plate structures, such as multilayered structures of aircraft fuselage, has been challenging in nondestructive evaluation societies. The remote field eddy current (RFEC) technique has shown advantages of deep penetration and high sensitivity to deeply buried anomalies. However, the RFEC technique is mainly used to evaluate ferromagnetic tubes. There are many problems that should be fixed before the expansion and application of this technique for the inspection of non-magnetic conductive plates. In this article, the pulsed remote field eddy current (PRFEC) technique for the detection of defects in non-magnetic conducting plates was investigated. First, the principle of the PRFEC technique was analysed, followed by the analysis of the differences between the detection of defects in ferromagnetic and non-magnetic plain structures. Three different models of the PRFEC probe were simulated using ANSYS. The location of the transition zone, defect detection sensitivity and the ability to detect defects in thick plates using three probes were analysed and compared. The simulation results showed that the probe with a ferrite core had the highest detecting ability. The conclusions derived from the simulation study were also validated by conducting experiments.

  9. Applying high resolution SyXRD analysis on sulfate attacked concrete field samples

    SciTech Connect

    Stroh, J.; Schlegel, M.-C.; Irassar, E.F.; Meng, B.; Emmerling, F.

    2014-12-15

    High resolution synchrotron X-ray diffraction (SyXRD) was applied for a microstructural profile analysis of concrete deterioration after sulfate attack. The cement matrices consist of ordinary Portland cement and different amounts of supplementary cementitious materials, such as fly ash, natural pozzolana and granulated blast furnace slag. The changes of the phase composition were determined along the direction of sulfate ingress. This approach allows the identification of reaction fronts and zones of different phase compositions and conclusions about the mechanisms of sulfate attack. Two reaction fronts were localized in the initial 4 mm from the sample surface. The mechanism of deterioration caused by the exposition in the sulfate-bearing soil is discussed. SyXRD is shown to be a reliable method for investigation of cementitious materials with aggregates embedded in natural environments.

  10. 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.

  11. Dynamic response of a graphene oxide-polyaniline composite suspension under an applied electric field

    NASA Astrophysics Data System (ADS)

    Zhang, Wen Ling; Choi, Hyoung Jin

    2012-11-01

    A suspension of semiconducting graphene oxide/polyaniline (GO/PANI) composite particles dispersed in silicone oil is considered as one of the potential candidates for an electrorheological (ER) fluid. The GO/PANI composite was synthesized by using chemical oxidation polymerization of aniline in the presence of a GO dispersion that contained GO that had been prepared by using a modified Hummers method. The characteristics of the composite were examined by using SEM images and FT-IR spectra and indicated the coexistence of GO and PANI in the composite. The GO/PANI-composite-based ER fluid was prepared by dispersing the fabricated particles in silicone oil, and its dynamic viscoelastic properties were measured using a rotational rheometer under different electric fields, which showed that the ER fluid exhibited typical solid-like ER behaviors.

  12. Lessons learned from applied field research activities in Africa during the malaria eradication era

    PubMed Central

    Bruce-Chwatt, Leonard J.

    1984-01-01

    The Malaria Conference in Equatorial Africa, convened by the World Health Organization in 1950 in Kampala, Uganda, was a milestone in the history of modern malaria control activities on the continent of Africa. It presented and assessed the available international information on epidemiological aspects of this disease and attempted to coordinate the various methods of research and control of malaria. Its two main recommendations were that malaria should be controlled by all available methods, irrespective of the degree of endemicity of the disease, and that the benefits that malaria control might bring to the indigenous population should be evaluated. The first period of field research and pilot control projects in Africa was between 1950 and 1964. A large number of studies in several African countries showed that the use of residual insecticides such as DDT and HCH might decrease, at times considerably, the amount of malaria transmission, but interruption of transmission could not be achieved, except in two relatively small projects in the forest areas of Cameroon and Liberia. During the second period, from 1965 to 1974, the difficulties of malaria eradication and control in Africa became more evident because of the development of resistance of Anopheles gambiae to DDT, HCH, and dieldrin; moreover administrative, logistic, and financial problems had emerged. It became clear that the prospects for malaria control (let alone those for eradication) were related to the availability of a network of basic health services. A number of “pre-eradication” programmes were set up in order to develop better methods of malaria control and to improve the rural health infrastructures. Much field research on the chemotherapy of malaria was carried out and the value of collective or selective administration of antimalarial drugs was fully recognized, although it became obvious that this could not play an important part in the decrease of transmission of malaria in Africa. The

  13. Theoretical and Applied Research in the Field of Higher Geodesy Conducted in Rzeszow

    NASA Astrophysics Data System (ADS)

    Kadaj, Roman; Świętoń, Tomasz

    2016-06-01

    Important qualitative changes were taking place in polish geodesy in last few years. It was related to application of new techniques and technologies and to introduction of European reference frames in Poland. New reference stations network ASG-EUPOS, together with Internet services which helps in precise positioning was created. It allows to fast setting up precise hybrid networks. New, accurate satellite networks became the basis of new definitions in the field of reference systems. Simultaneously arise the need of new software, which enables to execute the geodetic works in new technical conditions. Authors had an opportunity to participate in mentioned undertakings, also under the aegis of GUGiK, by creation of methods, algorithms and necessary software tools. In this way the automatic postprocessing module (APPS) in POZGEO service, a part of ASG-EUPOS system came into being. It is an entirely polish product which works in Trimble environment. Universal software for transformation between PLETRF89, PL-ETRF2000, PULKOWO'42 reference systems as well as defined coordinate systems was created (TRANSPOL v. 2.06) and published as open product. An essential functional element of the program is the quasi-geoid model PL-geoid-2011, which has been elaborated by adjustment (calibration) of the global quasi-geoid model EGM2008 to 570 geodetic points (satellite-leveling points). Those and other studies are briefly described in this paper.

  14. An applied sequence stratigraphic approach in reservoirs characterization, Eastern Venezuela: El Carito-El Furrial Fields

    SciTech Connect

    Sifontes de, R.; Hernandez, E. )

    1993-02-01

    Integration of biostratigraphic, sedimentologic and petrophysic data from cores and well logs in reservoirs in El Carito-El Furrial Fields, Northern Monagas, Eastern Venezuelan Basin, allows to differentiate two sedimentary sequences ranging between the Upper Cretaceous and the Oligocene. The Maastrichtian-Paleocene sequence is divided into two sedimentary units (C and 1) both representing a south to north progradation from shallow marine to fluvial environments, within a large regressive cycle. The Middle Eocene to Middle-Late Oligocene sequence includes sedimentary units II and III. Unit II represents a large transgressive cycle of mostly inner neritic deposits with a condensed section at the base which changes laterally from glauconitic to lutitic facies to the south. Unit III grades transitionally from the inner neritic deposits of unit II to shallow marine deposits, and changes to inner neritic deposits again to the top. Unit III is interpreted as a large regressive -transgressive cycle. In all these sedimentary units, lithofacies association, paleoenvironments variation and definition of large cycles helped to define the parasequence stacking sets. The petrographic analysis points out that sandstones in unit C are basically subarcosic, while in units I, I and III are quartzitic. Additionally, sandstones in units C and II are very cemented by quartz and carbonates respectively, showing chemical compaction, in contrast to units I and III where quartz dissolution is a porosity enhancing process. This indicates that sandstones in these units have the best porosity and permeability values, resulting in the best producing intervals in the study area.

  15. Field-Based and Airborne Hyperspectral Imaging for Applied Research in the State of Alaska

    NASA Astrophysics Data System (ADS)

    Prakash, A.; Buchhorn, M.; Cristobal, J.; Kokaly, R. F.; Graham, P. R.; Waigl, C. F.; Hampton, D. L.; Werdon, M.; Guldager, N.; Bertram, M.; Stuefer, M.

    2015-12-01

    Hyperspectral imagery acquired using Hyspex VNIR-1800 and SWIR-384 camera systems have provided unique information on terrestrial and aquatic biogeochemical parameters, and diagnostic mineral properties in exposed outcrops in selected sites in the state of Alaska. The Hyspex system was configured for in-situ and field scanning by attaching it to a gimbal-mounted rotational stage on a robust tripod. Scans of vertical faces of vegetation and rock outcrops were made close to the campus of the University of Alaska Fairbanks, in an abandoned mine near Fairbanks, and on exposures of Orange Hill in Wrangell-St. Elias National Park. Atmospherically corrected integrated VNIR_SWIR spectra were extracted which helped to study varying nitrogen content in the vegetation, and helped to distinguish the various micas. Processed imagery helped to pull out carbonates, clays, sulfates, and alteration-related minerals. The same instrument was also mounted in airborne configuration on two different aircrafts, a DeHavilland Beaver and a Found Bush Hawk. Test flights were flown over urban and wilderness areas that presented a variety of landcover types. Processed imagery shows promise in mapping man-made surfaces, phytoplankton, and dissolved materials in inland water bodies. Sample data and products are available on the University of Alaska Fairbanks Hyperspectral Imaging Laboratory (HyLab) website at http://hyperspectral.alaska.edu.

  16. Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?

    NASA Astrophysics Data System (ADS)

    Sintermann, J.; Neftel, A.; Ammann, C.; Häni, C.; Hensen, A.; Loubet, B.; Flechard, C. R.

    2011-10-01

    The EMEP/EEA guidebook 2009 for agricultural emission inventories reports average ammonia (NH3) emission factors (EF) by volatilisation of 55% of the applied total ammoniacal nitrogen (TAN) content for cattle slurry, and 35% losses for pig slurry, irrespective of the type of surface or slurry characteristics such as dry matter content and pH. In this review article, we compiled over 350 measurements of EFs published between 1991 and 2011. The standard slurry application technique during the early years of this period, when a large number of measurements were made, was spreading by splash plate, and as a result reference EFs given in many European inventories are predominantly based on this technique. However, slurry application practices have evolved since then, while there has also been a shift in measurement techniques and investigated plot sizes. We therefore classified the available measurements according to the flux measurement technique, measurement plot size, the year of measurement, and the year of publication. Medium size plots (usually circles between 20 to 50 m radius) generally yielded the highest EFs. The most commonly used measurement setups at this scale were based on the Integrated Horizontal Flux method (IHF or the ZINST method (a simplified IHF method)). Several empirical models were published in the years 1993 to 2003 predicting NH3 EFs as a function of meteorology and slurry characteristics (Menzi et al., 1998; Søgaard et al., 2002). More recent measurements that appeared subsequently show substantially lower EFs, and appear to indicate a need for a revision of the EF in emission inventories.

  17. Are ammonia emissions from field-applied slurry substantially over-estimated in European emission inventories?

    NASA Astrophysics Data System (ADS)

    Sintermann, J.; Neftel, A.; Ammann, C.; Häni, C.; Hensen, A.; Loubet, B.; Flechard, C. R.

    2012-05-01

    The EMEP/EEA guidebook 2009 for agricultural emission inventories reports an average ammonia (NH3) emission factor (EF) by volatilisation of 55% of the applied total ammoniacal nitrogen (TAN) content for cattle slurry, and 35% losses for pig slurry, irrespective of the type of surface or slurry characteristics such as dry matter content and pH. In this review article, we compiled over 350 measurements of EFs published between 1991 and 2011. The standard slurry application technique during the early years of this period, when a large number of measurements were made, was spreading by splash plate, and as a result reference EFs given in many European inventories are predominantly based on this technique. However, slurry application practices have evolved since then, while there has also been a shift in measurement techniques and investigated plot sizes. We therefore classified the available measurements according to the flux measurement technique or measurement plot size and year of measurement. Medium size plots (usually circles between 20 to 50 m radius) generally yielded the highest EFs. The most commonly used measurement setups at this scale were based on the Integrated Horizontal Flux method (IHF or the ZINST method (a simplified IHF method)). Several empirical models were published in the years 1993 to 2003 predicting NH3 EFs as a function of meteorology and slurry characteristics (Menzi et al., 1998; Søgaard et al., 2002). More recent measurements show substantially lower EFs which calls for new measurement series in order to validate the various measurement approaches against each other and to derive revised inputs for inclusion into emission inventories.

  18. Selecting and applying cesium-137 conversion models to estimate soil erosion rates in cultivated fields.

    PubMed

    Li, Sheng; Lobb, David A; Tiessen, Kevin H D; McConkey, Brian G

    2010-01-01

    The fallout radionuclide cesium-137 ((137)Cs) has been successfully used in soil erosion studies worldwide. However, discrepancies often exist between the erosion rates estimated using various conversion models. As a result, there is often confusion in the use of the various models and in the interpretation of the data. Therefore, the objective of this study was to test the structural and parametrical uncertainties associated with four conversion models typically used in cultivated agricultural landscapes. For the structural uncertainties, the Soil Constituent Redistribution by Erosion Model (SCREM) was developed and used to simulate the redistribution of fallout (137)Cs due to tillage and water erosion along a simple two-dimensional (horizontal and vertical) transect. The SCREM-predicted (137)Cs inventories were then imported into the conversion models to estimate the erosion rates. The structural uncertainties of the conversion models were assessed based on the comparisons between the conversion-model-estimated erosion rates and the erosion rates determined or used in the SCREM. For the parametrical uncertainties, test runs were conducted by varying the values of the parameters used in the model, and the parametrical uncertainties were assessed based on the responsive changes of the estimated erosion rates. Our results suggest that: (i) the performance/accuracy of the conversion models was largely dependent on the relative contributions of water vs. tillage erosion; and (ii) the estimated erosion rates were highly sensitive to the input values of the reference (137)Cs level, particle size correction factors and tillage depth. Guidelines were proposed to aid researchers in selecting and applying the conversion models under various situations common to agricultural landscapes.

  19. AC loss measurements of twisted and untwisted BSCCO multifilamentary tapes

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenan; Amemiya, Naoyuki; Nishioka, Takamasa; Oh, Sang-Soo

    2005-01-01

    AC losses in twisted and untwisted BSCCO multifilamentary superconducting tapes with Ag matrix developed in DAPAS program were measured by an electrical method. Magnetization and transport losses were measured by a pick-up coil and by a voltage taps. Total AC loss during simultaneous application of AC transport current and an AC transverse magnetic field was given by the sum of the magnetization and transport losses measured during this simultaneous application. The magnetization loss without transport current of untwisted and twisted tapes was measured first to evaluate the effect of twisting to decouple filaments. Then, the total AC loss of the twisted tape was measured in transverse magnetic fields with various amplitudes and orientations, while the amplitude of the transport current was fixed. The measured total AC loss in a parallel transverse magnetic field was compared with some theoretical models to study the detailed characteristics of the measured total AC loss of the sample.

  20. Nanocrystalline cellulose applied simultaneously as the gate dielectric and the substrate in flexible field effect transistors

    NASA Astrophysics Data System (ADS)

    Gaspar, D.; Fernandes, S. N.; de Oliveira, A. G.; Fernandes, J. G.; Grey, P.; Pontes, R. V.; Pereira, L.; Martins, R.; Godinho, M. H.; Fortunato, E.

    2014-03-01

    Cotton-based nanocrystalline cellulose (NCC), also known as nanopaper, one of the major sources of renewable materials, is a promising substrate and component for producing low cost fully recyclable flexible paper electronic devices and systems due to its properties (lightweight, stiffness, non-toxicity, transparency, low thermal expansion, gas impermeability and improved mechanical properties). Here, we have demonstrated for the first time a thin transparent nanopaper-based field effect transistor (FET) where NCC is simultaneously used as the substrate and as the gate dielectric layer in an ‘interstrate’ structure, since the device is built on both sides of the NCC films; while the active channel layer is based on oxide amorphous semiconductors, the gate electrode is based on a transparent conductive oxide. Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility (>7 cm2 V -1 s-1), drain-source current on/off modulation ratio higher than 105, enhancement n-type operation and subthreshold gate voltage swing of 2.11 V/decade. The NCC film FET characteristics have been measured in air ambient conditions and present good stability, after two weeks of being processed, without any type of encapsulation or passivation layer. The results obtained are comparable to ones produced for conventional cellulose paper, marking this out as a promising approach for attaining high-performance disposable electronics such as paper displays, smart labels, smart packaging, RFID (radio-frequency identification) and point-of-care systems for self-analysis in bioscience applications, among others.

  1. Automated decision algorithm applied to a field experiment with multiple research objectives: The DC3 campaign

    NASA Astrophysics Data System (ADS)

    Hanlon, Christopher J.; Small, Arthur A.; Bose, Satyajit; Young, George S.; Verlinde, Johannes

    2014-10-01

    Automated decision systems have shown the potential to increase data yields from field experiments in atmospheric science. The present paper describes the construction and performance of a flight decision system designed for a case in which investigators pursued multiple, potentially competing objectives. The Deep Convective Clouds and Chemistry (DC3) campaign in 2012 sought in situ airborne measurements of isolated deep convection in three study regions: northeast Colorado, north Alabama, and a larger region extending from central Oklahoma through northwest Texas. As they confronted daily flight launch decisions, campaign investigators sought to achieve two mission objectives that stood in potential tension to each other: to maximize the total amount of data collected while also collecting approximately equal amounts of data from each of the three study regions. Creating an automated decision system involved understanding how investigators would themselves negotiate the trade-offs between these potentially competing goals, and representing those preferences formally using a utility function that served to rank-order the perceived value of alternative data portfolios. The decision system incorporated a custom-built method for generating probabilistic forecasts of isolated deep convection and estimated climatologies calibrated to historical observations. Monte Carlo simulations of alternative future conditions were used to generate flight decision recommendations dynamically consistent with the expected future progress of the campaign. Results show that a strict adherence to the recommendations generated by the automated system would have boosted the data yield of the campaign by between 10 and 57%, depending on the metrics used to score success, while improving portfolio balance.

  2. Direct observation by laser scanning confocal microscopy of microstructure and phase migration of PVC gels in an applied electric field.

    PubMed

    Xia, Hong; Ueki, Takamitsu; Hirai, Toshihiro

    2011-02-01

    The fluorescent probe lucigenin was incorporated in poly(vinyl chloride) (PVC) gels, and laser scanning confocal microscopy (LSCM) was used to clarify the internal structures of the gels. From the two-dimensional and three-dimensional information by LSCM, we first observed the internal structure of the PVC gel at a wet status, where the PVC gels comprised a polymer-rich phase and a polymer-poor phase uniformly with a three-dimensional network structure. After an electric field was applied, an effect of the electric field resulted in the change of internal structure in the gels. The polymer-poor phase moved from the cathode to the anode and the polymer-rich phase formed linelike arrangement between electrodes due to the attraction force. On the other hand, the freeze-dried PVC gels with/without in-situ dc voltage casting were particularly fabricated to confirm above results by the field emission scanning electron microscopy (FE-SEM). It was found that many craters remained on the surface of the gel near the anode due to sublimation in freeze-drying. This phenomenon did not appear on the surface near the cathode. The results of in-situ dc voltage casting also suggested that a substantial amount of polymer-poor phase was moved and fixed at the anode. Thus, results of both LSCM and in-situ dc voltage casting corresponded to the effect of electric field on PVC gels and provided a convincing evidence for the interpretation of the deformation mechanism of PVC gel actuators by an applied electric field.

  3. AC losses in conductors based on high {Tc} superconductors

    SciTech Connect

    SUENAGA,M.

    2000-03-17

    In electrical power devices, ac losses from a superconductor is a primary factor which determines their usefulness as commercial power equipment. For this reason, extensive studies have been carried out on the losses of Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}/Ag, [Bi(2223)/Ag], tapes. These studies were mostly limited to a single isolated tape. However, a conductor in a power device is surrounded by other conductors and the precise magnetic field distribution around it is very different from that for a single conductor carrying currents or in ac fields. Since the precise field distribution in and around a superconductor is critical in determining the losses, it is very important to measure and to understand the losses in Bi(2223)/Ag tapes which are surrounded by other tapes as in a power device. Taking this fact into consideration, recently the authors have studied ac losses in stacks of Bi(2223)/Ag tapes in parallel and perpendicular applied fields and shown that they can calculate the losses in these cases utilizing the critical state model if a number of appropriate factors about properties of the tape are taken into a consideration. However, in a power device such as a transformer, magnetic fields near the ends of a solenoid vary from parallel to perpendicular with the tape face. Thus, it is important to learn the behavior of the losses in the stacks of Bi(2223)/Ag tapes with respect to the variations in the angle between the applied field direction and the tape face. In order to accomplish this, they measured the angular dependence of the losses in the stacks which were made from two different Bi(2223)/Ag tapes. Here they report this result and discuss under what conditions they can calculate the losses with a reasonable accuracy. The angular dependence of the losses in ac applied fields were measured using a series of stacked Bi(2223)/Ag tapes having the angles with the direction of applied fields of 0, 7.5, 15, 30, 45, 60, and 90 degrees. The measured

  4. A rapid two-dimensional data collection system for the study of ferroelectric materials under external applied electric fields.

    PubMed

    Vergentev, Tikhon; Bronwald, Iurii; Chernyshov, Dmitry; Gorfman, Semen; Ryding, Stephanie H M; Thompson, Paul; Cernik, Robert J

    2016-10-01

    Synchrotron X-rays on the Swiss Norwegian Beamline and BM28 (XMaS) at the ESRF have been used to record the diffraction response of the PMN-PT relaxor piezoelectric 67% Pb(Mg1/3Nb2/3)O3-33% PbTiO3 as a function of externally applied electric field. A DC field in the range 0-18 kV cm(-1) was applied along the [001] pseudo-cubic direction using a specially designed sample cell for in situ single-crystal diffraction experiments. The cell allowed data to be collected on a Pilatus 2M area detector in a large volume of reciprocal space using transmission geometry. The data showed good agreement with a twinned single-phase monoclinic structure model. The results from the area detector were compared with previous Bragg peak mapping using variable electric fields and a single detector where the structural model was ambiguous. The coverage of a significantly larger section of reciprocal space facilitated by the area detector allowed precise phase analysis.

  5. Modeling the stress dependence of Barkhausen phenomena for stress axis linear and noncollinear with applied magnetic field (abstract)

    SciTech Connect

    Sablik, M.J.; Augustyniak, B.; Chmielewski, M.

    1996-04-01

    The almost linear dependence of the maximum Barkhausen noise signal amplitude on stress has made it a tool for nondestructive evaluation of residual stress. Recently, a model has been developed to account for the stress dependence of the Barkhausen noise signal. The model uses the development of Alessandro {ital et} {ital al}. who use coupled Langevin equations to derive an expression for the Barkhausen noise power spectrum. The model joins this expression to the magnetomechanical hysteresis model of Sablik {ital et} {ital al}., obtaining both a hysteretic and stress-dependent result for the magnetic-field-dependent Barkhausen noise envelope and obtaining specifically the almost linear stress dependence of the Barkhausen noise maximum experimentally. In this paper, we extend the model to derive the angular dependence observed by Kwun of the Barkhausen noise amplitude when stress axis is taken at different angles relative to magnetic field. We also apply the model to the experimental observation that in XC10 French steel, there is an apparent almost linear correlation with stress of hysteresis loss and of the integral of the Barkhausen noise signal over applied field {ital H}. Further, the two quantities, Barkhausen noise integral and hysteresis loss, are linearly correlated with each other. The model shows how that behavior is to be expected for the measured steel because of its sharply rising hysteresis curve. {copyright} {ital 1996 American Institute of Physics.}

  6. A rapid two-dimensional data collection system for the study of ferroelectric materials under external applied electric fields

    PubMed Central

    Vergentev, Tikhon; Bronwald, Iurii; Chernyshov, Dmitry; Gorfman, Semen; Ryding, Stephanie H. M.; Thompson, Paul; Cernik, Robert J.

    2016-01-01

    Synchrotron X-rays on the Swiss Norwegian Beamline and BM28 (XMaS) at the ESRF have been used to record the diffraction response of the PMN–PT relaxor piezoelectric 67% Pb(Mg1/3Nb2/3)O3–33% PbTiO3 as a function of externally applied electric field. A DC field in the range 0–18 kV cm−1 was applied along the [001] pseudo-cubic direction using a specially designed sample cell for in situ single-crystal diffraction experiments. The cell allowed data to be collected on a Pilatus 2M area detector in a large volume of reciprocal space using transmission geometry. The data showed good agreement with a twinned single-phase monoclinic structure model. The results from the area detector were compared with previous Bragg peak mapping using variable electric fields and a single detector where the structural model was ambiguous. The coverage of a significantly larger section of reciprocal space facilitated by the area detector allowed precise phase analysis. PMID:27738414

  7. Influence of Applied Thermal Gradients and a Static Magnetic Field on Bridgman-Grown GeSi Alloys

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Szofran, F. R.; Cobb, S. D.; Ritter, T. M.

    1999-01-01

    The effect of applied axial and radial thermal gradients and an axial static magnetic field on the macrosegregation profiles of Bridgman-grown GeSi alloy crystals has been assessed. The axial thermal gradients were adjusted by changing the control setpoints of a seven-zone vertical Bridgman furnace. The radial thermal gradients were affected by growing samples in ampoules with different thermal conductivities, namely graphite, hot-pressed boron nitride (BN), and pyrolytic boron nitride (PBN). Those samples grown in a graphite ampoule exhibited radial profiles consistent with a highly concave interface and axial profiles indicative of complete mixing in the melt. The samples grown in BN and PBN ampoules had less radial variation. Axial macrosegregation profiles of these samples fell between the predictions for a completely mixed melt and one where solute transport is dominated by diffusion. All of the samples were grown on Ge seeds. This resulted in a period of free growth until the Si concentration in the solid was in equilibrium with the Si concentration in the liquid. The length of crystal grown during this period was inversely proportional to the applied axial thermal gradient. Several samples were grown in an axial 5 Tesla magnetic field. Measured macroscopic segregation profiles on these samples indicate that the magnetic field did not, in general, reduce the melt flow velocities to below the growth velocities.

  8. A geostatistical method applied to the geochemical study of the Chichinautzin Volcanic Field in Mexico

    NASA Astrophysics Data System (ADS)

    Robidoux, P.; Roberge, J.; Urbina Oviedo, C. A.

    2011-12-01

    The origin of magmatism and the role of the subducted Coco's Plate in the Chichinautzin volcanic field (CVF), Mexico is still a subject of debate. It has been established that mafic magmas of alkali type (subduction) and calc-alkali type (OIB) are produced in the CVF and both groups cannot be related by simple fractional crystallization. Therefore, many geochemical studies have been done, and many models have been proposed. The main goal of the work present here is to provide a new tool for the visualization and interpretation of geochemical data using geostatistics and geospatial analysis techniques. It contains a complete geodatabase built from referred samples over the 2500 km2 area of CVF and its neighbour stratovolcanoes (Popocatepetl, Iztaccihuatl and Nevado de Toluca). From this database, map of different geochemical markers were done to visualise geochemical signature in a geographical manner, to test the statistic distribution with a cartographic technique and highlight any spatial correlations. The distribution and regionalization of the geochemical signatures can be viewed in a two-dimensional space using a specific spatial analysis tools from a Geographic Information System (GIS). The model of spatial distribution is tested with Linear Decrease (LD) and Inverse Distance Weight (IDW) interpolation technique because they best represent the geostatistical characteristics of the geodatabase. We found that ratio of Ba/Nb, Nb/Ta, Th/Nb show first order tendency, which means visible spatial variation over a large scale area. Monogenetic volcanoes in the center of the CVF have distinct values compare to those of the Popocatepetl-Iztaccihuatl polygenetic complex which are spatially well defined. Inside the Valley of Mexico, a large quantity of monogenetic cone in the eastern portion of CVF has ratios similar to the Iztaccihuatl and Popocatepetl complex. Other ratios like alkalis vs SiO2, V/Ti, La/Yb, Zr/Y show different spatial tendencies. In that case, second

  9. Development of double-pulse lasers ablation system for generating gold ion source under applying an electric field

    NASA Astrophysics Data System (ADS)

    Khalil, A. A. I.

    2015-12-01

    Double-pulse lasers ablation (DPLA) technique was developed to generate gold (Au) ion source and produce high current under applying an electric potential in an argon ambient gas environment. Two Q-switched Nd:YAG lasers operating at 1064 and 266 nm wavelengths are combined in an unconventional orthogonal (crossed-beam) double-pulse configuration with 45° angle to focus on a gold target along with a spectrometer for spectral analysis of gold plasma. The properties of gold plasma produced under double-pulse lasers excitation were studied. The velocity distribution function (VDF) of the emitted plasma was studied using a dedicated Faraday-cup ion probe (FCIP) under argon gas discharge. The experimental parameters were optimized to attain the best signal to noise (S/N) ratio. The results depicted that the VDF and current signals depend on the discharge applied voltage, laser intensity, laser wavelength and ambient argon gas pressure. A seven-fold increases in the current signal by increasing the discharge applied voltage and ion velocity under applying double-pulse lasers field. The plasma parameters (electron temperature and density) were also studied and their dependence on the delay (times between the excitation laser pulse and the opening of camera shutter) was investigated as well. This study could provide significant reference data for the optimization and design of DPLA systems engaged in laser induced plasma deposition thin films and facing components diagnostics.

  10. 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

  11. Dynamic response of a thin sessile drop of conductive liquid to an abruptly applied or removed electric field.

    PubMed

    Corson, L T; Mottram, N J; Duffy, B R; Wilson, S K; Tsakonas, C; Brown, C V

    2016-10-01

    We consider, both theoretically and experimentally, a thin sessile drop of conductive liquid that rests on the lower plate of a parallel-plate capacitor. We derive analytical expressions for both the initial deformation and the relaxation dynamics of the drop as the electric field is either abruptly applied or abruptly removed, as functions of the geometrical, electrical, and material parameters, and investigate the ranges of validity of these expressions by comparison with full numerical simulations. These expressions provide a reasonable description of the experimentally measured dynamic response of a drop of conductive ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate.

  12. Dynamic response of a thin sessile drop of conductive liquid to an abruptly applied or removed electric field

    NASA Astrophysics Data System (ADS)

    Corson, L. T.; Mottram, N. J.; Duffy, B. R.; Wilson, S. K.; Tsakonas, C.; Brown, C. V.

    2016-10-01

    We consider, both theoretically and experimentally, a thin sessile drop of conductive liquid that rests on the lower plate of a parallel-plate capacitor. We derive analytical expressions for both the initial deformation and the relaxation dynamics of the drop as the electric field is either abruptly applied or abruptly removed, as functions of the geometrical, electrical, and material parameters, and investigate the ranges of validity of these expressions by comparison with full numerical simulations. These expressions provide a reasonable description of the experimentally measured dynamic response of a drop of conductive ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate.

  13. Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

    SciTech Connect

    Jing, C.; Konecny, R.; Antipov, S.; Chang, C.; Gold, S. H.; Schoessow, P.; Kanareykin, A.; Gai, W.

    2013-11-18

    Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications.

  14. Dipolar structures in magnetite ferrofluids studied with small-angle neutron scattering with and without applied magnetic field

    SciTech Connect

    Klokkenburg, M.; Erne, B. H.; Petukhov, A. V.; Philipse, A. P.; Wiedenmann, A.

    2007-05-15

    Field-induced structure formation in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment was studied with small-angle neutron scattering (SANS) as a function of the magnetic interactions. The interactions were tuned by adjusting the size of the well-defined, single-magnetic-domain magnetite (Fe{sub 3}O{sub 4}) particles and by applying an external magnetic field. For decreasing particle dipole moments, the data show a progressive distortion of the hexagonal symmetry, resulting from the formation of magnetic sheets. The SANS data show qualitative agreement with recent cryogenic transmission electron microscopy results obtained in 2D [Klokkenburg et al., Phys. Rev. Lett. 97, 185702 (2006)] on the same ferrofluids.

  15. The effect of applied electric field on pulsed radio frequency and pulsed direct current plasma jet array

    SciTech Connect

    Hu, J. T.; Liu, X. Y.; Liu, J. H.; Xiong, Z. L.; Liu, D. W.; Lu, X. P.; Iza, F.; Kong, M. G.

    2012-06-15

    Here we compare the plasma plume propagation characteristics of a 3-channel pulsed RF plasma jet array and those of the same device operated by a pulsed dc source. For the pulsed-RF jet array, numerous long life time ions and metastables accumulated in the plasma channel make the plasma plume respond quickly to applied electric field. Its structure similar as 'plasma bullet' is an anode glow indeed. For the pulsed dc plasma jet array, the strong electric field in the vicinity of the tube is the reason for the growing plasma bullet in the launching period. The repulsive forces between the growing plasma bullets result in the divergence of the pulsed dc plasma jet array. Finally, the comparison of 309 nm and 777 nm emissions between these two jet arrays suggests the high chemical activity of pulsed RF plasma jet array.

  16. Statistical Modeling Applied to Deformation-Relaxation Processes in a Composite Biopolymer Network Induced by Magnetic Field.

    PubMed

    Tarrío-Saavedra, Javier; González, Cécilia Galindo; Naya, Salvador; López-Beceiro, Jorge; Ponton, Alain

    2017-01-01

    This study investigated a methodology based on image processing and statistics to characterize and model the deformation upon controlled and uniform magnetic field and the relaxation under zero field of droplets observed in aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles stabilized by adsorption of citrate ions. The changes of droplet geometry were statistically analyzed using a new approach based on the data obtained from optical microscopy, image processing, nonlinear regression, evolutionary optimization, analysis of variance and resampling. Image enhancement and then image segmentation (Gaussian mixture modeling) processes were applied to extract features with reliable information of droplets dimensions from optical micrographs. The droplets deformation and relaxation trends were accurately adjusted by the Kohlrausch-Williams-Watts (KWW) function and a mean relaxation time was obtained by fitting the time evolution of geometry parameters. It was found to be proportional to the initial radius of the spherical droplets and was associated to interfacial tension.

  17. Statistical Modeling Applied to Deformation-Relaxation Processes in a Composite Biopolymer Network Induced by Magnetic Field

    PubMed Central

    Tarrío-Saavedra, Javier; González, Cécilia Galindo; Naya, Salvador; López-Beceiro, Jorge

    2017-01-01

    This study investigated a methodology based on image processing and statistics to characterize and model the deformation upon controlled and uniform magnetic field and the relaxation under zero field of droplets observed in aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles stabilized by adsorption of citrate ions. The changes of droplet geometry were statistically analyzed using a new approach based on the data obtained from optical microscopy, image processing, nonlinear regression, evolutionary optimization, analysis of variance and resampling. Image enhancement and then image segmentation (Gaussian mixture modeling) processes were applied to extract features with reliable information of droplets dimensions from optical micrographs. The droplets deformation and relaxation trends were accurately adjusted by the Kohlrausch-Williams-Watts (KWW) function and a mean relaxation time was obtained by fitting the time evolution of geometry parameters. It was found to be proportional to the initial radius of the spherical droplets and was associated to interfacial tension. PMID:28081239

  18. Memory effect in ac plasma displays

    NASA Astrophysics Data System (ADS)

    Szlenk, K.; Obuchowicz, E.

    1993-10-01

    The bistable or `memory' mode of operation of an ac plasma display panel is presented. The difference between dc and ac plasma panel operation from the point of view of memory function is discussed. The graphic ac plasma display with thin film Cr-Cu-Cr electrodes was developed in OBREP and its basic parameters are described. It consists of 36 X 59 picture elements, its outer dimensions are: 76 X 52 mm2 and the screen size is: 49 X 30 mm2. The different dielectric glass materials were applied as dielectric layers and the influence of the properties of these materials on display parameters and memory function was investigated.

  19. Modulation of the properties of thin ferromagnetic films with an externally applied electric field in ferromagnetic/piezoelectric/ferromagnetic hybrids

    NASA Astrophysics Data System (ADS)

    Stamopoulos, D.; Zeibekis, M.; Zhang, S. J.

    2013-10-01

    In many cases, technological advances are based on artificial low-dimensional structures of heterogeneous constituents, thus called hybrids, that when come together they provide stand-alone entities that exhibit entirely different properties. Such hybrids are nowadays intensively studied since they are attractive for both basic research and oncoming practical applications. Here, we studied hybrids constituted of piezoelectric (PE) and ferromagnetic (FM) components in the form FM/PE/FM, ultimately aiming to provide means for the controlled modulation of the properties of the FM electrodes, originating from the strain imposed to them by the PE mediator when an electric field is applied. The PE component is in single crystal form, 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (PMN-PT), while the FM outer layers are Cobalt (Co) in thin film form. Detailed magnetization measurements performed under variation of the electric field applied to PMN-PT demonstrated the efficient modulation of the properties of the Co electrodes at low temperature (coercive field modulation up to 27% and saturation magnetization absolute modulation up to 4% at T = 10 K for electric field not exceeding 6 kV/cm). The modulation degree faints upon increase of the temperature, evidencing that the thermal energy eventually dominates all other relevant energy scales. Candidate mechanisms are discussed for the explanation of these experimental observations. The results presented here demonstrate that commercially available materials can result in quantitatively noticeable effects. Thus, such elemental Co/PMN-PT/Co units can be used as a solid basis for the development of devices.

  20. Urban runoff treatment using nano-sized iron oxide coated sand with and without magnetic field applying

    PubMed Central

    2013-01-01

    Increase of impervious surfaces in urban area followed with increases in runoff volume and peak flow, leads to increase in urban storm water pollution. The polluted runoff has many adverse impacts on human life and environment. For that reason, the aim of this study was to investigate the efficiency of nano iron oxide coated sand with and without magnetic field in treatment of urban runoff. In present work, synthetic urban runoff was treated in continuous separate columns system which was filled with nano iron oxide coated sand with and without magnetic field. Several experimental parameters such as heavy metals, turbidity, pH, nitrate and phosphate were controlled for investigate of system efficiency. The prepared column materials were characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDXA) instruments. SEM and EDXA analyses proved that the sand has been coated with nano iron oxide (Fe3O4) successfully. The results of SEM and EDXA instruments well demonstrate the formation of nano iron oxide (Fe3O4) on sand particle. Removal efficiency without magnetic field for turbidity; Pb, Zn, Cd and PO4 were observed to be 90.8%, 73.3%, 75.8%, 85.6% and 67.5%, respectively. When magnetic field was applied, the removal efficiency for turbidity, Pb, Zn, Cd and PO4 was increased to 95.7%, 89.5%, 79.9%, 91.5% and 75.6% respectively. In addition, it was observed that coated sand and magnetic field was not able to remove NO3 ions. Statistical analyses of data indicated that there was a significant difference between removals of pollutants in two tested columns. Results of this study well demonstrate the efficiency of nanosized iron oxide-coated sand in treatment of urban runoff quality; upon 75% of pollutants could be removed. In addition, in the case of magnetic field system efficiency can be improved significantly. PMID:24360061

  1. Urban runoff treatment using nano-sized iron oxide coated sand with and without magnetic field applying.

    PubMed

    Khiadani Hajian, Mehdi; Zarrabi, Mansur; Foroughi, Maryam

    2013-12-20

    Increase of impervious surfaces in urban area followed with increases in runoff volume and peak flow, leads to increase in urban storm water pollution. The polluted runoff has many adverse impacts on human life and environment. For that reason, the aim of this study was to investigate the efficiency of nano iron oxide coated sand with and without magnetic field in treatment of urban runoff. In present work, synthetic urban runoff was treated in continuous separate columns system which was filled with nano iron oxide coated sand with and without magnetic field. Several experimental parameters such as heavy metals, turbidity, pH, nitrate and phosphate were controlled for investigate of system efficiency. The prepared column materials were characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDXA) instruments. SEM and EDXA analyses proved that the sand has been coated with nano iron oxide (Fe3O4) successfully. The results of SEM and EDXA instruments well demonstrate the formation of nano iron oxide (Fe3O4) on sand particle. Removal efficiency without magnetic field for turbidity; Pb, Zn, Cd and PO4 were observed to be 90.8%, 73.3%, 75.8%, 85.6% and 67.5%, respectively. When magnetic field was applied, the removal efficiency for turbidity, Pb, Zn, Cd and PO4 was increased to 95.7%, 89.5%, 79.9%, 91.5% and 75.6% respectively. In addition, it was observed that coated sand and magnetic field was not able to remove NO3 ions. Statistical analyses of data indicated that there was a significant difference between removals of pollutants in two tested columns. Results of this study well demonstrate the efficiency of nanosized iron oxide-coated sand in treatment of urban runoff quality; upon 75% of pollutants could be removed. In addition, in the case of magnetic field system efficiency can be improved significantly.

  2. Dependence of plasma responses to an externally applied perturbation field on MHD oscillation frequency on the J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Jin, W.; Ding, Y. H.; Rao, B.; Hu, Q. M.; Jin, X. S.; Wang, N. C.; Zhang, X. Q.; Wang, Z. J.; Y Chen, Z.; Zhuang, G.; the J-TEXT Team

    2013-03-01

    The plasma response to externally applied perturbation fields is investigated on the J-TEXT tokamak using a set of static resonant magnetic perturbation (SRMP) coils. Several different experimental results are obtained including partial or complete suppression of the existing m/n = 2/1 tearing mode, mode locking or non-uniform magnetohydrodynamic (MHD) oscillations. These results depend sensitively on the tearing mode frequency and the amplitude of the perturbation field. It is found that mode locking is most likely to happen at a lower rotation frequency (< ˜5 kHz) and the threshold for mode locking has a linear relation with MHD frequency. However, complete suppression of the tearing mode happens in a region where the MHD frequencies are higher (˜6 kHz). The experimental observations are explained by numerical simulations based on reduced MHD equations. The error field contributes to an offset between the mode-locking thresholds for the two opposite spatial phases of the SRMP, through which the intrinsic error field of J-TEXT can be estimated.

  3. Investigation of Resistive Wall Mode Stabilization Physics in High-beta Plasmas Using Applied Non-axisymmetric Fields in NSTX

    SciTech Connect

    Sontag, A. C.; Sabbagh, S. A.; Zhu, W.; Menard, J. E.; Bell, R. E.; Bialek, J. M.; Bell, M. G.; Gates, D. A.; Glasser, A. H.; LeBlanc, B. P.; Shaing, K. C.; Stutman, D.; Tritz, K. L.

    2009-06-16

    The National Spherical Torus Experiment (NSTX) offers an operational space characterized by high-beta (βt = 39%, βN > 7, βN/βno-wall N > 1.5) and low aspect ratio (A > 1.27) to leverage the plasma parameter dependences of RWM stabilization and plasma rotation damping physics giving greater confidence for extrapolation to ITER. Significant new capability for RWM research has been added to the device with the commissioning of a set of six nonaxisymmetric magnetic field coils, allowing generation of fields with dominant toroidal mode number, n, of 1–3. These coils have been used to study the dependence of resonant field amplification on applied field frequency and RWMstabilization physics by reducing the toroidal rotation profile belowits steady-state value through non-resonant magnetic braking. Modification of plasma rotation profiles shows that rotation outside q = 2.5 is not required for passive RWM stability and there is large variation in the RWM critical rotation at the q = 2 surface, both of which are consistent with distributed dissipation models.

  4. ACS: ALMA Common Software

    NASA Astrophysics Data System (ADS)

    Chiozzi, Gianluca; Šekoranja, Matej

    2013-02-01

    ALMA Common Software (ACS) provides a software infrastructure common to all ALMA partners and consists of a documented collection of common patterns and components which implement those patterns. The heart of ACS is based on a distributed Component-Container model, with ACS Components implemented as CORBA objects in any of the supported programming languages. ACS provides common CORBA-based services such as logging, error and alarm management, configuration database and lifecycle management. Although designed for ALMA, ACS can and is being used in other control systems and distributed software projects, since it implements proven design patterns using state of the art, reliable technology. It also allows, through the use of well-known standard constructs and components, that other team members whom are not authors of ACS easily understand the architecture of software modules, making maintenance affordable even on a very large project.

  5. The Behaviors of Ferro-Magnetic Nano-Particles In and Around Blood Vessels under Applied Magnetic Fields

    PubMed Central

    Nacev, A.; Beni, C.; Bruno, O.; Shapiro, B.

    2010-01-01

    In magnetic drug delivery, therapeutic magnetizable particles are typically injected into the blood stream and magnets are then used to concentrate them to disease locations. The behavior of such particles in-vivo is complex and is governed by blood convection, diffusion (in blood and in tissue), extravasation, and the applied magnetic fields. Using physical first-principles and a sophisticated vessel-membrane-tissue (VMT) numerical solver, we comprehensively analyze in detail the behavior of magnetic particles in blood vessels and surrounding tissue. For any blood vessel (of any size, depth, and blood velocity) and tissue properties, particle size and applied magnetic fields, we consider a Krogh tissue cylinder geometry and solve for the resulting spatial distribution of particles. We find that there are three prototypical behaviors (blood velocity dominated, magnetic force dominated, and boundary-layer formation) and that the type of behavior observed is uniquely determined by three non-dimensional numbers (the magnetic-Richardson number, mass Péclet number, and Renkin reduced diffusion coefficient). Plots and equations are provided to easily read out which behavior is found under which circumstances (Figures 5, 6, 7, and 8). We compare our results to previously published in-vitro and in-vivo magnetic drug delivery experiments. Not only do we find excellent agreement between our predictions and prior experimental observations, but we are also able to qualitatively and quantitatively explain behavior that was previously not understood. PMID:21278859

  6. Ferroelectric glass of spheroidal dipoles with impurities: polar nanoregions, response to applied electric field, and ergodicity breakdown

    NASA Astrophysics Data System (ADS)

    Takae, Kyohei; Onuki, Akira

    2017-04-01

    Using molecular dynamics simulation, we study dipolar glass in crystals composed of slightly spheroidal, polar particles and spherical, apolar impurities between metal walls. We present physical pictures of ferroelectric glass, which have been observed in relaxors, mixed crystals (such as KCN x KBr1‑x ), and polymers. Our systems undergo a diffuse transition in a wide temperature range, where we visualize polar nanoregions (PNRs) surrounded by impurities. In our simulation, the impurities form clusters and their space distribution is heterogeneous. The polarization fluctuations are enhanced at relatively high T depending on the size of the dipole moment. They then form frozen PNRs as T is further lowered into the nonergodic regime. As a result, the dielectric permittivity exhibits the characteristic features of relaxor ferroelectrics. We also examine nonlinear response to cyclic applied electric field and nonergodic response to cyclic temperature changes (ZFC/FC), where the polarization and the strain change collectively and heterogeneously. We also study antiferroelectric glass arising from molecular shape asymmetry. We use an Ewald scheme of calculating the dipolar interaction in applied electric field.

  7. [Effects of long-term applying sulfur- and chloride-containing chemical fertilizers on weed growth in paddy field].

    PubMed

    Shen, Pu; Gao, Ju-sheng; Xu, Ming-gang; Li, Dong-chu; Niu, De-kui; Qin, Dao-zhu

    2011-04-01

    An investigation was made at a double-rice paddy field in the Qiyang Red Soil Field Experimental Station, Hunan Province, China to study the species and biomass of weeds growing in rice (Oryza sativa L.) growth season after 34-year application of sulfur (SO4(2-)) and chloride (Cl(-))-containing chemical fertilizers under the same application rates of nitrogen (N), phosphorus (P), and potassium (K). Long-term application of Cl(-)-containing chemical fertilizer resulted in the greatest species number of weeds and the highest biomass of floating weeds and wet weeds, compared with long-term application of SO4(2-) and Cl(-) +SO4(2-)-containing chemical fertilizers. In early rice growth season, the biomass of weeds after applying Cl(-)-containing chemical fertilizer was 51.4% and 17.6% higher than that after applying Cl(-) + SO4(2-) and SO4(2-)-containing chemical fertilizers, respectively; in late rice growth season, the increment was 144% and 242%, respectively. More floating weeds were observed after applying Cl(-) + SO4(2-) and SO4(2-)-containing chemical fertilizers, but few of them were found after applying Cl(-)-containing chemical fertilizer. The total dry mass of weeds and the dry mass of wet weeds were positively correlated with soil Cl(-) content (r = 0.764, P < 0.01 and r = 0.948, P < 0.01, respectively), but negatively correlated with soil SO4(2-)-S content (r = 0.849, P < 0.01 and r = 0.641, P < 0.05). Soil alkali-hydrolyzable N and available P, under the co-effects of soil SO4(2-)-S, Cl(-), and pH, had indirect effects on the total dry mass of weeds. By adopting various fertilization measures to maintain proper soil pH and alkali-hydrolyzable N and available P contents, increase soil SO42(-)-S content, and decrease soil Cl(-) content, it could be possible to effectively inhibit the growth of wet weeds and to decrease the total biomass of weeds in double-rice paddy field.

  8. Effect of rare earth elements (Er, Ho) on semi-metallic materials (ScN) in an applied electric field

    NASA Astrophysics Data System (ADS)

    Kim, Hyunjung; Park, Yeonjoon; King, Glen C.; Lee, Kunik; Choi, Sang H.

    2012-04-01

    The development of materials and fabrication technology for field-controlled spectrally active optics is essential for applications such as membrane optics, filters for LIDARs, windows for sensors, telescopes, spectroscopes, cameras and flat-panel displays. The dopants of rare earth elements, in a host of optical systems, create a number of absorption and emission band structures and can easily be incorporated into many high quality crystalline and amorphous hosts. In wide band-gap semiconductors like ScN, the existing deep levels can capture or emit the mobile charges, and can be ionized with the loss or capture of the carriers which are the fundamental basis of concept for smart optic materials. The band gap shrinkage or splitting with dopants supports the possibility of this concept. In the present work, a semi-metallic material (ScN) was doped with rare earth elements (Er, Ho) and tested under an applied electric field to characterize spectral and refractive index shifts by either Stark or Zeeman Effect. These effects can be verified using the UV-Vis spectroscopy, the Hall Effect measurement and the ellipsometric spectroscopy. The optical band gaps of ScN doped with Er and doped with Ho were experimentally estimated as 2.33eV and 2.24eV (+/-0.2eV) respectively. This is less than that of undoped ScN (2.5+/-0.2eV). The red-shifted absorption onset is a direct evidence for the decrease of band gap energy (Eg), and the broadening of valence band states is attributable to the doping cases. A decrease in refractive index with an applied field was observed as a small shift in absorption coefficient using a variable angle spectroscopic ellipsometer. In the presence of an electric field, mobile carriers are redistributed within the space charge region (SCR) to produce this electro-refractive effect. The shift in refractive index is also affected by the density and location of deep potential wells within the SCR. In addition, the microstructure change was observed by a

  9. Effect of Rare Earth Elements (Er, Ho) on Semi-Metallic Materials (ScN) in an Applied Electric Field

    NASA Technical Reports Server (NTRS)

    Kim, Hyunjung; Park, Yeonjoon; King, Glen C.; Lee, Kunik; Choi, Sang H.

    2012-01-01

    The development of materials and fabrication technology for field-controlled spectrally active optics is essential for applications such as membrane optics, filters for LIDARs, windows for sensors, telescopes, spectroscopes, cameras and flat-panel displays. The dopants of rare earth elements, in a host of optical systems, create a number of absorption and emission band structures and can easily be incorporated into many high quality crystalline and amorphous hosts. In wide band-gap semiconductors like ScN, the existing deep levels can capture or emit the mobile charges, and can be ionized with the loss or capture of the carriers which are the fundamental basis of concept for smart optic materials. The band gap shrinkage or splitting with dopants supports the possibility of this concept. In the present work, a semi-metallic material (ScN) was doped with rare earth elements (Er, Ho) and tested under an applied electric field to characterize spectral and refractive index shifts by either Stark or Zeeman Effect. These effects can be verified using the UV-Vis spectroscopy, the Hall Effect measurement and the ellipsometric spectroscopy. The optical band gaps of ScN doped with Er and doped with Ho were experimentally estimated as 2.33eV and 2.24eV ( 0.2eV) respectively. This is less than that of undoped ScN (2.5 0.2eV). The red-shifted absorption onset is a direct evidence for the decrease of band gap energy (Eg), and the broadening of valence band states is attributable to the doping cases. A decrease in refractive index with an applied field was observed as a small shift in absorption coefficient using a variable angle spectroscopic ellipsometer. In the presence of an electric field, mobile carriers are redistributed within the space charge region (SCR) to produce this electro-refractive effect. The shift in refractive index is also affected by the density and location of deep potential wells within the SCR. In addition, the microstructure change was observed by a TEM

  10. First-principles studies of magnetoelectric coupling in hexagonal LuFeO3 under applied electric fields

    NASA Astrophysics Data System (ADS)

    Zhang, Yubo; Wang, Hongwei; Dhuvad, Pratikkumar; Xu, Xiaoshan; Stengel, Massimiliano; Wu, Xifan

    The recently stabilized hexagonal LuFeO3 thin-film provides an opportunity in realizing the magnetoelectric coupling in multiferroic materials, in which the weak ferromagnetism due to Dzyaloshinskii-Moriya interaction was found to be closely associated with the trimerization (K3) mode. Here, we performed first-principles calculations in hexagonal LuFeO3 and studied the variations of weak ferromagnetic moment under applied electric fields. It is found that the weak ferromagnetism is a property that can be directly tuned by the external electric fields. As an improper ferroelectric material, such a magnetoelectric coupling is realized by the strong interaction between the trimerization mode and ferroelectric mode. Under the electric field poling, ferroelectric mode will respond. A change in ferroelectric distortion will in turn affect the amplitude of trimerization mode, and therefore, the weak ferromagnetism. Interestingly, the magnetoelectric coupling in LuFeO3 shows a strong nonlinear behavior originating again from the coupling between the trimerization and ferroelectric modes due to its improper nature.

  11. 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

  12. Mapping of the resistance of a superconducting transition edge sensor as a function of temperature, current, and applied magnetic field

    NASA Astrophysics Data System (ADS)

    Zhang, Shuo; Eckart, Megan E.; Jaeckel, Felix T.; Kripps, Kari L.; McCammon, Dan; Morgan, Kelsey M.; Zhou, Yu

    2017-02-01

    We have measured the resistance R ( T , I , B ext ) of a superconducting transition edge sensor over the entire transition region on a fine scale, producing a four-dimensional map of the resistance surface. The dimensionless temperature and current sensitivities ( α ≡ ∂ log R / ∂ log T | I and β ≡ ∂ log R / ∂ log I | T ) of the TES resistance have been determined at each point. α and β are closely related to the sensor performance, but show a great deal of complex, large amplitude fine structure over large portions of the surface that is sensitive to the applied magnetic field. We discuss the relation of this structure to the presence of Josephson "weak link" fringes.

  13. AC losses of single-core MgB2 wires with different metallic sheaths

    NASA Astrophysics Data System (ADS)

    Kováč, J.; Šouc, J.; Kováč, P.; Hušek, I.

    2015-12-01

    AC losses of single-core MgB2 superconductors with different metallic sheaths (Cu, GlidCop, stainless steel and Monel) have been measured and analyzed. These wires were exposed to external magnetic field with frequencies 72 and 144 Hz and amplitudes up to 0.1 T at temperatures ranged from 18 to 40 K. The obtained results have shown that applied metallic sheath can affect the measured AC loss considerably. In the case of GlidCop and Stainless Steel a negligible small effect of metallic sheath was observed. Strong contribution of eddy currents has been found in the wire with well conductive copper sheath. In the case of Monel sheath, the hysteresis loss of magnetic sheath is dominated and AC loss of MgB2 core is practically not visible.

  14. Micro pumping methods based on AC electrokinetics and Electrorheologically actuated PDMS valves

    NASA Astrophysics Data System (ADS)

    Soni, Gaurav; Squires, Todd; Meinhart, Carl

    2006-11-01

    We have developed 2 different micropumping methods for transporting ionic fluids through microchannels. The first method is based on Induced Charge Electroosmosis (ICEO) and AC flow field-effect. We used an AC electric field to produce a symmetric ICEO flow on a planar electrode, called `gate'. In order to break the symmetry of ICEO, we applied an additional AC voltage to the gate electrode. Such modulation of the gate potential is called field effect and produces a unidirectional pumping over the gate surface. We used micro PIV to measure pumping velocities for a range of ionic concentration, AC frequency and gate voltage. We have also conducted numerical simulations to understand the deteriorating effect of lateral conduction of surface charge on the pumping velocities. The second method is based on vibration of a flexible PDMS diaphragm actuated by an electrorheological (ER) fluid. ER fluid is a colloidal suspension exhibiting a reversible liquid-to-solid transition under an electric field. This liquid-to-solid transition can yield very high shear stress and can be used to open and close a PDMS valve. Three such valves were fabricated and actuated in a peristaltic fashion in order to achieve positive displacement pumping of fluids.

  15. The effect of magnetisation relaxation of superconducting grains on time relaxation of the resistance of granular HTSC in constant applied magnetic field

    NASA Astrophysics Data System (ADS)

    Balaev, D. A.; Dubrovskiy, A. A.; Shaykhutdinov, K. A.; Popkov, S. I.; Petrov, M. I.

    2009-03-01

    In order to clarify the mechanism of hysteretic behavior of magnetoresistance of granular HTSC the magnetoresistance curves R(H) and time evolution of the resistance in constant applied magnetic fields have been studied in granular YBCO at T=77 K. It was found that on ascending branch of R(H) dependence the resistance at H=const decreased with time while on the descending branch the resistance increased with time in applied constant magnetic field. For the range of low magnetic fields (below the minimum point of the descending branch of R(H) dependence) the resistance at H=const decreased again. The behavior observed is well described by the model of granular HTSC, where the intergrain space is in effective magnetic field which is the superposition of the applied field and the field induced by superconducting grains. The time evolution of resistance reflects processes of time relaxation of magnetization of HTSC grains due to the intragrain flux creep.

  16. Enhancing filterability of activated sludge from landfill leachate treatment plant by applying electrical field ineffective on bacterial life.

    PubMed

    Akkaya, Gulizar Kurtoglu; Sekman, Elif; Top, Selin; Sagir, Ece; Bilgili, Mehmet Sinan; Guvenc, Senem Yazici

    2017-03-09

    The aim of this study is to investigate filterability enhancement of activated sludge supplied form a full-scale leachate treatment plant by applying DC electric field while keeping the biological operational conditions in desirable range. The activated sludge samples were received from the nitrification tank in the leachate treatment plant of Istanbul's Odayeri Sanitary Landfill Site. Experimental sets were conducted as laboratory-scale batch studies and were duplicated for 1A, 2A, 3A, 4A, and 5A of electrical currents and 2, 5, 10, 15, and 30 min of exposure times under continuous aeration. Physicochemical parameters such as temperature, pH, and oxidation reduction potential in the mixture right after each experimental set and biochemical parameters such as chemical oxygen demand, total phosphorus, and ammonia nitrogen in supernatant were analyzed to define the sets that remain in the range of ideal biological operational conditions. Later on, sludge filterability properties such as capillary suction time, specific resistance to filtration, zeta potential, and particle size were measured for remaining harmless sets. Additionally, cost analyses were conducted in respect to energy and electrode consumptions. Application of 2A DC electric field and 15-min exposure time was found to be the most favorable conditions to enhance filterability of the landfill leachate-activated sludge.

  17. Applying geographic profiling used in the field of criminology for predicting the nest locations of bumble bees.

    PubMed

    Suzuki-Ohno, Yukari; Inoue, Maki N; Ohno, Kazunori

    2010-07-21

    We tested whether geographic profiling (GP) can predict multiple nest locations of bumble bees. GP was originally developed in the field of criminology for predicting the area where an offender most likely resides on the basis of the actual crime sites and the predefined probability of crime interaction. The predefined probability of crime interaction in the GP model depends on the distance of a site from an offender's residence. We applied GP for predicting nest locations, assuming that foraging and nest sites were the crime sites and the offenders' residences, respectively. We identified the foraging and nest sites of the invasive species Bombus terrestris in 2004, 2005, and 2006. We fitted GP model coefficients to the field data of the foraging and nest sites, and used GP with the fitting coefficients. GP succeeded in predicting about 10-30% of actual nests. Sensitivity analysis showed that the predictability of the GP model mainly depended on the coefficient value of buffer zone, the distance at the mode of the foraging probability. GP will be able to predict the nest locations of bumble bees in other area by using the fitting coefficient values measured in this study. It will be possible to further improve the predictability of the GP model by considering food site preference and nest density.

  18. Applying the Ramer-Douglas-Peucker algorithm to compress and characterize time-series and spatial fields of precipitation

    NASA Astrophysics Data System (ADS)

    Ehret, Uwe; Neuper, Malte

    2014-05-01

    Well known in image processing and computer graphics, the Ramer-Douglas-Peucker(RDP) algorithm (Ramer, 1972; Douglas and Peucker, 1973) is a procedure to approximate a polygon (lines or areas) by a subset of its nodes. Typically it is used to represent a polygonal feature on a larger scale, e.g. when zooming out of an image. The algorithm is simple but effective: Starting from the simplest possible approximation of the original polygon (for a line it is the start and end point), the simplified polygon is built by successively adding always the node of the original polygon farthest from the simplified polygon. This is repeated until a chosen agreement between the original and the simplified polygon is reached. Compared to other smoothing and compression algorithms like moving-average filters or block aggregation, the RDP algorithm has the advantages that i) the simplified polygon is built from the original points, i.e. extreme values are preserved and ii) that the variability of the original polygon is preserved in a scale-independent manner, i.e. the simplified polygon is high-resolution where necessary and low-resolution where possible. Applying the RDP algorithm to time series of precipitation or 2d spatial fields of radar rainfall often reveals a large degree of compressibility while losing almost no information. In general, this is the case for any auto-correlated polygon such as discharge time series etc. While the RDP algorithm is thus interesting as a very efficient tool for compression, it can also be used to characterize time series or spatial fields with respect to their temporal or spatial structure by relating, over successive steps of simplification, the compression achieved and information lost. We will present and discuss the characteristics of the RDP-based compression and characterization at various examples, both observed (rainfall and discharge time series, 2-d radar rainfall fields) and artificial (random noise fields, random fields with known

  19. Microtubule alignment and manipulation using AC electrokinetics.

    PubMed

    Uppalapati, Maruti; Huang, Ying-Ming; Jackson, Thomas N; Hancock, William O

    2008-09-01

    The kinesin-microtubule system plays an important role in intracellular transport and is a model system for integrating biomotor-driven transport into microengineered devices. AC electrokinetics provides a novel tool for manipulating and organizing microtubules in solution, enabling new experimental geometries for investigating and controlling the interactions of microtubules and microtubule motors in vitro. By fabricating microelectrodes on glass substrates and generating AC electric fields across solutions of microtubules in low-ionic-strength buffers, bundles of microtubules are collected and aligned and the electrical properties of microtubules in solution are measured. The AC electric fields result in electro-osmotic flow, electrothermal flow, and dielectrophoresis of microtubules, which can be controlled by varying the solution conductivity, AC frequency, and electrode geometry. By mapping the solution conductivity and AC frequency over which positive dielectrophoresis occurs, the apparent conductivity of taxol-stabilized bovine-brain microtubules in PIPES buffer is measured to be 250 mS m(-1). By maximizing dielectrophoretic forces and minimizing electro-osmotic and electrothermal flow, microtubules are assembled into opposed asters. These experiments demonstrate that AC electrokinetics provides a powerful new tool for kinesin-driven transport applications and for investigating the role of microtubule motors in development and maintenance of the mitotic spindle.

  20. 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.

  1. Floating AC-DEP (dielectrophoretic) manipulations of fluorescent nanoparticle at metal nanostructure for plasmonic applications

    NASA Astrophysics Data System (ADS)

    Kim, J.; Shin, H. J.; Hwang, K. S.; Park, J. H.

    2014-11-01

    We propose the fluorescent nanoparticle manipulations at nano-metal structures with floating AC-DEP force for plasmonic applications. The electrode gap was optimized to induce enough DEP force around the nano-structure for manipulation of the nanoparticles. 10um wide gap of electrode was acquired to apply the floating AC-DEP force at various designed metal nano-structure such as nanowire, y-branch and vortex. The all shape of nano-metal structures are formed at the gap of microelectrode and not connected with microelectrode. The gold nano-structures in the gap of microelectrode were fabricated with e-beam lithography and lift-off process. Before the formation of metal nanostructure, micro electrodes for applying the electric field around the metal nano-structures were fabricated with photolithography and lift-off process. Cadmium selenide (CdSe/ZnS) QDs (0.8 nM, emission wavelength of 605 nm) with a 25 nm zinc sulfide capping layer and 100nm polystyrene nano bead (1 nM, emission wavelength of 610nm) were used as fluorescent nanoparticles. We applied the 8 Vpp, 3 MHz sine wave for the positive DEP force, and it resulted in 108 V/m electric field and 1011 V/m electric field gradient around gold nanowire with floating AC. The fluorescent nanoparticle's attachment at the nanowire is confirmed by the fluorescent optical analysis. The fluorescent nanoparticles are located successfully at designed metal nano-structures for plasmonic applications.

  2. 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.

  3. Situating Ontario's Colleges between the American and European Models for Providing Opportunity for the Attainment of Baccalaureate Degrees in Applied Fields of Study

    ERIC Educational Resources Information Center

    Skolnik, Michael L.

    2016-01-01

    During the last third of the twentieth century, college sectors in many countries took on the role of expanding opportunities for baccalaureate degree attainment in applied fields of study. In many European countries, colleges came to constitute a parallel higher education sector that offered degree programs of an applied nature in contrast to the…

  4. A galvanotaxis assay for analysis of neural precursor cell migration kinetics in an externally applied direct current electric field.

    PubMed

    Babona-Pilipos, Robart; Popovic, Milos R; Morshead, Cindi M

    2012-10-13

    The discovery of neural stem and progenitor cells (collectively termed neural precursor cells) (NPCs) in the adult mammalian brain has led to a body of research aimed at utilizing the multipotent and proliferative properties of these cells for the development of neuroregenerative strategies. A critical step for the success of such strategies is the mobilization of NPCs toward a lesion site following exogenous transplantation or to enhance the response of the endogenous precursors that are found in the periventricular region of the CNS. Accordingly, it is essential to understand the mechanisms that promote, guide, and enhance NPC migration. Our work focuses on the utilization of direct current electric fields (dcEFs) to promote and direct NPC migration - a phenomenon known as galvanotaxis. Endogenous physiological electric fields function as critical cues for cell migration during normal development and wound repair. Pharmacological disruption of the trans-neural tube potential in axolotl embryos causes severe developmental malformations(1). In the context of wound healing, the rate of repair of wounded cornea is directly correlated with the magnitude of the epithelial wound potential that arises after injury, as shown by pharmacological enhancement or disruption of this dcEF(2-3). We have demonstrated that adult subependymal NPCs undergo rapid and directed cathodal migration in vitro when exposed to an externally applied dcEF. In this protocol we describe our lab's techniques for creating a simple and effective galvanotaxis assay for high-resolution, long-term observation of directed cell body translocation (migration) on a single-cell level. This assay would be suitable for investigating the mechanisms that regulate dcEF transduction into cellular motility through the use of transgenic or knockout mice, short interfering RNA, or specific receptor agonists/antagonists.

  5. Improved Dynamic Response of Magnetic Feedback in DIII-D with AC Compensation

    NASA Astrophysics Data System (ADS)

    Piron, Lidia; Marrelli, Lionello; Martin, Piero; Piovesan, Paolo; Soppelsa, Anton; Hanson, Jeremy; Reimerdes, Holger; in, Yongkyoon; Okabayashi, Michio

    2010-11-01

    High-β tokamaks need robust magnetic feedback to cope with various MHD modes. A new algorithm was tested to improve the DIII-D feedback dynamic response. Magnetic sensor signals include contributions from vacuum sources, such as active coils. In the present algorithm, the plasma response to an applied field is computed by subtracting from the sensor signals the dc component of couplings to the coils. But, when the coil currents vary on fast enough time scales, wall eddy currents modify the contributions to the sensor field with respect to its dc value [1]. Such ac effects can be non-negligible. Transfer functions between coils and sensors were measured and an ac compensation scheme accounting for them was developed. Significant coil current was saved likely due to a better estimate of the plasma response. Ac effects may be more important at high-β, where uncorrected error fields are strongly amplified. [1] E.J. Strait et al. 2003 Nucl. Fusion 43 430. *Work supported in part by US DOE under by DE-FG02-04ER54761, DE-FG02-06ER84442, & DE-AC02-09CH11466.

  6. The Influence of temperature and applied magnetic field on the exchange bias effect of La1.5Ca0.5CoIrO6

    NASA Astrophysics Data System (ADS)

    Coutrim, L. T.; Bittar, E. M.; Baggio-Saitovitch, E.; Bufaiçal, L.

    2017-04-01

    La1.5Ca0.5CoIrO6 is a re-entrant spin-glass double-perovskite that exhibits a non-negligible spontaneous exchange bias effect at low temperatures. When performing magnetization as a function of applied field [M(H)] measurements after cooling the sample in the presence of a magnetic field, the exchange bias is greatly enhanced. In this work we report a detailed investigation of the influence of the maximum applied field (Hm) on the exchange bias effect for M (H) curves measured with and without the presence of an applied field on cooling. In both cases the shift in the hysteresis loops decreases for increasing Hm. We have also investigated the influence of the cooling field on the exchange bias effect. By increasing the applied field on cooling there is an initial increase of the exchange bias, followed by a decrease of the effect for larger cooling fields. A detailed study of the magnetic evolution of the system with temperature showed that despite the enhancement of the coercive field observed at temperatures above the freezing of the spin-glass phase, there is no trace of exchange bias effect at these temperatures. We discuss our results in terms of the pinning of the spins at the magnetic interfaces.

  7. Applying Neural Networks to Hyperspectral and Multispectral Field Data for Discrimination of Cruciferous Weeds in Winter Crops

    PubMed Central

    de Castro, Ana-Isabel; Jurado-Expósito, Montserrat; Gómez-Casero, María-Teresa; López-Granados, Francisca

    2012-01-01

    In the context of detection of weeds in crops for site-specific weed control, on-ground spectral reflectance measurements are the first step to determine the potential of remote spectral data to classify weeds and crops. Field studies were conducted for four years at different locations in Spain. We aimed to distinguish cruciferous weeds in wheat and broad bean crops, using hyperspectral and multispectral readings in the visible and near-infrared spectrum. To identify differences in reflectance between cruciferous weeds, we applied three classification methods: stepwise discriminant (STEPDISC) analysis and two neural networks, specifically, multilayer perceptron (MLP) and radial basis function (RBF). Hyperspectral and multispectral signatures of cruciferous weeds, and wheat and broad bean crops can be classified using STEPDISC analysis, and MLP and RBF neural networks with different success, being the MLP model the most accurate with 100%, or higher than 98.1%, of classification performance for all the years. Classification accuracy from hyperspectral signatures was similar to that from multispectral and spectral indices, suggesting that little advantage would be obtained by using more expensive airborne hyperspectral imagery. Therefore, for next investigations, we recommend using multispectral remote imagery to explore whether they can potentially discriminate these weeds and crops. PMID:22629171

  8. Applying neural networks to hyperspectral and multispectral field data for discrimination of cruciferous weeds in winter crops.

    PubMed

    de Castro, Ana-Isabel; Jurado-Expósito, Montserrat; Gómez-Casero, María-Teresa; López-Granados, Francisca

    2012-01-01

    In the context of detection of weeds in crops for site-specific weed control, on-ground spectral reflectance measurements are the first step to determine the potential of remote spectral data to classify weeds and crops. Field studies were conducted for four years at different locations in Spain. We aimed to distinguish cruciferous weeds in wheat and broad bean crops, using hyperspectral and multispectral readings in the visible and near-infrared spectrum. To identify differences in reflectance between cruciferous weeds, we applied three classification methods: stepwise discriminant (STEPDISC) analysis and two neural networks, specifically, multilayer perceptron (MLP) and radial basis function (RBF). Hyperspectral and multispectral signatures of cruciferous weeds, and wheat and broad bean crops can be classified using STEPDISC analysis, and MLP and RBF neural networks with different success, being the MLP model the most accurate with 100%, or higher than 98.1%, of classification performance for all the years. Classification accuracy from hyperspectral signatures was similar to that from multispectral and spectral indices, suggesting that little advantage would be obtained by using more expensive airborne hyperspectral imagery. Therefore, for next investigations, we recommend using multispectral remote imagery to explore whether they can potentially discriminate these weeds and crops.

  9. Full-field bulge test for planar anisotropic tissues: part I--experimental methods applied to human skin tissue.

    PubMed

    Tonge, Theresa K; Atlan, Lorre S; Voo, Liming M; Nguyen, Thao D

    2013-04-01

    The nonlinear anisotropic properties of human skin tissue were investigated using bulge testing. Full-field displacement data were obtained during testing of human skin tissues procured from the lower back of post-mortem human subjects using 3-D digital image correlation. To measure anisotropy, the dominant fiber direction of the tissue was determined from the deformed geometry of the specimen. Local strains and stress resultants were calculated along both the dominant fiber direction and the perpendicular direction. Variation in anisotropy and stiffness was observed between specimens. The use of stress resultants rather than the membrane stress approximation accounted for bending effects, which are significant for a thick nonlinear tissue. Of the six specimens tested, it was observed that specimens from older donors exhibited a stiffer and more isotropic response than those from younger donors. It was seen that the mechanical response of the tissue was negligibly impacted by preconditioning or the ambient humidity. The methods presented in this work for skin tissue are sufficiently general to be applied to other planar tissues, such as pericardium, gastrointestinal tissue, and fetal membranes. The stress resultant-stretch relations will be used in a companion paper to obtain material parameters for a nonlinear anisotropic hyperelastic model.

  10. Characterization of argon direct-current glow discharge with a longitudinal electric field applied at ambient air

    PubMed Central

    Jiang, Weiman; Tang, Jie; Wang, Yishan; Zhao, Wei; Duan, Yixiang

    2014-01-01

    A direct-current-driven plasma jet is developed by applying a longitudinal electric field on the flowing argon at ambient air. This plasma shows a torch shape with its cross-section increased from the anode to the cathode. Comparison with its counterparts indicates that the gas flow plays a key role in variation of the plasma structure and contributes much to enlarging the plasma volume. It is also found that the circular hollow metal base promotes generation of plasma with a high-power volume density in a limited space. The optical emission spectroscopy (OES) diagnosis indicates that the plasma comprises many reactive species, such as OH, O, excited N2, and Ar metastables. Examination of the rotational and vibrational temperature indicates that the plasma is under nonequilibrium condition and the excited species OH(A 2Σ+), O(5P), and N2(C 3Πu) are partly generated by energy transfer from argon metastables. The spatially resolved OES of plasma reveals that the negative glow, Faraday dark space, and positive column are distributed across the gas gap. The absence of the anode glow is attributed to the fact that many electrons in the vicinity of the anode follow ions into the positive column due to the ambipolar diffusion in the flowing gas. PMID:25205176

  11. Magnetostrictive gradient in Tb0.27Dy0.73Fe1.95 induced by high magnetic field gradient applied during solidification

    NASA Astrophysics Data System (ADS)

    Gao, Pengfei; Liu, Tie; Dong, Meng; Yuan, Yi; Wang, Kai; Wang, Qiang

    2016-09-01

    We investigated how high magnetic field gradients affected the magnetostrictive performance of Tb0.27Dy0.73Fe1.95 during solidification. At high applied magnetic field gradients, the magnetostriction exhibited a gradient distribution throughout the alloy. Increasing the magnetic field gradient also increased the magnetostriction gradient. We attributed the graded magnetostrictive performance to the gradient distribution of (Tb, Dy)Fe2 phase in the alloy and its orientation.

  12. Superconductivity and itinerant ferromagnetism of Y9Co7 probed by ac susceptibility.

    PubMed

    Gordon, R T; Vannette, M D; Strychalska, J; Klimczuk, T; Cava, R J; Prozorov, R

    2016-04-27

    The ac magnetic susceptibility of a single crystal sample of the compound Y9Co7 has been measured in applied dc fields ranging from 0-6.7 kOe by utilizing a tunnel diode resonator circuit. In agreement with previous measurements on this material, a superconducting transition has been observed to occur at T(SC)≈2.5 K. A broad maximum has been observed in the zero field susceptibility measurements from 2.5 K  <  T  <  8 K and its behavior with applied dc magnetic fields is consistent with that of the itinerant ferromagnet ZrZn2, which supports previous claims of itinerant ferromagnetism in this compound. The susceptibility has also been measured as a function of applied magnetic field and the results indicate that the actual Curie temperature for this system is higher than that suggested by previous reports based on Arrott plots constructed from dc magnetization.

  13. Fabrication of alumina films with laminated structures by ac anodization.

    PubMed

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  14. Fabrication of alumina films with laminated structures by ac anodization

    NASA Astrophysics Data System (ADS)

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  15. Self-field ac losses of a twisted multifilamentary (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape

    NASA Astrophysics Data System (ADS)

    Friend, C. M.; Huang, Y. B.

    2000-06-01

    Self-field loss measurements at 77 K on a superconducting (Bi, Pb)2Sr2Ca2Cu3O10/AgAu tape with twisted filaments are presented. Using the first- and third-harmonic components of the electric field, the hysteretic losses are separated from the total loss. At peak transport currents less than half the critical current, the hysteretic losses are considerably reduced. However, sizable nonhysteretic losses are also observed. At higher currents, the hysteretic loss increases, dominating the total loss, and is similar to that for an untwisted tape.

  16. Improving thrust by pulse-induced breakdown enhancement in AC surface dielectric barrier discharge actuators for airflow control

    NASA Astrophysics Data System (ADS)

    Yan, Huijie; Yang, Liang; Qi, Xiaohua; Ren, Chunsheng

    2016-07-01

    The characteristics of a plate-to-plate AC surface dielectric barrier discharge (SDBD) actuator using the pulse-induced breakdown enhancing method are experimentally investigated. The encapsulated electrode is supplied with a sine high AC voltage, while the exposed electrode is feed by a synchronized pulse voltage. Based on the thrust force and power consumption measurements, a parametric study was performed using a positive pulse applied at the trough phase of the AC cycles in which the thrust force was observed to increase by about 100% to 300% and the efficiency up to about 100% compared with the AC-only supply conditions for different AC voltages within the tested range. The pulse-induced breakdown effect was analyzed from the electrical and light emission waveforms to reveal the underlying mechanism. The surface potential due to the charge deposition effect was also measured using a specially designed corona-like discharge potential probe. It is shown that the pulse-induced breakdown was able to cause a temporarily intensified local electric field to enhance the glow-like discharge and meanwhile increase the time-average surface potential in the region further downstream. The improvement in the force by the enhancement in the pulse-induced breakdown was mainly due to enhancements in the glow-like discharge and the surface potential increment, with the latter being more important when the AC voltage is higher.

  17. On-Line Testing and Reconfiguration of Field Programmable Gate Arrays (FPGAs) for Fault-Tolerant (FT) Applications in Adaptive Computing Systems (ACS)

    DTIC Science & Technology

    2002-04-01

    GUI. She joined the project in May 2001 and received BSCS and MBA degrees in December 2001 and May 2002, respectively. 16. Thomas Slaughter was...Custom Integrated Circuits Conf., pp. 7.1.1-7.1.4, 1993. [24] N. Howard, A. Tyrrell, and N. Allinson , “The Yield Enhancement of Field Programmable Gate

  18. Field-amplified sample stacking capillary electrophoresis with electrochemiluminescence applied to the determination of illicit drugs on banknotes.

    PubMed

    Xu, Yuanhong; Gao, Ying; Wei, Hui; Du, Yan; Wang, Erkang

    2006-05-19

    Capillary electrophoresis (CE) with Ru(bpy)3(2+) electrochemiluminescence (ECL) detection system was established to the determination of contamination of banknotes with controlled drugs and a high efficiency on-column field-amplified sample stacking (FASS) technique was also optimized to increase the ECL intensity. The method was illustrated using heroin and cocaine, which are two typical and popular illicit drugs. Highest sample stacking was obtained when 0.01 mM acetic acid was chosen for sample dissolution with electrokinetical injection for 6 s at 17 kV. Under the optimized conditions: ECL detection at 1.2 V, separation voltage 10.0 kV, 20 mM phosphate-acetate (pH 7.2) as running buffer, 5 mM Ru(bpy)3(2+) with 50 mM phosphate-acetate (pH 7.2) in the detection cell, the standard curves were linear in the range of 7.50x10(-8) to 1.00x10(-5) M for heroin and 2.50x10(-7) to 1.00x10(-4) M for cocaine and detection limits of 50 nM for heroin and 60 nM for cocaine were achieved (S/N = 3), respectively. Relative standard derivations of the ECL intensity and the migration time were 3.50 and 0.51% for heroin and 4.44 and 0.12% for cocaine, respectively. The developed method was successfully applied to the determination of heroin and cocaine on illicit drug contaminated banknotes without any damage of the paper currency. A baseline resolution for heroin and cocaine was achieved within 6 min.

  19. Applying geophysical surveys for studying subsurface geology of monogenetic volcanic fields: the example of La Garrotxa Volcanic Field (NE of Iberian Peninsula)

    NASA Astrophysics Data System (ADS)

    Bolós, Xavier; Barde-Cabusson, Stéphanie; Pedrazzi, Dario; Martí, Joan; Casas, Albert; Lovera, Raúl; Nadal-Sala, Daniel

    2014-05-01

    Improving knowledge of the shallowest part of the feeding system of monogenetic volcanoes and the relationship with the subsurface geology is an important task. We applied high-precision geophysical techniques that are self-potential and electrical resistivity tomography, for the exploration of the uppermost part of the substrate of La Garrotxa Volcanic Field, which is part of the European Cenozoic Rift System. Previous geophysical studies carried out in the same area at a less detailed scale were aimed at identifying deeper structures, and together constitute the basis to establish volcanic susceptibility in La Garrotxa. Self-potential study allowed identifying key areas where electrical resistivity tomography could be conducted. Dykes and faults associated with several monogenetic cones were identified through the generation of resistivity models. The combined results confirm that shallow tectonics controlling the distribution of the foci of eruptive activity in this volcanic zone mainly correspond to NNW-SSE and accessorily by NNE-SSW Neogene extensional fissures and faults and concretely show the associated magmatic intrusions. These studies show that previous alpine tectonic structures played no apparent role in controlling the loci of this volcanism. Furthermore, the results obtained show that the changes in eruption dynamics occurring at different vents located at relatively short distances in this volcanic area can be controlled by shallow stratigraphical, structural, and hydrogeological features underneath these monogenetic volcanoes. This study was partially funded by the Beca Ciutat d'Olot en Ciències Naturals and the European Commission (FT7 Theme: ENV.2011.1.3.3-1; Grant 282759: "VUELCO").

  20. Anomalies in the applied magnetic fields in DIII-D and their implications for the understanding of stability experiments

    SciTech Connect

    Luxon, J. L.; Schaffer, M. J.; Jackson, G. L.; Leuer, J. A.; Nagy, A.; Scoville, J. T.; Strait, E. J.

    2003-12-01

    Small non-axisymmetric magnetic fields are known to cause serious loss of stability in tokamaks leading to loss of confinement and abrupt termination of plasma current (disruptions). The best known examples are the locked mode and the resistive wall mode. Understanding of the underlying field anomalies (departures in the hardware-related fields from ideal toroidal and poloidal fields on a single axis) and the interaction of the plasma with them is crucial to tokamak development. Results of both locked mode experiments and resistive wall mode experiments done in DIII-D tokamak plasmas have been interpreted to indicate the presence of a significant anomalous field. New measurements of the magnetic field anomalies of the hardware systems have been made on DIII-D. The measured field anomalies due to the plasma shaping coils in DIII-D are smaller than previously reported. Additional evaluations of systematic errors have been made. New measurements of the anomalous fields of the ohmic heating and toroidal coils have been added. Such detailed in situ measurements of the fields of a tokamak are unique. The anomalous fields from all of the coils are one third of the values indicated from the stability experiments. These results indicate limitations in the understanding of the interaction of the plasma with the external field. They indicate that it may not be possible to deduce the anomalous fields in a tokamak from plasma experiments and that we may not have the basis needed to project the error field requirements of future tokamaks.